Electrolytic capacitor and method for manufacturing same

Abstract

The electrolytic capacitor includes a capacitor element formed by winding an anode foil and a cathode foil with a separator holding a conductive polymer layer interposed therebetween, and the separator is mainly composed of glass fibers having a porosity of 75-90%.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor using a conductive polymer and a method for manufacturing the same. Background Art

[0002] The electrolytic capacitor has, for example, a structure in which an electrolyte is impregnated in a capacitor element obtained by winding an anode foil and a cathode foil of aluminum foil with a separator therebetween, and the capacitor element is installed in an outer casing together with a sealing body. Examples of aluminum electrolytic capacitors using conductive polymers include solid electrolytic capacitors in which conductive polymers are retained in capacitor elements, and hybrid electrolytic capacitors in which conductive polymers and electrolytes are retained in capacitor elements (see Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-59471

[0006] Patent Document 2: International Publication No. 2017 / 090241 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] For example, the separators such as cellulose fibers used in aluminum electrolytic capacitors using conductive polymers have low acid resistance and are therefore decomposed by strongly acidic polymers. When such separators are used to manufacture solid electrolytic capacitors, for example, in the process of chemically polymerizing monomers using an oxidant to generate a conductive polymer layer, the fibers of the separator may rapidly deteriorate due to the influence of chemical polymerization.

[0009] In addition, in contrast, when a conductive polymer layer is generated by immersing a capacitor element in a dispersion of a conductive polymer and drying it, the diaphragm will also deteriorate rapidly due to the dissolution of the conductive polymer after manufacture. For example, in the case of a hybrid electrolytic capacitor in which a conductive polymer layer is formed using the above-mentioned dispersion, the conductive polymer is easily dissolved into the electrolyte contained in the diaphragm. The more the electrolyte evaporates, the higher the acidity of the electrolyte becomes due to the conductive polymer dissolved from the conductive polymer layer into the electrolyte, and therefore, the faster the deterioration of the diaphragm becomes, and the more decomposition can be promoted.

[0010] As the separator decomposes due to acidification as described above, for example, the amount of the conductive polymer retained may decrease, resulting in an increase in ESR. In addition, the amount of the electrolyte retained may also decrease, resulting in an increase in leakage current.

[0011] Therefore, the present invention has been made in view of the above-mentioned technical problems, and an object of the present invention is to provide a highly reliable electrolytic capacitor and a method for manufacturing the same which can suppress acidification of the separator.

[0012] Means for solving technical problems

[0013] The electrolytic capacitor of the present invention is characterized by having a capacitor element in which an anode foil and a cathode foil are wound with a separator holding a conductive polymer layer interposed therebetween, wherein the separator is mainly composed of glass fiber having a porosity of 75 to 90 (%).

[0014] In the above electrolytic capacitor, the glass fiber may have a porosity of 85 to 90 (%).

[0015] In the above electrolytic capacitor, the separator may retain an electrolyte solution, and the average fiber diameter of the glass fiber may be 0.5 to 1 (μm).

[0016] In the above electrolytic capacitor, the glass fiber may include at least one of borosilicate glass, alkali-free borosilicate glass, and high-silica glass.

[0017] In the above electrolytic capacitor, the separator may include at least one of polyester fiber, polyethylene fiber, polypropylene fiber, aramid fiber, acrylic fiber, and cellulose fiber.

[0018] In the above electrolytic capacitor, the separator may include at least one of polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyurethane, polyvinylidene fluoride, styrene-butadiene rubber and acrylic resin as a binder.

[0019] In the above electrolytic capacitor, the capacitor element may be impregnated with the electrolytic solution containing at least one of ethylene glycol, γ-butyrolactone, and sulfolane.

[0020] The manufacturing method of the electrolytic capacitor of the present invention is characterized in that it includes: a step of winding an anode foil and a cathode foil with a separator interposed therebetween to form a capacitor element; a step of immersing the capacitor element in a dispersion or solution of a conductive polymer; and a step of drying the capacitor element, wherein the separator is mainly composed of glass fiber with a porosity of 75 to 90 (%).

[0021] In the above-mentioned production method, the void ratio of the glass fiber may be 85 to 90 (%).

[0022] In the above-mentioned manufacturing method, the step of further comprising immersing the capacitor element in an electrolyte solution may be included, and the average fiber diameter of the glass fiber may be 0.5 to 1 (μm).

[0023] In the above-mentioned manufacturing method, the glass fiber may include at least one of borosilicate glass, alkali-free borosilicate glass, and high-silica glass.

[0024] In the above manufacturing method, the separator may include at least one of polyester fiber, polyethylene fiber, polypropylene fiber, aramid fiber, acrylic fiber and cellulose fiber.

[0025] In the above-mentioned manufacturing method, the separator may include at least one of polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyurethane, polyvinylidene fluoride, styrene-butadiene rubber and acrylic resin as a binder.

[0026] In the above-described manufacturing method, the capacitor element may be impregnated with the electrolyte solution containing at least one of ethylene glycol, γ-butyrolactone, and sulfolane.

[0027] Effects of the Invention

[0028] According to the present invention, the acidification of the diaphragm can be suppressed and the reliability can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a side view showing an example of an aluminum electrolytic capacitor.

[0030] Figure 2 It is a perspective view showing an example of a capacitor element.

[0031] Figure 3 This is a diagram showing an example of a manufacturing process of an aluminum electrolytic capacitor. DETAILED DESCRIPTION

[0032] [Implementation Method]

[0033] (Structure of aluminum electrolytic capacitor)

[0034] Figure 1 1 is a side view showing an example of an aluminum electrolytic capacitor 1. Figure 1 In the paper of FIG. 1 , the internal cross section of the aluminum electrolytic capacitor 1 is shown in the right half of the center line L sandwiched therebetween.

[0035] The aluminum electrolytic capacitor 1 is a conductive polymer solid aluminum electrolytic capacitor (hereinafter referred to as a solid electrolytic capacitor) or a conductive polymer hybrid aluminum electrolytic capacitor (hereinafter referred to as a hybrid electrolytic capacitor). The aluminum electrolytic capacitor 1 can be mounted in an electronic circuit board and can be used for coupling, decoupling, smoothing, etc.

[0036] The aluminum electrolytic capacitor 1 includes a capacitor element 10, a case 11, a sealing body 12, a seat plate 13, a pair of round rods 111, and a pair of lead parts 110. The round rods 111 and the lead parts 110 are lead electrodes of the capacitor element 10, and the lead parts 110 extend from the front ends of the round rods 111. Figure 1 Only one round bar portion 111 is shown in FIG. 1 , but another round bar portion 111 is provided at a symmetrical position with respect to the center line L.

[0037] Case 11 is made of aluminum and has a cylindrical shape with an upper opening closed. Case 11 covers capacitor element 10 and sealing body 12 and functions as an exterior of aluminum electrolytic capacitor 1. The shape of case 11 is not limited to a cylindrical shape, but may also be a square cylinder shape.

[0038] Sealing body 12 is a substantially circular member formed of an elastic member such as butyl rubber, etc. Sealing body 12 is adjacent to capacitor element 10 and seals the lower opening of case 11 .

[0039] As described later, capacitor element 10 has a structure in which anode foil, cathode foil, and separator (electrolytic paper) are overlapped and wound. A pair of round rod portions 111 extend from the bottom of capacitor element 10 .

[0040] The round rod portion 111 and the lead portion 110 are rod-shaped components formed of aluminum or the like. The pair of round rod portions 111 are respectively joined to the anode foil and the cathode foil by riveting or other joining methods, and function as the anode terminal and the cathode terminal of the aluminum electrolytic capacitor 1. Each round rod portion 111 is respectively inserted into a pair of through holes 120 formed in the sealing body 12. In addition, Figure 1 Only one through hole 120 is shown in FIG. 1 , but another through hole 120 is provided at a symmetrical position with respect to the center line L.

[0041] The lead portion 110 has a flat plate shape, is bent in an L shape, and a portion on the front end side thereof extends along the plate surface of the seat plate 13. A portion on the round bar portion 111 side of the lead portion 110 is inserted into a through hole 130 of the seat plate 13. The lead portion 110 can be soldered to a pad on the electronic circuit board during a reflow process of the electronic circuit board.

[0042] The seat plate 13 is a plate-shaped member formed of resin or the like, and is disposed at the lower portion of the housing 11 and the sealing body 12. The seat plate 13 can support the housing 11 and the sealing body 12 relative to the electronic circuit board as the installation object. The seat plate 13 is provided with a through hole 130 for the lead portion 110 and a groove portion 131 for accommodating the bent front end portion of the lead portion 110. The groove portion 131 extends from near the center to the outside along the bottom surface of the seat plate 13. The bottom surface of the seat plate 13 becomes the mounting surface of the aluminum electrolytic capacitor 1 relative to the electronic circuit board, so the plate-shaped lead portion 110 can be soldered to the pad on the electronic circuit board. In addition, in this embodiment, a surface-mounted aluminum electrolytic capacitor 1 is listed, but the embodiments described later can also be applied to a lead-type aluminum electrolytic capacitor without a seat plate 13.

[0043] (Structure of capacitor element)

[0044] Figure 2 is a perspective view showing an example of capacitor element 10. Figure 2 In Figure 1 The same reference numerals are used for the same components, and their description is omitted. Capacitor element 10 includes a wound body 100 formed by winding anode foil 101 , cathode foil 102 , and separator (electrolytic paper) 103 , and a pair of extraction electrodes 19 connected to anode foil 101 and cathode foil 102 .

[0045] A pair of extraction electrodes 19 extend downwardly from the wound body 100. The round rod portion 111 of each extraction electrode 19 is connected to the anode foil 101 and the cathode foil 102, respectively. Figure 2 , the state before the lead portion 110 is bent and pressed into a flat plate shape is shown.

[0046] Anode foil 101 and cathode foil 102 are formed of valve metals such as aluminum, tantalum, titanium and niobium, and alloy foils thereof, as well as vapor-deposited foils, for example. The surface of anode foil 101 is etched to increase the electrode area. Thus, capacitor element 10 can ensure a specified electrostatic capacitance. Moreover, an extremely thin oxide film is formed on the surface of anode foil 101. Therefore, anode foil 101 is insulated from other components. The oxide film acts as a dielectric, so that capacitor element 10 acts as a capacitor.

[0047] On the other hand, although the surface of cathode foil 102 is etched, no oxide film is formed. Alternatively, an oxide film may be formed on the surface of cathode foil 102, or an inorganic layer or a carbon layer may be formed.

[0048] The separator 103 is wound in a state of being sandwiched between the anode foil 101 and the cathode foil 102. The separator 103 holds a conductive polymer in the case of a solid electrolytic capacitor, and holds a conductive polymer and an electrolyte in the case of a hybrid electrolytic capacitor. The separator 103 is formed mainly of glass fibers having a porosity of 75 to 90 (%), and may contain other organic fibers and adhesives in addition to the glass fibers. As described above, the separator 103 is mainly composed of glass fibers, and therefore, it is not easy to become acidic compared to, for example, a case where cellulose fibers are used as the main body.

[0049] The porosity of the glass fiber is 75 to 90 (%). Here, the porosity refers to the ratio of the volume of the voids to the volume of the entire fiber. When the porosity is less than 75 (%), the glass fiber cannot retain a sufficient amount of conductive polymers and electrolytes, so the ESR will increase. In addition, when the porosity is higher than 90 (%), the glass fiber can retain a sufficient amount of conductive polymers and electrolytes, so the ESR can be sufficiently reduced, but on the other hand, the strength required when winding the diaphragm 103 cannot be maintained, so it is not appropriate.

[0050] Therefore, when the porosity of the glass fiber is 75 to 90 (%), the amount of conductive polymer and electrolyte retained increases, so that the ESR can be appropriately reduced. Preferably, when the porosity of the glass fiber is 85 to 90 (%), more conductive polymer can be retained, so that the ESR can be further reduced. As a result, the reliability of the aluminum electrolytic capacitor 1 can be improved.

[0051] In addition, the average fiber diameter of the glass fiber is 0.5 to 1 (μm). When the fiber diameter exceeds 1 (μm), the evaporation rate of the electrolyte becomes too high, and the density of the conductive polymer dissolved from the conductive polymer layer into the electrolyte becomes high, so the acidification of the separator further develops. On the other hand, when the fiber diameter is less than 0.5 (μm), the retention of the conductive polymer deteriorates, so it is not appropriate. Therefore, by setting the average fiber diameter of the glass fiber to 0.5 to 1 (μm), the evaporation of the electrolyte can be appropriately suppressed, thereby suppressing the acidification.

[0052] The thickness of the diaphragm 103 is 40 (μm). If the thickness of the diaphragm 103 is less than 40 (μm), it is too thin, and thus the withstand voltage is reduced.

[0053] The glass fiber includes at least one of borosilicate glass, alkali-free borosilicate glass, and high-silica glass. By using these materials as the main body of the separator 103, an advantage of improved acid resistance can be obtained.

[0054] In addition, the separator 103 may include at least one of polyester fiber, polyethylene fiber, polypropylene fiber, aramid fiber, acrylic fiber, and cellulose fiber. When the separator 103 includes these materials, advantages of excellent solvent resistance and improved mechanical strength such as tensile strength can be obtained.

[0055] In addition, the separator 103 may contain at least one of polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyurethane, polyvinylidene fluoride, styrene-butadiene rubber and acrylic resin as a binder. By making the separator 103 contain these binders, advantages of excellent solvent resistance and improved mechanical strength such as tensile strength can be obtained.

[0056] In addition, when the aluminum electrolytic capacitor 1 is a solid electrolytic capacitor, an electrolyte is impregnated in the separator 103. The solvent of the electrolyte may include at least one of ethylene glycol, γ-butyrolactone, and sulfolane. By impregnating the separator 103 with the electrolyte containing these solvents, an advantage of lower evaporation than before can be obtained.

[0057] (Electrolytic Capacitor Manufacturing Process)

[0058] Figure 3 1 is a diagram showing an example of a manufacturing process of an aluminum electrolytic capacitor 1. The manufacturing process of an aluminum electrolytic capacitor 1 is an example of a method for manufacturing an electrolytic capacitor. In addition, in this example, a manufacturing process of a hybrid electrolytic capacitor is listed, but in the method for manufacturing a solid electrolytic capacitor, the following step St6 is omitted.

[0059] First, prepare the anode foil 101, the cathode foil 102 and the diaphragm 103 (step St1). The surface of the anode foil 101 is etched and an oxide film is formed as a dielectric layer. In addition, the diaphragm 103 has a porosity of 75 to 90 (%) and is mainly composed of glass fibers. Here, the porosity is preferably 85 to 90 (%). In addition, when the average fiber diameter of the glass fiber is 0.5 to 1 (μm), the evaporation rate of the electrolyte is good, which is preferred from the perspective of the impregnation of the conductive polymer. In addition, the thickness of the diaphragm 103 is 40 (μm).

[0060] Next, the separator 103, the anode foil 101, the cathode foil 102 and the separator 103 are stacked and wound in sequence, and the outer surface is fixed with a winding stopper to produce a wound body 100 (step St2). During the winding, the lead electrodes 19 are connected to the appropriate positions of the anode foil 101 and the cathode foil 102. As a connection method, riveting can be cited, but it is not limited to this.

[0061] Next, the wound body 100 is immersed in a conductive polymer dispersion containing water and an organic solvent for 20 minutes in a reduced pressure atmosphere, and then the wound body 100 is lifted out of the conductive polymer dispersion (step St3). By doing so, the conductive polymer can be impregnated in the wound body 100. In addition, in this step, a conductive polymer solution can be used instead of the conductive polymer dispersion.

[0062] Next, the wound body 100 is placed in a drying oven at 150 degrees, for example, and dried for 60 minutes (step St4 ). This allows the conductive polymers in the separator 103 to adhere to each other to form a conductive polymer layer, thereby forming a conductive path.

[0063] Next, in a reduced pressure atmosphere, the wound body 100 is impregnated with a predetermined amount of electrolyte (step St5). The electrolyte may be obtained by mixing a solute in a conductive polymer dispersion. In other words, a conductive polymer dispersion may be used as the electrolyte. In this case, the impregnation of the electrolyte and the impregnation of the conductive polymer are performed simultaneously.

[0064] Next, the winding body 100 is housed in the case 11 and sealed with the sealing body 12 (step St6). At this time, the lead electrode 19 extending from the winding body 100 is inserted into the through hole 120 of the sealing body 12. After that, the capacitor element 10 can be aged by applying the rated voltage. In this way, the manufacturing process of the aluminum electrolytic capacitor 1 is performed.

[0065] Example

[0066] Next, an embodiment of the aluminum electrolytic capacitor 1 is described. Samples No. 1 to 8 of the aluminum electrolytic capacitor 1 are produced according to the above-mentioned manufacturing method. In addition, for comparison, samples No. 9 and 10 of the aluminum electrolytic capacitor are produced using special artificial fibers (fibers obtained by subdividing cellulose fibers) and cellulose fibers instead of glass fibers as the main body of the diaphragm 103, respectively. The rated voltage and rated electrostatic capacitance of samples No. 1 to 10 are 63 (V) and 56 (μF), respectively. In addition, the diameter of the shell 11 is 10 (mm), and the height of the shell 11 is 10 (mm). The specific manufacturing method of the aluminum electrolytic capacitor 1 is described below.

[0067] (Production of wound body)

[0068] The lead-out electrode of the anode is connected to an anode foil that has been etched and formed with an oxide film. The lead-out electrode of the cathode is connected to a cathode foil that has a conductor layer on the end face and has been pre-treated to improve wettability. After that, the diaphragm, cathode foil, diaphragm and anode foil are stacked in sequence, and wound while each lead-out electrode is wound in, and the outer surface is fixed with a winding tape to produce a winding body. The thickness of the diaphragm, the fiber diameter of the fiber that becomes the main body of the diaphragm, and the porosity are different for each sample.

[0069] The produced wound body was immersed in an aqueous ammonium phosphate solution, and a chemical conversion treatment was performed again at 85° C. while a predetermined voltage was applied to the anode foil, thereby forming a dielectric layer mainly on the end surface of the anode foil.

[0070] (Impregnation of conductive polymer)

[0071] In a reduced pressure atmosphere (-93 kPa), the wound body is immersed in a dispersion of a conductive polymer contained in a predetermined container, and then the wound body is lifted from the dispersion. Next, the wound body impregnated with the conductive polymer is dried in a drying oven at 150°C for 60 minutes to fix the conductive polymers of each layer to each other to form a conductive path. Thus, a capacitor element that functions as a solid electrolytic capacitor is produced.

[0072] (Impregnation of electrolyte)

[0073] Furthermore, the capacitor element described above was impregnated with a predetermined amount of an electrolyte solution (ESE2 manufactured by TAYCA CORPORATION) in a reduced pressure atmosphere. Thus, a capacitor element functioning as a hybrid aluminum electrolytic capacitor was produced.

[0074] (Sealing of capacitor elements)

[0075] The capacitor element impregnated with the electrolyte is sealed to complete the electrolytic capacitor, and then an aging treatment is performed at a predetermined temperature for a predetermined time while applying a rated voltage.

[0076] (evaluate)

[0077] Samples No. 1 to 10 were evaluated as solid electrolytic capacitors and hybrid electrolytic capacitors. Using a 4-terminal LCR tester, the ESR (mΩ) of the solid electrolytic capacitors and hybrid electrolytic capacitors at a frequency of 100kHz was measured at 20°C. In addition, as an evaluation of the solid electrolytic capacitor, the retention amount (g) of the polymer (conductive polymer) was measured, and as an evaluation of the hybrid electrolytic capacitor, the evaporation rate (g / h) of the electrolyte at 150°C was measured. Table 1 shows the measurement results of the solid electrolytic capacitors, and Table 2 shows the measurement results of the hybrid electrolytic capacitors.

[0078] [Table 1]

[0079]

[0080] Table 1 shows the evaluation results of Samples No. 1 to 10 as solid electrolytic capacitors. The main body of the separators of Samples No. 1 to 8 is glass fiber, and the main body of the separators of Samples No. 9 and 10 is special artificial fiber and cellulose fiber, respectively. In addition, the weight ratio of the main fiber to the weight of the entire separator (see the weight ratio in Table 1) is 100 (%) in Samples No. 9 and 10, 65 (%) in Sample No. 4, and 75 (%) in the other samples.

[0081] The fiber diameter is the average value of the diameter of the fibers of the main body of the separator, and is measured by measuring the plane of the separator at 5000 times using a scanning electron microscope (SEM). The fiber diameters of samples No. 1 to 4, 6, and 8 are 0.5 (μm), the fiber diameter of sample No. 5 is 1.2 (μm), and the fiber diameter of sample No. 7 is 1.0 (μm). The fiber diameter of sample No. 9 is 2.0 (μm), and the fiber diameter of sample No. 10 is 5.0 (μm). In addition, the thickness of the separator of sample No. 6 is 30 (μm), and the thickness of the separators of the other samples is 40 (μm).

[0082] The porosity of the diaphragm is different for each sample. Samples No. 1 to 4 and 8 show a trend that the higher the porosity of the diaphragm, the higher the polymer retention and the lower the ESR. However, compared with sample No. 4, samples No. 5 and 7 have lower porosity, but larger fiber diameters and improved polymer impregnation, so the polymer retention increases and the ESR decreases. In addition, compared with sample No. 4, sample No. 6 has a lower porosity, but is thinner and has a shorter conductive path, so the ESR decreases.

[0083] The ESR of samples No. 9 and 10 as comparative examples was used as a reference to judge the goodness (OK / NG) of the ESR of samples No. 1 to 8 of the embodiment (refer to the judgment results in the table). The ESR of samples No. 1 to 7 is lower than that of samples No. 9 and 10, so they are judged to be OK. In addition, as for sample No. 8, although the thickness is the same as that of sample No. 9 and the porosity is higher than that of sample No. 9, the ESR is higher than that of sample No. 9, so it is judged to be NG. In addition, sample No. 1 with a porosity of 90 (%) and sample No. 2 with a porosity of 85 (%) have a large amount of polymer retention, so the ESR is further appropriately reduced.

[0084] Therefore, the ESR of samples No. 1 to 7 having a porosity of 75 to 90 (%) was appropriately reduced. Furthermore, the ESR of samples No. 1 and 2 having a porosity of 85 to 90 (%) was further appropriately reduced.

[0085] In addition, the thickness of sample No. 6 is thinner than other samples No. 1 to 5, 7, and 8. Therefore, the withstand voltage of sample No. 6 is lower than the withstand voltage of sample No. 9 of the comparative example. On the other hand, the withstand voltage of samples No. 1 to 5, 7, and 8 is higher than the withstand voltage of sample No. 9 of the comparative example. Therefore, the thickness of the separator is preferably 40 (μm).

[0086] [Table 2]

[0087]

[0088] Table 2 shows the evaluation results of the hybrid electrolytic capacitors of Sample Nos. 1 to 10. The contents described in Table 2 are the same except for the amount of electrolyte solution retained, ESR, the evaporation rate of the electrolyte solution, and the evaluation results.

[0089] Similar to the case of solid electrolytic capacitors, samples No. 1 to 4 and 8 show a trend that the higher the porosity of the diaphragm, the more the amount of electrolyte retained, and the lower the ESR. However, compared with sample No. 4, samples No. 5 and 7 have lower porosity, but larger fiber diameters and improved polymer impregnation, so the amount of electrolyte retained increases and the ESR decreases. In addition, compared with sample No. 4, sample No. 6 has a lower porosity, but a thinner thickness and a shorter conductive path, so the ESR decreases.

[0090] The ESR of samples No. 9 and 10 as comparative examples was used as a reference to judge the goodness (OK / NG) of the ESR of samples No. 1 to 8 of the embodiment (refer to the judgment results in the table). The ESR of samples No. 1 to 7 is lower than that of samples No. 9 and 10, so it is judged to be OK. In addition, for sample No. 8, although the thickness is the same as that of sample No. 9 and the porosity is higher than that of sample No. 9, the ESR is higher than that of sample No. 9, so it is judged to be NG.

[0091] Therefore, the ESR of samples No. 1 to 7 having a porosity of 75 to 90 (%) was appropriately reduced. Moreover, samples No. 1 and 2 having a porosity of 85 to 90 (%) had a large amount of polymer retained, and thus the ESR was further appropriately reduced.

[0092] In addition, the larger the fiber diameter, the faster the electrolyte evaporates. This is because when the fiber diameter increases, the contact area with the electrolyte decreases, thereby reducing the retention of the electrolyte. As the electrolyte evaporates further, the density of the conductive polymer eluted from the conductive polymer layer into the electrolyte increases, and the acidity increases, so the acidification of the separator further advances.

[0093] When the evaporation rate of the electrolyte of samples No. 9 and 10 as comparative examples is used as a reference, the evaporation rate of the electrolyte of sample No. 5, which has the largest fiber diameter among samples No. 1 to 8, is higher than the evaporation rate of the electrolyte of sample No. 9. This is because the fiber diameter of sample No. 5 is larger than that of other samples No. 1 to 4 and 6 to 8. On the other hand, the evaporation rate of the electrolyte of other samples No. 1 to 4 and 6 to 8 is lower than that of the electrolyte of samples No. 9 and 10. Therefore, by making the average value of the fiber diameter of the glass fiber 0.5 to 1 (μm), the evaporation of the electrolyte can be appropriately suppressed, thereby suppressing acidification. Here, when the average value of the fiber diameter is less than 0.5 (μm), the impregnation of the polymer is reduced, so it is not appropriate.

[0094] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. An electrolytic capacitor, characterized in that: A capacitor element is provided in which an anode foil and a cathode foil are wound with a separator for holding a conductive polymer layer interposed therebetween. The separator is mainly composed of glass fiber with a porosity of 75 to 90%.

2. The electrolytic capacitor according to claim 1, characterized in that: The void ratio of the glass fiber is 85-90%.

3. The electrolytic capacitor according to claim 1 or 2, characterized in that: The separator holds the electrolyte, The average fiber diameter of the glass fibers is 0.5 to 1 μm.

4. The electrolytic capacitor according to claim 1 or 2, characterized in that: The glass fiber includes at least one of borosilicate glass, alkali-free borosilicate glass, and high silica glass.

5. The electrolytic capacitor according to claim 1 or 2, characterized in that: The separator includes at least one of polyester fiber, polyethylene fiber, polypropylene fiber, aramid fiber, acrylic fiber, and cellulose fiber.

6. The electrolytic capacitor according to claim 1 or 2, characterized in that: The separator includes at least one of polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyurethane, polyvinylidene fluoride, styrene butadiene rubber, and acrylic resin as a binder.

7. The electrolytic capacitor according to claim 3, characterized in that: The capacitor element is impregnated with the electrolyte solution containing at least one of ethylene glycol, γ-butyrolactone, and sulfolane.

8. A method for manufacturing an electrolytic capacitor, characterized in that: include: The step of winding the anode foil and the cathode foil with a separator interposed therebetween to form a capacitor element; A step of immersing the capacitor element in a dispersion or solution of a conductive polymer; and a step of drying the capacitor element, The separator is mainly composed of glass fiber with a porosity of 75 to 90%.

9. The method for manufacturing an electrolytic capacitor according to claim 8, wherein: The void ratio of the glass fiber is 85-90%.

10. The method for manufacturing an electrolytic capacitor according to claim 8 or 9, characterized in that: The method further comprises immersing the capacitor element in an electrolyte. The average fiber diameter of the glass fibers is 0.5 to 1 μm.

11. The method for manufacturing an electrolytic capacitor according to claim 8 or 9, characterized in that: The glass fiber includes at least one of borosilicate glass, alkali-free borosilicate glass, and high silica glass.

12. The method for manufacturing an electrolytic capacitor according to claim 8 or 9, characterized in that: The separator includes at least one of polyester fiber, polyethylene fiber, polypropylene fiber, aramid fiber, acrylic fiber, and cellulose fiber.

13. The method for manufacturing an electrolytic capacitor according to claim 8 or 9, characterized in that: The separator includes at least one of polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyurethane, polyvinylidene fluoride, styrene butadiene rubber, and acrylic resin as a binder.

14. The method for manufacturing an electrolytic capacitor according to claim 10, wherein: The capacitor element is impregnated with the electrolyte solution containing at least one of ethylene glycol, γ-butyrolactone, and sulfolane.

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