JP5296860B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which has high electrostatic capacity and low ESR and also has more superior electric characteristics and heat resistance, and to provide a method of manufacturing the same. <P>SOLUTION: (1) This invention relates to the solid electrolytic capacitor that includes as a solid electrolyte a polymer obtained by polymerizing a compound which is a thiophene derivative having a heteroatom-containing cyclic substituent group and has an alkyl substituent at the heteroatom-containing cyclic substituent group. (2) This invention also relates to the method of manufacturing the solid electrolytic capacitor that includes a step of forming the high polymer described in (1) on a valve action metal having a dielectric oxide film formed. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor having a solid electrolyte layer, and more particularly to a method for manufacturing a solid electrolytic capacitor having a conductive polymer layer exhibiting high conductivity as a solid electrolyte layer and having excellent electrical characteristics. .

Examples of solid electrolyte forming materials used for solid electrolytic capacitors include inorganic conductive materials such as manganese dioxide and organic conductive materials such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex. Are known.
Furthermore, solid electrolytic capacitors using a conductive polymer material, which is more excellent in electrical conductivity than those solid electrolyte forming materials, as a solid electrolyte have been widely put into practical use.

As this conductive polymer material, a conductive polymer obtained by polymerizing 3,4-ethylenedioxythiophene (hereinafter abbreviated as “EDOT”) as a monomer is widely known.
This EDOT is useful as a solid electrolyte layer forming material for a solid electrolytic capacitor because it forms a conductive polymer layer having a moderate polymerization reaction rate and excellent adhesion to the dielectric oxide film of the anode.

However, in recent years, electronic devices are required to support more power saving and higher frequency, and in solid electrolytic capacitors used for such electronic devices, a smaller and larger capacity and a lower equivalent series resistance (hereinafter, It is abbreviated as “ESR.”) Further improvement in electrical characteristics is demanded.
The electrical characteristics of the solid electrolytic capacitor greatly depend on the type of solid electrolyte forming material used and the forming method. However, the development of an excellent conductive polymer monomer that surpasses the well-known EDOT and a new solid electrolyte layer forming method. Expectation is held.

In such a background, a solid electrolytic capacitor using a polymer of 3-alkyl-4-alkoxythiophene as a solid electrolyte is known as a conventional technique, and by using the polymer, excellent electrical characteristics even in a high frequency region. It has been reported that a solid electrolytic capacitor having the following can be obtained (Patent Document 1).

Further, a solid electrolytic capacitor has been proposed that uses a polymer obtained by polymerizing an alkylenedioxythiophene derivative having a site substituted with an alkoxy group as a solid electrolyte.
By adopting this polymer, it is possible to suppress crystallization of the oxidant for polymerization remaining in the polymer, and to reduce the leakage current of the obtained solid electrolytic capacitor (Patent Document 2).

JP 2001-332453 A JP 2004-096098 A

However, even with the polymers disclosed in the above documents, it is still difficult to obtain sufficient electrical characteristics and heat resistance, and further improvements in the electrical characteristics and heat resistance of solid electrolytic capacitors are desired.
On the other hand, in order to increase the capacitance of a solid electrolytic capacitor, a foil type used for an anode element by winding or laminating an aluminum foil whose surface has been expanded by etching, and a metal fine particle are sintered and porous. There is a sintered element type that can obtain a large capacity. Sintered molded element type has a finer particle diameter of metal fine particles for the purpose of increasing capacity, and its CV product (product of capacitance and voltage per 1 g of sintered molded element) is 100,000 μFV. / G or more.
In recent years, polypyrrole or PEDOT (polyethylenedioxythiophene) has been used as a solid electrolyte for high performance. These are polymerized by chemical oxidative polymerization or electrolytic polymerization, but the voids of the porous sintered molded element tend to be finer, and it is difficult to polymerize and fill polypyrrole or PEDOT in the voids.

  An object of the present invention is to provide a method for producing a solid electrolytic capacitor having both excellent electrical characteristics exhibiting high capacitance and low ESR, as well as excellent heat resistance.

As a result of intensive studies by the present inventors, it has been found that a solid electrolytic capacitor containing a polymer obtained by polymerizing a compound represented by the following general formula [1] as a solid electrolyte is suitable for the purpose of the present invention. It came to be completed.
That is, the present invention is as follows.

The first invention includes the following general formulas [2] and [3]
[2]
[3]
A solid electrolytic capacitor having a step of forming a polymer obtained by polymerizing at least one of the compounds represented by the formula (1) on a valve action metal on which a dielectric oxide film is formed,
When the equivalent series resistance (ESR) value of a solid electrolytic capacitor using a polymer obtained by polymerizing 3,4-ethylenedioxythiophene is 100,
A solid electrolytic capacitor using a polymer obtained under the same polymerization conditions as in the case of 3,4-ethylenedioxythiophene has a value of the ESR measured under the same measurement conditions as in the case of 3,4-ethylenedioxythiophene. A method for producing a solid electrolytic capacitor, wherein the ratio is in the range of 63 to 78,
(A) at least one selected from the group consisting of compounds represented by the above general formulas [2] and [3],
(B) a dopant,
And (C) a step of polymerizing by contacting the oxidizing agent in a liquid phase,
As the (B) dopant and (C) oxidizing agent, a compound having the properties of both (B) dopant and (C) oxidizing agent is used,
The compound having the properties of both the (B) dopant and the (C) oxidizing agent is an organic sulfonic acid ferric salt,
The liquid phase comprises an organic sulfonic acid ferric salt in the range of 40 to 70% by weight;
The liquid phase solvent is n-butanol;
The method for producing a solid electrolytic capacitor, wherein the valve metal is aluminum.

2nd invention implements the time heat test for 24 hours or more and 48 hours or less on the conditions of 125 degreeC with respect to the solid electrolytic capacitor obtained by the manufacturing method of the solid electrolytic capacitor of Claim 1,
The value of ESR of the solid electrolytic capacitor after the obtained heat resistance test is performed,
When the ESR value of the solid electrolytic capacitor when the heat resistance test is carried out using a polymer obtained by polymerizing 3,4-ethylenedioxythiophene is within the range of 57 to 76. A method for producing a solid electrolytic capacitor according to the first invention.

  3rd invention is a manufacturing method of the solid electrolytic capacitor as described in 1st invention or 2nd invention whose said solid electrolytic capacitor is an aluminum winding type | mold capacitor.

According to the present invention, a solid electrolytic capacitor having high capacitance, low ESR, and excellent heat resistance can be provided.
The following general formulas [2] and [3]
[2]
[3]
When a polymer obtained by polymerizing at least one of the compounds represented by is used as a solid electrolyte, the polymerization rate of these monomers is relatively moderate. The voids in the porous molded body obtained by sintering can be sufficiently filled.
Thereby, it is possible to provide a solid electrolytic capacitor having a high capacitance, a low ESR, and an excellent heat resistance.

It is the graph which took the carbon number of the substituent of EDOT on the horizontal axis, and took ESR (m (ohm)) on the vertical axis | shaft (Examples 7-9, Comparative Examples 4 and 7). It is the graph which took the carbon number of the substituent of EDOT on the horizontal axis | shaft, and took the polymerization rate (second) on the vertical axis | shaft (Examples 4-6 and Comparative Examples 1-2). It is a schematic cross section for demonstrating the structure of the solid electrolytic capacitor based on Example 10 of this invention.

The present invention is described in detail below.
The present invention is a solid electrolytic capacitor comprising, as a solid electrolyte, a polymer obtained by polymerizing a compound represented by the following general formula [1].

[1]

  In the said General formula [1], R1 shows a C1-C2 linear alkyl group. Z represents an oxygen atom.

Examples of the linear alkyl group having 1 to 2 carbon atoms include a methyl group and an ethyl group, and more preferably a methyl group.
In the case of a linear or branched alkyl group having 6 or more carbon atoms, the polymerization reactivity of the resulting compound is lowered, and it becomes difficult to obtain a polymer.

As the compound represented by the general formula [1], more preferably,
2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT),
2-ethyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-ethyl-EDOT),
Is mentioned.

The polymer obtained by polymerizing the compound represented by the general formula [1] exhibits high conductivity and is excellent in thermal stability.
The compound used in the present invention has an improved polymerization rate as compared with known conductive polymer monomers such as EDOT.
That is, although the polymerization rate is lower than that of EDOT, it has high polymerizability, so that it can penetrate and polymerize deeply into the hole of the porous metal having a complicated shape.
Therefore, the polymer of the compound used in the present invention is a conductive polymer material particularly suitable for the solid electrolyte of the solid electrolytic capacitor.

  In the above-described compounds, when at least one of the following general formulas [2] and [3] is used, a solid electrolytic capacitor having particularly excellent ESR characteristics and heat resistance can be obtained.

[2]
[3]

The polymer obtained by polymerizing at least one of the compounds represented by the general formulas [1] to [3] can be obtained by the polymerization method shown below.
For example, the polymer can be obtained by chemical oxidative polymerization of the above compound using an oxidizing agent, and the polymer can also be obtained by electrochemical oxidative polymerization.

As the oxidizing agent in chemical oxidative polymerization, halides such as iodine, bromine, bromine iodide, chlorine dioxide, iodic acid, periodic acid, chlorous acid,
Metal halides such as antimony pentafluoride, phosphorus pentachloride, phosphorus pentafluoride, aluminum chloride, molybdenum chloride,
High valence state transition metal ions such as permanganate, dichromate, chromic anhydride, ferric salt, cupric salt or salts thereof,
Protic acids such as sulfuric acid, nitric acid, trifluoromethanesulfonic acid,
Oxygen compounds such as sulfur trioxide and nitrogen dioxide,
Peroxo acids and salts such as hydrogen peroxide, ammonium persulfate, sodium perborate,
Examples include heteropolyacids and salts such as molybdophosphoric acid, tungstophosphoric acid, and tungstomolybdophosphoric acid.

  In addition, as electrochemical oxidative polymerization, polymerization is performed by electrolytic oxidation in an electrolytic solution in which at least one of the compounds represented by the above general formulas [1] to [3] and a dopant are dissolved in a solvent. And the like.

Examples of the dopant include halogen ions such as iodine, bromine, and chlorine, halide ions such as hexafluorolin, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, and perchloric acid,
Alkyl-substituted organic sulfonate ions such as methanesulfonic acid and dodecylsulfonic acid,
Cyclic sulfonate ions such as camphorsulfonate ions,
Alkyl-substituted or unsubstituted benzene mono- or disulfonic acid ions such as benzenesulfonic acid, paratoluenesulfonic acid, dodecylbenzenesulfonic acid, benzenedisulfonic acid,
Alkyl substituted or unsubstituted ions of naphthalene sulfonic acid substituted with 1 to 4 sulfonic acid groups such as 2-naphthalene sulfonic acid and 1,7-naphthalenedisulfonic acid,
Anthracene sulfonate ion, anthraquinone sulfonate ion,
Alkyl-substituted or unsubstituted biphenylsulfonic acid ions such as alkylbiphenylsulfonic acid and biphenyldisulfonic acid,
Polymer sulfonate ions such as polystyrene sulfonate, naphthalene sulfonate formalin condensate, etc.
Examples include heteropolyacid ions such as molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid, and the like, and these various salts can be used as the supporting electrolyte.

  An example of the solvent is butanol.

  As an electrochemical polymerization method, a polymer can be formed on the anode by electrolytically oxidizing the compound in the electrolytic solution.

The solid electrolytic capacitor of the present invention includes a solid electrolyte layer containing a polymer obtained by polymerizing at least one of the compounds represented by the general formulas [1] to [3], and has a high capacitance. Low ESR and excellent electrical properties.
In addition, the heat resistance is remarkably improved as compared with a solid electrolytic capacitor using a conventional poly-3,4-ethylenedioxythiophene (hereinafter abbreviated as “PEDOT”) as a solid electrolyte layer.

The reason why the solid electrolytic capacitor of the present invention exhibits low ESR is not clearly clarified, but the polymerization rate of the compound used in the present invention is relatively slow, and the polymerization reaction solution is good in the dielectric oxide film. This is probably because the polymer can be formed after the permeation, so that a solid electrolyte layer with higher adhesion can be formed.
Furthermore, an induced effect is caused by the resulting polymer having an alkyl group with a short chain length as a substituent, and the electron distribution is broader than that of PEDOT (a conjugated system is widened), resulting in an increase in conductivity. Presumed to be.

Next, the manufacturing method of the solid electrolytic capacitor of this invention is demonstrated.
The method for producing the solid electrolytic capacitor of the present invention includes:
On the valve action metal on which the dielectric oxide film is formed,
It has the process of forming the polymer obtained by polymerizing the compound represented by the general formula [1] on the valve action metal on which the dielectric oxide film is formed.

Aluminum can be used as the valve metal.
As the form of the valve action metal, a metal foil or a powder sintered body mainly containing the metal foil can be preferably used.

  As a method of forming a dielectric oxide film on the valve action metal, a dielectric oxide film can be formed on the valve action metal surface by anodizing in a chemical conversion solution such as diammonium adipate aqueous solution.

The step of forming the polymer may be the above-described chemical oxidative polymerization method or electrolytic oxidative polymerization method.
From the viewpoint of electrical characteristics of the obtained solid electrolytic capacitor and a simpler manufacturing process, it is preferably a process of forming a polymer by chemical oxidative polymerization.

  A preferred production method for forming a polymer by chemical oxidative polymerization is a method in which at least one of the compounds represented by the above [2] to [3] (A), dopant (B) and oxidizing agent (C) is used in a liquid phase. And forming a polymer on the valve action metal by contacting them.

As a method of bringing the compound (A), dopant (B) and oxidant (C) into contact in the liquid phase,
1. A solution in which at least one of the compounds represented by the above [2] to [3] (A), dopant (B) and oxidant (C) is mixed is prepared, and this solution is applied to or immersed in the valve action metal. 1. A method of obtaining a polymer by contacting with Prepare the compound solution, separately prepare a solution containing a dopant and an oxidant, and apply or immerse the valve action metal impregnated and held in the compound solution in the oxidant solution to bring it into contact with the polymer. 2. Obtaining method Examples thereof include a method in which a polymer containing a dopant and an oxidizing agent is obtained by applying or immersing the compound solution in a valve action metal that is applied or impregnated and held, and then contacting the metal.
These methods are not particularly limited.

As a method for forming a polymer on the valve metal, the liquid containing the compound (A), dopant (B) and oxidant (C) held on the valve metal is held at a predetermined temperature for a predetermined time. Can be formed.
Here, the predetermined temperature can be arbitrarily selected in the range of 0 ° C. to 150 ° C., and the predetermined time can be arbitrarily selected in the range of 1 minute to 24 hours.

  A more preferable form in the method for producing a solid electrolytic capacitor of the present invention is a method using a solution of a compound having properties of both a dopant (B) and an oxidizing agent (C).

  The compound having the properties of both the dopant (B) and the oxidizing agent (C) is an oxidizing agent containing an anionic component that serves as a dopant for a conductive polymer, and an anionic component that serves as a dopant for such a conductive polymer. By using an oxidizing agent containing, an anionic component is incorporated into the conductive polymer during chemical polymerization to function as a dopant, and a conductive polymer with improved conductivity can be obtained.

  Preferable anion components include organic acid ions such as organic sulfonate ions and carboxylate ions, inorganic acid ions such as boron compound ions, phosphate compound ions, and perchlorate ions.

  Particularly suitable as an oxidizing agent containing such anionic components are iron (III) salts of inorganic acids such as ferric chloride and ferric perchlorate, ferric benzenesulfonate and paratoluenesulfonic acid. An iron (III) salt of an organic acid such as a ferric salt or a ferric alkylnaphthalene sulfonic acid salt can be exemplified, and the most preferable one can include a ferric (III) salt of an organic sulfonic acid. .

(B) As a solvent for dissolving a compound having both properties of a dopant and (C) an oxidizing agent, n-butanol may be mentioned.

Among these, particularly preferred is iron (III) of the organic sulfonic acid in the alcohol solvent, 20% to 90% by weight, more preferably 30% to 80% by weight, and still more preferably 40% by weight. % To 70% by weight.
By using a compound having the properties of both (B) dopant and (C) oxidant dissolved in such a concentration, a polymer having excellent conductivity and durability can be converted into a valve metal having a complicated shape. In addition, it can be formed densely.

  Hereinafter, the manufacturing method of the solid electrolytic capacitor of the present invention will be described by taking a method of manufacturing an aluminum wound capacitor as a specific example.

  First, the surface of the aluminum foil serving as the anode is etched to be roughened, and then the anode lead is connected, followed by chemical conversion treatment in an aqueous solution of diammonium adipate or the like to form a dielectric oxide film. In practicing the present invention, it is preferable to use a foil having a large etching magnification, whereby a capacitor having a large capacitance can be obtained.

  Separately, a separator such as manila paper is sandwiched between the facing cathode aluminum foil to which the cathode lead is connected and the anode aluminum foil, wound up in a cylindrical shape, and then carbonized by heat treatment, and the winding type capacitor. Prepare the device.

  Next, a solid electrolyte layer made of a conductive polymer is formed on the anode foil of the capacitor element. As a method of forming this solid electrolyte layer, a method of immersing, coating, spraying, etc., a liquid containing a compound represented by at least one of the general formulas [1] to [3], which is a conductive polymer monomer, in a capacitor element Then, the impregnated compound is allowed to undergo a polymerization reaction by bringing an oxidant into contact therewith to form a solid electrolyte layer.

  In addition, the method of impregnating with an oxidizing agent first and then polymerizing by contacting the above compound, or the method of impregnating and polymerizing a solution in which the compound and the oxidizing agent are mixed at a time can be applied, and is not particularly limited.

  Moreover, it is preferable that chemical oxidation polymerization superposes | polymerizes by putting the compound, dopant, and oxidizing agent which were contacted in the liquid phase for a predetermined time at the temperature of 0-150 degreeC, and heat-drying a solvent. If it is less than 0 ° C., the polymerization reaction hardly occurs, and if it exceeds 150 ° C., the capacitor characteristics may be deteriorated.

  The impregnation and heating steps may be repeated a plurality of times.

  By the above process, a solid electrolyte layer in which the conductive polymer layer is sufficiently filled in the fine etching holes of the anode aluminum foil can be formed.

  Next, the capacitor case is sealed with an epoxy resin or the like, and a voltage is applied to perform aging, whereby the solid electrolytic capacitor of the present invention can be obtained.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited at all by an Example.
In the examples, “%” represents “% by mass”. Unless otherwise specified, capacitance (C) and dielectric loss (tan δ) were measured at a frequency of 120 Hz, and equivalent series resistance (ESR) was measured at a frequency of 100 kHz.
The capacity impregnation rate is a percentage of the capacitance of the obtained solid electrolytic capacitor with respect to the capacitance measured in a 15% diammonium adipate aqueous solution of the capacitor element before forming the solid electrolyte layer. is there.
LC represents a leakage current, which is a value obtained by measuring a direct current flowing through the solid electrolytic capacitor 60 seconds after applying the rated voltage.

[Production Method of Solid Electrolytic Capacitor Using 2-Methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT)]
After the surface of the aluminum foil is roughened by etching, the anode lead is connected by caulking, and then subjected to chemical conversion treatment in a 10% diammonium adipate aqueous solution at a voltage of 4 V, so that the surface of the aluminum foil is dielectrically treated. A body oxide film was formed.

  Next, a 50 μm-thick manila paper is sandwiched as a separator between the anode foil and the counter cathode aluminum foil in which the cathode lead is connected by resistance welding, and wound into a cylindrical shape. The capacitor element was prepared by heat treating for a minute to carbonize the Manila paper. The capacitance of the obtained capacitor element in a 15% diammonium adipate aqueous solution was 650 μF.

  Next, 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT) which is a compound used for polymerization and 50% p-toluenesulfone which is an oxidizing agent A ferric acid / n-butanol solution was prepared, and the capacitor element was immersed in a solution prepared by mixing the weight ratio of the two at 1: 2.5 for 120 seconds, then at 45 ° C. for 2 hours, at 105 ° C. for 35 minutes, It heated at 125 degreeC for 1 hour, chemical oxidation polymerization was performed, and poly-2-methyl-EDOT was formed in the capacitor | condenser element.

  Next, the capacitor case was sealed with an epoxy resin, and aging was performed by applying a voltage of 4 V to both electrodes to complete a solid electrolytic capacitor.

[Method for producing solid electrolytic capacitor using 2-ethyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-ethyl-EDOT)]

  A pre-polymerization-treated capacitor element similar to that of Example 1 was prepared, and 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2) of Example 1 was used as a compound for polymerization. The same method as in Example 1 except that 2-ethyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-ethyl-EDOT) was used instead of -methyl-EDOT) The solid electrolytic capacitor was manufactured by processing.

[Method for producing solid electrolytic capacitor using 2-propyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-propyl-EDOT)]

  A pre-polymerization-treated capacitor element similar to that of Example 1 was prepared, and 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2) of Example 1 was used as a compound for polymerization. The same method as in Example 1 except that 2-propyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-propyl-EDOT) was used instead of -methyl-EDOT) The solid electrolytic capacitor was manufactured by processing.

[Comparative Example 1]
[Method of Manufacturing Solid Electrolytic Capacitor Using 2,3-Dihydrothieno [3,4-b] -1,4-dioxin (EDOT)]
A pre-polymerization-treated capacitor element similar to that of Example 1 was prepared, and 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2) of Example 1 was used as a compound for polymerization. The solid electrolytic capacitor was treated in the same manner as in Example 1 except that 2,3-dihydrothieno [3,4-b] -1,4-dioxin (EDOT) was used instead of -methyl-EDOT). Was made.
Table 1 shows the initial electrical characteristics, capacity impregnation rate, and leakage current electrical characteristics of the solid electrolytic capacitors obtained in Examples 1 to 3 and Comparative Example 1, respectively.

As shown in Table 1, as a result of comparing various compounds, the solid electrolytic capacitors obtained in Examples 1 to 3 have a lower equivalent series resistance than the solid electrolytic capacitor using the EDOT of the comparative example. I understood it.
In particular, the solid electrolytic capacitor obtained in Example 1 was found to have a significantly reduced ESR.

0.3 g of 50% p-toluenesulfonic acid ferric sulfonate / n-butanol solution as an oxidizing agent was taken in a 6 ml vial and kept at 20 ° C. for 30 minutes.
Next, 0.1 g of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), which is a compound used for polymerization, is added to a vial and measured. Started.
5 seconds after the addition, the contents in the vial were vigorously stirred with a spatula for 10 seconds.
The time from the end of stirring until the solid began to precipitate in the vial was measured. The results are summarized in Table 2.
In addition, the polymerization rate in Table 2 is a value obtained by subtracting 10 seconds from the number of seconds in which the solid was precipitated.

  In the case of Example 4, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2-ethyl-2,3-dihydrothieno [ The experiment was performed in exactly the same manner as in Example 4 except that 3,4-b] -1,4-dioxin (2-ethyl-EDOT) was used. The results are shown in Table 2.

  In the case of Example 4, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2-propyl-2,3-dihydrothieno [ The experiment was performed in exactly the same manner as in Example 4 except that 3,4-b] -1,4-dioxin (2-propyl-EDOT) was used. The results are shown in Table 2.

[Comparative Example 2]
In the case of Example 4, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2-hexyl-2,3-dihydrothieno [ The experiment was performed in exactly the same manner as in Example 4 except that 3,4-b] -1,4-dioxin (2-hexyl-EDOT) was used. During the measurement of the polymerization rate, solid precipitation could not be confirmed. The viscosity of the contents increased with time, and the contents became tar-like. Table 2 shows the time when the liquid stopped moving.

[Comparative Example 3]
In the case of Example 4, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2,3-dihydrothieno [3,4- b] -1,4-dioxin (EDOT) was used, and the experiment was performed in exactly the same manner as in Example 4. The results are shown in Table 2.

About the result of Examples 4-6 and Comparative Examples 1-2, the carbon number of the methyl group, ethyl group, propyl group, and hexyl group which are the substituents of EDOT is taken on a horizontal axis, and a polymerization rate (second) is taken on a vertical axis. The graph taken is shown in FIG.
From FIG. 2, it was found that when EDOT is substituted with an alkyl group having 3 or more carbon atoms, the polymerization rate is greatly delayed.

In the case of Example 1, the amount of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT) was 1.10 g under the condition of a humidity of 22%. Then, 50% p-toluenesulfonic acid ferric / n-butanol solution as an oxidizing agent was prepared, and the weight ratio of both was prepared at 1: 2.5 and stirred for 60 seconds.
Next, the capacitor element used in Example 1 was immersed in this solution for 120 seconds, and after 30 minutes have passed in the glove box after being put into a sealed bottle, heated at 45 ° C. for 2 hours, and the capacitor element was taken out from the sealed bottle. Chemical oxidation polymerization was performed by heating at 105 ° C. for 35 minutes and at 125 ° C. for 1 hour to form poly-2-methyl-EDOT in the capacitor element.
The results are shown in Table 3.

  In the case of Example 7, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2-ethyl-2,3-dihydrothieno [ A solid electrolytic capacitor was produced by performing the same treatment as in Example 7 except that 3,4-b] -1,4-dioxin (2-ethyl-EDOT) was used. The results are shown in Table 3.

  In the case of Example 7, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2-propyl-2,3-dihydrothieno [ A solid electrolytic capacitor was produced by performing the same treatment as in Example 7 except that 3,4-b] -1,4-dioxin (2-propyl-EDOT) was used. The results are shown in Table 3.

[Comparative Example 4]
In the case of Example 7, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2-methyl-2,3-dihydrothieno [ The treatment was performed in the same manner as in Example 7 except that 3,4-b] -1,4-dioxin (2-hexyl-EDOT) was used to produce a solid electrolytic capacitor. The results are shown in Table 3.

[Comparative Example 5]
In the case of Example 7, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2,3-dihydrothieno [3,4- b] A solid electrolytic capacitor was produced by performing the same treatment as in Example 7 except that 2-hydroxymethyl-1,4-dioxin (2-hydroxymethyl-EDOT) was used. The results are shown in Table 3.

[Comparative Example 6]
In the case of Example 7, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2-methyl-2,3-dihydrothieno [ 3,4-b] -1,4-diocepin (2-methyl-PDOT) was used in the same manner as in Example 7 except that the solid electrolytic capacitor was produced. An electric field capacitor was not obtained.

[Comparative Example 7]
In the case of Example 7, instead of 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), 2,3-dihydrothieno [3,4- b] Except for using 1,4-dioxin (EDOT), a treatment was performed in the same manner as in Example 7 to produce a solid electrolytic capacitor. The results are shown in Table 3.

  The solid electrolytic capacitors obtained in Examples 7 to 9 and Comparative Examples 4 to 7 were subjected to a heat resistance test by applying a voltage of 4.0 V under the condition of 125 ° C. Table 3 shows the results before 24 hours and 48 hours before the heat resistance experiment.

For the solid electrolytic capacitors obtained in Examples 7 to 9 and Comparative Examples 4 and 7, the carbon number of methyl group, ethyl group, propyl group and hexyl group, which are substituents of EDOT, is plotted on the horizontal axis, and ESR (mΩ ) On the vertical axis is shown in FIG.
From FIG. 1, it was found that ESR is reduced when EDOT is substituted with an alkyl group having 1 or 2 carbon atoms, and especially when EDOT is substituted with an alkyl group having 1 carbon atom.

[Reference example]
A tantalum sintered body having a size of 5 × 3 × 1 mm ³ was used as an anode, and an anode body having a weight of about 100 mg using a tantalum wire as an anode wire was 150% at 80 ° C. and 25 V in a 0.05 wt% phosphoric acid aqueous solution. A capacitor element was anodized, washed with running deionized water, dried. This state was regarded as a capacitor, and the capacitance in the chemical conversion solution was measured and found to be 160 μF.

[Comparative Reference Example 10]
[Production Method of Solid Electrolytic Capacitor Using 2-Methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT)]
FIG. 3 is a schematic cross-sectional view for explaining the structure of a solid electrolytic capacitor according to Example 10 of the present invention.
An anode 11 formed by pressure-molding and sintering tantalum metal fine particles is formed, and this is subjected to chemical conversion treatment in an electrolyte solution of a phosphoric acid aqueous solution to form a capacitor element having a dielectric oxide film 12 formed on the surface thereof.

  Next, a chemical polymerization liquid comprising 2-methyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-methyl-EDOT), iron (III) p-toluenesulfonate, and butyl alcohol After the capacitor element is immersed in, a heat treatment is performed in the air, and a solid electrolyte 13 made of poly-2-methyl-EDOT is formed on the dielectric oxide film 12 by chemical oxidative polymerization. This dipping and heat treatment process is repeated 5 times or more. The heat treatment at this time was allowed to stand at room temperature for 10 minutes and then at 150 ° C. for 5 minutes.

  Thereafter, a graphite layer 14 and a silver paste layer 15 are sequentially formed on the solid electrolyte 13, and the cathode lead 17 is connected to the silver paste layer 15 via the conductive adhesive 19, and the anode lead 16 is connected to the anode 11. These were molded by the resin sheath 18 to complete a solid electrolytic capacitor.

[Comparative Reference Example 11]
[Method for producing solid electrolytic capacitor using 2-ethyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-ethyl-EDOT)]
The same prepolymerized capacitor element as in Example 1 was prepared, and 2-ethyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-ethyl-EDOT) was used as a monomer. Except for the above, treatment was performed in the same manner as in Example 10 to produce a solid electrolytic capacitor.

[Comparative Reference Example 12]
[Method for producing solid electrolytic capacitor using 2-propyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-propyl-EDOT)]
The same prepolymerized capacitor element as in Example 1 was prepared, and 2-propyl-2,3-dihydrothieno [3,4-b] -1,4-dioxin (2-propyl-EDOT) was used as a monomer. Except for the above, treatment was performed in the same manner as in Example 1 to produce a solid electrolytic capacitor.

Comparative Example 8
[Method of Manufacturing Solid Electrolytic Capacitor Using 2,3-Dihydrothieno [3,4-b] -1,4-dioxin (EDOT)]
The same prepolymerized capacitor element as in Example 9 was prepared, and the same method as in Example 1 except that the monomer was 2,3-dihydrothieno [3,4-b] -1,4-dioxin (EDOT). The solid electrolytic capacitor was manufactured by processing.

  Table 4 shows the initial electrical characteristics and the electrical characteristics of the capacity impregnation rate of the solid electrolytic capacitors obtained in Comparative Reference Examples 10 to 12 and Comparative Example 8, respectively.

  As shown in Table 4, as a result of comparing various monomers, the solid electrolytic capacitors (Example 9, Comparative Reference Examples 10 to 12) obtained by the present invention are compared with the conventional solid electrolytic capacitors using EDOT. It was found that the capacity impregnation rate was high and it had a low equivalent series resistance.

1 Comparative Example 3
2 Example 4
3 Example 5
4 Example 6
5 Comparative Example 2
6 Comparative Example 7
7 Example 7
8 Example 8
9 Example 9
10 Comparative Example 4
11 Anode 12 Dielectric oxide film 13 Solid electrolyte 14 Graphite layer 15 Silver paste layer 16 Anode lead 17 Cathode lead 18 Resin sheath 19 Conductive adhesive

Claims (3)

The following general formulas [2] and [3]
[2]
[3]
A solid electrolytic capacitor having a step of forming a polymer obtained by polymerizing at least one of the compounds represented by the formula (1) on a valve action metal on which a dielectric oxide film is formed,
When the equivalent series resistance (ESR) value of a solid electrolytic capacitor using a polymer obtained by polymerizing 3,4-ethylenedioxythiophene is 100,
A solid electrolytic capacitor using a polymer obtained under the same polymerization conditions as in the case of 3,4-ethylenedioxythiophene has a value of the ESR measured under the same measurement conditions as in the case of 3,4-ethylenedioxythiophene. A method for producing a solid electrolytic capacitor, wherein the ratio is in the range of 63 to 78,
(A) at least one selected from the group consisting of compounds represented by the above general formulas [2] and [3],
(B) a dopant,
And (C) a step of polymerizing by contacting the oxidizing agent in a liquid phase,
As the (B) dopant and (C) oxidizing agent, a compound having the properties of both (B) dopant and (C) oxidizing agent is used,
The compound having the properties of both the (B) dopant and the (C) oxidizing agent is an organic sulfonic acid ferric salt,
The liquid phase comprises an organic sulfonic acid ferric salt in the range of 40 to 70% by weight;
The liquid phase solvent is n-butanol;
The method for producing a solid electrolytic capacitor, wherein the valve metal is aluminum. Conducting a heat resistance test for 24 hours to 48 hours under a condition of 125 ° C. on the solid electrolytic capacitor obtained by the method for producing a solid electrolytic capacitor according to claim 1,
The value of ESR of the solid electrolytic capacitor after the obtained heat resistance test is performed,
When the ESR value of the solid electrolytic capacitor when the heat resistance test is carried out using a polymer obtained by polymerizing 3,4-ethylenedioxythiophene is within the range of 57 to 76. The manufacturing method of the solid electrolytic capacitor of Claim 1.   The method for producing a solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is an aluminum wound capacitor.