JP7736057B2 - Charge transport ink composition - Google Patents

Description

The present invention relates to a charge transport ink composition.

Organic electroluminescence (hereinafter referred to as OLED) elements have attracted attention due to their various advantages, such as high contrast, energy savings, and flexibility, and are being put to practical use in fields such as displays and lighting. OLED elements use multiple functional thin films, one of which is the hole injection layer, which handles the exchange of charges between the anode and the hole transport layer or light-emitting layer, and plays an important role in achieving low-voltage operation and high brightness in OLED elements.

Manufacturing methods for organic EL elements can be broadly divided into dry processes, such as vapor deposition, and wet processes, such as spin coating and inkjet printing. When comparing the two processes from the perspective of increasing the area of elements, wet processes can more efficiently produce highly flat films over large areas than dry processes. Therefore, given the current demand for large-area manufacturing of organic EL elements, it is important to provide hole injection layers and other layers with excellent functionality that can be formed using wet processes.

One of the functions required for charge-transport thin films such as hole injection layers is high transparency in the visible light range. Because coloring charge-transport thin films can reduce the color purity and color reproducibility of organic EL elements, high transparency in the visible light range has become increasingly important in recent years.

In light of this, various studies have been conducted to achieve high transparency in the visible light region. Patent Document 1 discloses the formation of a charge-transporting thin film with high transparency in the visible light region by using a composition containing metal oxide nanoparticles.

On the other hand, charge-transporting thin films such as hole injection layers require not only excellent charge-transporting properties and high transparency in the visible light region, but also film flatness and ink composition stability. Non-Patent Document 1 shows that reducing the surface roughness of the film improves the characteristics of organic EL devices. Furthermore, charge-transporting inks are generally susceptible to the effects of oxygen and moisture, and there is concern that their performance may change due to oxidation or decomposition of compounds in the ink. Therefore, from the perspective of reliability, it is important that charge-transporting inks are stable when exposed to the atmosphere.

International Publication No. 2018/135582

Korean Journal of Chemical Engineering 2005, Vol. 22, p.643-647

With the recent development of the organic electroluminescence field, the performance requirements for functional thin films, including hole injection layers, which can be deposited using wet processes, are increasing.

The present invention has been made in consideration of the above background, and aims to provide a charge transport ink composition that has charge transport properties, produces a film with excellent flatness, and is stable when exposed to the atmosphere.

After extensive research, the inventors discovered that when an amine compound is added to a charge transport ink composition containing a charge transport material and an organic solvent, such as the composition disclosed in Patent Document 1, the use of an amine compound with a specific structure as the amine compound improves the flatness of the charge transport thin film and also improves the stability of the ink when exposed to the atmosphere, leading to the completion of the present invention.

That is, the present invention provides the following charge transporting ink composition.
1. A charge transporting ink composition comprising an amine compound represented by the following formula (P1), a charge transporting substance, and an organic solvent:
(In the formula, ^Rm represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms; ^Rn represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms; or ^Rm and ^Rn combine with each other to form an alkanetriyl group having 3 to 40 carbon atoms; and the ^alkylene group having 1 to 20 carbon atoms and alkenylene group having 2 to 20 carbon atoms represented by ^Rn and the alkanetriyl groups represented by Rm and ^Rn are limited to those which form a -CH2 _{- NH2} group when bonded to _-NH2 in formula (P1).)
2. The charge transporting ink composition of 1, wherein R ^m is an alkyl group having 1 to 20 carbon atoms, and R ⁿ is an alkylene group having 1 to 20 carbon atoms.
3. The charge transporting ink composition of 1 or 2, wherein the charge transporting substance is a polythiophene derivative containing a repeating unit represented by the following formula (1) or an amine adduct thereof:
(In the formula, ^R1 and ^R2 are each independently a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, a fluoroalkoxy group having 1 to 40 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, -O-[Z-O] _p - ^Re , or a sulfonic acid group; or ^R1 and ^R2 are bonded to form -O-Y-O-; Y is an alkylene group having 1 to 40 carbon atoms which may contain an ether bond and which may be substituted with a sulfonic acid group; Z is an alkylene group having 1 to 40 carbon atoms which may be substituted with a halogen atom; p is an integer of 1 or greater; ^{and Re} is a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms.)
4. The charge transport ink composition of 3, wherein R ¹ is a sulfonic acid group, and R ² is an alkoxy group having 1 to 40 carbon atoms or —O—[ZO] _p —R ^e , or R ¹ and R ² are bonded to form —O—Y—O—.
5. The charge transport ink composition of any one of 1 to 4, further comprising a dopant substance.
6. The charge transport ink composition of 5, wherein the dopant substance comprises at least one selected from the group consisting of arylsulfonic acid compounds and heteropolyacid compounds.
7. The charge transport ink composition of any one of 1 to 6, further comprising metal oxide nanoparticles.
8. A charge transporting thin film obtained from the charge transporting ink composition of any one of 1 to 7.
9. An electronic device having the charge transport thin film of 8.
10. The electronic device of 9, which is an organic electroluminescent device.
11. A method for improving the storage stability of a charge transport ink composition containing an amine compound, a charge transport substance, and an organic solvent, wherein the amine compound is an amine compound represented by the following formula (P1):
(In the formula, ^Rm represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms; ^Rn represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms; or ^Rm and ^Rn combine with each other to form an alkanetriyl group having 3 to 40 carbon atoms; and the ^alkylene group having 1 to 20 carbon atoms and alkenylene group having 2 to 20 carbon atoms represented by ^Rn and the alkanetriyl groups represented by Rm and ^Rn are limited to those which form a -CH2 _{- NH2} group when bonded to _-NH2 in formula (P1).)
12. A method for improving the flatness of a charge-transporting thin film obtained from a charge-transporting ink composition containing an amine compound, a charge-transporting substance, and an organic solvent, comprising:
A method for improving the flatness of a charge-transporting thin film, characterized in that an amine compound represented by the following formula (P1) is used as the amine compound:
(In the formula, ^Rm represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms; ^Rn represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms; or ^Rm and ^Rn combine with each other to form an alkanetriyl group having 3 to 40 carbon atoms; and the ^alkylene group having 1 to 20 carbon atoms and alkenylene group having 2 to 20 carbon atoms represented by ^Rn and the alkanetriyl groups represented by Rm and ^Rn are limited to those which form a -CH2 _{- NH2} group when bonded to _-NH2 in formula (P1).)

By using the charge-transporting ink composition of the present invention, a charge-transporting thin film with excellent flatness can be obtained. Furthermore, the charge-transporting ink composition of the present invention has excellent stability when exposed to the atmosphere. This charge-transporting thin film can be suitably used as a thin film for electronic devices, including organic EL devices.

1 shows absorption spectra of charge transporting ink compositions obtained in Examples and Comparative Examples.

The present invention will be described in more detail below.
The charge transporting ink composition of the present invention comprises an amine compound represented by the following formula (P1), a charge transporting substance, and an organic solvent. In the present invention, the "solid content" of the charge transporting ink composition of the present invention means the components other than the solvent contained in the composition. Furthermore, charge transportability is synonymous with conductivity and hole transportability. The charge transporting ink composition of the present invention may itself have charge transportability, or a solid film obtained using the composition may have charge transportability.

In the formula, ^Rm represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms; ^Rn represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms; or ^Rm and ^Rn combine with each other to form an alkanetriyl group having 3 to 40 carbon atoms; and the ^alkylene group having 1 to 20 carbon atoms and alkenylene group having 2 to 20 carbon atoms represented by ^Rn and the alkanetriyl groups represented by Rm and ^Rn are limited to those which form a -CH2 _{- NH2} group when bonded to _-NH2 in formula (P1).

Alkyl groups having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, and n-eicosanyl.

Examples of alkenyl groups having 2 to 20 carbon atoms include ethenyl, n-1-propenyl, n-2-propenyl, 1-methylethenyl, n-1-butenyl, n-2-butenyl, n-3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylethenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, n-1-pentenyl, n-1-decenyl, and n-1-eicosenyl.

Examples of aryl groups having 6 to 20 carbon atoms include phenyl, tolyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, and 9-phenanthryl groups, with phenyl, tolyl, and naphthyl groups being preferred.

Alkylene groups having 1 to 20 carbon atoms are divalent groups derived by removing two hydrogen atoms from an alkane, and may be linear, branched, or cyclic. Specific examples include methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, nonadecylene, and eicosanylene.

Alkenylene groups having 2 to 20 carbon atoms are divalent groups derived by removing two hydrogen atoms from an alkene, and examples include vinylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octenylene, nonenylene, decenylene, undecenylene, dodecenylene, tridecenylene, tetradecenylene, pentadecenylene, hexadecenylene, heptadecenylene, octadecenylene, nonadecenylene, and icocenylene.

Examples of arylene groups having 6 to 20 carbon atoms include groups in which one hydrogen atom has been removed from the specific examples of aryl groups having 6 to 12 carbon atoms listed above, such as phenylene groups, naphthylene groups, and biphenylylene groups.

Alkanetriyl groups having 3 to 40 carbon atoms are trivalent groups derived by removing a hydrogen atom from an alkane, and examples include groups represented by the following formula (K1):

(In the formula, ^nr represents an integer of 0 to 10, ^nc represents an integer of 1 to 10, and * represents a bond.)

The above R ^m is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, even more preferably an alkyl group having 1 to 8 carbon atoms, and even more preferably an alkyl group having 1 to 5 carbon atoms.

The above R ⁿ is preferably an alkylene group having 1 to 20 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, even more preferably an alkylene group having 1 to 8 carbon atoms, and even more preferably an alkylene group having 1 to 5 carbon atoms.

The above ^nr is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1, and the above ^nc is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1.
As for the combination of ^nr and ^nc , preferably, ^nr and ^nc are both 1 to 3, more preferably, ^nr and ^nc are both 1 to 2, even more preferably, ^nr is 1 to 2 and ^nc is 1, and even more preferably, ^nr and ^nc are both 1.

Specific examples of amine compounds represented by formula (P1) include, but are not limited to, the following compounds:

In the charge-transporting ink composition of the present invention, the content of the amine compound represented by formula (P1) is not particularly limited, but from the viewpoints of stability against exposure to the atmosphere and obtaining a thin film with good reproducibility and excellent flatness, the content is approximately 0.01 to 10 times by mass, preferably approximately 0.01 to 8 times by mass, more preferably approximately 0.01 to 6 times by mass, and even more preferably approximately 0.01 to 4 times by mass, relative to 1 unit of charge-transporting substance.

The charge transporting substance used in the present invention is not particularly limited, and can be appropriately selected from charge transporting compounds, charge transporting oligomers, charge transporting polymers, etc. used in the field of organic EL devices.
Specific examples thereof include various charge transporting compounds and charge transporting oligomers such as arylamine derivatives such as oligoaniline derivatives, N,N'-diarylbenzidine derivatives and N,N,N',N'-tetraarylbenzidine derivatives, thiophene derivatives such as oligothiophene derivatives, thienothiophene derivatives and thienobenzothiophene derivatives, and pyrrole derivatives such as oligopyrrole, and charge transporting polymers such as polythiophene derivatives, polyaniline derivatives and polypyrrole derivatives, with polythiophene derivatives being particularly preferred.
In a preferred embodiment, the charge transporting substance is a polythiophene derivative containing a repeating unit represented by formula (1) or an amine adduct thereof.

In the formula, R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, a fluoroalkoxy group having 1 to 40 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, -O-[Z-O] _p -R ^e , or a sulfonic acid group, or R ¹ and R ² are bonded to form -O-Y-O-, Y is an alkylene group having 1 to 40 carbon atoms which may contain an ether bond and which may be substituted with a sulfonic acid group, Z is an alkylene group having 1 to 40 carbon atoms which may be substituted with a halogen atom, p is an integer of 1 or more, and R ^e is a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

The alkyl group having 1 to 40 carbon atoms may be linear, branched, or cyclic. Specific examples include the alkyl groups having 1 to 20 carbon atoms listed above, as well as behenyl, triacontyl, and tetracontyl groups. In the present invention, alkyl groups having 1 to 18 carbon atoms are preferred, and alkyl groups having 1 to 8 carbon atoms are more preferred.

The fluoroalkyl group having 1 to 40 carbon atoms is not particularly limited as long as it is an alkyl group having 1 to 40 carbon atoms in which at least one hydrogen atom on the carbon atom has been substituted with a fluorine atom, but specific examples include a fluoromethyl group, a difluoromethyl group, a perfluoromethyl group, a 1-fluoroethyl group, a 2-fluoroethyl group, a 1,2-difluoroethyl group, a 1,1-difluoroethyl group, a 2,2-difluoroethyl group, a 1,1,2-trifluoroethyl group, a 1,2,2-trifluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, a 1,2,2,2-tetrafluoroethyl group, a perfluoroethyl group, a 1-fluoropropyl group, a 2-fluoropropyl group, a 3-fluoropropyl group, a 1,1-difluoropropyl group, a 1,2-difluoropropyl group, a 1,3-difluoropropyl group, a 2,2-difluoropropyl group, a 2,3-difluoropropyl group, a 3,3-difluoropropyl group, a 1,1,2-trifluoropropyl group, 1,1,3-trifluoropropyl group, 1,2,3-trifluoropropyl group, 1,3,3-trifluoropropyl group, 2,2,3-trifluoropropyl group, 2,3,3-trifluoropropyl group, 3,3,3-trifluoropropyl group, 1,1,2,2-tetrafluoropropyl group, 1,1,2,3-tetrafluoropropyl group, 1,2,2,3-tetrafluoropropyl group, 1,3,3,3-tetrafluoropropyl group, 2,2,3,3-tetrafluoropropyl group, 2 , 3,3,3-tetrafluoropropyl group, 1,1,2,2,3-pentafluoropropyl group, 1,2,2,3,3-pentafluoropropyl group, 1,1,3,3,3-pentafluoropropyl group, 1,2,3,3,3-pentafluoropropyl group, 2,2,3,3,3-pentafluoropropyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, perfluoroheptyl group, and perfluorooctyl group.

In the alkoxy group having 1 to 40 carbon atoms, the alkyl group may be straight-chain, branched-chain, or cyclic. Specific examples include methoxy, ethoxy, n-propoxy, i-propoxy, c-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentoxy, n-hexoxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, n-tridecyloxy, n-tetradecyloxy, n-pentadecyloxy, n-hexadecyloxy, n-heptadecyloxy, n-octadecyloxy, n-nonadecyloxy, and n-eicosanyloxy.

The fluoroalkoxy group having 1 to 40 carbon atoms is not particularly limited as long as it is an alkoxy group having 1 to 40 carbon atoms in which at least one hydrogen atom on the carbon atom is substituted with a fluorine atom. Specific examples include a fluoromethoxy group, a difluoromethoxy group, a perfluoromethoxy group, a 1-fluoroethoxy group, a 2-fluoroethoxy group, a 1,2-difluoroethoxy group, a 1,1-difluoroethoxy group, a 2,2-difluoroethoxy group, and a 1,1,2-trifluoroethoxy group. , 1,2,2-trifluoroethoxy group, 2,2,2-trifluoroethoxy group, 1,1,2,2-tetrafluoroethoxy group, 1,2,2,2-tetrafluoroethoxy group, perfluoroethoxy group, 1-fluoropropoxy group, 2-fluoropropoxy group, 3-fluoropropoxy group, 1,1-difluoropropoxy group, 1,2-difluoropropoxy group, 1,3-difluoropropoxy group, 2,2-difluoropropoxy group, 2,3-difluoropropoxy group, 3 ,3-difluoropropoxy group, 1,1,2-trifluoropropoxy group, 1,1,3-trifluoropropoxy group, 1,2,3-trifluoropropoxy group, 1,3,3-trifluoropropoxy group, 2,2,3-trifluoropropoxy group, 2,3,3-trifluoropropoxy group, 3,3,3-trifluoropropoxy group, 1,1,2,2-tetrafluoropropoxy group, 1,1,2,3-tetrafluoropropoxy group, 1,2,2,3-tetrafluoropropoxy group Examples thereof include a silyl group, a 1,3,3,3-tetrafluoropropoxy group, a 2,2,3,3-tetrafluoropropoxy group, a 2,3,3,3-tetrafluoropropoxy group, a 1,1,2,2,3-pentafluoropropoxy group, a 1,2,2,3,3-pentafluoropropoxy group, a 1,1,3,3,3-pentafluoropropoxy group, a 1,2,3,3,3-pentafluoropropoxy group, a 2,2,3,3,3-pentafluoropropoxy group, and a perfluoropropoxy group.

The alkylene group having 1 to 40 carbon atoms may be linear, branched, or cyclic, and specific examples include those exemplified above.

Examples of aryl groups having 6 to 20 carbon atoms include those exemplified above. In the present invention, phenyl, tolyl, and naphthyl groups are preferred.

Examples of aryloxy groups having 6 to 20 carbon atoms include phenoxy groups, anthracenoxy groups, naphthoxy groups, phenanthrenoxy groups, and fluorenoxy groups.

Halogen atoms include fluorine atoms, chlorine atoms, bromine atoms and iodine atoms.

In the above formula (1), R ¹ and R ² are each independently a hydrogen atom, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, —O[C(R ^a R ^b )—C(R ^c R ^d )—O] _p —R ^e , —OR ^f , or a sulfonic acid group, or are preferably —O—Y—O— formed by combining R ¹ and R ² .
R ^a to R ^d each independently represent a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and specific examples of these groups are the same as those listed above.
Among these, it is preferable that R ^a to R ^d are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group.
R ^e is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group, and is preferably a hydrogen atom, a methyl group, a propyl group, or a butyl group.
Furthermore, p is preferably 1 to 5, and more preferably 1, 2 or 3.

^Rf is a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms, but is preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group, and more preferably —CH ₂ CF ₃ .

In the present invention, R ¹ is preferably a hydrogen atom or a sulfonic acid group, more preferably a sulfonic acid group, and R ² is preferably an alkoxy group having 1 to 40 carbon atoms or —O—[Z—O] _p —R ^e , more preferably —O[C(R ^a R ^b )—C(R ^c R ^d )—O] _p —R ^e or —OR ^f , even more preferably —O[C(R ^a R ^b )—C(R ^{c R d} )—O] _p —R ^e , —O—CH ₂ CH _{2 —O} —CH ₂ CH ₂ —O—CH ₃ , —O—CH ₂ CH ₂ —O—CH ₂ CH ₂ —OH or —O—CH ₂ CH 2 —OH, or —O—Y—O— formed by R ¹ and R ² bonding together.

For example, the polythiophene derivative according to a preferred embodiment of the present invention includes a repeating unit in which R ¹ is a sulfonic acid group and R ² is other than a sulfonic acid group, or a repeating unit in which R ¹ and R ² are bonded to form —O—Y—O—.
Preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a sulfonic acid group and R ² is an alkoxy group having 1 to 40 carbon atoms or -O-[Z-O] _p -R ^e , or contains a repeating unit in which R ¹ and R ² are bonded to form -O-Y-O-.
More preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a sulfonic acid group and R ² is —O[C(R ^a R ^b )—C(R ^c R ^d )—O] _p —R ^e or —OR ^f .
Even more preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a sulfonic acid group and R ² is —O[C(R ^a R ^b )—C(R ^c R ^d )—O] _p —R ^e , or a repeating unit in which R ¹ and R ² are bonded to form —O—Y—O—.
More preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a sulfonic acid group and R ² is —O—CH ₂ CH ₂ —O—CH ₂ CH ₂ —O—CH ₃ , —O—CH ₂ CH ₂ —O—CH ₂ CH ₂ —OH, or —O—CH ₂ CH ₂ —OH, or contains a repeating unit in which R ¹ and R ² are bonded to each other to form groups represented by the following formulae (Y1) and (Y2):

Preferred specific examples of the above polythiophene derivatives include polythiophenes containing at least one repeating unit represented by the following formulas (1-1) to (1-5):

An example of a suitable structure of the polythiophene derivative is a polythiophene derivative having a structure represented by the following formula (1a): In the formula, the units may be bonded randomly or as a block polymer.

In the formula, a to d represent the molar ratio of each unit, and satisfy the following: 0≦a≦1, 0≦b≦1, 0<a+b≦1, 0≦c<1, 0≦d<1, a+b+c+d=1.

Furthermore, the polythiophene derivatives may be homopolymers or copolymers (including statistical, random, gradient, and block copolymers). Examples of polymers containing monomer A and monomer B include block copolymers such as AB diblock copolymers, A-B-A triblock copolymers, and (AB) _m -multiblock copolymers. Polythiophenes may also contain repeating units derived from other types of monomers, such as thienothiophene, selenophene, pyrrole, furan, tellurophene, aniline, arylamine, and arylene (e.g., phenylene, phenylenevinylene, and fluorene).

In the present invention, the content of the repeating unit represented by formula (1) in the polythiophene derivative is preferably more than 50 mol % of all repeating units contained in the polythiophene derivative, more preferably 80 mol % or more, even more preferably 90 mol % or more, even more preferably 95 mol % or more, and most preferably 100 mol %.

In the present invention, depending on the purity of the starting monomers used in the polymerization, the polymer formed may contain repeating units derived from impurities. In the present invention, the term "homopolymer" refers to a polymer containing repeating units derived from one type of monomer, but may also contain repeating units derived from impurities. In the present invention, the polythiophene derivative is preferably a polymer in which essentially all repeating units are repeating units represented by formula (1), and more preferably a polymer containing at least one of the repeating units represented by formulas (1-1) to (1-5).

In the present invention, when the polythiophene derivative contains a repeating unit having a sulfonic acid group, it is preferable to form an amine adduct in which an amine compound is added to at least a portion of the sulfonic acid groups contained in the polythiophene derivative, in order to further improve solubility and dispersibility in organic solvents.

Examples of amine compounds that can be used to form the amine adduct include methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, s-butylamine, t-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-ethylhexylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, and n-octadecylamine. monoalkylamine compounds such as amine, n-nonadecylamine, and n-eicosanylamine; primary amine compounds such as monoarylamine compounds such as aniline, tolylamine, 1-naphthylamine, 2-naphthylamine, 1-anthrylamine, 2-anthrylamine, 9-anthrylamine, 1-phenanthrylamine, 2-phenanthrylamine, 3-phenanthrylamine, 4-phenanthrylamine, and 9-phenanthrylamine; primary amine compounds such as N-ethylmethylamine, N-methyl-n-propylamine, N-methylisopropylamine, N-methyl-n-butylamine, N- Methyl-s-butylamine, N-methyl-t-butylamine, N-methylisobutylamine, diethylamine, N-ethyl-n-propylamine, N-ethylisopropylamine, N-ethyl-n-butylamine, N-ethyl-s-butylamine, N-ethyl-t-butylamine, dipropylamine, N-n-propylisopropylamine, N-n-propyl-n-butylamine, N-n-propyl-s-butylamine, diisopropylamine, N-n-butylisopropylamine, N-t-butylisopropylamine, di(n-butyl)amine, di(s-butyl)amine dialkylamine compounds such as amine, diisobutylamine, aziridine (ethyleneimine), 2-methylaziridine (propyleneimine), 2,2-dimethylaziridine, azetidine (trimethyleneimine), 2-methylazetidine, pyrrolidine, 2-methylpyrrolidine, 3-methylpyrrolidine, 2,5-dimethylpyrrolidine, piperidine, 2,6-dimethylpiperidine, 3,5-dimethylpiperidine, 2,2,6,6-tetramethylpiperidine, hexamethyleneimine, heptamethyleneimine, and octamethyleneimine; diphenylamine, N-phenyl-1-naphthylamine, diarylamine compounds such as N-phenyl-2-naphthylamine, 1,1'-dinaphthylamine, 2,2'-dinaphthylamine, 1,2'-dinaphthylamine, carbazole, 7H-benzo[c]carbazole, 11H-benzo[a]carbazole, 7H-dibenzo[c,g]carbazole, and 13H-dibenzo[a,i]carbazole; N-methylaniline, N-ethylaniline, N-n-propylaniline, N-isopropylaniline, N-n-butylaniline, N-s-butylaniline, N-isobutylaniline, N-methyl-1-naphthylamine, N-ethylaniline, N-isopropylaniline, N-n-butylaniline, N-isobutylaniline, N-methyl-1-naphthylamine, N-ethylaniline, N-isopropyl ... secondary amine compounds such as alkylarylamine compounds such as N-n-naphthylamine, N-n-propyl-1-naphthylamine, indoline, isoindoline, 1,2,3,4-tetrahydroquinoline, and 1,2,3,4-tetrahydroisoquinoline; N,N-dimethylethylamine, N,N-dimethyl-n-propylamine, N,N-dimethylisopropylamine, N,N-dimethyl-n-butylamine, N,N-dimethyl-s-butylamine, N,N-dimethyl-t-butylamine, N,N-dimethylisobutylamine, N,N-diethylmethylamine, N-methyldimethylamine; Trialkylamine compounds such as (n-propyl)amine, N-methyldiisopropylamine, N-methyldi(n-butyl)amine, N-methyldiisobutylamine, triethylamine, N,N-diethyl-n-butylamine, N,N-diisopropylethylamine, N,N-di(n-butyl)ethylamine, tri(n-propyl)amine, tri(i-propyl)amine, tri(n-butyl)amine, tri(i-butyl)amine, 1-methylacetidine, 1-methylpyrrolidine, and 1-methylpiperidine; triarylamine compounds such as triphenylamine; N-methyldi Examples of tertiary amine compounds include alkyldiarylamine compounds such as phenylamine, N-ethyldiphenylamine, 9-methylcarbazole, and 9-ethylcarbazole; and dialkylarylamine compounds such as N,N-diethylaniline, N,N-di(n-propyl)aniline, N,N-di(i-propyl)aniline, and N,N-di(n-butyl)aniline. However, taking into consideration the balance between the solubility of the amine adduct, the charge transport property of the resulting charge transport thin film, and the like, tertiary amine compounds are preferred, trialkylamine compounds are more preferred, and triethylamine is even more preferred.
The amine adduct can be obtained by adding the polythiophene derivative to the amine itself or a solution thereof and stirring thoroughly.

In the present invention, the above polythiophene derivative or its amine adduct may be treated with a reducing agent before use.
In polythiophene derivatives or their amine adducts, some of the repeating units constituting them may have an oxidized chemical structure called a "quinoid structure." The term "quinoid structure" is used in contrast to the term "benzenoid structure." The latter is a structure containing an aromatic ring, while the former refers to a structure in which a double bond within the aromatic ring moves outside the ring (resulting in the disappearance of the aromatic ring), forming two exocyclic double bonds conjugated with other double bonds remaining within the ring. Those skilled in the art can easily understand the relationship between these two structures from the relationship between the structures of benzoquinone and hydroquinone. Quinoid structures for repeating units of various conjugated polymers are well known to those skilled in the art. As an example, a quinoid structure corresponding to a repeating unit of a polythiophene derivative containing a repeating unit represented by the above formula (1) is shown in the following formula (1').

(wherein ^R1 and ^R2 are as defined in formula (1) above.)

This quinoid structure is formed by a process known as a doping reaction, in which a polythiophene derivative containing the repeating unit represented by formula (1) undergoes an oxidation reaction with a dopant. It forms part of structures known as "polaron structures" and "bipolaron structures," which impart charge transport properties to the polythiophene derivative. These structures are publicly known. The introduction of a "polaron structure" and/or a "bipolaron structure" is essential for the fabrication of organic EL devices. In fact, this is achieved by intentionally inducing the doping reaction described above during the baking process of a thin film formed from a charge transport ink composition during the fabrication of organic EL devices. The presence of a quinoid structure in the polythiophene derivative prior to the doping reaction is believed to be due to an unintended oxidation reaction equivalent to the doping reaction occurring during the polythiophene derivative's manufacturing process (particularly the sulfonation step therein).

There is a correlation between the amount of quinoid structures contained in the polythiophene derivative and the solubility and dispersibility of the polythiophene derivative in organic solvents; as the amount of quinoid structures increases, the solubility and dispersibility tend to decrease. Therefore, although the introduction of quinoid structures after a thin film is formed from the charge transport ink composition does not cause any problems, if an excessive amount of quinoid structures is introduced into the polythiophene derivative due to the unintended oxidation reaction described above, this may cause problems in the production of the charge transport ink composition. It is known that polythiophene derivatives vary in solubility and dispersibility in organic solvents, and one of the reasons for this is thought to be that the amount of quinoid structures introduced into the polythiophene due to the unintended oxidation reaction described above varies depending on the production conditions of each polythiophene derivative.
Therefore, when the polythiophene derivative is subjected to a reduction treatment using a reducing agent, even if an excessive amount of quinoid structures has been introduced into the polythiophene derivative, the quinoid structures are reduced by the reduction, and the solubility and dispersibility of the polythiophene derivative in organic solvents are improved, making it possible to stably produce an excellent charge-transporting ink composition that gives a thin film with excellent homogeneity.

The conditions for the reduction treatment are not particularly limited as long as they can reduce the quinoid structure and appropriately convert it into a non-oxidized structure, i.e., the benzenoid structure (for example, in the case of a polythiophene derivative containing a repeating unit represented by formula (1) above, the quinoid structure represented by formula (1') above is converted into the structure represented by formula (1) above). For example, this treatment can be carried out by simply contacting the polythiophene derivative or the amine adduct with a reducing agent in the presence or absence of a suitable solvent.
There are no particular limitations on the reducing agent as long as it can perform the reduction appropriately, but suitable examples include aqueous ammonia, hydrazine, and the like, which are readily available commercially.
The amount of the reducing agent cannot be generally specified because it varies depending on the amount of reducing agent used. However, the amount is usually 0.1 parts by mass or more per 100 parts by mass of the polythiophene derivative or amine adduct to be treated in order to ensure appropriate reduction, and 10 parts by mass or less in order to prevent excess reducing agent from remaining.

One specific example of a reduction treatment method involves stirring the polythiophene derivative or amine adduct in 28% aqueous ammonia at room temperature overnight. Reduction treatment under these relatively mild conditions significantly improves the solubility and dispersibility of the polythiophene derivative or amine adduct in organic solvents.

When an amine adduct of a polythiophene derivative is used in the charge transport ink composition of the present invention, the above-mentioned reduction treatment may be carried out either before or after the formation of the amine adduct.

Note that this reduction treatment changes the solubility or dispersibility of the polythiophene derivative or its amine adduct in the solvent, and as a result, a polythiophene derivative or its amine adduct that was not dissolved in the reaction system at the start of the treatment may become dissolved by the end of the treatment. In such cases, the polythiophene derivative or its amine adduct can be recovered by adding an organic solvent that is incompatible with the polythiophene derivative or its amine adduct (e.g., acetone or isopropyl alcohol in the case of sulfonated polythiophene) to the reaction system to cause a precipitate of the polythiophene derivative or its amine adduct, and then filtering the precipitate.

The weight-average molecular weight of a polythiophene derivative containing a repeating unit represented by formula (1) or its amine adduct is preferably about 1,000 to 1,000,000, more preferably about 5,000 to 100,000, and even more preferably about 10,000 to about 50,000. By setting the weight-average molecular weight at or above the lower limit, good conductivity can be reproducibly obtained, while by setting it at or below the upper limit, solubility in solvents is improved. The weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography.

The polythiophene derivative or amine adduct thereof contained in the charge transport ink composition of the present invention may be a polythiophene derivative containing a repeating unit represented by formula (1) or an amine adduct thereof, or two or more types thereof may be used.
The polythiophene derivative containing the repeating unit represented by formula (1) may be a commercially available product or may be one polymerized by a known method using a thiophene derivative or the like as a starting material, but in either case, it is preferable to use one purified by a method such as reprecipitation or ion exchange. The use of a purified product can further improve the properties of an organic EL device having a thin film obtained from the charge transport ink composition of the present invention.

Sulfonation of conjugated polymers and sulfonated conjugated polymers (including sulfonated polythiophenes) are described in U.S. Patent No. 8,017,241 to Seshadri et al. Sulfonated polythiophenes are described in WO 2008/073149 and WO 2016/171935.

In the present invention, at least a portion of the polythiophene derivative or its amine adduct containing a repeating unit represented by formula (1) contained in the charge transport ink composition is dissolved in an organic solvent.

In the present invention, a polythiophene derivative containing a repeating unit represented by formula (1) or its amine adduct may be used in combination with a charge transporting substance consisting of another charge transporting compound, but it is preferable that only a polythiophene derivative containing a repeating unit represented by formula (1) or its amine adduct is used.

The content of the charge transport material in the charge transport ink composition of the present invention is typically determined appropriately within the range of 0.05 to 40% by mass, preferably 0.1 to 35% by mass, of the solid content, taking into consideration the desired film thickness and viscosity of the ink composition, etc.

The charge transporting ink composition of the present invention contains an organic solvent. There are no particular limitations on the organic solvent as long as it disperses or dissolves solids. Specific examples include aromatic or halogenated aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and chlorobenzene; aliphatic hydrocarbons such as n-heptane, n-hexane, and cyclohexane; ether solvents such as diethyl ether, tetrahydrofuran, dioxane, and 1,2-dimethoxyethane; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethyl acetate, n-hexyl acetate, ethyl lactate, γ-butyrolactone, and propylene. Ester-based solvents such as carbonate and diisopropyl malonate; halogenated hydrocarbon solvents such as methylene chloride, dichloromethane, 1,2-dichloroethane and chloroform; amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone; alcohol-based solvents such as methanol, ethanol, isopropanol, n-propanol, cyclohexanol, diacetone alcohol and 2-benzooxyethanol; ethylene glycol The solvent may be appropriately selected from glycol ether solvents such as glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol diglycidyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate; and glycol solvents such as ethylene glycol, propylene glycol, hexylene glycol, 1,3-octylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, and 1,4-butanediol.
In the present invention, among these, amide-based solvents, glycol ether-based solvents and glycol-based solvents are preferred, and 1,3-dimethyl-2-imidazolidinone, dipropylene glycol and dipropylene glycol monomethyl ether are more preferred.
These organic solvents can be used either alone or in combination of two or more.

The charge transport ink composition of the present invention may contain water as a solvent, but from the perspective of reproducibly obtaining organic EL elements with excellent durability, the water content is preferably 10% by mass or less of the total solvent, more preferably 5% by mass or less, and it is optimal to use only organic solvent as the solvent. Note that "organic solvent only" in this case means that only organic solvent is used as the solvent, and does not deny the presence of trace amounts of "water" contained in the organic solvent or solids used.

The charge transport ink composition of the present invention may contain metal oxide nanoparticles. Nanoparticles refer to fine particles having an average primary particle diameter of the order of nanometers (typically 500 nm or less). Metal oxide nanoparticles refer to metal oxides formed into nanoparticles.
The primary particle size of the metal oxide nanoparticles used in the present invention is not particularly limited as long as it is nano-sized, but in consideration of obtaining a thin film with good reproducibility and excellent flatness, it is preferably 2 to 150 nm, more preferably 3 to 100 nm, and even more preferably 5 to 50 nm. The particle size is measured using a nitrogen adsorption isotherm by the BET method.

The metals constituting the metal oxide nanoparticles used in the present invention include metals in the usual sense as well as semimetals.
The metal in the ordinary sense is not particularly limited, but it is preferable to use one or more selected from the group consisting of tin (Sn), titanium (Ti), aluminum (Al), zirconium (Zr), zinc (Zn), niobium (Nb), tantalum (Ta), and tungsten (W).
On the other hand, a metalloid refers to an element whose chemical and/or physical properties are intermediate between those of a metal and a nonmetal. Although a universal definition of a metalloid has not been established, in the present invention, a total of six elements, namely, boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te), are defined as metalloids. These metalloids may be used alone or in combination with two or more of them, or may be used in combination with metals in the usual sense.

The metal oxide nanoparticles used in the present invention preferably contain oxides of one or more metals selected from boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), tin (Sn), titanium (Ti), aluminum (Al), zirconium (Zr), zinc (Zn), niobium (Nb), tantalum (Ta), and tungsten (W). When two or more metals are combined, the metal oxide may be a mixture of oxides of individual metals or a composite oxide containing multiple metals.

Specific examples of metal oxides include _B2O3 , _B2O , _SiO2 , SiO, _GeO2 , GeO, _As2O4 , _As2O3 , _As2O5 , _Sb2O3 , _Sb2O5 , _TeO2 , _SnO2 , _ZrO2 , _{Al2O3 , and ZnO, but B2O3, B2O , SiO2 , SiO , GeO2 , GeO , As2O4} , _As2O3 , _As2O5 , _SnO2 , _{SnO , Sb2O3} , _TeO2 , and mixtures thereof are preferred, and _{SiO2 is more preferred .}

The metal oxide nanoparticles contained in the charge transport ink composition of the present invention may be of one type alone or two or more types.

It is preferable that the metal oxide nanoparticles contained in the charge transport ink composition of the present invention are uniformly dispersed throughout the composition.

The metal oxide nanoparticles may contain one or more organic capping groups. These organic capping groups may be reactive or non-reactive. Examples of reactive organic capping groups include organic capping groups that can be crosslinked by ultraviolet light or a radical initiator.

In the charge transport ink composition of the present invention, the content of metal oxide nanoparticles is not particularly limited, but from the viewpoint of suppressing particle aggregation in the charge transport ink composition and obtaining a thin film with excellent reproducibility and flatness, the content is preferably 40 to 95% by mass, more preferably 50 to 95% by mass, and most preferably 60 to 90% by mass of the solid content of the charge transport ink composition.

In particular, in the present invention, by using a metal oxide nanoparticle sol in which metal oxide nanoparticles are dispersed, a composition in which metal oxide nanoparticles are uniformly dispersed can be prepared with good reproducibility.
In other words, rather than mixing and dispersing metal oxide nanoparticles themselves in a solvent together with a charge transporting substance, etc., a metal oxide nanoparticle sol is prepared in advance and then mixed with a mixture in which a charge transporting substance, etc. is dissolved or dispersed in a solvent, thereby enabling the reproducible production of a charge transporting ink composition in which metal oxide nanoparticles are uniformly dispersed.
Such a metal oxide nanoparticle sol may be a commercially available product, or may be prepared by a known method using a solvent and metal oxide nanoparticles that may be contained in the charge transport ink composition of the present invention.

In particular, when preparing the charge transporting ink composition of the present invention, it is preferable to use a silica sol in which SiO ₂ nanoparticles are dispersed in a dispersion medium.
The silica sol is not particularly limited, and can be appropriately selected from known silica sols.
Commercially available silica sols are typically in the form of dispersions, including _SiO2 nanoparticles dispersed in various solvents, such as water, methanol, methyl ethyl ketone, methyl isobutyl ketone, N,N-dimethylacetamide, ethylene glycol, isopropanol, methanol, ethylene glycol monopropyl ether, cyclohexanone, ethyl acetate, toluene, and propylene glycol monomethyl ether acetate.
In particular, in the present invention, silica sols in which the dispersion medium is an alcohol-based solvent, a glycol-based solvent, or water are preferred, and silica sols in which the dispersion medium is an alcohol-based solvent or a glycol-based solvent are more preferred. As the alcohol-based solvent or glycol-based solvent, water-soluble alcohols or glycol-based solvents are preferred, and methanol, 2-propanol, and ethylene glycol are more preferred.

Specific examples of commercially available silica sols include water-dispersed silica sols such as Snowtex (registered trademark) ST-O, ST-OS, ST-O-40, and ST-OL manufactured by Nissan Chemical Industries, Ltd., and Silicadol 20, 30, and 40 manufactured by Nippon Chemical Industries, Ltd.; and organosilica sols such as methanol silica sol, MA-ST-M, MA-ST-L, IPA-ST, IPA-ST-L, IPA-ST-ZL, and EG-ST manufactured by Nissan Chemical Industries, Ltd., but are not limited to these.

The concentration of _SiO2 nanoparticles in silica sol is usually about 5 to 50 mass %. However, if the concentration of _SiO2 nanoparticles is high, when the silica sol is mixed with a mixture in which a charge transporting substance or the like is dissolved or dispersed in a solvent, the _SiO2 nanoparticles may aggregate depending on the type of solvent contained in the mixture; therefore, care must be taken when preparing the composition.

The charge transporting ink composition of the present invention contains an amine compound represented by formula (P1), a charge transporting substance, and an organic solvent, and may contain a dopant substance as necessary to improve charge transportability, etc. The dopant substance is not particularly limited as long as it is dispersible or soluble in at least one solvent used in the charge transporting ink composition, and both inorganic and organic dopant substances can be used.
When the charge transport ink composition of the present invention contains a dopant substance, the content thereof is appropriately set taking into consideration the type and amount of the charge transport substance, etc., but is usually in the range of 0.1 to 20.0 parts by mass per 1 part of the charge transport substance.

Inorganic dopant substances include inorganic acids such as hydrogen chloride, sulfuric acid, nitric acid, and phosphoric acid; metal halides such as aluminum chloride (III) (AlCl ₃ ), titanium tetrachloride (IV) (TiCl ₄ ), boron tribromide (BBr ₃ ), boron trifluoride ether complex (BF ₃ .OEt ₂ ), iron chloride (III) (FeCl ₃ ), copper chloride (II) (CuCl ₂ ), antimony pentachloride (V) (SbCl ₅ ), antimony pentafluoride (V) (SbF ₅ ), arsenic pentafluoride (V) (AsF ₅ ), phosphorus pentafluoride (PF ₅ ), and tris(4-bromophenyl)aluminum hexachloroantimonate (TBPAH); and metal halides such as Cl ₂ , Br ₂ , I ₂ , ICl, ICl ₃ , IBr, and IF. ₄ and the like; heteropolyacids such as phosphomolybdic acid and phosphotungstic acid;

In addition, examples of organic dopant substances include tetracyanoquinodimethanes such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane; tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), tetrachloro-7,7,8,8-tetracyanoquinodimethane, 2-fluoro-7,7,8,8-tetracyanoquinodimethane, 2-chloro-7,7,8,8-tetracyanoquinodimethane, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane; halotetracyanoquinodimethanes (haloTCNQs) such as quinodimethane and 2,5-dichloro-7,7,8,8-tetracyanoquinodimethane; benzoquinone derivatives such as tetrachloro-1,4-benzoquinone (chloranil) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ); benzenesulfonic acid, tosylic acid, p-styrenesulfonic acid, 2-naphthalenesulfonic acid, 4-hydroxybenzenesulfonic acid, 5-sulfosalicylic acid, p-dodecylbenzenesulfonic acid, dihexylbenzenesulfonic acid, 2,5-dihe xylbenzenesulfonic acid, dibutylnaphthalenesulfonic acid, 6,7-dibutyl-2-naphthalenesulfonic acid, dodecylnaphthalenesulfonic acid, 3-dodecyl-2-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, 4-hexyl-1-naphthalenesulfonic acid, octylnaphthalenesulfonic acid, 2-octyl-1-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, 7-hexyl-1-naphthalenesulfonic acid, 6-hexyl-2-naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, 2,7-dinonyl-4-naphthalenesulfonic acid Examples of the sulfonic acid include aryl sulfonic acid compounds such as phthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, 2,7-dinonyl-4,5-naphthalenedisulfonic acid, 1,4-benzodioxanedisulfonic acid derivatives described in WO 2005/000832, arylsulfonic acid derivatives described in WO 2006/025342, and dinonylnaphthalenesulfonic acid derivatives described in JP 2005-108828 A; aromatic sulfone compounds such as polystyrenesulfonic acid; and non-aromatic sulfone compounds such as 10-camphorsulfonic acid.
These inorganic and organic dopant substances may be used alone or in combination of two or more.

Among these dopant substances, arylsulfonic acid compounds are preferred in the present invention, and examples of preferred arylsulfonic acid compounds include arylsulfonic acid compounds represented by formula (H1) or (H2).

A ¹ represents O or S, with O being preferred.
^A2 represents a naphthalene ring or an anthracene ring, with a naphthalene ring being preferred.
^A3 represents a divalent to tetravalent perfluorobiphenyl group, s represents the number of bonds between ^A1 and ^A3 and is an integer satisfying 2≦s≦4, but it is preferred that ^A3 is a perfluorobiphenyldiyl group, preferably a perfluorobiphenyl-4,4′-diyl group, and s is 2.
q represents the number of sulfonic acid groups bonded to ^A2 and is an integer satisfying the relationship 1≦q≦4, with 2 being optimal.

A ⁴ to A ⁸ each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, or a halogenated alkenyl group having 2 to 20 carbon atoms, provided that at least three of A ⁴ to A ⁸ are halogen atoms.

Examples of halogenated alkyl groups having 1 to 20 carbon atoms include trifluoromethyl, 2,2,2-trifluoroethyl, 1,1,2,2,2-pentafluoroethyl, 3,3,3-trifluoropropyl, 2,2,3,3,3-pentafluoropropyl, 1,1,2,2,3,3,3-heptafluoropropyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl, 2,2,3,3,4,4,4-heptafluorobutyl, and 1,1,2,2,3,3,4,4,4-nonafluorobutyl.

Examples of the halogenated alkenyl group having 2 to 20 carbon atoms include a perfluorovinyl group, a perfluoropropenyl group (allyl group), and a perfluorobutenyl group.
Other examples of the halogen atom and the alkyl group having 1 to 20 carbon atoms include those similar to those mentioned above, but the halogen atom is preferably a fluorine atom.

Among these, it is preferred that A ⁴ to A ⁸ are hydrogen atoms, halogen atoms, cyano groups, alkyl groups having 1 to 10 carbon atoms, halogenated alkyl groups having 1 to 10 carbon atoms, or halogenated alkenyl groups having 2 to 10 carbon atoms, and that at least three of A ⁴ to A ⁸ are fluorine atoms, more preferred are hydrogen atoms, fluorine atoms, cyano groups, alkyl groups having 1 to 5 carbon atoms, fluorinated alkyl groups having 1 to 5 carbon atoms, or fluorinated alkenyl groups having 2 to 5 carbon atoms, and that at least three of A ⁴ to A ⁸ are fluorine atoms, and even more preferred are hydrogen atoms, fluorine atoms, cyano groups, perfluoroalkyl groups having 1 to 5 carbon atoms, or perfluoroalkenyl groups having 1 to 5 carbon atoms, and that A ⁴ , A ⁵ and A ⁸ are fluorine atoms.
The perfluoroalkyl group is a group in which all hydrogen atoms of an alkyl group have been substituted with fluorine atoms, and the perfluoroalkenyl group is a group in which all hydrogen atoms of an alkenyl group have been substituted with fluorine atoms.

r represents the number of sulfonic acid groups bonded to the naphthalene ring and is an integer satisfying the relationship 1≦r≦4, with 2 to 4 being preferred and 2 being optimal.

When an organic compound is used as the dopant substance, the molecular weight thereof is preferably 3,000 or less, more preferably 2,500 or less, taking into consideration the solubility in organic solvents.
In particular, the molecular weight of the arylsulfonic acid compound used as the dopant material is not particularly limited, but is preferably 2,000 or less, more preferably 1,500 or less, in consideration of solubility in organic solvents.

Examples of aryl sulfonic acid compounds that can be suitably used in the present invention include, but are not limited to, the following compounds:

The charge transport ink composition of the present invention may contain other amine compounds in addition to the amine compound represented by formula (P1) for the purpose of improving the dispersibility or solubility of the charge transport substance, such as a polythiophene derivative or an amine adduct thereof.
Such other amine compounds are not particularly limited as long as they are soluble in at least one solvent used in the ink composition, and may be used alone or in combination of two or more types.

Specific examples of primary amine compounds include methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, s-butylamine, t-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-ethylhexylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, and n-hexadecylamine. Examples of monoalkylamine compounds include decylamine, n-heptadecylamine, n-octadecylamine, n-nonadecylamine, and n-eicosanylamine; and monoarylamine compounds such as aniline, tolylamine, 1-naphthylamine, 2-naphthylamine, 1-anthrylamine, 2-anthrylamine, 9-anthrylamine, 1-phenanthrylamine, 2-phenanthrylamine, 3-phenanthrylamine, 4-phenanthrylamine, and 9-phenanthrylamine.

Specific examples of secondary amine compounds include N-ethylmethylamine, N-methyl-n-propylamine, N-methylisopropylamine, N-methyl-n-butylamine, N-methyl-s-butylamine, N-methyl-t-butylamine, N-methylisobutylamine, diethylamine, N-ethyl-n-propylamine, N-ethylisopropylamine, N-ethyl-n-butylamine, N-ethyl-s-butylamine, N-ethyl-t-butylamine, dipropylamine, N-n-propylisopropylamine, and N-n-propyl N-n-butylamine, N-n-propyl-s-butylamine, diisopropylamine, N-n-butylisopropylamine, N-t-butylisopropylamine, di(n-butyl)amine, di(s-butyl)amine, diisobutylamine, aziridine (ethyleneimine), 2-methylaziridine (propyleneimine), 2,2-dimethylaziridine, azetidine (trimethyleneimine), 2-methylazetidine, pyrrolidine, 2-methylpyrrolidine, 3-methylpyrrolidine, 2,5-dimethylpyrrolidine, piperidine, 2,6-di Dialkylamine compounds such as methylpiperidine, 3,5-dimethylpiperidine, 2,2,6,6-tetramethylpiperidine, hexamethyleneimine, heptamethyleneimine, and octamethyleneimine; diphenylamine, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, 1,1'-dinaphthylamine, 2,2'-dinaphthylamine, 1,2'-dinaphthylamine, carbazole, 7H-benzo[c]carbazole, 11H-benzo[a]carbazole, 7H-dibenzo[c,g]carbazole, 13H-di Examples thereof include diarylamine compounds such as benzo[a,i]carbazole; and alkylarylamine compounds such as N-methylaniline, N-ethylaniline, N-n-propylaniline, N-isopropylaniline, N-n-butylaniline, N-s-butylaniline, N-isobutylaniline, N-methyl-1-naphthylamine, N-ethyl-1-naphthylamine, N-n-propyl-1-naphthylamine, indoline, isoindoline, 1,2,3,4-tetrahydroquinoline, and 1,2,3,4-tetrahydroisoquinoline.

Specific examples of tertiary amine compounds include N,N-dimethylethylamine, N,N-dimethyl-n-propylamine, N,N-dimethylisopropylamine, N,N-dimethyl-n-butylamine, N,N-dimethyl-s-butylamine, N,N-dimethyl-t-butylamine, N,N-dimethylisobutylamine, N,N-diethylmethylamine, N-methyldi(n-propyl)amine, N-methyldiisopropylamine, N-methyldi(n-butyl)amine, N-methyldiisobutylamine, triethylamine, N,N-diethyl-n-butylamine, N,N-diisopropylethylamine, and N,N-di(n-butyl)ethylamine. trialkylamine compounds such as tri(n-propyl)amine, tri(i-propyl)amine, tri(n-butyl)amine, tri(i-butyl)amine, 1-methylacetidine, 1-methylpyrrolidine, and 1-methylpiperidine; triarylamine compounds such as triphenylamine; alkyldiarylamine compounds such as N-methyldiphenylamine, N-ethyldiphenylamine, 9-methylcarbazole, and 9-ethylcarbazole; and dialkylarylamine compounds such as N,N-diethylaniline, N,N-di(n-propyl)aniline, N,N-di(i-propyl)aniline, and N,N-di(n-butyl)aniline.

In particular, when the charge transport ink composition of the present invention contains other amine compounds, these have excellent ability to improve the dispersibility and solubility of the charge transport material, such as the polythiophene derivative or its amine adduct, used in the present invention. Therefore, it is preferable that the other amine compounds contain primary amine compounds, and it is preferable that they contain monoalkylamines, particularly monoalkylamines having from 2 to 20 carbon atoms.

When the charge transport ink composition of the present invention contains other amine compounds, the content thereof is typically less than about 10 times by mass of the charge transport substance, such as the polythiophene derivative or its amine adduct, used in the present invention.

Heteropolyacids can also be suitably used as dopant materials. Heteropolyacids are polyacids formed by condensing isopolyacids, which are oxyacids of elements such as vanadium (V), molybdenum (Mo), and tungsten (W), with oxyacids of other elements. Examples of such oxyacids of other elements include oxyacids of silicon (Si), phosphorus (P), and arsenic (As). Heteropolyacids are typically represented by the Keggin type chemical structure shown in formula (A) or the Dawson type chemical structure shown in formula (B), in which a heteroatom is located at the center of the molecule.

Specific examples of heteropolyacids include phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid, phosphotungstomolybdic acid, etc. These may be used alone or in combination of two or more. The heteropolyacids used in the present invention are commercially available products, or can be synthesized by known methods.
In particular, when only one type of heteropolyacid is contained, the one type of heteropolyacid preferably contains tungsten. That is, phosphotungstic acid, silicotungstic acid, phosphotungstomolybdic acid, etc. are preferred, and phosphotungstic acid and silicotungstic acid are more preferred.

In addition, even if the heteropolyacid has a large or small number of elements in the structure represented by the general formula in a quantitative analysis such as elemental analysis, it can be used in the present invention as long as it is available as a commercially available product or is appropriately synthesized according to a known synthesis method.
That is, for example, phosphotungstic acid is generally represented by the chemical formula _H3 ( _PW12O40 )· _nH2O , but whether the number of P (phosphorus), O (oxygen), or W (tungsten) in this formula is large or small in quantitative analysis, it can be used in _the present invention as long as it is commercially available or appropriately synthesized according to a known synthesis method. In this case, the mass of the heteropolyacid specified in the present invention does not mean the mass of pure phosphotungstic acid (phosphotungstic acid content) in a synthesized or commercially available product, but rather the total mass, including water of hydration and other impurities, in a form available as a commercially available product or in a form that can be isolated by a known synthesis method.

The charge transport ink composition of the present invention may contain a known organosilane compound. By including such an organosilane compound in the charge transport ink composition, when a charge transport thin film obtained from the ink composition is used as a hole injection layer in an organic EL device, the hole injection properties into the hole transport layer provided in contact with the charge transport thin film can be improved.

As the organic silane compound, alkoxysilanes are preferred, with trialkoxysilanes and tetraalkoxysilanes being more preferred. Examples of the alkoxysilanes include tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, dimethyldiethoxysilane, and dimethyldimethoxysilane. Among these, tetraethoxysilane (TEOS), tetramethoxysilane, and tetraisopropoxysilane are preferred for use in the present invention. These organic silane compounds can be used alone or in combination of two or more.

When the charge transport ink composition of the present invention contains an organic silane compound, its content is typically about 0.1 to 50% by mass of the solids. However, taking into consideration the balance between improving the flatness of the resulting thin film and preventing a decrease in charge transport properties, the content is preferably about 0.5 to 40% by mass, more preferably about 0.8 to 30% by mass, and even more preferably about 1 to 20% by mass.

The viscosity of the charge transport ink composition of the present invention is typically 1 to 50 mPa·s at 25°C, and the surface tension is typically 20 to 50 mN/m at 25°C. The viscosity and surface tension of the charge transport ink composition of the present invention can be adjusted by changing the type and ratio of organic solvents used, the solids concentration, etc., taking into consideration various factors such as the coating method used and the desired film thickness.

The solids concentration of the charge transport ink composition of the present invention is set appropriately taking into consideration the viscosity and surface tension of the charge transport ink composition, the thickness of the thin film to be produced, etc., but is typically approximately 0.1 to 15% by mass.From the viewpoint of suppressing aggregation of the charge transport substance and metal oxide nanoparticles in the ink composition, it is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less.

When preparing the charge transport ink composition of the present invention, the amine compound represented by formula (P1), the charge transport material, the solvent, and, if necessary, the metal oxide nanoparticles and the dopant material can be mixed in any order, as long as the solid content is uniformly dissolved or dispersed in the solvent. That is, for example, a method of dissolving the charge transport material and the amine compound represented by formula (P1) in a solvent to obtain a solution, and then dissolving the dopant material in the solution; a method of dissolving the dopant material in a solvent, and then dissolving the charge transport material and the amine compound represented by formula (P1) in the solution; or a method of mixing the amine compound represented by formula (P1), the charge transport material, and the dopant material, and then adding the mixture to a solvent to dissolve the mixture can all be employed, as long as the solid content is uniformly dissolved or dispersed in the solvent.
When metal oxide nanoparticles are used, examples of the method include a method in which an aqueous dispersion or an organic solvent dispersion of the metal oxide nanoparticles is added at any timing in the above-mentioned method, and a method in which a solution containing the amine compound represented by formula (P1) and the charge transporting substance, which has been prepared in advance, and other components or their solutions are added to an aqueous dispersion or an organic solvent dispersion of the metal oxide nanoparticles.
It should be noted that the charge transporting material and metal oxide nanoparticles may aggregate or precipitate when mixed together, depending on the type and amount of the solvent used.
In preparing the charge transporting ink composition, heating may be performed as appropriate within a range that does not cause decomposition or deterioration of the components.

In the present invention, the charge transport ink composition may be filtered using a sub-micrometer filter or the like during the production process of the charge transport ink composition or after all components have been mixed, in order to reproducibly obtain a thin film with higher flatness.

By applying the charge transport ink composition described above to a substrate and baking it, a charge transport thin film can be formed on the substrate.

The method for applying the ink composition is not particularly limited, and examples include dipping, spin coating, transfer printing, roll coating, brush coating, inkjet printing, spraying, and slit coating. It is preferable to adjust the viscosity and surface tension of the ink composition depending on the application method.

Furthermore, when using the charge-transporting ink composition of the present invention, the baking atmosphere is not particularly limited; a thin film with a uniform film surface and high charge transport properties can be obtained not only in air but also in an inert gas atmosphere such as nitrogen or in a vacuum. The baking temperature is appropriately set within the range of approximately 100 to 260°C, taking into consideration the intended use of the resulting thin film, the level of charge transport properties to be imparted to the resulting thin film, the type and boiling point of the solvent, etc. However, when the resulting thin film is used as a hole injection layer in an organic EL device, a temperature of approximately 140 to 250°C is preferred, and approximately 145 to 240°C is more preferred. During baking, two or more temperature steps may be used to achieve more uniform film formation or to promote the reaction on the substrate. Heating can be performed using appropriate equipment, such as a hot plate or oven.

There are no particular limitations on the film thickness of the charge-transporting thin film, but when used as a functional layer between the anode and light-emitting layer of an organic EL device, such as a hole injection layer, hole transport layer, or hole injection transport layer, a thickness of 5 to 300 nm is preferred. Methods for changing the film thickness include changing the solids concentration in the charge-transporting ink composition or changing the amount of solution on the substrate during application.

The organic EL device of the present invention has a pair of electrodes and a charge transport layer made of the above-mentioned charge transport thin film of the present invention between the electrodes.
Representative configurations of organic EL elements include, but are not limited to, the following (a) to (f). In the following configurations, an electron blocking layer or the like can be provided between the light-emitting layer and the anode, and a hole blocking layer or the like can be provided between the light-emitting layer and the cathode, as necessary. Furthermore, the hole injection layer, the hole transport layer, or the hole injection transport layer may also function as an electron blocking layer or the like, and the electron injection layer, the electron transport layer, or the electron injection transport layer may also function as a hole blocking layer or the like. Furthermore, an arbitrary functional layer can be provided between each layer as necessary.
(a) anode/hole injection layer/hole transport layer/light-emitting layer/electron transport layer/electron injection layer/cathode (b) anode/hole injection layer/hole transport layer/light-emitting layer/electron injection transport layer/cathode (c) anode/hole injection transport layer/light-emitting layer/electron transport layer/electron injection layer/cathode (d) anode/hole injection transport layer/light-emitting layer/electron injection transport layer/cathode (e) anode/hole injection layer/hole transport layer/light-emitting layer/cathode (f) anode/hole injection transport layer/light-emitting layer/cathode

The terms "hole injection layer,""hole transport layer," and "hole injection transport layer" refer to layers formed between the light-emitting layer and the anode, which have the function of transporting holes from the anode to the light-emitting layer. When only one layer of a hole-transporting material is provided between the light-emitting layer and the anode, it is the "hole injection transport layer." When two or more layers of a hole-transporting material are provided between the light-emitting layer and the anode, the layer closest to the anode is the "hole injection layer," and the remaining layers are "hole transport layers." In particular, the hole injection (transport) layer is a thin film that is excellent not only in the ability to accept holes from the anode but also in the ability to inject holes into the hole transport (light-emitting) layer.
The terms "electron injection layer,""electron transport layer," and "electron injection transport layer" refer to layers formed between a light-emitting layer and a cathode, which have the function of transporting electrons from the cathode to the light-emitting layer. When only one layer of an electron-transporting material is provided between the light-emitting layer and the cathode, it is the "electron injection transport layer." When two or more layers of an electron-transporting material are provided between the light-emitting layer and the cathode, the layer closest to the cathode is the "electron injection layer," and the other layers are "electron transport layers."
The "light-emitting layer" is an organic layer that has a light-emitting function, and when a doping system is used, it contains a host material and a dopant material. In this case, the host material mainly functions to promote the recombination of electrons and holes and confine excitons within the light-emitting layer, while the dopant material functions to efficiently emit light from the excitons obtained by the recombination. In the case of a phosphorescent element, the host material mainly functions to confine excitons generated by the dopant within the light-emitting layer.

The charge transport thin film prepared from the charge transport ink composition of the present invention can be used as a functional layer formed between the anode and the light-emitting layer in an organic EL element, but is suitable as a hole injection layer, hole transport layer, or hole injection transport layer, more suitable as a hole injection layer or hole transport layer, and even more suitable as a hole injection layer.

When producing an EL element using the charge transport ink composition of the present invention, the materials and production methods used include, but are not limited to, the following:

An example of a method for producing an OLED element having a hole injection layer made of a thin film obtained from the charge transport ink composition of the present invention is as follows: It is preferable to previously perform a surface treatment on the electrodes, such as washing with alcohol or pure water, or UV ozone treatment or oxygen plasma treatment, within a range that does not adversely affect the electrodes.
A hole injection layer is formed on an anode substrate using the charge transport ink composition by the above method. The resulting substrate is introduced into a vacuum deposition apparatus, and a hole transport layer, a light-emitting layer, an electron transport layer/hole blocking layer, an electron injection layer, and a cathode metal are sequentially deposited. Alternatively, instead of forming the hole transport layer and the light-emitting layer by deposition in this method, these layers are formed by a wet process using a hole transport layer-forming composition containing a hole transport polymer and a light-emitting layer-forming composition containing a light-emitting polymer. If necessary, an electron blocking layer may be provided between the light-emitting layer and the hole transport layer.

Examples of anode materials include transparent electrodes such as indium tin oxide (ITO) and indium zinc oxide (IZO), metal anodes made of metals such as aluminum, or alloys thereof, and preferably those that have been subjected to a planarization treatment.Polythiophene derivatives and polyaniline derivatives having high charge transport properties can also be used.
Other metals that may be used to form the metal anode include, but are not limited to, gold, silver, copper, indium, and alloys thereof.

Materials for forming the hole transport layer include triarylamines such as (triphenylamine) dimer derivatives, [(triphenylamine) dimer] spiro dimer, N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (α-NPD), 4,4',4"-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA), and 4,4',4"-tris[1-naphthyl(phenyl)amino]triphenylamine (1-TNATA), and oligothiophenes such as 5,5"-bis-{4-[bis(4-methylphenyl)amino]phenyl}-2,2':5',2"-terthiophene (BMA-3T).

Examples of materials for forming the light-emitting layer include, but are not limited to, low-molecular-weight light-emitting materials such as metal complexes such as aluminum complexes of 8-hydroxyquinoline, metal complexes of 10-hydroxybenzo[h]quinoline, bisstyrylbenzene derivatives, bisstyrylarylene derivatives, metal complexes of (2-hydroxyphenyl)benzothiazole, and silole derivatives; and systems in which a light-emitting material and an electron transfer material are mixed with a polymer compound such as poly(p-phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly(3-alkylthiophene), or polyvinylcarbazole.
Furthermore, when forming the light-emitting layer by vapor deposition, it may be co-deposited with a light-emitting dopant. Examples of the light-emitting dopant include, but are not limited to, metal complexes such as tris(2-phenylpyridine)iridium( _III ) (Ir(ppy)), naphthacene derivatives such as rubrene, quinacridone derivatives, and fused polycyclic aromatic rings such as perylene.

Materials for forming the electron transport layer/hole blocking layer include, but are not limited to, oxydiazole derivatives, triazole derivatives, phenanthroline derivatives, phenylquinoxaline derivatives, benzimidazole derivatives, pyrimidine derivatives, etc.

Materials for forming the electron injection layer include, but are not limited to, metal oxides such as lithium oxide ( _Li2O ), magnesium oxide ( _{MgO), and alumina (Al2O3 )} , and metal fluorides such as lithium fluoride (LiF) and sodium fluoride (NaF).
Cathode materials include, but are not limited to, aluminum, magnesium-silver alloy, aluminum-lithium alloy, and the like.
Examples of materials for forming the electron blocking layer include, but are not limited to, tris(phenylpyrazole)iridium.

Examples of hole-transporting polymers include poly[(9,9-dihexylfluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,4-diaminophenylene)], poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,1'-biphenylene-4,4-diamine)], poly[(9,9-bis{1'-penten-5'-yl}fluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,4-diaminophenylene)], and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine]-end-capped with Examples thereof include polysilcisquinoxane and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(p-butylphenyl))diphenylamine)].

Examples of luminescent polymers include polyfluorene derivatives such as poly(9,9-dialkylfluorene) (PDAF), polyphenylenevinylene derivatives such as poly(2-methoxy-5-(2'-ethylhexoxy)-1,4-phenylenevinylene) (MEH-PPV), polythiophene derivatives such as poly(3-alkylthiophene) (PAT), and polyvinylcarbazole (PVCz).

The materials constituting the anode, cathode and layers formed therebetween differ depending on whether an element having a bottom emission structure or a top emission structure is to be manufactured, and therefore, the materials are selected appropriately taking this into consideration.
Typically, in a bottom-emission element, a transparent anode is used on the substrate side, and light is extracted from the substrate side, whereas in a top-emission element, a reflective anode made of metal is used, and light is extracted from the transparent electrode (cathode) side opposite the substrate. Therefore, for example, in terms of anode material, a transparent anode such as ITO is used when manufacturing a bottom-emission element, and a reflective anode such as Al/Nd is used when manufacturing a top-emission element.

To prevent deterioration of the characteristics of the organic EL element of the present invention, it may be sealed, if necessary, with a moisture scavenger or the like, according to standard methods.

As described above, the charge transport ink composition of the present invention is suitable for use in forming a functional layer formed between the anode and light-emitting layer of an organic EL element. It can also be used to form charge transport thin films in electronic devices such as organic photoelectric conversion elements, organic thin-film solar cells, organic perovskite photoelectric conversion elements, organic integrated circuits, organic field-effect transistors, organic thin-film transistors, organic light-emitting transistors, organic optical inspectors, organic photoreceptors, organic field-quenching elements, light-emitting electrochemical cells, quantum dot light-emitting diodes, quantum lasers, organic laser diodes, and organic plasmon light-emitting elements.

The method of the present invention for improving the storage stability of a charge transport ink composition is a method for improving the storage stability of a charge transport ink composition containing an amine compound, a charge transport substance, and an organic solvent, in which the amine compound is an amine compound represented by formula (P1) above, and the preferred conditions for the solid contents of the amine compound, the charge transport substance, etc., and the type and amount of the organic solvent are the same as those described above.
The improvement in the storage stability of the charge transport ink composition can be evaluated by the change in absorbance. Specifically, when the absorbance of the charge transport ink composition at the maximum absorption (for example, a wavelength of 620 nm) before exposure to the atmosphere is a(initial), the absorbance of the charge transport ink composition after 10 days of exposure is a(atmospheric exposure), and the difference in absorbance before and after exposure to the atmosphere (a(initial) - a(atmospheric exposure)) is Δa, the absolute value of the rate of change in absorbance (%) = Δa/a(initial) is usually 10% or less, in a preferred embodiment 9% or less, in a more preferred embodiment 8% or less, in an even more preferred embodiment 7% or less, and in an even more preferred embodiment 6% or less.

The method of the present invention for improving the flatness of a charge-transporting thin film is a method for improving the flatness of a charge-transporting thin film obtained from a charge-transporting ink composition containing an amine compound, a charge-transporting substance, and an organic solvent, and the preferred conditions for the solid contents of the amine compound, the charge-transporting substance, etc., the type and amount of the organic solvent, and the conditions for forming the charge-transporting thin film are the same as those described above.
The improvement in the flatness of the charge-transporting thin film can be evaluated by the average surface roughness Ra. Specifically, when the charge-transporting thin film formed on the substrate is measured using an atomic force microscope in a measurement area of 3 μm × 3 μm, the average surface roughness Ra (nm) is usually 2.80 nm or less, preferably 2.70 nm or less, more preferably 2.60 nm or less, and even more preferably 2.50 nm or less.
In the present invention, the average surface roughness (Ra) of the charge-transporting thin film can be measured using, for example, an atomic force microscope Park-NX10 manufactured by Park Systems Corporation and an average surface roughness measuring cantilever OMCL-AC 160TS 10M manufactured by Olympus Corporation.

The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to the following examples. The equipment used is as follows:

(1) Coating of charge transporting ink composition: Spin coater MS-A100, manufactured by Mikasa Co., Ltd.
(2) Measurement of the average surface roughness (Ra) of the charge transport thin film: Atomic force microscope Park-NX10 manufactured by Park Systems Co., Ltd. and average surface roughness measurement cantilever OMCL-AC 160TS 10M manufactured by Olympus Corporation
(3) Measurement of solution absorption spectrum of ink composition: UV-3600 ultraviolet-visible-near infrared spectrophotometer, manufactured by Shimadzu Science Co., Ltd.
(4) Preparation of organic EL element: Multifunctional deposition system C-E2L1G1-N manufactured by Choshu Sangyo Co., Ltd.
(5) Measurement of the luminance of organic EL elements: Multi-channel IVL measuring device manufactured by EHC Co., Ltd.

[1] Synthesis of Compound [Production Example 1]
An amine adduct of a polythiophene derivative, which is a polymer containing a repeating unit represented by formula (1a), was synthesized according to the methods described in U.S. Pat. No. 8,017,241 and WO 2016/171935.

(wherein a to d are the same as above.)

[Production Example 2]
An arylsulfonic acid compound A represented by formula (b-1) was synthesized according to the method described in WO 2006/025342.

[2] Preparation of solution and dispersion for preparing charge transport ink composition [Preparation Example 1]
A 1,3-dimethyl-2-imidazolidinone solution containing 10% by mass of arylsulfonic acid compound A was prepared by stirring using a hot stirrer at 400 rpm and 50° C. for 1 hour.

[Preparation Example 2]
100 g of ST-OS (manufactured by Nissan Chemical Industries, Ltd.), which is a water-dispersed silica sol, and dipropylene glycol monomethyl ether (manufactured by Kanto Chemical Co., Ltd.; the same applies hereinafter) were placed in a recovery flask, and the water contained in the ST-OS was replaced with dipropylene glycol monomethyl ether using an evaporator, thereby obtaining a silica sol (silica concentration 9.43% by mass) in which dipropylene glycol monomethyl ether was used as a dispersion medium.

[3] Preparation of charge transport ink composition [Example 1-1]
3.24 g of 1,3-dimethyl-2-imidazolidinone, 5.17 g of dipropylene glycol (manufactured by Junsei Chemical Co., Ltd., the same applies hereinafter), and 3.55 g of dipropylene glycol monomethyl ether were placed in an Erlenmeyer flask and stirred at room temperature for 30 minutes using a stirrer. Thereafter, 0.21 g of the 1,3-dimethyl-2-imidazolidinone solution of arylsulfonic acid compound A obtained in Preparation Example 1 was added, and the mixture was stirred at room temperature for 30 minutes using a stirrer.
To the resulting mixture, 1.05 g of a solution obtained by stirring 0.10 g of the amine adduct of the polythiophene derivative obtained in Production Example 1, 4.75 g of 1,3-dimethyl-2-imidazolidinone (manufactured by Kanto Chemical Co., Inc.; the same applies hereinafter) and 0.15 g of 3-ethoxypropylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) at 80°C for 3 hours using a hot stirrer was added, and the mixture was stirred at room temperature for 30 minutes.
Next, 1.78 g of the silica sol containing dipropylene glycol monomethyl ether as a dispersion medium obtained in Preparation Example 2 was added to the resulting mixture, and the mixture was stirred at room temperature for 30 minutes.
Finally, the resulting mixture was filtered through a PP syringe filter with a pore size of 0.2 μm to obtain a charge transporting ink composition.

[Example 1-2]
3.24 g of 1,3-dimethyl-2-imidazolidinone, 5.17 g of dipropylene glycol, and 3.55 g of dipropylene glycol monomethyl ether were placed in an Erlenmeyer flask and stirred at room temperature for 30 minutes using a stirrer. Thereafter, 0.21 g of the 1,3-dimethyl-2-imidazolidinone solution of arylsulfonic acid compound A obtained in Preparation Example 1 was added, and the mixture was stirred at room temperature for 30 minutes using a stirrer.
To the resulting mixture, 1.05 g of a mixture obtained by stirring 0.10 g of the amine adduct of the polythiophene derivative obtained in Production Example 1, 4.75 g of 1,3-dimethyl-2-imidazolidinone, and 0.15 g of 3-isopropoxypropylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) at 80°C for 3 hours using a hot stirrer was added, and the mixture was stirred at room temperature for 30 minutes.
Next, 1.78 g of the silica sol containing dipropylene glycol monomethyl ether as a dispersion medium obtained in Preparation Example 2 was added to the resulting mixture, and the mixture was stirred at room temperature for 30 minutes.
Finally, the resulting mixture was filtered through a PP syringe filter with a pore size of 0.2 μm to obtain a charge transporting ink composition.

[Comparative Example 1-1]
3.24 g of 1,3-dimethyl-2-imidazolidinone, 5.17 g of dipropylene glycol, and 3.55 g of dipropylene glycol monomethyl ether were placed in an Erlenmeyer flask and stirred at room temperature for 30 minutes using a stirrer. Thereafter, 0.21 g of the 1,3-dimethyl-2-imidazolidinone solution of arylsulfonic acid compound A obtained in Preparation Example 1 was added, and the mixture was stirred at room temperature for 30 minutes using a stirrer.
To the resulting mixture, 1.05 g of a mixture obtained by stirring 0.10 g of the amine adduct of the polythiophene derivative obtained in Production Example 1, 4.75 g of 1,3-dimethyl-2-imidazolidinone, and 0.15 g of n-butylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) at 80°C for 3 hours using a hot stirrer was added, and the mixture was stirred at room temperature for 30 minutes.
Next, 1.78 g of the silica sol containing dipropylene glycol monomethyl ether as a dispersion medium obtained in Preparation Example 2 was added to the resulting mixture, and the mixture was stirred at room temperature for 30 minutes.
Finally, the resulting mixture was filtered through a PP syringe filter with a pore size of 0.2 μm to obtain a charge transporting ink composition.

[Comparative Example 1-2]
3.24 g of 1,3-dimethyl-2-imidazolidinone, 5.17 g of dipropylene glycol, and 3.55 g of dipropylene glycol monomethyl ether were placed in an Erlenmeyer flask and stirred at room temperature for 30 minutes using a stirrer. Thereafter, 0.21 g of the 1,3-dimethyl-2-imidazolidinone solution of arylsulfonic acid compound A obtained in Preparation Example 1 was added, and the mixture was stirred at room temperature for 30 minutes using a stirrer.
To the resulting mixture, 1.05 g of a mixture obtained by stirring 0.10 g of the amine adduct of the polythiophene derivative obtained in Production Example 1, 4.75 g of 1,3-dimethyl-2-imidazolidinone, and 0.15 g of isoamylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) at 80°C for 3 hours using a hot stirrer was added, and the mixture was stirred at room temperature for 30 minutes.
Next, 1.78 g of the silica sol containing dipropylene glycol monomethyl ether as a dispersion medium obtained in Preparation Example 2 was added to the resulting mixture, and the mixture was stirred at room temperature for 30 minutes.
Finally, the resulting mixture was filtered through a PP syringe filter with a pore size of 0.2 μm to obtain a charge transporting ink composition.

[Comparative Examples 1-3]
0.10 g of the amine adduct of a polythiophene derivative obtained in Production Example 1 was added to 4.75 g of 1,3-dimethyl-2-imidazolidinone and 0.15 g of 3-aminopropanol (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred at 80°C for 3 hours using a hot stirrer. However, the amine adduct of a polythiophene derivative was not sufficiently dissolved or dispersed, and a composition uniform enough to be used for forming a charge-transporting thin film could not be prepared.

[Comparative Examples 1-4]
0.10 g of the amine adduct of the polythiophene derivative obtained in Production Example 1 was added to 4.75 g of 1,3-dimethyl-2-imidazolidinone and 0.15 g of 2-amino-1-methoxybutane (Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred at 80°C for 3 hours using a hot stirrer. However, the amine adduct of the polythiophene derivative was not sufficiently dissolved or dispersed, and a composition uniform enough to be used for forming a charge-transporting thin film could not be prepared.

[Comparative Examples 1-5]
0.10 g of the amine adduct of a polythiophene derivative obtained in Production Example 1 was added to 4.75 g of 1,3-dimethyl-2-imidazolidinone and 0.15 g of bis(2-ethoxyethyl)amine (Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred at 80°C for 3 hours using a hot stirrer. However, the amine adduct of a polythiophene derivative was not sufficiently dissolved or dispersed, and a composition uniform enough to be used for forming a charge-transporting thin film could not be prepared.

[4] Preparation of charge transport thin film and evaluation of average surface roughness Ra [Example 2-1]
The charge transporting ink composition obtained in Example 1-1 was applied to an ITO substrate using a spin coater, and heated in the atmosphere at 120°C for 1 minute, and then heated at 230°C for 15 minutes to form a uniform thin film having a thickness of 30 nm on the ITO substrate.
The ITO substrate used was a 25 mm × 25 mm × 0.7 mm glass substrate on which indium tin oxide (ITO) was patterned to a film thickness of 50 nm. Prior to use, impurities on the surface were removed using an _O2 plasma cleaning device (150 W, 30 seconds).

[Example 2-2, Comparative Examples 2-1 and 2-2]
A uniform thin film having a thickness of 30 nm was formed on an ITO substrate in the same manner as in Example 2-1, except that the charge transporting ink composition obtained in Example 1-2 and Comparative Examples 1-1 and 1-2 were used instead of the charge transporting ink composition of Example 1-1.

The average surface roughness Ra of the charge transport thin films formed on the ITO substrates in Example 2-1, Example 2-2, Comparative Example 2-1, and Comparative Example 2-2 was evaluated using an atomic force microscope. The measurement range of the atomic force microscope was 3 μm x 3 μm. The results are shown in Table 1.

As shown in Table 1, the average surface roughness of the thin film formed from the charge transport ink composition of the present invention was lower than that of the thin film formed from the charge transport ink composition of the comparative example. This is presumably because the use of the amine compound represented by formula (P1) contained in the charge transport ink composition of the present invention enables a more stable interaction between the amine compound and the charge transport substance, thereby mitigating or suppressing aggregation of the charge transport substance during the heating process after application of the composition.

[5] Evaluation of stability of charge transport ink composition against atmospheric exposure [Example 3-1]
0.2 g of the charge transporting ink composition obtained in Example 1-1 was mixed with 4.14 g of 1,3-dimethyl-2-imidazolidinone, 4.83 g of dipropylene glycol, and 4.83 g of dipropylene glycol monomethyl ether, and the absorption spectrum of the resulting mixture was measured.
Next, 3.0 g of the charge-transporting ink composition obtained in Example 1-1 was added to a 20 mL glass vial, and the vial was left uncovered and exposed to the atmosphere at room temperature for 10 days. 0.2 g of the exposed charge-transporting ink composition was mixed with 4.14 g of 1,3-dimethyl-2-imidazolidinone, 4.83 g of dipropylene glycol, and 4.83 g of dipropylene glycol monomethyl ether, and the absorption spectrum of the resulting mixture was measured.
The absorption spectrum was measured using a quartz cell with an optical path length of 1 cm.

[Example 3-2, Comparative Examples 3-1 to 3-2]
The absorption spectra were measured in the same manner as in Example 3-1, except that the charge transporting ink compositions obtained in Example 1-2 and Comparative Examples 1-1 and 1-2 were used instead of the charge transporting ink composition obtained in Example 1-1.

The measured absorption spectrum is shown in Figure 1. Table 2 also shows the absorbance (a (initial)) of the charge transport ink composition before exposure to the atmosphere, the absorbance (a (exposed to the atmosphere)) of the charge transport ink composition after 10 days of exposure, the difference in absorbance before and after exposure to the atmosphere (Δa), and the rate of change in absorbance (%) at the wavelength of 620 nm where the absorption is maximum.

As shown in Figure 1 and Table 2, the change in absorbance of the charge transport ink composition of the present invention was smaller than that of the charge transport ink composition of the comparative example. This is presumably because the use of the amine compound represented by formula (P1) contained in the charge transport ink composition of the present invention makes it possible to achieve stable interaction between the amine compound and the charge transport substance in the composition, thereby suppressing oxidation of the charge transport substance.

[6] Preparation of organic EL element and evaluation of its characteristics [Example 4-1]
The charge-transporting ink composition obtained in Example 1-1 was applied to an ITO substrate using a spin coater, and heated in the atmosphere at 120°C for 1 minute, and then heated at 230°C for 15 minutes, to form a uniform charge-transporting thin film having a thickness of 30 nm on the ITO substrate.
The ITO substrate used was a 25 mm × 25 mm × 0.7 mm glass substrate with a patterned ITO film of 150 nm formed on its surface. Prior to use, impurities on the surface were removed using an _O2 plasma cleaning device (150 W, 30 seconds).
Next, a 30 nm film of α-NPD (N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine) was formed at 0.2 nm/sec on the charge transporting thin film formed on the ITO substrate using a vapor deposition apparatus (vacuum degree 1.0×10 ⁻⁵ Pa).
A 10-nm thick film of electron blocking material HTEB-01 (manufactured by Kanto Chemical Co., Inc.) was deposited on the α-NPD film, and then NS60 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) emitting layer host material and Ir(ppy) ₃ (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) emitting layer dopant material were co-deposited on top of the film. The deposition rate was controlled so that the Ir(ppy) ₃ concentration was 6%, resulting in a 40-nm thick film. Next, thin films of _Alq3 , lithium fluoride, and aluminum were sequentially deposited to obtain an organic EL device. The deposition rates for _Alq3 and aluminum were 0.2 nm/sec, and for lithium fluoride, 0.02 nm/sec, resulting in film thicknesses of 20 nm, 0.5 nm, and 80 nm, respectively.

To prevent deterioration of characteristics due to the effects of oxygen, water, etc. in the air, the organic EL elements were sealed with sealing substrates before their characteristics were evaluated. Sealing was performed using the following procedure. In a nitrogen atmosphere with an oxygen concentration of 2 ppm or less and a dew point of -76°C or less, the organic EL elements were placed between sealing substrates, and the sealing substrates were bonded together with an adhesive (Moresco Moisture Cut WB90US(P) manufactured by MORESCO Corporation). At this time, a moisture scavenger (HD-071010W-40 manufactured by DYNIC Corporation) was placed inside the sealing substrates together with the organic EL elements. The bonded sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ/ ^cm2 ) and then annealed at 80°C for 1 hour to cure the adhesive.

[Example 4-2]
An organic EL device was obtained in the same manner as in Example 4-1, except that the charge transporting ink composition obtained in Example 1-2 was used instead of the charge transporting ink composition obtained in Example 1-1.

The devices obtained in Examples 4-1 and 4-2 were measured for their driving voltage, current density, and luminous efficiency when driven at a luminance of 10,000 cd/ ^m² , as well as their luminance half-life (the time required for the luminance to decrease by half from the initial luminance of 10,000 cd/ ^m² ). The results are shown in Table 3.

The organic EL elements obtained in Examples 4-1 and 4-2 both exhibited good element characteristics.

Claims (13)

A charge transporting ink composition comprising an amine compound represented by the following formula (P1), a charge transporting substance, and an organic solvent:
(wherein R ^m represents any alkyl group selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group , an n-octyl group, and an n-nonyl group; any alkenyl group selected from the group consisting of an ethenyl group, an n-1-propenyl group, an n-2-propenyl group, a 1-methylethenyl group, an n-1-butenyl group, an n-2-butenyl group, an n-3-butenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-ethylethenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, and an n-1-pentenyl group ; or any aryl group selected from the group consisting of a phenyl group and a tolyl group , ⁿ represents any alkylene group selected from the group consisting of methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, and nonylene ; any alkenylene group selected from the group consisting of vinylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octenylene, and nonenylene ; or a phenylene group , or an alkyl group having 1 to 5 carbon atoms for ^Rm and an alkylene group having 1 to 5 carbon atoms for ^Rn are bonded to each other to form an alkanetriyl group having 3 to 10 carbon atoms, provided that the alkylene group and alkenylene group for ^Rn and the alkanetriyl groups for Rm and ^Rn are ^limited to those which form a -CH2 _{- NH2} group when bonded to _-NH2 in formula ( ^P1 ). (Except when the total number of carbon atoms in ⁿ is 11 or more.) 2. The charge transport ink composition according to claim 1, wherein R ^m is an alkyl group selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and n-nonyl, and R ⁿ is an alkylene group selected from the group consisting of methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, and nonylene . 3. The charge transporting ink composition according to claim 1, wherein the charge transporting substance is a polythiophene derivative containing a repeating unit represented by the following formula (1) or an amine adduct thereof:
(In the formula, ^R1 and ^R2 are each independently a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, a fluoroalkoxy group having 1 to 40 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, -O-[Z-O] _p - ^Re , or a sulfonic acid group; or ^R1 and ^R2 are bonded to form -O-Y-O-; Y is an alkylene group having 1 to 40 carbon atoms which may contain an ether bond and which may be substituted with a sulfonic acid group; Z is an alkylene group having 1 to 40 carbon atoms which may be substituted with a halogen atom; p is an integer of 1 or greater; ^{and Re} is a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms.) 4. The charge transporting ink composition according to claim 3, wherein R ¹ is a sulfonic acid group, R ² is an alkoxy group having 1 to 40 carbon atoms or -O-[ZO] _p -R ^e , or R ¹ and R ² are bonded to form -O-Y-O-. The charge transport ink composition according to any one of claims 1 to 4, further comprising a dopant substance. The charge transport ink composition according to claim 5, wherein the dopant substance includes at least one selected from the group consisting of arylsulfonic acid compounds and heteropolyacid compounds. The charge transport ink composition according to any one of claims 1 to 6, further comprising metal oxide nanoparticles. A charge transporting thin film obtained from the charge transporting ink composition described in any one of claims 1 to 7. An electronic device comprising the charge transport thin film of claim 8. 10. The electronic device according to claim 9, wherein the charge transporting thin film is a hole injection layer, a hole transport layer, or a hole injection transport layer. The electronic device according to claim 9, which is an organic electroluminescence device. A method for improving the storage stability of a charge transporting ink composition containing an amine compound, a charge transporting substance, and an organic solvent, comprising:
A method for improving the storage stability of a charge transporting ink composition, comprising using an amine compound represented by the following formula (P1) as the amine compound:
(wherein R ^m represents any alkyl group selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group , an n-octyl group, and an n-nonyl group; any alkenyl group selected from the group consisting of an ethenyl group, an n-1-propenyl group, an n-2-propenyl group, a 1-methylethenyl group, an n-1-butenyl group, an n-2-butenyl group, an n-3-butenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-ethylethenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, and an n-1-pentenyl group ; or any aryl group selected from the group consisting of a phenyl group and a tolyl group , ⁿ represents any alkylene group selected from the group consisting of methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, and nonylene ; any alkenylene group selected from the group consisting of vinylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octenylene, and nonenylene ; or a phenylene group, or an alkyl group having 1 to 5 carbon atoms for R ^m and an alkylene group having 1 to 5 carbon atoms for R ⁿ are bonded to each other to form an alkanetriyl group having 3 to 10 carbon atoms, provided that the alkylene group and alkenylene group for R ⁿ and the alkanetriyl groups for R ^m and R ⁿ are limited to those which, when bonded to —NH ₂ in formula (P1), form a —CH ₂ —NH ₂ group. (Except when the total number of carbon atoms in ^m and Rn ^is 11 or more.) A method for improving the flatness of a charge-transporting thin film obtained from a charge-transporting ink composition containing an amine compound, a charge-transporting substance, and an organic solvent, comprising:
A method for improving the flatness of a charge-transporting thin film, characterized in that an amine compound represented by the following formula (P1) is used as the amine compound:
(wherein R ^m represents any alkyl group selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group , an n-octyl group, and an n-nonyl group; any alkenyl group selected from the group consisting of an ethenyl group, an n-1-propenyl group, an n-2-propenyl group, a 1-methylethenyl group, an n-1-butenyl group, an n-2-butenyl group, an n-3-butenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-ethylethenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, and an n-1-pentenyl group ; or any aryl group selected from the group consisting of a phenyl group and a tolyl group , ⁿ represents any alkylene group selected from the group consisting of methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, and nonylene ; any alkenylene group selected from the group consisting of vinylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octenylene, and nonenylene ; or a phenylene group , or an alkyl group having 1 to 5 carbon atoms for ^Rm and an alkylene group having 1 to 5 carbon atoms for ^Rn are bonded to each other to form an alkanetriyl group having 3 to 10 carbon atoms, provided that the alkylene group and alkenylene group for ^Rn and the alkanetriyl groups for Rm and ^Rn are ^limited to those which form a -CH2 _{- NH2} group when bonded to _-NH2 in formula ( ^P1 ). (Except when the total number of carbon atoms in ⁿ is 11 or more.)