JP7644638B2 - Organic thin film, organic electroluminescence element, material for organic electroluminescence element, display device and lighting device - Google Patents

Description

The present invention relates to organic thin films, organic electroluminescence (hereinafter, electroluminescence (field emission) may be abbreviated as "EL") elements, materials for organic electroluminescence elements, display devices, and lighting devices.

Organic EL elements are thin, soft, and flexible. Furthermore, displays using organic EL elements are capable of displaying images with higher brightness and resolution than the currently mainstream liquid crystal display devices and plasma display devices. Furthermore, displays using organic EL elements have a wider viewing angle than liquid crystal display devices. For this reason, display devices using organic EL elements are currently being used increasingly as displays for televisions and mobile phones. Organic EL elements are also expected to be used as lighting devices.

In the case of displays using organic EL elements, there are two manufacturing processes: a (printing) coating process and a vacuum deposition process. Currently, in order to produce products that can be driven at a low voltage and have a long life, manufacturers generally use the vacuum deposition process, in which materials are heated under a high vacuum to sublimate and form a film on the substrate. In organic EL elements, a method is widely used in which a p-type dopant material is added to improve hole injection performance when holes are injected into the organic layer from an anode such as ITO.

Common hole injection materials include materials that form charge transfer complexes with host materials due to their deep LUMO (lowest energy of conduction band) levels, such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane and molybdenum oxide, and materials to which a strongly acidic dopant such as sulfonic acid has been added, such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). Among these, the use of an acidic dopant makes it possible to lower the hole injection barrier from the anode to the organic film, regardless of the HOMO (highest energy of valence band) level of the host material capable of transporting holes, and has the advantage of broadening the selection of usable materials.

However, it has been confirmed that sulfonic acid-containing materials dissolve the ITO anode, which is the lower electrode, due to their high acidity, and the dissolved indium ions migrate to the vicinity of the light-emitting layer, impairing the operating life of the element (Non-Patent Document 1).

Sung Jin Jo et al., J. Appl. Phys. , 103, 114502 (2008)

In addition, many acidic materials have the problems of being easily dehydrated and decomposed by heating, which impairs the performance of the material, and being highly hygroscopic and difficult to store. In particular, dopants containing sulfonic acid or trifluoromethanesulfonyl (Tf) groups, which have high electron-withdrawing properties, are easily decomposed and eliminated by heat, making it difficult to apply a vapor deposition process. For this reason, there have been no reports yet of acidic dopant materials that can be stably stored and vapor-deposited, have a low driving voltage, and can improve driving stability.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology, and to provide an organic thin film that can be produced by a vapor deposition process, capable of reducing the driving voltage of an organic EL element, and capable of improving the driving stability, as well as a material for an organic EL element that can be applied to a vapor deposition process, capable of reducing the driving voltage of an organic EL element, and capable of improving the driving stability.
Another object of the present invention is to provide an organic EL element using the organic thin film or the material for an organic EL element, and a display device and a lighting device including the organic EL element.

In order to solve the above problems, the present inventors have conducted various studies on acidic materials that can be added to a hole injection layer located between an anode and a light-emitting layer of an organic EL element to improve both the hole injection performance and driving stability of the organic EL element, and can be formed into a film by a vacuum deposition method. As a result, they have come to the conclusion that an acidic material containing a specific fluorobenzoic acid structure or a fluoronaphthalenedicarboxylic acid structure is suitable for manufacturing an organic EL element by a deposition process, and that by using the acidic material containing the fluorobenzoic acid structure or the fluoronaphthalenedicarboxylic acid structure as an acidic dopant in the hole injection layer of an organic EL element, the driving voltage of the organic EL element to which the deposition process is applied is reduced and the driving stability is improved, thereby solving the above problems, and have arrived at the present invention.
The gist of the present invention for solving the above problems is as follows.

（一般式（１）中、Ｒ^１は、置換基を有していてもよい芳香族炭化水素基、芳香族複素環基、アリールアルキレン基、２価若しくは３価の環状炭化水素基、又は、これらの基を２つ以上組み合わせてできる基、これらの基の１つ若しくは２つ以上と硫黄原子とを組み合わせてできる基を表す。ｎは、２～６の整数である。）
かかる有機薄膜は、蒸着プロセスで製造することが可能で、また、有機ＥＬ素子に適用することで、有機ＥＬ素子の駆動電圧を低減でき、駆動安定性を向上させることができる。 The organic thin film according to one embodiment of the present invention is characterized in that it is a single film containing a first material, which is a tetrafluorobenzoic acid derivative having a structure represented by the following general formula (1), and a second material that transports holes, or a laminated film containing a film containing the first material and a film containing the second material.

(In general formula (1), R ¹ represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent or trivalent cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a sulfur atom. n is an integer from 2 to 6.)
Such an organic thin film can be produced by a vapor deposition process, and by applying it to an organic EL element, the driving voltage of the organic EL element can be reduced and the driving stability can be improved.

In a preferred embodiment of the organic thin film of the present invention, the first material is a tetrafluorobenzoic acid derivative in which n in the above general formula (1) is 2 or 3. In this case, by applying the same to an organic EL element, the driving voltage of the organic EL element can be further reduced and the driving stability can be further improved.

（一般式（１）中、Ｒ^１は、置換基を有していてもよい芳香族炭化水素基、芳香族複素環基、アリールアルキレン基、２価若しくは３価の環状炭化水素基、又は、これらの基を２つ以上組み合わせてできる基、これらの基の１つ若しくは２つ以上と硫黄原子とを組み合わせてできる基を表す。ｎは、２～６の整数である。）
かかる有機エレクトロルミネッセンス素子は、蒸着プロセスで製造することが可能で、また、駆動電圧が低く、駆動安定性に優れる。 The organic electroluminescence device according to one embodiment of the present invention has a light-emitting layer between a cathode and an anode,
The present invention is characterized in that a layer containing a first material, which is a tetrafluorobenzoic acid derivative having a structure represented by the following general formula (1), is provided between the anode and the light-emitting layer.

(In general formula (1), R ¹ represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent or trivalent cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a sulfur atom. n is an integer from 2 to 6.)
Such an organic electroluminescence device can be manufactured by a deposition process, and has a low driving voltage and excellent driving stability.

Here, it is preferable to have a laminated film of a layer containing the first material and a layer containing a second material that transports holes between the anode and the light-emitting layer. In this case, the driving voltage is further reduced and driving stability is further improved.

a layer including the first material and a second material that transports holes between the anode and the light-emitting layer;
It is also preferable to have a layer containing the second material between the light-emitting layer and the layer containing the first material and the second material. In this case, too, the driving voltage is further reduced and driving stability is further improved.

（一般式（２）中、Ｒ^２及びＲ^３のいずれか一方は、カルボキシル基であり、もう一方は、フッ素元素、トリフルオロメチル基、シアノ基、又はニトロ基である。）
かかる有機薄膜は、蒸着プロセスで製造することが可能で、また、有機ＥＬ素子に適用することで、有機ＥＬ素子の駆動電圧を低減でき、駆動安定性を向上させることができる。 In addition, the organic thin film according to another embodiment of the present invention is characterized in that it is a single film containing a first material, which is a fluoronaphthalene dicarboxylic acid derivative having a structure represented by the following general formula (2), and a second material that transports holes, or a laminated film containing a film containing the first material and a film containing the second material.

(In general formula (2), one of ^R2 and ^R3 is a carboxyl group, and the other is a fluorine group, a trifluoromethyl group, a cyano group, or a nitro group.)
Such an organic thin film can be produced by a vapor deposition process, and by applying it to an organic EL element, the driving voltage of the organic EL element can be reduced and the driving stability can be improved.

（一般式（２）中、Ｒ^２及びＲ^３のいずれか一方は、カルボキシル基であり、もう一方は、フッ素元素、トリフルオロメチル基、シアノ基、又はニトロ基である。）
かかる有機エレクトロルミネッセンス素子用材料は、蒸着プロセスに適用でき、有機ＥＬ素子に適用することで、有機ＥＬ素子の駆動電圧を低減でき、駆動安定性を向上させることができる。 A material for an organic electroluminescence device according to one embodiment of the present invention is characterized by containing a fluoronaphthalenedicarboxylic acid derivative having a structure represented by the following general formula (2).

(In general formula (2), one of ^R2 and ^R3 is a carboxyl group, and the other is a fluorine group, a trifluoromethyl group, a cyano group, or a nitro group.)
Such a material for an organic electroluminescence device can be applied to a vapor deposition process, and by applying it to an organic EL device, the driving voltage of the organic EL device can be reduced and the driving stability can be improved.

The organic electroluminescence device according to another embodiment of the present invention has a light-emitting layer between a cathode and an anode,
The present invention is characterized in that a layer containing the above-mentioned material for an organic electroluminescence device is provided between the anode and the light-emitting layer.
Such an organic electroluminescence device can be manufactured by a deposition process, and has a low driving voltage and excellent driving stability.

The display device of the present invention is characterized by comprising the organic electroluminescence element described above. The display device of the present invention has a low driving voltage and excellent driving stability.

The lighting device of the present invention is characterized by comprising the organic electroluminescence element described above. The lighting device of the present invention has a low driving voltage and excellent driving stability.

According to the present invention, it is possible to provide an organic thin film that can be produced by a vapor deposition process, capable of reducing the driving voltage of an organic EL element, and capable of improving the driving stability, as well as a material for an organic EL element that can be applied to a vapor deposition process, capable of reducing the driving voltage of an organic EL element, and capable of improving the driving stability.
Furthermore, according to the present invention, it is possible to provide an organic EL element which uses the organic thin film or the material for an organic EL element and has a low driving voltage and excellent driving stability, and a display device and a lighting device which include the organic EL element.

FIG. 1 is a schematic cross-sectional view illustrating an example of an organic EL element of the present invention. 1 is a ¹⁹ F-NMR spectrum of a compound represented by structural formula (3). 1 is a ¹ H-NMR spectrum of a compound represented by structural formula (3). 1 is a ¹⁹ F-NMR spectrum of a compound represented by structural formula (4). 1 is a ¹ H-NMR spectrum of a compound represented by structural formula (4). 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Examples 1 to 3 and Comparative Example 1. 1 is a graph showing the change over time in luminance of the organic EL elements produced in Examples 1 to 3 and Comparative Example 1.

The organic thin film, organic electroluminescence element, material for organic electroluminescence element, display device, and lighting device of the present invention will be described in detail below with reference to their embodiments.

（一般式（１）中、Ｒ^１は、置換基を有していてもよい芳香族炭化水素基、芳香族複素環基、アリールアルキレン基、２価若しくは３価の環状炭化水素基、又は、これらの基を２つ以上組み合わせてできる基、これらの基の１つ若しくは２つ以上と硫黄原子とを組み合わせてできる基を表す。一般式（１）中、ｎは、２～６の整数である。） [Materials for organic thin films and organic EL devices]
The organic thin film according to one embodiment of the present invention is characterized in that it is a single film containing a first material, which is a tetrafluorobenzoic acid derivative having a structure represented by the following general formula (1), and a second material that transports holes, or a laminated film containing a film containing the first material and a film containing the second material.

(In general formula (1), R ¹ represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent or trivalent cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a sulfur atom. In general formula (1), n is an integer of 2 to 6.)

（一般式（２）中、Ｒ^２及びＲ^３のいずれか一方は、カルボキシル基であり、もう一方は、フッ素元素、トリフルオロメチル基、シアノ基、又はニトロ基である。） In addition, the organic thin film according to another embodiment of the present invention is characterized in that it is a single film containing a first material, which is a fluoronaphthalene dicarboxylic acid derivative having a structure represented by the following general formula (2), and a second material that transports holes, or a laminated film containing a film containing the first material and a film containing the second material.
The material for an organic electroluminescence device of the present invention is characterized by containing a fluoronaphthalenedicarboxylic acid derivative having a structure represented by the following general formula (2).

(In general formula (2), one of ^R2 and ^R3 is a carboxyl group, and the other is a fluorine group, a trifluoromethyl group, a cyano group, or a nitro group.)

The tetrafluorobenzoic acid derivative having the structure represented by the general formula (1) and the fluoronaphthalenedicarboxylic acid derivative having the structure represented by the general formula (2) are not easily decomposed by heating and have excellent storage stability, and therefore can be applied to a vapor deposition process.
Furthermore, the tetrafluorobenzoic acid derivative having the structure represented by the general formula (1) and the fluoronaphthalenedicarboxylic acid derivative having the structure represented by the general formula (2) have lower acidity than the strongly acidic dopants such as the above-mentioned sulfonic acids, and are less likely to dissolve the anode made of ITO, etc., which is the lower electrode. Therefore, by applying the tetrafluorobenzoic acid derivative having the structure represented by the general formula (1) and/or the fluoronaphthalenedicarboxylic acid derivative having the structure represented by the general formula (2) to an organic EL element, the driving stability of the organic EL element can be improved.
In addition, the organic thin film of the present embodiment contains a second material that transports holes. Since the second material transports holes, for example, by disposing the organic thin film between the light-emitting layer and the anode of an organic EL element, the hole injection performance can be improved and the driving voltage of the organic EL element can be reduced.
Therefore, the organic thin film of this embodiment can be manufactured by a vapor deposition process, and by applying it to an organic EL element, the driving voltage of the organic EL element can be reduced and the driving stability can be improved. Also, the material for an organic electroluminescence element of this embodiment can be applied to a vapor deposition process, and by applying it to an organic EL element, the driving voltage of the organic EL element can be reduced and the driving stability can be improved.

^R1 in the above general formula (1) represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent or trivalent cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a sulfur atom.
The aromatic hydrocarbon group and aromatic heterocyclic group preferably have 3 to 30 carbon atoms, more preferably have 4 to 24 carbon atoms, and even more preferably have 5 to 20 carbon atoms.
Examples of the aromatic hydrocarbon group include a compound consisting of only one aromatic ring, such as benzene; a compound in which a plurality of aromatic rings, such as biphenyl and diphenylbenzene, are directly bonded to each other via one carbon atom; and a group obtained by removing one to three hydrogen atoms from any of the aromatic rings of a condensed ring aromatic hydrocarbon compound, such as naphthalene, anthracene, phenanthrene, or pyrene.
Examples of the aromatic heterocyclic group include compounds consisting of only one aromatic heterocycle, such as thiophene, furan, pyrrole, oxazole, oxadiazole, thiazole, thiadiazole, imidazole, pyridine, pyrimidine, pyrazine, and triazine; compounds in which a plurality of such compounds consisting of only one aromatic heterocycle are directly bonded to each other via one carbon atom (such as bipyridine); and groups obtained by removing 1 to 3 hydrogen atoms from any of the aromatic heterocycles of condensed ring heteroaromatic hydrocarbon compounds, such as quinoline, quinoxaline, benzothiophene, benzothiazole, benzimidazole, benzoxazole, indole, carbazole, dibenzofuran, dibenzothiophene, thieno[2,3-d]thiophene, acridine, and phenanthroline.
The arylalkylene group includes a group formed by combining the above aromatic hydrocarbon group with an alkylene group having 1 to 3 carbon atoms.
The divalent or trivalent cyclic hydrocarbon group preferably has 3 to 12 carbon atoms, and more preferably has 3 to 6 carbon atoms.
Furthermore, R ¹ may be a group formed by combining two or more of the above-mentioned aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent or trivalent cyclic hydrocarbon groups.
Furthermore, ^R1 may be a group formed by combining one or more of the above aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent or trivalent cyclic hydrocarbon groups with a sulfur atom. Examples of such groups include diaryl sulfides such as diphenyl sulfide and groups formed by removing 1 to 3 hydrogen atoms from diphenyl sulfide.

The aromatic hydrocarbon group, aromatic heterocyclic group, or arylalkylene group may have one or more monovalent substituents.
Examples of the monovalent substituent include a fluorine atom; haloalkyl groups such as a fluoromethyl group, a difluoromethyl group, and a trifluoromethyl group; linear or branched alkyl groups having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group; cyclic alkyl groups having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; linear or branched alkoxy groups having 1 to 20 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group; a nitro group; a cyano group; alkylamino groups having an alkyl group having 1 to 10 carbon atoms such as a methylamino group, an ethylamino group, a dimethylamino group, and a diethylamino group; cyclic amino groups such as a pyrrolidino group, a piperidino group, and a morpholino group; group, diarylamino groups such as a carbazolyl group; acyl groups such as an acetyl group, a propionyl group, a butyryl group; alkenyl groups having 2 to 30 carbon atoms such as a styryl group; aryl groups having 5 to 20 carbon atoms which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group described above); heterocyclic groups containing one or more of a nitrogen atom, a sulfur atom, and an oxygen atom having 4 to 20 carbon atoms which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (heterocyclic groups may be those consisting of only one ring, or may be compounds in which a plurality of compounds consisting of only one aromatic heterocyclic ring are directly bonded to each other at one carbon atom, or may be condensed heterocyclic groups. Specific examples of heterocyclic groups include the specific examples of the aromatic heterocyclic groups described above); ester groups, thioether groups, and the like. These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, or the like.

In the above general formula (1), n is an integer from 2 to 6, preferably 2 or 3.

A specific example of the tetrafluorobenzoic acid derivative having the structure represented by the above general formula (1) is a compound represented by the following structural formula (3) (DF4CA-TT).

In the above general formula (2), one of ^R2 and ^R3 is a carboxyl group, and the other is a fluorine group, a trifluoromethyl group, a cyano group, or a nitro group.
A fluoronaphthalene dicarboxylic acid derivative having a structure represented by general formula (2) is a compound in which two hydrogen atoms on the naphthalene ring are substituted with carboxyl groups, five hydrogen atoms on the naphthalene ring are substituted with elemental fluorine, and the remaining hydrogen atom on the naphthalene ring is substituted with elemental fluorine, a trifluoromethyl group, a cyano group, or a nitro group.

A specific example of the fluoronaphthalenedicarboxylic acid derivative having the structure represented by the above general formula (2) is a compound represented by the following structural formula (4) (F6-DCA).

The compound represented by the above structural formula (4) may be used as a mixture with its isomers or as a pure substance.

The second material may be any material that transports holes, and is preferably an organic material. The second material is more preferably an organic material with a highest occupied molecular orbital (HOMO) level of 4.0 eV to 7.0 eV, and among these, a p-type organic semiconductor material with a HOMO level of 4.5 eV to 6.0 eV is particularly preferred. For example, any of the conventionally known materials shown below may be used as the material for the hole transport layer of an organic EL element, but among these, a material that satisfies the above HOMO level requirements is preferred. In addition, various p-type polymer materials and various p-type low molecular materials can be used alone or in combination.

Examples of the p-type polymeric material (organic polymer) include polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly(N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly(p-phenylenevinylene), polytinylenevinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin, and derivatives thereof. These polymeric materials can also be used as mixtures with other compounds. As an example, a mixture containing polythiophene is poly(3,4-ethylenedioxythiophene/styrenesulfonic acid) (PEDOT/PSS).

The p-type low molecular weight materials include arylcycloalkane compounds such as 1,1-bis(4-di-para-triaminophenyl)cyclohexane and 1,1'-bis(4-di-para-tolylaminophenyl)-4-phenyl-cyclohexane, 4,4',4"-trimethyltriphenylamine, N,N,N',N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, and N,N'-diphenyl-N ,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1), N,N'-diphenyl-N,N'-bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD2), N,N,N',N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD3), N,N'-di(1-naphthyl)-N,N'-diphenyl arylamine compounds such as N-phenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) and 4,4'-bis[N-phenyl-N-[4'-diphenylamino-1,1'-biphenyl-4-yl]amino]-1,1'-biphenyl (TPTE); phenylenediamine compounds such as N,N,N',N'-tetraphenyl-para-phenylenediamine, N,N,N',N'-tetra(para-tolyl)-para-phenylenediamine, and N,N,N',N'-tetra(meta-tolyl)-meta-phenylenediamine (PDA); carbazole compounds such as carbazole, N-isopropylcarbazole, and N-phenylcarbazole; stilbene compounds such as stilbene and 4-di-para-tolylaminostilbene; oxazole compounds such as OxZ; triphenylmethane, 4,4',4"-tris(N-3-methyl triphenylmethane compounds such as 1-phenyl-3-(para-dimethylaminophenyl)pyrazoline; benzine (cyclohexadiene) compounds; triazole compounds such as triazole; imidazole compounds such as imidazole; oxadiazole compounds such as 1,3,4-oxadiazole and 2,5-di(4-dimethylaminophenyl)-1,3,4-oxadiazole; anthracene compounds such as anthracene and 9-(4-diethylaminostyryl)anthracene; fluorenone compounds such as fluorenone, 2,4,7-trinitro-9-fluorenone, and 2,7-bis(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone; and anilines such as polyaniline. These include compounds based on phthalocyanine, silane compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo-(3,4-c)pyrrolopyrrole, fluorene compounds such as fluorene, porphyrin compounds such as porphyrin and metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, metal or non-metallic phthalocyanine compounds such as phthalocyanine, copper phthalocyanine, tetra(t-butyl)copper phthalocyanine, and iron phthalocyanine, metal or non-metallic naphthalocyanine compounds such as copper naphthalocyanine, vanadyl naphthalocyanine, and monochlorogallium naphthalocyanine, and benzidine compounds such as N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine and N,N,N',N'-tetraphenylbenzidine, and the like. One or more of these compounds may be used. Among these, arylamine compounds such as TPTE are particularly preferred.

The organic thin film of this embodiment may be a single film containing a first material, which is a tetrafluorobenzoic acid derivative having a structure represented by general formula (1) and/or a fluoronaphthalenedicarboxylic acid derivative having a structure represented by general formula (2), and a second material that transports holes, or may be a laminated film of a film containing the first material and a film containing the second material. Whether it is a single film or a laminated film, it can be manufactured by a vapor deposition process, and by applying it to an organic EL element, the driving voltage of the organic EL element can be reduced and the driving stability can be improved.

The ratio of the first material to the second material contained in the organic thin film of this embodiment is not particularly limited and can be appropriately determined depending on the type of compound used for each of the first and second materials. The ratio of the first material to the second material is preferably 0.1:99.9 to 1:1 in mass ratio (first material:second material), more preferably 0.5:99.5 to 1:2, and even more preferably 1:99 to 1:3. When the ratio is as above, the effect of improving the hole transport property and hole injection property due to the inclusion of the first material and the second material in the organic thin film becomes significant.

The organic thin film is preferably formed by a vacuum deposition method such as resistance heating.
When the organic thin film is manufactured by a vapor deposition process, it can be manufactured by the same method as when other layers constituting the organic EL element are manufactured by a vapor deposition process, and the first material and the second material may be simultaneously vapor-deposited or sequentially vapor-deposited. When vapor-depositing sequentially, either the first material or the second material may be vapor-deposited first. In addition, either one may be vapor-deposited first and then both may be vapor-deposited, or either one may be vapor-deposited after both are vapor-deposited. Such a method for manufacturing an organic thin film including a step of simultaneously vapor-depositing a first material which is a tetrafluorobenzoic acid derivative having a structure represented by the above general formula (1) and/or a first material which is a fluoronaphthalenedicarboxylic acid derivative having a structure represented by the above general formula (2) and a second material which transports holes on a surface on which the organic thin film is to be formed is one of the preferred embodiments of the method for manufacturing an organic thin film of the present invention.
In addition, a method for producing an organic thin film comprising a step of first depositing either a first material or a second material onto a surface on which an organic thin film is to be formed, and then depositing the other material or both of the materials, or a method for producing an organic thin film comprising a step of simultaneously depositing a first material and a second material onto a surface on which an organic thin film is to be formed, and then depositing either the first material or the second material onto the surface on which an organic thin film is to be formed, is also one of the preferred embodiments of the method for producing an organic thin film of the present invention.

[Organic EL element]
The organic electroluminescence element according to one embodiment of the present invention is characterized in that it has an emitting layer between a cathode and an anode, and has a layer containing a first material, which is a tetrafluorobenzoic acid derivative having a structure represented by the above general formula (1), between the anode and the emitting layer.

Another embodiment of the organic electroluminescence element of the present invention is characterized in that it has an emission layer between a cathode and an anode, and a layer containing the above-mentioned material for organic electroluminescence elements (in other words, a layer containing a first material that is a fluoronaphthalenedicarboxylic acid derivative having a structure represented by the above general formula (2)) between the anode and the emission layer.

These organic EL elements of the present embodiment use the tetrafluorobenzoic acid derivative having the structure represented by the above general formula (1) or the fluoronaphthalenedicarboxylic acid derivative having the structure represented by the above general formula (2), which are not easily decomposed by heating, have excellent storage stability, and have a relatively low acidity, and therefore can be manufactured by a vapor deposition process, have a low driving voltage, and have excellent driving stability.

The organic EL element of the present embodiment preferably has a laminate film of a layer containing the first material and a layer containing a second material that transports holes between the anode and the light-emitting layer, which further reduces the driving voltage and improves driving stability.
Here, either the layer containing the first material or the layer containing the second material may be disposed on the anode side, but it is preferable that the layer containing the first material is disposed on the anode side, that is, it is preferable to have a layer containing the second material between the light-emitting layer and the layer containing the first material.

The organic EL element of this embodiment also preferably has a layer containing the first material and a second material that transports holes between the anode and the light-emitting layer, and a layer containing the second material between the light-emitting layer and the layer containing the first material and the second material. In this case, the driving voltage is further reduced, and driving stability is further improved.

Next, the organic EL element of the present invention will be described in detail with reference to examples.
Fig. 1 is a schematic cross-sectional view for explaining one example of an organic EL element of the present invention. The organic EL element 1 of the present embodiment shown in Fig. 1 has an emitting layer 6 between an anode 3 and a cathode 9. The organic EL element 1 shown in Fig. 1 has a hole injection layer 4 between the anode 3 and the emitting layer 6, the hole injection layer 4 containing the organic thin film of the present invention, or a first material which is a tetrafluorobenzoic acid derivative having a structure represented by the above general formula (1), or a first material which is a fluoronaphthalenedicarboxylic acid derivative having a structure represented by the above general formula (2).
The organic EL element 1 of the present embodiment has a laminated structure in which an anode 3, a hole injection layer 4, a hole transport layer 5, a light emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 are formed in this order on a substrate 2.

The organic EL element 1 shown in FIG. 1 may be a top-emission type that extracts light on the side opposite the substrate 2, or a bottom-emission type that extracts light on the substrate 2 side.

(substrate)
Examples of the material for the substrate 2 include a resin material, a glass material, etc. The material for the substrate 2 may be one type alone or a combination of two or more types.
Examples of the resin material used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, polyarylate, etc. When a resin material is used as the material for the substrate 2, it is preferable because an organic EL element 1 having excellent flexibility can be obtained.
On the other hand, examples of the glass material used for the substrate 2 include quartz glass and soda glass.

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

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

(electrode)
In the organic EL element 1 of the present embodiment, a known conductive material can be appropriately used for the anode 3 and the cathode 9, but it is preferable that at least one of them is transparent in order to extract light. Examples of known transparent conductive materials include ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped indium oxide), etc.
On the other hand, examples of opaque conductive materials include calcium, magnesium, aluminum, barium, tin, indium, copper, silver, ytterbium, and alloys thereof.
Of these, ITO, IZO, and FTO are preferable for the anode 3 .
On the other hand, among these, Al and AgMg alloys are preferable for the cathode 9 .

The average thickness of the anode 3 is not particularly limited, but is preferably 10 to 500 nm, and more preferably 70 to 200 nm. The average thickness of the anode 3 can be measured by a stylus step gauge or spectroscopic ellipsometry.

The average thickness of the cathode 9 is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 30 to 150 nm. Even when an opaque material is used, the cathode 9 can be used as a top emission type or transparent type by setting the average thickness to, for example, about 10 to 30 nm. The average thickness of the cathode 9 can be measured during deposition using a quartz crystal film thickness gauge.

(Hole Injection Layer)
The hole injection layer 4 can have the same structure as the organic thin film described above, and this structure makes it possible to form a hole injection layer 4 having improved hole injection properties and stability.
Also, a part of the organic thin film described above may be the hole injection layer 4, and another part of the organic thin film may be the hole transport layer 5 described later. For example, a mixed film of the first material and the second material may be the hole injection layer 4, and a film made of the second material may be the hole transport layer 5, a film made only of the first material may be the hole injection layer 4, and a film made only of the second material may be the hole transport layer 5, a laminated film of the second material and the first material may be the hole injection layer 4, and a film made only of the second material may be the hole transport layer 5, or a mixed film of the first material and the second material may be the hole injection layer 4 and hole transport layer 5.
In addition, when the hole injection layer 4 contains a first material (dopant) and a second material (host material), the ratio of the first material to the second material in terms of mass ratio (first material:second material) is preferably 0.1:99.9 to 1:1, and more preferably 1:99 to 1:2.

The average thickness of the hole injection layer 4 is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 5 to 50 nm.
The average thickness of the hole injection layer 4 can be measured by, for example, a stylus step gauge or spectroscopic ellipsometry.

(Hole transport layer)
Any compound that can be generally used as a material for a hole transport layer can be used as the material for the hole transport layer 5, and various p-type polymeric materials and various p-type low molecular weight materials can be used alone or in combination. For example, the various materials exemplified as the second material for the organic thin film described above can be used.

Examples of the p-type polymeric material (organic polymer) include polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly(N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly(p-phenylenevinylene), polytinylenevinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin, and derivatives thereof. These polymeric materials can also be used as mixtures with other compounds. As an example, a mixture containing polythiophene is poly(3,4-ethylenedioxythiophene/styrenesulfonic acid) (PEDOT/PSS).

The p-type low molecular weight materials include arylcycloalkane compounds such as 1,1-bis(4-di-para-triaminophenyl)cyclohexane and 1,1'-bis(4-di-para-tolylaminophenyl)-4-phenyl-cyclohexane, 4,4',4"-trimethyltriphenylamine, N,N,N',N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, and N,N'-diphenyl-N ,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1), N,N'-diphenyl-N,N'-bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD2), N,N,N',N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD3), N,N'-di(1-naphthyl)-N,N'-diphenyl arylamine compounds such as N-phenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) and 4,4'-bis[N-phenyl-N-[4'-diphenylamino-1,1'-biphenyl-4-yl]amino]-1,1'-biphenyl (TPTE); phenylenediamine compounds such as N,N,N',N'-tetraphenyl-para-phenylenediamine, N,N,N',N'-tetra(para-tolyl)-para-phenylenediamine, and N,N,N',N'-tetra(meta-tolyl)-meta-phenylenediamine (PDA); carbazole compounds such as carbazole, N-isopropylcarbazole, and N-phenylcarbazole; stilbene compounds such as stilbene and 4-di-para-tolylaminostilbene; oxazole compounds such as OxZ; triphenylmethane, 4,4',4"-tris(N-3-methyl triphenylmethane compounds such as 1-phenyl-3-(para-dimethylaminophenyl)pyrazoline; benzine (cyclohexadiene) compounds; triazole compounds such as triazole; imidazole compounds such as imidazole; oxadiazole compounds such as 1,3,4-oxadiazole and 2,5-di(4-dimethylaminophenyl)-1,3,4-oxadiazole; anthracene compounds such as anthracene and 9-(4-diethylaminostyryl)anthracene; fluorenone compounds such as fluorenone, 2,4,7-trinitro-9-fluorenone, and 2,7-bis(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone; and anilines such as polyaniline. These include compounds based on phthalocyanine, silane compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo-(3,4-c)pyrrolopyrrole, fluorene compounds such as fluorene, porphyrin compounds such as porphyrin and metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, metal or non-metallic phthalocyanine compounds such as phthalocyanine, copper phthalocyanine, tetra(t-butyl)copper phthalocyanine, and iron phthalocyanine, metal or non-metallic naphthalocyanine compounds such as copper naphthalocyanine, vanadyl naphthalocyanine, and monochlorogallium naphthalocyanine, and benzidine compounds such as N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine and N,N,N',N'-tetraphenylbenzidine, and the like. One or more of these compounds may be used. Among these, arylamine compounds such as TPTE are particularly preferred.

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

(Light Emitting Layer)
In the organic EL element 1 of the present embodiment, the material forming the light-emitting layer 6 may be a low molecular weight compound or a high molecular weight compound, or a mixture of these may be used. In the present invention, the low molecular weight material means a material that is not a high molecular weight material (polymer), and does not necessarily mean an organic compound with a low molecular weight.

Examples of polymeric materials for forming the light-emitting layer 6 include polyacetylene compounds such as trans-polyacetylene, cis-polyacetylene, poly(diphenylacetylene) (PDPA), and poly(alkyl, phenylacetylene) (PAPA); poly(para-phenylenevinylene) (PPV), poly(2,5-dialkoxy-para-phenylenevinylene) (RO-PPV), cyano-substituted-poly(para-phenylenevinylene) (CN-PPV), and poly(2 poly(2-methoxy,5-(2'-ethylhexoxy)-para-phenylenevinylene) (MEH-PPV) and other polyparaphenylenevinylene-based compounds; poly(3-alkylthiophene) (PAT) and poly(oxypropylene)triol (POPT) and other polythiophene-based compounds; poly(9,9-dialkylfluorene) (PDAF) and poly(dioctylfluorene) -alto-benzothiadiazole) (F8BT), α,ω-bis[N,N'-di(methylphenyl)aminophenyl]-poly[9,9-bis(2-ethylhexyl)fluorene-2,7-dyl] (PF2/6am4), poly(9,9-dioctyl-2,7-divinylenefluorenyl-ortho-co(anthracene-9,10-diyl), and other polyfluorene-based compounds; poly(para-phenylene) (PPP), poly(1,5-dialkoxy-para-phenylene) Examples of suitable compounds include polyparaphenylene compounds such as poly(N-vinylcarbazole) (PVK); polycarbazole compounds such as poly(methylphenylsilane) (PMPS), poly(naphthylphenylsilane) (PNPS), and poly(biphenylylphenylsilane) (PBPS); and boron compound-based polymer materials described in JP-A-2011-184430 and JP-A-2012-151148.

Examples of low molecular weight materials for forming the light emitting layer 6 include three-coordinate iridium complexes having 2,2'-bipyridine-4,4'-dicarboxylic acid as a ligand, such as factorys(2-phenylpyridine)iridium (Ir(ppy) ₃ ), 8-hydroxyquinoline aluminum (Alq ₃ ), tris(4-methyl-8-quinolinolato)aluminum(III) (Almq ₃ ), 8-hydroxyquinoline zinc (Znq ₂ ), (1,10-phenanthroline)-tris-(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dionate)europium(III) (Eu(TTA) _{3 ), and} the like. (phen)), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum (II) and other metal complexes; benzene-based compounds such as distyrylbenzene (DSB) and diaminodistyrylbenzene (DADSB), naphthalene-based compounds such as naphthalene and Nile Red, phenanthrene-based compounds such as phenanthrene, chrysene-based compounds such as chrysene and 6-nitrochrysene, perylene, N,N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-di-cal perylene compounds such as bis(9-dicarbazolyl)-2,2'-biphenyl (BPPC), coronene compounds such as coronene, anthracene compounds such as anthracene and bisstyrylanthracene, pyrene compounds such as pyrene, pyran compounds such as 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM), acridine compounds such as acridine, stilbene compounds such as stilbene, 4,4'-bis[9-dicarbazolyl]-2,2'-biphenyl (CBP), 4,4'-bis(9-ethyl-3-carbazolyl)-2,2'-biphenyl (CBP), carbazole compounds such as 2,5-dibenzoxazolethiophene; thiophene compounds such as 2,5-dibenzoxazolethiophene; benzoxazole compounds such as benzoxazole; benzimidazole compounds such as benzimidazole; benzothiazole compounds such as 2,2'-(para-phenylenedivinylene)-bisbenzothiazole; butadiene compounds such as bistyryl(1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene; naphthalimide compounds such as naphthalimide; Examples of the compounds include mide compounds, coumarin compounds such as coumarin, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, cyclopentadiene compounds such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP), quinacridone compounds such as quinacridone and quinacridone red, pyridine compounds such as pyrrolopyridine and thiadiazolopyridine, spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene, metal or non-metal phthalocyanine compounds such as phthalocyanine (H ₂ Pc) and copper phthalocyanine, and boron compound materials described in JP-A-2009-155325 and JP-A-5660371. One or more of these compounds can be used. Quantum dots and perovskite materials can also be used as the light-emitting layer.

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

(Electron Transport Layer)
As the material for the electron transport layer 7, a wide variety of known materials capable of transporting electrons can be used. Specifically, phosphine oxide derivatives such as phenyl-dipyrenylphosphine oxide (POPy ₂ ), pyridine derivatives such as tris-1,3,5-(3'-(pyridin-3"-yl)phenyl)benzene (TmPhPyB), quinoline derivatives such as (2-(3-(9-carbazolyl)phenyl)quinoline (mCQ)), pyrimidine derivatives such as 2-phenyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT), 2,4,6-tris(m-pyridin-3-yl-phenyl)pyrimidine (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT), triazine derivatives such as 3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), triazole derivatives such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), imidazole derivatives such as 2,2',2"-(1,3,5-benzotriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic ring tetracarboxylic anhydrides such as naphthalene and perylene, bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ) ₂ ), various metal complexes represented by tris(8-hydroxyquinolinato)aluminum (Alq ₃ ), and the like; organosilane derivatives represented by silole derivatives such as 2,5-bis(6'-(2',2"-bipyridyl-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy); and boron-containing compounds described in JP-A-2013-239691, WO 2014/133141, JP-A-2016-172728, JP-A-2016-199507, and JP-A-2016-199508, and one or more of these can be used.

The average thickness of the electron transport layer 7 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 20 to 100 nm.
The average thickness of the electron transport layer 7 can be measured by a stylus step gauge or spectroscopic ellipsometry.

(Electron Injection Layer)
The material used for the electron injection layer 8 is selected from the viewpoints of the work function of the cathode 9 and the LUMO level of the electron transport layer 7. When the electron transport layer 7 is not provided, the material is selected in consideration of the LUMO level of the material used for the light emitting layer 6. The material for the electron injection layer 8 may be an organic compound or an inorganic compound. When the electron injection layer 8 is made of an inorganic compound, for example, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, cesium carbonate, etc., in addition to alkali metals and alkaline earth metals, can be used. When the electron injection layer 8 is made of an organic compound, for example, 8-quinolinolatolithium (Liq) can be used.

The average thickness of the electron injection layer 8 can be from 1 nm to several μm, but in order to obtain an organic EL element that can be driven at a low voltage, it is preferably 1 to 1000 nm, and more preferably 2 to 100 nm. The average thickness of the electron injection layer 8 can be measured by a stylus step gauge or spectroscopic ellipsometry.

(Formation method)
The organic EL element 1 shown in FIG. 1 can be manufactured by forming an anode 3, a hole injection layer 4, a hole transport layer 5, a light emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 in this order on a substrate 2. The method of forming each layer of the anode 3, the hole injection layer 4, the hole transport layer 5, the light emitting layer 6, the electron transport layer 7, the electron injection layer 8, and the cathode 9 is not particularly limited, and each layer can be formed by appropriately using various conventionally known forming methods according to the characteristics of the material used for each layer. As a method of forming each layer, a chemical vapor deposition method (CVD) such as plasma CVD, thermal CVD, and laser CVD, which is a gas phase film formation method, a dry plating method such as vacuum deposition, sputtering, and ion plating, a thermal spraying method, a wet plating method such as electrolytic plating, immersion plating, and electroless plating, which is a liquid phase film formation method, a sol-gel method, a MOD method, a spray pyrolysis method, a doctor blade method using a fine particle dispersion, a spin coating method, an inkjet method, a screen printing method, and the like can be used. It is preferable to select these methods depending on the characteristics of the material of each layer, and the manufacturing method may differ for each layer.

The organic EL element 1 of this embodiment can change the emitted light color by appropriately selecting the material of the light-emitting layer 6, and can also obtain the desired emitted light color by using a color filter or the like in combination. For this reason, the organic EL element of the present invention can be suitably used in display devices and lighting devices.

(Other examples)
The organic EL element of the present invention is not limited to the organic EL element described in the above-mentioned embodiment.
Specifically, in the above-described embodiment, the organic EL element 1 having a forward structure in which the anode 3 is disposed between the substrate 2 and the light-emitting layer 6 has been described as an example, but the organic EL element of the present invention may have an inverted structure in which the cathode is disposed between the substrate and the light-emitting layer.

In the organic EL element of the present invention, the hole transport layer, the electron transport layer and the electron injection layer may be formed as necessary, and may not be provided.
In addition, each of the anode, hole injection layer, hole transport layer, light emitting layer, electron transport layer, electron injection layer, and cathode may be formed as a single layer or may be formed as two or more layers.
The organic EL device of the present invention may have other layers between the anode, hole injection layer, hole transport layer, light emitting layer, electron transport layer, electron injection layer, and cathode. Specifically, the organic EL device may have an electron blocking layer, etc., if necessary, for the purpose of further improving the properties of the organic EL device.

[Display Device]
The display device of the present invention is characterized by comprising the organic electroluminescence element described above. The display device of the present invention has a low driving voltage and excellent driving stability because it comprises the organic EL element described above, which has a low driving voltage and excellent driving stability. The display device of the present invention can comprise, in addition to the organic electroluminescence element described above, other components that are generally used in display devices.

[Lighting equipment]
The lighting device of the present invention is characterized by comprising the organic electroluminescence element described above. The lighting device of the present invention has a low driving voltage and excellent driving stability because it comprises the organic EL element described above, which has a low driving voltage and excellent driving stability. The lighting device of the present invention can comprise other components commonly used in lighting devices in addition to the organic electroluminescence element described above.

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

<NMR measurement method>
The spectrometer used was an AL-Series spectrometer, and the probe was a TH5ATFG2 probe.

<Method for synthesizing compound (DF4CA-TT) represented by structural formula (3)>
Bistrimethylstannylbithiophene (1.2 g, 2.57 mmol, 1.0 eq.), methyl 4-bromo-2,3,5,6-tetrafluorobenzoate (1.85 g, 6.44 mmol, 2.5 eq.), (Ph ₃ P) ₄ Pd (89 mg, 0.773 mmol, 0.03 eq.), and deoxygenated anhydrous toluene (25 mL) were added to a 100 mL reactor. The solution was heated to 110° C. and stirred for 18 hours. The suspension was allowed to cool, and hexane (20 mL) was added to separate the precipitated solid. The filter bed was washed with ethanol and dried at 60° C. under high vacuum to obtain a beige powder (1.09 g). Chlorobenzene (350 mL) was added to this, heated to 130°C, scavenger (Kyoward 1000) (1.1 g) was added and stirred, the suspension was filtered through Celite so that the temperature did not fall below 100°C, the filter bed was washed with heated chlorobenzene (50 mL), and the filter part was allowed to cool. The filter bed was dispersed and washed with chlorobenzene (80 mL) heated to 130°C, Galleon Earth V2R (2 g) was added, stirred for 5 minutes, and filtered through Celite when the internal temperature was 80°C or higher. The filtrate was combined and left to stand for 16 hours, the precipitated solid was filtered, and the filter bed was washed successively with ethyl acetate and ethanol. The mixture was dried under high vacuum at 80°C to obtain an orange powder (0.78 g). The obtained powder was confirmed to be a compound represented by the following structural formula (5) by ¹⁹ F-NMR and ¹ H-NMR.
Next, a compound represented by structural formula (5) (0.76 g, 0.923 mmol, 1.0 eq.), 4N NaOH aqueous solution (7.06 mL, 28.2 mmol, 20 eq.), and THF (156 mL) were added to a 500 mL reactor. The mixture was stirred at a bath temperature of 75 ° C. for 36 hours. After cooling, 2N HCl aqueous solution (15 mL) was slowly dropped into the yellow suspension to obtain an acidic yellow solution. Distilled water (200 mL) was added to the solution, and the precipitated solid was filtered through a membrane, and the filter bed was washed with distilled water until the washing liquid became neutral, after which it was washed with a small amount of methanol and dried at 60 ° C. under high vacuum to obtain an orange powder (0.62 g). This solid was washed successively with heated acetonitrile, ethyl acetate, and acetone, and further washed by heating and dispersion with THF, and heated at 90° C. under high vacuum to obtain a compound (DF4CA-TT) (0.5 g, 0.953 mmol) represented by the following structural formula (3). The purity measured by HPLC was 90.1%. The synthesis scheme is as follows. The synthesized product was confirmed by ¹⁹ F-NMR and ¹ H-NMR (FIGS. 2 and 3).

<Method for synthesizing compound (F6-DCN) represented by structural formula (4)>
Octafluoronaphthalene (5.0 g, 18.3 mmol, 1.0 eq.) and anhydrous diethyl ether (50 mL) were added to a 200 mL reactor under an argon atmosphere. Methyllithium (1.1 mol/L Et ₂ O solution) (35.1 mL, 38.6 mmol, 2.1 eq.) was added to this solution over 15 minutes in a water bath, and the solution was stirred for 1 hour. The cooling bath was then removed and the solution was stirred at room temperature for 14 hours. The solution was quenched with 3% aqueous ammonium chloride solution (50 mL), and the organic layer and aqueous layer were separated. The aqueous layer was extracted with hexane/ethyl acetate = 1/1 (100 mL x 2), and the organic layer was combined, washed with city water and saturated saline, dried, and concentrated to obtain a light yellow solid (6.92 g). This was purified by column chromatography (SiO ₂ = 55 g, heated heptane only) to obtain a colorless solid compound (4.35 g, 16.4 mmol, 89%) represented by the following structural formula (6), which was analyzed by ¹⁹ F-NMR and ¹ H-NMR and found to be a mixture of 1,6- and 1,7-substituted compounds.
Next, a compound represented by structural formula (6) (4.35 g, 16.5 mmol, 1.0 eq.), NBS (8.79 g, 49.4 mmol, 3.0 eq.), BPO (1.06 g, 3.29 mmol, 0.2 eq.), and carbon tetrachloride (60 mL) were added to a 100 mL reactor. The suspension was heated to 75° C. and stirred at the same temperature for 18 hours. After cooling, the suspension was poured into city water (100 mL) and chloroform (100 mL) was added to separate into two layers. The aqueous layer was extracted with chloroform (50 mL), and the organic layer was combined and washed with city water and saturated saline, dried over sodium sulfate, and concentrated to obtain a brown solid (8.9 g). This was purified using a column (SiO ₂ =100 g, heptane/chloroform=1/1) to obtain a colorless solid (5.76 g, 13.6 mmol, 82%). Next, this colorless solid (3.7 g, 8.77 mmol, 1.0 eq.), sodium acetate (1.8 g, 21.9 mmol, 2.5 eq.), 18-crown 6-ether (0.463 g, 1.75 mmol, 0.2 eq.), and anhydrous acetonitrile (40 mL) were added to a 100 mL reactor. The bath temperature of this suspension was raised to 80° C., and the suspension was stirred at the same temperature for 12 hours. After cooling, the suspension was concentrated, and city water (30 mL) and ethyl acetate (30 mL) were added to the residue, and the mixture was separated into two layers. The aqueous layer was extracted with ethyl acetate (25 mL), and the organic layer was combined, washed with city water and saturated saline, dried, and then concentrated to obtain a reddish-brown powder (3.27 g). This was purified using a column (SiO ₂ =120 g, heptane/ethyl acetate = 4/1 → 3/1) to obtain a colorless solid compound represented by the following structural formula (7) (2.29 g, 6.02 mmol, 68%, mixture of 1,6-substituted and 1,7-substituted compounds).
A compound represented by the structural formula (7) (2.29 g, 6.02 mmol, 1 eq.), THF (23 mL), and 4N-NaOH aqueous solution (6 mL, 24.1 mmol, 4.0 eq.) were added to a 100 mL reactor, and the mixture was stirred at a bath temperature of 60° C. for 6 hours. After cooling, a 10% ammonium chloride aqueous solution (20 mL) and ethyl acetate (50 mL) were added to the solution to separate it into two layers. The aqueous layer was extracted with ethyl acetate (25 mL), and the organic layer was combined and washed with city water and saturated saline in that order, dried, and concentrated to obtain a reddish-black brown powder (2.41 g). This was purified by column purification (NH-SiO ₂ = 50 g, heptane/ethyl acetate = 1/1 → 1/2) to obtain a colorless solid (1.19 g, 4.01 mmol, 66%). Next, this solid (1.19 g, 4.02 mmol, 1.0 eq.) and acetone (30 mL) were added to a 100 mL reactor. Jones reagent was added dropwise to this suspension until the content turned reddish brown (ca. 8 g, excess). After stirring this for 2 hours at room temperature, 2-propanol was added until the content turned pale yellow, and the mixture was stirred at the same temperature for 2 hours. City water (80 mL) and diethyl ether (80 mL) were added to this, and the mixture was separated into two layers. The aqueous layer was extracted with diethyl ether (50 mL), and the organic layer was combined, washed with city water and saturated saline, dried, and concentrated to obtain a pale yellow powder (1.36 g). This powder was dissolved by heating in acetonitrile (20 mL), the insoluble solid was filtered through a membrane while still hot, the filtered solution was concentrated to half its volume, chloroform (10 mL) was added, the mixture was stirred, the precipitated solid was filtered, the filtrate was concentrated, acetonitrile (5 mL) was added to the residue, the mixture was heated and stirred, the mixture was allowed to cool, and then filtered. The filter bed was dispersed and washed with acetone, and dried at 60° C. for 3 hours under high vacuum to obtain a compound (F6-DCN) (0.52 g, 1.60 mmol) represented by the following structural formula (4). The purity measured by HPLC was 88.6%. The synthesis scheme is as follows. The synthesized product was also confirmed by ¹⁹ F-NMR and ¹ H-NMR (FIGS. 4 and 5).

Example 1
<Manufacture of Organic EL Element>
Organic EL element 1 was produced by the following method.
As the substrate 2, a commercially available transparent glass substrate with an average thickness of 0.7 mm on which a patterned electrode (anode 3) made of ITO with a thickness of 150 nm was formed was prepared. Then, the substrate 2 having the anode 3 was ultrasonically cleaned in a weak alkaline cleaner, in acetone, and in isopropanol, and then UV ozone cleaning was performed for 20 minutes. Then, an annealing treatment was performed at 150° C. for 30 minutes in the atmosphere, and O ₂ plasma was irradiated for 5 minutes. Next, the substrate 2 was fixed to a substrate holder in a chamber of a vacuum deposition apparatus, and the pressure in the chamber of the vacuum deposition apparatus was reduced to a pressure of 2×10 ⁻⁵ Pa, and a hole injection layer 4, a hole transport layer 5, a light-emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 were successively formed by a vacuum deposition method using resistance heating.

First, a compound (DF4CA-TT) represented by the above structural formula (3) was used as a first material (dopant) and a compound (TPTE) represented by the following structural formula (8) was used as a second material (host) to perform co-evaporation to a thickness of 15 nm to form a hole injection layer 4 made of a mixture of the first material and the second material. At this time, the concentration of the first material was adjusted to 5 mass % of the entire hole injection layer 4.

Subsequently, a hole transport layer 5 having a thickness of 35 nm and made of a compound (α-NPD) represented by the following structural formula (9) was formed.

Subsequently, a compound (Zn(BTZ) ₂ ) represented by the following structural formula (10) was used as a host, and a compound (Ir(piq) ₃ ) represented by the following structural formula (11) was used as a dopant, and co-evaporated to a thickness of 30 nm to form an emitting layer 6. At this time, the doping concentration of Ir(piq) ₃ was set to 6 mass % relative to the entire emitting layer 6.

Next, on the substrate on which the light-emitting layer 6 had been formed, a compound (TmPPyTz) represented by the following structural formula (12) was formed to a thickness of 50 nm, and a compound (Liq) represented by the following structural formula (13) was formed to a thickness of 1.2 nm, to form an electron transport layer 7 and an electron injection layer 8, respectively.

Next, a cathode 9 made of aluminum and having a thickness of 100 nm was formed on the substrate on which the electron injection layer 8 had been formed.
The cathode 9 was formed using a stainless steel deposition mask so that the deposition surface would be in the shape of a strip having a width of 3 mm, and the light-emitting area of the fabricated organic EL element 1 was 9 ^mm2 .

Example 2
An organic EL element 1 of Example 2 was obtained in the same manner as in Example 1, except that the first material (dopant) of the hole injection layer 4 in Example 1 was changed to the compound represented by the above structural formula (4) (F6-DCN, first material).

Example 3
An organic EL element 1 of Example 3 was obtained in the same manner as in Example 1, except that in Example 1, a layer of the compound represented by the above structural formula (3) (DF4CA-TT, first material) was formed to a thickness of 1 nm on an anode 3 made of ITO, and a layer of the compound represented by the above structural formula (5) (TPTE, second material) was formed to a thickness of 15 nm thereon to form a laminated layer.

(Comparative Example 1)
An organic EL element 1 of Comparative Example 1 was obtained in the same manner as in Example 1, except that a film of the compound represented by the above structural formula (5) (TPTE, second material) was formed to a thickness of 15 nm on the anode 3 made of ITO in Example 1 to serve as the hole injection layer 4.

<Measurement of Light Emitting Characteristics of Organic EL Element>
A voltage was applied to the organic EL elements produced in Examples 1 to 3 and Comparative Example 1 using a Keithley 2400 Source Meter, and the luminance was measured using a Konica Minolta LS-100 to examine the relationship between the applied voltage and the luminance, and the change over time in the luminance under a constant current density when the initial luminance was 1000 nits. The results are shown in Figures 6 and 7.

<Results>
In all of Examples 1 to 3, organic EL elements having a lower driving voltage and a longer life than those in Comparative Example 1 were obtained.
In particular, in Examples 1 and 2 in which the hole injection layer 4 was formed as a mixed film of the first material and the second material, in addition to reducing the voltage, a lifespan that was more than twice as long was achieved, which is considered to be due to the effects of the acidic material in reducing the voltage and lengthening the lifespan.

The organic thin film of the present invention can be used in organic electroluminescence devices, display devices, lighting devices, etc.

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

Claims (10)

An organic thin film, characterized in that it is a single film containing a first material, which is a tetrafluorobenzoic acid derivative having a structure represented by the following general formula (1), and a second material that transports holes, or a laminated film of a film containing the first material and a film containing the second material.

(In general formula (1), R ¹ represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent or trivalent cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a sulfur atom. n is an integer from 2 to 6.) The organic thin film according to claim 1, wherein the first material is a tetrafluorobenzoic acid derivative in which n in the general formula (1) is 2 or 3. An organic electroluminescence element having a light-emitting layer between a cathode and an anode,
An organic electroluminescence element, comprising a layer between the anode and the light-emitting layer, the layer containing a first material which is a tetrafluorobenzoic acid derivative having a structure represented by the following general formula (1):

(In general formula (1), R ¹ represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent or trivalent cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a sulfur atom. n is an integer from 2 to 6.) The organic electroluminescence element according to claim 3, having a laminated film of a layer containing the first material and a layer containing a second material that transports holes between the anode and the light-emitting layer. a layer including the first material and a second material that transports holes between the anode and the light-emitting layer;
The organic electroluminescence device according to claim 3 , further comprising a layer containing the second material between the light emitting layer and the layer containing the first material and the second material. An organic thin film, characterized in that it is a single film containing a first material, which is a fluoronaphthalene dicarboxylic acid derivative having a structure represented by the following general formula (2), and a second material that transports holes, or a laminated film of a film containing the first material and a film containing the second material.

(In general formula (2), one of ^R2 and ^R3 is a carboxyl group, and the other is a fluorine group, a trifluoromethyl group, a cyano group, or a nitro group.) A material for an organic electroluminescence device, comprising a fluoronaphthalenedicarboxylic acid derivative having a structure represented by the following general formula (2):

(In general formula (2), one of ^R2 and ^R3 is a carboxyl group, and the other is a fluorine group, a trifluoromethyl group, a cyano group, or a nitro group.) An organic electroluminescence element having a light-emitting layer between a cathode and an anode,
10. An organic electroluminescence device comprising a layer comprising the material for an organic electroluminescence device according to claim 7 between said anode and said light-emitting layer. A display device comprising an organic electroluminescence element according to any one of claims 3 to 5 and 8. A lighting device comprising an organic electroluminescence element according to any one of claims 3 to 5 and 8.

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