JP2016004914A - Method of manufacturing electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor having reduced ESR.SOLUTION: A method of manufacturing an electrolytic capacitor comprises a first step of preparing for an anode body having a dielectric layer, a second step of impregnating the anode body with first treatment liquid in which electroconductive polymer is dissolved or dispersed in first solvent, a third step of removing a part of the first solvent impregnated in the anode body after the second step, and a fourth step of impregnating the anode body with second treatment liquid containing second solvent which is immingled with the first solvent, thereby obtaining a capacitor element after the third step. In the third step, the anode body is exposed to an environment of 15°C or more in temperature and 60% or more in relative humidity.

Description

  The present invention relates to a method for manufacturing an electrolytic capacitor, and more particularly to a method for manufacturing an electrolytic capacitor having low ESR characteristics.

  Along with the digitization of electronic equipment, a capacitor used therefor is required to have a small size, a large capacity, and a low equivalent series resistance (ESR) in a high frequency range.

  As a small-sized, large-capacity, low-ESR capacitor, an electrolytic capacitor using a conductive polymer such as polypyrrole, polythiophene, polyfuran, or polyaniline as a cathode material is promising. For example, a capacitor element has been proposed in which a solid electrolyte layer containing a conductive polymer as a cathode material is provided on an anode foil on which a dielectric layer is formed.

  In Patent Document 1, an anode body having a dielectric layer is immersed in a dispersion of a conductive polymer, and then dried to form a solid electrolyte layer, and then contacted with a solvent or a solution and dried again. A method for obtaining a solid electrolytic capacitor has been proposed.

JP 2011-109024 A

  In patent document 1, after forming a solid electrolyte layer through a drying process, it is made to contact with another solvent and solution. This is because the adhesion between the solid electrolyte layer and the dielectric layer is improved by passing through the drying step. Further, when the solvent remains in the solid electrolyte layer, there is a concern about fluctuations in characteristics of the obtained capacitor. However, in the method of Patent Document 1, it may be difficult to reduce ESR.

  According to a first aspect of the present invention, there is provided a first step of preparing an anode body having a dielectric layer, and impregnating the anode body with a first treatment liquid in which a conductive polymer is dissolved or dispersed in a first solvent. After the second step, after the second step, a third step of removing a part of the first solvent impregnated in the anode body, and after the third step, the anode solvent and the first solvent And a fourth step of obtaining a capacitor element by impregnating a second treatment liquid containing a second solvent to be mixed, and in the third step, the anode body is placed in an atmosphere having a temperature of 15 ° C. or higher and a relative humidity of 60% or higher. It is related with the manufacturing method of the electrolytic capacitor exposed to.

  According to the present invention, an electrolytic capacitor with reduced ESR can be obtained.

It is a cross-sectional schematic diagram of the electrolytic capacitor obtained by one Embodiment of this invention. It is the schematic for demonstrating the structure of the capacitor | condenser element obtained by the same embodiment.

  Hereinafter, the present invention will be described more specifically based on embodiments. However, the following embodiments do not limit the present invention.

≪Electrolytic capacitor≫
FIG. 1 is a schematic cross-sectional view of an electrolytic capacitor obtained by the manufacturing method according to the present embodiment, and FIG. 2 is a schematic developed view of a part of the capacitor element according to the electrolytic capacitor.

  In FIG. 1, an electrolytic capacitor includes 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 14 </ b> A and 14 </ b> B led out from the sealing member 12 and penetrating the seat plate 13, and lead tabs 15 </ b> A and 15 </ b> B for connecting each lead wire and each electrode of the capacitor element 10 are provided. The vicinity of the open end of the bottomed case 11 is drawn inward, and the open end is curled so as to caulk the sealing member 12.

  The capacitor element 10 is produced from the element. The element is a semi-finished product of the capacitor element 10 and includes an anode body 21 having a dielectric layer, and a solid electrolyte layer containing a conductive polymer is not formed. As shown in FIG. 2, the element may include an anode body 21 connected to the lead tab 15A, a cathode body 22 connected to the lead tab 15B, and a separator 23. In this case, since the anode body 21 and the cathode body 22 are wound through the separator 23, this element is also referred to as a wound body (hereinafter referred to as an anode body (element) having a dielectric layer. May be referred to as a round body). The outermost periphery of the wound body is fixed by a winding tape 24. In addition, FIG. 2 has shown the state by which one part was expand | deployed before stopping the outermost periphery of a wound body.

  The anode body 21 includes a metal foil roughened so that the surface has irregularities, and a dielectric layer is formed on the metal foil having irregularities.

  Capacitor element 10 has a solid electrolyte layer covering at least part of the surface of the dielectric layer formed on the metal foil. The solid electrolyte layer may cover at least a part of the surface of the cathode body 22 and / or the separator 23. Capacitor element 10 may be housed in an outer case made up of bottomed case 11, sealing member 12, and the like together with the electrolytic solution.

≪Method for manufacturing electrolytic capacitor≫
Hereinafter, an example of the method for manufacturing the electrolytic capacitor according to the present embodiment will be described for each process.

(I) Step of preparing anode body 21 having a dielectric layer (first step)
First, a metal foil that is a raw material of the anode body 21 is prepared. 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 the valve metal because the dielectric layer can be easily formed.

  Next, the surface of the metal foil is roughened. By roughening, a plurality of irregularities are formed on the surface of the metal foil. The roughening is preferably performed by etching the metal foil. The etching process may be performed by, for example, a direct current electrolytic method or an alternating current electrolytic method.

  Next, a dielectric layer is formed on the surface of the roughened metal foil. Although the formation method of a dielectric material layer is not specifically limited, It can form by performing a chemical conversion treatment of metal foil. As the chemical conversion treatment, for example, a metal foil may be immersed in a chemical conversion solution such as an ammonium adipate solution to apply a voltage.

  Usually, from the viewpoint of mass productivity, a roughening treatment and a chemical conversion treatment are performed on a foil (metal foil) such as a large valve metal. In that case, the anode body 21 is prepared by cutting the foil after processing into a desired size.

(Ii) Step of Preparing Cathode Body 22 Similarly to 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 action metal such as aluminum, tantalum, or niobium or an alloy containing the valve action metal. If necessary, the surface of the cathode body 22 may be roughened.

(Iii) Production of Winding Body Next, a winding body is produced using the anode body 21 and the cathode body 22.
First, the anode body 21 and the cathode body 22 are wound through the separator 23. At this time, by winding the lead tabs 15A and 15B while winding them, the lead tabs 15A and 15B can be planted from the wound body as shown in FIG.

  As the material of the separator 23, for example, a nonwoven fabric mainly composed of cellulose, nylon, polyethylene terephthalate, vinylon, aramid fiber, or the like can be used.

  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 each of the lead tabs 15A and 15B is not particularly limited as long as it is a conductive material.

  Next, the winding tape 24 is disposed on the outer surface of the cathode body 22 located in the outermost layer among the wound anode body 21, cathode body 22 and separator 23, and the end of the cathode body 22 is fastened. Secure with tape 24. When the anode body 21 is prepared by cutting a large-sized metal foil, the wound body may be further subjected to chemical conversion treatment in order to provide a dielectric layer on the cut surface of the anode body 21. .

(Iv) Step of impregnating the anode body (rolled body) with the first treatment liquid (second step)
Next, a conductive polymer solution in which the conductive polymer is dissolved in the first solvent or a first treatment liquid that is a conductive polymer dispersion containing the first solvent and particles of the conductive polymer is wound. Impregnating the rotating body and applying the first treatment liquid to the wound body.

  A method for impregnating the wound body with the first treatment liquid is not particularly limited. For example, a method of immersing the wound body in the first treatment liquid accommodated in the container, a method of dropping the first treatment liquid onto the wound body, or the like can be used. The impregnation time is, for example, 1 second to 5 hours, preferably 1 minute to 30 minutes, depending on the size of the wound body. The impregnation may be performed under reduced pressure. Moreover, you may provide an ultrasonic vibration to a wound body or a 1st process liquid, immersing a wound body in a 1st process liquid.

  Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polythiophene vinylene, and the like. These may be used alone or in combination of two or more, or may be a copolymer of two or more monomers.

  In the present specification, polypyrrole, polythiophene, polyfuran, polyaniline and the like mean polymers having a basic skeleton of polypyrrole, polythiophene, polyfuran, polyaniline and the like, respectively. Accordingly, polypyrrole, polythiophene, polyfuran, polyaniline and the like can also include respective derivatives. For example, polythiophene includes poly (3,4-ethylenedioxythiophene) and the like.

  The conductive polymer contained in the conductive polymer solution is dissolved in the first solvent. Further, the conductive polymer contained in the conductive polymer dispersion is dispersed in the first solvent in the form of particles. The conductive polymer dispersion can be obtained by, for example, a method of dispersing conductive polymer particles in a first solvent, or by polymerizing a precursor monomer of a conductive polymer in the first solvent, and conducting the conductive polymer in the first solvent. It can be obtained by a method of generating a conductive polymer particle.

  The conductive polymer may contain a dopant. A polyanion can be used as the dopant. As the polyanion, a polyanion derived from polystyrene sulfonic acid is preferable. Specific examples of polyanions include 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, poly Anions such as acrylic acid can be mentioned. These may be used alone or in combination of two or more. These may be a single monomer polymer or a copolymer of two or more monomers.

  Although the weight average molecular weight of a polyanion is not specifically limited, For example, it is 1,000-1,000,000. Such a polyanion is easily dispersed homogeneously in the first solvent and is likely to form a homogeneous solid electrolyte layer.

  When the conductive polymer is dispersed in the first solvent in the form of particles, the average particle diameter D50 of the particles is preferably 0.01 to 0.5 μm, for example. Here, the average particle diameter D50 is a median diameter in a volume particle size distribution measured by a particle size measuring apparatus using a dynamic light scattering method.

  The concentration of the conductive polymer (including the dopant or polyanion) in the first treatment liquid is preferably 0.5 to 10% by mass. The first treatment liquid containing the conductive polymer at such a concentration is suitable for forming a solid electrolyte layer having an appropriate thickness and is easy to be impregnated into the wound body, so that the productivity can be improved. It is advantageous.

  The first solvent may be water, a mixture of water and a non-aqueous solvent, or a non-aqueous solvent. The non-aqueous solvent is a general term for liquids excluding water and liquids containing water, and includes organic solvents and ionic liquids. The first solvent is not particularly limited, and may be a protic solvent or an aprotic solvent. Examples of the protic solvent include alcohols such as methanol, ethanol, 1-propanol, butanol, ethylene glycol, propylene glycol, polyethylene glycol, diethylene glycol monobutyl ether, glycerin and polyglycerin, and ethers such as formaldehyde and 1,4-dioxane. And water. Examples of the aprotic solvent include amides such as N-methylacetamide, N, N-dimethylformamide and N-methyl-2-pyrrolidone, esters such as methyl acetate and γ-butyrolactone, and ketones such as methyl ethyl ketone. And sulfur-containing compounds such as dimethyl sulfoxide and sulfolane, and carbonate compounds such as propylene carbonate. As a 1st solvent, these may be used independently and may be used in combination of 2 or more type.

  In particular, the first solvent preferably contains a protic solvent. Furthermore, it is preferable that the 1st solvent contains 50 mass% or more of water. In this case, the handleability and the dispersibility when the conductive polymer is dispersed are improved. Further, since the first solvent has a low viscosity, it can be expected that the contact property between the conductive polymer and the second solvent is improved.

(V) Step of removing a part of the first solvent impregnated in the anode body (rolled body) (third step)
Next, a part of the first solvent is evaporated and removed by exposing the wound body provided with the first treatment liquid to an atmosphere having a temperature of 15 ° C. or higher and a relative humidity of 60% or higher. The temperature for evaporating a part of the first solvent is preferably 25 ° C. or higher. The upper limit of the evaporation temperature is preferably 85 ° C, and more preferably 60 ° C. Further, the upper limit of the relative humidity is preferably 100%, and more preferably 90%.

  The winding body to which the first treatment liquid is applied is dried under a mild condition of an atmosphere having a temperature of 15 ° C. or more and a relative humidity of 60% or more, thereby making it possible to make the arrangement of the conductive polymer uniform during the drying process. It is considered to go forward. Further, as will be described later, in the subsequent impregnation step of the second treatment liquid, the uniform arrangement of the conductive polymer proceeds.

  The evaporation amount of the first solvent is preferably 10 to 80% by mass, and more preferably 10 to 50% by mass. The exposure time may be appropriately selected depending on the amount to be evaporated, and may be, for example, 5 minutes to 12 hours.

  Here, when the mass of the wound body immediately after the first treatment liquid is applied is 1A, the mass of the wound body immediately before the second treatment liquid is applied is 2B, and the mass of the wound body is 1B, The evaporation amount (ratio) of one solvent is [(1A-1B) × mixing ratio of the first solvent in the first treatment liquid − {(2B-1B) − (1A-1B) × conductivity in the first treatment liquid]. The ratio of the first solvent evaporated from the wound body is represented by {(1A-1B) × the mixing ratio of the first solvent in the first treatment liquid)}, represented by It can be calculated by dividing by the amount of the first solvent given to the wound body represented and multiplying by 100.

  When the evaporation amount of the first solvent is a part of the first solvent applied to the wound body, the second solvent and the conductive polymer are likely to come into contact with each other. It becomes sufficiently uniform and it becomes easy to obtain the desired effect of reducing the ESR value. When all of the first solvent evaporates, the conductive polymer is solidified, and even if the second solvent comes into contact with the conductive polymer, the conductive polymer is less likely to be uniformized. In addition, if the first solvent is not removed, the contact between the conductive polymer and the second solvent is likely to be hindered by the first solvent, and the uniformization of the conductive polymer is difficult to occur.

(Vi) Step of impregnating the anode body (rolled body) with the second treatment liquid (fourth step)
After evaporating a part of the first solvent, the wound body is impregnated with the second treatment liquid containing the second solvent. That is, the second solvent is applied to the surface of the dielectric layer having the remainder of the first solvent and the conductive polymer. Since the first solvent remains on the surface of the dielectric layer, the second solvent that is miscible with the first solvent is applied to the surface of the dielectric layer 31 together with the second solvent. Contact with the conducting polymer. At this time, the second solvent makes the arrangement of the conductive polymer uniform.

  Since the drying process of the first solvent is performed in a humid environment with a relative humidity of 60% or more, the first solvent applied to the wound body is uniformly removed. Therefore, the first solvent remains in a uniform state on the wound body. When the second solvent mixed with the first solvent is impregnated there, the second solvent enters the portion where the first solvent remains uniformly, and the conductive polymer and the second solvent are in contact with each other without unevenness. become. Thereby, the arrangement of the conductive polymer is further uniformized over the entire surface of the dielectric layer. When the relative humidity is lower than 60%, the first solvent does not evaporate uniformly, and a locally dried portion occurs. Therefore, the uniform arrangement of the conductive polymer is not sufficient. Thus, in the drying step and the impregnation step of the second treatment liquid, the conductive polymer is uniformly arranged, whereby the conductivity is improved and the ESR value is reduced.

  The method for impregnating the wound body with the second treatment liquid is not particularly limited, and examples thereof include a method of immersing the wound body in the second treatment liquid and a method of dropping the second treatment liquid onto the wound body. Moreover, you may apply | coat a 2nd process liquid to a wound body.

  The second solvent is not particularly limited as long as it is miscible with the first solvent. Here, mixing means that the first solvent and the second solvent are mixed and become a homogeneous state, and the solvent mixed with the first solvent is mixed with the first solvent and becomes a homogeneous state. A solvent that can be used.

  The second solvent may be the same as or different from the first solvent. The second solvent preferably has an action of further homogenizing the arrangement of the conductive polymer. This is because the effect of reducing the ESR value is further improved. Moreover, it is preferable that a 2nd solvent contains the solvent whose boiling point is higher than a 1st solvent. This is because, in the second solvent removal step (fifth step) performed as necessary, the evaporation of the first solvent is moderated and the arrangement of the conductive polymer is considered to be more uniform.

  As the second solvent, the same solvent as the first solvent can be exemplified. That is, it may be water, a mixture of water and a non-aqueous solvent, or a non-aqueous solvent. The second solvent is not particularly limited, and may be a protic solvent or an aprotic solvent. As a 2nd solvent, these may be used independently and may be used in combination of 2 or more type. Especially, when the 1st solvent contains a protic solvent, it is preferred that the 2nd solvent contains an aprotic solvent. This is because the effect of reducing the ESR value is further improved.

  The second solvent is preferably applied to the wound body in an amount of 200 to 10,000 parts by weight with respect to 100 parts by weight of the conductive polymer applied to the wound body. This is because the uniformity of the arrangement of the conductive polymer is further improved.

  As described above, the solid electrolyte layer is formed between the anode body 21 and the cathode body 22 so as to cover at least a part of the surface of the dielectric layer. At this time, the solid electrolyte layer may be formed not only on the surface of the dielectric layer but also on the surface of the cathode body 22 and / or the separator 23. The solid electrolyte layer formed on the surface of the dielectric layer functions as a practical cathode material.

(Vii) Step of removing at least a part of the second solvent (fifth step)
After impregnating the wound body with the second treatment liquid, at least a part of the second solvent may be removed. Among these, from the viewpoint of fixing the solid electrolyte layer, it is preferable to remove at least a part of the second solvent. Almost all of the second solvent may be removed. When removing the 2nd solvent by heating, the temperature higher than the boiling point of the 2nd solvent may be sufficient as heating temperature, for example, 50-300 ° C is preferred and 100-200 ° C is more preferred. The amount for evaporating the second solvent is not particularly limited. When the first solvent contains water, the water is also removed at this time.

  A step of impregnating the wound body with the first treatment liquid (second step), a step of removing a part of the first solvent (third step), and a step of impregnating the second treatment liquid (fourth step). These may be repeated two or more times as a series of steps. By performing this series of steps a plurality of times, the coverage of the solid electrolyte layer with respect to the dielectric layer can be increased. Moreover, after performing a 2nd process in multiple times, you may perform a 3rd process and a 4th process.

(Viii) Step of impregnating capacitor element with electrolyte (sixth step)
After impregnating the second solvent, the capacitor element may be impregnated with an electrolytic solution. Thereby, the repair function of a dielectric material layer improves, and the withstand voltage characteristic of an electrolytic capacitor can be improved.
The electrolytic solution may be a non-aqueous solvent or a mixture of a non-aqueous solvent and an ionic substance (solute) dissolved therein. As the solute, an organic salt is preferable.

  The non-aqueous solvent may be an organic solvent or an ionic liquid. As the non-aqueous solvent, a high boiling point solvent is preferable. For example, polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane, lactones such as γ-butyrolactone, formaldehyde, N-methylacetamide, N, N-dimethylformamide, N-methyl-2- Amides such as pyrrolidone, esters such as methyl acetate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and the like can be used.

  An organic salt is a salt in which at least one of an anion and a cation contains an organic substance. Examples of organic salts include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono 1,2,3,4-tetramethylimidazolinium phthalate, mono 1,3-dimethyl-2-phthalate Ethyl imidazolinium or the like may be used.

  The method for impregnating the capacitor element 10 with the electrolytic solution is not particularly limited. For example, a method of immersing the capacitor element 10 in an electrolytic solution accommodated in a container, a method of dropping the electrolytic solution onto the capacitor element 10, or the like can be used. The impregnation may be performed under reduced pressure.

(Ix) Capacitor element sealing step (seventh step)
Next, the capacitor element 10 is sealed. Specifically, first, the capacitor element 10 is housed in the bottomed case 11 so that the lead wires 14 </ b> A and 14 </ b> B are positioned on the upper surface of the bottomed case 11. As a material of the bottomed case 11, a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy thereof can be used.

  Next, the sealing member 12 formed so that the lead wires 14 </ b> A and 14 </ b> B penetrate is disposed above the capacitor element 10, and the capacitor element 10 is sealed in the bottomed case 11. The sealing member 12 may be an insulating material. As the insulating substance, an elastic body is preferable, among which silicone rubber, fluorine rubber, ethylene propylene rubber, hyperon rubber, butyl rubber, isoprene rubber, and the like having high heat resistance are preferable.

  Next, a lateral drawing process is performed in the vicinity of the opening end of the bottomed case 11, and the opening end is caulked by caulking the sealing member 12. And the electrolytic capacitor as shown in FIG. 1 is completed by arrange | positioning the seat board 13 in a curl part. Then, you may perform an aging process, applying a rated voltage.

  In the above embodiment, the wound type electrolytic capacitor has been described. However, the scope of the present invention is not limited to the above, and other electrolytic capacitors, for example, a chip type electrolytic capacitor using a metal sintered body as an anode body. The present invention can also be applied to a capacitor or a multilayer electrolytic capacitor using a metal plate as an anode body.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to an Example.

Example 1
In this example, a wound type electrolytic capacitor (Φ8 mm × L (length) 12 mm) having a rated voltage of 100 V and a rated capacitance of 15 μF was produced. Below, the specific manufacturing method of an electrolytic capacitor is demonstrated.

(Process for preparing anode body)
Etching was performed on an aluminum foil having a thickness of 100 μm to roughen the surface of the aluminum foil. Thereafter, a dielectric layer was formed on the surface of the aluminum foil by chemical conversion treatment. Thereafter, the aluminum foil was cut so that the length × width was 6 mm × 120 mm to prepare an anode body.

(Process for preparing cathode body)
The aluminum foil having a thickness of 50 μm was etched to roughen the surface of the aluminum foil. Thereafter, the aluminum foil was cut so that the length × width was 6 mm × 120 mm to prepare a cathode body.

(Production of wound body)
The anode lead tab and the cathode lead tab were connected to the anode body and the cathode body, and the anode body and the cathode body were wound through the separator while winding the lead tab. An anode lead wire and a cathode lead wire were respectively connected to the end portions of the lead tabs protruding from the wound body. Then, the formed wound body was subjected to chemical conversion treatment again, and a dielectric layer was formed on the cut end portion of the anode body. Next, the end of the outer surface of the wound body was fixed with a winding tape to produce a wound body.

(Preparation of first treatment liquid)
A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid as a dopant in ion-exchanged water (first solvent). While stirring the resulting mixed solution, a p-toluenesulfonic acid ferric salt solution (oxidant) dissolved in ion-exchanged water was added to perform a polymerization reaction. After the reaction, the resulting reaction solution was dialyzed to remove unreacted monomers and excess oxidant to obtain a solution containing polyethylene dioxythiophene doped with about 5% by mass of polystyrene sulfonic acid. Imidazole was uniformly dispersed in the obtained solution to obtain a first treatment liquid. The particle of the conductive polymer is a median diameter in a volume particle size distribution measured by a particle size measuring device by dynamic light scattering method (manufactured by Horiba, Ltd., dynamic light scattering particle size distribution measuring device LB-500). Was 100 nm.

(Impregnation of the first treatment liquid)
In a reduced-pressure atmosphere (40 kPa), the wound body was immersed for 5 minutes in the first treatment liquid contained in a predetermined container, and then the wound body was pulled up from the first treatment liquid.

(Removal of the first solvent)
Next, the wound body was dried in an environment of 45 ° C. and a relative humidity of 60% for 30 minutes to remove a part of the first solvent. At this time, the evaporation amount of the first solvent was 40% by mass.

(Impregnation of the second treatment liquid)
Next, the wound body was impregnated with a second treatment liquid containing dimethyl sulfoxide (second solvent). At this time, 1,000 mass parts of 2nd solvent was provided with respect to 100 mass parts of conductive polymers provided to the wound body.

(Removal of second solvent)
The wound body impregnated with the second treatment liquid was dried in a drying furnace at 150 ° C. for 20 minutes to remove at least a part of the second solvent, and a capacitor element having a solid electrolyte layer was produced.

(Impregnation with electrolyte)
The capacitor element was impregnated with a mixed solvent (nonaqueous solvent) of γ-butyrolactone and sulfolane in a reduced pressure atmosphere (40 kPa).

(Capacitor element sealing)
The capacitor element impregnated with the nonaqueous solvent was sealed to complete an electrolytic capacitor as shown in FIG. Thereafter, an aging treatment was performed at 130 ° C. for 2 hours while applying a rated voltage.

  The obtained electrolytic capacitor was measured for capacitance, ESR, and leakage current (LC). The results are shown in Table 1.

Further, in order to evaluate long-term reliability, it is held at 125 ° C. for 1000 hours while applying a rated voltage, and the ESR increase rate (ΔESR: ratio of ESR (X) after 1000 hours holding to the initial value (X ₀ )) (X / X ₀ )) was determined. The case where ΔESR was 1.2 or less was evaluated as ○, and the case where ΔESR exceeded 1.2 was evaluated as ×. The results are also shown in Table 1. Each characteristic value is an average value of 300 samples.

<< Examples 2 to 4 and Comparative Examples 1 to 4 >>
An electrolytic capacitor was produced in the same manner as in Example 1 except that the first solvent was evaporated under the conditions shown in Table 1, and evaluated in the same manner as described above. In Example 4, ethylene glycol was used as the second solvent, and in Comparative Example 3, the first solvent was not evaporated.

  In Examples 1 to 4, both ESR and leakage current were low. This is considered to be a result of an increase in the uniformity of the arrangement of the conductive polymer because the conditions for removing a part of the first solvent were mild. In Comparative Example 4 in which the first solvent was completely removed, the ESR was very large.

  For reference, the characteristics of the electrolytic capacitor were evaluated in the same manner as in Example 1 by leaving it to stand under conditions of a temperature of 25 ° C. and a relative humidity of 0% to evaporate a part of the first solvent. The results are shown in Table 2.

  From the results in Table 2, it was found that ESR was also reduced by increasing the evaporation rate of the first solvent to 10 to 50% by mass. The reason for this is not clear, but can be considered as follows.

  When impregnating the second solvent, the first solvent remains in the wound body. Therefore, the conductive polymer is not yet solidified sufficiently. If the 2nd solvent mixed with the 1st solvent is given there, a 2nd solvent will enter into the part in which the 1st solvent of a winding object exists, and conductive polymer and the 2nd solvent will contact. Become. Thereby, the arrangement of the conductive polymer is made more uniform. As a result, the conductivity is improved and the ESR value is reduced.

  That is, it is considered that one of the points for reducing the ESR value is that the conductive polymer and the second solvent come into contact with each other. The more the contact between the conductive polymer and the second solvent, the more the ESR value. The reduction effect becomes higher. The remaining amount of the first solvent greatly affects the contact between the conductive polymer and the second solvent.

  That is, a step of preparing an anode body having a dielectric layer, a step of impregnating the anode body with a first treatment solution in which the conductive polymer is dissolved or dispersed in a first solvent, and impregnation of the anode body. After the step of evaporating 10 to 50% by mass of the first solvent contained in the first treatment liquid and the step of evaporating the first solvent, the second solvent mixed with the first solvent in the anode body The electrolytic capacitor obtained by the manufacturing method having a step of obtaining a capacitor element by impregnating with has low ESR characteristics.

  In addition, the method and conditions for evaporating the first solvent are not particularly limited, and examples include heat drying and reduced pressure drying. The evaporation amount of the first solvent is preferably 15 to 25% by mass. If the amount of evaporation is within this range, the effect of reducing the ESR value is further increased.

  The present invention can be used for an electrolytic capacitor having a solid electrolyte layer as a cathode material.

  10: capacitor element, 11: bottomed case, 12: sealing member, 13: seat plate, 14A, 14B: lead wire, 15A, 15B: lead tab, 21: anode body, 22: cathode body, 23: separator, 24 : Winding tape

Claims (5)

A first step of preparing an anode body having a dielectric layer;
A second step of impregnating the anode body with a first treatment liquid in which a conductive polymer is dissolved or dispersed in a first solvent;
A third step of removing a part of the first solvent impregnated in the anode body after the second step;
After the third step, a fourth step of impregnating the anode body with a second treatment liquid containing a second solvent mixed with the first solvent to obtain a capacitor element,
In the third step, the electrolytic capacitor is manufactured by exposing the anode body to an atmosphere having a temperature of 15 ° C. or higher and a relative humidity of 60% or higher.   2. The method for producing an electrolytic capacitor according to claim 1, wherein in the third step, 10 to 50 mass% of the first solvent contained in the impregnated first treatment liquid is removed.   The method for producing an electrolytic capacitor according to claim 1, further comprising a fifth step of removing at least a part of the second solvent after the fourth step.   The manufacturing method of the electrolytic capacitor as described in any one of Claims 1-3 with which the said 1st solvent contains 50 mass% or more of water.   The manufacturing method of the electrolytic capacitor as described in any one of Claims 1-4 which has a 6th process which impregnates the electrolyte solution to the said capacitor | condenser element after the said 4th process.

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