JP2020043203A - Manufacturing method of electrode for electrolytic capacitor - Google Patents

Abstract

To provide a manufacturing method of electrode for electrolytic capacitor, capable of reducing carbon residual in an electrode for an electrolytic capacitor and suppressing a leakage current in the electrolytic capacitor.SOLUTION: The manufacturing method of electrode for electrolytic capacitor includes: a process of applying slurry containing metal powder 4 and at least one type of solvent to a surface of metal foil 1 and forming a coating film 2; and a process of heating the coating film 2 and sintering the metal powder 4. The viscosity of solvent at 25°C is 400 Pa s or more and 500 Pa s or less and the viscosity of solvent in a range of 40°C or more and 60°C or less is 0.2 Pa s or more and 20 Pa s or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an electrode for an electrolytic capacitor.

  In a conventional method for manufacturing an electrode (anode) for an electrolytic capacitor, a large number of pores extending from the surface of the metal foil to the inside are formed by etching the metal foil having a valve action, and the specific surface area of the metal foil increases. By oxidizing the surface of the metal foil after the etching, a dielectric film covering the surface of the metal foil is formed. Since the etching solution used for etching may not sufficiently act on the inside of the metal foil, the thickness of the metal foil capable of sufficiently oxidizing the inside is limited to at most about 150 μm. As a method of manufacturing an electrode having a large specific surface area without performing etching, a method of forming an electrode using metal powder having a valve action as described below is known.

  For example, in a method for manufacturing a solid electrolytic capacitor described in Patent Document 1, a slurry containing metal powder such as tantalum, an organic binder, and a solvent is applied to the surface of a metal foil to form a slurry layer. After removing the organic binder and the solvent from the slurry layer by heating and drying the slurry layer, the metal powder in the slurry layer is sintered. As a result, a sintered layer made of a porous metal is formed on the surface of the metal foil. By oxidizing the surface of the sintered layer including the inner wall of the hole, an anode having a thickness of about 200 μm is obtained.

  Patent Document 2 listed below discloses a step of obtaining a granulated material from a metal powder and an organic binder, a step of forming a molded body on the surface of a metal foil (metal lead) by press molding of the granulated substance, and a step of sintering the molded body. Discloses a method for manufacturing a solid electrolytic capacitor comprising: a step of forming a sintered body by performing electrolytic cleaning of a sintered body; a step of oxidizing the sintered body after the electrolytic cleaning to form a dielectric film. Have been.

  As described above, according to the method of sintering the metal powder bound via the organic binder, it is possible to achieve the electrode thickness and the specific surface area, which are difficult to achieve by the conventional manufacturing method using etching.

JP 2003-243262 A JP 2009-064846 A

  As described above, by using an organic binder and a solvent together with a metal powder as a material for the electrode, the moldability of a slurry containing the metal powder can be improved, or a coating film formed from the metal powder (the above-described slurry layer or the formed Or the shape of the body) is easily maintained. However, when residues of materials such as an organic binder and a solvent remain in the finally obtained electrode, the performance and reliability of the electrode and the electrolytic capacitor are impaired. For example, when the organic binder is heated as the metal powder is sintered, the resin component (resin-based polymer) constituting the organic binder becomes a carbon residue, and the carbon residue remains in the electrode. Since the carbon residue has conductivity, the carbon residue in the electrode causes a leakage current in the electrolytic capacitor, thereby impairing the reliability of the electrolytic capacitor.

  In order to solve the above problems, the organic binder and the solvent are removed by heating, drying or washing before oxidizing the sintered layer (sintered body) of the metal powder to form the dielectric film. Is desirable. However, removal of the organic binder and the solvent (particularly, removal of the organic binder) involves the following problems.

  In order to degrease the organic binder in the coating film formed on the surface of the metal foil, it is necessary to heat the coating film at a high temperature of about 200 ° C. to 400 ° C. for several hours. As a result, the lead time and cost of manufacturing the electrodes are increased. It is difficult to remove the organic binder and the solvent from the surface of the coating film in contact with the metal foil. In particular, the thicker the coating, the more difficult it is to remove the organic binder and the solvent from the coating. By rapidly heating the coating, gas derived from the organic binder and the solvent is generated. Depending on the pressure of the gas, the metal powders are separated from each other, or the coating film is separated from the metal foil. When the organic binder is excessively removed from the coating film before sintering, the shape of the coating film is hardly maintained, and defects such as cracks, peeling, wrinkles, and chipping of the sintered layer formed from the coating film are likely to occur. When a step of cleaning the sintered layer before oxidation is added to remove carbon residues derived from the organic binder, the lead time for manufacturing the electrode becomes longer. Further, when water (such as pure water) or an organic solvent used for the cleaning liquid remains in the sintered layer, defects in the sintered layer occur due to oxidation of the sintered layer (formation of a dielectric film). As a result, the performance of the electrode decreases, and the leakage current in the electrode and the electrolytic capacitor tends to increase.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing an electrode for an electrolytic capacitor, which reduces carbon residues in the electrode for an electrolytic capacitor and reduces leakage current in the electrolytic capacitor. I do.

  The method for manufacturing an electrode for an electrolytic capacitor according to the first aspect of the present invention, a step of applying a slurry containing metal powder and at least one solvent to the surface of a metal foil to form a coating film, Heating, and sintering the metal powder, wherein the viscosity of the solvent at 25 ° C is 400 Pa · s or more and 500 Pa · s or less, and the viscosity of the solvent in the range of 40 ° C or more and 60 ° C or less is It is 0.2 Pa · s or more and 20 Pa · s or less.

  In the method for producing an electrode for an electrolytic capacitor according to the first aspect of the present invention, the solvent may be at least one of bornane and a derivative of bornane.

  A method for producing an electrode for an electrolytic capacitor according to the second aspect of the present invention, a step of applying a slurry containing metal powder and at least one solvent to the surface of a metal foil to form a coating film, Heating and sintering the metal powder, wherein the solvent is at least one of bornane and a derivative of bornane.

In the first and second aspects of the present invention, the solvent may be represented by the following structural formula (1).

  In the first and second aspects of the invention, the solvent may be isobornylcyclohexanol.

  In the first and second aspects of the invention, the slurry may be free of polymer.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode for electrolytic capacitors which reduces the carbon residue in the electrode for electrolytic capacitors and the leakage current in an electrolytic capacitor is provided.

FIG. 1A shows a cross section of an electrode for an electrolytic capacitor according to an embodiment of the present invention (a cross section of the electrode before a sintering step), and FIG. 1 shows a cross section (a cross section of an electrode after a sintering step) of an electrode for an electrolytic capacitor according to an embodiment. FIG. 2 shows the temperature characteristics of the viscosity of the solvent (isobonylcyclohexanol) used in the examples of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

  The method for producing an electrode (anode) for an electrolytic capacitor according to the present embodiment includes a step of applying a slurry containing a metal powder and at least one solvent to a surface of a metal foil to form a coating film (application step); Heating the coating film and sintering the metal powder (sintering step). Specific examples of these steps are shown in (a) and (b) of FIG. The coating film 2 shown in (a) of FIG. 1 is formed from the above slurry, and includes a metal powder 4 and at least one solvent. Although the solvent is not shown in FIG. 1A for convenience of illustration, the solvent is interposed between the metal particles constituting the metal powder 4. The coating film 2 may cover part or all of the surface of the metal foil 1. The coating 2 may cover both surfaces of the metal foil 1, and the coating 2 may cover only one surface of the metal foil 1. By heating the coating film 2, the metal particles constituting the metal powder 4 are sintered together, and the metal particles facing the metal foil 1 are sintered with the metal foil 1. As a result, a porous sintered layer 3 is formed on the surface of the metal foil 1. Some of the solvent in the coating film 2 may be removed from the coating film 2 by a drying process performed before the sintering process. The solvent in the coating film 2 may be removed from the coating film 2 in the sintering step without going through the drying step.

  The viscosity of the solvent at room temperature (25 ° C.) is 400 Pa · s or more and 500 Pa · s or less, and the viscosity of the solvent in the range of 40 ° C. or more and 60 ° C. or less is 0.2 Pa · s or more and 20 Pa · s or less. The viscosity of the solvent may be 0.2 Pa · s or more and 20 Pa · s or less throughout the range of 40 ° C. or more and 60 ° C. or less. It may be 2 Pa · s or more and 20 Pa · s or less. The viscosity of the solvent at each temperature may be a value measured by a rheometer (dynamic viscoelasticity measuring device) under a shear rate of 1 [1 / s]. The "viscosity characteristics" described below means that the viscosity of the solvent at 25 ° C is 400 Pa · s or more and 500 Pa · s or less, and the viscosity of the solvent in the range of 40 ° C or more and 60 ° C or less is 0.2 Pa It means that it is not less than s and not more than 20 Pa · s. Hereinafter, a solvent having the above viscosity characteristics may be referred to as a “first solvent”.

  The slurry containing the first solvent can have a viscosity as high as that of a conventional slurry containing an organic binder (resin-based polymer). That is, since the slurry according to the present embodiment can have a sufficiently high viscosity by including the first solvent having the above-described viscosity characteristics, it does not need to include the organic binder (resin-based polymer). Therefore, according to this embodiment, the carbon residue derived from the organic binder or the like hardly remains in the electrode, the leakage current of the electrolytic capacitor caused by the carbon residue in the electrode is suppressed, and the reliability of the electrolytic capacitor is improved. However, as long as the effect of the present invention is not impaired, the slurry may contain a small amount of an organic binder in addition to the first solvent.

  Since the slurry according to the present embodiment does not need to include an organic binder (resin-based polymer), a step of degreasing the organic binder in the coating film 2 formed from the slurry is unnecessary, and the coating film 2 is used for degreasing. There is no need to heat the coating at elevated temperatures for several hours. As a result, the lead time and cost of manufacturing the electrodes are reduced.

  When the coating contains an organic binder, it is difficult to increase the thickness of the coating 2 since the organic binder is harder to remove from the coating as the coating 2 is thicker, and the sintering formed from the coating 2 is difficult. It is also difficult to increase the thickness of layer 3. On the other hand, since the slurry according to the present embodiment can have a sufficiently high viscosity without containing an organic binder (resin-based polymer), it is not necessary to make the coating film 2 thin for removing the organic binder. . Therefore, according to this embodiment, a sufficiently thick sintered layer 3 and electrodes can be easily formed.

  In the present embodiment, since the coating film 2 does not need to include an organic binder, a phenomenon that a gas derived from the organic binder is generated due to rapid heating of the coating film 2 can be prevented or suppressed. Therefore, the phenomenon that the metal powders 4 are separated from each other or the coating film 2 peels off from the metal foil 1 due to the gas pressure is also prevented or suppressed. In addition, since the coating film 2 contains the first solvent, the shape of the coating film 2 is easily maintained, and defects such as cracking, peeling, wrinkling, and chipping of the sintered layer 3 formed from the coating film 2 are suppressed. For these reasons, according to the present embodiment, the metal powder 4 in the coating film 2 can be easily sintered without defects, and an electrode having excellent appearance and electrical performance can be obtained.

  Since the slurry according to the present embodiment does not need to include an organic binder (a polymer such as a resin component), in the method for manufacturing an electrode according to the present embodiment, the carbon residue derived from the organic binder is removed from the sintered layer 3. Cleaning process is not required. Therefore, according to the embodiment, the lead time for manufacturing the electrode is shortened, and the phenomenon that the residue derived from the cleaning liquid remains in the sintered layer 3 is prevented or suppressed.

Since the first solvent tends to have the above-mentioned viscosity characteristics, the first solvent may be at least one of bornane and a derivative of bornane. Derivatives of bornane are, for example, bornyl, borneol, isoborneol, camphor, camphorquinone, camsylate, camsylate, camphene, norbornane, norbornane, norbornane at least one selected from the group consisting of norbornyl, norbornadiene, norcamphor, tricyclene, quadricycle, camphanic acid, and derivatives thereof. The first solvent is preferably isobornyl represented by the following structural formula (1), and the first solvent is represented by the following structural formula (2) because the first solvent easily has the above viscosity characteristics. More preferably, it is isobornylcyclohexanol. The first solvent may be isobornylphenol. The slurry may contain, as the first solvent, plural kinds of solvents among the above compounds.

  The first solvent has a function of increasing the viscosity of the slurry. That is, due to the viscosity characteristics of the first solvent, the moldability of the slurry is improved, and the shape of the coating film formed from the slurry is easily maintained. The slurry may further include a second solvent in addition to the metal powder 4 and the first solvent. The second solvent has a function of diluting the slurry and adjusting the viscosity of the entire slurry to improve the formability of the slurry and the dispersibility of the metal powder 4 in the slurry. Neither the first solvent nor the second solvent is a resin-based polymer conventionally used as an organic binder. The resin-based polymer is, for example, ethyl cellulose or acrylic resin. The viscosity of the slurry is freely adjusted to a desired viscosity depending on the mixing ratio of the metal powder 4, the first solvent, and the second solvent, so that the slurry does not need to include an organic binder (resin-based polymer).

  The second solvent is a solvent other than the first solvent and may be any compound other than the resin-based polymer, and is not particularly limited. The boiling point of the second solvent may be, for example, 80 ° C or more and 300 ° C or less. The second solvent may be at least one selected from the group consisting of aromatic hydrocarbons, ethers, ketones, esters, alcohols, cellosolves, amides, and water. Specific second solvents include, for example, cyclohexanone, anisole, xylene, toluene, dioxane, ethyl acetate, acetone, methyl ethyl ketone, isophorone, methanol, isopropyl alcohol, benzyl alcohol, diethylene glycol, methyl cellosolve, N, N-dimethylformamide and It may be at least one selected from the group consisting of water. The slurry may contain, as the second solvent, a plurality of solvents among the above compounds.

  The mass of the first solvent contained in the slurry may be from 1 part by mass to 30 parts by mass with respect to 100 parts by mass of the metal powder 4. The mass of the second solvent contained in the slurry may be 0 to 50 parts by mass with respect to 100 parts by mass of the metal powder 4. The viscosity of the whole slurry at 25 ° C. may be 1 Pa · s to 100 Pa · s, and the viscosity of the whole slurry in the range of 40 ° C. to 60 ° C. is 0.1 Pa · s to 50 Pa · s. May be.

  The metal powder 4 may be a metal powder having a valve action. The metal powder 4 may be, for example, at least one selected from the group consisting of tantalum, niobium, and aluminum. The metal powder 4 may be, for example, an alloy containing at least one selected from the group consisting of tantalum, niobium, and aluminum. The purity of the metal powder 4 may be, for example, 99.8% by mass or more and 100% by mass or less. The metal powder 4 may contain elements other than the above as inevitable impurities. The metal powder 4 further contains at least one element selected from the group consisting of silicon, iron, copper, magnesium, manganese, titanium, chromium, zinc, gallium, vanadium, nickel, lead, and boron, in addition to the above elements. May be included. The shape of the individual metal particles constituting the metal powder 4 is not particularly limited, and may be spherical, irregular, scaly, fibrous, or the like. The average particle size of the metal powder 4 may be, for example, 2 μm or more and 10 μm or less. As the particle size of the metal powder 4 is smaller, the specific surface area of the electrode increases, and the capacitance of the electrolytic capacitor increases. As the particle size of the metal powder 4 is larger, the dielectric film formed on the surface of the electrode by oxidation can be made thicker, so that the withstand voltage of the electrolytic capacitor is improved.

  The metal foil 1 may be a metal foil having a valve action. The metal foil 1 may be, for example, at least one selected from the group consisting of tantalum, niobium, and aluminum. The metal foil 1 may be, for example, an alloy containing at least one selected from the group consisting of tantalum, niobium, and aluminum. The purity of the metal foil 1 may be, for example, 99.8% by mass or more and 100% by mass or less. The metal foil 1 may contain elements other than the above as inevitable impurities. The metal foil 1 further includes at least one element selected from the group consisting of silicon, iron, copper, magnesium, manganese, titanium, chromium, zinc, gallium, vanadium, nickel, lead, and boron, in addition to the above elements. May be included. The thickness of the metal foil 1 may be, for example, 10 μm or more and 150 μm or less. As the metal foil 1 is thinner, the mechanical strength of the metal foil 1 is lower, and handling and processing of the metal foil 1 are more difficult. As the metal foil 1 is thicker, the flexibility of the metal foil 1 is lower, and handling and processing of the metal foil 1 are more difficult.

  The thickness of the sintered layer 3 may be, for example, not less than 50 μm and not more than 1000 μm. The thinner the sintered layer 3, the lower the capacitance density of the electrolytic capacitor. The thicker the sintering layer 3, the thicker the coating film 2 as its precursor must be. However, as the coating film 2 is thicker, the shrinkage of the coating film 2 due to sintering of the metal powders 4 is more difficult to control, and defects such as cracking, peeling, wrinkling, and chipping of the sintered layer 3 are likely to occur. Further, the thicker the coating film 2, the more difficult it is for the solvent to be removed from the coating film 2.

  The above-mentioned slurry may be prepared by mixing the metal powder 4 and the solvent with various kneading / dispersing machines and dispersing the metal powder 4 in the solvent. As the kneading / dispersing machine, a stirrer may be used. As the kneading / dispersing machine, a roll-type kneading machine such as a two-roll mill and a three-roll mill may be used. As the kneading / dispersing machine, a blade-type kneading machine such as a vertical kneader, a pressure kneader, and a planetary mixer may be used. As the kneading / dispersing machine, a dispersing machine such as a ball-type rotary mill, a sand mill and an attritor may be used. As the kneading / dispersing machine, an ultrasonic dispersing machine or a nanomizer may be used. The slurry may be applied to the metal foil 1 by various methods such as roll printing or screen printing.

  As described above, a part of the solvent in the coating film 2 may be removed from the coating film 2 by a drying step performed before the sintering step. For example, the coating film 2 may be dried by heating the coating film 2 at a temperature of 50 ° C. or more and 150 ° C. or less (drying temperature). It is preferable to leave an appropriate amount of the first solvent (and the second solvent) in the dried coating film 2 so that the shape of the dried coating film 2 is easily maintained. For example, the total amount of the solvent remaining in the coating film 2 after drying is from 3.0% by mass to 20.0% by mass, preferably from 5.0% by mass to 0.0% by mass or less. The lower the drying temperature is, the longer the time required for removing the solvent is. The higher the drying temperature is, the more difficult it is to control the amount of the solvent remaining in the dried coating film 2. The smaller the amount of the solvent remaining in the dried coating film 2, the more difficult it is to handle and process the coating film 2, and the easier the occurrence of defects such as cracking, peeling, wrinkles, and chipping of the sintered layer 3. As the amount of the solvent remaining in the dried coating film 2 increases, the carbon residue tends to remain in the electrode, and the performance of the electrode tends to decrease. The method of drying is not particularly limited, and may be at least one method selected from the group consisting of hot air drying, vacuum drying, steam drying, barrel drying, spin drying, Marangoni drying, and infrared drying. Further, in order to increase the density of the coating film 2 and to make the thickness of the coating film 2 uniform, a pressing process or a calendering process of the coating film 2 may be performed at any time before or after drying.

  In the sintering step, the coating film 2 may be heated at a temperature (sintering temperature) of 550 ° C. or more and 700 ° C. or less, and preferably, the coating film 2 is heated at a sintering temperature of 600 ° C. or more and 650 ° C. or less. May be. As the sintering temperature is lower, the coating film 2 is less likely to be sufficiently sintered, and the sintered layer 3 is more likely to have defects such as cracks, peeling, wrinkles and chips. The higher the sintering temperature, the more easily the coating film 2 is sintered, the lower the performance of the electrode is, and the lower the capacitance of the electrolytic capacitor is. The atmosphere during sintering is not particularly limited, and may be air, vacuum, an inert gas, a reducing gas, or the like. From the viewpoint of easily suppressing the oxidation of the metal powder 4 in the coating film 2, the atmosphere during sintering is preferably argon gas. When sintering the coating film 2 in an air atmosphere, an oxide is easily formed on the surface of each metal particle constituting the metal powder 4, and the coating film 2 is not easily sintered. In particular, when the metal powder 4 is aluminum which is easily oxidized, it is preferable to suppress the oxidation of the metal powder 4 in the sintering step.

  Before the following oxidation step (chemical formation step), a pretreatment of the sintered layer 3 may be performed. The pre-treatment may be, for example, at least one selected from the group consisting of a degreasing treatment, a UV treatment, a blast treatment, a polishing treatment, and an etching treatment. By the pretreatment, the surface of the sintered layer 3 becomes clean, or the surface of the sintered layer 3 becomes rough and the specific surface area of the sintered layer 3 increases. However, the pretreatment of the sintered layer 3 may not be performed.

  The method for manufacturing an electrode for an electrolytic capacitor includes, in addition to the above-described coating step and sintering step, a step of oxidizing the surface of the sintered layer 3 to form a dielectric film covering the surface of the sintered layer 3 (oxidizing step). ) Is further provided. The surface of the sintered layer 3 includes, in addition to the outer surface of the sintered layer 3, the surface of the inner wall of a large number of pores formed in the sintered layer 3. Hereinafter, a laminate having the sintered layer 3 and the metal foil 1 covered with the sintered layer 3 is referred to as an “unoxidized electrode”.

  In the oxidation step (chemical formation step), for example, a voltage is applied between an unoxidized electrode arranged in the electrolytic solution and the counter electrode. The potential of the unoxidized electrode is adjusted to a value higher than the potential of the counter electrode. As a result, the surface of the unoxidized electrode (sintered layer 3) is oxidized to form a dielectric film. Electrolyte for the oxidation step, for example, boric acid, phosphoric acid, sulfuric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, lactic acid, malic acid, citric acid, benzoic acid, A solution (for example, an aqueous solution) containing one selected from the group consisting of phthalic acid and a salt thereof (for example, an ammonium salt or a sodium salt) may be used.

  An electrode (anode foil) for an electrolytic capacitor is completed through the above-described coating step, sintering step, and oxidation step.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Example 1)
[Coating process]
Aluminum powder (metal powder), isobonylcyclohexanol (first solvent) and methylcellosolve (second solvent) were mixed to prepare a slurry in which aluminum powder was dispersed. The average particle size of the aluminum powder was 4 μm. The mass of isobonylcyclohexanol contained in the slurry was 20 parts by mass with respect to 100 parts by mass of aluminum powder. The mass of methyl cellosolve contained in the slurry was 50 parts by mass with respect to 100 parts by mass of aluminum powder.

  The slurry was applied to one surface of an aluminum foil to form a plurality of rectangular coating films. The thickness of the aluminum foil was 60 μm, and the purity of the aluminum foil was 99.9% by mass or more. After the coating film was semi-dried, the slurry was applied to the back surface of the aluminum foil to form a plurality of rectangular coating films.

[Drying process]
After forming a coating film on both surfaces of the aluminum foil, each coating film was dried by heating both surfaces of the aluminum foil at 100 ° C. for 30 minutes. The dimensions of each coating film formed on both surfaces of the aluminum foil were 30 mm long × 20 mm wide.

[Sintering process]
By sintering each coating film formed on both sides of the aluminum foil at 650 ° C. in an argon gas atmosphere, a laminate (unoxidized electrode) having a sintered layer and a metal foil covered with the sintered layer is formed Obtained. The total thickness of the laminate was 500 μm.

[Oxidation step]
After covering the portion to be the extraction electrode portion on the surface of each sintered layer with a mask, the entire surface of the sintered layer (excluding the portion covered with the mask) is oxidized by the following oxidation step. An oxide film was formed.

  The laminate was immersed in boiling pure water to form pseudo-boehmite on the surface of each coating film of the laminate. In the subsequent oxidation treatment, a voltage of 500 V was applied between the laminate and the counter electrode while the laminate and the counter electrode were arranged in the electrolytic solution. That is, the potential of the stacked body was adjusted to 500 V with respect to the counter electrode. An aqueous solution of boric acid was used as an electrolyte.

  After the above oxidation treatment, the heat treatment, the depolarization treatment and the oxidation treatment were repeated. Finally, the laminate was washed and dried to complete the chemical conversion step.

  After the chemical conversion step, the laminate was cut out to obtain an electrode (anode foil) for an electrolytic capacitor.

(Example 2)
In the drying step of Example 2, each coating film was dried by heating both surfaces of the aluminum foil at 100 ° C. for 10 minutes. Except for the drying step, an electrode (anode foil) for an electrolytic capacitor of Example 2 was produced in the same manner as in Example 1.

(Comparative Example 1)
In preparing the slurry of Comparative Example 1, an acrylic resin as an organic binder (resin-based polymer) was used instead of isobonylcyclohexanol. The mass of the acrylic resin contained in the slurry was 20 parts by mass with respect to 100 parts by mass of the aluminum powder.

  In the case of Comparative Example 1, after the drying step, the acrylic resin contained in each coating film was decomposed and removed by heating both surfaces of the aluminum foil at 300 ° C. for 5 hours in an argon atmosphere.

  Except for the above, an electrode (anode foil) for an electrolytic capacitor of Comparative Example 1 was produced in the same manner as in Example 1.

<Measurement of viscosity of isobonylcyclohexanol>
At a shear rate of 1 [1 / s], the viscosity of isobornylcyclohexanol was measured in a temperature range of 25 ° C. or more and 60 ° C. or less. HAAKE ^TM Rheostress 6000 was used as a measuring device. The measured values of the viscosity of isobonylcyclohexanol at each temperature are shown in Table 1 and FIG.

<Measurement of carbon residue>
A sample was prepared by finely pulverizing the electrode of Example 1. The content of carbon (amount of carbon residue) in the sample was measured by a high-frequency combustion infrared absorption method. As a measuring device, CSLS-600 manufactured by LECO Japan Ltd. was used.

  In the same manner as in Example 1, the amounts of carbon residues in Example 2 and Comparative Example 1 were individually measured. The measurement results of the carbon residue amount are shown in Table 2 below.

<Measurement of leakage current>
As samples for measurement, 50 electrodes (anode foils) of Example 1 were used. Each electrode was an electrode that had undergone anodizing treatment (chemical conversion step). An aqueous boric acid solution was used as a measurement solution. The leakage current of each sample was measured for 5 minutes using a micro ammeter manufactured by Advandes. The average value of the leakage current in 50 samples was calculated. The average value of the leakage current in Example 1 is shown in Table 2 below.

  In the same manner as in Example 1, the leakage current at 50 electrodes of Example 2 was measured. The average value of the leakage current in Example 2 is shown in Table 2 below.

  In the same manner as in Example 1, the leakage current at 50 electrodes of Comparative Example 1 was measured. The average value of the leakage current of Comparative Example 1 is shown in Table 2 below.

  As shown in Table 2, the amount of carbon residue in each of Examples 1 and 2 was smaller than the amount of carbon residue in Comparative Example 1. The leakage current of each of Examples 1 and 2 was smaller than the leakage current of Comparative Example 1. Although the amounts of carbon residues in Examples 1 and 2 were the same, the leakage current of Example 1 was smaller than the leakage current of Example 2.

  ADVANTAGE OF THE INVENTION According to the manufacturing method of the electrode for electrolytic capacitors which concerns on this invention, it is possible to manufacture an electrode with high reliability with respect to electrical characteristics.

DESCRIPTION OF SYMBOLS 1 ... Metal foil, 2 ... Coating, 3 ... Sintered layer, 4 ... Metal powder.

Claims (6)

A step of applying a slurry containing metal powder and at least one solvent to the surface of the metal foil to form a coating film,
Heating the coating film and sintering the metal powder;
With
The viscosity of the solvent at 25 ° C. is 400 Pa · s or more and 500 Pa · s or less,
The viscosity of the solvent in a range of 40 ° C. or more and 60 ° C. or less is 0.2 Pa · s or more and 20 Pa · s or less,
A method for manufacturing an electrode for an electrolytic capacitor. The solvent is at least one of bornane and a derivative of bornane;
A method for producing an electrode for an electrolytic capacitor according to claim 1. A step of applying a slurry containing metal powder and at least one solvent to the surface of the metal foil to form a coating film,
Heating the coating film and sintering the metal powder;
With
The solvent is at least one of bornane and a derivative of bornane;
A method for manufacturing an electrode for an electrolytic capacitor. The solvent is represented by the following structural formula (1):
A method for producing an electrode for an electrolytic capacitor according to claim 1.

The solvent is isobornylcyclohexanol,
A method for producing an electrode for an electrolytic capacitor according to claim 1. The slurry does not contain a polymer;
A method for producing an electrode for an electrolytic capacitor according to claim 1.

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