WO2024106474A1

WO2024106474A1 - Electrolytic capacitor comprising conductive polymer compound and method for producing same

Info

Publication number: WO2024106474A1
Application number: PCT/JP2023/041118
Authority: WO
Inventors: 真之坂口; 陽介野澤
Original assignee: ルビコン株式会社
Priority date: 2022-11-15
Filing date: 2023-11-15
Publication date: 2024-05-23

Abstract

The purpose of the present disclosure is to provide: an electrolytic capacitor which comprises a conductive polymer compound and a liquid substance phase, and which exhibits excellent liquid resistivity and excellent heat resistance; and a method for producing this electrolytic capacitor. An electrolytic capacitor according to the present invention is provided with an anode foil, on the surface of which an oxide coating film is formed, and a cathode foil; this electrolytic capacitor has, between the anode foil and the cathode foil, a solid electrolyte phase that contains a conductive polymer compound and a liquid substance phase that contains a liquid substance; the liquid substance phase additionally contains an acid component and a base component; the acid dissociation constant (pKa) of a conjugate acid in the base component is 10.0 or less; the amounts of the base component and the acid component in the liquid substance phase satisfy the relational expression (number of moles of base component) > (number of moles of acid component); and the acid component accounts for 2.6% by mass to 20% by mass in the liquid substance phase.

Description

Electrolytic capacitor having conductive polymer compound and method for manufacturing same

The present invention relates to an electrolytic capacitor having a conductive polymer compound. In particular, the present invention relates to an electrolytic capacitor having a liquid substance phase containing an acid component and a basic component in addition to a solid electrolyte phase containing a conductive polymer compound. The present invention also relates to a method for producing an electrolytic capacitor.

Solid electrolytic capacitors that use conductive polymer compounds as the electrolyte (solid electrolyte) are known. Such capacitors can exhibit low ESR and excellent low-temperature characteristics. In addition, by using a conductive polymer that is solid and highly heat-resistant as the electrolyte, such capacitors can provide capacitors with high reliability.

Also known is an electrolytic capacitor (hybrid capacitor) that uses a conductive polymer compound and an electrolytic solution as the electrolyte. Such a capacitor has advantages, for example, in terms of the capacitance appearance rate and film repairability in the initial capacitor characteristics.

Patent Document 1 describes a method for manufacturing an electrolytic capacitor, which includes impregnating a capacitor element with a dispersion containing a conductive solid, evaporating the solvent to form a conductive solid layer, and impregnating the gaps in the conductive solid layer with an electrolyte.

Patent Document 2 and Patent Document 3 describe an electrolytic capacitor having a driving electrolyte solution containing an acid component and a base component, and state that the acid component is in excess of the base component in terms of molar ratio.

Patent Document 4 describes a hybrid solid electrolytic capacitor that includes a solid electrolyte phase that includes a conductive polymer compound, and a liquid substance phase that surrounds the solid electrolyte phase and includes a liquid substance, and describes that the amounts of base and acid components in the liquid substance phase satisfy the relationship (number of moles of base component) > (number of moles of acid component) ≥ 0. This document describes that the liquid substance can include a base component in an amount of 0.3% to 50% by weight based on the weight of the liquid substance, but that the amount of base component included in the liquid substance phase is preferably 10% by weight or less based on the weight of the liquid substance phase, and further describes that in the examples, a liquid substance that includes 0.3 to 1.5% by weight of base component is used.

Patent document 5 describes an electrolytic capacitor that includes a solid electrolyte layer and an electrolyte solution, and describes that the solute contained in the electrolyte solution has a carboxylic acid component and a base component, and that the carboxylic acid component in the solute is 200 parts by mass or more per 100 parts by mass of the base component.

JP 2008-10657 A JP 2012-109635 A JP 2013-191897 A JP 2020-119916 A International Publication No. 2017/017947

　Conventional electrolytic capacitors that contain conductive polymer compounds and electrolytes are sometimes insufficient in terms of the electrolyte's liquid resistivity and heat resistance (especially changes in characteristics after reflow). In particular, when the concentration of the solute is relatively high, changes in characteristics after reflow can be problematic.

The present disclosure aims to provide an electrolytic capacitor having a conductive polymer compound and a liquid substance phase, which exhibits excellent liquid resistivity and excellent heat resistance.

The above problems related to the present disclosure can be solved by the inventions related to the present disclosure described below.
<Aspect 1>
an anode foil having an oxide film formed on its surface;
A cathode foil;
In a gap between the anode foil and the cathode foil,
A solid electrolyte phase including a conductive polymer compound;
and a liquid material phase including a liquid material,
The liquid phase further comprises an acid component and a base component;
the acid dissociation constant (pKa) of the conjugate acid of the base component is 10.0 or less;
The amount of the base component and the acid component in the liquid substance phase is
(number of moles of the base component)>(number of moles of the acid component)
The relationship formula is satisfied, and the acid component is 2.6% by mass to 20% by mass in the liquid substance phase.
Electrolytic capacitor.
<Aspect 2>
2. The electrolytic capacitor of claim 1, wherein the mass (B) of the base component and the mass (A) of the acid component in the liquid substance phase satisfy B>A/2.
<Aspect 3>
3. The electrolytic capacitor of claim 1 or 2, wherein the base component comprises an amine.
<Aspect 4>
4. The electrolytic capacitor according to claim 3, wherein the base component contains at least one selected from morpholine, methylmorpholine, ethylmorpholine, triethanolamine, and diethanolamine.
<Aspect 5>
5. The electrolytic capacitor according to any one of aspects 1 to 4, wherein the acid component is phthalic acid.
<Aspect 6>
6. The electrolytic capacitor according to any one of aspects 1 to 5, wherein the liquid substance comprises diethylene glycol or ethylene glycol.
<Aspect 7>
The electrolytic capacitor according to any one of aspects 1 to 6, wherein the liquid substance phase has a resistivity of 6.0 kΩ cm or less.
<Aspect 8>
1. A method for manufacturing an electrolytic capacitor, comprising:
forming a capacitor element including an anode foil and a cathode foil each having an oxide film formed on a surface thereof;
introducing a solid electrolyte phase containing a conductive polymer compound into a gap between the anode foil and the cathode foil; and
introducing a liquid material phase, the liquid material phase including a liquid material, into a gap between the anode foil and the cathode foil;
The liquid phase further comprises an acid component and a base component;
the acid dissociation constant (pKa) of the conjugate acid of the base component is 10.0 or less;
The amount of base component and acid component in the liquid substance phase is
(number of moles of the base component)>(number of moles of the acid component)
The relationship formula is satisfied, and the acid component is 2.6% by mass to 20% by mass in the liquid substance phase.
Method.

The electrolytic capacitor according to the present disclosure is an electrolytic capacitor having a conductive polymer compound and a liquid substance phase, and exhibits excellent liquid resistivity and excellent heat resistance.

FIG. 1a is a cross-sectional schematic diagram of an electrolytic capacitor according to one embodiment of the present disclosure. FIG. 1b is a perspective schematic diagram of a capacitor element according to one embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of a main part of the solid electrolyte phase of FIG.

<< Capacitor >>
The electrolytic capacitor according to the present disclosure comprises:
an anode foil having an oxide film formed on its surface;
A cathode foil;
In the gap between the anode foil and the cathode foil,
A solid electrolyte phase including a conductive polymer compound;
and a liquid material phase including a liquid material,
The liquid phase further comprises an acid component and a base component;
the acid dissociation constant (pKa) of the conjugate acid of the base component is 10.0 or less;
The amount of base and acid components in the liquid phase is
(number of moles of base component)>(number of moles of acid component)
The acid component is in a range of 2.6% by mass to 20% by mass in the liquid phase.
It is.

　Conventionally, electrolytic capacitors that use a conductive polymer compound and an electrolytic solution as the electrolyte are known (hybrid capacitors). Such capacitors can provide excellent film repairability and an excellent capacitance appearance rate. However, conventional capacitors can have problems with heat resistance. In particular, when the concentration of the solute in conventional capacitors is relatively high, the characteristics of the capacitor can deteriorate when exposed to high temperatures during the reflow process.

In response to this, the inventors of the present invention have discovered that even when a relatively high concentration of solute (acid component and base component) is used, by using a base component with a relatively low basicity as the base component that constitutes the solute, the change in characteristics after reflow can be suppressed. By increasing the solute concentration, the liquid resistivity of the liquid material phase contained in the capacitor can be reduced, so that according to the present invention, an electrolytic capacitor with improved electrical characteristics can be obtained while avoiding problems such as changes in characteristics after reflow.

The drawings are used to explain exemplary embodiments of the present invention in more detail. Note that these drawings and exemplary embodiments are not intended to limit the present invention. The drawings are schematic and are not necessarily drawn to scale.

<Configuration of electrolytic capacitor 1 according to embodiment>
1A and 1B are diagrams for explaining an electrolytic capacitor 1 according to an embodiment of the present invention. Fig. 1A is a cross-sectional view of the electrolytic capacitor 1, and Fig. 1B is a perspective view of a capacitor element 20.

FIG. 2 is a diagram for explaining the main parts of the electrolytic capacitor 1 according to the embodiment. FIG. 2 is a cross-sectional view of the main parts of the electrolytic capacitor 1.

The electrolytic capacitor 1 according to the embodiment is a wound-type electrolytic capacitor, and as shown in FIG. 1, includes a cylindrical metal case 10 with a bottom, a capacitor element 20, and a sealing member 40.

The bottom surface of the metal case 10 is substantially circular, with a valve (not shown) located near the center. This allows the valve to break and release the internal pressure to the outside when the internal pressure rises. The side surface of the metal case 10 stands upright in a substantially vertical direction from the outer edge of the bottom surface. The opening of the metal case 10 is sealed with a sealing member 40, and the two leads 29, 30 of the capacitor element 20 are pulled out to the outside through a through hole provided in the sealing member 40.

The capacitor element 20 is housed inside the metal case 10, and as shown in Figures 1(b) and 2, it comprises an anode foil 21, a cathode foil 23, and a separator 25 disposed between the anode foil 21 and the cathode foil 23, and the anode foil 21 and the cathode foil 23 are overlapped and wound with the separator 25 in between.

In the embodiment shown in FIG. 2, a solid electrolyte phase consisting of a fine particle conductive polymer compound 26 and a liquid substance phase 27 containing a liquid substance are introduced into the gap between the anode foil 21 and the cathode foil 23, and the liquid substance phase 27 is present so as to surround the solid electrolyte consisting of the conductive polymer compound 26. The anode foil 21 and the cathode foil 23 have oxide films 22 and 24 on their surfaces, respectively.

<Gaps>
In the present disclosure, the term "gap between the anode foil and the cathode foil" includes not only "gaps between the anode foil and the separator and between the cathode foil and the separator" but also "gaps between fibers in the separator." In addition, the term "gap between the anode foil and the cathode foil" also includes "gaps in etching pits (recesses) formed in the surface of the anode foil or cathode foil by roughening through etching."

<Liquid substance phase>
A capacitor according to the present disclosure includes a liquid substance phase. The liquid substance phase includes a liquid substance, and further includes an acid component and a base component.

Regarding the content of each component in the liquid substance phase, basically, the content in the liquid substance phase impregnated into the capacitor during the capacitor manufacturing process ("liquid substance phase before impregnation") is the same as the content in the capacitor after manufacturing. However, if additives (e.g. polyols) are used in the conductive polymer dispersion during the capacitor manufacturing process, the additives may be added to the liquid substance phase as liquid substances. In this case, the content of each component in the liquid substance phase is determined taking into account the additives.

The liquid phase can be present surrounding the solid electrolyte phase.

The liquid substance phase is preferably composed of a liquid substance, an acid component, and a base component, and contains other components at a ratio of 10% by weight or less, 5% by weight or less, 2% by weight or less, 1% by weight or less, or even 0.1% by weight or less. In one embodiment, the liquid substance phase may be a liquid in which the acid component, the base component, and optionally other components are dissolved and/or dispersed in the liquid substance, and in particular may be a liquid in which these components are dissolved in the liquid substance.

"Other components" include aromatic nitro compounds.

In the capacitor according to the present disclosure, the proportion of the liquid material phase in the gap between the anode foil and the cathode foil may be 10 vol% to 99 vol%, particularly 50 vol% to 99 vol%, or even 70 vol% to 99 vol%.

(Liquid substance)
The liquid substance constituting the liquid substance phase is a liquid capable of retaining an acid component and a base component. The liquid substance is, in particular, a solvent in which the acid component and the base component as solutes can be dissolved. Note that even if the acid component and the base component are liquid substances by themselves, they are not included in the "liquid substance" according to the present application.

The liquid substance may be an organic solvent, particularly a polymeric organic solvent, but is not particularly limited. The liquid substance may be, for example, water, a hydrophilic polymer compound, a component having a hydroxyl group, such as polyoxyalkylene and its derivatives (polyglycerin), water-soluble polyurethane, water-soluble polyester, water-soluble polyamide, water-soluble polyimide, water-soluble polyacrylic, water-soluble polyacrylamide, water-soluble silicone, polyvinyl alcohol, polyacrylic acid, etc., or a mixture thereof.

Particularly, examples of liquid substances include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, other polyethylene glycols, and their derivatives, glycerin, diglycerin, and their derivatives, γ-butyrolactone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, and dimethylformamide. These may be used alone or in combination of two or more. Of these, glycol compounds, that is, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, other polyethylene glycols, and their derivatives, are preferred, with ethylene glycol and diethylene glycol being most preferred. When ethylene glycol and/or diethylene glycol are used as the liquid substance, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

The content of the liquid substance (particularly the solvent) may be 50% by mass or more, or 60% by mass or more, and/or 95% by mass or less, 92% by mass or less, or 90% by mass or less, relative to the liquid substance phase.

The content of the liquid substance (particularly the solvent) is preferably 80% by mass to 95% by mass, more preferably 85% by mass to 92% by mass, relative to the liquid substance phase.

In particular, the liquid substance phase contains glycol compounds (in particular ethylene glycol and/or diethylene glycol) in a total amount of 60% to 95% by weight, or even 65% to 90% by weight.

<Acid component>
The liquid substance phase contains an acid component. The acid component is generally a substance that is acidic (pH of the aqueous solution is <7) and acts in pairs with a base, and refers to a chemical species that donates a proton (H ⁺ ) or accepts an electron pair.

The acid component is contained in the liquid substance phase at 2.6% to 20% by mass.

This content of the acid component in the liquid substance phase may be 2.7% by weight or more, 2.8% by weight or more, 2.9% by weight or more, 3% by weight or more, 3.5% by weight or more, 4% by weight or more, 4.5% by weight or more, 5% by weight or more, 6% by weight or more, 7% by weight or more, or 8% by weight or more, and/or 19% by weight or less, 18% by weight or less, 17% by weight or less, 16% by weight or less, 15% by weight or less, 14% by weight or less, 13% by weight or less, 12% by weight or less, 11% by weight or less, or 10% by weight or less.

The content of the acid component in the liquid substance phase is preferably 3% by mass to 18% by mass, more preferably 4% by mass to 16% by mass, even more preferably 5% by mass to 14% by mass, and particularly preferably 6% by mass to 12% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

The content of the acid component in the liquid substance phase may be 3% by mass to 24% by mass relative to the total amount of glycol compounds (particularly ethylene glycol and/or diethylene glycol) contained in the liquid substance phase.

This content ratio of the acid component to the total of the glycol compounds (particularly ethylene glycol and/or diethylene glycol) contained in the liquid substance phase may be 3.2% by mass or more, 3.4% by mass or more, 3.6% by mass or more, 3.8% by mass or more, 4% by mass or more, 4.2% by mass or more, 4.4% by mass or more, 4.6% by mass or more, 4.8% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, or 8% by mass or more, and/or 22% by mass or less, 20% by mass or less, 19% by mass or less, 18% by mass or less, 17% by mass or less, 16% by mass or less, 15% by mass or less, 14% by mass or less, 13% by mass or less, 12% by mass or less, 11% by mass or less, or 10% by mass or less.

The content ratio of the acid component to the total of the glycol compounds (particularly ethylene glycol and/or diethylene glycol) contained in the liquid substance phase is preferably 3% by mass to 22% by mass, more preferably 3.5% by mass to 20% by mass, even more preferably 4% by mass to 18% by mass, and particularly preferably 4% by mass to 16% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

In addition, in the capacitor, the liquid substance phase used for impregnation may be diluted by additives contained in the conductive polymer dispersion during the manufacturing process. Therefore, it may be preferable that the liquid substance phase used for impregnation in the capacitor manufacturing process ("liquid substance phase before impregnation") contains an acid component and/or a base component at a relatively higher concentration than desired in the capacitor.

Specifically, the content of the acid component in the liquid substance phase before impregnation may be 3% by mass to 20% by mass, and in particular, 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, or 8% by mass or more, and/or 19% by mass or less, 18% by mass or less, 17% by mass or less, 16% by mass or less, 15% by mass or less, 14% by mass or less, 13% by mass or less, 12% by mass or less, 11% by mass or less, or 10% by mass or less.

The content of the acid component in the liquid substance phase before impregnation is preferably 4% by mass to 18% by mass, more preferably 5% by mass to 16% by mass, and even more preferably 6% by mass to 14% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

In addition, with respect to the liquid substance phase before impregnation, the content ratio of the acid component to the total amount of glycol compounds (particularly ethylene glycol and/or diethylene glycol) contained in the liquid substance phase may be the same as the above-mentioned content.

The acid components include organic acids, inorganic acids, and complex compounds thereof.

Organic acids include carboxylic acids, phenols, and sulfonic acids. Carboxylic acids include formic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, sulfosalicylic acid, maleic acid, adipic acid, benzoic acid, tricarboxylic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, resorcylic acid, phloroglucinic acid, gallic acid, and citric acid.

Inorganic acids include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid.

Examples of composite compounds of organic and inorganic acids include borodisalicylic acid, borodioxalic acid, and borodiglycolic acid.

The above-mentioned acid components may be used alone or in combination of two or more.

The acid component is particularly preferably phthalic acid.

<Base component>
The liquid substance phase contains a base component. The base component is generally a substance that exhibits basicity (pH of the aqueous solution is >7) and acts in combination with an acid, and refers to a chemical species that accepts a proton (H ⁺ ) or donates an electron pair.

The base component may be one or more selected from amines, amidines, and ammonia, and is preferably an amine.

(Dissociation constant of base component)
The base component contained in the liquid substance phase of the electrolytic capacitor according to the present disclosure has an acid dissociation constant (pKa) of the conjugate acid of 10.0 or less. This pKa can be measured by neutralization titration at 25°C.

Such base components include:
4-methylmorpholine (pKa=7.4 at 25° C.),
4-Ethylmorpholine (pKa=7.7 at 25° C.),
Triethanolamine (pKa=7.8 at 25° C.)
Morpholine (pKa=8.3 at 25° C.),
Diethanolamine (pKa=8.9 at 25° C.)
Examples include:

The pKa of the base component is preferably 9.5 or less, more preferably 9.0 or less, even more preferably 8.5 or less, and particularly preferably 8.0 or less. There is no particular limit to this lower limit, but it may be, for example, 7.2 or more, or 7.3 or more.

The base component may be contained in an amount of 1% to 20% by mass relative to the liquid substance phase.

The content of the base component may be 1.5% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or more, and/or 18% by mass or less, 15% by mass or less, 14% by mass or less, 12% by mass or less, 10% by mass or less, or 8% by mass or less, based on the liquid substance phase.

<Acid and base components>
In the electrolytic capacitor according to the present disclosure, the amount of the base component and the acid component in the liquid substance phase is:
(number of moles of base component)>(number of moles of acid component)
The following relation is satisfied.

In particular, when the number of moles of the acid component is taken as 1, the number of moles of the base component may be greater than 1, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, and/or 3.0 or less, 2.5 or less, 2.0 or less, 1.8 or less, or 1.6 or less. Particularly preferably, when the number of moles of the acid component is taken as 1, the number of moles of the base component is greater than 1 and 1.5 or less, or even greater than 1 and 1.3 or less.

Furthermore, in an electrolytic capacitor according to one embodiment of the present disclosure, the mass (B) of the base component and the mass (A) of the acid component in the liquid substance phase are:
B>A/2
Meet the following.

<Liquid resistivity>
Preferably, the liquid substance phase contained in the electrolytic capacitor according to the present disclosure has a resistivity of 6.0 kΩ cm or less when measured with an electric conductivity meter. This resistivity can be measured using an extract obtained by disassembling the electrolytic capacitor and subjecting it to centrifugation or the like as the liquid substance phase.

This resistivity is more preferably 5.5 kΩ·cm or less, 5.0 kΩ·cm or less, 4.5 kΩ·cm or less, 4.0 kΩ·cm or less, or even 3.5 kΩ·cm or less. There is no particular limit to this lower limit, but it may be, for example, 0.1 kΩ·cm or more.

The resistivity of the liquid material phase before impregnation used in the capacitor manufacturing process may show a different value from the resistivity of the liquid material phase in the finished electrolytic capacitor. This is thought to be because additives (e.g. polyols) used in the conductive polymer dispersion or solution also affect the resistivity value in the finished electrolytic capacitor.

Therefore, in order to obtain an electrolytic capacitor with a desired resistivity, it may be preferable for the liquid material phase impregnated into the capacitor during the capacitor manufacturing process to have a resistivity of 3.0 kΩ·cm or less, 2.5 kΩ·cm or less, 2.0 kΩ·cm or less, or even 1.5 kΩ·cm or less. There is no particular lower limit to this, but it may be, for example, 0.1 kΩ·cm or more.

<Aromatic nitro compounds>
The liquid substance phase of the electrolytic capacitor according to the present disclosure may contain an aromatic nitro compound. The aromatic nitro compound is an aromatic compound having a nitro group. The aromatic nitro compound can have the effect of improving the pressure resistance and heat resistance of the capacitor by absorbing hydrogen gas generated by a re-chemical reaction or the like.

When an aromatic nitro compound is used, the proportion of the aromatic nitro compound in the liquid phase may be 0.5% to 10% by weight, 0.5% to 5% by weight, or even 1% to 5% by weight.

The aromatic nitro compound may be at least one selected from the group consisting of nitrophenol, nitroacetophenone, nitrobenzyl alcohol, nitrobenzoic acid, nitrobenzaldehyde, nitroanisole, nitrobenzene carboxylic acid, nitrobenzene dicarboxylic acid, nitroaniline, nitroacetanilide, nitrotoluene, nitrophenyl acetic acid, nitrocresol, dinitrobenzoic acid, methyl nitrobenzoic acid, nitroterephthalic acid, and nitroisophthalic acid. These may be used alone or in combination of two or more.

Preferably, the aromatic nitro compound is at least one selected from the group consisting of nitrophenol, nitroacetophenone, nitrobenzyl alcohol, nitrobenzoic acid, and nitrobenzaldehyde. The aromatic nitro compound is particularly preferably nitroacetophenone.

<Water>
The liquid phase may contain water.

If the liquid substance phase present in the gap between the anode foil and the cathode foil contains "water" in addition to the liquid water-soluble polymer compound, even if defects occur in the oxide film during the process of manufacturing the electrolytic capacitor, it is possible to use the moisture from the "water" in addition to the moisture held by the water-soluble polymer compound to repair the defects. As a result, particularly good effects can be obtained in terms of reducing the density of defects in the oxide film and reducing leakage current.

The water content may be 0% to 10% by mass, preferably 0.1% to 10% by mass, and more preferably 0.5 to 5% by mass, relative to the liquid substance phase. When the water content is within this range, the oxide film defect repair effect can be sufficiently obtained, and adverse effects caused by an excessive water content (such as expansion of the capacitor that can occur when used for a long period of time in a high-temperature environment) can be avoided or suppressed.

<Anode foil>
A capacitor according to the present disclosure includes an anode foil having an oxide film formed on its surface.

The anode foil may be formed from a valve metal such as aluminum, tantalum, or niobium.

The anode foil has an oxide film on its surface. For example, an oxide film can be formed on the surface of the anode foil by roughening it with an etching process according to a known method and then performing a chemical conversion treatment.

<Cathode foil>
A capacitor according to the present disclosure includes a cathode foil.

The cathode foil, like the anode foil, may be formed from a valve metal such as aluminum, tantalum, or niobium.

The cathode foil may have an oxide film formed on its surface. The surface of the cathode foil may be roughened by etching in the same manner as the anode foil, and then an oxide film may be formed by natural oxidation. The cathode foil may also be subjected to a chemical conversion treatment at a desired voltage (e.g., 2 V), which may result in the formation of an oxide film.

<Separator>
A capacitor according to the present disclosure includes a separator disposed between the anode foil and the cathode foil.

As the separator, those formed from cellulose fibers that are chemically compatible with conductive polymer particles and water-soluble polymers, and synthetic resins such as nylon, PET, and PPS that have excellent heat resistance are preferable, and for example, heat-resistant cellulose paper and heat-resistant flame-retardant paper can be used. More specifically, examples of the separator include cellulose and mixed papers such as kraft, Manila hemp, esparto, hemp, and rayon, polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and derivatives thereof, polytetrafluoroethylene-based resins, polyvinylidene fluoride-based resins, vinylon-based resins, polyamide-based resins such as aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides, polyimide-based resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, and polyvinyl alcohol resins, and these resins can be used alone or in combination.

<Solid electrolyte phase>
Capacitors according to the present disclosure include a solid electrolyte phase in the gap between the anode and cathode foils.

(Conductive polymer compound)
The solid electrolyte phase contains a conductive polymer compound, and in particular is substantially composed of a conductive polymer compound.

The solid electrolyte phase may be in various forms, for example a continuous uniform thick or thin layer, a membrane (film-like), or an aggregate of fine particles containing a conductive polymer compound and optionally a dopant, or a structure in which such fine particles and their aggregates (particularly chains) are bonded to each other to form a network. The solid electrolyte phase may also be a fine particle layer composed of fine particles containing a conductive polymer compound and optionally a dopant.

The conductive polymer compound may be at least one selected from polythiophene, polypyrrole, polyaniline, and derivatives thereof. The conductive polymer compound may be at least one of these. A preferred conductive polymer compound is polyethylenedioxythiophene (PEDOT) (particularly poly(3,4-ethylenedioxythiophene)).

The solid electrolyte phase may further include a dopant. Examples of the dopant include aromatic sulfonic acids such as benzenesulfonic acid or its derivatives, naphthalenesulfonic acid or its derivatives, and anthraquinonesulfonic acid or its derivatives; polymeric sulfonic acids such as polystyrenesulfonic acid (PSS), sulfonated polyester, phenolsulfonic acid novolac resin, and copolymers of styrenesulfonic acid and non-sulfonic acid monomers (methacrylic acid esters, acrylic acid esters, unsaturated hydrocarbon-containing alkoxysilane compounds or their hydrolysates); and chain sulfones such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid. These may be used alone or in combination of two or more.

The polystyrene sulfonic acid preferably has a weight average molecular weight of 10,000 to 1,000,000.

In a preferred embodiment, the solid electrolyte phase comprises polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS) as a dopant.

The conductive polymer compound may be in the form of fine particles. The average particle size of the fine particle conductive polymer compound is preferably in the range of 1 nm to 300 nm, or even 5 nm to 200 nm (e.g., 20 nm). The fine particle conductive polymer compound may contain a dopant. The average particle size of the fine particles composed of a conductive polymer and, optionally, a dopant, can be determined, for example, from the particle size distribution measured by dynamic light scattering.

In the capacitor according to the present disclosure, the proportion of the conductive polymer compound in the gap between the anode foil and the cathode foil may be 0.5 vol% to 20 vol%, or even 1 vol% to 10 vol%.

(Formation of solid electrolyte phase)
The method for forming the solid electrolyte phase containing the conductive polymer compound is not particularly limited, but it can be formed by, for example, a dipping impregnation method. For example, the solid electrolyte phase can be formed by filling a dispersion liquid (conductive polymer compound dispersion liquid) in which the conductive polymer compound is dispersed in a dispersion medium or a solution (conductive polymer compound solution) in which the conductive polymer compound is dissolved in a solvent into the voids, and then removing the dispersion medium or the solvent from the voids by heating and drying or the like.

More specifically, for example, a capacitor element is immersed in a conductive polymer dispersion liquid or a conductive polymer solution using an introduction tank. The capacitor element is then removed from the conductive polymer dispersion liquid or the conductive polymer solution, and the capacitor element is heat-treated to form a solid electrolyte phase in the gap between the anode foil and the cathode foil of the capacitor element. This operation may be repeated multiple times, thereby increasing the amount of solid electrolyte phase filled.

The solid electrolyte phase containing the conductive polymer compound may be formed by polymerizing the monomer in a so-called "in-situ polymerization".

The conductive polymer content in the conductive polymer compound dispersion or conductive polymer compound solution may be 0.1 to 10 mass%, 0.2 to 5 mass%, and particularly 0.5 to 3 mass%.

As a dispersion medium for the conductive polymer compound dispersion, for example, protic solvents such as water, alcohol (e.g., methanol, ethanol, 1-propanol, butanol), and mixtures thereof can be used. As a solvent for the conductive polymer compound solution, for example, protic solvents such as water, alcohol (e.g., methanol, ethanol, 1-propanol, butanol), and mixtures thereof can be used. An aromatic nitro compound may be contained in the conductive polymer compound dispersion or the conductive polymer compound solution.

The conductive polymer dispersion or conductive polymer solution may contain other compounds as additives, for example, high boiling point compounds (particularly compounds having a boiling point of 150°C or higher). Examples of additives include glycerin, diglycerin, polyglycerin, ethylene glycol, diethylene glycol, and other polyethylene glycols, as well as derivatives thereof, gamma-butyrolactone, butanediol, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, dimethyl sulfolane, and polyethylene glycol, as well as derivatives thereof. These may be used alone, or two or more of them may be used in combination.

The content of the additive in the conductive polymer compound dispersion or conductive polymer compound solution may be 1 to 40% by mass, in particular 2 to 30% by mass, or even 5 to 25% by mass. This content may be 1 to 20% by mass.

<Capacitor>
(CAP)
Capacitors according to the present disclosure can have a capacitance of 1 to 5000 μF, or even 10 to 1000 μF, when measured at 120 Hz according to the method described in the Examples.

(ESR)
Capacitors according to the present disclosure may have an ESR of 5 to 30 mΩ, or even 8 to 20 mΩ, when measured at 100 kHz according to the method described in the Examples.

<<Capacitor manufacturing method>>
The method for manufacturing the capacitor according to the present invention is not particularly limited. The capacitor according to the present invention includes, for example, a capacitor element manufacturing step, a chemical conversion treatment step, a solid electrolyte phase introduction step, a liquid substance phase introduction step, and an assembly and sealing step in this order. Below, the manufacturing method of the electrolytic capacitor in the exemplary embodiment will be described along with each step.

(1) Capacitor Element Preparation Process In an exemplary method for an electrolytic capacitor, first, an aluminum foil is provided as an anode foil 21. After the surface of the aluminum foil is roughened by a surface enlarging process, a predetermined voltage of 2V to 500V is applied to the roughened surface of the aluminum foil to perform a chemical conversion process, thereby forming an oxide film 22 on the surface of the aluminum foil. Then, a capacitor element is prepared that includes an anode foil 21 having an oxide film 22, a cathode foil 23, and a separator 25 disposed between the anode foil 21 and the cathode foil 23 (see FIG. 1(b)). Specifically, the anode foil 21 having an uneven surface (rough surface) and the oxide film 22 formed on the uneven surface and the cathode foil 23 having an uneven surface are overlapped and wound through the separator 25 to prepare a capacitor element 20. At this time, a lead 30 is connected to the anode foil 21, and a lead 29 is connected to the cathode foil 23.

(2) Chemical Conversion Treatment Step Next, the capacitor element 20 is immersed in a chemical conversion solution in a chemical conversion solution tank, and a predetermined voltage (e.g., 100 V) is applied between the anode lead 30 and the chemical conversion solution for 5 minutes. This operation repairs defects in the oxide film present at the edge of the anode foil 21 and defects in the oxide film that may be present on the surface.

The chemical conversion liquid may be an aqueous solution of, for example, ammonium adipate, ammonium borate, ammonium phosphate, ammonium glutarate, ammonium azelaate, ammonium tartrate, ammonium sebacate, ammonium pimelate, or ammonium suberate.

(3) Solid Electrolyte Phase Introducing Step Next, a solid electrolyte phase consisting of fine particle conductive polymer compound 26 is introduced into the gap between the anode foil 21 and the cathode foil 23 so that the ratio of the solid electrolyte phase occupying the gap is within a range of, for example, 2 vol % to 30 vol %. In the solid electrolyte phase introducing step, for example, a conductive polymer compound dispersion liquid in which a conductive polymer compound is dispersed in a dispersion medium is filled into the gap, and then the dispersion medium is removed from the gap, thereby introducing the solid electrolyte phase into the gap. Instead of the conductive polymer compound dispersion liquid, a solution in which a conductive polymer compound is dissolved in a solvent (conductive polymer compound solution) may be used.

More specifically, the solid electrolyte phase introduction step can be performed by a dipping impregnation method. That is, after filling an introduction tank with a conductive polymer compound dispersion liquid (e.g., conductive polymer compound concentration 2 vol%), the capacitor element is immersed in the conductive polymer compound dispersion liquid. Next, the capacitor element is removed from the introduction tank, and then the capacitor element is heat-treated.

The conductive polymer dispersion liquid can be produced by polymerizing (radical polymerization or oxidative polymerization) a monomer (e.g., PEDOT monomer) in suspension to produce a conductive polymer compound in the form of fine particles made of a conductive polymer compound (e.g., PEDOT polymer) to which a dopant or emulsifier has been added, and dispersing the fine particles of the conductive polymer compound in a specified dispersion medium. The average particle size of the conductive polymer compound can be adjusted by appropriately setting the polymerization reaction conditions (e.g., concentrations of initiator, monomer, polymerization aid, etc., reaction temperature, stirring conditions of the reaction solution, etc.). It can also be adjusted by carrying out a known crushing process (e.g., stirring crushing process, vibration crushing process, etc.). The particle size can also be made uniform by a preparative filtration process.

In order to increase the proportion of the solid electrolyte phase occupying the voids, the number of times the above operation is repeated can be increased and/or the polymer concentration in the conductive polymer compound dispersion can be increased. On the other hand, in order to decrease the proportion of the solid electrolyte phase occupying the voids, the number of times the above operation is repeated can be decreased and/or the polymer concentration in the conductive polymer compound dispersion can be decreased.

(4) Liquid substance phase introducing step In the liquid substance phase introducing step, for example, the liquid substance phase 27 is introduced into the gap between the anode foil 21 and the cathode foil 23 so as to surround the solid electrolyte and so that the ratio of the liquid substance phase 27 occupying the gap is within a range of 10 vol % to 99 vol %. Specifically, the liquid substance phase introducing step can be performed as follows (a) and (b).

(a) Preparation of liquid substance phase A liquid substance phase can be prepared by providing a liquid substance (e.g., ethylene glycol), adding a predetermined amount of an acid component and a base component to the liquid substance, and then stirring the mixture. These operations may be performed by heating the mixture to, for example, about 40 to 60°C.

(b) Introduction of Liquid Material Phase When the filling of the liquid material phase is carried out by the immersion impregnation method, the liquid material phase is filled into an introduction tank, and then the capacitor element is immersed in the liquid material phase to introduce the liquid material phase into the voids.

(5) Assembly and sealing process In the assembly and sealing process, the sealing member 40 is attached to the capacitor element 20, and the capacitor element 20 is inserted into the metal case 10, and then the metal case 10 is crimped near the open end of the metal case 10. As the sealing member 40, for example, isobutylene-isoprene rubber (IIR) can be used. Instead of isobutylene-isoprene rubber (IIR), rubber materials such as ethylene-propylene terpolymer (EPT), EPT-IIR blend rubber, silicone rubber, and rubber composite materials in which resins such as phenolic resin (Bakelite), epoxy resin, and fluororesin are bonded to rubber can also be used. Thereafter, an aging process is performed by applying a predetermined voltage in a high-temperature atmosphere as desired. This completes the electrolytic capacitor 1 according to the embodiment.

The capacitor according to the present disclosure can be produced in particular by the method for producing an electrolytic capacitor according to the present disclosure as follows:
1. A method for manufacturing an electrolytic capacitor, comprising the steps of:
forming a capacitor element including an anode foil and a cathode foil having an oxide film formed on the surface thereof (capacitor element fabrication process);
Introducing a solid electrolyte phase containing a conductive polymer compound into a gap between the anode foil and the cathode foil (solid electrolyte phase introduction step); and
A liquid substance phase containing a liquid substance is introduced into the gap between the anode foil and the cathode foil (liquid substance phase introduction step).
Including,
The liquid phase further comprises an acid component and a base component;
the acid dissociation constant (pKa) of the conjugate acid of the base component is 10.0 or less;
The amount of base and acid components in the liquid phase is
(number of moles of the base component)>(number of moles of the acid component)
The relationship formula is satisfied, and the acid component is 2.6% by mass to 20% by mass in the liquid substance phase.
Method.

For details of each step and each component of the manufacturing method according to the present disclosure, please refer to the above description of the electrolytic capacitor according to the present disclosure and the above specific description of the manufacturing method of the capacitor.

In the liquid substance phase introduction step of this manufacturing method, the content of the acid component in the liquid substance phase may be, in particular, 3 to 20% by mass, and may further be 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, or 8% by mass or more, and/or 19% by mass or less, 18% by mass or less, 17% by mass or less, 16% by mass or less, 15% by mass or less, 14% by mass or less, 13% by mass or less, 12% by mass or less, 11% by mass or less, or 10% by mass or less.

In the liquid phase introduction step of this manufacturing method, the content of the acid component in the liquid phase is preferably 4% by mass to 18% by mass, more preferably 5% by mass to 16% by mass, and even more preferably 6% by mass to 14% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

The content ratio of the acid component to the total amount of glycol compounds (particularly ethylene glycol and/or diethylene glycol) contained in the liquid substance phase may be the same as the above-mentioned content.

In the liquid substance phase introduction step, the content of the liquid substance (particularly the solvent) may be 45 mass% or more, 50 mass% or more, or 60 mass% or more, and/or 95 mass% or less, 92 mass% or less, 90 mass% or less, or 80 mass% or less, relative to the liquid substance phase. The content of the liquid substance (particularly the solvent) is preferably 70 mass% to 95 mass%, or 82 mass% to 92 mass%, more preferably 85 mass% to 90 mass%, relative to the liquid substance phase.

In the liquid substance phase introduction step, the base component may be contained in an amount of 0.5% to 20% by mass, or 1% to 18% by mass, relative to the liquid substance phase. The content of the base component may be 1.0% by mass or more, 1.5% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or more, relative to the liquid substance phase, and/or 20% by mass or less, 18% by mass or less, 15% by mass or less, 14% by mass or less, 12% by mass or less, 10% by mass or less, or 8% by mass or less.

When an aromatic nitro compound is used, the proportion of the aromatic nitro compound in the liquid phase in the liquid phase introduction step may be 0.1% by mass to 10% by mass, 0.5% by mass to 8% by mass, 0.5% by mass to 5% by mass, or even 1% by mass to 5% by mass.

In the liquid substance phase introduction step, the water content may be 0% by mass to 10% by mass, or 0% by mass to 9% by mass, relative to the liquid substance phase. In one embodiment, it is preferably 0.1% by mass to 9% by mass, and more preferably 0.4% by mass to 4% by mass.

In one preferred embodiment of the above-mentioned manufacturing method according to the present disclosure, it may further have at least one of the following features:
With respect to the mass (B) of the base component and the mass (A) of the acid component in the liquid substance phase, B>A/2; and/or the base component contains an amine; and/or the base component contains at least one selected from morpholine, methylmorpholine, ethylmorpholine, triethanolamine, and diethanolamine; and/or the acid component is phthalic acid; and/or the liquid substance contains diethylene glycol or ethylene glycol; and/or the resistivity of the liquid substance phase is 6.0 kΩ·cm or less.

Below, the embodiments of the present invention will be described in more detail with reference to examples. The following examples and comparative examples are not intended to limit the present invention.

<<Measurement method>>
The measurement methods used in the examples and comparative examples are as follows.

<CAP>
The CAP (μF) of the capacitor was measured at room temperature and 120 Hz using an LCR meter (Keysight Technologies Precision LCR Meter (E4980A)).

<ESR>
The ESR (mΩ) of the capacitor was measured at room temperature and 100 kHz using an LCR meter (Keysight Technologies Precision LCR Meter (E4980A)).

<Resistivity>
The resistivity of the liquid substance phase was measured at a liquid temperature of 30.0±0.2° C. using the liquid substance phase before it was impregnated into the capacitor element with an electric conductivity meter (manufactured by Toa DKK: CM-40S, cell: CG-511B).

If the resistivity value of the liquid substance phase before impregnation is relatively reduced, it is believed that the resistivity value of the liquid substance phase in the completed electrolytic capacitor will also be relatively reduced. Note that the resistivity value of the liquid substance phase before impregnation may differ from the resistivity value of the liquid substance phase extracted from the electrolytic capacitor. This is believed to be because additives (e.g. polyols) used in the conductive polymer dispersion or solution may affect the resistivity value of the liquid extracted from the electrolytic capacitor.

For Examples 1 and 2, the liquid extracted from the capacitor was used as the liquid substance phase, and the electrical conductivity and resistivity of the liquid substance phase were measured at 25°C using an electrical conductivity meter (HORIBA Compact Conductivity Meter B-173).

<pH>
The pH of the liquid substance phase was measured at a liquid temperature of 25 to 30° C. using the liquid substance phase before it was impregnated into the capacitor element with a pH meter (manufactured by Toa DKK, model number: HM-30R, cell: GST-5741C).

<<Examples 1-2 and Comparative Examples 1-2>>
In Examples 1 and 2 and Comparative Examples 1 and 2, a base component with a relatively low basicity and a base component with a relatively high basicity were used, respectively, and the case where the concentration of the solute was relatively high was examined.

Example 1
(Capacitor manufacturing)
Anode foil (made of aluminum) and cathode foil (made of aluminum) with a withstand voltage of about 60V were wound with a separator (made of cellulose) between them, and then the end faces and defects were chemically formed using a chemical formation solution, and then the solid electrolyte was vacuum-impregnated and dried to produce a capacitor element having a solid electrolyte phase. The solid electrolyte phase contained polyethylenedioxythiophene (PEDOT) as a conductive polymer compound and polystyrenesulfonic acid (PSS) as a dopant. The capacitor element was impregnated with the following liquid substance phase to obtain the capacitor according to Example 1.

The liquid phase impregnated in the capacitor of Example 1 had the following composition:
Solvent: 90.9% by weight ethylene glycol; Acid component: 4.0% by weight phthalic acid; Base component: 3.3% by weight ethylmorpholine (pKa=7.7)
Water: 0.9% by mass
Nitroacetophenone: 0.9% by mass

In the liquid substance phase of Example 1, the molar ratio of the acid component to the base component was 1:1.2.

(Performance evaluation)
The manufactured capacitor according to Example 1 was subjected to a performance evaluation before and after the reflow treatment, and the rate of change in capacitance (ΔC) and the rate of change in ESR (ΔESR) were measured.

The reflow process was performed twice with a peak temperature of 260°C.

The results for Example 1 are shown in Tables 1-1 and 1-2 below. Note that Table 1-1 shows the solute content in the liquid material phase before impregnation, and Table 1-2 shows the solute content in the liquid material phase taking into account the additives used in the conductive polymer dispersion.

Table 1-2 also lists the solute content of glycol compounds in the liquid substance phase.

Example 2
In Example 2, except that the amount of solute was changed as shown in Table 1-1 below, a capacitor was manufactured and its performance was evaluated in the same manner as in Example 1. The results of Example 2 are shown in Table 1-2 below.

<Comparative Example 1>
In Comparative Example 1, a capacitor was manufactured and its performance was evaluated in the same manner as in Example 1, except that diethylamine (pKa = 11.0) was used instead of ethylmorpholine as the base component and the amount of solute was changed as shown in Table 1-1 below. The results of Comparative Example 1 are shown in Table 1-2 below.

<Comparative Example 2>
In Comparative Example 2, except that the amount of solute was changed as shown in Table 1-1 below, a capacitor was manufactured and its performance was evaluated in the same manner as in Comparative Example 1. The results of Comparative Example 2 are shown in Table 1-2 below.

As can be seen from Table 1-2, when the concentrations of the acid and base components are relatively high (acid component before impregnation = 4-6 wt %, molar ratio of acid component:base component = 1:1.2), the use of a base component with relatively low basicity (pKa = 7.7) suppresses the characteristic fluctuations of the capacitor after reflow (ΔC and ΔESR) compared to when a base component with relatively high basicity (pKa = 11.0) is used.

In Examples 1 and 2, the electrical conductivity and resistivity were measured using the liquid substance phase before impregnation and the capacitor extract as the liquid substance phase. As can be seen in Table 1-2, the capacitors of Examples 1 and 2 exhibited good resistivity. Furthermore, the resistivity value was higher when measured using the capacitor extract compared to when measured using the liquid substance phase before impregnation. Although there is no intention to be limited by theory, it is believed that in the case of the capacitor extract, the additives added to the conductive polymer dispersion during the capacitor manufacturing process affected the resistivity value.

<<Reference Examples 1 to 3 and Reference Examples 4 to 6>>
In Reference Examples 1 to 3 and Reference Examples 4 to 6, a base component with a relatively low basicity and a base component with a relatively high basicity were used, respectively, and the solute concentration was relatively low.

<Reference Examples 1 to 3>
In Reference Examples 1 to 3, capacitors were manufactured and their performance evaluated in the same manner as in Example 1 above, except that the amount of solute was set as shown in Table 2-1 below. The results for Reference Examples 1 to 3 are shown in Table 2-2 below. Note that Table 2-1 shows the content of the solute in the liquid substance phase before impregnation, and Table 2-2 shows the content of the solute in the liquid substance phase taking into account the additives used in the conductive polymer dispersion. Table 2-2 also shows the content of the solute relative to the glycol compound in the liquid substance phase.

<Reference Examples 4 to 6>
In Reference Examples 4 to 6, capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that diethylamine was used instead of ethylmorpholine as the base component and the amount of solute was set as shown in Table 2 below. The results of Reference Examples 4 to 6 are shown in Table 2-2 below.

As can be seen from Table 2-2, when the concentrations of the acid and base components are relatively low (acid component before impregnation = 0.5 to 2.0 wt %, molar ratio of acid component:base component = 1:1.2), the characteristic fluctuations of the capacitor after reflow (ΔC and ΔESR) are suppressed to a certain degree in both cases where a base component exhibiting relatively low basicity (pKa = 7.7) is used, and where a base component exhibiting relatively high basicity (pKa = 11.0) is used.

<<Examples 3 to 5 and Comparative Examples 3 to 5>>
In Examples 3 to 5 and Comparative Examples 3 to 5, a base component with a relatively low basicity and a base component with a relatively high basicity were used, respectively, and the case where the concentration of the solute was relatively high was investigated.

(Examples 3 to 5)
In Examples 3 to 5, capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that morpholine (pKa = 8.3) was used instead of ethylmorpholine as the base component, and the amount of solute was set as shown in Table 3-1 below. In Examples 3 to 5, the resistivity and pH of the liquid substance phase were measured. The results of Examples 3 to 5 are shown in Table 3-2 below. Table 3-1 shows the content of the solute in the liquid substance phase before impregnation, and Table 3-2 shows the content of the solute in the liquid substance phase taking into account the additives used in the conductive polymer dispersion. Table 3-2 also shows the content of the solute relative to the glycol compound in the liquid substance phase.

(Comparative Examples 3 to 5)
In Comparative Examples 3 to 5, capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that diethylamine (pKa = 11.0) was used instead of ethylmorpholine as the base component and the amount of solute was set as shown in Table 3-1 below. In Comparative Examples 3 to 5, the resistivity and pH of the liquid substance phase were measured. The results for Comparative Examples 3 to 5 are shown in Table 3-2 below.

As can be seen from Table 3-2, even when the concentrations of the acid and base components are relatively high (acid component before impregnation = 4.3 to 12.9 wt %, molar ratio of acid component < molar ratio of base component), the use of a base component with relatively low basicity (pKa = 8.3) suppresses the characteristic fluctuations of the capacitor after reflow (ΔC and ΔESR) compared to when a base component with relatively high basicity (pKa = 11.0) is used.

Furthermore, as can be seen in Table 3-2, as the concentrations of acid and base components increase, the resistivity of the liquid substance phase decreases.

<<Examples 6 to 9 and Comparative Examples 6 to 7>>
In Examples 6 to 9 and Comparative Examples 6 to 7, the cases where base components having various basicities were used were investigated under conditions where the mass ratio of the acid component and the molar ratio of the acid component and the base component were constant.

In Examples 6 to 9 and Comparative Examples 6 to 7, capacitors were manufactured and their performance evaluated in the same manner as in Example 1 above, except that the substances shown in Table 4-1 below were used instead of ethylmorpholine as the base component, and the amount of solute was set as shown in Table 4-1 below. The results for Examples 6 to 9 and Comparative Examples 6 to 7 are shown in Table 4-2 below. Note that Table 4-1 shows the solute content in the liquid substance phase before impregnation, and Table 4-2 shows the solute content in the liquid substance phase taking into account the additives used in the conductive polymer dispersion. Table 4-2 also shows the solute content relative to the glycol compound in the liquid substance phase.

As can be seen from Table 4-2, when the concentrations of the acid and base components are relatively high (acid component before impregnation = 4.3 wt%, molar ratio of acid component < molar ratio of base component), the use of a base component with relatively low basicity (pKa = 7.7 to 8.9) suppresses the characteristic fluctuations of the capacitor after reflow (ΔC and ΔESR) compared to when a base component with relatively high basicity (pKa = 10.8 to 11.0) is used.

<<Example 10 and Comparative Examples 8 to 10>>
In Example 10 and Comparative Examples 8 to 10, in addition to the characteristic variation after reflow, the characteristic variation after a life test was also examined.

(Life Test)
In the life test of the capacitor, the capacitor was left to stand for 2000 hours under conditions of 135° C. and an applied voltage of 25 V. The characteristics of the capacitor were measured before and after this life test, and the changes in characteristics were measured (ΔC and ΔESR).

Example 10
In Example 10, a capacitor was manufactured and its performance was evaluated in the same manner as in Example 1, except that morpholine was used instead of ethylmorpholine as the base component and the amount of solute was set as shown in Table 5-1 below. In Example 10, the resistivity and pH of the liquid substance phase were measured. The results of Example 10 are shown in Table 5-2 below. Note that Table 5-1 shows the content of the solute in the liquid substance phase before impregnation, and Table 5-2 shows the content of the solute in the liquid substance phase taking into account the additives used in the conductive polymer dispersion. Table 5-2 also shows the content of the solute relative to the glycol compound in the liquid substance phase.

(Comparative Example 8)
In Comparative Example 8, a capacitor was manufactured and its performance was evaluated in the same manner as in Example 1, except that diethylamine was used instead of ethylmorpholine as the base component and the amount of solute was changed as shown in Table 5-1 below. In Comparative Example 8, the resistivity and pH of the liquid substance phase were measured. The results of Comparative Example 8 are shown in Table 5-2 below.

(Comparative Examples 9 to 10)
In Comparative Examples 9 and 10, except that azelaic acid and adipic acid were used instead of phthalic acid as the acid component, respectively, capacitors were manufactured and their performance was evaluated in the same manner as in Comparative Example 8. The results of Comparative Examples 9 to 10 are shown in Table 5-2 below.

As can be seen from Table 5-2 (particularly Example 10 and Comparative Example 8), when the concentrations of the acid and base components are relatively high (acid component before impregnation = 3-4 wt %, molar ratio of acid component < molar ratio of base component), the use of a base component with relatively low basicity (pKa = 8.3) suppresses the characteristic fluctuations of the capacitor after reflow (ΔC and ΔESR) compared to the use of a base component with relatively high basicity (pKa = 11.0), and the characteristic fluctuations after the life test are also suppressed.

Also, as can be seen from Table 5-2 (particularly Comparative Examples 9 and 10), when a base component with relatively strong basicity is used, the characteristic variation after reflow and the characteristic variation after the life test are both relatively large, even if the type of acid component is changed.

REFERENCE SIGNS LIST 1 electrolytic capacitor 10 metal case 20 capacitor element 21 anode foil 22, 24 oxide film 23 cathode foil 25 separator 26 solid electrolyte phase 27 liquid material phase 29, 30 lead 40 sealing member

Claims

an anode foil having an oxide film formed on its surface;
A cathode foil;
In a gap between the anode foil and the cathode foil,
A solid electrolyte phase including a conductive polymer compound;
and a liquid material phase including a liquid material,
The liquid phase further comprises an acid component and a base component;
the acid dissociation constant (pKa) of the conjugate acid of the base component is 10.0 or less;
The amount of the base component and the acid component in the liquid substance phase is
(number of moles of the base component)>(number of moles of the acid component)
The relationship formula is satisfied, and the acid component is 2.6% by mass to 20% by mass in the liquid substance phase.
Electrolytic capacitor.
The electrolytic capacitor according to claim 1, wherein the mass (B) of the base component and the mass (A) of the acid component in the liquid substance phase are B>A/2.
The electrolytic capacitor according to claim 1 or 2, wherein the base component includes an amine.
The electrolytic capacitor according to claim 3, wherein the base component contains at least one selected from morpholine, methylmorpholine, ethylmorpholine, triethanolamine, and diethanolamine.
The electrolytic capacitor according to claim 1 or 2, wherein the acid component is phthalic acid.
The electrolytic capacitor according to claim 1 or 2, wherein the liquid substance contains diethylene glycol or ethylene glycol.
The electrolytic capacitor according to claim 1 or 2, wherein the resistivity of the liquid substance phase is 6.0 kΩ·cm or less.
1. A method for manufacturing an electrolytic capacitor, comprising the steps of:
forming a capacitor element including an anode foil and a cathode foil each having an oxide film formed on a surface thereof;
introducing a solid electrolyte phase containing a conductive polymer compound into a gap between the anode foil and the cathode foil; and
introducing a liquid material phase, the liquid material phase including a liquid material, into a gap between the anode foil and the cathode foil;
The liquid phase further comprises an acid component and a base component;
the acid dissociation constant (pKa) of the conjugate acid of the base component is 10.0 or less;
The amount of base component and acid component in the liquid substance phase is
(number of moles of the base component)>(number of moles of the acid component)
The relationship formula is satisfied, and the acid component is 2.6% by mass to 20% by mass in the liquid substance phase.
Method.