Electrode foil for electrolytic capacitors, electrolytic capacitor, and method for producing electrode foil for electrolytic capacitors

Abstract

This electrode foil for electrolytic capacitors comprises a metal foil containing a valve action metal, wherein the metal foil has a core part and a porous part that is continuous with the core part. The porous part has the main surface of the metal foil. The hardness X of the porous part as measured by a nano-indentation method, when the maximum indentation load with respect to the main surface is 100 mN, is not less than 40 mN / mm2.

Description

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

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

[0002] The electrode foil of the electrolytic capacitor contains a valve metal and has a porous portion and a core portion continuous with the porous portion. The porous portion provides the 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 aluminum foil that has been subjected to a surface expansion treatment by etching is compressed in the foil thickness direction, thereby increasing the surface area per unit volume compared to before compression.

[0004] Japanese Patent Application Publication No. 11-26320

[0005] One aspect of the present disclosure provides a metal foil containing a valve 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 a nanoindentation method when a maximum indentation load on the main surface is 100 mN is 40 mN / mm ２ The above relates to the electrode foil for electrolytic capacitors.

[0006] Another aspect of the present disclosure relates to an electrolytic capacitor including a capacitor element, the capacitor element including a wound body and an electrolyte, the wound body being configured by winding an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil, the anode foil including the electrode foil and a dielectric layer covering a metal skeleton that forms the porous portion of the electrode foil.

[0007] Yet another aspect of the present disclosure provides a method for manufacturing a sheet including a valve metal, the method comprising: etching a sheet including a valve metal to form a porous portion on a main surface of the sheet; and compressing the sheet after the etching process in a thickness direction to form a porous portion having a hardness X of 40 mN / mm. ２and a compression step of forming the porous portion, wherein the hardness X is the hardness measured by a nanoindentation method when a maximum indentation load on the main surface is 100 mN.

[0008] According to the present disclosure, a highly reliable, high-capacity electrolytic capacitor can be obtained.

[0009] Fig. 3 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. Fig. 4 is a view 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. Fig. 5 is a cross-sectional view schematically showing an example of an electrolytic capacitor according to an embodiment of the present disclosure. Fig. 6 is a perspective view schematically showing a configuration of a wound body in the electrolytic capacitor of Fig. 3.

[0010] The porous portion of the electrode foil has not yet been sufficiently studied, and further improvement in the performance (capacity, reliability) of electrolytic capacitors equipped with electrode foil having a porous portion is required. If the mechanical strength of the electrode foil having a porous portion is low, it is difficult to manufacture an electrolytic capacitor with high performance (high capacity, high reliability), and therefore improvement in the strength of the electrode foil (porous portion) is required.

[0011] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits are exemplified for numerical values ​​of specific physical properties or conditions, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of the materials may be selected and used alone, or two or more materials may be used in combination.

[0012] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0013] (Electrode foil for electrolytic capacitor) An electrode foil for electrolytic capacitor (electrode foil A) according to an embodiment of the present disclosure comprises 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 of the porous portion measured by nanoindentation when the maximum indentation load on the main surface is 100 mN (hereinafter also simply referred to as "hardness X") is 40 mN / mm ２ That's all.

[0014] The porous portion contains numerous pores (pits), and increasing the pit density or the thickness of the porous portion to increase the surface area of ​​the foil is one possible approach to achieving higher capacitance. However, increasing the pit density or the thickness of the porous portion reduces the strength of the electrode foil, which can lead to cracks or foil breaks in the electrode foil during the manufacturing process of electrolytic capacitors. The reduction in electrode foil strength is due to a reduction in the strength of the surface layer of the porous portion, and this reduction in surface strength is particularly noticeable when the pit density or the thickness of the porous portion is high.

[0015] The following factors (a) to (c) are presumed to be factors that cause a decrease in the strength of the surface layer of the porous portion. (a) The surface layer is likely to deteriorate when the etching solution comes into contact with 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 be large in the surface layer of the metal foil. This stress is large, for example, when the diameter of the roller that winds the metal foil is small. Furthermore, this stress is larger on the outer periphery of the wound metal foil than on the inner periphery. (c) Long sheets containing valve metals used as raw materials for the metal foil (e.g., aluminum foil) are usually rolled foils, which have rolling marks and tend to remain on the surface layer of the porous portion even after etching.

[0016] In contrast, in the present disclosure, the hardness X is set to 40 mN / mm ２By setting the thickness to 40 mN / mm or more, it is possible to suppress a decrease in the strength of the surface layer. The hardness X of the porous portion can be increased by compressing the etched foil, etc. For example, the greater the thickness reduction rate during compression, the greater the tendency for hardness X to increase. The hardness X may be increased by adjusting the etching conditions (such as the amount of dissolution of the sheet surface) to suppress deterioration of the surface layer and a decrease in strength during etching, but in the case of high-capacity electrode foils with a thick porous layer, it is difficult to increase hardness X to 40 mN / mm or more by adjusting the etching conditions alone. ２ It is difficult to increase the hardness X beyond this value. The hardness X may be increased by adjusting the etching conditions and the compression conditions in combination.

[0017] Hardness X is 40 mN / mm ２ In the above cases, the decrease in strength of the surface layer when the pit density or the thickness of the porous portion is increased is suppressed, and the tensile strength of the electrode foil is increased. Furthermore, the capacitance per unit volume is sufficiently increased. By using such an electrode foil, a highly reliable, high-capacity electrolytic capacitor can be obtained. Furthermore, the retention of the electrolyte in the pores of the porous portion is improved, and the contact between the dielectric layer and the electrolyte is improved.

[0018] From the viewpoint of suppressing the decrease in strength of the surface layer and improving the capacity per unit volume, the hardness X is 40 mN / mm ２ or more, preferably 54 mN / mm ２ More preferably, 57 mN / mm ２ That is all. If the hardness of the porous layer is high, the density (occupancy) of the metal skeleton of the porous layer increases, the pits become smaller, and the actual surface area of ​​the porous portion becomes smaller, so that the strength increases but the capacitance of the electrode foil decreases. Therefore, from the viewpoint of suppressing the decrease in capacitance, the hardness X is set to, for example, 85 mN / mm ２ or less, and ２ It may be the following:

[0019] The elastic modulus (Young's modulus) indicates the ease of deformation of a material, and in the elastic deformation range, the stress and strain applied to the material are generally proportional, with the elastic modulus being the proportionality constant (Hooke's law). Generally, the higher the hardness, the higher the elastic modulus tends to be. In the case of electrode foils for electrolytic capacitors, the higher the hardness, the higher the elastic modulus tends to be. In particular, as the hardness of the porous portion increases, the tensile strength increases, and the elastic modulus, like hardness, is an important parameter from the perspective of increasing the strength of electrode foils for electrolytic capacitors. The elastic modulus of the porous portion when the maximum indentation load on the main surface of the metal foil (porous portion) is 100 mN, as measured by the nanoindentation method, is preferably 520 mN / mm ２ More preferably, 560 mN / mm ２ More preferably, it is 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 etched foil (porous portion) to be compressed and the rate of thickness reduction during compression, the elastic modulus can be increased within the above range.

[0020] The creep amount indicates the ease with which a material deforms when a constant load is applied for a certain period of time. In the case of porous electrode foils for electrolytic capacitors, the greater the creep amount, the higher the tensile strength. Like hardness and elastic modulus, the creep amount is also an important parameter from the viewpoint of increasing the strength of electrode foils for electrolytic capacitors. The creep amount of the porous portion measured by nanoindentation when the maximum indentation load on the main surface of the metal foil (porous portion) is 100 mN is preferably 5% or more, more preferably 5.3% or more, and even more preferably 5.4% or more. The upper limit of the creep amount is, for example, 6.5% or less. The greater the thickness reduction rate during compression, the greater the creep amount tends to be.

[0021] The hardness X, modulus of elasticity, and creep amount of the porous portion are determined by nanoindentation in accordance with ISO 14577-1 (2014). An indenter is pressed into the main surface of a metal foil having a porous portion, and an indentation load is applied up to 100 mN. The hardness X and modulus of elasticity are measured based on the indentation behavior of the indenter into the porous portion at this time. The creep amount is determined by the change in indentation depth when a maximum load of 100 mN is held for 5 seconds. That is, if the indentation depth when the maximum load of 100 mN is reached is defined as h1, and the indentation depth when the maximum load of 100 mN is held for 5 seconds after reaching the maximum load of 100 mN is defined as h2, the creep amount (%) is calculated as (h2 - h1) / h1 x 100.

[0022] The measurement conditions are as follows.

[0023] (Measurement conditions) Measuring device: Ultra-microindentation hardness tester "ENT-5" manufactured by Elionix Co., Ltd. Ambient temperature: 30°C Indenter: Berkovich-type diamond indenter Test load (maximum indentation load): 100 mN Measurement points: Average of three points During the measurement, the electrode foil sample is fixed to the sample stage using STE TAPE manufactured by SHINTO PAINT.

[0024] The porous portion has a thickness T (thickness per side of the metal foil) and has an inner layer region on the core side and a surface layer region on the opposite side of the core. The surface layer region is a region that is at a distance of T / 4 or less from the outer surface of the porous portion when the porous portion has a thickness T (μm). The inner layer region is a region that is at a distance of T / 4 or less from the boundary between the porous portion and the core. When the hardness X is within the above range, the average diameter D of the pores in the surface layer region is １ (nm) is the average diameter D of the pores in the inner layer region ２ In this specification, when simply referring to "diameter", it means "diameter".

[0025] From the viewpoint of suppressing the decrease in strength of the surface layer and improving the capacity per unit volume, the average diameter D ２ Average diameter D １ Ratio D １ / D ２is preferably 0.98 or less, more preferably 0.95 or less, and may be 0.9 or less. １ / D ２ is preferably 0.5 or more, more preferably 0.55 or more, may be 0.6 or more, or may be 0.7 or more. １ / D ２ The range may be any combination of the above upper and lower limits, but is preferably 0.5 or more and 0.98 or less, and more preferably 0.55 or more and 0.95 or less. When the hardness X is within the above range, D １ / D ２ is easily adjusted to 0.98 or less.

[0026] The above average diameter D １ and average diameter D ２ can be determined as follows: (i) A cross-sectional image of the electrode foil is obtained using a scanning electron microscope (SEM). Using this image, the thickness of 10 arbitrary points in the porous portion is measured, and the average value is calculated to determine the thickness T of the porous portion. (ii) The region that is a distance of T / 4 or less from the outer surface of the porous portion (surface S1 in Figure 1) is determined to be the surface region. (iii) A cross-sectional image of the surface region is obtained, and the image is subjected to a binarization process to distinguish between the metal skeleton region that constitutes the surface region and the pore (pit) region other than the metal skeleton region. (iv) A point in the pore region of the surface region is arbitrarily selected, and a line segment that passes through the point and crosses the pore region is drawn, and the length of the line segment at the shortest length is measured. This measurement is performed for 20 arbitrary points in the pore region of the surface region, and the average of the obtained measurements is calculated to determine the average diameter D of the pores in the surface region. １ (v) The region of the porous portion at a distance of T / 4 or less from the boundary with the core portion (surface B in FIG. 1) is defined as the inner layer region. The average diameter D of the pores in the inner layer region ２ is also calculated in the same manner as in (iii) and (iv) above.

[0027] When the hardness X is within the above range, the porosity P of the surface layer region １ is the porosity P of the inner layer region ２ From the viewpoint of suppressing the decrease in strength of the surface layer and improving the capacity per unit volume, the porosity P ２Porosity P １ The ratio P １ / P ２ is preferably 0.95 or less, more preferably 0.92 or less, and may be 0.85 or less. １ / P ２ is preferably 0.5 or more, more preferably 0.55 or more, may be 0.6 or more, or may be 0.7 or more. １ / P ２ The range may be any combination of the above upper and lower limits, but is 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, P １ / P ２ is easily adjusted to 0.95 or less.

[0028] Porosity of the surface layer P １ is the average diameter D １ The cross-sectional image of the surface layer region after the binarization process (iii) obtained in the process of calculating the area S of the entire region of the image is used. ０ and the area S of the region occupied by the pore in the image. １ Measure (S １ / S ０ ) × 100. ２ can be calculated in the same manner as above.

[0029] 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 means the arithmetic mean roughness, and the arithmetic mean roughness Ra is determined in accordance with JIS B 0601:2001.

[0030] When the surface roughness Ra of the metal foil is reduced to 1.5 μm or less by the compression process described below, the influence of rolling marks can be sufficiently reduced. The surface roughness of the metal foil can be made smaller than the surface roughness due to the rolling marks of the original foil, 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 more, the surface area of ​​the metal foil is sufficiently secured, making it easy to increase the capacity.

[0031] In the pore distribution of the porous portion measured by mercury intrusion porosimetry, V Ｓ１ / V ０ It is preferable that the relationship of V≦0.07 is satisfied. Ｓ２ / V ０ When the hardness X is within the above range, it is preferable that the relationship of V≦0.05 (or 0.04) is satisfied. Ｓ１ / V ０ (Furthermore V Ｓ２ / V ０ ) is likely to be within the above range.

[0032] In addition, V ０ is the cumulative pore volume (cm) of pores with diameters of 0.01 μm or more and 1 μm or less ３ / g). Ｓ１ is the cumulative pore volume (cm) of pores with diameters of 0.01 μm or more and 0.06 μm or less ３ / g). Ｓ２ is the cumulative pore volume (cm) of pores with diameters of 0.01 μm or more and 0.05 μm or less ３ / g). For measuring the pore size distribution, for example, an AutoPore V series manufactured by Micromeritics Corporation is used.

[0033] 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 increasing capacity, reducing ESR, and strength. Portions of the porous portion where the pores are blocked by the dielectric layer not only do not contribute to improving capacity, but also become hard and brittle. As the number of small pores and the number of blocked portions increase, the strength of the electrode foil decreases, and cracks or breaks may occur in the electrode foil during the manufacturing process of the electrolytic capacitor (transporting, slitting, winding, connecting to the lead member by crimping, etc.). V Ｓ１ / V ０ (Furthermore V Ｓ２ / V ０ When the ratio (μm) is within the above range, the number of small pores is small and the number of pores having a pore size suitable for increasing the capacity is large, which facilitates achieving a high capacity. In addition, in this case, the number of blocked portions is small, which facilitates suppressing a decrease in strength.

[0034] In addition, in the pore distribution of the porous portion measured by mercury intrusion porosimetry, V Ｌ１ / V ０ It is preferable that the relationship of V≦0.4 is satisfied, and furthermore, V Ｌ２ / V ０ It is more preferable that the relationship of V≦0.1 (or 0.08) is satisfied. Ｌ１ / V ０ (Furthermore V Ｌ２ / V ０ ) is likely to be within the above range.

[0035] In addition, V Ｌ１ is the cumulative pore volume (cm) of pores with diameters of 0.16 μm or more and 1 μm or less ３ / g). Ｌ２ is the cumulative pore volume (cm) of pores with diameters of 0.5 μm or more and 1 μm or less ３ / g).

[0036] 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 improving capacity. Large pores are disadvantageous in terms of expanding the surface area of ​​the electrode foil. For example, in the case of large pores, if two pores are formed in close proximity, they tend to crush each other, reducing the perimeter of the pores (the total length of the contours of the inner wall surfaces of the pores present per unit area of ​​the cross section of the porous portion), making it difficult to contribute to improving capacity. V Ｌ１ / V ０ (Furthermore V Ｌ２ / V ０ ) is within the above range, there are few large pores and many pores having pore diameters suitable for improving capacity are distributed, which makes it easy to increase the surface area of ​​the electrode foil and to achieve high capacity.

[0037] From the viewpoint of improving strength and capacity, the thickness T of the metal foil Ａ is, for example, 60 μm or more, preferably 90 μm or more, more preferably 110 μm or more, and even more preferably 120 μm or more. Ａ From the viewpoint of improving the capacity, the thickness T of the porous portion may be 25 μm or more and 90 μm or less, or 35 μm or more and 80 μm or less. ＡWhen the thickness T of the porous portion is within the above range, the thickness of the core portion can be sufficiently secured while the thickness T of the porous portion can be increased within the above range. The thickness of the core portion may be, for example, 20 μm or more, or 25 μm or more.

[0038] Metal foil thickness T Ａ When the hardness X is large (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 large, and therefore, when the hardness X is within the above range, the effect of improving the surface layer strength (the effect of suppressing the occurrence of cracks due to the stress) can be significantly obtained.

[0039] The metal foil contains a valve metal. Examples of the valve metal include aluminum (Al), tantalum (Ta), and niobium (Nb). The metal foil may be a foil of a valve metal (e.g., Al), or may be a foil containing an alloy or compound containing a valve metal (e.g., Al). When the metal foil is used as the anode foil, a dielectric layer may be formed so as to cover the metal skeleton that constitutes the porous portion. The dielectric layer is, for example, a layer containing an oxide of the valve metal.

[0040] 1 is a cross-sectional view schematically illustrating an example of an electrode foil for electrolytic capacitors according to an embodiment of the present disclosure. FIG. 1 shows a cross section in the thickness direction of the electrode foil. It should be noted that the electrode foil for electrolytic capacitors according to the present disclosure is not limited to this.

[0041] The electrode foil (metal foil 300) contains a valve 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 the first main surface S1. The first porous portion 310 and the second porous portion 320 are formed 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 an anode foil described below, a dielectric layer covering the surfaces of the metal skeletons constituting the first porous portion 310 and the second porous portion 320 is formed by chemical conversion treatment or the like.

[0042] First hardness X of the first porous portion 310 １ and the second hardness X of the second porous portion 320 ２At least one of the first hardness X and the second hardness X is within the above range. １ is the hardness of the first porous portion 310 measured by nanoindentation when the maximum indentation load on the first main surface S1 is 100 mN. ２ is the hardness of the second porous portion 320 measured by nanoindentation when the maximum indentation load on the second main surface S2 is 100 mN. １ and second hardness X ２ At least one of the first hardness X and the second hardness X has a hardness X within the above range. １ and second hardness X ２ It is preferable that all of the first hardness X be within the above range. １ is the second hardness X ２ are usually approximately the same, but may be different.

[0043] The porous portion 310 has a thickness T (μm) and includes an inner layer region 312 on the core portion 330 side and a surface layer region 311 on the opposite side of the core portion 330. The surface layer region 311 is a region that is a distance of T / 4 or less from the outer surface S1 of the porous portion 310. The inner layer region 312 is a region that is a distance of T / 4 or less from the boundary B between the porous portion 310 and the core portion 330. First hardness X １ When the hardness X is within the above range, the average diameter D of the pores in the surface layer region 311 １ (nm) is the average diameter D of the pores in the inner layer region 312 ２ The same can be said for the porous portion 320 (surface layer region 321 and inner layer region 322).

[0044] (Method for manufacturing electrode foil for electrolytic capacitor) A method for manufacturing electrode foil for electrolytic capacitor according to an embodiment of the present disclosure includes an etching step of etching a sheet containing a valve metal to form porous portions on a main surface of the sheet, and a compressing step of compressing the sheet after the etching step in the thickness direction to form a porous portion having a hardness X of 40 mN / mm ２ and a compression step of forming the porous portion as 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.

[0045] The sheet used in the etching process (hereinafter also referred to as "raw material sheet") contains a valve metal. Examples of the valve metal include Al, Ta, and Nb. The raw material sheet may be a sheet of a valve metal (e.g., Al), or may be a sheet containing an alloy or compound containing a valve metal (e.g., Al). A long or strip-shaped rolled sheet (rolled foil) is usually used as the raw material sheet.

[0046] The etching process forms a porous portion on the main surface of the sheet, and the portion other than the porous portion remains as a core portion. That is, after the etching process, the sheet 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 both main surfaces of the sheet, sandwiching the core portion. In the compression process, the sheet having the porous portion formed by the etching process is compressed. The surface layer of the porous portion has 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 before and after compression may be slightly smaller, but it is desirable that it remains almost the same.

[0047] For example, by the above compression process (by appropriately adjusting the thickness reduction rate, etc.), the hardness X, D １ / D ２ , P １ / P ２ , V Ｓ１ / V ０ , V Ｓ２ / V ０ , V Ｌ１ / V ０ , V Ｌ２ / V ０ etc. can be controlled within the above-mentioned ranges.

[0048] During the manufacturing process of electrolytic capacitors, the sheet comes into contact with processing liquids (e.g., etching solutions, chemical conversion solutions) and rollers, which can cause unevenness (or scratches). During this manufacturing process, stress can concentrate on these unevennesses, causing the sheet to break (or crack). Furthermore, the aluminum foil used for the sheet has rolling marks created during the manufacturing process, and etching pits can be formed unevenly along the rolling marks, i.e., along the length direction (rolling direction) of the long sheet. The rolling marks can cause the sheet to break (or crack). To address this issue, as described above, by appropriately compressing the sheet after etching, the effects of the unevenness and rolling marks can be reduced, the strength of the surface layer of the sheet can be increased, and the sheet breakage, etc. can be suppressed.

[0049] After the compression process, the thickness of the sheet T Ａ After the compression step, the thickness T of the porous portion per side is 25 μm or more, {(T Ａ / 2)-10} μm or less. When the thickness T is within the above range, the core can be ensured to have a sufficient thickness. Furthermore, the thickness T may be 25 μm or more and 90 μm or less, or 35 μm or more (or 40 μm or more) and 80 μm or less. In high-capacity foils, the thickness T of the porous portion is large, and the effect of improving the surface layer strength by compression is significantly obtained. In particular, in capacitors containing a solid electrolyte and a liquid component (electrolytic solution, etc.), high-capacity foils are used, and the thickness T of the sheet (electrode foil) Ａ The thickness T of the porous portion per surface is preferably 25 μm or more or 35 μm or more (or 40 μm or more).

[0050] (Etching Process) In the etching process, the surface of the sheet containing the valve metal is subjected to an etching treatment to roughen the surface of the sheet and form a porous portion continuous with the core portion. The etching treatment may be electrolytic etching or chemical etching, and can be performed using a known method. For example, the hardness X can be adjusted to some extent by changing the etching treatment conditions.

[0051] From the viewpoint of forming large diameter pores, the electrolytic etching is performed at 2.0 A / cm ２ It may be performed at a current density of 1.5 A / cm ２ It may be performed at a current density of 1.2 A / cm ２ The etching may be performed at the following current density: The current density may be changed during etching: The larger the pore diameter, the easier it is to form a thicker dielectric layer, and this is advantageous in terms of increasing voltage.

[0052] The electrolytic etching is preferably AC etching, but DC etching may also be used. AC etching is likely to form porous portions containing sponge-like pits with relatively small diameters, while DC etching is likely to form porous portions containing tunnel-like pits with relatively large diameters.

[0053] The etching time is T Ｅ When this is done, 0 to 0.7T Ｅ During this time, the temperature of the etching solution is set to 10°C or higher and 60°C or lower, and Ｅ ~T Ｅ During the etching time T, the temperature of the etching solution may be set to 5° C. or more and 40° C. or less. In this case, the variation in pit diameter in the thickness direction of the porous portion can be reduced. Ｅ is, for example, 15 minutes or more and 30 minutes or less.

[0054] (Compression Step) In the compression step, the etched sheet may be conveyed between a pair of rollers and compressed. The etched sheet conveyed between the pair of rollers is compressed by the pressure of the pair of rollers. By appropriately adjusting the conditions of the roll press as described below, the hardness X, D １ / D ２ (Further P １ / P ２ ), V Ｓ１ / V ０ (Furthermore V Ｓ２ / V ０ ), and V Ｌ１ / V ０ (Furthermore V Ｌ２ / V ０ ) can be easily controlled within the above range.

[0055] The sheet may be compressed in stages by arranging a pair of rollers in multiple stages. In this case, the diameter of the pair of rollers may be changed for each stage or may be reduced as the sheet is compressed. The compression process may include a process of conveying the sheet by rollers and a process of winding up the compressed sheet. Compression increases the strength of the surface layer of the sheet, thereby preventing the sheet from breaking when wound up by the rollers.

[0056] Here, Fig. 2 is a configuration diagram showing an example of the compression process. Arrow X in Fig. 2 indicates the conveying direction of the long sheet 400. In the compression process, for example, a compression device shown in Fig. 2 is used. The compression device includes a pair of rollers 500 that compress the sheet 400. The thickness T after etching Ｂ The sheet 400 having a thickness of T Ａ The sheet delivery speed may be 0.5 m / min or more, or may be 0.5 m / min or more and 50 m / min or less.

[0057] From the viewpoint of facilitating the production of the electrode foil, the thickness reduction rate of the sheet in the compression step 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. Ｂ From T Ａ When it decreases to {(T Ｂ -T Ａ ) / T Ｂ}×100.

[0058] When the roller 500 is viewed 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 central angle θ of the roller 500 relative to the arc of the contact area 410 may be 0.15° or more and 1.5° or less (or 1.75° or less).

[0059] When the area obtained by projecting the contact area 410 between the sheet 400 and the roller 500 onto a virtual plane parallel to the main surface of the sheet 400 is defined as the projection area, the length L of the projection area in the conveying direction X of the sheet 400 may be 0.5 mm or more and 5 mm or less.

[0060] The sheet 400 may be compressed with 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 T of the porous portion of the sheet 400 before compression ０ (mm) and the diameter D (mm) of the roller 500 are 380≦D / T ０ The relationship may be satisfied.

[0061] The device may further include a roller for conveying the sheet 400, and may also include a roller for winding up the compressed sheet 400. The device may also include a control unit for controlling the rotation speed of the rollers 500, etc. The feed speed of the sheet 400 may also be controlled by the control unit.

[0062] The method for manufacturing an electrode foil may include a step of slitting the compressed sheet. The slitting step uses a slitting device and a roller for winding up the slit sheet. The compression increases the strength of the surface layer of the sheet, thereby preventing the sheet from breaking when wound up by the roller.

[0063] (Electrolytic Capacitor) The electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure is suitable for use in an electrolytic capacitor including a wound capacitor element. The wound capacitor element includes a wound body and an electrolyte. The wound body is configured by winding an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil. The anode foil includes an electrode foil according to an embodiment of the present disclosure (hereinafter also referred to as "electrode foil A") and a dielectric layer covering a metal skeleton that forms a porous portion of the electrode foil A.

[0064] In electrolytic capacitors with a rated voltage of 20 V or higher, for example, aluminum foils chemically treated at a chemical conversion voltage of 30 V or higher are used as anode foils. Furthermore, in electrolytic capacitors containing a solid electrolyte (conductive polymer) and a liquid component (such as an electrolyte solution), aluminum foils chemically treated at a chemical conversion voltage of 40 V or higher are often used as anode foils. In such anode foils, electrode foils with relatively large pit diameters are used, forming dielectric layers with relatively large thicknesses (e.g., 45 nm or greater), which tend to reduce the strength of the surface layer. Therefore, the electrode foil A significantly improves the surface layer strength. At chemical conversion voltages of 30 V or higher (or 40 V or higher), the resulting chemical conversion film becomes thick. Therefore, using an electrode foil with a large pit diameter prevents the pits from being blocked by the thick chemical conversion film, thereby efficiently increasing capacity.

[0065] (Anode Foil) The anode foil includes 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 obtained, for example, by anodizing (chemical conversion treatment) to form an oxide film of a valve metal on the surface of the metal skeleton constituting the porous portion. When performing chemical conversion treatment on an aluminum foil, the chemical conversion voltage may be, for example, 5 V or more, or 40 V or more.

[0066] The anode foil may have a first main surface and a second main surface opposite to the first main surface. The porous portion may include a first porous portion having the first main surface and a second porous portion having the second main surface, sandwiching the core. 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, the first hardness X of the first porous portion may be １ , and the second hardness X of the second porous portion ２ At least one of the first hardness X and the second hardness X has a hardness X within the above range. １ and second hardness X ２ It is preferable that both of the first hardness X and the second hardness X are within the above range. １ is the second hardness X ２ and at least a first hardness X １ In this case, the first hardness X in the wound body may be１ The anode foil is preferably wound so that the first main surface of the first porous portion having the first porous portion faces the outer periphery of the wound body. In this case, the tensile stress generated on the outer periphery of the wound body is greater than that on the outer periphery of the wound body, and therefore, the effect of improving the strength of the surface layer (the effect of suppressing the occurrence of cracks during winding) can be significantly obtained.

[0067] The thickness of the anode foil may be 60 μm or more and 200 μm or less, preferably 90 μm or more and 200 μm or less, and more preferably 120 μm or more and 200 μm or less. The thickness of the dielectric layer is, for example, 45 nm or more.

[0068] (Cathode Foil) The cathode foil may be a metal foil containing a valve metal such as Al, Ta, or Nb. If necessary, the surface of the metal foil may be roughened by etching. That is, the cathode foil may be a metal foil having a porous portion and a core portion continuous with the porous portion. The electrode foil for an electrolytic capacitor according to the present disclosure may be used for the cathode foil. The thickness of the cathode foil is, for example, 10 μm or more and 70 μm or less.

[0069] (Separator) The separator is not particularly limited, and may be, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (for example, aliphatic polyamide, aromatic polyamide such as aramid).

[0070] (Electrolyte) The electrolyte covers at least a portion of the anode foil (dielectric layer) and is interposed between the anode foil (dielectric layer) and the cathode foil. The electrolyte includes at least one of a solid electrolyte and an electrolytic solution. The capacitor element may include a solid electrolyte, or may include a solid electrolyte and a liquid component (electrolytic solution or a non-aqueous solvent).

[0071] The dielectric layer is coated with an electrolyte by, for example, impregnating the anode foil (or the wound body) with a treatment solution (or an electrolyte solution) containing a conductive polymer. ２ than the average diameter D １ is smaller (and the porosity P ２ than the porosity P １is smaller), the treatment solution impregnated in the porous portion is more likely to remain in the pores, the inner walls of the pores are more likely to be covered with electrolyte, and the contact between the anode foil (dielectric layer) and the electrolyte is improved.

[0072] The solid electrolyte includes 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 types, or may be a copolymer of two or more types of monomers. The weight-average molecular weight of the conductive polymer is, for example, 1,000 to 100,000.

[0073] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene), etc.

[0074] The conductive polymer may be doped with a dopant. The solid electrolyte may contain a dopant together with the conductive polymer. Examples of the dopant include polystyrene sulfonic acid. The solid electrolyte may further contain an additive, if necessary.

[0075] The liquid component may be an electrolytic solution or a non-aqueous solvent. The electrolytic solution includes a non-aqueous solvent and an ionic substance (solute (e.g., organic salt)) dissolved therein. The non-aqueous solvent may be an organic solvent or an ionic liquid.

[0076] The non-aqueous solvent is preferably a high-boiling solvent, for example, a polyol compound such as ethylene glycol, a sulfone compound such as sulfolane, a lactone compound such as γ-butyrolactone, an ester compound such as methyl acetate, a carbonate compound such as propylene carbonate, an ether compound such as 1,4-dioxane, or a ketone compound such as methyl ethyl ketone.

[0077] The liquid component may contain an acid component (anion) and a base component (cation). The acid component and the base component may form a salt (solute). The acid component contributes to the film repair function. Examples of the acid component include organic carboxylic acids and inorganic acids. Examples of the inorganic acid include phosphoric acid, boric acid, and sulfuric acid. Examples of the base component include primary to tertiary amine compounds.

[0078] The organic salt is a salt in which at least one of the anion and 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.

[0079] From the viewpoint of suppressing dedoping of the dopant from the conductive polymer (deterioration of the solid electrolyte), the liquid component preferably contains more acid components than base components. Furthermore, since the acid components contribute to the film repair function of the liquid component, it is also preferable that the liquid component contains more acid components than base components. The molar ratio of the acid component to the base component (acid component / base component) is, for example, 1.1 or more. From the viewpoint of suppressing dedoping of the dopant from the conductive polymer, the pH of the liquid component may be 6 or less, or may be 1 or more and 5 or less.

[0080] 3 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor according to an embodiment of the present disclosure, and FIG. 4 is a perspective view schematically illustrating the configuration of a wound body in the electrolytic capacitor of FIG.

[0081] Electrolytic capacitor 200 includes a capacitor element, and the capacitor element includes 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.

[0082] One end of each of lead tabs 50A and 50B is connected to anode foil 10 and cathode foil 20, respectively, and lead tabs 50A and 50B are wound to form wound body 100. Lead wires 60A and 60B are connected to the other ends of lead tabs 50A and 50B, respectively.

[0083] A stop 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 stop tape 40. When the anode foil 10 is prepared by cutting it from a large foil, the wound body 100 may further be subjected to a chemical conversion treatment in order to provide a dielectric layer on the cut surface.

[0084] An electrolyte is interposed between the anode foil 10 (dielectric layer) and the cathode foil 20 in the wound body 100. The capacitor element is obtained, for example, by impregnating the wound body 100 with a treatment liquid containing an electrolyte. The impregnation may be performed under reduced pressure, for example, in an atmosphere of 10 kPa to 100 kPa.

[0085] The wound body 100 is housed in the bottomed case 211 so that the lead wires 60A and 60B are located on the opening side of the bottomed case 211. The bottomed case 211 can be made of a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy of these metals.

[0086] A sealing member 212 is placed at the opening of a bottomed case 211 that contains the wound body 100 and the electrolyte, the open end of the bottomed case 211 is crimped to the sealing member 212 and curled, and a seat plate 213 is placed on the curled portion, thereby sealing the wound body 100 inside the bottomed case 211.

[0087] The sealing member 212 is formed so that the lead wires 60A and 60B pass through it. The sealing member 212 may be made of any insulating material, and is preferably made of an elastic material. Among these, highly heat-resistant materials such as silicone rubber, fluororubber, ethylene propylene rubber, hypalon rubber, butyl rubber, and isoprene rubber are preferred.

[0088] The electrode foil according to the embodiment of the present disclosure can be used in an electrolytic capacitor including the above-described wound capacitor element, but may also be used in an electrolytic capacitor including a laminated capacitor element. In this case, the porous portion may be formed on a portion of the electrode foil surface. The laminated capacitor element includes an anode body, a solid electrolyte layer, and a cathode extraction layer covering the solid electrolyte layer. The anode body includes an electrode foil and a dielectric layer covering a portion of the electrode foil surface. The solid electrolyte layer is formed so as to cover the dielectric layer. The cathode extraction layer includes, 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 extraction layer.

[0089] [Examples] Hereinafter, the present disclosure will be described in more detail based on examples, but the present disclosure is not limited to the examples.

[0090] Examples 1 and 2 (Etching process) A foil-shaped aluminum (Al) sheet (thickness T Ｂ The Al sheet was etched to form porous portions (thickness per side T ０ In the etching process, AC etching was performed at a current density of 1.5 A / cm ２ The etching time was also adjusted appropriately to obtain the desired amount of dissolution.

[0091] (Compression Step) The Al sheet after etching was compressed in the thickness direction to obtain electrode foils a1 and a2. In the compression step, the thickness of the Al sheet was reduced by the ratio (reduction rate) shown in Table 1. Sheet Thickness T Ａ The thickness (μm) of the porous portion per surface, T (μm), was set to the values ​​shown in Table 2.

[0092] As shown in Figure 2, in the compression process, the Al sheet was conveyed between a pair of rollers (diameter D: 75 mm) and compressed. The pressing force and linear pressure of the rollers were the values ​​shown in Table 1. The feed rate of the Al sheet was the value shown in Table 1. The thickness T of the porous portion before compression of the sheet ０ Ratio of roller diameter D (mm) to roller diameter (mm): D / T ０The angle θ in FIG. 2 was set to a value shown in Table 1. The length L in FIG. 2 was set to a value shown in Table 1.

[0093]

[0094] Hardness X, elastic modulus, creep amount, D １ / D ２ , and P １ / P ２ The arithmetic mean roughness Ra of the electrode foil was the value shown in Table 2. V determined by the above-mentioned method Ｓ１ / V ０ , V Ｓ２ / V ０ , V Ｌ１ / V ０ , and V Ｌ２ / V ０ The values ​​are shown in Table 2. The values ​​of the thickness T, hardness X, etc. of the porous portion indicate the measured values ​​of the porous portion on one surface of the Al sheet, but almost the same measured values ​​were also obtained for the porous portion on the other surface of the Al sheet.

[0095]

[0096] (Formation of Dielectric Layer) The electrode foils a1 and a2 were subjected to a chemical conversion treatment to form a dielectric layer covering the metal skeleton constituting the porous portion. The chemical conversion treatment was performed at a chemical conversion voltage of 65 V in accordance with the test method for electrode foils for aluminum electrolytic capacitors of the Electronic Industry Standards of Japan (EIAJ RC-2364A). In this manner, anode foils A1 and A2 were produced.

[0097] Electrode foils a1 and a2 are examples 1 and 2, and anode foils A1 and A2 are electrode foils a1 and a2 that have been chemically treated.

[0098] Comparative Example 1 Electrode foil b1 was produced in the same manner as electrode foil a1, except that the Al sheet was not compressed after the etching treatment. 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.

[0099] (Evaluation 1: Tensile Strength of Electrode Foil) For each electrode foil, a strip-shaped sample (70 mm in the length direction, 10 mm in the width direction) was prepared, and the tensile strength of the sample in the length direction was measured in accordance with the test method for electrode foils for aluminum electrolytic capacitors of the Electronic Industry Standards of Japan (EIAJ RC-2364A). The measurement results are shown in Table 1. In Table 2, the tensile strength is shown as a relative value when the tensile strength of electrode foil b1 is set to 100.

[0100] (Evaluation 2: Capacitance of Anode Foil) The capacitance of each anode foil was measured in accordance with the test method for electrode foils for aluminum electrolytic capacitors of the Electronic Industrial Standards of Japan (EIAJ RC-2364A). The measurement results are shown in Table 3. In Table 3, the capacitance is shown as a relative value when the capacitance of anode foil B1 is set to 100. Table 3 also shows the capacitance per unit volume of the anode foil.

[0101]

[0102] The electrode foils a1 and a2 had a higher tensile strength than the electrode foil b1. The anode foils A1 and A2 all had good capacitance, and it was confirmed that they had a high capacitance per unit volume.

[0103] Examples 3 to 5 (Etching process) A foil-shaped Al sheet (thickness T Ｂ The Al sheet was etched to form porous portions (thickness per side T ０ In the etching process, AC etching was performed at a current density of 1.5 A / cm ２ The amount was adjusted appropriately within the following range, and the etching time was also adjusted appropriately so as to obtain a predetermined amount of dissolution.

[0104] (Compression Step) The etched Al sheet was compressed in the thickness direction to obtain electrode foils a3 to a5. In the compression step, the thickness of the sheet was reduced by the ratio (reduction rate) shown in Table 4. Sheet Thickness T Ａ The thickness (μm) of the porous portion per surface, T (μm), was set to the values ​​shown in Table 5.

[0105] As shown in Figure 2, in the compression process, the Al sheet was conveyed between a pair of rollers (diameter D: 75 mm) and compressed. The pressing force and linear pressure of the rollers were the values ​​shown in Table 4. The feed rate of the Al sheet was the value shown in Table 4. The thickness T of the porous portion before compression of the sheet ０ Ratio of roller diameter D (mm) to roller diameter (mm): D / T ０ The angle θ in FIG. 2 was set to a value shown in Table 4. The length L in FIG. 2 was set to a value shown in Table 4.

[0106]

[0107] Hardness X, elastic modulus, creep amount, D １ / D ２ , and P １ / P ２ The arithmetic mean roughness Ra of the electrode foil was the value shown in Table 5. V determined by the above-mentioned method Ｓ１ / V ０ , V Ｓ２ / V ０ , V Ｌ１ / V ０ , and V Ｌ２ / V ０ The values ​​are shown in Table 5.

[0108]

[0109] (Formation of Dielectric Layer) Electrode foils a3 to a5 were subjected to a chemical conversion treatment to form a dielectric layer covering the metal skeleton constituting the porous portion. The chemical conversion treatment was performed at a chemical conversion voltage of 65 V in accordance with the test method for electrode foils for aluminum electrolytic capacitors of the Electronic Industry Standards of Japan (EIAJ RC-2364A). In this manner, anode foils A3 to A5 were produced.

[0110] Electrode foils a3 to a5 are examples 3 to 5, and anode foils A3 to A5 are electrode foils a3 to a5 that have been chemically treated.

[0111] Comparative Example 2 Electrode foil b2 was produced in the same manner as electrode foil a3, except that the Al sheet was not compressed after the etching treatment. 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.

[0112] The above-mentioned 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 shown as a relative value when the tensile strength of electrode foil b2 is set to 100. The above-mentioned Evaluation 2 was performed on anode foils A3 to A5 and B2. The evaluation results are shown in Table 6. In Table 6, the capacitance is shown as a relative value when the capacitance of anode foil B2 is set to 100. Table 6 also shows the capacitance per unit volume of the anode foils.

[0113]

[0114] Electrode foils a3 to a5 had a higher tensile strength than electrode foil b2. Anode foils A3 to A5 all had good capacitance, and it was confirmed that they had a high capacitance per unit volume.

[0115] <<Supplementary Note>> The above description of the embodiment discloses the following techniques.

[0116] (Technology 1) A metal foil containing a valve metal is provided, wherein 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 measured by a nanoindentation method when a maximum indentation load on the main surface is 100 mN is 40 mN / mm ２ This is the electrode foil for an electrolytic capacitor.

[0117] (Technology 2) The hardness X is 54 mN / mm ２ The electrode foil for an electrolytic capacitor according to Technical 1 is as described above.

[0118] (Technology 3) The elastic modulus of the porous portion when the maximum indentation load on the main surface is 100 mN, as measured by a nanoindentation method, is 520 mN / mm ２ The electrode foil for an electrolytic capacitor according to Technical 1 or 2.

[0119] (Technology 4) The electrode foil for an electrolytic capacitor according to any one of Technologies 1 to 3, wherein the amount of creep 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.

[0120] (Technology 5) The porous portion has a thickness T and includes an inner layer region on the core portion side and a surface layer region on the opposite side to the core portion, the surface layer region being a region at a distance of T / 4 or less from the outer surface of the porous portion, the inner layer region being a region at a distance of T / 4 or less from the boundary between the porous portion and the core portion, and the average diameter D of pores in the surface layer region １ is the average diameter D of the pores in the inner layer region ２ The electrode foil for an electrolytic capacitor according to any one of techniques 1 to 4, wherein the thickness is smaller than

[0121] (Technology 6) The average diameter D ２ The average diameter D １ Ratio D １ / D ２ The electrode foil for an electrolytic capacitor according to claim 5, wherein the σ is 0.5 or more and 0.98 or less.

[0122] (Technology 7) The porosity P of the surface layer region １ is the porosity P of the inner layer region ２ 7. The electrode foil for an electrolytic capacitor according to claim 5 or 6, wherein the thickness of the electrode foil is smaller than or equal to 100 μm.

[0123] (Technology 8) The porosity P ２ The porosity P １ The ratio P １ / P ２ The electrode foil for an electrolytic capacitor according to claim 7, wherein the σ is 0.5 or more and 0.95 or less.

[0124] (Technology 9) The electrode foil for electrolytic capacitors according to any one of Technologies 1 to 8, wherein the surface roughness Ra of the metal foil is 1.5 μm or less.

[0125] (Technology 10) In the pore distribution of the porous portion measured by mercury intrusion porosimetry, the cumulative pore volume V of pores with a pore diameter of 0.01 μm or more and 1 μm or less ０ (cm ３ / g) and the cumulative pore volume V for pore diameters of 0.01 μm or more and 0.06 μm or less Ｓ１ (cm ３ / g) means V Ｓ１ / V ０ 10. The electrode foil for electrolytic capacitors according to any one of claims 1 to 9, which satisfies the relationship of ≦0.07.

[0126] (Technology 11) In the pore distribution of the porous portion measured by mercury intrusion porosimetry, the cumulative pore volume V of pores with a pore diameter of 0.01 μm or more and 1 μm or less ０ (cm ３ / g) and the cumulative pore volume V for pore diameters of 0.16 μm or more and 1 μm or less Ｌ１ (cm ３ / g) means V Ｌ１ / V ０ 11. The electrode foil for electrolytic capacitors according to any one of claims 1 to 10, which satisfies the relationship of ≦0.4.

[0127] (Technology 12) The thickness T of the metal foil Ａ 12. The electrode foil for electrolytic capacitors according to any one of claims 1 to 11, wherein the thickness is 90 μm or more and 200 μm or less.

[0128] (Technology 13) The electrode foil for an electrolytic capacitor according to any one of Techniques 1 to 12, wherein the thickness T of the porous portion is 30 μm or more and 90 μm or less.

[0129] (Technology 14) The main surface of the metal foil includes a first main surface and a second main surface opposite to the first main surface, and the porous portion includes a first porous portion having the first main surface and a second porous portion having the second main surface, sandwiching the core portion, and a first hardness X of the first porous portion measured by a nanoindentation method when a maximum indentation load on the first main surface is 100 mN. １ and a second hardness X of the second porous portion when a maximum indentation load on the second main surface is 100 mN, as measured by a nanoindentation method. ２ 14. The electrode foil for electrolytic capacitors according to any one of claims 1 to 13, wherein at least one of the hardnesses is X.

[0130] (Technology 15) The first hardness X １ is the second hardness X ２ The electrode foil for an electrolytic capacitor according to Technical 14, which is different from

[0131] (Technology 16) An electrolytic capacitor comprising: a capacitor element, the capacitor element comprising: a wound body; and an electrolyte; the wound body being configured by winding an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil; and the anode foil comprising: the electrode foil according to any one of Technologies 1 to 15; and a dielectric layer covering a metal skeleton constituting the porous portion of the electrode foil.

[0132] (Technology 17) The electrolytic capacitor according to Technology 16, wherein the thickness of the dielectric layer is 45 nm or more.

[0133] (Technology 18) The electrolytic capacitor according to Technology 16 or 17, wherein the capacitor element contains a solid electrolyte as the electrolyte and may further contain a liquid component, and the solid electrolyte contains a conductive polymer.

[0134] (Technology 19) A 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, sandwiching the core portion, the dielectric layer includes a first dielectric layer covering a metal skeleton constituting the first porous portion and a second dielectric layer covering a metal skeleton constituting the second porous portion, and a first hardness X of the first porous portion measured by a nanoindentation method when a maximum indentation load on the first main surface is 100 mN １ is the second hardness X of the second porous portion when the maximum indentation load on the second main surface is 100 mN, as measured by a nanoindentation method. ２ and at least the first hardness X １ is the hardness X, and in the wound body, the anode foil is wound so that the first main surface faces the outer periphery of the wound body.

[0135] (Technology 20) An etching process for etching a sheet containing a valve metal to form porous portions on a main surface of the sheet; and compressing the sheet after the etching process in a thickness direction to obtain a hardness X of 40 mN / mm. ２a compressing step of forming the porous portion, wherein the hardness X is a hardness measured by a nanoindentation method when a maximum indentation load on the main surface is 100 mN.

[0136] (Technology 21) The hardness X is 54 mN / mm ２ The method for producing an electrode foil for an electrolytic capacitor according to technique 20, as described above.

[0137] (Technology 22) The method for producing an electrode foil for an electrolytic capacitor according to Technology 20 or 21, wherein the sheet contains aluminum.

[0138] (Technology 23) After the compression step, the thickness T of the sheet Ａ (μm) and the thickness T (μm) of the porous portion per side are 90≦T Ａ ≦200, and 25≦T≦(T Ａ 23. The method for producing an electrode foil for an electrolytic capacitor according to any one of techniques 20 to 22, wherein the relationship:

[0139] (Technique 24) In the etching process, 2.0 A / cm ２ The method for producing an electrode foil for an electrolytic capacitor according to any one of techniques 20 to 23, wherein electrolytic etching is performed at the following current density:

[0140] (Technology 25) The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 20 to 24, wherein in the compressing step, the thickness of the sheet is reduced by 5% or more and 40% or less.

[0141] (Technology 26) The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 20 to 25, wherein in the compressing step, the sheet is conveyed between a pair of rollers and compressed.

[0142] (Technology 27) The method for producing an electrode foil for an electrolytic capacitor according to Technology 26, wherein the sheet is fed at a speed of 0.5 m / min or more.

[0143] (Technology 28) The method for manufacturing an electrode foil for an electrolytic capacitor according to Technology 26 or 27, wherein when the roller is viewed from a direction parallel to the rotation axis of the roller, a contact area between the roller and the sheet is arc-shaped, and a central angle θ of the roller with respect to the arc of the contact area is 0.15° or more and 1.5° or less.

[0144] (Technology 29) The method for manufacturing an electrode foil for an electrolytic capacitor according to any one of Techniques 26 to 28, wherein when a contact area between the sheet and the roller is projected onto a virtual plane parallel to a main surface of the sheet to form a projected area, a length L of the projected area in the conveying direction of the sheet is 0.5 mm or more and 5 mm or less.

[0145] (Technology 30) The method for producing an electrode foil for an electrolytic capacitor according to any one of Techniques 26 to 29, wherein the sheet is compressed at a linear pressure of 1 kN / cm or more and 14 kN / cm or less.

[0146] (Technology 31) The thickness T of the porous portion before compression of the sheet ０ (mm) and the diameter D (mm) of the roller are 380≦D / T ０ 31. The method for producing an electrode foil for an electrolytic capacitor according to any one of techniques 26 to 30, wherein the relationship of ≦9800 is satisfied.

[0147] The electrode foil according to the present disclosure is suitable for use in electrolytic capacitors that require high reliability and capacity.

[0148] 10: Anode foil, 20: Cathode foil, 30: Separator, 40: Winding stop tape, 50A, 50B: Lead tabs, 60A, 60B: Lead wires, 100, 400: Wound body, 200: Electrolytic capacitor, 211: Bottomed case, 212: Sealing member, 213: Seat plate, 300: Electrode foil, 310, 320: Porous portion, 311: Surface region, 312: Inner region, 330: Core, 400: Sheet, 410: Contact region, 500: Roller

Claims

1. a metal foil containing a valve 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 when the maximum indentation load on the main surface is 100 mN, as measured by a nanoindentation method, is 40 mN / mm ２ This is the electrode foil for an electrolytic capacitor.

2. The hardness X is 54 mN / mm ２ The electrode foil for an electrolytic capacitor according to claim 1 .

3. The elastic modulus of the porous portion when the maximum indentation load on the main surface is 100 mN, as measured by a nanoindentation method, is 520 mN / mm ２ The electrode foil for an electrolytic capacitor according to claim 1 .

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

5. The porous portion has a thickness T and includes an inner layer region on the core portion side and a surface layer region on the opposite side to the core portion, the surface region is a region that is at a distance of T / 4 or less from the outer surface of the porous portion, the inner layer region is a region whose distance from the boundary between the porous portion and the core portion is T / 4 or less, The average diameter D of the pores in the surface layer region １ is the average diameter D of the pores in the inner layer region ２ The electrode foil for an electrolytic capacitor according to claim 1 , wherein the thickness of the electrode foil is smaller than the thickness of the electrode foil for an electrolytic capacitor.

6. The average diameter D ２ The average diameter D １ Ratio D １ / D ２ The electrode foil for an electrolytic capacitor according to claim 5, wherein is 0.5 or more and 0.98 or less.

7. The porosity P of the surface layer region １ is the porosity P of the inner layer region ２ The electrode foil for an electrolytic capacitor according to claim 5 , wherein the thickness of the electrode foil is smaller than the thickness of the electrode foil for an electrolytic capacitor.

8. The porosity P ２ The porosity P １ The ratio P １ / P ２ The electrode foil for an electrolytic capacitor according to claim 7, wherein is 0.5 or more and 0.95 or less.

9. 2. The electrode foil for an electrolytic capacitor according to claim 1, wherein the metal foil has a surface roughness Ra of 1.5 μm or less.

10. In the pore distribution of the porous portion measured by mercury intrusion porosimetry, Cumulative pore volume V for pore diameters of 0.01 μm or more and 1 μm or less ０ (cm ３ / g) and Cumulative pore volume V for pore diameters of 0.01 μm or more and 0.06 μm or less Ｓ１ (cm ３ / g) means V Ｓ１ / V ０ ≦0.07 2. The electrode foil for an electrolytic capacitor according to claim 1, which satisfies the following relationship:

11. In the pore distribution of the porous portion measured by mercury intrusion porosimetry, Cumulative pore volume V for pore diameters of 0.01 μm or more and 1 μm or less ０ (cm ３ / g) and Cumulative pore volume V for pore diameters of 0.16 μm or more and 1 μm or less Ｌ１ (cm ３ / g) means V Ｌ１ / V ０ ≦0.4 2. The electrode foil for an electrolytic capacitor according to claim 1, which satisfies the following relationship:

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

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

14. 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, the first porous portion sandwiching the core portion; a first hardness X of the first porous portion measured by a nanoindentation method when a maximum indentation load on the first main surface is 100 mN; １ and a second hardness X of the second porous portion when a maximum indentation load on the second main surface is 100 mN, as measured by a nanoindentation method. ２ 2. The electrode foil for an electrolytic capacitor according to claim 1, wherein at least one of the hardnesses is X.

15. Said first hardness X １ is the second hardness X ２ The electrode foil for an electrolytic capacitor according to claim 14, wherein the thickness of the electrode foil is different from that of the electrode foil for an electrolytic capacitor according to claim 14.

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

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

18. the capacitor element contains a solid electrolyte as the electrolyte and a liquid component, 17. The electrolytic capacitor of claim 16, wherein the solid electrolyte comprises a conductive polymer.

19. a 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, the first porous portion sandwiching the core portion; the dielectric layer includes a first dielectric layer covering a metal skeleton constituting the first porous portion, and a second dielectric layer covering a metal skeleton constituting the second porous portion, a first hardness X of the first porous portion measured by a nanoindentation method when a maximum indentation load on the first main surface is 100 mN; １ is the second hardness X of the second porous portion when the maximum indentation load on the second main surface is 100 mN, as measured by a nanoindentation method. ２ is larger than At least the first hardness X １ is the hardness X, 17. The electrolytic capacitor according to claim 16, wherein the anode foil is wound in the wound body such that the first main surface faces an outer periphery of the wound body.

20. an etching step of etching a sheet containing a valve metal to form a porous portion on a main surface of the sheet; The sheet after the etching treatment is compressed in the thickness direction to have a hardness X of 40 mN / mm ２ a compression step of forming the porous portion, The method for producing an electrode foil for an electrolytic capacitor, wherein the hardness X is a hardness measured by a nanoindentation method when a maximum indentation load on the main surface is 100 mN.

21. 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 contains aluminum.

23. After the compression step, the thickness T of the sheet Ａ (μm) and the thickness T (μm) of the porous portion per side, 90≦T Ａ ≦200, and 25≦T≦(T Ａ / 2)-10 The method for producing an electrode foil for an electrolytic capacitor according to claim 20 , which satisfies the following relationship:

24. In the etching step, 2.0 A / cm ２ The method for producing an electrode foil for an electrolytic capacitor according to claim 20, wherein electrolytic etching is carried out at a current density of:

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

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

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

28. When the roller is viewed from a direction parallel to the rotation axis of the roller, a contact area between the roller and the sheet is arc-shaped, 27. The method for producing an electrode foil for an electrolytic capacitor according to claim 26, wherein a central angle θ of the roller with respect to the arc of the contact area is 0.15° or more and 1.5° or less.

29. When the area obtained by projecting the contact area between the sheet and the roller onto a virtual plane parallel to the main surface of the sheet is defined as a projected area, 27. The method for producing an electrode foil for an electrolytic capacitor according to claim 26, wherein a length L of the projection region in the sheet transport direction is 0.5 mm or more and 5 mm or less.

30. The method for producing 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 thickness T of the porous portion of the sheet before compression ０ (mm) and the diameter D (mm) of the roller are 380≦D / T ０ The method for producing an electrode foil for an electrolytic capacitor according to claim 26, wherein the relationship of ≦9800 is satisfied.