WO2020189236A1

WO2020189236A1 - Organic film and organic electroluminescent element

Info

Publication number: WO2020189236A1
Application number: PCT/JP2020/008650
Authority: WO
Inventors: 一磨小田; 隆太郎菅原; 大樹巽
Original assignee: コニカミノルタ株式会社
Priority date: 2019-03-18
Filing date: 2020-03-02
Publication date: 2020-09-24
Also published as: JPWO2020189236A1

Abstract

An organic film according to the present invention contains a charge-transport material having a structure represented by general formula (1). [In general formula (1), n represents an integer of 4-6 and m represents an integer of 0-2, provided that n+m=6 is satisfied. X represents a hydrogen atom or a substituent, and a plurality of X's may be the same as or different from each other. An aromatic ring A is a specific nitrogen-containing aromatic compound, a plurality of aromatic rings A may be the same as or different from each other, but when n is 6, there are at least two types of aromatic rings A.]

Description

Organic membranes and organic electroluminescence devices

The present invention relates to an organic film and an organic electroluminescence device, and the organic film having high electron mobility while reducing the cohesiveness by suppressing π stacking with a bulky aromatic substituent and mixing axial isomers, particularly organic electroluminescence. The present invention relates to an organic film or the like used as an electron transport layer of an element.

Organic semiconductors are expected as materials for realizing flexible electronic devices, and have been put into practical use in field effect transistors, organic electroluminescence (hereinafter abbreviated as "EL") elements, and the like.

When organic materials are used as electronic devices, the magnitude of carrier mobility is an important property. The carrier mobility is theoretically calculated by two types of methods, a band model and a hopping model, but in the case of organic semiconductors, a hopping model is often considered. The carrier mobility k _et in the hopping model is given by the Marcus equation (Equation (1) below).

In the above equation (1), λ represents the energy of molecular structure change due to carrier transfer (reorientation energy), t represents the degree of overlap of frontier orbitals between molecules (movement integration), and k _B represents the Boltzmann constant. From the equation (1), in order to increase the carrier mobility k _et of the organic semiconductor, it has a rigid structure so that the reorientation energy (λ) is small, and the moving average (t) is large (that is, the frontier). It can be seen that a molecular design that enhances the intermolecular interaction is necessary so that the distance between the orbitals becomes small (see below)).

Examples of the compound satisfying the above requirements include condensed polycyclic aromatic molecules typified by anthracene, pyrene, carbazole, dibenzofuran, phenanthrene, benzimidazole and the like. Condensed polycyclic aromatic molecules have a condensed ring structure and are highly rigid, and strong π-π interaction between molecules is possible between wide π-conjugated planes, so they are widely studied as organic semiconductor materials. (See, for example, Patent Document 1).

However, if the intermolecular interaction is enhanced by the π stack, the cohesiveness of the molecules is enhanced, which becomes a big problem especially when used as an organic device material.

For example, under the driving conditions of an organic EL element, molecular aggregation is likely to occur due to application of an electric field and thermal motion, resulting in generation of a carrier trap region and fluctuation of carrier balance. Fluctuations in the carrier balance are likely to cause an increase in drive voltage and a decrease in luminous efficiency, that is, element deterioration, which causes a decrease in element drive life.

It is possible to inhibit the π stack by introducing a bulky aliphatic substituent such as a tertiary butyl group around the condensed polycyclic aromatic molecule, but the distance between the frontier orbitals becomes large and the mobility (movement) The mobile integral (t)) decreases.

Therefore, it is considered that the π stack can be suppressed while maintaining the mobility by introducing an aromatic substituent instead of an aliphatic substituent.
Patent Document 2, Patent Document 3 and Non-Patent Document 1 disclose a technique for using a compound having an aromatic substituent introduced at an adjacent position around a benzene ring as a hole transport material or a host material. However, there is no mention of reduction of cohesion by suppressing π stack, stability of film state, and electron transfer ability.

Further, it can be seen that all of the exemplified compounds shown in Patent Documents 2 and 3 have high molecular structure symmetry. It is considered that a structure with high symmetry tends to have a thermodynamically stable structure and easily aggregates. When a molecule having high cohesiveness is used as an electronic device material, as described above, an increase in driving voltage and a decrease in luminous efficiency, that is, device deterioration is likely to occur. It is necessary to reduce the symmetry of the molecular structure in order to further suppress the cohesiveness and improve the membrane stability.

Non-Patent Document 2 discloses a technique relating to luminescence of a compound having a structure having a structure having a lower symmetry than Patent Documents 2 and 3 by introducing five carbazoles into a benzene ring, but stacking the compounds. No mention is made of structure, cohesiveness or electron transportability.

Japanese Patent No. 54933333 Japanese Unexamined Patent Publication No. 2006-100394 Special Table 2007-513217

The present invention has been made in view of the above problems and situations, and the problem to be solved is an organic film having high electron mobility, a small voltage rise rate when a voltage is applied, and excellent film stability. Another object of the present invention is to provide an organic electroluminescence device using the organic film.

In order to solve the above problems, the present inventor introduces bulky aromatic substituents at positions orthogonal to the mother skeleton and adjacent to each other in the process of examining the cause of the above problems, thereby causing steric hindrance to adjacent molecules. It was found that axial isomers can be formed by suppressing π-π stacking with and using an asymmetric substituent, and by increasing the entropy of the film, the film cohesiveness can be reduced and the voltage rise due to energization can be suppressed. It led to the invention.
The above problem according to the present invention is solved by the following means.

1. 1. An organic film containing a charge transport material having a structure represented by the following general formula (1).

[In the general formula (1), n represents an integer of 4 to 6, and m represents an integer of 0 to 2. However, it satisfies n + m = 6.
X represents a hydrogen atom or a substituent, and a plurality of Xs may be the same or different.
The aromatic ring A is a nitrogen-containing aromatic compound having a structure represented by the following general formula (2), and a plurality of aromatic rings A may be the same or different, but when n is 6, the aromatic ring A may be the same or different. It has at least two types of aromatic rings A. Any one of the aromatic rings A has a structure in which at least one of Y ₁₁ to Y ₁₈ is a nitrogen atom. ]

[In the general formula (2), Y ₁₁ to Y ₁₈ independently represent a nitrogen atom or CR, respectively. R is a hydrogen atom or a substituent, and a plurality of the substituents may be bonded to each other to form a ring, and # represents a connection position in the general formula (1). ]

2. The organic membrane according to item 1, wherein in the general formula (1), any one of the substituents X is an electron-withdrawing substituent.

3. The organic film according to the first or second term, wherein in the general formula (1), any one of the substituents X is a cyano group.

4. The organic film according to any one of the first to third items, wherein n is 5 and m is 1 in the general formula (1).

5. The organic film according to any one of items 1 to 4, wherein in the general formula (1), any one of the aromatic rings A has a structure in which Y ₁₄ is a nitrogen atom.

6. The organic film according to any one of items 1 to 5, wherein the charge transport material is a compound exhibiting heat-activated delayed fluorescence.

7. The organic film according to any one of items 1 to 6 formed by a wet method.

8. The organic film according to any one of items 1 to 7, wherein the charge transporting material is an electron transporting material.

9. An organic electroluminescence device having one or more organic compound layers between an anode and a cathode.
An organic electroluminescence device in which at least one organic compound layer has an organic film according to any one of items 1 to 8 as an electron transporting layer.

10. The organic electroluminescence device according to Item 9, wherein the at least one organic compound layer contains a luminescent compound exhibiting thermally activated delayed fluorescence.

11. The organic electroluminescence device according to item 9 or 10, wherein the at least one organic compound layer is formed by a wet method.

In the present invention, by introducing bulky aromatic substituents at positions orthogonal to the mother skeleton and adjacent to each other, π-π stacking with adjacent molecules is suppressed due to steric hindrance. In addition, the asymmetric substituents increase the entropy of the membrane. As a result, it is possible to provide an organic film having high electron mobility, capable of suppressing a voltage rise when a voltage is applied, and having excellent film stability, and an organic electroluminescence using the organic film. Can be done.
Although the mechanism of expression or mechanism of action of the effect of the present invention has not been clarified, it is inferred as follows.
It is considered that the charge transport material having a highly flat structure based on the conventional design guideline is tightly packed due to the strong π-π interaction between the highly flat parts.

On the other hand, in the compound of the present invention in which bulky aromatic substituents are introduced at positions orthogonal to the mother skeleton and adjacent to each other, it is considered that π-π stacking between molecules cannot be formed due to steric hindrance of the adjacent substituents. ..

Further, since the substituents are located adjacent to each other, the rotation of the substituents is suppressed with respect to the mother nucleus, and when the substituents are asymmetrical, an axial isomer is formed. Since the magnitude and direction of the intramolecular dipole moment are different for each axial isomer, the electrostatic force between the isomers decreases.
It is considered that the above two effects reduce the intermolecular interaction and suppress the cohesiveness of the molecules.
Furthermore, when a compound containing an axial isomer is present in the membrane, it is considered that the entropy of the membrane before the device is driven increases because the number of molecular components increases. The compounds in the membrane aggregate with each other due to the thermal motion driven by the drive, but when the membrane is stabilized by the increase in entropy, the aggregation can be suppressed.
In addition, since it does not have an insulating site such as a long-chain aliphatic chain around the substituent and forms a film by the interaction between π-conjugated compounds, it is considered that high electron mobility can be exhibited. ..
It is presumed that the above effects can suppress aggregation when a voltage is applied and reduce a voltage rise while having high electron mobility.

Schematic diagram showing an example of a method for manufacturing an organic EL element using an inkjet printing method. Schematic external view showing an example of the structure of an inkjet head applicable to an inkjet printing method. Schematic external view showing an example of the structure of an inkjet head applicable to an inkjet printing method. Schematic diagram of the lighting device Schematic diagram of the lighting device

The organic film of the present invention contains a charge transport material having a structure represented by the general formula (1). This feature is a technical feature common to or corresponding to each of the following embodiments.

In the embodiment of the present invention, in the general formula (1), it is preferable that any one of the substituents X is an electron-withdrawing substituent from the viewpoint of improving the electron injectability.
Further, in the general formula (1), it is preferable that any one of the substituents X is a cyano group in terms of further improving the electron injectability.

In the general formula (1), it is preferable that n is 5 and m is 1 from the viewpoint of improving film stability.
In the general formula (1), it is preferable that any one of the aromatic rings A has a structure in which Y ₁₄ is a nitrogen atom from the viewpoint of further improving the film stability.

It is preferable that the charge transport material is a compound exhibiting heat-activated delayed fluorescence in terms of reducing the influence of fluctuations in the light emitting region and improving the half-life of brightness.
It is preferable that the thin film formed by the wet method is easy to obtain a homogeneous thin film and has high productivity.
Further, it is preferable that the charge transporting material is an electron transporting material from the viewpoint of exhibiting the effect of the present invention.

The organic film of the present invention is suitably used for an organic electroluminescence device having one or more organic compound layers between an anode and a cathode, and at least one organic compound layer is the organic film as an electron transporting layer. Have. As a result, it is possible to obtain an organic electroluminescence device having high electron mobility and having a small voltage rise rate and excellent film stability when a voltage is applied.

It is preferable that at least one organic compound layer contains a luminescent compound exhibiting thermally activated delayed fluorescence in that the association between the light emitting layer material and the charge transport material is suppressed and the luminance half life is improved.
It is preferable that at least one organic compound layer is formed by a wet method from the viewpoint of easy to obtain a homogeneous thin film and high productivity.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described. In the present application, "-" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

[Overview of Organic Membrane of the Present Invention]
The organic film of the present invention contains a charge transport material having a structure represented by the following general formula (1).

In the general formula (1), X represents a hydrogen atom or a substituent, and a plurality of Xs may be the same or different.
Examples of the substituent represented by X include a linear or branched alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group, a pentyl group, a hexyl group, etc.) and an alkenyl group (eg, For example, vinyl group, allyl group, etc.), alkynyl group (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (also referred to as aromatic carbocyclic group, aryl group, etc., for example, benzene ring, biphenyl, naphthalene, etc.) Ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysen ring, naphthacene ring, triphenylene ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaften ring, coronen ring, inden ring, Fluolene ring, fluorantene ring, naphthacene ring, pentacene ring, perylene ring, pentaphene ring, pixene ring, pyrene ring, pyranthrene ring, anthrananthrene ring, tetraline, etc.), aromatic heterocyclic group (for example) , Fran ring, dibenzofuran ring, thiophene ring, dibenzothiophene ring, oxazole ring, pyrrole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, benzoimidazole ring, oxaziazole ring, triazole ring, imidazole ring, Pyrazole ring, thiazole ring, indole ring, indazole ring, benzoimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, synnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, naphthylidine ring, carbazole ring, carboline ring. , A diazacarbazole ring (a group derived from a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom, etc.), a non-aromatic hydrocarbon ring group (for example, a cyclopentyl group). , Cyclohexyl group, etc.), non-aromatic heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholic group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy) Groups, etc.), cycloalkoxy groups (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy groups (eg, phenoxy group, naphthyloxy group, etc.), alkylthio groups (eg, methylthio group, ethylthio group, propylthio group, pentylthio). Group, hexylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, cyclopentylthio group, etc.) Sulfonylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), Sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc. ), Acyl group (eg, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (eg, acetyloxy group, ethyl) Carbonyloxy group, butylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group , 2-Ethylhexylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (eg, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexyl Aminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, phenylureido group, naphthylureido group, 2-Pyridylaminoureid group, etc.), Sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkyl Sulfonyl groups (eg, methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexylsulfonyl, arylsulfonyl or heteroarylsulfonyl groups (eg, phenylsulfo) Nyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (eg, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, anilino group, naphthylamino group, 2-pyridylamino group Etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group , Nitro group, hydroxy group, thiol group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), heavy hydrogen atom and the like.

In particular, in the general formula (1), it is preferable that any one of the substituents X is an electron-withdrawing substituent from the viewpoint of improving the electron injectability.
Examples of the electron-withdrawing substituent represented by X include a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, etc.) and a fluorinated hydrocarbon group (for example, a fluoromethyl group, a trifluoromethyl group, and a pentafluoro). Ethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, thiol group, alkoxycarbonyl group (for example, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxy) Carbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (eg, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylamino) Sulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (eg, acetyl group, ethylcarbonyl group, propylcarbonyl) Group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (eg, acetyloxy group, ethylcarbonyloxy) Group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentyl Carbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (eg, aminocarbonyl group, methylaminocarbonyl) Group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc. ), Sulfinyl group (eg, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkyl Sulfonyl groups (eg, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group) Groups, 2-pyridylsulfonyl groups, etc.), aromatic hydrocarbon ring groups substituted with electron-attracting groups, electron-attracting heterocyclic groups optionally substituted, and the like.

Examples of the aromatic ring group in the aromatic hydrocarbon ring group substituted with the electron-attracting group include a benzene ring and a naphthalene ring.
Examples of electron-attracting groups that the aromatic hydrocarbon ring group may have include a fluorine atom, a cyano group, an alkyl group that may be substituted with fluorine, a carbonyl group that may be substituted, and a substituent. Examples thereof include a sulfonyl group which may be substituted, a phosphine oxide group which may be substituted, a boryl group which may be substituted, and an electron-attracting heterocyclic group which may be substituted.

The optionally substituted electron-withdrawing heterocyclic group is preferably a group derived from an electron-withdrawing aromatic heterocycle having 3 to 24 carbon atoms.
Examples of such electron-attracting aromatic heterocycles include dibenzothiophene oxide ring, dibenzothiophene dioxide ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, quinazoline. Rings, cinnoline rings, quinoxaline rings, phthalazine rings, pteridine rings, phenanthridin rings, phenanthrolin rings, dibenzofuran rings, azadibenzofuran rings, diazadibenzofuran rings, dibenzosilol rings, dibenzoborol rings, dibenzophosphor oxide rings, etc. included. Among them, a pyridine ring, a pyrimidine ring, a pyrazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, a phenanthridin ring, a phenanthroline ring, a dibenzofuran ring, an azadibenzofuran ring, and a diazadibenzofuran ring are preferable. Aromatic heterocycles are more preferred, and nitrogen-containing aromatic six-membered rings, azadibenzofuran rings, and diazadibenzofuran rings are even more preferred.
The electron-attracting aromatic heterocycle may be a combination of two or more of the same or different aromatic heterocycles.

Examples of substituents that the electron-attracting heterocyclic group may have include a heavy hydrogen atom, a fluorine atom, a cyano group, an alkyl group optionally substituted with fluorine, and an alkyl optionally substituted with fluorine. An aromatic hydrocarbon ring group which may be substituted with a group, an aromatic hydrocarbon ring group which may be substituted with fluorine is included, and an alkyl which may be substituted with a fluorine atom, a cyano group or fluorine is preferable. A group and an aromatic hydrocarbon ring group that may be substituted with fluorine.

Further, in the general formula (1), it is preferable that any one of the substituents X is a cyano group in terms of further improving the electron injectability.

In the general formula (1), n represents an integer of 4 to 6, and m represents an integer of 0 to 2. However, it satisfies n + m = 6. Further, it is preferable that n is 5 and m is 1, from the viewpoint of further improving the film stability.

In the general formula (1), the aromatic ring A is a nitrogen-containing aromatic compound having a structure represented by the general formula (2). The plurality of aromatic rings A may be the same or different, but when n is 6, it has at least two types of aromatic rings A.

In the general formula (2), Y ₁₁ to Y ₁₈ independently represent a nitrogen atom or CR, respectively.
The R is a hydrogen atom or a substituent, and a plurality of the substituents may be bonded to each other to form a ring, and # represents a connection position in the general formula (1).

In the general formula (2), examples of the substituent represented by R include a linear or branched alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, etc. Hexyl group, etc.), alkenyl group (for example, vinyl group, allyl group, etc.), alkynyl group (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (aromatic carbon ring group, aryl group, etc.). For example, benzene ring, biphenyl, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysen ring, naphthacene ring, triphenylene ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaphthene. A group derived from a ring, a coronen ring, an inden ring, a fluorene ring, a fluorantene ring, a naphthacene ring, a pentacene ring, a perylene ring, a pentaphen ring, a pixene ring, a pyrene ring, a pyranthrene ring, an anthrantene ring, a tetraline, etc. , Aromatic heterocyclic groups (eg, furan ring, dibenzofuran ring, thiophene ring, dibenzothiophene ring, oxazole ring, pyrrole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, benzoimidazole ring, oxadiazole Ring, triazole ring, imidazole ring, pyrazole ring, thiazole ring, indole ring, indazole ring, benzoimidazole ring, benzothiazole ring, benzoxazole ring, quinoxalin ring, quinazoline ring, synnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, Naftilidine ring, carbazole ring, carbolin ring, diazacarbazole ring (a group derived from a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carbolin ring is further substituted with a nitrogen atom, etc.), non-aromatic carbide Hydrogen ring group (eg, cyclopentyl group, cyclohexyl group, etc.), non-aromatic heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholic group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy) Group, pentyloxy group, hexyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group) , Ethylthio group, propylthio group, pentylthio group, hexylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.) ), Arylthio groups (eg, phenylthio groups, naphthylthio groups, etc.), alkoxycarbonyl groups (eg, methyloxycarbonyl groups, ethyloxycarbonyl groups, butyloxycarbonyl groups, etc.), aryloxycarbonyl groups (eg, phenyloxycarbonyl groups, etc.) Naftyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group , 2-Pyridylaminosulfonyl group, etc.), Acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (eg For example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonyl Amino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group) , Pentylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, etc. Sulfonyl ureido group Naftyl ureido group, 2-pyridyl amino ureido group, etc.), sulfinyl group (for example, methyl sulfinyl group, ethyl sulfinyl group, butyl sulfinyl group, cyclohexyl sulfinyl group, dodecyl sulfinyl group, phenyl sulfinyl group, naphthyl sulfinyl group, 2- Pyridylsulfinyl group, etc.), alkylsulfonyl group (eg, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, arylsulfonyl group or heteroarylsulfoni) Lu group (eg, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (eg, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, anilino group, naphthylamino) Group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), fluoride hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl) Groups, etc.), cyano groups, nitro groups, hydroxy groups, thiol groups, silyl groups (eg, trimethylsilyl groups, triisopropylsilyl groups, triphenylsilyl groups, phenyldiethylsilyl groups, etc.), dear hydrogen atoms and the like.

Any of the aromatic rings A in the general formula (1) has a structure in which at least one of Y ₁₁ to Y ₁₈ in the general formula (2) is a nitrogen atom. In particular, it is preferable that any one of the aromatic rings A has a structure in which Y ₁₄ is a nitrogen atom in that the film stability is further improved.

The exemplary compounds of the charge transport material having the structure represented by the general formula (1) are shown below, but the compound is not limited thereto.

The charge transport material having the structure represented by the general formula (1) according to the present invention is preferably an electron transport material from the viewpoint of exhibiting the effect of the present invention.

[Method for manufacturing a charge transport material having a structure represented by the general formula (1)]
In the method for producing a charge transport material having a structure represented by the general formula (1), the substituent X and the aromatic ring A are introduced into the benzene ring by a nucleophilic substitution reaction, respectively.
Specifically, 2,3,4,5,6-pentafluorobenzonitrile is dissolved in a solvent (THF, DMF, NMP, etc.) and a strong base (potassium carbonate, cesium carbonate, sodium hydride, potassium hydride, etc.) is dissolved. ) In the presence, it can be produced by reacting carbazole or azacarbazole, which may have a substituent.

Next, before explaining the organic EL element of the present invention, the light emitting method and the light emitting material of the organic EL related to the technical idea will be described.

<Light emission method of organic EL>
There are two types of light emission methods for organic EL: "phosphorescence emission" that emits light when returning from the excited triplet state to the ground state, and "fluorescence emission" that emits light when returning from the excited singlet state to the ground state. is there.

When excited by an electric field such as an organic EL, triplet excitons are generated with a 75% probability and singlet excitons are generated with a 25% probability, so phosphorescence emission is more efficient than fluorescence emission. It is an excellent method to realize low power consumption.

On the other hand, even in fluorescence emission, triplet exciters, which are normally generated with a 75% probability and whose energy of the exciter is normally only heat due to non-radiation deactivation, are present at high density. A method using a TTA (Triplet-Triplet Annihilation, or Triplet-Triplet Fusion: abbreviated as "TTF") mechanism that generates one singlet-excited element from two triplet-excited states to improve light emission efficiency is available. It has been found.

Furthermore, in recent years, by reducing the energy gap between the excited singlet state and the excited triplet state by the discovery of Adachi et al., Excitation with a low energy level due to Joule heat during light emission and / or the ambient temperature at which the light emitting element is placed. A phenomenon in which inverse intersystem crossing occurs from a triplet state to an excited singlet state, resulting in fluorescence emission of nearly 100% (also referred to as thermal excitation type delayed fluorescence or thermal excitation type delayed fluorescence: "TADF"). Fluorescent substances that make this possible have been found (see, for example, Non-Patent Document 1 and the like).

<Phosphorescent compound>
As mentioned above, phosphorus light emission is theoretically three times more advantageous than fluorescence emission in terms of emission efficiency, but energy deactivation (= phosphorus light emission) from the excited triplet state to the singlet base state is prohibited. Since it is a transition and the intersystem crossing from the excited singlet state to the excited triplet state is also a forbidden transition, its velocity constant is usually small. That is, since the transition is unlikely to occur, the exciton lifetime becomes long on the order of milliseconds to seconds, and it is difficult to obtain desired light emission.

However, when a complex using a heavy metal such as iridium or platinum emits light, the rate constant of the forbidden transition increases by 3 orders of magnitude or more due to the heavy atom effect of the central metal, and depending on the selection of the ligand, 100 It is also possible to obtain a phosphorus photon yield of%.

However, in order to obtain such ideal light emission, it is necessary to use precious metals such as iridium, palladium, and platinum, which are rare metals, so-called white metals, and when they are used in large quantities, their reserves and their reserves The price of the metal itself becomes a major industrial problem.

<Fluorescent compound>
A general fluorescent compound does not need to be a heavy metal complex like a phosphorescent compound, and is a so-called organic compound composed of a combination of general elements such as carbon, oxygen, nitrogen and hydrogen. In addition, other non-metal elements such as phosphorus, sulfur, and silicon can be used, and complexes of typical metals such as aluminum and zinc can also be used, so that the variety can be said to be almost infinite.

However, since only 25% of excitons can be applied to light emission with a conventional fluorescent compound as described above, high-efficiency light emission such as phosphorescence light emission cannot be expected.

<Delayed fluorescent compound>
[Excited triplet-triplet annihilation (TTA) delayed fluorescent compound]
A light emitting method using delayed fluorescence has been introduced to solve the problems of fluorescent compounds. The TTA method originating from collisions between triplet excitons can be described by the following general formula. That is, there is an advantage that a part of triplet excitons, in which the exciton energy is conventionally converted only into heat by non-radiation deactivation, can cross the singlet excitons that can contribute to light emission. Even in an actual organic EL element, it is possible to obtain an external extraction quantum efficiency about twice that of a conventional fluorescent light emitting element.

General formula: T * + T * → S * + S
(In the equation, T * represents a triplet exciton, S * represents a singlet exciton, and S represents a ground state molecule.)
However, as can be seen from the above equation, since only one singlet exciton that can be used for light emission is generated from the two triplet excitons, it is not possible in principle to obtain 100% internal quantum efficiency by this method.

<Thermal active delayed fluorescence (TADF) compound>
The TADF method, which is another high-efficiency fluorescence emission method, is a method that can solve the problems of TTA.

Fluorescent compounds have the advantage of being able to design an infinite number of molecules as described above. That is, among the molecularly designed compounds, there are compounds in which the energy level differences between the excited triplet state and the excited singlet state are extremely close to each other.

Although such a compound does not have a heavy atom in the molecule, an intersystem crossing from an excited triplet state to an excited singlet state, which cannot normally occur due to a small ΔEst, occurs. Furthermore, since the rate constant of deactivation (= fluorescence emission) from the excited singlet state to the ground state is extremely large, the triplet exciter itself is thermally deactivated to the ground state (non-radiation deactivation). It is more rhythmically advantageous to return to the ground state while emitting fluorescence via the excited singlet state. Therefore, TADF can theoretically emit 100% fluorescence.

<Molecular design concept for ΔEst>
The molecular design for reducing the above ΔEst will be described.

In principle, in order to reduce ΔEst, it is most effective to reduce the spatial overlap between the highest occupied molecular orbital (HOMO) and the lowest empty orbital (Lowest Unoccupied Molecular Orbital: LUMO). Is.

It is generally known that HOMO is distributed in an electron donating site and LUMO is distributed in an electron attracting site in an electron orbit of a molecule. By introducing an electron donating and electron attracting skeleton into the molecule, HOMO is distributed. And the position where LUMO exists can be moved away.

For example, in Applied Physics Vol. 82, No. 6, 2013 of "Organic Optoelectronics Reaching the Practical Use Stage", electron-withdrawing skeletons such as cyano groups and triazines and electron donations such as carbazole and diphenylamino groups are provided. LUMO and HOMO are localized by introducing a sexual skeleton.

It is also effective to reduce the change in the molecular structure between the ground state and the excited triplet state of the compound. As a method for reducing the structural change, for example, it is effective to make the compound rigid. Rigidity described here means that there are few parts in the molecule that can move freely, such as suppressing free rotation in the bond between rings in the molecule and introducing a fused ring with a large π-conjugated surface. means. In particular, it is possible to reduce the structural change in the excited state by making the portion involved in light emission rigid.

<General problems with TADF compounds>
The TADF compound has various problems in terms of its light emitting mechanism and molecular structure. The following describes some of the problems that TADF compounds generally have.

In TADF compounds, it is necessary to separate the sites where HOMO and LUMO are present as much as possible in order to reduce ΔEst. Therefore, the electronic state of the molecule is a donor / acceptor type molecule in which the HOMO site and LUMO site are separated. It becomes a state close to the inner CT (intramolecular charge transfer state).

When a plurality of such molecules exist, stabilization is achieved by bringing the donor portion of one molecule and the acceptor portion of the other molecule close to each other. Such a stabilized state is not limited to the formation between two molecules, but can be formed between a plurality of molecules such as between three molecules or five molecules, and as a result, various stabilized states having a wide distribution can be obtained. It will be present and the shapes of the absorption and emission spectra will be broad. In addition, even when a multimolecular aggregate of more than two molecules is not formed, various existence states can be taken depending on the difference in the direction and angle of interaction between the two molecules, so basically the absorption spectrum and The shape of the emission spectrum is broad.

Broadening the emission spectrum poses two major problems.
One is the problem that the color purity of the emitted color becomes low. It does not pose a big problem when applied to lighting applications, but when used for electronic displays, the color reproduction range becomes smaller and the color reproducibility of pure colors becomes lower, so it is actually applied as a product. Will be difficult.

Another problem is that the rising wavelength on the short wavelength side of the emission spectrum (called the "fluorescence 0-0 band") is shortened, that is, the S _{1 is} increased (the lowest excited single term energy level is increased). It is to do.

Naturally, when the fluorescence 0-0 band has a shorter wavelength, the phosphorescence 0-0 band derived from T _{1, which} has a lower energy than S ₁ , also has a shorter wavelength (higher T ₁ ). Therefore, the compound used as the host compound needs to have a high S ₁ and a high T ₁ in order to prevent reverse energy transfer from the dopant.

This is a very big problem. A host compound basically composed of an organic compound takes a state of a plurality of active and unstable chemical species such as a cationic radical state, an anionic radical state and an excited state in an organic EL element, and these chemical species are intramolecular. It can be made to exist relatively stably by expanding the π-conjugated system of.

However, in order to achieve high S ₁ and high T ₁ , it is necessary to reduce or cut off the π-conjugated system in the molecule, which makes it difficult to achieve both stability and, as a result. This will shorten the life of the light emitting element.

Further, in the TADF compound containing no heavy metal, the transition from the excited triplet state to the ground state is a forbidden transition, so the existence time (exciton lifetime) in the excited triplet state is from several hundred μs to millimeters. Extremely long, on the order of seconds. Therefore, even if the T ₁ energy level of the host compound is higher than that of the fluorescent compound, the excited triplet state of the fluorescent compound changes to the host compound due to the length of its existence time. The probability of reverse energy transfer increases. As a result, the inverse intersystem crossing from the excited triplet state to the excited singlet state of the TADF compound, which was originally intended, does not sufficiently occur, and the unfavorable reverse energy transfer to the host compound becomes the mainstream, resulting in sufficient emission efficiency. Will not be obtained.

In order to solve the above problems, it is necessary to sharpen the emission spectrum shape of the TADF compound and reduce the difference between the emission maximum wavelength and the rising wavelength of the emission spectrum. This can be basically achieved by reducing the change in the molecular structure of the excited singlet state and the excited triplet state.

Further, in order to suppress the reverse energy transfer to the host compound, it is effective to shorten the existence time (exciton lifetime) of the excited triplet state of the TADF compound. To achieve this, we need to take measures such as reducing the change in the molecular structure between the ground state and the excited triplet state and introducing substituents and elements suitable for unwinding the forbidden transition. Can be solved.

[Organic EL element]
The organic electroluminescence element of the present invention is an organic electroluminescence element having one or a plurality of organic compound layers between an anode and a cathode, and the at least one organic compound layer is the organic film as an electron transport layer. Has.

Typical element configurations in the organic EL device of the present invention include, but are not limited to, the following configurations.
(I) Anode / light emitting layer / cathode (ii) anode / light emitting layer / electron transport layer / cathode (iii) anode / hole transport layer / light emitting layer / cathode (iv) anode / hole transport layer / light emitting layer / electron Transport layer / cathode (v) anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (vi) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode ( vii) Anophode / hole injection layer / hole transport layer / (electron blocking layer /) light emitting layer / (hole blocking layer /) electron transport layer / electron injection layer / cathode Among the above, the configuration of (vii) is preferable. It is used, but is not limited to this.

The light emitting layer according to the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers. If necessary, a hole blocking layer (also referred to as a hole barrier layer) or an electron injection layer (also referred to as a cathode buffer layer) may be provided between the light emitting layer and the anode, and the light emitting layer and the anode may be provided. An electron blocking layer (also referred to as an electron barrier layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided between them.
The electron transport layer according to the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. Further, it may be composed of a plurality of layers.
The hole transport layer according to the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Further, it may be composed of a plurality of layers.
In the above typical device configuration, the layer excluding the anode and the cathode is also referred to as an "organic compound layer (or organic layer)".

(Tandem structure)
The organic EL element of the present invention may be an element having a so-called tandem structure in which a plurality of light emitting units including at least one light emitting layer are laminated.
As a typical element configuration of the tandem structure, for example, the following configuration can be mentioned.
Anode / 1st light emitting unit / 2nd light emitting unit / 3rd light emitting unit / cathode Anode / 1st light emitting unit / intermediate layer / 2nd light emitting unit / intermediate layer / 3rd light emitting unit / cathode Here, the first light emitting unit , The second light emitting unit and the third light emitting unit may all be the same or different. Further, the two light emitting units may be the same, and the remaining one may be different.
Further, the third light emitting unit may not be provided, while a light emitting unit or an intermediate layer may be further provided between the third light emitting unit and the electrode.

The plurality of light emitting units may be directly laminated or may be laminated via an intermediate layer, and the intermediate layer is generally an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, or an intermediate layer. A known material and structure can be used as long as it is also called an insulating layer and has a function of supplying electrons to the adjacent layer on the anode side and holes to the adjacent layer on the cathode side.

Examples of the material used for the intermediate layer include ITO (inorganic tin oxide), IZO (inorganic zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, and CuAlO _2. , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ , Al and other conductive inorganic compound layers, Au / Bi ₂ O _{3 and} other bilayer films, SnO ₂ / Ag / SnO ₂ , ZnO / Ag / Multilayer films such as ZnO, Bi ₂ O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO ₂ , and fullerenes such as C ₆₀ , conductive organic substances such as oligothiophene. , Metallic phthalocyanines, metal-free phthalocyanines, metal porphyrins, conductive organic compound layers such as metal-free porphyrins, etc., but the present invention is not limited thereto.

Preferred configurations in the light emitting unit include, for example, configurations in which the anode and the cathode are removed from the configurations (i) to (vii) mentioned in the above typical element configurations, but the present invention is limited thereto. Not done.

Specific examples of the tandem organic EL element include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734, US Pat. No. 6,337,492, International. Publication No. 2005/09087, Japanese Patent Application Laid-Open No. 2006-228712, Japanese Patent Application Laid-Open No. 2006-24791, Japanese Patent Application Laid-Open No. 2006-49393, Japanese Patent Application Laid-Open No. 2006-49394, Japanese Patent Application Laid-Open No. 2006-49396, Japanese Patent Application Laid-Open No. 2011 -96679, Japanese Patent Application Laid-Open No. 2005-340187, Japanese Patent No. 4711424, Japanese Patent No. 3496681, Japanese Patent No. 38845664, Japanese Patent No. 421369, Japanese Patent Application Laid-Open No. 2010-192719, Japanese Patent Application Laid-Open No. 2009-07629, The element configurations and constituent materials described in Japanese Patent Application Laid-Open No. 2008-0784414, Japanese Patent Application Laid-Open No. 2007-059848, Japanese Patent Application Laid-Open No. 2003-272860, Japanese Patent Application Laid-Open No. 2003-045676, International Publication No. 2005/094130, etc. are listed. However, the present invention is not limited thereto.

Hereinafter, each layer constituting the organic EL device of the present invention will be described.
《Light emitting layer》
The light emitting layer according to the present invention is a layer that provides a place where electrons and holes injected from an electrode or an adjacent layer are recombined and emit light via excitons, and the light emitting portion is a layer of the light emitting layer. It may be inside or at the interface between the light emitting layer and the adjacent layer.
The total thickness of the light emitting layer is not particularly limited, but the homogeneity of the formed layer, prevention of applying an unnecessary high voltage at the time of light emission, and improvement of the stability of the light emitting color with respect to the driving current are improved. From the viewpoint, it is preferably adjusted within the range of 2 nm to 5 μm, more preferably adjusted within the range of 2 to 500 nm, and further preferably adjusted within the range of 5 to 200 nm.
The thickness of each light emitting layer is preferably adjusted within the range of 2 nm to 1 μm, more preferably adjusted within the range of 2 to 200 nm, and further preferably adjusted within the range of 3 to 150 nm. ..

The light emitting layer preferably contains a light emitting dopant (a light emitting dopant compound, a dopant compound, also simply referred to as a dopant) and a host compound (a matrix material, a light emitting host compound, also simply referred to as a host).

(1) Light-emitting dopant The light-emitting dopant includes a fluorescent dopant (also referred to as a fluorescent dopant or a fluorescent compound), a delayed fluorescent dopant, or a phosphorescent dopant (also referred to as a phosphorescent dopant or a phosphorescent compound). Is preferably used. In the present invention, it is preferable that at least one light emitting layer contains a compound (charge transport material) having a structure represented by the general formula (1).
In the present invention, the light emitting layer preferably contains the light emitting dopant in the range of 5 to 100% by mass, and more preferably in the range of 10 to 30% by mass.
The concentration of the light emitting dopant in the light emitting layer can be arbitrarily determined based on the specific light emitting dopant used and the requirements of the device, and is contained at a uniform concentration with respect to the layer thickness direction of the light emitting layer. It may have an arbitrary concentration distribution.
Further, a plurality of types of light emitting dopants may be used in combination, and a combination of light emitting dopants having different structures, a π-conjugated compound of the present invention, or a combination of a fluorescent light emitting compound and a phosphorescent light emitting compound may be used. You may use it. Thereby, an arbitrary emission color can be obtained.

The color emitted by the organic EL element according to the present invention is as shown in FIG. It is determined by the color when the result measured by Konica Minolta Co., Ltd. is applied to the CIE chromaticity coordinates.
In the present invention, it is also preferable that the light emitting layer of one layer or a plurality of layers contains a plurality of light emitting dopants having different light emitting colors and exhibits white light emission.
The combination of luminescent dopants showing white color is not particularly limited, and examples thereof include a combination of blue and orange, a combination of blue and green and red, and the like.
The white color in the organic EL element according to the present invention is not particularly limited and may be white color closer to orange or white color closer to blue, but when the 2 degree viewing angle front luminance is measured by the above method. In addition, it is preferable that the chromaticity in the CIE 1931 color system at 1000 cd / m2 is within the region of x = 0.39 ± 0.09 and y = 0.38 ± 0.08.

(1.1) Phosphorescent Dopant A phosphorescent dopant according to the present invention (hereinafter, also referred to as “phosphorescent dopant”) will be described.
The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescent light at room temperature (25 ° C.), and has a phosphorescent quantum yield of 25. It is defined as a compound of 0.01 or more at ° C, but a preferable phosphorescence quantum yield is 0.1 or more.

The phosphorus photon yield can be measured by the method described on page 398 (1992 edition, Maruzen) of Spectroscopy II of the 4th edition Experimental Chemistry Course 7. The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescence dopant according to the present invention can achieve the above phosphorescence quantum yield (0.01 or more) in any of any solvents. Just do it.
There are two types of light emission of the phosphorescent dopant in principle. One is that carrier recombination occurs on the host compound to which the carrier is transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent dopant. It is an energy transfer type that obtains light emission from a phosphorescent dopant. The other is a carrier trap type in which the phosphorescent dopant serves as a carrier trap, and carriers are recombined on the phosphorescent dopant to obtain light emission from the phosphorescent dopant. In either case, the excited state energy of the phosphorescent dopant is required to be lower than the excited state energy of the host compound.

As the phosphorescent dopant that can be used in the present invention, it can be appropriately selected from known ones used for the light emitting layer of the organic EL element.
Specific examples of known phosphorescent dopants that can be used in the present invention include compounds described in the following documents.
Nature 395, 151 (1998), Apple. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17,1059 (2005), International Publication No. 2009/10991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Publication No. 2006/835469, US Patent Publication No. 2006/20202194, USA Patent Publication No. 2007/0087321, US Patent Publication No. 2005/0244673,
Inorg. Chem. 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. Int. Ed. 2006, 45, 7800, Apple. Phys. Lett. 86, 153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42, 1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, US Patent Publication No. 2002/0034656, US Patent No. 7332232, US Patent Publication No. 2009/01087737, US Patent Publication No. 2009/00397776, US Patent No. 6921915, US Patent No. 6687266, US Patent Publication No. 2007/0190359, US Patent Publication No. 2006/0008670, US Patent Publication No. 2009/ 0165846, U.S. Patent Publication No. 2008/0015355, U.S. Patent No. 7250226, U.S. Patent No. 7396598, U.S. Patent Publication No. 2006/0263635, U.S. Patent Publication No. 2003/0138657, U.S. Patent Publication No. 2003/0152802 , U.S. Pat. No. 70090928, Angew. Chem. Int. Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Apple. Phys. Lett. 74, 1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/090024, International Publication No. 2006/056418, International Publication No. 2005/019373, International Publication No. 2005/123873, International Publication No. 2007/004380, International Publication No. 2006/082742, U.S. Patent Publication No. 2006/0251923, U.S. Patent Publication No. 2005/0260441, U.S. Patent No. 73935999, U.S. Pat. Patent Publication No. 2007/0190359, US Patent Publication No. 2008/0297033, US Patent No. 73338722, US Patent Publication No. 2002/0134984, US Patent No. 7279704, US Patent Publication No. 2006/098120, US Patent Publication 2006/103874, International Publication 2005/076380, International Publication 2010/032663, International Publication 2008/140115, International Publication No. 2007/05/2431, International Publication No. 2011/134013, International Publication No. 2011 / 157339, International Publication No. 2010/086089, International Publication No. 2009/1163646, International Publication No. 2012/20327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149 No., US Patent Publication No. 2012/228583, US Patent Publication No. 2012/212126, Japanese Patent Application Laid-Open No. 2012-069737, Japanese Patent Application Laid-Open No. 2012-195554, Japanese Patent Application Laid-Open No. 2009-114086, Japanese Patent Application Laid-Open No. 2003-81988 Japanese Patent Application Laid-Open No. 2002-302671 and Japanese Patent Application Laid-Open No. 2002-363552.

Among them, a preferable phosphorescent dopant is an organometallic complex having Ir as a central metal. More preferably, a complex containing at least one coordination mode of metal-carbon bond, metal-nitrogen bond, metal-oxygen bond, and metal-sulfur bond is preferable.

(1.2) Fluorescent Dopant A fluorescent dopant according to the present invention (hereinafter, also referred to as “fluorescent dopant”) will be described.
The fluorescent dopant according to the present invention is a compound capable of emitting light from the excited singlet, and is not particularly limited as long as light emission from the excited singlet is observed.
As the fluorescent dopant according to the present invention, a compound having a structure represented by the general formula (1) of the present invention may be used, or a known fluorescent dopant or delayed fluorescence used in the light emitting layer of an organic EL device. It may be appropriately selected and used from the dopant.

Examples of the fluorescent dopant according to the present invention include anthracene derivatives, pyrene derivatives, chrysene derivatives, fluorantene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, arylamine derivatives, boron complexes and coumarin derivatives. , Pyran derivatives, cyanine derivatives, croconium derivatives, squalium derivatives, oxobenzanthracene derivatives, fluorescein derivatives, rhodamine derivatives, pyrylium derivatives, perylene derivatives, polythiophene derivatives, rare earth complex compounds and the like.

Specific examples of the delayed fluorescent dopant include the compounds described in International Publication No. 2011/156793, Japanese Patent Application Laid-Open No. 2011-213643, Japanese Patent Application Laid-Open No. 2010-93181, and the like. Not limited.

(2) Host Compound The host compound according to the present invention is a compound mainly responsible for injection and transport of electric charges in the light emitting layer, and its own light emission is not substantially observed in the organic EL device.
A compound having a phosphorescent quantum yield of less than 0.1 at room temperature (25 ° C.) is preferable, and a compound having a phosphorescent quantum yield of less than 0.01 is more preferable. Further, among the compounds contained in the light emitting layer, the mass ratio in the layer is preferably 20% or more.
Further, the excited state energy of the host compound is preferably higher than the excited state energy of the light emitting dopant contained in the same layer.

The host compound may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the charge transfer, and it is possible to improve the efficiency of the organic EL device.
As the host compound, a compound having a structure represented by the general formula (1) of the present invention may be used, and there is no particular limitation, and a compound conventionally used in an organic EL device can be used. It may be a low molecular weight compound, a high molecular weight compound having a repeating unit, or a compound having a reactive group such as a vinyl group or an epoxy group.
From the viewpoint of reverse energy transfer, those having an excitation energy higher than the excitation single-term energy level of the dopant are preferable, and those having an excitation triple-term energy higher than the excitation triple-term energy level of the dopant are more preferable.

The host compound is responsible for carrier transport and exciton generation in the light emitting layer. Therefore, it can exist stably in all active species in the cation radical state, the anion radical state, and the excited state, does not cause chemical changes such as decomposition and addition reaction, and further, the host molecule is present in the layer over time of energization. It is preferable not to move at the angstrom level.

Further, especially when the light emitting dopant used in combination exhibits TADF emission, the existence time of the excited triplet state of the TADF compound is long, so that the T1 energy level of the host compound itself is high, and the host compounds are associated with each other. Appropriate molecular structure such that the low T1 state is not formed in the state, the TADF compound and the host compound do not form an exciplex, the host compound does not form an electromer by an electric field, and the host compound does not have a low T1 state. Design is required.

In order to satisfy such requirements, it is necessary that the host compound itself has high electron hopping mobility, high hole hopping mobility, and a small structural change in the excited triplet state. Is. As a representative of the host compound satisfying such a requirement, those having a high T1 energy level such as a carbazole skeleton, an azacarbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton or an azadibenzofuran skeleton are preferably mentioned.

As a known host compound, it has hole transporting ability or electron transporting ability, prevents the wavelength of light emission from being lengthened, and further stabilizes the organic EL device against heat generation during high temperature driving or device driving. It is preferable to have a high glass transition temperature (Tg) from the viewpoint of operating the device. Tg is preferably 90 ° C. or higher, and more preferably 120 ° C. or higher.
Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Calorimetry).

Specific examples of known host compounds used in the organic EL device in the present invention include, but are not limited to, the compounds described in the following documents.
JP 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786, 2002-8860, 2002-334787A, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002. 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003 -3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002- 302516, 2002-305083, 2002-305084, 2002-308837, US Patent Publication No. 2003/01755553, US Patent Publication No. 2006/0280965, US Patent Publication No. 2005/0112407 No., US Patent Publication No. 2009/0017330, US Patent Publication No. 2009/0030202, US Patent Publication No. 2005/02389919, International Publication No. 2001/039234, International Publication No. 2009/021126, International Publication No. 2008 / 056746, International Publication No. 2004/093207, International Publication No. 2005/089025, International Publication No. 2007/0637996, International Publication No. 2007/0637554, International Publication No. 2004/107822, International Publication No. 2005/030900 , International Publication No. 2006/114966, International Publication No. 2009/086028, International Publication No. 2009/003898, International Publication No. 2012/0293947, JP-A-2008-074939, JP-A-2007-254297, EP2034538 , Etc.

《Electronic transport layer》
In the present invention, the electron transport layer may be made of a material having a function of transporting electrons and may have a function of transmitting electrons injected from the cathode to the light emitting layer.
The total film thickness of the electron transport layer in the present invention is not particularly limited, but is usually in the range of 2 nm to 5 μm, more preferably in the range of 2 to 500 nm, and further preferably in the range of 5 to 200 nm. Is.

The material used for the electron transport layer (hereinafter referred to as an electron transport material) may have any of electron injectability, transportability, and hole barrier property, and the general formula of the present invention (hereinafter referred to as electron transport material). A compound having the structure represented by 1) may be used, or any of conventionally known compounds can be selected and used.
Conventionally known compounds include, for example, nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one or more carbon atoms constituting the carbazole ring substituted with nitrogen atoms), pyridine derivatives, pyrimidine derivatives. , Pyrazine derivative, pyridazine derivative, triazine derivative, quinoline derivative, quinoxalin derivative, phenanthroline derivative, azatriphenylene derivative, oxazole derivative, thiazole derivative, oxaziazole derivative, thiadiazol derivative, triazole derivative, benzimidazole derivative, benzoxazole derivative, benzthiazole derivative Derivatives, etc.), dibenzofuran derivatives, dibenzothiophene derivatives, silol derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenylene, etc.) and the like.

Further, metal complexes having a quinolinol skeleton or a dibenzoquinolinol skeleton as ligands, for example, tris (8-quinolinol) aluminum (Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7) -Dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and metal complexes thereof. A metal complex in which the central metal of the above is replaced with In, Mg, Cu, Ca, Sn, Ga or Pb can also be used as an electron transport material.

In addition, metal-free or metal phthalocyanines, or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like can also be preferably used as an electron transport material. Further, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transporting material, and an inorganic semiconductor such as n-type-Si or n-type-SiC is used like the hole injection layer and the hole transporting layer. Can also be used as an electron transport material.
Further, it is also possible to use a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain.

In the electron transport layer according to the present invention, the electron transport layer may be doped with a doping material as a guest material to form a highly n-type (electron-rich) electron transport layer. Examples of the doping material include n-type dopants such as metal compounds and metal compounds such as metal halides. Specific examples of the electron transport layer having such a structure include, for example, JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Mol. Apple. Phys. , 95, 5773 (2004) and the like.

Specific examples of known and preferable electron transporting materials used in the organic EL device according to the present invention include, but are not limited to, the compounds described in the following documents.
U.S. Patent No. 6528187, U.S. Patent No. 7230107, U.S. Patent Publication No. 2005/0025993, U.S. Patent Publication No. 2004/0036077, U.S. Patent Publication No. 2009/0115316, U.S. Patent Publication No. 2009/0101870, U.S. Patent Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132805, Appl. Phys. Lett. 75, 4 (1999), Apple. Phys. Lett. 79, 449 (2001), Apple. Phys. Lett. 81, 162 (2002), Apple. Phys. Lett. 81, 162 (2002), Apple. Phys. Lett. 79, 156 (2001), U.S. Pat. No. 7,964,293, U.S. Patent Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2004/063159, International Publication No. 2005/085387, International Publication No. 2006 / 067931, International Publication No. 2007/0865552, International Publication No. 2008/114690, International Publication No. 2009/069424, International Publication No. 2009/06679, International Publication No. 2009/054253, International Publication No. 2011/086935 No., International Publication No. 2010/150593, International Publication No. 2010/047707, EP23111826, JP-A-2010-251675, JP-A-2009-209133, JP-A-2009-124114, JP-A-2008-277810 Japanese Patent Application Laid-Open No. 2006-156445, Japanese Patent Application Laid-Open No. 2005-340122, Japanese Patent Application Laid-Open No. 2003-456662, Japanese Patent Application Laid-Open No. 2003-31367, Japanese Patent Application Laid-Open No. 2003-282270, International Publication No. 2012/115034 , Etc.

More preferable electron transporting materials in the present invention include pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, azacarbazole derivatives, and benzimidazole derivatives.
The electron transport material may be used alone or in combination of two or more.

《Hole blocking layer》
The hole blocking layer is a layer having a function of an electron transporting layer in a broad sense, and is preferably made of a material having a function of transporting electrons and a small ability to transport holes, and a hole while transporting electrons. It is possible to improve the recombination probability of electrons and holes by blocking the above.
In addition, the structure of the electron transport layer described above can be used as the hole blocking layer according to the present invention, if necessary.
The hole blocking layer is preferably provided adjacent to the cathode side of the light emitting layer.
The film thickness of the hole blocking layer is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm.
As the material used for the hole blocking layer, the material used for the electron transport layer described above containing the compound having the structure represented by the general formula (1) of the present invention is preferably used, and the material of the present invention is also used. A material used as the above-mentioned host compound containing a compound having a structure represented by the general formula (1) is also preferably used for the hole blocking layer.

《Electronic injection layer》
The electron injection layer (also referred to as “cathode buffer layer”) according to the present invention is a layer provided between the cathode and the light emitting layer in order to reduce the driving voltage and improve the emission brightness, and is “organic EL element and its addition”. It is described in detail in Volume 2, Chapter 2, "Electrode Materials" (pages 123-166) of "Forefront of Industrialization (published by NTS Co., Ltd. on November 30, 1998)".
In the present invention, the electron injection layer may be provided as needed and may be present between the cathode and the light emitting layer or between the cathode and the electron transport layer as described above.
The electron injection layer is preferably a very thin film, and the film thickness is preferably in the range of 0.1 to 5 nm, although it depends on the material. Further, it may be a non-uniform film in which the constituent material is intermittently present.

The details of the electron-injected layer are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like, and specific examples of materials preferably used for the electron-injected layer include , Metals such as strontium and aluminum, alkali metal compounds such as lithium fluoride, sodium fluoride and potassium fluoride, alkaline earth metal compounds such as magnesium fluoride and calcium fluoride, oxidation Examples thereof include metal oxides typified by aluminum, metal complexes typified by lithium 8-hydroxyquinolate (Liq) and the like. It is also possible to use a compound having the structure represented by the above-mentioned general formula (1), which contains the π-conjugated compound of the present invention.
Further, the material used for the above-mentioned electron injection layer may be used alone or in combination of two or more.

《Hole transport layer》
In the present invention, the hole transport layer may be made of a material having a function of transporting holes and may have a function of transmitting holes injected from the anode to the light emitting layer.
The total film thickness of the hole transport layer is not particularly limited, but is usually in the range of 5 nm to 5 μm, more preferably in the range of 2 to 500 nm, and further preferably in the range of 5 to 200 nm. is there.

The material used for the hole transport layer (hereinafter referred to as the hole transport material) may have any of hole injection property, transport property, and electron barrier property, and the general formula of the present invention may be used. A compound having the structure represented by (1) may be used, or any of conventionally known compounds can be selected and used.
For example, porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stillben derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives. , Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polymer materials or oligomers in which polyvinylcarbazole and aromatic amines are introduced into the main chain or side chains, polysilane, conductivity. Examples thereof include sex polymers or oligomers (for example, PEDOT: PSS, aniline-based copolymers, polyaniline, polythiophene, etc.).

Examples of the triarylamine derivative include a benzidine type represented by α-NPD, a starburst type represented by MTDATA, and a compound having fluorene or anthracene in the triarylamine connecting core portion.
Hexaazatriphenylene derivatives as described in JP-A-2003-591432 and JP-A-2006-135145 can also be used as the hole transport material.
Further, a hole transport layer having a high p property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, and JP-A-2001-102175. Apple. Phys. , 95, 5773 (2004) and the like.
In addition, JP-A-11-251667, J. Am. Hung et. al. So-called p-type hole transporting materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in the authored literature (Applied Physics Letters 80 (2002), p.139), can also be used. Further, an orthometalated organometallic complex having Ir or Pt in the central metal as represented by Ir (ppy) ₃ is also preferably used.
As the hole transport material, the above can be used, but a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organic metal complex, and an aromatic amine are introduced into the main chain or side chain. A high molecular weight material or an oligomer is preferably used.

Specific examples of known and preferable hole transporting materials used in the organic EL device according to the present invention include the compounds described in the following documents in addition to the above-mentioned documents, and the present invention includes these. Not limited.
For example, Apple. Phys. Lett. 69, 2160 (1996), J. Mol. Lumin. 72-74, 985 (1997), Apple. Phys. Lett. 78, 673 (2001), Apple. Phys. Lett. 90, 183503
(2007), Apple. Phys. Lett. 90, 183503 (2007), Apple. Phys. Lett. 51, 913 (1987), Synth. Met. 87, 171 (1997), Synth. Met. 91, 209 (1997), Synth. Met. 111,421 (2000), SID SymposiumDigest, 37, 923 (2006), J. Mol. Mater. Chem. 3, 319 (1993), Adv. Mater. 6, 677 (1994), Chem. Mater. 15,3148 (2003), U.S. Patent Publication No. 2003/0162053, U.S. Patent Publication No. 2002/0158242, U.S. Patent Publication No. 2006/0240279, U.S. Patent Publication No. 2008/0220265, U.S. Patent No. 5061569, International Publication No. 2007/002683, International Publication No. 2009/01809, EP650955, US Patent Publication No. 2008/01245772, US Patent Publication No. 2007/0278938, US Patent Publication No. 2008/0106190, US Patent Publication No. 2008 / 0018221, International Publication No. 2012/115344, Japanese Patent Application Laid-Open No. 2003-591432, Japanese Patent Application Laid-Open No. 2006-135145, US Patent Application No. 13/585981, and the like.
The hole transporting material may be used alone or in combination of two or more.

《Electronic blocking layer》
The electron blocking layer is a layer having a function of a hole transporting layer in a broad sense, and is preferably made of a material having a function of transporting holes and a small ability to transport electrons, and is composed of a material having a small ability to transport electrons while transporting holes. It is possible to improve the recombination probability of electrons and holes by blocking the above.
Further, the structure of the hole transport layer described above can be used as an electron blocking layer according to the present invention, if necessary.
The electron blocking layer is preferably provided adjacent to the anode side of the light emitting layer.
The film thickness of the electron blocking layer is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm.
As the material used for the electron blocking layer, the material used for the hole transport layer described above containing the compound having the structure represented by the general formula (1) of the present invention is preferably used, and the host compound described above is also used. The material used as is also preferably used for the electron blocking layer.

《Hole injection layer》
The hole injection layer (also referred to as “anode buffer layer”) according to the present invention is a layer provided between the anode and the light emitting layer in order to reduce the driving voltage and improve the emission brightness, and is an “organic EL element”. It is described in detail in Volume 2, Chapter 2, "Electrode Materials" (pages 123-166) of "The Forefront of Industrialization (published by NTS Co., Ltd. on November 30, 1998)".
In the present invention, the hole injection layer may be provided as needed and may be present between the anode and the light emitting layer or between the anode and the hole transport layer as described above.

The details of the hole injection layer are also described in JP-A-9-45479, 9-2660062, 8-288609, etc., and examples of the material used for the hole injection layer include Examples of the material used for the hole transport layer described above containing the compound having the structure represented by the general formula (1) of the present invention.
Among them, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives as described in Japanese Patent Application Laid-Open No. 2003-591432 and JP-A-2006-135145, metal oxides typified by vanadium oxide, amorphous carbon, polyaniline (emeral). Conductive polymers such as din) and polythiophene, orthometallated complexes typified by tris (2-phenylpyridine) iridium complexes, triarylamine derivatives and the like are preferred.
The material used for the hole injection layer described above may be used alone or in combination of two or more.

<< Other additives >>
The organic layer in the present invention described above may further contain other additives.
Examples of the additive include halogen elements such as bromine, iodine and chlorine, halogenated compounds, alkali metals and alkaline earth metals such as Pd, Ca and Na, compounds and complexes of transition metals, salts and the like.
The content of the additive can be arbitrarily determined, but is preferably 1000 ppm or less, more preferably 500 ppm or less, still more preferably 50 ppm or less, based on the total mass% of the contained layer. ..
However, it is not within this range depending on the purpose of improving the transportability of electrons and holes and the purpose of favoring the energy transfer of excitons.

<< Method of forming organic layer >>
A method for forming an organic layer (hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) in the present invention will be described.
The method for forming the organic layer in the present invention is not particularly limited, and conventionally known methods such as a vacuum vapor deposition method and a wet method (also referred to as a wet process) can be used.
The wet method includes a spin coating method, a casting method, an inkjet printing method, a printing method, a die coating method, a blade coating method, a roll coating method, a spray coating method, a curtain coating method, an LB method (Langmuir-Blogget method), and the like. However, a method having high suitability for the roll-to-roll method such as a die coating method, a roll coating method, an inkjet printing method, and a spray coating method is preferable from the viewpoint of easy to obtain a homogeneous thin film and high productivity.

Examples of the liquid medium for dissolving or dispersing the organic EL material according to the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene and mesitylene. , Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.
Further, as a dispersion method, dispersion can be performed by a dispersion method such as ultrasonic waves, high shear force dispersion, or media dispersion.

Further, a different film forming method may be applied to each layer. When a thin-film deposition method is used for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally the boat heating temperature is 50 to 450 ° C, the degree of vacuum is ^10-6 to ^10-2 Pa, and the vapor deposition rate is 0.01 to. It is desirable to appropriately select in the range of 50 nm / sec, substrate temperature -50 to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 to 200 nm.
The formation of the organic layer in the present invention is preferably carried out consistently from the hole injection layer to the cathode by one vacuuming, but it may be taken out in the middle and subjected to a different film forming method. In that case, it is preferable to carry out the work in a dry inert gas atmosphere.

"anode"
As the anode in the organic EL element, a metal, an alloy, an electrically conductive compound having a large work function (4 eV or more, preferably 4.5 V or more) and a mixture thereof as an electrode material are preferably used. Specific examples of such an electrode material include metals such as Au and conductive transparent materials such as CuI, tin oxide (ITO), SnO ₂ , and ZnO. Further, a material such as IDIXO (In ₂ O _3- ZnO) that is amorphous and can produce a transparent conductive film may be used.

For the anode, a thin film may be formed by forming a thin film of these electrode materials by a method such as thin film deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not required so much (about 100 μm or more). , The pattern may be formed through a mask having a desired shape during vapor deposition or sputtering of the electrode material.
Alternatively, when a coatable substance such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can also be used. When extracting light from this anode, it is desirable to increase the transmittance to more than 10%, and the sheet resistance as the anode is several hundred Ω /
sq. The following is preferable.
The film thickness of the anode depends on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

"cathode"
As the cathode, a metal having a small work function (5 eV or less) (referred to as an electron-injectable metal), an alloy, an electrically conductive compound, or a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, silver, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al). ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, aluminum, rare earth metals and the like.
Among these, from the viewpoint of electron injectability and durability against oxidation and the like, a mixture of an electron injectable metal and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture. Magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture, aluminum and the like are suitable.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. Alternatively, when a coatable substance such as metal nanoparticles is used, a wet film forming method such as a printing method or a coating method can also be used. Sheet resistance as a cathode is several hundred Ω / sq. The following is preferable, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.
In order to transmit the emitted light, it is convenient that the emission brightness is improved if either the anode or the cathode of the organic EL element is transparent or translucent.
Further, a transparent or translucent cathode can be produced by producing the above metal on the cathode having a thickness of 1 to 20 nm and then producing the conductive transparent material mentioned in the description of the anode on the cathode. By applying the above, it is possible to manufacture an element in which both the anode and the cathode are transparent.

《Support board》
The type of support substrate (hereinafter, also referred to as a substrate, substrate, substrate, support, etc.) that can be used for the organic EL element in the present invention is not particularly limited in the types such as glass and plastic, and is transparent. It may be opaque. When light is taken out from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of imparting flexibility to the organic EL element.

Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, and cellulose acetate propionate. CAP), cellulose acetate phthalate, cellulose esters such as cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyether sulfone (PES), polyphenylene sulfide, polysulfones, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylates, Arton (registered trademark) (manufactured by JSR) Alternatively, cycloolefin resins such as Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.) can be mentioned.

A film of an inorganic substance, an organic substance, or a hybrid film of both of them may be formed on the surface of the resin film, and the water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. oxygen relative humidity (90 ± 2)% RH) is preferably a barrier film of 0.01g / (m ² · 24h) or less, still more, as measured by the method based on JIS K 7126-1987 the ^{^{permeability, 10 -3 mL / (m 2}} · 24h · atm) or less, the water vapor permeability is preferably a high barrier film of 10-5g / (m ² · 24h) or less.

As the material for forming the gas barrier film, any material that causes deterioration of the element such as water and oxygen but has a function of suppressing infiltration can be used, and for example, silicon oxide, silicon dioxide, silicon nitride and the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of an organic material. The stacking order of the inorganic layer and the organic layer is not particularly limited, but it is preferable to stack the inorganic layer and the organic layer alternately a plurality of times.

The method for forming the gas barrier film is not particularly limited, and for example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma polymerization method. , Plasma CVD method, laser CVD method, thermal CVD method, coating method and the like can be used, but the atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

Examples of the opaque support substrate include a metal plate such as aluminum and stainless steel, a film or opaque resin substrate, and a ceramic substrate.
The external extraction quantum efficiency of the light emission of the organic EL device according to the present invention at room temperature is preferably 1% or more, more preferably 5% or more.
Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons passed through the organic EL element × 100.
Further, a hue improving filter such as a color filter may be used in combination, or a color conversion filter that converts the color emitted from the organic EL element into multiple colors using a phosphor may be used in combination.

<Method of manufacturing organic EL element>
A method for forming an organic layer (hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) in the present invention will be described.
The method for forming the organic layer is not particularly limited, and conventionally known methods such as a vacuum vapor deposition method and a wet method (also referred to as a wet process) can be used.
As the wet method, for example, in addition to printing methods such as gravure printing method, flexographic printing method, screen printing method, spin coating method, casting method, inkjet printing method, die coating method, blade coating method, bar coating method, roll coating method, etc. There are dip coating method, spray coating method, curtain coating method, doctor coating method, LB method (Langmuir-Bloget method), etc., but the coating liquid can be applied easily and accurately, and it is highly productive. Therefore, it is more preferable to apply by an inkjet printing method using an inkjet head.

<< Inkjet printing method >>
Hereinafter, an example of a method for forming an organic layer by an inkjet printing method will be described with reference to the drawings.

FIG. 1 is a schematic view showing an example of a method for manufacturing an organic EL element using an inkjet printing method.

FIG. 1 shows an organic functional material or the like (if necessary, a π-conjugated compound of the present invention) that forms an organic layer of an organic EL element on a base material 2 by using an inkjet printing apparatus provided with an inkjet head 30. An example of a method of discharging (including) is shown.

As shown in FIG. 1, as an example, while continuously transporting the base material 2, the organic functional material or the like is sequentially ejected as ink droplets onto the base material 2 by the inkjet head 30, and the organic EL is used. The organic functional layer of the element 1 is formed.

The inkjet head 30 applicable to the method for manufacturing an organic EL element according to the present invention is not particularly limited. For example, the ink pressure chamber has a diaphragm provided with a piezoelectric element, and the ink pressure chamber using the diaphragm has a diaphragm. It may be a shear mode type (piezo type) head that ejects the ink composition by a pressure change, or it has a heat generating element, and the heat energy from the heat generating element causes a sudden volume change due to the film boiling of the ink composition from the nozzle. It may be a thermal type head that ejects the ink composition.

The inkjet head 30 is connected to a supply mechanism of an ink composition for injection. The ink composition is supplied to the inkjet head 30 by the tank 38A. In this example, the liquid level in the tank is kept constant so that the pressure of the ink composition in the inkjet head 30 is always kept constant. As a method, the ink composition is overflowed from the tank 38A and returned to the tank 38B by natural flow. The ink composition is supplied from the tank 38B to the tank 38A by the pump 31, and the liquid level of the tank 38A is controlled to be stable and constant according to the injection conditions.

When returning the ink composition to the tank 38A by the pump 31, it is performed after passing through the filter 32. As described above, it is preferable that the ink composition is passed through a filter medium having an absolute filtration accuracy or a quasi-absolute filtration accuracy of 0.05 to 50 μm at least once before being supplied to the inkjet head 30.

Further, the ink composition can be forcibly supplied from the tank 36 and the cleaning solvent can be forcibly supplied from the tank 37 to the inkjet head 30 by the pump 39 in order to perform the cleaning work and the liquid filling work of the inkjet head 30. Such tank pumps may be divided into a plurality of such tank pumps with respect to the inkjet head 30, a branch of a pipe may be used, or a combination thereof may be used.

In FIG. 1, the pipe branch 33 is used. Further, in order to sufficiently remove the air in the inkjet head 30, the ink composition is forcibly sent from the tank 36 to the inkjet 30 by the pump 39, and the ink composition is extracted from the air bleeding pipe described below to be a waste liquid tank. It may be sent to 34.

FIG. 2 is a schematic external view showing an example of the structure of an inkjet head applicable to an inkjet printing method.

FIG. 2A is a schematic perspective view showing an inkjet head 100 applicable to the present invention, and FIG. 2B is a bottom view of the inkjet head 100.

The inkjet head 100 applicable to the present invention is mounted on an inkjet recording device (not shown), and includes a head chip that ejects ink from a nozzle, a wiring board on which the head chip is arranged, and this wiring. A drive circuit board connected via a substrate and a flexible substrate, a manifold for introducing ink into a channel of a head chip via a filter, a housing 56 in which a manifold is housed inside, and a bottom opening of the housing 56. The cap receiving plate 57 attached so as to close the above, the first and

second joints

81a and 81b attached to the first ink port and the second ink port of the manifold, and the third ink port attached to the third ink port of the manifold. It includes a 3-joint 82 and a cover member 59 attached to the housing 56. Further, mounting holes 68 for mounting the housing 56 on the printer main body side are formed.

Further, the cap receiving plate 57 shown in FIG. 2B is formed as a substantially rectangular plate whose outer shape is long in the left-right direction corresponding to the shape of the cap receiving plate mounting portion 62, and a plurality of nozzles are formed in the substantially central portion thereof. In order to expose the arranged nozzle plate 61, a long nozzle opening 71 is provided in the left-right direction. Further, regarding the specific structure inside the inkjet head shown in FIG. 2A, for example, FIG. 2 and the like described in Japanese Patent Application Laid-Open No. 2012-140017 can be referred to.

A typical example of the inkjet head is shown in FIG. 2, but in addition to the above, for example, JP-A-2012-140017, JP-A-2013-010227, JP-A-2014-058171 and JP-A-2014-097644. Japanese Patent Application Laid-Open No. 2015-142979, Japanese Patent Application Laid-Open No. 2015-142980, Japanese Patent Application Laid-Open No. 2016-002675, JP-A-2016-002682, JP-A-2016-107401, JP-A-2017-109476, An inkjet head having the configuration described in JP-A-2017-177626 or the like can be appropriately selected and applied.

《Inkjet head》
Examples of the inkjet head applicable to the present invention include JP2012-140017, JP2013-010227, 2014-058771, 2014-097644, and 2015-142979. Japanese Patent Application Laid-Open No. 2015-142980, Japanese Patent Application Laid-Open No. 2016-002675, Japanese Patent Application Laid-Open No. 2016-002682, Japanese Patent Application Laid-Open No. 2016-107401, Japanese Patent Application Laid-Open No. 2017-109476, Japanese Patent Application Laid-Open No. 2017-177626, etc. An inkjet head having the configuration described in the above can be appropriately selected and applied.

The coating liquid used in the wet method may be a solution in which the material forming the organic layer is uniformly dissolved in the liquid medium, or a dispersion liquid in which the material is dispersed in the liquid medium as a solid content. As a dispersion method, dispersion can be performed by a dispersion method such as ultrasonic waves, high shear force dispersion, or media dispersion.
The liquid medium is not particularly limited, and for example, halogen-based solvents such as chloroform, carbon tetrachloride, dichloromethane, 1,2-dichloroethane, dichlorobenzene and dichlorohexanone, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone and n-propyl. Ketone solvents such as methyl ketone and cyclohexanone, aromatic solvents such as benzene, toluene, xylene, mesitylene and cyclohexylbenzene, aliphatic solvents such as cyclohexane, decalin and dodecane, ethyl acetate, n-propyl acetate, n-acetate Ester solvents such as butyl, methyl propionate, ethyl propionate, γ-butyrolactone, diethyl carbonate, ether solvents such as tetrahydrofuran and dioxane, amide solvents such as dimethylformamide and dimethylacetamide, methanol, ethanol, 1-butanol, Examples thereof include alcohol solvents such as ethylene glycol, nitrile solvents such as acetonitrile and propionitrile, dimethyl sulfoxide, water, or a mixed solution medium thereof.
The boiling point of these liquid media is preferably a boiling point lower than the temperature of the drying treatment from the viewpoint of quickly drying the liquid medium, specifically in the range of 60 to 200 ° C, more preferably 80 to 180 ° C. Is within the range of.

The coating liquid contains a surfactant depending on the purpose of controlling the coating range and suppressing the liquid flow (for example, the liquid flow that causes a phenomenon called coffee ring) associated with the surface tension gradient after coating. Can be done.
Examples of the surfactant include anionic or nonionic surfactants from the viewpoints of the influence of water contained in the solvent, leveling property, wettability to the substrate f1 and the like. Specifically, surfactants such as fluorine-containing activators and the like listed in International Publication No. 08/146681 and JP-A-2-41308 can be used.

Similar to the film thickness, the viscosity of the coating film can be appropriately selected depending on the function required as the organic layer and the solubility or dispersibility of the organic material. Specifically, for example, 0.3 to 100 mPa. It can be selected within the range of s.
The film thickness of the coating film can be appropriately selected depending on the function required as the organic layer and the solubility or dispersibility of the organic material, and specifically, can be selected in the range of, for example, 1 to 90 μm.
After forming the coating film by the wet method, it is possible to have a coating step of removing the above-mentioned liquid medium. The temperature of the drying step is not particularly limited, but it is preferable to perform the drying treatment at a temperature that does not damage the organic layer, the transparent electrode, or the base material. Specifically, it cannot be said unconditionally because it differs depending on the composition of the coating liquid and the like, but for example, the temperature can be set to 80 ° C. or higher, and the upper limit is considered to be a possible range up to about 300 ° C. The time is preferably about 10 seconds or more and 10 minutes or less. Under such conditions, drying can be performed quickly.

《Seal》
Examples of the sealing means used for sealing the organic EL element include a method of adhering the sealing member, the electrode, and the support substrate with an adhesive. The sealing member may be arranged so as to cover the display area of the organic EL element, and may be intaglio-shaped or flat-plate-shaped. Further, transparency and electrical insulation are not particularly limited.
Specific examples thereof include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium and tantalum.

In the present invention, a polymer film or a metal film can be preferably used because the organic EL element can be thinned. Furthermore, the polymer film has an oxygen permeability measured by a method according to JIS K 7126-1987 of 1 × 10 ^-3 mL / m ² / 24h or less, and is measured by a method according to JIS K 7129-1992. The water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)%) is preferably 1 × 10 ^-3 g / (m ² / 24h) or less.

Sandblasting, chemical etching, etc. are used to process the sealing member into a concave shape.
Specific examples of the adhesive include a photocurable and thermosetting adhesive having a reactive vinyl group of an acrylic acid-based oligomer and a methacrylic acid-based oligomer, and a moisture-curable adhesive such as 2-cyanoacrylic acid ester. be able to. In addition, heat and chemical curing type (two-component mixture) such as epoxy type can be mentioned. Further, hot melt type polyamide, polyester and polyolefin can be mentioned. In addition, a cation-curable type ultraviolet-curable epoxy resin adhesive can be mentioned.
Since the organic EL element may be deteriorated by heat treatment, it is preferable that the organic EL element can be adhesively cured from room temperature to 80 ° C. Further, the desiccant may be dispersed in the adhesive. A commercially available dispenser may be used to apply the adhesive to the sealing portion, or printing may be performed as in screen printing.

Further, it is also possible to preferably cover the electrode and the organic layer on the outside of the electrode on the side facing the support substrate with the organic layer sandwiched therein, and form a layer of an inorganic substance or an organic substance in contact with the support substrate to form a sealing film. .. In this case, the material for forming the film may be any material having a function of suppressing infiltration of a material that causes deterioration of the element such as moisture and oxygen, and for example, silicon oxide, silicon dioxide, silicon nitride or the like may be used. it can.

Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of an organic material. The method for forming these films is not particularly limited, and for example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight. Legal, plasma CVD method, laser CVD method, thermal CVD method, coating method and the like can be used.

In the gas phase and liquid phase, an inert gas such as nitrogen or argon or an inert liquid such as fluorinated hydrocarbon or silicone oil may be injected into the gap between the sealing member and the display region of the organic EL element. preferable. It is also possible to create a vacuum. Further, a hygroscopic compound can be enclosed inside.
Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide, etc.) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate, etc.). , Metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchlorates (eg barium perchlorate, etc.) Magnesium perchlorate, etc.) and the like, and anhydrous salts are preferably used for sulfates, metal halides and perchlorates.

《Protective film, protective plate》
A protective film or protective plate may be provided on the outside of the sealing film or the sealing film on the side facing the support substrate with the organic layer sandwiched in order to increase the mechanical strength of the element. In particular, when the sealing is performed by the sealing film, its mechanical strength is not necessarily high, so it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, a glass plate, a polymer plate / film, a metal plate / film, etc. similar to those used for the sealing can be used, but the polymer film is lightweight and thin. It is preferable to use.

<< Technology for improving light extraction >>
The organic EL element in the present invention emits light inside a layer having a refractive index higher than that of air (within a refractive index of about 1.6 to 2.1), and 15% to 20% of the light generated in the light emitting layer. It is generally said that only a degree of light can be taken out. This is because light incident on the interface (intersection between the transparent substrate and air) at an angle θ equal to or greater than the critical angle causes total internal reflection and cannot be taken out of the element, and the transparent electrode or light emitting layer and the transparent substrate This is because the light is totally reflected between them, the light is waveguideed through the transparent electrode or the light emitting layer, and as a result, the light escapes toward the side surface of the element.

As a method for improving the efficiency of light extraction, for example, a method of forming irregularities on the surface of a transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (for example, US Pat. No. 4,774,435), the substrate A method of improving efficiency by providing light-collecting property (for example, Japanese Patent Application Laid-Open No. 63-314795), a method of forming a reflective surface on a side surface of an element (for example, Japanese Patent Application Laid-Open No. 1-220394), a substrate A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the light emitting body and the light emitting body (for example, Japanese Patent Application Laid-Open No. 62-172691), which has a lower refractive index than the substrate between the substrate and the light emitting body. A method of introducing a flat layer having a refractive index (for example, Japanese Patent Application Laid-Open No. 2001-202827), a method of forming a diffraction lattice between layers of a substrate, a transparent electrode layer or a light emitting layer (including between the substrate and the outside world) ( JP-A-11-283751) and the like.

In the present invention, these methods can be used in combination with the organic EL element, but a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate and a transparent electrode layer. A method of forming a diffraction grating between any layer (including between the substrate and the outside world) of the light emitting layer can be preferably used.
When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the lower the refractive index of the medium, the higher the efficiency of extracting the light emitted from the transparent electrode to the outside. Become.
In the present invention, by combining these means, an element having higher brightness or excellent durability can be obtained.

Examples of the low refractive index layer include airgel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally in the range of about 1.5 to 1.7, it is preferable that the low refractive index layer has a refractive index of about 1.5 or less. Further, it is preferably 1.35 or less.
Further, it is desirable that the thickness of the low refractive index medium is at least twice the wavelength in the medium. This is because the effect of the low refractive index layer diminishes when the thickness of the low refractive index medium becomes about the wavelength of light and the electromagnetic wave exuded by evanescent enters the substrate.

The method of introducing the diffraction grating into the interface where total reflection occurs or any medium is characterized in that the effect of improving the light extraction efficiency is high. This method is generated from the light emitting layer by utilizing the property that the diffraction lattice can change the direction of light to a specific direction different from the refraction by so-called Bragg diffraction such as first-order diffraction or second-order diffraction. Of the generated light, the light that cannot go out due to total reflection between the layers is diffracted by introducing a diffraction lattice into one of the layers or in the medium (inside the transparent substrate or in the transparent electrode). , Trying to get the light out.
It is desirable that the diffraction grating to be introduced has a two-dimensional periodic refractive index. This is because the light emitted by the light emitting layer is randomly generated in all directions, so a general one-dimensional diffraction grating that has a periodic refractive index distribution only in one direction diffracts only the light that travels in a specific direction. The light extraction efficiency does not increase so much.
However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and the light extraction efficiency is improved.
The position where the diffraction grating is introduced may be in any of the layers or in the medium (inside the transparent substrate or in the transparent electrode), but it is desirable that the diffraction grating is introduced in the vicinity of the organic light emitting layer where light is generated. At this time, the period of the diffraction grating is preferably in the range of about 1/2 to 3 times the wavelength of the light in the medium. It is preferable that the arrangement of the diffraction grating is two-dimensionally repeated, such as a square lattice shape, a triangular lattice shape, and a honeycomb lattice shape.

《Condensing sheet》
The organic EL element in the present invention is processed so as to provide a structure on a microlens array, for example, on the light extraction side of a support substrate (substrate), or by combining with a so-called condensing sheet, for example, an element By condensing light in the front direction with respect to the light emitting surface, it is possible to increase the brightness in a specific direction.
As an example of a microlens array, a quadrangular pyramid having a side of 30 μm and an apex angle of 90 degrees is arranged two-dimensionally on the light extraction side of the substrate. One side is preferably in the range of 10 to 100 μm. If it is smaller than this, the effect of diffraction occurs and it is colored, and if it is too large, the thickness becomes thick, which is not preferable.

As the condensing sheet, for example, a sheet that has been put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness increasing film (BEF) manufactured by Sumitomo 3M Ltd. can be used. The shape of the prism sheet may be, for example, a base material having a Δ-shaped stripe having an apex angle of 90 degrees and a pitch of 50 μm, or a shape having a rounded apex angle and a random pitch change. It may have a right angle or other shape.
Further, the light diffusing plate / film may be used in combination with the condensing sheet in order to control the light emission angle from the organic EL element. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

《Use》
The organic EL element in the present invention can be used as a display device, a display, and various light emitting light sources.
Light sources include, for example, lighting devices (household lighting, interior lighting), clock and liquid crystal backlights, signage advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, and light. Examples thereof include, but are not limited to, a light source for a sensor, but the light source can be effectively used as a backlight for a liquid crystal display device and a light source for lighting.
If necessary, the organic EL device of the present invention may be patterned by a metal mask, an inkjet printing method, or the like at the time of film formation. In the case of patterning, only the electrodes may be patterned, the electrodes and the light emitting layer may be patterned, or all the layers of the device may be patterned. In the fabrication of the device, a conventionally known method is used. Can be done.

<< One aspect of lighting equipment >>
An aspect of the lighting device provided with the organic EL element in the present invention will be described.
The non-light emitting surface of the organic EL element is covered with a glass case, a glass substrate having a thickness of 300 μm is used as a sealing substrate, and an epoxy-based photocurable adhesive (Luxtrac LC0629B manufactured by Toa Synthetic Co., Ltd.) is used as a sealing material around it. ) Is applied, and this is overlaid on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured, sealed, and an illuminating device as shown in FIGS. Can be formed.
FIG. 3 shows a schematic view of the lighting device, and the organic EL element 101 according to the present invention is covered with a glass cover 102 (note that the sealing operation with the glass cover brings the organic EL element 101 into contact with the atmosphere. The glove box was carried out in a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more).
FIG. 3 shows a cross-sectional view of the lighting device. In FIG. 4, reference numeral 105 indicates a cathode, reference numeral 106 indicates an organic EL layer, and reference numeral 107 indicates a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108, and a water catching agent 109 is provided.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

The compounds used below are shown.

[Example 1]
<Synthesis of Exemplified Compound B-1>
It was synthesized by the following scheme.

Carboline (10.9 g, 64.6 mol) was dissolved in NMP (42 ml), NaH (2.80 g, 70.0 mol) was added, and the mixture was stirred for 30 minutes. Then, 2,3,4,5,6-pentafluorobenzonitrile (1.32 g, 10.8 mol) was added to the solution, and the mixture was heated and stirred at 120 ° C. for 5 hours. Water was added to the reaction solution, and the precipitate was collected by filtration. This was recrystallized to obtain 9.20 g of the target exemplary compound (B-1).

<Synthesis of Exemplified Compound B-2>
It was synthesized by the following scheme.

Carboline (6.54 g, 38.68 mol) was dissolved in THF (42 ml), NaH (1.68 g, 42.0 mol) was added, and the mixture was stirred for 30 minutes. Then, 2,3,4,5,6-pentafluorobenzonitrile (1.32 g, 10.8 mol) was added to the solution, and the mixture was stirred with heating under reflux for 5 hours. Water was added to the reaction solution, and the precipitate was collected by filtration. This was recrystallized to obtain 6.50 g of an intermediate. Next, 9H-carbazole (4.10 g, 24.5 mol) was dissolved in NMP (42 ml), NaH (0.98 g, 24.5 mol) was added, and the mixture was stirred for 30 minutes. Then, an intermediate (6.50 g, 10.2 mol) was added to the solution, and the mixture was heated and stirred at 120 ° C. for 5 hours. Water was added to the reaction solution, and the precipitate was collected by filtration. This was recrystallized to obtain 8.20 g of the target exemplary compound (B-2).

<Synthesis of Exemplified Compound A-11>
It was synthesized by the following scheme.

3-Cyanocarbazole (1.92 g, 10.0 mmol) was dissolved in THF (40 ml), NaH (0.40 g, 10.0 mmol) was added, and the mixture was stirred for 30 minutes. Then, hexafluorobenzene (11.2 g, 60.0 mmol) was added to the solution, and the mixture was heated and stirred at 0 ° C. for 1 hour. Water was added to the reaction solution, and the precipitate was collected by filtration. This was purified by column chromatography to obtain 2.5 g of an intermediate.
Next, 5H-pyrido [3,2-b] indole (8.07 g, 48.0 mmol) was dissolved in THF (40 ml), NaH (2.0 g, 48.0 mmol) was added, and the mixture was stirred for 30 minutes. Then, 2.5 g of the intermediate was added to the solution, and the mixture was heated and stirred at 70 ° C. for 5 hours. Water was added to the reaction solution, and the precipitate was collected by filtration. This was purified by column chromatography to obtain 1.9 g of the target exemplary compound (A-11).

<Synthesis of other compounds>
Other compounds (B-21, C-7, comparative compounds 1 to 4) were synthesized in the same manner as described above except that the raw materials were mainly changed.

<Making EOD1-1>
A single charge device (electron-only device: EOD): ITO / Ca / organic layer / Ag was prepared as described below.
After patterning on a substrate (NA-45 manufactured by NH Technoglass Co., Ltd.) in which ITO (indium tin oxide) was deposited at 100 nm on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode, this ITO transparent electrode was provided. The transparent support substrate was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed for 5 minutes.
The transparent support substrate provided with the ITO transparent electrode was attached to a vacuum vapor deposition apparatus, and the vacuum chamber was depressurized to 4 × 10 ^-4 Pa. Ca is vapor-deposited at a vapor deposition rate of 0.2 Å / sec to a film thickness of 5 nm, and the exemplary compound "B-1" is further deposited at a vapor deposition rate of 1.0 Å / sec to a film thickness of 100 nm. Was done.
Finally, 100 nm of silver was vapor-deposited as a cathode to form a cathode, and EOD1-1 was prepared.

<Preparation of EOD1-2 to 1-11>
In the production of the single charge device EOD1-1, EOD1-2 to 1- were similarly changed to the organic layer compound (charge transport material) shown in Table I instead of the exemplary compound “B-1”. 11 was prepared.

<Evaluation of EOD1-1 to 1-11>
Using the prepared EOD1-1 to 1-11, the degree of film quality stabilization by the compound of the present invention was evaluated by the method described below.

The applied voltage when a current of 10 mA / cm ² was passed through each EOD for a certain period of time was measured, and those with less voltage fluctuation (rise) after a certain period of time were evaluated as having high film quality stability.
When the starting voltage is V ₀ , the voltage after 100 hours is V ₁₀₀ , the drive voltage change rate V ₁₀₀ / V ₀ is calculated, and the drive voltage change rate of the comparative EOD 1-9 is 100. The relative values are shown in Table I.

As shown in the results of Table I above, when the drive voltage change rates of EOD1-1 to EOD1-6 and EOD1-7 to EOD1-11 are compared, the structure represented by the general formula (1) of the present invention is obtained. It is clear that the compound having the compound suppresses the aggregation of the compound and has high film stability.

[Example 2]
<Evaluation of EOD1-1, 1-2, 1-4, 1-5, 1-8, 1-9 and 1-10>
Using the prepared EOD1-1, 1-2, 1-4, 1-5, 1-8, 1-9 and 1-10, the properties of the compound of the present invention as a charge transport material are described below. Was evaluated by.

A voltage was applied to each EOD to measure the electron mobility and the injection voltage, and a material having a high electron mobility and a small injection voltage was evaluated as being excellent as a charge transport material.
Table II shows the relative values of the comparative EOD1-8 when the electron mobility and injection voltage are 100.

As shown in the results in Table II above, EOD1-1, EOD1-2, EOD1-4, EO
Comparing the electron mobilities of D1-5 and EOD1-8 to EOD1-10, the compound having the structure represented by the general formula (1) of the present invention has a high electron mobility and a low injection voltage. It is clear that it has excellent properties as a charge transport material.

[Example 3]
<Manufacturing of organic EL element 1-1>
Patterning was performed on a substrate (NA45 manufactured by AvanStrate Inc.) in which ITO (indium tin oxide) was deposited at 100 nm on a glass substrate having a size of 100 mm × 100 mm × 1.1 mm as an anode. Then, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed for 5 minutes.
On this transparent support substrate, poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Bayer P Al 4083) diluted to 70% with pure water was used at 3000 rpm. After forming a thin film by a spin coating method under the condition of 30 seconds, it was dried at 200 ° C. for 1 hour to provide a hole injection layer having a layer thickness of 20 nm.
Then, a thin film was formed by a spin coating method under the conditions of 2000 rpm and 30 seconds using a solution of polyvinylcarbazole (Mw to 110000) in 1,2 dichlorobenzene, and then dried at 120 ° C. for 10 minutes to form a layer. A hole transport layer having a thickness of 15 nm was provided.
Further, a thin film was prepared by a spin coating method under the conditions of 2000 rpm and 30 seconds using a solution in which PXZ-TRZ as a luminescent compound and mCBP as a host compound were dissolved in toluene so as to be 10% and 90% by mass, respectively. After forming, it was dried at 100 ° C. for 10 minutes to provide a light emitting layer having a layer thickness of 35 nm.

Next, this substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent materials of each layer in the optimum amount for manufacturing the device. As the crucible for vapor deposition, a crucible made of molybdenum or tungsten made of a resistance heating material was used.
After depressurizing to a degree of vacuum of 1 × 10 ^-4 Pa, Exemplified Compound B-1 was vapor-deposited at a vapor deposition rate of 1.0 nm / sec to form an electron transport layer having a layer thickness of 30 nm.
Further, after forming lithium fluoride with a film thickness of 0.5 nm, aluminum 100 nm was vapor-deposited to form a cathode.
The non-light emitting surface side of the element was covered with a can-shaped glass case in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more, and an electrode take-out wiring was installed to prepare an organic EL element 1-1.

<Manufacturing of organic EL elements 1-2 to 1-3>
Organic EL devices 1-2 to 1-3 were produced in the same manner as the organic EL device 1-1 except that the electron transport material was changed as shown in Table III below.

[Evaluation]
<Relative brightness half time>
The elements described above prepared, the initial luminance 100 cd / m ² luminance half-life when lit (time required for luminance to decrease from 100 cd / m ² to 50 cd / m ²⁾ were measured, respectively.
Then, Table III below shows the relative values of the luminance half-time of each element with respect to the luminance half-time of the organic EL element 1-3).

From the above results, the organic EL device using the compound of the present invention suppresses the fluctuation of the film, suppresses the association between the light emitting material and the electron transport material, and reduces the influence of the fluctuation of the light emitting region than the organic EL device using the comparative compound. Due to the effect, it showed a long half-brightness time.

INDUSTRIAL APPLICABILITY According to the present invention, an organic film having a high electron mobility, which reduces agglomeration by suppressing π stacking with a bulky aromatic substituent and mixing axial isomers, particularly an organic film used as an electron transport layer of an organic electroluminescence device. And can be used for the organic electroluminescence device.

1, 101 Organic EL element 2

Base material

30, 100

Inkjet head

31, 39 Pump 32 Filter 33 Piping branch 34 Waste liquid tank 35

Control unit

36, 37, 38A, 38B Tank 56 Housing 57 Cap receiving plate 59 Cover member 61 Nozzle plate 62 Cap receiving plate mounting part 68 Mounting hole 71 Nozzle opening 81a 1st join 81b 2nd joint 82 3rd joint 102 Glass cover 102 Glass cover 105 Cathode 106 Organic EL layer 107 Glass substrate with transparent electrode 108 Nitrogen gas 109 capture Liquid

Claims

An organic film containing a charge transport material having a structure represented by the following general formula (1).

[In the general formula (1), n represents an integer of 4 to 6, and m represents an integer of 0 to 2. However, it satisfies n + m = 6.
X represents a hydrogen atom or a substituent, and a plurality of Xs may be the same or different.
The aromatic ring A is a nitrogen-containing aromatic compound having a structure represented by the following general formula (2), and a plurality of aromatic rings A may be the same or different, but when n is 6, the aromatic ring A may be the same or different. It has at least two types of aromatic rings A. Any one of the aromatic rings A has a structure in which at least one of Y 11 to Y 18 is a nitrogen atom. ]

[In the general formula (2), Y 11 to Y 18 independently represent a nitrogen atom or CR, respectively. R is a hydrogen atom or a substituent, and a plurality of the substituents may be bonded to each other to form a ring, and # represents a connection position in the general formula (1). ]
The organic membrane according to claim 1, wherein in the general formula (1), any one of the substituents X is an electron-withdrawing substituent.
The organic film according to claim 1 or 2, wherein in the general formula (1), any one of the substituents X is a cyano group.
The organic film according to any one of claims 1 to 3, wherein n is 5 and m is 1 in the general formula (1).
The organic film according to any one of claims 1 to 4, wherein in the general formula (1), any one of the aromatic rings A has a structure in which Y 14 is a nitrogen atom.
The organic film according to any one of claims 1 to 5, wherein the charge transport material is a compound exhibiting heat-activated delayed fluorescence.
The organic film according to any one of claims 1 to 6, which is formed by a wet method.
The organic film according to any one of claims 1 to 7, wherein the charge transport material is an electron transport material.
An organic electroluminescence device having one or more organic compound layers between an anode and a cathode.
An organic electroluminescence device in which at least one organic compound layer has an organic film as an electron transporting layer according to any one of claims 1 to 8.
The organic electroluminescence element according to claim 9, wherein the at least one organic compound layer contains a luminescent compound exhibiting thermally activated delayed fluorescence.
The organic electroluminescence device according to claim 9 or 10, wherein the at least one organic compound layer is formed by a wet method.