Method for producing conductive polymer dispersion liquid and method for producing conductive laminate

Abstract

To provide a method for producing a conductive polymer dispersion liquid in which a conductive composite exhibiting excellent conductivity is dispersed, and a method for producing a conductive laminate using the dispersion liquid.SOLUTION: A method for producing a conductive polymer dispersion liquid comprises a step of adding an oxidizing agent that polymerizes a monomer forming a π-conjugated conductive polymer to a reaction liquid containing a polyanion, the monomer forming the π-conjugated conductive polymer, and an aqueous dispersion medium to cause a polymerization reaction and to form a conductive composite containing the π-conjugated conductive polymer and the polyanion, wherein a ratio represented by absorbance A at 600 nm of the reaction liquid immediately before addition of the oxidizing agent divided by a concentration C on a mass basis of the monomer contained in the reaction liquid (absorbance A / concentration C) is 90 or more and 650 or less.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 polyanion, 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 producing a conductive film has been disclosed in which a coating material made from a conductive polymer-containing liquid containing a conductive complex is applied to the surface of the film and dried to form a conductive layer (for example, Patent Document 1). According to this disclosure, the atmospheric exposure resistance of the conductive layer is improved by blending a curing agent having an aziridinyl group into the conductive polymer-containing liquid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-040594 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have carefully investigated the manufacturing process of a conductive composite and found that when a monomer that forms a π-conjugated conductive polymer is chemically oxidized in the presence of a polyanion, a change occurs in the reaction solution after the preparation of the reaction solution containing the polyanion and the monomer and before the addition of an oxidizing agent. This change can be observed as a change in absorbance at 600 nm, and they have found that a conductive composite with excellent conductivity can be obtained by controlling this change within a specific range in relation to the monomer concentration, thereby completing the present invention.

[0005] The present invention provides a method for producing a conductive polymer dispersion in which a conductive composite having excellent conductivity is dispersed, and a method for producing a conductive laminate using the same. [Means for solving the problem]

[0006] [1] A method for producing a conductive polymer dispersion, comprising the step of adding an oxidizing agent that polymerizes a monomer to a reaction solution containing a polyanion, a monomer that forms a π-conjugated conductive polymer, and an aqueous dispersion medium to initiate a polymerization reaction and form a conductive composite containing the π-conjugated conductive polymer and the polyanion, wherein the ratio of absorbance A at 600 nm of the reaction solution immediately before the addition of the oxidizing agent to the concentration C of the monomer on a mass basis contained in the reaction solution, expressed as (absorbance A / concentration C), is 90 or more and 650 or less. [2] The method for producing a conductive polymer dispersion according to [1], wherein a catalyst containing a transition metal is preliminarily blended into the reaction liquid immediately before the addition of the oxidizing agent. [3] The method for producing a conductive polymer dispersion according to [1] or [2], wherein the oxidizing agent is added by dropwise adding an aqueous solution containing the oxidizing agent to the reaction liquid. [4] The method for producing a conductive polymer dispersion according to any one of [1] to [3], wherein the content of the monomer relative to the total mass of the reaction liquid immediately before the addition of the oxidizing agent is 0.1 mass % or more and 2.0 mass % or less. [5] The method for producing a conductive polymer dispersion according to any one of [1] to [4], wherein the content of the polyanion relative to the total mass of the reaction liquid immediately before the addition of the oxidizing agent is 0.3 mass % or more and 6.0 mass % or less. [6] The method for producing a conductive polymer dispersion according to any one of [1] to [5], further comprising a preliminary step of preparing an aqueous solution containing the polyanion to be added to the reaction solution, wherein in the preliminary step, the aqueous solution is brought into contact with an ion exchange resin to reduce the ion concentration in the aqueous solution. [7] The method for producing a conductive polymer dispersion according to [6], wherein the aqueous solution containing the polyanion, which has been subjected to the treatment and has a sulfate ion concentration of 1000 ppm or less, is used as at least a part of the reaction solution immediately before the addition of the oxidizing agent. [8] The method for producing a conductive polymer dispersion according to any one of [1] to [7], wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene). [9] The method for producing a conductive polymer dispersion according to any one of [1] to [8], wherein the polyanion is polystyrene sulfonic acid.

[10] A method for producing a conductive laminate, comprising: obtaining a conductive polymer dispersion by the production method according to any one of [1] to [9]; and applying the conductive polymer dispersion to at least a part of the surface of a substrate and drying the applied conductive polymer dispersion to form a conductive layer. [Effects of the Invention]

[0007] According to the present invention, there is provided a method for producing a conductive polymer dispersion in which a conductive composite having excellent conductivity is dispersed. The conductive polymer dispersion produced in this manner is suitable for producing a conductive laminate or 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] FIG. 1 is a cross-sectional view illustrating one embodiment of a capacitor. 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 the step of adding an oxidizing agent that polymerizes a monomer to a reaction liquid containing a polyanion, a monomer that forms a π-conjugated conductive polymer, and an aqueous dispersion medium, to cause a polymerization reaction, thereby forming a conductive composite containing the π-conjugated conductive polymer and the polyanion.

[0012] In this embodiment, the ratio of the absorbance A at 600 nm of the reaction solution immediately before the addition of the oxidizing agent to the concentration C of the monomer contained in the reaction solution based on mass (absorbance A / concentration C) (hereinafter also referred to as the "absorbance / concentration ratio") is preferably 90 to 650, more preferably 95 to 600, and even more preferably 100 to 550. Examples of preferred ranges include 100 to 500, 110 to 450, 120 to 400, 130 to 350, 140 to 300, and 140 to 250. When the [absorbance / concentration] ratio is within the above preferred range, a conductive polymer dispersion liquid in which a conductive complex with excellent conductivity is dispersed can be obtained.

[0013] The range of the [absorbance / concentration] ratio can be controlled by adjusting the concentration of the monomer to be added to the reaction solution and by adjusting the length of time until the addition of the oxidizing agent to the reaction solution containing materials other than the oxidizing agent is started. The longer the time, the greater the absorbance A tends to be.

[0014] As a specific example of this embodiment, the following steps A and B can be mentioned.

[0015] <Process A (preliminary process)> In step A, an aqueous polyanion solution is prepared. Step A is a step of adding a polymerization initiator to a first reaction liquid containing a polymerizable anionic monomer and water to obtain a second reaction liquid (aqueous polyanion solution) containing a polyanion formed by polymerization of the polymerizable anionic monomer.

[0016] Polymerizable anionic monomers are organic compounds that form polyanions upon polymerization and contain at least one anionic group per molecule. The anionic group is a functional group that can be ionized in water and may form a salt with a cation such as sodium or potassium. The polymerizable anionic monomer used in this step is preferably one or more selected from known monomers capable of forming polyanions, examples of which will be given later. Among them, styrene sulfonic acid or a salt thereof is most preferred, as it can form polystyrene sulfonic acid, which is particularly excellent as a dopant for π-conjugated conductive polymers. The amount of the polymerizable anionic monomer to be mixed relative to the total mass of the first reaction liquid is, for example, preferably 1.0 to 20.0 mass %, more preferably 5.0 to 15.0 mass %, and even more preferably 8.0 to 13.0 mass %. When the amount is at least the lower limit of the above range, the yield per reaction increases, and production efficiency improves. When the content is equal to or less than the upper limit of the above range, the amount of low-molecular-weight polyanions formed can be reduced.

[0017] Examples of the polymerization initiator include persulfates such as ammonium persulfate, sodium persulfate, potassium persulfate, etc. The amount of the polymerization initiator to be added relative to the total mass of the first reaction liquid is, for example, 0.1 to 1.0 mass %.

[0018] The completion of the polymerization reaction of the polyanion in step A is determined when all of the polymerization initiator added to the first reaction solution has been consumed. For example, when the reaction is carried out at 70 to 95°C with stirring, the reaction may be completed in about 4 to 12 hours.

[0019] The second reaction solution (polyanion aqueous solution) contains the formed polyanion. It is preferable to bring the second reaction solution into contact with an ion exchange resin to reduce the ion concentration in the second reaction solution. By performing this treatment, the chemical polymerization reaction in the next step B can be strictly controlled.

[0020] When the anion group of the polyanion forms a salt with a counter cation, it is preferable to remove the cation by contacting the polyanion with a cation exchange resin. The second reaction solution preferably contains a high molecular weight polyanion polymerized to have an Mw of 10,000 or more, preferably 50,000 or more and 1,000,000 or less.

[0021] The second reaction liquid may contain sulfate ions as a by-product of hydrolysis of the polymerization initiator. From the viewpoint of reducing the amount of sulfate ions carried over into the reaction liquid in the subsequent step B, it is preferable to remove the sulfate ions from the second reaction liquid to obtain an aqueous polyanion solution and use this as at least a part of the reaction liquid in step B.

[0022] Examples of methods for purifying the polyanion by removing sulfate ions from the second reaction solution include ultrafiltration and anion exchange resin adsorption. In ultrafiltration, low molecular weight sulfate ions pass through the ultrafiltration membrane, while high molecular weight polyanions do not, so the two can be separated. In the anion exchange resin adsorption method, if an anion exchange resin is used that preferentially binds low molecular weight sulfate ions, low molecular weight substances will be adsorbed while high molecular weight polyanions will hardly be adsorbed, so the two can be separated. An example of such an anion exchange resin is Duolite A368MS manufactured by Sumika Chemtex Co., Ltd.

[0023] The sulfate ion concentration in the aqueous polyanion solution to be subjected to the next step B is preferably 1000 ppm or less, more preferably 600 ppm or less, and even more preferably 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, or 50 ppm or less. The lower the sulfate ion concentration in the aqueous polyanion solution, the more strictly the chemical polymerization reaction in the subsequent step B can be controlled.

[0024] The sulfate ion concentration in the aqueous polyanion solution or reaction solution can be measured by a known method using ion chromatography. In this case, it is preferable to prepare a calibration curve in advance using standard samples with known sulfate ion concentrations. For example, measurements can be performed using an Integrion RFIC (Thermo Fisher Scientific) measuring device, a Dionex IonPac AS19 column, and an electrical conductivity detector. The column temperature is 30°C, and an anion mixed standard solution IV is used as the standard substance. 0.03 g of the sample is diluted with 50 g of ultrapure water to form the measurement sample, and its electrical conductivity peak is measured. A method for calculating the quantitative value is to calculate the concentration of the measurement sample using a calibration curve of concentration versus peak area, convert this to the amount (concentration) in the original sample, and use it as the measurement value.

[0025] The aqueous polyanion solution used in the next step B may be the one obtained in step A, or may be an aqueous solution prepared by dissolving a commercially available polyanion in water.

[0026] <Process B> In step B, an oxidizing agent that polymerizes the monomer is added to a reaction solution containing a polyanion, a monomer that forms a π-conjugated conductive polymer, and an aqueous dispersion medium to cause a polymerization reaction, thereby forming a conductive composite that contains the π-conjugated conductive polymer and the polyanion.

[0027] It is preferable that a catalyst containing a transition metal is preliminarily blended into the reaction liquid immediately before the addition of the oxidizing agent, since preliminarily blending the catalyst can promote polymerization of the monomers simultaneously with the addition of the oxidizing agent, making it easier to obtain a conductive polymer dispersion in which a conductive composite with excellent conductivity is dispersed.

[0028] The catalyst is preferably one that decomposes the oxidizing agent to generate radicals. From the viewpoint of enhancing this catalytic action, the catalyst preferably contains an iron compound or a copper compound, and more preferably contains an iron compound. Specific examples include ferric chloride, ferric sulfate, ferric nitrate, ferric citrate, ammonium ferric citrate, and cupric chloride. The type of catalyst to be blended in the reaction liquid may be one type or two or more types.

[0029] The content of the catalyst relative to the total mass of the reaction liquid immediately before the addition of the oxidizing agent is, for example, preferably 0.01 mass% or more and 0.50 mass% or less, more preferably 0.05 mass% or more and 0.35 mass% or less, and even more preferably 0.10 mass% or more and 0.20 mass% or less. When the content is within the above preferred range, a conductive polymer dispersion liquid in which a conductive composite having excellent conductivity is dispersed can be more easily obtained.

[0030] The oxidizing agent may be any agent that promotes or initiates polymerization by chemical oxidation of the monomer, and is preferably a radical polymerization initiator that is generally used in the production of polymers. The oxidizing agent is preferably one that decomposes under the action of the catalyst to generate radicals, and preferably one that has a peracid structure represented by "-SO2-OO-" in the molecule. Specifically, peroxodisulfuric acid or a salt thereof, or peroxomonosulfuric acid or a salt thereof is preferred. Here, the salt has a counter cation such as sodium, potassium, or ammonium. Among these, peroxodisulfates (persulfates) are more preferred. The type of the oxidizing agent added to the reaction liquid may be one type, or two or more types.

[0031] The oxidizing agent is preferably added last to the reaction liquid in which all other materials have been mixed. The oxidizing agent is preferably dissolved in a small amount of water and added to the reaction liquid. The oxidizing agent may be added all at once or may be added stepwise. From the viewpoint of stably progressing the polymerization reaction, it is preferable to slowly add a certain amount dropwise over a predetermined period of time (for example, 2 to 4 hours). The dropping method makes it easier to obtain a conductive polymer dispersion in which a conductive complex with excellent conductivity is dispersed.

[0032] The amount of the oxidizing agent added relative to the total mass of the reaction liquid immediately before the addition of the oxidizing agent is preferably 0.10 mass% or more and 1.50 mass% or less, more preferably 0.30 mass% or more and 1.30 mass% or less, and even more preferably 0.50 mass% or more and 1.20 mass% or less. When the content is within the above preferred range, a conductive polymer dispersion liquid in which a conductive composite having excellent conductivity is dispersed can be more easily obtained.

[0033] The content of the monomer relative to the total mass of the reaction liquid immediately before the addition of the oxidizing agent is preferably 0.1 mass% or more and 2.0 mass% or less (i.e., 0.001 to 0.020), more preferably 0.3 mass% or more and 1.5 mass% or less (i.e., 0.003 to 0.015), and even more preferably 0.5 mass% or more and 1.0 mass% or less (i.e., 0.005 to 0.010). When the content is within the above preferred range, a conductive polymer dispersion liquid in which a conductive composite having excellent conductivity is dispersed can be more easily obtained.

[0034] The content of the polyanion relative to the total mass of the reaction solution immediately before the addition of the oxidizing agent is preferably 0.3% by mass or more and 6.0% by mass or less, more preferably 1.0% by mass or more and 3.0% by mass or less, and even more preferably 1.5% by mass or more and 2.0% by mass or less. When the content is within the above preferred range, a conductive polymer dispersion liquid in which a conductive composite having excellent conductivity is dispersed can be more easily obtained.

[0035] The sulfate ion concentration in the reaction solution immediately before the addition of the oxidizing agent is preferably 1000 ppm or less, more preferably 900 ppm or less, and the lower the concentration, the more preferable it is, such as 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, or 50 ppm or less, by mass relative to the total mass of the reaction solution. The lower the sulfate ion concentration in the reaction solution, the more stable the doping of the polyanion into the π-conjugated conductive polymer becomes, and the easier it becomes to produce a conductive composite with excellent conductivity.

[0036] The monomer forming the π-conjugated conductive polymer is preferably one or more selected from known monomers capable of forming π-conjugated conductive polymers, which will be exemplified later. Among them, 3,4-ethylenedioxythiophene, which can form PEDOT having excellent conductivity and heat resistance, is most preferred.

[0037] The reaction temperature in the reaction solution can be, for example, 20 to 30°C. At the reaction temperature, the polymerization reaction is usually completed in about 4 to 12 hours. The completion of the polymerization reaction can be determined by measuring the amount of unreacted monomer in the reaction solution using gas chromatography or the like.

[0038] It is preferable to remove residues of the catalyst and oxidizing agent added to the reaction liquid from the conductive polymer dispersion after the polymerization reaction. Examples of methods for removing unnecessary components include a method of bringing the conductive polymer dispersion into contact with an ion exchange resin to adsorb unnecessary components onto the ion exchange resin, and a method of ultrafiltrating the conductive polymer dispersion to replace the dispersion medium and remove the unnecessary components. Of 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.

[0039] The conductive polymer dispersion thus obtained may be subjected to a dispersion treatment by a conventional method such as a high-pressure homogenizer, or any other additives may be added thereto.

[0040] <Conductive composite> The conductive complex contains a π-conjugated conductive polymer and a polyanion. In water, the π-conjugated conductive polymer is positively charged and the polyanion is negatively charged, so it is thought that the two form the complex mainly through electrostatic interaction. Typically, the conductive complex is formed by polymerizing a monomer of the π-conjugated conductive polymer in water containing the polyanion, and then naturally doping the polyanion into the formed π-conjugated conductive polymer.

[0041] In the polyanion constituting the conductive composite, only a portion of the anionic groups is doped into the π-conjugated conductive polymer, and there are excess anionic groups that are not involved in the doping. Because the excess anionic groups are hydrophilic groups, the conductive composite has water dispersibility. When the number of all anionic groups in the polyanion is taken as 100 mol %, the excess anionic groups are preferably 30 mol % or more and 90 mol % or less, and more preferably 45 mol % or more and 75 mol % or less.

[0042] (π-conjugated conductive polymer) The π-conjugated conductive polymer may be an organic polymer whose main chain is composed of a π-conjugated system, and examples thereof include polypyrrole-based conductive polymers, polythiophene-based conductive polymers, polyacetylene-based conductive polymers, polyphenylene-based conductive polymers, polyphenylene vinylene-based conductive polymers, polyaniline-based conductive polymers, polyacene-based conductive polymers, polythiophene vinylene-based conductive polymers, and copolymers thereof. From the viewpoint of stability in air, polypyrrole-based conductive polymers, polythiophenes, and polyaniline-based conductive polymers are preferred, and from the viewpoint of transparency, polythiophene-based conductive polymers are more preferred.

[0043] 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). Examples of polypyrrole-based conductive polymers include polypyrrole, poly(N-methylpyrrole), poly(3-methylpyrrole), poly(3-ethylpyrrole), poly(3-n-propylpyrrole), poly(3-butylpyrrole), poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3-dodecylpyrrole), poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole), poly(3-carboxypyrrole), poly(3-methyl-4-carboxypyrrole), poly(3-methyl-4-carboxyethylpyrrole), poly(3-methyl-4-carboxybutylpyrrole), poly(3-hydroxypyrrole), poly(3-methoxypyrrole), poly(3-ethoxypyrrole), poly(3-butoxypyrrole), poly(3-hexyloxypyrrole), and poly(3-methyl-4-hexyloxypyrrole). Examples of polyaniline-based conductive polymers include polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), and poly(3-anilinesulfonic acid). Among these π-conjugated conductive polymers, poly(3,4-ethylenedioxythiophene) is particularly preferred because of its excellent conductivity, transparency, and heat resistance. The conductive composite may contain one type of π-conjugated conductive polymer, or two or more types of polymers.

[0044] (polyanion) A polyanion is a polymer having two or more monomer units with an anionic group in the molecule. The anionic group of this polyanion functions as a dopant for a π-conjugated conductive polymer, improving the conductivity of the π-conjugated conductive polymer. The anionic group of the polyanion is preferably a sulfo group or a carboxy group. Specific examples of such polyanions 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 (for example, 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 types of monomers. Among these polyanions, polymers having sulfo groups are preferred, and polystyrene sulfonic acid is more preferred, since they can further increase the conductivity.

[0045] The content of the polyanion in the conductive composite is, for example, 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, relative to 100 parts by mass of the π-conjugated conductive polymer. If the content of the polyanion is equal to or greater than the lower limit, the doping effect on the π-conjugated 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 content of the π-conjugated conductive polymer is sufficient, thereby ensuring sufficient conductivity.

[0046] <Conductive polymer dispersion> The conductive polymer dispersion produced in the first embodiment is a conductive polymer dispersion containing a conductive complex and water.

[0047] The content of the polyanion contained in the conductive polymer dispersion is, for example, 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, relative to 100 parts by mass of the π-conjugated conductive polymer. If the content of the polyanion is equal to or greater than the lower limit, the doping effect on the π-conjugated 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, a sufficient amount of the π-conjugated conductive polymer can be contained, thereby ensuring sufficient conductivity.

[0048] (dispersion medium) The dispersion medium contained in the conductive polymer dispersion is preferably an aqueous dispersion medium containing water because the conductive composite is hydrophilic. Alternatively, the dispersion medium may contain a dispersion medium other than water. The dispersion medium other than water is not particularly limited as long as it does not significantly impair the dispersibility of the conductive composite. Since the conductive composite has excess anionic groups derived from the polyanion and has high dispersibility in water, the dispersion medium other than water is preferably a water-soluble organic solvent. Here, the 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, and examples thereof include alcohol-based solvents, ketone-based solvents, and ester-based solvents. The water-soluble organic solvent contained as the dispersion medium may be one type or two or more types.

[0049] 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. As the water-soluble organic solvent, an alcohol-based solvent or a ketone-based solvent is preferred, and an alcohol-based solvent is more preferred, since this improves the wettability of the conductive polymer dispersion liquid with respect to the substrate.

[0050] The water content relative to the total mass of the dispersion medium excluding the solid content (non-volatile components) of the conductive polymer dispersion is preferably 50 mass% or more, more preferably 70 mass% or more, even more preferably 90 mass% or more, and may be 100 mass%. When water is contained in an amount equal to or greater than the above lower limit, the dispersibility of the conductive composite contained in the conductive polymer dispersion is increased, and storage stability is improved.

[0051] The content of the water-soluble organic solvent relative to the total mass of the aqueous dispersion medium is preferably 70 mass % or less, more preferably 60 mass % or less. Within this preferred range, the wettability of the conductive composite to the substrate can be improved while suppressing deterioration over time in the dispersion stability of the conductive composite in the conductive polymer dispersion.

[0052] The content of the conductive complex relative to the total mass of the conductive polymer dispersion (i.e., the total content of the π-conjugated conductive polymer and the polyanion) is preferably 0.01% by mass or more and 5.0% by mass or less, more preferably 1.0% by mass or more and 4.0% by mass or less, and even more preferably 1.5% by mass or more and 3.0% by mass or less. 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 improved.

[0053] (Optional additives) The conductive polymer dispersion of this embodiment may contain any additive other than the conductive composite within a range that does not impair the spirit of the present invention. The content ratio of the additive is determined appropriately depending on the type of additive, but can be, for example, 1 to 1000 parts by mass per 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion.

[0054] Examples of optional additives include surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers. The surfactant may be a nonionic, anionic, or cationic surfactant, with nonionic surfactants being preferred from the standpoint of storage stability. Polymer surfactants such as polyvinyl alcohol and 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. Examples of the coupling agent include silane coupling agents having a vinyl group, an amino group, an epoxy group, or the like. Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and sugars. 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.

[0055] <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 partial surface of a substrate and drying the applied conductive polymer dispersion to form a conductive layer.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] <Conductive laminate> The conductive laminate produced 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 the conductive layer contains a cured product of the conductive polymer dispersion.

[0060] [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.

[0061] 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.

[0062] [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.

[0063] (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.

[0064] 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.

[0065] 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.

[0066] (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.

[0067] 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.

[0068] <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.

[0069] 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.

[0070] [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.

[0071] [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.

[0072] [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.

[0073] 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.

[0074] 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.

[0075] <Capacitor> The capacitor manufactured in the third embodiment 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.

[0076] An example of an embodiment of the capacitor will be described with reference to Fig. 1. 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 dielectric layer 12, and a cathode 13 provided on the outermost side. Cathode 13 is provided on the opposite side of anode 11, with dielectric layer 12 and solid electrolyte layer 14 sandwiched therebetween.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] [Electrolyte] The capacitor may have an electrolyte solution impregnating the solid electrolyte layer. Examples of solvents that constitute 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;

[0082] The capacitor 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]

[0083] <Production of Polyanions> [Production Example 1: PSS, Mw 100,000, sulfate ion content 0 ppm] 110 g of sodium styrene sulfonate was dissolved in 820 ml of ion-exchanged water, and while stirring at 80 °C, 8.54 g of sodium peroxodisulfate, previously dissolved in 55 ml of water, was added dropwise over 2 hours, and the solution was stirred for 4 hours. A cation exchange resin was added to the resulting sodium polystyrene sulfonate-containing solution to remove sodium ions. The solids content of the resulting polystyrene sulfonate (PSS) aqueous solution was 10% by mass. The sulfuric acid was then removed using an anion exchange resin, and the solution was filtered to produce a solution. The weight-average molecular weight of the PSS aqueous solution was measured using a HPLC (high-performance liquid chromatography) system equipped with a GPC (gel permeation chromatography) column and a refractive index detector, using pullulan manufactured by Showa Denko K.K. as a standard substance. Analysis of the GPC chart, in which the vertical axis represents the refractive index signal intensity and the horizontal axis represents retention time, revealed that the polystyrene sulfonic acid peak showed a weight-average molecular weight (Mw) of 100,000. Furthermore, measurement of the sulfate ion content by ion chromatography revealed that the sulfate ion content was 0 ppm.

[0084] Example 1 6.86 g of 3,4-ethylenedioxythiophene (EDOT), 162 g of the aqueous polystyrene sulfonic acid solution obtained in Preparation Example 1, and 739.92 g of ion-exchanged water were mixed at 26°C. While stirring the resulting mixture, maintained at 26°C, 23.02 g of an oxidation catalyst solution (1.38 g of ferric sulfate dissolved in ion-exchanged water) was added and stirring continued for 5 minutes. At this point, the absorbance at 600 nm measured immediately before adding the oxidizer was 0.803. The EDOT concentration in this mixture was approximately 0.00736 (≒6.86 g / 931.8 g), and the [absorbance / concentration] ratio, rounded to one decimal place, was 109. Immediately after the 5-minute stirring, 68.20 g of an oxidizing agent solution (7.50 g of sodium peroxodisulfate dissolved in ion-exchanged water) was added dropwise to initiate the polymerization of EDOT. The solution was added dropwise at a constant rate over 2 hours, and the mixture was stirred for an additional 4 hours. A cation exchange resin (Duolite C255LFH, manufactured by Sumika Chemtex Co., Ltd.) and an anion exchange resin (Duolite A368S, manufactured by Sumika Chemtex Co., Ltd.) were added to the resulting reaction solution to remove the oxidant and iron. This resulted in a blue PEDOT-PSS aqueous dispersion with a PEDOT:PSS ratio of 1:2.4 (by mass). The solids content (non-volatile components) of the resulting dispersion was 1.8% by mass.

[0085] <Example 2> In the manufacturing method of Example 1, the oxidation catalyst solution was added and stirring was continued for 30 minutes. At this point, the absorbance at 600 nm measured immediately before adding the oxidizing agent was 1.245. The [absorbance / concentration] ratio was 169, rounded to one decimal place. Other than that, the same procedure as in Example 1 was carried out to obtain a PEDOT-PSS aqueous dispersion.

[0086] Example 3 In the manufacturing method of Example 1, the oxidation catalyst solution was added and stirring was continued for 60 minutes. At this point, the absorbance at 600 nm measured immediately before adding the oxidizing agent was 1.574. The [absorbance / concentration] ratio was 214, rounded to one decimal place. Other than that, the same procedure as in Example 1 was carried out to obtain a PEDOT-PSS aqueous dispersion.

[0087] Example 4 In the manufacturing method of Example 1, the oxidation catalyst solution was added and stirring was continued for 120 minutes. At this point, the absorbance at 600 nm measured immediately before adding the oxidizing agent was 2.086. The [absorbance / concentration] ratio was 283, rounded to one decimal place. Other than that, the same procedure as in Example 1 was carried out to obtain a PEDOT-PSS aqueous dispersion.

[0088] <Example 5> In the manufacturing method of Example 1, the oxidation catalyst solution was added and stirring was continued for 240 minutes. At this point, the absorbance at 600 nm measured immediately before adding the oxidizing agent was 2.791. The [absorbance / concentration] ratio was 379, rounded to the nearest tenth. Other than that, the same procedure as in Example 1 was carried out to obtain a PEDOT-PSS aqueous dispersion.

[0089] Example 6 In the manufacturing method of Example 1, the oxidation catalyst solution was added and stirring was continued for 360 minutes. At this point, the absorbance at 600 nm measured immediately before adding the oxidizing agent was 3.511. The [absorbance / concentration] ratio was 477, rounded to one decimal place. Other than that, the same procedure as in Example 1 was carried out to obtain a PEDOT-PSS aqueous dispersion.

[0090] <Comparative Example 1> In the production method of Example 1, the absorbance at 600 nm measured immediately after adding the oxidation catalyst solution and immediately before adding the oxidizing agent was 0.599. The [absorbance / concentration] ratio was 81, rounded to one decimal place. Immediately after the addition of the oxidation catalyst solution, the oxidizing agent was added dropwise with stirring, and a PEDOT-PSS aqueous dispersion was obtained in the same manner as in Example 1.

[0091] <Comparative Example 2> In the manufacturing method of Example 1, the oxidation catalyst solution was added and stirring was continued for 1,440 minutes (24 hours). At this point, the absorbance at 600 nm measured immediately before adding the oxidizing agent was 5.178. The [absorbance / concentration] ratio was 703, rounded to the nearest tenth. Other than that, the same procedure as in Example 1 was carried out to obtain a PEDOT-PSS aqueous dispersion.

[0092] [Method for measuring absorbance] The absorbance in each example was measured in accordance with JIS K0115:2020 under the following conditions. Measurement equipment: UV-visible spectrophotometer (Shimadzu Corporation, UV-1900i) Analysis: LabSolution UV-Vis Color Measurement Software Cell: Polystyrene cell ·Optical path length: 10mm ·Measurement wavelength range: 380-780nm ·Viewing angle: 10° ·Light source: D65 standard light source ·Measurement temperature: 25℃

[0093] [Surface resistance measurement] 5 g of the PEDOT-PSS aqueous dispersion obtained in each example was mixed with 5 g of methanol and 0.25 g of dimethyl sulfoxide, and the resulting coating was applied to a polyethylene terephthalate film using a No. 8 bar coater and dried at 100°C for 1 minute to obtain a conductive film. The surface resistance of the conductive film was measured using a resistivity meter (Loresta manufactured by Nitto Seiko Analytech Co., Ltd.) at an applied voltage of 10 V (unit: Ω / □). The results are shown in Table 1.

[0094] [Table 1]

[0095] It is clear that Examples 1 to 6 according to the present invention can form conductive layers that exhibit better conductivity than Comparative Examples 1 and 2.

Claims

1. A method for producing a conductive polymer dispersion, comprising: adding an oxidizing agent that polymerizes a monomer to a reaction liquid containing a polyanion, a monomer that forms a π-conjugated conductive polymer, and an aqueous dispersion medium to cause a polymerization reaction, thereby forming a conductive composite containing the π-conjugated conductive polymer and the polyanion, a ratio, expressed as (absorbance A / concentration C), of an absorbance A at 600 nm of the reaction solution immediately before the addition of the oxidizing agent to a concentration C based on mass of the monomer contained in the reaction solution is 90 or more and 650 or less.

2. 2. The method for producing a conductive polymer dispersion according to claim 1, wherein a catalyst containing a transition metal is previously mixed into the reaction liquid immediately before the addition of the oxidizing agent.

3. The method for producing a conductive polymer dispersion according to claim 1 , wherein the method for adding the oxidizing agent is a method for adding dropwise an aqueous solution containing the oxidizing agent to the reaction liquid.

4. 2. The method for producing a conductive polymer dispersion according to claim 1, wherein a content of the monomer relative to a total mass of the reaction liquid immediately before the addition of the oxidizing agent is 0.1 mass % or more and 2.0 mass % or less.

5. 2. The method for producing a conductive polymer dispersion according to claim 1, wherein a content of the polyanion relative to a total mass of the reaction liquid immediately before the addition of the oxidizing agent is 0.3 mass % or more and 6.0 mass % or less.

6. a preliminary step of preparing an aqueous solution containing the polyanion to be added to the reaction solution; 2. The method for producing a conductive polymer dispersion according to claim 1, wherein the preliminary step comprises contacting the aqueous solution containing the polyanion with an ion exchange resin to reduce the ion concentration in the aqueous solution.

7. 7. The method for producing a conductive polymer dispersion according to claim 6, wherein the aqueous solution containing the polyanion, which has been subjected to the treatment and has a sulfate ion concentration of 1000 ppm or less, is used as at least a part of the reaction solution immediately before the addition of the oxidizing agent.

8. 2. The method for producing a conductive polymer dispersion according to claim 1, wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene).

9. The method for producing a conductive polymer dispersion according to claim 1 , wherein the polyanion is polystyrene sulfonic acid.

10. 10. A method for producing a conductive laminate, comprising: obtaining a conductive polymer dispersion by the production method according to any one of claims 1 to 9; and applying the conductive polymer dispersion to at least a part of a surface of a substrate and drying the applied conductive polymer dispersion to form a conductive layer.

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