Method for manufacturing conductive polymer dispersion and method for manufacturing conductive laminate

Abstract

To provide: a method for manufacturing a conductive polymer dispersion which has low initial viscosity immediately after manufacturing and which is designed to reduce viscosity increase during preservation and have good conductivity after drying and curing; and a method for manufacturing a conductive laminate.SOLUTION: One embodiment of the invention is a method for manufacturing a conductive polymer dispersion. The method includes a polymerization step of obtaining a polythiophene conductive polymer by polymerizing a thiophene compound in a reaction solution including water, an ion adsorbent, an iron compound as a catalyst, the thiophene compound, and an arbitrary polyanion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a conductive polymer dispersion containing a π-conjugated conductive polymer, and a method for producing a conductive laminate. [Background technology]

[0002] A π-conjugated conductive polymer whose main chain is composed of a π-conjugated system forms a conductive complex by doping with a polyanion having an anionic group, and becomes dispersible in water. A method for manufacturing a capacitor has been disclosed (for example, Patent Document 1), in which a paint made from a conductive polymer dispersion containing a conductive complex is applied to a dielectric layer provided on the surface of an anode made of a valve metal, dried to form a solid electrolyte layer, and then a cathode is placed opposite this. According to this disclosure, the performance of the capacitor is improved by adding a specific unsaturated aliphatic alcohol compound to the paint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-071400 Summary of the Invention [Problem to be solved by the invention]

[0004] The conductive polymer dispersion liquid used in the production of capacitors must have low viscosity so that it can penetrate into the porous structure of the dielectric layer, and the solid electrolyte layer formed by drying the soaked conductive polymer dispersion liquid must also have high conductivity. However, conventional conductive polymer dispersions have a problem in that their viscosity increases during storage. The increase in viscosity has been a problem not only in the production of capacitors, but also in the production of conductive laminates in which a conductive polymer dispersion is applied to a substrate to form a conductive layer.

[0005] The present invention provides a method for producing a conductive polymer dispersion that has a low initial viscosity immediately after production, a reduced increase in viscosity during storage, and good conductivity after drying and curing, and a method for producing a conductive laminate. [Means for solving the problem]

[0006] [1] A method for producing a conductive polymer dispersion, comprising a polymerization step of polymerizing a thiophene-based compound in a reaction solution containing water, an ion adsorbent, an iron compound as a catalyst, and a thiophene-based compound to obtain a polythiophene-based conductive polymer. [2] The method for producing a conductive polymer dispersion according to [1], wherein the reaction liquid further contains a polyanion. [3] The method for producing a conductive polymer dispersion according to [1] or [2], wherein the base material of the ion adsorbent is a polymer material. [4] The method for producing a conductive polymer dispersion according to any one of [1] to [3], wherein the ion adsorbent is a cation exchange resin having a sulfonic acid group or a carboxylic acid group as an ion exchange group. [5] The method for producing a conductive polymer dispersion according to any one of [1] to [4], wherein the value of X / Y is in the range of 1 to 50, where X equivalents / L is the ion exchange capacity of the ion adsorbent and Y moles / L is the amount of iron ions in the iron compound used as a catalyst. [6] The method for producing a conductive polymer dispersion according to any one of [1] to [5], wherein the total concentration of the thiophene compound and the polyanion blended in the reaction solution is 2.5 to 10.0 mass % with respect to the total mass of the reaction solution. [7] The method for producing a conductive polymer dispersion according to any one of [1] to [6], wherein the polythiophene-based conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrenesulfonic acid. [8] The method for producing a conductive polymer dispersion according to any one of [1] to [7], further comprising an ion exchange step of contacting the conductive polymer dispersion obtained in the polymerization step with at least one of a cation exchange resin and an anion exchange resin. [9] A method for producing a conductive laminate, comprising: obtaining the conductive polymer dispersion by the production method according to any one of [1] to [8]; and applying a liquid containing the conductive polymer dispersion to at least a part of a surface of a substrate to form a conductive layer. [Effects of the Invention]

[0007] According to the method for producing a conductive polymer dispersion of the present invention, it is possible to obtain a conductive polymer dispersion that has a low initial viscosity immediately after production and that is inhibited from increasing in viscosity during storage. In addition, the conductive polymer dispersion has good electrical conductivity when cured. According to the method for producing a conductive laminate of the present invention, since the above-mentioned excellent conductive polymer dispersion is used, a conductive laminate with stable quality can be easily produced. The same applies to the production of a capacitor.

[0008] This invention is believed to contribute to SDG Goal 12, "Responsible Consumption and Production."

[0009] In this specification and claims, the lower and upper limits of numerical ranges indicated with "to" are included in the numerical range. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an embodiment of a capacitor of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Method for producing conductive polymer dispersion> A first aspect of the present invention is a method for producing a conductive polymer dispersion, comprising a step of polymerizing a thiophene-based compound in a reaction liquid containing water, an ion adsorbent, an iron compound as a catalyst, and a thiophene-based compound, thereby obtaining a polythiophene-based conductive polymer. According to the production method of this embodiment, a conductive polymer dispersion containing the polythiophene-based conductive polymer and water is obtained.

[0012] In the reaction solution, iron ions, which are a catalyst in the polymerization reaction process, are adsorbed onto the ion adsorbent, forming a suitable reaction field for the thiophene-based compound, which is thought to result in a moderate polymerization reaction rate and suppression of rapid and excessive polymerization. The conductive polymer dispersion containing the polythiophene-based conductive polymer obtained in this way has low viscosity immediately after production and excellent storage stability.

[0013] A polyanion may be blended into the reaction solution. By carrying out the polymerization in the presence of the polyanion, a conductive polymer dispersion containing water and a conductive complex containing the polythiophene-based conductive polymer and the polyanion can be obtained. As will be described later, the polyanion functions as a dopant for the conductive polymer, and can significantly improve the conductivity thereof.

[0014] [Ion adsorbent] The ion adsorbent is preferably an ion exchange resin whose matrix (main material) is a polymer material. The matrix may be a gel in which polymers are cross-linked with each other, or may be porous particles that have been given physical porosity. The particle size may be, for example, about 0.3 to 1.2 mm. The ion exchange resin absorbs water and swells, forming pores (micropores) within the resin phase. It is believed that iron ions in the reaction solution are adsorbed into the micropores and / or the surface of the resin.

[0015] The ion adsorbent is preferably a cation exchange resin having sulfonic acid or carboxylic acid groups as ion exchange groups, as these acid groups are suitable for adsorbing iron ions and are less likely to interfere with the catalytic action in the polymerization reaction.

[0016] The ion exchange capacity of the ion adsorbent is preferably 1.0 to 20 equivalents / L, more preferably 2.0 to 10 equivalents / L, and even more preferably 2.0 to 5.0 equivalents / L. When the ion exchange capacity is within the above range, iron ions in the reaction solution can be sufficiently adsorbed, and the polymerization reaction can be controlled gently. In this specification and claims, the ion exchange capacity refers to the total exchange capacity. An ion exchange capacity of 1.0 equivalent / L (sometimes referred to as eq / L) means that 1 L of the ion adsorbent can adsorb 1 mole of ions converted into monovalent ions.

[0017] When the ion exchange capacity (unit: equivalent / L) of the ion adsorbent is X and the amount of iron ions (unit: mole / L) in the iron compound used as a catalyst is Y, the ratio represented by X / Y is preferably 1 to 50, more preferably 1 to 40, even more preferably 1 to 10, and particularly preferably 1 to 5. Here, the iron ions are preferably trivalent. When the X / Y ratio is 1 or more, iron ions can be sufficiently adsorbed. When the X / Y ratio is equal to or less than the upper limit, it becomes easy to adjust the amount of iron compound to be blended in the reaction solution. When the X / Y ratio is within these preferred ranges, the polymerization reaction proceeds gently, and a conductive polymer dispersion liquid having a low initial viscosity and excellent storage stability can be easily obtained.

[0018] [Iron compounds] The iron compound used as the catalyst in this embodiment may be either a ferrous compound or a ferric compound, but from the viewpoint of enhancing the catalytic activity, a ferric compound is preferred. Generally, iron in a ferric compound is trivalent (Fe 3+ ) Specifically, preferred iron compounds include iron (III) sulfate, iron (III) nitrate, iron (III) citrate, and ammonium iron citrate.

[0019] The concentration of the iron compound contained in the reaction solution is, for example, 0.01 to 3.0% by mass, preferably 0.1 to 1.0% by mass, relative to the total mass of the reaction solution. The concentration of the iron compound contained in the reaction solution is preferably an amount that satisfies the above-mentioned X / Y ratio.

[0020] [Oxidizing agent] An oxidizing agent that promotes the polymerization reaction is preferably added to the reaction solution. The type of oxidizing agent is preferably one that decomposes due to the catalytic action of the iron compound to generate radicals. The oxidizing agent preferably has a peracid structure represented by "-SO2-OO-" in its molecule. Specifically, peroxodisulfuric acid or its salts, or peroxomonosulfuric acid or its salts are preferred. The salts here have a counter cation such as sodium or potassium.

[0021] The method for adding the oxidizing agent to the reaction solution is not particularly limited, and the entire amount may be added at once, or an aqueous solution of the oxidizing agent may be gradually added dropwise. The amount of the oxidizing agent added may be the same as the amount of oxidizing agents known to be added in chemical polymerization reactions of thiophene compounds, and is, for example, preferably 0.6 to 2.0 molar equivalents, more preferably 0.8 to 1.5 molar equivalents, and even more preferably 0.9 to 1.3 molar equivalents, relative to 1 mole of the thiophene monomer used as a raw material. When the viscosity is equal to or greater than the lower limit, the polymerization reaction can be completed in a relatively short time, and when the viscosity is equal to or less than the upper limit, a conductive polymer dispersion liquid having a low initial viscosity and excellent storage stability can be obtained.

[0022] [Thiophene compounds] The thiophene compound added to the reaction solution is a monomer that polymerizes to form a polythiophene conductive polymer, the main chain of which constitutes a π-conjugated system. Polythiophene-based conductive polymers include polythiophene, poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly(3-chlorothiophene), and poly(3-iodothiophene). thiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene) oxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxythiophene), poly(3,4-dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-dihexyloxythiophene), poly(3,4-diheptyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-didecyloxythiophene), poly(3,4-di dodecyloxythiophene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butylenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl-4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), and poly(3-methyl-4-carboxybutylthiophene). Among these polythiophene-based conductive polymers, poly(3,4-ethylenedioxythiophene) is particularly preferred because of its excellent conductivity, transparency, and heat resistance. The thiophene-based compound to be blended in the mixed solution may be one type or two or more types.

[0023] (polyanion) The polyanion added to the reaction solution is a polymer having two or more monomer units each having an anionic group in the molecule. The anionic group of this polyanion functions as a dopant for the polythiophene-based conductive polymer, improving the conductivity of the polythiophene-based conductive polymer. The anion group of the polyanion is preferably a sulfo group or a carboxy group. Specific examples include polymers having sulfo groups, such as polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyacrylic acid esters having sulfo groups, polymethacrylic acid esters having sulfo groups (e.g., poly(4-sulfobutyl methacrylate, polysulfoethyl methacrylate, polymethacryloyloxybenzenesulfonic acid), poly(2-acrylamido-2-methylpropanesulfonic acid), and polyisoprene sulfonic acid; and polymers having carboxy groups, such as polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanecarboxylic acid), and polyisoprene carboxylic acid. The polyanion may be a homopolymer formed by polymerizing a single monomer, or a copolymer formed by polymerizing two or more monomers. Among these polyanions, polymers having sulfo groups are preferred, and polystyrene sulfonic acid is more preferred, since they can further increase the conductivity. The polyanion to be added to the reaction solution may be one type or two or more types.

[0024] The weight average molecular weight Mw of the polyanion is preferably 20,000 or more and 1,000,000 or less. When the weight-average molecular weight Mw is in the above-mentioned preferred range, the storage stability of the conductive polymer dispersion of this embodiment is further improved. The weight-average molecular weight Mw is the average molecular weight on a mass basis measured using gel filtration chromatography and calculated as pullulan.

[0025] In a polyanion doped into a polythiophene-based conductive polymer, some anionic groups do not dope into the polythiophene-based conductive polymer, leaving excess anionic groups that are not involved in the doping. Because these excess anionic groups are hydrophilic groups, the conductive composite has high water dispersibility but low organic solvent dispersibility. When the number of all anionic groups in the polyanion is taken as 100 mol%, the excess anionic groups are preferably 30 mol% to 90 mol%, more preferably 45 mol% to 75 mol%.

[0026] [Conductive composite] When a polyanion is previously blended in the reaction solution, the polyanion naturally dopes the polythiophene-based conductive polymer formed by the polymerization reaction, forming a conductive composite having conductivity.

[0027] The content of the polyanion in the conductive composite is preferably in the range of 1 part by mass to 1,000 parts by mass, more preferably 10 parts by mass to 700 parts by mass, and even more preferably 100 parts by mass to 500 parts by mass, per 100 parts by mass of the polythiophene-based conductive polymer. If the content of the polyanion is equal to or greater than the lower limit, the doping effect on the polythiophene-based conductive polymer tends to be stronger, resulting in higher conductivity. On the other hand, if the content of the polyanion is equal to or less than the upper limit, the relative proportion of the polythiophene-based conductive polymer can be increased, thereby ensuring conductivity.

[0028] The content ratio (by mass) of polythiophene-based conductive polymer to polyanion contained in the conductive composite formed in the reaction solution is approximately the same as the content ratio of the thiophene-based compound to the polyanion blended in the reaction solution. In other words, the blending ratio of the thiophene-based compound to the polyanion blended in the reaction solution is reflected in the content ratio of the polythiophene-based conductive polymer to the polyanion in the formed conductive composite.

[0029] The ratio of the thiophene compound to the polyanion contained in the reaction solution is preferably from 1.0:2.0 to 1.0:5.0 by mass, more preferably from 1.0:2.0 to 1.0:4.0, and even more preferably from 1.0:2.5 to 1.0:3.5. Within this range, a conductive polymer dispersion having excellent water dispersibility can be formed.

[0030] In this embodiment, since the reaction solution contains an adsorbent, the total concentration of the thiophene compound and polyanion to be mixed in the reaction solution can be made higher than in conventional reaction systems. The total concentration of the thiophene compound and the polyanion blended in the reaction solution is preferably 2.0 to 10.0 mass %, more preferably 3.0 to 9.0 mass %, and even more preferably 3.5 to 8.0 mass %, relative to the total mass of the reaction solution. When the concentration is equal to or greater than the lower limit, the production efficiency of the conductive composite (the amount produced per reaction) is improved. When the concentration is equal to or less than the upper limit, a conductive polymer dispersion liquid having a low initial viscosity and excellent storage stability can be obtained. The total mass of the reaction solution includes the mass of all oxidizing agents added from the start to the end of the reaction, but does not include the mass of the ion adsorbent.

[0031] When the polymerization reaction in the reaction solution is completed by the above method, the reaction solution becomes the target conductive polymer dispersion. The content of the monomer in the reaction solution is measured by gas chromatography or the like, and the completion of the polymerization reaction is preferably determined when the presence of the monomer is substantially no longer confirmed.

[0032] Since decomposition products of the catalyst and oxidizing agent contained in the conductive polymer dispersion (reaction liquid) remain after the polymerization reaction, it may be preferable to remove these before using the conductive polymer dispersion. Examples of removal methods include contacting the conductive polymer dispersion with an ion exchange resin to adsorb the catalyst and oxidizing agent onto the ion exchange resin, and ultrafiltration of the conductive polymer dispersion to remove the catalyst and oxidizing agent while replacing the dispersion medium. Among these, the method using an ion exchange resin is preferred because it is simple. It is preferable to use a cation exchange resin and an anion exchange resin in combination as the ion exchange resin.

[0033] The conductive polymer dispersion may be subjected to dispersion treatment by a conventional method such as using a high-pressure homogenizer.

[0034] The content of the conductive complex relative to the total mass of the conductive polymer dispersion is preferably 0.01% by mass to 5.0% by mass, more preferably 1.0% by mass to 4.0% by mass, and even more preferably 1.5% by mass to 3.0% by mass. When the content is at least as large as the lower limit of the above range, the conductivity of the conductive layer formed by curing the conductive polymer dispersion can be further improved. When the content is equal to or less than the upper limit of the above range, the dispersibility of the conductive composite in the conductive polymer dispersion can be improved, and the storage stability can be further improved.

[0035] The viscosity of the conductive polymer dispersion at 23°C, when the concentration of the conductive composite relative to the total mass of the conductive polymer dispersion is adjusted to 1.8% by mass, is preferably 80 mPa·s or less, more preferably 60 mPa·s or less, and even more preferably 40 mPa·s or less, as measured within 24 hours after the adjustment. There are no particular restrictions on the lower limit of the viscosity, and a guideline is 1 mPa·s or more. When a viscosity within this preferred range is used in the production of a capacitor, the production of a solid electrolyte becomes easier and the capacitor performance is improved. When measuring the viscosity, the conductive polymer dispersion preferably contains only ion-exchanged water as a dispersion medium, and preferably contains no additives other than the conductive composite. The viscosity was measured at 23°C using a tuning fork vibration viscometer in accordance with JIS Z8803:2011 (viscosity measurement method using a vibration viscometer).

[0036] In order to improve the wettability of the conductive polymer dispersion to the substrate, a water-soluble organic solvent may be added to the conductive polymer dispersion. The conductive polymer dispersion to which the water-soluble organic solvent has been added is sometimes called a coating composition (paint).

[0037] <Coating composition (paint)> The coating composition contains water, the polythiophene-based conductive polymer obtained by the production method of the first embodiment or the conductive composite described above, and a water-soluble organic solvent. A mixture of water and a water-soluble organic solvent is sometimes called an aqueous dispersion medium.

[0038] A water-soluble organic solvent is an organic solvent that dissolves in an amount of 1 g or more in 100 g of water at 20°C. Examples of the water-soluble organic solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, nitrogen atom-containing solvents, and ester-based solvents. Examples of alcohol-based solvents include methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 2-methyl-2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, allyl alcohol, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and ethylene glycol monomethyl ether. Examples of the ether solvent include diethyl ether, dimethyl ether, propylene glycol dialkyl ether, and diethylene glycol diethyl ether. Examples of ketone solvents include diethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl amyl ketone, diisopropyl ketone, methyl ethyl ketone, acetone, and diacetone alcohol. Examples of nitrogen atom-containing solvents include N-methylpyrrolidone, dimethylacetamide, and dimethylformamide. The water-soluble organic solvent may be contained alone or in combination of two or more kinds. The water-soluble organic solvent is preferably an alcohol-based solvent or a ketone-based solvent, more preferably an alcohol-based solvent, because this improves the applicability of the coating composition to the substrate.

[0039] The content of the water-soluble organic solvent relative to the total mass of the aqueous dispersion medium is preferably 30 to 70 mass %, more preferably 40 to 60 mass %, and the content of water relative to the total mass of the aqueous dispersion medium is preferably 70 to 30 mass %, more preferably 60 to 40 mass %. When the content is within the above preferred range, it is possible to improve the wettability of the conductive composite to the substrate while suppressing deterioration over time in the dispersion stability of the conductive composite in the coating composition.

[0040] The content of the polythiophene-based conductive polymer or conductive complex relative to the total mass of the coating composition is, for example, preferably 0.1 to 2.5 mass%, more preferably 0.3 to 2.0 mass%, and even more preferably 0.5 to 1.5 mass%. Within this range, it is possible to suppress deterioration over time in the dispersion stability of the conductive complex in the coating composition, and it is possible to form a conductive layer or the like with good conductivity.

[0041] (Polyol compound) The coating composition may further contain one or more polyol compounds. Here, the polyol compound refers to a compound having two or more hydroxy groups. The inclusion of the polyol compound can increase the conductivity of the conductive layer formed by curing the conductive polymer dispersion and reduce the equivalent series resistance in the solid electrolyte layer of the capacitor.

[0042] Examples of the polyol compound include one or more selected from ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-butynediol, glycerin, pentaerythritol, trimethylolpropane, and trimethylolethane.

[0043] The content of the polyol compound in the coating composition is, for example, preferably 100 parts by mass or more and 10,000 parts by mass or less, more preferably 200 parts by mass or more and 2,000 parts by mass or less, and even more preferably 300 parts by mass or more and 1,000 parts by mass or less, relative to 100 parts by mass of the conductive composite. Within the above range, the above-mentioned effects can be more effectively obtained.

[0044] The content of the polyol compound relative to the total mass of the coating composition is, for example, preferably from 1 to 20 mass %, more preferably from 2 to 10 mass %, and even more preferably from 3 to 8 mass %. When the content is within the above range, the coatability of the coating composition is improved, and the above-mentioned effects are further obtained.

[0045] (Other additives) The coating composition and the conductive polymer dispersion may contain other known additives. Examples of additives that can be used include surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers. The surfactant may be a nonionic, anionic, or cationic surfactant, with the nonionic surfactant being preferred from the standpoint of storage stability. A polymer surfactant such as polyvinylpyrrolidone may also be added. Examples of inorganic conductive agents include metal ions, conductive carbon, etc. Metal ions can be generated by dissolving a metal salt in water. Examples of the antifoaming agent include silicone resin, polydimethylsiloxane, and silicone oil. The coupling agent may be a silane coupling agent having a vinyl group or an amino group. Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, oxanilide-based ultraviolet absorbers, hindered amine-based ultraviolet absorbers, and benzoate-based ultraviolet absorbers. When the above-mentioned additives are contained, the content ratio thereof is determined appropriately depending on the type of additive, but can be, for example, in the range of 0.001 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the conductive composite.

[0046] <Method for manufacturing conductive laminate> A second aspect of the present invention is a method for producing a conductive laminate, comprising the steps of obtaining a conductive polymer dispersion by the production method of the first aspect, and applying the conductive polymer dispersion to at least a part of a surface of a substrate to form a conductive layer.

[0047] Examples of a method for coating (applying) the conductive polymer dispersion onto any surface of a substrate include a method using a coater such as a gravure coater, a roll coater, a curtain flow coater, a spin coater, a bar coater, a reverse coater, a kiss coater, a fountain coater, a rod coater, an air doctor coater, a knife coater, a blade coater, a cast coater, or a screen coater; a method using a sprayer such as an air spray, an airless spray, or a rotor dampening; and an immersion method such as dipping.

[0048] The amount of the conductive polymer dispersion applied to the substrate is not particularly limited, but for example, it is 0.01 to 10.0 g / m as a non-volatile component. 2 The range is preferred.

[0049] The conductive layer can be formed by drying the coating film made of the conductive polymer dispersion applied onto the substrate to remove at least a portion of the dispersion medium and curing the coating film. Methods for drying the coating film include heat drying, vacuum drying, etc. Heat drying can be performed using, for example, hot air heating or infrared heating. When heat drying is applied, the heating temperature is appropriately set depending on the dispersion medium used, but is usually within the range of 50°C to 200°C. Here, the heating temperature is the temperature set in the drying device. A suitable drying time within the above heating temperature range is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 15 minutes.

[0050] <Conductive laminate> The conductive laminate obtained by the production method of the second aspect comprises a substrate and a conductive layer formed on at least a portion of the surface of the substrate and comprising a cured product of the conductive polymer dispersion of the first aspect.

[0051] [Conductive layer] The conductive layer may be formed over the entire surface of the substrate or over only a portion of the surface. In a conductive film, it is preferable that a conductive layer of substantially uniform thickness is formed over substantially the entire surface of one or the other of the film substrate. When a conductive layer is formed over only a portion of the surface of the substrate, the conductive layer may be, for example, a fine conductive pattern such as a circuit or electrode, or may be simply a roughly divided area where a conductive layer is provided and an area where a conductive layer is not provided exist on the same surface.

[0052] The average thickness of the conductive layer is, for example, preferably 10 nm or more and 100 μm or less, more preferably 20 nm or more and 50 μm or less, and even more preferably 30 nm or more and 30 μm or less. When the average thickness of the conductive layer is equal to or greater than the lower limit, high conductivity can be exhibited, and when the average thickness is equal to or less than the upper limit, the adhesiveness of the conductive layer to the substrate is further improved.

[0053] [Base material] The substrate may be made of an insulating material or a conductive material. The shape of the substrate is not particularly limited, and examples thereof include a shape mainly having a flat surface, such as a film or a substrate. Examples of insulating materials include glass, synthetic resin, and ceramics. Examples of conductive materials include metals, conductive metal oxides, and carbon.

[0054] (Film substrate) When a film substrate is used as the substrate, the conductive laminate becomes a conductive film. Examples of the film substrate include plastic films made of synthetic resins, such as ethylene-methyl methacrylate copolymer resin, ethylene-vinyl acetate copolymer resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacrylate, polycarbonate, polyvinylidene fluoride, polyarylate, styrene-based elastomers, polyester-based elastomers, polyethersulfone, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyimide, cellulose triacetate, and cellulose acetate propionate. From the viewpoint of improving the adhesion between the film substrate and the conductive layer, the synthetic resin for the film substrate is preferably a polyester resin, and among these, polyethylene terephthalate is preferred.

[0055] The synthetic resin for the film substrate may be amorphous or crystalline. The film substrate may be unstretched or stretched. The film substrate may be subjected to a surface treatment such as corona discharge treatment, plasma treatment, or flame treatment in order to further improve the adhesion of the conductive layer.

[0056] The average thickness of the film substrate is preferably 5 μm or more and 500 μm or less, and more preferably 20 μm or more and 200 μm or less. When the average thickness of the film substrate is equal to or more than the lower limit, the film is less likely to break, and when the average thickness is equal to or less than the upper limit, the film can have sufficient flexibility. The average thickness of the film substrate is determined by measuring the thickness at 10 randomly selected locations and averaging the measured values.

[0057] (glass substrate) Examples of the glass substrate include an alkali-free glass substrate, a soda-lime glass substrate, a borosilicate glass substrate, and a quartz glass substrate. If the substrate contains an alkali component, the conductivity of the conductive layer tends to decrease. Therefore, among the glass substrates, an alkali-free glass is preferred. Here, alkali-free glass refers to a glass composition having an alkali component content of 0.1% by mass or less relative to the total mass of the glass composition.

[0058] The average thickness of the glass substrate is preferably 100 μm or more and 3000 μm or less, and more preferably 100 μm or more and 1000 μm or less. When the average thickness of the glass substrate is equal to or more than the lower limit, the glass substrate is less likely to break, and when the average thickness is equal to or less than the upper limit, the conductive laminate can be made thinner. The average thickness of the glass substrate is determined by measuring the thickness at 10 randomly selected locations and averaging the measured values.

[0059] <Capacitor manufacturing method> A third aspect of the present invention is a method for producing a capacitor, comprising the steps of obtaining a conductive polymer dispersion by the production method of the first aspect, and applying the conductive polymer dispersion to a surface of a dielectric layer formed on the surface of an anode made of a porous valve metal, and drying the applied conductive polymer dispersion to form a solid electrolyte layer.

[0060] The method for manufacturing a capacitor of this embodiment preferably includes the steps of: oxidizing the surface of an anode made of a porous valve metal to form a dielectric layer (dielectric forming step), arranging a cathode in a position opposite to the dielectric layer (cathode forming step), and forming a solid electrolyte layer on at least a part of the surface of the dielectric layer (film forming step). Each step will be described below with reference to FIG.

[0061] [Dielectric formation process] In this step, the surface of anode 11 made of a porous valve metal is oxidized to form dielectric layer 12. The method for forming dielectric layer 12 is not particularly limited, and examples thereof include a method of anodizing the surface of anode 11 in a chemical conversion treatment electrolyte such as an aqueous solution of ammonium adipate, an aqueous solution of ammonium borate, or an aqueous solution of ammonium phosphate.

[0062] [Cathode formation process] In this step, the cathode 13 is disposed at a position facing the dielectric layer 12. The method for disposing the cathode 13 is not particularly limited, and examples thereof include a method of forming the cathode 13 using a conductive paste such as a carbon paste or a silver paste, and a method of disposing a metal foil such as an aluminum foil facing the dielectric layer 12.

[0063] [Film forming process] In this step, the conductive polymer dispersion liquid is applied to at least a portion of the surface of the dielectric layer 12 and then dried to form the solid electrolyte layer 14.

[0064] Examples of methods that can be used to apply the conductive polymer dispersion include immersion (dip coating), comma coating, reverse coating, lip coating, and microgravure coating. Of these, a method in which the anode 11 is immersed in the conductive polymer dispersion under reduced pressure is preferred. The immersion method allows the conductive polymer dispersion to be applied thoroughly, even to the interior of the porous structure on the surface of the dielectric layer 12. After immersion, the anode is removed and then subjected to the next drying process.

[0065] Drying methods include, for example, room temperature drying, hot air drying, far infrared drying, etc. Among these, hot air drying is preferred. The drying temperature is, for example, preferably 100 to 180° C., more preferably 120 to 150° C. The drying time is, for example, preferably 0.2 to 1 hour. After the drying process, the capacitor can be assembled in the usual manner.

[0066] <Capacitor> A fourth aspect of the present invention comprises an anode made of a porous body of a valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the dielectric layer opposite the anode, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer contains a cured product of the conductive polymer dispersion obtained by the production method of the first aspect. The capacitor of the fourth aspect can be manufactured by the manufacturing method of the third aspect.

[0067] An example of an embodiment of the fourth aspect will be described with reference to Fig. 1. A capacitor 10 shown in Fig. 1 includes an anode 11 made of a porous valve metal, a dielectric layer 12 made of an oxide of the valve metal, a solid electrolyte layer 14 formed on the surface of the dielectric layer 12, and a cathode 13 provided on the outermost side. The cathode 13 is provided on the opposite side of the anode 11, with the dielectric layer 12 and the solid electrolyte layer 14 sandwiched therebetween.

[0068] Examples of valve metals that can be used to form the anode 11 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Of these, aluminum, tantalum, and niobium are preferred. Specific examples of the anode 11 include an aluminum foil that has been etched to increase its surface area and then oxidized, and a tantalum or niobium particle sintered body whose surface has been oxidized and then pelletized. Such a processed body becomes a porous body with irregularities formed on the surface.

[0069] The dielectric layer 12 in this embodiment is a layer formed by oxidizing the surface of the anode 11, for example, by anodizing the surface of the metallic anode 11 in an electrolyte such as an aqueous solution of ammonium adipate. Similar to the anode 11, the dielectric layer 12 also has projections and recesses.

[0070] The cathode 13 in this embodiment may be a conductive layer formed from a conductive paste or a metal layer made of a conductive material such as aluminum foil.

[0071] The solid electrolyte layer 14 in this embodiment is formed on the surface of the dielectric layer 12. The solid electrolyte layer 14 covers at least a portion of the surface of the dielectric layer 12, and may cover the entire surface of the dielectric layer 12. The thickness of the solid electrolyte layer 14 may or may not be constant, and may be, for example, 1 μm or more and 100 μm or less.

[0072] [Electrolyte] The capacitor of this embodiment may have an electrolyte solution that impregnates the solid electrolyte layer. Examples of the solvent that constitutes the electrolytic solution include alcohol-based solvents such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and glycerin; lactone-based solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; sulfur-based solvents such as sulfolane, dimethyl sulfoxide, and dimethyl sulfone; amide-based solvents such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, and N-methylpyrrolidinone; nitrile-based solvents such as acetonitrile and 3-methoxypropionitrile; and water. Examples of the electrolyte constituting the electrolytic solution include organic acids such as adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid, decanedicarboxylic acids such as 1,6-decanedicarboxylic acid and 5,6-decanedicarboxylic acid, octanedicarboxylic acids such as 1,7-octanedicarboxylic acid, azelaic acid, and sebacic acid; or boric acid, polyhydric alcohol complex compounds of boric acid obtained from boric acid and polyhydric alcohols; inorganic acids such as phosphoric acid, carbonic acid, and silicic acid; and primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, etc.), secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo(5,4,0)-undecene-7, etc.), tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), etc. as a cationic component;

[0073] The capacitor of this embodiment is not limited to the above configuration, and a separator may be provided between the dielectric layer and the cathode. An example of a capacitor having a separator provided between the dielectric layer and the cathode is a wound capacitor. Examples of the separator include sheets (including nonwoven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., and nonwoven fabrics of glass fibers. The density of the separator is, for example, 0.1 g / cm 3 More than 1.0g / cm 3 The following are included: When a separator is provided, a method of forming a cathode by impregnating the separator with carbon paste or silver paste can also be applied. [Example]

[0074] [Preparation of polyanions] As a raw material, an aqueous solution (concentration 30%) of poly(sodium 4-styrenesulfonate) having a weight average molecular weight of 200,000 manufactured by Sigma-Aldrich was used. First, ion-exchanged water was added to an aqueous solution of poly(sodium 4-styrenesulfonate) to adjust it to a uniform aqueous solution with a solids concentration of 15 wt%, and cation-exchange resin was added until the pH was less than 1. Then, the cation-exchange resin was filtered off using a stainless steel mesh filter, and the solids concentration was adjusted to 10 wt% with ion-exchanged water to obtain an aqueous solution of polystyrenesulfonic acid (PSS).

[0075] [Preparation of thiophene compounds] Commercially available 3,4-ethylenedioxythiophene (Tokyo Chemical Industry Co., Ltd.) was purchased and purified by vacuum distillation before use in the reaction.

[0076] [Ion adsorbent] Cation exchange resin A: Duolite C255LHF manufactured by Sumika Chemitech Co., Ltd. (ion exchange group: sulfonic acid group, synthetic resin: styrene-based, ion exchange capacity: 2.0 eq / L) Cation exchange resin B: Amberlite HPR1024H manufactured by Organo Corporation (ion exchange group: sulfonic acid group, synthetic resin: styrene-based, ion exchange capacity: 2.1 eq / L) Cation exchange resin C: Amberlite IRC76 manufactured by Organo Corporation (ion exchange group: carboxylic acid group, synthetic resin: acrylic, ion exchange capacity: 3.9 eq / L)

[0077] [Example 1] A 1000ml three-neck flask was charged with 108g of PSS aqueous solution, 134g of ion-exchange water, 2.27g of iron(III) nitrate nonahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.), and 6ml of cation exchange resin A. Nitrogen was bubbled through the solution at a flow rate of 1L / min for 10 minutes, and the mixture was stirred under a nitrogen atmosphere and maintained at 25°C. 4.0g of purified 3,4-ethylenedioxythiophene was added to the solution, and 233.1g of a 2.5wt% aqueous solution of sodium peroxodisulfate (Junsei Chemical Co., Ltd.) was added over 2 hours using a metering pump. The mixture was then stirred at 25°C for 3 hours to synthesize the conductive polymer PEDOT-PSS. In this reaction, the solids concentration of the thiophene compound and polyanion was 3.1wt%, and the ratio (X / Y) of the ion exchange capacity (X) to the iron ion content (Y) was 2.1. To the synthesized PEDOT-PSS reaction solution, 100 ml of cation exchange resin (Duolite C255LFH, manufactured by Sumika Chemtex Co., Ltd.) and 100 ml of anion exchange resin (Duolite A368MS, manufactured by Sumika Chemtex Co., Ltd.) were added, and after stirring for 30 minutes, the ion exchange resin was filtered off using a stainless steel mesh filter. After homogenization using a high-pressure wet atomizer, the mixture was concentrated under reduced pressure to obtain a conductive polymer dispersion with a solids concentration of 1.8 wt%.

[0078] [Example 2] A conductive polymer dispersion with a solids concentration of 1.8 wt% was obtained in the same manner as in Example 1, except that the iron catalyst used in the reaction was changed to 3.20 g of iron (III) sulfate n-hydrate (60 to 80% as anhydrous, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and the amount of cation exchange resin A was changed to 35 ml. In Example 2, the solids concentration of the thiophene compound and polyanion was 3.1 wt%, and the ratio of the ion exchange capacity to the amount of iron ions (X / Y) was 5.5 to 7.4.

[0079] [Example 3] A 1000 ml three-neck flask was charged with 108 g of PSS aqueous solution, 54 g of ion-exchange water, 2.27 g of iron(III) nitrate nonahydrate, and 80 ml of cation exchange resin A. Nitrogen was bubbled through the solution at a flow rate of 1 L / min for 10 minutes, and the mixture was stirred under a nitrogen atmosphere and maintained at 25 °C. 4.0 g of 3,4-ethylenedioxythiophene was added to the solution, and 1.52 g of sodium peroxodisulfate was added four times at 30-minute intervals. The mixture was then stirred at 25 °C for 3 hours to synthesize the conductive polymer PEDOT-PSS. The solids concentration of the thiophene compound and polyanion in this reaction was 8.5 wt%, and the ratio of ion exchange capacity (X) to iron ion content (Y) (X / Y) was 28.5. Thereafter, the mixture was subjected to ion exchange treatment and homogenization treatment in the same manner as in Example 1, and diluted with ion-exchanged water to obtain a conductive polymer dispersion liquid with a solid content concentration of 1.8 wt %.

[0080] [Example 4] A 1000ml three-neck flask was charged with 108g of PSS aqueous solution, 54g of ion-exchange water, 1.84g of iron(III) chloride hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.), and 13ml of cation exchange resin B. Nitrogen was bubbled through the flask at a flow rate of 1L / min for 10 minutes, and the mixture was stirred under a nitrogen atmosphere and maintained at 25°C. 4.0g of 3,4-ethylenedioxythiophene was added to the solution, and 233.1g of a 2.5wt% aqueous solution of sodium peroxodisulfate was added over 2 hours using a metering pump. The mixture was then stirred at 25°C for 3 hours to synthesize the conductive polymer PEDOT-PSS. In this reaction, the solids concentration of the thiophene compound and polyanion was 3.7wt%, and the ratio of the ion exchange capacity (X) to the iron ion content (Y) (X / Y) was 4.0. Thereafter, the mixture was subjected to ion exchange treatment and homogenization treatment in the same manner as in Example 1, and diluted with ion-exchanged water to obtain a conductive polymer dispersion liquid with a solid content concentration of 1.8 wt %.

[0081] [Example 5] A conductive polymer dispersion liquid with a solid content concentration of 1.8 wt% was obtained in the same manner as in Example 4, except that 13 ml of cation exchange resin B was changed to 8 ml of cation exchange resin C. In Example 5, the ratio (X / Y) of the ion exchange capacity to the amount of iron ions was 4.6.

[0082] [Example 6] A 1000ml three-neck flask was charged with 108g of PSS aqueous solution, 110g of ion-exchange water, 2.27g of iron(III) nitrate nonahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.), and 10ml of cation exchange resin A. Nitrogen was bubbled through the solution at a flow rate of 1L / min for 10 minutes, and the mixture was stirred under a nitrogen atmosphere and maintained at 25°C. 4.0g of purified 3,4-ethylenedioxythiophene was added to the solution, and 312.0g of a 2.5wt% aqueous solution of ammonium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) was added over 2 hours using a metering pump. The mixture was then stirred at 25°C for 3 hours to synthesize the conductive polymer PEDOT-PSS. In this reaction, the solids concentration of the thiophene compound and polyanion was 2.8wt%, and the ratio (X / Y) of the ion exchange capacity (X) to the iron ion content (Y) was 3.6. Thereafter, the mixture was subjected to ion exchange treatment and homogenization treatment in the same manner as in Example 1, and diluted with ion-exchanged water to obtain a conductive polymer dispersion liquid with a solid content concentration of 1.8 wt %.

[0083] [Comparative Example 1] A conductive polymer dispersion liquid with a solid content concentration of 1.8 wt % was obtained in the same manner as in Example 1, except that the cation exchange resin A was not used.

[0084] Comparative Example 2 A conductive polymer dispersion liquid with a solid content concentration of 1.8 wt % was obtained in the same manner as in Example 1, except that a styrene-divinylbenzene copolymer (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) having no ion exchange groups was used instead of cation exchange resin A.

[0085] Comparative Example 3 Synthesis was carried out in the same manner as in Example 3 except that cation exchange resin A was not used, but the reaction solution gelled, and a conductive polymer dispersion could not be obtained.

[0086] The conductive polymer dispersions obtained in the examples and comparative examples were evaluated by the following methods.

[0087] <Viscosity evaluation> The viscosity of the conductive polymer dispersion liquid having a solid content concentration of 1.8 wt % obtained in each example was measured at 23° C. using a vibration viscometer. The measurement results of the initial viscosity are shown in Table 1. The viscosity values ​​mentioned above are values ​​measured at 23°C using a tuning fork vibration viscometer in accordance with JIS Z8803:2011 (viscosity measurement method using a vibration viscometer).

[0088] <Evaluation of storage stability> The conductive polymer dispersion obtained in each example was stored at 40°C for 10 days, and then the viscosity was measured. The measurement results of the viscosity after storage and the calculated increase rate (%) relative to the initial viscosity are shown in Table 1. Note that a lower increase rate indicates less viscosity change and better storage stability.

[0089] <Evaluation of conductivity> To 50 g of the conductive polymer dispersion obtained in each example, 0.01 g of an acetylene-based surfactant (Dynol 604, manufactured by Nissin Chemical Industry Co., Ltd.), 45 g of methanol, and 5 g of ethylene glycol were added and thoroughly mixed to prepare a coating composition. This coating was applied to a polyethylene terephthalate film (Lumirror T60, manufactured by Toray Industries, Inc.) using a bar coater with a wet film thickness of 8 μm, and then heated and dried at 100°C for 1 minute to obtain a conductive film. The surface resistance of the resulting conductive film was measured using a resistivity meter (Loresta, manufactured by Nitto Seiko Analytech Co., Ltd.) at an applied voltage of 10 V. The results are shown in Table 1.

[0090] [Table 1]

[0091] From the above, it is clear that the manufacturing methods of the examples according to the present invention can provide conductive polymer dispersions that have low initial viscosity and high storage stability. [Explanation of symbols]

[0092] 10 Capacitors 11 Anode 12 Dielectric layer 13 Cathode 14 Solid electrolyte layer

Claims

1. A method for producing a conductive polymer dispersion, comprising: a polymerization step of polymerizing a thiophene-based compound in a reaction solution containing water, an ion adsorbent, an iron compound as a catalyst, and a thiophene-based compound to obtain a polythiophene-based conductive polymer.

2. The method for producing a conductive polymer dispersion according to claim 1 , wherein the reaction solution further contains a polyanion.

3. The method for producing a conductive polymer dispersion according to claim 2 , wherein the base material of the ion adsorbent is a polymer material.

4. 4. The method for producing a conductive polymer dispersion according to claim 3, wherein the ion adsorbent is a cation exchange resin having a sulfonic acid group or a carboxylic acid group as an ion exchange group.

5. 5. The method for producing a conductive polymer dispersion according to claim 4, wherein the value of X / Y is in the range of 1 to 50, where X equivalents / L is the ion exchange capacity of the ion adsorbent and Y moles / L is the amount of iron ions in the iron compound used as a catalyst.

6. 3. The method for producing a conductive polymer dispersion according to claim 2, wherein a total concentration of the thiophene compound and the polyanion blended in the reaction solution is 2.5 to 10.0 mass % with respect to the total mass of the reaction solution.

7. 7. The method for producing a conductive polymer dispersion according to claim 6, wherein the polythiophene-based conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrene sulfonic acid.

8. 8. The method for producing a conductive polymer dispersion according to claim 7, further comprising an ion exchange step of contacting the conductive polymer dispersion obtained in the polymerization step with at least one of a cation exchange resin and an anion exchange resin.

9. 9. A method for producing a conductive laminate, comprising: obtaining the conductive polymer dispersion by the production method according to claim 1; and applying a liquid containing the conductive polymer dispersion to at least a part of a surface of a substrate to form a conductive layer.

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