Method for producing conductive polymer dispersion, method for manufacturing conductive laminate, and method for manufacturing capacitor

Abstract

To provide a method for producing a conductive polymer dispersion having a reduced increase in viscosity during storage and good conductivity after drying and curing and to provide a method for manufacturing a conductive laminate and a capacitor using the same.SOLUTION: There is provided a method for producing a conductive polymer dispersion, which comprises a step in which a polymerization reaction is started by adding a polymerization initiator for polymerizing a monomer for forming a π-conjugated conductive polymer into a reaction liquid containing a polyanion, the monomer and a water-based dispersion medium to form a conductive composite containing the π-conjugated conductive polymer and the polyanion, wherein the sulfate ion concentration contained in the reaction liquid immediately before adding the polymerization initiator is less than 1180 ppm.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, a method for producing a conductive laminate, and a method for producing a capacitor.

Background Art

[0002] A π-conjugated conductive polymer whose main chain is composed of a π-conjugated system forms a conductive composite by doping with a polyanion having an anion group, and exhibits dispersibility in water. A method for manufacturing a capacitor is disclosed in which a paint made of a conductive polymer dispersion containing a conductive composite is applied to a dielectric layer provided on the surface of an anode made of valve metal, dried to form a solid electrolyte layer, and a cathode is disposed opposite thereto (for example, Patent Document 1). According to this disclosure, the performance of the capacitor is improved by including a specific unsaturated aliphatic alcohol compound in the paint.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The conductive polymer dispersion used in the production of a capacitor is required to have a low viscosity in order to penetrate into the porous structure of the dielectric layer. Furthermore, the solid electrolyte layer formed by drying the infiltrated conductive polymer dispersion is also required to have high conductivity. However, there has been a problem that the viscosity of conventional conductive polymer dispersions 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 formed by applying a conductive polymer dispersion to a substrate to form a conductive layer.

[0005] The present invention provides a method for producing a conductive polymer dispersion having a reduced increase in viscosity during storage and good conductivity after drying and curing, a method for producing a conductive laminate using the same, and a method for producing a capacitor.

Means for Solving the Problems

[0006] [1] A method for producing a conductive polymer dispersion, comprising a step of adding a polymerization initiator for polymerizing the monomer to a reaction solution containing a polyanion, a monomer for forming a π-conjugated conductive polymer, and an aqueous dispersion medium to start a polymerization reaction, and forming a conductive composite containing the π-conjugated conductive polymer and the polyanion, wherein the sulfate ion concentration contained in the reaction solution immediately before adding the polymerization initiator is less than 1180 ppm. [2] The method for producing a conductive polymer dispersion according to [1], wherein a polyanion for blending in the reaction solution and an aqueous polyanion solution containing sulfate ions are prepared in advance, and after removing the sulfate ions contained in the aqueous polyanion solution, the solution is blended into the reaction solution. [3] The method for producing a conductive polymer dispersion according to [2], including a preliminary step of subjecting a monomer for forming the polyanion to radical polymerization in the presence of water to obtain the aqueous polyanion solution, wherein in the preliminary step, a persulfate is used to initiate the radical polymerization, and sulfate ions are generated as a by-product. [4] The method for producing a conductive polymer dispersion according to [3], wherein the sulfate ion concentration contained in the aqueous polyanion solution obtained in the preliminary step is 600 ppm or more before the treatment for removing sulfate ions and less than 600 ppm after the treatment for removing sulfate ions. [5] The method for producing a conductive polymer dispersion according to any one of [2] to [4], wherein the sulfate ions contained in the aqueous polyanion solution are removed using an ion exchange resin. [6] The method for producing a conductive polymer dispersion according to any one of [1] to [5], wherein an anionic surfactant different from the polyanion is further blended into the conductive polymer dispersion containing the conductive composite and the aqueous dispersion medium. [7] The method for producing a conductive polymer dispersion according to any one of [1] to [6], wherein the π-conjugated system conductive polymer is poly(3,4-ethylenedioxythiophene). [8] The method for producing a conductive polymer dispersion according to any one of [1] to [7], wherein the polyanion is polystyrene sulfonic acid. [9] A method for producing a conductive laminate, comprising: a step of obtaining a conductive polymer dispersion by the production method according to any one of [1] to [8]; and a step of applying the conductive polymer dispersion to at least a part of the surface of a substrate and drying to form a conductive layer.

[10] A method for producing a capacitor, comprising: a step of obtaining a conductive polymer dispersion by the production method according to any one of [1] to [8]; and a step of applying the conductive polymer dispersion to the surface of a dielectric layer formed on the surface of an anode made of a valve metal porous body and drying to form a solid electrolyte layer. [Advantages of the Invention]

[0007] According to the present invention, it is possible to provide a method for producing a conductive polymer dispersion in which the increase in viscosity during storage is reduced and the conductivity after drying and curing is also good. The conductive polymer dispersion produced thereby is suitable for the production of conductive laminates and capacitors.

[0008] The present invention is considered to contribute to SDGs Goal 12, "Responsibility for Production and Consumption".

[0009] In this specification and the claims, the lower and upper limit values of the numerical range indicated by "~" are included in the numerical range. [Brief Description of the Drawings]

[0010]

Figure 1

[0011] [[Manufacturing Method of Conductive Polymer Dispersion]] The first aspect of the present invention is a method for producing a conductive polymer dispersion, which includes a step of adding a polymerization initiator for polymerizing a monomer to a reaction solution containing a polyanion, a monomer for forming a π-conjugated conductive polymer, and an aqueous dispersion medium to initiate a polymerization reaction, thereby forming a conductive composite containing the π-conjugated conductive polymer and the polyanion.

[0012] In this aspect, the sulfate ion concentration in the reaction solution immediately before adding the polymerization initiator is preferably less than 1180 ppm, more preferably 900 ppm or less, and even more preferably as small 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, 50 ppm or less, based on the mass of the total mass of the reaction solution. The lower the sulfate ion concentration in the reaction solution, the higher the storage stability of the produced conductive polymer dispersion.

[0013] In this aspect, a persulfate may be used as the polymerization initiator. The persulfate added to the reaction solution hydrolyzes to function as a radical polymerization initiator and generates sulfate ions as a by-product. Since it is difficult to define the temporal increase in the sulfate ion concentration due to the addition of the polymerization initiator, in this aspect, the sulfate ion concentration in the reaction solution immediately before adding the polymerization initiator is defined.

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

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

[0016] The polymerizable anionic monomer is an organic compound that forms a polyanion upon polymerization and has at least one anionic group in one molecule. The anionic group is a functional group that can ionize 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 that can form a polyanion, which will be exemplified later. Among them, styrenesulfonic acid or a salt thereof, which can form polystyrenesulfonic acid, is most preferable as it is particularly excellent as a dopant for π-conjugated conductive polymers. The compounding amount of the polymerizable anionic monomer with respect to the total mass of the first reaction solution is preferably, for example, 1.0 to 20.0% by mass, more preferably 5.0 to 15.0% by mass, and even more preferably 8.0 to 13.0% by mass. When it is above the lower limit value of the above range, the yield per reaction increases and the production efficiency is enhanced. When it is below the upper limit value of the above range, the amount of low molecular weight polyanion formed can be reduced.

[0017] Examples of the polymerization initiator include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate. The compounding amount of the polymerization initiator with respect to the total mass of the first reaction solution is, for example, 0.1 to 1.0% by mass.

[0018] The completion of the polymerization reaction of the polyanion in Step A is judged by the fact that all the polymerization initiator added to the first reaction solution has been consumed. For example, when reacting with stirring at 70 to 95 °C, the reaction can be completed in about 4 to 12 hours.

[0019] The second reaction solution contains the formed polyanion. When the anionic group of the polyanion forms a salt with a counter cation, it is preferable to contact it with a cation exchange resin to remove the cation. The second reaction solution preferably contains a high molecular weight polyanion polymerized to a Mw of 10,000 or more, preferably 50,000 or more.

[0020] The second reaction solution may contain sulfate ions as by-products due to the hydrolysis of the polymerization initiator. From the perspective of reducing the introduction of sulfate ions into the reaction solution in the subsequent step B, it is preferable to obtain an aqueous polyanion solution from which the sulfate ions contained in the second reaction solution have been removed and use this as the reaction solution for step B.

[0021] Examples of methods for removing sulfate ions from the second reaction solution to purify the polyanion include ultrafiltration and anion exchange resin adsorption. In the ultrafiltration method, low-molecular-weight sulfate ions permeate 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 to which low-molecular-weight sulfate ions are preferentially easily bound is used, the low-molecular-weight ones are adsorbed while the high-molecular-weight polyanions are hardly adsorbed, so the two can be separated. Examples of such anion exchange resins include Duolite A368MS manufactured by Sumika Chemtex Corporation.

[0022] The sulfate ion concentration in the aqueous polyanion solution obtained in step A may be 600 ppm or more on a mass basis with respect to the total mass of the aqueous polyanion solution before the treatment for removing sulfate ions. In this case, it is preferably less than 600 ppm, more preferably 550 ppm or less, and even more preferably as small as 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, 50 ppm or less after the treatment for removing sulfate ions. The lower the sulfate ion concentration contained in the aqueous polyanion solution, the higher the storage stability of the conductive polymer dispersion produced in the subsequent step B.

[0023] The sulfate ion concentration in the aqueous polyanion solution or the 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 a standard sample with a known sulfate ion concentration. For example, as the measuring device, Integrion RFIC (manufactured by Thermo Fisher Scientific K.K.) can be used, and the measurement can be carried out using the column: Dionex IonPac AS19 and the detector: conductivity detector. Also, with a column temperature of 30°C, using an anion mixed standard solution IV as the standard substance, a sample diluted with 0.03 g of the sample and 50 g of ultrapure water was used as the measurement sample, and the peak of its conductivity was measured. As a method for calculating the quantitative value, there is a method of calculating the concentration of the measurement sample by a calibration curve of concentration - peak area, converting this to the amount (concentration) in the original sample, and using this as the measured value.

[0024] <Process B> Next, in Process B, a polymerization initiator for polymerizing the monomer is added to a reaction solution containing a polyanion, a monomer for forming a π - conjugated conductive polymer, and an aqueous dispersion medium to initiate a polymerization reaction, thereby forming a conductive composite containing the π - conjugated conductive polymer and the polyanion.

[0025] Process B is preferably a process of obtaining a third reaction solution containing a conductive composite in which the π - conjugated conductive polymer and the polyanion are complexed by adding a polymerizable monomer for forming a π - conjugated conductive polymer and an arbitrary radical polymerization initiator to the aqueous polyanion solution obtained in Process A and forming the π - conjugated conductive polymer. The aqueous polyanion solution used in Process B may be the one obtained in Process A or may be a commercially available polyanion dissolved in water to prepare an aqueous solution. When the aqueous solution of the commercially available polyanion contains sulfate ions, it is preferably removed before use in Process B.

[0026] In Process B, a third reaction solution containing a conductive composite can be obtained by a known method, except that the sulfate ion concentration immediately before the start of polymerization of the reaction solution is set to a predetermined value. In Project B, the concentration of sulfate ions contained in the reaction solution immediately before adding the polymerization initiator is less than 1180 ppm, preferably less than 700 ppm, more preferably less than 600 ppm, still more preferably 550 ppm or less, and even more preferably as small as 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, 50 ppm or less. The lower the concentration of sulfate ions contained in the reaction solution, the higher the storage stability of the conductive polymer dispersion to be produced.

[0027] The polymerizable monomer that forms the π-conjugated conductive polymer is preferably one or more selected from known monomers that can form the π-conjugated conductive polymers exemplified later. Among them, 3,4-ethylenedioxythiophene, which can form PEDOT with excellent conductivity and heat resistance, is most preferred.

[0028] Examples of the radical polymerization initiator include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate. It is preferable to incorporate a catalyst such as a transition metal compound such as ferric chloride, ferrous sulfate, ferric nitrate, and cupric chloride into the reaction solution together with the radical polymerization initiator.

[0029] The radical polymerization initiator is preferably added last to the reaction solution in which all other reaction components have been mixed to initiate the polymerization. The radical polymerization initiator is preferably dissolved in a small amount of water and added to the reaction solution. The addition method may be to add the whole amount at once or to add it stepwise and sequentially. It is preferable to add it slowly over a predetermined time (for example, 2 to 4 hours).

[0030] As the compounding amount of the radical polymerization initiator with respect to the total mass of the reaction solution during the polymerization reaction, for example, 0.10% by mass or more and 1.50% by mass or less is preferable, 0.30% by mass or more and 1.30% by mass or less is more preferable, and 0.50% by mass or more and 1.20% by mass or less is still more preferable.

[0031] The content of the monomer relative to the total mass of the reaction solution during the polymerization reaction is preferably, for example, 0.01% by mass or more and 2.0% by mass or less, more preferably 0.1% by mass or more and 1.0% by mass or less, and even more preferably 0.3% by mass or more and 0.8% by mass or less. The content of the polyanion relative to the total mass of the reaction solution during the polymerization reaction is preferably, for example, 0.1% by mass or more and 3.0% by mass or less, more preferably 0.5% by mass or more and 2.0% by mass or less, and even more preferably 1.0% by mass or more and 1.5% by mass or less. By setting it within the above-mentioned preferred range, a conductive polymer dispersion liquid with the concentration of the conductive composite within the preferred content described later can be easily obtained.

[0032] The reaction temperature in the reaction solution can be, for example, 20 to 30°C. At the above reaction temperature, the polymerization reaction usually completes in about 4 to 12 hours. The completion of the polymerization reaction can be known by measuring the amount of unreacted monomer in the reaction solution by means such as gas chromatography.

[0033] It is preferable to remove the residues of the catalyst and the radical polymerization initiator added to the reaction solution from the conductive polymer dispersion liquid after the polymerization reaction. As a method of removal, for example, a method of bringing the conductive polymer dispersion liquid into contact with an ion exchange resin to adsorb the catalyst and the radical polymerization initiator onto the ion exchange resin, a method of removing the dispersion medium by ultrafiltration of the conductive polymer dispersion liquid and removing it together with the substitution of the dispersion medium, etc. can be mentioned. Among these, the method of using an ion exchange resin is preferable because it is simple. It is preferable to use a combination of a cation exchange resin and an anion exchange resin for the ion exchange resin.

[0034] The conductive polymer dispersion liquid may be subjected to a dispersion treatment by a conventional method such as a high-pressure homogenizer.

[0035] An anionic surfactant, a polyol compound, an arbitrary additive, etc. may be further added to the conductive polymer dispersion liquid obtained above.

[0036] <Conductive composite> The conductive composite 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 considered that the two mainly form a composite by electrostatic interaction. Usually, the conductive composite is formed by polymerizing a monomer of a π-conjugated conductive polymer in water containing a polyanion, and the formed π-conjugated conductive polymer is naturally doped with the polyanion.

[0037] In the polyanion constituting the conductive composite, only some anion groups are doped into the π-conjugated conductive polymer, and there are surplus anion groups that do not participate in the doping. Since the surplus anion groups are hydrophilic groups, the conductive composite has water dispersibility. When the number of all anion groups of the polyanion is 100 mol%, the surplus anion groups are preferably 30 mol% or more and 90 mol% or less, and more preferably 45 mol% or more and 75 mol% or less.

[0038] (π-conjugated conductive polymer) The π-conjugated conductive polymer may be an organic polymer whose main chain is composed of a π-conjugated system. For example, 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 can be mentioned. From the viewpoint of stability in air, polypyrrole-based conductive polymers, polythiophenes, and polyaniline-based conductive polymers are preferable, and from the viewpoint of transparency, polythiophene-based conductive polymers are more preferable.

[0039] Examples of 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), poly(3-iodothiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxytiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxytiophene), 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-didodecyloxythiophene), 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), 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 π-conjugated conductive polymer contained in the conductive composite may be one type or two or more types.

[0040] (Polyanion) A polyanion is a polymer having two or more monomer units with anionic groups in the molecule. The anionic groups of this polyanion function as dopants for the π-conjugated conductive polymer and improve 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 polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyacrylate esters having a sulfo group, polymethacrylate esters having a sulfo group (for example, poly(4-sulfobutyl methacrylate), polysulfoethyl methacrylate, polymethacryloyloxybenzene sulfonic acid), polymers having a sulfo group such as poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, etc., and polymers having a carboxy group such as polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropane carboxylic acid), polyisoprene carboxylic acid, etc. The polyanion may be a homopolymer obtained by polymerizing a single monomer, or a copolymer obtained by polymerizing two or more monomers. Among these polyanions, polymers having a sulfo group are preferable and polystyrene sulfonic acid is more preferable because the conductivity can be made higher.

[0041] The content ratio of the polyanion contained in the conductive composite is preferably in the range of, for example, 1 part by mass or more and 1000 parts by mass or less, more preferably 10 parts by mass or more and 700 parts by mass or less, and even more preferably 100 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the π-conjugated conductive polymer. If the content ratio of the polyanion is at least the above lower limit value, the doping effect on the π-conjugated conductive polymer tends to be stronger and the conductivity becomes higher. On the other hand, if the content of the polyanion is at most the above upper limit value, the content ratio of the π-conjugated conductive polymer becomes sufficient, so that sufficient conductivity can be ensured.

[0042] <Conductive polymer dispersion liquid> The conductive polymer dispersion liquid produced in the first aspect is a conductive polymer dispersion liquid containing a conductive composite and water.

[0043] The content ratio of the polyanion contained in the conductive polymer dispersion is preferably in the range of, for example, 1 part by mass or more and 1000 parts by mass or less, more preferably 10 parts by mass or more and 700 parts by mass or less, and even more preferably 100 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the π-conjugated conductive polymer. If the content ratio of the polyanion is equal to or higher than the lower limit value, the doping effect on the π-conjugated conductive polymer tends to be enhanced, and the conductivity becomes higher. On the other hand, if the content of the polyanion is equal to or lower than the upper limit value, the π-conjugated conductive polymer can be sufficiently contained, so that sufficient conductivity can be ensured.

[0044] The total content of the π-conjugated conductive polymer and the polyanion with respect to the total mass of the conductive polymer dispersion is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.5% by mass or more and 2.5% by mass or less. Within the above preferred range, the dispersibility of the conductive composite is enhanced and the storage stability is improved. In addition, the ESR of the capacitor having the solid electrolyte layer formed from the conductive polymer dispersion can be further reduced.

[0045] (Dispersion medium) Since the conductive composite is hydrophilic, the dispersion medium contained in the conductive polymer dispersion is preferably an aqueous dispersion medium containing water. In addition, a dispersion medium other than water may be included. The dispersion medium other than water is not particularly limited as long as it does not significantly impair the dispersibility of the conductive composite. The conductive composite has an excess anion group derived from the polyanion and has high dispersibility in water. Therefore, the dispersion medium other than water is preferably a water-soluble organic solvent. Here, the water-soluble organic solvent is an organic solvent having a dissolution amount of 1 g or more in 100 g of water at 20°C, and examples thereof include alcohol solvents, ketone solvents, and ester solvents. The water-soluble organic solvent contained as the dispersion medium may be one kind or two or more kinds.

[0046] Examples of the alcohol 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, ethylene glycol monomethyl ether, and the like. Examples of the ether solvents include diethyl ether, dimethyl ether, propylene glycol dialkyl ether, diethylene glycol diethyl ether, and the like. Examples of the 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, diacetone alcohol, and the like. Examples of the nitrogen atom-containing solvents include N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and the like. The water-soluble organic solvent may contain only one kind or two or more kinds. Since the wettability of the conductive polymer dispersion liquid with respect to the base material is improved, an alcohol solvent or a ketone solvent is preferable as the water-soluble organic solvent, and an alcohol solvent is more preferable.

[0047] The water content with respect to the total mass of the dispersion medium excluding the solid content (non-volatile component) of the conductive polymer dispersion liquid is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and may be 100% by mass. When water is contained at or above the above lower limit value, the dispersibility of the conductive composite contained in the conductive polymer dispersion liquid is enhanced, and the storage stability is improved. In addition, the ESR of the capacitor having a solid electrolyte layer formed from the conductive polymer dispersion liquid can be further reduced.

[0048] The content of the water-soluble organic solvent with respect to the total mass of the aqueous dispersion medium is preferably 30 to 70% by mass, more preferably 40 to 60% by mass or more. Further, the content of water with respect to the total mass of the aqueous dispersion medium is preferably 70 to 30% by mass, more preferably 60 to 40% by mass or less. When it is within the above preferable range, it is possible to improve the wettability with respect to the base material while suppressing the temporal decrease in the dispersion stability of the conductive composite in the conductive polymer dispersion liquid.

[0049] The content of the conductive composite with respect to the total mass of the conductive polymer dispersion liquid 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 still more preferably 1.5% by mass or more and 3.0% by mass or less. When it is equal to or higher than the lower limit value of the above range, the conductivity of the conductive layer formed by curing the conductive polymer dispersion liquid can be further improved. When it is equal to or lower than the upper limit value of the above range, the dispersibility of the conductive composite in the conductive polymer dispersion liquid can be enhanced, and the storage stability can be further enhanced.

[0050] The initial viscosity (viscosity within 1 day after production) of the conductive polymer dispersion liquid at 23 °C is preferably 25 mPa·s or less, more preferably 20 mPa·s or less, still more preferably 15 mPa·s or less, and particularly preferably 10 mPa·s or less when the concentration of the conductive composite with respect to the total mass of the conductive polymer dispersion liquid is adjusted to 1.6% by mass. The lower limit value of the above viscosity is not particularly limited, and 1 mPa·s or more can be mentioned as a guideline. The increase rate of the viscosity after storage {= viscosity after storage ÷ initial viscosity × 100%} of the conductive polymer dispersion liquid having the above viscosity after standing and storing at 20 to 25 °C for 2 weeks is preferably lower, for example, less than 190%. If it is less than 190%, it can be said that the storage stability is sufficiently high. When measuring the above viscosity, the dispersion medium contained in the conductive polymer dispersion liquid is preferably only ion-exchanged water. Further, the conductive polymer dispersion liquid for measuring the viscosity may contain an anionic surfactant, but it is preferably free of other additives. The measurement of the viscosity was carried out at 23°C in accordance with JIS Z8803:2011 (Method for Measuring Viscosity by Vibration Viscometer) using a tuning fork vibration viscometer, and the measured value is used.

[0051] (Anionic surfactant) The conductive polymer dispersion may further contain an anionic surfactant different from the polyanion constituting the conductive composite. By containing an anionic surfactant, the initial viscosity before storage can be reduced, and the storage stability can also be improved.

[0052] As the anionic surfactant, those having a hydrophilic sulfonic acid group and a hydrophobic hydrocarbon group in the molecule are preferred. Specifically, for example, linear alkylbenzene sulfonic acids such as dodecylbenzene sulfonic acid (DBSA) or salts thereof are preferred. Also included are branched alkylbenzene sulfonic acids, alkyl sulfonic acids, alkyl phosphate esters, alkyl carboxylic acids, and salts thereof.

[0053] The content of the anionic surfactant with respect to the total mass of the conductive polymer dispersion is preferably, for example, 0.001% by mass or more and 1.0% by mass or less, more preferably 0.01% by mass or more and 0.50% by mass or less, and even more preferably 0.10% by mass or more and 0.30% by mass or less. When it is at or above the above lower limit value, the initial viscosity of the conductive polymer dispersion can be further reduced, and the storage stability can also be further improved. When it is at or below the above upper limit value, foaming of the conductive polymer dispersion can be reduced, and a decrease in the conductivity of the conductive layer, which is a cured product thereof, can be reduced.

[0054] (Polyol compound) The conductive polymer dispersion may contain one or more polyol compounds. Here, the polyol compound refers to a compound having two or more hydroxy groups, which is different from the π-conjugated conductive polymer, the polyanion, and the anionic surfactant. By containing a polyol compound, the conductivity of the conductive layer, which is a cured product of the conductive polymer dispersion, can be further increased.

[0055] Examples of the polyol compound include one or more selected from ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, glycerin, pentaerythritol, trimethylolpropane, and trimethylolethane.

[0056] The content of the polyol compound contained in the conductive polymer dispersion is preferably, for example, 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 with respect to a total of 100 parts by mass of the π-conjugated conductive polymer and the polyanion. When it is within the above preferable range, the coatability of the conductive polymer dispersion is improved, and the ESR of the capacitor can be further reduced.

[0057] The content of the polyol compound with respect to the total mass of the conductive polymer dispersion is preferably 1% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less. When it is within the above preferable range, the coatability of the conductive polymer dispersion is improved, and the ESR of the capacitor can be further reduced.

[0058] (Optional additive) The conductive polymer dispersion of this aspect may contain any additive other than the conductive composite within a range not impairing the gist of the present invention, and the content ratio thereof can be appropriately determined according to the type of the additive, but it can be, for example, 1 to 1,000 parts by mass with respect to a total of 100 parts by mass of the π-conjugated conductive polymer and the polyanion. Here, the optional additive is a compound other than the anionic surfactant, the polyol compound, and the dispersion medium.

[0059] Examples of the optional additive include surfactants, inorganic conductive agents, defoaming agents, coupling agents, antioxidants, ultraviolet absorbers, and the like. Examples of surfactants include nonionic, anionic, and cationic surfactants. From the perspective of storage stability, nonionic surfactants are preferred. Additionally, polymer surfactants such as polyvinyl alcohol and polyvinyl pyrrolidone may be added. Examples of inorganic conductive agents include metal ions and conductive carbon. Metal ions can be generated by dissolving metal salts in water. Examples of defoamers include silicone resins, polydimethylsiloxane, and silicone oil. Examples of coupling agents include silane coupling agents having vinyl groups, amino groups, epoxy groups, etc. Examples of antioxidants include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur antioxidants, and sugars. Examples of ultraviolet absorbers 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, benzoate-based ultraviolet absorbers, etc.

[0060] ≪Method for manufacturing a conductive laminate≫ The second aspect of the present invention is a method for manufacturing a conductive laminate, including a step of obtaining a conductive polymer dispersion liquid by the manufacturing method of the first aspect, and a step of applying the conductive polymer dispersion liquid to at least a part of the surface of a base material and drying it to form a conductive layer.

[0061] As a method for applying (coating) the conductive polymer dispersion liquid to an arbitrary surface of the base material, for example, methods using coaters such as gravure coaters, roll coaters, curtain flow coaters, spin coaters, bar coaters, reverse coaters, kiss coaters, fountain coaters, rod coaters, air doctor coaters, knife coaters, blade coaters, cast coaters, screen coaters, etc., methods using sprayers such as air spray, airless spray, and rotor damping, dipping methods such as dip, etc. can be applied.

[0062] The coating amount of the conductive polymer dispersion on the substrate is not particularly limited. For example, as the non-volatile component, it is preferably in the range of 0.01 to 10.0 g / m 2 is preferred.

[0063] A conductive layer can be formed by drying a coating film composed of the conductive polymer dispersion applied on the substrate to remove at least a part of the dispersion medium and then curing it. Examples of the method for drying the coating film include heat drying and vacuum drying. As the heat drying, for example, methods such as hot air heating and infrared heating can be adopted. When applying heat drying, the heating temperature is appropriately set according to the dispersion medium used, but usually it is within the range of 50°C or higher and 200°C or lower. Here, the heating temperature is the set temperature of the drying device. The preferred drying time within the above range of the heating temperature is preferably 0.5 minutes or more and 30 minutes or less, and more preferably 1 minute or more and 15 minutes or less.

[0064] <Conductive laminate> The conductive laminate produced by the production method of the second aspect includes a substrate and a conductive layer formed on at least a part of the surface of the substrate, and the conductive layer contains a cured product of the conductive polymer dispersion.

[0065] [Conductive layer] The formation range of the conductive layer may be the entire surface of any surface of the substrate or a part thereof. In the conductive film, it is preferable that a conductive layer with a substantially uniform thickness is formed on substantially the entire surface of one side or the other side of the film substrate. When the conductive layer is formed only on a part of the surface of the substrate, for example, the conductive layer may be a fine conductive pattern such as a circuit or an electrode, or the region where the conductive layer is provided and the region where it is not provided may exist on the same surface and be roughly divided.

[0066] 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. If the average thickness of the conductive layer is equal to or greater than the lower limit value, high conductivity can be exhibited. If it is equal to or less than the upper limit value, the adhesion of the conductive layer to the base material is further improved.

[0067] [Base material] The base material may be a base material made of an insulating material or a base material made of a conductive material. The shape of the base material is not particularly limited, and examples thereof include shapes mainly having a plane such as a film and a substrate. Examples of the insulating material include glass, synthetic resin, and ceramics. Examples of the conductive material include metal, conductive metal oxide, and carbon.

[0068] (Film substrate) When a film substrate is used as the base material, the conductive laminate becomes a conductive film. Examples of the film substrate include plastic films made of synthetic resin. Examples of the synthetic resin include 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 elastomer, polyester-based elastomer, polyethersulfone, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyimide, cellulose triacetate, cellulose acetate propionate, and the like. From the viewpoint of enhancing the adhesion between the film substrate and the conductive layer, the synthetic resin for the film substrate is preferably a polyester resin, and among them, polyethylene terephthalate is preferable.

[0069] The synthetic resin for the film substrate may be amorphous or crystalline. The film substrate may be unstretched or stretched. The film base material may be subjected to surface treatments such as corona discharge treatment, plasma treatment, and flame treatment in order to further improve the adhesion of the conductive layer.

[0070] The average thickness of the film base material is preferably 5 μm or more and 500 μm or less, more preferably 20 μm or more and 200 μm or less. If the average thickness of the film base material is at least the lower limit value, it becomes difficult to break, and if it is at most the upper limit value, sufficient flexibility as a film can be ensured. The average thickness of the film base material is a value obtained by measuring the thickness at 10 randomly selected locations and averaging the measured values.

[0071] (Glass base material) Examples of the glass base material include an alkali-free glass base material, a soda-lime glass base material, a borosilicate glass base material, and a quartz glass base material. When the base material contains an alkali component, the conductivity of the conductive layer tends to decrease. Therefore, among the above glass base materials, an alkali-free glass is preferred. Here, the alkali-free glass is a glass composition in which the content of the alkali component is 0.1% by mass or less based on the total mass of the glass composition.

[0072] The average thickness of the glass base material is preferably 100 μm or more and 3000 μm or less, more preferably 100 μm or more and 1000 μm or less. If the average thickness of the glass base material is at least the lower limit value, it becomes difficult to break, and if it is at most the upper limit value, it can contribute to thinning of the conductive laminate. The average thickness of the glass base material is a value obtained by measuring the thickness at 10 randomly selected locations and averaging the measured values.

[0073] <<Manufacturing method of capacitor>> A third aspect of the present invention is a method for manufacturing a capacitor, which includes a step of obtaining a conductive polymer dispersion liquid by the manufacturing method of the first aspect, and a step of applying the conductive polymer dispersion liquid to the surface of a dielectric layer formed on the surface of an anode made of a porous body of valve metal and drying it to form a solid electrolyte layer.

[0074] The manufacturing method of the capacitor according to this aspect preferably includes a step of forming a dielectric layer by oxidizing the surface of an anode made of a porous body of valve metal (dielectric formation step), a step of disposing a cathode at a position facing the dielectric layer (cathode formation step), and a step of forming a solid electrolyte layer on at least a part of the surface of the dielectric layer (film formation step). Hereinafter, each step will be described with reference to FIG. 1.

[0075] [Dielectric Formation Step] In this step, the surface of the anode 11 made of a porous body of valve metal is oxidized to form a dielectric layer 12. The method of forming the dielectric layer 12 is not particularly limited. For example, a method of anodizing the surface of the anode 11 in an electrolytic solution for forming treatment such as an ammonium adipate aqueous solution, an ammonium borate aqueous solution, or an ammonium phosphate aqueous solution can be mentioned.

[0076] [Cathode Formation Step] In this step, the cathode 13 is disposed at a position facing the dielectric layer 12. The method of disposing the cathode 13 is not particularly limited. For example, a method of forming the cathode 13 using a conductive paste such as a carbon paste or a silver paste, a method of disposing a metal foil such as an aluminum foil facing the dielectric layer 12, etc. can be mentioned.

[0077] [Film Formation Step] In this step, the solid electrolyte layer 14 is formed by applying the aforementioned conductive polymer dispersion liquid to at least a part of the surface of the dielectric layer 12 and drying it.

[0078] As a method of applying the conductive polymer dispersion liquid, for example, dipping (dip coating), comma coating, reverse coating, lip coating, microgravure coating, etc. can be applied. Among these, a method of dipping the anode 11 in the conductive polymer dispersion liquid under reduced pressure is preferable. In the case of the dipping method, the conductive polymer dispersion liquid can be sufficiently applied to the inside of the porous structure on the surface of the dielectric layer 12. After dipping, it is taken out and the next drying treatment is carried out.

[0079] Examples of the drying method include room temperature drying, hot air drying, far-infrared drying, etc. Among these, hot air drying is preferred. As the drying temperature, for example, 100 to 180 °C is preferred, and 120 to 150 °C is more preferred. As the drying time, for example, 0.2 to 1 hour is preferred. After the drying treatment, the capacitor may be assembled by a conventional method.

[0080] <Capacitor> The capacitor manufactured in the third aspect includes an anode made of a porous body of valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the opposite side of the dielectric layer from the anode, and a solid electrolyte layer formed between the dielectric layer and the cathode, and the solid electrolyte layer contains a cured product of the conductive polymer dispersion liquid.

[0081] An example of an embodiment of the capacitor will be described with reference to FIG. 1. The capacitor 10 shown in FIG. 1 includes an anode 11 made of a porous body of 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 interposed therebetween.

[0082] Examples of the valve metal constituting the anode 11 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc. Among these, aluminum, tantalum, and niobium are suitable. Specific examples of the anode 11 include those obtained by etching an aluminum foil to increase the surface area and then subjecting the surface to an oxidation treatment, and those obtained by subjecting the surface of a sintered body of tantalum particles or niobium particles to an oxidation treatment to form pellets. Those treated in this way become porous bodies with uneven surfaces formed on the surface.

[0083] The dielectric layer 12 in this embodiment is a layer formed by oxidizing the surface of the anode 11. For example, it is formed by anodizing the surface of the metal anode 11 in an electrolytic solution such as an ammonium adipate aqueous solution. Similar to the anode 11, irregularities are also formed on the dielectric layer 12.

[0084] As the cathode 13 in this embodiment, a metal layer made of a conductive substance such as a conductive layer formed from a conductive paste or an aluminum foil can be used.

[0085] 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 part 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 be constant or not constant. For example, the thickness may be 1 μm or more and 100 μm or less.

[0086] [Electrolytic solution] The capacitor may have an electrolytic solution that impregnates the solid electrolyte layer. Examples of the solvent constituting the electrolytic solution include alcohol solvents such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and glycerin; lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; sulfur solvents such as sulfolane, dimethyl sulfoxide, and dimethyl sulfone; amide solvents such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, and N-methylpyrrolidone; nitrile 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, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, octanedicarboxylic acids such as 1,7-octanedicarboxylic acid, azelaic acid, sebacic acid; or boric acid, a polyhydric alcohol complex compound of boric acid obtained from boric acid and a polyhydric alcohol; inorganic acids such as phosphoric acid, carbonic acid, silicic acid, etc. as anionic components, 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 cationic components; and the like.

[0087] The capacitor is not limited to the above configuration, and a separator may be provided between the dielectric layer and the cathode. Examples of the capacitor having a separator provided between the dielectric layer and the cathode include a wound capacitor. Examples of the separator include sheets (including non-woven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., non-woven fabrics of glass fibers, and the like. The density of the separator is, for example, 0.1 g / cm 3 to 1.0 g / cm 3 or less. When providing a separator, a method of impregnating the separator with carbon paste or silver paste to form a cathode can also be applied.

Example

[0088] <Production of Polyanion> [Production Example 1; PSS, Mw 170,000, Sulfate Ion Content 3400 ppm] 110 g of sodium styrenesulfonate was dissolved in 820 ml of ion-exchanged water, and while stirring at 80 °C, 4.88 g of sodium peroxydisulfate 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 polystyrenesulfonate-containing solution to remove sodium ions. The solid content of the obtained aqueous solution 1 of polystyrenesulfonic acid (PSS) was 10% by mass. For PSS aqueous solution 1, using an HPLC (High Performance Liquid Chromatography) system equipped with a GPC (Gel Permeation Chromatography) column and a differential refractive index detector, the weight average molecular weight was measured using pullulan manufactured by Showa Denko K.K. as a standard substance. When analyzing the GPC chart where the vertical axis represents the signal intensity of the differential refractive index and the horizontal axis represents the retention time, the peak of the first polystyrenesulfonic acid showed a weight average molecular weight (Mw) of 170,000. For PSS aqueous solution 1, the content of sulfate ions was measured by the aforementioned method, and it was 3400 ppm It was.

[0089] [Production Example 2; PSS, Mw 170,000, Sulfate Ion Content: Below Detection Limit] 50 g of an anion exchange resin (Duolite A368MS, manufactured by Sumika Chemtex Corporation) was added to 1000 g of PSS aqueous solution 1 produced in Production Example 1, and the mixture was stirred for 1 hour. Then, after filtration to remove the anion exchange resin, the solid content of the obtained PSS aqueous solution 2 was 8.5% by mass. For PSS aqueous solution 2, the content of sulfate ions was measured by ion chromatography in the same manner as in Production Example 1, and the content of sulfate ions was below the detection limit (less than 25 ppm).

[0090] [Production Example 3; PSS, Mw 170,000, Sulfate Ion Content 4132 ppm] The 4.88 g of sodium peroxydisulfate dissolved in 55 ml of water was changed to 5.69 g, and it was added dropwise over 2 hours, and the solution was stirred for 2 hours. Otherwise, it was carried out in the same manner as in Production Example 1 to obtain an aqueous PSS solution 3 having a solid content of 10% by mass. When the amount of sulfate ions in the aqueous PSS solution 3 was measured by ion chromatography in the same manner as in Production Example 1, the amount of sulfate ions was 4132 ppm.

[0091] [Production Example 4; PSS, Mw 120000, amount of sulfate ions 5745 ppm] The 4.88 g of sodium peroxydisulfate dissolved in 55 ml of water was changed to 8.54 g. Otherwise, it was carried out in the same manner as in Production Example 1 to obtain an aqueous PSS solution 4 having a solid content of 10% by mass. When the amount of sulfate ions in the aqueous PSS solution 4 was measured by ion chromatography in the same manner as in Production Example 1, the amount of sulfate ions was 5745 ppm.

[0092] [Production Example 5; PSS, Mw 120000, amount of sulfate ions: below the detection limit] 75 g of an anion exchange resin was added to 1000 g of the aqueous PSS solution 4 produced in Production Example 4, and it was stirred for 1 hour. Then, it was filtered to remove the anion exchange resin, and the solid content of the obtained aqueous PSS solution 5 was 8.2% by mass. When the amount of sulfate ions in the aqueous PSS solution 5 was measured by ion chromatography in the same manner as in Production Example 1, the amount of sulfate ions was below the detection limit (less than 25 ppm).

[0093] [Production Example 6; PSS, Mw 100000, amount of sulfate ions 6357 ppm] The 4.88 g of sodium peroxydisulfate dissolved in 55 ml of water was changed to 9.76 g. Otherwise, it was carried out in the same manner as in Production Example 1 to obtain an aqueous PSS solution 6 having a solid content of 10% by mass. When the amount of sulfate ions in the aqueous PSS solution 6 was measured by ion chromatography in the same manner as in Production Example 1, the amount of sulfate ions was 6357 ppm.

[0094] [Production Example 7; PSS, Mw 100000, amount of sulfate ions: below the detection limit] To 1000 g of the PSS aqueous solution 6 produced in Production Example 6, 100 g of an anion exchange resin was added and stirred for 1 hour. Thereafter, it was filtered to remove the anion exchange resin, and the solid content of the PSS aqueous solution 7 thus obtained was 8.2% by mass. When the amount of sulfate ions in the PSS aqueous solution 7 was measured by ion chromatography in the same manner as in Production Example 1, the amount of sulfate ions was below the detection limit (less than 25 ppm).

[0095] <Example 1> 5.71 g of 3,4-ethylenedioxythiophene, 142.5 g of the PSS aqueous solution 1 obtained in Production Example 1, and 777.55 g of ion-exchanged water were mixed. The amount of sulfate ions in this mixed solution was 513 ppm. While maintaining this mixed solution at 26°C and stirring, an oxidation catalyst solution of 1.15 g of ferric sulfate (about 0.86 g excluding the hydrated water) dissolved in 18.05 g of ion-exchanged water was added, and 6.25 g of sodium peroxydisulfate dissolved in 50.55 g of ion-exchanged water was gradually added dropwise at a constant rate over 2 hours, and further stirred for 4 hours to cause a reaction. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 1171 ppm. To the obtained reaction solution, a cation exchange resin (manufactured by Sumitomo Chemical Tex Co., Ltd., Duolite C255LFH) and an anion exchange resin (manufactured by Sumitomo Chemical Tex Co., Ltd., Duolite A368S) were added to remove the polymerization initiator and iron. As a result, a blue PEDOT-PSS aqueous dispersion with PEDOT:PSS = 1:2.5 (mass ratio) was obtained. The solid content (non-volatile component) of the obtained dispersion was as shown in Table 1.

[0096] <Example 2> The PSS aqueous solution 1 was changed to 167.94 g of the PSS aqueous solution 2 obtained in Production Example 2, and the amount of ion-exchanged water was changed to 750.36 g. Otherwise, the procedure was the same as in Example 1, and a PEDOT-PSS aqueous dispersion with the concentration shown in Table 1 was obtained. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 658 ppm.

[0097] <Example 3> was changed to 174.09 g of the PSS aqueous solution 5 obtained in Production Example 5, and the blending amount of ion-exchanged water was changed to 747.21 g. Otherwise, the procedure was the same as in Example 1, and a PEDOT-PSS aqueous dispersion having the concentration shown in Table 1 was obtained. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 658 ppm.

[0098] <Example 4> was changed to 174.09 g of the PSS aqueous solution 7 obtained in Production Example 7, and the blending amount of ion-exchanged water was changed to 747.21 g. Otherwise, the procedure was the same as in Example 1, and a PEDOT-PSS aqueous dispersion having the concentration shown in Table 1 was obtained. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 658 ppm.

[0099] <Example 5> was changed to 167.94 g of the PSS aqueous solution 2 obtained in Production Example 2, the blending amount of ion-exchanged water was changed to 748.93 g, and 1.43 g of dodecylbenzenesulfonic acid was added. Otherwise, the procedure was the same as in Example 1, and a PEDOT-PSS aqueous dispersion having the concentration shown in Table 1 was obtained. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 658 ppm.

[0100] <Example 6> was changed to 174.09 g of the PSS aqueous solution 6 obtained in Production Example 7, the blending amount of ion-exchanged water was changed to 742.79 g, and 1.43 g of dodecylbenzenesulfonic acid was added. Otherwise, the procedure was the same as in Example 1, and a PEDOT-PSS aqueous dispersion having the concentration shown in Table 1 was obtained. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 658 ppm.

[0101] <Comparative Example 1> Except for changing the PSS aqueous solution 1 to the PSS aqueous solution 3 obtained in Production Example 3, the procedure was the same as in Example 1 to obtain a PEDOT-PSS aqueous dispersion having the concentration described in Table 1. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 1282 ppm.

[0102] <Comparative Example 2> Except for changing the PSS aqueous solution 1 to the PSS aqueous solution 4 obtained in Production Example 4, the procedure was the same as in Example 1 to obtain a PEDOT-PSS aqueous dispersion having the concentration described in Table 1. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 1524 ppm.

[0103] <Comparative Example 3> Except for changing the PSS aqueous solution 1 to the PSS aqueous solution 6 obtained in Production Example 6, the procedure was the same as in Example 1 to obtain a PEDOT-PSS aqueous dispersion having the concentration described in Table 1. The sulfate ion concentration of the reaction solution at the start of EDOT polymerization (start of addition of the polymerization initiator) in this example was about 1617 ppm.

[0104] <Evaluation of Viscosity> The solid content concentration of the PEDOT-PSS aqueous dispersion obtained in each example was adjusted to 1.6 mass% by the ultrafiltration method, and the viscosity at 23°C was measured using a vibrating viscometer. The measurement results of the initial viscosity are shown in Table 1. The above viscosity was measured at 23°C using a tuning fork vibrating viscometer in accordance with JIS Z8803:2011 (Method for Measuring Viscosity by Vibration Viscometer).

[0105] <Evaluation of Storage Stability> The viscosity of the conductive polymer dispersion (after adjustment to a concentration of 1.6 mass%) obtained in each example was measured after storage at 24°C for 2 weeks. The measurement results of the viscosity after storage and the calculated value as the increase rate (%) based on the ratio to the initial viscosity are shown in Table 1. Note that the lower the increase rate, the less the viscosity change and the better the storage stability.

[0106] <Evaluation of Conductivity> To 1.9 g of the conductive polymer dispersion (PEDOT-PSS aqueous dispersion) obtained in each example, 4.0 g of methanol and 0.1 g of propylene glycol were added and thoroughly mixed to obtain a paint. This paint was applied to a polyethylene terephthalate film (manufactured by Toray Industries, Inc., Lumirror T60) using a No. 12 bar coater and heat-dried at a drying temperature of 120 °C for 1 minute to obtain a conductive film. The surface resistance value of the obtained conductive film was measured using a resistivity meter (R Loresta manufactured by Nitto Seiko Analytic Co., Ltd.) under the condition of an applied voltage of 10 V. The results are shown in Table 1. The lower the value of the surface resistance, the higher and better the conductivity.

[0107]

Table 1

[0108] From the above, it is clear that Examples 1 to 6 according to the present invention can form a conductive layer exhibiting good conductivity, and a highly storage-stable conductive polymer dispersion having a low viscosity maintained during storage can be obtained. In particular, the low initial viscosity rates of Examples 5 to 6 to which an anionic surfactant was added are remarkable.

Explanation of Symbols

[0109] 10 Capacitor 11 Anode 12 Dielectric layer 13 Cathode 14 Solid electrolyte layer

Claims

1. A polymerization initiator for polymerizing the monomer is added to a reaction solution containing a polyanion, a monomer for forming a π-conjugated conductive polymer, and an aqueous dispersion medium to initiate a polymerization reaction, and a conductive composite containing the π-conjugated conductive polymer and the polyanion is formed. A method for producing a conductive polymer dispersion liquid, comprising: A method for producing a conductive polymer dispersion liquid, wherein the concentration of sulfate ions contained in the reaction solution immediately before adding the polymerization initiator is less than 1180 ppm.

2. The method for producing a conductive polymer dispersion liquid according to claim 1, wherein a polyanion for being blended in the reaction solution and an aqueous polyanion solution containing sulfate ions are prepared in advance, and after removing the sulfate ions contained in the aqueous polyanion solution, it is blended in the reaction solution.

3. A preliminary step of subjecting the monomer forming the polyanion to radical polymerization in the presence of water to obtain the aqueous polyanion solution is included, The method for producing a conductive polymer dispersion liquid according to claim 2, wherein in the preliminary step, a persulfate is used to initiate the radical polymerization, and sulfate ions are generated as a by-product.

4. The concentration of sulfate ions contained in the aqueous polyanion solution obtained in the preliminary step is 600 ppm or more before the treatment for removing sulfate ions, less than 600 ppm after the treatment for removing sulfate ions, The method for producing a conductive polymer dispersion liquid according to claim 3.

5. The method for producing a conductive polymer dispersion liquid according to claim 2, wherein the sulfate ions contained in the aqueous polyanion solution are removed using an ion exchange resin.

6. The method for producing a conductive polymer dispersion liquid according to claim 5, wherein an anionic surfactant different from the polyanion is further blended in the conductive polymer dispersion liquid containing the conductive composite and the aqueous dispersion medium.

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

8. The method for producing a conductive polymer dispersion liquid according to claim 4, wherein the polyanion is polystyrene sulfonic acid.

9. A method for producing a conductive laminate, comprising: a step of obtaining a conductive polymer dispersion liquid by the production method according to any one of claims 1 to 8; and a step of applying the conductive polymer dispersion liquid to at least a part of the surface of a substrate and drying to form a conductive layer.

10. A step of obtaining a conductive polymer dispersion by the production method according to any one of claims 1 to 8; A method for manufacturing a capacitor, comprising: a step of applying the conductive polymer dispersion onto the surface of a dielectric layer formed on the surface of an anode made of a porous body of valve metal, and drying the applied dispersion to form a solid electrolyte layer.

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