Composition for forming conductive thin film

Abstract

Provided as a composition for forming a conductive thin film which is suitable for the formation of a conductive thin film that is superposed on an electrode foil such as an aluminum foil constituting an electrolytic capacitor is, for example, a composition for forming a conductive thin film which contains a thiophene compound represented by formula (1-1), a heteropolyacid, and a solvent, and does not contain an iron-containing compound.

Description

Composition for forming conductive thin film

[0001] This invention relates to a composition for forming conductive thin films.

[0002] Electrolytic capacitors are capacitors that use an oxide film of aluminum or tantalum as a dielectric. Electrolytic capacitors are characterized by their ability to be miniaturized and have high capacitance, and are widely used in power supply circuits of various electronic devices as components that perform functions such as power supply smoothing circuits and AC-DC conversion. In recent years, with the expansion of the electric vehicle market, there has been a demand for electrolytic capacitors with increased capacitance, reduced equivalent series resistance (ESR), improved heat resistance, higher voltage resistance, high ripple current capability, miniaturization, and longer lifespan (Non-Patent Literature 1).

[0003] In recent years, similar performance improvements have been required for data center and communication base station applications to cope with the increased load on servers due to the application of artificial intelligence (AI), i.e., increased power consumption and increased burden on cooling systems to suppress temperature rises around the servers.

[0004] Electrolytic capacitors come in various types, such as aluminum electrolytic capacitors and tantalum electrolytic capacitors, but aluminum electrolytic capacitors are widely used due to their low cost.

[0005] On the other hand, conductive polymer solid electrolytic capacitors replace the electrolyte in electrolytic capacitors with a conductive polymer. Compared to electrolytic capacitors, they have an even lower equivalent series resistance (ESR) and can achieve higher capacitance, thus expanding their range of applications. However, because they rely solely on an aluminum oxide layer as the dielectric material, they tend to have high leakage currents and low dielectric strength. Furthermore, while aluminum electrolytic capacitors maintain reliability because the electrolyte contains aluminum oxide with a repair function, the conductive polymer in conductive polymer solid electrolytic capacitors has a lower function in this regard, leading to challenges in leakage current, lifespan, and reliability. There is also a strong demand for improved heat resistance of the conductive polymer itself (Non-Patent Documents 1 and 2).

[0006] Polythiophene-based conductive materials such as polyethylene dioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS) and polypyrrole are widely used as conductive polymers in conductive polymer solid electrolytic capacitors.

[0007] PEDOT / PSS has two main application methods: pre-polymerization and in-device polymerization.

[0008] The pre-polymerization method involves first polymerizing ethylenedioxythiophene (EDOT), a monomer, in an aqueous solution containing PSS to prepare a PEDOT / PSS aqueous dispersion. Then, etched aluminum foil is immersed in this dispersion, or the dispersion is coated onto the etched aluminum foil, and the foil is subsequently dried before use.

[0009] The in-element polymerization method is a method in which components such as etched aluminum foil are pre-formed into the shape of a capacitor (element), and a monomer solution is placed inside to carry out a polymerization reaction. For example, the components formed into an element are immersed in a solution containing EDOT and an EDOT polymerization catalyst such as p-toluenesulfonate iron(III), or the solution is coated onto the necessary parts of the components. Next, by heating and drying this to polymerize the EDOT, PEDOT can be formed on the aluminum oxide layer of the etched aluminum foil inside the element.

[0010] Polypyrrole is generally produced by immersing etched aluminum compound foil in a dispersion containing the monomer pyrrole and a surfactant, or by coating the etched aluminum compound foil with the dispersion, and then polymerizing the pyrrole by chemical polymerization or electropolymerization to form a polypyrrole layer on the etched aluminum compound foil.

[0011] However, in the pre-polymerization method of PEDOT / PSS, it is difficult to adequately coat the inside of the micropores (especially those with a diameter of 50 nm or less) of the etched aluminum foil for the following reasons: (1) Due to limitations imposed by the polymerization method and the strong hydrophilicity of PSS, it is necessary to use water or a solvent mainly composed of water as the solvent. As a result, the PEDOT / PSS dispersion has a very high surface tension, which results in a high contact angle on the aluminum oxide layer, making it difficult to penetrate deep into the pores. (2) PEDOT, in particular, has low solubility in solvents, so even when compounded with PSS, it exists in the liquid as particulate matter, and furthermore, its low dispersibility makes it prone to aggregation between particles, making it difficult to penetrate into the micropores. (3) For the reason in (3) above, it is difficult to increase the solid content concentration of the PEDOT / PSS dispersion (generally 1 to 4 mass%), so even if the pores are completely filled with the dispersion, the amount of solids in the pores after drying is small, and it is not possible to adequately coat the inside of the pores.

[0012] For the reasons stated above, when a PEDOT / PSS layer is formed on an aluminum oxide layer on etched aluminum foil using a pre-polymerization method, it is difficult to cover the inside of the micropores, and ultimately, voids remain in most of the pores. As a result, it is difficult to increase the capacitance of the resulting capacitor, and it is difficult to reduce the resistance due to the reduction in conductive paths (Patent Document 1).

[0013] On the other hand, in the in-device polymerization method of PEDOT / PSS, iron(III) p-toluenesulfonate ((FeOTs)3) is generally used as a polymerization catalyst, but for the following reasons, it is common to perform a washing operation with an aqueous solvent after in-device polymerization: (1) Fe(OTs)3 has a high acidity and is prone to corroding the aluminum oxide layer. (2) When Fe(OTs)3 migrates within the device, iron salts that are prone to causing current leakage and corrosion are generated at the locations where Fe(OTs)3 adheres.

[0014] However, the cleaning operation presents several challenges: it increases process costs, may lead to a decrease in conductivity due to the removal of Fe(OTs)3 and toluenesulfonic acid, which function as dopants (conductivity-enhancing additives), and may damage the conductive polymer layer or aluminum oxide layer during the cleaning operation (Non-Patent Literature 1).

[0015] Furthermore, to improve immersion into pores, conductive polymers such as water-soluble polythiophene-based materials and polyaniline-based materials are sometimes used as a pre-coat layer beneath the PEDOT / PSS layer. However, the above pre-coat layer has low water resistance, making it prone to damage when laminating PEDOT / PSS dispersions (Patent Document 2). Additionally, it is prone to becoming highly resistant when adjusting the pH to suppress corrosion, and its complex chemical structure tends to result in high costs.

[0016] The PEDOT / PSS layer has low resistance to water, highly polar organic solvents, and electrolytes, which can easily lead to reduced reliability when applied to hybrid capacitors or during cleaning operations.

[0017] In the case of polypyrrole, the challenges include lower conductivity compared to PEDOT, lower heat resistance, high corrosivity of the supporting electrolyte, dopant, and additives (similar to PEDOT / PSS), the use of an aqueous monomer immersion solvent, and the possibility of failure to achieve the desired polymerization during electrolytic polymerization.

[0018] International Publication No. 2025 / 023099, International Publication No. 2024 / 203133

[0019] Automotive Technology, 2023, Vol. 10, No. 10, pp. 22-27; Journal of Cleaner Production, 2022, Vol. 375, p. 134044

[0020] The present invention has been made in view of the above circumstances, and in particular aims to provide a conductive thin film forming composition suitable for forming conductive thin films laminated on electrode foils such as aluminum foil (hereinafter sometimes referred to as "substrates") that constitute electrolytic capacitors.

[0021] The inventors, through diligent research to achieve the above objectives, have discovered that a conductive thin film forming composition containing a specific thiophene compound, a heteropoly acid, and a non-aqueous solvent such as an alcohol, and free of iron-containing compounds, penetrates into the interior of the micropores on a substrate for electrolytic capacitors when coated with the composition. Furthermore, by heating and drying the composition in this state to polymerize the thiophene compound, the interior of the micropores can be coated with a thin film. The inventors have also discovered that the thin film has excellent conductivity, and that a composition can be applied in which a heteropoly acid compound, which is soluble in organic solvents such as alcohol, is used as a polymerization agent and dopant, and which does not contain iron salts, peroxides, sulfonic acid compounds, etc., which are commonly used in the past and tend to cause corrosion and leakage current, and which has a non-aqueous solvent as its main component, thereby reducing corrosiveness through the solvent effect. After polymerization of the specific thiophene compound on the substrate or within the device, the composition becomes a water-resistant cured film, and the film itself can suppress corrosion to surrounding components. The inventors have thus completed the present invention. Furthermore, by using a specific compound (excluding polymers) with a melting point below 200°C and a boiling point above 200°C, or a specific polymer with a weight-average molecular weight of 1,000 or more and a glass transition temperature below 200°C as a film-forming aid, the electronic resistance of the resulting film can be reduced for reasons such as improved polymerizability of the thiophene compound, improved uniformity of the resulting film, improved adhesion to adjacent substrates, and the expression of secondary dopant function.

[0022] In other words, the present invention provides the following compositions for forming conductive thin films: 1. A composition for forming conductive thin films comprising a thiophene compound represented by the following formula (1), a heteropoly acid, and a solvent, but not containing an iron-containing compound. (In the formula, R 1 , R 2 These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryloxy group, and -O-[Z-O] p -R e , or R 1 and R 2is -O-Y-O- formed by bonding, Y is an alkylene group having 1 to 40 carbon atoms which may contain an ether bond, 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, 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.) 2. The composition for forming a conductive thin film according to 1, further comprising a film-forming auxiliary, wherein the film-forming auxiliary is a specific compound (excluding a polymer) having a melting point of lower than 200°C and a boiling point of 200°C or higher at normal pressure, or a specific polymer having a weight average molecular weight of 1,000 or more and a glass transition temperature of 200°C or lower. 3. The composition for forming a conductive thin film according to 1 or 2, wherein the content of the heteropolyacid is 0.1 to 10 by mass ratio relative to 1 part by mass of the thiophene compound. 4. The composition for forming a conductive thin film according to 2 or 3, wherein the content of the film-forming auxiliary is 0.1 to 10 by mass ratio relative to 1 part by mass of the thiophene compound. 5. The composition for forming a conductive thin film according to any one of 2 to 4, wherein the contents of the thiophene compound, the heteropolyacid and the film-forming auxiliary are each 15% by mass or more based on the total solid content. 6. The composition for forming a conductive thin film according to any one of 1 to 5, wherein the heteropolyacid is phosphomolybdic acid. 7. The composition for forming a conductive thin film according to any one of 2 to 6, wherein the melting point of the specific compound is 50°C or higher and lower than 200°C. 8. The composition for forming a conductive thin film according to any one of 2 to 7, wherein the specific compound is a compound represented by the following formula (S1) or (S2). R 3 -SO-R 4     (S1) (wherein, R 3 , R 4 each independently represent 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 aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, or -O-[Z-O] p -R e , 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(This 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.) 5 -SO2-R 6 (S2) (wherein, R 5 , R 6 These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryl group, or a C6-C20 aryloxy group, -O-[Z-O] p -R e Z is an alkylene group having 1 to 40 carbon atoms, which may be substituted with halogen atoms, p is an integer of 1 or more, and R e (wherein 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.) 9. A conductive thin film forming composition of 8, wherein the above-mentioned specific compound is a compound represented by the following formula (S1-1) or (S2-1). 10. A conductive thin film forming composition of any of 2 to 9, wherein the specified polymer is polyhydroxystyrene. 11. A conductive thin film forming composition of any of 1 to 10, wherein the thiophene compound is a compound represented by the following formula (1-1). 12. A conductive thin film forming composition from any of 1 to 11, wherein the solvent contains 80% by mass or more of an alcohol-based solvent or a glycol ether-based solvent. 13. A conductive thin film forming composition from 12, wherein the solvent further contains 3% by mass or more of water. 14. A conductive thin film forming composition from any of 1 to 13, wherein the surface tension is 60 mN / m or less at 20°C. 15. A conductive thin film forming composition from any of 1 to 14, wherein the viscosity is 100 mPa·s or less at 25°C. 16. A conductive thin film forming composition from any of 1 to 15, wherein the solid content concentration is 1 to 80% by mass. 17. A conductive thin film forming composition from any of 1 to 16 for use in electrolytic capacitors. 18. A conductive thin film forming composition from any of 1 to 16 for use in solid electrolytes. 19. A conductive thin film obtained from any of the conductive thin film forming compositions from 1 to 16, comprising a polymer of a thiophene compound represented by formula (1). 20. An electrolytic capacitor comprising the conductive thin film of 19. 21. 20 electrolytic capacitors, which are conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors. 22. A solid electrolyte comprising 19 conductive thin films. 23. A method for producing a conductive thin film, comprising the step of applying any of the conductive thin film forming compositions 1 to 16 to a substrate and drying it at a temperature of 80°C or higher.

[0023] The present invention provides a composition for forming conductive thin films suitable for forming conductive thin films for electrolytic capacitors. By using the composition of the present invention, not only can a thin film with excellent conductivity be formed, but the conductive thin film can also be formed inside the micropores of the substrate surface, resulting in a film without voids within the pores. Furthermore, the thin film has excellent conductivity, as well as excellent properties such as low resistance, low corrosion resistance, high heat resistance, high scratch resistance, and high water resistance, and can exhibit high performance as a conductive thin film for electrolytic capacitors. As a result, it is expected that the capacitance of the resulting electrolytic capacitor will increase, the frequency characteristics of the ESR will improve, and the resistance will be reduced and the durability improved due to an increase in conductive paths. In addition, since the conductive thin film forming composition does not contain corrosive compounds such as iron, cleaning operations are unnecessary when manufacturing capacitors, thus eliminating the disadvantages associated with cleaning operations. Furthermore, since the conductive thin film forming composition can be made highly concentrated, the number of coating operations that need to be performed multiple times can be reduced, which also has advantages in the manufacturing process.

[0024] This is a scanning electron microscope image showing the entire pore region of the cross-section of the etched aluminum foil. This is a scanning electron microscope image showing a magnified view of the pore region near the surface of the cross-section of the etched aluminum foil. This is a scanning electron microscope image showing a magnified view of the central pore region of the cross-section of the etched aluminum foil. This is a scanning electron microscope image showing a magnified view of the bottom pore region of the cross-section of the etched aluminum foil. This is a scanning electron microscope image showing the entire pore region of the cross-section of the coated foil E-1 prepared in Example 3-1. This is a scanning electron microscope image showing a magnified view of the pore region near the surface of the cross-section of the coated foil E-1 prepared in Example 3-1. This is a scanning electron microscope image showing a magnified view of the central pore region of the cross-section of the coated foil E-1 prepared in Example 3-1. This is a scanning electron microscope image showing a magnified view of the bottom pore region of the cross-section of the coated foil E-1 prepared in Example 3-1. This is the result of the SEM-EDX analysis of the elemental distribution of carbon in the coated cross-section of coated foil E-1 prepared in Example 3-1. This is the result of the SEM-EDX analysis of the elemental distribution of sulfur in the coated cross-section of coated foil E-1 prepared in Example 3-1. This is the result of the SEM-EDX analysis of the elemental distribution of molybdenum in the coated cross-section of coated foil E-1 prepared in Example 3-1.

[0025] The conductive thin film forming composition of the present invention is characterized by comprising a predetermined thiophene compound, a heteropoly acid, and a solvent, and not containing an iron-containing compound. Since the conductive thin film forming composition of the present invention does not contain corrosive substances such as iron or substances that generate leakage current, a cleaning operation is unnecessary when manufacturing capacitors, thus eliminating the disadvantages associated with the cleaning operation.

[0026] In this invention, "free of iron-containing compounds" means that iron-containing compounds are not intentionally included as components of the composition, and does not negate the possibility of iron being present as an impurity in the raw materials or from the equipment and apparatus used in preparing the composition.

[0027] [1] Thiophene compound The conductive thin film forming composition of the present invention contains a thiophene compound represented by the following formula (1).

[0028]

[0029] In the formula, R 1 , R 2 These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryloxy group, and -O-[Z-O] p -R e , or R 1 and R 2 The -O-Y-O- is formed by the bonding of the following: Y is an alkylene group having 1 to 40 carbon atoms, which may contain an ether bond; 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; R e This 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.

[0030] The alkyl group having 1 to 40 carbon atoms may be linear, branched, or cyclic. 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, n-eicosanyl, 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.

[0031] As for fluoroalkyl groups having 1 to 40 carbon atoms, there are no particular limitations as long as they are alkyl groups having 1 to 40 carbon atoms in which at least one hydrogen atom on a carbon atom is substituted with a fluorine atom, but for example, fluoromethyl group, difluoromethyl group, trifluoromethyl group, 1-fluoroethyl group, 2-fluoroethyl group, 1,2-difluoroethyl group, 1,1-difluoroethyl group, 2,2-difluoroethyl group, 1,1,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 1,2,2,2-tetrafluoroethyl group, perfluoroethyl group, 1-fluoropropyl group, 2-fluoropropyl group, 3-fluoropropyl group, 1,1-difluoropropyl group, 1,2-difluoropropyl group, 1,3-difluoropropyl group, 2,2-difluoropropyl group, 2,3-difluoropropyl group, 3,3-difluoropropyl group, 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, Examples include the 3,3,3-tetrafluoropropyl group, the 1,1,2,2,3-pentafluoropropyl group, the 1,2,2,3,3-pentafluoropropyl group, the 1,1,3,3,3-pentafluoropropyl group, the 1,2,3,3,3-pentafluoropropyl group, the 2,2,3,3,3-pentafluoropropyl group, the perfluoropropyl group, the perfluorobutyl group, the perfluoropentyl group, the perfluorohexyl group, the perfluoroheptyl group, and the perfluorooctyl group.

[0032] The alkoxy group having 1 to 40 carbon atoms may have a linear, branched, or cyclic alkyl group. 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.

[0033] 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 a carbon atom is substituted with a fluorine atom, for example, fluoromethoxy group, difluoromethoxy group, trifluoromethoxy group, 1-fluoroethoxy group, 2-fluoroethoxy group, 1,2-difluoroethoxy group, 1,1-difluoroethoxy group, 2,2-difluoroethoxy group, 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 Examples include the group, 1,3,3,3-tetrafluoropropoxy group, 2,2,3,3-tetrafluoropropoxy group, 2,3,3,3-tetrafluoropropoxy group, 1,1,2,2,3-pentafluoropropoxy group, 1,2,2,3,3-pentafluoropropoxy group, 1,1,3,3,3-pentafluoropropoxy group, 1,2,3,3,3-pentafluoropropoxy group, 2,2,3,3,3-pentafluoropropoxy group, and perfluoropropoxy group.

[0034] The alkylene group having 1 to 40 carbon atoms may be linear, branched, or cyclic. Examples include methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, nonadecylene, and eicosanylene.

[0035] 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.

[0036] Examples of aryloxy groups having 6 to 20 carbon atoms include phenoxy, anthracenox, naphthoxy, phenantrenoxy, and fluorenoxy groups.

[0037] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0038] In the above formula (1), R 1 and R 2 These are, independently of each other, a hydrogen atom, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, and -O[C(R a R b )-C(R c R d )-O] p -R e , -OR f , or a sulfonic acid group, or R 1 and R 2 A -O-Y-O- formed by the bonding of these elements is preferred. a ~R dThese 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 them, R a ~R d These are preferably a hydrogen atom, a C1-C8 alkyl group, a C1-C8 fluoroalkyl group, or a phenyl group, independently of each other. e The group is a hydrogen atom, a C1-C8 alkyl group, a C1-C8 fluoroalkyl group, or a phenyl group, but a hydrogen atom, a methyl group, a propyl group, or a butyl group is preferred. Furthermore, p is preferably 1-5, and more preferably 1, 2, or 3.

[0039] R f The group 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 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 is preferred, and -CH2CF3 is more preferred.

[0040] 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 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 f , more preferably -O[C(R a R b )-C(R c R d )-O] p -R e , -O-CH2CH2-O-CH2CH2-O-CH3, -O-CH2CH2-O-CH2CH2-OH or -O-CH2CH2-OH, or R 1 and R 2which is -O-Y-O- formed by mutual binding.

[0041] For example, in the polythiophene compound according to a preferred embodiment of the present invention, R 1 is a sulfonic acid group, and R 2 contains a repeating unit other than a sulfonic acid group, or R 1 and R 2 contains a repeating unit which is -O-Y-O- formed by binding of R and R. Preferably, in the polythiophene compound, 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 contains a repeating unit of , or R 1 and R 2 contains a repeating unit which is -O-Y-O- formed by binding of R and R. More preferably, in the polythiophene compound, 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 contains the repeating unit of . Still more preferably, in the polythiophene compound, 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 contains the repeating unit of , or R 1 and R 2 contains a repeating unit which is -O-Y-O- formed by binding of R and R. Even more preferably, in the polythiophene compound, R 1 is a sulfonic acid group, and R 2 contains a repeating unit that is -O-CH2CH2-O-CH2CH2-O-CH3, -O-CH2CH2-O-CH2CH2-OH, or -O-CH2CH2-OH, or R1 and R 2 bond to each other, and comprises a repeating unit which is a group represented by the following formulas (Y1) and (Y2).

[0042]

[0043] Specific examples of the polythiophene compound include, but are not limited to, compounds represented by the following formulas (1-1) to (1-5).

[0044]

[0045] In the present invention, among these, the compound represented by formula (1-1) is preferred.

[0046] In the present invention, one type of the thiophene compound may be used alone, or two or more types may be used in combination.

[0047] [2] Heteropolyacid The composition for forming a conductive thin film of the present invention comprises a heteropolyacid. A heteropolyacid is typically a polyacid formed by condensation of an isopolyacid, which is an oxygen acid of vanadium (V), molybdenum (Mo), tungsten (W) or the like, and an oxygen acid of a different element, having a structure in which a heteroatom is located at the center of the molecule and represented by the chemical structure of Keggin type represented by formula (D1) or Dawson type represented by formula (D2). Examples of such oxygen acids of different elements mainly include oxygen acids of silicon (Si), phosphorus (P) and arsenic (As).

[0048]

[0049] Specific examples of heteropolyacids include phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid, phosphotungstomolybdic acid, and the like. In the present invention, phosphomolybdic acid is preferred from the viewpoints of improving polymerizability and the dopant (conductivity improving) function. One type of the heteropolyacid may be used alone, or two or more types may be used in combination.

[0050] Furthermore, in quantitative analysis such as elemental analysis, heteropoly acids can be used in the present invention even if the number of elements in the structure shown by the general formula is large or small, as long as they are commercially available or appropriately synthesized according to known synthesis methods. That is, for example, generally, phosphotungstic acid has the chemical formula H3(PW). 12 O 40 Although represented as )・nH2O, in quantitative analysis, even if the number of P (phosphorus), O (oxygen), or W (tungsten) in this formula is large or small, it can be used in the present invention as long as it is obtained as a commercially available product or is appropriately synthesized according to a known synthesis method. In this case, the mass of the heteropoly acid as defined in the present invention does not mean the mass of pure phosphotungstic acid (phosphotungstic acid content) in the synthesized product or commercially available product, but rather the total mass including hydrate water and other impurities in the form available as a commercially available product and in the form that can be isolated by a known synthesis method.

[0051] From the viewpoint of suppressing monomer volatilization, promoting polymerization, expressing dopant function after film formation, ensuring film uniformity, and improving substrate adhesion, the amount of heteropoly acid used is preferably 0.1 to 10, more preferably 0.2 to 5, and even more preferably 0.3 to 3, per 1 thiophene compound by mass ratio.

[0052] In this invention, the heteropoly acid functions as a polymerization catalyst for the thiophene compound, allowing the polymerization of the thiophene compound on the substrate to proceed to a high degree. This results in a highly reliable conductive thin film with low resistance, low corrosion resistance, high heat resistance, high scratch resistance, and high water resistance. Furthermore, the heteropoly acid functions as a dopant in the conductive thin film, contributing to the improvement of the conductivity of the conductive thin film. Moreover, because it is a compound that retains many polar groups, it is possible to improve uniform film formation and substrate adhesion, and it can also be expected to regenerate the chemically formed film with phosphate functional groups.

[0053] Furthermore, since the above heteropoly acids are soluble in organic solvents such as alcohols, solutions can be prepared by applying an organic solvent as the main solvent. Generally, in organic solvents, protons (H) in proton-acid compounds such as sulfonic acid compounds, phosphoric acid compounds, and heteropoly acid compounds + As the degree of dissociation of the heteropoly acid decreases and the acidity decreases, applying an organic solvent as the main solvent can reduce the corrosiveness of the heteropoly acid to metallic substances in solution. Furthermore, the thin film composed of the polymer of the thiophene compound has high water resistance and hardens while encapsulating the corrosive heteropoly acid compound, resulting in a thin film with high water resistance and low corrosion.Therefore, unlike iron sulfonate-based catalysts conventionally used for conductive polymer aluminum solid electrolytic capacitors with in-device polymerization, there is less need for removal by washing, and the resulting thin film has high water resistance and scratch resistance, so damage can be suppressed even if washing is performed.In the above, "main solvent" means a solvent that accounts for more than 50% by mass of the total solvent.

[0054] [3] Solvent The charge-transporting ink composition of the present invention contains a solvent. Such a solvent is not particularly limited as long as it disperses or dissolves the solid content. Specific examples include, for example, water; alcohol-based solvents such as methanol, ethanol, n-propanol, i-propanol (2-propanol), n-butanol, 1-octanol, 1-nonanol, 1-decanol, tetrahydrofurfuryl alcohol, terpineol, cyclohexanol, diacetone alcohol, benzyl alcohol, 2-phenoxyethanol, 2-benzyloxyethanol; ethylene glycol, propylene glycol, 2-methyl-2,4-pentanediol, 1,3-octylene glycol, diethylene glycol, di Glycol solvents such as propylene glycol, triethylene glycol, tripylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, and 3-methyl-1,5-pentanediol; ketone solvents such as acetone, acetylacetone, methyl ethyl ketone, diethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-amyl ketone, 4-hydroxy-4-methyl-2-pentanone, 2-heptanone, cyclohexanone, methylcyclopentanone, and isophorone;Dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-hexyl acetate, benzyl acetate, 2-hydroxyethyl acetate, methyl lactate, ethyl lactate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dimethyl adipate, diethyl adipate, dipropyl adipate, diisopropyl malonate, dimethyl sebacate, diethyl sebacate, methyl benzoate, ethyl benzoate, butyl benzoate, dimethyl phthalate, di oxalate Ester solvents such as ethyl oxalate, dibutyl oxalate, diethyl fumarate, ethylene glycol monomethyl ether acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, triacetin, γ-butyrolactone, etc.; ether solvents such as dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, anisole, 4-methoxytoluene, etc.Glycol ether solvents such as ethylene glycol monoethyl ether, ethylene glycol monopropyl 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, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol butyl ether; N-methylformamide, N-methyl A suitable solvent may be selected from among amide solvents such as cetoamide, N-methylformanilide, N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylisobutylamide, N-methyl-2-pyrrolidone, N-ethylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone; aromatic or halogenated aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, cyclohexylbenzene, chlorobenzene, tetralin, and decylbenzene; aliphatic hydrocarbon solvents such as n-hexane, n-heptane, n-octane, n-nonane, n-decane, i-octane, i-nonane, and i-decane; halogenated hydrocarbon solvents such as methylene chloride, dichloromethane, 1,2-dichloroethane, and chloroform; cyano solvents such as acetonitrile and 3-methoxypropionitrile; and sulfoxide solvents such as dimethyl sulfoxide. These organic solvents can be used individually or in combination of two or more.

[0055] In the present invention, among these, alcohol-based solvents, ether-based solvents, and glycol ether-based solvents are preferred, and alcohol-based solvents and glycol ether-based solvents are more preferred, because they have high solubility of the solids contained in the composition, allow for the preparation of a solution with low surface tension, and can be easily concentrated.

[0056] Furthermore, from the viewpoint of low surface tension and low corrosiveness, the above solvent preferably contains 50% by mass or more of an alcohol-based solvent or a glycol ether-based solvent, and more preferably 80% by mass or more.

[0057] When using an alcohol-based solvent or a glycol ether-based solvent as the solvent, it is preferable to further include 3% by mass or more of water. There is no particular upper limit, but it is generally preferable to include 20% by mass or less. By including a small amount of water in the alcohol-based solvent or glycol ether-based solvent, the storage stability of the resulting composition can be improved.

[0058] [4] Film-forming aid The conductive thin film-forming composition of the present invention may further contain a film-forming aid to assist in the polymerization of the thiophene compound. In the present invention, it is preferable that the film-forming aid is dissolved in the solvent while the solvent is present during film formation (specifically, the step of heating and drying a coating of the conductive thin film-forming composition applied to a substrate to form a conductive thin film), but melts after the solvent evaporates during film formation and functions as a polymerization support. Furthermore, it is preferable that the substance promotes the polymerization reaction by interacting with the thiophene compound and functions as a dopant or secondary dopant after polymerization.

[0059] The presence of such film-forming aids during film formation allows the polymerization of the thiophene compound to continue even after the solvent has evaporated, thereby increasing the molecular weight of the resulting polymer. This is expected to improve the conductivity of the resulting conductive thin film, and furthermore, it is expected to result in a highly reliable conductive thin film with low resistance, low corrosion resistance, high heat resistance, high scratch resistance, and high water resistance.

[0060] The preferred film-forming aids are specific compounds (excluding polymers) having a melting point of less than 200°C and a boiling point of 200°C or higher at atmospheric pressure, or specific polymers having a weight-average molecular weight of 1,000 or higher and a glass transition temperature (hereinafter sometimes referred to as "Tg") of 200°C or lower. The weight-average molecular weight is the polystyrene equivalent value obtained by gel permeation chromatography (GPC).

[0061] The lower limit of the melting point of the above-mentioned specific compound is not particularly limited, but considering the operational stability and reliability of the capacitor, it is preferably 50°C or higher. The upper limit of the melting point of the above-mentioned specific compound is not particularly limited, but considering the drying temperature and the thermal stability of the surrounding materials, it is preferably 200°C or lower. The lower and upper limits of the boiling point of the above-mentioned specific compound are not particularly limited, but since the weight will decrease if the drying temperature during film formation exceeds the boiling point of the above-mentioned specific compound, considering the drying temperature during film formation, it is preferably 200°C or higher at atmospheric pressure, more preferably 250°C or higher, and even more preferably 300°C or higher. In this invention, compounds whose boiling point is unknown or compounds whose boiling point cannot be determined for some reason are included in compounds with a boiling point of 200°C or higher at atmospheric pressure if they do not completely volatilize below 200°C at atmospheric pressure.

[0062] The specified compounds mentioned above are preferably compounds represented by the following formulas (S1) or (S2) (hereinafter, these may be referred to as "specified compound (S1)" or "specified compound (S2)").

[0063] R 3 -SO-R 4 (S1) (wherein, R 3 , R 4 These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryl group, or a C6-C20 aryloxy group, -O-[Z-O] p -R e Z is an alkylene group having 1 to 40 carbon atoms, which may be substituted with halogen atoms, p is an integer of 1 or more, and R e (These are 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.)

[0064] R 5 -SO2-R 6 (S2) (wherein, R 5 , R 6These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryl group, or a C6-C20 aryloxy group, -O-[Z-O] p -R e Z is an alkylene group having 1 to 40 carbon atoms, which may be substituted with halogen atoms, p is an integer of 1 or more, and R e (These are 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.)

[0065] The alkyl group having 1 to 40 carbon atoms may be linear, branched, or cyclic. 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, n-eicosanyl, 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.

[0066] As for fluoroalkyl groups having 1 to 40 carbon atoms, there are no particular limitations as long as they are alkyl groups having 1 to 40 carbon atoms in which at least one hydrogen atom on a carbon atom is substituted with a fluorine atom, but for example, fluoromethyl group, difluoromethyl group, trifluoromethyl group, 1-fluoroethyl group, 2-fluoroethyl group, 1,2-difluoroethyl group, 1,1-difluoroethyl group, 2,2-difluoroethyl group, 1,1,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 1,2,2,2-tetrafluoroethyl group, perfluoroethyl group, 1-fluoropropyl group, 2-fluoropropyl group, 3-fluoropropyl group, 1,1-difluoropropyl group, 1,2-difluoropropyl group, 1,3-difluoropropyl group, 2,2-difluoropropyl group, 2,3-difluoropropyl group, 3,3-difluoropropyl group, 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, Examples include the 3,3,3-tetrafluoropropyl group, the 1,1,2,2,3-pentafluoropropyl group, the 1,2,2,3,3-pentafluoropropyl group, the 1,1,3,3,3-pentafluoropropyl group, the 1,2,3,3,3-pentafluoropropyl group, the 2,2,3,3,3-pentafluoropropyl group, the perfluoropropyl group, the perfluorobutyl group, the perfluoropentyl group, the perfluorohexyl group, the perfluoroheptyl group, and the perfluorooctyl group.

[0067] The alkoxy group having 1 to 40 carbon atoms may have a linear, branched, or cyclic alkyl group. 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.

[0068] 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 a carbon atom is substituted with a fluorine atom, for example, fluoromethoxy group, difluoromethoxy group, trifluoromethoxy group, 1-fluoroethoxy group, 2-fluoroethoxy group, 1,2-difluoroethoxy group, 1,1-difluoroethoxy group, 2,2-difluoroethoxy group, 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 Examples include the group, 1,3,3,3-tetrafluoropropoxy group, 2,2,3,3-tetrafluoropropoxy group, 2,3,3,3-tetrafluoropropoxy group, 1,1,2,2,3-pentafluoropropoxy group, 1,2,2,3,3-pentafluoropropoxy group, 1,1,3,3,3-pentafluoropropoxy group, 1,2,3,3,3-pentafluoropropoxy group, 2,2,3,3,3-pentafluoropropoxy group, and perfluoropropoxy group.

[0069] The alkylene group having 1 to 40 carbon atoms may be linear, branched, or cyclic. Examples include methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, nonadecylene, and eicosanylene.

[0070] 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.

[0071] Examples of aryloxy groups having 6 to 20 carbon atoms include phenoxy, anthracenox, naphthoxy, phenantrenoxy, and fluorenoxy groups.

[0072] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0073] In the above formula (S1), R 3 and R 4 , and also R in the above formula (S2) 5 and R 6 These are, independently of each other, a hydrogen atom, an aryl group having 6 to 20 carbon atoms, or -O-[Z-O] p -R e It is preferable.

[0074] -O-[Z-O] p -R e For example, -O[C(R a1 R b1 )-C(R c1 R d1 )-O] p1 -R e1 , and -OR f1 Preferably, -O[C(R a1 R b1 )-C(Rc1 R d1 )-O] p1 -R e1 This is more preferable. a1 ~R d1 These 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 them, R a1 ~R d1 These are preferably a hydrogen atom, a C1-C8 alkyl group, a C1-C8 fluoroalkyl group, or a phenyl group, independently of each other. e1 The group is a hydrogen atom, a C1-C8 alkyl group, a C1-C8 fluoroalkyl group, or a phenyl group, but a hydrogen atom, a methyl group, a propyl group, or a butyl group is preferred. Furthermore, p1 is preferably 1 to 5, and more preferably 1, 2, or 3.

[0075] R f1 The group 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 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 is preferred, and -CH2CF3 is more preferred.

[0076] -O-[Z-O] p -R e Suitable specific examples include, but are not limited to, -O-CH2CH2-O-CH2CH2-O-CH3, -O-CH2CH2-O-CH2CH2-OH, and -O-CH2CH2-OH.

[0077] In the present invention, the above R 3 ~R 6 Each of these is independently preferably a hydrogen atom or an aryl group having 6 to 20 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl group.

[0078] Preferred specific examples of the above-mentioned specific compound (S1) include, but are not limited to, the compounds represented by the following formulas (S1-1) to (S1-4).

[0079]

[0080] In this invention, among these, the compound represented by formula (S1-1) (diphenyl sulfoxide) is preferred.

[0081] Preferred specific examples of the above-mentioned specific compound (S2) include, but are not limited to, the compounds represented by the following formulas (S2-1) to (S2-4).

[0082]

[0083] In this invention, among these, the compound represented by formula (S2-1) (diphenyl sulfone) is preferred.

[0084] The weight-average molecular weight of the above-mentioned specific polymer is preferably 1,000 or more, and more preferably 2,000 or more, from the viewpoint of improving uniform film formation and polymerization reactivity. Furthermore, there is no particular upper limit to the weight-average molecular weight, but considering solubility and glass transition temperature, it is preferably 1,000,000 or less, and more preferably 100,000 or less.

[0085] The glass transition temperature (Tg) is preferably 200°C or lower, and more preferably 150°C or lower, from the viewpoint of softening during heating and drying. Furthermore, while the lower limit of Tg is not particularly limited, considering the stability of the capacitor function, it is preferably 50°C or higher, and more preferably 100°C or higher.

[0086] The above-mentioned specific polymer is not particularly limited as long as it is soluble in alcohol-based solvents, ether-based solvents, and glycol-ether-based solvents and satisfies the above-mentioned weight-average molecular weight and Tg. However, it is preferable that it has a functional group that interacts with the thiophene compound, and a polymer having an aromatic functional group is preferred. In the present invention, polyhydroxystyrene (PHS) and the like can be suitably used.

[0087] Specific examples of the above-mentioned specific polymers include, but are not limited to, polymers having repeating units represented by the following formula (P-1), polyacrylic acid, phenolic resins, epoxy resins, etc.

[0088]

[0089] In the present invention, among these, a polymer having repeating units represented by formula (P-1) (polyhydroxystyrene) is preferred.

[0090] If the above-mentioned conductive thin film forming composition contains a film-forming aid, its content is preferably 0.1 to 10, more preferably 0.2 to 5, and even more preferably 0.3 to 3, in mass ratio with respect to 1 thiophene compound, from the viewpoint of improving the degree of polymerization of the thiophene compound, the conductivity of the resulting film, uniform film formation, and adhesion.

[0091] Furthermore, if the above-mentioned conductive thin film forming composition contains a film-forming aid, it is preferable that the content of the thiophene compound, heteropoly acid, and film-forming aid be 15% by mass or more of the solid content, from the viewpoint of improving the degree of polymerization of the thiophene compound, the conductivity of the resulting film, uniformity of film formation, and adhesion.

[0092] [5] Other additives The conductive thin film forming composition of the present invention may contain other additives as needed.

[0093] [6] Conductive Thin Film Forming Composition and Conductive Thin Film The method for preparing the conductive thin film forming composition of the present invention is not particularly limited, and can be prepared by mixing a thiophene compound represented by formula (1), a heteropoly acid and a solvent, and optionally other additives in any order.

[0094] In the present invention, the solid content concentration of the above composition is not particularly limited, but considering the solubility of the solid content, the storage stability of the solution, the ability to embed in pores, and the low resistance of the resulting film, it is preferably 1 to 80% by mass, more preferably 2 to 60% by mass, and even more preferably 3 to 40% by mass. In the present invention, the term "solid content" refers to components other than the solvent that constitute the composition.

[0095] The surface tension of the above composition is preferably 60 mN / m or less, more preferably 20 to 40 mN / m, and even more preferably 20 to 35 mN / m at 20°C, considering the coatability to the substrate and the penetration into micropores. The above surface tension is measured using a surface tension meter DY-700 (manufactured by Kyowa Interface Science Co., Ltd.) by the plate method under conditions of 20°C.

[0096] The viscosity of the above conductive thin film forming composition is preferably 100 mPa·s or less, more preferably 1 to 30 mPa·s, and more preferably 1 to 10 mPa·s at 25°C, considering the coating properties to the substrate and the penetration into micropores. The above viscosity refers to the viscosity measured at 25°C using an E-type viscometer.

[0097] In the present invention, the conductive thin film forming composition may be filtered using a sub-micrometer-order filter or the like during the manufacturing process or after all components have been mixed, in order to obtain a thin film with higher flatness and reproducibility.

[0098] The conductive thin-film forming composition of the present invention is expected to have a low surface tension and low viscosity, resulting in a low contact angle and high dynamic performance. This is expected to enable advanced penetration and immersion into the micropores of the substrate surface, such as etched aluminum foil. The formation of a conductive polymer layer within the micropores and on the aluminum oxide layer is anticipated.

[0099] By coating the conductive thin film forming composition described above onto a predetermined substrate and evaporating the organic solvent from the resulting coating by appropriate means such as firing or vacuum drying, a conductive thin film containing a polymer of the thiophene compound represented by formula (1) can be formed on the substrate. In the conductive thin film forming composition of the present invention, the thiophene compound represented by formula (1) is not conductive, but the polymer of the thiophene compound represented by formula (1), or its complex with a dopant such as a heteropoly acid, is conductive, so the resulting conductive thin film is conductive.

[0100] When one compound is used as the compound (monomer) represented by formula (1) above, the resulting conductive thin film will be a homopolymer containing repeating units corresponding to the structure of the monomer. When two or more compounds are used as the compound (monomer) represented by formula (1) above, the resulting copolymer will be a copolymer containing repeating units corresponding to the structures of the compounds used. In the case of a copolymer, it may be either a random copolymer or a block copolymer.

[0101] As the substrate mentioned above, the valve metal described later, which has been conventionally used as electrode foil (anode foil and cathode foil) for electrolytic capacitors, can be used. The thickness of the electrode foil is not particularly limited, but in the present invention, 10 to 300 μm is preferred.

[0102] Examples of methods for applying the composition include spin coating, dip coating, flow coating, inkjet coating, casting, spray coating, bar coating, gravure coating, slit coating, roll coating, flexographic printing, transfer printing, brush coating, blade coating, air knife coating, and die coating. However, from the standpoint of work efficiency, inkjet coating, casting, dip coating, bar coating, blade coating, roll coating, gravure coating, flexographic printing, spray coating, and die coating are preferred.

[0103] For heating and drying, the conditions can be within the range shown in the description of the capacitor below.

[0104] The optimal thickness of the charge-transporting thin film varies depending on the substrate used, but considering substrate coverage and resistance, 10 nm to 100 μm is preferred. The thickness of the charge-transporting thin film can be determined, for example, by cutting a test piece of an appropriate size from the substrate on which the charge-transporting thin film is formed, exposing the cross-section by methods such as tearing it by hand, and observing it with a microscope such as a scanning electron microscope (SEM) to determine the portion of the charge-transporting thin film that is exposed in the cross-section.

[0105] The conductive thin film obtained from the conductive thin film forming composition of the present invention can be suitably used for electrolytic capacitors. Furthermore, because this conductive thin film exhibits the above-mentioned useful properties such as high conductivity, it can be applied to various other uses besides conductive thin films for electrolytic capacitors, such as conductive layers for various electronic devices and antistatic films.

[0106] [7] Electrolytic Capacitors Electrolytic capacitors include aluminum electrolytic capacitors, tantalum electrolytic capacitors, niobium electrolytic capacitors, etc. Among the above aluminum electrolytic capacitors, there are wound aluminum electrolytic capacitors, multilayer aluminum electrolytic capacitors, and flat-plate aluminum electrolytic capacitors, but the conductive thin film forming composition of the present invention can be applied to any of these electrolytic capacitors. These capacitors will be described below.

[0107] First, as the capacitor element of a wound aluminum electrolytic capacitor, it is preferable to use an anode foil (etched chemically converted aluminum foil) which has a dielectric layer formed by etching the surface of an aluminum foil and then chemically converting it, to which lead terminals are attached, and a cathode foil made of aluminum foil is also fitted with lead terminals, and these anode foils with lead terminals and cathode foils are wound together with a separator in between.

[0108] The anode foil and cathode foil are long foil bodies made of valve metal. Examples of valve metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. The purity of the material is preferably 99.9% or higher for the anode foil and approximately 99% or higher for the cathode foil, but impurities such as silicon, iron, copper, magnesium, and zinc may be present.

[0109] The anode foil is formed by creating a molded body from valve metal powder, a sintered body from a molded body, or an etched foil from a rolled foil, and its surface is enlarged. Examples of enlarged surface structures include tunnel-shaped pits, spongy pits, or voids between densely packed powder particles. These enlarged surface structures can be formed, for example, by DC etching, which involves applying a direct current in an acidic aqueous solution containing halogen ions such as hydrochloric acid, or by AC etching, which involves applying an alternating current. They can also be formed by depositing or sintering metal particles or the like onto the core.

[0110] The cathode foil may also be given an expanded surface structure by vapor deposition, sintering, or etching.

[0111] A dielectric oxide film is formed on the surface of the anode foil. For example, if the anode foil is aluminum foil, the dielectric oxide film is formed from aluminum oxide with an oxidized surface structure. This dielectric oxide film is formed by a chemical conversion treatment in which a voltage is applied in an aqueous solution of adipic acid, boric acid, or phosphoric acid. Alternatively, a thin dielectric oxide film (approximately 1 to 10V) may be formed on the surface of the cathode foil by a chemical conversion treatment as needed. Furthermore, the dielectric oxide film may be formed by a layer of metal nitride, metal carbide, or metal carbonitride formed by vapor deposition, or by using a material containing carbon on its surface.

[0112] Examples of the above-mentioned separators include cellulose such as kraft paper, Manila hemp, esparto paper, hemp, and rayon, and mixed papers thereof; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and derivatives thereof; polytetrafluoroethylene resins; polyvinylidene fluoride resins; vinylon resins; polyamide resins such as aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides; polyimide resins; polyethylene resins; polypropylene resins; trimethylpentene resins; polyphenylene sulfide resins; acrylic resins; and polyvinyl alcohol resins. These resins may be used individually or in combination of two or more types.

[0113] When manufacturing a wound-type aluminum electrolytic capacitor by applying the conductive thin-film forming composition of the present invention to the capacitor element described above, an in-element polymerization method can be suitably employed. The method will be described in detail below.

[0114] First, the capacitor element is immersed in the conductive thin film forming composition of the present invention, and after being removed, the monomer (thiophene compound represented by formula (1) above) is polymerized at room temperature or under heating to form an electrolyte layer (conductive thin film) containing the polymer of the thiophene compound. Next, the capacitor element having the electrolyte layer is enclosed with an outer covering material to manufacture a wound aluminum electrolytic capacitor.

[0115] In the manufacture of electrolytic capacitors other than the wound-type aluminum electrolytic capacitor described above, such as multilayer aluminum electrolytic capacitors, planar aluminum electrolytic capacitors, tantalum electrolytic capacitors, and niobium electrolytic capacitors, a capacitor element is used that has an anode made of a porous valve metal such as aluminum, tantalum, or niobium, and a dielectric layer made of an oxide film of these valve metals. The conductive thin film forming composition of the present invention is coated or immersed on the anode for the capacitor element, similar to the case of the wound-type aluminum electrolytic capacitor, and the monomer (thiophene compound represented by formula (1) above) is polymerized under heating. After repeating these steps to form an electrolyte layer made of a conductive thin film, carbon paste and silver paste are applied, dried, and then the capacitor is enclosed, thereby manufacturing multilayer aluminum electrolytic capacitors, planar aluminum electrolytic capacitors, tantalum electrolytic capacitors, niobium electrolytic capacitors, and the like.

[0116] In the above description, the case in which the conductive thin film forming composition of the present invention is immersed in the capacitor element and impregnated with it, may also be impregnated with the composition by, for example, applying it to the capacitor element with a spray.

[0117] In the above method, after impregnation with the composition, polymerization of the thiophene compound is carried out at room temperature or under heating. The reaction temperature (heating and drying temperature) is preferably 80°C or higher, and more preferably 120°C or higher, from the viewpoint of sufficient polymerization of the thiophene compound. The upper limit of the reaction temperature is not particularly limited, but it is preferably 300°C or lower from the viewpoint of the heat resistance of the compound. Furthermore, if the composition contains a film-forming aid, it is preferable to set the temperature so that the component does not disappear, and in particular, if it contains a specific compound, it is preferable to set the temperature so as not to exceed its boiling point. Furthermore, the reaction time (heating and drying time) is preferably 0.1 to 180 minutes, more preferably 1 to 30 minutes, and even more preferably 1 to 15 minutes, from the viewpoint of sufficient polymerization of the thiophene compound.

[0118] Preferably, the conductive thin film forming composition of the present invention completely coats the surface of the aluminum oxide layer within the pores of the etched aluminum foil as a solution, and after drying, the reaction product of the composition of the present invention similarly completely coats the surface of the aluminum oxide layer.

[0119] A different type of conductive polymer may be laminated on top of the conductive thin film obtained by the composition of the present invention. While a high packing density of the film obtained by the composition of the present invention within the pores is preferable, if a different type of conductive polymer is laminated on top of the conductive thin film, or if the electrolyte is immersed in a hybrid capacitor, appropriate voids may be set within the pores even after the conductive thin film of the present invention is formed.

[0120] Furthermore, in the manufacture of an electrolytic capacitor, as described above, a conductive thin film may be formed using the conductive thin film forming composition of the present invention, and then a conductive polymer layer may be formed on the conductive thin film using a dispersion of a π-conjugated conductive polymer (excluding polymers of thiophene compounds represented by formula (1) above), thereby forming an electrolytic capacitor in which the electrolyte is composed of both.

[0121] As the π-conjugated conductive polymer mentioned above, a π-conjugated conductive polymer using polymer anions as dopants can be used.

[0122] This polymer anion is mainly composed of high-molecular-weight sulfonic acid. Examples of the polymer anion include copolymers of at least one sulfonic acid monomer selected from the group consisting of polystyrene sulfonic acid, sulfonated polyester, phenol sulfonic acid novolac resin, and styrene sulfonic acid, and a non-sulfonic acid monomer.

[0123] The weight-average molecular weight of the polystyrene sulfonic acid described above varies depending on the type of monomers it comprises, but considering the conductivity of the resulting conductive polymer and the viscosity of the dispersion used, a value of 10,000 to 1,000,000 is preferred.

[0124] Specific examples of π-conjugated conductive polymers include those disclosed in International Publication No. 2015 / 129515.

[0125] The conductive thin film forming composition of the present invention is suitable for forming conductive thin films on a substrate of an electrolytic capacitor, and is particularly suitable for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors. Furthermore, since the conductive thin film forming composition of the present invention results in a thin film with high conductivity after film formation, it is also suitable as a solid electrolyte for electrolytic capacitors.

[0126] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The measuring devices used in the examples are as follows: Viscosity measuring device: E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) Surface tension measuring device: Surface tension meter DY-700 (manufactured by Kyowa Interface Science Co., Ltd.) Surface resistance measuring device: Low resistivity meter Lorestar-GP, ASP probe (manufactured by Mitsubishi Chemical Corporation)

[0127] (1) Preparation of a composition for forming conductive thin films (conductive precursor ink) [Example 1-1] 0.250 g of phosphomolybdic acid n hydrate (manufactured by Junsei Chemical Co., Ltd.), 9.50 g of 2-propanol (manufactured by Junsei Chemical Co., Ltd., special grade), and 0.250 g of 3,4-ethylenedioxythiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) were sequentially added to a 20 mL screw-cap glass bottle and stirred to dissolve each, obtaining 10 g of a yellow transparent solution A-1 (solid content concentration 5.0% by mass; the solid content here conveniently includes the liquid 3,4-ethylenedioxythiophene and the water of crystallization in phosphomolybdic acid; the same applies hereafter).

[0128] [Example 1-2] Except for replacing 2-propanol in Example 1-1 with 1-methoxy-2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade), 10 g of a yellow transparent solution A-2 was obtained using the same method as in Example 1-1 (solid content concentration 5.0% by mass).

[0129] [Examples 1-3] In a 20 mL screw-cap glass bottle, 0.250 g of phosphomolybdate n hydrate (manufactured by Junsei Chemical Co., Ltd.), 9.00 g of 1-methoxy-2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade), 0.50 g of pure water, and 0.250 g of 3,4-ethylenedioxythiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) were sequentially added and stirred to dissolve each component, yielding 10 g of a yellow transparent solution A-3 (solid content concentration 5.0% by mass). When the obtained A-3 was stored at 23°C under light shielding for 7 days, the liquid turned green, but no solid precipitation was observed, and no change in conductive function was observed.

[0130] [Example 1-4] Except that the amount of 1-methoxy-2-propanol used in Example 1-3 was changed to 8.55 g and the amount of pure water used was changed to 0.95 g, the same method as in Example 1-3 was used to obtain 10 g of a yellow transparent solution A-4 (solid content concentration 5.0 mass%). When the obtained A-4 was stored at 23°C under light shielding for 7 days, the liquid changed to yellowish-green, but no solid precipitation was observed, and no change in the conductive function was observed.

[0131] [Examples 1-5] In a 20 mL screw-cap glass bottle, 0.167 g of phosphomolybdate n hydrate (manufactured by Junsei Chemical Co., Ltd.), 9.50 g of 1-methoxy-2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade), 0.167 g of diphenyl sulfoxide (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.167 g of 3,4-ethylenedioxythiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) were added sequentially and stirred to dissolve each component, yielding 10 g of a yellow transparent solution A-5 (solid content concentration 5.0% by mass).

[0132] [Example 1-6] Except for using 8.55 g of 1-methoxy-2-propanol in Example 1-5, and adding 0.95 g of pure water after adding 1-methoxy-2-propanol, 10 g of a yellow transparent solution A-6 was obtained using the same method as in Example 1-5 (solid content concentration 5.0 mass%). When the obtained A-6 was stored at 23°C under light shielding for 7 days, the liquid changed to yellowish-green, but no solid precipitation was observed, and no change in conductive function was observed. The viscosity of A-6 was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C and was found to be 3.0 mPa·s. Since the viscosity is sufficiently low, it is presumed that this solution has high penetration into the pores of the etched aluminum foil of conductive polymer electrolytic capacitors. The surface tension of A-6 was measured using a surface tensimeter DY-700 (manufactured by Kyowa Interface Science Co., Ltd.) at a temperature of 20°C and was found to be 29.8 mN / m. Since this is a sufficiently low surface tension, it is presumed that this solution has a low contact angle within the pores of the etched aluminum foil of the conductive polymer electrolytic capacitor and exhibits high permeability.

[0133] [Example 1-7] Except for changing the amount of phosphomolybdate n-hydrate used to 0.667 g, the amount of 1-methoxy-2-propanol used to 7.20 g, the amount of pure water used to 0.80 g, the amount of diphenyl sulfoxide to 0.667 g, and the amount of 3,4-ethylenedioxythiophene used to 0.667 g, 10 g of orange transparent solution A-7 was obtained using the same method as in Example 1-6 (solid content concentration 20.0 mass%). When the obtained A-7 was stored at 23°C under light shielding for 7 days, the liquid changed to dark green, but no solid precipitation was observed, and no change in conductive function was observed. The viscosity of A-7 was measured using an E-type viscometer TVE-22L (manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C and was found to be 3.8 mPa·s. Since the viscosity is sufficiently low, it is presumed that this solution has high penetration into the pores of the etched aluminum foil of conductive polymer aluminum electrolytic capacitors. The surface tension of A-7 was measured using a surface tensile meter DY-700 (manufactured by Kyowa Interface Science Co., Ltd.) at a temperature of 20°C and was found to be 30.9 mN / m. Since this is a sufficiently low surface tension, it is presumed that this solution has a low contact angle within the pores of the etched aluminum foil of the conductive polymer electrolytic capacitor and exhibits high permeability.

[0134] [Example 1-8] Except for changing the amount of phosphomolybdate n-hydrate used to 1.667 g, the amount of 1-methoxy-2-propanol used to 0.45 g, the amount of pure water used to 0.05 g, the amount of diphenyl sulfoxide to 1.667 g, and the amount of 3,4-ethylenedioxythiophene used to 1.667 g, 10 g of red transparent solution A-8 was obtained using the same method as in Example 1-6 (solid content concentration 50.0% by mass).

[0135] [Example 1-9] Except for changing the diphenyl sulfoxide in Example 1-5 to diphenyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 g of a yellow transparent solution A-9 was obtained using the same method as in Example 1-5 (solid content concentration 5.00% by mass).

[0136] [Example 1-10] Except for replacing diphenyl sulfoxide in Example 1-6 with diphenyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 g of a yellow transparent solution A-10 was obtained using the same method as in Example 1-6 (solid content concentration 5.0% by mass). When the obtained A-10 was stored at 23°C under light shielding for 7 days, the liquid changed to yellowish-green, but no solid precipitation was observed, and no change in conductive function was observed.

[0137] [Example 1-11] Except that the diphenyl sulfoxide in Example 1-5 was replaced with poly(4-vinylphenol) (Sigma-Aldrich, molecular weight ~25,000, Tg 130-185°C), 10 g of a yellow transparent solution A-11 was obtained using the same method as in Example 1-5 (solid content concentration 5.0% by mass).

[0138] [Example 1-12] Except that the diphenyl sulfoxide in Example 1-5 was replaced with poly(4-vinylphenol) (Sigma-Aldrich, molecular weight ~25,000, Tg 130-185°C), 10 g of a yellow transparent solution A-12 was obtained using the same method as in Example 1-6 (solid content concentration 5.0% by mass).

[0139] [Example 1-13] Except for changing the amount of phosphomolybdate n-hydrate used to 0.125 g, the amount of diphenyl sulfoxide used to 0.125 g, and the amount of 3,4-ethylenedioxythiophene used to 0.250 g in Example 1-6, 10 g of a yellow transparent solution A-13 was obtained using the same method as in Example 1-6 (solid content concentration 5.0% by mass). When the obtained A-16 was stored at 23°C under light shielding for 7 days, the liquid changed to yellowish-green, but no solid precipitation was observed, and no change in the conductive function was observed.

[0140] [Example 1-14] Except for changing the amount of phosphomolybdate n-hydrate used to 0.250 g, the amount of diphenyl sulfoxide used to 0.125 g, and the amount of 3,4-ethylenedioxythiophene used to 0.125 g in Example 1-6, 10 g of a yellow transparent solution A-14 was obtained using the same method as in Example 1-6 (solid content concentration 5.0% by mass). When the obtained A-14 was stored at 23°C under light shielding for 7 days, the liquid changed to yellowish-green, but no solid precipitation was observed, and no change in the conductive function was observed.

[0141] [Example 1-15] Except for changing the amount of phosphomolybdate n-hydrate used to 0.125 g, the amount of diphenyl sulfoxide used to 0.250 g, and the amount of 3,4-ethylenedioxythiophene used to 0.125 g in Example 1-6, 10 g of a yellow transparent solution A-15 was obtained using the same method as in Example 1-6 (solid content concentration 5.0% by mass). When the obtained A-15 was stored at 23°C under light shielding for 7 days, the liquid changed to yellowish-green, but no solid precipitation was observed, and no change in the conductive function was observed.

[0142] [Example 1-16] Except for changing the diphenyl sulfoxide in Example 1-6 to methylphenyl sulfoxide (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 g of a yellow transparent solution A-16 was obtained using the same method as in Example 1-6 (solid content concentration 5.0% by mass).

[0143] [Example 1-17] Except for changing the diphenyl sulfoxide in Example 1-6 to p-tolyl sulfoxide (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 g of a yellow transparent solution A-17 was obtained using the same method as in Example 1-6 (solid content concentration 5.0% by mass).

[0144] [Example 1-18] In a 20 mL screw-cap glass bottle, 0.0833 g of phosphomolybdate n hydrate (manufactured by Junsei Chemical Co., Ltd.), 0.0417 g of diphenyl sulfoxide (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.0417 g of p-tolyl sulfoxide (manufactured by Tokyo Chemical Industry Co., Ltd.), 4.275 g of 1-methoxy-2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade), 0.475 g of pure water, and 0.0833 g of 3,4-ethylenedioxythiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) were added sequentially and stirred to dissolve each component, yielding 5 g of a yellow transparent solution A-18 (solid content concentration 5.0% by mass).

[0145] [Comparative Example 1-1] In a 20 mL screw-cap glass bottle, 0.366 g of ammonium persulfate (manufactured by Junsei Chemical Co., Ltd., 1.60 mmol), 2.11 g of pure water, 8.45 g of 1-methoxy-2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade), and 0.190 g of 3,4-ethylenedioxythiophene (manufactured by Tokyo Chemical Industry Co., Ltd., 1.34 mmol) were sequentially added and stirred to dissolve each, yielding 10 g of a yellow transparent solution B-1 (solid content concentration 5.0% by mass). When the obtained B-1 was stored at 23°C under light shielding for 7 days, the liquid turned brown and precipitation of black solids was observed. This indicates that when ammonium persulfate is used as a polymerizable additive, the storage stability of the conductive thin film forming composition is low and it is not suitable for practical use.

[0146] [Comparative Example 1-2] 0.572 g of p-ferric toluenesulfonate hexahydrate (Sigma-Aldrich, 0.844 mmol), 11.03 g of 1-methoxy-2-propanol (Kanto Chemical Co., Ltd., special grade), and 0.100 g of 3,4-ethylenedioxythiophene (Tokyo Chemical Industries, Ltd., 0.703 mmol) were sequentially added to a 20 mL screw-cap glass bottle and stirred to obtain 11.61 g of a yellow-orange transparent solution B-2 (solid content concentration 5.0% by mass). When the obtained B-2 was stored at 23°C under light shielding for 7 days, the liquid turned black and precipitation of black solids was observed. This indicates that when p-ferric toluenesulfonate hexahydrate is used as a polymerizable additive, the storage stability of this composition for forming conductive thin films is low and it is not suitable for practical use.

[0147] [Comparative Example 1-3] The amount of 1-methoxy-2-propanol used in Comparative Example 1-2 was 9.93 g, and 1.10 g of pure water was added immediately after adding the 1-methoxy-2-propanol and stirred. The same method as in Comparative Example 1-2 was used to obtain 11.61 g of a yellow-orange transparent solution B-3 (solid content concentration 5.0 mass%). When the obtained B-3 was stored at 23°C under light shielding for 7 days, the liquid changed to yellowish-brown, but no solid precipitation was observed, and no change in the conductive function was observed.

[0148] [Comparative Example 1-4] In a 20 mL screw-cap glass bottle, 0.298 g of iron(III) p-toluenesulfonate hexahydrate (manufactured by Sigma-Aldrich, 0.250 g as anhydrous), 8.55 g of 1-methoxy-2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade), 0.902 g of pure water, and 0.250 g of 3,4-ethylenedioxythiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) were sequentially added and stirred to dissolve each component, yielding 10.00 g of a yellow transparent solution B-4 (solid content concentration 5.0% by mass). When the obtained B-4 was stored in the dark at 23°C for 7 days, the liquid changed to yellowish-brown, but no solid precipitation was observed, and no change in the conductive function was observed.

[0149] [Comparative Example 1-5] In a 20 mL screw-cap glass bottle, 1.970 g of iron(III) p-toluenesulfonate hexahydrate (Sigma-Aldrich, 2.908 mmol), 5.76 g of 1-methoxy-2-propanol (Kanto Chemical Co., Ltd., special grade), 0.33 g of pure water, and 0.345 g of 3,4-ethylenedioxythiophene (Tokyo Chemical Industries, Ltd., 2.427 mmol) were sequentially added and stirred to dissolve each component, yielding 10.00 g of an orange transparent solution B-5 (solid content concentration 20.0% by mass). When the obtained B-5 was stored at 23°C under light shielding for 1 day, the liquid turned black and precipitation of black solids was observed. Under high concentration conditions of 20.0% by mass, this composition exhibits low storage stability as a conductive thin film forming composition and is unsuitable for practical use.

[0150] [Comparative Example 1-6] In a 20 mL screw-cap glass bottle, 1.190 g of iron(III) p-toluenesulfonate hexahydrate (manufactured by Sigma-Aldrich, 1.000 g as anhydrous), 5.76 g of 1-methoxy-2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade), 0.45 g of pure water, and 1.000 g of 3,4-ethylenedioxythiophene (manufactured by Tokyo Chemical Industry Co., Ltd.) were sequentially added and stirred to dissolve each component, yielding 10.00 g of an orange transparent solution B-6 (solid content concentration 20.0% by mass). When the obtained B-6 was stored at 23°C under light shielding for 1 day, the liquid turned black and precipitation of black solids was observed. Under high concentration conditions of 20.0% by mass solid content, this composition exhibits low storage stability as a conductive thin film forming composition and is unsuitable for practical use.

[0151] [Comparative Example 1-7] The viscosity of a commercially available PEDOT-PSS aqueous dispersion (Sigma-Aldrich, conductive grade, product number 483095, solid content concentration 1.3% by mass, solution number B-7) was measured using an E-type viscometer TVE-22H (Toki Sangyo Co., Ltd.) at 25°C and was found to be 17.0 mPa·s. Since this is a higher viscosity compared to the composition described in Example 1, it is presumed that this solution has low penetration into the pores of the etched aluminum foil of the conductive polymer aluminum electrolytic capacitor. The surface tension of the above PEDOT-PSS aqueous dispersion was measured using a surface tensile meter DY-700 (Kyowa Interface Science Co., Ltd.) at 20°C and was found to be 72.7 mN / m. Since this is a higher surface tension compared to the composition described in Example 1, it is presumed that this solution has a high contact angle within the pores of the etched aluminum foil of the conductive polymer aluminum electrolytic capacitor and low penetration.

[0152] The compositions of the conductive thin film forming compositions prepared above are summarized in Table 1.

[0153]

[0154] (2) Preparation of conductive thin film [Example 2-1] 400 μL of solution A-3 was dropped onto a glass substrate (30 mm x 30 mm, 1 mm thick) which was standing in a glass petri dish. With the liquid surface spread over the entire surface of the glass substrate, it was heated and dried on a hot plate at 120°C for 10 minutes to obtain a glass substrate C-1 with a black film.

[0155] [Example 2-2] A glass substrate C-2 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-5, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes.

[0156] [Example 2-3] A glass substrate C-3 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-5.

[0157] [Example 2-4] A glass substrate C-4 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-6, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes.

[0158] [Example 2-5] A glass substrate C-5 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-6.

[0159] [Example 2-6] A glass substrate C-6 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-6, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0160] [Example 2-7] A glass substrate C-7 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-6, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 200°C for 10 minutes.

[0161] [Example 2-8] A glass substrate C-8 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-6 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0162] [Example 2-9] A glass substrate C-9 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-6 and the heating and drying conditions were changed to 200°C for 10 minutes.

[0163] [Example 2-10] A glass substrate C-10 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-7, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes.

[0164] [Example 2-11] A glass substrate C-11 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-7.

[0165] [Example 2-12] A glass substrate C-12 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-7, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0166] [Example 2-13] A glass substrate C-13 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-7, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 200°C for 10 minutes.

[0167] [Example 2-14] A glass substrate C-14 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-7 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0168] [Example 2-15] A glass substrate C-15 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-7 and the heating and drying conditions were changed to 200°C for 10 minutes.

[0169] [Example 2-16] A glass substrate C-16 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-9, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes.

[0170] [Example 2-17] A glass substrate C-17 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-9.

[0171] [Example 2-18] A glass substrate C-18 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-10 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0172] [Example 2-19] A glass substrate C-19 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-10 and the heating and drying conditions were changed to 200°C for 10 minutes.

[0173] [Example 2-20] A glass substrate C-20 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-11, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes.

[0174] [Example 2-21] A glass substrate C-21 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-11.

[0175] [Example 2-22] A glass substrate C-22 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-12 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0176] [Example 2-23] A glass substrate C-23 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-12 and the heating and drying conditions were changed to 200°C for 10 minutes.

[0177] [Example 2-24] A glass substrate C-24 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-13, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0178] [Example 2-25] A glass substrate C-25 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-13 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0179] [Example 2-26] A glass substrate C-26 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-14, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0180] [Example 2-27] A glass substrate C-27 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-14 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0181] [Example 2-28] A glass substrate C-28 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution A-15, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0182] [Example 2-29] A glass substrate C-29 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution A-15 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0183] [Example 2-30] 300 μL of solution A-16 was dropped onto a glass substrate (25 mm x 250 mm, 1 mm thick) placed in a glass petri dish. With the liquid surface spread across the entire surface of the glass substrate, it was heated and dried on a hop plate at 80°C for 10 minutes, and then heated and dried at 160°C for 10 minutes to obtain black-coated glass substrate C-30.

[0184] [Example 2-31] A glass substrate C-31 with a black film was obtained using the same method as in Example 2-30, except that the heating and drying conditions were changed to 160°C for 10 minutes.

[0185] [Example 2-32] A glass substrate C-32 with a black film was obtained using the same method as in Example 2-31, except that solution A-16 in Example 2-31 was changed to A-17.

[0186] [Example 2-33] A glass substrate C-33 with a black film was obtained using the same method as in Example 2-31, except that solution A-16 in Example 2-31 was changed to A-18.

[0187] [Comparative Example 2-1] An attempt was made to form a conductive thin film using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-1, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes. However, a glass substrate D-1 with dot-like solid matter attached was obtained, and no film was formed. Since the solid matter after heating and drying was white, it is thought that the chemical oxidative polymerization of EDOT on the substrate was insufficient or did not proceed. Ammonium persulfate is conventionally used as a catalyst for the polymerization reaction of EDOT in a solvent, but it is clear that it cannot be directly applied to the polymerization reaction on the substrate.

[0188] [Comparative Example 2-2] An attempt was made to form a conductive thin film using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution B-1. However, a glass substrate D-2 with dot-like solid matter attached was obtained, and no film was formed. Since the solid matter after heating and drying was white, it is thought that the chemical oxidative polymerization of EDOT on the substrate was insufficient or did not proceed. Ammonium persulfate is conventionally used as a catalyst for the polymerization reaction of EDOT in a solvent, but it is clear that it cannot be directly applied to the polymerization reaction on the substrate.

[0189] [Comparative Example 2-3] A glass substrate D-3 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution B-2, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes.

[0190] [Comparative Example 2-4] A glass substrate D-4 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution B-2.

[0191] [Comparative Example 2-5] A glass substrate D-5 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-3, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0192] [Comparative Example 2-6] A glass substrate D-6 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-3, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 200°C for 10 minutes.

[0193] [Comparative Example 2-7] A glass substrate D-7 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-3 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0194] [Comparative Example 2-8] A glass substrate D-8 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with solution B-3 and the heating and drying conditions were changed to 200°C for 10 minutes.

[0195] [Comparative Example 2-9] A glass substrate D-9 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-4, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0196] [Comparative Example 2-10] A glass substrate D-10 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-4, and the heating and drying conditions were changed to 80°C for 10 minutes followed by 200°C for 10 minutes.

[0197] [Comparative Example 2-11] A glass substrate D-11 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-4 and the heating and drying conditions were changed to 160°C for 10 minutes.

[0198] [Comparative Example 2-12] A glass substrate D-12 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was changed to solution B-4 and the heating and drying conditions were changed to 200°C for 10 minutes.

[0199] [Comparative Example 2-13] A glass substrate D-13 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with a commercially available PEDOT-PSS aqueous dispersion (Sigma-Aldrich, conductive grade, product number 483095, solid content concentration 1.3% by mass), and the heating and drying conditions were changed to 80°C for 10 minutes followed by 160°C for 10 minutes.

[0200] [Comparative Example 2-14] A glass substrate D-14 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with a commercially available PEDOT-PSS aqueous dispersion (Sigma-Aldrich, conductive grade, product number 483095, solid content concentration 1.3% by mass), and the heating and drying conditions were changed to 80°C for 10 minutes followed by 200°C for 10 minutes.

[0201] [Comparative Example 2-15] A glass substrate D-15 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with a commercially available PEDOT-PSS aqueous dispersion (Sigma-Aldrich, conductive grade, product number 483095, solid content concentration 1.3% by mass), and the heating and drying conditions were changed to 160°C for 10 minutes.

[0202] [Comparative Example 2-16] A glass substrate D-16 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with a commercially available PEDOT-PSS aqueous dispersion (Sigma-Aldrich, conductive grade, product number 483095, solid content concentration 1.3% by mass), and the heating and drying conditions were changed to 200°C for 10 minutes.

[0203] [Comparative Example 2-17] A glass substrate D-17 with a black film was obtained using the same method as in Example 2-1, except that solution A-3 in Example 2-1 was replaced with a commercially available PEDOT-PSS aqueous dispersion (Sigma-Aldrich, conductive grade, product number 483095, solid content concentration 1.3% by mass), and the heating and drying conditions were changed to 80°C for 10 minutes followed by 120°C for 10 minutes.

[0204] [Comparative Example 2-18] Except that solution A-3 in Example 2-1 was replaced with a commercially available PEDOT-PSS aqueous dispersion (Sigma-Aldrich, conductive grade, product number 483095, solid content concentration 1.3% by mass), a glass substrate D-18 with a black film was obtained using the same method as in Example 2-1.

[0205] The black-coated glass substrates obtained above were evaluated for coating uniformity, water scratch resistance, and surface resistance. The evaluation results are shown in Tables 2 to 4. Coating uniformity and water scratch resistance were evaluated using the following methods. <Coating Uniformity> The condition of the film surface of the black-coated glass substrate was observed visually and evaluated according to the following criteria. <Evaluation Criteria> ○: Uniform ○ to △: Some unevenness △: Unevenness across the entire surface ×: No film formed <Water Scratch Resistance> Contact area 1 cm² when wet with water 2 50g / cm² of nonwoven fabric wiper (Asahi Kasei Corporation, Bencot M-1) 2 The wiper was moved once horizontally across the film surface while applying pressure. The condition of the film surface in the wiped area was visually observed and evaluated according to the following criteria: <Evaluation Criteria> ○: No film-derived substances adhered to the wiper △: Film-derived substances adhered to the wiper ×: Film surface peeled off

[0206]

[0207]

[0208]

[0209] The results in Tables 2 and 3 show that the conductive thin films obtained in Examples 2-1 to 2-29 have high coating uniformity, high water scratch resistance, low surface resistance, and are stable.

[0210] In contrast, in Comparative Examples 2-1 to 2-18, conductive thin films were often not obtained, or even if conductive thin films were obtained, uniformity was often not achieved due to the low coating uniformity of the composition. Furthermore, the obtained thin films were found to have low water scratch resistance and high or unstable surface resistance.

[0211] Details of the conductive thin film obtained in the comparative example are shown below.

[0212] The conductive thin film obtained in Comparative Example 2-3 (glass substrate D-3 with black film) exhibits lower water scratch resistance and unstable surface resistance compared to the conductive thin film obtained in the above example, indicating lower performance as a conductive thin film. The low water scratch resistance suggests that it would be unreliable and prone to performance degradation in applications such as conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors, which often involve a water washing process and require resistance to electrolytes that use highly polar solutions similar to water.

[0213] The conductive thin film obtained in Comparative Example 2-4 (glass substrate D-4 with black film) has lower water scratch resistance and unstable surface resistance compared to the conductive thin film obtained in the above example, indicating that it has lower performance as a conductive thin film.

[0214] The conductive thin film obtained in Comparative Example 2-5 (glass substrate D-5 with black film) has lower water scratch resistance, unstable and high surface resistance, and lower performance as a conductive thin film compared to the conductive thin film obtained in the above example.

[0215] The conductive thin film obtained in Comparative Example 2-6 (glass substrate D-6 with black film) has lower water scratch resistance, unstable and high surface resistance, and lower performance as a conductive thin film compared to the conductive thin film obtained in the above example.

[0216] The conductive thin film obtained in Comparative Example 2-7 (glass substrate D-7 with black film) exhibits lower water scratch resistance compared to the conductive thin film obtained in the above examples, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors. Although the surface resistance was good, the resistance increased significantly after drying at low temperatures of around 80°C, as in Comparative Example 2-5, suggesting that the resistance characteristics are unstable.

[0217] The conductive thin film obtained in Comparative Example 2-8 (glass substrate D-8 with black film) exhibits lower water scratch resistance compared to the conductive thin film obtained in the above examples, raising concerns about its reliability for use in electrolytic polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors. Although the surface resistance was good, the resistance increased significantly after drying at low temperatures of around 80°C, as in Comparative Example 2-6, suggesting that the resistance characteristics are unstable.

[0218] The conductive thin film obtained in Comparative Example 2-9 (glass substrate D-9 with black film) exhibits lower coating uniformity, lower water scratch resistance, and unstable surface resistance compared to the conductive thin film obtained in the above example, indicating lower performance as a conductive thin film.

[0219] The conductive thin film obtained in Comparative Example 2-10 (glass substrate D-10 with black film) exhibits lower coating uniformity, lower water scratch resistance, and unstable surface resistance compared to the conductive thin film obtained in the above example, indicating lower performance as a conductive thin film.

[0220] The conductive thin film obtained in Comparative Example 2-11 (glass substrate D-11 with black film) has lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0221] The conductive thin film obtained in Comparative Example 2-12 (glass substrate D-12 with black film) has lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0222] The conductive thin film obtained in Comparative Example 2-13 (glass substrate D-13 with black film) has lower coating uniformity and lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0223] The conductive thin film obtained in Comparative Example 2-14 (glass substrate D-14 with black film) has lower coating uniformity and lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0224] The conductive thin film obtained in Comparative Example 2-15 (glass substrate D-15 with black film) has lower coating uniformity and lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0225] The conductive thin film obtained in Comparative Example 2-16 (glass substrate D-16 with black film) has lower coating uniformity and lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0226] The conductive thin film obtained in Comparative Example 2-17 (glass substrate D-17 with black film) has lower coating uniformity and lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0227] The conductive thin film obtained in Comparative Example 2-18 (glass substrate D-18 with black film) has lower coating uniformity and lower water scratch resistance compared to the conductive thin film obtained in the above example, raising concerns about its reliability for use in conductive polymer aluminum electrolytic capacitors or conductive polymer hybrid aluminum electrolytic capacitors.

[0228] (3) Embedding test and cross-sectional observation of etched aluminum foil [Example 3-1] Solution A-7 prepared in Example 1-7 was dropped onto etched aluminum foil (manufactured by Nippon Chikudenki Kogyo Co., Ltd., model no. 115LT23B-36VF), and the foil was coated and spread at a coating speed of 3 m / min using a bar coater and a wireless bar OSP-22 (maximum wet film thickness 22 μm). After standing at room temperature for 3 minutes, it was heated and dried in an atmospheric oven at 160°C for 10 minutes. The same method of bar coater coating, standing at room temperature, and drying in an atmospheric oven at 160°C for 10 minutes was repeated four times to obtain etched aluminum foil E-1 embedded with conductive thin film forming composition (hereinafter referred to as coated foil E-1). The coated cross-section of the obtained coated foil E-1 was exposed by CP processing, and the cross-section was observed using a scanning electron microscope (JEOL Ltd., JSM-7400F, acceleration voltage 1.0 kV). The observation results of the uncoated foil are shown in Figures 1-1 to 1-4 (each showing the entire pore region, a magnified view of the pore region near the surface, a magnified view of the central pore region, and a magnified view of the bottom pore region, respectively), and the observation results of coated foil E-1 are shown in Figures 2-1 to 2-4 (each showing the entire pore region, a magnified view of the pore region near the surface, a magnified view of the central pore region, and a magnified view of the bottom pore region, respectively).

[0229] In Figures 1-1 to 1-4 and Figures 2-1 to 2-4, the black areas represent voids in the etched aluminum foil, while the non-black areas surrounding them represent areas occupied by aluminum derived from the etched aluminum foil, aluminum oxide, or conductive material after coating and drying with the conductive thin film forming composition of the present invention. In coated foil E-1, it can be seen that the solid components of solution A-7 and materials derived from its polymer are densely embedded in most of the pores, even down to the micropores.

[0230] Figures 3-1 to 3-3 show the results of SEM-EDX analysis of the elemental distribution of carbon, sulfur, and molybdenum in the coated cross-section of coated foil E-1. It can be seen that within the pores, the elements carbon, sulfur, and molybdenum, which originate from the solid components of solution A-7 and its polymer, are all uniformly distributed within the pore region.

[0231] The porosity of the pore region of the coated foil was calculated by image analysis according to the following formula: Porosity [%] = Area of ​​black area ÷ Area of ​​non-black area × 100

[0232] As a result, the total porosity of the pore region in Figure 1-1 was 44%, and the total porosity of the pore region in Figure 2-1 was 22%. The 50% conductive material filling rate was calculated using the following formula and was 50%: Conductive material filling rate [%] = Porosity after coating and drying of the conductive thin film forming composition ÷ Porosity before coating and drying × 100

[0233] The conductive thin-film forming composition obtained by the above method exhibits high embedding ability, as evidenced by the reduced porosity of the pores after the embedding test due to its high immersion into the pores of the etched aluminum foil. Further reductions in the number of coating applications are possible by increasing the solid content concentration or the amount of coating solution.

Claims

The mixture comprises a thiophene compound represented by the following formula (1), a heteropoly acid, and a solvent. A composition for forming conductive thin films that does not contain iron-containing compounds. (In the formula, R 1 , R 2 These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryloxy group, and -O-[Z-O] p -R e , or R 1 and R 2 The -O-Y-O- is formed by the bonding of the following: Y is an alkylene group having 1 to 40 carbon atoms, which may contain an ether bond; 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; R e (These are 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.) 　 Furthermore, it contains a film-forming aid, The conductive thin film forming composition according to claim 1, wherein the above-mentioned film-forming aid is a specific compound (excluding polymers) having a melting point of less than 200°C and a boiling point of 200°C or higher at normal pressure, or a specific polymer having a weight-average molecular weight of 1,000 or higher and a glass transition temperature of 200°C or lower. 　 The conductive thin film forming composition according to claim 1, wherein the content of the heteropoly acid is 0.1 to 10 by mass ratio with respect to 1 thiophene compound. 　 The conductive thin film forming composition according to claim 2, wherein the content of the above-mentioned film-forming aid is 0.1 to 10 by mass ratio with respect to 1 thiophene compound. 　 The conductive thin film forming composition according to claim 2, wherein the content of the thiophene compound, heteropoly acid, and film-forming aid is 15% by mass or more of the solid content. 　 The conductive thin film forming composition according to claim 1, wherein the heteropoly acid is phosphomolybdic acid. 　 The conductive thin film forming composition according to claim 2, wherein the melting point of the specified compound is 50°C or higher and less than 200°C. 　 The conductive thin film forming composition according to claim 2, wherein the specified compound is a compound represented by the following formula (S1) or (S2). R 3 -SO-R 4 (S1) (In the formula, R 3 , R 4 These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryl group, or a C6-C20 aryloxy group, -O-[Z-O] p -R e Z is an alkylene group having 1 to 40 carbon atoms, which may be substituted with halogen atoms, p is an integer of 1 or more, and R e (These are 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.) R 5 -SO2-R 6 (S2) (In the formula, R 5 , R 6 These are, independently of each other, a hydrogen atom, a C1-C40 alkyl group, a C1-C40 fluoroalkyl group, a C1-C40 alkoxy group, a C1-C40 fluoroalkoxy group, a C6-C20 aryl group, or a C6-C20 aryloxy group, -O-[Z-O] p -R e Z is an alkylene group having 1 to 40 carbon atoms, which may be substituted with halogen atoms, p is an integer of 1 or more, and R e (These are 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 conductive thin film forming composition according to claim 8, wherein the specified compound is a compound represented by the following formula (S1-1) or (S2-1). The conductive thin film forming composition according to claim 2, wherein the specified polymer is polyhydroxystyrene. 　 The conductive thin film forming composition according to claim 1, wherein the thiophene compound is a compound represented by the following formula (1-1). The conductive thin film forming composition according to claim 1, wherein the solvent comprises 80% by mass or more of an alcohol-based solvent or a glycol ether-based solvent. 　 The conductive thin film forming composition according to claim 12, wherein the solvent further contains 3% by mass or more of water. 　 The conductive thin film forming composition according to claim 1, wherein the surface tension is 60 mN / m or less at 20°C. 　 The conductive thin film forming composition according to claim 1, wherein the viscosity is 100 mPa·s or less at 25°C. 　 The conductive thin film forming composition according to claim 1, wherein the solid content concentration is 1 to 80% by mass. 　 A composition for forming a conductive thin film according to any one of claims 1 to 16, for use in electrolytic capacitors. 　 A conductive thin film forming composition according to any one of claims 1 to 16, for use as a solid electrolyte. 　 A conductive thin film obtained from a conductive thin film forming composition according to any one of claims 1 to 16, comprising a polymer of a thiophene compound represented by formula (1). 　 An electrolytic capacitor comprising a conductive thin film according to claim 19. The electrolytic capacitor according to claim 20, which is a conductive polymer aluminum electrolytic capacitor or a conductive polymer hybrid aluminum electrolytic capacitor. 　 A solid electrolyte comprising a conductive thin film according to claim 19. 　 A method for producing a conductive thin film, comprising the steps of applying a conductive thin film forming composition according to any one of claims 1 to 16 to a substrate and drying it at a temperature of 80°C or higher.

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