JP2006278794A - Solid electrolytic capacitor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having low impedance, and a solid electrolytic capacitor manufacturing method with which a solid electrolytic capacitor having low impedance can be easily manufactured. <P>SOLUTION: A solid electrolytic capacitor 10 includes an anode 11 composed of a valve metal porous body, a dielectric layer 12 formed by oxidizing the surface of the anode 11, and a cathode 13 which is disposed on the dielectric layer 12 and comprises, at the side of the dielectric layer 12, a solid electrolytic layer 13a containing a π-conjugate conductive polymer. At least the surface of the dielectric layer 12 at the side of the cathode 13 is coated with an electron-donative compound containing an electron-donative element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor such as an aluminum electrolytic capacitor, a tantalum electrolytic capacitor, and a niobium electrolytic capacitor, and a method for manufacturing the same.

 In recent years, with the digitization of electronic devices, capacitors used in electronic devices are required to reduce impedance (ESR) in a high frequency region. Conventionally, in order to meet this requirement, an oxide film of valve metal such as aluminum, tantalum, or niobium is used as a dielectric, and a π-conjugated conductive polymer such as polypyrrole or polythiophene is formed on this surface as a cathode. Solid electrolytic capacitors are used.

As shown in Patent Document 1, the structure of this solid electrolytic capacitor includes an anode made of a valve metal porous body, a dielectric layer formed by oxidizing the surface of the anode, and a solid electrolyte layer and carbon on the dielectric layer. It is common to have a cathode having a laminated layer and a silver layer. A π-conjugated conductive polymer such as pyrrole or thiophene is used for the solid electrolyte layer of the solid electrolytic capacitor.
As a method for forming a π-conjugated conductive polymer, an electrolytic polymerization method (see Patent Document 2) and a chemical oxidation polymerization method (see Patent Document 3) are widely known.
However, in the electropolymerization method, it is necessary to previously form a conductive layer made of manganese oxide on the surface of the anode on the dielectric layer, which is very complicated, and manganese oxide has low conductivity and high conductivity. There is a problem that the effect of using a conductive π-conjugated conductive polymer is reduced.
On the other hand, in the chemical oxidative polymerization method, the polymerization time is long, and it is necessary to repeat the polymerization in order to ensure the thickness, so that the production efficiency of the solid electrolytic capacitor is low and the conductivity is low.

Thus, it is complicated and difficult to perform the electrolytic polymerization method and the chemical oxidation polymerization method in the capacitor manufacturing process. Therefore, Patent Document 4 proposes forming a solid electrolyte layer by applying and drying a polyaniline solution obtained by polymerizing aniline in the presence of a polyanion having a sulfo group, a carboxy group or the like.
JP 2003-37024 A JP-A-63-158829 JP 63-173313 A JP-A-7-105718

However, in the method described in Patent Document 4, since the permeability of the polyaniline solution into the valve metal porous body is low, it is difficult to obtain an impedance equivalent to the electrolytic polymerization method or the chemical oxidation polymerization method.
An object of the present invention is to provide a solid electrolytic capacitor with low impedance. Moreover, it aims at providing the manufacturing method of the solid electrolytic capacitor which can manufacture a solid electrolytic capacitor with low impedance simply.

The solid electrolytic capacitor of the present invention includes an anode made of a porous body of a valve metal, a dielectric layer formed by oxidizing the surface of the anode, and disposed on the dielectric layer, and has a π-conjugated conductive high conductivity. In a solid electrolytic capacitor having a cathode provided with a solid electrolyte layer containing molecules on the dielectric layer side,
An electron donating compound containing an electron donating element is coated on at least the cathode side surface of the dielectric layer.
In the solid electrolytic capacitor of the present invention, the electron donating element of the electron donating compound is preferably at least one selected from nitrogen, oxygen, sulfur and phosphorus.
Alternatively, the electron donating compound is preferably at least one selected from pyrroles, thiophenes, and furans.
Alternatively, the electron donating compound is preferably an amine.

The method for producing a solid electrolytic capacitor of the present invention includes a step of oxidizing a surface of an anode made of a porous body of valve metal to form a dielectric layer;
Applying an electron donating compound containing an electron donating element to the surface of the dielectric layer;
And a step of forming a solid electrolyte layer containing a π-conjugated conductive polymer on the surface of the dielectric layer coated with at least the electron donating compound.
In the method for producing a solid electrolytic capacitor of the present invention, it is preferable to apply a conductive polymer solution containing a π-conjugated conductive polymer when forming the solid electrolyte layer.

The solid electrolytic capacitor of the present invention has a low impedance.
Moreover, according to the method for producing a solid electrolytic capacitor of the present invention, a solid electrolytic capacitor having a low impedance can be easily produced.

Hereinafter, an embodiment of a solid electrolytic capacitor (hereinafter abbreviated as a capacitor) of the present invention will be described.
FIG. 1 is a diagram illustrating a configuration of a capacitor according to the present embodiment. The capacitor 10 includes an anode 11 made of a porous body of valve metal, a dielectric layer 12 formed by oxidizing the surface of the anode 11, and a cathode 13 disposed on the dielectric layer 12. It is roughly structured.

<Anode>
Examples of the valve metal forming the anode 11 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Of these, aluminum, tantalum, and niobium are preferable.
Specific examples of the anode 11 include those obtained by etching an aluminum foil to increase the surface area and then oxidizing the surface, or oxidizing the surface of a sintered body of tantalum particles and niobium particles into pellets. Can be mentioned. As for the thing processed in this way, the unevenness | corrugation is formed in the surface.

<Dielectric layer>
The dielectric layer 12 is formed, for example, by anodizing the surface of the anode 11 in an electrolytic solution such as an aqueous solution of ammonium adipate. Therefore, as shown in FIG. 1, the surface of the dielectric layer 12 is uneven as in the anode 11.

<Cathode>
The cathode 13 includes a solid electrolyte layer 13a and a cathode conductive layer 13b made of carbon, silver, aluminum, or the like formed on the solid electrolyte layer 13a. The solid electrolyte layer 13a includes a π-conjugated conductive polymer. And is provided on the dielectric layer 12 side.
When the cathode conductive layer 13b is made of carbon, silver, or the like, it can be formed from, for example, a conductive paste containing a conductor such as carbon or silver. Moreover, when the cathode conductive layer 13b is comprised with aluminum, it can form from aluminum foil, for example.
Moreover, a separator can be provided between the solid electrolyte layer 13a and the anode 11 as necessary.

[Π-conjugated conductive polymer]
The π-conjugated conductive polymer can be used as long as the main chain is an organic polymer having a π-conjugated system. Examples thereof include polypyrroles, polythiophenes, polyacetylenes, polyphenylenes, polyphenylene vinylenes, polyanilines, polyacenes, polythiophene vinylenes, and copolymers thereof.

  Specific examples of such π-conjugated conductive polymers include polypyrrole, poly (N-methylpyrrole), poly (3-methylpyrrole), poly (3-ethylpyrrole), and poly (3-n-propylpyrrole). ), Poly (3-butylpyrrole), poly (3-octylpyrrole), poly (3-decylpyrrole), poly (3-dodecylpyrrole), poly (3,4-dimethylpyrrole), poly (3,4 Dibutylpyrrole), poly (3-carboxypyrrole), poly (3-methyl-4-carboxypyrrole), poly (3-methyl-4-carboxyethylpyrrole), poly (3-methyl-4-carboxybutylpyrrole), Poly (3-hydroxypyrrole), poly (3-methoxypyrrole), poly (3-ethoxypyrrole), poly (3-butoxypyrrole), poly 3-methyl-4-hexyloxypyrrole), polythiophene, poly (3-methylthiophene), poly (3-ethylthiophene), poly (3-propylthiophene), poly (3-butylthiophene), poly (3-hexyl) Thiophene), poly (3-heptylthiophene), poly (3-octylthiophene), poly (3-decylthiophene), poly (3-dodecylthiophene), poly (3-octadecylthiophene), poly (3-bromothiophene) , Poly (3-chlorothiophene), poly (3-iodothiophene), poly (3-cyanothiophene), poly (3-phenylthiophene), poly (3,4-dimethylthiophene), poly (3,4-dibutyl) Thiophene), poly (3-hydroxythiophene), poly (3-methoxythiophene), poly Li (3-ethoxythiophene), poly (3-butoxythiophene), poly (3-hexyloxythiophene), poly (3-heptyloxythiophene), poly (3-octyloxythiophene), poly (3-decyloxythiophene) ), Poly (3-dodecyloxythiophene), poly (3-octadecyloxythiophene), poly (3-methyl-4-methoxythiophene), poly (3,4-ethylenedioxythiophene), poly (3-methyl- 4-ethoxythiophene), poly (3-carboxythiophene), poly (3-methyl-4-carboxythiophene), poly (3-methyl-4-carboxyethylthiophene), poly (3-methyl-4-carboxybutylthiophene) ), Polyaniline, poly (2-methylaniline), poly (3-isobutene) Ruanirin), poly (2-aniline sulfonic acid), poly (3-aniline sulfonic acid), and the like.

Among these, one or two selected from polypyrrole, polythiophene, poly (N-methylpyrrole), poly (3-methylthiophene), poly (3-methoxythiophene), and poly (3,4-ethylenedioxythiophene) A (co) polymer consisting of seeds is preferably used from the viewpoint of resistance and reactivity. Furthermore, polypyrrole and poly (3,4-ethylenedioxythiophene) are more preferable because they have higher conductivity and improved heat resistance.
Moreover, what has a C6 or more alkyl group in a substituent is preferable at the point which can provide solvent solubility, without using the polyanion mentioned later. In addition, a π-conjugated conductive polymer having an anionic group as a substituent in the molecule is preferable because it itself dissolves in water.

The π-conjugated conductive polymer can be easily obtained by chemical oxidative polymerization of a precursor monomer of the π-conjugated conductive polymer in a solvent in the presence of an oxidizing agent or an oxidation polymerization catalyst.
At that time, pyrroles and derivatives thereof, thiophenes and derivatives thereof, anilines and derivatives thereof, and the like can be used as precursor monomers for the π-conjugated conductive polymer.
As oxidizing agents, peroxodisulfates such as ammonium peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate, transition metal compounds such as ferric chloride, cupric chloride, silver oxide, cesium oxide, etc. Metal oxides, peroxides such as hydrogen peroxide and ozone, organic peroxides such as benzoyl peroxide, oxygen, boron trifluoride and the like can be used.

  The solvent used in performing the chemical oxidative polymerization is not particularly limited as long as it is a solvent that can dissolve or disperse the precursor monomer, the oxidizing agent, or the oxidative polymerization catalyst. For example, water, polar solvents such as N-methyl-2-pyrrolidone, N, N′-dimethylformamide, N, N′-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphortriamide, and phenols such as cresol, phenol, xylenol , Alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone and methyl ethyl ketone, hydrocarbons such as hexane, benzene and toluene, carboxylic acids such as formic acid and acetic acid, carbonate compounds such as ethylene carbonate and propylene carbonate, Ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, polypropylene glycol Chain ethers such as alkyl ethers, 3-methyl-2-oxazolidinone heterocyclic compounds such as, acetonitrile, glutarodinitrile, methoxy acetonitrile, propionitrile, nitrile compounds such as benzonitrile and the like. These solvents may be used alone as appropriate, as a mixture of two or more kinds, or as a mixture with other organic solvents.

  In the capacitor 10, an electron donating compound containing an electron donating element is applied to the surface of the dielectric layer 12 on the cathode 13 side. Therefore, the electron donating compound is attached to the surface of the dielectric layer 12 on the cathode 13 side.

[Electron donating compound]
The electron donating compound in the present invention is a compound containing an electron donating element and is not a polymer.
As the electron donating element contained in the electron donating compound, the electrical affinity between the dielectric layer and the cathode containing the π-conjugated conductive polymer becomes higher. Of the genus elements, at least one selected from nitrogen, oxygen, phosphorus, and sulfur is preferable.

  As the electron-donating compound containing nitrogen, amines such as primary amine, secondary amine, tertiary amine and the like are preferable because the electrical affinity between the dielectric layer and the cathode becomes higher. Specific examples of amines include aliphatic amines such as ethylamine, diethylamine, methylethylamine, and triethylamine, aromatic amines such as aniline, benzylamine, pyrrole, imidazole, pyridine, pyrimidine, pyrazine, and triazine, or these amines. Derivatives.

  Examples of the electron donating compound containing oxygen include alcohols, ethers, and ketones. Specifically, lauryl alcohol, hexadecyl alcohol, benzyl alcohol, ethylene glycol, propylene glycol, glycerin, diphenyl ether, cyclohexanone. , Diacetone alcohol, isophorone, furan and derivatives thereof.

  Examples of the electron-donating compound containing phosphorus include phosphate esters, phosphites, phosphonic acids, alkylphosphines, alkylphosphonium salts, and the like. Specifically, trimethyl phosphate, triphosphate phosphate, and the like. Phenyl, trimethyl phosphite, triethyl phosphite, dimethyl phosphonate, diethyl phosphonate, triethylphosphine, tri-n-butylphosphine, tri-n-butylphosphine oxide, tetraethylphosphonium bromide, tetra-n-butylphosphonium bromide, etc. Is mentioned.

  Examples of the electron-donating compound containing sulfur include sulfides, thiols, isothiocyanates, thiophene, and derivatives thereof, and specifically, dimethyl sulfide, diethyl sulfide, methyl mercaptan, ethyl mercaptan, phenyl isocaps. Examples include thiocyanate, n-butylisothiocyanate, thiophene, and 3-methylthiophene.

  Among these electron donating compounds, a compound containing nitrogen, oxygen, or sulfur in the aromatic ring is preferable because the equivalent series resistance can be prevented from being lowered even if it remains in the dielectric layer. Examples of the compound containing nitrogen in the aromatic ring include pyrrole and derivatives thereof (pyrroles), imidazole, pyridine, pyrimidine, pyrazine, triazine and derivatives thereof. As the compound containing oxygen in the aromatic ring, Examples include furan and derivatives thereof (furans), and examples of the compound containing sulfur in the aromatic ring include thiophene and derivatives thereof (thiophenes). Among them, at least one selected from pyrroles, thiophenes, and furans is preferable because the electrical affinity between the dielectric layer and the cathode is higher.

In an electron-donating compound containing nitrogen, oxygen, and sulfur in the aromatic ring, since a non-shared electron pair exists in the nitrogen atom, oxygen atom, and sulfur atom, a substituent or a proton is coordinated on these atoms. Easy to be combined. When a substituent or proton is coordinated or bonded to a nitrogen atom, oxygen atom or sulfur atom, it tends to have a cationic charge on these atoms. In addition, since the nitrogen atom, oxygen atom, sulfur atom and other atoms have a conjugated relationship, the cation charge generated by the coordination or bonding of a substituent or proton on these atoms is an aromatic ring. It diffuses in and becomes stable.
For this reason, the electron donating compound containing nitrogen, oxygen, and sulfur in the aromatic ring as described above may form a cation by introducing a substituent into the nitrogen, oxygen, or sulfur atom. Further, a salt may be formed by combining the cation and the anion. Even a salt exhibits the same effect as an electron donating compound that is not a cation.

 The capacitor described above includes the dielectric layer and the π-conjugated conductive polymer because the surface of the dielectric layer is coated with an electron donating compound and the charge on the surface of the dielectric layer is neutralized. The electrical affinity with the solid electrolyte layer is high. As a result, since the resistance at the interface between the dielectric layer and the cathode is reduced, the impedance of the capacitor is low and the capacitance is high.

(Capacitor manufacturing method)
Next, an embodiment of a capacitor manufacturing method according to the present invention will be described.
The method of manufacturing a capacitor according to this embodiment includes a step of oxidizing a surface of an anode made of a porous body of a valve metal to form a dielectric layer, and a step of applying an electron donating compound to the surface of the dielectric layer. Forming a layer containing a π-conjugated conductive polymer (solid electrolyte layer) on the surface of the dielectric layer coated with the electron donating compound, and providing a cathode conductive layer on the solid electrolyte layer to form a cathode Forming the method.

  In this method of manufacturing a capacitor, examples of a method for oxidizing the anode surface include a method for anodizing the anode surface in an electrolytic solution such as an aqueous solution of ammonium adipate.

As a method for applying the electron donating compound to the surface of the dielectric layer, a known application method such as coating, dipping or spraying can be employed. When the electron donating compound is a solid, a solution in which the electron donating compound is dissolved in a solvent may be applied. In that case, it is preferable to remove the solvent by drying after coating. It is also preferable to remove the solvent when the liquid electron donating compound is diluted.
The concentration of the solution containing the electron-donating compound is not particularly limited. However, if it is too thin, the effect is difficult to express, and if it is too thick, it may be difficult to apply or ESR may be reduced. It is preferable that it is 5 to 50% by mass.

  In order to form a layer containing a π-conjugated conductive polymer, it is easy and the electrical affinity between the dielectric layer and the cathode can be improved more easily. A method of applying a conductive polymer solution in which a conductive polymer is dissolved in a solvent is preferable. Alternatively, the precursor monomer constituting the π-conjugated conductive polymer may be formed on the dielectric layer by directly performing chemical oxidative polymerization or electrolytic polymerization.

The conductive polymer solution is obtained by polymerizing a precursor monomer of a π-conjugated conductive polymer in the presence of a polyanion. Alternatively, it can be obtained by dissolving a π-conjugated conductive polymer having solvent solubility in a solvent.
As a specific example of a method for preparing a conductive polymer solution by polymerizing a precursor monomer of a π-conjugated conductive polymer in the presence of a polyanion, first, a polyanion is dissolved in a solvent capable of dissolving it. A precursor monomer of a π-conjugated conductive polymer is added to the solution obtained by the above. Next, an oxidizing agent is added to polymerize the precursor monomer, and then the excess oxidizing agent and precursor monomer are separated and purified to obtain a conductive polymer solution.

The polyanion used here is selected from, for example, substituted or unsubstituted polyalkylene, substituted or unsubstituted polyalkenylene, substituted or unsubstituted polyimide, substituted or unsubstituted polyamide, substituted or unsubstituted polyester, Even if it is a polymer which consists only of the structural unit which has an anion group, the polymer which consists of the structural unit which has an anion group, and the structural unit which does not have an anion group may be sufficient.
The polyanion not only solubilizes the π-conjugated conductive polymer in a solvent, but also functions as a dopant for the π-conjugated conductive polymer.

Here, polyalkylene is a polymer whose main chain is composed of repeating methylene. Examples of polyalkenylene include a polymer composed of structural units containing one vinyl group in the main chain, and there is an interaction between an unsaturated bond and a conductive polymer compound, and substituted or unsubstituted butadiene. Since it is easy to synthesize as a starting material, substituted or unsubstituted butenylene can be exemplified.
Examples of polyimide include pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, 2,2,3,3-tetracarboxydiphenyl ether dianhydride, 2,2- [4,4 Examples include polyimides from acid anhydrides such as' -di (dicarboxyphenyloxy) phenyl] propane dianhydride and diamines such as oxydianiline, paraphenylenediamine, metaphenylenediamine, and benzophenonediamine.
Examples of the polyamide include polyamide 6, polyamide 6,6, polyamide 6, 10, and the like.
Examples of the polyester include polyethylene terephthalate and polybutylene terephthalate.

 Examples of the substituent of the polymer constituting the polyanion include an alkyl group, a hydroxy group, a carboxy group, a cyano group, a phenyl group, a phenol group, an ester group, an alkoxy group, and a carbonyl group. Alkyl groups can increase solubility and dispersibility in polar or nonpolar solvents, compatibility and dispersibility in resins, and hydroxy groups form hydrogen bonds with other hydrogen atoms. This makes it easy to increase solubility in organic solvents, compatibility with resins, dispersibility, and adhesion. In addition, the cyano group and the hydroxyphenyl group can increase the compatibility and solubility in the polar resin, and can also increase the heat resistance. Among the above substituents, an alkyl group, a hydroxy group, an ester group, and a cyano group are preferable.

Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, butyl, isobutyl, t-butyl, pentyl, hexyl, octyl, decyl, and dodecyl, and cycloalkyl groups such as cyclopropyl, cyclopentyl, and cyclohexyl. In consideration of solubility in an organic solvent, dispersibility in a resin, steric hindrance, and the like, an alkyl group having 1 to 12 carbon atoms is more preferable.
Examples of the hydroxy group include a hydroxy group directly bonded to the main chain of the polyanion, a hydroxy group bonded to the terminal of the alkyl group having 1 to 7 carbon atoms bonded to the main chain of the polyanion, and 2 to 2 carbon atoms bonded to the main chain of the polyanion. And a hydroxy group bonded to the terminal of 7 alkenyl group. Among these, a hydroxy group bonded to the terminal of an alkyl group having 1 to 6 carbon atoms bonded to the main chain is more preferable from the viewpoint of compatibility with a resin and solubility in an organic solvent.
Examples of the ester group include an alkyl ester group directly bonded to the main chain of the polyanion, an aromatic ester group, and an alkyl ester group or an aromatic ester group having another functional group interposed therebetween.
The cyano group includes a cyano group directly bonded to the main chain of the polyanion, a cyano group bonded to the terminal of the alkyl group having 1 to 7 carbon atoms bonded to the main chain of the polyanion, and 2 to 2 carbon atoms bonded to the main chain of the polyanion. And a cyano group bonded to the terminal of 7 alkenyl group.

The anion group in the polyanion may be any functional group that can undergo chemical oxidation doping to the π-conjugated conductive polymer. Among them, from the viewpoint of ease of production and stability, a mono-substituted sulfate group, A substituted phosphate group, carboxylic acid group, sulfonic acid group and the like are preferred. Furthermore, a sulfonic acid group and a monosubstituted sulfate group are more preferable from the viewpoint of the doping effect of the functional group on the conductive polymer compound.
Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacryl sulfonic acid, poly-2-acrylamido-2-methylpropane sulfonic acid, polyisoprene sulfonic acid, polyacrylic. An acid etc. are mentioned.
Of these, polyacrylsulfonic acid and polymethacrylsulfonic acid absorb heat energy and decompose by themselves, so that thermal decomposition of the conductive polymer component is alleviated, so heat resistance and environmental resistance are excellent. Furthermore, since it has an ester group, it is particularly preferable because it has excellent compatibility and dispersibility with the binder resin.

 In order to improve the conductivity of the π-conjugated conductive polymer, a dopant other than the polyanion may be added to the conductive polymer solution. Usually, halogen compounds, Lewis acids, proton acids and the like are used as dopants. Specifically, for example, organic acids such as organic carboxylic acids and organic sulfonic acids, organic cyano compounds, fullerenes, hydrogenated fullerenes, and fullerene hydroxides. Carboxylic acid fullerene, sulfonated fullerene and the like.

Examples of organic acids include alkylbenzene sulfonic acid, alkyl naphthalene sulfonic acid, alkyl naphthalene disulfonic acid, naphthalene sulfonic acid formalin polycondensate, melamine sulfonic acid formalin polycondensate, naphthalene disulfonic acid, naphthalene trisulfonic acid, dinaphthylmethane disulfonic acid, Anthraquinone sulfonic acid, anthraquinone disulfonic acid, anthracene sulfonic acid, pyrene sulfonic acid and the like can be mentioned. These metal salts can also be used.
As the organic cyano compound, a compound containing two or more cyano groups in a conjugated bond can be used. Examples include tetracyanoethylene, tetracyanoethylene oxide, tetracyanobenzene, dichlorodicyanobenzoquinone (DDQ), tetracyanoquinodimethane, and tetracyanoazanaphthalene.

 The ratio of the π-conjugated conductive polymer to the dopant is preferably 97: 3 to 10:90 as a molar ratio of π-conjugated conductive polymer: dopant. Even if there are more or less dopants, the conductivity tends to decrease.

  The solvent that can be used in the conductive polymer solution is not particularly limited, and alcohol solvents such as methanol, ethanol, isopropyl alcohol (IPA), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF) Examples include amide solvents such as methyl ethyl ketone (MEK), ketone solvents such as acetone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, toluene, xylene, water, and the like. They may be used or mixed. Among these, from the viewpoint of environmental protection in recent years, water and alcohol solvents having a low environmental load are preferable.

  Examples of the method for applying the conductive polymer solution include known methods such as coating, dipping, and spraying. Moreover, well-known methods, such as hot air drying, are mentioned as a drying method for removing a solvent.

After forming the solid electrolyte layer, a method of forming a cathode conductive layer by impregnating an electrolytic solution as necessary and then applying a carbon paste or a silver paste, or a cathode conductive layer such as an aluminum foil via a separator A capacitor can be obtained by forming a cathode by a known method of arranging
When using a separator, as the separator, for example, a single or mixed nonwoven fabric such as cellulose fiber, glass fiber, polypropylene fiber, polyester fiber, polyamide fiber, carbonized nonwoven fabric obtained by carbonizing these, or the like is used.

In the capacitor manufacturing method described above, by applying an electron donating compound to the surface of the dielectric layer, the electrical affinity between the dielectric layer and the solid electrolyte layer can be improved, and the impedance of the capacitor can be lowered. Can do. Moreover, the application of the electron donating compound is simple. Therefore, the capacitor manufacturing method described above can easily manufacture a capacitor with low impedance.
Furthermore, the capacitor obtained by this manufacturing method has a high capacity and excellent heat resistance.

Note that the present invention is not limited to the above-described embodiments. In the embodiment described above, an electron donating compound was applied to the surface of the dielectric layer, and after forming a solid electrolyte layer, a conductive cathode layer was provided to form a cathode to obtain a capacitor. The timing for providing the cathode conductive layer is not limited. For example, after disposing the cathode conductive layer so as to face the dielectric layer, an electron donating compound may be applied to the surface of the dielectric layer, and then the solid electrolyte layer may be formed. In that case, it is preferable to arrange a separator between the cathode conductive layer and the dielectric layer.
The electron donating compound may be applied not only to the surface of the dielectric layer, but also to the surface of the cathode conductive layer on the dielectric layer side and the separator.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
(1) Preparation of conductive polymer solution 14.2 g (0.1 mol) of 3,4-ethylenedioxythiophene and 27.5 g (0.15 mol) of polystyrene sulfonic acid (molecular weight; about 150,000) A solution dissolved in 2000 ml of ion-exchanged water was mixed at 20 ° C.
29.64 g (0.13 mol) of ammonium persulfate and 8.0 g (0.02 mol) of ferric sulfate dissolved in 200 ml of ion-exchanged water were kept at 20 ° C. while stirring the mixed solution thus obtained. The oxidation catalyst solution was added and stirred for 3 hours to react.
The resulting reaction solution is dialyzed to remove unreacted monomers and oxidants, and a conductive polymer solution containing about 1.5% by weight of blue polystyrenesulfonic acid-doped poly (3,4-ethylenedioxythiophene). Got.
(2) Preparation of electron donating compound solution 7.79 g of imidazole was dissolved in 100 ml of distilled water to obtain an electron donating compound solution.

(3) Manufacture of capacitor After connecting the anode lead terminal to the etched aluminum foil, it was formed (oxidized) in an aqueous solution of 10% by weight of ammonium adipate to form a dielectric layer on the surface of the aluminum foil to form the anode foil. Obtained.
Next, a separator made of cell roll was sandwiched between the anode foil and the opposed aluminum cathode foil to which the cathode lead terminal was welded, and wound into a cylindrical shape to obtain a capacitor element.
Next, after immersing the capacitor element in the electron donating compound solution prepared in (2) under reduced pressure, the capacitor element is dried for 2 minutes in a hot air dryer at 120 ° C., and then the conductive polymer prepared in (1). The capacitor element was immersed in the solution under reduced pressure, and then dried for 10 minutes with a hot air dryer at 150 ° C. Then, immersion in the conductive polymer solution was repeated five times to form a solid electrolyte layer containing a π-conjugated conductive polymer on the surface of the dielectric layer.
Next, a capacitor element on which a solid electrolyte layer was formed was loaded into an aluminum case and sealed with a sealing rubber to produce a capacitor.
Using the LCZ meter 2353 (manufactured by NF Circuit Design Block Co., Ltd.), measured the capacitance at 120 Hz, the initial value of the equivalent series resistance (ESR) at 100 kHz, and the ESR after 1000 hours at 125 ° C. did. The results are shown in Table 1. Note that ESR is an index of impedance.

(Example 2)
The same procedure as in Example 1 was used except that a solution obtained by dissolving 10 g of pyrrole in 100 ml of methyl ethyl ketone was used as an electron donating compound solution instead of a solution obtained by dissolving 7.79 g of imidazole in 100 ml of distilled water. To obtain a capacitor. And it evaluated similarly to Example 1. FIG. The evaluation results are shown in Table 1.

(Comparative Example 1)
A capacitor was produced in the same manner as in Example 1 except that the capacitor element was not immersed in the electron donating compound solution in the production of the capacitor of Example 1. And it evaluated similarly to Example 1. FIG. The evaluation results are shown in Table 1.

The capacitors of Examples 1 and 2 in which the electron donating compound was applied to the surface of the dielectric layer had high capacitance and low ESR (impedance was low). In addition, a decrease in ESR after heating was prevented, and heat resistance was excellent.
On the other hand, the capacitor of Comparative Example 1 in which the electron donating compound was not applied to the surface of the dielectric layer had a low capacitance and a high ESR (high impedance). Moreover, after heating, ESR was significantly increased and the heat resistance was low.

It is sectional drawing which shows one example of embodiment in the solid electrolytic capacitor of this invention.

Explanation of symbols

10 Capacitor (solid electrolytic capacitor)
11 Anode 12 Dielectric Layer 13 Cathode 13a Solid Electrolyte Layer (Layer Containing π-Conjugated Conductive Polymer)

Claims (6)

An anode made of a porous body of valve metal, a dielectric layer formed by oxidizing the surface of the anode, and a solid electrolyte layer disposed on the dielectric layer and containing a π-conjugated conductive polymer In a solid electrolytic capacitor having a cathode provided on the body layer side,
A solid electrolytic capacitor, wherein an electron donating compound containing an electron donating element is applied to at least a cathode side surface of a dielectric layer.   2. The solid electrolytic capacitor according to claim 1, wherein the electron donating element of the electron donating compound is at least one selected from nitrogen, oxygen, sulfur and phosphorus.   2. The solid electrolytic capacitor according to claim 1, wherein the electron donating compound is at least one selected from pyrroles, thiophenes, and furans.   2. The solid electrolytic capacitor according to claim 1, wherein the electron donating compound is an amine. Oxidizing the surface of the anode made of a porous body of valve metal to form a dielectric layer;
Applying an electron donating compound containing an electron donating element to at least the surface of the dielectric layer;
And a step of forming a solid electrolyte layer containing a π-conjugated conductive polymer on the surface of the dielectric layer coated with the electron donating compound. 6. The method for manufacturing a solid electrolytic capacitor according to claim 5, wherein a conductive polymer solution containing a π-conjugated conductive polymer is applied when forming the solid electrolyte layer.

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