Electrolytic capacitor and method for manufacturing the same

Abstract

To provide a highly reliable electrolytic capacitor. [Solution] The electrolytic capacitor includes a capacitor element having an anode body with a dielectric layer formed thereon, a conductive polymer covering at least a portion of the surface of the dielectric layer, and an electrolyte solution containing a non-aqueous solvent, a glycerin compound, and an ionic solute. The non-aqueous solvent is at least one selected from the group consisting of lactones, glycols, cyclic carbonates, and sulfones. The content of the glycerin compound in the electrolyte solution is 5% by mass or more and 50% by mass or less.

Description

[Technical field]

[0001] The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor having high reliability. [Background technology]

[0002] As electronic devices become more digitalized, there is a growing demand for the capacitors used in them to be small, have large capacity, and have a low equivalent series resistance (ESR) in the high frequency range.

[0003] As a small, large-capacity, low-ESR capacitor, electrolytic capacitors that use conductive polymers such as polypyrrole, polythiophene, polyfuran, and polyaniline as the cathode material are promising. For example, an electrolytic capacitor has been proposed in which a conductive polymer layer is provided as the cathode material on an anode foil (anode body) on which a dielectric layer is formed.

[0004] Patent Document 1 proposes a method for producing an electrolytic capacitor comprising a conductive solid layer and an electrolytic solution by impregnating an element having a separator with a dispersion of a conductive polymer to form a conductive solid layer, and then impregnating the element with an electrolytic solution. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-010657 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, electrolytic capacitors have been used not only in electronic devices but also in automotive electrical equipment. In particular, electrolytic capacitors used in automotive electrical equipment are used for long periods of time in high-temperature environments, and therefore electrolytic capacitors are required to have even higher reliability over a longer period of time than in the past. Therefore, an object of the present invention is to provide an electrolytic capacitor with even higher reliability. [Means for solving the problem]

[0007] One aspect of the present invention is a capacitor element including an anode body having a dielectric layer formed thereon; a conductive polymer covering at least a part of the surface of the dielectric layer; an electrolyte solution including a non-aqueous solvent, a glycerin compound, and an ionic solute; the non-aqueous solvent is at least one selected from the group consisting of lactones, glycols, cyclic carbonates, and sulfones; The present invention relates to an electrolytic capacitor, wherein the content of the glycerin compound in the electrolytic solution is 10% by mass or more and 50% by mass or less. Effect of the Invention

[0008] According to the present invention, a highly reliable electrolytic capacitor can be obtained. [Brief description of the drawings]

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

[0010] Hereinafter, embodiments of the electrolytic capacitor of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments.

[0011] <Electrolytic capacitor> Fig. 1 is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present invention, and Fig. 2 is a schematic exploded view of a portion of a capacitor element included in the electrolytic capacitor.

[0012] 1, the electrolytic capacitor includes a capacitor element 10 having an anode body 21 on which a dielectric layer is formed, a conductive polymer (not shown) covering at least a portion of the surface of the dielectric layer (or attached to at least a portion of the surface), and an electrolyte (not shown). The capacitor element 10 is housed in an exterior case together with the electrolyte, with at least a portion of the surface of the dielectric layer covered with the conductive polymer. The exterior case includes a bottomed case 11 that houses the capacitor element 10 therein, an insulating sealing member 12 that closes the opening of the bottomed case 11, and a seat plate 13 that covers the sealing member 12. 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.

[0013] For example, capacitor element 10 as shown in Fig. 2 is called a wound body. This capacitor element 10 includes an anode body 21 connected to lead tab 15A, a cathode body 22 connected to lead tab 15B, and a separator 23. Anode body 21 and cathode body 22 are wound with separator 23 interposed therebetween. The outermost periphery of capacitor element 10 is fixed by a stop tape 24. Note that Fig. 2 shows a partially unfolded state of capacitor element 10 before the outermost periphery is fixed.

[0014] The 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 the projections and recesses. In the electrolytic capacitor, the conductive polymer is attached so as to cover at least a portion of the surface of the dielectric layer formed on the anode body 21, but this is not limited to the case, and the conductive polymer may be attached to any position between the anode body 21 and the cathode body 22. For example, the conductive polymer may cover at least a portion of the surface of the dielectric layer formed on the anode body 21, and further cover at least a portion of the surface of the cathode body 22 and / or at least a portion of the surface of the separator 23. In electrolytic capacitors, the conductive polymer (specifically, a coating containing a conductive polymer) that covers at least a portion of the surfaces of the anode body, the cathode body, the separator, etc. may generally be referred to as a conductive polymer layer.

[0015] The configuration of the electrolytic capacitor according to the embodiment of the present invention will be described in more detail below. The capacitor element includes an anode body on which a dielectric layer is formed. The conductive polymer attached to the surface of the dielectric layer functions as a cathode material. The capacitor element may further include a cathode body and / or a separator, as necessary.

[0016] (Capacitor element) (Anode body) The anode body may be, for example, a metal foil having a roughened surface. The type of metal constituting the metal foil 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, in terms of ease of forming a dielectric layer.

[0017] The metal foil surface can be roughened by a known method. By roughening, a plurality of projections and recesses are formed on the surface of the metal foil. The roughening is preferably performed, for example, by etching the metal foil. The etching may be performed, for example, by DC electrolysis or AC electrolysis.

[0018] (Dielectric layer) The dielectric layer is formed on the surface of the anode body (specifically, on the roughened surface of the metal foil). The method for forming the dielectric layer is not particularly limited, but the dielectric layer can be formed by subjecting a metal foil to a chemical conversion treatment. The chemical conversion treatment may be performed, for example, by immersing the metal foil in a chemical conversion solution such as an ammonium adipate solution. In the chemical conversion treatment, a voltage may be applied to the metal foil while it is immersed in the chemical conversion solution, if necessary.

[0019] Usually, from the viewpoint of mass production, a metal foil made of a large-sized 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 the anode body 21.

[0020] (cathode body) As with the anode body, a metal foil may 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 metal foil may be roughened. The surface of cathode body 22 may be provided with a chemical conversion coating, or with a coating of a metal (dissimilar metal) different from the metal constituting the cathode body or a nonmetal. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon.

[0021] (Separator) Separator 23 may be made of, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (for example, aliphatic polyamide, aromatic polyamide such as aramid).

[0022] Capacitor element 10 can be produced by a known method. For example, capacitor element 10 may be produced by stacking anode body 21 and cathode body 22 with separator 23 interposed therebetween. Anode body 21 and cathode body 22 may be wound with separator 23 interposed therebetween to form a wound body as shown in Fig. 2. At this time, lead tabs 15A and 15B may be wound while being wound, so that lead tabs 15A and 15B are planted from the wound body as shown in Fig. 2.

[0023] The material of the lead tabs 15A and 15B is not particularly limited as long as it is a conductive material. The surfaces of the lead tabs 15A and 15B may be subjected to a chemical conversion treatment. Furthermore, the portions of the lead tabs 15A and 15B that contact the sealing member 12 and the portions connected to the lead wires 14A and 14B may be covered with a resin material. The material of the lead wires 14A, 14B connected to the lead tabs 15A, 15B, respectively, is not particularly limited, and may be a conductive material or the like.

[0024] Of anode body 21, cathode body 22, and separator 23, the one located in the outermost layer of the wound body (cathode body 22 in FIG. 2) has an end of the outer surface fixed with stop tape 24. When anode body 21 is prepared by cutting a large metal foil, a chemical conversion treatment may be further performed on the capacitor element in the state of a wound body, in order to provide a dielectric layer on the cut surface of anode body 21.

[0025] (conductive polymer) Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophene. These may be used alone or in combination of two or more kinds, or may be copolymers of two or more kinds of monomers.

[0026] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene), etc.

[0027] The conductive polymer may contain a dopant. As the dopant, a polyanion may be used. Specific examples of the polyanion include anions such as polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacryl sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. Among them, polyanions derived from polystyrene sulfonic acid are preferred. These may be used alone or in combination of two or more. These may also be polymers of a single monomer or copolymers of two or more monomers.

[0028] The weight-average molecular weight of the polyanion is not particularly limited, but is, for example, 1,000 to 1,000,000. A conductive polymer containing such a polyanion is likely to be uniformly dispersed in a liquid solvent, and is likely to be uniformly attached to the surface of the dielectric layer.

[0029] The conductive polymer may be attached to at least a portion of the surface of the dielectric layer in the anode body 21 so as to cover the dielectric layer, but it is preferable to attach it so as to cover as much of the area as possible. When the capacitor element includes a cathode body and / or a separator, the conductive polymer may be attached not only to the surface of the dielectric layer but also to the surface of the cathode body and / or separator. That is, the conductive polymer may be in contact with the separator and / or the cathode body.

[0030] The conductive polymer can be attached by a step (first step) of impregnating a capacitor element including an anode body on which a dielectric layer is formed with a first treatment liquid containing the conductive polymer, and, if necessary, a step (second step) of impregnating the capacitor element with a second treatment liquid after the first step. The conductive polymer is attached to the surface of the dielectric layer by performing the first step or the first and second steps. The method for producing an electrolytic capacitor may include a step (third step) of removing at least a part of the solvent component contained in the first treatment liquid after the first step, and may include a step (fourth step) of removing at least a part of the solvent component contained in the first treatment liquid and / or the second treatment liquid after the second step.

[0031] (i) A step of impregnating the capacitor element (wound body) 10 with a first treatment liquid (first step) The impregnation of the capacitor element 10 with the first treatment liquid is not particularly limited as long as the first treatment liquid can be applied to at least the anode body (particularly, at least the dielectric layer), and for example, the capacitor element may be immersed in the first treatment liquid, or the first treatment liquid may be poured into the capacitor element. The impregnation may be performed under atmospheric pressure, or may be performed under a reduced pressure, for example, an atmosphere of 10 kPa to 100 kPa, preferably 40 kPa to 100 kPa. The impregnation may be performed under ultrasonic vibration as necessary. The impregnation time depends on the size of the capacitor element 10, and is, for example, 1 second to 5 hours, preferably 1 minute to 30 minutes. Through this step, the first treatment liquid is applied to the capacitor element 10.

[0032] The first treatment liquid may include a conductive polymer and a liquid solvent. The first treatment liquid may be either a solution in which the conductive polymer is dissolved in a liquid solvent or a dispersion in which the conductive polymer is dispersed in a liquid solvent. In the dispersion, the conductive polymer is dispersed in the liquid solvent in the form of particles. The dispersion may be one obtained by polymerizing a raw material of the conductive polymer (e.g., a precursor such as a monomer and / or oligomer of the conductive polymer) in the presence of a dopant in the liquid solvent to generate conductive polymer particles containing the dopant. The dispersion may be one obtained by polymerizing a raw material of the conductive polymer in the liquid solvent to generate conductive polymer particles, or one obtained by dispersing particles of a conductive polymer previously synthesized in the liquid solvent.

[0033] The liquid solvent of the first treatment liquid may contain the first solvent, or may contain the first solvent and a solvent other than the first solvent. The liquid solvent contained in the first treatment liquid may contain a plurality of different types of first solvents. The first solvent may, for example, account for 30% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more of the liquid solvent of the first treatment liquid.

[0034] The first solvent is not particularly limited, and may be water or a non-aqueous solvent. The non-aqueous solvent is a general term for liquids other than water and liquids containing water, and includes organic solvents and ionic liquids. In particular, the first solvent is preferably a polar solvent. The polar solvent may be a protic solvent or an aprotic solvent.

[0035] Examples of protic solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol (EG), propylene glycol, polyethylene glycol, diethylene glycol monobutyl ether, glycerin, 1-propanol, butanol, and polyglycerin, formaldehyde, and water.

[0036] Examples of aprotic solvents include amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, ketones such as methyl ethyl ketone and γ-butyrolactone (γBL), ethers such as 1,4-dioxane, sulfur-containing compounds such as dimethyl sulfoxide and sulfolane, and carbonate compounds such as propylene carbonate.

[0037] Among them, the first solvent is preferably a protic solvent. In particular, the first solvent is preferably water. In this case, the handleability of the first treatment liquid and the dispersibility of the conductive polymer are improved. In addition, since water has a low viscosity, it is expected that the contactability between the conductive polymer and the second treatment liquid is improved in the subsequent second step. When the first solvent is water, water preferably accounts for 50% by mass or more of the liquid solvent of the first treatment liquid, more preferably 70% by mass or more, and particularly preferably 90% by mass or more.

[0038] The conductive polymer particles dispersed in the dispersion liquid preferably have a median diameter in the volumetric particle size distribution measured by a particle size measuring device using a dynamic light scattering method (hereinafter simply referred to as the median diameter by the dynamic light scattering method) of 0.01 μm to 0.5 μm. The particle diameter of the conductive polymer can be adjusted by the polymerization conditions, dispersion conditions, etc.

[0039] The concentration of the conductive polymer (including a dopant or a polyanion) in the first treatment liquid is preferably 0.5 to 10 mass %. A first treatment liquid of such a concentration is suitable for depositing an appropriate amount of the conductive polymer, and is also advantageous in terms of improving productivity, since the first treatment liquid is easily impregnated into the capacitor element 10.

[0040] (ii) A step of impregnating the capacitor element with a second treatment liquid (second step) In the second step, the capacitor element to which the first treatment liquid has been applied is impregnated with a second treatment liquid. The second step is an optional step.

[0041] In the second step, it is preferable to impregnate the capacitor element (particularly, the anode body) with the second treatment liquid while at least a part of the liquid solvent (such as the first solvent) of the first treatment liquid remains. A capacitor element including an anode body with the liquid solvent remaining therein has extremely high permeability to the second treatment liquid. Therefore, when the second treatment liquid is applied to a capacitor element in such a state, the second treatment liquid can be permeated further inside. This effect is particularly likely to be obtained when the treatment is performed while at least water remains. Therefore, it is preferable to use a liquid solvent containing at least water as the first solvent for the first treatment liquid. When a liquid solvent containing water is used as the first solvent, the stability of the first treatment liquid is also increased, which is advantageous from this viewpoint as well.

[0042] In the capacitor element subjected to the second step, the remaining amount of liquid solvent is preferably 5 mass % or more (e.g., 5 to 100 mass %), and more preferably 20 mass % or more (e.g., 20 to 100 mass %) or 50 mass % or more (e.g., 50 to 100 mass %). When the remaining amount of liquid solvent is within such a range, the second treatment liquid tends to mix uniformly with the conductive polymer inside the capacitor element in the second step, making it easier to attach the conductive polymer more uniformly to the surface of the dielectric layer.

[0043] The remaining amount of liquid solvent is the ratio (mass %) of the mass of liquid solvent contained in the capacitor element subjected to the second step to the mass of liquid solvent contained in the first treatment liquid impregnated into the capacitor element in the first step.

[0044] A solvent (second solvent) is used as the second treatment liquid. The capacitor element can be impregnated with the second treatment liquid in the same manner as the first treatment liquid. The second solvent can be a polar solvent or a non-polar solvent. Examples of the non-polar solvent include hydrocarbons, ethyl acetate, and diethyl ether.

[0045] The second solvent is preferably a polar solvent, for example, the protic solvents exemplified as the first solvent as well as aprotic solvents. Examples of the aprotic solvent include, among those exemplified for the first solvent, amides, lactones such as γBL, cyclic ethers such as 1,4-dioxane, sulfones such as dimethyl sulfoxide and sulfolane, cyclic carbonates such as propylene carbonate, etc. The second treatment liquid may contain one type of second solvent, or may contain two or more types of second solvents.

[0046] As the protic solvent, preferred are protic organic solvents such as water, alcohols (specifically, alkanols such as methanol and ethanol, polyol compounds such as glycols (EG, PEG, etc.), and glycerins (glycerin, polycerin, etc.)), and glycol monoethers such as diethylene glycol monobutyl ether. At least one second solvent is preferably a protic solvent, and the second treatment liquid may be a mixture of a protic solvent and an aprotic solvent. When a plurality of second solvents are used, for example, a polyol compound having three or more hydroxyl groups per molecule may be combined with a polar solvent other than the polyol compound (a protic organic solvent and / or an aprotic solvent). As the protic organic solvent, alcohols other than the polyol compound (specifically, alkanols, glycols), glycol monoethers, etc. are preferred.

[0047] (iii) Steps for removing the solvent component (Steps 3 and 4) After the first step, the solvent component remaining in the capacitor element can be removed in the third step. After the second step, the solvent component remaining in the capacitor element may be removed in the fourth step. In the third or fourth step, it is sufficient to remove at least a part of the solvent component, and the entire solvent component may be removed. By removing the solvent component in the fourth step, the conductive polymer can be more uniformly attached to the surface of the dielectric layer. The solvent component here refers to the liquid solvent contained in the first treatment liquid and the second solvent contained in the second treatment liquid. Among these, it is preferable to remove at least a part of the first solvent and / or the second solvent (particularly the first solvent) in the fourth step.

[0048] In each of the third and fourth steps, the solvent component can be removed by evaporation under heating, and may be removed under atmospheric pressure, or may be removed under reduced pressure as necessary. The temperature at which the solvent component is removed may be equal to or higher than the boiling point of the first solvent (or the second solvent). The removal of the solvent component may be performed, for example, in multiple stages (for example, two or three or more stages) at different temperatures, or may be performed while increasing the temperature. In this manner, the conductive polymer is adhered between anode body 21 and cathode body 22 (particularly to the surface of the dielectric layer), and capacitor element 10 having the conductive polymer adhered thereto is produced.

[0049] The conductive polymer is preferably attached so as to cover at least a part of the surface of the dielectric layer. In this case, the conductive polymer may be attached not only to the surface of the dielectric layer but also to the surface of the cathode body 22 and / or the separator 23. In addition, at least one step selected from the group consisting of a first step (i) of impregnating the capacitor element 10 including the anode body 21 having a dielectric layer with a first processing liquid, a third step (optional step) of removing a solvent component (such as a liquid solvent such as the first solvent) after the first step, a second step (ii) of impregnating the capacitor element with a second processing liquid, and a fourth step (iv) (optional step) of removing a solvent component (such as a liquid solvent such as the first solvent and / or the second solvent) after the second step may be repeated two or more times as necessary. Steps selected from these steps may be repeated two or more times as a series of steps. For example, after the first step is repeated multiple times, another step may be performed, and the first step, the third step if necessary, and the second step may be repeated multiple times as a series of steps. From the viewpoint of easily increasing the coverage of the conductive polymer on the dielectric layer, it is advantageous to repeat at least the first step multiple times.

[0050] The solvent component may be entirely removed from the capacitor element 10 obtained in the second or fourth step. The capacitor element 10 obtained in the second or fourth step may have the solvent component remaining. When the solvent component remains, the repair function of the dielectric layer can be further improved. In addition, since the remaining solvent component exists between the particles of the conductive polymer, the electrolyte can easily penetrate between the particles of the conductive polymer when the capacitor element is impregnated with the electrolyte. Therefore, the repair function of the dielectric layer by the electrolyte can be easily obtained. By improving the repair function of the dielectric layer, it is also possible to effectively suppress short circuits even after the guaranteed life of the electrolytic capacitor has expired.

[0051] (electrolyte) The electrolyte contains a non-aqueous solvent containing γBL and at least one glycerin compound selected from the group consisting of glycerin and polyglycerin. The electrolyte may further contain an ionic substance (solute), or may not contain a solute. The ionic substance used is one that dissolves in the glycerin compound and / or the non-aqueous solvent.

[0052] By including γBL in the electrolyte, the impregnation of the electrolyte into the capacitor element can be improved, even though a glycerin compound with a relatively high viscosity is used. By including a glycerin compound in the electrolyte, the conductive polymer can be swollen. Therefore, the conductive polymer can be present in every corner of the multiple projections and recesses formed by roughening the anode foil. As a result, in addition to being able to reduce the ESR during the initial charging and discharging period, the electrolytic capacitor can maintain a low ESR even after long-term use, resulting in high reliability.

[0053] The electrolytic solution refers to the electrolytic solution (solvent component) contained in the assembled electrolytic capacitor (specifically, in the exterior case). The electrolytic solution also includes the solvent component remaining in the electrolytic capacitor during the manufacturing process of the electrolytic capacitor. Examples of such solvent components include the solvent components contained in the first treatment liquid and / or the second treatment liquid (for example, the liquid medium and / or the first solvent contained in the first treatment liquid, the second solvent contained in the second treatment liquid, etc.).

[0054] The polyglycerin contains, for example, 2 to 20 (preferably 2 to 12, 2 to 10, or 2 to 6) glycerin units. As the polyglycerin, diglycerin, triglycerin, and the like are also preferred.

[0055] Glycerin compounds have a high affinity for conductive polymers and tend to exist stably between particles of conductive polymers. Glycerin compounds also have low volatility. Therefore, by including a glycerin compound in the electrolyte, it becomes easier to retain the electrolyte around the dielectric layer, which can improve the film repairability of the dielectric layer and increase the effect of suppressing leakage current. Therefore, even if the guaranteed life of the electrolytic capacitor has expired, short circuits can be effectively suppressed.

[0056] The content of the glycerin compound in the electrolytic solution may be, for example, 5% by mass or more, and may be 10% by mass or more or 20% by mass or more. The content of the glycerin compound in the electrolytic solution may be, for example, 50% by mass or less, preferably 30% by mass or less. These lower and upper limits can be arbitrarily combined. The content of the glycerin compound in the electrolytic solution may be, for example, 5 to 50% by mass, or 10 to 30% by mass. When the content of the glycerin compound in the electrolyte is within the above range, higher reliability can be obtained.

[0057] In an electrolytic capacitor, the mass of the glycerin compound contained in the electrolytic solution may be 2 to 100 times, or 3 to 80 times, the mass of the conductive polymer impregnated in the capacitor element. When the mass ratio is within such a range, the effect of swelling the conductive polymer is easily obtained.

[0058] The non-aqueous solvent may contain a non-aqueous solvent (organic solvent and / or ionic liquid) other than γBL. An organic solvent (organic solvent other than γBL) is preferably used. Such a non-aqueous solvent is preferably one having a high boiling point, and examples of the non-aqueous solvent having a high boiling point include ionic liquid and / or organic solvent having a high boiling point. The boiling point of the non-aqueous solvent is, for example, higher than 100°C, preferably 150°C or higher, and more preferably 200°C or higher. Examples of the organic solvent include the organic solvents exemplified as the first solvent of the first treatment liquid and the second solvent exemplified as the second treatment liquid. The non-aqueous solvent can be used alone or in combination of two or more.

[0059] As the non-aqueous solvent, it is preferable to use one that dissolves a glycerin compound (or one that is miscible or compatible with a glycerin compound). Examples of such non-aqueous solvents include protic organic solvents, as well as aprotic solvents such as amides, lactones, cyclic ethers, sulfones, and cyclic carbonates. As the protic organic solvent, alcohols other than glycerins (specifically, alkanols and glycols), glycol monoethers, and the like are preferable. Among the non-aqueous solvents, at least one selected from the group consisting of glycols, lactones, sulfones, and cyclic carbonates is preferable. The non-aqueous solvent may contain at least one selected from the group consisting of EG, sulfolane, and PC together with γBL.

[0060] Such aprotic solvents and protic organic solvents have high affinity with glycerin compounds and can be mixed uniformly with the glycerin compounds, so that the use of such solvents makes it easy for the electrolyte to penetrate between the particles of the conductive polymer.

[0061] As the solute, a salt of an anion and a cation is used, and an organic salt in which at least one of the anion and the cation is an organic substance is preferred. Examples of the organic salt include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate. The solute may be used alone or in combination of two or more kinds.

[0062] The impregnation of the capacitor element 10 with the electrolytic solution can be carried out by a known method without any particular limitation. For example, the capacitor element may be immersed in the electrolytic solution, or the electrolytic solution may be poured into a container containing the capacitor element. The impregnation of the capacitor element with the electrolytic solution may be carried out under reduced pressure (for example, 10 to 100 kPa) as necessary.

[0063] (others) Capacitor element 10 may be sealed. More specifically, capacitor element 10 is first housed in bottomed case 11 such that lead wires 14A and 14B are located on the open upper surface of bottomed case 11. The material of bottomed case 11 may be a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy of these metals.

[0064] 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 within bottomed case 11. Sealing member 12 may be made of an insulating material. As the insulating material, an elastic body is preferable, and among them, silicone rubber, fluororubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber (such as Hypalon rubber), butyl rubber, isoprene rubber, and the like, which have high heat resistance, are preferable.

[0065] Next, a horizontal drawing process is performed near the open end of bottomed case 11, and the open end is curled by crimping it to sealing member 12. Then, seat plate 13 is placed on the curled portion to complete the electrolytic capacitor as shown in Fig. 1. After that, an aging process may be performed while applying the rated voltage.

[0066] 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, for example, 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. EXAMPLES

[0067] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0068] Example 1 Using the procedure below, a wound-type electrolytic capacitor (diameter 6.3 mm, length 5.8 mm) with a rated voltage of 35 V and a rated capacitance of 47 μF, as shown in Figure 1, was fabricated and evaluated.

[0069] (1) Manufacturing of electrolytic capacitors (Preparation of anode body with dielectric layer) An aluminum foil having a thickness of 100 μm was subjected to an etching treatment to roughen the surface of the aluminum foil, and then a dielectric layer was formed on the surface of the aluminum foil by a chemical conversion treatment using an aqueous solution of ammonium adipate, thereby preparing an anode body having a dielectric layer.

[0070] (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, thereby preparing a cathode body.

[0071] (Production of capacitor element (wound body)) An anode lead tab and a cathode lead tab were connected to the anode body and the cathode body, and the anode body and the cathode body were wound with the lead tabs interposed therebetween to obtain a capacitor element. An anode lead wire and a cathode lead wire were connected to the ends of the lead tabs protruding from the capacitor element, respectively. The produced capacitor element was then subjected to a chemical conversion treatment again to form a dielectric layer on the cut ends of the anode body. Next, the ends of the outer surface of the capacitor element were fixed with a winding stop tape.

[0072] (Impregnation of first treatment liquid) A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrenesulfonic acid as a dopant in ion-exchanged water (first solvent). While stirring the obtained mixed solution, ferric sulfate and sodium persulfate (oxidizing agent) dissolved in ion-exchanged water were added to carry out a polymerization reaction. After the reaction, the obtained reaction solution was dialyzed to remove unreacted monomers and excess oxidizing agent, and a dispersion liquid (first treatment liquid) containing poly3,4-ethylenedioxythiophene (PEDOT) doped with approximately 5% by mass of polystyrenesulfonic acid was obtained. The capacitor element was impregnated with the obtained first treatment liquid for 5 minutes, and then the capacitor element was heated at 150° C. for 20 minutes to remove the solvent component. In this manner, a capacitor element having a conductive polymer attached thereto was produced.

[0073] (Electrolyte Impregnation) The capacitor element was then impregnated with an electrolyte under reduced pressure, using a solution containing γBL:glycerin:mono(ethyldimethylamine)phthalate (solute) in a mass ratio of 50:25:25.

[0074] (Sealing of capacitor elements) The capacitor element impregnated with the electrolytic solution was housed in an exterior case as shown in Figure 1 and sealed to produce an electrolytic capacitor. A total of 300 electrolytic capacitors were produced in the same manner.

[0075] (2) Performance evaluation (a) Capacitance and ESR value The initial characteristics of the electrolytic capacitor were measured: capacitance (μF) and ESR value (mΩ). Specifically, the initial capacitance (μF) of the electrolytic capacitor was measured at a frequency of 120 Hz using an LCR meter for four-terminal measurement. In addition, the ESR value (mΩ) of the electrolytic capacitor was measured at a frequency of 100 kHz using an LCR meter for four-terminal measurement. As an accelerated test, the electrolytic capacitor was left at 125°C for 4000 hours, after which the capacitance (μF) and ESR value (mΩ) were measured in the same manner as for the initial characteristics described above. The capacitance and ESR values ​​were each measured for 120 randomly selected electrolytic capacitors, and the average values ​​were calculated.

[0076] Comparative Example 1 An electrolytic capacitor was produced and its performance was evaluated in the same manner as in Example 1, except that a solution containing γBL:mono(ethyldimethylamine) phthalate (solute)=75:25 (mass ratio) was used as the electrolyte.

[0077] Example 2 An electrolytic capacitor was fabricated and its performance was evaluated in the same manner as in Example 1, except that a solution containing γBL:sulfolane:glycerin:mono(ethyldimethylamine)phthalate (solute) = 25:25:25:25 (mass ratio) was used as the electrolyte.

[0078] Example 3 An electrolytic capacitor was produced and its performance was evaluated in the same manner as in Example 1, except that a solution containing γBL:glycerin:mono(ethyldimethylamine)phthalate (solute)=70:5:25 (mass ratio) was used as the electrolyte. The results of the examples and comparative examples are shown in Table 1.

[0079] [Table 1]

[0080] As shown in Table 1, in the examples, the capacitance was ensured and the ESR was kept low even after the accelerated test. On the other hand, in the comparative example 1, the capacitance decreased and the ESR increased after the accelerated test. [Industrial Applicability]

[0081] The present invention can be applied to an electrolytic capacitor that uses a conductive polymer as a cathode material. [Explanation of symbols]

[0082] 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 stop tape

Claims

1. An anode body having an uneven surface; a dielectric layer formed on a surface of the anode body; a conductive polymer layer including a conductive polymer and covering at least a portion of a surface of the dielectric layer; an electrolyte solution containing a non-aqueous solvent, a glycerin compound, and an ionic solute, the electrolyte solution being in contact with the dielectric layer and the conductive polymer layer; The conductive polymer contains a dopant, The dopant contains a polyanion having a weight average molecular weight of 1,000 to 1,000,000, the non-aqueous solvent comprises at least one aprotic solvent selected from the group consisting of lactones and sulfones; The content of the glycerin compound in the electrolyte solution is 5% by mass or more and 30% by mass or less, an electrolytic capacitor, wherein a total mass of the lactones and the sulfones contained in the electrolytic solution is greater than a mass of the glycerin compound contained in the electrolytic solution.

2. 2. The electrolytic capacitor according to claim 1, wherein the dopant comprises at least one selected from the group consisting of polystyrene sulfonic acid, a copolymer containing styrene sulfonic acid as a monomer unit, and a polyanion derived from polystyrene sulfonic acid.

3. 10. The electrolytic capacitor of claim 1, wherein the dopant comprises polystyrene sulfonic acid.

4. An anode body having an uneven surface; a dielectric layer formed on a surface of the anode body; a conductive polymer layer including a conductive polymer and covering at least a portion of a surface of the dielectric layer; an electrolyte solution containing a non-aqueous solvent, a glycerin compound, and an ionic solute, the electrolyte solution being in contact with the dielectric layer and the conductive polymer layer; The conductive polymer contains a dopant, The dopant comprises polystyrene sulfonic acid; the non-aqueous solvent comprises at least one aprotic solvent selected from the group consisting of lactones and sulfones; The content of the glycerin compound in the electrolyte solution is 5% by mass or more and 30% by mass or less, an electrolytic capacitor, wherein a total mass of the lactones and the sulfones contained in the electrolytic solution is greater than a mass of the glycerin compound contained in the electrolytic solution.

5. 5. The electrolytic capacitor according to claim 1, wherein the conductive polymer comprises at least one selected from the group consisting of polythiophene and derivatives thereof, and the dopant.

6. 6. The electrolytic capacitor according to claim 1, wherein the non-aqueous solvent contains at least one aprotic solvent selected from the group consisting of γ-butyrolactone and sulfolane.

7. 7. The electrolytic capacitor according to claim 1, wherein the non-aqueous solvent contains γ-butyrolactone.

8. A method for producing the electrolytic capacitor according to any one of claims 1 to 7, comprising the steps of: a treatment liquid in which the conductive polymer is dissolved or dispersed in a liquid solvent is applied to the anode body on which the dielectric layer is formed, thereby forming the conductive polymer layer.

9. An anode body having an uneven surface; a dielectric layer formed on a surface of the anode body; a conductive polymer layer including a conductive polymer and covering at least a portion of a surface of the dielectric layer; a method for producing an electrolytic capacitor comprising: an electrolytic solution containing a non-aqueous solvent, a glycerin compound, and an ionic solute, the electrolytic solution being in contact with the dielectric layer and the conductive polymer layer, the method comprising: the non-aqueous solvent comprises at least one aprotic solvent selected from the group consisting of lactones and sulfones; The content of the glycerin compound in the electrolyte solution is 5% by mass or more and 30% by mass or less, the total mass of the lactones and the sulfones contained in the electrolytic solution is greater than the mass of the glycerin compound contained in the electrolytic solution, a treatment liquid in which the conductive polymer is dissolved or dispersed in a liquid solvent is applied to the anode body on which the dielectric layer is formed, thereby forming the conductive polymer layer.

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