Method for manufacturing an aluminum conversion foil

Abstract

To provide chemically formed aluminum foil capable of preventing or suppressing breakage of aluminum foil due to bending when the aluminum foil having a porous layer made of a sintered body of powder is anodized, and a method for manufacturing the same.SOLUTION: Chemically formed aluminum foil 1 includes: aluminum foil 10 having a first porous layer 3 made of a sintered body of aluminum or aluminum alloy powder laminated on a first surface 2a of both surfaces of a foil-shaped base layer 2 made of aluminum or an aluminum alloy; and a first chemical conversion film 5 formed on the first porous layer 3. On the surface of the first porous layer 3, a plurality of cracks 7 extending in an in-plane direction in a Y direction with a length of 300 μm or more are formed at intervals of 30 μm to 150 μm in the in-plane direction in an X direction perpendicular to the Y direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an aluminum formed foil obtained by forming an aluminum foil provided with a porous layer made of a sintered body of aluminum or aluminum alloy powder, an electrode for an aluminum electrolytic capacitor, and a method for manufacturing an aluminum formed foil.

Background Art

[0002] As an electrode for an aluminum electrolytic capacitor, it is known to use an aluminum formed foil obtained by subjecting an aluminum foil provided with a porous layer made of a sintered body of aluminum powder to anodic oxidation. In such an aluminum formed foil, there is a problem that when the aluminum foil is bent during the anodic oxidation process of forming a conversion film by subjecting the aluminum foil to anodic oxidation, the aluminum foil breaks. In Patent Document 1, embossing is performed on the surface of the sintered body to make the surface roughness of the sintered body within a predetermined value range, and then the anodic oxidation process is performed to reduce the breakage of the aluminum foil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The reason why the bending strength of the aluminum foil decreases in the anodizing process is that it becomes difficult to release stress from the aluminum foil as the conversion coating grows. That is, in the anodizing process, a conversion coating grows on the surface of the porous layer made of a sintered body of powder. As a result, adjacent powders are bonded via the conversion coating. In such a state, when the aluminum foil is bent, since the bonding between the powders is strong, the stress generated due to the deformation cannot be released from the aluminum foil. As a result, local cracks occur in the bonding between the powders. Further, this crack spreads and the aluminum foil breaks.

[0005] Here, even when anodizing is performed on an aluminum foil with an embossed surface on the porous layer, adjacent powders are bonded via the conversion coating as the conversion coating grows. Therefore, even when the technique of Patent Document 1 is used, it is not easy to release the stress caused by deformation from the aluminum foil, and it is difficult to sufficiently suppress the decrease in the bending strength of the aluminum foil.

[0006] In view of the above problems, an object of the present invention is to provide an aluminum conversion foil that can prevent or suppress the aluminum foil from breaking due to bending when anodizing is performed on an aluminum foil provided with a porous layer made of a sintered body of powder. Another object is to propose a method for manufacturing such an aluminum conversion foil.

Means for Solving the Problems

[0023] In order to solve the above problems, the method for manufacturing an aluminum chemical conversion foil of the present invention includes a chemical conversion step of forming a first chemical conversion film on an aluminum foil in which a first porous layer made of a sintered body of aluminum or aluminum alloy powder is laminated on the first surface of both surfaces of a foil-shaped base layer made of aluminum or an aluminum alloy. The chemical conversion step includes an anodizing step of subjecting the aluminum foil to anodization. In the chemical conversion step, a crack formation treatment is performed to generate stress in the aluminum foil and provide a plurality of cracks extending in the first direction on the surface of the first porous layer, the cracks being spaced apart in a second direction orthogonal to the first direction. In the anodizing step, an anodization treatment after crack formation is performed in which the aluminum foil is subjected to anodization after the crack formation treatment. The chemical conversion step includes a hydration step of forming a hydrated film on the aluminum foil before the anodizing step. The anodizing step subjects the aluminum foil on which the hydrated film is formed to anodization. The crack formation treatment is performed during the hydration step inside and in the crack formation treatment, a plurality of the cracks extending in the first direction with a length of 300 μm or more are provided at intervals of 30 μm to 150 μm in the second direction.

[0024] According to the present invention, by generating stress in the aluminum foil in the chemical conversion step, a plurality of cracks extending in the first direction are provided on the surface of the first porous layer, spaced apart in the second direction. Also Then, after the formation of cracks, anodization is performed on the aluminum foil. Here, by forming cracks in the first porous layer during the chemical conversion process, even when the first chemical conversion film grows due to subsequent anodization, it is possible to suppress the closing of the cracks by the first chemical conversion film. Therefore, an aluminum chemical conversion foil having a plurality of cracks can be obtained. Accordingly, even when the aluminum foil in which adjacent powder bodies are bonded via the first chemical conversion film bends as the first chemical conversion film grows, the stress generated due to the deformation can escape from the cracks. Thereby, it is possible to prevent or suppress the occurrence of local cracks in the bond between the powder bodies, and thus it is possible to prevent or suppress the local cracks from spreading and causing the aluminum foil to break. Further, since anodization is performed on the aluminum foil after forming the cracks, the first chemical conversion film can be reformed on the first porous layer after the cracks are generated. Thereby, the newly formed aluminum surface (the surface of the exposed metallic aluminum) exposed on the surface of the first porous layer due to the formation of the cracks can be covered with the reformed first chemical conversion film. Therefore, it is possible to prevent or suppress breakage while reducing the leakage current of the aluminum foil or the electrode for an aluminum electrolytic capacitor during anodization caused by the cracks. Further, according to the present invention, a hydrated film is formed on the surface of the first porous layer in the hydration process. Further, cracks are provided in the first porous layer during the hydration process. Thereby, due to the crack formation treatment, a newly formed aluminum surface is exposed on the surface of the first porous layer through the cracks. That is, on the fracture surface of the first porous layer due to the cracks, powder bodies on which a hydrated film is not formed on the surface are exposed. Thereafter, a hydrated film is formed on the newly formed aluminum surface in the hydration process that continues after the crack formation treatment. Here, the hydrated film covering the newly formed aluminum surface inhibits or suppresses the bonding of the powder bodies located on both sides sandwiching the cracks via the first chemical conversion film in the anodization process. According to the present invention, since the crack formation treatment is performed during the hydration process, when the first chemical conversion film grows in the anodization process performed after the crack formation treatment and the hydration process, it is possible to prevent or suppress the closing of the cracks by the first chemical conversion film. ., thenFurther, according to the present invention, a plurality of cracks extending in the first direction with a length of 300 μm or more are provided at intervals of 30 μm to 150 μm in the second direction. By providing such cracks, even when the first conversion coating grows by anodization, it is possible to prevent or suppress the cracks from being closed by the first conversion coating.

[0025] In the present invention before In the crack formation process, a plurality of cracks extending in the first direction with a length of 300 μm or more can be provided at intervals of 30 μm to 150 μm in the second direction. By providing such cracks, even when the first conversion coating grows by anodization, it is possible to prevent or suppress the cracks from being closed by the first conversion coating.

[0026] In the present invention, in the crack formation process, it is desirable that each crack reaches the boundary between the base layer and the first porous layer. By doing so, since the cracks are deep, even when the aluminum foil bends during anodization, it becomes easy to release the stress generated due to the deformation from the cracks.

[0027] Note that the thickness of the first conversion coating that grows before the voltage during anodization reaches a predetermined anodization voltage can be estimated. Therefore, if a pre-crack formation anodization process of subjecting the aluminum foil to anodization until a predetermined anodization voltage is reached before the crack formation process is performed, it is possible to avoid the first conversion coating becoming too thick and the aluminum foil becoming too hard at the time of performing the crack formation process. As a result, it is possible to avoid the aluminum foil from breaking when stress is generated in the aluminum foil. Further, when stress is generated in the aluminum foil, it becomes possible to uniformly provide a plurality of cracks on the surface of the first porous layer. Here, if a plurality of cracks are uniformly formed on the surface of the first porous layer, it is possible to suppress a decrease in the bending strength even when the thickness of the first conversion coating increases until the target film breakdown voltage is reached.

[0028] ​The above-described predetermined anodic oxidation voltage can be 400 V or less. Note that until reaching the predetermined anodic oxidation voltage, it includes the time point when the predetermined anodic oxidation voltage is reached. By doing so, compared with the case where the crack formation treatment is performed after the voltage during anodic oxidation reaches the predetermined anodic oxidation voltage, the first conversion coating does not become too thick and the aluminum foil does not become too hard at the time of forming cracks. Therefore, when stress is generated in the aluminum foil, the aluminum foil is less likely to break. Also, if the crack formation treatment is performed before the voltage during anodic oxidation reaches the predetermined anodic oxidation voltage, the first conversion coating does not become too thick and the aluminum foil does not become too hard. Therefore, by generating stress in the aluminum foil, a plurality of cracks can be uniformly provided on the surface of the first porous layer. Here, if a plurality of cracks can be uniformly provided on the surface of the first porous layer, even when the first conversion coating is thickly formed by anodic oxidation after the voltage during anodic oxidation reaches the predetermined anodic oxidation voltage, a decrease in bending strength can be suppressed.

[0029] In the present invention, in the crack formation treatment, the first crack formation roller extending in the first direction may be brought into contact with the second surface on the opposite side of the first surface of the two surfaces of the aluminum foil, and the aluminum foil and the first crack formation roller may be relatively moved in the second direction. By doing so, stress can be generated in the aluminum foil by the first crack formation roller, and cracks can be formed in the first porous layer.

[0030] In the present invention, in the chemical conversion step, the aluminum foil may be run in the second direction by a plurality of rollers arranged along the second direction, and among the plurality of rollers, a roller having a smaller diameter than the other rollers may be arranged as the first crack formation roller. If a roller with a small diameter is used as the first crack formation roller, it becomes easy to generate stress in the aluminum foil by the first crack formation roller.

[0031] In the present invention, on the second surface of the aluminum foil, which is opposite to the first surface of the base layer, a second porous layer made of a sintered body of aluminum or aluminum alloy powder is laminated. In the chemical conversion process, a second chemical conversion film is formed on the second porous layer. In the crack formation process, a second crack formation roller extending in the first direction is brought into contact with the first surface at a position different from that of the first crack formation roller in the second direction, and the aluminum foil and the second crack formation roller are relatively moved in the second direction. In this way, stress can be generated in the aluminum foil by the second crack formation roller, and a plurality of cracks can be formed in the second porous layer. Therefore, even when the aluminum foil has porous layers on both surfaces of the base layer, or when the aluminum foil bends during anodization, the stress generated due to deformation can be released from the aluminum foil. Thus, breakage of the aluminum foil can be prevented or suppressed.

[0034] In the present invention, it is desirable to provide a rehydration treatment for forming a hydrated film on the aluminum foil following the crack formation process. In this way, a hydrated film is formed on the newly exposed aluminum surface on the surface of the first porous layer due to the formation of cracks, in the rehydration treatment that is carried out subsequent to the crack formation process. Here, the hydrated film covering the newly exposed aluminum surface inhibits or suppresses the bonding of the powders located on both sides with the crack in between via the first chemical conversion film in the anodization process. Therefore, if the rehydration treatment is carried out following the crack formation process, it is possible to suppress the closing of the cracks by the first chemical conversion film when the first chemical conversion film grows thereafter.

Advantages of the Invention

[0037] In the method for manufacturing an aluminum conversion foil of the present invention, a chemical conversion step of forming a first chemical conversion film on an aluminum foil having a first porous layer laminated thereon is provided, and the chemical conversion step includes an anodization step of subjecting the aluminum foil to anodization. Further, in the chemical conversion step, cracks are formed in the first porous layer, and in the anodization step, anodization is performed on the aluminum foil after the cracks are formed. Thus, by forming cracks in the first porous layer during the chemical conversion step, an aluminum conversion foil having a plurality of cracks can be obtained. Therefore, the stress generated due to the deformation of the aluminum conversion foil can be released from the cracks. As a result, the occurrence of local cracks in the bonding between powders can be prevented or suppressed, so that the spread of local cracks and the breakage of the aluminum foil can be prevented or suppressed. Further, by the anodization treatment after providing the cracks, a first chemical conversion film can be reformed on the first porous layer after the cracks are generated. Thus, the surface of the metallic aluminum exposed by the formation of the cracks can be covered with the reformed chemical conversion film. Therefore, it is possible to prevent or suppress breakage while reducing the leakage current of the aluminum foil or the electrode for an aluminum electrolytic capacitor during anodization caused by the cracks. Further, according to the present invention, a hydration film is formed on the surface of the first porous layer in the hydration step. Further, cracks are provided in the first porous layer during the hydration step. As a result, by the crack formation treatment, an aluminum fresh surface is exposed through the cracks. That is, powders on the fracture surface of the first porous layer due to the cracks, on which a hydration film is not formed on the surface, are exposed. Thereafter, a hydration film is formed on the aluminum fresh surface in the hydration step that is continued after the crack formation treatment. Here, the hydration film covering the aluminum fresh surface inhibits or suppresses the bonding between the powders located on both sides sandwiching the cracks via the first chemical conversion film in the anodization step. According to the present invention, since the crack formation treatment is performed during the hydration step, when the first chemical conversion film grows in the anodization step performed after the crack formation treatment and the hydration step, it is possible to prevent or suppress the closing of the cracks by the first chemical conversion film. Through the cracks, an aluminum fresh surface is exposed. That is, powders on the fracture surface of the first porous layer due to the cracks, on which a hydration film is not formed on the surface, are exposed. Thereafter, a hydration film is formed on the aluminum fresh surface in the hydration step that is continued after the crack formation treatment. Here, the hydration film covering the aluminum fresh surface inhibits or suppresses the bonding between the powders located on both sides sandwiching the cracks via the first chemical conversion film in the anodization step. According to the present invention, since the crack formation treatment is performed during the hydration step, when the first chemical conversion film grows in the anodization step performed after the crack formation treatment and the hydration step, it is possible to prevent or suppress the closing of the cracks by the first chemical conversion film. ., thenFurther, according to the present invention, a plurality of cracks extending in the first direction with a length of 300 μm or more are provided at intervals of 30 μm to 150 μm in the second direction. By providing such cracks, even when the first conversion coating grows by anodization, it is possible to prevent or suppress the cracks from being closed by the first conversion coating.

Brief Description of the Drawings

[0038]

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Embodiments for Carrying Out the Invention

[0039] Hereinafter, with reference to the drawings, embodiments of the aluminum conversion foil of the present invention and a method for manufacturing the aluminum conversion foil will be described. However, the present invention is not limited only to the following embodiments. Also, the components in the embodiments can be appropriately combined in part or in whole. The aluminum conversion foil in this example is used as an electrode for an aluminum electrolytic capacitor. Hereinafter, after describing an aluminum electrolytic capacitor having the aluminum conversion foil as an electrode for an aluminum electrolytic capacitor (anode foil), the aluminum conversion foil and a method for manufacturing the aluminum conversion foil will be described. In this specification, when a numerical range is expressed by a lower limit value and an upper limit value using the symbol "~", both the lower limit value and the upper limit value are included.

[0040] (Aluminum Electrolytic Capacitor) To manufacture an aluminum electrolytic capacitor using an aluminum conversion foil, an anode foil made of the aluminum conversion foil (electrode for an aluminum electrolytic capacitor) and a cathode foil are laminated with a separator interposed therebetween, wound, and a capacitor element is formed. Next, the capacitor element is impregnated with an electrolytic solution (paste). Thereafter, the capacitor element containing the electrolytic solution is housed in an outer case, and the case is sealed with a sealing body.

[0041] Also, when a solid electrolyte is used instead of the electrolytic solution, after forming a solid electrolyte layer on the surface of the anode foil made of the aluminum conversion foil (electrode for an aluminum electrolytic capacitor), a cathode layer is formed on the surface of the solid electrolyte layer, and then it is externally packaged with resin or the like. At that time, an anode terminal electrically connected to the anode and a cathode terminal electrically connected to the cathode layer are provided. In this case, a plurality of anode foils may be laminated.

[0042] (Aluminum Conversion Foil) FIG. 1 is a photograph taken by magnifying the surface of the aluminum conversion foil of the present invention with a scanning electron microscope. FIG. 2 is a photograph taken by magnifying the cross-section obtained by cutting the aluminum conversion foil of FIG. 1 along the longitudinal direction with a scanning electron microscope. FIG. 3 is an explanatory diagram showing the relationship between the powder constituting the porous layer and the conversion film in the aluminum conversion foil. In FIG. 3, the base layer, powder, and conversion film constituting the aluminum conversion foil are schematically shown. FIG. 4 is an explanatory diagram of a measuring method for measuring the interval between cracks provided on the surface of the aluminum conversion foil.

[0043] The aluminum conversion foil 1 is manufactured by subjecting an aluminum foil composed of a base layer 2 and a porous layer (a first porous layer 3 and a second porous layer 4) to anodic oxidation. The aluminum conversion foil 1 (electrode for an aluminum electrolytic capacitor) is in a long shape.

[0044] As shown in FIG. 2, the aluminum conversion foil 1 includes a foil-shaped base layer 2 made of aluminum or an aluminum alloy, a first porous layer 3 laminated on the first surface 2a of the base layer 2, and a second porous layer 4 laminated on the second surface 2b opposite to the first surface 2a of the base layer 2. The first porous layer 3 and the second porous layer 4 are each composed of a sintered body of powder of aluminum or an aluminum alloy. Further, the aluminum conversion foil 1 has a first conversion film 5 formed on the first porous layer 3 and a second conversion film 6 formed on the second porous layer 4.

[0045] In the following description, three directions orthogonal to each other are defined as the X direction, the Y direction, and the Z direction, and the X direction is the longitudinal direction of the aluminum conversion foil 1. The Y direction is the short-side direction of the aluminum conversion foil 1. The Z direction is the direction in which the first porous layer 3 and the second porous layer 4 are laminated with respect to the base layer 2 and are present.

[0046] In this example, the base layer 2 is a foil made of pure aluminum. As the base layer 2, a foil made of an aluminum alloy can be used. The aluminum alloy is aluminum to which at least one metal element selected from the group consisting of silicon, iron, copper, manganese, magnesium, chromium, zinc, titanium, vanadium, gallium, nickel, and boron is added, or aluminum containing any of these elements as inevitable impurity elements. The thickness dimension T1 of the base layer 2 is usually 10 μm or more, preferably 20 μm or more, and usually 100 μm or less, preferably 50 μm or less.

[0047] The first porous layer 3 and the second porous layer 4 are sintered bodies of powder containing at least one selected from the group consisting of aluminum and aluminum alloys. As shown in FIG. 3, the first porous layer 3 and the second porous layer 4 have a three-dimensional network structure by sintering and connecting while maintaining voids between the powders. The first chemical conversion film 5 and the second chemical conversion film 6 are formed on the surface of the three-dimensional network structure by the powder 11. Here, since the first porous layer 3 and the second porous layer 4 have a three-dimensional network structure, their surface area is large. Therefore, when the aluminum formed foil 1 is used as an electrode for an aluminum electrolytic capacitor, a capacitor with a large capacitance can be manufactured.

[0048] The purity of the aluminum powder 11 is 99.80% by mass or more. The aluminum alloy used as the powder 11 contains one or more selected from silicon, iron, copper, manganese, magnesium, chromium, zinc, titanium, vanadium, gallium, nickel, boron, zirconium, etc. in aluminum. The content of these elements in the aluminum alloy is desirably 100 ppm by mass or less, particularly 50 ppm by mass or less.

[0049] The thickness of the first porous layer 3 and the thickness of the second porous layer 4 are usually the same or approximately the same. However, the thickness of the first porous layer 3 and the thickness of the second porous layer 4 may be different. In this case, the thickness of the first porous layer 3 may be greater than the thickness of the second porous layer 4, or the thickness of the second porous layer 4 may be greater than the thickness of the first porous layer 3. In this example, the thickness dimension T2 of the first porous layer 3 and the thickness dimension T3 of the second porous layer 4 are each 10 μm or more and 500 μm or less. Also, the thickness dimension T2 of the first porous layer 3 and the thickness dimension T3 of the second porous layer 4 are preferably 50 μm or more and 200 μm or less. That is, the thickness of the porous layer obtained by summing the thickness of the first porous layer 3 and the thickness of the second porous layer 4 is 20 μm or more and 1000 μm or less. Also, the thickness of the porous layer obtained by summing the thickness of the first porous layer 3 and the thickness of the second porous layer 4 is preferably 100 μm or more and 400 μm. Also, the average particle diameter K of the powder 11 constituting the first porous layer 3 and the second porous layer 4 is 1 μm or more and 20 μm or less.

[0050] The average particle diameter K of the powder 11 shall be obtained by measuring the cross section of the first porous layer 3 or the second porous layer 4 with a scanning electron microscope. Specifically, when observing the sintered powder 11, a part is in a molten state or the powders 11 are connected to each other, but the portion having a substantially circular shape can be approximately regarded as a particle. Therefore, in cross-sectional observation, the maximum diameter of each particle having a substantially circular shape is taken as the particle diameter of the particle, the particle diameters of about 50 particles are measured, and the average of these is taken as the average particle diameter K of the sintered powder 11.

[0051] As shown in FIG. 1, on the surface of the first porous layer 3, a plurality of cracks 7 extending in the Y direction (first direction) with a length of 300 μm or more in the in-plane direction are provided at intervals of 30 μm to 150 μm in the X direction (second direction) in the in-plane direction. As shown in FIG. 2, each crack 7 provided in the first porous layer 3 reaches the boundary between the base layer 2 and the first porous layer 3. The same Similarly, on the surface of the second porous layer 4, a plurality of cracks 7 extending in the Y direction with a length of 300 μm or more are provided at intervals of 30 μm to 150 μm in the X direction orthogonal to the Y direction. Each crack 7 provided in the second porous layer 4 reaches the boundary between the base layer 2 and the second porous layer 4.

[0052] The length and interval of each crack 7 provided in the first porous layer 3 and the second porous layer 4 shall be obtained by measurement through observation with a scanning electron microscope. More specifically, as shown in FIG. 4, observe in a field of view of 500 μm or more in the X direction and 1000 μm or more in the Y direction of the aluminum anodized foil 1, and draw an auxiliary line 8 in the X direction near the center of the field of view. Then, count the number of intersections 9 with the crack 7 having a length of 300 μm or more. After that, divide the length of the auxiliary line 8 converted from the scale by the number of intersections 9 to calculate the interval of the crack 7 having a length of 300 μm or more. The average of such measurements and calculations performed in three or more fields of view shall be taken as the interval between adjacent cracks 7.

[0053] (Function and effect of aluminum anodized foil) The aluminum anodized foil 1 of this example includes cracks 7 extending in the Y direction with a length of 300 μm or more on the surface of the porous layer (the first porous layer 3 and the second porous layer 4). Further, the cracks 7 are provided in a plurality at intervals of 30 μm to 150 μm in the X direction of the aluminum anodized foil 1. In the aluminum anodized foil 1 having such a plurality of cracks 7, even when the adjacent powder bodies 11 are bent in the aluminum foil bonded through the anodic oxide film (the first anodic oxide film 5 and the second anodic oxide film) by anodization, the stress generated due to the deformation can be released from the portion that becomes the crack 7 after the completion of anodization. Thereby, it is possible to prevent or suppress the occurrence of local cracks in the bonding between the powder bodies 11, so that it is possible to prevent or suppress the spread of these cracks and the breakage of the aluminum foil.

[0054] In addition, each of the plurality of cracks 7 reaches the boundary between the base layer 2 and the porous layer (the first porous layer 3 and the second porous layer 4). Therefore, it becomes easy to release the stress generated due to the deformation from the aluminum foil.

[0055] Here, when the aluminum conversion foil 1 is used as the electrode for an aluminum electrolytic capacitor, the electrode for the aluminum electrolytic capacitor includes a plurality of cracks 7 in the porous layers (the first porous layer 3 and the second porous layer 4). Therefore, the specific surface area of the electrode for the aluminum electrolytic capacitor is larger than that in the case where the porous layers (the first porous layer 3 and the second porous layer 4) do not have the cracks 7. Thus, if the aluminum conversion foil is used as the electrode for the aluminum electrolytic capacitor, the capacitance can be increased.

[0056] Also, when the aluminum conversion foil 1 is wound into a roll-shaped electrode for an aluminum electrolytic capacitor, it is easy to wind in the X direction in which the plurality of cracks 7 are arranged. Therefore, the aluminum conversion foil 1 having the cracks 7 can be wound into a shape closer to a perfect circle as compared with the case where the aluminum conversion foil does not have the cracks 7.

[0057] FIG. 5 is a schematic diagram of an electrode for an aluminum electrolytic capacitor in which the aluminum conversion foil 1 is wound in a spiral curve shape in the second direction, and shows a side view of the aluminum conversion foil 1 as viewed from the first direction. In FIG. 5, the aluminum conversion foil 1 is wound around the outer peripheral surface of a roll 16 having a diameter dimension of 1 mm to form a roll shape. Even when wound around such a roll 16, the aluminum conversion foil 1 (the electrode 15 for the aluminum electrolytic capacitor) is wound into a shape close to a perfect circle without bending in the middle. That is, when the aluminum conversion foil without the cracks 7 is wound, a plurality of bent portions are formed in the middle of the aluminum conversion foil. On the other hand, when the aluminum conversion foil 1 having a plurality of cracks 7 is wound, it becomes a roll shape wound in the X direction without having a portion bent in the middle.

[0058] Here, if the electrode 15 for an aluminum electrolytic capacitor in a roll shape obtained by winding the aluminum etched foil 1 into a shape close to a perfect circle is used as the capacitor element, when the capacitor element is housed in the exterior case, compared with the case where the electrode for the aluminum electrolytic capacitor is not wound in a state close to a perfect circle, the electrode 15 for the aluminum electrolytic capacitor having a dimension longer in the X direction can be accommodated. As a result, since the surface area of the electrode 15 for the aluminum electrolytic capacitor increases, the capacitance of the aluminum electrolytic capacitor can be increased. Further, if the roll shape is formed by winding the aluminum etched foil 1 in a spiral curve shape, compared with the case where the aluminum etched foil 1 has a portion bent in the middle, breakage of the aluminum etched foil 1 generated in the bent portion can be prevented. Therefore, the winding property of the aluminum etched foil 1 can be improved.

[0059] (Method for manufacturing aluminum etched foil) FIG. 6 is an explanatory view of the aluminum foil serving as the base material of the aluminum etched foil 1. In FIG. 6, the aluminum foil is schematically shown. FIG. 7 is a flowchart showing the first manufacturing method of the aluminum etched foil 1. FIG. 8 is a flowchart showing the second manufacturing method of the aluminum etched foil 1. FIG. 9 is a flowchart showing the third manufacturing method of the aluminum etched foil 1. FIG. 10 is a flowchart showing the fourth manufacturing method of the aluminum etched foil 1. FIG. 11 is a flowchart showing the fifth manufacturing method of the aluminum etched foil 1.

[0060] Next, with reference to FIGS. 6 to 11, a method for manufacturing the aluminum conversion foil 1 will be described. As shown in FIG. 6, when manufacturing the aluminum conversion foil 1, an aluminum foil 10 is used as a base material. The aluminum foil 10 includes a foil-shaped base layer 2 made of aluminum or an aluminum alloy. A first porous layer 3 made of a sintered body of powder 11 of aluminum or an aluminum alloy is laminated on the first surface 2a of the base layer 2, and a second porous layer 4 made of a sintered body of powder 11 of aluminum or an aluminum alloy is laminated on the second surface 2b of the base layer 2. In this example, the powder 11 of the first porous layer 3 and the powder 11 of the second porous layer 4 are made of the powder 11 of the same metal. Also, the thickness of the first porous layer 3 and the thickness of the second porous layer 4 are the same or substantially the same.

[0061] As shown in FIGS. 7 to 11, the method for manufacturing the aluminum conversion foil 1 includes a chemical conversion step ST1 of forming a first chemical conversion film 5 on the first porous layer 3 of the aluminum foil 10 (base material) and forming a second chemical conversion film 6 on the second porous layer 4. The chemical conversion step ST1 includes a hydration step ST2 of performing a hydration treatment to form a hydration film on the aluminum foil 10, and an anodization step ST3 of performing an anodization treatment on the aluminum foil 10 on which the hydration film is formed, in this order. Also, in this example, in the anodization step ST3, a heat treatment ST31 of heating the aluminum foil 10 during the constant voltage chemical conversion treatment step to expose the defective portions is performed. That is, as shown in FIGS. 7 to 11, in the anodization step ST3, an anodization treatment (not shown) is performed before and after the heat treatment ST31. In this specification, the same applies when explaining using a flowchart in other cases.

[0062] Also, in the chemical conversion step ST1, a crack formation treatment ST11 is performed in which stress is applied to the aluminum foil 10 to provide a plurality of cracks 7 extending in the Y direction and spaced apart in the X direction on the surfaces of the first porous layer 3 and the second porous layer 4.

[0063] To describe the manufacturing method of the aluminum conversion foil 1 of this example in more detail, in the anodizing step ST3, after the crack formation treatment ST11, a post-crack anodizing treatment ST3A for anodizing the aluminum foil 10 is performed. Note that in the drawings and the following description, the post-crack anodizing treatment ST3A is abbreviated as the post-anodizing treatment ST3A.

[0064] Here, in FIGS. 7 and 11, the crack formation treatment ST11 is performed during the chemical conversion step ST1 and also during the hydration treatment ST2. That is, in the hydration step ST2, hydration treatments (not shown) are performed before and after the crack formation treatment ST11.

[0065] Also, in FIGS. 9 and 10, the crack formation treatment ST11 is performed during the chemical conversion step ST1 and also during the anodizing step ST3. That is, in the anodizing step ST3, before the crack formation treatment ST11, a pre-crack anodizing treatment ST3B for anodizing the aluminum foil 10 until the voltage during anodizing reaches a predetermined anodizing voltage is performed. Note that in the drawings and the following description, the pre-crack anodizing treatment ST3B is abbreviated as the pre-anodizing treatment ST3B. That is, when the crack formation treatment ST11 is performed during the anodizing step ST3, in the anodizing step ST3, the pre-anodizing treatment ST3B, the crack formation treatment ST11, and the post-anodizing treatment ST3A are performed in this order.

[0066] In the hydration step ST2, the aluminum foil 10 is boiled in a hydration treatment liquid with a liquid temperature of 80°C or higher to form an aluminum hydration film such as boehmite on the aluminum foil 10. As the hydration treatment liquid, pure water can be used. Also, the rehydration treatment ST21 described later can be performed in the same manner.

[0067] In anodization step ST3, aluminum foil 10 is immersed in a chemical conversion treatment solution, and the voltage during anodization (the voltage output from the power supply) is brought to a predetermined anodization voltage. Thereby, a chemical conversion film (first chemical conversion film 5 and second chemical conversion film 6) is formed on the aluminum foil 10. As the chemical conversion treatment solution, sulfuric acid or its salt, selenic acid or its salt, boric acid or its salt, phosphoric acid or its salt, organic acid or its salt (for example, adipic acid or its salt, citric acid or its salt, sebacic acid or its salt, oxalic acid or its salt, etc.), sodium hydroxide or its salt, etc. can be used. The anodization voltage is set between 5V and 1000V. Needless to say, the anodization treatment (post-anodization treatment ST3A and pre-anodization treatment ST3B) performed in the anodization step ST3 can be performed in the same manner.

[0068] In the heat treatment ST31 performed during the anodization step ST3, the aluminum foil 10 is, for example, placed in a heat treatment furnace and heated. The atmosphere in the heat treatment furnace has a temperature of 300°C or higher and 600°C or lower. The atmosphere in the heat treatment furnace may be any of an air atmosphere, an inert gas atmosphere, and a water vapor atmosphere.

[0069] In the manufacturing method of the aluminum chemical conversion foil 1 of this example, a crack formation treatment ST11 is performed during the hydration step ST2 before the chemical conversion film (first chemical conversion film 5 and second chemical conversion film 6) is provided, or between the hydration step ST2 and the anodization step ST3. In this case, in the anodization step ST3 (post-anodization treatment ST3A) following the crack formation treatment ST11, anodization is performed on the aluminum foil 10 after crack formation.

[0070] Alternatively, in the method for manufacturing the aluminum conversion foil 1 of this example, in the anodizing step ST3, the crack formation treatment ST11 is performed before the voltage during anodization reaches the final anodization voltage which is the final target. In this case, since the crack formation treatment ST11 is performed during the anodizing step ST3, the pre-anodizing treatment ST3B and the post-anodizing treatment ST3A are performed before and after the crack formation. In the post-anodizing treatment ST3A, the aluminum foil 10 is subjected to anodization to reach an anodization voltage higher than the predetermined anodization voltage reached in the pre-anodizing treatment ST3B.

[0071] The above-mentioned predetermined anodization voltage is usually 400 V or less. Also, the predetermined anodization voltage is preferably 300 V or less, more preferably 250 V or less. In this example, in the anodizing step ST3, the aluminum foil 10 is subjected to anodization until the anodization voltage reaches these upper limit values, and then the crack formation treatment ST11 is performed. Thereby, the conversion film does not become too thick, and stress can be generated in the aluminum foil 10 at a timing when the aluminum foil 10 does not become too hard. As a result, when stress is generated in the aluminum foil 10, breakage of the aluminum foil 10 can be suppressed, and a plurality of cracks can be uniformly provided on the surface of the porous layer. Here, since the crack formation treatment ST11 may be performed before the conversion film is formed as long as it is during the conversion step ST1, the lower limit value of the predetermined anodization voltage is not particularly limited. Therefore, the lower limit value of the predetermined anodization voltage is usually 0 V or more. Note that the lower limit value of the predetermined anodization voltage is preferably 10 V or more, more preferably 50 V or more. Also, in the anodizing step ST3, the final anodization voltage which is the final target of the voltage during anodization can be appropriately set according to the properties of the target aluminum conversion foil 1. Therefore, the final anodization voltage is not particularly limited, but can be set to 1000 V or less, for example.

[0072] Note that in the anodizing step ST3, the aluminum foil 10 may be subjected to anodization by other known methods.

[0073] Here, in the formation process ST1, when the anodizing process ST3 is completed, the aluminum foil 10 after formation, that is, the aluminum formed foil 1, is wound around a take-up roller and becomes a roll.

[0074] As specific examples of the method for manufacturing the aluminum formed foil 1, the following first to fifth manufacturing methods with different timings for performing the crack formation treatment ST11 can be cited.

[0075] In the first manufacturing method of the aluminum formed foil 1, as shown in FIG. 7, the crack formation treatment ST11 is performed during the hydration process ST2. Then, in the anodizing process ST3 performed subsequent to the hydration process ST2, a post-anodizing treatment ST3A is performed.

[0076] In the second manufacturing method of the aluminum formed foil 1, as shown in FIG. 8, the crack formation treatment ST11 is performed between the hydration process ST2 and the anodizing process ST3. Then, in the anodizing process ST3 performed subsequent to the crack formation treatment ST11, a post-anodizing treatment ST3A is performed.

[0077] In the third manufacturing method of the aluminum formed foil 1, as shown in FIG. 9, the crack formation treatment ST11 is performed during the anodizing process ST3. Specifically, in the anodizing process ST3, a pre-anodizing treatment ST3B is performed to subject the aluminum foil 10 to anodization until a predetermined anodizing voltage is reached, the crack formation treatment ST11 is performed subsequent to the pre-anodizing treatment ST3B, and after the crack formation treatment ST11, a post-anodizing treatment ST3A is performed.

[0078] In the fourth manufacturing method of the aluminum conversion foil 1, as shown in FIG. 10, similar to the third manufacturing method, the crack formation process ST11 is performed during the anodization process ST3. Specifically, in the anodization process ST3, a pre-anodization treatment ST3B is performed on the aluminum foil 10 until a predetermined anodization voltage is reached, and the crack formation process ST11 is performed following the pre-anodization treatment ST3B. Further, following the crack formation process ST11, a rehydration process ST21 for forming a hydrated film on the aluminum foil 10 is performed, and a post-anodization treatment ST3A is performed after the rehydration process ST21. That is, in the fourth manufacturing method of the aluminum conversion foil 1, the crack formation process ST11 and the rehydration process ST21 are continuously performed during the anodization process ST3.

[0079] The fifth manufacturing method of the aluminum conversion foil 1 is, as shown in FIG. 11, to perform the crack formation process ST11 during the hydration process ST2. Also, the crack formation process ST11 is performed during the anodization process ST3. Specifically, in the hydration process ST2, the crack formation process ST1 1 is performed, and hydration treatments are performed before and after the crack formation process ST11. In the anodization process ST3, a pre-anodization treatment ST3B is performed on the aluminum foil 10 until a predetermined anodization voltage is reached, and the crack formation process ST11 and the rehydration process ST21 are continuously performed following the pre-anodization treatment ST3B, and a post-anodization treatment ST3A is performed after the rehydration process ST21.

[0080] Next, a specific method for generating stress in the aluminum foil 10 in the crack formation process ST11 will be exemplified. FIG. 12 is an explanatory diagram of the crack formation process ST11. As shown in FIG. 12, in the crack formation process ST11, the aluminum foil 10 is run along a plurality of rollers 21 arranged in the X direction.

[0081] Each of the plurality of rollers 21 has a rotation axis extending in the Y direction. Among the plurality of rollers 21 arranged in the X direction, there are rollers 21 having a smaller diameter compared to other rollers 21. Among these rollers 21 with a smaller diameter, the roller 21 that contacts the second surface 2b of the traveling aluminum foil 10 is arranged as a first crack forming roller 21(1) that generates stress in the aluminum foil 10 to generate cracks 7 in the first porous layer 3. Also, among these rollers 21 with a smaller diameter, the roller 21 that contacts the first surface 2a of the traveling aluminum foil 10 is arranged as a second crack forming roller 21(2) that generates stress in the aluminum foil 10 to generate cracks 7 in the second porous layer 4. The diameter dimensions M of the first crack forming roller 21(1) and the second crack forming roller 21(2) are each 5 mm to 60 mm. In this example, an example is shown where the diameter dimensions M of the first crack forming roller 21(1) and the second crack forming roller 21(2) are the same, but these diameter dimensions M may be different.

[0082] In this example, the first crack forming roller 21(1) and the second crack forming roller 21(2) are made of metal. Pressing rollers 23 are pressed against the first crack forming roller 21(1) and the second crack forming roller 21(2), respectively. The surface of each pressing roller 23 is covered with an elastic member such as rubber. It is desirable that the diameter of each pressing roller 23 is larger than the diameter of the first crack forming roller 21(1) and the diameter of the second crack forming roller 21(2).

[0083] When the aluminum foil 10 travels between the first crack forming roller 21(1) and the pressing roller 23, stress is generated in the aluminum foil 10. Therefore, a plurality of predetermined cracks 7 are formed in the first porous layer 3. Also, when the aluminum foil 10 travels between the second crack forming roller 21(2) and the pressing roller 23, stress is generated in the aluminum foil 10. Therefore, a plurality of predetermined cracks 7 are formed in the second porous layer 4.

[0084] When the aluminum foil 10 travels between the first crack-forming roller 21(1) and the pressing roller 23, the holding angle of the first crack-forming roller 21(1) is usually -180° to 180°, preferably -45° to 45°. When the aluminum foil 10 travels between the second crack-forming roller 21(2) and the pressing roller 23, the holding angle of the second crack-forming roller 21(2) is usually -180° to 180°, preferably -45° to 45°. Further, it is more desirable that the holding angles of the first crack-forming roller 21(1) and the second crack-forming roller 21(2) be 0° or more. Therefore, the holding angles of the first crack-forming roller 21(1) and the second crack-forming roller 21(2) are 0° to 180°, preferably 0° to 45°. Here, if the holding angle of the first crack-forming roller 21(1) is within the above range, when the first crack-forming roller 21(1) contacts the second surface 2b of the aluminum foil 10, it is easy to form the desired crack 7 in the first porous layer 3. Also, if the holding angle of the second crack-forming roller 21(2) is within the above range, when the second crack-forming roller 21(2) contacts the first surface 2a of the aluminum foil 10, it is easy to form the desired crack 7 in the second porous layer in 4.

[0085] Note that a plurality of the first crack-forming rollers 21(1) can also be provided among the plurality of rollers 21. When a plurality of the first crack-forming rollers 21(1) are provided, it is desirable to provide the same number of the second crack-forming rollers 21(2) as the number of the first crack-forming rollers 21(1) among the plurality of rollers 21. At this time, it is preferable that the first crack-forming roller 21(1) and the second crack-forming roller 21(2) contact the aluminum foil 10 at different positions.

[0086] (Function and Effect) In the method for manufacturing the aluminum conversion foil 1 of this example, by generating stress in the aluminum foil 10 in the conversion step ST1, a plurality of cracks 7 extending in the Y direction are spaced apart in the X direction on the surface of the porous layer (the first porous layer 3 and the second porous layer 4). Further, after the formation of the cracks 7, a post-anodization treatment ST3A of performing anodization on the aluminum foil 10 is carried out. Here, by forming the cracks 7 in the porous layer (the first porous layer 3 and the second porous layer 4) during the conversion step ST1, even when the conversion film (the first conversion film 5 and the second conversion film 6) grows due to subsequent anodization, it is possible to suppress the cracks 7 from being closed by the conversion film (the first conversion film 5 and the second conversion film 6). Therefore, an aluminum conversion foil 1 having a plurality of cracks 7 can be obtained. Accordingly, even when bending occurs in the aluminum foil 10 in which the adjacent powder bodies 11 are bonded via the conversion film (the first conversion film 5 and the second conversion film 6) as the conversion film (the first conversion film 5 and the second conversion film 6) grows, the stress generated due to the deformation can be released from the cracks 7. Thereby, it is possible to prevent or suppress the occurrence of local cracks in the bond between the powder bodies 11, so that it is possible to prevent or suppress the local cracks from spreading and the aluminum foil 10 from breaking. Also, since anodization is performed on the aluminum foil 10 after forming the cracks 7, it is possible to reform the conversion film (the first conversion film 5 and the second conversion film 6) on the porous layer (the first porous layer 3 and the second porous layer 4) after the cracks 7 have occurred. Thereby, the newly formed aluminum surface (the surface of the exposed metallic aluminum) on the surface of the porous layer (the first porous layer 3 and the second porous layer 4) caused by the formation of the cracks 7 can be covered with the reformed conversion film (the first conversion film 5 and the second conversion film 6). Therefore, it is possible to prevent or suppress breakage while reducing the leakage current of the aluminum foil 10 or the electrode for an aluminum electrolytic capacitor during anodization caused by the cracks 7.

[0087] Also, in the formation process ST1, the thickness of the formation film (the first formation film 5 and the second formation film 6) that grows until the voltage output from the power source during anodization reaches a predetermined anodization voltage can be estimated. Therefore, the thickness of the formation film (the first formation film 5 and the second formation film 6) can be controlled based on the voltage output from the power source during anodization. Thus, before the crack formation process ST11, a pre-anodization process ST3B is performed to subject the aluminum foil 10 to anodization until the voltage during anodization reaches the predetermined anodization voltage, and then the crack formation process ST11 is performed. This can avoid the situation where the formation film (the first formation film 5 and the second formation film 6) becomes too thick and the aluminum foil 10 becomes too hard when the crack formation process ST11 is carried out. Therefore, when stress is applied to the aluminum foil 10 in the crack formation process ST11, it is possible to avoid breaking the aluminum foil 10.

[0088] Furthermore, in this example, since it is possible to avoid the aluminum foil 10 becoming too hard when performing the crack formation process ST11, by generating stress in the aluminum foil 10, it becomes possible to uniformly provide a plurality of cracks 7 on the surface of the porous layer (the first porous layer 3 and the second porous layer 4). Here, if a plurality of cracks 7 are uniformly formed on the surface of the porous layer (the first porous layer 3 and the second porous layer 4), even when the thickness of the formation film (the first formation film 5 and the second formation film 6) increases until the target film withstand voltage is reached, it is possible to suppress a decrease in the bending strength. This can be suppressed.

[0089] Also, in the crack formation process ST11, a plurality of cracks 7 extending in the Y direction with a length of 300 μm or more are provided at intervals of 30 μm to 150 μm in the X direction. By providing such cracks 7, even when the formation film (the first formation film 5 and the second formation film 6) grows due to anodization, it is possible to prevent or suppress the cracks 7 from being closed by the formation film (the first formation film 5 and the second formation film 6).

[0090] Furthermore, in the crack formation process ST11, each crack 7 is made to reach the boundary between the base layer 2 and the porous layers (the first porous layer 3 and the second porous layer 4). Thereby, even when the aluminum foil 10 is bent during anodization, it becomes easy to release the stress generated due to the deformation from the crack 7.

[0091] In addition, as shown in the embodiments described later, as long as it is before the voltage during anodization (anodization voltage) reaches 250V, the conversion coatings (the first conversion coating 5 and the second conversion coating 6) do not become too thick, and the hardness of the aluminum foil 10 is suitable for forming the crack 7. Therefore, in the conversion process ST1, the pre-crack anodization treatment ST3B is performed until 250V is reached, and then the crack formation process ST11 is provided to apply stress to the aluminum foil 10, so that it is easier to uniformly provide a plurality of cracks 7 on the surface of the porous layers (the first porous layer 3 and the second porous layer 4).

[0092] Furthermore, in the crack formation process ST11, stress is generated in the aluminum foil 10 by the crack forming rollers (the first crack forming roller 21(1) and the second crack forming roller 21(2)). Therefore, it is easy to form a plurality of cracks 7 in the porous layers (the first porous layer 3 and the second porous layer 4).

[0093] Also, in the crack formation process ST11, among the plurality of rollers 21 that run the aluminum foil 10, rollers 21 having a smaller diameter than the other rollers 21 are arranged as the crack forming rollers (the first crack forming roller 21(1) and the second crack forming roller 21(2)). By using a roller with a small diameter as the crack forming roller (the first crack forming roller 21(1) and the second crack forming roller 21(2)), it is easy to generate stress in the aluminum foil 10 and form the crack 7.

[0094] Furthermore, in the first manufacturing method and the fifth manufacturing method, the formation process ST1 includes a hydration process ST2 of forming a hydrated film on the aluminum foil 10 before the anodization process ST3. Then, the crack formation treatment ST11 is performed during the hydration process ST2. In this way, first, a hydrated film is formed on the surface of the porous layers (the first porous layer 3 and the second porous layer 4) in the hydration process ST2. Then, cracks 7 are provided in the porous layers (the first porous layer 3 and the second porous layer 4) during the hydration process ST2. As a result, due to the crack formation treatment ST11, on the surface of the porous layers (the first porous layer 3 and the second porous layer 4), an aluminum fresh surface (the surface of the exposed metallic aluminum) is exposed through the cracks 7. That is, powder 11 whose surface is not formed with a hydrated film is exposed on the fracture surface of the porous layers (the first porous layer 3 and the second porous layer 4) due to the cracks 7. Thereafter, a hydrated film is formed on the aluminum fresh surface in the hydration process ST2 that continues after the crack formation treatment ST11. Here, the hydrated film covering the aluminum fresh surface inhibits or suppresses the bonding of the powders 11 located on both sides sandwiching the cracks 7 through the formation films (the first formation film 5 and the second formation film 6) in the anodization process ST3. Therefore, if the crack formation treatment ST11 is performed during the hydration process ST2, when the formation films (the first formation film 5 and the second formation film 6) grow in the anodization process ST3 performed after the crack formation treatment ST11 and the hydration process ST2, it is possible to prevent or suppress the closing of the cracks 7 by the formation films (the first formation film 5 and the second formation film

[0095] In the second manufacturing method, the third manufacturing method, and the fourth manufacturing method, the formation step ST1 includes a hydration step ST2 of forming a hydrated film on the aluminum foil 10 before the anodization step ST3. The anodization step ST3 performs anodization on the aluminum foil 10 on which the hydrated film is formed. Then, in the second manufacturing method and the third manufacturing method, the crack formation treatment ST11 is performed after the hydration step ST2. By doing so, a hydrated film is formed on the surface of the porous layers (the first porous layer 3 and the second porous layer 4) in the hydration step ST2. Here, the hydrated film inhibits or suppresses the bonding of the powders 11 to each other via the formation films (the first formation film 5 and the second formation film 6) in the anodization step ST3. Therefore, if the crack formation treatment ST11 is provided after the hydration step ST2, it is easy to suppress the cracks 7 formed in the porous layers (the first porous layer 3 and the second porous layer 4) from being closed by the formation films (the first formation film 5 and the second formation film 6) formed after the hydration step ST2.

[0096] In the fourth and fifth manufacturing methods, in the anodizing step ST3, before reaching a predetermined anodizing voltage, a pre-crack formation anodizing treatment ST3B is performed, and then a crack formation treatment ST11 is performed. Further, following the crack formation treatment ST11, a rehydration treatment ST21 for forming a hydrated film on the aluminum foil 10 is continuously performed. Furthermore, a post-anodizing treatment ST3A is performed after the rehydration treatment ST21. By doing so, a hydrated film is formed on the surface of the porous layer (the first porous layer 3 and the second porous layer 4) in the hydration step ST2. Here, the hydrated film inhibits or suppresses the bonding of the powders 11 to each other via the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) in the anodizing step ST3. Therefore, it is easy to suppress the closing of the cracks 7 formed in the porous layer (the first porous layer 3 and the second porous layer 4) by the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6). Also, on the newly exposed aluminum surface of the porous layer (the first porous layer 3 and the second porous layer 4) due to the formation of the cracks 7, a hydrated film is formed in the rehydration treatment ST21 that is continuously performed after the crack formation treatment ST11. Here, the hydrated film covering the newly exposed aluminum surface inhibits or suppresses the bonding of the powders 11 located on both sides with the crack 7 in between via the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) in the subsequent anodizing. Therefore, if the rehydration treatment ST21 is performed following the crack formation treatment ST11, when the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) grow in the post-anodizing treatment ST3A, it is possible to further suppress the closing of the crack 7 by the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6).

[0097] Here, in each manufacturing method, when the anodizing step ST3 is completed, the aluminum foil 10 after chemical conversion, that is, the aluminum chemical conversion foil 1, is wound around a winding roller and becomes a roll shape wound in a spiral curve. At this time, since the aluminum chemical conversion foil 1 has a plurality of cracks 7, it is easy to wind in the X direction. Therefore, the aluminum chemical conversion foil 1 can be wound in a shape closer to a perfect circle compared to the case where the aluminum chemical conversion foil 1 does not have the crack 7. That is, when the aluminum chemical conversion foil 1 without cracks is wound, a plurality of bent portions are formed in the middle of the aluminum chemical conversion foil 1. On the other hand, when the aluminum chemical conversion foil 1 having a plurality of cracks 7 is wound, it becomes a roll shape wound in the X direction without having a portion bent in the middle. As a result, the roll around which the aluminum chemical conversion foil 1 is wound has a smaller outer dimension of the roll with respect to the X-direction dimension of the wound aluminum chemical conversion foil 1 compared to the roll in the case where the aluminum chemical conversion foil 1 does not have cracks. In other words, when wound until the outer dimensions of the rolls are the same, the roll around which the aluminum chemical conversion foil 1 is wound has a longer X-direction dimension of the wound aluminum chemical conversion foil 1 compared to the roll in the case where the aluminum chemical conversion foil 1 does not have cracks. Therefore, in this example, the working efficiency of the winding operation using the aluminum chemical conversion foil 1 as a roll is improved. Also, when the aluminum chemical conversion foil 1 is wound into a roll shape in a spiral curve and If so, it is possible to prevent the breakage of the aluminum chemical conversion foil 1 occurring in the bent portion compared to the case where the aluminum chemical conversion foil 1 has a bent portion in the middle. Therefore, the winding property of the aluminum chemical conversion foil 1 can be improved.

[0098] (Example) FIG. 13 is a table explaining the timing of performing the crack formation process ST11 in the manufacturing method of the aluminum conversion foil 1 of Examples 1 to 5. FIG. 14 is an explanatory diagram of the timing of performing the crack formation process ST11 in the manufacturing method of the aluminum conversion foil 1 of Examples 1 to 5. In the manufacturing methods of the aluminum conversion foils 1 of Examples 1 to 5, although the timing of performing the crack formation process ST11 is different, in the conversion process ST1, the processes applied to the aluminum foil 10 are the same.

[0099] In Examples 1 to 5, as the base material, an aluminum foil 10 is used in which the thickness dimension T1 of the base layer 2 is 30 μm, the thickness dimensions T2 of the first porous layer 3 and T3 of the second porous layer 4 are each 50 μm, and the average particle diameter K of the powder 11 forming the first porous layer 3 and the second porous layer 4 is 3 μm. In the hydration process ST2, pure water is used as the hydration treatment solution. Also, in the hydration process ST2, the aluminum foil 10 is boiled at 95° C. for 10 minutes. In the anodization process ST3, the first anodization treatment ST41, the second anodization treatment ST42, and the third anodization treatment ST43 are performed. Also, in the anodization process ST3, a heat treatment ST31 is performed between the second anodization treatment ST42 and the third anodization treatment ST43. In the heat treatment ST31, the aluminum foil 10 is heated in an atmosphere of 500° C. for 2 minutes to expose the defective portions.

[0100] In the first anodizing treatment ST41, anodizing is performed on the aluminum foil 10 until the anodizing voltage reaches 400V. The chemical conversion treatment liquid for the first anodizing treatment ST41 contains ammonium adipate. The amount of ammonium adipate in the chemical conversion treatment liquid is 1 g / L. The temperature of the chemical conversion treatment liquid is 80°C. In the second anodizing treatment ST42, the voltage is increased until the anodizing voltage reaches 550V and then held for an additional 30 minutes to perform anodizing on the aluminum foil 10. The chemical conversion treatment liquid for the second anodizing treatment ST42 contains boric acid and ammonium pentaborate octahydrate. The amount of boric acid in the chemical conversion treatment liquid is 80 g / L, and the amount of ammonium pentaborate octahydrate is 0.5 g / L. The temperature of the chemical conversion treatment liquid is 80°C. In the third anodizing treatment ST43, the voltage is increased until the anodizing voltage reaches 550V and then held for an additional 10 minutes to perform anodizing on the aluminum foil 10. In the third anodizing treatment ST43, the same chemical conversion treatment liquid as that of the second anodizing treatment ST42 is used. The temperature of the chemical conversion treatment liquid is 80°C. The diameter dimension M of the first crack forming roller 21(1) and the diameter dimension M of the second crack forming roller 21(2) used in the crack forming treatment ST11 are 10 mm.

[0101] As shown in FIGS. 13 and 14, Example 1 is the first manufacturing method and includes the crack forming treatment ST11 during the hydration step ST2. Example 2 is the second manufacturing method and includes the crack forming treatment ST11 between the hydration step ST2 and the anodizing step ST3. In Examples 1 and 2, the first anodizing treatment ST41, the second anodizing treatment ST42, and the third anodizing treatment ST43 correspond to the post-anodizing treatment ST3A.

[0102] Examples 3 to 5 are the third manufacturing method, and in the anodizing step ST3 included in the chemical conversion step ST1, the crack forming treatment ST11 is performed before reaching the final target anodizing voltage (550V).

[0103] In Example 3, in the first anodizing process ST41, the crack formation process ST11 is performed when the anodizing voltage reaches 100V. In Example 3, up to when the anodizing voltage of the first anodizing process ST41 reaches 100V corresponds to the pre-anodizing process ST3B. After the crack formation process ST11 of the first anodizing process ST41, the second anodizing process ST42 and the third anodizing process ST43 correspond to the post-anodizing process ST3A. The anodizing process ST43 corresponds to the post-anodizing process ST3A.

[0104] In Example 4, in the first anodizing process ST41, the crack formation process ST11 is performed when the anodizing voltage reaches 200V. In Example 4, up to when the anodizing voltage of the first anodizing process ST41 reaches 200V corresponds to the pre-anodizing process ST3B. After the crack formation process ST11 of the first anodizing process ST41, the second anodizing process ST42 and the third anodizing process ST43 correspond to the post-anodizing process ST3A.

[0105] In Example 5, in the first anodizing process ST41, the crack formation process ST11 is performed when the anodizing voltage reaches 400V. In Example 5, up to when the anodizing voltage of the first anodizing process ST41 reaches 400V corresponds to the pre-anodizing process ST3B. The second anodizing process ST42 and the third anodizing process ST43 correspond to the post-anodizing process ST3A.

[0106] Note that the manufacturing method of Comparative Example 1 does not include the crack formation process ST11 during the chemical conversion process ST1. The manufacturing method of Comparative Example 2 performs the crack formation process ST11 immediately after the second anodizing process ST42 in the anodizing process ST3. In the manufacturing method of Comparative Example 2, at the time when the crack formation process ST11 is performed, the voltage output from the power source during anodizing exceeds the predetermined anodizing voltage (400V) and reaches the final anodizing voltage (550V) which is the final target of the voltage during anodizing.

[0107] FIG. 15 is a table showing the intervals of cracks 7, bending strength, tensile strength, capacitance, and film withstand voltage of the aluminum foil 10 after chemical conversion treatment, that is, the aluminum chemical conversion foil 1, for Examples 1 to 5 and Comparative Examples 1 and 2. Note that the manufacturing method of Comparative Example 1 does not include the crack formation treatment ST11. Therefore, as shown in FIG. 15, the aluminum chemical conversion foil 1 obtained by the manufacturing method of Comparative Example 1 does not have cracks in the first porous layer 3 and the second porous layer 4. Therefore, the column of the crack interval in FIG. 15 is described as unmeasurable.

[0108] Here, the bending strength, tensile strength, and capacitance were measured in accordance with "EIAJ RC-2364A", which is a standard of the Japan Electronic Machinery Industry Association. The bending strength is indicated by the number of bending times at which the aluminum chemical conversion foil 1 breaks. The number of bending times is counted as 1 when the aluminum chemical conversion foil 1 extending in the X direction is bent 90° in the Z direction intersecting the X direction and the Y direction, counted as 2 when bent back, counted as 3 when bent 90° in the Z direction opposite to the first time, counted as 4 when bent back, and so on. After 5 times, it is counted by bending in the same way as from 1 to 4 times. The tensile strength is the tensile force when the aluminum chemical conversion foil 1 is pulled in the X direction until it breaks.

[0109] FIG. 16 is a photograph taken by magnifying the surface of the aluminum chemical conversion foil 1 manufactured by the manufacturing method of Example 5 with a scanning electron microscope. Note that FIG. 1 is a photograph taken by magnifying the surface of the aluminum chemical conversion foil 1 manufactured by the manufacturing method of Example 1 with a scanning electron microscope. FIG. 2 is a photograph taken by magnifying the cross section of the aluminum chemical conversion foil 1 manufactured by the manufacturing method of Example 1 with a scanning electron microscope.

[0110] As shown in FIGS. 1, 2, and 16, in the aluminum chemical conversion foil 1 obtained by the manufacturing methods of Examples 1 to 5, cracks 7 extending in the Y direction with a length of 300 μm or more are provided on the surfaces of the first porous layer 3 and the second porous layer 4 at intervals of 30 μm to 150 μm, in plural. Specifically, as shown in FIG. 15, a plurality of cracks 7 are provided at intervals of 95 μm to 110 μm.

[0111] In such an anodized aluminum foil 1, even when the aluminum foil 10 is bent when adjacent powder bodies 11 are bonded via an anodic oxide film (first anodic oxide film 5 and second anodic oxide film 6) by subjecting the aluminum foil 10 to anodic oxidation, the stress generated due to the deformation can be released from the crack 7. Therefore, in the anodized aluminum foil 1 obtained by the production methods of Examples 1 to 5, the bending strength is such that the number of bending times is 150 or more, and it is more resistant to bending than the anodized aluminum foil 1 obtained by the production methods of Comparative Examples 1 and 2. Here, in the anodized aluminum foil 1 (see FIG. 1) obtained by the production methods of Examples 1 to 4, the interval of the cracks 7 is narrower than that of the anodized aluminum foil 1 (see FIG. 16) obtained by the production method of Example 5. Therefore, as shown in FIG. 15, the number of bending times indicating the bending strength is more than that of the anodized aluminum foil 1 obtained by the production method of Example 5, and it is more resistant to bending. Here, according to the verification by the inventors, if the crack formation treatment ST11 is performed before the anodic oxidation voltage reaches 250V in the anodic oxidation step ST3, the anodized aluminum foil 1 can be made more resistant to bending as compared with the case where the crack formation treatment ST11 is performed after the anodic oxidation voltage exceeds 250V.

[0112]

[0113] Further, when the anodized aluminum foil 1 obtained by the production methods of Examples 1 to 5 is used as an electrode for an aluminum electrolytic capacitor, the capacitance is higher than when the anodized aluminum foil obtained by the production method of Comparative Example 1 is used as an electrode for an aluminum electrolytic capacitor. That is, since the anodized aluminum foil 1 obtained by the production methods of Examples 1 to 5 has the crack 7, the specific surface area is larger than that of the anodized aluminum foil 1 obtained by the production method of Comparative Example 1. As a result, in the anodized aluminum foil 1 (electrode for an aluminum electrolytic capacitor) obtained by the production methods of Examples 1 to 5, the capacitance becomes higher.

[0114] ​Here, FIG. 17 is a photograph taken by magnifying the surface of the aluminum conversion foil 1' manufactured by the manufacturing method of Comparative Example 1 with a scanning electron microscope. FIG. 18 is a photograph taken by magnifying the cross-section of the aluminum conversion foil 1' of Comparative Example 1 with a scanning electron microscope. As shown in FIGS. 17 and 18, the aluminum conversion foil 1' manufactured by the manufacturing method of Comparative Example 1 does not have cracks. In such an aluminum conversion foil 1', in the anodizing step ST3, when the conversion films (the first conversion film 5 and the second conversion film 6) grow on the surface of the porous layers (the first porous layer 3 and the second porous layer 4) made of the sintered body of the powder 11, the adjacent powders 11 are bonded via the conversion film. Therefore, when the aluminum foil is bent, since the bonding between the powders 11 is strong, the stress generated due to the deformation cannot be released from the aluminum foil. As a result, local cracks occur in the bonding between the powders 11. Further, this crack spreads and the aluminum foil breaks. Therefore, as shown in FIG. 15, the bending strength of the aluminum conversion foil 1' manufactured by the manufacturing method of Comparative Example 1 is low.

[0115] FIG. 19 is a table explaining the timing of performing the crack formation treatment ST11 in the manufacturing method of the aluminum conversion foils 1 of Examples 6 to 8. FIG. 20 is an explanatory diagram of the timing of performing the crack formation treatment ST11 in the manufacturing method of the aluminum conversion foils 1 of Examples 6 to 8.

[0116] Examples 6 to 8 are the fourth manufacturing method. In the anodizing step ST3 included in the chemical conversion step ST1, before reaching the final target final anodizing voltage (550V), the crack formation treatment ST11 and the rehydration treatment ST21 are continuously performed. In Examples 6 to 8, the aluminum foil 10 used as the base material is the same as that in Examples 1 to 5. That is, in Examples 6 to 8, as the base material, an aluminum foil 10 having a base layer 2 with a thickness dimension T1 of 30 μm, a first porous layer 3 with a thickness dimension T2 and a second porous layer 4 with a thickness dimension T3 of 50 μm each, and an average particle diameter K of the powder 11 forming the first porous layer 3 and the second porous layer 4 of 3 μm is used.

[0117] Also, in the manufacturing method of the aluminum chemical conversion foil 1 of Examples 6 to 8, the treatment applied to the aluminum foil 10 in the chemical conversion step ST1 is the same as that in Examples 1 to 5. The diameter dimension M of the first crack formation roller 21(1) and the diameter dimension M of the second crack formation roller 21(2) used in the crack formation treatment ST11 are 10 mm. In the rehydration treatment ST21, pure water is used as the hydration treatment liquid. Also, in the rehydration treatment ST21, the aluminum foil 10 is boiled at 95°C for 2 minutes.

[0118] Here, in Example 6, in the first anodization treatment ST41, when the anodization voltage reaches 100 V, the crack formation treatment ST11 and the rehydration treatment ST21 are continuously performed. In Example 6, up to the point where the anodization voltage of the first anodization treatment ST41 reaches 100 V corresponds to the pre-anodization treatment ST3B, and after the crack formation treatment ST11 and the rehydration treatment ST21 of the first anodization treatment ST41, the second anodization treatment ST42 and the third anodization treatment ST43 correspond to the post-anodization treatment ST3A.

[0119] In Example 7, in the first anodization treatment ST41, when the anodization voltage reaches 200 V, the crack formation treatment ST11 and the rehydration treatment ST21 are continuously performed. In Example 7, up to the point where the anodization voltage of the first anodization treatment ST41 reaches 200 V corresponds to the pre-anodization treatment ST3B, and after the crack formation treatment ST11 and the rehydration treatment ST21 of the first anodization treatment ST41, the second anodization treatment ST42 and the third anodization treatment ST43 correspond to the post-anodization treatment ST3A.

[0120] In Example 8, in the first anodization treatment ST41, when the anodization voltage reaches 400 V, the crack formation treatment ST11 and the rehydration treatment ST21 are continuously performed. In Example 8, up to the point where the anodization voltage of the first anodization treatment ST41 reaches 400 V corresponds to the pre-anodization treatment ST3B, and the second anodization treatment ST42 and the third anodization treatment ST43 correspond to the post-anodization treatment ST3A.

[0121] FIG. 21 is an explanatory diagram showing the interval of cracks 7, bending strength, tensile strength, capacitance, and film withstand voltage of the aluminum foil 10 after chemical conversion treatment, that is, the aluminum chemically converted foil 1, for Examples 6 to 8. In the aluminum chemically converted foil 1 obtained by the manufacturing method of Examples 6 to 8, a plurality of cracks 7 extending in the Y direction with a length of 300 μm or more are provided on the surfaces of the first porous layer 3 and the second porous layer 4 at intervals of 30 μm to 150 μm. That is, as shown in FIG. 21, in the aluminum chemically converted foil 1 obtained by the manufacturing method of Examples 6 to 8, a plurality of cracks 7 are provided at intervals of 105 μm to 110 μm. Therefore, even when the aluminum foil 10 is bent when adjacent powders 11 are bonded through the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) by subjecting the aluminum foil 10 to anodic oxidation, the stress generated due to the deformation can be released from the cracks 7.

[0122] Therefore, in the aluminum chemically converted foil 1 obtained by the manufacturing method of Examples 6 to 8, the bending strength is such that the number of bending times is 161 times or more, and it is more resistant to bending compared to the aluminum chemically converted foil 1 obtained by the manufacturing methods of Comparative Examples 1 and 2.

[0123] Also, since the aluminum chemically converted foil 1 obtained by the manufacturing method of Examples 6 to 8 continuously performs the crack formation treatment ST11 and the rehydration treatment ST21 in this order, when the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) grow in the anodic oxidation step ST3, it is possible to prevent or suppress the cracks 7 from being closed by the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6). Furthermore, since the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) have cracks 7, when the aluminum chemically converted foil 1 obtained by the manufacturing method of Examples 6 to 8 is used as an electrode for an aluminum electrolytic capacitor, compared with the case where the aluminum chemically converted foil 1 obtained by the manufacturing methods of Comparative Examples 1 and 2 is used as an electrode for an aluminum electrolytic capacitor, the capacitance is high. When used as an electrode for an aluminum electrolytic capacitor, the capacitance is high compared to the case where the aluminum chemically converted foil 1 obtained by the manufacturing methods of Comparative Examples 1 and 2 is used as an electrode for an aluminum electrolytic capacitor.

[0124] Here, in the aluminum conversion foil 1 obtained by the production methods of Examples 6 and 7, the interval of the cracks 7 is narrower than that of the aluminum conversion foil 1 obtained by the production method of Example 8. Therefore, as shown in FIG. 21, the aluminum conversion foil 1 obtained by the production methods of Examples 6 and 7 has a larger number of bending times indicating the bending strength than the aluminum conversion foil 1 obtained by the production method of Example 8 and is more resistant to bending. Further, according to the verification by the inventors, in the anodizing step ST3, if the crack formation treatment ST11 and the rehydration treatment ST21 are performed before the anodizing voltage reaches 250V, compared with the case where the crack formation treatment ST11 is performed after the anodizing voltage exceeds 250V, the aluminum conversion foil 1 can be made more resistant to bending.

[0125] FIG. 22 is a table explaining the timing of performing the crack formation treatment ST11 in the production method of the aluminum conversion foil 1 of Examples 9 to 11. FIG. 23 is an explanatory diagram of the timing of performing the crack formation treatment ST11 in the production method of the aluminum conversion foil 1 of Examples 9 to 11.

[0126] Examples 9 to 11 are the fifth production method, and the crack formation treatment ST11 is performed during the hydration step ST2 included in the conversion step ST1. Further, in Examples 9 to 11, in the anodizing step ST3 included in the conversion step ST1, before the voltage output from the power supply reaches the final target final anodizing voltage (550V), the crack formation treatment ST11 and the rehydration treatment ST21 are continuously performed. Also, in Examples 9 to 11, as the base material, an aluminum foil 10 is used in which the thickness dimension T1 of the base layer 2 is 30μm, the thickness dimensions T2 of the first porous layer 3 and T3 of the second porous layer 4 are each 100μm, and the average particle diameter K of the powder 11 forming the first porous layer 3 and the second porous layer 4 is 3μm. That is, in Examples 9 to 11, as the base material, an aluminum foil 10 having a total thickness dimension of the porous layers (the sum of the thickness dimension T2 of the first porous layer 3 and the thickness dimension T3 of the second porous layer 4) of 200μm is used.

[0127] In Examples 9 to 11, the treatment applied to the aluminum foil 10 in the formation process ST1 is the same as that in Examples 1 to 8. Also, the diameter dimension M of the first crack formation roller 21(1) and the diameter dimension M of the second crack formation roller 21(2) used in the crack formation process ST11 are 10 mm. In the rehydration process ST21, pure water is used as the hydration treatment liquid. In the rehydration process ST21, the aluminum foil 10 is boiled at 95°C for 2 minutes.

[0128] Here, in Example 9, in the first anodization process ST41, when the anodization voltage reaches 100 V, the crack formation process ST11 and the rehydration process ST21 are continuously performed. In Example 9, the period until the anodization voltage of the first anodization process ST41 reaches 100 V corresponds to the pre-anodization process ST3B, and after the crack formation process ST11 and the rehydration process ST21 of the first anodization process ST41, the second anodization process ST42 and the third anodization process ST43 correspond to the post-anodization process ST3A.

[0129] In Example 10, in the first anodization process ST41, when the anodization voltage reaches 200 V, the crack formation process ST11 and the rehydration process ST21 are continuously performed. In Example 10, the period until the anodization voltage of the first anodization process ST41 reaches 200 V corresponds to the pre-anodization process ST3B, and after the crack formation process ST11 and the rehydration process ST21 of the first anodization process ST41, the second anodization process ST42 and the third anodization process ST43 correspond to the post-anodization process ST3A.

[0130] In Example 11, in the first anodization process ST41, when the anodization voltage reaches 400 V, the crack formation process ST11 and the rehydration process ST21 are continuously performed. In Example 1 1, the period until the anodization voltage of the first anodization process ST41 reaches 400 V corresponds to the pre-anodization process ST3B, and the second anodization process ST42 and the third anodization process ST43 correspond to the post-anodization process ST3A.

[0131] FIG. 24 is an explanatory diagram showing the interval, bending strength, tensile strength, capacitance, and film breakdown voltage of the aluminum foil 10 after formation treatment, i.e., the aluminum formed foil 1, for Examples 9 to 11. In the aluminum formed foil 1 obtained by the manufacturing methods of Examples 9 to 11, a plurality of cracks 7 extending in the Y direction with a length of 300 μm or more are provided on the surfaces of the first porous layer 3 and the second porous layer 4 at intervals between 35 μm and 150 μm. That is, as shown in FIG. 24, a plurality of cracks 7 are provided at intervals between 135 μm and 150 μm. In such an aluminum formed foil 1, when adjacent powder bodies 11 are bonded via a formed film (the first formed film 5 and the second formed film 6) by subjecting the aluminum foil 10 to anodic oxidation and the aluminum foil 10 bends, the stress generated due to the deformation can be released from the cracks 7.

[0132] Therefore, in the aluminum formed foil 1 obtained by the manufacturing methods of Examples 9 to 11, the bending strength is such that the number of bending times is 120 or more, and it is more resistant to bending compared to the aluminum formed foil 1 obtained by the manufacturing methods of Comparative Examples 1 and 2.

[0133] Also, in the aluminum formed foil 1 obtained by the manufacturing methods of Examples 9 to 11, the crack formation treatment ST11 is performed twice. The first crack formation treatment ST11 is performed during the hydration step ST2, and in the second crack formation treatment ST11, the rehydration treatment ST21 is continuously performed following the crack formation treatment ST11. Therefore, even when an aluminum foil 10 with a total thickness dimension of the porous layers (the sum of the thickness dimension T2 of the first porous layer 3 and the thickness dimension T3 of the second porous layer 4) of 200 μm is used as the base material, when the formed film (the first formed film 5 and the second formed film 6) grows in the anodic oxidation step ST3, it is possible to prevent or suppress the cracks 7 from being closed by the formed film (the first formed film 5 and the second formed film 6).

[0134] Furthermore, since the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) have cracks 7, when the aluminum chemical conversion foil 1 obtained by the production methods of Examples 9 to 11 is used as an electrode for an aluminum electrolytic capacitor, the capacitance is higher than that when the aluminum chemical conversion foil 1 obtained by the production methods of Comparative Examples 1 and 2 is used as an electrode for an aluminum electrolytic capacitor.

[0135] Here, in the aluminum chemical conversion foil 1 obtained by the production methods of Examples 9 and 10, the interval of the cracks 7 is narrower than that of the aluminum chemical conversion foil 1 obtained by the production method of Example 11. Therefore, as shown in FIG. 24, the aluminum chemical conversion foil 1 obtained by the production methods of Examples 9 and 10 has a larger number of bending times indicating the bending strength than the aluminum chemical conversion foil 1 obtained by the production method of Example 11 and is more resistant to bending. Further, according to the verification by the inventors, in the anodizing step ST3, if the crack formation treatment ST11 and the rehydration treatment ST21 are performed before the anodizing voltage reaches 250V, the aluminum chemical conversion foil 1 can be made more resistant to bending as compared with the case where the crack formation treatment ST11 is performed after the anodizing voltage exceeds 250V.

[0136] Also, in Examples 8 to 11, the porous layers (the first porous layer 3 and the second porous layer 4) laminated on the base layer 2 of the aluminum chemical conversion foil 1 are thick. Therefore, when the aluminum chemical conversion foil 1 produced by the production methods of Examples 8 to 11 is used as an electrode for an aluminum electrolytic capacitor, the capacitance is higher than that when the aluminum chemical conversion foil 1 obtained by the production methods of other examples is used as an electrode for an aluminum electrolytic capacitor.

[0137] (Other Embodiments) FIG. 25 is a flowchart of a sixth manufacturing method of the aluminum conversion foil 1. FIG. 26 is a flowchart of a seventh manufacturing method of the aluminum conversion foil 1. In the sixth manufacturing method of the aluminum conversion foil 1, in the second manufacturing method shown in FIG. 8, a rehydration process ST21 for forming a hydrated film on the aluminum foil 10 is provided following the crack formation process ST11. That is, as shown in FIG. 25, the sixth manufacturing method of the aluminum conversion foil 1 continuously performs the crack formation process ST11 and the rehydration process ST21 between the hydration step ST2 and the anodization step ST3. By doing so, a hydrated film can be provided on the newly exposed aluminum surface exposed through the crack 7 provided by the crack formation process ST11. Therefore, when the conversion film (the first conversion film 5 and the second conversion film 6) grows in the post-anodization treatment ST3A in the subsequent anodization step ST3, it is easy to prevent or suppress the crack 7 from being closed by the conversion film (the first conversion film 5 and the second conversion film 6).

[0138] Also, in the pre-anodization treatment ST3B performed before the crack formation process ST11, when the predetermined anodization voltage reached when performing anodization before the crack formation process ST11 is low, for example, when the predetermined anodization voltage is set to 5V or more and 150V or less, the hydration step ST2 may be omitted. That is, the conversion step ST1 can be configured to include only the anodization step ST3.

[0139] In the manufacturing method of the seventh manufacturing method in this case, as shown in Fig. 26, in the anodizing process ST3, before the anodizing treatment ST3B of applying anodizing to the aluminum foil 10 until reaching the predetermined anodizing voltage described above, the crack formation process ST11 is performed, and then the crack formation process ST11 is performed. And after the crack formation process ST11, the post-anodizing treatment ST3A is performed. Even in this way, on the surface of the first porous layer 3, a plurality of cracks 7 extending in the Y direction (Y direction) with a length of 300 μm or more can be provided at intervals of 30 μm to 150 μm in the X direction (X direction). Also, on the surface of the second porous layer 4, a plurality of cracks 7 extending in the Y direction with a length of 300 μm or more can be provided at intervals of 30 μm to 150 μm in the X direction orthogonal to the Y direction. Therefore, even when the aluminum foil 10 bends when the adjacent powder bodies 11 are bonded through the chemical conversion films (the first chemical conversion film 5 and the second chemical conversion film 6) by applying anodizing to the aluminum foil 10, the stress generated due to the deformation can be released from the cracks 7.

[0140] In addition, in the manufacturing method of the aluminum chemical conversion foil 1 described with reference to Figs. 7 to 11, Fig. 25, and Fig. 26, the case where the heat treatment ST31 is performed after the post-anodizing treatment ST3A is exemplified. The heat treatment ST31 may be performed during the anodizing process ST3, may be performed before the pre-anodizing treatment ST3B, may be performed later, may be performed before the post-anodizing treatment ST3A, or may be performed later. Also, the heat treatment ST31 may be performed during the pre-anodizing treatment ST3B, or may be performed during the post-anodizing treatment ST3A. Also, the heat treatment ST31 can be omitted.

[0141] Also, as the base material of the aluminum chemical conversion foil 1, an aluminum foil 10 including only the base layer 2 and the first porous layer 3 laminated on the first surface 2a of the base layer 2 may be used. In this case, in the crack formation process ST11 performed during the chemical conversion process ST1, the crack 7 is provided in the first porous layer 3 using only the first crack formation roller 21(1).

[0142] In the crack formation process ST11, the first crack formation roller 21(1) and the second crack formation roller 21(2) may be brought into contact with the aluminum foil 10, and either the first crack formation roller 21(1) or the second crack formation roller 21(2) may be moved to generate stress in the aluminum foil 10. That is, in the crack formation In the process ST11, if the aluminum foil 10 and the first crack formation roller 21(1) and the second crack formation roller 21(2) are relatively moved in the X direction, a crack 7 can be imparted to the aluminum foil 10.

[0143] Furthermore, in the crack formation process ST11, the aluminum foil 10 and the first crack formation roller 21(1) or the second crack formation roller 21(2) may be brought into contact at a predetermined nip angle and the aluminum foil 10 may be run. That is, the aluminum foil 10 may be stressed by the first crack formation roller 21(1) that contacts the second surface 2b of the aluminum foil 10 or the second crack formation roller 21(2) that contacts the first surface 2a without running between the first crack formation roller 21(1) or the second crack formation roller 21(2) and the pressing roller 23. In this case, the nip angle of the first crack formation roller 21(1) and the nip angle of the second crack formation roller 21(2) can be normally greater than 0° and 180° or less. Also, in this case, the nip angle of the first crack formation roller 21(1) and the nip angle of the second crack formation roller 21(2) are preferably greater than 0° and 45° or less. If the nip angles of the first crack formation roller 21(1) and the second crack formation roller 21(2) are within the above range, it is easy to form a desired crack 7 in the first porous layer 3 or the second porous layer 4.

[0144] Here, the anodized aluminum foil 1 of the present invention can be used as a diffusion member for diffusing a liquid such as a test solution or blood on its surface. In this case, since the anodized aluminum foil 1 has cracks 7 on its surface, it is easy to diffuse the liquid.

Claims

1. A chemical conversion step of forming a first chemical conversion film on an aluminum foil in which a first porous layer made of a sintered body of aluminum or aluminum alloy powder is laminated on a first surface of two surfaces of a foil-shaped base layer made of aluminum or aluminum alloy, The chemical conversion step includes an anodizing step of subjecting the aluminum foil to anodization, In the chemical conversion step, a crack formation treatment is performed in which stress is generated in the aluminum foil to provide a plurality of cracks extending in a first direction on the surface of the first porous layer, spaced apart in a second direction orthogonal to the first direction, In the anodizing step, an anodization treatment after crack formation is performed in which the aluminum foil is subjected to anodization after the crack formation treatment, The chemical conversion step includes a hydration step of forming a hydrated film on the aluminum foil before the anodizing step, In the anodizing step, the aluminum foil on which the hydrated film is formed is subjected to anodization, The crack formation treatment is performed during the hydration step, In the crack formation treatment, a method for manufacturing an aluminum chemical conversion foil, characterized in that a plurality of cracks extending in the first direction with a length of 300 μm or more are provided at intervals of 30 μm to 150 μm in the second direction.

2. The method for manufacturing an aluminum chemical conversion foil according to claim 1, wherein in the crack formation treatment, a plurality of cracks extending in the first direction with a length of 300 μm or more are provided at intervals of 95 μm to 150 μm in the second direction.

3. The method for manufacturing an aluminum chemical conversion foil according to claim 1 or 2, wherein in the crack formation treatment, each crack reaches the boundary between the base layer and the first porous layer.

4. In the anodizing step, an anodization treatment before crack formation is performed in which the aluminum foil is subjected to anodization until a predetermined anodization voltage is reached before the crack formation treatment, The method for manufacturing an aluminum chemical conversion foil according to any one of claims 1 to 3, wherein the predetermined anodization voltage in the anodization treatment before crack formation is 400 V or less. Manufacturing method.

5. In the crack formation process, the first crack formation roller extending in the first direction is brought into contact with the second surface on the opposite side of the first surface of the both surfaces of the aluminum foil, and the aluminum foil and the first crack formation roller are relatively moved in the second direction. The method for manufacturing an aluminum formed foil according to any one of claims 1 to 4, characterized in that.

6. In the chemical conversion process, the aluminum foil is caused to travel in the second direction by a plurality of rollers arranged along the second direction. The method for manufacturing an aluminum formed foil according to claim 5, characterized in that, among the plurality of rollers, a roller having a smaller diameter than the other rollers is arranged as the first crack formation roller.

7. On the second surface of the aluminum foil, which is opposite to the first surface of the base layer, a second porous layer made of a sintered body of powder of aluminum or an aluminum alloy is laminated. In the chemical conversion process, a second chemical conversion film is formed on the second porous layer. In the crack formation process, the second crack formation roller extending in the first direction is brought into contact with the first surface at a position different from the first crack formation roller in the second direction, and the aluminum foil and the second crack formation roller are relatively moved in the second direction. The method for manufacturing an aluminum formed foil according to claim 5 or 6, characterized in that.

8. The method for manufacturing an aluminum formed foil according to claim 1, further comprising a rehydration process of forming a hydration film on the aluminum foil following the crack formation process.

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