Method for producing a conductive polymer, monomer composition for producing a conductive polymer, and method for producing an electrolytic capacitor

Abstract

To provide: an electrolytic capacitor having excellent voltage resistance and a production method thereof; an electrically conductive polymer which enables the electrolytic capacitor to be constituted and a production method thereof; and an oxidant and dopant solution and a monomer composition for producing the electrically conductive polymer.SOLUTION: The electrically conductive polymer of the present invention contains: a polymer of thiophene or a derivative thereof including an organic sulfonic acid as a dopant; and a component derived from an oxetane compound or a compound derived from a ring opened compound of an oxetane compound. The oxidant and dopant solution of the present invention for producing the electrically conductive polymer contains: a ferric organic sulfonate; water or a lower alcohol; and an oxetane compound or a ring-opened compound thereof, and the monomer composition of the present invention contains thiophene or a derivative thereof and an oxetane compound or a derivative thereof. Further, the electrolytic capacitor of the present invention has the electrically conductive polymer of the present invention as a solid electrolyte.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor having excellent withstand voltage properties 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 oxidizing agent / dopant solution and a monomer composition for manufacturing the conductive polymer.

Background Art

[0002] Due to its high conductivity, conductive polymers are used as electrolytes (solid electrolytes) in, for example, aluminum electrolytic capacitors, tantalum electrolytic capacitors, niobium electrolytic capacitors, etc.

[0003] As the conductive polymer in this application, for example, those obtained by chemically oxidizing or electrolytically oxidizing thiophene or its derivatives are used.

[0004] In recent years, there has been a demand for increasing the capacitance of electrolytic capacitors. To achieve this, for example, it is preferable to increase the withstand voltage properties of the electrolytic capacitor.

[0005] As a technique for increasing the withstand voltage properties of electrolytic capacitors, the present applicant has proposed a method using a monomer for producing a conductive polymer in which 3,4-ethylenedioxythiophene and alkylated ethylenedioxythiophene are mixed, and a method of polymerizing a conductive polymer using an oxidizing agent / dopant solution for a conductive polymer to which a compound having a glycidyl group or a ring-opened compound thereof is added (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention provides an electrolytic capacitor excellent in withstand voltage and a method for manufacturing the same by a method different from those of Patent Documents 1 and 2, and also provides a conductive polymer capable of constituting the electrolytic capacitor and a method for manufacturing the same, and an oxidizing agent / dopant solution and a monomer composition for manufacturing the conductive polymer.

Means for Solving the Problems

[0008] The conductive polymer of the present invention is characterized by containing a polymer of thiophene or its derivative 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] Further, the oxidizing agent / dopant solution for producing a conductive polymer of the present invention (hereinafter, may be referred to as "oxidizing agent / dopant solution") contains ferric bis(organic sulfonate) which is an oxidizing agent / dopant for producing a conductive polymer (hereinafter, may be referred to as "oxidizing agent / 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 "monomer composition") is characterized by containing thiophene or its derivative which is a monomer for producing a conductive polymer (hereinafter, may be referred to as "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 in which thiophene or its derivative is chemically oxidative polymerized in the presence of ferric bis(organic sulfonate) and an oxetane compound or a ring-opened compound thereof.

[0012] In addition, 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 manufactured by the manufacturing method of the present invention that uses the conductive polymer manufactured by the manufacturing method of the conductive polymer of the present invention as a solid electrolyte.

Effects of the Invention

[0014] According to the present invention, it is possible to provide an electrolytic capacitor excellent in withstand voltage, a manufacturing method thereof, a conductive polymer that can constitute the electrolytic capacitor and a manufacturing method thereof, and an oxidizing agent / dopant solution and a monomer composition for manufacturing the conductive polymer.

Modes for Carrying Out 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 above conductive polymer has excellent withstand voltage characteristics 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 above conductive polymer as a solid electrolyte, an electrolytic capacitor excellent in withstand voltage can be obtained.

[0017] As derivatives of thiophene in thiophene or its derivatives which are monomers of polymers of thiophene or its derivatives constituting a conductive polymer, for example, 3,4-ethylenedioxythiophene (EDOT), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene, and alkylated ethylenedioxythiophene (alkylated EDOT) obtained by modifying the above 3,4-ethylenedioxythiophene with an alkyl group can be mentioned. The number of carbon atoms of the alkyl group or alkoxy group is preferably 1 or more, preferably 16 or less, more preferably 10 or less, and even more preferably 4 or less.

[0018] Regarding the alkylated EDOT obtained by modifying the above EDOT with an alkyl group in detail, EDOT and alkylated EDOT correspond to the compounds represented by the following general formula (1).

[0019]

Chemical formula

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

[0021] And the compound in which R 1 in the above general formula (1) is hydrogen is EDOT. When expressed by its IUPAC name, it is "2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine", but this compound is more often expressed by the common 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 expressed as "3,4-ethylenedioxythiophene (EDOT)". And R 1When it is an alkyl group, the alkyl group preferably has 1 to 10 carbon atoms, particularly preferably 1 to 4 carbon atoms. That is, as the alkyl group, a methyl group, an ethyl group, a propyl group, and a butyl group are particularly preferred. Specifically exemplifying them, R in the general formula (1) 1 The compound in which 1 is a methyl group, when expressed by the IUPAC name, is "2-Methyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine", but in this specification, hereinafter, this is simplified and expressed as "methylated ethylenedioxythiophene (methylated EDOT)". R in the general formula (1) 1 The compound in which 1 is an ethyl group, when expressed by the IUPAC name, is "2-Ethyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine", but in this specification, this is simplified and expressed as "ethylated ethylenedioxythiophene (ethylated EDOT)".

[0022] R in the general formula (1) 1 The compound in which 1 is a propyl group, when expressed by the IUPAC name, is "2-Propyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine", but in this specification, this is simplified and expressed as "propylated ethylenedioxythiophene (propylated EDOT)". And R in the general formula (1) 1The compound with a butyl group, when expressed by its IUPAC name, is "2-Butyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine", but in this specification, it is simplified and expressed as "butylated ethylenedioxythiophene (butylated EDOT)". Also, "2-alkyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine" is simplified and expressed as "alkylated ethylenedioxythiophene (alkylated EDOT)" in this specification. Among these alkylated EDOTs, methylated EDOT, ethylated EDOT, propylated EDOT, and butylated EDOT are preferred.

[0023] And it is preferable to use a mixture of EDOT (that is, 2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine) and alkylated EDOT (that is, 2-alkyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxine). The mixing ratio is preferably 0.05:1 to 1:0.1 in molar ratio, 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.

[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 its derivatives, naphthalenesulfonic acid or its derivatives, anthraquinonesulfonic acid or its derivatives; polymeric sulfonic acids such as polystyrenesulfonic acid, sulfonated polyester, phenolsulfonic acid novolak resin, copolymers of styrenesulfonic acid and non-sulfonic acid monomers (such as methacrylic acid esters, acrylic acid esters, unsaturated hydrocarbon-containing alkoxysilane compounds or their hydrolyzates); chain sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid; and the like.

[0025] Among these, aromatic sulfonic acids in particular are preferable because they are more likely to produce electrolytic capacitors with excellent capacitor characteristics, such as lower ESR (equivalent series resistance) and larger capacitance, and can be used alone. Chain sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid have a higher acidity than aromatic sulfonic acids, and thus it is preferable to use them in combination with the above-mentioned aromatic sulfonic acids rather than alone. That is, although aromatic sulfonic acids tend to produce conductive polymers with good characteristics due to the proper progress of the reaction under low humidity (humidity of about 35% or less), they have the property that the reaction hardly progresses under high humidity (humidity of about 50% or more). Therefore, the strong acidity of chain sulfonic acids can be used to improve this situation and allow the reaction to proceed properly.

[0026] In addition, examples of benzene sulfonic acid derivatives in benzene sulfonic acid or its derivatives include toluene sulfonic acid, ethylbenzene sulfonic acid, propylbenzene sulfonic acid, butylbenzene sulfonic acid, dodecylbenzene sulfonic acid, methoxybenzene sulfonic acid, ethoxybenzene sulfonic acid, propoxybenzene sulfonic acid, butoxybenzene sulfonic acid, phenol sulfonic acid, cresol sulfonic acid, benzene disulfonic acid, and the like. Further, examples of naphthalene sulfonic acid derivatives in naphthalene sulfonic acid or its derivatives include naphthalene disulfonic acid, naphthalene trisulfonic acid, methylnaphthalene sulfonic acid, ethylnaphthalene sulfonic acid, propylnaphthalene sulfonic acid, butylnaphthalene sulfonic acid, and the like. Also, examples of anthraquinone sulfonic acid derivatives in anthraquinone sulfonic acid or its derivatives include anthraquinone disulfonic acid, anthraquinone trisulfonic acid, and the like. Among these aromatic sulfonic acids, toluene sulfonic acid, methoxybenzene sulfonic acid, phenol sulfonic acid, naphthalene sulfonic acid, naphthalene trisulfonic acid, etc. are preferable, para-toluene sulfonic acid, methoxybenzene sulfonic acid, naphthalene sulfonic acid are more preferable, and para-toluene sulfonic acid, naphthalene sulfonic acid are even more preferable.

[0027] The conductive polymer contains a component derived from an oxetane compound or a component derived from a ring-opening compound of the oxetane compound. The conductive polymer of the present invention can be produced by chemically oxidizing and polymerizing thiophene or its derivative in the coexistence of an oxetane compound or its ring-opening compound. However, it is possible that the oxetane compound or its ring-opening compound reacts to form another compound during this polymerization. However, since it is difficult to grasp the structure in which the oxetane compound or its ring-opening compound exists after the chemical oxidative polymerization of thiophene or its derivative, in the present invention, it is specified as a component derived from an oxetane compound or a component derived from a ring-opening compound of the oxetane compound. The components derived from the oxetane compound and the ring-opening compound of the oxetane compound contained in the conductive polymer include, in addition to the oxetane compound and its ring-opening compound, reaction products of these molecules with each other, and reaction products of these with the polymer of thiophene or its derivative.

[0028] Examples of the oxetane compound used for producing the conductive polymer include those represented by the following general formula (2) and the following general formula (3).

[0029]

Chemical formula

[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 and may contain oxygen.

[0031]

Chemical formula

[0032] In the above general formula (3), R 4 contains one or two benzene rings, two carbons not constituting the benzene ring, and is a hydrocarbon group that may contain oxygen. n is an integer from 1 to 3, and R 5 and R6 is each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may contain oxygen.

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

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

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

[0036] In the production of the conductive polymer, only one of the above-exemplified oxetane compounds and its ring-opening compound may be used, or two or more thereof may be used in combination.

[0037] The amount of the organic sulfonic acid in the conductive polymer may be an amount contained in the conductive polymer obtained by satisfying the preferred ratio of the ferric organic sulfonate and the monomer described in the production method of the conductive polymer described later. Further, the content of the component derived from the oxetane compound or the component derived from the ring-opening compound of the oxetane compound in the conductive polymer may be an amount contained in the conductive polymer obtained by satisfying the preferred ratio of the oxetane compound or its ring-opening compound to the ferric organic sulfonate described in the production method of the conductive polymer described later.

[0038] The conductive polymer of the present invention can be produced by chemically oxidatively polymerizing thiophene or its derivative in the presence of ferric organic sulfonate and an oxetane compound or its ring-opened compound.

[0039] Ferric organic sulfonate functions as an oxidizing agent and a dopant for producing the conductive polymer. Examples of the organic sulfonic acid constituting the ferric organic sulfonate include the various organic sulfonic acids exemplified above as dopants for the conductive polymer.

[0040] Ferric organic sulfonate preferably has an organic sulfonic acid molar ratio to iron of less than 1:3. This is because by reducing the organic sulfonic acid molar ratio to iron to less than 1:3, which is its stoichiometric molar ratio, the reaction rate of the ferric organic sulfonate can be slightly reduced. The organic sulfonic acid molar ratio 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.

[0041] A conductive polymer can be produced by the following methods: (a) preparing a polymerization solution containing (a) thiophene or its derivative as a monomer, ferric organosulfonate, and an oxetane compound or its ring-opened compound, and subjecting the monomer to chemical oxidative polymerization; (b) immersing a substrate (such as a capacitor element of an electrolytic capacitor) in the above polymerization solution, pulling it out, and then subjecting the monomer to chemical oxidative polymerization; (c) diluting the monomer with a solvent, immersing the substrate in the monomer solution, pulling it out and drying it, then immersing the substrate in an oxidizing agent-cum-dopant solution (described later), pulling it out, and then subjecting the monomer to chemical oxidative polymerization; (d) immersing the substrate in an oxidizing agent-cum-dopant solution, pulling it out and drying it, then immersing the substrate in a monomer (or monomer solution), pulling it out, and then subjecting the monomer to chemical oxidative polymerization; (e) immersing the substrate in a monomer composition (described later), pulling it out and drying it, then immersing the substrate in a solution containing ferric organosulfonate and a solvent (water or lower alcohol), pulling it out, and then subjecting the monomer to chemical oxidative polymerization; (f) immersing the substrate in a solution containing ferric organosulfonate and a solvent (water or lower alcohol), pulling it out and drying it, then immersing the substrate in a monomer composition (described later), pulling it out, and then subjecting the monomer to chemical oxidative polymerization; etc. Chemical oxidative polymerization is carried out, for example, at 5 to 95 °C for 1 to 72 hours.

[0042] In producing the conductive polymer, it is preferable that the molar ratio of ferric organosulfonate to the monomer is ferric organosulfonate: monomer = 2:1 to 15:1. Also, the content of the monomer in the polymerization solution is preferably, for example, 20 to 40% by mass. Further, the content of ferric organosulfonate in the polymerization solution is preferably, for example, 20 to 50% by mass.

[0043] Furthermore, in the polymerization solution, from the viewpoint of further enhancing the withstand voltage of the conductive polymer, the content (concentration) of the oxetane compound and its ring-opened compound is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. In addition, if the amount of the oxetane compound and its ring-opened compound in the polymerization solution is too large, the initial characteristics may deteriorate. Therefore, the content of the oxetane compound and its ring-opened compound in the polymerization solution is preferably 30% by mass or less, and more preferably 20% by mass or less.

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

[0045] Thiophene and its derivatives that serve as monomers are liquid at room temperature, so they can be used as they are in the polymerization. However, in order to make the polymerization reaction proceed more smoothly, water or a lower alcohol may be used as a solvent in the polymerization solution. Examples of the lower alcohol include alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol, and butanol. As the solvent of the polymerization solution, only one of the various solvents exemplified above may be used, or two or more thereof may be used.

[0046] In the production of the conductive polymer, the oxidizing agent-cum-dopant solution of the present invention containing ferric organic sulfonate as an oxidizing agent-cum-dopant, water or a lower alcohol as a solvent, and an oxetane compound or its ring-opened compound can be used.

[0047] As the solvent of the oxidizing agent-cum-dopant solution, water or a lower alcohol (the same as the polymerization solution) can be used.

[0048] In the oxidizing agent-cum-dopant solution, from the viewpoint of further enhancing the withstand voltage of the conductive polymer, the content (concentration) of the oxetane compound and its ring-opened compound is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. In addition, if the amount of the oxetane compound and its ring-opened compound in the oxidizing agent-cum-dopant solution is too large, the initial characteristics may deteriorate. Therefore, the content of the oxetane compound and its ring-opened compound in the oxidizing agent-cum-dopant solution is preferably 30% by mass or less, more preferably 20% by mass or less.

[0049] Furthermore, the content of ferric organic sulfonate in the oxidizing agent-cum-dopant solution is preferably 20% by mass or more, more preferably 30% by mass or more, from the viewpoint of enabling the function as an oxidizing agent during the synthesis of the conductive polymer to be exhibited well and enabling an amount sufficient to act as a dopant to be contained in the synthesized conductive polymer. However, if the amount of ferric organic sulfonate in the oxidizing agent-cum-dopant solution is too large, it may be difficult to dissolve ferric organic sulfonate well in the solution. Therefore, the content of ferric organic sulfonate in the oxidizing agent-cum-dopant solution is preferably 70% by mass or less, more preferably 65% by mass or less.

[0050] When producing a conductive polymer using the oxidizing agent-cum-dopant solution, in addition to the method of (c) or (d) above, thiophene or its derivative may be added as it is to the oxidizing agent-cum-dopant solution, or a solution obtained by diluting thiophene or its derivative with water or a lower alcohol may be added to prepare a polymerization solution, which may then be subjected to the method of (a) or (b) above.

[0051] Also, in the production of the conductive polymer, the monomer composition of the present invention containing thiophene or its derivative as a monomer and an oxetane compound or its ring-opened compound can also be used.

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

[0053] In the monomer composition, from the viewpoint of further enhancing the withstand voltage property of the conductive polymer, the content (concentration) of the oxetane compound and its ring-opened compound is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. In addition, if the amount of the oxetane compound and its ring-opened compound in the monomer composition is too large, the initial properties may deteriorate. Therefore, the content of the oxetane compound and its ring-opened compound in the monomer composition is preferably 40% by mass or less, and more preferably 30% by mass or less.

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

[0055] When producing a conductive polymer using the monomer composition, in addition to the methods (e) or (f) above, ferric organic sulfonate can be directly added to the monomer composition, or a solution obtained by diluting ferric organic sulfonate with water or a lower alcohol can be added to prepare a polymerization solution, which may then be subjected to the methods (a) or (b) above.

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

[0057] In addition to the above components, other additives may be added to the polymerization solution, the oxidizing agent-cum-dopant solution, and the monomer composition as required. Examples of such additives include compounds having a glycidyl group (epoxy group) or their ring-opened compounds; polymerized compounds such as silane coupling agents; polymers such as polysiloxane, alcohol-soluble resins, and polyethylene glycol; and the like.

[0058] Examples of the compound having a glycidyl group or its ring-opened compound include the following monoglycidyl compounds, the following diglycidyl compounds, glycerin diglycidyl ether, diglycerin tetraglycidyl ether, alcohol-soluble epoxy resin, alcohol-soluble polyglycerin polyglycidyl, and their ring-opened compounds, epoxy polysiloxane (the above-mentioned "polysiloxane" means "having two or more siloxane bonds") or its ring-opened compound, etc.

[0059] Examples of the above-mentioned monoglycidyl compounds include epoxypropanol (i.e., glycidol), methyl glycidyl ether, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, epoxybutane (i.e., glycidyl methane), epoxy pentane (i.e., glycidyl ethane), epoxyhexane (i.e., glycidyl propane), epoxyheptane (i.e., glycidyl butane), epoxyoctane (i.e., glycidyl pentane), glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, glycidyl methacrylate, etc.

[0060] Examples of the above-mentioned diglycidyl compounds 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, polypropylene glycol diglycidyl ether, etc.

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

[0062] As described above, the polymerization solution may be prepared by mixing a monomer or the like with an oxidizing agent / dopant solution prepared in advance, or by mixing ferric organic sulfonate, a solvent, or the like with a monomer composition prepared in advance. Further, a polymerization solution may be prepared by mixing a monomer, ferric organic sulfonate, an oxetane compound or its ring-opened compound, a solvent, and the like.

[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 aluminum electrolytic capacitors, laminated or flat aluminum electrolytic capacitors; tantalum electrolytic capacitors; niobium electrolytic capacitors; and the like.

[0065] For example, in the case of a wound aluminum electrolytic capacitor, as the capacitor element, after etching the surface of an aluminum foil and then performing a forming treatment to form a dielectric layer, a lead terminal is attached to the anode, and a lead terminal is attached to the cathode made of an aluminum foil. It is preferable to use a wound product of the anode and cathode with lead terminals via a separator.

[0066] And the production of the wound aluminum electrolytic capacitor using the above capacitor element is performed, for example, as follows.

[0067] On the surface of the above capacitor element, a solid electrolyte layer made of a conductive polymer is formed by, for example, any of the methods (b) to (f) above. Then, the capacitor element with the solid electrolyte layer formed is externally 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 aluminum electrolytic capacitor, for example, multilayer or flat aluminum electrolytic capacitors, tantalum electrolytic capacitors, niobium electrolytic capacitors, etc., an anode made of a porous body of valve metals such as aluminum, tantalum, niobium, etc. is used as a capacitor element, and a dielectric layer made of an oxide film of these valve metals is used. The capacitor element is formed with a solid electrolyte layer made of a conductive polymer by, for example, any of the above-mentioned methods (b) to (f) in the same manner as in the case of the wound aluminum electrolytic capacitor. Then, a carbon paste or a silver paste is applied to the capacitor element having the solid electrolyte layer, dried, and then externally packaged to manufacture multilayer or flat aluminum electrolytic capacitors, tantalum electrolytic capacitors, niobium electrolytic capacitors, etc.

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

[0070] Also, in the manufacture of electrolytic capacitors, as described above, after manufacturing a conductive polymer on a substrate, a layer may be formed on the conductive polymer using a dispersion of a π-conjugated conductive polymer, and an electrolytic capacitor may be formed in which a solid electrolyte is composed of both of them.

[0071] As the above-mentioned π-conjugated conductive polymer, a π-conjugated conductive polymer using a polymer anion as a dopant is used. This polymer anion is mainly composed of a polymer sulfonic acid. Specific examples thereof include, for example, polystyrene sulfonic acid, sulfonated polyester, phenol sulfonic acid novolak 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 hydrolyzates).

[0072] In addition, the solid electrolyte of the electrolytic capacitor can also contain a conductive auxiliary liquid including a high-boiling organic solvent with a boiling point of 150°C or higher or a high-boiling organic solvent with a boiling point of 150°C or higher and an aromatic compound having at least one hydroxyl group or carboxyl group.

[0073] Examples of the high-boiling organic solvent with 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)], polyethylene glycol, and the like.

[0074] In addition, as the aromatic compound having at least one hydroxyl group (referring to the hydroxyl group bonded to the constituent carbon of the aromatic ring, not meaning the -OH moiety such as in the carboxyl group) or carboxyl group, any of benzene-based, naphthalene-based, 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, trihydroxybenzene, dihydroxybenzenecarboxylic acid, trihydroxybenzenecarboxylic acid, hydroxybenzene dicarboxylic acid, dihydroxybenzene dicarboxylic acid, hydroxytoluene carboxylic acid, nitronaphthol, aminonaphthol, dinitronaphthol, hydroxynaphthalenecarboxylic acid, dihydroxynaphthalenecarboxylic acid, trihydroxynaphthalenecarboxylic acid, hydroxynaphthalene dicarboxylic acid, dihydroxynaphthalene dicarboxylic acid, hydroxyanthracene, dihydroxyanthracene, trihydroxyanthracene, tetrahydroxyanthracene, hydroxyanthracenecarboxylic acid, hydroxyanthracene dicarboxylic acid, dihydroxyanthracene dicarboxylic acid, tetrahydroxyanthraquinone, benzenecarboxylic acid, benzene dicarboxylic acid, naphthalenecarboxylic acid, naphthalene dicarboxylic acid, and the like.

[0075] In addition, at least one binder selected from the group consisting of an epoxy compound or its hydrolyzate, a silane compound or its hydrolyzate, and a polyalcohol can also be contained in the high-boiling organic solvent or the conductive auxiliary liquid having a boiling point of 150°C or higher.

[0076] The electrolytic capacitor of the present invention can be applied to the same uses as the conventionally known electrolytic capacitors, but has excellent withstand voltage characteristics and can thereby achieve a high capacitance, so it can also be preferably applied to uses that require such characteristics. Further, the conductive polymer of the present invention is suitable as a solid electrolyte of an electrolytic capacitor. Furthermore, the oxidizing agent-cum-dopant solution for producing the conductive polymer of the present invention and the monomer composition for producing the conductive polymer of the present invention are suitable for producing a conductive polymer that constitutes a solid electrolyte of an electrolytic capacitor having excellent withstand voltage characteristics.

Examples

[0077] Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

[0078] 〔Preparation of oxidizing agent-cum-dopant solution〕 Example 1 Ferric p-toluenesulfonate (PTS) in an amount such that the concentration becomes 60% by mass, 3-methyl-3-hydroxymethyloxetane in an amount such that the concentration becomes 0.5% by mass, and water were mixed to prepare an oxidizing agent-cum-dopant solution.

[0079] Example 2 An oxidizing agent-cum-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% by mass.

[0080] Example 3 PTS in an amount such that the concentration becomes 40% by mass, 3-ethyl-3-hydroxymethyloxetane in an amount such that the concentration becomes 3% by mass, and methanol were mixed to prepare an oxidizing agent-cum-dopant solution.

[0081] Example 4 An oxidizing agent-cum-dopant solution was prepared in the same manner as in Example 3, except that (3-ethyl-3-oxetanyl)methoxymethyl methacrylate in an amount such that the concentration becomes 10% by mass was used instead of 3-ethyl-3-hydroxymethyloxetane, and ethanol was used instead of methanol.

[0082] Example 5 Ferric naphthalenesulfonate (NS) in an amount such that the concentration becomes 40% by mass, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl in an amount such that the concentration becomes 10% by mass, and ethanol were mixed to prepare an oxidizing agent / dopant solution.

[0083] Example 6 NS in an amount such that the concentration becomes 40% by mass, 3-ethyl-3-(4-hydroxybutyloxymethyl)oxetane in an amount such that the concentration becomes 10% by mass, and butanol were mixed to prepare an oxidizing agent / dopant solution.

[0084] Example 7 NS in an amount such that the concentration becomes 40% by mass, bis[(3-ethyl-3-oxetanyl)methyl]isophthalate in an amount such that the concentration becomes 20% by mass, and butanol were mixed to prepare an oxidizing agent / dopant solution.

[0085] Comparative Example 1 p-Toluenesulfonic acid (PTS) in an amount such that the concentration becomes 40% by mass and ethanol were mixed to prepare an oxidizing agent / dopant solution [hereinafter sometimes referred to as "oxidizing agent / dopant solution (X)"].

[0086] The compositions of the oxidizing agent / dopant solutions of Examples 1 to 7 and Comparative Example 1 are shown in Table 1. In the column of the oxetane compound in Table 1, the "ratio to ferric organic sulfonate" means the ratio (parts by mass) of the oxetane compound to 100 parts by mass of ferric organic sulfonate. The descriptions in the column of the oxetane compound in Table 1 are as follows (the same applies to Table 3 described later). 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 capacitor〕 Example 8 An aluminum foil with its surface etched was immersed in an aqueous ammonium adipate solution with a concentration of 12% by mass. With 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 as an anode, and a lead body was attached to this anode. Also, a lead body was attached to a cathode made of aluminum foil. These anode and cathode were overlapped with each other via a separator and wound to fabricate a capacitor element for a wound aluminum electrolytic capacitor.

[0089] The above 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, pulled out, and then dried at 50 °C for 10 minutes. Then, the above capacitor element was immersed in the oxidizing agent and dopant solution of Example 1, pulled out, heated at 70 °C for 2 hours, and further heated at 180 °C for 1 hour to polymerize the monomer, thereby forming a solid electrolyte layer made of a conductive polymer having a copolymer of EDOT and butylated EDOT as a polymer backbone on the surface of the above capacitor element. This capacitor element was externally packaged to fabricate 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 oxidizing agent 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, CAP (capacitance), ESR, and BDV (breakdown voltage) were measured by the following methods, respectively.

[0092] (CAP) Using an LCR meter (4284A) manufactured by HEWLETT PACKARD, the measurement was carried out at 120 Hz under the condition of 25°C.

[0093] (ESR) Using an LCR meter (4284A) manufactured by HEWLETT PACKARD, the measurement was carried out at 100 kHz under the condition of 25°C.

[0094] (BDV) Using "PRK650-2.5" manufactured by Matsudai Precision, the measurement was carried out under the condition of 25°C by increasing the voltage at a rate of 1 V / min.

[0095] The above measurements were carried out for 10 samples each. The results are shown in Table 2. In Table 2, for CAP and ESR, the average value obtained by rounding to the second decimal place of the 10 measured values is shown, and for BDV, the average value obtained by rounding the decimal part of the 10 measured values is shown.

[0096]

Table 2

[0097] As shown in Table 2, the wound aluminum electrolytic capacitors of Examples 8 to 14, which were obtained using an oxidizing agent and dopant solution containing iron bis(organic sulfonate) and an oxetane compound and had a conductive polymer containing a component derived from the oxetane compound and an organic sulfonic acid as a dopant as a solid electrolyte, had a higher BDV and excellent withstand voltage characteristics compared to the electrolytic capacitor of Comparative Example 2, which had a conductive polymer not containing a component derived from the oxetane compound as a solid electrolyte.

[0098] [Preparation of Monomer Composition] Example 15 An amount of EDOT with a concentration of 19.9% by mass, an amount of 3-methyl-3-hydroxymethyloxetane with a concentration of 0.1% by mass, and methanol were mixed to prepare a monomer composition.

[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 An amount of a 1:1 (mass ratio) mixture of EDOT and ethylated EDOT with a concentration of 19.4% by mass, an amount of 3-ethyl-3-hydroxymethyloxetane with a concentration of 0.6% by mass, and methanol were mixed to prepare a monomer composition.

[0101] Example 18 An amount of a 1:1 (mass ratio) mixture of EDOT and ethylated EDOT with a concentration of 18% by mass, an amount of (3-ethyl-3-oxetanyl)methoxymethyl methacrylate with a concentration of 2% by mass, and methanol were mixed to prepare a monomer composition.

[0102] Example 19 An amount of a 1:1 (mass ratio) mixture of EDOT and propylated EDOT with a concentration of 18% by mass, an amount of 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl with a concentration of 2% by mass, and methanol were mixed to prepare a monomer composition.

[0103] Example 20 An amount of a 1:1 (mass ratio) mixture of EDOT and propylated EDOT with a concentration of 16% by mass, an amount of 3-ethyl-3-(4-hydroxybutyloxymethyl)oxetane with a concentration of 4% by mass, and methanol were mixed to prepare a monomer composition.

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

[0105] Table 3 shows the compositions of the monomer compositions of Examples 15 to 21. 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 capacitor〕 Example 22 The 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. Thereafter, the capacitor element was immersed in the same oxidizing agent / dopant solution (X) prepared in Comparative Example 1, pulled out, heated at 70 °C for 2 hours, and further heated at 180 °C for 1 hour to polymerize the monomer, thereby forming a solid electrolyte layer made of a conductive polymer having a polymer skeleton of a polymer of EDOT on the surface of the capacitor element. This capacitor element was encapsulated with an exterior body to fabricate a wound aluminum electrolytic capacitor having 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 fabricated in the same manner as in Example 22, except that the monomer composition was changed to those of Examples 16 to 18.

[0109] Example 26 An oxidizing agent-cum-dopant solution (Y) was prepared in the same manner as in Comparative Example 1, except that PTS was changed to NS. Then, a wound-type aluminum electrolytic capacitor was produced in the same manner as in Example 22, except that the monomer composition was changed to that of Example 19 and the oxidizing agent-cum-dopant solution (X) was changed to the oxidizing agent-cum-dopant solution (Y).

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

[0111] Comparative Example 3 A wound-type aluminum electrolytic capacitor was produced in the same manner as in Comparative Example 2, except that the oxidizing agent-cum-dopant solution (Y) was used instead of the oxidizing agent-cum-dopant solution (X).

[0112] For the wound-type aluminum electrolytic capacitors of Examples 22 to 28 and Comparative Example 3, CAP, ESR, and BDV were measured in the same manner as for the electrolytic capacitor of Example 8 and the like. The results are shown in Table 4. In the column of the oxidizing agent-cum-dopant solution in Table 4, "X" means the oxidizing agent-cum-dopant solution (X), and "Y" means the oxidizing agent-cum-dopant solution (Y). Also, in the column of the monomer composition in Comparative Example 3 of Table 4, "-" means that no monomer composition was used. In this Comparative Example 3, as described above, a mixture of EDOT and butylated EDOT without adding 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 using a monomer composition added with an oxetane compound and having a conductive polymer containing a component derived from the oxetane compound and an organic sulfonic acid as a dopant as a solid electrolyte had a higher BDV and excellent withstand voltage characteristics compared to the electrolytic capacitor of Comparative Example 3 using a conductive polymer not containing a component derived from the oxetane compound as a solid electrolyte.

Claims

1. A monomer composition for producing a conductive polymer, comprising thiophene or a derivative thereof, which is a monomer for producing a conductive polymer, and an oxetane compound represented by the following general formula (2) or (3) or a ring-opened compound thereof. 【Chemical 1】 〔In the above general formula (2), R2 and R3 are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms and may contain oxygen.〕 [Chemical 2] 〔In the above general formula (3), R4 is a hydrocarbon group containing one or two benzene rings, two carbons not constituting the benzene ring, and may contain oxygen, n is an integer of 1 to 3, and R5 and R6 are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms and may contain oxygen.〕

2. A method for producing a conductive polymer, characterized by chemically oxidizing and polymerizing thiophene or a derivative thereof in the presence of ferric organosulfonate and an oxetane compound represented by the following general formula (2) or (3) or a ring-opened compound thereof. 【Chemical Formula 3】 〔In the above general formula (2), R2 and R3 are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms and may contain oxygen.〕 [Chemical Formula 4] 〔In the above general formula (3), R4 is a hydrocarbon group containing one or two benzene rings, two carbons not constituting the benzene ring, and may contain oxygen, n is an integer of 1 to 3, and R5 and R6 are each a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms and may contain oxygen.〕

3. The method for producing a conductive polymer according to Claim 2, wherein thiophene or a derivative thereof is chemically oxidatively polymerized using the monomer composition for producing a conductive polymer according to Claim 1 in the presence of ferric organosulfonate.

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, characterized by having a step of manufacturing the conductive polymer by the method for manufacturing a conductive polymer according to Claim 2.

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