Conductive polymer and method for producing the same, oxidant and dopant solution for producing conductive polymer, monomer composition for producing conductive polymer and electrolytic capacitor and method for manufacturing the same

Abstract

To provide an electrolytic capacitor having excellent voltage resistance and low ESR and a method for manufacturing the same, a conductive polymer capable of constituting the electrolytic capacitor and a method for manufacturing the same and an oxidant / dopant solution and a monomer composition for manufacturing the conductive polymer.SOLUTION: There is provided a conductive polymer which contains a polymer of thiophene or a derivative thereof which contains an organic sulfonic acid as a dopant and a multifunctional acrylate having three or more polymerizable double bonds in the molecule or a polymerization product thereof. In addition, there are provided: an oxidant and dopant solution for the production of a conductive polymer which contains an organic ferric sulfonate, water or a lower alcohol and the multifunctional acrylate; and a monomer composition which contains thiophene or its derivative and the multifunctional acrylate. Further, the electrolytic capacitor has a conductive polymer as a solid electrolyte.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an electrolytic capacitor having excellent voltage resistance and low ESR (equivalent series resistance) and a method for producing the same, a conductive polymer that can be used to form the electrolytic capacitor and a method for producing the same, and an oxidant / dopant solution and a monomer composition for producing the conductive polymer. [Background technology]

[0002] Due to their high electrical conductivity, conductive polymers are used as electrolytes (solid electrolytes) in, for example, aluminum electrolytic capacitors, tantalum electrolytic capacitors, niobium electrolytic capacitors, and the like.

[0003] As the conductive polymer for this application, for example, one obtained by chemical oxidative polymerization or electrolytic oxidative polymerization of thiophene or its derivatives is used.

[0004] Furthermore, in recent years, there has been a demand for electrolytic capacitors with larger capacitance, and in order to achieve this, it is preferable to increase the voltage resistance of the electrolytic capacitor, for example.

[0005] As a technique for improving the voltage resistance of electrolytic capacitors, the present applicant has proposed a method of using a monomer for producing a conductive polymer, which is a mixture of 3,4-ethylenedioxythiophene and alkylated ethylenedioxythiophene, and a method of polymerizing a conductive polymer using an oxidizer / dopant solution for a conductive polymer to which a compound having a glycidyl group or a ring-opened compound thereof, or an oxetane compound or a ring-opened compound of an oxetane compound has been added (Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2011 / 068026 [Patent Document 2] International Publication No. 2012 / 023221 [Patent Document 3] JP 2023-20170 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide an electrolytic capacitor having excellent voltage resistance and low ESR and a method for producing the same, by using a technique different from that described in Patent Documents 1 to 3, as well as to provide a conductive polymer that can constitute the electrolytic capacitor and a method for producing the same, and an oxidant / dopant solution and a monomer composition for producing the conductive polymer. [Means for solving the problem]

[0008] The conductive polymer of the present invention is characterized by containing a polymer of thiophene or a derivative thereof, which contains an organic sulfonic acid as a dopant, and a polyfunctional acrylate containing three or more polymerizable double bonds in the molecule (hereinafter, may be simply referred to as a "polyfunctional acrylate") or a polymer thereof.

[0009] The oxidant and dopant solution for producing a conductive polymer of the present invention (hereinafter may be referred to as "oxidant and dopant solution") is characterized by containing an organic ferric sulfonate as an oxidant and dopant for producing a conductive polymer (hereinafter may be referred to as "oxidant and dopant"), water or a lower alcohol as a solvent, and a polyfunctional acrylate containing three or more polymerizable double bonds in the molecule.

[0010] Furthermore, the monomer composition for producing a conductive polymer of the present invention (hereinafter may be referred to as the "monomer composition") is characterized by containing thiophene or a derivative thereof, which is a monomer for producing a conductive polymer (hereinafter may be referred to as the "monomer"), and a polyfunctional acrylate having three or more polymerizable double bonds in the molecule.

[0011] The conductive polymer of the present invention can be produced by the production method of the present invention, in which thiophene or a derivative thereof is chemically oxidatively polymerized in the presence of an organic ferric sulfonate and a polyfunctional acrylate having three or more polymerizable double bonds in the molecule.

[0012] The electrolytic capacitor of the present invention is characterized in that it has the conductive polymer of the present invention as a solid electrolyte.

[0013] The electrolytic capacitor of the present invention can be produced by the production method of the present invention using, as a solid electrolyte, the conductive polymer produced by the production method of the conductive polymer of the present invention. Effect of the Invention

[0014] According to the present invention, it is possible to provide an electrolytic capacitor having excellent voltage resistance and low ESR and a method for producing the same, a conductive polymer that can constitute the electrolytic capacitor and a method for producing the same, and an oxidant / dopant solution and a monomer composition for producing the conductive polymer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Conductive polymer> The conductive polymer of the present invention contains a polymer of thiophene or a derivative thereof, which contains an organic sulfonic acid as a dopant, and a polyfunctional acrylate or a polymer thereof containing three or more polymerizable double bonds in the molecule.

[0016] The conductive polymer has excellent voltage resistance due to the action of a multifunctional acrylate containing three or more polymerizable double bonds in the molecule or a polymer thereof. Therefore, by using the conductive polymer as a solid electrolyte, an electrolytic capacitor with excellent voltage resistance can be obtained. In addition, by using the conductive polymer as a solid electrolyte, the ESR of the electrolytic capacitor can be reduced.

[0017] Examples of thiophene derivatives in thiophene or its derivatives, which are monomers in polymers of thiophene or its derivatives that constitute conductive polymers, include 3,4-ethylenedioxythiophene (EDOT), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene, and alkylated ethylenedioxythiophene (alkylated EDOT) in which the above-mentioned 3,4-ethylenedioxythiophene is modified with an alkyl group. The number of carbon atoms in the alkyl group or alkoxy group is preferably 1 or more, and is preferably 16 or less, more preferably 10 or less, and even more preferably 4 or less.

[0018] To explain in detail about alkylated EDOT, which is the above-mentioned EDOT modified with an alkyl group, EDOT and alkylated EDOT correspond to the compounds represented by the following general formula (1).

[0019] [ka]

[0020] In general formula (1), R 1 is hydrogen or an alkyl group having 1 to 10 carbon atoms.

[0021] And, R in the above general formula (1) 1 The compound where R is hydrogen is EDOT, and its IUPAC name is "2,3-Dihydro-thieno[3,4-b][1,4]dioxine". However, this compound is more often represented by its general name "3,4-ethylenedioxythiophene" than by its IUPAC name, so in this specification, this "2,3-Dihydro-thieno[3,4-b][1,4]dioxine" is represented as "3,4-ethylenedioxythiophene (EDOT)". And, R in the above general formula (1) 1When R is an alkyl group, the alkyl group preferably has 1 to 10 carbon atoms, and more preferably has 1 to 4 carbon atoms. That is, the alkyl group is particularly preferably a methyl group, an ethyl group, a propyl group, or a butyl group. Specific examples of these include R in the general formula (1). 1 The compound where R is a methyl group is called "2-Methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine" in IUPAC name, but in the following of this specification, this will be abbreviated to "methylated ethylenedioxythiophene (methylated EDOT)". 1 The IUPAC name for the compound with an ethyl group is "2-Ethyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine," but in this specification, this is abbreviated to "ethylated ethylenedioxythiophene (ethylated EDOT)."

[0022] R in general formula (1) 1 The compound with a propyl group is called "2-propyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine" in IUPAC name, but in this specification, this is abbreviated to "propylated ethylenedioxythiophene (propylated EDOT)". 1The compound with a butyl group is represented by the IUPAC name "2-butyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine", but in this specification, this is abbreviated to "butylated ethylenedioxythiophene (butylated EDOT)". Also, in this specification, "2-alkyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine" is abbreviated to "alkylated ethylenedioxythiophene (alkylated EDOT)". Among these alkylated EDOTs, methylated EDOT, ethylated EDOT, propylated EDOT, and butylated EDOT are preferred.

[0023] It is preferable to use a mixture of EDOT (i.e., 2,3-dihydro-thieno[3,4-b][1,4]dioxine) and alkylated EDOT (i.e., 2-alkyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine), with the mixing ratio being preferably 0.05:1 to 1:0.1, more preferably 0.1:1 to 1:0.1, even more preferably 0.2:1 to 1:0.2, and particularly preferably 0.3:1 to 1:0.3, in terms of molar ratio.

[0024] Examples of the organic sulfonic acid that is a dopant contained in the conductive polymer include aromatic sulfonic acids such as benzenesulfonic acid or a derivative thereof, naphthalenesulfonic acid or a derivative thereof, and anthraquinonesulfonic acid or a derivative thereof; polymeric sulfonic acids such as polystyrenesulfonic acid, sulfonated polyester, phenolsulfonic acid novolac resin, and copolymers of styrenesulfonic acid and non-sulfonic acid monomers (methacrylic acid esters, acrylic acid esters, unsaturated hydrocarbon-containing alkoxysilane compounds or hydrolysates thereof, etc.); and chain sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid.

[0025] Among these, aromatic sulfonic acids are particularly preferred because they are easy to manufacture electrolytic capacitors with excellent capacitor characteristics, such as lower ESR and larger capacitance, and can be used alone. Chain sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid have higher acidity than aromatic sulfonic acids, so they are preferably used in combination with the aromatic sulfonic acids rather than used alone. In other words, aromatic sulfonic acids have the property that the reaction proceeds properly under low humidity (humidity of about 35% or less) and a conductive polymer with good characteristics is easily obtained, but the reaction does not proceed easily under high humidity (humidity of about 50% or more). Therefore, the strong acidity of chain sulfonic acids can improve this and allow the reaction to proceed properly.

[0026] In addition, examples of the benzenesulfonic acid derivatives in benzenesulfonic acid or its derivatives include toluenesulfonic acid, ethylbenzenesulfonic acid, propylbenzenesulfonic acid, butylbenzenesulfonic acid, dodecylbenzenesulfonic acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, propoxybenzenesulfonic acid, butoxybenzenesulfonic acid, phenolsulfonic acid, cresolsulfonic acid, and benzenedisulfonic acid. In addition, examples of the naphthalenesulfonic acid derivatives in naphthalenesulfonic acid or its derivatives include naphthalene disulfonic acid, naphthalene trisulfonic acid, methylnaphthalenesulfonic acid, ethylnaphthalenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid. In addition, examples of the anthraquinonesulfonic acid derivatives in anthraquinonesulfonic acid or its derivatives include anthraquinone disulfonic acid and anthraquinone trisulfonic acid. Among these aromatic sulfonic acids, toluenesulfonic acid, methoxybenzenesulfonic acid, phenolsulfonic acid, naphthalenesulfonic acid, naphthalenetrisulfonic acid, etc. are preferred, paratoluenesulfonic acid, methoxybenzenesulfonic acid, and naphthalenesulfonic acid are more preferred, and paratoluenesulfonic acid and naphthalenesulfonic acid are even more preferred.

[0027] The conductive polymer contains a polyfunctional acrylate having three or more polymerizable double bonds in the molecule, or a polymer thereof. The conductive polymer of the present invention can be produced by chemically oxidizing and polymerizing thiophene or a derivative thereof in the coexistence of a polyfunctional acrylate having three or more polymerizable double bonds in the molecule, and during this polymerization, molecules of the polyfunctional acrylate having three or more polymerizable double bonds in the molecule may react with each other to form a polymer, which may be contained in the conductive polymer.

[0028] Examples of polyfunctional acrylates containing three or more polymerizable double bonds in the molecule and used in the production of conductive polymers include the following.

[0029] The compound having three polymerizable double bonds in the molecule (trifunctional acrylate) is represented by the following formula (2): 2 ~R 5 one of which is hydrogen and the remaining three are acryloyl groups [the following formula (3)]; 6 ~R 9 one of which is hydrogen, a methyl group, or an ethyl group, and the remaining three are acryloyl groups;

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] The acrylate having four polymerizable double bonds in the molecule (tetrafunctional acrylate) is represented by the above formula (2), 2 ~R 5are either an acryloyl group or a group represented by the following formula (5) in which the average value of n is 1.5 to 6; 11 , R 12 , R 14 , R 15 is an acryloyl group, and R 10 , R 13 are each a hydrogen atom, a methyl group, or an ethyl group;

[0034] [ka]

[0035] [ka]

[0036] The acrylate having five polymerizable double bonds in the molecule (pentafunctional acrylate) is represented by the following formula (7): 16 ~R 21 one of which is hydrogen and the remaining five are each an acryloyl group or a group represented by the above formula (5) in which the average value of n is 1.5 to 6.

[0037] [ka]

[0038] The acrylate having six polymerizable double bonds in the molecule (hexafunctional acrylate) is represented by the above formula (7), 16 ~R 21 are each an acryloyl group, a group represented by the above formula (5) in which the average value of n is 1.5 to 6, or a group represented by the following formula (8) in which the average value of m is 1.5 to 10.

[0039] [ka]

[0040] When producing the conductive polymer, only one of the above-exemplified polyfunctional acrylates may be used, or two or more of them may be used in combination.

[0041] The amount of organic sulfonic acid in the conductive polymer may be the amount contained in a conductive polymer obtained by satisfying the suitable ratio of organic ferric sulfonate to monomer described in the conductive polymer manufacturing method described later. The content of polyfunctional acrylate or its polymer in the conductive polymer may be the amount contained in a conductive polymer obtained by satisfying the suitable ratio of polyfunctional acrylate to organic ferric sulfonate described in the conductive polymer manufacturing method described later.

[0042] The conductive polymer of the present invention can be produced by chemical oxidative polymerization of thiophene or a derivative thereof in the presence of an organic ferric sulfonate and a polyfunctional acrylate.

[0043] The ferric organic sulfonate functions as an oxidizing agent and a dopant for producing a conductive polymer. Examples of the organic sulfonic acid constituting the ferric organic sulfonate include the various organic sulfonic acids exemplified above as dopants for conductive polymers.

[0044] The ferric organic sulfonate preferably has a molar ratio of organic sulfonic acid to iron of less than 1:3. This is because by reducing the molar ratio of organic sulfonic acid to iron below the stoichiometric molar ratio of 1:3, the reaction rate of the ferric organic sulfonate can be slightly reduced, and the molar ratio of organic sulfonic acid to iron is preferably up to about 1:2, more preferably up to about 1:2.2, particularly preferably up to about 1:2.4, and even more preferably up to about 1:2.75.

[0045] Conductive polymers can be produced by (a) preparing a polymerization solution containing a monomer, thiophene or a derivative thereof, organic ferric sulfonate, and a polyfunctional acrylate, and then chemically oxidizing the monomer; (b) immersing a substrate (such as a capacitor element of an electrolytic capacitor) in the polymerization solution, removing the substrate, and then chemically oxidizing the monomer; (c) diluting the monomer with a solvent, immersing the substrate in the monomer solution, removing the substrate and drying the substrate, immersing the substrate in an oxidizer / dopant solution (described later), removing the substrate, and then chemically oxidizing the monomer; or (d) immersing the substrate in an oxidizer / dopant solution, removing the substrate, and then chemically oxidizing the monomer. (e) a method in which the substrate is immersed in a monomer (or a monomer solution) after drying, and then pulled up, and then chemically oxidatively polymerized the monomer; (f) a method in which the substrate is immersed in a solution containing an organic ferric sulfonate and a solvent (water or a lower alcohol), and then pulled up, and then chemically oxidatively polymerized the monomer; etc. Chemical oxidative polymerization can be performed, for example, at 5 to 95°C for 1 to 72 hours.

[0046] In producing a conductive polymer, the molar ratio of the organic ferric sulfonate to the monomer is preferably organic ferric sulfonate:monomer=2:1 to 15:1. The content (concentration) of the monomer in the polymerization solution is preferably, for example, 20 to 40 mass %. Furthermore, the content (concentration) of the organic ferric sulfonate in the polymerization solution is preferably, for example, 20 to 50 mass %.

[0047] Furthermore, in the polymerization solution, from the viewpoint of further increasing the voltage resistance of the conductive polymer and further reducing the ESR of the electrolytic capacitor, the content (concentration) of the polyfunctional acrylate is preferably 0.2% by mass or more, and more preferably 3% by mass or more. If the amount of the polyfunctional acrylate in the polymerization solution is too large, the initial characteristics of the electrolytic capacitor tend to deteriorate and there is a risk of the ESR reduction effect being reduced, so the content of the polyfunctional acrylate in the polymerization solution is preferably 13% by mass or less, and more preferably 6% by mass or less.

[0048] In producing the conductive polymer, the ratio of the polyfunctional acrylate to 100 parts by mass of the organic ferric sulfonate is preferably 1 to 65 parts by mass.

[0049] Thiophene or its derivatives, which are monomers, are liquid at room temperature and can be used as they are for polymerization, but in order to make the polymerization reaction proceed more smoothly, water or a lower alcohol may be used as a solvent for the polymerization solution. Examples of lower alcohols include alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, propanol, and butanol. As the solvent for the polymerization solution, only one of the various solvents exemplified above may be used, or two or more of them may be used.

[0050] In producing a conductive polymer, the oxidant / dopant solution of the present invention containing an organic ferric sulfonate as an oxidant / dopant, water or a lower alcohol as a solvent, and a polyfunctional acrylate can be used.

[0051] The solvent for the oxidant / dopant solution can be water or a lower alcohol (the same as the polymerization solution).

[0052] In the oxidizer / dopant solution, from the viewpoint of further increasing the voltage resistance of the conductive polymer and further reducing the ESR of the electrolytic capacitor, the content (concentration) of the multifunctional acrylate is preferably 1% by mass or more, and more preferably 10% by mass or more. If the amount of the multifunctional acrylate in the oxidizer / dopant solution is too large, the initial characteristics of the electrolytic capacitor tend to deteriorate and there is a risk of the ESR reduction effect being reduced, so the content of the multifunctional acrylate in the oxidizer / dopant solution is preferably 25% by mass or less, and more preferably 20% by mass or less.

[0053] Furthermore, the content (concentration) of the ferric organic sulfonate in the oxidizer / dopant solution is preferably 20% by mass or more, more preferably 30% by mass or more, from the viewpoint of enabling the ferric organic sulfonate to function well as an oxidizer during the synthesis of a conductive polymer and being contained in the conductive polymer in an amount sufficient to act as a dopant. However, if the amount of ferric organic sulfonate in the oxidizer / dopant solution is too large, it may be difficult to dissolve the ferric organic sulfonate well in the solution. Therefore, the content of the ferric organic sulfonate in the oxidizer / dopant solution is preferably 70% by mass or less, more preferably 65% ​​by mass or less.

[0054] When a conductive polymer is produced using an oxidant / dopant solution, the above method (c) or (d) can be employed, or thiophene or a derivative thereof may be added as is to the oxidant / dopant solution, or a solution of thiophene or a derivative thereof diluted with water or a lower alcohol may be added to prepare a polymerization solution, which may then be subjected to the above method (a) or (b).

[0055] In addition, in producing a conductive polymer, the monomer composition of the present invention containing thiophene or a derivative thereof as a monomer and a polyfunctional acrylate can also be used.

[0056] The monomer composition may be composed of only thiophene or a derivative thereof, and a polyfunctional acrylate, but water or a lower alcohol (the same as the polymerization solution) may also be used as a solvent.

[0057] In the monomer composition, from the viewpoint of further increasing the voltage resistance of the conductive polymer and further reducing the ESR of the electrolytic capacitor, the content (concentration) of the polyfunctional acrylate is preferably 1% by mass or more, more preferably 10% by mass or more. If the amount of the polyfunctional acrylate in the monomer composition is too large, the initial characteristics of the electrolytic capacitor tend to decrease and the effect of reducing the ESR may become small, so the content of the polyfunctional acrylate in the monomer composition is preferably 30% by mass or less, more preferably 20% by mass or less.

[0058] The content (concentration) of thiophene or a derivative thereof in the monomer composition is preferably, for example, 10 to 60 mass %.

[0059] When a conductive polymer is produced using the monomer composition, the above method (e) or (f) can be employed, or alternatively, ferric organic sulfonate can be added directly to the monomer composition, or a solution of ferric organic sulfonate diluted with water or a lower alcohol can be added to prepare a polymerization solution, which can then be subjected to the above method (a) or (b).

[0060] In the solution containing the ferric organic sulfonate and water or a lower alcohol used in the above method (e) or (f), the concentration of the ferric organic sulfonate is preferably 30 to 65 mass %.

[0061] In addition to the above-mentioned components, other additives may be added to the polymerization solution, the oxidizing agent / dopant solution, and the monomer composition as necessary. Examples of such additives include compounds having a glycidyl group (epoxy group) or ring-opening compounds thereof; polymerized compounds such as silane coupling agents; polymers such as polysiloxane, alcohol-soluble resin, and polyethylene glycol; etc.

[0062] Suitable examples of the compound having a glycidyl group or a ring-opened compound thereof include the monoglycidyl compounds shown below, the diglycidyl compounds shown below, glycerin diglycidyl ether, diglycerin tetraglycidyl ether, alcohol-soluble epoxy resins, alcohol-soluble polyglycerin polyglycidyls and ring-opened compounds thereof, and epoxy polysiloxanes (the above "polysiloxane" means one having two or more siloxane bonds) and ring-opened compounds thereof.

[0063] Examples of the monoglycidyl compound include epoxypropanol (i.e., glycidol), methyl glycidyl ether, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, epoxybutane (i.e., glycidylmethane), epoxypentane (i.e., glycidylethane), epoxyhexane (i.e., glycidylpropane), epoxyheptane (i.e., glycidylbutane), epoxyoctane (i.e., glycidylpentane), glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and glycidyl methacrylate.

[0064] Examples of the diglycidyl compound include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butylene glycol diglycidyl ether, pentylene glycol diglycidyl ether, hexylene glycol diglycidyl ether, glycerin diglycidyl ether, diethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0065] The amount of the compound having a glycidyl group or a ring-opened compound thereof used in producing the conductive polymer is preferably 5 to 100 parts by mass per 100 parts by mass of the organic ferric sulfonate.

[0066] As described above, the polymerization solution may be prepared by mixing a monomer, etc., with a previously prepared oxidizer / dopant solution, or by mixing a previously prepared monomer composition with ferric organic sulfonate, a solvent, etc. Furthermore, the polymerization solution may be prepared by mixing a monomer, ferric organic sulfonate, a polyfunctional acrylate, and a solvent, etc.

[0067] <Electrolytic capacitor> The electrolytic capacitor of the present invention has the conductive polymer of the present invention as a solid electrolyte.

[0068] The electrolytic capacitor of the present invention includes aluminum electrolytic capacitors such as wound type aluminum electrolytic capacitors and laminated or flat type aluminum electrolytic capacitors; tantalum electrolytic capacitors; niobium electrolytic capacitors; and the like.

[0069] For example, in the case of a wound aluminum electrolytic capacitor, the capacitor element is preferably prepared by attaching a lead terminal to an anode having a dielectric layer formed by etching the surface of an aluminum foil and then chemically treating the anode, attaching a lead terminal to a cathode made of aluminum foil, and winding the anode with the lead terminals and the cathode with a separator interposed therebetween.

[0070] The above-mentioned capacitor element is used to manufacture a wound aluminum electrolytic capacitor, for example, as follows.

[0071] A solid electrolyte layer made of a conductive polymer is formed on the surface of the capacitor element by, for example, any of the above methods (b) to (f).Then, the capacitor element on which the solid electrolyte layer is formed is packaged with an exterior material to produce a wound aluminum electrolytic capacitor.

[0072] In the manufacture of electrolytic capacitors other than the above-mentioned wound aluminum electrolytic capacitor, for example, stacked or flat aluminum electrolytic capacitors, tantalum electrolytic capacitors, niobium electrolytic capacitors, etc., a capacitor element having an anode made of a porous body of a valve metal such as aluminum, tantalum, niobium, etc. and a dielectric layer made of an oxide film of the valve metal is used, and a solid electrolyte layer made of a conductive polymer is formed on the capacitor element by, for example, any of the above methods (b) to (f) in the same manner as in the case of the above-mentioned wound aluminum electrolytic capacitor. Then, a carbon paste or a silver paste is applied to the capacitor element with the solid electrolyte layer formed thereon, and the capacitor element is dried and then packaged to manufacture a stacked or flat aluminum electrolytic capacitor, a tantalum electrolytic capacitor, a niobium electrolytic capacitor, etc.

[0073] The preparation of the conductive polymer on the surface of the capacitor element can be repeated several times if necessary.

[0074] In addition, in manufacturing an electrolytic capacitor, as described above, a conductive polymer may be manufactured on a substrate, and then a layer may be formed on the conductive polymer using a dispersion liquid of a π-conjugated conductive polymer, thereby forming an electrolytic capacitor in which the two constitute a solid electrolyte.

[0075] The π-conjugated conductive polymer is a π-conjugated conductive polymer using a polymer anion as a dopant. The polymer anion is mainly composed of polymeric sulfonic acid, and specific examples thereof include polystyrene sulfonic acid, sulfonated polyester, phenolsulfonic acid novolac resin, and copolymers of styrene sulfonic acid and non-sulfonic acid monomers (methacrylic acid esters, acrylic acid esters, and unsaturated hydrocarbon-containing alkoxysilane compounds or their hydrolysates).

[0076] In addition, the solid electrolyte of the electrolytic capacitor may contain a conductive auxiliary liquid containing a high-boiling organic solvent having a boiling point of 150°C or higher, or a high-boiling organic solvent having a boiling point of 150°C or higher and an aromatic compound having at least one hydroxyl group or carboxyl group.

[0077] Examples of high-boiling organic solvents having a boiling point of 150°C or higher that can be used in the conductive auxiliary liquid include γ-butyrolactone (boiling point: 203°C), butanediol (boiling point: 230°C), dimethyl sulfoxide (boiling point: 189°C), sulfolane (boiling point: 285°C), N-methylpyrrolidone (boiling point: 202°C), dimethylsulfolane (boiling point: 233°C), ethylene glycol (boiling point: 198°C), diethylene glycol (boiling point: 244°C), triethyl phosphate (boiling point: 215°C), tributyl phosphate (289°C), triethylhexyl phosphate [215°C (4mmHg)], polyethylene glycol, and the like.

[0078] In addition, as the above-mentioned hydroxyl group (meaning a hydroxyl group bonded to a constituent carbon of an aromatic ring, and not meaning an -OH moiety in a carboxyl group, etc.) or aromatic compound having at least one carboxyl group, any of benzene-based compounds, naphthalene-based compounds, and anthracene-based compounds can be used. Specific examples thereof include, for example, hydroxybenzenecarboxylic acid, nitrophenol, dinitrophenol, trinitrophenol, aminonitrophenol, hydroxyanisole, hydroxydinitrobenzene, dihydroxydinitrobenzene, alkylhydroxyanisole, hydroxynitroanisole, hydroxynitrobenzenecarboxylic acid (i.e., hydroxynitrobenzoic acid), dihydroxynitrobenzenecarboxylic acid (i.e., dihydroxynitrobenzoic acid), phenol, dihydroxybenzene, trihydrophenyl ether, ... Examples of the hydroxybenzene include hydroxybenzene, dihydroxybenzene carboxylic acid, trihydroxybenzene carboxylic acid, hydroxybenzene dicarboxylic acid, dihydroxybenzene dicarboxylic acid, hydroxytoluene carboxylic acid, nitronaphthol, aminonaphthol, dinitronaphthol, hydroxynaphthalene carboxylic acid, dihydroxynaphthalene carboxylic acid, trihydroxynaphthalene carboxylic acid, hydroxynaphthalene dicarboxylic acid, dihydroxynaphthalene dicarboxylic acid, hydroxyanthracene, dihydroxyanthracene, trihydroxyanthracene, tetrahydroxyanthracene, hydroxyanthracene carboxylic acid, hydroxyanthracene dicarboxylic acid, dihydroxyanthracene dicarboxylic acid, tetrahydroxyanthracene dione, benzene carboxylic acid, benzene dicarboxylic acid, naphthalene carboxylic acid, and naphthalene dicarboxylic acid.

[0079] In addition, the high-boiling organic solvent having a boiling point of 150° C. or higher or the conductive auxiliary liquid may contain at least one binder selected from the group consisting of an epoxy compound or a hydrolysate thereof, a silane compound or a hydrolysate thereof, and a polyalcohol.

[0080] The electrolytic capacitor of the present invention can be used in the same applications as conventionally known electrolytic capacitors, but because it has excellent voltage resistance, which allows it to have a high capacity and low ESR, it can also be used in applications where such characteristics are required. The conductive polymer of the present invention is also suitable as a solid electrolyte for electrolytic capacitors. Furthermore, the oxidizing agent / dopant solution for producing a conductive polymer of the present invention and the monomer composition for producing a conductive polymer of the present invention are suitable for producing a conductive polymer that constitutes a solid electrolyte for an electrolytic capacitor that has excellent voltage resistance and low ERS. EXAMPLES

[0081] The present invention will be described in detail below with reference to examples, although the present invention is not limited to the following examples.

[0082] [Preparation of Oxidant and Dopant Solution] Example 1 As the polyfunctional acrylate, the compound represented by the above formula (2) 2 ~R 5 and a trifunctional acrylate represented by the above formula (2) in which one of R is hydrogen and the remaining three are acryloyl groups. 2 ~R 5 A mixture of a tetrafunctional acrylate in which all of the groups are acryloyl groups ("KAYARAD PET-30 (trade name)" manufactured by Nippon Kayaku Co., Ltd.) was used.

[0083] An oxidant and dopant solution was prepared by mixing ferric paratoluenesulfonate (PTS) in an amount to give a concentration of 60 mass %, the polyfunctional acrylate in an amount to give a concentration of 10 mass %, and ethanol.

[0084] Example 2 The multifunctional acrylate is represented by the above formula (2), 2 ~R 5 All of the above are represented by the formula (5) and the average value of n is 4. A tetrafunctional acrylate represented by the formula (2) and R 2 ~R 5one of which is an acryloyl group and the remaining three are groups represented by the above formula (5) where the average value of n is 4; and a tetrafunctional acrylate represented by the above formula (2) where R 2 ~R 5 and a tetrafunctional acrylate having a group represented by the above formula (2) in which two of the groups are acryloyl groups and the remaining two are groups represented by the above formula (5) and the average value of n is 4. 2 ~R 5 An oxidant and dopant solution was prepared in the same manner as in Example 1, except that three of the groups were acryloyl groups and the remaining one was changed to a mixture of a tetrafunctional acrylate having a group represented by the above formula (5) where the average value of n is 4 ("KAYARAD RP-1040 (product name)" manufactured by Nippon Kayaku Co., Ltd.).

[0085] Example 3 As the polyfunctional acrylate, the compound represented by the above formula (7) 16 ~R 21 and a pentafunctional acrylate represented by the above formula (7), in which one of the groups is hydrogen and the remaining five are acryloyl groups. 16 ~R 21 A mixture of a hexafunctional acrylate in which all of the groups are acryloyl groups ("KAYARAD DPHA (trade name)" manufactured by Nippon Kayaku Co., Ltd.) was used.

[0086] An oxidant and dopant solution was prepared by mixing PTS in an amount to give a concentration of 50% by mass, the above multifunctional acrylate in an amount to give a concentration of 10% by mass, and butanol.

[0087] Example 4 The multifunctional acrylate is represented by the above formula (7), 16 ~R 21 An oxidant and dopant solution was prepared in the same manner as in Example 3, except that all of the above were changed to a hexafunctional acrylate having a group represented by the above formula (5) and n being 2 ("KAYARAD DPEA-12 (product name)" manufactured by Nippon Kayaku Co., Ltd.).

[0088] Example 5 As the polyfunctional acrylate, the compound represented by the above formula (7) 16 ~R 21Four of the groups are acryloyl groups, and the remaining two are groups represented by the following formula (8) in which m is an average value of 5. A hexafunctional acrylate (manufactured by Nippon Kayaku Co., Ltd., "KAYARAD DPCA-20 (product name)") was used.

[0089] An oxidant and dopant solution was prepared by mixing ferric naphthalenesulfonate (NS) in an amount to give a concentration of 50 mass %, the above-mentioned polyfunctional acrylate in an amount to give a concentration of 1 mass %, and butanol.

[0090] Example 6 An oxidant and dopant solution was prepared in the same manner as in Example 5, except that the concentration of the multifunctional acrylate was changed to 10% by mass.

[0091] Example 7 An oxidant and dopant solution was prepared in the same manner as in Example 5, except that the concentration of NS was changed to 40% by mass and the concentration of the multifunctional acrylate was changed to 25% by mass.

[0092] Comparative Example 1 An oxidant and dopant solution was prepared by mixing PTS and butanol in amounts such that the concentration became 50% by mass.

[0093] Comparative Example 2 An oxidant and dopant solution was prepared in the same manner as in Example 3, except that a monofunctional acrylate having one acryloyl group in the molecule ("KAYARAD R-128H (product name)" manufactured by Nippon Kayaku Co., Ltd.) was used instead of the multifunctional acrylate.

[0094] Comparative Example 3 An oxidant and dopant solution was prepared in the same manner as in Example 3, except that a bifunctional acrylate having two acryloyl groups in the molecule ("KAYARAD NPGDA (product name)" manufactured by Nippon Kayaku Co., Ltd.) was used instead of the multifunctional acrylate.

[0095] The compositions of the oxidant / dopant solutions of Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1. In Comparative Examples 2 and 3, a monofunctional or difunctional acrylate is used instead of a polyfunctional acrylate, and the composition thereof is shown in the "polyfunctional acrylate" column in Table 1. In addition, the "ratio to ferric organic sulfonate" in the "polyfunctional acrylate" column in Table 1 means the ratio (parts by mass) of polyfunctional acrylate (however, in Comparative Examples 2 and 3, a monofunctional or difunctional acrylate is used) to 100 parts by mass of ferric organic sulfonate.

[0096] [Table 1]

[0097] [Preparation of electrolytic capacitor] Example 8 The aluminum foil with the surface etched was immersed in an aqueous solution of 12% by mass of ammonium adipate, and in this state, a voltage of 70 V was applied to the aluminum foil to form a dielectric layer on the surface of the aluminum foil to serve as an anode, to which a lead body was attached. A lead body was also attached to a cathode made of aluminum foil. The anode and cathode were stacked with a separator interposed therebetween and wound to produce a capacitor element for a wound aluminum electrolytic capacitor.

[0098] The above capacitor element was immersed in a monomer solution prepared by adding 80g of methanol to 20g of a 1:1 (mass ratio) mixture (monomer) of EDOT and butylated EDOT, and then dried at 50°C for 10 minutes after pulling up. The above capacitor element was then immersed in the oxidant and dopant solution of Example 1, pulled up, heated at 70°C for 2 hours, and further heated at 180°C for 1 hour to polymerize the monomer, forming a solid electrolyte layer made of a conductive polymer having a polymer skeleton of a copolymer of EDOT and butylated EDOT on the surface of the above capacitor element. The capacitor element was then exteriorized with an exterior body to produce a wound aluminum electrolytic capacitor with a set capacitance of 35μF or more and a set ESR of 19mΩ or less.

[0099] Examples 9 to 14 and Comparative Examples 4 to 6 A wound type aluminum electrolytic capacitor was produced in the same manner as in Example 8, except that the oxidant / dopant solution was changed to that in Examples 2-7 or Comparative Examples 1-3.

[0100] For the wound aluminum electrolytic capacitors of Examples 8 to 14 and Comparative Examples 4 to 6, the CAP (capacitance), ESR, and BDV (breakdown voltage) were measured by the following methods.

[0101] (CAP) The measurements were performed at 25° C. and 120 Hz using a Hewlett Packard LCR meter (4284A).

[0102] (ESR) The measurements were performed at 25° C. and 100 kHz using a Hewlett Packard LCR meter (4284A).

[0103] (BDV) The measurement was carried out using a Matsusada Precision Co., Ltd. "PRK650-2.5" at 25°C by increasing the voltage at a rate of 1 V / min.

[0104] The above measurements were performed on 10 samples for each sample. The results are shown in Table 2. In Table 2, the average values ​​of 10 measurements rounded to the first decimal place are shown for CAP and ESR, and the average values ​​of 10 measurements rounded to the nearest whole number are shown for BDV.

[0105] [Table 2]

[0106] As shown in Table 2, the wound aluminum electrolytic capacitors of Examples 8 to 14, which were obtained using an oxidizer / dopant solution to which was added an organic ferric sulfonate and a multifunctional acrylate having three or more polymerizable double bonds, and which had a conductive polymer containing a multifunctional acrylate or its polymer and an organic sulfonic acid as a dopant as a solid electrolyte, had a high BDV and excellent voltage resistance, and also had a low ESR, compared to the electrolytic capacitors of Comparative Examples 4 to 6, which had a conductive polymer that did not contain a multifunctional acrylate having three or more polymerizable double bonds or its polymer as a solid electrolyte.

[0107] [Preparation of Monomer Composition] Example 15 The same multifunctional acrylate as used in Example 1 was used, and EDOT in an amount to give a concentration of 20% by mass, the multifunctional acrylate in an amount to give a concentration of 10% by mass, and ethanol were mixed to prepare a monomer composition.

[0108] Example 16 The same multifunctional acrylate as used in Example 1 was used, and a monomer composition was prepared by mixing a 1:1 (mass ratio) mixture of EDOT and butylated EDOT in an amount to give a concentration of 20 mass%, the multifunctional acrylate in an amount to give a concentration of 10 mass%, and ethanol.

[0109] Example 17 A monomer composition was prepared in the same manner as in Example 15, except that the multifunctional acrylate was changed to the same one as that used in Example 2.

[0110] Example 18 The same multifunctional acrylate as used in Example 3 was used, and a monomer composition was prepared by mixing a 1:1 (mass ratio) mixture of EDOT and ethylated EDOT in an amount to give a concentration of 20 mass%, the multifunctional acrylate in an amount to give a concentration of 10 mass%, and ethanol.

[0111] Example 19 A monomer composition was prepared in the same manner as in Example 16, except that the multifunctional acrylate was changed to the same one as that used in Example 3.

[0112] Example 20 A monomer composition was prepared in the same manner as in Example 18, except that the multifunctional acrylate was changed to the same one as that used in Example 4.

[0113] Example 21 A monomer composition was prepared in the same manner as in Example 16, except that the multifunctional acrylate was changed to the same one as that used in Example 4.

[0114] Example 22 The same multifunctional acrylate as used in Example 5 was used, and a monomer composition was prepared by mixing a 1:1 (mass ratio) mixture of EDOT and propylated EDOT in an amount to give a concentration of 20 mass%, the multifunctional acrylate in an amount to give a concentration of 1 mass%, and ethanol.

[0115] Example 23 The same multifunctional acrylate as used in Example 5 was used, and a monomer composition was prepared by mixing a 1:1 (mass ratio) mixture of EDOT and butylated EDOT in an amount to give a concentration of 20 mass%, the multifunctional acrylate in an amount to give a concentration of 1 mass%, and ethanol.

[0116] Example 24 A monomer composition was prepared in the same manner as in Example 23, except that the concentration of the multifunctional acrylate was changed to 10% by mass.

[0117] Example 25 A monomer composition was prepared in the same manner as in Example 23, except that the concentration of the multifunctional acrylate was changed to 30% by mass.

[0118] Comparative Example 7 A monomer composition was prepared in the same manner as in Example 16, except that the polyfunctional acrylate was changed to the same one as that used in Comparative Example 2.

[0119] Comparative Example 8 A monomer composition was prepared in the same manner as in Example 16, except that the polyfunctional acrylate was changed to the same one as that used in Comparative Example 3.

[0120] The configurations of the monomer compositions of Examples 15 to 25 and Comparative Examples 7 and 8 are shown in Table 3. In Table 3, "EDOT / Et-EDOT" means a mixture of EDOT and ethylated EDOT, "EDOT / Pr-EDOT" means a mixture of EDOT and propylated EDOT, and "EDOT / Bu-EDOT" means a mixture of EDOT and butylated EDOT.

[0121] [Table 3]

[0122] [Preparation of electrolytic capacitor] Example 26 An oxidant and dopant solution was prepared by mixing PTS in an amount to give a concentration of 50% by mass with ethanol.

[0123] A capacitor element prepared in the same manner as in Example 8 was immersed in the monomer composition of Example 15, pulled out, and then dried at 50°C for 10 minutes. The capacitor element was then immersed in the oxidizer / dopant solution, pulled out, and then heated at 70°C for 2 hours and then heated at 180°C for 1 hour to polymerize the monomer, thereby forming a solid electrolyte layer made of a conductive polymer having an EDOT polymer as a polymer skeleton on the surface of the capacitor element. The capacitor element was then sheathed with an exterior body to prepare a wound aluminum electrolytic capacitor having a set capacitance of 35μF or more and a set ESR of 19mΩ or less.

[0124] Examples 27 to 32 A wound type aluminum electrolytic capacitor was produced in the same manner as in Example 26, except that the monomer compositions were changed to those in Examples 16 to 21.

[0125] Example 33 An oxidant and dopant solution was prepared in the same manner as in Example 26, except that PTS was changed to NS. Then, a wound aluminum electrolytic capacitor was produced in the same manner as in Example 26, except that the monomer composition was changed to that of Example 22 and the oxidant and dopant solution was changed to the above.

[0126] Examples 34 to 36 A wound type aluminum electrolytic capacitor was produced in the same manner as in Example 33, except that the monomer compositions were changed to those in Examples 23-25.

[0127] Comparative Example 9 A wound aluminum electrolytic capacitor was prepared in the same manner as in Example 26, except that a monomer solution prepared by mixing a 1:1 (mass ratio) mixture of EDOT and butylated EDOT in an amount to give a concentration of 20 mass% with ethanol was used instead of the monomer composition.

[0128] Comparative Example 10 A wound type aluminum electrolytic capacitor was produced in the same manner as in Example 26, except that the monomer composition was changed to that of Comparative Example 7.

[0129] Comparative Example 11 A wound type aluminum electrolytic capacitor was produced in the same manner as in Example 26, except that the monomer composition was changed to that of Comparative Example 8.

[0130] The CAP, ESR and BDV were measured for the wound aluminum electrolytic capacitors of Examples 26 to 36 and Comparative Examples 9 to 11 in the same manner as for the electrolytic capacitor of Example 8. These results are shown in Table 4. In Table 4, the "-" in the column for the monomer composition in Comparative Example 9 means that no monomer composition was used, but in this Comparative Example 9, as described above, an ethanol solution of a mixture of EDOT and butylated EDOT to which no multifunctional acrylate was added was used instead of the monomer composition.

[0131] [Table 4]

[0132] As shown in Table 4, the wound aluminum electrolytic capacitors of Examples 26 to 36, which were obtained using a monomer composition to which a multifunctional acrylate having three or more polymerizable double bonds was added, and in which a conductive polymer containing a multifunctional acrylate or its polymer and an organic sulfonic acid as a dopant was used as a solid electrolyte, had a high BDV and excellent voltage resistance, and also had a low ESR, compared to the electrolytic capacitors of Comparative Examples 9 to 11, which used a conductive polymer that did not contain a multifunctional acrylate having three or more polymerizable double bonds or its polymer as a solid electrolyte.

Claims

1. A conductive polymer comprising a polymer of thiophene or a derivative thereof, containing an organic sulfonic acid as a dopant, and a polyfunctional acrylate or a polymer thereof having three or more polymerizable double bonds in the molecule.

2. An oxidant / dopant solution for producing a conductive polymer, comprising an organic ferric sulfonate as an oxidant / dopant for producing a conductive polymer, water or a lower alcohol as a solvent, and a polyfunctional acrylate having three or more polymerizable double bonds in the molecule.

3. A monomer composition for producing a conductive polymer, comprising thiophene or a derivative thereof, which is a monomer for producing a conductive polymer, and a polyfunctional acrylate having three or more polymerizable double bonds in the molecule.

4. A method for producing a conductive polymer, comprising chemically oxidatively polymerizing thiophene or a derivative thereof in the presence of an organic ferric sulfonate and a polyfunctional acrylate having three or more polymerizable double bonds in the molecule.

5. 5. The method for producing a conductive polymer according to claim 4, which comprises chemically oxidizing and polymerizing thiophene or a derivative thereof in the presence of the oxidizing agent / dopant solution for producing a conductive polymer according to claim 2.

6. 5. The method for producing a conductive polymer according to claim 4, which comprises chemically oxidatively polymerizing thiophene or a derivative thereof using the monomer composition for producing a conductive polymer according to claim 3 in the presence of an organic ferric sulfonate.

7. An electrolytic capacitor containing a solid electrolyte, 10. An electrolytic capacitor comprising the conductive polymer according to claim 1 as said solid electrolyte.

8. 1. A method for producing an electrolytic capacitor containing a solid electrolyte, comprising:

5. A method for producing an electrolytic capacitor, comprising using, as the solid electrolyte, a conductive polymer produced by the method for producing a conductive polymer according to claim 4.

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