JP5557638B2 - Oxidant solution for producing conductive polymer and method for producing solid electrolytic capacitor using the same - Google Patents

Description

  The present invention relates to an oxidant solution for producing a conductive polymer that chemically oxidatively polymerizes a conductive polymer monomer, and a solid electrolyte using a conductive polymer obtained by chemical oxidative polymerization using the oxidant solution as a solid electrolyte. The present invention relates to a method for manufacturing a capacitor.

  In recent years, π-conjugated conductive polymers have been studied in various fields, and various electronic device elements have been put to practical use by taking advantage of the lightness and high conductivity of organic materials. For example, aluminum solid electrolytic capacitors and It is used as a solid electrolyte for tantalum solid electrolytic capacitors.

  The conductive polymer can be produced by chemical oxidative polymerization of conductive polymer monomers such as pyrrole, thiophene, aniline, and derivatives thereof. As disclosed in Patent Document 1, 3,4-alkylenedioxythiophene, which is a thiophene derivative as a conductive polymer monomer, and an organic sulfonic acid that is a conductive polymer dopant as an oxidizing agent for chemical oxidative polymerization, Salts composed of transition metal cations having an oxidizing action have been proposed, and among these, ferric paratoluenesulfonate is most commonly used.

  However, when ferric toluene sulfonate is applied as an oxidizing agent for conductive polymer monomers, the amount of anion that functions as a dopant is not sufficient. When exposed to the lower side, there is a drawback in that it tends to cause a decrease in capacitor capacity and an increase in capacitor resistance loss.

  Patent Document 2 discloses a method of increasing the amount of anions contributing to a dopant by adding 10% by mass or more of an organic sulfonic acid to an organic sulfonic acid transition metal salt solution with respect to the amount of solvent. However, in this method, since an acid is added, the polymerization rate increases, and there is a disadvantage that the electric characteristics of the obtained solid electrolytic capacitor are inferior.

Japanese Patent Laid-Open No. 1-313521 JP 2004-107552 A

  An object of the present invention is to provide an oxidizing agent for producing a conductive polymer having an appropriate polymerization rate and an increased amount of anion contributing to a dopant, and a method for producing a solid electrolytic capacitor produced using the same. That is.

  As a result of intensive studies, the present inventors have found that an oxidant solution for producing a conductive polymer in which a sulfonic acid ester compound is added to an alcohol solution containing ferric organic sulfonate as a solute, and the conductive polymer It has been found that the above-mentioned problems can be solved by using a method for producing a solid electrolytic capacitor produced using an oxidizing solution for production, and the present invention has been completed.

  That is, the present invention is as follows.

  A first invention is an oxidant solution for producing a conductive polymer in which ferric organic sulfonate is dissolved in an alcohol solvent, and the sulfonate compound is added to the oxidant solution for producing a conductive polymer. An oxidizing agent solution for producing a conductive polymer, characterized in that it is contained.

  The second invention is characterized in that the content of ferric organic sulfonate in the oxidant solution for producing a conductive polymer is 30 to 70% by mass, according to the first invention. This is an oxidant solution for production.

  3rd invention is 1-20 mass% in moisture content in the oxidizing agent solution for conductive polymer manufacture, The oxidizing agent for conductive polymer manufacture as described in 1st or 2nd invention characterized by the above-mentioned It is a solution.

  A fourth invention is an oxidizing agent solution for producing a conductive polymer according to any one of the first to third inventions, wherein the ferric organic sulfonate is ferric paratoluenesulfonate. is there.

  5th invention is a sulfonic acid ester compound represented by following General formula (1), The sulfonic acid ester compound is for conductive polymer manufacture in any one of Claim 1 to 4 characterized by the above-mentioned. It is an oxidant solution.

（式（１）中、Ｒ^１は炭素数１〜８のアルキル基を示し、Ｒ^２は炭素数１〜４のアルキル基を示す。）

(In formula (1), R ¹ represents an alkyl group having 1 to 8 carbon atoms, and R ² represents an alkyl group having 1 to 4 carbon atoms.)

  6th invention is characterized by the content of the sulfonic acid ester compound in the oxidizing agent solution for electroconductive polymer manufacture being 0.01-20 mol% with respect to 1 mol of ferric organic sulfonates. It is an oxidizing agent solution for electroconductive polymer manufacture in any one of the 1st to 5th invention.

  A seventh invention is the oxidant solution for producing a conductive polymer according to any one of the first to sixth inventions, wherein the alcohol solvent is a mixed solvent of butanol and methanol.

An eighth invention is a method for producing a solid electrolytic capacitor comprising a solid electrolyte made of a conductive polymer on a valve metal having a dielectric oxide film formed thereon,
Conductive oxidizer solution according to any one of the first to seventh inventions and chemical oxidative polymerization by contacting the conductive polymer monomer in a liquid layer to form a dielectric oxide film It is a manufacturing method of a solid electrolytic capacitor characterized by having a process of forming a conductive polymer in the valve action metal made.

  According to the present invention, an oxidizing agent solution for producing a conductive polymer having an appropriate polymerization rate and an increased amount of anion contributing to a dopant, and excellent ESR characteristics and heat resistance produced using the same. The manufacturing method of the solid electrolytic capacitor which shows the property can be provided.

  The oxidant solution for producing a conductive polymer of the present invention is obtained by containing ferric organic sulfonate and a sulfonate compound in an alcohol solvent.

  When a sulfonic acid ester compound is added, hydrolysis of the sulfonic acid ester compound occurs due to residual moisture in the oxidant solution and moisture in the atmosphere during heating during chemical oxidative polymerization, and sulfonic acid and alcohol are generated. Therefore, the amount of sulfonic acid that functions as a dopant in the oxidant solution for producing the conductive polymer increases, and the amount of the dopant incorporated into the conductive polymer increases. By using the conductive polymer as a solid electrolyte, a solid electrolytic capacitor having excellent equivalent series resistance (ESR) and high heat resistance can be manufactured.

Since the amount of dopant in the oxidant solution is increased by using the above method, when the moisture content in the oxidant solution increases, the hydrolysis proceeds more smoothly, and the effect of adding the sulfonate compound increases. .
The moisture content in the oxidant solution is preferably 1 to 20% by mass. When the amount is less than 1% by mass, the effect of adding the sulfonic acid ester compound is reduced. When the amount exceeds 20% by mass, ferric organic sulfonate dissolved in the oxidant solution is precipitated. There is a problem that the performance becomes low.

  Examples of the organic sulfonic acid compound that is a constituent of the organic sulfonic acid ferric salt include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, ethylbenzenesulfonic acid, and propyl. Benzenesulfonic acid, xylenesulfonic acid, styrenesulfonic acid, isopropylbenzenesulfonic acid, butylbenzenesulfonic acid, dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid, naphthalenesulfonic acid, methylnaphthalenesulfonic acid, ethylnaphthalenesulfonic acid, propylnaphthalenesulfone Acid, butyl naphthalene sulfonic acid, dibutyl naphthalene sulfonic acid, nonyl naphthalene sulfonic acid, dinonyl naphthalene sulfonic acid, etc. Acid, among others preferred.

  Although content of ferric organic sulfonate in the oxidizing agent solution for conductive polymer manufacture is not specifically limited, 30-70 mass% is mentioned preferably.

The sulfonic acid ester compound can be represented by a general formula (R ^a SO ₂ OR ^b ), and R ^a represents an aliphatic hydrocarbon group having 1 to 18 carbon atoms or an aromatic hydrocarbon group having 1 to 18 carbon atoms. The sulfonic acid ester compound used in the invention is preferably a compound containing an aromatic hydrocarbon group having 1 to 18 carbon atoms. R ^b is an aliphatic hydrocarbon group having 1 to 18 carbon atoms.
Among the sulfonic acid esters, a sulfonic acid ester compound represented by the following general formula (1) is particularly preferable.

In the general formula (1), R ¹ represents an alkyl group having 1 to 8 carbon atoms, and R ² represents an alkyl group having 1 to 4 carbon atoms.

  Examples of the sulfonic acid ester compounds include methyl sulfate, ethyl sulfate, propyl sulfate, isopropyl sulfate, butyl sulfate, methyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate, neopentyl benzenesulfonate, methyl toluenesulfonate, toluenesulfone. Ethyl sulfonate, propyl toluenesulfonate, butyl toluenesulfonate, methoxyethyl toluenesulfonate, hexyl toluenesulfonate, heptyl toluenesulfonate, octyl toluenesulfonate, dodecyl toluenesulfonate, phenyl toluenesulfonate, phenethyl toluenesulfonate, toluene Examples include octadecyl sulfonate, naphthyl toluenesulfonate, methyl toluenesulfonate, ethyl toluenesulfonate, toluenesulfonic acid. Propyl, butyl toluenesulfonic acid more preferably.

  By containing the sulfonic acid ester compound in the oxidizing agent for producing the conductive polymer, the amount of anions contributing to the dopant can be increased without increasing the polymerization rate.

  The content of the sulfonic acid ester compound in the oxidant solution for producing the conductive polymer is preferably 0.01 to 20 mol% with respect to 1 mol of ferric organic sulfonate, and 0.1 to 10 mol% is preferable. Particularly preferred is mentioned.

Examples of the alcohol solvent used in the oxidant solution for producing the conductive polymer used in the present invention include methanol, ethanol, propanol, butanol and the like, and these can be used alone or in combination.
Among these, butanol and methanol are more preferable, and a mixed solvent of butanol and methanol is particularly preferable.

  Next, an example is given and demonstrated about the manufacturing method of the oxidizing agent solution for conductive polymer manufacture of this invention.

An aqueous solution of an organic sulfonic acid compound is prepared, and ferric oxide is added to the aqueous solution and heated to reflux. By filtering this, an aqueous solution of a ferric salt having an organic sulfonic acid compound as an anion is obtained. The aqueous solution is removed with a solvent to obtain ferric organic sulfonate.
The obtained ferric organic sulfonate, sulfonic acid ester compound and water can be added to an alcohol solvent to produce the oxidant solution for producing a conductive polymer of the present invention.

  Examples of the conductive polymer monomer used in the present invention include at least one selected from the group consisting of pyrrole, thiophene, and derivatives thereof.

  Specific examples of the conductive polymer monomer include, for example, pyrrole, thiophene, 1-alkyl-3-alkylpyrrole, 3-alkylthiophene, 1-alkyl-3,4-alkylenedioxypyrrole, 3,4-alkylenediylene. And oxythiophene. Among these, 3,4-alkylenedioxythiophene and pyrrole are preferable. The said conductive polymer monomer can contain 1 type (s) or 2 or more types simultaneously.

  The conductive polymer used in the present invention can be produced by contacting and mixing the above oxidizing polymer solution for producing a conductive polymer and a conductive polymer monomer.

In the present invention, the polymerization rate was evaluated as the time obtained by measurement by the following method.
An oxidant solution for producing a conductive polymer and 3,4-ethylenedioxythiophene (EDOT) were each put in a screw tube and held on a 20 ° C. thermoplate for 10 minutes or more. The oxidant solution and EDOT were mixed at 5: 1 (mass ratio) and stirred for 10 seconds. Thereafter, the time until a lump of polymer of 1 mm or more was deposited was measured and used as the polymerization rate.

An appropriate polymerization rate in the present invention is 70 to 160 seconds when EDOT is used as the conductive polymer monomer. A more suitable polymerization rate is 70 to 130 seconds.
When the time is less than 70 seconds, the polymerization rate is too high, and polymerization is performed without penetrating into the porous valve metal oxide film, resulting in poor ESR of the obtained solid electrolytic capacitor.
If it exceeds 160 seconds, the polymerization rate is too slow, which makes it difficult to polymerize.
By adjusting the amount of water contained in the oxidant solution for producing the conductive polymer to 1 to 20% by mass, the polymerization rate can be easily adjusted, and a solid electrolytic capacitor having excellent electrical characteristics can be obtained. it can.

  Next, the manufacturing method of the solid electrolytic capacitor of this invention is demonstrated below.

  In the method of manufacturing a solid electrolytic capacitor comprising a solid electrolyte made of a conductive polymer on a valve action metal on which a dielectric oxide film is formed, the oxidizing agent solution for manufacturing a conductive polymer of the present invention, and the conductive polymer A method for producing a solid electrolytic capacitor comprising a step of chemical oxidation polymerization by bringing a monomer into contact with a liquid layer and forming a conductive polymer on a valve metal having a dielectric oxide film formed thereon. is there.

  More specifically, the oxidant solution for producing the conductive polymer used in the present invention is applied to the surface of the valve action metal such as aluminum, tantalum and niobium on which the dielectric oxide film is formed, and the conductive polymer monomer. Immerse it in a solution, apply a conductive polymer monomer solution, immerse it in an oxidant solution for producing a conductive polymer, or mix the oxidant solution and the monomer into a single solution. Immerse to form a conductive polymer film. This conductive polymer film becomes a solid electrolyte of the solid electrolytic capacitor.

  Next, a carbon paste and a silver paste are applied and dried on the conductive polymer film, and a cathode layer is formed to obtain a capacitor element. The valve metal of the capacitor element is used as an anode terminal, and the cathode layer is formed. After connecting to the cathode terminal, the solid electrolytic capacitor of the present invention can be obtained by coating with resin.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited at all by this Example. “%” In the examples represents “% by mass”.

(Evaluation of oxidant solution for conductive polymer production)
Example 1
To a solution obtained by dissolving 15.5 g (8.4 × 10 ⁻² mol) of paratoluenesulfonic acid monohydrate in 50 ml of pure water, 4.45 g (2.8 × 10 ⁻² mol) of ferric oxide was added. For 12 hours.

  The reaction solution was filtered and an aqueous solution of ferric paratoluenesulfonate was obtained. Thereafter, the solvent was removed to obtain ferric paratoluenesulfonate.

Next, in 100 g of a mixed solvent of 1-butanol and methanol (mass ratio 1: 1), the obtained ferric paratoluenesulfonate and 0.051 g (2.8 × 10 ⁻⁴ mol) of methyl paratoluenesulfonate were obtained. ) After addition, water was added so that the water content was 6%, and an oxidizing agent solution for producing a conductive polymer, which was a mixed solution of 1-butanol and methanol of 60% concentration of ferric paratoluenesulfonate ( An oxidant solution (1)) was obtained. (The content of the sulfonic acid ester compound with respect to 1 mol of ferric organic sulfonate is 1 mol%.)
The moisture content was measured using a Karl Fischer moisture meter (KF-100, manufactured by Mitsubishi Chemical Corporation).

(Example 2)
An oxidizing agent solution (oxidizing agent solution (2)) for producing a conductive polymer in the same manner as in Example 1 except that the content of methyl paratoluenesulfonate in Example 1 was changed from 1 mol% to 5 mol%. Got.

(Example 3)
An oxidant solution (oxidant solution (3)) for producing a conductive polymer in the same manner as in Example 1, except that the content of methyl paratoluenesulfonate in Example 1 was changed from 1 mol% to 10 mol%. Got.

(Example 4)
An oxidizing agent solution (oxidizing agent solution (4)) for producing a conductive polymer in the same manner as in Example 1 except that the content of methyl paratoluenesulfonate in Example 1 was changed from 1 mol% to 20 mol%. Got.

( Reference Example 1 )
An oxidant solution for producing a conductive polymer (oxidant solution (5)) in the same manner as in Example 1 except that the content of methyl paratoluenesulfonate in Example 1 was changed from 1 mol% to 30 mol%. Got.

( Reference Example 2 )
An oxidant solution for producing a conductive polymer (oxidant solution (6)) in the same manner as in Example 1 except that the content of methyl paratoluenesulfonate in Example 1 was changed from 1 mol% to 50 mol%. Got.

(Comparative Example 1)
An oxidizing agent solution (oxidizing agent solution (7)) for producing a conductive polymer was obtained in the same manner as in Example 1 except that the methyl paratoluenesulfonate of Example 1 was not contained.

(Comparative Example 2)
To a solution obtained by dissolving 15.5 g (8.4 × 10 ⁻² mol) of paratoluenesulfonic acid monohydrate in 50 ml of pure water, 4.45 g (2.8 × 10 ⁻² mol) of ferric oxide was added. For 12 hours.

  The reaction solution was filtered and an aqueous solution of ferric paratoluenesulfonate was obtained. Thereafter, the solvent was removed to obtain ferric paratoluenesulfonate.

  Next, in 100 g of a mixed solvent of 1-butanol and methanol (mass ratio 1: 1), the obtained paratoluenesulfonic acid ferric acid and paratoluenesulfonic acid are 10% by mass with respect to the oxidizing agent solvent. Then, water is added so that the water content becomes 6%, and an oxidizing agent solution for producing a conductive polymer (oxidation solution) is a mixed solution of 1-butanol and methanol of ferric paratoluenesulfonate 60% in concentration. An agent solution (8) was obtained.

  The oxidant solutions (1) to (8) obtained in the above steps were prepared, and the polymerization rate was evaluated. The polymerization rate was as follows: each oxidant solution and 3,4-ethylenedioxythiophene (EDOT) were each put in a screw tube and kept on a 20 ° C. thermoplate for 10 minutes or more. The oxidant solution and EDOT were mixed 5: 1 (weight ratio) and stirred for 10 seconds. Then, the time until a polymer lump having a diameter of 1 mm or more was deposited was measured and used as a polymerization rate. The measurement results are shown in Table 1.

表中の略語
ＰＴＳ：パラトルエンスルホン酸

Abbreviations in the table PTS: p-toluenesulfonic acid

  From Table 1, it can be seen that the oxidizing agent solutions (1) to (6) have an appropriate polymerization rate.

(Evaluation of solid electrolytic capacitors)
(Example 7)
A tantalum sintered body element having an anode lead was subjected to chemical conversion treatment by applying a voltage of 25 V in an aqueous phosphoric acid solution to form a dielectric oxide film. The capacitance of the device in an aqueous sulfuric acid solution was 300 μF.

  Next, the oxidizing agent solution (1) described in Example 1 and EDOT as a conductive polymer monomer were mixed at a molar ratio of 1: 1, and prepared as a one-component chemical oxidation polymerization solution in a container.

  The tantalum sintered body element is immersed in the above chemical oxidation polymerization solution at room temperature for 5 minutes, the element is pulled up and heat-treated at 50 ° C. for 1 hour to advance chemical oxidation polymerization, and a conductive polymer layer is formed on the surface of the element. Formed.

  Next, a carbon paste and a silver paste are applied to the cathode layer of the device to form a conductive coating film, and a counter electrode is taken out from a part thereof, then molded with an epoxy resin, and then a voltage of 8 V is applied. Aging was then performed to complete a solid electrolytic capacitor having a rated voltage of 6.3 V and a rated capacitance of 250 μF.

(Example 8)
A solid electrolytic capacitor was completed in the same manner as in Example 7 except that the oxidant solution (2) was used instead of the oxidant solution (1) in Example 7.

Example 9
A solid electrolytic capacitor was completed in the same manner as in Example 7 except that the oxidant solution (3) was used instead of the oxidant solution (1) in Example 7.

(Example 10)
A solid electrolytic capacitor was completed in the same manner as in Example 7 except that the oxidant solution (4) was used instead of the oxidant solution (1) in Example 7.

( Reference Example 3 )
A solid electrolytic capacitor was completed in the same manner as in Example 7 except that the oxidant solution (5) was used instead of the oxidant solution (1) in Example 7.

( Reference Example 4 )
A solid electrolytic capacitor was completed in the same manner as in Example 7 except that the oxidant solution (6) was used instead of the oxidant solution (1) in Example 7.

(Comparative Example 3)
A solid electrolytic capacitor was completed in the same manner as in Example 7 except that the oxidant solution (7) was used instead of the oxidant solution (1) in Example 7.

(Comparative Example 4)
A solid electrolytic capacitor was completed in the same manner as in Example 7 except that the oxidant solution (8) was used instead of the oxidant solution (1) in Example 7.

About the solid electrolytic capacitors obtained from Examples 7 to 10, Reference Examples 3 and 4 and Comparative Examples 3 and 4, electrostatic capacity at 120 Hz (hereinafter abbreviated as Cs), dielectric loss at 120 Hz (hereinafter, tan δ), and equivalent series resistance at 100 kHz (hereinafter abbreviated as ESR) was measured. Further, a high temperature load test (held in an atmosphere at a temperature of 260 ° C. for 3 minutes) was performed. The measurement results are shown in Table 2.

As shown in Table 2, it can be seen that Examples 7 to 10 are superior to Comparative Examples 3 and 4 in ESR characteristics and heat resistance.
In particular, it was found that a solid electrolytic capacitor manufactured using an oxidizing agent solution containing 5 mol% of a sulfonic acid ester compound with respect to 1 mol of ferric organic sulfonate has excellent ESR characteristics.

  Since the solid electrolytic capacitor manufactured using the oxidant solution for manufacturing a conductive polymer of the present invention has excellent electrical characteristics, it can be applied to high-frequency digital devices and the like.

Claims (6)

In an oxidizing agent solution for producing a conductive polymer in which ferric organic sulfonate is dissolved in an alcohol solvent ,
In the oxidant solution for producing the conductive polymer, a sulfonic acid ester compound is contained,
The content of the sulfonic acid ester compound in the oxidant solution for producing the conductive polymer is 0.01 to 20 mol% with respect to 1 mol of the ferric organic sulfonate,
An oxidant solution for producing a conductive polymer, wherein the moisture content in the oxidant solution for producing a conductive polymer is 1 to 20% by mass.   2. The oxidant solution for producing a conductive polymer according to claim 1, wherein the content of ferric organic sulfonate in the oxidant solution for producing the conductive polymer is 30 to 70% by mass. The oxidant solution for producing a conductive polymer according to claim 1 or 2 , wherein the ferric organic sulfonate is ferric paratoluenesulfonate. The oxidizing agent solution for producing a conductive polymer according to any one of claims 1 to 3 , wherein the sulfonic acid ester compound is a sulfonic acid ester compound represented by the following general formula (1).

(In formula (1), R ¹ represents an alkyl group having 1 to 8 carbon atoms, and R ² represents an alkyl group having 1 to 4 carbon atoms.) The oxidant solution for producing a conductive polymer according to any one of claims 1 to 4 , wherein the alcohol solvent is a mixed solvent of butanol and methanol. In a method for producing a solid electrolytic capacitor comprising a solid electrolyte made of a conductive polymer on a valve action metal on which a dielectric oxide film is formed,
A oxidant solution for producing a conductive polymer according to any one of claims 1 to 5 and a conductive polymer monomer are brought into contact with each other in a liquid layer for chemical oxidative polymerization to form a dielectric oxide film. A method for producing a solid electrolytic capacitor comprising a step of forming a conductive polymer on a valve metal.