JP2018166145A - Manufacturing method of solid electrolytic capacitor - Google Patents

Abstract

A method for manufacturing a solid electrolytic capacitor having high durability and high reliability is provided. A method for manufacturing a solid electrolytic capacitor comprising a step of forming a conductive polymer layer on a surface of a valve metal having a dielectric oxide film formed thereon, wherein the step includes the following (A) to (D): ) (A) a conductive polymer, (B) colloidal silica, (C) a compound reactive with silanol groups, and (D) a conductive polymer dispersion containing at least a dispersion medium is brought into contact with the dielectric oxide film. and then removing (D) at least partially to form a conductive polymer layer on the dielectric oxide film. [Selection figure] None

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor.

  Conductive polymers such as polyaniline, polypyrrole and polythiophene have excellent stability and conductivity, so various antistatic agents, electrolytes for solid electrolytic capacitors, anticorrosion paints, EMI shields, chemical sensors, display elements, nonlinear materials Application to plating primer is expected.

  These conductive polymers generally have a problem that they are difficult to form and process because they are insoluble or hardly soluble in solvents and insoluble.

  For this reason, a technique for improving the moldability and workability is known by finely pulverizing the conductive polymer into fine particles or a filler and dispersing it in a dispersion medium such as water or an organic solvent.

  A solid electrolytic capacitor is generally formed by forming a solid electrolyte layer containing a conductive polymer on a valve action metal having a dielectric oxide film.

  As a method for forming a solid electrolyte layer containing a conductive polymer, there are a chemical oxidative polymerization method and an electrolytic polymerization method. In the chemical oxidative polymerization method, for example, an oxidant is attached onto a valve action metal on which a dielectric oxide film is formed, and then contacted with a solution containing the monomer compound, whereby the monomer compound is chemically oxidatively polymerized. A solid electrolyte layer containing a conductive polymer can be formed on the valve action metal.

  However, this chemical oxidative polymerization method has a problem that the withstand voltage of the solid electrolytic capacitor is lowered because the dielectric oxide film is damaged by the oxidant used during the chemical oxidative polymerization.

Patent Document 1 discloses a method for improving an electrical parameter in a capacitor containing PEDOT / PSS as a solid electrolyte by polyalkylene glycol.
According to this document, it is described that a capacitor having a high breakdown voltage can be manufactured while suppressing a decrease in capacitance at a low temperature.
However, the solid electrolytic capacitor is insufficient from the viewpoint of durability and reliability.

  From the above, a manufacturing method that can provide a solid electrolytic capacitor having high durability and high reliability has been demanded.

Special table 2013-539227 gazette

  An object of the present invention is to provide a method for producing a solid electrolytic capacitor having high durability and high reliability.

In the method for producing a solid electrolytic capacitor having a step of forming a conductive polymer layer on the surface of a valve metal having a dielectric oxide film formed thereon,
The above steps are the following (A) to (D)
(A) Conductive polymer (B) Colloidal silica (C) A compound having reactivity with silanol groups (D) A conductive polymer dispersion containing at least a dispersion medium was brought into contact with the dielectric oxide film. And (D) removing at least partly to form a conductive polymer layer on the dielectric oxide film. As a result, the present invention has been completed.

  That is, the present invention is as follows.

A first invention is a method for producing a solid electrolytic capacitor having a step of forming a conductive polymer layer on the surface of a valve metal having a dielectric oxide film formed thereon.
This process is the following (A)-(D)
(A) Conductive polymer (B) Colloidal silica (C) A compound having reactivity with silanol groups (D) A conductive polymer dispersion containing at least a dispersion medium was brought into contact with the dielectric oxide film. rear,
Removing (D) at least partially;
A method for producing a solid electrolytic capacitor, comprising the step of forming a conductive polymer layer on the dielectric oxide film.

The second invention is
The compound having reactivity with the (C) silanol group,
A linear and / or branched compound having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an isocyanate group, and a glycidyl group at the end and having a number average molecular weight of 100 to 10,000. A method for producing a solid electrolytic capacitor according to the first aspect of the invention.

  A third invention is the method for producing a solid electrolytic capacitor according to the first or second invention, wherein the compound (C) having reactivity with a silanol group is polyalkylene glycol.

  A fourth invention is characterized in that the content of the compound (C) having reactivity with a silanol group is 0.01 to 30% by weight with respect to the conductive polymer dispersion. It is a manufacturing method of the solid electrolytic capacitor as described in any one of 1st to 3rd invention.

  According to a fifth invention, the conductive polymer is a conductive polymer having a polymer of a thiophene compound represented by the following general formula (1) and a dopant: It is a manufacturing method of the solid electrolytic capacitor as described in any one of invention.

  In the above formula (1), Ra represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and X represents an oxygen atom or a sulfur atom which may be the same or different.

  A sixth invention is characterized in that the dopant is at least one selected from the group consisting of polystyrenesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid and xylenesulfonic acid. The method for producing a solid electrolytic capacitor according to the fifth invention.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the solid electrolytic capacitor which gives the solid electrolytic capacitor which has high durability and high reliability can be provided.
That is, a highly durable solid electrolytic capacitor can be manufactured with very little change over time particularly in the heat resistance test of capacitance and ESR.

  First, the present invention will be described.

The method for producing a solid electrolytic capacitor according to the present invention includes:
On the surface of the valve action metal on which the dielectric oxide film is formed,
In the method for producing a solid electrolytic capacitor having a step of forming a conductive polymer layer,
The above steps are the following (A) to (D)
(A) Conductive polymer (B) Colloidal silica (C) A compound having reactivity with silanol groups (D) A conductive polymer dispersion containing at least a dispersion medium was brought into contact with the dielectric oxide film. And (D) is at least partially removed to form a conductive polymer layer on the dielectric oxide film.

[(A) Conductive polymer]
The conductive polymer used in the present invention is preferably a polymer doped with a dopant. The monomer compound used for producing the polymer is not particularly limited, and for example, pyrroles, thiophenes, anilines, and the like can be used. The thiophene compound represented by 1) is more preferable.

  In the general formula (1), Ra represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and X represents an oxygen atom or a sulfur atom which may be the same or different.

  Specific examples of the thiophene compound represented by the general formula (1) include 3,4-ethylenedioxythiophene, methyl-3,4-ethylenedioxythiophene, ethyl-3,4-ethylenedioxythiophene, Propyl-3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, methyl-3,4-propylenedioxythiophene, ethyl-3,4-propylenedioxythiophene, propyl-3,4-propylenedi Oxythiophene, 3,4-ethylenedithiathiophene, methyl-3,4-ethylenedithiathiophene, ethyl-3,4-ethylenedithiathiophene, propyl-3,4-ethylenedithiathiophene, 3,4-propylene Dithiathiophene, methyl-3,4-propylene dithiathiophene, ethyl-3,4 Propylene dithiastannolane thiophene, propyl-3,4-propylene di-thia thiophene and the like.

  Among these, 3,4-ethylenedioxythiophene, methyl-3,4-ethylenedioxythiophene, and ethyl-3,4-ethylenedioxythiophene are particularly preferred because they are particularly excellent in electrical characteristics in solid electrolytic capacitors. .

  The conductive polymer used in the present invention can be obtained by chemical oxidative polymerization of a monomer compound such as the thiophene compound represented by the general formula (1) in the presence of the dopant. As the oxidizing agent for chemical oxidative polymerization, for example, a known oxidizing agent described in JP 2010-31160 A can be used.

  The dopant only needs to have a functional group capable of causing chemical oxidation doping to the polymer, and preferred examples include a sulfate ester group, a phosphate ester group, a phosphate group, a carboxyl group, and a sulfo group. Among these, from the point of the dope effect, a sulfate group, a carboxyl group, and a sulfo group are more preferable, and a sulfo group is particularly preferable.

  Examples of the dopant include halogen ions such as iodine, bromine, and chlorine, halide ions such as hexafluorolin, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, and perchloric acid, or methanesulfonic acid and dodecylsulfonic acid. Cyclic sulfonate ions such as alkyl-substituted organic sulfonate ions and camphor sulfonate ions, or alkyl-substituted or unsubstituted benzene mono- or disulfonate ions such as benzene sulfonic acid, para-toluene sulfonic acid, dodecyl benzene sulfonic acid, and benzene disulfonic acid Alkyl substituted or unsubstituted ions of naphthalenesulfonic acid substituted with 1 to 4 sulfonic acid groups such as 2-naphthalenesulfonic acid and 1,7-naphthalenedisulfonic acid, anthracenesulfonic acid ion, anthracene Non-sulfonate ions, alkyl-substituted or unsubstituted biphenyl sulfonate ions such as alkylbiphenyl sulfonate and biphenyl disulfonate, polymer sulfonate ions such as polystyrene sulfonate and naphthalene sulfonate formalin condensate, etc., or molybdophosphate and tongue Examples include heteropolyacid ions such as strinic acid and tungstomolybdophosphoric acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, and xylenesulfonic acid. Among these, at least one selected from polystyrenesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid and xylenesulfonic acid is more preferable, and polystyrenesulfonic acid is particularly preferable.

[(B) Colloidal silica]
Next, (B) colloidal silica will be described.
Colloidal silica is a colloid of SiO ₂ or its hydrate and is an amorphous structure having a particle size of 1 to 300 nm. Colloidal silica can typically be obtained by dialysis after dilute hydrochloric acid is allowed to act on the silicate. As for the particle size of colloidal silica, 10-200 nm is mentioned preferably, More preferably, 10-100 nm is mentioned. The colloidal silica having the particle size can exist stably for a long time in the conductive polymer dispersion.

  The colloidal silica content in the conductive polymer dispersion is preferably 0.01 to 20% by weight, more preferably 0.01 to 15% by weight, and 0.01 to 10% by weight. Is particularly preferred. By making it within this range, it is possible to produce a solid electrolytic capacitor having an excellent withstand voltage, and further by using a compound having reactivity with a silanol group in combination, colloidal silica and a conductive material formed on the oxide film. Since the layer of the conductive polymer becomes a stronger film, durability and reliability can be particularly improved.

[(C) Compound having reactivity with silanol group]
Next, (C) a compound having reactivity with a silanol group will be described. The compound having reactivity with a silanol group in the present invention means a compound having a functional group having reactivity with a silanol group on the surface of (B) colloidal silica.
Specifically, the terminal has at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an isocyanate group, and a glycidyl group, and has a number average molecular weight of 100 to 10,000. It is preferably a branched chain compound.
Examples of such a compound include polyalkylene glycol, polyvinyl alcohol, water-soluble polyester resin, phenol novolac resin, block isocyanate type aqueous urethane resin, and emulsion type aqueous epoxy resin.
Among these, polyalkylene glycol is particularly preferable.
Polyalkylene glycols include polyalkylene glycols based on ethylene glycol, propylene glycol, statistical copolymers of ethylene glycol and propylene glycol.

  (C) The number average molecular weight of the compound having reactivity with the silanol group is preferably from 100 to 10,000, more preferably from 100 to 1,000, and more preferably from 100 to 300 in terms of excellent capacitance and ESR of the capacitor. It is done.

The content of the compound having reactivity with the (C) silanol group is preferably 0.01 to 30% by weight, more preferably 0.1 to 20% by weight with respect to the conductive polymer dispersion. -20% by weight is particularly preferred.
If the content is less than 0.01% by weight, the content is small and the characteristics cannot be sufficiently extracted.
Moreover, you may add a reaction catalyst further as needed.

[(D) Dispersion medium]
Preferred dispersion media are water or other protic solvents such as alcohols such as methanol, ethanol, i-propanol and butanol, and mixtures of water and these alcohols, with a particularly preferred dispersion medium being water.

[Solid electrolytic capacitor]
Examples of the valve metal include one selected from the group consisting of aluminum, tantalum, niobium, and titanium, and are used in the form of a sintered body or foil.

  Depending on the type and shape of the valve metal used, it can be either a tip type or a wound type.

  The dielectric oxide film can be formed on the surface of the valve metal by subjecting the valve metal to a known chemical conversion treatment.

  Next, the valve metal having a dielectric oxide film is brought into contact with the conductive polymer dispersion, and dried by a treatment such as heating, and (D) the dispersion medium is at least partially removed to form the dielectric oxide film. A conductive polymer layer is formed thereon.

[Example using only conductive polymer dispersion]
This formation process may be repeated a plurality of times. The drying temperature is not particularly limited, but is preferably performed in the range of room temperature to 120 ° C.

[Example of using conductive polymer dispersion as precoat]
After the formation of the conductive polymer layer, the conductive polymer layer may be formed by in situ polymerization using a monomer solution and an oxidant solution.

  That is, after the conductive polymer layer of the present invention is formed, a monomer solution containing a monomer compound is applied or immersed in a valve metal in which an oxidant solution containing a dopant is applied or impregnated and held, And a method of forming a solid electrolyte layer having a conductive polymer in contact with each other.

Moreover, when performing the said chemical oxidation polymerization, the solid electrolyte layer which has a conductive polymer can be formed by hold | maintaining for a predetermined time at predetermined temperature.
Here, the predetermined temperature can be arbitrarily selected in the range of 0 to 250 ° C., and the predetermined time can be arbitrarily selected in the range of 1 minute to 24 hours.

[Example of hybrid: conductive polymer dispersion + electrolyte]
An electrolytic capacitor can also be produced by impregnating an electrolytic solution for a capacitor after forming a conductive polymer layer. In this case, a known electrolytic solution can be used as the electrolytic solution. Specifically, the electrolytic solution for electrolytic capacitors described in JP-A-2016-9770 can be used.

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

  First, an anode lead is connected to the aluminum foil anode roughened by the etching treatment, and then a chemical conversion treatment is performed in an aqueous solution such as diammonium adipate to form a dielectric oxide film.

  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 containing a conductive polymer is formed on the valve action metal having the dielectric oxide film of the capacitor element. The method for forming the solid electrolyte layer is as described above.

  Next, the element is sealed in the capacitor case, and a voltage is applied to perform aging to complete the solid electrolytic capacitor of the present invention.

  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, “part” represents “part by weight”, and “%” represents “% by weight”.

(Manufacture of conductive polymer dispersion)
14.2 parts of 3,4-ethylenedioxythiophene and 42.6 parts of polystyrene sulfonic acid (weight average molecular weight: 75,000) dissolved in 2000 ml of ion-exchanged water were mixed at 20 ° C. A mixed solution was obtained.
While maintaining the obtained mixed solution at 20 ° C., 29.6 parts of ammonium persulfate dissolved in 200 ml of ion-exchange water and 8.0 parts of an oxidation catalyst solution of ferric sulfate were added while stirring. The reaction was stirred for an hour.

After the reaction, a strongly acidic cation exchange resin (PK-216 manufactured by Mitsubishi Plastics) was added to remove the ammonium salt, and then the ion exchange resin was removed. Finally, after adding a strongly basic anion exchange resin (PA-418 manufactured by Mitsubishi Plastics) to remove the sulfate, the ion exchange resin was removed and 1.5% polyethylenedioxythiophene / polystyrenesulfonic acid aqueous dispersion Got.

Example 1
100 parts of 1.5% polyethylenedioxythiophene / polystyrenesulfonic acid aqueous dispersion, 0.2 part of colloidal silica (Nissan Chemicals Snowtex ST-OXS), 0.1 part of PEG200 (Daiichi Kogyo Seiyaku PEG200) To obtain a conductive polymer dispersion for producing a solid electrolytic capacitor.

(Manufacture of solid electrolytic capacitors)
As the valve metal used for the anode, etched aluminum foil whose surface has been etched and roughened is used, and the aluminum foil is subjected to chemical conversion treatment at a voltage of 90 V in an aqueous solution of ammonium adipate to form a dielectric layer. A lead element was attached to the anode, and a lead terminal was attached to the cathode made of aluminum foil, and the anode with the lead terminal and the cathode were opposed to each other through a separator to produce a capacitor element.

  Next, the process of immersing the capacitor element in the conductive polymer dispersion obtained above for 5 minutes and drying at 150 ° C. for 5 minutes was repeated three times, and then heat treatment was performed at 150 ° C. for 1 hour. The reaction between the silanol group of the colloidal silica and the reaction terminal was completed to obtain a capacitor element.

(Examples 2 to 4)
A capacitor element was produced in the same manner as in Example 1 except that the content of PEG200 was changed to the content described in Table 1.

(Examples 5 to 9)
A capacitor element was produced in the same manner as in Example 1 except that the polyethylene glycol and the content corresponding to Table 1 were used.

(Comparative Example 1)
A capacitor element was produced in the same manner as in Example 1 except that PEG200 described in Example 1 was not used.

(Comparative Example 2)
A capacitor element was produced in the same manner as in Example 1 except that the colloidal silica described in Example 1 was not used.

(Comparative Example 3)
A capacitor element was produced in the same manner as in Example 1 except that PEG 20,000 (manufactured by Wako Pure Chemical Industries, Ltd., average molecule: 15,000 to 25,000) was used instead of PEG 200 described in Example 1.

(Withstand voltage and heat resistance evaluation of capacitor elements)
Table 1 shows the measurement results of Examples 1 to 9 and Comparative Examples 1 to 3.

Abbreviations in Table 1 are as follows.
PEG200: Polyethylene glycol 200 (Wako Pure Chemical Industries, average molecular weight 180-220)
PEG300: Polyethylene glycol 300 (Wako Pure Chemical Industries, average molecular weight 260-340)
PEG400: Polyethylene glycol 400 (manufactured by Wako Pure Chemical Industries, average molecular weight 360 to 440)
PEG 1,000: polyethylene glycol 1,000 (manufactured by Wako Pure Chemical Industries, average molecular weight 900 to 1,100)
PEG2,000: Polyethylene glycol 2,000 (Wako Pure Chemical Industries, average molecular weight 1,800-2,200)
PEG 4,000: Polyethylene glycol 4,000 (Wako Pure Chemical Industries, average molecular weight 2,700-3,300)
PEG 20,000: Polyethylene glycol 20,000 (manufactured by Wako Pure Chemical Industries, average molecular weight 15,000-25,000)

  Since the solid electrolytic capacitor of the present invention is excellent in reliability and durability, it can be applied to high frequency digital devices and the like.

Claims (6)

In the method for producing a solid electrolytic capacitor having a step of forming a conductive polymer layer on the surface of the valve action metal on which the dielectric oxide film is formed,
The step
The following (A) to (D)
(A) Conductive polymer (B) Colloidal silica (C) A compound having reactivity with silanol groups (D) A conductive polymer dispersion containing at least a dispersion medium was brought into contact with the dielectric oxide film. rear,
Removing (D) at least partially;
A method for producing a solid electrolytic capacitor, comprising a step of forming a conductive polymer layer on the dielectric oxide film. The compound having reactivity with the (C) silanol group,
It is a linear and / or branched compound having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an isocyanate group, and a glycidyl group at the terminal and having a number average molecular weight of 100 to 10,000. The method for producing a solid electrolytic capacitor according to claim 1.   The method for producing a solid electrolytic capacitor according to claim 1, wherein the compound (C) having reactivity with a silanol group is polyalkylene glycol.   The content of the compound having reactivity with the (C) silanol group is 0.01 to 30% by weight based on the conductive polymer dispersion. The manufacturing method of the solid electrolytic capacitor as described in any one. The conductive polymer is represented by the following general formula (1)

(In formula (1), Ra represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and X represents an oxygen atom or a sulfur atom which may be the same or different.)
The method for producing a solid electrolytic capacitor according to any one of claims 1 to 4, wherein the polymer is a conductive polymer having a polymer of a thiophene compound represented by formula (1) and a dopant.   6. The dopant according to claim 5, wherein the dopant is at least one selected from the group consisting of polystyrenesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, and xylenesulfonic acid. Manufacturing method for solid electrolytic capacitor.