Manufacturing method for electrolytic capacitors

Abstract

The objective is to provide a method for manufacturing electrolytic capacitors with good characteristics. [Solution] A method for manufacturing an electrolytic capacitor containing a conductive polymer is provided, comprising (a) providing a capacitor element, (b) impregnating the capacitor element with a conductive polymer-containing dispersion, and (c) drying the capacitor element impregnated with the conductive polymer-containing dispersion, characterized in that, during impregnation, the lower end of the capacitor element is brought into contact with the dispersion to allow the dispersion to penetrate into the capacitor element.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electrolytic capacitor.

Background Art

[0002] Conventionally, solid electrolytic capacitors using a conductive polymer compound as a solid electrolyte are known. Such capacitors can exhibit low ESR properties and excellent low-temperature characteristics.

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

[0004] As a method for manufacturing the above electrolytic capacitor, a method of immersing a capacitor element in a liquid containing a conductive polymer compound or a precursor thereof is known.

[0005] Patent Document 1 describes a method for manufacturing an electrolytic capacitor using a capacitor element having a winding stop tape on the side surface and a conductive polymer precursor solution, wherein the conductive polymer precursor solution is brought into contact with the upper end side relative to the winding stop tape, so that the conductive polymer precursor solution penetrates into the capacitor element.

[0006] Patent Document 2 describes a method for manufacturing a solid electrolytic capacitor that includes immersing the entire electrolytic capacitor in a liquid containing a conductive polymer.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of Invention

[0008] Conventional immersion methods sometimes failed to produce electrolytic capacitors with sufficient characteristics.

[0009] This disclosure aims to provide a method for manufacturing a capacitor that can provide an electrolytic capacitor having good characteristics. [Means for solving the problem]

[0010] The present invention can solve the above problems in the following embodiments. <Aspect 1> A method for manufacturing an electrolytic capacitor containing a conductive polymer, (a) To provide a capacitor element, (b) Impregnating the capacitor element with a conductive polymer-containing dispersion, (c) Drying the capacitor element impregnated with the conductive polymer-containing dispersion, Includes, The impregnation process is characterized by bringing the lower end portion of the capacitor element into contact with the dispersion and allowing the dispersion to penetrate into the capacitor element. method. <Aspect 2> The method according to embodiment 1, wherein, during the impregnation (b), the lower end of the capacitor element is brought into contact with the dispersion and held under reduced pressure for 250 to 350 seconds, thereby allowing the dispersion to penetrate into the capacitor element. <Aspect 3> The method according to embodiment 1 or 2, wherein, during the impregnation (b), the lower end of the capacitor element is brought into contact with the dispersion liquid to allow the dispersion liquid to permeate into the capacitor element, and then the capacitor element is removed from the dispersion liquid without immersing the entire body of the capacitor element in the dispersion liquid. <Aspect 4> The method according to embodiment 1 or 2, wherein, during the impregnation (b), the lower end of the capacitor element is brought into contact with the dispersion liquid to allow the dispersion liquid to permeate into the capacitor element, the entire body of the capacitor element is then immersed in the dispersion liquid, and the capacitor element is subsequently removed from the dispersion liquid. <Aspect 5> The method according to any one of embodiments 1 to 4, wherein the conductive polymer contained in the conductive polymer-containing dispersion is in the form of fine particles. <Aspect 6> The method according to any one of embodiments 1 to 5, wherein the capacitor element is a wound-type capacitor element having an anode having an oxide film, a cathode, and a separator and solid electrolyte between the anode and the cathode. <Aspect 7> The method according to any one of embodiments 1 to 6, wherein when the lower end portion of the capacitor element is brought into contact with the dispersion, 1 / 10 to 6 / 10 of the dimension of the capacitor element in the height direction is impregnated into the dispersion. <Aspect 8> The method according to any one of embodiments 1 to 7, wherein the capacitor element has a non-water-repellent winding-retaining tape for preventing the capacitor element from unraveling. <Pattern 9> The capacitor element has a winding-retaining tape to prevent the capacitor element from unwinding, and when the lower end of the capacitor element is brought into contact with the dispersion, the conductive polymer-containing dispersion does not come into contact with the side surface of the capacitor element above the winding-retaining tape, according to any one of embodiments 1 to 8. <Aspect 10> During the aforementioned impregnation, (b1) Depressurizing the chamber in which the storage tank containing the conductive polymer-containing dispersion is installed to a predetermined pressure, (b2) The lower end of the capacitor element is immersed in the conductive polymer-containing dispersion by raising the liquid level at a predetermined rate, and then left to stand for a predetermined time while maintaining a reduced pressure state. (b3) while the capacitor element remains immersed in the conductive polymer-containing dispersion, returning the inside of the chamber to the state before pressure reduction, and leaving it to stand for a predetermined period of time, The method for producing an electrolytic capacitor according to any one of aspects 1 to 9, comprising the above. <Aspect 11> A method for producing an electrolytic capacitor containing a conductive polymer, comprising: (a) providing a capacitor element, (b) impregnating the capacitor element with a conductive polymer-containing dispersion, wherein a lower end portion of the capacitor element is brought into contact with the dispersion to allow the dispersion to permeate into the capacitor element, and (c) drying the capacitor element impregnated with the conductive polymer-containing dispersion, comprising the above, further comprising, (d) after the impregnation (b) and the drying (c), re-impregnating the capacitor element with the conductive polymer-containing dispersion, and (e) drying the capacitor element re-impregnated with the dispersion, the method comprising the above. <Aspect 12> The method according to aspect 9, wherein in the re-impregnation (d), the entire main body of the capacitor element is immersed in the dispersion. [Advantageous Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a method for producing a capacitor that can provide an electrolytic capacitor with favorable characteristics. In particular, according to the present disclosure, it is possible to provide a production method capable of providing an electrolytic capacitor having favorable characteristics, for example, favorable characteristics in terms of capacitance, tanδ, ESR, and the like. [Brief Description of the Drawings]

[0012] [Figure 1] Figure 1 shows an example of an impregnation step in a conventional method for producing an electrolytic capacitor. [Figure 2] Figure 2 shows an impregnation step (partial immersion) in one aspect of the production method of the present invention. [Figure 3] Figure 3 shows an impregnation step (partial immersion + full immersion) in another embodiment of the manufacturing method of the present invention. [Figure 4a] Figure 4a is a schematic cross-sectional view of a solid electrolytic capacitor according to one embodiment of the present disclosure. [Figure 4b] Figure 4b is a schematic perspective view of a capacitor element according to one embodiment of the present disclosure. [Figure 5] Figure 5 is a schematic cross-sectional view of the main part of an electrolytic capacitor. [Modes for carrying out the invention]

[0013] <<Manufacturing Method for Electrolytic Capacitors>> The method for manufacturing an electrolytic capacitor according to the present invention is: A method for manufacturing an electrolytic capacitor containing a conductive polymer, (a) To provide a capacitor element (providing process), (b) Impregnating the capacitor element with a conductive polymer-containing dispersion (impregnation step), and (c) Drying the capacitor element impregnated with a conductive polymer-containing dispersion (drying step), Includes, The method is characterized by bringing the lower end of the capacitor element into contact with the dispersion during impregnation, thereby allowing the dispersion to penetrate into the capacitor element.

[0014] The method for manufacturing the electrolytic capacitor of the present invention will be described with reference to the drawings. The drawings are illustrative and do not limit the present invention. The drawings are not to scale. In the drawings, H represents the height direction and W represents the width direction.

[0015] Conventionally, a method is known for manufacturing electrolytic capacitors having a conductive polymer compound as an electrolyte by impregnating a capacitor element with a liquid containing a conductive polymer.

[0016] In conventional manufacturing methods, the entire capacitor element is immersed in a liquid containing a conductive polymer. In this case, it is not possible to sufficiently impregnate the capacitor element with the liquid, resulting in a problem where the characteristics of the resulting capacitor are not sufficient.

[0017] Figure 1 shows an example of a conventional electrolytic capacitor manufacturing method. In the example in Figure 1, the entire capacitor element 20 is completely immersed in a liquid 50 containing a conductive polymer (1-c to 1-d). In this case, the liquid 50 containing the conductive polymer may not penetrate sufficiently to the center of the capacitor element. Although not shown in the figure, a method of impregnation using a precursor (monomer) of a conductive polymer instead of a conductive polymer is also known.

[0018] In contrast, in this invention, the lower end of the capacitor element is brought into contact with a conductive polymer-containing dispersion, allowing the dispersion to penetrate into the capacitor element. In this disclosure, this impregnation method is referred to as "partial immersion." According to this invention, a capacitor with sufficient characteristics can be provided.

[0019] Figure 2 shows the impregnation step in one embodiment of the manufacturing method of the invention. In the example in Figure 2, after steps 2-b to 2-d, in which the lower end of the capacitor element 20 is brought into contact with the dispersion 50 and the dispersion is allowed to permeate into the capacitor element, the capacitor element is removed from the dispersion without immersing the entire body of the capacitor element in the dispersion (2-e). In this case, the conductive polymer-containing dispersion has sufficiently permeated to the center of the capacitor element.

[0020] In this disclosure, the "lower end" of the capacitor element refers to the circular bottom surface, for example, in the case of a cylindrical capacitor element. It is sufficient that the "lower end" of the capacitor element is in contact, and in this case, the portion of the side of the capacitor element adjacent to the "lower end" (particularly the side) may be immersed in the dispersion. Preferably, the portion of the side of the capacitor element immersed in the dispersion in this case is 6 / 10 or less of the height of the capacitor element, and in one particular embodiment, it is 2 / 10 or less or even 1 / 10 or less.

[0021] On the other hand, the "entire body" of a capacitor element refers to the part that is intended to be impregnated with a conductive polymer-containing dispersion, that is, the "impregnation portion" of the capacitor element. This corresponds to the part in the resulting electrolytic capacitor where the solid electrolyte is formed, and in the case of a cylindrical electrolytic capacitor, for example, it corresponds to the part in which the anode foil and cathode foil are wound.

[0022] In a preferred embodiment of the present invention, the lower end of the capacitor element is brought into contact with the dispersion and held under reduced pressure (particularly 4 kPa to 12 kPa) for 250 to 350 seconds, thereby allowing the dispersion to penetrate into the capacitor element.

[0023] Although not limited by theory, in the conventional method of immersing the entire capacitor element in liquid without performing "partial immersion" from the lower end, the liquid penetrates from both the upper and lower ends in the height direction. As a result, the air originally contained within the capacitor element has no escape route during the penetration process, and it is thought that air enters the resulting capacitor element. When air enters the capacitor element, it is more likely to cause a decrease in the capacitance appearance rate and oxidation of the conductive polymer, making it impossible to obtain a capacitor with sufficient characteristics. This problem is particularly serious as the height dimension of the capacitor element increases, so it is thought that this will also impose constraints on the size of the capacitor.

[0024] Furthermore, in conventional methods that involve impregnation using a precursor solution of conductive polymer, the polymerization reaction of monomers proceeds as the precursor solution penetrates the capacitor element. As a result, before the polymerization solution can sufficiently penetrate the interior of the capacitor element, the solidified conductive polymer may inhibit further penetration of the precursor solution.

[0025] Although not limited by theory, according to the present invention, the lower end of the capacitor element is brought into contact with a conductive polymer-containing dispersion, and it is believed that the dispersion penetrates toward the upper end of the capacitor element due to capillary action. In this case, the air inside the capacitor element is effectively pushed out to the outside as the conductive polymer-containing dispersion penetrates the capacitor element, so it is believed that a capacitor element with relatively little air inside can be obtained. Furthermore, it is believed that the degree of freedom in the height dimension of the capacitor element is also improved.

[0026] Furthermore, since a conductive polymer-containing dispersion is used in this invention, it is believed that problems such as the penetration being inhibited by the conductive polymer solidified within the capacitor element by polymerization, which can occur when a precursor is used, will not occur.

[0027] The manufacturing method according to this disclosure is particularly advantageous when impregnating wound capacitor elements. Wound capacitor elements have gaps at their lower and upper ends corresponding to the void between the anode foil and cathode foil, through which the conductive polymer-containing dispersion can penetrate into the capacitor element, and the dispersion medium (particularly water) of the conductive polymer-containing dispersion can also penetrate into the capacitor element via the separator. In the method according to this disclosure, by performing "partial immersion," a good balance is brought about among these multiple penetration paths, and as a result, good impregnation of the conductive polymer compound can be obtained.

[0028] Figure 3 shows an impregnation step in another embodiment of the manufacturing method of the invention. In the example in Figure 3, after steps 3-b to 3-d ("partial immersion") in which the lower end of the capacitor element 20 is brought into contact with the dispersion 50 and the dispersion penetrates into the capacitor element, the entire body of the capacitor element is impregnated in the dispersion for a predetermined time (3-e to 3-f), and the capacitor element is removed from the dispersion (3-g). Even in this case, the conductive polymer-containing dispersion penetrates sufficiently to the center of the capacitor element by "partial immersion".

[0029] The steps of the present invention will be described in more detail below.

[0030] <Process (a)> (Capacitor element) The manufacturing method of the present invention includes providing a capacitor element (step a).

[0031] Examples of capacitor elements include wound-type capacitors having an anode foil with at least an oxide film formed on its surface, a cathode foil, and a separator in the gap between them. The provided capacitor elements may be known ones.

[0032] In one embodiment, the capacitor element has a non-water-repellent winding-retaining tape to prevent the capacitor element from unraveling.

[0033] Other detailed embodiments of the capacitor element will be described later.

[0034] <Process (b)> (Impregnation with conductive polymer-containing dispersion) The manufacturing method of the present invention includes impregnating a capacitor element with a conductive polymer-containing dispersion (step b), characterized in that, during impregnation, the lower end of the capacitor element is brought into contact with the dispersion to allow the dispersion to penetrate into the capacitor element.

[0035] In the "partial immersion" method, the lower end of the capacitor element is brought into contact with the dispersion, and the dispersion is allowed to penetrate the capacitor element by holding it under reduced pressure (particularly 4kPa to 12kPa) for 250 to 350 seconds. The pressure under reduced pressure is preferably 6kPa to 10kPa, and more preferably 9kPa to 10kPa. The holding time is preferably 270 to 330 seconds, and more preferably 290 to 310 seconds.

[0036] Contact of the dispersion with the lower end of the capacitor element may be achieved by raising the liquid level of the dispersion at a predetermined rate. In this case, the liquid level rise may be performed at a rate of 0.2 to 0.8 mm / second, preferably 0.3 to 0.7 mm / second, and more preferably 0.4 to 0.6 mm / second.

[0037] In one particular embodiment, during impregnation, 1 / 10 to 6 / 10, preferably 4 / 10 to 6 / 10, of the capacitor element's height is impregnated into the dispersion. This allows the conductive polymer-containing dispersion to penetrate more deeply into the capacitor element, resulting in an electrolytic capacitor with good capacitor characteristics.

[0038] In one particular embodiment, during impregnation, 1 / 100 to 20 / 100, 1 / 100 to 15 / 100, or even 1 / 100 to 10 / 100 of the dimensions of the capacitor element in the height direction may be impregnated in the dispersion.

[0039] In one embodiment, the capacitor element has a winding-retaining tape to prevent the capacitor element from unwinding, and in the impregnation process, the conductive polymer-containing dispersion does not come into contact with the upper end of the winding-retaining tape on the side of the capacitor element. According to this embodiment, it is possible to prevent the dispersion (or at least the dispersion medium) from penetrating into the capacitor element from both the up and down directions of the winding-retaining tape, thereby preventing the retention of air in the capacitor element and the resulting insufficient impregnation.

[0040] (Examples of specific impregnation conditions for "partial immersion") In one embodiment, the manufacturing method of the present invention, during the impregnation step (b) described above, (b1) Depressurizing the chamber containing a storage tank holding a dispersion liquid containing a conductive polymer to a predetermined pressure. (b2) The lower end of the capacitor element is immersed in a conductive polymer-containing dispersion by raising the liquid level at a predetermined rate, and then left to stand for a predetermined time while maintaining a reduced pressure state. (b3) With the electrolytic capacitor element still immersed in the conductive polymer-containing dispersion, the chamber is returned to its state before depressurization, and left to stand for a predetermined time. Includes.

[0041] In this embodiment, the conductive polymer-containing dispersion penetrates more deeply into the capacitor element, resulting in an electrolytic capacitor with good capacitor characteristics.

[0042] In step (b1), the pressure inside the chamber may be reduced to 4k to 12kPa, preferably to 6k to 10kPa, and more preferably to 9k to 10kPa.

[0043] In step (b2), the liquid level may be raised at a speed of 0.2 to 0.8 mm / second, preferably at 0.3 to 0.7 mm / second, and more preferably at 0.4 to 0.6 mm / second.

[0044] In step (b2), the reduced pressure state may be maintained for 100 to 240 seconds, preferably for 130 to 210 seconds, and more preferably for 160 to 180 seconds.

[0045] In process (b3), the state before depressurization can be atmospheric pressure.

[0046] In step (b3), after returning to the state before depressurization, the system may be left to stand for 70 to 170 seconds, preferably 90 to 150 seconds, and more preferably 110 to 130 seconds.

[0047] (Partial immersion only) In one embodiment, during impregnation, the lower end of the capacitor element is brought into contact with the dispersion liquid to allow the dispersion liquid to permeate into the capacitor element ("partial immersion"), and then the capacitor element is removed from the dispersion liquid without immersing the entire body of the capacitor element in the dispersion liquid (see Figure 2 as an example).

[0048] For details regarding "partial immersion" in this embodiment, please refer to the description above.

[0049] According to this embodiment, since the dispersion penetrates into the capacitor element from only one direction (the lower end), it is possible to suppress or prevent air from remaining in the capacitor element, thereby ensuring that the dispersion is sufficiently impregnated into the capacitor element.

[0050] (half immersion + full immersion) In another embodiment, during impregnation, the lower end of the capacitor element is brought into contact with the dispersion to allow the dispersion to penetrate into the capacitor element ("partial immersion"), then the entire capacitor element is immersed in the dispersion ("full immersion"), and then the capacitor element is removed from the dispersion (see Figure 3 as an example).

[0051] In this embodiment, although the entire capacitor element is fully immersed, sufficient penetration is achieved through partial immersion beforehand. This differs from conventional methods in which the entire capacitor element is immersed, and the effects of partial immersion can be obtained.

[0052] In other words, according to this embodiment, by performing "partial immersion" to allow the dispersion to penetrate (impregnate) into the capacitor element from one direction, and then immersing the entire capacitor element in the dispersion, it is possible to minimize the undesirable effects caused by the dispersion penetrating the capacitor element from multiple directions, while simultaneously obtaining the desirable effects of immersing the entire capacitor in the dispersion.

[0053] For details regarding "partial immersion" in this embodiment, please refer to the description above.

[0054] The partial immersion may be performed for 100 to 260 seconds, preferably for 150 to 210 seconds, and more preferably for 170 to 190 seconds.

[0055] "Total immersion" may be performed for 50 to 190 seconds, preferably for 90 to 150 seconds, and more preferably for 110 to 130 seconds.

[0056] In this embodiment, immersion of the entire capacitor element body in the dispersion ("total immersion") may be performed by raising the liquid level of the dispersion at a predetermined rate. In this case, the liquid level rise may be performed at a rate of 0.01 to 1.0 mm / second, preferably 0.02 to 0.5 mm / second, and more preferably 0.03 to 0.07 mm / second.

[0057] "Total immersion" is preferably carried out under reduced pressure, for example, under ambient atmospheric pressure of 4k to 12kPa, preferably 6k to 10kPa, and more preferably 7k to 9kPa.

[0058] (Dispersion containing conductive polymer) A conductive polymer-containing dispersion refers to a dispersion in which a conductive polymer compound and an optional dopant are dispersed in a dispersion medium. Suitable dispersion media for a conductive polymer-containing dispersion include, for example, water, protic solvents such as alcohol (e.g., methanol, ethanol, 1-propanol, butanol), and mixtures thereof. A conductive polymer compound solution may be used instead of a conductive polymer-containing dispersion; in this case, suitable solvents for the conductive polymer compound solution include, for example, water, protic solvents such as alcohol (e.g., methanol, ethanol, 1-propanol, butanol), and mixtures thereof.

[0059] (conductive polymer) Examples of conductive polymers (conductive polymer compounds) include at least one selected from polythiophene, polypyrrole, and polyaniline, as well as their derivatives. The conductive polymer may be at least one of these. Preferably, the conductive polymer is a polymer of EDOT and its derivatives. Particularly preferred conductive polymers are polyethylenedioxythiophene (PEDOT) (especially poly(3,4-ethylenedioxythiophene)).

[0060] In one embodiment, the conductive polymer contained in the conductive polymer-containing dispersion is in the form of fine particles. This allows the conductive polymer-containing dispersion to penetrate sufficiently into the capacitor element, resulting in an electrolytic capacitor with good capacitor characteristics.

[0061] The average particle size of the particulate conductive polymer may be 1 nm to 600 nm, preferably 1 nm to 300 nm, or even more preferably in the range of 5 nm to 200 nm (e.g., 20 nm). The average particle size of the particulate conductive polymer can be determined, for example, from the particle size distribution obtained by dynamic light scattering.

[0062] (Dopant) The conductive polymer-containing dispersion further contains a dopant. The dopant may be a polyanion. Specific examples of dopants include aromatic sulfonic acids such as benzenesulfonic acid or its derivatives, naphthalenesulfonic acid or its derivatives, and anthraquinonesulfonic acid or its derivatives; polymeric sulfonic acids such as polystyrene sulfonic acid (PSS), sulfonated polyesters, phenolsulfonic acid novolac resins, and copolymers of styrenesulfonic acid and non-sulfonic monomers (such as methacrylic acid esters, acrylic acid esters, unsaturated hydrocarbon-containing alkoxysilane compounds or their hydrolysates); and chain-like sulfones such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid. These may be used individually or in combination of two or more.

[0063] Polystyrene sulfonic acid (PSS) with a weight-average molecular weight of 10,000 to 1,000,000 is preferred.

[0064] In a particularly preferred embodiment, the conductive polymer-containing dispersion comprises polyethylenedioxythiophene (PEDOT) as the conductive polymer compound and polystyrene sulfonic acid (PSS) as the dopant.

[0065] A conductive polymer compound dispersion can be produced, for example, by polymerizing (radical polymerization or oxidative polymerization) a monomer in a suspended state (e.g., EDOT monomer) to produce a conductive polymer compound (e.g., PEDOT polymer) to which dopants and emulsifiers have been added, and then dispersing the conductive polymer compound in a predetermined dispersion medium. The average particle size of the conductive polymer compound can be adjusted by appropriately setting the polymerization reaction conditions (e.g., concentrations of initiators, monomers, polymerization aids, etc., reaction temperature, stirring conditions of the reaction solution, etc.). It can also be adjusted by known grinding treatments (e.g., stirring grinding, vibration grinding, etc.). Furthermore, the particle size can be made uniform by preparative filtration.

[0066] As a specific example of a method for preparing a conductive polymer compound dispersion, the preparation procedure (i) to (v) for a PEDOT / PSS fine particle dispersion is shown below: (i) Prepare a PEDOT / PSS fine particle dispersion (e.g., 2% by mass) using ethylenedioxythiophene (EDOT) monomer and polystyrene sulfonic acid (PSS). (ii) Remove excess cationic and / or anionic components by ion exchange treatment. (iii) The process is carried out using a rotary homogenizer or an ultrasonic homogenizer to produce microparticles. (iv) Adjust the pH to 2-5 by neutralization treatment. (v) Add a high-boiling point compound to the PEDOT / PSS fine particle dispersion. This may improve conductivity.

[0067] <Process (c)> The manufacturing method of the present invention includes drying a capacitor element impregnated with a conductive polymer-containing dispersion (step c). The drying method may be a known method, but for example, it may be carried out by heat drying, which removes the dispersion medium or solvent from the voids, thereby forming an electrolyte portion in the void between the anode foil and the cathode foil.

[0068] <<Methods including "double impregnation">> One aspect of the manufacturing method of the present invention is: (a) To provide a capacitor element, (b) Impregnating the capacitor element with a conductive polymer-containing dispersion, (c) Drying the capacitor element impregnated with a conductive polymer-containing dispersion, Includes, During impregnation (b), the lower end of the capacitor element is brought into contact with the dispersion liquid, allowing the dispersion liquid to penetrate into the capacitor element. moreover, (d) After drying (c), the capacitor element is impregnated again with a dispersion containing a conductive polymer, and (e) Dry the capacitor element that has been re-impregnated with the dispersion. Includes.

[0069] By performing this two-step impregnation process, the conductive polymer-containing dispersion penetrates more deeply into the capacitor element, potentially resulting in a capacitor with even better characteristics.

[0070] For details of steps (a) to (c) of the "double impregnation" method, please refer to the above descriptions regarding "partial immersion" and "partial immersion + full immersion".

[0071] In step (d), the capacitor element that has been impregnated with the conductive polymer dispersion is impregnated with the conductive polymer dispersion again.

[0072] The second impregnation in step (d) may be carried out in the same manner as the first impregnation step, i.e., step (b) above. Examples of combinations of the first impregnation step and the second impregnation step include the following: (d a ) 1st time "half immersion" → 2nd time "half immersion" (d b ) 1st time “half immersion” → 2nd time “half immersion + full immersion” (d c ) 1st time “half immersion + full immersion” → 2nd time “half immersion” (d d ) 1st time “Half immersion + Full immersion” → 2nd time “Half immersion + Full immersion” (d e ) 1st time “half immersion” → 2nd time “full immersion”

[0073] In one embodiment, the entire body of the capacitor element is immersed in the dispersion during the second impregnation step (d).

[0074] In step (e) of the "double impregnation" method, the capacitor element that has been impregnated again with the dispersion is dried. This drying step may be carried out by a known method.

[0075] (Regarding full immersion after partial immersion) When partial immersion is followed by full immersion, the full immersion may be performed by raising the liquid level of the dispersion at a speed of, for example, 0.5 mm / second or more, thereby immersing the entire capacitor element in the dispersion. In the capacitor manufacturing process, it is known that impregnation of the element with a conductive polymer-containing dispersion is performed solely by full immersion at such a speed without any partial immersion (referred to as "conventional filling"), and the method is not particularly limited. In the manufacturing method including "double impregnation" according to the present invention, a capacitor with particularly excellent characteristics can be obtained by performing such full immersion after partial immersion.

[0076] When performing full immersion after partial immersion, the full immersion may be performed by raising the liquid level of the dispersion at a speed of less than 0.5 mm / second to immerse the entire capacitor element in the dispersion. Capacitors with particularly excellent characteristics can also be obtained by performing full immersion at such a speed after "partial immersion".

[0077] In one embodiment, when performing full immersion after partial immersion, the rise in the liquid level during full immersion may be carried out at a speed of 0.01 to 1.0 mm / second, preferably 0.02 to 0.5 mm / second, and more preferably 0.03 to 0.07 mm / second.

[0078] (Capacitor element) The following describes the details of the capacitor elements that can be used with each of the above manufacturing methods.

[0079] The capacitor element is not particularly limited, and its thickness, size, and shape are not particularly limited. For example, a cylindrical element may have a height (H) dimension of 3 to 17 mm, or even 6 to 12 mm, and an element diameter of 4 to 13 mm, or even 5 to 10 mm.

[0080] Examples of capacitor elements include those having an anode foil with an oxide film formed on its surface, a cathode foil, and a separator in the gap between them.

[0081] (Anode foil) The anode foil may be formed from a valve metal such as aluminum, tantalum, or niobium.

[0082] The anode foil has an oxide film on its surface. For example, an oxide film can be formed on the surface of the anode foil by roughening the surface by etching according to a known method and then by a chemical conversion treatment.

[0083] (Cathode foil) The cathode foil, like the anode foil, may be formed from a valve metal such as aluminum, tantalum, or niobium. The cathode foil may also be formed from an aluminum alloy containing copper.

[0084] The cathode foil may have an oxide film formed on its surface. For example, the surface of the cathode foil may be roughened by etching, similar to the anode foil, and then an oxide film may be formed by natural oxidation. Alternatively, the cathode foil may be subjected to a chemical conversion treatment at a desired voltage (e.g., 2V), which may also form an oxide film.

[0085] (Separator) Preferably, the separator is made of conductive polymer particles, cellulose fibers that are chemically compatible with water-soluble polymers, or synthetic resins such as nylon, PET, and PPS that have excellent heat resistance. For example, heat-resistant cellulose paper or heat-resistant flame-retardant paper can be used. More specifically, examples of separators include cellulose and mixed papers such as kraft, Manila hemp, esparto, hemp, and rayon; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and their derivatives; polytetrafluoroethylene resins; polyvinylidene fluoride resins; vinylon resins; polyamide resins such as aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides; polyimide resins; polyethylene resins; polypropylene resins; trimethylpentene resins; polyphenylene sulfide resins; acrylic resins; and polyvinyl alcohol resins. These resins can be used individually or in mixtures.

[0086] <Electrolytic capacitors containing conductive polymers> According to the manufacturing method of the present invention, an electrolytic capacitor having a conductive polymer compound as a solid electrolyte can be obtained.

[0087] (Solid electrolyte section) The solid electrolyte portion, composed of a solid electrolyte, exists in the void between the anode foil and the cathode foil. In this disclosure, "the void between the anode foil and the cathode foil" includes not only "the void between the anode foil and the separator and the void between the cathode foil and the separator," but also "the void between fibers within the separator." Furthermore, "the void between the anode foil and the cathode foil" also includes "the void in etching pits (recesses) formed on the surface of the anode foil or cathode foil by roughening through etching."

[0088] The solid electrolyte portion, composed of a solid electrolyte, is in at least partial contact with the oxide film formed on the surface of the anode foil. The solid electrolyte portion contains a conductive polymer compound and a dopant.

[0089] The solid electrolyte portion may take various forms, for example, a continuous, uniform thick or thin layer, a film, or an aggregate of fine particles, or a network of fine particle chains. In particular, the solid electrolyte portion may take the form of a layer of fine particles composed of fine particles containing a conductive polymer compound (and optionally a dopant).

[0090] The solid electrolyte portion is in direct contact with the oxide film of the anode foil, at least partially, and in direct contact with the metal surface and / or oxide film of the cathode foil, at least partially.

[0091] <Configuration of the resulting electrolytic capacitor 1> Figures 4a and 4b are diagrams illustrating the solid electrolytic capacitor 1 obtained by the method of the present invention. Figure 4a is a cross-sectional view of the solid electrolytic capacitor 1, and Figure 4b is a perspective view of the capacitor element 20.

[0092] Figure 5 is a cross-sectional view of the main part of the electrolytic capacitor 1 obtained by the method of the present invention, illustrating the main part of the capacitor.

[0093] The electrolytic capacitor 1 obtained by the method of the present invention is a wound electrolytic capacitor, and as shown in Figure 4a, comprises a bottomed cylindrical metal case 10, a capacitor element 20, and a sealing member 40.

[0094] The bottom of the metal case 10 is nearly circular in shape, and a valve (not shown) is provided near the center. Therefore, when the internal pressure rises, the valve can break, releasing the internal pressure to the outside. The side surfaces of the metal case 10 are erected almost perpendicularly to the outer edge of the bottom surface. The opening of the metal case 10 is sealed by a sealing member 40, and the two leads 29 and 30 of the capacitor element 20 are led out through a through-hole in the sealing member 40.

[0095] The capacitor element 20 is housed inside the metal case 10 and, as shown in Figures 4(b) and 5, comprises an anode foil 21, a cathode foil 23, and a separator 25 disposed between the anode foil 21 and the cathode foil 23, with the anode foil 21 and the cathode foil 23 overlapping and wound together via the separator 25.

[0096] In the embodiment shown in Figure 5, the anode foil 21 and cathode foil 23 each have oxide films 22 and 24 on their surfaces, respectively. A solid electrolyte 26, composed of fine particles of a conductive polymer compound / dopant, is placed in contact with the oxide film 22 on the surface of the anode foil 21, forming a solid electrolyte portion. [Examples]

[0097] Embodiments of the present invention will be described in more detail below with reference to examples. The following examples and comparative examples are not intended to limit the present invention.

[0098] <<Examples 1-3 and Comparative Example 1> In Examples 1-3 and Comparative Example 1, the characteristics of electrolytic capacitors manufactured by contacting the lower end of the capacitor element with a conductive polymer-containing dispersion and allowing it to permeate, or by immersing the entire capacitor element in the dispersion and allowing it to permeate, were evaluated.

[0099] <Example 1 (Partial Immersion)> (Manufacturing of electrolytic capacitors) In Example 1, an electrolytic capacitor was manufactured by bringing the lower end of a capacitor element into contact with a conductive polymer-containing dispersion and allowing it to penetrate (partial immersion). The conductive polymer dispersion was an aqueous solvent dispersion containing conductive polymer compound fine particles composed of 2% by mass of PEDOT and PSS. A capacitor element with a height (H) dimension of 6.4 mm was used.

[0100] The conductive polymer compound dispersion was stored in a storage tank, and the pressure inside the chamber where the storage tank was installed was reduced to 8 kPa. The lower end of the capacitor element was brought into contact with the dispersion at a liquid level rise rate of 0.5 mm / s. The rise was stopped when the liquid level reached 3.2 mm from the bottom surface of the capacitor element (the liquid level when standing under reduced pressure), and it was left standing for 173 seconds. Next, the pressure inside the chamber was returned to atmospheric pressure, and after being left for 120 seconds, the capacitor element was removed from the dispersion by lowering the liquid level. An electrolytic capacitor was obtained by drying the removed capacitor element.

[0101] (Characteristic evaluation) For the electrolytic capacitor obtained in Example 1, the capacitance at 120 Hz and 10 kHz, the tanδ at 120 Hz, and the ESR values ​​at 120 Hz, 10 kHz, and 100 kHz were measured. The results are shown in Table 2 below.

[0102] <Comparative Example 1 (Conventional Filling)> In Comparative Example 1, the electrolytic capacitor according to Comparative Example 1 was manufactured in the same manner as in Example 1, except that the entire body of the capacitor element was brought into contact with the dispersion at a liquid level rise rate of 0.5 mm / s, the entire body of the capacitor element was immersed in the dispersion, and then left to stand for 167 seconds before being returned to atmospheric pressure. The characteristics of the electrolytic capacitor according to Comparative Example 1 were then investigated. The results are shown in Table 2 below.

[0103] [Table 1]

[0104] [Table 2]

[0105] As can be seen in Table 2, the electrolytic capacitor according to Example 1, manufactured by the manufacturing method of the present invention, showed better capacitor characteristics compared to Comparative Example 1, which was manufactured by a manufacturing method in which the entire capacitor element was immersed in a dispersion liquid.

[0106] <<Examples 2-4>> In Examples 2-4, the characteristics of electrolytic capacitors manufactured by contacting and allowing the lower end of a capacitor element to penetrate a conductive polymer-containing dispersion under various reduced-pressure conditions were evaluated.

[0107] <Example 2 (Partial Immersion)> In Example 2, an electrolytic capacitor according to Example 2 was manufactured in the same manner as in Example 1, and its characteristics were investigated. The results are shown in Table 4 below.

[0108] <Example 3 (Partial Immersion)> In Example 3, an electrolytic capacitor according to Example 3 was manufactured in the same manner as in Example 1, except that the liquid level height during standing under reduced pressure was changed as shown in Table 3 below, and its characteristics were investigated. The results are shown in Table 4 below.

[0109] <Example 4 (Partial Immersion)> In Example 4, an electrolytic capacitor according to Example 4 was manufactured in the same manner as in Example 1, except that the liquid level height during standing under reduced pressure was changed as shown in Table 3 below, and its characteristics were investigated. The results are shown in Table 4 below.

[0110] [Table 3]

[0111] [Table 4]

[0112] Table 4 shows the characteristic values ​​of Example 2 as the baseline (100%). As can be seen in Table 4, no difference in characteristics was observed depending on the immersion position for the electrolytic capacitors according to Examples 2 to 4 manufactured by the manufacturing method of the present invention, and all showed good capacitor characteristics.

[0113] <<Examples 5-8 and Comparative Example 1>> <Partial immersion + Full immersion> In Examples 5 to 8, impregnation was performed by first immersing the entire body of the capacitor element in the dispersion ("full immersion") after performing the "partial immersion" method according to the present invention (Table 5).

[0114] <Example 5 (Partial Immersion + Full Immersion)> In Example 5, the lower end of the capacitor element was brought into contact with the dispersion at a liquid level rise rate of 0.5 mm / s, the rise was stopped when the liquid level reached 1 mm from the bottom surface of the capacitor element (liquid level when stationary), and it was left to stand for 169 seconds (standing time). After that, the liquid level was raised at a rate of 0.5 mm / s until the entire capacitor element was immersed in the dispersion, and then returned to atmospheric pressure. Except for these steps, an electrolytic capacitor according to Example 5 was manufactured in the same manner as in Example 1, and its characteristics were investigated. The results are shown in Table 6 below.

[0115] <Example 6 (Partial Immersion + Full Immersion)> In Example 6, an electrolytic capacitor was manufactured in the same manner as in Example 5, except that the liquid level during standing and the standing time were changed as shown in Table 5, and its characteristics were investigated. The results are shown in Table 6 below.

[0116] <Example 7 (Partial Immersion + Full Immersion)> In Example 7, the electrolytic capacitor according to Example 7 was manufactured in the same manner as in Example 5, except that the standing time and the rate of liquid level rise during full immersion were changed as shown in Table 5, and its characteristics were investigated. The results are shown in Table 6 below.

[0117] <Example 8 (Partial Immersion + Full Immersion)> In Example 8, the electrolytic capacitor according to Example 8 was manufactured in the same manner as in Example 5, except that the liquid level during standing, the standing time, and the rate of liquid level rise during full immersion were changed as shown in Table 5, and its characteristics were investigated. The results are shown in Table 6 below.

[0118] [Table 5]

[0119] [Table 6]

[0120] As can be seen in Table 6, the electrolytic capacitors according to Examples 5 to 8, manufactured by the manufacturing method of the present invention, showed better capacitor characteristics compared to Comparative Example 1, which was manufactured by a method in which the entire capacitor element was immersed in the dispersion without partial immersion.

[0121] <<Examples 9-11 and Examples 2-4>> In Examples 9-11, electrolytic capacitors were fabricated using a method including "double impregnation" according to the present invention (Table 7). The results of comparing the characteristics with those of Examples 2-4 are shown in Table 8 below.

[0122] <Example 9 (Partial immersion in the first step → Partial immersion in the second step)> In Example 9, an electrolytic capacitor according to Example 9 was manufactured in the same manner as in Example 1, except that the partially immersed capacitor element was dried and then partially immersed again in the same manner as in Example 1. The characteristics of the capacitor were then investigated. The results are shown in Table 8 below.

[0123] <Example 10 (Partial immersion in the first step → Full immersion in the second step (speed 0.5 mm / s))> In Example 10, an electrolytic capacitor according to Example 10 was manufactured in the same manner as in Example 1, except that the partially immersed capacitor element was dried and then fully immersed under the same conditions as in Comparative Example 1, and its characteristics were investigated. The results are shown in Table 8 below.

[0124] <Example 11 (Partial immersion in the first step → Full immersion in the second step (speed 0.05 mm / s))> In Example 11, an electrolytic capacitor was manufactured in the same manner as in Example 1, except that after drying the partially immersed capacitor element, the entire capacitor element was brought into contact with the dispersion at a liquid level rise rate of 0.05 mm / s, the capacitor element was left to stand for 52 seconds after being fully immersed in the dispersion, then returned to atmospheric pressure, left for 120 seconds, and then the capacitor element was removed from the dispersion by lowering the liquid level, and the capacitor element was dried to obtain an electrolytic capacitor. The characteristics of the electrolytic capacitor according to Example 11 were investigated, and the results are shown in Table 8 below.

[0125] [Table 7]

[0126] [Table 8]

[0127] As can be seen in Table 8, the electrolytic capacitors according to Examples 9 to 11, manufactured using the manufacturing method including "double impregnation" according to the present invention, showed even better capacitor characteristics compared to Examples 2 to 4, which were manufactured using a manufacturing method that involved only one impregnation by partial immersion.

[0128] Furthermore, electrolytic capacitors manufactured using the "first partial immersion → second full immersion" method exhibited even better capacitor characteristics than those manufactured using the "first partial immersion → second partial immersion" method. [Explanation of Symbols]

[0129] 1 Electrolytic capacitor 10 Metal Cases 20 Capacitor elements 21 Anode foil 22, 24 Oxide film 23 Cathode foil 25 Separators 26 Solid electrolyte 27. Liquid substances 29, 30 Lead 40 Sealing material 50 Dispersion containing conductive polymer

Claims

1. A method for manufacturing an electrolytic capacitor containing a conductive polymer, (a) To provide a capacitor element, (b) Impregnating the capacitor element with a conductive polymer-containing dispersion, (c) Drying the capacitor element impregnated with the conductive polymer-containing dispersion, Includes, The impregnation process is characterized by bringing the lower end portion of the capacitor element into contact with the dispersion and allowing the dispersion to penetrate into the capacitor element. method.

2. The method according to claim 1, wherein, during the impregnation (b), the lower end of the capacitor element is brought into contact with the dispersion and held under reduced pressure for 250 to 350 seconds, thereby allowing the dispersion to penetrate into the capacitor element.

3. The method according to claim 1 or 2, wherein, during the impregnation (b), the lower end portion of the capacitor element is brought into contact with the dispersion liquid to allow the dispersion liquid to permeate into the capacitor element, and then the capacitor element is removed from the dispersion liquid without immersing the entire body of the capacitor element in the dispersion liquid.

4. The method according to claim 1 or 2, wherein, during the impregnation (b), the lower end portion of the capacitor element is brought into contact with the dispersion liquid to allow the dispersion liquid to permeate into the capacitor element, the entire body of the capacitor element is then immersed in the dispersion liquid, and the capacitor element is subsequently removed from the dispersion liquid.

5. The method according to claim 1, wherein the conductive polymer contained in the conductive polymer-containing dispersion is in the form of fine particles.

6. The method according to claim 1 or 2, wherein the capacitor element is a wound-type capacitor element having an anode having an oxide film, a cathode, and a separator and solid electrolyte between the anode and the cathode.

7. The method according to claim 1 or 2, wherein when the lower end portion of the capacitor element is brought into contact with the dispersion, 1 / 10 to 6 / 10 of the dimension of the capacitor element in the height direction is impregnated into the dispersion.

8. The method according to claim 1 or 2, wherein the capacitor element has a non-water-repellent winding-preventing tape for preventing the capacitor element from unraveling.

9. The method according to claim 1 or 2, wherein the capacitor element has a winding-retaining tape for preventing the capacitor element from unwinding, and when the lower end portion of the capacitor element is brought into contact with the dispersion, the conductive polymer-containing dispersion does not come into contact with the side surface of the capacitor element above the winding-retaining tape.

10. During the impregnation (b) described above, (b1) Depressurizing the chamber in which the storage tank containing the conductive polymer-containing dispersion is installed to a predetermined pressure, (b2) The lower end portion of the capacitor element is immersed in the conductive polymer-containing dispersion by raising the liquid level at a predetermined rate, and then left to stand for a predetermined time while maintaining a reduced pressure state. (b3) With the capacitor element still immersed in the conductive polymer-containing dispersion, the chamber is returned to its state before depressurization and left to stand for a predetermined time. A method for manufacturing an electrolytic capacitor according to claim 1 or 2, including the method described above.

11. A method for manufacturing an electrolytic capacitor containing a conductive polymer, (a) To provide a capacitor element, (b) Impregnating the capacitor element with a conductive polymer-containing dispersion, wherein the lower end of the capacitor element is brought into contact with the dispersion, and the dispersion is allowed to penetrate into the capacitor element. And, (c) Drying the capacitor element impregnated with a conductive polymer-containing dispersion, Includes, moreover, (d) After drying (c), impregnate the capacitor element again with the conductive polymer-containing dispersion, and (e) Dry the capacitor element that has been impregnated again. Methods that include...

12. The method according to claim 11, wherein, during the subsequent impregnation (d), the entire body of the capacitor element is immersed in the dispersion.

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