Electrode foil for electrolytic capacitor, electrolytic capacitor, and method for manufacturing electrode foil for electrolytic capacitor

Abstract

The electrode foil for an electrolytic capacitor is provided with a metal foil containing a valve action metal, the metal foil has a core portion and a porous portion continuous with the core portion, the porous portion has a main surface of the metal foil, and the hardness X of the porous portion is 40 mN / mm2 or more when the maximum press-in load on the main surface is 100 mN as measured by a nanoindentation method.

Description

Technical Field

[0001] The present disclosure relates to an electrode foil for an electrolytic capacitor, an electrolytic capacitor, and a method for manufacturing the electrode foil for an electrolytic capacitor. Background Art

[0002] Electrode foil for electrolytic capacitors is made of valve-acting metal and includes a porous portion and a core portion continuous with the porous portion. The porous portion provides an electrode foil with a large surface area, thereby increasing the capacitance of the electrolytic capacitor.

[0003] Patent Document 1 proposes an electrode foil for an aluminum electrolytic capacitor, characterized in that an aluminum foil subjected to surface expansion by etching is compressed in the foil thickness direction to increase the surface area per unit volume compared to before compression.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 11-26320 Summary of the Invention

[0007] One technical solution disclosed herein relates to an electrode foil for an electrolytic capacitor, comprising a metal foil containing a valve-acting metal, the metal foil having a core portion and a porous portion continuous with the core portion, the porous portion having a main surface of the metal foil, and a hardness X of the porous portion measured by nanoindentation at a maximum indentation load of 100 mN on the main surface of the metal foil of 40 mN / mm 2 above.

[0008] Another technical solution disclosed herein relates to an electrolytic capacitor comprising a capacitor element, wherein the capacitor element comprises a wound body and an electrolyte, wherein the wound body is formed by winding an anode foil, a cathode foil, and a separator arranged between the anode foil and the cathode foil, wherein the anode foil comprises the above-mentioned electrode foil and a dielectric layer covering the metal skeleton of the porous portion constituting the electrode foil.

[0009] Another technical solution disclosed herein relates to a method for manufacturing an electrode foil for an electrolytic capacitor, comprising: an etching step of etching a sheet containing a valve metal to form a porous portion on a main surface of the sheet; and a compression step of compressing the etched sheet in a thickness direction to form a hardness X of 40 mN / mm. 2 In the porous portion described above, the hardness X is a hardness measured by a nanoindentation method when a maximum indentation load on the main surface is 100 mN.

[0010] According to the present disclosure, it is possible to obtain an electrolytic capacitor having high reliability and large capacitance. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view schematically showing an example of an electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure.

[0012] Figure 2 This is a diagram schematically showing an example of a compression step in a method for producing an electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure.

[0013] Figure 3 This is a cross-sectional view schematically showing an example of an electrolytic capacitor according to an embodiment of the present disclosure.

[0014] Figure 4 It is schematically represented Figure 3 A three-dimensional diagram of the structure of a wound body of an electrolytic capacitor. DETAILED DESCRIPTION

[0015] Research on the porous portion of electrode foil is still insufficient, and there is a demand for further improvement in the performance (capacitance, reliability) of electrolytic capacitors equipped with electrode foil having a porous portion. If the mechanical strength of the electrode foil having a porous portion is low, it is difficult to manufacture a high-performance (high capacitance, high reliability) electrolytic capacitor, and it is therefore necessary to increase the strength of the electrode foil (porous portion).

[0016] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials will sometimes be given as examples, but other numerical values ​​and materials may also be used as long as the effects of the present disclosure can be obtained. In this specification, the description of "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "above numerical value A and below numerical value B". In the following description, with respect to numerical values ​​of specific physical properties, conditions, etc., when lower limits and upper limits are given as examples, any one of the lower limits given as examples and any one of the upper limits given as examples may be arbitrarily combined as long as the lower limit is not above the upper limit. When multiple materials are given as examples, one may be selected and used alone, or two or more may be used in combination.

[0017] Furthermore, the present invention includes combinations of matters described in two or more claims arbitrarily selected from the plurality of claims recited in the appended claims. In other words, matters described in two or more claims arbitrarily selected from the plurality of claims recited in the appended claims may be combined as long as no technical contradiction arises.

[0018] (Electrode foil for electrolytic capacitors)

[0019] The electrode foil for electrolytic capacitors (electrode foil A) of the embodiment of the present disclosure has a metal foil containing a valve metal. The metal foil has a core and a porous portion continuous with the core. The porous portion has a main surface of the metal foil. The hardness X (hereinafter also referred to as "hardness X") of the porous portion when the maximum indentation load on the main surface is 100mN measured by nanoindentation is 40mN / mm 2 above.

[0020] The porous portion contains numerous pores (pits). To achieve higher capacitance, increasing the pit density and the thickness of the porous portion can be considered to increase the surface area of ​​the foil. However, increasing the pit density and the thickness of the porous portion reduces the strength of the electrode foil, which can lead to cracks or breakage during the electrolytic capacitor manufacturing process. This reduction in electrode foil strength is caused by a decrease in the strength of the surface layer of the porous portion, and this decrease in surface strength becomes particularly significant when the pit density and the thickness of the porous portion are high.

[0021] The following (a) to (c) are presumed to be the main reasons for the decrease in the strength of the surface layer of the porous portion. (a) The surface layer is easily degraded due to the contact between the etching solution and the surface of the metal foil during electrolytic etching. (b) The stress generated when the metal foil is wound during the manufacturing process of the electrolytic capacitor is likely to increase on the surface layer of the metal foil. This stress increases, for example, when the diameter of the roller for winding the metal foil is small. In addition, the stress is greater on the outer peripheral side of the wound metal foil than on the inner peripheral side. (c) The long strips containing valve metal used as the raw material of the metal foil (such as aluminum foil) are generally rolled foils with rolling marks, and rolling marks are likely to remain on the surface layer of the porous portion even after etching.

[0022] In contrast, in the present disclosure, by setting the hardness X to 40 mN / mm 2 The above mentioned properties can suppress the decrease in the strength of the surface layer. The hardness X of the porous portion can be increased by, for example, compressing the etched foil. For example, there is a tendency that the greater the thickness reduction rate during compression, the greater the hardness X. The hardness X can also be increased by adjusting the etching conditions (such as the amount of dissolution on the sheet surface) to suppress the degradation of the surface layer during etching and the decrease in strength. However, in high-capacitance electrode foils with a large porous layer thickness, it is difficult to increase the hardness X to 40 mN / mm by simply adjusting the etching conditions. 2 The hardness X can also be increased by adjusting etching conditions and combining compression conditions.

[0023] When the hardness X is 40mN / mm 2In the above case, the decrease in the strength of the surface layer caused by increasing the pit density and the thickness of the porous portion can be suppressed, thereby improving the tensile strength of the electrode foil. In addition, the capacitance per unit volume can be fully increased. By using this electrode foil, an electrolytic capacitor with high capacitance and excellent reliability can be obtained. In addition, the retention of the electrolyte in the pores of the porous portion can be improved, and the contact between the dielectric layer and the electrolyte is improved.

[0024] From the viewpoint of suppressing the decrease in strength of the surface layer and increasing the capacitance per unit volume, the hardness X is 40 mN / mm 2 Above, preferably 54mN / mm 2 More than 57mN / mm 2 If the hardness of the porous layer is high, the density (occupancy rate) of the metal skeleton of the porous layer increases, the pits become smaller, or the actual surface area of ​​the porous portion becomes smaller, so the strength increases, but the electrostatic capacitance of the electrode foil decreases. Therefore, from the perspective of suppressing the decrease in electrostatic capacitance, the hardness X can be, for example, 85mN / mm 2 Below, can also be 75mN / mm 2 the following.

[0025] The elastic modulus (Young's modulus) indicates the ease of deformation of a material. Within the range of elastic deformation, the elastic modulus is usually set to a proportional constant, and the stress and strain applied to the material become a proportional relationship (Hooke's law). Generally speaking, there is a tendency that the higher the hardness, the higher the elastic modulus. In the case of an electrode foil for electrolytic capacitors, there is also a tendency that the higher the hardness, the higher the elastic modulus. In particular, if the hardness of the porous portion increases, the tensile strength increases. As with hardness, from the perspective of the high strength of the electrode foil for electrolytic capacitors, the elastic modulus also becomes an important parameter. The elastic modulus of the porous portion when the maximum indentation load for the main surface of the metal foil (porous portion) is 100mN, as measured by nanoindentation, is preferably 520mN / mm 2 More than 560 mN / mm 2 More than 580 mN / mm 2 The upper limit of the elastic modulus is, for example, 800 mN / mm 2 For example, by appropriately adjusting the thickness of the compressed etched foil (porous portion) and the thickness reduction rate during compression, the elastic modulus can be increased within the above range.

[0026] The creep amount indicates the ease with which a material deforms when a constant load is applied for a constant time. In the case of a porous electrolytic capacitor electrode foil, the greater the creep amount, the higher the tensile strength. Like hardness and elastic modulus, creep amount is also an important parameter from the perspective of increasing the strength of the electrolytic capacitor electrode foil. The creep amount of the porous portion when the maximum indentation load on the main surface of the metal foil (porous portion) is 100mN, as measured by the nanoindentation method, is preferably 5% or more, more preferably 5.3% or more, and further preferably 5.4% or more. The upper limit of the creep amount is, for example, 6.5% or less. There is a tendency that the creep amount increases as the thickness reduction rate during compression increases.

[0027] The hardness X, elastic modulus and creep amount of the porous portion are determined in accordance with ISO 14577-1 (2014) of the International Organization for Standardization and by the nanoindentation method. The indenter is pressed into the main surface of the metal foil having the porous portion, and an indentation load of 100 mN is applied. The hardness X and elastic modulus are measured based on the indentation behavior of the indenter into the porous portion at this time. The creep amount is determined based on the change in the indentation depth when the maximum load of 100 mN is maintained for 5 seconds. That is, when the indentation depth when the maximum load of 100 mN is reached is set to h1, and the indentation depth when the maximum load of 100 mN is maintained for 5 seconds after the maximum load of 100 mN is reached is set to h2, (h2-h1) / h1×100 is determined as the creep amount (%).

[0028] The measurement conditions are as follows.

[0029] (Measurement conditions)

[0030] Measuring device: ELIONIX Corporation's ultra-micro indentation hardness tester "ENT-5"

[0031] Ambient temperature: 30℃

[0032] Indenter: Berkovich-type diamond indenter

[0033] Test load (maximum press load): 100mN

[0034] Measuring points: Averaging 3 points

[0035] In addition, during the measurement, the electrode foil sample was fixed to the sample stand using STE TAPE manufactured by SHINTO PAINT.

[0036] The porous portion has a thickness T (the thickness of each side of the metal foil), an inner region on the core side, and a surface region on the side opposite to the core. Furthermore, the surface region refers to a region that is less than or equal to T / 4 from the outer surface of the porous portion when the porous portion has a thickness T (μm). The inner region refers to a region that is less than or equal to T / 4 from the boundary between the porous portion and the core. When the hardness X is within the above range, the average diameter D1 (nm) of the pores in the surface region is likely to be smaller than the average diameter D2 (nm) of the pores in the inner region. Furthermore, in this specification, when abbreviated as "diameter," it refers to "diameter."

[0037] From the viewpoint of suppressing the decrease in strength of the surface layer and increasing the capacitance per unit volume, the ratio D1 / D2 of the average diameter D1 to the average diameter D2 is preferably 0.98 or less, more preferably 0.95 or less, and may also be 0.9 or less. From the viewpoint of increasing electrostatic capacitance, D1 / D2 is preferably 0.5 or more, more preferably 0.55 or more, and may be 0.6 or more, and may also be 0.7 or more. The range of D1 / D2 may also be a range obtained by arbitrarily combining the above-mentioned upper and lower limits, for example, preferably 0.5 or more and 0.98 or less, more preferably 0.55 or more and 0.95 or less. When the hardness X is within the above-mentioned range, D1 / D2 is easily adjusted to 0.98 or less.

[0038] The above-mentioned average diameter D1 and average diameter D2 can be obtained as follows.

[0039] (i) A cross-sectional image of the electrode foil is obtained using a scanning electron microscope (SEM). Using this image, the thickness of the porous portion is measured at 10 arbitrary points, and the average value thereof is calculated as the thickness T of the porous portion.

[0040] (ii) From the outer surface of the porous portion ( Figure 1 The area with a distance of less than T / 4 from the surface S1 in the figure is defined as the surface area.

[0041] (iii) A cross-sectional image of the surface layer region is obtained, and the image is binarized to distinguish between the metal skeleton region constituting the surface layer region and the pore (pit) region excluding the metal skeleton region.

[0042] (iv) Randomly select a point within the pore region of the surface layer, draw a line segment passing through that point and crossing the pore region, and measure the length of the line segment at its shortest point. Repeat this measurement for 20 random points within the pore region of the surface layer, and calculate the average of the measured values ​​to be the average diameter D1 of the pores in the surface layer.

[0043] (v) From the boundary between the porous part and the core part ( Figure 1The region at a distance of T / 4 or less from the surface B) is defined as the inner region. The average diameter D2 of the pores in the inner region is also determined in the same manner as in (iii) and (iv) above.

[0044] When the hardness X is within the above range, the porosity P1 of the surface area is likely to be smaller than the porosity P2 of the inner area. From the viewpoint of suppressing the decrease in strength of the surface layer and increasing the capacitance per unit volume, the ratio P1 / P2 of the porosity P1 to the porosity P2 is preferably 0.95 or less, more preferably 0.92 or less, and may also be 0.85 or less. From the viewpoint of improving electrostatic capacitance, P1 / P2 is preferably 0.5 or more, more preferably 0.55 or more, and may be 0.6 or more, and may also be 0.7 or more. The range of P1 / P2 may be a range obtained by arbitrarily combining the above upper and lower limits, for example, preferably 0.5 or more and 0.95 or less, and more preferably 0.55 or more and 0.92 or less. When the hardness X is within the above range, P1 / P2 is easily adjusted to 0.95 or less.

[0045] The porosity P1 of the surface region is determined by using the binarized cross-sectional image of the surface region obtained in the process of determining the average diameter D1 described above (iii), measuring the area S0 of the entire image and the area S1 of the region occupied by the pores within the image, and then calculating (S1 / S0) × 100. The porosity P2 of the inner region is determined in the same manner.

[0046] The surface roughness Ra of the metal foil (roughness of the outer surface of the porous portion) is preferably 1.5 μm or less, more preferably 0.1 μm or more and 1.5 μm or less, and may be 0.5 μm or more and 1.5 μm or less. The surface roughness Ra of the metal foil refers to the arithmetic mean roughness, which is determined in accordance with Japanese Industrial Standard JIS B0601:2001.

[0047] By reducing the surface roughness Ra of the metal foil to 1.5 μm or less through the compression process described later, the effects of rolling marks can be significantly reduced. The surface roughness of the metal foil can be made smaller than that of the original foil due to rolling marks, and unnecessary oxides along the rolling marks can be removed. Furthermore, when the surface roughness Ra of the metal foil is 0.1 μm or greater, the surface area of ​​the metal foil can be sufficiently ensured, making it easier to increase the capacitance.

[0048] In the pore distribution of the porous portion measured by mercury intrusion porosimetry, it is preferable to satisfy V S1 / V0≤0.07. More preferably, V S2 / V0≤0.05 (or 0.04). When the hardness X is within the above range, V S1 / V0 (and then V S2 / V0) is easily within the above range.

[0049] V0 is the cumulative pore volume (cm2) of pores with a diameter of 0.01 μm or more and 1 μm or less. 3 / g). V S1 The cumulative pore volume (cm2) of pores with a diameter of 0.01 μm or more and 0.06 μm or less 3 / g). V S2 The cumulative pore volume (cm2) of pores with a diameter of 0.01 μm or more and 0.05 μm or less 3 The pore size distribution is measured using, for example, AutoPore V series manufactured by Micromeritics.

[0050] Small pores with a pore diameter of 0.01 μm or more and 0.06 μm or less (or 0.05 μm or less) are easily blocked by the dielectric layer, which is disadvantageous in terms of high capacitance, low ESR and strength. The part of the porous part where the pores are blocked by the dielectric layer not only does not contribute to the improvement of capacitance, but also becomes hard and brittle. If the number of small pores increases and the number of the above-mentioned blocked parts increases, the strength of the electrode foil decreases, and in the manufacturing process of the electrolytic capacitor (electrode foil transportation, slitting, winding, connection with the lead member by riveting, etc.), cracks sometimes occur in the electrode foil or the foil breaks. In V S1 / V0 (and then V S2 When V / V0) is within the above range, there are fewer small pores, and pores with a pore diameter suitable for increasing capacitance are distributed in large numbers, which facilitates high capacitance. In addition, in this case, there are fewer blocked areas, which easily suppresses strength reduction.

[0051] In addition, in the pore distribution of the porous portion measured by mercury intrusion porosimetry, it is preferable to satisfy V L1 / V0≤0.4, more preferably satisfying V L2 / V0≤0.1 (or 0.08). When the hardness X is within the above range, V L1 / V0 (and then V L2 / V0) is likely to be within the above range.

[0052] In addition, V L1 The cumulative pore volume (cm2) of pores with a diameter of 0.16 μm or more and 1 μm or less 3 / g). V L2 The cumulative pore volume (cm2) of pores with a diameter of 0.5 μm or more and 1 μm or less 3 / g).

[0053] Large pores with a pore diameter of 0.16 μm or more (or 0.5 μm or more) and 1 μm or less are unlikely to contribute to an increase in capacitance. Large pores are disadvantageous in expanding the surface area of ​​the electrode foil. For example, in the case of large pores, if two pores are formed in a relatively close position, they press against each other, and the perimeter of the pores (the total length of the contour of the inner wall of the pores present per unit area of ​​the cross section of the porous portion) tends to become smaller, making it difficult to contribute to an increase in capacitance. At V L1 / V0 (and then V L2 When V / V0) is within the above range, there are fewer large pores, and pores having a pore diameter suitable for increasing capacitance are distributed in large numbers, so that the surface area of ​​the electrode foil is likely to be increased, and capacitance is likely to be increased.

[0054] From the perspective of improving strength and capacitance, the thickness of the metal foil is A For example, it is 60 μm or more, preferably 90 μm or more, more preferably 110 μm or more, and further preferably 120 μm or more. A From the perspective of improving capacitance, the thickness T of the porous portion may be 25 μm to 90 μm, or 35 μm to 80 μm. A When the thickness falls within the above range, the thickness T of the porous portion can be increased within the above range while ensuring a sufficient thickness of the core portion. The thickness of the core portion may be, for example, 20 μm or more, or 25 μm or more.

[0055] The thickness of the metal foil is T A In the case of a larger diameter (for example, when it is 90 μm or more or 120 μm or more), the stress generated in the metal foil (surface layer) during winding becomes larger, so the effect of improving the surface layer strength (the effect of suppressing the generation of cracks caused by this stress) can be significantly obtained when the hardness X is within the above range.

[0056] The metal foil contains a valve metal. Examples of valve metals include aluminum (Al), tantalum (Ta), and niobium (Nb). The metal foil may be a foil of a valve metal (e.g., Al) or a foil of an alloy or compound containing a valve metal (e.g., Al). When the metal foil is used as an anode foil, a dielectric layer may be formed to cover the metal skeleton constituting the porous portion. The dielectric layer may be, for example, a layer containing an oxide of the valve metal.

[0057] Here, Figure 1 This is a cross-sectional view schematically showing an example of an electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure. Figure 1 The cross section of the electrode foil in the thickness direction is shown. However, the electrode foil for electrolytic capacitors disclosed in the present disclosure is not limited thereto.

[0058] The electrode foil (metal foil 300) contains a valve-acting metal and includes a core portion 330, and a first porous portion 310 and a second porous portion 320 connected to the core portion 330. The metal foil 300 has a first main surface S1 and a second main surface S2 opposite to the first main surface S1. The first porous portion 310 and the second porous portion 320 are formed so as to sandwich the core portion 330. The first porous portion 310 has the first main surface S1 of the metal foil 300. The second porous portion 320 has the second main surface S2 of the metal foil 300. In the case of the anode foil described later, a dielectric layer is formed by chemical conversion treatment or the like, and this dielectric layer covers the surface of the metal skeleton constituting the first porous portion 310 and the second porous portion 320.

[0059] At least one of the first hardness X1 of the first porous portion 310 and the second hardness X2 of the second porous portion 320 is a hardness X within the above-mentioned range. The first hardness X1 is the hardness of the first porous portion 310 when the maximum indentation load onto the first main surface S1 is 100 mN, as measured by the nanoindentation method. The second hardness X2 is the hardness of the second porous portion 320 when the maximum indentation load onto the second main surface S2 is 100 mN, as measured by the nanoindentation method. At least one of the first hardness X1 and the second hardness X2 is sufficient to be a hardness X within the above-mentioned range. Preferably, both the first hardness X1 and the second hardness X2 are hardness X within the above-mentioned range. The first hardness X1 and the second hardness X2 are generally substantially the same, but may be different.

[0060] The porous portion 310 has a thickness T (μm) and includes an inner region 312 on the core portion 330 side and a surface region 311 on the opposite side of the core portion 330. The surface region 311 is a region that is a distance T / 4 or less from the outer surface S1 of the porous portion 310. The inner region 312 is a region that is a distance T / 4 or less from the boundary B between the porous portion 310 and the core portion 330. When the first hardness X1 is within the hardness X range described above, the average diameter D1 (nm) of the pores in the surface region 311 can be smaller than the average diameter D2 (nm) of the pores in the inner region 312. The same can be said for the porous portion 320 (the surface region 321 and the inner region 322).

[0061] (Method for Manufacturing Electrode Foil for Electrolytic Capacitors)

[0062] The method for manufacturing an electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure includes: an etching step of etching a sheet containing a valve metal to form a porous portion on a main surface of the sheet; and a compression step of compressing the etched sheet in the thickness direction to form a hardness X of 40 mN / mm. 2The hardness X is the hardness measured by nanoindentation when the maximum indentation load on the main surface is 100 mN.

[0063] The sheet used for etching (hereinafter also referred to as a "raw material sheet") contains a valve metal. Examples of valve metals include Al, Ta, and Nb. The raw material sheet may be a sheet of a valve metal (e.g., Al) or a sheet of an alloy or compound containing a valve metal (e.g., Al). The raw material sheet is typically a rolled sheet (rolled foil) in the form of a long strip or ribbon.

[0064] A porous portion is formed on the main surface of the sheet by etching, and the portion other than the porous portion remains as a core portion. That is, the sheet after etching has a core portion and a porous portion continuous with the core portion, and the porous portion has the main surface of the sheet. The porous portion is usually formed on the two main surfaces of the sheet, forming a structure that sandwiches the core portion. In the compression process, the sheet having the porous portion formed by etching is compressed. The surface layer of the porous portion has a low strength and is easily compressed in the compression process. The thickness of the porous portion (especially the surface layer) is reduced by compression. The thickness of the core portion may be slightly reduced before and after compression, but is preferably almost unchanged.

[0065] For example, the hardness X, D1 / D2, P1 / P2, V S1 / V0、V S2 / V0、V L1 / V0、V L2 / V0, etc. are controlled within the above range.

[0066] During the manufacturing process of electrolytic capacitors, the sheet comes into contact with the treatment liquid (such as etching solution, chemical conversion liquid) and the roller, which may cause bumps (or damage). During the manufacturing process, stress is concentrated on the bumps, and sometimes the sheet breaks (or the sheet cracks). In addition, the aluminum foil used for the sheet has rolling marks generated during its manufacturing process, and etching pits can be unevenly formed along the rolling marks, that is, along the length direction (rolling direction) of the long strip. Due to the influence of the rolling marks, the sheet sometimes breaks (or the sheet cracks). In contrast, as mentioned above, by moderately compressing the sheet after the etching process, the influence of the above-mentioned bumps and rolling marks is reduced, the strength of the surface layer of the sheet is improved, and the breakage of the above-mentioned sheet is suppressed.

[0067] After the compression process, the thickness of the sheet is T A It may be 90 μm or more and 200 μm or less, or 120 μm or more and 200 μm or less. After the compression step, the thickness T per single side of the porous portion may be 25 μm or more and {(T A / 2)-10}μm or less. When the thickness T is within the above range, the core can be ensured with sufficient thickness. In addition, the thickness T can be greater than 25μm and less than 90μm, or greater than 35μm (or greater than 40μm) and less than 80μm. In high-capacitance foils, the thickness T of the porous portion is large, which can significantly improve the surface strength brought about by compression. In particular, in capacitors with solid electrolytes and liquid components (electrolytes, etc.), high-capacitance foils are used, and the thickness T of the sheet (electrode foil) is greater than 10μm. A It is preferably 90 μm or more or 120 μm or more, and the thickness T per one side of the porous portion is preferably 25 μm or more or 35 μm or more (or 40 μm or more).

[0068] (Etching process)

[0069] In the etching process, the surface of the valve metal sheet is etched to roughen the surface, forming a porous portion that is continuous with the core. Etching can be performed using either electrolytic or chemical etching, and known methods can be used. For example, the hardness X can be adjusted to a certain extent depending on the etching conditions.

[0070] From the perspective of forming pores with larger diameters, electrolytic etching can be performed at 2.0 A / cm 2 The current density can be as low as 1.5A / cm 2 The current density can be as low as 1.2A / cm 2 The etching is performed at the following current density. The current density can also be changed during etching. A larger pore diameter makes it easier to form a thicker dielectric layer, which is more advantageous in terms of increasing the voltage.

[0071] Electrolytic etching is preferably AC etching, but DC etching may also be used. In the case of AC etching, a porous portion containing sponge-like pits with a relatively small diameter is easily formed. In the case of DC etching, a porous portion containing channel-like pits with a relatively large diameter is easily formed.

[0072] When the etching time is set to T E When the temperature is between 0 and 0.7T, E During the period, the temperature of the etching solution is set to 10°C or higher and 60°C or lower. E ~T E During the etching time T, the temperature of the etching solution is set to 5°C or higher and 40°C or lower. In this case, the variation in the pit diameter in the thickness direction of the porous portion can be reduced. E For example, it is 15 minutes or more and 30 minutes or less.

[0073] (Compression process)

[0074] In the compression process, the etched sheet can also be conveyed between a pair of rollers for compression. The etched sheet conveyed between the pair of rollers is compressed by the pressure of the pair of rollers. As described later, by appropriately adjusting the roller pressing conditions, it is easy to adjust the hardness X, D1 / D2 (and further P1 / P2), V S1 / V0 (and then V S2 / V0) and V L1 / V0 (and then V L2 / V0) is controlled within the above range.

[0075] Alternatively, a pair of rollers can be configured in multiple sections to compress the sheet in stages. In this case, the diameter of the rollers can vary for each section, or can decrease as the sheet is compressed. The compression process can also include conveying the sheet using the rollers and winding the compressed sheet. Compression increases the strength of the sheet's surface layer and prevents breakage during sheet winding using the rollers.

[0076] Here, Figure 2 This is a structural diagram showing an example of a compression process. Figure 2 The arrow X in FIG. 4 represents the conveying direction of the long strip of sheet material 400. In the compression process, for example, Figure 2 The compression device shown in FIG. The compression device includes a pair of rollers 500 for compressing the sheet 400. The thickness T after the etching process is reduced by pressing the pair of rollers 500. B (mm) sheet 400 is compressed to a thickness T A The sheet feeding speed may be 0.5 m / min or more, or 0.5 m / min or more and 50 m / min or less.

[0077] From the viewpoint of easily obtaining the above-mentioned electrode foil, the thickness reduction rate of the sheet in the compression process is preferably 5% or more and 40% or less, more preferably 10% or more (or 12% or more) and 30% or less, and even more preferably 10% or more and 25% or less. In addition, the thickness reduction rate refers to the thickness of the sheet reduced from T to T by compression. B Reduce to T A When according to {(T B -T A ) / T B}×100 to calculate the value.

[0078] When the roller 500 is observed from a direction parallel to its rotation axis, the contact area 410 between the roller 500 and the sheet 400 is arc-shaped, and the center angle θ of the arc of the roller 500 relative to the contact area 410 can be greater than 0.15° and less than 1.5° (or less than 1.75°).

[0079] When the contact area 410 between the sheet 400 and the roller 500 is projected onto an imaginary plane parallel to the main surface of the sheet 400 , the length L of the projection area in the conveyance direction X of the sheet 400 may be 0.5 mm to 5 mm.

[0080] The sheet 400 may be compressed at a linear pressure of 0.55 kN / cm or more and 14 kN / cm or less. The diameter D of the roller 500 may be 75 mm or more and 1800 mm or less. The thickness T0 (mm) of the porous portion of the sheet 400 before compression and the diameter D (mm) of the roller 500 may satisfy the relationship 380 ≤ D / T0 ≤ 9800.

[0081] The apparatus may further include rollers for conveying the sheet 400 or rollers for winding the compressed sheet 400. The apparatus may also include a control unit for controlling the rotation speed of the rollers 500. The feeding speed of the sheet 400 may also be controlled by the control unit.

[0082] The electrode foil manufacturing method may include a step of slitting the compressed sheet. The slitting process uses a slitting device and a roller for winding the slitting sheet. Compression increases the strength of the sheet's surface layer and prevents breakage when the sheet is wound by the roller.

[0083] (Electrolytic Capacitors)

[0084] The electrode foil for electrolytic capacitors according to the embodiment of the present disclosure is suitable for use in electrolytic capacitors having a wound capacitor element. The wound capacitor element comprises a wound body and an electrolyte. The wound body is formed by winding an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil. The anode foil comprises an electrode foil according to the embodiment of the present disclosure (hereinafter also referred to as "electrode foil A") and a dielectric layer covering a metal skeleton constituting a porous portion of the electrode foil A.

[0085] In electrolytic capacitors with a rated voltage of 20V or more, for example, aluminum foil that has been chemically converted using a chemical conversion voltage of 30V or more is used as anode foil. In addition, in electrolytic capacitors with a solid electrolyte (conductive polymer) and a liquid component (electrolyte, etc.), aluminum foil that has been chemically converted using a chemical conversion voltage of 40V or more is used as anode foil in many cases. In such anode foil, an electrode foil with a relatively large pit diameter is used to form a dielectric layer with a relatively large thickness (for example, a thickness of 45nm or more), and the strength of the surface layer is easily reduced. Therefore, the improvement effect of the surface layer strength brought by the electrode foil A can be significantly obtained. Under a chemical conversion voltage of 30V or more (or more than 40V), the generated chemical conversion film thickens, and therefore by using an electrode foil with a larger pit diameter to suppress the clogging of the pits caused by the larger chemical conversion film of thickness, high capacitance can be efficiently sought.

[0086] (Anode foil)

[0087] The anode foil comprises an electrode foil A and a dielectric layer covering a metal skeleton constituting the porous portion of the electrode foil A. The dielectric layer is formed, for example, by anodizing (chemical conversion treatment) to form an oxide film of a valve-acting metal on the surface of the metal skeleton constituting the porous portion. When the aluminum foil is subjected to chemical conversion treatment, the chemical conversion voltage can be, for example, 5V or higher, or 40V or higher.

[0088] The main surface of the anode foil may include a first main surface and a second main surface on the side opposite to the first main surface. The porous portion may include a first porous portion having a first main surface and a second porous portion having a second main surface, sandwiching a core portion. The dielectric layer may include a first dielectric layer covering the metal skeleton constituting the first porous portion and a second dielectric layer covering the metal skeleton constituting the second porous portion. In this case, it is sufficient that at least one of the first hardness X1 of the first porous portion and the second hardness X2 of the second porous portion is a hardness X within the above-mentioned range. Preferably, both the first hardness X1 and the second hardness X2 are hardness X within the above-mentioned range. Alternatively, the first hardness X1 may be greater than the second hardness X2, and at least the first hardness X1 is a hardness X within the above-mentioned range. In this case, it is preferred that the anode foil is wound in a manner such that the first main surface of the first porous portion having the first hardness X1 faces the outer circumference of the wound body. In this case, since the tensile stress generated on the main surface of the outer peripheral side of the wound body during winding is large, the effect of improving the strength of the surface layer (the effect of suppressing the occurrence of cracks during winding) can be significantly obtained.

[0089] The thickness of the anode foil may be 60 μm to 200 μm, preferably 90 μm to 200 μm, and more preferably 120 μm to 200 μm. The thickness of the dielectric layer is, for example, 45 nm or more.

[0090] (Cathode foil)

[0091] The cathode foil can be made of a metal foil containing a valve-action metal such as Al, Ta, or Nb. The surface of the metal foil can be roughened by etching as needed. Specifically, the cathode foil can include a porous portion and a core portion continuous with the porous portion. The electrode foil for electrolytic capacitors disclosed herein can also be used as the cathode foil. The thickness of the cathode foil is, for example, not less than 10 μm and not more than 70 μm.

[0092] (Separator)

[0093] The separator is not particularly limited, and for example, nonwoven fabrics containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (for example, aliphatic polyamide, aromatic polyamide such as aramid) can be used.

[0094] (Electrolyte)

[0095] The electrolyte covers at least a portion of the anode foil (dielectric layer) and is sandwiched between the anode foil (dielectric layer) and the cathode foil. The electrolyte comprises at least one of a solid electrolyte and an electrolyte solution. The capacitor element may comprise a solid electrolyte or a solid electrolyte and a liquid component (electrolyte solution or non-aqueous solvent).

[0096] Coating the dielectric layer with an electrolyte is performed, for example, by impregnating the anode foil (or wound body) with a treatment solution (or electrolyte solution) containing a conductive polymer. In the aforementioned electrode foil, since average diameter D1 is smaller than average diameter D2 (and thus, porosity P1 is smaller than porosity P2), the treatment solution impregnated into the porous portion is more likely to remain within the pores, and the inner walls of the pores are more likely to be covered with the electrolyte, thereby improving the contact between the anode foil (dielectric layer) and the electrolyte.

[0097] The solid electrolyte comprises a conductive polymer. Examples of the conductive polymer include π-conjugated polymers. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, and polyaniline. The conductive polymer may be used alone or in combination of two or more, or may be a copolymer of two or more monomers. The weight average molecular weight of the conductive polymer is, for example, 1,000 to 100,000.

[0098] In this specification, polypyrrole, polythiophene, polyfuran, and polyaniline refer to polymers with polypyrrole, polythiophene, polyfuran, and polyaniline as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, and polyaniline may also include their derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene).

[0099] The conductive polymer may be doped with a dopant. The solid electrolyte may contain both the conductive polymer and the dopant. Examples of the dopant include polystyrene sulfonic acid. The solid electrolyte may further contain additives as needed.

[0100] The liquid component can be an electrolyte or a non-aqueous solvent. The electrolyte contains a non-aqueous solvent and an ionic substance (solute (e.g., an organic salt)) dissolved in the non-aqueous solvent. The non-aqueous solvent can be an organic solvent or an ionic liquid.

[0101] As the non-aqueous solvent, a high-boiling-point solvent is preferably used. For example, polyol compounds such as ethylene glycol, sulfone compounds such as sulfolane, lactone compounds such as γ-butyrolactone, ester compounds such as methyl acetate, carbonate compounds such as propylene carbonate, ether compounds such as 1,4-dioxane, and ketone compounds such as methyl ethyl ketone can be used.

[0102] The liquid component may contain an acid component (anion) and an alkaline component (cation). A salt (solute) may also be formed from the acid component and the alkaline component. The acid component contributes to the film repair function. Examples of the acid component include organic carboxylic acids and inorganic acids. Examples of inorganic acids include phosphoric acid, boric acid, and sulfuric acid. Examples of the alkaline component include primary to tertiary amine compounds.

[0103] An organic salt is a salt in which at least one of the anion and the cation contains an organic substance. Examples of the organic salt include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate.

[0104] From the viewpoint of suppressing dedoping of the conductive polymer by the dopant (deterioration of the solid electrolyte), it is preferred that the liquid component contains more acid components than alkaline components. In addition, from the viewpoint that the acid component contributes to the film repair function of the liquid component, it is also preferred that the acid component is contained in an amount greater than the alkaline component. The molar ratio of the acid component to the alkaline component: (acid component / alkaline component) is, for example, greater than 1.1. From the viewpoint of suppressing dedoping of the conductive polymer by the dopant, the pH of the liquid component may be less than 6, or may be greater than 1 and less than 5.

[0105] Here, Figure 3 This is a cross-sectional view schematically showing an example of an electrolytic capacitor according to an embodiment of the present disclosure. Figure 4 It is schematically represented Figure 3 A three-dimensional diagram of the structure of a wound body of an electrolytic capacitor.

[0106] Electrolytic capacitor 200 includes a capacitor element, and the capacitor element includes a wound body 100 and an electrolyte (not shown). Wound body 100 is formed by winding anode foil 10 and cathode foil 20 with separator 30 interposed therebetween.

[0107] Lead pieces 50A and 50B are connected to one end of anode foil 10 and cathode foil 20, respectively, and lead pieces 50A and 50B are wound together to form wound body 100. Lead wires 60A and 60B are connected to the other ends of lead pieces 50A and 50B, respectively.

[0108] A winding fixing tape 40 is disposed on the outer surface of the cathode foil 20 located at the outermost layer of the wound body 100, and the ends of the cathode foil 20 are fixed by the winding fixing tape 40. Furthermore, when the anode foil 10 is prepared by cutting from a large sheet of foil, the wound body 100 may also be subjected to a chemical conversion treatment to provide a dielectric layer on the cut surface.

[0109] An electrolyte is interposed between anode foil 10 (dielectric layer) and cathode foil 20 of wound body 100. The capacitor element is obtained by, for example, impregnating wound body 100 with a treatment liquid containing an electrolyte. The impregnation can be performed under reduced pressure, for example, an atmosphere of 10 kPa to 100 kPa.

[0110] The wound body 100 is housed in the bottomed case 211 with the leads 60A and 60B positioned on the opening side of the bottomed case 211. The bottomed case 211 may be made of a metal such as aluminum, stainless steel, copper, iron, or brass, or an alloy thereof.

[0111] A sealing member 212 is arranged at the opening of a bottom shell 211 that accommodates the wound body 100 and the electrolyte. The open end of the bottom shell 211 is riveted to the sealing member 212 and curled, and a seat plate 213 is arranged at the curled portion, thereby sealing the wound body 100 in the bottom shell 211.

[0112] Sealing member 212 is formed so that lead wires 60A and 60B pass through. Sealing member 212 can be made of any insulating material, preferably an elastomer. Preferred materials include silicone rubber, fluororubber, ethylene propylene rubber, chlorosulfonated polyethylene synthetic rubber, butyl rubber, and isoprene rubber, which have high heat resistance.

[0113] The electrode foil of the embodiment of the present disclosure can be used for an electrolytic capacitor having the above-mentioned wound capacitor element, but can also be used for an electrolytic capacitor having a stacked capacitor element. In this case, the porous portion can be formed on a portion of the surface of the electrode foil. The stacked capacitor element comprises an anode body, a solid electrolyte layer, and a cathode lead layer covering the solid electrolyte layer. The anode body comprises an electrode foil and a dielectric layer covering a portion of the surface of the electrode foil. The solid electrolyte layer is formed to cover the dielectric layer. The cathode lead layer comprises, for example, a carbon layer and a silver paste layer. An anode lead is connected to the portion of the anode body not covered by the dielectric layer, and a cathode lead is connected to the cathode lead layer.

[0114] [Example]

[0115] Hereinafter, the present disclosure will be described in more detail based on examples, but the present disclosure is not limited to the examples.

[0116] Example 1-Example 2

[0117] (Etching process)

[0118] Aluminum (Al) foil (thickness T B :130μm) were etched to form porous parts on both sides of the Al sheet (thickness T0 of each side: 50μm). In the etching process, AC etching was performed at 1.5A / cm 2 The current density is appropriately adjusted within the following ranges, and the etching time is also appropriately adjusted to achieve a predetermined dissolution amount.

[0119] (Compression process)

[0120] The Al sheet after etching was compressed in the thickness direction to obtain electrode foils a1 to a2. In the compression process, the thickness of the Al sheet was reduced at the ratio (reduction rate) shown in Table 1. A The values ​​shown in Table 2 are used as the values ​​of the thickness T (μm) per single surface of the porous portion.

[0121] like Figure 2 As shown in FIG. 1 , in the compression step, the Al sheet was conveyed between a pair of rollers (diameter D: 75 mm) for compression. The roller pressure and linear pressure were set to the values ​​shown in Table 1. The Al sheet feed rate was set to the values ​​shown in Table 1. The ratio of the roller diameter D (mm) to the thickness T0 (mm) of the porous portion of the sheet before compression, D / T0, was 1500. Figure 2 The angle θ in is set to the value shown in Table 1. Figure 2 The length L in is set to the value shown in Table 1.

[0122] [Table 1]

[0123]

[0124] The hardness X, elastic modulus, creep amount, D1 / D2 and P1 / P2 obtained by the above-mentioned method are the values ​​shown in Table 2. The arithmetic mean roughness Ra of the electrode foil is the value shown in Table 2. S1 / V0、V S2 / V0、V L1 / V0 and V L2 / V0 is the value shown in Table 2. The values ​​of thickness T, hardness X, etc. related to the porous portion are measured values ​​of the porous portion on one surface of the Al sheet, and substantially the same values ​​were obtained for the porous portion on the other surface of the Al sheet.

[0125] [Table 2]

[0126]

[0127] (Formation of Dielectric Layer)

[0128] Electrode foils a1 and a2 were chemically converted to form a dielectric layer covering the metal skeleton that constituted the porous portion. The chemical conversion treatment was performed in accordance with the Japanese Electronics and Machinery Industry Standards Test Methods for Aluminum Electrolytic Capacitor Electrode Foil (EIAJRC-2364A) at a chemical conversion voltage of 65 V. This produced anode foils A1 and A2.

[0129] The electrode foils a1 and a2 are those of Examples 1 and 2, and the anode foils A1 and A2 are chemically converted products of the electrode foils a1 and a2.

[0130] Comparative Example 1

[0131] Electrode foil b1 was produced in the same manner as electrode foil a1, except that the Al sheet was not compressed after etching. Anode foil B1 was produced in the same manner as anode foil A1, except that electrode foil b1 was used instead of electrode foil a1.

[0132] (Evaluation 1: Tensile Strength of Electrode Foil)

[0133] For each electrode foil, strip-shaped samples (70 mm in length and 10 mm in width) were prepared and the tensile strength of these samples in the longitudinal direction was measured according to the Japanese Electronics and Machinery Industry Standards Test Method for Electrode Foil for Aluminum Electrolytic Capacitors (EIAJ RC-2364A). The measurement results are shown in Table 1. In Table 2, the tensile strength is expressed as a relative value, with the tensile strength of electrode foil b1 being set to 100.

[0134] (Evaluation 2: Capacitance of anode foil)

[0135] The capacitance of each anode foil was measured according to the Japanese Electronics and Machinery Industry Standards Test Method for Electrode Foil for Aluminum Electrolytic Capacitors (EIAJ RC-2364A). The measurement results are shown in Table 3. In Table 3, the capacitance is expressed relative to the capacitance of anode foil B1, which is set to 100. Table 3 also shows the capacitance per unit volume of the anode foil.

[0136] [Table 3]

[0137]

[0138] Electrode foils a1 and a2 exhibited higher tensile strength than electrode foil b1. Anode foils A1 and A2 all exhibited good capacitance, confirming high capacitance per unit volume.

[0139] Example 3 to Example 5

[0140] (Etching process)

[0141] For Al foil (thickness T B :150μm) were etched to form porous parts on both sides of the Al sheet (thickness T0 of each side: 60μm). In the etching process, AC etching was performed at 1.5A / cm 2 The current density is appropriately adjusted within the following range, and the etching time is also appropriately adjusted so as to achieve a predetermined dissolution amount.

[0142] (Compression process)

[0143] The Al sheet after etching was compressed in the thickness direction to obtain electrode foils a3 to a5. In the compression process, the thickness of the sheet was reduced at the ratio (reduction rate) shown in Table 4. A The values ​​shown in Table 5 are used as the values ​​of the thickness T (μm) per single surface of the porous portion.

[0144] like Figure 2 As shown in Table 4, in the compression step, the Al sheet was conveyed between a pair of rollers (diameter D: 75 mm) for compression. The roller pressure and linear pressure were set to the values ​​shown in Table 4. The Al sheet feed rate was set to the values ​​shown in Table 4. The ratio of the roller diameter D (mm) to the thickness T0 (mm) of the porous portion before sheet compression, D / T0, was 1250. Figure 2 The angle θ in is set to the value shown in Table 4. Figure 2 The length L in is set to the value shown in Table 4.

[0145] [Table 4]

[0146]

[0147] The hardness X, elastic modulus, creep amount, D1 / D2 and P1 / P2 obtained by the above-mentioned method are the values ​​shown in Table 5. The arithmetic mean roughness Ra of the electrode foil is the value shown in Table 5. S1 / V0、V S2 / V0、V L1 / V0 and V L2 / V0 is the value shown in Table 5.

[0148] [Table 5]

[0149]

[0150] (Formation of Dielectric Layer)

[0151] Electrode foils a3 through a5 were chemically converted to form a dielectric layer covering the metal skeleton that constituted the porous portion. The chemical conversion treatment was performed in accordance with the Japanese Electronics and Machinery Industry Standards Test Methods for Aluminum Electrolytic Capacitor Electrode Foil (EIAJRC-2364A) at a chemical conversion voltage of 65 V. This produced anode foils A3 through A5.

[0152] The electrode foils a3 to a5 are Examples 3 to 5, and the anode foils A3 to A5 are chemically converted products of the electrode foils a3 to a5.

[0153] Comparative Example 2

[0154] Electrode foil b2 was produced in the same manner as electrode foil a3, except that the Al sheet was not compressed after etching. Anode foil B2 was produced in the same manner as anode foil A3, except that electrode foil b2 was used instead of electrode foil a3.

[0155] The aforementioned evaluation 1 was performed on electrode foils a3 to a5 and b2. The evaluation results are shown in Table 5. In Table 5, the tensile strength is expressed as a relative value, with the tensile strength of electrode foil b2 being 100. The aforementioned evaluation 2 was performed on anode foils A3 to A5 and B2. The evaluation results are shown in Table 6. In Table 6, the electrostatic capacitance is expressed as a relative value, with the electrostatic capacitance of anode foil B2 being 100. Table 6 also shows the capacitance per unit volume of the anode foil.

[0156] [Table 6]

[0157]

[0158] Electrode foils a3 to a5 exhibited higher tensile strength than electrode foil b2. Anode foils A3 to A5 all exhibited good capacitance, confirming high capacitance per unit volume.

[0159] Postscript

[0160] Based on the description of the above embodiments, the following technology is disclosed.

[0161] (Technique 1)

[0162] An electrode foil for an electrolytic capacitor, wherein:

[0163] The electrode foil for electrolytic capacitors includes a metal foil containing a valve-acting metal.

[0164] The metal foil has a core portion and a porous portion continuous with the core portion.

[0165] The porous portion has a main surface of the metal foil,

[0166] The hardness X of the porous portion measured by nanoindentation when the maximum indentation load on the main surface was 100 mN was 40 mN / mm. 2 above.

[0167] (Technique 2)

[0168] The electrode foil for electrolytic capacitors according to technique 1, wherein

[0169] The hardness X is 54 mN / mm 2 above.

[0170] (Technique 3)

[0171] The electrode foil for electrolytic capacitors according to technique 1 or 2, wherein

[0172] The elastic modulus of the porous portion measured by nanoindentation when the maximum indentation load on the main surface was 100 mN was 520 mN / mm. 2 above.

[0173] (Technique 4)

[0174] The electrode foil for electrolytic capacitors according to any one of techniques 1 to 3, wherein

[0175] The creep amount of the porous portion when the maximum indentation load on the main surface is 100 mN, as measured by a nanoindentation method, is 5% or more.

[0176] (Technique 5)

[0177] The electrode foil for electrolytic capacitors according to any one of techniques 1 to 4, wherein

[0178] The porous portion has a thickness T and includes an inner layer region on the core side and a surface layer region on the side opposite to the core.

[0179] The surface region is a region that is less than or equal to a distance T / 4 from the outer surface of the porous portion.

[0180] The inner layer region is a region having a distance T / 4 or less from the boundary between the porous portion and the core portion.

[0181] The average diameter D1 of the pores in the surface layer region is smaller than the average diameter D2 of the pores in the inner layer region.

[0182] (Technique 6)

[0183] The electrode foil for electrolytic capacitors according to technique 5, wherein

[0184] A ratio D1 / D2 of the average diameter D1 to the average diameter D2 is greater than or equal to 0.5 and less than or equal to 0.98.

[0185] (Technique 7)

[0186] The electrode foil for electrolytic capacitors according to technology 5 or 6, wherein

[0187] The porosity P1 of the surface layer region is smaller than the porosity P2 of the inner layer region.

[0188] (Technique 8)

[0189] The electrode foil for electrolytic capacitors according to technology 7, wherein

[0190] A ratio P1 / P2 of the porosity P1 to the porosity P2 is greater than or equal to 0.5 and less than or equal to 0.95.

[0191] (Technique 9)

[0192] The electrode foil for electrolytic capacitors according to any one of techniques 1 to 8, wherein

[0193] The surface roughness Ra of the metal foil is 1.5 μm or less.

[0194] (Technique 10)

[0195] The electrode foil for electrolytic capacitors according to any one of techniques 1 to 9, wherein

[0196] In the pore distribution of the porous portion measured by mercury intrusion porosimetry,

[0197] The cumulative pore volume V0 (cm2) of pores with a diameter of 0.01 μm or more and 1 μm or less 3 / g) and a cumulative pore volume V of 0.01 μm or more and 0.06 μm or less in pore diameter. S1 (cm 3 / g) meets V S1 / V0≤0.07.

[0198] (Technology 11)

[0199] The electrode foil for electrolytic capacitors according to any one of techniques 1 to 10, wherein

[0200] In the pore distribution of the porous portion measured by mercury intrusion porosimetry,

[0201] The cumulative pore volume V0 (cm2) of pores with a diameter of 0.01 μm or more and 1 μm or less 3 / g) and a cumulative pore volume V of 0.16 μm or more and 1 μm or less in pore diameter. L1 (cm 3 / g) meets V L1 / V0≤0.4.

[0202] (Technology 12)

[0203] The electrode foil for electrolytic capacitor according to any one of techniques 1 to 11, wherein

[0204] The thickness T of the metal foil A It is 90 μm or more and 200 μm or less.

[0205] (Technology 13)

[0206] The electrode foil for electrolytic capacitors according to any one of techniques 1 to 12, wherein

[0207] The thickness T of the porous portion is 30 μm or more and 90 μm or less.

[0208] (Technique 14)

[0209] The electrode foil for electrolytic capacitors according to any one of techniques 1 to 13, wherein

[0210] The main surface of the metal foil includes a first main surface and a second main surface opposite to the first main surface.

[0211] The porous portion includes a first porous portion having the first main surface and a second porous portion having the second main surface, which sandwich the core portion.

[0212] The hardness X is at least one of a first hardness X1 of the first porous portion when the maximum indentation load on the first main surface is 100 mN as measured by the nanoindentation method, and a second hardness X2 of the second porous portion when the maximum indentation load on the second main surface is 100 mN as measured by the nanoindentation method.

[0213] (Technology 15)

[0214] The electrode foil for electrolytic capacitor according to technique 14, wherein

[0215] The first hardness X1 is different from the second hardness X2.

[0216] (Technology 16)

[0217] An electrolytic capacitor, wherein

[0218] The electrolytic capacitor includes a capacitor element,

[0219] The capacitor element includes a wound body and an electrolyte.

[0220] The wound body is formed by winding an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil.

[0221] The anode foil includes the electrode foil according to any one of techniques 1 to 15, and a dielectric layer covering the metal skeleton constituting the porous portion of the electrode foil.

[0222] (Technology 17)

[0223] The electrolytic capacitor according to technique 16, wherein

[0224] The thickness of the dielectric layer is greater than 45 nm.

[0225] (Technology 18)

[0226] The electrolytic capacitor according to technique 16 or 17, wherein

[0227] The capacitor element includes a solid electrolyte as the electrolyte and may further include a liquid component.

[0228] The solid electrolyte includes a conductive polymer.

[0229] (Technology 19)

[0230] The electrolytic capacitor according to any one of Techniques 16 to 18, wherein:

[0231] The main surface of the metal foil of the anode foil includes a first main surface and a second main surface opposite to the first main surface.

[0232] The porous portion includes a first porous portion having the first main surface and a second porous portion having the second main surface, which sandwich the core portion.

[0233] The dielectric layer includes a first dielectric layer covering the metal skeleton constituting the first porous portion and a second dielectric layer covering the metal skeleton constituting the second porous portion.

[0234] a first hardness X1 of the first porous portion when the maximum indentation load on the first main surface is 100 mN as measured by nanoindentation is greater than a second hardness X2 of the second porous portion when the maximum indentation load on the second main surface is 100 mN as measured by nanoindentation,

[0235] At least the first hardness X1 is the hardness X,

[0236] In the wound body, the anode foil is wound such that the first main surface faces the outer periphery of the wound body.

[0237] (Technology 20)

[0238] A method for manufacturing an electrode foil for an electrolytic capacitor, wherein:

[0239] The manufacturing method comprises:

[0240] an etching step of etching a sheet containing a valve metal to form a porous portion on a main surface of the sheet; and

[0241] Compression step: compress the etched sheet in the thickness direction to form a hardness X of 40mN / mm 2 The porous portion described above,

[0242] The hardness X is the hardness measured by a nanoindentation method when the maximum indentation load on the main surface is 100 mN.

[0243] (Technology 21)

[0244] The method for manufacturing an electrode foil for an electrolytic capacitor according to technique 20, wherein:

[0245] The hardness X is 54 mN / mm 2 above.

[0246] (Technology 22)

[0247] The method for manufacturing an electrode foil for an electrolytic capacitor according to technique 20 or 21, wherein:

[0248] The sheet comprises aluminum.

[0249] (Technique 23)

[0250] The method for manufacturing an electrode foil for an electrolytic capacitor according to any one of Techniques 20 to 22, wherein:

[0251] After the compression process, the thickness of the sheet is T A (μm) and the thickness T (μm) per single side of the porous portion satisfy 90≤T A≤200 and 25≤T≤(T A / 2)-10 relationship.

[0252] (Technique 24)

[0253] The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 20 to 23, wherein:

[0254] In the etching process, the 2 Electrolytic etching was performed at the following current density.

[0255] (Technique 25)

[0256] The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 20 to 24, wherein:

[0257] In the compression step, the thickness of the sheet is reduced by 5% or more and 40% or less.

[0258] (Technique 26)

[0259] The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 20 to 25, wherein:

[0260] In the compression step, the sheet is conveyed between a pair of rollers and compressed.

[0261] (Technique 27)

[0262] The method for manufacturing an electrode foil for an electrolytic capacitor according to technique 26, wherein:

[0263] The sheet is fed out at a speed of 0.5 m / min or more.

[0264] (Technique 28)

[0265] The method for manufacturing an electrode foil for an electrolytic capacitor according to technique 26 or 27, wherein:

[0266] When the roller is viewed from a direction parallel to the rotation axis of the roller, the contact area between the roller and the sheet is in the shape of an arc.

[0267] A central angle θ of the roller relative to the arc of the contact region is greater than or equal to 0.15° and less than or equal to 1.5°.

[0268] (Technique 29)

[0269] The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 26 to 28, wherein:

[0270] When the contact area between the sheet and the roller is projected onto an imaginary plane parallel to the main surface of the sheet as a projection area,

[0271] A length L of the projection area in the conveyance direction of the sheet is greater than or equal to 0.5 mm and less than or equal to 5 mm.

[0272] (Technique 30)

[0273] The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 26 to 29, wherein:

[0274] The sheet is compressed at a linear pressure of 1 kN / cm or more and 14 kN / cm or less.

[0275] (Technology 31)

[0276] The method for manufacturing an electrode foil for an electrolytic capacitor according to any one of Techniques 26 to 30, wherein:

[0277] The thickness T0 (mm) of the porous portion of the sheet before compression and the diameter D (mm) of the roller satisfy the relationship of 380≤D / T0≤9800.

[0278] Industrial applicability

[0279] The electrode foil disclosed herein is suitable for use in electrolytic capacitors requiring high reliability and capacitance.

[0280] Description of Reference Numerals

[0281] 10. Anode foil; 20. Cathode foil; 30. Separator; 40. Winding and fixing tape; 50A, 50B, lead sheet; 60A, 60B, lead; 100, 400, wound body; 200, electrolytic capacitor; 211, bottom shell; 212, sealing member; 213, seat plate; 300, electrode foil; 310, 320, porous portion; 311, surface area; 312, inner area; 330, core; 400, sheet; 410, contact area; 500, roller.

Claims

1. An electrode foil for an electrolytic capacitor, wherein: The electrode foil for electrolytic capacitors includes a metal foil containing a valve-acting metal. The metal foil has a core portion and a porous portion continuous with the core portion. The porous portion has a main surface of the metal foil, The hardness X of the porous portion measured by nanoindentation when the maximum indentation load on the main surface was 100 mN was 40 mN / mm. 2 above.

2. The electrode foil for electrolytic capacitors according to claim 1, wherein The hardness X is 54 mN / mm 2 above.

3. The electrode foil for electrolytic capacitors according to claim 1, wherein The elastic modulus of the porous portion measured by nanoindentation when the maximum indentation load on the main surface was 100 mN was 520 mN / mm. 2 above.

4. The electrode foil for electrolytic capacitors according to claim 1, wherein The creep amount of the porous portion when the maximum indentation load on the main surface is 100 mN, as measured by a nanoindentation method, is 5% or more.

5. The electrode foil for electrolytic capacitors according to claim 1, wherein The porous portion has a thickness T and includes an inner layer region on the core side and a surface layer region on the side opposite to the core. The surface region is a region that is less than or equal to a distance T / 4 from the outer surface of the porous portion. The inner layer region is a region having a distance T / 4 or less from the boundary between the porous portion and the core portion. The average diameter D1 of the pores in the surface layer region is smaller than the average diameter D2 of the pores in the inner layer region.

6. The electrode foil for electrolytic capacitors according to claim 5, wherein A ratio D1 / D2 of the average diameter D1 to the average diameter D2 is greater than or equal to 0.5 and less than or equal to 0.

98.

7. The electrode foil for electrolytic capacitors according to claim 5, wherein The porosity P1 of the surface layer region is smaller than the porosity P2 of the inner layer region.

8. The electrode foil for electrolytic capacitors according to claim 7, wherein A ratio P1 / P2 of the porosity P1 to the porosity P2 is greater than or equal to 0.5 and less than or equal to 0.

95.

9. The electrode foil for electrolytic capacitors according to claim 1, wherein The surface roughness Ra of the metal foil is 1.5 μm or less.

10. The electrode foil for electrolytic capacitors according to claim 1, wherein In the pore distribution of the porous portion measured by mercury intrusion porosimetry, The cumulative pore volume V0 of pores with a pore diameter of 0.01 μm or more and 1 μm or less and the cumulative pore volume V of pores with a pore diameter of 0.01 μm or more and 0.06 μm or less S1 Meet V S1 / V0≤0.07, the cumulative pore volume V0 and the cumulative pore volume V S1 The unit is cm 3 / g.

11. The electrode foil for electrolytic capacitors according to claim 1, wherein In the pore distribution of the porous portion measured by mercury intrusion porosimetry, The cumulative pore volume V0 of pores with a diameter of 0.01 μm or more and 1 μm or less and the cumulative pore volume V of pores with a diameter of 0.16 μm or more and 1 μm or less L1 Meet V L1 / V0≤0.4, the cumulative pore volume V0 and the cumulative pore volume V L1 The unit is cm 3 / g.

12. The electrode foil for electrolytic capacitors according to claim 1, wherein The thickness T of the metal foil A It is 90 μm or more and 200 μm or less.

13. The electrode foil for electrolytic capacitors according to claim 1, wherein The thickness T of the porous portion is 30 μm or more and 90 μm or less.

14. The electrode foil for electrolytic capacitors according to claim 1, wherein The main surface of the metal foil includes a first main surface and a second main surface opposite to the first main surface. The porous portion includes a first porous portion having the first main surface and a second porous portion having the second main surface, which sandwich the core portion. The hardness X is at least one of a first hardness X1 of the first porous portion when the maximum indentation load on the first main surface is 100 mN as measured by the nanoindentation method, and a second hardness X2 of the second porous portion when the maximum indentation load on the second main surface is 100 mN as measured by the nanoindentation method.

15. The electrode foil for electrolytic capacitor according to claim 14, wherein The first hardness X1 is different from the second hardness X2.

16. An electrolytic capacitor, wherein: The electrolytic capacitor includes a capacitor element, The capacitor element includes a wound body and an electrolyte. The wound body is formed by winding an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil. The anode foil includes the electrode foil according to claim 1 and a dielectric layer covering the metal skeleton constituting the porous portion of the electrode foil.

17. The electrolytic capacitor according to claim 16, wherein The thickness of the dielectric layer is greater than 45 nm.

18. The electrolytic capacitor according to claim 16, wherein The capacitor element includes a solid electrolyte as the electrolyte and may further include a liquid component. The solid electrolyte includes a conductive polymer.

19. The electrolytic capacitor according to claim 16, wherein The main surface of the metal foil of the anode foil includes a first main surface and a second main surface opposite to the first main surface. The porous portion includes a first porous portion having the first main surface and a second porous portion having the second main surface, which sandwich the core portion. The dielectric layer includes a first dielectric layer covering the metal skeleton constituting the first porous portion and a second dielectric layer covering the metal skeleton constituting the second porous portion. a first hardness X1 of the first porous portion when the maximum indentation load on the first main surface is 100 mN as measured by nanoindentation is greater than a second hardness X2 of the second porous portion when the maximum indentation load on the second main surface is 100 mN as measured by nanoindentation, At least the first hardness X1 is the hardness X, In the wound body, the anode foil is wound such that the first main surface faces the outer periphery of the wound body.

20. A method for manufacturing an electrode foil for an electrolytic capacitor, wherein: The manufacturing method comprises: an etching step of etching a sheet containing a valve metal to form a porous portion on a main surface of the sheet; and Compression step: compress the etched sheet in the thickness direction to form a hardness X of 40mN / mm 2 The porous portion described above, The hardness X is the hardness measured by a nanoindentation method when the maximum indentation load on the main surface is 100 mN.

21. The method for producing an electrode foil for an electrolytic capacitor according to claim 20, wherein: The hardness X is 54 mN or more.

22. The method for producing an electrode foil for an electrolytic capacitor according to claim 20, wherein: The sheet comprises aluminum.

23. The method for producing an electrode foil for an electrolytic capacitor according to claim 20, wherein: After the compression process, the thickness of the sheet is T A The thickness T of each side of the porous portion satisfies 90≤T A ≤200 and 25≤T≤(T A / 2)-10, thickness T A The unit of thickness T is μm.

24. The method for manufacturing an electrode foil for an electrolytic capacitor according to claim 20, wherein: In the etching process, the 2 Electrolytic etching was performed at the following current density.

25. The method for manufacturing an electrode foil for an electrolytic capacitor according to claim 20, wherein: In the compression step, the thickness of the sheet is reduced by 5% or more and 40% or less.

26. The method for producing an electrode foil for an electrolytic capacitor according to claim 20, wherein: In the compression step, the sheet is conveyed between a pair of rollers and compressed.

27. The method for producing an electrode foil for an electrolytic capacitor according to claim 26, wherein: The sheet is fed out at a speed of 0.5 m / min or more.

28. The method for producing an electrode foil for an electrolytic capacitor according to claim 26, wherein: When the roller is viewed from a direction parallel to the rotation axis of the roller, the contact area between the roller and the sheet is in the shape of an arc. A central angle θ of the roller relative to the arc of the contact region is greater than or equal to 0.15° and less than or equal to 1.5°.

29. The method for producing an electrode foil for an electrolytic capacitor according to claim 26, wherein: When the contact area between the sheet and the roller is projected onto an imaginary plane parallel to the main surface of the sheet as a projection area, A length L of the projection area in the conveyance direction of the sheet is greater than or equal to 0.5 mm and less than or equal to 5 mm.

30. The method for manufacturing an electrode foil for an electrolytic capacitor according to claim 26, wherein: The sheet is compressed at a linear pressure of 1 kN / cm or more and 14 kN / cm or less.

31. The method for manufacturing an electrode foil for an electrolytic capacitor according to claim 26, wherein: The thickness T0 of the porous portion before compression of the sheet and the diameter D of the roller satisfy the relationship of 380≤D / T0≤9800, and the units of the thickness T0 and the diameter D are mm.

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