JP7631810B2 - Conductive polymer composition and its uses - Google Patents

Description

The present invention relates to a novel conductive polymer composition and its uses.

In recent years, conductive polymer materials have been developed in which π-conjugated polymers, such as polyacetylene, polythiophene, polyaniline, and polypyrrole, are doped with electron-accepting compounds as dopants. Applications of these materials to, for example, antistatic agents, solid electrolytes for electrolytic capacitors, conductive paints, electrochromic elements, electrode materials, thermoelectric conversion materials, transparent conductive films, chemical sensors, actuators, and the like are being considered. In the field of electrolytic capacitors, there is a strong demand for electrolytic capacitors with high capacity and low ESR as electronic devices become faster and higher in frequency. Polythiophene-based conductive polymer materials are practically useful as conductive polymer materials that meet this demand due to their chemical stability.

Known polythiophene-based conductive polymer materials include (i) a PEDOT/PSS aqueous dispersion solution obtained by polymerizing 3,4-ethylenedioxythiophene (EDOT) in an aqueous solution of polystyrene sulfonic acid (PSS) as a dopant, and (ii) so-called self-doped conductive polymers (e.g., sulfonated polyaniline, PEDOT-S, etc.) that have substituents (sulfo groups, sulfonate groups, etc.) that combine water solubility and doping properties directly or via a spacer in the polymer main chain (see, for example, Non-Patent Documents 1 and 2).

Electrolytic capacitors using PEDOT/PSS are known (Patent Document 1). However, since PEDOT/PSS exists in particulate form, it is known that it is not possible to cover every corner of the surface of the electrolytic capacitor dielectric that has been subjected to an expansion treatment, making it difficult to fully utilize the capacitance of the electrolytic capacitor. As a method for solving this problem, development is being carried out of self-doped conductive polymers that are water-soluble and have the potential to cover every corner of the electrolytic capacitor dielectric surface.

Journal of American Chemical Society, 112, 2801-2803 (1990) Advanced Materials, Vol. 23 (38) 4403-4408 (2011)

JP 2017-147466 A

A desirable characteristic of electrolytic capacitors is a low ESR. It is known that low ESR electrolytic capacitors can be made by filling the gaps between the electrodes of an electrolytic capacitor with a conductive polymer with high conductivity. Since PEDOT/PSS exists in particulate form, it is easy to fill the gaps between the electrodes and to make low ESR electrolytic capacitors, but since self-doped conductive polymers are not particulate, it is difficult to fill the gaps between the electrodes, making it difficult to lower the ESR. There is a demand for improvements in the ESR characteristics of conventionally known self-doped conductive polymers.

The present invention aims to provide a self-doped conductive polymer composition for producing electrolytic capacitors that have excellent low ESR properties while maintaining high capacity.

As a result of extensive research into solving the above problems, the inventors discovered that the conductive polymer composition shown below can provide an electrolytic capacitor with excellent low ESR properties, and thus completed the present invention.

That is, the present invention relates to a conductive polymer composition, a conductive polymer film, and an electrolytic capacitor using the same, as described below.
[1] A conductive polymer composition comprising 0.01 to 10% by weight of polythiophene (A) containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), 0.01 to 3% by weight of insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less, and water:

[In general formulas (1) and (2), ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.]
[2] The conductive polymer composition according to [1], wherein the insulating inorganic particles (B) have a particle size (D50) of 60 nm or less.
[3] The conductive polymer composition according to [1] or [2], wherein the insulating inorganic particles (B) are one or a mixture of two or more selected from the group consisting of aluminum oxide, titanium oxide, silicon dioxide, magnesium oxide, zinc oxide, barium titanate, strontium titanate, aluminum nitride, boron nitride, kaolin, hydroxyapatite, bentonite, and hydrotalcite.
[4] The conductive polymer composition according to any one of [1] to [3], further comprising, in addition to the (A), (B), and water, a compound (C) selected from the group consisting of an alkali metal compound, ammonia, an organic amine compound, and a quaternary ammonium compound, and having a pH in the range of 1.5 to 10.0.
[5] A conductive polymer film comprising: a polythiophene (A) containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2); and insulating inorganic particles (B) having a particle size (D50) of 80 nm or less:

[In general formulas (1) and (2), ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.]
[6] A method for producing a conductive polymer film according to [5], comprising applying and drying a conductive polymer composition containing 0.01 to 10% by weight of polythiophene (A) containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), 0.01 to 3% by weight of insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less, and water:

[In general formulas (1) and (2), ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.]
[7] An electrolytic capacitor comprising the conductive polymer film according to [5] above.

The present invention makes it possible to provide an electrolytic capacitor with low ESR while maintaining high capacity.

The present invention is described in detail below.

The present invention is a conductive polymer composition that contains 0.01 to 10% by weight of polythiophene (A) that contains at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and structural units represented by the following general formula (2), contains 0.01 to 3% by weight of insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less, and contains water.

[In general formulas (1) and (2), ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.]
In the above general formulas (1) and (2), R ² represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom.

The linear or branched alkyl group having 3 to 6 carbon atoms is not particularly limited, but examples thereof include an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a cyclopentyl group, an n-hexyl group, a 2-ethylbutyl group, and a cyclohexyl group.

From the viewpoint of film-forming properties, ^R2 is preferably a hydrogen atom, a methyl group, an ethyl group, or a fluorine atom, and more preferably a hydrogen atom or a methyl group.

In the above general formulas (1) and (2), m represents an integer of 1 to 10, and from the viewpoint of film-forming properties, it is preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and even more preferably 2 or 3.

In the above general formulas (1) and (2), n represents 0 or 1, and it is preferable that n is 1 in terms of excellent electrical conductivity.

The structural unit represented by the above general formula (2) represents the doped state of the structural unit represented by the above general formula (1).

Dopants that cause an insulator-metal transition by doping can be divided into acceptors and donors. The former enter close to the polymer chain of a conductive polymer and take away π electrons from the conjugated system of the main chain. As a result, a positive charge (positive hole) is injected into the main chain, so it is also called a p-type dopant. Conversely, the latter donates electrons to the conjugated system of the main chain, and these electrons move through the conjugated system of the main chain, so it is also called an n-type dopant.

The dopant in the present invention is a sulfo group or a sulfonate group that is covalently bonded within the polymer molecule, and is a p-type dopant. Polymers that exhibit conductivity without the addition of an external dopant are called self-doped polymers.

The polythiophene (A) of the present invention can be produced by polymerizing a thiophene monomer represented by the following general formula (3) in water or an alcohol solvent in the presence of an oxidizing agent, and then optionally treating with an acid.

[In the above general formula (3), M represents a hydrogen ion or a metal ion. ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom. m represents an integer of 1 to 10, and n represents 0 or 1.]
The metal ion represented by M in the general formula (3) is not particularly limited, but examples thereof include transition metal ions, precious metal ions, non-ferrous metal ions, alkali metal ions (e.g., Li ions, Na ions, and K ions), and alkaline earth metal ions.

When the polymer obtained after polymerization of the thiophene monomer represented by the general formula (3) is a salt of a metal ion (when M is a metal ion), M can be converted to a hydrogen ion by treating the obtained metal salt polymer with an acid. That is, even if M in the general formula (3) is a metal ion, it is possible to produce a polythiophene (A) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2). Furthermore, by mixing the polythiophene (A) with an alkali metal compound or an amine compound, it is possible to produce a polythiophene containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1') and the structural unit represented by the general formula (2').

The thiophene monomer represented by the above general formula (3) is not particularly limited, but specifically includes 6-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonic acid, sodium 6-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonate, lithium 6-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonate, 8-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonic acid potassium salt, 8-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)octane-1-sulfonic acid sodium salt, 8-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)octane-1-sulfonic acid potassium salt, 3-[(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methoxy]-1-propanesulfonic acid potassium salt sodium sulfonate, potassium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-ethyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-ethyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-ethyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-propyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-pentyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-hexyl-1-propanesulfonate sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopropyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isobutyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopentyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]- sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate, potassium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid ammonium, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate triethylammonium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butanesulfonate sodium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butanesulfonate potassium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butanesulfonate ) methoxy]-1-methyl-1-butanesulfonate sodium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl) methoxy]-1-methyl-1-butanesulfonate potassium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl) methoxy]-1-fluoro-1-butanesulfonate sodium, or 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl) methoxy]-1-fluoro-1-butanesulfonate potassium.

In the present invention, the electrical conductivity of the polythiophene (A) is not particularly limited, but it is preferable that the electrical conductivity (electrical conductivity) in the film state is 10 S/cm or more.

In addition, the polythiophene (A) used in the present invention may be one synthesized based on publicly known information.

In the conductive polymer composition of the present invention, the concentration of polythiophene (A) containing at least one structural unit selected from the group consisting of structural units represented by the above-mentioned general formula (1) and structural units represented by the general formula (2) is 0.01 to 10% by weight. In terms of excellent low ESR, the concentration of polythiophene (A) in the conductive polymer composition of the present invention is preferably 0.05 to 8% by weight, and more preferably 0.1 to 7% by weight.

The insulating inorganic particles (B) in the present invention having a particle diameter (D50) of 80 nm or less are not particularly limited, but examples thereof include any one or a mixture of any one selected from the group consisting of aluminum oxide, titanium oxide, silicon dioxide, magnesium oxide, zinc oxide, barium titanate, strontium titanate, aluminum nitride, boron nitride, kaolin, hydroxyapatite, bentonite, and hydrotalcite.

The insulating inorganic particles are characterized by having a particle diameter (D50) of 80 nm or less. From the viewpoint of excellent ESR characteristics and storage stability, the particle diameter (D50) is preferably 60 nm or less, and more preferably 50 nm or less.

There are no particular limitations on the shape of the insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less, and particles in the shape of fillers, rods, tubes, particles, etc. can be used.

In the conductive polymer composition of the present invention, the content of the insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less is 0.01 to 3% by weight, but in terms of excellent low ESR, it is preferably 0.01 to 2% by weight, more preferably 0.1 to 2% by weight, and even more preferably 0.1 to 1% by weight.

The conductive polymer composition of the present invention may further contain a compound (C) capable of forming an ion pair with the sulfonic acid group of the polythiophene (A) in order to have an excellent low ESR. The compound (C) capable of forming an ion pair with the sulfonic acid group is not particularly limited, but examples thereof include alkali metal compounds, ammonia, organic amine compounds, and quaternary ammonium salts. These compounds react with the sulfonic acid group of the polythiophene (A) to form alkali metal ion salts, ammonium ion salts, organic ammonium ion salts, and quaternary ammonium ion salts of the polythiophene (A), respectively.

The alkali metal compound is not particularly limited, but examples thereof include alkali metal salt compounds (e.g., lithium chloride, potassium chloride, sodium chloride, rubidium chloride, cesium chloride, lithium bromide, potassium bromide, sodium bromide, rubidium bromide, cesium bromide, etc.) and alkali metal hydroxides (e.g., lithium hydroxide, potassium hydroxide, sodium hydroxide, rubidium hydroxide, cesium hydroxide, etc.).

By incorporating the alkali metal compound into the conductive polymer composition of the present invention, the alkali metal ion salt of the lithiophene (A) can be prepared. The alkali metal ion is not particularly limited, but examples thereof include lithium ion, potassium ion, sodium ion, rubidium ion, and cesium ion.

The organic amine compound is not particularly limited, but examples thereof include primary, secondary, or tertiary organic amine compounds having a total carbon number of 1 to 30. More specifically, examples thereof include methylamine, dimethylamine, trimethylamine, ethylamine, triethylamine, normal-propylamine, isopropylamine, normal-butylamine, hexylamine, aminoethanol, dimethylaminoethanol, methylaminoethanol, diethanolamine, N-methyldiethanolamine, triethanolamine, 3-amino-1,2-propanediol, 3-methylamino-1,2-propanediol, 3-dimethylamino-1,2-propanediol, 1,4-butanediamine, triisobutylamine, triisopentylamine, triisooctylamine, imidazole, N-methylimidazole, 1,2-dimethylimidazole, pyridine, picoline, and lutidine.

By incorporating the organic amine compound into the conductive polymer composition of the present invention, the organic amine compound reacts with the polythiophene (A) to form an organic ammonium ion, and an organic ammonium ion salt of polythiophene (A) is prepared. The organic ammonium ion is not particularly limited, but examples thereof include primary, secondary, and tertiary organic ammonium ions having a total carbon number of 1 to 30. More specifically, examples of the organic ammonium ion include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, triethylammonium, normal-propylammonium, isopropylammonium, normal-butylammonium, hexylammonium, 2-hydroxyethylammonium, N,N-dimethyl-N-(2-hydroxyethyl)ammonium, N-methyl-N-(2-hydroxyethyl)ammonium, di(2-hydroxyethyl)ammonium, and the like. ammonium, N-methyl-N,N-di(2-hydroxyethyl)ammonium, N,N,N-tri(2-hydroxyethyl)ammonium, 2,3-dihydroxypropylammonium, N-methyl-N-(2,3-dihydroxypropyl)ammonium, N,N-dimethyl-N-(2,3-dihydroxypropyl)ammonium, 1,4-butanediammonium, triisobutylammonium, triisopentylammonium, triisooctylammonium, imidazole cation, N-methylimidazole cation, 1,2-dimethylimidazole cation, pyridinium ion, picolinium ion, or lutidinium ion.

The quaternary ammonium compound is not particularly limited, but examples thereof include tetramethylammonium chloride, tetraethylammonium chloride, tetra-n-propylammonium chloride, tetra-n-butylammonium chloride, and tetra-n-hexylammonium chloride.

By incorporating the quaternary ammonium compound into the conductive polymer composition of the present invention, the quaternary ammonium compound reacts with the polythiophene (A) to form a quaternary ammonium ion, and a quaternary ammonium ion salt of polythiophene (A) is prepared. The quaternary ammonium ion is not particularly limited, but examples thereof include tetramethylammonium ion, tetraethylammonium ion, tetra-n-propylammonium ion, tetra-n-butylammonium ion, and tetra-n-hexylammonium ion.

In the conductive polymer composition of the present invention, the content of the aforementioned compound (C) is preferably 0.001 to 20% by weight, and from the viewpoint of excellent low ESR, it is preferably 0.01 to 15% by weight, and more preferably 0.1 to 10% by weight.

The conductive polymer composition of the present invention has a pH preferably in the range of 1.5 to 10.0, more preferably in the range of 2.0 to 8.0, and even more preferably in the range of 2.5 to 7.0, in terms of its excellent low ESR. The pH can be controlled by the type and content of the compound (C) described above.

When the conductive polymer composition of the present invention contains the compound (C), a part or all of the polythiophene (A) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2) interacts with the compound (C) to form a polythiophene (A) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1') and the structural unit represented by the general formula (2'). That is, a mixture of the polythiophene (A) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2) and the compound (C) and the polythiophene (A) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1') and the structural unit represented by the general formula (2') are the same.

[In the above general formula (1') and general formula (2'), the definitions and preferred ranges of R ² , m, and n are the same as those in the above general formula ( ¹ ) and general formula (2). M represents a hydrogen ion, an alkali metal ion, an ammonium ion, an organic ammonium ion, or a quaternary ammonium ion.]
The alkali metal ion, ammonium ion, organic ammonium ion, and quaternary ammonium ion in M are as described above.

The conductive polymer composition of the present invention may contain additives (D) other than those described above.

The additives (D) other than those mentioned above are not particularly limited, but examples thereof include binders, surfactants, solvents, etc. The additives (D) may be used alone or in combination with one another.

The binder is not particularly limited, but is preferably, for example, a water-soluble resin, and more specific examples include polyvinyl alcohol, polyvinylpyrrolidone, cellulose, a water-soluble polyester resin compound, a water-soluble polyurethane resin compound, or a mixture of a polyhydric alcohol and an organic acid having two or more carboxyl groups.

Examples of the water-soluble polyester resin compound include polyethylene terephthalate and polytrimethylene terephthalate. The water-soluble polyester resin compound may be a self-emulsifying type or a reinforced emulsifying type, but from the viewpoint of water resistance and solvent resistance, it is preferable to use a self-emulsifying water-soluble polyester resin compound.

Examples of the water-soluble polyester resin compound that can be easily obtained commercially include products manufactured by Toyobo Co., Ltd. under the trade name Vylonal, manufactured by Takamatsu Oil Co., Ltd. under the trade name Pesresin, manufactured by GOO Chemical Co., Ltd. under the trade name Pluscoat, manufactured by Toagosei Co., Ltd. under the trade name Aronmelt, manufactured by Takamatsu Oil Co., Ltd. under the trade name Pesresin A, and manufactured by DIC Corporation under the trade name Watersol.

The water-soluble polyester resin compounds can be used alone or in combination of two or more.

The water-soluble polyurethane resin compound is used mainly for industrial purposes as a urethane resin emulsion, and may be a self-emulsifying type or a reinforced emulsion type. From the viewpoint of water resistance and solvent resistance, however, a self-emulsifying water-soluble polyurethane resin compound is preferable. Examples of the self-emulsifying type include an anionic type, a cationic type, and a non-ionic type, and any of them may be used. In addition, the water-soluble polyurethane resin compound is not particularly limited, but examples thereof include a polyether type, a polyester type, and a polycarbonate type.

Examples of water-soluble polyurethane resin compounds that can be easily obtained commercially include those manufactured by Sanyo Chemical Industries, Ltd. under the trade names U-coat (registered trademark), Permalin (registered trademark), and Euprene (registered trademark), manufactured by Kusumoto Chemical Industries, Ltd. under the trade name NeoRez, manufactured by ADEKA Corporation under the trade name Adeka Bontiter (registered trademark), manufactured by Meisei Chemical Industry Co., Ltd. under the trade name Pascall (registered trademark), and manufactured by DIC Corporation under the trade name Hydran (registered trademark).

The water-soluble polyurethane resin compounds can be used alone or in combination of two or more.

The polyhydric alcohol is not particularly limited, but examples thereof include erythritol and pentaerythritol.

The organic acid having two or more carboxyl groups is not particularly limited, but examples include adipic acid and phthalic acid.

The surfactant is not particularly limited, but may be, for example, an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, a fluorine-based surfactant, or a silicone-based surfactant, and more preferably at least one selected from the group consisting of a nonionic surfactant and an amphoteric surfactant.

The anionic surfactant is not particularly limited, but examples include sodium lauryl alcohol sulfate and sodium dodecylbenzenesulfonate.

The cationic surfactant is not particularly limited, but a commercially available product can be used, or a commonly known product can be separately manufactured and used.

The nonionic surfactant is not particularly limited, but examples thereof include polyethylene glycol type surfactants, acetylene glycol type surfactants, polyhydric alcohol type surfactants, polymer type nonionic surfactants, etc.

The polyethylene glycol surfactant is not particularly limited, but examples thereof include higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, higher alkylamine ethylene oxide adducts, ethylene oxide adducts of fats and oils, and polypropylene glycol ethylene oxide adducts.

The acetylene glycol surfactant is not particularly limited, but examples thereof include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, Surfynol (manufactured by Air Products, registered trademark), and Olfine (manufactured by Nissin Chemical Industry Co., Ltd., registered trademark).

The polyhydric alcohol surfactant is not particularly limited, but examples thereof include fatty acid esters of glycerol, fatty acid esters of pentaerythritol, fatty acid esters of sorbitol and sorbitan, fatty acid esters of sucrose, alkyl ethers of higher alcohols, fatty acid amides of alkanolamines, etc.

The amphoteric surfactant is not particularly limited, but examples thereof include betaine-type amphoteric surfactants. The betaine-type amphoteric surfactant is not particularly limited, but examples thereof include alkyl dimethyl betaine, lauryl dimethyl betaine, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, etc.

The fluorosurfactant is not particularly limited as long as it has a perfluoroalkyl group, but examples include PLASCOAT (registered trademark) RY-2, perfluoroalkane, perfluoroalkyl carboxylic acid, perfluoroalkyl sulfonic acid, and perfluoroalkyl ethylene oxide adducts.

The silicone surfactant is not particularly limited, but examples thereof include polyether-modified polydimethylsiloxane, polyetherester-modified polydimethylsiloxane, hydroxyl group-containing polyether-modified polydimethylsiloxane, acrylic group-containing polyether-modified polydimethylsiloxane, acrylic group-containing polyester-modified polydimethylsiloxane, perfluoropolyether-modified polydimethylsiloxane, perfluoropolyester-modified polydimethylsiloxane, and silicone-modified acrylic compounds.

Furthermore, fluorosurfactants and silicone surfactants are effective as leveling agents to improve the flatness of the coating film.

The solvent is not particularly limited, but may be, for example, alcohol, and more specific examples include methanol, ethanol, propanol, butanol, methoxyethanol, ethoxyethanol, butoxyethanol, ethylene glycol, etc.

In the conductive polymer composition of the present invention, the content of the additive (D) is 0.001 to 20% by weight, but from the viewpoint of excellent operability, it is preferably 0.01 to 15% by weight, and more preferably 0.1 to 10% by weight.

The conductive polymer composition of the present invention is characterized by containing 0.01 to 10% by weight of polythiophene (A) containing at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and structural units represented by the following general formula (2), containing 0.01 to 0.5% by weight of a water-dispersible metal (B), and containing water.

The concentration (content) of the water is not particularly limited, but in terms of excellent workability, it is preferably in the range of 80 to 99.5% by weight, and more preferably 85 to 99.5% by weight.

The method for preparing the conductive polymer composition of the present invention is not particularly limited, but may be, for example, a method in which an aqueous solution or solid of the polythiophene (A) is mixed with insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less, and water as necessary, and homogenized by stirring or the like. In this case, the compound (C) and additive (D) may be added and mixed as necessary, or a conductive polymer composition containing the polythiophene (A) and insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less may be prepared first, and then the compound (C) and additive (D) may be added and mixed to adjust the conductive polymer composition. Note that each material is preferably added to water and mixed, but the order in which the materials are added and mixed is not particularly limited, and the conductive polymer composition of the present invention can be prepared by mixing these materials in any order.

Here, the temperature during mixing is not particularly limited, but for example, mixing can be performed at room temperature or under heating. A temperature between 0°C and 100°C is preferable.

The atmosphere in which the mixture is mixed is not particularly limited, but may be air or an inert gas.

When mixing, in addition to the general mixing and dissolving operation using a stirrer tip or stirring blade, ultrasonic irradiation and homogenization treatment (for example, using a mechanical homogenizer, ultrasonic homogenizer, high-pressure homogenizer, etc.) may be performed. When homogenization treatment is performed, it is preferable to perform it at a low temperature to prevent thermal degradation of the polymer.

The concentration of each component in the conductive polymer composition of the present invention may be adjusted by the blending ratio, or may be adjusted by concentrating after blending. The concentrating method may be a method of distilling off the solvent under reduced pressure, or a method of using an ultrafiltration membrane.

For the conductive polymer composition of the present invention, the concentration of all components other than water is preferably in the range of 0.5 to 20% by weight, and more preferably in the range of 0.5 to 15% by weight.

The conductive polymer composition of the present invention is dried and dehydrated after application, so a good uniform film can be obtained within the above concentration range.

The viscosity (20°C) of the conductive polymer composition of the present invention is preferably 200 mPa·s or less, more preferably 100 mPa·s or less, and even more preferably 50 mPa·s or less.

The conductive polymer film of the present invention can be formed using the conductive polymer composition of the present invention. The method for forming the conductive polymer film of the present invention is not particularly limited, but may be, for example, a method in which the conductive polymer composition of the present invention is applied to or immersed in a substrate and then dried.

The drying atmosphere may be air, an inert gas, a vacuum, or a reduced pressure. From the viewpoint of preventing deterioration of the polymer film, an inert gas such as nitrogen or argon is preferable.

The above substrate is not particularly limited, but examples include glass, plastic, polyester, polyacrylate, polycarbonate, metal oxide, ceramic, or resist substrate.

The above coating method is not particularly limited, but examples include casting, dipping, bar coating, roll coating, gravure coating, flexographic printing, spray coating, spin coating, and inkjet printing.

The drying temperature for the coating is not particularly limited as long as a uniform conductive film is obtained, but it is preferably in the range of room temperature to 300°C, more preferably in the range of room temperature to 250°C, and even more preferably in the range of room temperature to 200°C.

The thickness of the coating film is not particularly limited, but is preferably in the range of 10 ⁻² to 10 ² μm. The surface resistance of the resulting coating film is not particularly limited, but is preferably in the range of 1 to 10 ⁹ Ω/.

The conductivity of the conductive polymer film obtained by the present invention is not particularly limited, but it is preferable that the conductivity (electrical conductivity) in the film state is 10 S/cm or more.

The conductive polymer film of the present invention can be used, for example, as an antistatic agent, a solid electrolyte for electrolytic capacitors, a conductive paint, an electrochromic element, an electrode material, a thermoelectric conversion material, a transparent conductive film, a chemical sensor, an actuator, etc. In particular, it is extremely useful as a solid electrolyte for electrolytic capacitors. When used in electrolytic capacitors, it is possible to provide an electrolytic capacitor that has excellent characteristics such as low ESR while maintaining a high capacity.

The conductive polymer film is characterized by containing polythiophene (A) containing at least one structural unit selected from the group consisting of structural units represented by the general formula (1') and structural units represented by the general formula (2') and insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less.

The present invention will be described in detail below with reference to examples. However, the present invention should not be construed as being limited in any way by these examples.

The analytical instruments and measurement methods used in this example are listed below.

[NMR Measurement]
Equipment: VARIAN, Gemini-200
[Method of producing conductive polymer film]
Specifically, 0.5 mL of the composition of the present invention described below was applied to a 25 mm square alkali-free glass plate, heated on a hot plate in air at 60° C. for 30 minutes, and further heated at 200° C. for 60 minutes to obtain a conductive polymer film.

[Measurement of Conductive Polymer Film Thickness]
Apparatus: DEKTAK XT manufactured by BRUKER.

The conductive polymer film produced by the above method was cut at intervals of 6.25 mm in the x direction and 6.25 mm in the y direction to expose the glass portion, and the film thickness was measured at nine measurement points in an atmosphere of 25°C and 50% RH.

[Measurement of surface resistivity of conductive polymer film]
Apparatus: Mitsubishi Chemical Loresta GP MCP-T600.
Using a surface resistance measuring instrument Loresta GP MCP-T600 and a measuring probe as an ASP, the surface resistance was measured at nine measurement points at intervals of 6.25 mm in the x direction and 6.25 mm in the y direction in an atmosphere of 25° C. and 50% RH.

[Conductivity measurement of conductive polymer film]
The electrical conductivity was calculated from the film thickness and surface resistivity of the conductive polymer film measured by the above-mentioned measuring method according to the following formula.

Electrical conductivity [S/cm] = 10 ⁴ / (Surface resistivity [Ω/□] x Film thickness [μm])
[Fabrication of Solid Electrolytic Capacitor]
An aluminum foil having a thickness of 100 μm was used, and the surface of the aluminum foil was etched. An aluminum foil was welded to a part of the etched aluminum foil having a thickness of 100 μm, and a lead wire was attached. The etched aluminum foil was immersed in an aqueous solution of ammonium dihydrogen phosphate having a concentration of 0.2 wt% at a liquid temperature of 80° C., and a direct current voltage of 130 V was applied for 20 minutes to form a dielectric layer of aluminum oxide (anode). Separately, an etched aluminum foil having a thickness of 50 μm and a lead wire was used as a cathode, and a separator made of insulating paper was interposed between the anode and the cathode to prepare a wound element. Next, the wound element was immersed in a conductive polymer composition, taken out, and then dried at 150° C. for 30 minutes to obtain a solid electrolytic capacitor.

[Characteristics measurement of solid electrolytic capacitors]
The characteristics of the solid electrolytic capacitor prepared by the above method were evaluated using the following device, including the initial capacitance [μF] at initial 120 Hz, the ESR [mΩ] at initial 100 kHz, and the leakage current [μA] after 2 minutes when 63 V was applied.

Equipment: Hioki E.E. Corporation LCR meter IM3536
Synthesis Example 1
According to Synthesis Examples 1 and 2 of the known literature (JP 2019-196443), an aqueous solution of poly(3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid [polymer containing a structural unit represented by the following formula (4) and a structural unit represented by the following formula (5)] (hereinafter referred to as "PEDOT-MPS") (conductive polymer aqueous solution) was prepared. The amount of polymer contained in the aqueous solution was 0.74 wt%. In addition, iron ions and sodium ions were contained in amounts of 44 ppm and 12 ppm (relative to the polymer), respectively. The conductivity of this polymer was 342 S/cm.

Example 1
(Preparation of Conductive Polymer Solution)
The conductive polymer aqueous solution obtained in Synthesis Example 1 was dehydrated under reduced pressure to prepare an aqueous solution containing 2.0% by weight of PEDOT-MPS. 0.5 g of aluminum oxide (Sigma-Aldrich, product number 544833) having a particle size (D50) of less than 50 nm was added to 100 g of the aqueous solution containing 2.0% by weight of PEDOT-MPS, and the mixture was thoroughly stirred and mixed. Next, 0.4 g of ethanolamine was added and the mixture was thoroughly stirred and mixed to obtain a conductive polymer composition with a pH of 3. A solid electrolytic capacitor was produced using the conductive polymer composition according to the above-mentioned method, and the characteristics were evaluated. The evaluation results are shown in Table 1.

Example 2
The capacitor characteristics were evaluated in the same manner as in Example 1, except that 0.1 g of silicon dioxide (Adelight AT-20Q, manufactured by ADEKA Corporation) having a particle diameter (D50) of 10 to 20 nm was used instead of 0.5 g of aluminum oxide having a particle diameter (D50) of less than 50 nm. Note that, in order to achieve a pH of 3, the amount of ethanolamine added was set to 0.4 g, as in Example 1. The evaluation results are shown in Table 1.

Comparative Example 1
A conductive polymer composition was prepared by the same procedure as in Example 1, except that 0.1 g of silicon dioxide (Sea Hoster KE-P10, manufactured by Nippon Shokubai Co., Ltd.) having a particle diameter (D50) of 100 nm was used instead of 0.5 g of aluminum oxide having a particle diameter (D50) of less than 50 nm. However, a uniform dispersion was not obtained, and the capacitor characteristics could not be evaluated. In order to achieve a pH of 3, the amount of ethanolamine added was set to 0.4 g, as in Example 1. The evaluation results are shown in Table 1.

Example 3
The capacitor characteristics were evaluated in the same manner as in Example 1, except that 0.1 g of hydroxyapatite (Sigma-Aldrich, product number 900194) having a particle diameter (D50) of less than 50 nm was used instead of 0.5 g of aluminum oxide having a particle diameter (D50) of less than 50 nm in Example 1. Note that the amount of ethanolamine added was 0.4 g in the same manner as in Example 1 to achieve a pH of 3. The evaluation results are shown in Table 1.

Example 4
The capacitor characteristics were evaluated in the same manner as in Example 1, except that 0.01 g of hydroxyapatite (Sigma-Aldrich, product number 900194) having a particle diameter (D50) of less than 50 nm was used instead of 0.5 g of aluminum oxide having a particle diameter (D50) of less than 50 nm in Example 1. In addition, the amount of ethanolamine added was 0.4 g, as in Example 1, to achieve a pH of 3. The evaluation results are shown in Table 1.

Example 5
The capacitor characteristics were evaluated in the same manner as in Example 1, except that 1 g of hydroxyapatite (Sigma-Aldrich, product number 900194) having a particle diameter (D50) of less than 50 nm was used instead of 0.5 g of aluminum oxide having a particle diameter (D50) of less than 50 nm in Example 1. Note that, in order to achieve a pH of 3, the amount of ethanolamine added was set to 0.4 g, as in Example 1. The evaluation results are shown in Table 1.

Comparative Example 2
The capacitor characteristics were evaluated in the same manner as in Example 1, except that 5 g of hydroxyapatite (Sigma-Aldrich, product number 900194) having a particle diameter (D50) of less than 50 nm was used instead of 0.5 g of aluminum oxide having a particle diameter (D50) of less than 50 nm in Example 1. In addition, the amount of ethanolamine added was 0.4 g, as in Example 1, to achieve a pH of 3. The evaluation results are shown in Table 1.

Reference Example 1
The conductive polymer aqueous solution obtained in Synthesis Example 1 was dehydrated under reduced pressure to prepare an aqueous solution containing 2.0% by weight of PEDOT-MPS. 0.4 g of ethanolamine was added to 100 g of the aqueous solution containing 2.0% by weight of PEDOT-MPS, and the mixture was thoroughly stirred and mixed to obtain an aqueous conductive polymer solution with a pH of 3. A solid electrolytic capacitor was produced using the aqueous conductive polymer solution according to the method described above, and its characteristics were evaluated. The evaluation results are shown in Table 1.

Reference Example 2
0.3 g of ethanolamine was added to 100 g of a dispersion of poly(3,4-ethylenedioxythiophene) externally doped with polystyrenesulfonic acid (Clevios PH500 manufactured by Heraeus) and thoroughly stirred and mixed to obtain a conductive polymer dispersion with a pH of 3. A solid electrolytic capacitor was produced using the conductive polymer dispersion according to the method described above, and its characteristics were evaluated. The evaluation results are shown in Table 1.

Comparative Example 3
0.5 g of aluminum oxide having a particle size (D50) of less than 50 nm was added to 100 g of a dispersion of poly(3,4-ethylenedioxythiophene) externally doped with polystyrene sulfonic acid (Clevios PH500 manufactured by Heraeus was used) and thoroughly mixed. Next, 0.3 g of ethanolamine was added and thoroughly mixed, obtaining a conductive polymer dispersion with a pH of 3. A solid electrolytic capacitor was produced using the conductive polymer dispersion according to the method described above, and its characteristics were evaluated. The evaluation results are shown in Table 1.

Comparative Example 4
The capacitor characteristics were evaluated in the same manner as in Comparative Example 2, except that 0.1 g of silicon dioxide (Adelight AT-20Q, manufactured by ADEKA Corporation) having a particle diameter (D50) of 10 to 20 nm was used instead of 0.5 g of aluminum oxide having a particle diameter (D50) of less than 50 nm. The amount of ethanolamine added was 0.3 g to achieve a pH of 3. The evaluation results are shown in Table 1.

From the results shown in Table 1, Examples 1 to 5 using the conductive polymer composition of the present invention achieved the effect of achieving low ESR while maintaining high capacity. This is presumably the result of the conductive polymer composition of the present invention filling the gap between the anode foil and the cathode foil. Furthermore, it was found that when the conductive polymer composition of the present invention is used, an electrolytic capacitor with low leakage current can be obtained. This effect is presumably due to the conductive polymer composition of the present invention having a high ability to repair oxide film defects that occur in the process of making an electrolytic capacitor. When PEDOT/PSS was used instead, a decrease in capacity and an increase in ESR were confirmed.

As described above, by using the conductive polymer composition of the present invention, it is possible to provide an electrolytic capacitor that has excellent characteristics such as low ESR while maintaining a high capacity.

Claims (7)

A conductive polymer composition for producing an electrolytic capacitor (excluding compositions containing a fluorine-based surfactant), comprising 0.01 to 10% by weight of polythiophene (A) containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2) :

[In general formulas (1) and (2), R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.] The conductive polymer composition according to claim 1, wherein the particle diameter (D50) of the insulating inorganic particles (B) is 60 nm or less. The conductive polymer composition according to claim 1 or 2, wherein the insulating inorganic particles (B) are one or a mixture of two or more selected from the group consisting of aluminum oxide, titanium oxide, silicon dioxide, magnesium oxide, zinc oxide, barium titanate, strontium titanate, aluminum nitride, boron nitride, kaolin, hydroxyapatite, bentonite, and hydrotalcite. The conductive polymer composition according to any one of claims 1 to 3, which further contains, in addition to (A), (B), and water, a compound (C) selected from the group consisting of an alkali metal compound, ammonia, an organic amine compound, and a quaternary ammonium compound, and has a pH in the range of 1.5 to 10.0. A conductive polymer film for electrolytic capacitors (excluding conductive polymer films containing a fluorine-based surfactant), comprising: polythiophene (A) containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2) :

[In general formulas (1) and (2), R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.] 6. A method for producing a conductive polymer film according to claim 5, comprising applying and drying a conductive polymer composition containing 0.01 to 10% by weight of polythiophene (A) containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), 0.01 to 3% by weight of insulating inorganic particles (B) having a particle diameter (D50) of 80 nm or less, and water:

[In general formulas (1) and (2), R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.] An electrolytic capacitor comprising the conductive polymer film according to claim 5.