JP2011009569A - Method of manufacturing conductive polymer electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method that obtains a solid electrolyte capacitor having a sintered type electrode superior in anodic oxidation capability, more specifically, having both properties a low LC and also a high breakdown voltage.SOLUTION: The manufacturing method of the solid electrolyte capacitor includes the following steps (1)-(4), the step (2) and/or the step (4) being performed under the existence of ionic liquid, wherein (1) is the step to form a dielectric oxide film in an anode surface fabricated by sintering tantalum or niobium powder, (2) is the step to form an electrolyte by in situ polymerization of conductive polymer monomer on the dielectric film. (3) is the step to wash the formed electrolyte, and (4) is the step to fill a conductive polymer dispersion liquid in the electrolyte after washing.

Description

  The present invention relates to a method for producing a conductive polymer electrolytic capacitor using an ionic liquid.

  In recent years, solid electrolytic capacitors using tantalum or niobium as an anode are widely used in small electronic devices such as mobile phones, and the market is expanding.

  The solid electrolytic capacitor is a capacitor using a conductive polymer such as manganese dioxide, polypyrrole, or polythiophene derivative as an electrolyte. Among them, a solid electrolytic capacitor using a conductive polymer as an electrolyte can reduce internal impedance because of its much higher electric conductivity (that is, electronic conductivity), and exhibits excellent characteristics. As a general method for producing a conductive polymer solid electrolytic capacitor, a valve metal made of tantalum or the like is powder-molded to form an element with a lead, and a chemical conversion treatment is performed on the surface of the valve metal (including the surface of the micropore). A dielectric oxide film is formed to obtain a sintered body, and the anode is composed of a sintered body made of a valve metal and a dielectric film and a lead. A cathode layer made of a conductive polymer and a graphite layer is formed on the dielectric oxide film, a conductive paste is applied to the cathode layer, the cathode terminal and the cathode layer are connected, and an anode lead drawn from the element is applied. A tantalum solid electrolytic capacitor is obtained by connecting an anode terminal, coating with an exterior resin, and performing an aging treatment. As a method for forming the cathode layer, a conductive polymer is formed in close contact with the dielectric oxide film, washed, and then immersed in a graphite powder-containing suspension solution to form a graphite layer on the conductive polymer. And a silver conductive layer is formed thereon.

  In the conventional method of manufacturing a solid electrolytic capacitor, after forming a dielectric oxide film by chemical conversion, a conductive polymer is formed by in situ polymerization (chemical polymerization method or electrolytic polymerization method), washed, graphite paste, silver After the paste is applied and dried, the capacitor is completed by aging treatment, but the edge of the sintered body is hard to be filled with conductive polymer, and the filling becomes insufficient due to washing, so it was applied There is a problem in that the paste penetrates into the oxide film, resulting in an increase in leakage current (hereinafter abbreviated as LC) and a decrease in withstand voltage.

  In order to solve this increase in LC, a solution or dispersion containing conductive polymer particles is used as the outermost layer after filling the electrolyte, so that the edge portion of the sintered body can be satisfactorily covered, Since it can be filled with a conductive polymer, a technique has been reported that a solid electrolytic capacitor having a low LC can be realized (Patent Documents 1 and 2). However, no attention is paid to the effect of solving the problem of lowering the withstand voltage, and this problem remains unsolved.

  On the other hand, an electrolyte composed of an ionic liquid and a conductive polymer has been developed to solve the problems of an increase in LC and a decrease in withstand voltage (Patent Document 3). This was made by discovering that the ionic liquid has excellent anodizing action of the valve metal and can repair defects of, for example, aluminum oxide film. By this invention, high withstand voltage characteristics and low LC are achieved. A solid electrolytic capacitor can be realized. However, there is still a problem that even if the ionic liquid described in Patent Document 3 and its method are applied to a sintered body such as tantalum, a capacitor having a sufficient withstand voltage improvement and excellent LC characteristics cannot be obtained.

JP 2006-295184 A JP 2007-27767 A International Publication WO2005 / 012599 Pamphlet

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to provide a sintered mold having excellent anodizing ability, that is, having both low LC and high withstand voltage characteristics. It is to provide a solid electrolytic capacitor having electrodes.

  As a result of intensive studies in view of the above, the inventors of the present invention have found that in a method for producing a solid electrolytic capacitor using tantalum or niobium as an anode, an electrolyte is formed on a dielectric film of the anode by in situ polymerization of a conductive polymer monomer. In carrying out the forming step and the step of filling the formed electrolyte with the conductive polymer dispersion, if an ionic liquid is present in one or both of these steps, high withstand voltage characteristics and excellent The present inventors have found that a solid electrolytic capacitor having LC characteristics can be obtained and completed the present invention.

That is, the present invention
[1] A method for producing a solid electrolytic capacitor, including the following steps (1) to (4), wherein step (2) and / or step (4) are performed in the presence of an ionic liquid:
(1) a step of forming a dielectric oxide film on the surface of an anode produced by sintering tantalum or niobium powder;
(2) forming an electrolyte on the dielectric film by in situ polymerization of a conductive polymer monomer;
(3) a step of washing the formed electrolyte;
(4) filling the electrolyte after washing with a conductive polymer dispersion;
[2] The anion component of the ionic liquid is a formate anion and the general formula (1);

(Wherein R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, a straight chain or branched or alkyl group optionally C ₁ -C ₂₀ also form a ring, straight or branched or alkenyl group optionally C ₂ -C ₂₀ also form a ring, to form a straight or branched or cyclic C ₂ -C ₂₀ alkynyl group, C ₆ -C ₂₀ aryl group, C ₄ -C ₂₀ heteroaryl group, C ₇ -C ₂₀ aralkyl group, C ₄ -C ₂₀ heteroaralkyl group Which may be the same as or different from each other, and together may form a ring.The above alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, aralkyl group and heteroarral group The hydrogen atom may be substituted in the kill group.) The method for producing a solid electrolytic capacitor according to the above [1], which is at least one selected from the group consisting of carboxylate anions represented by:
[3] The method for producing an electrolytic capacitor according to the above [1] or [2], wherein the in situ polymerization is chemical polymerization and / or electrolytic polymerization,
[4] The solid according to any one of [1] to [3], wherein the conductive polymer monomer is at least one selected from the group consisting of thiophene, thiophene derivatives, pyrrole, pyrrole derivatives, aniline and aniline derivatives. Manufacturing method of electrolytic capacitor,
[5] In any one of the above [1] to [4], the conductive polymer dispersion contains at least one selected from the group consisting of polythiophene, polythiophene derivatives, polypyrrole, polypyrrole derivatives, polyaniline, and polyaniline derivatives. A method for producing the solid electrolytic capacitor according to claim 1,
[6] A solid electrolytic capacitor produced by the method for producing a solid electrolytic capacitor according to [1] to [5] above,
About.

  According to the production method of the present invention, an excellent tantalum or niobium solid electrolytic capacitor having both high breakdown voltage and low LC characteristics can be obtained.

  In the present invention, the step (2) and / or the step (4) are performed in the presence of an ionic liquid. The ionic liquid used in the present invention (hereinafter sometimes abbreviated as “ILs”) is also referred to as a room temperature molten salt, and refers to a liquid that is liquid at room temperature despite being composed only of ions, such as imidazolium. It consists of a combination of a cation and a suitable anion.

  Examples of ILs used in the present invention include ionic liquids having non-halogen anions. Among these, an ionic liquid in which the anion component is a carboxylate anion is preferable from the viewpoint of superior anodic oxidation ability.

  Examples of the carboxylate anion include formate anion and general formula (1);

The carboxylate anion represented by these is mentioned.

  The carboxylate anion represented by the formula (1) is paired with a cation described later to form ILs.

In the formula (1), R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, chain or branched or alkyl group optionally C ₁ -C ₂₀ also form a ring, straight or branched or alkenyl group optionally C ₂ -C ₂₀ also form a ring, a straight or branched or cyclic C ₂ -C ₂₀ alkynyl group, C ₆ -C ₂₀ aryl group, C ₄ -C ₂₀ heteroaryl group, C ₇ -C ₂₀ aralkyl group, C ₄ -C ₂₀ hetero ring which may be formed Represents an aralkyl group, which may be the same or different from each other, and together may form a ring; In the alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, aralkyl group and heteroaralkyl group, a hydrogen atom may be substituted. Examples of the substituent include a hydroxyl group, an alkyl group, an alkoxy group, an alkylthio group, a nitro group, an amino group, a cyano group, a carboxyl group, and a halogen atom.

The C ₁ -C ₂₀ alkyl group that may form a straight chain, branched chain or ring is not particularly limited, but examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group. Group, n-butyl group, sec-butyl group, tert-butyl group, cyclobutyl group, n-pentyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, n-octyl group, n-decyl group, etc. In addition, an alkyl group in which an arbitrary number of hydrogen atoms are substituted with fluorine atoms, such as a trifluoromethyl group, can be exemplified.

The alkenyl group of straight or branched or optionally C ₂ -C ₂₀ also form a ring, for example, vinyl group, propenyl group, a styryl group, an isopropenyl group, a cyclopropenyl group, a butenyl group, a cyclobutenyl group, a cycloalkyl A pentenyl group, a hexenyl group, a cyclohexenyl group and the like can be mentioned.

Examples of the C ₂ -C ₂₀ alkynyl group which may form a straight chain, branched chain or ring include, for example, ethynyl group, propynyl group, phenylethynyl group, cyclopropylethynyl group, butynyl group, pentynyl group, cyclobutylethynyl Group, hexynyl group and the like.

Examples of the C _{6 to} C ₂₀ aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a terphenyl group.

Examples of the C _{4 to} C ₂₀ heteroaryl group include pyrrolinyl group, pyridyl group, quinolyl group, imidazolyl group, furyl group, indolyl group, thienyl group, oxazolyl group, and thiazolyl group.

Examples of the C _{7 to} C ₂₀ aralkyl group include a benzyl group, a naphthylmethyl group, and an anthracenylmethyl group.

Examples of the C _{4 to} C ₂₀ heteroaralkyl group include a pyridylmethyl group, a quinolylmethyl group, an indolylmethyl group, a furfuryl group, and a thienylmethyl group.

R ¹ and R ² may be combined to form a ring, and examples thereof include a cyclohexyl group and a phenyl group.

When R ¹ and / or R ² is a hydroxyl group or an amino group, the hydroxyl group and amino group may be protected or unprotected, and when protected, the protecting group is not particularly limited. However, for example, a general protecting group may be used, and examples thereof include those described in “PROTECTIVE GROUPS in ORGANIC SYNTHESIS THIRD EDITION” (pages 17 and 494, WILEY-INTERSCIENCE). In the case where the amino group is protected, the method including the various ethers, the method including the various esters, the method including the various sulfonate esters, the method including the various carbonate esters, and the method including the various amides when the amino group is protected. , Various imides, various carbamates How to, and the like.

These ILs may be used alone, or two or more kinds of ILs may be mixed and used in an arbitrary ratio. Moreover, when it has an asymmetric point in a molecule | numerator, an optically active body may be sufficient and a racemic body may be sufficient. From the viewpoint of anodic oxidation ability and availability, at least one of R ¹ and R ² is preferably a hydrogen atom or a hydroxyl group. When R ¹ or R ² is a hydrogen atom or a hydroxyl group, the other is preferably a methyl group, an ethyl group, a phenyl group, a benzyl group, a naphthyl group, or the like. When at least one of R ¹ and R ² is a hydroxyl group, it may be protected or unprotected, but generally unprotected is preferable because it exhibits a higher anodic oxidation ability.

A preferable example is one in which R ¹ and R ² together form a cyclohexyl group or a phenyl group.

  The cationic component of ILs includes ammonium and its derivatives, imidazolium and its derivatives, pyridinium and its derivatives, pyrrolidinium and its derivatives, pyrrolinium and its derivatives, pyrazinium and its derivatives, pyrimidinium and its derivatives, triazonium and its derivatives, triazinium and its derivatives Derivatives thereof, triazine and derivatives thereof, quinolinium and derivatives thereof, isoquinolinium and derivatives thereof, indolinium and derivatives thereof, quinoxalinium and derivatives thereof, piperazinium and derivatives thereof, oxazolinium and derivatives thereof, thiazolinium and derivatives thereof, morpholinium and derivatives thereof , Piperazine and its derivatives. Since the resulting ionic liquid exhibits a relatively low viscosity, imidazolium derivatives are preferred, and imidazolium derivatives are preferably diethyl imidazolium, ethyl butyl imidazolium, and dimethyl imidazolium, particularly preferably ethyl methyl imidazolium, methyl butyl. Imidazolium.

  The ILs of the present invention are substances obtained by combining the above anions and the above cations, and can be synthesized by a known method. Specifically, a method such as an anion exchange method, an acid ester method, or a neutralization method can be used.

  Next, the conductive polymer monomer used in the step (2) of the present invention will be described. The conductive polymer monomer is not particularly limited, and examples thereof include thiophene or a derivative thereof, pyrrole or a derivative thereof, aniline or a derivative thereof.

  Thiophene derivatives include 3,4-ethylenedioxythiophene, 3-alkylthiophene (alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, dodecyl, etc.), fluoro Examples include phenylthiophene, allylthiophene, 3-methoxythiophene, 3-chlorothiophene, and 3-acetylthiophene.

  Examples of the pyrrole derivative include 3-methylpyrrole and 1- (dimethylamino) pyrrole.

  As aniline derivatives, o-toluidine, m-toluidine, 1,3-benzenediamine, 1,2-benzenediamine, 2-aminophenol, 3-aminophenol, 2-fluoroaniline, 3-fluoroaniline, 2-ethynyl Aniline, 3-ethynylaniline, 2-aminobenzonitrile, 3-aminobenzonitrile, 3-vinylaniline, 2,3-dimethylaniline, 3,5-dimethylaniline, 2,5-dimethylaniline, 2- (aminomethyl ) Aniline, 4-methyl-1,2-benzenediamine, 2-methyl-1,3-benzenediamine, 4-methyl-1,3-benzenediamine, 2-methoxyaniline, 3-methoxyaniline, 2,3- Diaminophenol, 5-fluoro-2-methylaniline, 2-fluoro-5-methyla Phosphorus, 3-fluoro-2-methylaniline, 2-chloro aniline.

  A thiophene derivative or pyrrole is preferable, and 3,4-ethylenedioxythiophene or pyrrole is more preferable because the obtained conductive polymer has high conductivity and is stable in the air.

  Only one type of conductive polymer monomer may be used, or two or more types may be used.

  The conductive polymer dispersion used in the step (4) of the present invention will be described. The conductive polymer dispersion includes at least a cationic form of a conductive polymer, a counter anion, and a solvent.

  Examples of the conductive polymer include polythiophene, polythiophene derivatives, polypyrrole, polypyrrole derivatives, polyaniline, and polyaniline derivatives. The derivative here includes a polymer obtained from a monomer having an arbitrary substituent, and a polymer having an arbitrary substituent at an arbitrary position in the polymer. If the polythiophene derivative is mentioned, as the specific example of the former, poly (3-hexylthiophene) obtained from 3-hexylthiophene having a hexyl group at the 3-position, poly (3,4-ethylenedioxythiophene), etc. Poly (thiophene derivative). Specific examples of the latter include a polymer in which the end of poly (3,4-ethylenedioxythiophene) is capped with polyethylene glycol. Examples of the pyrrole derivative and the aniline derivative in the polypyrrole derivative and the polyaniline derivative include the same as the pyrrole derivative and the aniline derivative of the conductive polymer monomer described above. Here, the “substituent” is not particularly limited as long as it does not adversely affect the reaction, and specifically includes a hydroxyl group, an alkyl group, an alkoxy group, an alkylthio group, a nitro group, an amino group, a cyano group, a carboxyl group. Group, halogen atom and the like.

  Poly 3,4-ethylenedioxythiophene, polypyrrole or polyaniline is preferred from the viewpoint of stability in the conductive polymer dispersion.

  In the conductive polymer dispersion, only one type of conductive polymer may be used, or two or more types may be used. (2) The conductive polymer polymerized from the conductive polymer monomer used in the step may be the same type or different.

  The conductive polymer contained in the conductive polymer dispersion is dispersed in the solvent as solid particles, and the particle size is not particularly limited but is preferably 1 μm or less. This is because if the particle size is too large, it will be difficult to fill between the grains of the sintered body when applied to a capacitor.

  The concentration of the dispersed conductive polymer is not limited. However, if the concentration is too low, the effect is not exhibited. Therefore, the concentration is preferably 1 part by weight or more with respect to 100 parts by weight of the solvent.

  The counter anion is necessary as an anion of the pair in order to supplement the positive charge of the conductive polymer, and also functions as a dopant for the conductive polymer. Examples of the counter anion include polyacrylic acid, polymethacrylic acid, polymaleic acid, polystyrene sulfonic acid, and polyvinyl sulfonic acid anions. These polycarboxylic acids and sulfonic acids may be copolymers of vinyl carboxylic acid and vinyl sulfonic acid with other polymerizable monomers such as acrylic acid ester and styrene. The concentration of the counter anion is preferably 0.5 parts by weight or more with respect to 100 parts by weight of the solvent from the viewpoint of effect expression.

  The solvent is used to disperse the conductive polymer and the counter anion, and includes water and / or an organic solvent. The organic solvent is not particularly limited, and may be an aprotic solvent or a protic solvent. Examples include alcohol-based, ether-based, nitrile-based, ketone-based, amide-based, carbonate-based, ester-based, lactone-based, sulfur-containing solvents, halogenated hydrocarbons, and hydrocarbon-based solvents. It may be used.

  (4) The conductive polymer dispersion used in the step may contain the following additives. Examples of the additive include a surfactant, a crosslinking agent, and a binder, and these may be used alone or in combination of two or more. Although it is speculated, it is considered that the inclusion of the additive improves the adhesion to the sintered body and further improves the LC characteristics. The additive is not particularly limited, but preferably has heat resistance enough to withstand solder reflow. Examples of the surfactant include ionic and nonionic surfactants, and examples thereof include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, polyethylene glycol, and polyvinyl alcohol. Examples of the binder include polyvinyl pyrrolidone, polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate, polyacrylic acid ester, polyacrylic acid amide, polymethacrylic acid amide, styrene / acrylic acid ester, vinyl acetate / acrylic acid ester, Ethylene / vinyl acetate copolymer, polybutadiene, polyisoprene, polyurethane, polyamide, polyimide, polysulfone, melamine / formaldehyde resin, epoxy resin, silicone resin, cellulose, polyvinyl acetate, polycarbonate, polybityl butyral, polystyrene, polyacrylonitrile, polyvinyl chloride, Examples thereof include polybutadiene, polyisoprene, polyether, and polyester. Examples of the crosslinking agent include melamine compounds, masked isocyanates, functional silanes and hydrolysates thereof, and epoxy silanes such as 3-glycidoxypropyltrialkoxysilane, tetraethoxysilane, polyacrylate, and polyolefin dispersions. It is done.

  In the present invention, step (4) may be carried out in the presence of an ionic liquid. Specifically, an embodiment in which a conductive polymer dispersion containing an ionic liquid is used. In this case, it is preferable to dissolve ILs in the conductive polymer dispersion. This is because a capacitor having a high withstand voltage as well as a low LC can be obtained due to the anodizing ability of ILs. The concentration of ILs is preferably 0.01 wt% to 95 wt%, more preferably 0.05 wt% to 20 wt%, still more preferably 0.01 wt% to 10 wt%, in a total of 100 wt% of the conductive polymer dispersion and ILs. Most preferably, it is in the range of 0.05 wt% to 5 wt%. In the case of 0.01 wt% or less, the effect of adding ILs may not be observed. The concentration of ILs affects the mechanical or electrical properties of the conductive polymer film formed in the step (4). Generally, when 10 wt% or more of ILs is added, the mechanical strength and electrical characteristics are poor. Therefore, the effect as the outermost electrolyte layer may be lowered.

  The conductive polymer dispersion is prepared by adding at least a conductive polymer and a counter anion to the solvent at respective concentrations and stirring for 1 minute to 96 hours. When ILs and / or additives are added, they may be added simultaneously with the addition of the conductive polymer and the counter anion, or may be further added after preparing the conductive polymer dispersion.

  In the solid electrolytic capacitor of the present invention, a valve metal is powder-molded, a dielectric oxide film is formed on the valve metal by an electrochemical method, and an electrolyte is formed on the film by in situ polymerization using a conductive polymer monomer. After washing, the capacitor element obtained by filling the dispersion on the electrolyte is manufactured by connecting the cathode and the lead and performing an aging treatment.

  Step (1) of the Present Invention A step of forming a dielectric oxide film on the anode surface produced by sintering tantalum or niobium powder will be described. The anode of the solid electrolytic capacitor of the present invention is composed of a sintered body made of a valve metal and a dielectric film, and a lead. Using an element with a lead formed by powder molding a valve metal made of tantalum or niobium, a sintered body is formed by combining a dielectric film made of an oxide film formed by chemical conversion treatment such as anodizing on the surface of the valve metal. Form. The anodic oxidation can be performed by immersing the valve metal in, for example, an aqueous phosphoric acid solution, applying a voltage, and performing a chemical conversion treatment.

  Next, the electrolyte formation method of the process (2) in this invention is demonstrated.

  In the present invention, step (2) may be carried out in the presence of an ionic liquid. That is, in the presence of an ionic liquid, in situ polymerization of a conductive polymer monomer is performed on the dielectric film obtained in step (1). Here, in situ polymerization includes chemical polymerization and electrolytic polymerization.

  Chemical polymerization is a method of synthesizing a raw material conductive polymer monomer by oxidative polymerization in the presence of an appropriate oxidizing agent.

  Examples of the oxidizing agent include iron salts such as ferric paratoluene sulfonate, ferric naphthalene sulfonate, ferric n-butyl naphthalene sulfonate, ferric triisopropyl naphthalene sulfonate, persulfate, and peroxidation. Hydrogen, diazonium salts, halogens and halides, or transition metal salts such as copper and manganese can be used. The conductive polymer synthesized by chemical polymerization can obtain a polymer having conductivity in a one-step reaction by incorporating an anion of an oxidant into the polymer as a dopant in the polymerization process. It is preferable to use ferric paratoluenesulfonate containing paratoluenesulfonate ions having high mobility as an oxidizing agent.

  A solvent may be used for chemical polymerization. The solvent may be a known one and is not particularly limited. For example, methanol, ethanol, n-butanol, 2-propanol, acetone, diethyl ether, ethyl acetate, THF, DMF, acetonitrile, DMSO, dimethyl carbonate, Examples thereof include ethylene carbonate, propylene carbonate, hexane, toluene, chloroform and the like, and particularly preferred is n-butanol. These solvents may use only 1 type and may use 2 or more types.

  When chemical polymerization is performed using a solution containing ILs and a conductive polymer monomer, ILs are present in the formed electrolyte, and as a result, the effect of increasing the breakdown voltage due to the anodic oxidation ability of the ILs in the vicinity of the dielectric oxide film. Is estimated to be expressed. In the case of the polymerization, after adding an oxidizing agent to a solution containing a conductive polymer monomer and ILs, a sintered body on which a dielectric film is formed may be immersed, or a sintered body on which a dielectric film is formed After impregnating with a solution containing a conductive polymer monomer and ILs, an oxidant may be impregnated. In these cases, the viscosity and concentration may be appropriately adjusted by adding a solvent.

  The polymerization conditions may be known polymerization conditions, and the temperature range is from -100 ° C to 200 ° C, particularly preferably from -30 ° C to 150 ° C. The polymerization time is 1 minute to 120 hours, particularly preferably 1 minute to 1440 minutes. In the step of impregnating the sintered body with the polymerization liquid of the above chemical polymerization, it is preferable to repeat several times from the point that the sintered body is sufficiently filled with the electrolyte.

  Next, electrolytic polymerization will be described. Electrolytic polymerization is a method in which a conductive polymer monomer is dissolved in a solvent and anodized to dehydrogenate the conductive polymer monomer. Electropolymerization is, for example, a method in which a pyrrole monomer is dissolved in a solvent together with a supporting electrolyte and subjected to dehydrogenation polymerization by anodic oxidation, whereby polypyrrole, which is a conductive polymer, can be deposited on the anode. Generally, since the oxidation-reduction potential of the polymer is lower than that of the monomer, the oxidation of the polymer skeleton proceeds further during the polymerization process, and accordingly, the anion of the supporting electrolyte is incorporated into the polymer as a dopant. In electropolymerization, such a mechanism has an advantage that a polymer having conductivity can be obtained without adding a dopant later. Therefore, it is preferable that the electropolymerization is performed in a solution containing ILs, and the presence of ILs in the formed electrolyte presumes that a capacitor having a high breakdown voltage can be obtained by the anodizing ability of ILs in the vicinity of the dielectric oxide film. Is done. When synthesizing conductive polymers by electropolymerization, the oxide film on the valve metal is a dielectric, so a conductive film is formed on the dielectric beforehand to make it conductive, and the current or voltage is supplied from the power supply. Is applied to perform electropolymerization. As the conductive film used for such a purpose, a conductive polymer synthesized by chemical polymerization, pyrolytic manganese dioxide, or the like can be used.

  Chemical polymerization may be used after electrolytic polymerization, and electrolytic polymerization may be used after chemical polymerization.

  ILs have ionic conductivity but no electronic conductivity, and therefore behave as an insulator in the electrolyte. Therefore, when the step (2) is performed in the presence of an ionic liquid, the impedance characteristic tends to be deteriorated if too much ILs is added, so the total amount of ILs added is 1 with respect to the conductive polymer monomer. It is preferably a molar equivalent or less, more preferably 0.01 molar equivalent or more and 0.8 molar equivalent or less, and most preferably 0.05 molar equivalent or more and 0.5 molar equivalent or less.

  The step (3) in the present invention, that is, the step of washing the formed electrolyte will be described. Step (3) refers to a step of washing the electrolyte obtained in step (2) with water and / or an organic solvent. The term “cleaning” as used herein is not particularly limited, but it is preferably immersed in water and / or an organic solvent that has been stirred for 1 minute to 1 hour between room temperature and 80 ° C. The organic solvent to be used is not particularly limited, but alcohols, ethers, nitriles, ketones, amides, carbonates, esters, lactones, sulfur-containing solvents, halogenated hydrocarbons and A hydrocarbon-type solvent is mentioned, These solvent may use only 1 type, and may use 2 or more types. From the viewpoint of the cleaning effect, an alcohol type is preferably used, and methanol, ethanol, and n-butanol are particularly preferable.

  In the step (3), the components of the conductive polymer monomer and / or the oxidizing agent incorporated into the electrolyte are eluted by washing the electrolyte obtained in the step (2) with water and / or an organic solvent, By washing away unreacted monomers and oxidant components that are not polymerized, components that deteriorate the impedance characteristics and pressure resistance characteristics can be removed. When the ionic liquid is added in the step (2), a part of the ionic liquid is eluted in this washing step, but it is impossible to elute all the ionic liquid in normal washing. (2) About 10% to 60% of the ionic liquid added in the step is considered to remain in the electrolyte. The remaining ionic liquid can contribute to the improvement of the capacitor characteristics.

  (3) It is preferable to perform a re-chemical conversion treatment after the step. The re-chemical conversion treatment is performed for the purpose of repairing deterioration and defects of the dielectric oxide film caused by the stress at the time of electrolyte formation in the step (2) and reducing LC, and immersing the electrolyte in the same solution as the chemical conversion treatment. It refers to the step of applying a constant voltage for a certain time. Although the conditions are not particularly limited, it is preferable to apply a voltage 0.5 to 0.95 times the formation voltage for 1 minute to 24 hours, and an example of the solution is an aqueous phosphoric acid solution. In addition, after the re-chemical conversion treatment, washing is preferably performed in order to wash away the solution used in the treatment. Although not particularly limited, the solution is immersed in stirred water and / or organic solvent for 1 minute to 1 hour. It is preferable to keep it. The organic solvent is not particularly limited, but alcohol, ether, nitrile, ketone, amide, carbonate, ester, lactone, sulfur-containing solvents, halogenated hydrocarbons and hydrocarbon solvents can be used. These solvents may be used alone or in combination of two or more.

  From the viewpoint that a dense electrolyte can be formed, it is preferable to repeat the step (2), the step (3) and the re-chemical conversion treatment.

  Next, the step (4), that is, the step of filling the conductive polymer dispersion will be described. (4) The step is a step performed to suppress the increase in LC by covering the edge portion of the sintered body with the conductive polymer and the counter anion and sufficiently filling the edge portion.

  The step (4) is applied by a conventionally known method, and examples of the filling method include spin coating and impregnation (immersion), and it is preferable to repeat several times from the point of sufficient filling. When impregnated and repeatedly filled, in the first step, after being dipped to the half height of the sintered body and dried, then dipped deeper than the first and dried. It is estimated that the coating can be sufficiently performed by repeating these operations one or more times.

  After filling, drying is performed after cleaning, but the cleaning may or may not be performed. Washing refers to a step of washing with water and / or an organic solvent. The term “cleaning” as used herein is not particularly limited, but it is preferably immersed in water and / or an organic solvent that has been stirred for 1 minute to 1 hour between room temperature and 80 ° C. The organic solvent to be used is not particularly limited, but alcohols, ethers, nitriles, ketones, amides, carbonates, esters, lactones, sulfur-containing solvents, halogenated hydrocarbons and A hydrocarbon-type solvent is mentioned, These solvent may use only 1 type, and may use 2 or more types. From the viewpoint of the cleaning effect, an alcohol type is preferably used, and methanol, ethanol, and n-butanol are particularly preferable. The drying conditions are not particularly limited, and the heating is performed between room temperature and 180 ° C. for 1 minute to 24 hours. Alternatively, it can be accelerated by heating with hot air or heat radiation. In drying, the solvent is preferably removed, but some may remain. Depending on the binder or crosslinker used, further treatments such as curing or crosslinking by heating or light can also be carried out.

  (4) It is preferable to repeat the operation of the process because the sintered body can be coated more densely, and as a result, a low LC capacitor can be obtained.

  In the present invention, the step (2) and / or the step (4) are performed in the presence of an ionic liquid. That is, it is necessary to apply ILs in at least one of the steps (2) and (4). By adding ILs in either step (2) or step (4), the effect of improving the withstand voltage is exhibited as described above. Preferably, ILs is applied in both steps (2) and (4). When ILs is applied in both steps, the effects in both steps are manifested, and as a result, it is estimated that the withstand voltage is further improved.

  As the cathode of the solid electrolytic capacitor of the present invention, for example, carbon paste and silver paste can be formed by a conventionally known method. The capacitor element and the cathode are each connected to a lead. A conductive coating film is formed on the capacitor element surface with a conductive paste such as carbon paste or silver paste, and leads are connected.

  Thereafter, it is covered with a resin mold or an outer case, and further subjected to aging treatment to form a solid electrolytic capacitor. The aging process is a process performed for the purpose of reducing LC, and the conditions are not particularly limited, but a rated voltage is applied between room temperature and 180 ° C. for 1 minute to 24 hours.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

<Anode>
In step (1), a 50000 CV / g element having an anode lead and tantalum as a valve metal is used, and a chemical treatment is performed by applying a voltage of 20 V in a phosphoric acid aqueous solution at 60 ° C. for 24 hours. An oxide film was formed to obtain a sintered body, which was used as an anode.

<ILs>
First, a method for synthesizing or obtaining ILs used as examples will be described.

  [BMIm] [MA] (1-butyl-3-methylimidazolium mandelate)

1-butyl-3-methylimidazolium hydrogen carbonate 50% aqueous solution (5000 mg, 12.48 mmol) was cooled to 0 ° C. Thereafter, an aqueous solution of mandelic acid (1899 mg, 12.48 mmol) was slowly added dropwise and stirred at room temperature for 1 hour. The reaction solution was concentrated as it was, the solvent was distilled off under reduced pressure, dichloromethane was added to the resulting residue, and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 3622.3 mg of the target compound as a light brown oil. (Yield 100%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 0.93 (t, 3H), 1.29-1.34 (m, 2H), 1.74-1.79 (m, 2H), 3.84 (s, 3H), 4.10 (t, 2H), 4.92 (s, 1H), 7.04 (s, 1H), 7.14-7.26 (m, 1H), 7.23-7.26 (M, 3H), 7.54 (d, 2H), 10.74 (s, 1H)
[EMIm] [LA] (1-ethyl-3-methylimidazolium lactate, manufactured by Aldrich)

  [EMIm] [AC] (1-ethyl-3-methylimidazolium acetate, manufactured by Aldrich)

<Conductive polymer dispersion>
Poly 3,4-ethylenedioxythiophene / polystyrene sulfonic acid aqueous dispersion (Sigma Aldrich high conductivity coating type dispersion concentration 1.3-1.7 wt%) 90 parts EDOT 2 parts DMSO 4 parts polyvinyl alcohol 4 parts were added and stirred for 1 hour.

<LC>
“HA-3001A” manufactured by Hokuto Denko Co., Ltd. was used as the apparatus, and 6.3 V was continuously applied before and after the aging treatment, and the value after 5 minutes from the start of application was used. In general, LC refers to LC after aging processing, and in this embodiment also indicates LC after aging processing.

<Withstand voltage measurement>
The withstand voltage (V) was measured by increasing the voltage at a rate of 100 mV / sec. A model number “TR6143” manufactured by Advantest Corporation was used as the apparatus, and the withstand voltage value was defined as a voltage value when a current of 100 mA flowed.

Example 1
A tantalum solid electrolytic capacitor was produced by applying [BMIm] [MA] as ILs to the polymerization liquid for chemical polymerization in step (2) and the conductive polymer dispersion used in step (4).

  That is, using the anode, a conductive polymer is formed by chemical polymerization of 3,4-ethylenedioxythiophene (hereinafter abbreviated as EDOT, manufactured by HC Stark-V TECH) as the step (2). A tantalum solid electrolytic capacitor was produced by applying the conductive polymer dispersion as a step (4).

  (2) The polymerization solution for chemical polymerization in the step is EDOT, and the oxidizing agent is iron paratoluenesulfonate (40 wt% 1-butanol solution) and [BMIm] [MA] in a molar ratio of EDOT: oxidizing agent: ILs = 1. The mixture was prepared at a mixing ratio of 1: 0.1.

  This polymerization solution was mixed in a well-dried beaker, and then the anode was immersed in the polymerization solution and pulled up, followed by heat treatment at 26 ° C. for 1 hour. After repeating this treatment three times, the mixture was further heated at 50 ° C. for 3 hours, washed with ethanol, re-formed with phosphoric acid solution at 6.3 V for 5 minutes, washed with water for 5 minutes, and then washed at 120 ° C. for 30 minutes. Drying was performed. The above steps from immersion to drying of the polymerization solution were repeated 6 times to form an electrolyte.

  Next, as a filling step of step (4), a conductive polymer dispersion containing 0.1 wt% [BMIm] [MA] was produced. Specifically, after adding [BMIm] [MA] to the above conductive polymer dispersion and stirring for 10 minutes, the anode on which the electrolyte was formed was immersed in the conductive polymer dispersion to which the ionic liquid was added, After pulling up, it was heated and dried at 120 ° C. for 30 minutes. The process was performed 3 times.

  Thereafter, graphite paste, silver paste and copper foil were applied and dried, and subjected to aging treatment at 6.3 V and 105 ° C. for 1 hour. Using the capacitor thus obtained as a sample, the withstand voltage was measured.

  Table 1 shows the characteristics of the obtained capacitor.

(Example 2)
(2) In the polymerization liquid for chemical polymerization in the step, [BMIm] [MA] was mixed in the molar ratio of EDOT: oxidant: ILs = 1: 1: 0.3 in the same manner as in Example 1. The experiment was conducted.

  The obtained results are shown in Table 1.

(Example 3)
In the step (4), an experiment was conducted in the same manner as in Example 1 except that a conductive polymer dispersion containing 0.2 wt% [BMIm] [MA] was used.

  The obtained results are shown in Table 1.

(Examples 4 to 6)
Experiments were performed in the same manner as in Example 1 except that ILs were changed to the types shown in Table 1. The obtained results are shown in Table 1.

(Example 7)
(4) The experiment was performed in the same manner as in Example 1 except that ILs was not used in the dispersion liquid in the step and the type of ILs used in the step (1) was changed.

  That is, [EMIm] [AC] was used as ILs and mixed at a molar ratio of EDOT: oxidant: ILs = 1: 1: 0.1 to prepare a polymerization solution for chemical polymerization in step (1). .

  This polymerization solution was mixed in a well-dried beaker, and then the anode was immersed in the polymerization solution. After being pulled up, it was heated at 26 ° C. for 1 hour. After repeating the same treatment three times, further heat treatment was performed at 50 ° C. for 3 hours, washed with ethanol, re-formed at 6.3 V for 5 minutes, washed with water for 5 minutes, and then dried at 120 ° C. for 30 minutes. . The above steps from immersion to drying of the polymerization solution were repeated 6 times to form an electrolyte.

  Next, as the filling step of the step (4), the anode on which the electrolyte was formed was immersed in the conductive polymer dispersion, and after being pulled up, heated and dried at 120 ° C. for 30 minutes. The process was performed 3 times.

  Thereafter, graphite paste, silver paste and copper foil were applied and dried, and subjected to aging treatment at 6.3 V and 105 ° C. for 1 hour. Using the capacitor thus obtained as a sample, the withstand voltage was measured.

  Table 1 shows the characteristics of the obtained capacitor.

(Example 8)
(2) The experiment was performed in the same manner as in Example 1 except that ILs was not used in the step and a conductive polymer dispersion containing 0.1 wt% [EMIm] [AC] was used in the step (4). .

  The obtained results are shown in Table 1.

(Comparative Example 1)
Experiments were performed in the same manner as in Example 1 except that ILs were not used in either step (2) or step (4).

  The obtained results are shown in Table 1.

  By containing ILs shown in Examples 1 to 8, it can be seen that the withstand voltage is higher than that of the comparative example. In particular, as in Examples 1 to 6, it can be seen that by applying ILs in both the steps (2) and (4), the withstand voltage is further improved and a capacitor with excellent withstand voltage characteristics can be obtained.

  On the other hand, as shown in Comparative Example 1, when no ILs is contained, the withstand voltage is very low.

  With respect to LC, it can be seen that the example provides the same or better characteristics than the case of not containing ILs at all as in Comparative Example 1.

Claims (6)

Including the following steps (1) to (4),
(2) The manufacturing method of a solid electrolytic capacitor in which a process and / or (4) process are performed in ionic liquid presence.
(1) a step of forming a dielectric oxide film on the surface of an anode produced by sintering tantalum or niobium powder;
(2) forming an electrolyte on the dielectric film by in situ polymerization of a conductive polymer monomer;
(3) a step of washing the formed electrolyte;
(4) A step of filling the electrolyte after washing with a conductive polymer dispersion. The anion component of the ionic liquid is a formate anion and the general formula (1);

(Wherein R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, a straight chain or branched or alkyl group optionally C ₁ -C ₂₀ also form a ring, straight or branched or alkenyl group optionally C ₂ -C ₂₀ also form a ring, to form a straight or branched or cyclic C ₂ -C ₂₀ alkynyl group, C ₆ -C ₂₀ aryl group, C ₄ -C ₂₀ heteroaryl group, C ₇ -C ₂₀ aralkyl group, C ₄ -C ₂₀ heteroaralkyl group Which may be the same or different from each other, and together may form a ring.The alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, aralkyl group and heteroarral group The method for producing a solid electrolytic capacitor according to claim 1, wherein the kill group is at least one selected from the group consisting of carboxylate anions represented by:   The method for producing an electrolytic capacitor according to claim 1 or 2, wherein the in situ polymerization is chemical polymerization and / or electrolytic polymerization.   The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive polymer monomer is at least one selected from the group consisting of thiophene, thiophene derivatives, pyrrole, pyrrole derivatives, aniline and aniline derivatives.   The solid electrolytic capacitor according to claim 1, wherein the conductive polymer dispersion contains at least one selected from the group consisting of polythiophene, polythiophene derivatives, polypyrrole, polypyrrole derivatives, polyaniline, and polyaniline derivatives. Production method.   A solid electrolytic capacitor produced by the method for producing a solid electrolytic capacitor according to claim 1.