Electrolytic capacitor having a conductive polymer compound and method for manufacturing the same

Abstract

The present invention provides an electrolytic capacitor having a conductive polymer compound and a liquid substance phase, exhibiting excellent liquid resistivity and excellent heat resistance, and a method for manufacturing the same. [Solution] The electrolytic capacitor 1 comprises an anode foil 21 having an oxide film formed on its surface and a cathode foil 23, and has a solid electrolyte phase 26 containing a conductive polymer compound and a liquid substance phase 27 containing a liquid substance in the void between the anode foil and the cathode foil. The liquid substance phase contains an acid component and a basic component, the acid dissociation constant (pKa) of the conjugate acid of the basic component is 10.0 or less, the amounts of the basic component and the acid component in the liquid substance phase satisfy the relationship (moles of basic component) > (moles of acid component), and the amount of the acid component in the liquid substance phase is 2.6% by mass to 20% by mass.

Description

Technical Field

[0001] 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 manufacturing an electrolytic capacitor.

Background Art

[0002] Conventionally, solid electrolytic capacitors using a conductive polymer compound as an electrolyte (solid electrolyte) are known. Such capacitors can exhibit low ESR characteristics and excellent low-temperature characteristics. Also, in such capacitors, by using a solid and highly heat-resistant conductive polymer as the electrolyte, a capacitor with high reliability can be provided.

[0003] Also, electrolytic capacitors (hybrid-type capacitors) using a conductive polymer compound and an electrolytic solution as the electrolyte are known. Such capacitors are advantageous, for example, in terms of the capacitance appearance rate and film restorability in initial capacitor characteristics.

[0004] 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 of the conductive solid layer with an electrolytic solution.

[0005] Patent Documents 2 and 3 describe an electrolytic capacitor having a driving electrolytic solution containing an acid component and a base component, and describe making the acid component in excess in terms of molar ratio compared to the base component.

[0006] Patent Document 4 describes a hybrid solid electrolytic capacitor comprising a solid electrolyte phase containing a conductive polymer compound and a liquid substance phase surrounding the solid electrolyte phase and containing a liquid substance. It states that the amounts of basic and acidic components in the liquid substance phase satisfy the relationship (moles of basic component) > (moles of acidic component) ≥ 0. This document states that the liquid substance may contain basic components in an amount of 0.3% to 50% by weight, based on the weight of the liquid substance, while it states that the amount of basic components contained in the liquid substance phase is preferably 10% or less by weight, based on the weight of the liquid substance phase. Furthermore, the examples use a liquid substance containing 0.3 to 1.5% by weight of basic components.

[0007] Patent Document 5 describes an electrolytic capacitor comprising a solid electrolyte layer and an electrolyte solution, wherein the solute contained in the electrolyte solution has a carboxylic acid component and a basic component, and the carboxylic acid component in the solute is 200 parts by mass or more per 100 parts by mass of the basic component. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2008-10657 [Patent Document 2] Japanese Patent Publication No. 2012-109635 [Patent Document 3] Japanese Patent Publication No. 2013-191897 [Patent Document 4] Japanese Patent Publication No. 2020-119916 [Patent Document 5] International Publication No. 2017 / 017947 [Overview of the project] [Problems that the invention aims to solve]

[0009] Conventional electrolytic capacitors, which contain conductive polymer compounds and electrolytes, sometimes had shortcomings in terms of the electrolyte's specific resistivity and heat resistance (especially changes in characteristics after reflow). In particular, when the solute concentration was relatively high, changes in characteristics after reflow could become problematic.

[0010] 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. [Means for solving the problem]

[0011] The above-mentioned problems relating to this disclosure can be solved by the invention relating to this disclosure described below. <Aspect 1> Anode foil with an oxide film formed on its surface, Cathode foil and Equipped with In the gap between the anode foil and the cathode foil, A solid electrolyte phase containing a conductive polymer compound, A liquid substance phase containing liquid substances and An electrolytic capacitor having, The liquid phase further comprises an acidic component and a basic component. The acid dissociation constant (pKa) of the conjugate acid of the aforementioned basic component is 10.0 or less. The amounts of the basic component and the acid component in the liquid phase are, (Number of moles of the base component) > (Number of moles of the acid component) The relationship satisfies, and The acid component is present in the liquid phase in an amount of 2.6% to 20% by mass. Electrolytic capacitor. <Aspect 2> The electrolytic capacitor according to embodiment 1, wherein, with respect to the mass (B) of the basic component and the mass (A) of the acid component in the liquid substance phase, B > A / 2. <Aspect 3> The electrolytic capacitor according to embodiment 1 or 2, wherein the base component contains an amine. <Aspect 4> The electrolytic capacitor according to embodiment 3, wherein the base component contains at least one selected from morpholine, methylmorpholine, ethylmorpholine, triethanolamine, and diethanolamine. <Embodiment 5> The electrolytic capacitor according to any one of embodiments 1 to 4, wherein the acid component is phthalic acid. <Embodiment 6> The electrolytic capacitor according to any one of embodiments 1 to 5, wherein the liquid substance contains diethylene glycol or ethylene glycol. <Embodiment 7> The electrolytic capacitor according to any one of embodiments 1 to 6, wherein the specific resistance of the liquid substance phase is 6.0 kΩ·cm or less. <Embodiment 8> A method for manufacturing an electrolytic capacitor, comprising: forming a capacitor element including an anode foil and a cathode foil having an oxide film formed on the surface; introducing a solid electrolyte phase containing a conductive polymer compound into the gap between the anode foil and the cathode foil; and introducing a liquid substance phase containing a liquid substance into the gap between the anode foil and the cathode foil. including the liquid substance phase further contains 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 amounts of the base component and the acid component in the liquid substance phase are (the number of moles of the base component) > (the number of moles of the acid component) satisfying the relational expression, and the acid component is 2.6% to 20% by mass in the liquid substance phase. Method.

Advantages of the Invention

[0012] According to the electrolytic capacitor of the present disclosure, an electrolytic capacitor having a conductive polymer compound and a liquid substance phase, which exhibits excellent liquid specific resistance and excellent heat resistance, can be provided.

Brief Description of the Drawings

[0013] [Figure 1a] Figure 1a is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present disclosure. [Figure 1b] Figure 1b is a schematic perspective view of a capacitor element according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view of the main part of the solid electrolyte phase shown in Figure 1. [Modes for carrying out the invention]

[0014] <<Capacitor>> The electrolytic capacitor relating to this disclosure is Anode foil with an oxide film formed on its surface, Cathode foil and Equipped with In the gap between the anode foil and the cathode foil, A solid electrolyte phase containing a conductive polymer compound, A liquid substance phase containing liquid substances and It has, The liquid phase further contains acidic and basic components. The acid dissociation constant (pKa) of the conjugate acid of the basic component is 10.0 or less. The amounts of basic and acidic components in the liquid phase are (Number of moles of base component) > (Number of moles of acid component) The relationship satisfies, and The acidic component is present in the liquid phase at a concentration of 2.6% to 20% by mass. That is the case.

[0015] Conventionally, electrolytic capacitors using a conductive polymer compound and an electrolyte solution as the electrolyte are known (hybrid capacitors). Such capacitors can achieve excellent film repair properties and excellent capacitance emergence rates. However, conventional capacitors sometimes had problems with heat resistance. In particular, with conventional capacitors, when the solute concentration was relatively high, the capacitor's characteristics could deteriorate when exposed to high temperatures during the reflow process.

[0016] In contrast, the inventors of the present invention have found that even when using relatively high concentrations of solute (acid and base components), the change in characteristics after reflow can be suppressed by using a base component with relatively low basicity as the base component constituting the solute. By increasing the solute concentration, the liquid resistivity of the liquid substance phase contained in the capacitor can be reduced. Therefore, according to the present invention, it is possible to obtain an electrolytic capacitor with improved electrical characteristics while avoiding problems such as the change in characteristics after reflow.

[0017] Exemplary embodiments of the present invention will be described in more detail with reference to the drawings. Note that these drawings and exemplary embodiments are not limiting to the present invention. The drawings are schematic diagrams and are not necessarily to scale.

[0018] <Configuration of electrolytic capacitor 1 according to the embodiment> Figure 1 is a diagram illustrating an electrolytic capacitor 1 according to an embodiment. Figure 1(a) is a cross-sectional view of the electrolytic capacitor 1, and Figure 1(b) is a perspective view of the capacitor element 20.

[0019] Figure 2 is a diagram illustrating the main parts of the electrolytic capacitor 1 according to the embodiment. Figure 2 is a cross-sectional view of the main parts of the electrolytic capacitor 1.

[0020] The electrolytic capacitor 1 according to this embodiment is a wound-type electrolytic capacitor, and as shown in Figure 1, comprises a bottomed cylindrical metal case 10, a capacitor element 20, and a sealing member 40.

[0021] The bottom of the metal case 10 is nearly circular in shape, and a valve (not shown) is provided near the center. Therefore, when the internal pressure rises, the valve can break, releasing the internal pressure to the outside. The side surfaces of the metal case 10 are erected almost perpendicularly to the outer edge of the bottom surface. The opening of the metal case 10 is sealed by a sealing member 40, and the two leads 29 and 30 of the capacitor element 20 are led out through a through-hole in the sealing member 40.

[0022] The capacitor element 20 is housed inside the metal case 10 and, as shown in Figures 1(b) and 2, comprises an anode foil 21, a cathode foil 23, and a separator 25 disposed between the anode foil 21 and the cathode foil 23, with the anode foil 21 and cathode foil 23 overlapping and wound together via the separator 25.

[0023] In the embodiment shown in Figure 2, a solid electrolyte phase consisting of particulate conductive polymer compound 26 and a liquid substance phase 27 containing a liquid substance are introduced into the void between the anode foil 21 and the cathode foil 23, with the liquid substance phase 27 surrounding 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.

[0024] <Void> In this disclosure, "voids between the anode foil and the cathode foil" includes not only "voids between the anode foil and the separator and between the cathode foil and the separator," but also "voids between fibers within the separator." Furthermore, "voids between the anode foil and the cathode foil" also include "voids in etching pits (recesses) formed on the surface of the anode foil or cathode foil by roughening through etching."

[0025] <Liquid substance phase> The capacitor relating to this disclosure includes a liquid substance phase. The liquid substance phase includes a liquid substance and further includes an acidic component and a basic component.

[0026] Regarding the content of each component in the liquid substance phase, in principle, 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 the additives into consideration.

[0027] The liquid phase can exist surrounding the solid electrolyte phase.

[0028] The liquid substance phase preferably consists of a liquid substance and acid and base components, and contains other components in proportions of 10% by mass or less, 5% by mass or less, 2% by mass or less, 1% by mass or less, or even 0.1% by mass or less. In one embodiment, the liquid substance phase may be a liquid in which acid components, base components, and optional other components are dissolved and / or dispersed in a liquid substance, and in particular, a liquid in which these components are dissolved in a liquid substance.

[0029] Examples of "other components" include aromatic nitro compounds.

[0030] In the capacitor according to this disclosure, the proportion of the liquid substance 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%.

[0031] (Liquid substance) The liquid substance constituting the liquid substance phase is a liquid capable of holding acidic and basic components. In particular, the liquid substance is a solvent, capable of dissolving acidic and basic components as solutes within it. Even if acidic and basic components are liquid substances on their own, they are not included in the "liquid substance" as defined in this application.

[0032] The liquid substance may be an organic solvent, particularly a polymeric organic solvent, and 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, or a mixture thereof.

[0033] In particular, examples of liquid substances include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and other polyethylene glycols, as well as their derivatives, glycerin and diglycerin, as well as their derivatives, γ-butyrolactone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, and dimethylformamide. These may be used individually or in combination of two or more. Of these, glycol compounds, namely 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 the most preferred. When ethylene glycol and / or diethylene glycol are used as the liquid substance, electrolytic capacitors with particularly good reflow characteristics can be obtained.

[0034] The content of the liquid substance (especially 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.

[0035] The content of the liquid substance (particularly the solvent) is preferably 80% to 95% by mass, more preferably 85% to 92% by mass, relative to the liquid substance phase.

[0036] Furthermore, the liquid phase contains glycol compounds (particularly ethylene glycol and / or diethylene glycol) in a total proportion of 60% to 95% by mass, or even more specifically, 65% to 90% by mass.

[0037] <Acid component> The liquid phase contains acidic components. Acidic components are generally substances that exhibit acidity (pH < 7 in aqueous solutions) and work in conjunction with bases, and contain protons (H + This refers to a chemical species that donates or accepts electron pairs.

[0038] The acidic component is present in an amount of 2.6% to 20% by mass relative to the liquid phase.

[0039] The content of the acid component in the liquid phase may be 2.7% by mass or more, 2.8% by mass or more, 2.9% by mass or more, 3% by mass or more, 3.5% by mass or more, 4% by mass or more, 4.5% 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.

[0040] The content of the acid component in the liquid phase is preferably 3% to 18% by mass, more preferably 4% to 16% by mass, even more preferably 5% to 14% by mass, and particularly preferably 6% to 12% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

[0041] The proportion of acidic components in the liquid phase may be 3% to 24% by mass relative to the total amount of glycol compounds (particularly ethylene glycol and / or diethylene glycol) contained in the liquid phase.

[0042] The proportion of the acid component relative to the total amount of 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.

[0043] The ratio of the acid component to the total glycol compounds (particularly ethylene glycol and / or diethylene glycol) contained in the liquid phase is preferably 3% to 22% by mass, more preferably 3.5% to 20% by mass, even more preferably 4% to 18% by mass, and most preferably 4% to 16% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

[0044] Furthermore, in capacitors, the liquid substance phase used for impregnation may be diluted during the manufacturing process by additives contained in conductive polymer dispersions, etc. Therefore, it is preferable that the liquid substance phase used for impregnation during the manufacturing process of the capacitor ("liquid substance phase before impregnation") contains acidic and / or basic components at a relatively higher concentration than desired in the capacitor.

[0045] Specifically, the content of the acid component in the liquid substance phase before impregnation may be 3% to 20% by mass, and in particular may be 4% or more by mass, 5% or more by mass, 6% or more by mass, 7% or more by mass, or 8% or more by mass, and / or 19% or less by mass, 18% or less by mass, 17% or less by mass, 16% or less by mass, 15% or less by mass, 14% or less by mass, 13% or less by mass, 12% or less by mass, 11% or less by mass, or 10% or less by mass.

[0046] The content of the acid component in the liquid phase before impregnation is preferably 4% to 18% by mass, more preferably 5% to 16% by mass, and even more preferably 6% to 14% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

[0047] Furthermore, with respect to the liquid substance phase before impregnation, the ratio of acidic components 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 content described above.

[0048] Examples of acidic components include organic acids, inorganic acids, and complex compounds thereof.

[0049] Examples of organic acids include carboxylic acids, phenols, and sulfonic acids. Examples of carboxylic acids include formic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, sulfosalicylic acid, maleic acid, adipic acid, benzoic acid, triylic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, resorcinic acid, phloroglucinic acid, gallic acid, and citric acid.

[0050] Examples of inorganic acids include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid.

[0051] Examples of complex compounds of organic and inorganic acids include borodisalicylic acid, borodisuoic acid, and borodiglycolic acid.

[0052] The acidic components described above may be used individually or in combination of two or more.

[0053] The acidic component is, in particular, phthalic acid.

[0054] <Basic components> The liquid phase contains basic components. Basic components are generally substances that exhibit basicity (pH > 7 in aqueous solution) and work in conjunction with acids, and contain protons (H + This refers to a chemical species that accepts electrons or donates electron pairs.

[0055] The basic component may be one or more selected from amines, amidines, and ammonia, and is preferably an amine.

[0056] (Dissociation constant of base components) Regarding the basic component contained in the liquid phase of the electrolytic capacitor according to this disclosure, the acid dissociation constant (pKa) of the conjugate acid is 10.0 or less. This pKa can be measured by neutralization titration at 25°C.

[0057] Examples of such basic 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) These are some examples.

[0058] 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. This lower limit is not particularly limited, but may be, for example, 7.2 or more, or 7.3 or more.

[0059] The basic component may be present in an amount of 1% to 20% by mass relative to the liquid phase.

[0060] The content of the basic 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 relative to the liquid phase, 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.

[0061] <Acid and basic components> In the electrolytic capacitor relating to this disclosure, the amounts of basic and acidic components in the liquid phase are (Number of moles of base component) > (Number of moles of acid component) The relationship satisfies the given equation.

[0062] In particular, when the number of moles of the acid component is set to 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, or 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 preferred is that when the number of moles of the acid component is set to 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.

[0063] Furthermore, in an electrolytic capacitor according to one embodiment of the present disclosure, the mass (B) of the basic component and the mass (A) of the acid component in the liquid substance phase are, B > A / 2 It satisfies the condition.

[0064] <Liquid specific resistance> Preferably, the liquid substance phase contained in the electrolytic capacitor according to this disclosure exhibits a resistivity of 6.0 kΩ·cm or less when measured with an electrical conductivity meter. This resistivity can be measured using an extract obtained by disassembling and centrifuging the electrolytic capacitor as the liquid substance phase.

[0065] 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. This lower limit is not particularly limited, but may be, for example, 0.1 kΩ·cm or more.

[0066] The resistivity of the liquid substance phase used in the manufacturing process of a capacitor before impregnation may differ from the resistivity of the liquid substance phase in the finished electrolytic capacitor. This is thought to be because additives (such as polyols) used in the conductive polymer dispersion or solution in the finished electrolytic capacitor also affect the resistivity value.

[0067] Therefore, in order to obtain an electrolytic capacitor with a desired resistivity, it is preferable that the liquid substance phase impregnated into the capacitor during the manufacturing process has 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. This lower limit is not particularly limited, but for example, it may be 0.1 kΩ·cm or more.

[0068] <Aromatic nitro compounds> The liquid phase of the electrolytic capacitor according to this disclosure may contain an aromatic nitro compound. The aromatic nitro compound is an aromatic compound having a nitro group. The aromatic nitro compound may have the effect of improving the voltage resistance and heat resistance of the capacitor by absorbing hydrogen gas generated by recombination reactions, etc.

[0069] When using aromatic nitro compounds, the proportion of aromatic nitro compounds in the liquid phase may be 0.5% to 10% by mass, 0.5% to 5% by mass, or even 1% to 5% by mass.

[0070] 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, nitrophenylacetic acid, nitrocresol, dinitrobenzoic acid, methylnitrobenzoic acid, nitroterephthalic acid, and nitroisophthal. These may be used individually or in combination of two or more.

[0071] 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.

[0072] <Water> The liquid phase may contain water.

[0073] If the liquid phase in the void between the anode foil and cathode foil contains "water" in addition to a liquid water-soluble polymer compound, then even if defects occur in the oxide film during the manufacturing process of the electrolytic capacitor, it becomes possible to use the moisture derived from "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 reducing the defect density of the oxide film and reducing leakage current.

[0074] The water content may be 0% to 10% by mass relative to the liquid substance phase, preferably 0.1% to 10% by mass, and more preferably 0.5% to 5% by mass. When the water content is within this range, a sufficient repair effect on defects in the oxide film can be obtained, and adverse effects caused by excessive water content (such as expansion of the capacitor that may occur when used for a long period of time in a high-temperature environment) can be avoided or suppressed.

[0075] <Anode foil> The capacitor relating to this disclosure includes an anode foil on which an oxide film is formed on its surface.

[0076] The anode foil may be formed from a valve metal such as aluminum, tantalum, or niobium.

[0077] 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 the surface by etching according to a known method and then by a chemical conversion treatment.

[0078] <Cathode Foil> The capacitor relating to this disclosure includes cathode foil.

[0079] The cathode foil, like the anode foil, may be formed from a valve metal such as aluminum, tantalum, or niobium.

[0080] The cathode foil may have an oxide film formed on its surface. For example, the surface of the cathode foil may be roughened by etching, similar to the anode foil, and then an oxide film may be formed by natural oxidation. Alternatively, the cathode foil may be subjected to a chemical conversion treatment at a desired voltage (e.g., 2V), which may also form an oxide film.

[0081] <Separator> The capacitor relating to this disclosure includes a separator. The separator is disposed between the anode foil and the cathode foil.

[0082] Preferably, the separator is made of conductive polymer particles, cellulose fibers that are chemically compatible with water-soluble polymers, or synthetic resins such as nylon, PET, and PPS that have excellent heat resistance. For example, heat-resistant cellulose paper or heat-resistant flame-retardant paper can be used. More specifically, examples of separators include cellulose and mixed papers such as kraft, Manila hemp, esparto, hemp, and rayon; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and their derivatives; polytetrafluoroethylene resins; polyvinylidene fluoride resins; vinylon resins; polyamide resins such as aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides; polyimide resins; polyethylene resins; polypropylene resins; trimethylpentene resins; polyphenylene sulfide resins; acrylic resins; and polyvinyl alcohol resins. These resins can be used individually or in mixtures.

[0083] <Solid electrolyte phase> The capacitor relating to this disclosure includes a solid electrolyte phase in the gap between the anode foil and the cathode foil.

[0084] (Conductive polymer compound) The solid electrolyte phase includes, and in particular is substantially composed of, conductive polymer compounds.

[0085] The solid electrolyte phase may take various forms, for example, a continuous, uniform thick or thin layer, a film, or an aggregate of fine particles containing a conductive polymer compound and optionally a dopant, or a structure in which such fine particles and aggregates thereof (especially chains) are bonded to each other to form a network. Alternatively, the solid electrolyte phase may be a layer of fine particles composed of fine particles containing a conductive polymer compound and optionally a dopant.

[0086] Examples of conductive polymer compounds include at least one selected from polythiophene, polypyrrole, and polyaninin, as well as their derivatives. The conductive polymer compound may be at least one of these. A preferred conductive polymer compound is polyethylenedioxythiophene (PEDOT) (particularly poly(3,4-ethylenedioxythiophene)).

[0087] The solid electrolyte phase may further contain a dopant. Examples of dopants include aromatic sulfonic acids such as benzenesulfonic acid or its derivatives, naphthalenesulfonic acid or its derivatives, anthraquinonesulfonic acid or its derivatives; polymeric sulfonic acids such as polystyrenesulfonic acid (PSS), sulfonated polyesters, phenolsulfonic acid novolac resins, and copolymers of styrenesulfonic acid and non-sulfonic monomers (such as methacrylic acid esters, acrylic acid esters, unsaturated hydrocarbon-containing alkoxysilane compounds or their hydrolysates); and chain-like sulfones such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid. These may be used individually or in combination of two or more.

[0088] Polystyrene sulfonic acid with a weight-average molecular weight of 10,000 to 1,000,000 is preferred.

[0089] In a preferred embodiment, the solid electrolyte phase comprises polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) as a dopant.

[0090] The conductive polymer compound may be in the form of particulate matter. The average particle size of the particulate conductive polymer compound is preferably in the range of 1 nm to 300 nm, or more preferably in the range of 5 nm to 200 nm (e.g., 20 nm). The particulate conductive polymer compound may contain dopants. The average particle size of the fine particles composed of the conductive polymer and optionally dopants can be determined, for example, from the particle size distribution measured by dynamic light scattering.

[0091] In the capacitor according to this disclosure, the proportion of the conductive polymer compound in the void between the anode foil and the cathode foil may be 0.5 vol% to 20 vol%, or even 1 vol% to 10 vol%.

[0092] (Formation of the solid electrolyte phase) The method for forming a solid electrolyte phase containing a conductive polymer compound is not particularly limited, but it can be formed, for example, by immersion impregnation. For example, a solid electrolyte phase can be formed by filling the void with a dispersion liquid (conductive polymer compound dispersion) in which a conductive polymer compound is dispersed in a dispersion medium or a solution (conductive polymer compound solution) in which a conductive polymer compound is dissolved in a solvent, and then removing the dispersion medium or solvent from the void by heating or drying.

[0093] More specifically, for example, a capacitor element is immersed in a conductive polymer compound dispersion or conductive polymer compound solution using an introduction tank. Then, the capacitor element is removed from the conductive polymer compound dispersion or solution and heat-treated to form a solid electrolyte phase in the void between the anode and cathode foils of the capacitor element. This operation can be repeated multiple times, thereby increasing the amount of solid electrolyte phase packed in.

[0094] The solid electrolyte phase containing the conductive polymer compound may be formed by polymerizing monomers using so-called "in-situ polymerization."

[0095] The content of the conductive polymer in the conductive polymer compound dispersion or conductive polymer compound solution may be 0.1 to 10% by mass, 0.2 to 5% by mass, and particularly 0.5 to 3% by mass.

[0096] For dispersions of conductive polymer compounds, for example, water, protic solvents such as alcohols (e.g., methanol, ethanol, 1-propanol, butanol), and mixtures thereof can be used as dispersion media. For solutions of conductive polymer compounds, for example, water, protic solvents such as alcohols (e.g., methanol, ethanol, 1-propanol, butanol), and mixtures thereof can be used as solvents. Furthermore, aromatic nitro compounds may be included in the dispersion or solution of conductive polymer compounds.

[0097] Conductive polymer compound dispersions or solutions may contain other compounds as additives, such as high-boiling-point compounds (particularly compounds with 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 their derivatives, γ-butyrolactone, butanediol, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, dimethyl sulfolane, and polyethylene glycol, as well as their derivatives. These may be used individually or in combination of two or more.

[0098] The content of additives in a conductive polymer compound dispersion or conductive polymer compound solution may be 1 to 40% by mass, more particularly 2 to 30% by mass, or even more specifically 5 to 25% by mass. This content may also be 1 to 20% by mass.

[0099] <Capacitor> (CAP) The capacitors relating to this disclosure may 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.

[0100] (ESR) The capacitors relating to this 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.

[0101] <<Capacitor Manufacturing Method>> The method for manufacturing the capacitor according to the present invention is not particularly limited. For example, the capacitor according to the present invention includes 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. The method for manufacturing an electrolytic capacitor in an exemplary embodiment will be described below along with each step.

[0102] (1) Capacitor element fabrication process In an exemplary method for an electrolytic capacitor, first, an aluminum foil is provided as the anode foil 21. After roughening the surface of the aluminum foil by a surface-expanding process, a predetermined voltage of 2V to 500V is applied to the roughened surface of the aluminum foil to perform a chemical conversion treatment, thereby forming an oxide film 22 on the surface of the aluminum foil. Then, a capacitor element is fabricated comprising the anode foil 21 having the oxide film 22, a cathode foil 23, and a separator 25 disposed between the anode foil 21 and the cathode foil 23 (see Figure 1(b)). Specifically, the capacitor element 20 is fabricated by overlapping and winding the anode foil 21, which has an uneven surface (rough surface) and on which the oxide film 22 is formed, and the cathode foil 23, which also has an uneven surface, via the separator 25. At this time, a lead 30 is connected to the anode foil 21 and a lead 29 is connected to the cathode foil 23.

[0103] (2) Chemical treatment process Next, the capacitor element 20 is immersed in the chemical conversion solution in the chemical conversion solution tank, and a predetermined voltage (e.g., 100V) is applied between the anode lead 30 and the chemical conversion solution for 5 minutes. This operation repairs oxide film defects present at the edges of the anode foil 21 and any oxide film defects that may be present on the surface.

[0104] As the chemical conversion solution, a chemical conversion solution (for example, an aqueous solution of ammonium adipate, ammonium borate, ammonium phosphate, ammonium glutarate, ammonium azelaate, ammonium tartrate, ammonium sebacate, ammonium pimephosphate, ammonium suberate, etc.) can be used.

[0105] (3) Solid electrolyte phase introduction process Next, a solid electrolyte phase consisting of particulate conductive polymer compound 26 is introduced into the void between the anode foil 21 and the cathode foil 23, such that the proportion of the solid electrolyte phase in the void is, for example, within the range of 2 vol% to 30 vol%. In the solid electrolyte phase introduction step, for example, the solid electrolyte phase can be introduced into the void by filling the void with a conductive polymer compound dispersion, which is obtained by dispersing the conductive polymer compound in a dispersion medium, and then removing the dispersion medium from the void. Instead of a conductive polymer compound dispersion, a solution obtained by dissolving the conductive polymer compound in a solvent (conductive polymer compound solution) may be used.

[0106] More specifically, the solid electrolyte phase introduction process can be carried out by immersion impregnation. That is, a conductive polymer compound dispersion (for example, a conductive polymer compound concentration of 2 vol%) is filled into the introduction tank, and then the capacitor element is immersed in the conductive polymer compound dispersion. Next, the capacitor element is removed from the introduction tank, and then the capacitor element is heat-treated.

[0107] A conductive polymer compound dispersion can be produced by polymerizing (radical polymerization or oxidative polymerization) a suspended monomer (e.g., PEDOT monomer) to create a conductive polymer compound (e.g., PEDOT polymer) to which dopants and emulsifiers have been added, thereby producing particulate conductive polymer compounds, and then dispersing these particulate conductive polymer compounds in a predetermined 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 initiators, monomers, polymerization aids, etc., reaction temperature, stirring conditions of the reaction solution, etc.). It can also be adjusted by known grinding treatments (e.g., stirring grinding, vibration grinding, etc.). Furthermore, the particle size can be made uniform by preparative filtration.

[0108] Furthermore, in order to increase the proportion of the solid electrolyte phase in the voids, the number of repetitions of the above operation 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 in the voids, the number of repetitions of the above operation can be decreased, and / or the polymer concentration in the conductive polymer compound dispersion can be decreased.

[0109] (4) Liquid substance phase introduction process In the liquid substance phase introduction step, for example, the liquid substance phase 27 is introduced into the void between the anode foil 21 and the cathode foil 23 so as to surround the solid electrolyte, and so that the proportion of the liquid substance phase 27 in the void is within the range of 10 vol% to 99 vol%. Specifically, the liquid substance phase introduction step can be carried out as described in (a) and (b) below.

[0110] (a) Preparation of the liquid phase A liquid substance phase can be prepared by providing a liquid substance (e.g., ethylene glycol), adding predetermined amounts of acid and base components to this liquid substance, and then stirring. These operations may be carried out by heating to, for example, 40-60°C.

[0111] (b) Introduction of a liquid substance phase When filling with the liquid substance phase by immersion impregnation, the liquid substance phase is introduced into the voids by filling the introduction tank with the liquid substance phase and then immersing the capacitor elements in the liquid substance phase.

[0112] (5) Assembly and sealing process In the assembly and sealing process, the sealing member 40 is attached to the capacitor element 20, and after inserting the capacitor element 20 into the metal case 10, the metal case 10 is crimped near the open end of the metal case 10. For example, isobutylene-isoprene rubber (IIR) can be used as the sealing member 40. Instead of isobutylene-isoprene rubber (IIR), rubber materials such as ethylene-propylene terpolymer (EPT), EPT-IIR blend rubber, and silicone rubber, or rubber composite materials made by bonding resin and rubber such as phenolic resin (Bakelite), epoxy resin, and fluororesin can also be used. After that, 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.

[0113] The capacitor relating to this disclosure can be manufactured in particular by the electrolytic capacitor manufacturing method relating to this disclosure described below: A method for manufacturing electrolytic capacitors, Forming a capacitor element comprising an anode foil and a cathode foil, each having an oxide film formed on its surface (capacitor element manufacturing process), Introducing a solid electrolyte phase containing a conductive polymer compound into the void between the anode foil and the cathode foil (solid electrolyte phase introduction step), and Introducing a liquid substance phase containing a liquid material into the void between the anode foil and the cathode foil (liquid substance phase introduction process) Includes, The liquid phase further contains acidic and basic components. The acid dissociation constant (pKa) of the conjugate acid of the basic component is 10.0 or less. The amounts of basic and acidic components in the liquid phase are (Number of moles of the base component) > (Number of moles of the acid component) The relationship satisfies, and The acid component is present in the liquid phase in an amount of 2.6% to 20% by mass. method.

[0114] For details of each step and component of the manufacturing method relating to this disclosure, refer to the above description relating to electrolytic capacitors and the above specific description relating to the manufacturing method of capacitors relating to this disclosure.

[0115] In the liquid substance phase introduction step of this manufacturing method, the content ratio of the acid component in the liquid substance phase may be particularly 3 to 20% by mass, and moreover may 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 may be 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.

[0116] In the liquid substance phase introduction step of this manufacturing method, the content of the acid component in the liquid substance phase is preferably 4% to 18% by mass, more preferably 5% to 16% by mass, and even more preferably 6% to 14% by mass. In this case, an electrolytic capacitor with particularly good reflow characteristics can be obtained.

[0117] Furthermore, the ratio of acidic components to the total amount of glycol compounds (particularly ethylene glycol and / or diethylene glycol) contained in the liquid phase may be the same as the content described above.

[0118] In the liquid substance phase introduction step, the content of the liquid substance (particularly the solvent) may be 45% by mass or more, 50% by mass or more, or 60% by mass or more, and / or 95% by mass or less, 92% by mass or less, 90% by mass or less, or 80% by mass or less, relative to the liquid substance phase. Preferably, the content of the liquid substance (particularly the solvent) is 70% by mass to 95% by mass, or 82% by mass to 92% by mass, more preferably 85% by mass to 90% by mass, relative to the liquid substance phase.

[0119] In the liquid substance phase introduction step, the basic component may be contained in the liquid substance phase in an amount of 0.5% to 20% by mass, or 1% to 18% by mass. The content of the basic component may be 1.0% or more by mass, 1.5% or more by mass, 2% or more by mass, 3% or more by mass, or 4% or more by mass, and / or 20% or less by mass, 18% or less by mass, 15% or less by mass, 14% or less by mass, 12% or less by mass, 10% or less by mass, or 8% or less by mass.

[0120] When using aromatic nitro compounds, the proportion of aromatic nitro compounds in the liquid substance phase during the liquid substance phase introduction step may be 0.1% to 10% by mass, 0.5% to 8% by mass, 0.5% to 5% by mass, or even 1% to 5% by mass.

[0121] In the liquid substance phase introduction step, the water content may be 0% to 10% by mass, or 0% to 9% by mass, relative to the liquid substance phase. In one embodiment, it is preferably 0.1% to 9% by mass, and more preferably 0.4% to 4% by mass.

[0122] One preferred embodiment of the manufacturing method relating to this disclosure may further have at least one of the following features: With respect to the mass of the basic component (B) and the mass of the acidic component (A) in the liquid phase, B > A / 2; and / or The basic component contains an amine; and / or The basic component contains at least one selected from morpholine, methylmorpholine, ethylmorpholine, triethanolamine, and diethanolamine; and / or The acidic component is phthalic acid; and / or The liquid substance contains diethylene glycol or ethylene glycol; and / or The resistivity of the liquid phase is 6.0 kΩ·cm or less. [Examples]

[0123] Embodiments of the present invention will be described in more detail below with reference to examples. The following examples and comparative examples are not intended to limit the present invention.

[0124] <<Measurement method>> The measurement methods used in the examples and comparative examples are as follows.

[0125] <cap> The capacitance (μF) of the capacitor was measured at room temperature at 120Hz using an LCR meter (Keysight Technologies Precision LCR Meter (E4980A)).

[0126] <esr> The ESR (mΩ) of the capacitor was measured at room temperature at 100 kHz using an LCR meter (Keysight Technologies Precision LCR Meter (E4980A)).

[0127] <Specific resistance> The resistivity of the liquid substance phase was measured using an electrical conductivity meter (Toa DKK: CM-40S, cell: CG-511B) at a liquid temperature of 30.0 ± 0.2°C, using the liquid substance phase before impregnation into the capacitor element.

[0128] If the resistivity of the liquid substance phase before impregnation is relatively reduced, it is expected that the resistivity of the liquid substance phase in the completed electrolytic capacitor will also be relatively reduced. However, the resistivity of the liquid substance phase before impregnation may differ from the resistivity of the liquid substance phase extracted from the electrolytic capacitor. This is thought to be because additives (such as polyols) used in the conductive polymer dispersion or solution in the extract from the electrolytic capacitor can affect the resistivity.

[0129] In Examples 1 and 2, the extract obtained from the capacitor was used as the liquid phase, and the conductivity and resistivity of the liquid phase were measured at 25°C using an electrical conductivity meter (HORIBA Compact Conductivity Meter B-173).

[0130] <ph> The pH of the liquid substance phase was measured using a pH meter (Toa DKK, model number: HM-30R, cell: GST-5741C) at a liquid temperature of 25-30°C, using the liquid substance phase before impregnation into the capacitor element.

[0131] <<Examples 1-2 and Comparative Examples 1-2>> Examples 1 and 2 and Comparative Examples 1 and 2 investigated the use of relatively low-basicity and relatively high-basicity base components, respectively, and the case where the solute concentration was relatively high.

[0132] <Example 1> (Capacitor manufacturing) An anode foil (made of aluminum) and a cathode foil (made of aluminum) with a voltage rating of approximately 60V were wound together via a separator (made of cellulose). Subsequently, the end faces and defective areas were treated with a chemical conversion solution, and then a 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 polystyrene sulfonic acid (PSS) as a dopant. The following liquid substance phase was impregnated into this capacitor element to obtain the capacitor according to Example 1.

[0133] The liquid substance phase impregnated into the capacitor in Example 1 had the following composition. • Solvent: 90.9% by mass of ethylene glycol • Acid component: 4.0% by mass of phthalic acid • Basic component: 3.3% by mass of ethylmorpholine (pKa=7.7) ·Water: 0.9% by mass Nitroacetophenone: 0.9% by mass

[0134] In the liquid phase according to Example 1, the molar ratio of the acid component to the base component was 1:1.2.

[0135] (Performance evaluation) The capacitors manufactured according to Example 1 were evaluated for performance before and after reflow processing, and the rate of change in capacitance (ΔC) and the rate of change in ESR (ΔESR) were measured.

[0136] During the reflow process, a total of two reflow cycles were performed with a peak temperature of 260°C.

[0137] The results for Example 1 are shown in Tables 1-1 and 1-2 below. Table 1-1 lists the solute content in the liquid substance phase before impregnation, while Table 1-2 lists the solute content in the liquid substance phase, taking into account the additives used in the conductive polymer dispersion.

[0138] Table 1-2 also shows the solute content relative to the glycol compound in the liquid phase.

[0139] <Example 2> In Example 2, the capacitor was manufactured and its performance evaluated in the same manner as in Example 1, except that the amount of solute was changed as shown in Table 1-1 below. The results for Example 2 are shown in Table 1-2 below.

[0140] <Comparative Example 1> In Comparative Example 1, the capacitor was manufactured and its performance evaluated in the same manner as in Example 1, except that diethylamine (pKa=11.0) was used as the base component instead of ethylmorpholine, and the amount of solute was changed as shown in Table 1-1 below. The results for Comparative Example 1 are shown in Table 1-2 below.

[0141] <Comparative Example 2> In Comparative Example 2, the capacitor was manufactured and its performance evaluated in the same manner as in Comparative Example 1, except that the amount of solute was changed as shown in Table 1-1 below. The results for Comparative Example 2 are shown in Table 1-2 below.

[0142] [Table 1]

[0143] [Table 2]

[0144] As can be seen in Table 1-2, when the concentrations of acid and base components are relatively high (acid component before impregnation = 4-6% by weight, molar ratio of acid component to base component = 1:1.2), using a base component exhibiting relatively low basicity (pKa = 7.7) suppresses the characteristic variation (ΔC and ΔESR) of the capacitor after reflow compared to using a base component exhibiting relatively high basicity (pKa = 11.0).

[0145] In Examples 1 and 2, conductivity and resistivity were measured using the liquid substance phase before impregnation and the capacitor extract as the liquid substance phase, respectively. As can be seen in Table 1-2, the capacitors in Examples 1 and 2 showed good resistivity. Furthermore, the resistivity value was higher when measured with the capacitor extract compared to when measured with the liquid substance phase before impregnation. Although there is no intention to limit the theory, in the case of the capacitor extract, it is thought that the additives added to the conductive polymer dispersion during the capacitor manufacturing process affected the resistivity value.

[0146] <<Reference Examples 1-3 and 4-6>> Reference Examples 1-3 and 4-6 examined the use of relatively low-basicity and relatively high-basicity base components, respectively, and the case where the solute concentration was relatively low.

[0147] <Reference examples 1~3> In Reference Examples 1 to 3, the capacitors were manufactured and their performance evaluated in the same manner as in Example 1, 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. Table 2-1 lists the solute content in the liquid substance phase before impregnation, while Table 2-2 lists the solute content in the liquid substance phase, taking into account the additives used in the conductive polymer dispersion. Table 2-2 also lists the solute content relative to the glycol compound in the liquid substance phase.

[0148] <Reference examples 4~6> In Reference Examples 4-6, the capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that diethylamine was used as the base component instead of ethylmorpholine, and the amount of solute was set as shown in Table 2 below. The results for Reference Examples 4-6 are shown in Table 2-2 below.

[0149] [Table 3]

[0150] [Table 4]

[0151] As can be seen in Table 2-2, when the concentrations of acid and base components are relatively low (acid component before impregnation = 0.5-2.0% by weight, molar ratio of acid component to base component = 1:1.2), it can be seen that the characteristic changes (ΔC and ΔESR) of the capacitor after reflow are suppressed to a certain extent in both cases: when a base component exhibiting relatively low basicity (pKa = 7.7) is used, and when a base component exhibiting relatively high basicity (pKa = 11.0) is used.

[0152] <<Examples 3-5 and Comparative Examples 3-5>> Examples 3-5 and Comparative Examples 3-5 investigated the use of relatively low-basicity and relatively high-basicity base components, respectively, and also examined the case where the solute concentration was relatively high.

[0153] (Examples 3-5) In Examples 3-5, capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that morpholine (pKa=8.3) was used as the base component instead of ethylmorpholine, and the amount of solute was set as shown in Table 3-1 below. In Examples 3-5, the resistivity and pH of the liquid substance phase were also measured. The results for Examples 3-5 are shown in Table 3-2 below. Table 3-1 lists the solute content in the liquid substance phase before impregnation, and Table 3-2 lists the solute content in the liquid substance phase considering the additives used in the conductive polymer dispersion. Table 3-2 also lists the solute content relative to the glycol compound in the liquid substance phase.

[0154] (Comparative Examples 3-5) In Comparative Examples 3 to 5, the capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that diethylamine (pKa=11.0) was used as the base component instead of ethylmorpholine, and the amount of solute was set as shown in Table 3-1 below. In addition, the resistivity and pH of the liquid phase were measured in Comparative Examples 3 to 5. The results for Comparative Examples 3 to 5 are shown in Table 3-2 below.

[0155] [Table 5]

[0156] [Table 6]

[0157] As can be seen in Table 3-2, even when the concentrations of acid and base components are relatively high (acid component before impregnation = 4.3-12.9% by weight, molar ratio of acid component < molar ratio of base component), it can be seen that using a base component exhibiting relatively low basicity (pKa = 8.3) suppresses the characteristic variation (ΔC and ΔESR) of the capacitor after reflow compared to using a base component exhibiting relatively high basicity (pKa = 11.0).

[0158] Furthermore, as can be seen in Table 3-2, the resistivity of the liquid phase decreases as the concentrations of the acidic and basic components increase.

[0159] <<Examples 6-9 and Comparative Examples 6-7>> Examples 6-9 and Comparative Examples 6-7 investigated the use of various basic components under conditions where the mass ratio of the acid component and the molar ratio of the acid component to the basic component were constant.

[0160] In Examples 6-9 and Comparative Examples 6-7, the capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that the substances shown in Table 4-1 below were used as the base component instead of ethylmorpholine, and the amount of solute was set as shown in Table 4-1 below. The results for Examples 6-9 and Comparative Examples 6-7 are shown in Table 4-2 below. Table 4-1 lists the solute content in the liquid substance phase before impregnation, and Table 4-2 lists the solute content in the liquid substance phase considering the additives used in the conductive polymer dispersion. Table 4-2 also lists the solute content relative to the glycol compound in the liquid substance phase.

[0161] [Table 7]

[0162] [Table 8]

[0163] As can be seen in Table 4-2, when the concentrations of acid and base components are relatively high (acid component before impregnation = 4.3 wt%, molar ratio of acid component < molar ratio of base component), using a base component exhibiting relatively low basicity (pKa = 7.7~8.9) suppresses the characteristic variation (ΔC and ΔESR) of the capacitor after reflow compared to using a base component exhibiting relatively high basicity (pKa = 10.8~11.0).

[0164] <<Example 10 and Comparative Examples 8-10>> In Example 10 and Comparative Examples 8-10, in addition to the changes in characteristics after reflow soldering, the changes in characteristics after the life test were also investigated.

[0165] (Lifespan test) In the capacitor lifetime test, the capacitors were left undisturbed for 2000 hours under conditions of 135°C and an applied voltage of 25V. The characteristics of the capacitors were measured before and after this lifetime test, and the changes in characteristics (ΔC and ΔESR) were measured.

[0166] (Example 10) In Example 10, capacitors were manufactured and their performance evaluated in the same manner as in Example 1, except that morpholine was used as the base component instead of ethylmorpholine, 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 also measured. The results for Example 10 are shown in Table 5-2 below. Table 5-1 lists the solute content in the liquid substance phase before impregnation, and Table 5-2 lists the solute content in the liquid substance phase considering the additives used in the conductive polymer dispersion. Table 5-2 also lists the solute content relative to the glycol compound in the liquid substance phase.

[0167] (Comparative Example 8) In Comparative Example 8, the capacitor was manufactured and its performance evaluated in the same manner as in Example 1, except that diethylamine was used as the base component instead of ethylmorpholine, 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 phase were also measured. The results for Comparative Example 8 are shown in Table 5-2 below.

[0168] (Comparative Examples 9-10) In Comparative Examples 9 and 10, the capacitors were manufactured and their performance evaluated in the same manner as in Comparative Example 8, except that azelaic acid and adipic acid were used as the acid component instead of phthalic acid, respectively. The results for Comparative Examples 9 and 10 are shown in Table 5-2 below.

[0169] [Table 9]

[0170] [Table 10]

[0171] As can be seen in Table 5-2 (especially Example 10 and Comparative Example 8), when the concentrations of the acid and base components are relatively high (acid component before impregnation = 3-4% by weight, molar ratio of acid component < molar ratio of base component), using a base component exhibiting relatively low basicity (pKa = 8.3) suppresses the characteristic variation (ΔC and ΔESR) of the capacitor after reflow compared to using a base component exhibiting relatively high basicity (pKa = 11.0), and similarly suppresses the characteristic variation after the lifetime test.

[0172] Furthermore, as can be seen in Table 5-2 (especially Comparative Examples 9 and 10), when a base component with relatively strong basicity is used, even if the type of acid component is changed, both the variation in properties after reflow and the variation in properties after the lifetime test become relatively large. [Explanation of symbols]

[0173] 1 Electrolytic capacitor 10 Metal Cases 20 Capacitor elements 21 Anode foil 22, 24 Oxide film 23 Cathode foil 25 Separators 26 Solid electrolyte phase 27. Liquid Substance Phase 29, 30 Lead 40 Sealing material< / ph> < / esr> < / cap>

Claims

1. Anode foil with an oxide film formed on its surface, Cathode foil and Equipped with In the gap between the anode foil and the cathode foil, A solid electrolyte phase containing a conductive polymer compound, A liquid substance phase containing liquid substances and An electrolytic capacitor having, The liquid phase further comprises an acidic component and a basic component. The acid dissociation constant (pKa) of the conjugate acid of the aforementioned basic component is 10.0 or less. The amounts of the basic component and the acid component in the liquid phase are, (Number of moles of the base component) > (Number of moles of the acid component) The relationship satisfies, and The acid component is present in the liquid phase in an amount of 2.6% to 20% by mass. Electrolytic capacitor.

2. The electrolytic capacitor according to claim 1, wherein, with respect to the mass (B) of the basic component and the mass (A) of the acid component in the liquid substance phase, B > A / 2.

3. The electrolytic capacitor according to claim 1 or 2, wherein the base component includes an amine.

4. The electrolytic capacitor according to claim 3, wherein the base component contains at least one selected from morpholine, methylmorpholine, ethylmorpholine, triethanolamine, and diethanolamine.

5. The electrolytic capacitor according to claim 1 or 2, wherein the acid component is phthalic acid.

6. The electrolytic capacitor according to claim 1 or 2, wherein the liquid substance comprises diethylene glycol or ethylene glycol.

7. The electrolytic capacitor according to claim 1 or 2, wherein the resistivity of the liquid substance phase is 6.0 kΩ·cm or less.

8. A method for manufacturing electrolytic capacitors, To form a capacitor element comprising an anode foil and a cathode foil, each having an oxide film formed on its surface, Introducing a solid electrolyte phase containing a conductive polymer compound into the void between the anode foil and the cathode foil, and Introducing a liquid substance phase containing a liquid substance into the gap between the anode foil and the cathode foil. Includes, The liquid phase further comprises an acidic component and a basic component. The acid dissociation constant (pKa) of the conjugate acid of the aforementioned basic component is 10.0 or less. The amounts of basic and acidic components in the aforementioned liquid phase are (Number of moles of the base component) > (Number of moles of the acid component) The relationship satisfies, and The acid component is present in the liquid phase in an amount of 2.6% to 20% by mass. method.

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