Oxidant and dopant solution for producing conductive polymer, method for producing conductive polymer, and method for producing electrolytic capacitor

Abstract

To provide a method for producing an electrolytic capacitor with high withstand voltage, a method for producing a conductive polymer usable as a component in the electrolytic capacitor, and an oxidant and dopant solution for producing the conductive polymer.SOLUTION: An oxidant and dopant solution for producing a conductive polymer according to the present invention contains ferric organic sulfonate serving as both an oxidant and a dopant for conductive polymer production, water or a lower alcohol as a solvent, and an oxetane compound or a ring-opened compound thereof. A method for producing a conductive polymer according to the present invention includes chemically oxidative polymerization of thiophene or a derivative thereof in the presence of the oxidant and dopant solution for conductive polymer production of the present invention. A method for producing an electrolytic capacitor according to the present invention is a method for producing an electrolytic capacitor having a solid electrolyte layer containing a conductive polymer on a surface of a capacitor element having a dielectric layer, the method comprising a step of producing the conductive polymer by the production method for conductive polymer according to the present invention.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Due to their high 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, electrolytic capacitors have been required to have larger capacitances, and in order to achieve this, it is preferable to increase the voltage resistance of the electrolytic capacitors, 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 oxidant / dopant solution for a conductive polymer to which a compound having a glycidyl group or a ring-opening compound thereof has been added (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

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

[0007] The present invention aims to provide a method for manufacturing an electrolytic capacitor with excellent voltage resistance by a method different from that described in Patent Documents 1 and 2, as well as a method for manufacturing a conductive polymer that can be used to form the electrolytic capacitor, and an oxidant / dopant solution for manufacturing 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 containing an organic sulfonic acid as a dopant, and a component derived from an oxetane compound or a component derived from a ring-opened compound of an oxetane compound.

[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 an oxetane compound or a ring-opened compound thereof.

[0010] Furthermore, the monomer composition for producing a conductive polymer of the present invention (hereinafter may be referred to as a "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 a "monomer"), and an oxetane compound or a ring-opened compound thereof.

[0011] The conductive polymer of the present invention can be produced by the production method of the present invention, which involves chemical oxidative polymerization of thiophene or a derivative thereof in the presence of an organic ferric sulfonate and an oxetane compound or a ring-opening compound thereof.

[0012] The electrolytic capacitor of the present invention is characterized by having 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. [Effects of the Invention]

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

[0015] <Conductive polymer> The conductive polymer of the present invention contains a polymer of thiophene or a derivative thereof containing an organic sulfonic acid as a dopant, and a component derived from an oxetane compound or a component derived from a ring-opened compound of an oxetane compound.

[0016] The conductive polymer has excellent voltage resistance due to the action of a component derived from an oxetane compound or a component derived from a ring-opened compound of an oxetane compound. Therefore, by using the conductive polymer as a solid electrolyte, an electrolytic capacitor with excellent voltage resistance can be obtained.

[0017] Examples of thiophene derivatives in thiophene or its derivatives, which are monomers for 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 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] In addition, R in the 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 referred to by its general name, "3,4-ethylenedioxythiophene," than by its IUPAC name. Therefore, in this specification, this "2,3-Dihydro-thieno[3,4-b][1,4]dioxine" is referred to as "3,4-ethylenedioxythiophene (EDOT)." Furthermore, R in the above general formula (1) 1 When 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 general formula (1). 1 The compound where R is a methyl group is designated by the IUPAC name "2-Methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine", but in this specification, this will be abbreviated and referred to as "methylated ethylenedioxythiophene (methylated EDOT)". 1The compound with an ethyl group has the IUPAC name "2-Ethyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine," but in this specification it is abbreviated to "ethylated ethylenedioxythiophene (ethylated EDOT)."

[0022] R in general formula (1) 1 The compound where R is a propyl group is expressed in IUPAC name as "2-propyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine", but in this specification, this is abbreviated to "propylated ethylenedioxythiophene (propylated EDOT)". 1 The IUPAC name for compounds with a butyl group is "2-butyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine," but this specification abbreviates it to "butylated ethylenedioxythiophene (butylated EDOT)." Furthermore, this specification abbreviates "2-alkyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine" 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]dioxin) and alkylated EDOT (i.e., 2-alkyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), 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 organic sulfonic acids that are dopants contained in conductive polymers include aromatic sulfonic acids such as benzenesulfonic acid or derivatives thereof, naphthalenesulfonic acid or derivatives thereof, and anthraquinonesulfonic acid or derivatives thereof; polymeric sulfonic acids such as polystyrenesulfonic acid, sulfonated polyester, phenolsulfonic acid novolac resin, and copolymers of styrenesulfonic acid and non-sulfonic acid monomers (such as methacrylic acid esters, acrylic acid esters, unsaturated hydrocarbon-containing alkoxysilane compounds, or hydrolysates thereof); 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 facilitate the production of electrolytic capacitors with excellent capacitor characteristics, such as lower ESR (equivalent series resistance) and higher capacitance, and can be used alone. Furthermore, chain sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid are more acidic than aromatic sulfonic acids, and are therefore preferably used in combination with the aromatic sulfonic acids rather than alone. Aromatic sulfonic acids tend to react well at low humidity (approximately 35% or less) to produce conductive polymers with good properties, but they tend to react poorly at high humidity (approximately 50% or more). The strong acidity of chain sulfonic acids can improve this and allow the reaction to proceed properly.

[0026] Furthermore, examples of 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. Furthermore, examples of naphthalenesulfonic acid derivatives in naphthalenesulfonic acid or its derivatives include naphthalenedisulfonic acid, naphthalenetrisulfonic acid, methylnaphthalenesulfonic acid, ethylnaphthalenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid. Furthermore, examples of anthraquinonesulfonic acid derivatives in anthraquinonesulfonic acid or its derivatives include anthraquinonedisulfonic acid and anthraquinonetrisulfonic 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 component derived from an oxetane compound or a component derived from a ring-opened compound of an oxetane compound. The conductive polymer of the present invention can be produced by chemical oxidative polymerization of thiophene or its derivative in the coexistence of an oxetane compound or its ring-opened compound. However, during this polymerization, the oxetane compound or its ring-opened compound may react to form a different compound. However, since it is difficult to determine the structure of the oxetane compound or its ring-opened compound after chemical oxidative polymerization of thiophene or its derivative, the present invention specifies the component as a component derived from an oxetane compound or a component derived from a ring-opened compound of an oxetane compound. The oxetane compound-derived component and the component derived from a ring-opened compound of an oxetane compound contained in the conductive polymer include not only the oxetane compound and its ring-opened compound, but also reaction products between these molecules and a polymer of these with thiophene or its derivative.

[0028] Examples of oxetane compounds used in the production of conductive polymers include those represented by the following general formula (2) and the following general formula (3).

[0029] [ka]

[0030] In the above general formula (2), R 2 and R 3 are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may contain oxygen.

[0031] [ka]

[0032] In the above general formula (3), R 4 is a hydrocarbon group containing one or two benzene rings and two carbon atoms that do not constitute the benzene rings, and which may contain oxygen, n is an integer of 1 to 3, and R 5 and R 6are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may contain oxygen.

[0033] Examples of ring-opened compounds of oxetane compounds used in the production of conductive polymers include compounds in which the ring of the oxetane compound represented by the above general formula (2) is opened (ring-opened compounds), and compounds in which the ring of the oxetane compound represented by the above general formula (3) is opened (ring-opened compounds).

[0034] Specific examples of the oxetane compound represented by the general formula (2) and its ring-opened compound include 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, (3-ethyl-3-oxetanyl)methoxymethyl methacrylate, 3-ethyl-3-(4-hydroxybutyloxymethyl)oxetane; ring-opened compounds thereof; and the like.

[0035] Specific examples of the oxetane compound represented by the general formula (3) and its ring-opened compound include 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl, bis[(3-ethyl-3-oxetanyl)methyl]isophthalate, and ring-opened compounds thereof.

[0036] When producing a conductive polymer, only one of the above-exemplified oxetane compounds and their ring-opened compounds may be used, or two or more of them may be used in combination.

[0037] The amount of organic sulfonic acid in the conductive polymer may be the amount contained in a conductive polymer obtained by satisfying the preferred ratio of ferric organic sulfonate to monomer, which will be described later in the description of the method for producing a conductive polymer. The content of a component derived from an oxetane compound or a component derived from a ring-opened compound of an oxetane compound in the conductive polymer may be the amount contained in a conductive polymer obtained by satisfying the preferred ratio of oxetane compound or its ring-opened compound to ferric organic sulfonate, which will be described later in the description of the method for producing a conductive polymer.

[0038] 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 an oxetane compound or a ring-opening compound thereof.

[0039] The ferric organic sulfonate functions as both 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 listed above as examples of dopants for conductive polymers.

[0040] The ferric organic sulfonate preferably has a molar ratio of iron to organic sulfonic acid 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 iron to organic sulfonic acid is preferably up to about 1:2, more preferably up to about 1:2.2, particularly up to about 1:2.4, and even more preferably up to about 1:2.75.

[0041] Conductive polymers can be produced by (a) preparing a polymerization solution containing the monomer thiophene or a derivative thereof, organic ferric sulfonate, and an oxetane compound or a ring-opening compound thereof, and then chemically oxidizing the monomer; (b) immersing a substrate (such as a capacitor element of an electrolytic capacitor) in the polymerization solution, then lifting it out, and then chemically oxidizing the monomer; (c) diluting the monomer with a solvent, then immersing the substrate in the monomer solution, then lifting it out and drying it, then immersing the substrate in an oxidant / dopant solution (described later), then lifting it out, and then chemically oxidizing the monomer; or (d) immersing a substrate in an oxidant / dopant solution, then lifting it out, and then chemically oxidizing the monomer. (e) a method in which the substrate is immersed in a monomer composition (described below), withdrawn, and dried, then immersed in a monomer (or a monomer solution), 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), withdrawn, and then dried, then immersed in a monomer composition (described below), and then chemically oxidatively polymerized the monomer; or (g) a method in which the substrate is immersed in a solution containing an organic ferric sulfonate and a solvent (water or a lower alcohol), withdrawn, and then dried, then immersed in a monomer composition (described below), and then chemically oxidatively polymerized the monomer. Chemical oxidative polymerization is carried out, for example, at 5 to 95°C for 1 to 72 hours.

[0042] In producing a conductive polymer, the molar ratio of organic ferric sulfonate to monomer is preferably organic ferric sulfonate:monomer=2:1 to 15:1. The content of the monomer in the polymerization solution is preferably, for example, 20 to 40 mass %. The content of organic ferric sulfonate in the polymerization solution is preferably, for example, 20 to 50 mass %.

[0043] Furthermore, in order to further increase the voltage resistance of the conductive polymer, the content (concentration) of the oxetane compound and its ring-opening compound in the polymerization solution is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. However, if the amount of the oxetane compound and its ring-opening compound in the polymerization solution is too large, there is a risk of the initial characteristics being reduced, so the content of the oxetane compound and its ring-opening compound in the polymerization solution is preferably 30% by mass or less, and more preferably 20% by mass or less.

[0044] In producing the conductive polymer, the ratio of the oxetane compound and its ring-opened compound to 100 parts by mass of the organic ferric sulfonate is preferably 0.2 to 50 parts by mass.

[0045] Thiophene and its derivatives, which serve as monomers, are liquid at room temperature and can be used as they are in polymerization. However, to facilitate smoother polymerization reaction, water or a lower alcohol may be used as a solvent in the polymerization solution. Examples of lower alcohols include alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, propanol, and butanol. The solvent for the polymerization solution may be one or more of the above-listed solvents.

[0046] When producing a conductive polymer, the oxidant and dopant solution of the present invention can be used, which contains an organic ferric sulfonate as an oxidant and dopant, water or a lower alcohol as a solvent, and an oxetane compound or a ring-opened compound thereof.

[0047] The solvent for the oxidant / dopant solution can be water or a lower alcohol (the same as the polymerization solution).

[0048] In the oxidant and dopant solution, from the viewpoint of further increasing the voltage resistance of the conductive polymer, the content (concentration) of the oxetane compound and its ring-opening compound is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. Note that if the amount of the oxetane compound and its ring-opening compound in the oxidant and dopant solution is too large, there is a risk of the initial characteristics being reduced, so the content of the oxetane compound and its ring-opening compound in the oxidant and dopant solution is preferably 30% by mass or less, and more preferably 20% by mass or less.

[0049] Furthermore, the content of the ferric organic sulfonate in the oxidant / dopant solution is preferably 20% by mass or more, more preferably 30% by mass or more, from the viewpoint of ensuring that the ferric organic sulfonate functions well as an oxidant during the synthesis of a conductive polymer and that an amount sufficient to function as a dopant is contained in the synthesized conductive polymer. However, if the amount of ferric organic sulfonate in the oxidant / dopant solution is too high, it may be difficult to dissolve the ferric organic sulfonate well in the solution. Therefore, the content of the ferric organic sulfonate in the oxidant / dopant solution is preferably 70% by mass or less, more preferably 65% by mass or less.

[0050] When a conductive polymer is produced using an oxidant / dopant solution, the above method (c) or (d) can be employed. Alternatively, thiophene or a derivative thereof may be added directly 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).

[0051] In addition, when producing a conductive polymer, the monomer composition of the present invention containing thiophene or a derivative thereof as a monomer and an oxetane compound or a ring-opened compound thereof can also be used.

[0052] The monomer composition may be composed only of thiophene or its derivative, and oxetane compound or its ring-opened compound, but water or a lower alcohol (the same as the polymerization solution) may also be used as a solvent.

[0053] In the monomer composition, from the viewpoint of further increasing the voltage resistance of the conductive polymer, the content (concentration) of the oxetane compound and its ring-opening compound is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. Note that if the amount of the oxetane compound and its ring-opening compound in the monomer composition is too large, there is a risk of the initial properties being reduced, so the content of the oxetane compound and its ring-opening compound in the monomer composition is preferably 40% by mass or less, more preferably 30% by mass or less.

[0054] The content of thiophene or its derivative in the monomer composition is preferably, for example, 10 to 80 mass %.

[0055] When a conductive polymer is produced using a monomer composition, the above method (e) or (f) can be employed. Alternatively, an organic ferric sulfonate may be added directly to the monomer composition, or a solution of the organic ferric sulfonate 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).

[0056] In the solution containing organic ferric sulfonate and water or a lower alcohol used in the above method (e) or (f), the concentration of the organic ferric sulfonate is preferably 30 to 65 mass %.

[0057] In addition to the above components, other additives may be added to the polymerization solution, the oxidant / dopant solution, and the monomer composition as needed. 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.

[0058] 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" refers to those having two or more siloxane bonds) and ring-opened compounds thereof.

[0059] 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.

[0060] 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.

[0061] The amount of the compound having a glycidyl group or its ring-opened compound used in producing the conductive polymer is preferably 5 to 100 parts by mass relative to 100 parts by mass of the organic ferric sulfonate.

[0062] As described above, the polymerization solution may be prepared by mixing a monomer or the like with a previously prepared oxidant / dopant solution, or by mixing a previously prepared monomer composition with an organic ferric sulfonate, a solvent, etc. Furthermore, the polymerization solution may be prepared by mixing a monomer, an organic ferric sulfonate, an oxetane compound or a ring-opened compound thereof, and a solvent, etc.

[0063] <Electrolytic capacitor> The electrolytic capacitor of the present invention has the conductive polymer of the present invention as a solid electrolyte.

[0064] 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.

[0065] 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 on which a dielectric layer is formed by etching the surface of an aluminum foil and then chemically treating it, and by attaching a lead terminal to a cathode made of aluminum foil, and then winding the anode with the lead terminal and the cathode with a separator interposed therebetween.

[0066] A wound aluminum electrolytic capacitor using the above capacitor element is manufactured, for example, as follows.

[0067] A solid electrolyte layer made of a conductive polymer is formed on the surface of the capacitor element by, for example, any of the methods (b) to (f) above.The capacitor element with the solid electrolyte layer formed thereon is then packaged with an exterior material to produce a wound aluminum electrolytic capacitor.

[0068] In the manufacture of electrolytic capacitors other than the above-mentioned wound-type aluminum electrolytic capacitor, such as stacked or flat-type aluminum electrolytic capacitors, tantalum electrolytic capacitors, and niobium electrolytic capacitors, a capacitor element having an anode made of a porous body of a valve metal such as aluminum, tantalum, or niobium 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 above-mentioned wound-type aluminum electrolytic capacitor. Then, carbon paste or silver paste is applied to the capacitor element with the solid electrolyte layer formed, and the capacitor element is dried and then packaged to produce a stacked or flat-type aluminum electrolytic capacitor, tantalum electrolytic capacitor, niobium electrolytic capacitor, etc.

[0069] The formation of the conductive polymer on the surface of the capacitor element can be repeated several times if necessary.

[0070] Furthermore, 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 of a π-conjugated conductive polymer, thereby forming an electrolytic capacitor in which both of them constitute a solid electrolyte.

[0071] The π-conjugated conductive polymer is a π-conjugated conductive polymer using a polymer anion as a dopant. This polymer anion is mainly composed of a 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 (such as methacrylic acid esters, acrylic acid esters, and unsaturated hydrocarbon-containing alkoxysilane compounds or their hydrolysates).

[0072] The solid electrolyte of the electrolytic capacitor may also 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.

[0073] 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), dimethyl sulfolane (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 (4 mmHg)], and polyethylene glycol.

[0074] Furthermore, as the above-mentioned hydroxyl group (which refers to a hydroxyl group bonded to a constituent carbon of an aromatic ring, and does not mean 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, and specific examples thereof include 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, trihydrobenzoic acid, ... hydroxybenzene, dihydroxybenzenecarboxylic acid, trihydroxybenzenecarboxylic acid, hydroxybenzenedicarboxylic acid, dihydroxybenzenedicarboxylic acid, hydroxytoluenecarboxylic acid, nitronaphthol, aminonaphthol, dinitronaphthol, hydroxynaphthalenecarboxylic acid, dihydroxynaphthalenecarboxylic acid, trihydroxynaphthalenecarboxylic acid, hydroxynaphthalene dicarboxylic acid, dihydroxynaphthalene dicarboxylic acid, hydroxyanthracene, dihydroxyanthracene, trihydroxyanthracene, tetrahydroxyanthracene, hydroxyanthracenecarboxylic acid, hydroxyanthracenedicarboxylic acid, dihydroxyanthracenedicarboxylic acid, tetrahydroxyanthracenedione, benzenecarboxylic acid, benzenedicarboxylic acid, naphthalenecarboxylic acid, and naphthalene dicarboxylic acid.

[0075] In addition, the high-boiling organic solvent or conductive auxiliary liquid having a boiling point of 150°C or higher may contain at least one binder selected from the group consisting of epoxy compounds or hydrolysates thereof, silane compounds or hydrolysates thereof, and polyalcohols.

[0076] The electrolytic capacitor of the present invention can be used in the same applications as conventional electrolytic capacitors, but because it has excellent voltage resistance and can therefore achieve high capacity, it is also suitable for applications requiring such characteristics. The conductive polymer of the present invention is also suitable as a solid electrolyte for electrolytic capacitors. Furthermore, the oxidant / 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 with excellent voltage resistance. [Example]

[0077] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0078] [Preparation of Oxidant and Dopant Solution] Example 1 An oxidant and dopant solution was prepared by mixing ferric paratoluenesulfonate (PTS) in an amount to give a concentration of 60 mass %, 3-methyl-3-hydroxymethyloxetane in an amount to give a concentration of 0.5 mass %, and water.

[0079] Example 2 An oxidant and dopant solution was prepared in the same manner as in Example 1, except that the concentration of 3-methyl-3-hydroxymethyloxetane was changed to 1 mass %.

[0080] Example 3 An oxidant and dopant solution was prepared by mixing PTS in an amount to give a concentration of 40 mass %, 3-ethyl-3-hydroxymethyloxetane in an amount to give a concentration of 3 mass %, and methanol.

[0081] Example 4 An oxidant and dopant solution was prepared in the same manner as in Example 3, except that (3-ethyl-3-oxetanyl)methoxymethyl methacrylate was used in place of 3-ethyl-3-hydroxymethyloxetane in an amount to give a concentration of 10 mass %, and ethanol was used in place of methanol.

[0082] Example 5 An oxidant and dopant solution was prepared by mixing ferric naphthalenesulfonate (NS) in an amount to give a concentration of 40% by mass, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl in an amount to give a concentration of 10% by mass, and ethanol.

[0083] Example 6 An oxidant and dopant solution was prepared by mixing NS in an amount to give a concentration of 40 mass %, 3-ethyl-3-(4-hydroxybutyloxymethyl)oxetane in an amount to give a concentration of 10 mass %, and butanol.

[0084] Example 7 An oxidant and dopant solution was prepared by mixing NS in an amount to give a concentration of 40 mass %, bis[(3-ethyl-3-oxetanyl)methyl]isophthalate in an amount to give a concentration of 20 mass %, and butanol.

[0085] Comparative Example 1 An oxidant and dopant solution (hereinafter sometimes referred to as "oxidant and dopant solution (X)") was prepared by mixing PTS in amounts to give a concentration of 40% by mass with ethanol.

[0086] The compositions of the oxidant and dopant solutions of Examples 1 to 7 and Comparative Example 1 are shown in Table 1. In Table 1, the "ratio to ferric organic sulfonate" in the oxetane compound column means the ratio (parts by mass) of oxetane compound to 100 parts by mass of ferric organic sulfonate. The descriptions in the oxetane compound column in Table 1 are as follows (the same applies to Table 3 described below): A: 3-methyl-3-hydroxymethyloxetane B: 3-ethyl-3-hydroxymethyloxetane C: (3-ethyl-3-oxetanyl) methoxymethyl methacrylate D: 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl E: 3-ethyl-3-(4-hydroxybutyloxymethyl)oxetane F: Bis[(3-ethyl-3-oxetanyl)methyl]isophthalate

[0087] [Table 1]

[0088] [Fabrication of electrolytic capacitors] Example 8 The surface-etched aluminum foil was immersed in a 12% by mass aqueous solution of ammonium adipate, and a voltage of 70 V was applied to the aluminum foil in this state to form a dielectric layer on the surface of the aluminum foil, forming an anode. A lead body was attached to the anode. A lead body was also attached to the aluminum foil cathode. The anode and cathode were stacked with a separator interposed between them and wound to produce a capacitor element for a wound aluminum electrolytic capacitor.

[0089] The capacitor element was immersed in a monomer solution prepared by adding 80 g of methanol to 20 g of a 1:1 (mass ratio) mixture (monomer) of EDOT and butylated EDOT. The capacitor element was then removed and dried at 50°C for 10 minutes. The capacitor element was then immersed in the oxidant / dopant solution of Example 1, removed, and heated at 70°C for 2 hours, then at 180°C for 1 hour to polymerize the monomer. A solid electrolyte layer composed of a conductive polymer with a copolymer of EDOT and butylated EDOT as the polymer backbone was formed on the surface of the capacitor element. The capacitor element was then packaged in an outer casing to produce a wound aluminum electrolytic capacitor with a set capacitance of 35 μF or more and a set ESR of 19 mΩ or less.

[0090] Examples 9 to 14 and Comparative Example 2 A wound aluminum electrolytic capacitor was fabricated in the same manner as in Example 8, except that the oxidant and dopant solution was changed to that of Examples 2 to 7 or Comparative Example 1.

[0091] For the wound aluminum electrolytic capacitors of Examples 8 to 14 and Comparative Example 2, the CAP (capacitance), ESR, and BDV (breakdown voltage) were measured by the following methods.

[0092] (CAP) Measurements were made at 25°C and 120 Hz using an LCR meter (4284A) manufactured by Hewlett Packard.

[0093] (ESR) Measurements were made at 25°C and 100 kHz using an LCR meter (4284A) manufactured by Hewlett Packard.

[0094] (BDV) Measurements were carried out using a Matsusada Precision "PRK650-2.5" at 25°C by increasing the voltage at a rate of 1 V / min.

[0095] The above measurements were carried out on 10 samples for each type of sample. The results are shown in Table 2. In Table 2, the CAP and ESR values are shown as average values of 10 measurements rounded to the nearest tenth, and the BDV values are shown as average values of 10 measurements rounded to the nearest tenth.

[0096] [Table 2]

[0097] 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 an organic ferric sulfonate and an oxetane compound had been added, and which had a conductive polymer solid electrolyte containing a component derived from the oxetane compound and an organic sulfonic acid dopant, had a higher BDV and excellent voltage resistance than the electrolytic capacitor of Comparative Example 2, which had a conductive polymer solid electrolyte that did not contain a component derived from the oxetane compound.

[0098] [Preparation of Monomer Composition] Example 15 A monomer composition was prepared by mixing EDOT in an amount to give a concentration of 19.9% by mass, 3-methyl-3-hydroxymethyloxetane in an amount to give a concentration of 0.1% by mass, and methanol.

[0099] Example 16 A monomer composition was prepared in the same manner as in Example 15, except that the concentration of EDOT was changed to 19.8% by mass and the concentration of 3-methyl-3-hydroxymethyloxetane was changed to 0.2% by mass.

[0100] Example 17 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 19.4 mass%, 3-ethyl-3-hydroxymethyloxetane in an amount to give a concentration of 0.6 mass%, and methanol.

[0101] Example 18 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 18% by mass, (3-ethyl-3-oxetanyl)methoxymethyl methacrylate in an amount to give a concentration of 2% by mass, and methanol.

[0102] Example 19 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 18% by mass, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl in an amount to give a concentration of 2% by mass, and methanol.

[0103] Example 20 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 16% by mass, 3-ethyl-3-(4-hydroxybutyloxymethyl)oxetane in an amount to give a concentration of 4% by mass, and methanol.

[0104] Example 21 A monomer composition was prepared by mixing a 1:1 (by mass) mixture of EDOT and butylated EDOT in an amount to give a concentration of 14% by mass, bis[(3-ethyl-3-oxetanyl)methyl]isophthalate in an amount to give a concentration of 6% by mass, and methanol.

[0105] The compositions of the monomer compositions of Examples 15 to 21 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.

[0106] [Table 3]

[0107] [Fabrication of electrolytic capacitors] Example 22 A capacitor element prepared in the same manner as in Example 8 was immersed in the monomer composition of Example 15, removed, and then dried at 50°C for 10 minutes. The capacitor element was then immersed in the same oxidant / dopant solution (X) prepared in Comparative Example 1, removed, and then heated at 70°C for 2 hours and then at 180°C for 1 hour to polymerize the monomer and form a solid electrolyte layer made of a conductive polymer with an EDOT polymer as the polymer backbone on the surface of the capacitor element. This capacitor element was then packaged in an outer casing to prepare a wound aluminum electrolytic capacitor with a set capacitance of 35 μF or more and a set ESR of 19 mΩ or less.

[0108] Examples 23 to 25 A wound aluminum electrolytic capacitor was produced in the same manner as in Example 22, except that the monomer compositions were changed to those in Examples 16 to 18.

[0109] Example 26 Except for changing PTS to NS, an oxidant and dopant solution (Y) was prepared in the same manner as in Comparative Example 1. Then, except for changing the monomer composition to that of Example 19 and changing the oxidant and dopant solution (X) to the oxidant and dopant solution (Y), a wound aluminum electrolytic capacitor was fabricated in the same manner as in Example 22.

[0110] Examples 27 and 28 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 Examples 20 and 21.

[0111] Comparative Example 3 A wound aluminum electrolytic capacitor was fabricated in the same manner as in Comparative Example 2, except that the oxidant and dopant solution (Y) was used instead of the oxidant and dopant solution (X).

[0112] The CAP, ESR, and BDV of the wound aluminum electrolytic capacitors of Examples 22 to 28 and Comparative Example 3 were measured in the same manner as the electrolytic capacitor of Example 8. These results are shown in Table 4. In Table 4, "X" in the column for "oxidant and dopant solution" refers to the oxidant and dopant solution (X), and "Y" refers to the oxidant and dopant solution (Y). In Table 4, "-" in the column for "monomer composition" in Comparative Example 3 indicates that no monomer composition was used. However, in Comparative Example 3, as described above, a mixture of EDOT and butylated EDOT without the addition of an oxetane compound was used instead of the monomer composition.

[0113] [Table 4]

[0114] As shown in Table 4, the wound aluminum electrolytic capacitors of Examples 22 to 28, which were obtained using a monomer composition to which an oxetane compound had been added and which had a conductive polymer solid electrolyte containing a component derived from the oxetane compound and an organic sulfonic acid dopant, had a higher BDV and excellent voltage resistance than the electrolytic capacitor of Comparative Example 3, which had a conductive polymer solid electrolyte that did not contain a component derived from the oxetane compound.

Claims

1. An oxidant and dopant solution for producing a conductive polymer, comprising an organic ferric sulfonate as an oxidant and dopant for producing a conductive polymer, water or a lower alcohol as a solvent, and an oxetane compound or a ring-opened compound thereof.

2. 2. The oxidizing agent / dopant solution for producing a conductive polymer according to claim 1, wherein the oxetane compound is represented by the following general formula (2) or (3): 【Chemical 1】 [In the above general formula (2), R ２ and R ３ are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms and which may contain oxygen. 【Chemistry 2】 [In the above general formula (3), R ４ is a hydrocarbon group containing one or two benzene rings and two carbon atoms that do not constitute the benzene rings, and which may contain oxygen, n is an integer of 1 to 3, and R ５ and R ６ are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms and which may contain oxygen.

3. 3. A method for producing a conductive polymer, comprising 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 1.

4. A method for manufacturing an electrolytic capacitor having a solid electrolyte layer containing a conductive polymer on the surface of a capacitor element having a dielectric layer, comprising: A method for producing an electrolytic capacitor, comprising the step of producing the conductive polymer by the method for producing a conductive polymer according to claim 3.

Images