electrolytic capacitor

Abstract

To provide an electrolytic capacitor superior in withstand voltage characteristics and heat resistance and capable of maintaining low ESR (equivalent series resistance).SOLUTION: In the electrolytic capacitor, a capacitor element 10 includes: an anode body 21 having a dielectric layer; a solid electrolyte layer in contact with the dielectric layer; and an electrolyte. The electrolyte contains a solvent and a solute. The solvent contains a glycol compound, and the solute contains a carboxylic acid component and a base component. A proportion of the glycol compound contained in the solvent is 50 mass% or more, the carboxylic acid component is an aromatic compound that has a carboxyl group. The base component is at least one selected from the group consisting of first-class amines, second-class amines, and tertiary amines. The solute contains 200 pts.mass or more of the carboxylic acid component per 100 pts.mass of the base component.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor having a solid electrolyte layer and an electrolyte solution. [Background technology]

[0002] Electrolytic capacitors, which include an anode body with a dielectric layer, a solid electrolyte layer formed so as to cover at least a portion of the dielectric layer, and an electrolytic solution, are considered promising as small-sized, large-capacity capacitors with low ESR (equivalent series resistance).

[0003] A π-conjugated conductive polymer is used for the solid electrolyte layer. On the other hand, it has been proposed to use a solvent containing ethylene glycol and γ-butyrolactone for the electrolyte solution in order to improve the withstand voltage characteristics of electrolytic capacitors (see Patent Document 1). It has also been proposed to add an antioxidant to the electrolyte solution in order to increase the spark voltage (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2014 / 021333 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-114540 Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to voltage resistance, electrolytic capacitors are also required to have low ESR and heat resistance. From the perspective of improving both voltage resistance and heat resistance, it is considered desirable to include an acid in the solute of the electrolyte and to use a glycol compound as the solvent for the electrolyte. However, when a glycol compound is used as the solvent, if a long-term load test is conducted at 100°C or higher, although a low ESR is exhibited initially, the ESR tends to increase rapidly after a certain period of time.

[0006] In view of the above, an object of the present invention is to provide an electrolytic capacitor that has excellent withstand voltage characteristics and heat resistance and can maintain a low ESR. [Means for solving the problem]

[0007] One aspect of the present invention relates to an electrolytic capacitor including: an anode body having a dielectric layer; a solid electrolyte layer in contact with the dielectric layer of the anode body; and an electrolytic solution, wherein the electrolytic solution includes a solvent and a solute, the solvent includes a glycol compound, the solute includes a carboxylic acid component and a base component, and the solute includes 200 parts by mass or more of the carboxylic acid component per 100 parts by mass of the base component. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an electrolytic capacitor that is excellent in withstand voltage characteristics and heat resistance and can maintain a low ESR. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an electrolytic capacitor according to an embodiment of the present invention; [Figure 2] 2 is a schematic diagram for explaining the configuration of a capacitor element according to the same embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The electrolytic capacitor according to the present invention includes an anode body having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer, and an electrolytic solution. The electrolytic solution contains a solvent and a solute, and the solvent is glycol. The solute contains a compound, and the solute contains a carboxylic acid component and a base component. The solute contains 200 parts by mass or more of the carboxylic acid component per 100 parts by mass of the base component.

[0011] When the solvent contains a glycol compound, the orientation or crystallinity of the conductive polymer contained in the solid electrolyte layer is enhanced. This improves the conductivity of the solid electrolyte layer and reduces the ESR of the electrolytic capacitor. It also improves the contact between the solid electrolyte layer and the dielectric layer, improving the voltage resistance characteristics. It is thought that the conductive polymer swells due to the glycol compound. A conductive polymer in a swollen state is prone to rearrangement, which is thought to improve the orientation or crystallinity. It is also thought that the electrolyte is more easily retained between the dielectric layer and the solid electrolyte layer, making it easier to maintain appropriate insulation.

[0012] When the solute contains 200 parts by mass or more of a carboxylic acid component per 100 parts by mass of a base component, the ESR of the electrolytic capacitor can be maintained low not only initially but also over the long term. It is believed that the excess carboxylic acid component in the electrolyte solution suppresses the deterioration of the conductivity of the solid electrolyte layer. One of the causes of the deterioration of the solid electrolyte layer is thought to be the de-doping of the dopant from the conductive polymer.

[0013] The above-mentioned configuration is expected to improve the heat resistance and ripple resistance of the electrolytic capacitor. This is because the glycol compound is unlikely to volatilize from the electrolytic capacitor to the outside. While the electrolyte volatilizes at the seal portion of the electrolytic capacitor, the glycol compound is thought to be unlikely to permeate the seal portion.

[0014] The amount of the carboxylic acid component may be 200 parts by mass or more per 100 parts by mass of the base component, but is preferably 400 parts by mass or more, more preferably 600 parts by mass or more, and even more preferably 900 parts by mass or more. This gradually increases the effect of suppressing deterioration of the conductivity of the solid electrolyte layer. However, if the amount of the carboxylic acid component is too large, it becomes difficult to dissociate the carboxylic acid component, so the amount of the carboxylic acid component is preferably 4,500 parts by mass or less per 100 parts by mass of the base component.

[0015] The pH of the electrolyte is preferably 4 or less, more preferably 3.8 or less, and even more preferably 3.6 or less. By setting the pH of the electrolyte to 4 or less, deterioration of the conductive polymer is further suppressed. Although it is generally believed that the anode body corrodes in the pH range of 4 or less, the above electrolyte also suppresses corrosion of the anode body. It is more preferable that the pH be 2.0 or more.

[0016] The proportion of the glycol compound contained in the solvent is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. When the electrolyte contains a glycol compound as the main solvent, the effects of reducing the ESR of the electrolytic capacitor and improving the heat resistance are enhanced.

[0017] In addition to glycol compounds, the solvent may contain, for example, sulfone compounds, lactone compounds, carbonate compounds, monohydric or trihydric or higher alcohols, etc. Examples of sulfone compounds that can be used include sulfolane, dimethyl sulfoxide, and diethyl sulfoxide. Examples of lactone compounds that can be used include γ-butyrolactone and γ-valerolactone. Examples of carbonate compounds that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC). Examples of alcohols that can be used include glycerin. These may be used alone or in combination.

[0018] The glycol compound preferably contains at least ethylene glycol. Furthermore, when the solvent contains multiple types of glycol compounds, it is preferable that ethylene glycol be the main component of the glycol compound. Among glycol compounds, ethylene glycol has a low viscosity, so it easily dissolves excess carboxylic acid components. Furthermore, ethylene glycol has high thermal conductivity and excellent heat dissipation properties when ripple current occurs, so it is also highly effective in improving heat resistance.

[0019] The proportion of ethylene glycol in the glycol compound is desirably 30% by mass or more, more desirably 50% by mass or more, and the glycol compound may be 100% by mass of ethylene glycol.

[0020] In addition to ethylene glycol, the glycol compound may include, for example, diethylene glycol, triethylene glycol, propylene glycol, or polyethylene glycol having an average molecular weight of about 190 to 400. For example, 3 to 25 mass % of the solvent may be polyethylene glycol having an average molecular weight of 200 to 300. This can further improve the heat resistance of the electrolytic capacitor.

[0021] A part of the carboxylic acid component may be derived from a salt with a base component. That is, a salt of a carboxylic acid component and a base component may be used as a part of the solute. By using such a salt, the effect of improving the degree of dissociation of the carboxylic acid component can be obtained. For example, it is desirable that 10% by mass to 50% by mass of the carboxylic acid component is derived from a salt with a base component.

[0022] The base component is preferably at least one selected from the group consisting of primary amines, secondary amines, and tertiary amines. The use of an amine component, particularly a primary to tertiary amine, enhances the effect of stabilizing ESR over the long term. Although a quaternary amine may be used, primary to tertiary amines that exhibit moderate basicity are preferred from the viewpoint of minimizing side reactions. Although aliphatic amines, aromatic amines, heterocyclic amines, etc. can be used as each amine, aliphatic amines with a molecular weight of 72 to 102 are preferred because of their high degree of dissociation.

[0023] Examples of primary to tertiary amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, N,N-diisopropylethylamine, tetramethylethylenediamine, hexamethylenediamine, spermidine, spermine, amantadine, aniline, phenethylamine, toluidine, pyrrolidine, piperidine, piperazine, morpholine, imidazole, pyridine, pyridazine, pyrimidine, pyrazine, and 4-dimethylaminopyridine. These may be used alone or in combination of two or more. Among these, tertiary amines such as triethylamine and monoethyldimethylamine are particularly preferred.

[0024] The solute may further include an aromatic compound (first aromatic compound) containing two or more hydroxyl groups. The hydroxyl groups of the first aromatic compound have the effect of stabilizing the conductive polymer by complementing the effect of the carboxylic acid component. This stabilizing effect is thought to be related to the weak acidity of the hydroxyl groups of the first aromatic compound. Furthermore, the hydroxyl groups of the first aromatic compound are stable and do not easily promote side reactions such as esterification reactions. Therefore, the first aromatic compound exerts the effect of stabilizing the conductive polymer over a long period of time.

[0025] The aromatic ring of the first aromatic compound is preferably a C6 benzene ring or a C10 naphthalene ring from the viewpoint of suppressing an increase in the viscosity of the electrolyte. Furthermore, the first aromatic compound preferably has two or more phenolic hydroxyl groups directly bonded to the aromatic ring from the viewpoint of long-term stability. Among these, divalent to tetravalent phenolic compounds are preferred. More specifically, it is more preferable to use at least one selected from the group consisting of catechol and pyrogallol as the first aromatic compound. Pyrogallol is particularly preferable because it exhibits moderate acidity, and it is desirable that 90 mass % or more of the first aromatic compound is pyrogallol.

[0026] The carboxylic acid component preferably contains an aromatic compound (second aromatic compound) having two or more carboxyl groups. The carboxyl groups of the second aromatic compound are stable and do not easily cause side reactions. Therefore, the first aromatic compound exerts the effect of stabilizing the conductive polymer over a long period of time. Furthermore, the second aromatic compound exhibits moderate acidity in the electrolyte, so there is little possibility that the anode body will be damaged by corrosion.

[0027] The aromatic ring of the second aromatic compound is preferably a C6 benzene ring or a C10 naphthalene ring from the viewpoint of suppressing an increase in the viscosity of the electrolyte. Furthermore, the second aromatic compound is preferably a divalent to tetravalent carboxylic acid from the viewpoint of exhibiting moderate acidity, and more preferably has at least two carboxyl groups directly bonded to the ortho-position of the aromatic ring from the viewpoint of facilitating stabilization of the carboxyl group. More specifically, it is more preferable to use at least one selected from the group consisting of o-phthalic acid and pyromellitic acid as the second aromatic compound. o-phthalic acid is particularly preferable from the viewpoint of facilitating stabilization of the carboxyl group and exhibiting the effect of stabilizing the conductive polymer for a longer period of time, and it is desirable that 90% by mass or more of the second aromatic compound be o-phthalic acid.

[0028] The proportion of solute contained in the electrolytic solution is preferably 2 to 30% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 30% by mass. This allows the electrolytic solution to contain an excess of carboxylic acid component while containing an appropriate amount of base component that is effective in dissociating the carboxylic acid component. Within the above range, the increase in viscosity of the electrolytic solution is small, and voltage drop is also unlikely to occur. For example, the total amount of the carboxylic acid component (or second aromatic compound), base component, and first aromatic compound is preferably 2 to 30% by mass of the electrolytic solution, more preferably 10 to 30% by mass, and even more preferably 15 to 30% by mass.

[0029] From the viewpoint of further improving the heat resistance of the electrolytic capacitor and further suppressing deterioration of the solid electrolyte layer, the proportion of the first aromatic compound containing two or more hydroxyl groups is preferably 0.3 to 70 mass % of the total solute, more preferably 3 to 40 mass %, and even more preferably 3 to 25 mass %.

[0030] From the viewpoint of further suppressing deterioration of the solid electrolyte layer, the proportion of the second aromatic compound having two or more carboxyl groups is preferably 3 to 99 mass % of the total solute, more preferably 50 to 95 mass %, and even more preferably 70 to 95 mass %.

[0031] The solid electrolyte layer may be formed by applying a solution containing a monomer, a dopant, an oxidant, etc. to the dielectric layer and then chemically or electrolytically polymerizing the layer in situ. However, because excellent voltage resistance characteristics can be expected, it is preferable to form the solid electrolyte layer by applying a conductive polymer to the dielectric layer. That is, the solid electrolyte layer is preferably formed by impregnating the dielectric layer with a polymer dispersion containing a liquid component and a conductive polymer dispersed in the liquid component, forming a film covering at least a portion of the dielectric layer, and then volatilizing the liquid component from the film. The above-mentioned electrolyte solution is particularly effective in suppressing deterioration of the conductive polymer contained in the polymer dispersion and is also effective in improving orientation.

[0032] The concentration of the conductive polymer contained in the polymer dispersion is preferably 0.5 to 10% by mass. The average particle size D50 of the conductive polymer is preferably, for example, 0.01 to 0.5 μm. Here, the average particle size D50 is determined by a particle size distribution measuring device using the dynamic light scattering method. This is the median diameter in the volume particle size distribution. A polymer dispersion having such a concentration is suitable for forming a solid electrolyte layer of appropriate thickness and is easily impregnated into the dielectric layer.

[0033] The conductive polymer contained in the solid electrolyte layer is preferably polypyrrole, polythiophene, polyaniline, or the like. These may be used alone, in combination of two or more types, or as a copolymer of two or more types of monomers. By including such a conductive polymer in the solid electrolyte layer, further improvement in voltage resistance characteristics can be expected.

[0034] In this specification, polypyrrole, polythiophene, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene) (PEDOT), etc.

[0035] The weight average molecular weight of the conductive polymer is not particularly limited, but is, for example, 1,000 to 100,000.

[0036] A dopant may be added to the conductive polymer. That is, the solid electrolyte layer may contain a dopant, and from the viewpoint of suppressing dedoping from the conductive polymer, it is desirable to contain a polymer dopant. Examples of polymer dopants include polyanions such as polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. These may be used alone or in combination of two or more. Furthermore, these may be homopolymers or copolymers of two or more monomers. Among these, polystyrene sulfonic acid (PSS) is preferred.

[0037] The weight average molecular weight of the dopant is not particularly limited, but is preferably, for example, 1,000 to 100,000 in terms of facilitating the formation of a homogeneous solid electrolyte layer.

[0038] The present invention will be described in more detail below based on embodiments, but the present invention is not limited to the following embodiments.

[0039] FIG. 1 is a cross-sectional view of the electrolytic capacitor according to this embodiment, and FIG. 2 is a schematic view of a partially developed capacitor element of the electrolytic capacitor.

[0040] The electrolytic capacitor includes, for example, a capacitor element 10, a bottomed case 11 that houses the capacitor element 10, a sealing member 12 that closes the opening of the bottomed case 11, a seat plate 13 that covers the sealing member 12, lead wires 14A and 14B that extend from the sealing member 12 and pass through the seat plate 13, lead tabs 15A and 15B that connect the lead wires to the electrodes of the capacitor element 10, and an electrolyte (not shown). The vicinity of the open end of the bottomed case 11 is drawn inward, and the open end is curled so as to be crimped to the sealing member 12.

[0041] The sealing member 12 is made of an elastic material containing a rubber component. Examples of the rubber component that can be used include butyl rubber (IIR), nitrile rubber (NBR), ethylene propylene rubber, ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), isoprene rubber (IR), Hypalon rubber, silicone rubber, and fluororubber. The sealing member 12 may contain fillers such as carbon black and silica.

[0042] In designing the electrolyte, the electrolyte is prevented from leaking to the outside through the sealing member 12 that forms the seal portion. In this regard, since the electrolyte solution according to this embodiment contains a glycol compound, it is difficult for the electrolyte solution to permeate the sealing portion even at high temperatures, thereby providing an electrolytic capacitor with excellent heat resistance.

[0043] Capacitor element 10 is produced from a wound body as shown in Fig. 2. The wound body is a semi-finished product of capacitor element 10, in which a solid electrolyte layer is not formed between anode body 21 having a dielectric layer on the surface and cathode body 22. The wound body includes anode body 21 connected to lead tab 15A, cathode body 22 connected to lead tab 15B, and separator 23.

[0044] Anode body 21 and cathode body 22 are wound with separator 23 interposed therebetween. The outermost periphery of the wound body is fixed with stop tape 24. Note that Fig. 2 shows a partially unfolded state of the wound body before the outermost periphery is fixed.

[0045] Anode body 21 comprises a metal foil whose surface has been roughened to have projections and recesses, and a dielectric layer is formed on the metal foil having projections and recesses. A conductive polymer is attached to at least a portion of the surface of the dielectric layer to form a solid electrolyte layer. The solid electrolyte layer may cover at least a portion of the surface of cathode body 22 and / or the surface of separator 23. Capacitor element 10 with the solid electrolyte layer formed thereon is housed in an exterior case together with an electrolytic solution.

[0046] <Manufacturing method of electrolytic capacitors> Hereinafter, an example of a method for manufacturing an electrolytic capacitor according to this embodiment will be described step by step. (i) preparing an anode body 21 having a dielectric layer First, prepare a metal foil, which is the raw material of anode body 21. The type of metal is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal, because this facilitates the formation of a dielectric layer.

[0047] Next, the surface of the metal foil is roughened. By roughening, a plurality of projections and depressions are formed on the surface of the metal foil. The roughening is preferably carried out by etching the metal foil. The etching may be carried out by, for example, direct current electrolysis or alternating current electrolysis.

[0048] Next, a dielectric layer is formed on the roughened surface of the metal foil. The formation method is not particularly limited, but the dielectric layer can be formed by subjecting the metal foil to a chemical conversion treatment. For example, the chemical conversion treatment involves immersing the metal foil in a chemical conversion solution such as an ammonium adipate solution and then heat treating it. Alternatively, the metal foil may be immersed in the chemical conversion solution and a voltage applied thereto.

[0049] Typically, from the viewpoint of mass productivity, a large-sized foil (metal foil) of a valve metal or the like is subjected to a surface roughening treatment and a chemical conversion treatment. In this case, the treated foil is cut to a desired size to prepare anode body 21.

[0050] (ii) Step of preparing cathode body 22 Like the anode body, a metal foil can be used for the cathode body 22. The type of metal is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal. If necessary, the surface of the anode body 22 may be roughened.

[0051] (iii) Preparation of the wound body Next, a wound body is produced using anode body 21 and cathode body 22. First, the anode body 21 and the cathode body 22 are wound together with the separator 23 interposed therebetween. By winding the lead tabs 15A and 15B while winding them, the lead tabs 15A and 15B can be planted upright from the wound body as shown in FIG.

[0052] The separator 23 may be made of a nonwoven fabric containing synthetic cellulose, polyethylene terephthalate, vinylon, aramid fiber, or the like as its main component.

[0053] The material of the lead tabs 15A and 15B is not particularly limited as long as it is a conductive material. The material of the lead wires 14A and 14B connected to the lead tabs 15A and 15B, respectively, is also not particularly limited as long as it is a conductive material.

[0054] Next, of the wound anode body 21, cathode body 22, and separator 23, stop tape 24 is placed on the outer surface of cathode body 22, which is the outermost layer, and an end of cathode body 22 is fixed with stop tape 24. Note that if anode body 21 is prepared by cutting a large metal foil, the wound body may further be subjected to a chemical conversion treatment in order to provide a dielectric layer on the cut surface of anode body 21.

[0055] (iv) Step of forming capacitor element 10 Next, the dielectric layer is impregnated with the polymer dispersion to form a film that covers at least a portion of the dielectric layer. The polymer dispersion includes a liquid component and a conductive polymer dispersed in the liquid component. The polymer dispersion may be a solution in which the conductive polymer is dissolved in the liquid component, or a dispersion in which conductive polymer particles are dispersed in the liquid component. Next, the liquid component is volatilized from the formed film by drying, thereby forming a dense solid electrolyte layer that covers at least a portion of the dielectric layer. Because the polymer dispersion is uniformly distributed in the liquid component, it is easy to form a uniform solid electrolyte layer. This results in a capacitor element 10.

[0056] The polymer dispersion can be obtained, for example, by dispersing a conductive polymer in a liquid component or by polymerizing a precursor monomer in the liquid component to generate conductive polymer particles. A preferred polymer dispersion is, for example, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS), i.e., PEDOT / PSS. An antioxidant for the conductive polymer may be added, but since PEDOT / PSS is hardly oxidized, it is not necessary to use an antioxidant.

[0057] The liquid component may be water, a mixture of water and a non-aqueous solvent, or a non-aqueous solvent. The non-aqueous solvent is not particularly limited, and for example, a protic solvent or an aprotic solvent can be used. Examples of protic solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, and propylene glycol, and ethers such as formaldehyde and 1,4-dioxane. Examples of aprotic solvents include amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, and ketones such as methyl ethyl ketone.

[0058] A simple and preferred method for applying the polymer dispersion to the surface of the dielectric layer is, for example, immersing the wound body in the polymer dispersion contained in a container. The immersion time varies depending on the size of the wound body, but is, for example, 1 second to 5 hours, preferably 1 minute to 30 minutes. The impregnation is preferably carried out under reduced pressure, for example, in an atmosphere of 10 to 100 kPa, preferably 40 to 100 kPa. Ultrasonic vibrations may be applied to the wound body or the polymer dispersion while immersed in the polymer dispersion. After the wound body is removed from the polymer dispersion, it is dried, for example, preferably at 50 to 300°C, more preferably at 100 to 200°C.

[0059] The step of applying the polymer dispersion to the surface of the dielectric layer and the step of drying the wound body are performed twice. The above steps may be repeated. By performing these steps multiple times, the coverage of the solid electrolyte layer with respect to the dielectric layer can be increased. In this case, the solid electrolyte layer may be formed not only on the surface of the dielectric layer, but also on the surfaces of cathode body 22 and separator 23.

[0060] In this manner, a solid electrolyte layer is formed between anode body 21 and cathode body 22, producing capacitor element 10. The solid electrolyte layer formed on the surface of the dielectric layer effectively functions as a cathode material.

[0061] (v) A step of impregnating the capacitor element 10 with an electrolyte Next, the capacitor element 10 is impregnated with the electrolyte solution. This results in an electrolytic capacitor with excellent dielectric layer repair function. The method for impregnating the capacitor element 10 with the electrolyte solution is not particularly limited. For example, a simple and preferable method is to immerse the capacitor element 10 in the electrolyte solution contained in a container. The immersion time varies depending on the size of the capacitor element 10, but is, for example, 1 second to 5 minutes. The impregnation is preferably carried out under reduced pressure, for example, in an atmosphere of 10 to 100 kPa, preferably 40 to 100 kPa.

[0062] (vi) Sealing the capacitor element Next, capacitor element 10 is sealed. Specifically, capacitor element 10 is first housed in bottomed case 11 so that lead wires 14A and 14B are located on the open upper surface of bottomed case 11. Bottomed case 11 can be made of a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy of these metals.

[0063] Next, sealing member 12, which is formed so that lead wires 14A and 14B pass through it, is placed above capacitor element 10, and capacitor element 10 is sealed in bottomed case 11. Next, a horizontal drawing process is performed near the open end of bottomed case 11, and the open end is crimped to sealing member 12 to form a curl. Then, seat plate 13 is placed on the curled portion, completing the electrolytic capacitor as shown in FIG. 1. Thereafter, an aging process may be performed while applying a rated voltage.

[0064] In the above embodiment, a wound-type electrolytic capacitor has been described, but the scope of application of the present invention is not limited to the above, and the present invention can also be applied to other electrolytic capacitors, such as chip-type electrolytic capacitors that use a metal sintered body as an anode body, and stacked-type electrolytic capacitors that use a metal plate as an anode body. [Example] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0065] Example 1 In this example, a wound electrolytic capacitor (Φ10.0 mm×L (length) 10.0 mm) with a rated voltage of 80 V and a rated capacitance of 38 μF was fabricated. A specific method for manufacturing the electrolytic capacitor will be described below.

[0066] (Preparation of the anode body) An aluminum foil with a thickness of 100 μm was subjected to an etching treatment to roughen the surface of the aluminum foil. Then, a dielectric layer was formed on the surface of the aluminum foil by chemical conversion treatment. The chemical conversion treatment was performed by immersing the aluminum foil in an ammonium adipate solution and applying a voltage of 150 V. The aluminum foil was then cut into pieces measuring 6 mm x 120 mm to prepare anode bodies.

[0067] (Preparation of the cathode body) An aluminum foil having a thickness of 50 μm was subjected to an etching treatment to roughen the surface of the aluminum foil, and then cut into a size of 6 mm length × 120 mm width to prepare a cathode body.

[0068] (Production of wound body) An anode lead tab and a cathode lead tab were connected to the anode body and the cathode body, respectively, and the anode body and the cathode body were wound around the lead tabs, with a separator interposed therebetween. An anode lead wire and a cathode lead wire were connected to the ends of each lead tab protruding from the wound body, respectively. The wound body was then subjected to a chemical conversion treatment again, and a dielectric layer was formed on the cut end of the anode body. Next, the ends of the outer surface of the wound body were fixed with a winding tape to produce the wound body.

[0069] (Preparation of polymer dispersion) 3,4-ethylenedioxythiophene and a polymer dopant, polystyrene sulfonic acid (PSS, weight-average molecular weight 100,000), were dissolved in ion-exchanged water (liquid component) to prepare a mixed solution. While stirring the mixed solution, iron (III) sulfate (acid) dissolved in ion-exchanged water was added. After the reaction, the resulting reaction solution was dialyzed to remove unreacted monomers and excess oxidizing agent, yielding a polymer dispersion containing approximately 5% by mass of PSS-doped polyethylenedioxythiophene (PEDOT / PSS).

[0070] (Formation of solid electrolyte layer) The wound body was immersed in a polymer dispersion contained in a container in a reduced pressure atmosphere (40 kPa) for 5 minutes, and then removed from the polymer dispersion. The wound body impregnated with the polymer dispersion was then dried in a drying oven at 150°C for 20 minutes to form a solid electrolyte layer that covered at least a portion of the dielectric layer.

[0071] (Electrolyte impregnation) An electrolyte solution having the composition shown in Table A below, containing ethylene glycol (EG) as a glycol compound and polyethylene glycol (PEG) with an average molecular weight of approximately 300, was prepared, and the capacitor element was immersed in the electrolyte solution for 5 minutes in a reduced pressure atmosphere (40 kPa). A part of the carboxylic acid component and the base component (triethylamine) were added as triethylamine phthalate (salt).

[0072] [Table A]

[0073] (Sealing of capacitor elements) The capacitor element impregnated with the electrolyte was sealed to complete the electrolytic capacitor. Specifically, the capacitor element was placed in a bottomed case with the lead wires positioned on the open side of the case, and a sealing member (elastic material containing butyl rubber as a rubber component) formed so that the lead wires could pass through was placed above the capacitor element, sealing the capacitor element inside the bottomed case. The bottomed case was then drawn near the open end, and the open end was further curled. A seat plate was placed on the curled portion to complete the electrolytic capacitor (A1) shown in Figure 1. The capacitor was then aged for 2 hours at 130°C while applying the rated voltage.

[0074] Example 2 An electrolytic capacitor A2 was produced in the same manner as in Example 1 except that an electrolytic solution having the composition shown in Table B below was used, and was evaluated in the same manner.

[0075] [Table B]

[0076] Example 3 An electrolytic capacitor A3 was produced in the same manner as in Example 1 except that an electrolytic solution having the composition shown in Table C below was used, and was evaluated in the same manner.

[0077] [Table C]

[0078] Comparative Example 1 An electrolytic capacitor B1 was produced in the same manner as in Example 1 except that an electrolytic solution having the composition shown in Table D below was used, and was evaluated in the same manner.

[0079] [Table D]

[0080] [evaluation] The electrolytic capacitors were measured for capacitance, ESR, and breakdown voltage (BDV). The breakdown voltage (BDV) was measured by applying a voltage increasing at a rate of 1.0 V / sec, and measuring the voltage when an overcurrent of 0.5 A flows.

[0081] Furthermore, to evaluate long-term reliability, the capacitors were held at 125°C for 5000 hours while applying the rated voltage, and the increase rate of ESR (ΔESR) was confirmed. ΔESR is the change from the initial value (X0) to The results are shown in Table 1.

[0082] [Table 1]

[0083] Example 4 An electrolytic capacitor A4 was produced in the same manner as in Example 1 except that an electrolytic solution having the composition shown in Table E below was used, and was evaluated in the same manner.

[0084] [Table E]

[0085] Example 5 An electrolytic capacitor A5 was produced in the same manner as in Example 1 except that the electrolyte solution having the composition in Table F below was used, and was evaluated in the same manner.

[0086] [Table F]

[0087] Example 6 Except for using the electrolyte solution having the composition shown in Table G below, an electrolytic capacitor A6 was produced and evaluated in the same manner as in Example 1. Note that a part of the carboxylic acid component (pyromellitic acid) and the base component (triethylamine) were added as pyromellitic acid ditriethylamine (salt).

[0088] [Table G]

[0089] Example 7 An electrolytic capacitor A7 was produced in the same manner as in Example 1 except that an electrolytic solution having the composition shown in Table H below was used, and was evaluated in the same manner.

[0090] [Table H]

[0091] Example 8 An electrolytic capacitor A8 was produced in the same manner as in Example 1 except that an electrolytic solution having the composition shown in Table I below was used, and was evaluated in the same manner.

[0092] [Table I]

[0093] Example 9 An electrolytic capacitor A9 was produced in the same manner as in Example 1 except that an electrolytic solution having the composition shown in Table J below was used, and was similarly evaluated.

[0094] [Table J]

[0095] The evaluation results of Examples 4 to 9 are shown in Table 2.

[0096] [Table 2] [Industrial Applicability]

[0097] The present invention can be used in an electrolytic capacitor comprising a solid electrolyte layer that covers at least a part of a dielectric layer, and an electrolytic solution. [Explanation of symbols]

[0098] 10: Capacitor element, 11: Bottomed case, 12: Sealing member, 13: Seat plate, 14A, 14B: Lead wires, 15A, 15B: Lead tabs, 21: Anode body, 22: Cathode body, 23: Separator, 24: Winding tape

Claims

1. an anode body having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer of the anode body, and an electrolytic solution; the electrolyte solution includes a solvent and a solute; the solvent comprises a glycol compound; the solute includes a carboxylic acid component and a base component; the proportion of the glycol compound contained in the solvent is 50% by mass or more; the carboxylic acid component is at least one selected from the group consisting of a compound having two or more carboxyl groups and an aromatic compound having a carboxyl group, the base component is at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine; The solute contains the carboxylic acid component in an amount of 400 parts by mass or more relative to 100 parts by mass of the base component, A portion of the carboxylic acid component is derived from a salt with the base component. or The solute includes an aromatic compound having two or more hydroxyl groups. or The carboxylic acid component includes an aromatic compound having two or more carboxyl groups, and the aromatic compound having two or more carboxyl groups is at least one selected from the group consisting of o-phthalic acid and pyromellitic acid.

2. an anode body having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer of the anode body, and an electrolytic solution; the electrolyte solution includes a solvent and a solute; the solvent comprises a glycol compound; the solute includes a carboxylic acid component and a base component; the proportion of the glycol compound contained in the solvent is 50% by mass or more; The carboxylic acid component is a compound having two or more carboxyl groups, the base component is at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine; The electrolytic capacitor, wherein the solute contains 400 parts by mass or more of the carboxylic acid component per 100 parts by mass of the base component.

3. an anode body having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer of the anode body, and an electrolytic solution; the electrolyte solution includes a solvent and a solute; the solvent comprises a glycol compound; the solute includes a carboxylic acid component and a base component; the proportion of the glycol compound contained in the solvent is 50% by mass or more; the carboxylic acid component is at least one selected from the group consisting of a compound having two or more carboxyl groups and an aromatic compound having a carboxyl group, the base component is at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine; The solute contains the carboxylic acid component in an amount of 400 parts by mass or more (excluding cases where the amount is 600 parts by mass or less) relative to 100 parts by mass of the base component, The electrolytic capacitor, wherein the proportion of the solute contained in the electrolytic solution is 10 to 30 mass %.

4. an anode body having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer of the anode body, and an electrolytic solution; the electrolyte solution includes a solvent and a solute; the solvent comprises a glycol compound; the solute includes a carboxylic acid component and a base component; the proportion of the glycol compound contained in the solvent is 50% by mass or more; the carboxylic acid component is a second aromatic compound having a carboxyl group (excluding compounds having two or more hydroxyl groups); the base component is at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine; the solute further includes a first aromatic compound (excluding compounds having a carboxyl group) having two or more hydroxyl groups different from those of the second aromatic compound; The electrolytic capacitor, wherein the proportion of the first aromatic compound is 3 to 40 mass % of the total solute.

5. An electrolytic capacitor described in any one of claims 1 to 4, wherein the pH of the electrolyte is 4 or less.

6. an anode body having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer of the anode body, and an electrolytic solution; the electrolyte solution includes a solvent and a solute; the solvent comprises a glycol compound; the solute includes a carboxylic acid component and a base component; the proportion of the glycol compound contained in the solvent is 50% by mass or more; the carboxylic acid component is at least one selected from the group consisting of a compound having two or more carboxyl groups and an aromatic compound having a carboxyl group, the base component is at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine; An electrolytic capacitor, wherein the pH of the electrolytic solution is 4 or less, A portion of the carboxylic acid component is derived from a salt with the base component. or The solute includes an aromatic compound having two or more hydroxyl groups. or The carboxylic acid component includes an aromatic compound having two or more carboxyl groups, and the aromatic compound having two or more carboxyl groups is at least one selected from the group consisting of o-phthalic acid and pyromellitic acid.

7. 7. The electrolytic capacitor according to claim 1, wherein the glycol compound is ethylene glycol.

8. 8. The electrolytic capacitor according to claim 1, wherein the proportion of the solute contained in the electrolytic solution is 2 to 30 mass %.

9. 9. The electrolytic capacitor according to claim 1, wherein a portion of the carboxylic acid component is derived from a salt with the base component.

10. 10. The electrolytic capacitor according to claim 1, wherein the solute comprises an aromatic compound having two or more hydroxyl groups.

11. 11. The electrolytic capacitor according to claim 4, wherein the aromatic compound having two or more hydroxyl groups or the first aromatic compound is at least one selected from the group consisting of catechol and pyrogallol.

12. 12. The electrolytic capacitor according to claim 1, wherein the carboxylic acid component includes an aromatic compound having two or more carboxyl groups.

13. 13. The electrolytic capacitor according to claim 12, wherein the aromatic compound having two or more carboxyl groups is at least one selected from the group consisting of o-phthalic acid and pyromellitic acid.

14. 14. The electrolytic capacitor according to claim 1, wherein the solid electrolyte layer contains a conductive polymer.

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