WO2014119311A1

WO2014119311A1 - Electrolytic capacitor manufacturing method and electrolytic capacitor

Info

Publication number: WO2014119311A1
Application number: PCT/JP2014/000474
Authority: WO
Inventors: 慶明石丸; 貴行松本
Original assignee: 三洋電機株式会社; 佐賀三洋工業株式会社
Priority date: 2013-01-31
Filing date: 2014-01-30
Publication date: 2014-08-07
Also published as: JPWO2014119311A1; JP6326633B2

Abstract

This electrolytic capacitor manufacturing method involves a step for preparing a positive electrode body having a dielectric film, a step for preparing a first liquid composition containing a first conductive polymer, a step for impregnating the positive electrode body with the first liquid composition and thereafter drying the same to form a capacitor element that has a solid electrolyte layer disposed on the surface of the dielectric film and containing the first conductive polymer, a step for preparing a second liquid composition that contains a non-aqueous solvent and a second conductive polymer dissolved in the non-aqueous solvent, a step for impregnating the capacitor element with the second composition, and a step for housing the capacitor element impregnated with the second liquid composition in an exterior case.

Description

Electrolytic capacitor manufacturing method and electrolytic capacitor

The present invention relates to an electrolytic capacitor manufacturing method and an electrolytic capacitor, and more particularly to a wound electrolytic capacitor manufacturing method.

With the digitization of electronic devices, the capacitors used for them are also required to be small, large in capacity, and have low equivalent series resistance (ESR) in the high frequency range.

Conventionally, plastic film capacitors, multilayer ceramic capacitors, and the like are frequently used as capacitors for high-frequency regions, but these have a relatively small capacity.

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 conductive polymer layer is provided as a cathode material on an anode foil on which a dielectric coating is formed.

Patent Document 1 proposes to form a conductive polymer layer by immersing a capacitor element in a solution obtained by dissolving a soluble conductive polymer in a solvent and then drying the capacitor element. . In Patent Document 2, a conductive polymer layer is formed by immersing a capacitor element in a dispersion obtained by dispersing conductive polymer particles or powder in a dispersion medium and then drying the capacitor element. Propose that. Thereafter, the capacitor element is sealed in the case together with the electrolytic solution, and the electrolytic capacitor is completed through aging.

Japanese Patent Laid-Open No. 05-144677 JP 2008-10657 A

However, in Patent Documents 1 and 2, the conductive polymer may dissolve into the electrolyte from the conductive polymer layer, and the conductivity of the conductive polymer layer may gradually decrease. Therefore, the ESR changes with time, and it is difficult to ensure the long-term reliability of the electrolytic capacitor.

In view of the above, an object of the present invention is to provide an electrolytic capacitor manufacturing method and an electrolytic capacitor excellent in long-term reliability.

One aspect of the present invention includes a step of preparing an anode body having a dielectric coating, a step of preparing a first liquid composition containing a first conductive polymer, and the anode body including the first liquid composition. Forming a capacitor element having a solid electrolyte layer containing the first conductive polymer on the surface of the dielectric coating, impregnating, and then drying, a non-aqueous solvent, and the non-aqueous solvent Preparing a second liquid composition containing a second conductive polymer dissolved in the capacitor, impregnating the capacitor element with the second liquid composition, and impregnating the second liquid composition And a step of accommodating the capacitor element in an outer case.

According to the above method, since the second conductive polymer is dissolved in the nonaqueous solvent existing around the solid electrolyte layer containing the first conductive polymer, the first conductivity from the solid electrolyte layer is reduced. Dissolution of the polymer into the non-aqueous solvent is suppressed. This is presumably because the dissolution of the first conductive polymer into the non-aqueous solvent has an aspect as an equilibrium reaction.

The second conductive polymer may include the same monomer unit as the monomer unit constituting the first conductive polymer. Thereby, the dissolution of the first conductive polymer into the non-aqueous solvent is further suppressed.

The boiling point of the nonaqueous solvent in the second liquid composition is preferably 100 ° C. or higher from the viewpoints of heat resistance and reflow resistance. Moreover, the density | concentration of the 2nd conductive polymer contained in a 2nd liquid composition should just be 0.5 mass% or more and a saturation concentration or less, for example.

Another aspect of the present invention includes a capacitor element having an anode body having a dielectric film, a solid electrolyte layer including a first conductive polymer formed on a surface of the dielectric film, a non-aqueous solvent, A liquid composition (second liquid composition) impregnated in the capacitor element, and the second liquid composition impregnated with the second conductive polymer dissolved in the non-aqueous solvent. And an outer case containing a capacitor element, wherein the concentration of the second conductive polymer contained in the second liquid composition is 0.5 mass% or more and a saturation concentration or less.

According to the present invention, since the dissolution of the first conductive polymer from the solid electrolyte layer into the non-aqueous solvent is suppressed, the change in ESR with time is reduced, and the long-term reliability of the electrolytic capacitor is improved.

It is a cross-sectional schematic diagram of the electrolytic capacitor which concerns on one Embodiment of this invention. It is the schematic for demonstrating the structure of the capacitor | condenser element which concerns on the same embodiment. It is a cross-sectional schematic diagram which shows the principal part structure in the capacitor | condenser element which concerns on the same embodiment.

In the method for producing an electrolytic capacitor of the present invention, the anode body having a dielectric film is impregnated with the first liquid composition containing the first conductive polymer, and then dried, so that the surface of the dielectric film is A solid electrolyte layer containing a first conductive polymer is formed. Such a method is easier than a method of generating a conductive polymer by a polymerization reaction. Therefore, it is possible to provide an electrolytic capacitor with low cost, low ESR, and low leakage current.

By impregnating the anode body on which the solid electrolyte layer is formed as described above with a non-aqueous solvent, it is possible to improve the withstand voltage of the electrolytic capacitor and to enhance the repair ability of the dielectric film. On the other hand, when a non-aqueous solvent is present around the solid electrolyte layer, a phenomenon in which the first conductive polymer is dissolved in the non-aqueous solvent is observed due to the molecules of the non-aqueous solvent attacking the solid electrolyte layer. When such elution progresses over a long period of time, the conductivity of the solid electrolyte layer decreases and ESR increases. Therefore, from the viewpoint of improving the long-term reliability of the electrolytic capacitor, in the present invention, a second liquid composition (hereinafter referred to as a second liquid composition) containing a non-aqueous solvent and a second conductive polymer dissolved in the non-aqueous solvent. (Also referred to as a polymer solution) is impregnated in an anode body having a solid electrolyte layer.

The dissolution of the conductive polymer from the solid electrolyte layer into the nonaqueous solvent has an aspect as an equilibrium reaction. Therefore, when the conductive polymer is dissolved in the nonaqueous solvent, the dissolution of the conductive polymer from the solid electrolyte layer is suppressed, the change in ESR over time is reduced, and the long-term reliability of the electrolytic capacitor is improved. .

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 according to the present embodiment, FIG. 2 is a schematic diagram in which a part of the capacitor element according to the embodiment is developed, and FIG. 3 is an anode body in the capacitor element. It is a cross-sectional schematic diagram which shows the principal part structure containing the interface of a solid electrolyte layer.

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

14A and 14B led out from the sealing member 12 and penetrating the seat plate 13, and

lead tabs

15A and 15B connecting the lead wires and the electrodes 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 be crimped to the sealing member 12.

As shown in FIG. 2, the capacitor element 10 includes an anode body 21 connected to the lead tab 15A, a cathode body 22 connected to the lead tab 15B, and a separator 23. The anode body 21 and the cathode body 22 are wound through a separator 23. 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.

More specifically, the capacitor element 10 includes an anode body 21 having a dielectric film and a solid electrolyte layer containing a first conductive polymer formed on the surface of the dielectric film. As shown in FIG. 3, the anode body 21 is preferably made of a metal foil or a metal sintered body having a concave portion on the surface. A dielectric coating 31 is provided on the anode body 21 having a recess. A solid electrolyte layer 32 containing a conductive polymer is provided between the dielectric coating 31 and the separator 23.

The capacitor element 10 is impregnated with a second liquid composition 33 containing a non-aqueous solvent and a second conductive polymer dissolved in the non-aqueous solvent. The capacitor element impregnated with the second liquid composition 33 is accommodated in the outer case. Here, the concentration of the second conductive polymer contained in the second liquid composition 33 is, for example, not less than 0.5 mass% and not more than the saturation concentration.
≪Method for manufacturing electrolytic capacitor≫
Next, an example of a method for manufacturing the electrolytic capacitor according to the present embodiment will be described.
(I) Step of Preparing Anode Body Having Dielectric Film 31 First, the anode body 21 having the dielectric film 31 is prepared. As the anode body 21, a metal foil can be used. Specifically, the surface of the metal foil cut into a predetermined size is roughened. The type of metal is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium because the dielectric film 31 can be easily formed. In roughening, a plurality of recesses are formed on the surface of the metal foil. For example, a plurality of recesses can be formed on the surface of the metal foil by etching the metal foil.

Next, a dielectric coating 31 is formed on the surface of the roughened anode body 21. The method of forming the dielectric film 31 is not particularly limited. For example, when the anode body 21 is made of a valve metal, the anode body 21 is subjected to chemical conversion treatment to form the dielectric film 31 on the surface of the anode body 21. can do. In the chemical conversion treatment, for example, the anode body 21 is immersed in a chemical conversion solution such as an ammonium adipate solution and heat-treated. Alternatively, the voltage may be applied by immersing the anode body 21 in the chemical conversion solution. Usually, from the viewpoint of mass productivity, roughening treatment and chemical conversion treatment are performed on a large-sized valve action metal foil. In that case, the anode body 21 can be prepared by cutting the treated metal foil into a desired size.
(Ii) Production of wound body Next, a wound body is produced using the anode body 21. The wound body is a semi-finished product of the capacitor element 10 and means that the solid electrolyte layer 32 is not formed between the anode body 21 and the cathode body 22 or the separator 23.

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.

The cathode body 22 is made of, for example, a metal foil cut to the same size as the anode body 21. The type of metal is not particularly limited, and for example, a valve metal such as aluminum, tantalum, or niobium can be used. Chemical conversion treatment may be performed on the surface of the cathode body 22 in the same manner as the anode body 21.

As the material of the separator 23, for example, a nonwoven fabric mainly composed of synthetic cellulose, 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 metal foil, a chemical conversion treatment may be further performed on the wound body in order to provide a dielectric coating on the cut surface of the anode body 21. .
(Iii) Step of impregnating the wound body with the first liquid composition Next, the anode body 21 is impregnated with the first liquid composition by impregnating the wound body with the first liquid composition. The first liquid composition is, for example, a solution containing a solvent and a first conductive polymer dissolved in the solvent (hereinafter also referred to as a first polymer solution), a dispersion medium, and the dispersion medium. Any dispersion liquid (hereinafter also referred to as a first polymer dispersion liquid) may be used as long as it contains the first conductive polymer dispersed in the liquid crystal. The solvent and the dispersion medium 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. For example, alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, formaldehyde, N-methylacetamide, N, N-dimethylformamide, N-methyl-2 -Amides such as pyrrolidone, esters such as methyl acetate, ethers such as 1,4-dioxane, and ketones such as methyl ethyl ketone.

The first conductive polymer contained in the first polymer solution is dissolved in the solvent and is uniformly distributed in the solution. Therefore, the first polymer solution is preferable in that it can easily form a more uniform solid electrolyte layer. The first conductive polymer contained in the first polymer dispersion is dispersed in a dispersion medium in the form of particles or powder. Therefore, even when there is a defect in the dielectric film, it is preferable in that the first conductive polymer does not easily enter the defect and a micro short-circuit hardly occurs. The first polymer dispersion can be obtained, for example, by dispersing the first conductive polymer in the dispersion medium, or by polymerizing the precursor monomer of the first conductive polymer in the dispersion medium. It can be obtained by a method of generating conductive polymer particles.

The concentration of the first conductive polymer in the first polymer solution is preferably 0.5 to 10% by mass, and the concentration of the particles or powder of the first conductive polymer in the first polymer dispersion is also The content is preferably 0.5 to 10% by mass. The first polymer solution or dispersion having 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, and is advantageous in improving productivity. is there.

The first conductive polymer may be, for example, polypyrrole, polythiophene, polyfuran, polyaniline, or the like. In the present specification, polypyrrole, polythiophene, polyfuran and polyaniline mean polymers having polypyrrole, polythiophene, polyfuran and polyaniline as basic skeletons, respectively. Thus, polypyrrole, polythiophene, polyfuran and polyaniline can also include their respective derivatives. These may be used alone or in combination of two or more.

The weight average molecular weight of the first conductive polymer is preferably 1000 to 100,000. This is because such a first conductive polymer is easy to form a homogeneous solid electrolyte layer on the dielectric film, and does not easily enter the defects of the dielectric film. The first conductive polymer may have a cross-linked structure. When the first conductive polymer is dispersed in the dispersion medium in the form of particles or powder, the average particle diameter D50 of the particles or powder 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 obtained by a laser diffraction particle size distribution measuring apparatus.

The method for impregnating the wound body with the first liquid composition is not particularly limited, but for example, a method of immersing the wound body in the first liquid composition housed in the container is simple and preferable. The immersion 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 is preferably performed under reduced pressure, for example, in an atmosphere of 10 to 100 kPa, preferably 40 to 100 kPa. Further, ultrasonic vibration may be applied to the wound body or the first liquid composition while being immersed in the first liquid composition.
(Iv) Step of drying the wound body to form a solid electrolyte layer Next, the wound body is pulled up from the first liquid composition, and the wound body is dried, whereby the surface of the dielectric coating 31 is formed. 1 A solid electrolyte layer containing a conductive polymer is formed. At this time, a solid electrolyte layer may be formed not only on the surface of the dielectric coating 31 but also on the surfaces of the separator and the cathode foil.

After elevating the wound body from the first liquid composition, the anode body 21 may be heated to promote evaporation of the solvent or the dispersion medium. The temperature for heating the anode body is preferably, for example, 50 to 300 ° C., particularly preferably 100 to 200 ° C.

The step (iii) of impregnating the wound body with the first liquid composition and the step (iv) of forming the solid electrolyte layer by drying the wound body may be repeated twice or more. By performing these steps a plurality of times, the coverage of the solid electrolyte layer 32 with respect to the dielectric coating 31 can be increased.

Thus, the solid electrolyte layer 32 is formed between the anode body 21 and the separator 23, and the capacitor element 10 is manufactured. Note that the solid electrolyte layer formed on the surface of the dielectric film effectively functions as a cathode material. Therefore, the anode body provided with the solid electrolyte layer can be referred to as a capacitor element by itself.
(V) Step of impregnating the capacitor element with the second liquid composition Next, the anode body 21 (capacitor element) on which the solid electrolyte layer is formed is coated with a nonaqueous solvent and the second conductive polymer dissolved therein. The second liquid composition 33 is impregnated. As a result, the second liquid composition 33 enters the gaps of the capacitor element, particularly the gaps of the solid electrolyte layer 32 formed on the dielectric coating 31. Further, since the second liquid composition 33 can also enter the gaps in the dielectric film 31 that is not covered with the solid electrolyte layer 32, the repair function of the dielectric film 31 is improved. Furthermore, since the second conductive polymer is dissolved in the second liquid composition 33, the dissolution of the first conductive polymer from the solid electrolyte layer into the second liquid composition 33 is suppressed.

The second conductive polymer preferably contains the same monomer unit as the monomer unit constituting the first conductive polymer. Thereby, the effect of suppressing the dissolution of the first conductive polymer into the non-aqueous solvent (second liquid composition) is increased. Therefore, when the first conductive polymer is polypyrrole, polythiophene, polyfuran, or polyaniline, the second conductive polymer is preferably polypyrrole, polythiophene, polyfuran, or polyaniline, respectively.

The weight average molecular weight of the second conductive polymer is preferably 1000 to 100,000. This is because such a second conductive polymer is easily dissolved in a non-aqueous solvent and does not easily increase the viscosity of the second polymer solution.

The non-aqueous solvent in the second liquid composition is not particularly limited as long as it is a solvent that dissolves the second conductive polymer, and examples thereof include propylene glycol, sulfolane, γ-butyrolactone, and ethylene glycol. The boiling point of the non-aqueous solvent is preferably 100 ° C. or higher, and more preferably 200 ° C. or higher. This is because the second liquid composition remains in the capacitor element, so that it is desired to have excellent heat resistance and reflow resistance. The second liquid composition may further contain an electrolyte component such as an organic salt. By containing the electrolyte component, it is easy to obtain an electrolytic capacitor with low ESR and high reliability.

From the viewpoint of suppressing the dissolution of the first conductive polymer into the second liquid composition, it is desirable that the concentration of the second conductive polymer contained in the second liquid composition is high, but when the concentration is high, The viscosity of the second liquid composition increases. Therefore, the concentration of the second conductive polymer contained in the second liquid composition is preferably 0.5% by mass or more and a saturation concentration or less, and preferably 1% by mass or more and 5% by mass or less. . If the concentration of the second conductive polymer is 0.5% by mass or more, the concentration is sufficiently high and the effect of suppressing the dissolution of the first conductive polymer into the second liquid composition is high. Become. When the concentration of the second conductive polymer exceeds the saturation concentration, the second conductive polymer is precipitated in the capacitor element, which may cause an internal short circuit.

The method of impregnating the wound liquid body with the second liquid composition is not particularly limited, but a method of immersing the wound body in the second liquid composition housed in the container is simple and preferable. The immersion time is, for example, 1 second to 5 minutes, depending on the size of the wound body. The impregnation is preferably performed under reduced pressure, for example, in an atmosphere of 10 to 100 kPa, preferably 40 to 100 kPa.

Note that the second liquid composition may contain an organic salt as an ionic substance. An organic salt is a salt in which at least one of an anion and a cation contains an organic substance. As the organic salt, an organic amine salt is preferable, and a salt of an organic amine and an organic acid is particularly preferable. Specifically, trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono 1,2,3,4-tetramethylimidazolinium phthalate, mono 1,3-dimethyl-2-ethyl imidazole phthalate Linium or the like can be used. The concentration of the organic salt in the second liquid composition can be 5 to 50% by weight, for example. Note that the second liquid composition may be referred to as an electrolytic solution regardless of whether or not the ionic substance is dissolved.
(Vi) Step of sealing the capacitor element Next, the capacitor element 10 is sealed. Specifically, first, the capacitor element 10 is accommodated in the bottomed case 11 so that the lead wires 14 </ b> A and 14 </ b> B are positioned on the upper surface where the bottomed case 11 is opened. 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, lateral drawing is performed in the vicinity of the opening end of the bottomed case 11, and the opening end is crimped to the sealing member 12 for curling. 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 (Φ8.0 mm × L (length) 12.0 mm) having a rated voltage of 35 V and a rated capacitance of 22 μF was produced. Below, the specific manufacturing method of an electrolytic capacitor is demonstrated.
(I) Step of preparing an anode body First, the aluminum foil was etched to roughen the surface of the aluminum foil. Thereafter, a dielectric coating was formed on the surface of the aluminum foil by chemical conversion treatment. The chemical conversion treatment was performed by immersing an aluminum foil in an ammonium adipate solution and applying a voltage thereto. Thereafter, the aluminum foil was cut so that the length × width was 6 mm × 120 mm to prepare an anode body.
(Production of wound body)
Next, a separator and a cathode body having the same area as the anode body were prepared, and the anode body and the cathode body were wound through the separator while winding the lead tab. Next, the end of the outer surface of the wound body was fixed with a winding tape to produce a wound body.

An aluminum foil was used as the cathode body, and a lead wire was connected to the end protruding from the wound body of the lead tab. Then, the formed wound body was subjected to a chemical conversion treatment again, and a dielectric film was formed on the cut end portion of the anode body.
(Preparation of the first liquid composition)
A toluene solution containing 3% by mass of polyaniline, which is a first conductive polymer having a weight average molecular weight of 10,000 to 20,000, was prepared as a first liquid composition.
(Impregnation of the first liquid composition)
The wound body was immersed in the first liquid composition for 5 minutes in a reduced pressure atmosphere (40 kPa), and then the wound body was pulled up from the first liquid composition.
(Drying the wound body)
The wound body impregnated with the first liquid composition was dried in a drying furnace at 150 ° C. for 20 minutes to form a solid electrolyte layer containing the first conductive polymer on the dielectric film of the anode body.
(Preparation of second liquid composition)
A γ-butyrolactone solution containing 3% by mass of the same conductive polymer as the first conductive polymer (polyaniline having a weight average molecular weight of 10,000 to 20,000) as the second conductive polymer was prepared as the second liquid composition.
(Impregnation of the second liquid composition)
In a reduced pressure atmosphere (40 kPa), the wound body (capacitor element) having the solid electrolyte layer was immersed in the second liquid composition for 5 minutes, and then the wound body was pulled up from the second liquid composition.
(Process of sealing the capacitor element)
The capacitor element impregnated with the second liquid composition was sealed to complete the electrolytic capacitor. Specifically, first, the capacitor element is housed in the bottomed case so that the lead wire is positioned on the opening side of the bottomed case, and the rubber packing which is a sealing member formed so that the lead wire penetrates the capacitor The capacitor element was sealed in the bottomed case by placing it above the element. Then, the electrolytic capacitor as shown in FIG. 1 was completed by drawing the vicinity of the open end of the bottomed case, curling the open end, and arranging a seat plate on the curled portion. Thereafter, an aging treatment was performed at 135 ° C. for 2 hours while applying a rated voltage.

The capacitance and ESR of the obtained electrolytic capacitor were measured. The results are shown in Table 1. Further, a voltage was applied while boosting at a rate of 1.0 V / second, and a breakdown voltage (BDV) in which an overcurrent of 0.5 A flows was measured. Furthermore, in order to evaluate long-term reliability, it was held at 125 ° C. for 1000 hours while applying the rated voltage, and the rate of increase in ESR (ΔESR) was confirmed. With respect to ΔESR, Table 1 shows the case where ESR after holding for 1000 hours is less than 1.5 times the initial value, and × where 1.5 times or more. Each characteristic was determined as an average value of 20 samples.

Example 2
(Preparation of the first liquid composition)
A propylene glycol solution containing 3% by mass of polythiophene, which is a first conductive polymer having a weight average molecular weight of 10,000 to 20,000, was prepared as a first liquid composition.
(Preparation of second liquid composition)
A propylene glycol solution containing 3% by mass of the same conductive polymer (polythiophene having a weight average molecular weight of 10,000 to 20,000) as the first conductive polymer as a second conductive polymer was prepared as a second liquid composition.

An electrolytic capacitor was prepared and evaluated in the same manner as in Example 1 except that the first and second liquid compositions were used. The results are shown in Table 1.
<< Comparative Example 1 >>
(Preparation of second liquid composition)
A γ-butyrolactone solution containing 20% by mass of trimethylamine maleate was prepared.

An electrolytic capacitor was prepared and evaluated in the same manner as in Example 1 except that the second liquid composition was used. The results are shown in Table 1.
<< Comparative Example 2 >>
An electrolytic capacitor was prepared and evaluated in the same manner as in Example 2 except that the same second liquid composition as in Comparative Example 1 was used. The results are shown in Table 1.

From Table 1, when the second liquid composition impregnated in the capacitor element is a solution made of a non-aqueous solvent containing a conductive polymer, the ESR is low, the BDV is high, and the long-term reliability is excellent. Understandable.

The present invention can be used for an electrolytic capacitor, and in particular, can be suitably used for an electrolytic capacitor using an anode body having a plurality of fine concave portions on the surface.

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, 31: dielectric coating, 32: solid electrolyte layer, 33: second liquid composition

Claims

Preparing an anode body having a dielectric coating;
Preparing a first liquid composition containing a first conductive polymer;
A step of forming a capacitor element having a solid electrolyte layer containing the first conductive polymer on the surface of the dielectric coating by impregnating the anode body with the first liquid composition and then drying. When,
Preparing a second liquid composition comprising a non-aqueous solvent and a second conductive polymer dissolved in the non-aqueous solvent;
Impregnating the capacitor element with the second liquid composition;
And a step of housing the capacitor element impregnated with the second liquid composition in an outer case.
The method for producing an electrolytic capacitor according to claim 1, wherein the second conductive polymer includes the same monomer unit as the monomer unit constituting the first conductive polymer.
The method for producing an electrolytic capacitor according to claim 1 or 2, wherein the first conductive polymer includes at least one selected from the group consisting of polyaniline and a polyaniline derivative.
The method for producing an electrolytic capacitor according to any one of claims 1 to 3, wherein a boiling point of the non-aqueous solvent is 100 ° C or higher.
The production of the electrolytic capacitor according to any one of claims 1 to 4, wherein a concentration of the second conductive polymer contained in the second liquid composition is 0.5 mass% or more and a saturation concentration or less. Method.
A capacitor element comprising: an anode body having a dielectric coating; and a solid electrolyte layer containing a first conductive polymer formed on a surface of the dielectric coating;
A liquid composition comprising a non-aqueous solvent and a second conductive polymer dissolved in the non-aqueous solvent, and impregnating the capacitor element;
An outer case containing the capacitor element impregnated with the liquid composition;
Comprising
The electrolytic capacitor whose density | concentration of the said 2nd conductive polymer contained in the said liquid composition is 0.5 mass% or more and a saturated concentration or less.