JP2008166602A - Aluminum material for electrolytic capacitor electrode, its manufacturing method, electrode material for aluminum electrolytic capacitor and aluminum electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum material for an electrolytic capacitor electrode excellent in etching characteristics, which can surely increase the expanded surface rate and increase the electrostatic capacitance further by forming uniform etch pits in a high density and starting deep etching from these etch pits to make coupling hard within a tunnel. <P>SOLUTION: An anodic oxide film 3 is formed on the surface of the aluminum material 1, and many fine recessed parts 6, which have the average size of 0.01 to 10 μm by a circle equivalent diameter and for which the anodic oxide film thinner than the periphery remains at the bottom part or an aluminum base is exposed, are formed in a dispersed state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aluminum material for an electrolytic capacitor electrode and a method for producing the same, an electrode material for an aluminum electrolytic capacitor, and an aluminum electrolytic capacitor, which are preferably used as an electrode material having an excellent electrostatic capacity.

  In this specification, the term “aluminum” is used to include the alloy thereof, and the aluminum material includes a foil, a plate, and a molded body using these.

  Usually, the aluminum material used for the electrode material for electrolytic capacitors is subjected to an etching process in order to increase the surface expansion ratio and improve the capacitance. And, as the number of etch pits formed by the etching process increases, the surface expansion ratio increases as the number of etch pits increases, so that various processes are performed on the aluminum material as a pre-process of the etching process in order to improve the etching characteristics. Yes.

  For example, control of (100) crystal orientation, addition of trace elements such as Cu and Pb to an aluminum material, degreasing cleaning before final annealing, formation treatment of a crystalline oxide film by final annealing, etc. (non-patent document) 1, patent documents 1-3).

  In addition, attempts have been made in the past to attach foreign substances or mechanically form defects to improve electrostatic capacity (Patent Documents 4 to 7).

  Patent Document 8 describes applying ink containing metal powder.

  Further, as an example aiming at uniform etch pits using a resin ball, Patent Document 9 discloses a method of etching after a resin ball is attached by static electricity and fixed by thermocompression bonding or the like.

  Further, Patent Document 10 discloses an example in which unevenness is imparted by anodizing using resin balls and the resin balls are removed.

Furthermore, as a method for imparting a metal element different from aluminum to the aluminum surface and controlling the distribution of etch pits, Patent Document 11 discloses that aluminum is mixed by rolling and mixed with organic molecules bonded with Cu in a lubricating oil for rolling. A method of attaching to the surface is described, and Patent Document 12 describes a method of regularly attaching a metal compound by dot printing.
Kenshiro Yamaguchi: Light Metal, 35 (1985), P365 JP 2002-239773 A Japanese Patent Publication No. 58-34925 Japanese Patent Laid-Open No. 3-122260 Japanese Patent Publication No. 5-28486 Japanese Unexamined Patent Publication No. 63-157882 Japanese Patent No. 2545429 Japanese Patent Publication No.7-19732 Japanese Patent Publication No. 7-109036 Japanese Patent Laid-Open No. 8-138977 Japanese Unexamined Patent Publication No. 63-220512 JP-A-8-269601 JP 2004-266024 A

  However, simply increasing the number and length of each etch pit is approaching the limit of capacity improvement. In order to improve the surface expansion ratio of the aluminum material, it is necessary to reduce local etching, non-etching, and surface dissolution, and to generate etch pits uniformly and densely on the etched surface. 1. The methods described in Patent Documents 1 to 3 are not sufficient in that etch pits are uniformly generated at high density, and cannot meet the increasing demand for capacitance.

  Since the current aluminum material cannot control the distribution of pitting pits during the etching process, the tunnels of the etch pits are combined and the surface expansion ratio does not reach the ideal state. For this reason, the current capacitance remains at 50 to 65% of the ideal capacitance.

  In addition, in the techniques described in Patent Documents 4 to 7 in which foreign substances are attached or mechanical defects are formed, uniform nucleation cannot be realized, and high capacitance is not realized.

  In addition, as in Patent Document 8, in the method of applying ink containing metal powder, a strong oxide film is formed on the surface of the metal element, and diffusion to aluminum does not proceed, or between aluminum and metal powder. Since the potential difference required for triggering the generation of etch pits cannot be secured, a sufficient effect cannot be achieved.

  Further, in the method of Patent Document 9 aiming at uniform etch pits using resin balls, masking for controlling the distribution of etch pits is not sufficient.

  In addition, in the method of Patent Document 10 in which unevenness is imparted by anodizing treatment using a resin sphere and the resin sphere is removed, a natural oxide film at a portion where the resin sphere and aluminum are in contact with each other or a contact portion is wrapped around. There was a problem that the anodized film became an obstacle to etching, and on the contrary, an uneven distribution of etch pits was generated.

  Further, in the methods of Patent Document 11 and Patent Document 12 in which a metal element different from aluminum is applied to the aluminum surface and the distribution of etch pits is controlled, the former does not have a regular distribution. Even if it becomes possible, the distribution cannot be changed, and since the latter part is not actively masked except for the metal element adhesion part, both are insufficient for controlling the etch pit nuclei. there were.

  The present invention has been made in view of such a technical background, and etch pits are formed with high density and uniformity, and the etching pits are deeply formed from the starting point and are reliably etched by being less likely to cause bonding in the tunnel. To provide an aluminum material for an electrolytic capacitor electrode excellent in etching characteristics, a method for producing the same, an electrode material for an aluminum electrolytic capacitor, and an aluminum electrolytic capacitor capable of further increasing the area expansion ratio and further increasing the capacitance. With the goal.

In view of the above problems, as a result of intensive investigations, the present inventors have conducted regular etching on the aluminum material to be electrolytically etched by anodizing it in a state where fine particles made of resin spheres are arranged on the surface of the aluminum material. An anodic oxide film is formed, and then fine particles are "removed" to form fine microscopic recesses (regions where the anodic oxide film thickness is locally smaller than the surrounding thickness) in the anodic oxide film, and start of etch pits It became possible to form the nucleus that becomes a point effectively. In addition, what has the exposed part of the aluminum base body formed in the bottom part may be contained in the fine recessed part. The term “exposed portion of the aluminum substrate” is used to include a state in which a natural oxide film is covered.
In addition, a porous oxide film can be preferentially formed on the bottom of the fine recess.
Furthermore, it is possible to chemically form a hole having a predetermined length at the bottom of the fine recess where the porous oxide film is not formed or at the bottom of the fine recess where the porous oxide film is formed. did.
According to these inventions, the arrangement of etching pits becomes more regular, and a high capacitance can be obtained.
That is, the said subject is solved by the following means.
(1) An anodic oxide film is formed on the surface of the aluminum material, and an average equivalent circle diameter of 0.01 to 10 μm and an anodic oxide film thinner than the surroundings remains on the bottom, or aluminum An aluminum material for electrolytic capacitor electrodes, wherein a large number of fine recesses exposed on a substrate are formed in a dispersed state.
(2) The aluminum material for electrolytic capacitor electrodes as recited in the aforementioned Item 1, wherein the fine recesses are dispersed at a density of 10 ⁴ to 10 ⁸ pieces / mm ² and the total area ratio is 1 to 80%.
(3) The aluminum material for an electrolytic capacitor electrode according to any one of the preceding items 1 or 2, wherein a hole having a depth of 0.01 μm or more is formed at the bottom of the fine recess inward in the thickness direction of the aluminum material. .
(4) After the anodization treatment is performed with the fine particles to be the masking part arranged and attached to the surface of the aluminum material, the fine particles can be reduced by reducing the thickness of the anodized film following or simultaneously with the removal of the fine particles. The diameter of the circle is 0.01 to 10 μm in the equivalent circle diameter, and an anodic oxide film thinner than the surroundings remains on the bottom, or a large number of fine recesses in which the aluminum substrate is exposed are formed in a dispersed state. The manufacturing method of the aluminum material for electrolytic capacitor electrodes characterized by the above-mentioned.
(5) The method for producing an aluminum material for electrolytic capacitor electrodes as recited in the aforementioned Item 4, wherein at least one layer of the fine particles serving as the masking portion is arranged and adhered.
(6) The method for producing an aluminum material for electrolytic capacitor electrodes as recited in the aforementioned Item 4 or 5, wherein the fine particles have a sphere equivalent diameter and an average size of 0.03 to 20 μm.
(7) The electrolytic capacitor electrode aluminum as described in any one of 4 to 6 above, wherein the fine particles are resin spheres having an equivalent sphere diameter and an average size of 0.03 to 20 μm formed as a colloidal crystal from a suspension. A method of manufacturing the material.
(8) The method for producing an aluminum material for electrolytic capacitor electrodes as recited in the aforementioned Item 7, wherein the resin sphere is heated to a glass transition point or higher to adhere to the surface of the aluminum material.
(9) The method for producing an aluminum material for electrolytic capacitor electrodes as described in any one of 4 to 8 above, wherein the anodizing treatment is performed using an electrolytic solution having a pH of 4 to 8.
(10) As an electrolytic solution, hydrochloric acid, sulfuric acid, nitric acid, boric acid, adipic acid, tartaric acid, phosphoric acid, citric acid, malonic acid, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and compounds thereof 10. The method for producing an aluminum material for electrolytic capacitor electrodes as described in 9 above, wherein one containing at least one of them is used.
(11) The aluminum material in which the fine recess is formed is subjected to chemical etching to form a hole having a depth of 0.01 μm or more inward in the thickness direction of the aluminum material at the bottom of the fine recess. The manufacturing method of the aluminum material for electrolytic capacitor electrodes in any one.
(12) An anodic oxide film is formed on the surface of the aluminum material, and an average equivalent circle diameter of 0.01 to 10 μm and an anodic oxide film thinner than the surroundings remains at the bottom, or aluminum Porous oxidation in which a large number of fine recesses exposed on the substrate are formed in a dispersed state, and one or more pores having an average equivalent circle diameter of 0.01 to 0.50 μm are dispersed at the bottom of the fine recesses An aluminum material for electrolytic capacitor electrodes, comprising a film.
(13) The aluminum material for electrolytic capacitor electrodes as recited in the aforementioned Item 12, wherein the fine recesses are dispersed at a density of 10 ⁴ to 10 ⁸ pieces / mm ² and the total area ratio is 1 to 80%.
(14) The aluminum material for electrolytic capacitor electrodes as recited in the aforementioned Item 12 or 13, wherein a hole having a depth of 0.01 μm or more is formed at the bottom of the fine recess inward in the thickness direction of the aluminum material.
(15) After the first anodic oxidation treatment with the fine particles serving as masking portions arranged and adhered to the surface of the aluminum material, the thickness of the anodic oxide film is reduced following or simultaneously with the removal of the fine particles. In the presence of fine particles, the average equivalent circle diameter is 0.01 to 10 μm, and the bottom is left with an anodized film that is thinner than the surrounding area, or a large number of fine recesses with an aluminum substrate exposed are dispersed. And a second anodic oxidation treatment is performed to form a porous oxide film containing pores having an average equivalent circle diameter of 0.01 to 0.50 μm at the bottom of the fine recesses. Manufacturing method of aluminum material for electrodes.
(16) The second anodic oxidation treatment is performed using an electrolytic solution containing at least one of oxalic acid, phosphoric acid, sulfuric acid, and a compound thereof, or an electrolytic solution capable of forming a porous oxide film according to the electrolytic solution, 16. The method for producing an aluminum material for electrolytic capacitor electrodes according to 15 above, which is carried out at a voltage equal to or lower than that of the first anodizing treatment.
(17) The above-described item 15 or 15 wherein the aluminum material on which the porous oxide film is formed is subjected to chemical etching to form a hole having a depth of 0.01 μm or more inward in the thickness direction of the aluminum material at the bottom of the fine recess. 16. The method for producing an aluminum material for electrolytic capacitor electrodes according to 16.
(18) The aluminum material for electrolytic capacitor electrodes described in the preceding items 1 to 3 and 12 to 14 is used, the purity of the aluminum material is 99.9% by mass or more, and the (100) crystal orientation density is 97% or more. An electrode material for an aluminum electrolytic capacitor.
(19) The electrode material for an aluminum electrolytic capacitor as described in 18 above, which is used as an anode material.
(20) An aluminum electrolytic capacitor in which the electrode material according to item 19 is used.

  According to the invention described in the preceding item (1), an anodic oxide film having an average equivalent circle diameter of 0.01 to 10 μm and thinner than the surroundings remains at the bottom during etching for improving the surface expansion ratio. Or a large number of exposed fine recesses in the aluminum substrate serve as the nucleus of the etch pit, so that the etch pit can be formed with high density and uniformity, and the etch pit is deep and connected in the tunnel. Therefore, it is possible to obtain an aluminum material for an electrolytic capacitor electrode that can reliably increase the area expansion ratio and can increase the capacitance.

According to the invention described in item (2) above, the fine recesses are dispersed at a density of 10 ⁴ to 10 ⁸ pieces / mm ² and the total area ratio is 1 to 80%. Can be formed stably.

  According to the invention described in the preceding item (3), since the hole having a depth of 0.01 μm or more toward the inside of the thickness direction of the aluminum material is formed in the bottom of the fine recess, the high density can be more reliably increased. In addition, etch pits can be formed uniformly.

  According to the invention described in item (4), the aluminum material for electrolytic capacitor electrodes described in item (1) can be manufactured.

  According to the invention described in item (5), the fine recesses can be reliably formed because at least one layer of the fine particles to be the masking portion is arranged and attached.

  According to the invention described in item (6) above, since the fine particles have an average sphere equivalent diameter of 0.03 to 20 μm, fine concave portions having an average equivalent circle diameter of 0.01 to 10 μm are formed in a dispersed state. can do.

  According to the invention described in item (7), the fine recess can be formed more simply and reliably.

  According to the invention described in the above item (8), the resin sphere is heated to a temperature higher than the glass transition point and adhered to the surface of the natural oxide film of the aluminum material, whereby fine concave portions can be formed more reliably and uniformly. .

  According to the invention described in the preceding item (9), since the anodizing treatment is performed using the electrolytic solution having a pH of 4 to 8, it is possible to produce a barrier type film without generating pores on the surface of the aluminum material. .

  According to the invention described in item (10) above, the electrolyte solution having a pH of 4 to 8 includes hydrochloric acid, sulfuric acid, nitric acid, boric acid, adipic acid, tartaric acid, phosphoric acid, citric acid, malonic acid, sodium hydroxide, potassium hydroxide. Since one containing at least one of calcium hydroxide, magnesium hydroxide and their compounds is used, an anodic oxide film can be more easily and stably formed around the fine particles.

According to the invention described in the above item (11), since the hole having a depth of 0.01 μm or more inward in the thickness direction of the aluminum material is formed at the bottom of the fine recess, the etch pit is more reliably and densely and uniformly etched It is possible to manufacture an aluminum material that can form the film.
According to the invention described in item (12) above, the porous oxide film in which one or more pores having an equivalent circle diameter and an average size of 0.01 to 0.50 μm formed at the bottom of the fine recesses are dispersed is an etch pit. Therefore, the etch pits can be formed with high density and uniformity, and the etch pits as a starting point are deep and bonding is difficult to occur in the tunnel. Therefore, the area expansion rate can be reliably increased. As a result, the capacitance can be increased.

According to the invention described in item (13) above, the fine recesses are dispersed at a density of 10 ⁴ to 10 ⁸ pieces / mm ² and the total area ratio is 1 to 80%. Can be formed stably.

  According to the invention described in the preceding item (14), since the hole having a depth of 0.01 μm or more toward the inside in the thickness direction of the aluminum material is formed in the bottom of the fine recess, the high density can be more reliably increased. In addition, etch pits can be formed uniformly.

According to the invention described in item (15), the aluminum material for electrolytic capacitor electrodes described in item (12) can be manufactured.
According to the invention described in the above item (16), the second anodic oxidation treatment is carried out by using an electrolytic solution containing at least one of oxalic acid, phosphoric acid, sulfuric acid, and compounds thereof, or a porous oxide film equivalent thereto A porous oxide film can be reliably formed by using an electrolytic solution that can form a film at a voltage equal to or lower than that of the first anodic oxidation treatment.
According to the invention described in the above item (17), since a hole having a depth of 0.01 μm or more inward in the thickness direction of the aluminum material is formed at the bottom of the fine concave portion, it is possible to reliably form a high-density and uniform etch pit. An aluminum material that can be formed can be manufactured.
According to the invention described in item (18), the purity of the aluminum material for electrolytic capacitor electrodes described in items 1 to 3 and 12 to 14 is 99.9% by mass or more, and the (100) crystal orientation density is 97% or more. Therefore, when forming a chemical conversion film after etching, a chemical conversion film with few defects can be formed, and a large capacitance can be realized.
According to the invention described in the preceding item (19), it can be formed as an anode material for an aluminum electrolytic capacitor having a large capacitance.
According to the invention described in item (20), an aluminum electrolytic capacitor having a large capacitance can be obtained.

Next, an embodiment of the present invention will be described.
[About aluminum materials]
The aluminum material used in the present invention only needs to have a natural oxide film on the surface and can form tunnel pits. For example, the thickness may be in a range that can sufficiently secure the strength of the aluminum material after etching, and is set to, for example, about 0.006 to 0.25 mm, and more preferably about 0.010 to 0.18 mm. .

  Examples of the trace element in the aluminum material include Si, Fe, Cu, Mn, Mg, Zn, Ti, V, Ga, and Zr. However, in the present invention, the type and amount of the element are not particularly limited. However, in order to prevent chemical conversion film defects, it is better to have as few trace elements as possible, and it is desirable to use an aluminum material having a purity of 99.9% by mass or more. In addition, the addition of Cu, Mg, Zn, Pb, Sn, Sb and the like as elements for improving the etching characteristics has been conventionally proposed for aluminum materials for electrolytic capacitors. Also in the present invention, these elements may be added within a range that does not cause the chemical conversion film defect.

  In addition, regarding the heat treatment of the aluminum material in the case of diffusing the metal element, it can also be combined with the high-temperature annealing at 450 to 600 ° C. necessary for forming a high cubic texture, which has been conventionally proposed. Alternatively, diffusion treatment at 300 ° C. or higher necessary for thermal diffusion may be performed separately within a range that does not cause abnormal dissolution during etching due to precipitation of Si. Specific conditions for the heat treatment are, for example, 500 ° C. × 1-8 h when the metal element to be diffused is Cu, 480 ° C. × 0.5-2 h when Pb is used, and 550 ° C. × when Fe is used. Conditions such as 10 to 30 h can be given. Of course, other than these conditions, the objective can be achieved.

  In order to obtain a larger capacitance, the (100) crystal orientation density of the aluminum material is desirably 97% or more.

  Further, the shape of the aluminum material may be a coiled shape or a cut sheet, and is not limited at all.

[Production method]
First, an aluminum material is prepared. A natural oxide film may be formed on the surface of the aluminum material or on the aluminum base.
As shown in FIG. 1A, the aluminum material 1 is anodized in a state where resin spheres or fine particles 2 conforming to the resin spheres are arranged on the surface of the aluminum material 1, and as shown in FIG. Then, an anodized film 3 is formed.

The resin spheres or the fine particles 2 based on the resin spheres are not particularly limited, and can be arranged on the surface of the aluminum material 1 and change in dissolution, elution, swelling, etc. in anodizing treatment and cleaning treatment. Anything that doesn't wake up. As an example, PS (polystyrene), PP (polypropylene), etc. can be mentioned.
The average diameter of the resin spheres or fine particles 2 conforming to the resin spheres is preferably 0.03 μm or more and 20 μm or less in terms of equivalent sphere diameter. If it is less than 0.03 μm, the interval between etch pits to be formed after that becomes too narrow and coalescence of the etch pits increases, and the capacitance may decrease instead. On the other hand, if it exceeds 20 μm, the density of etch pits becomes too low, and the capacitance may decrease. The average value of the equivalent circle diameter of the fine particles 2 conforming to a particularly preferable resin sphere or resin sphere is 0.5 to 3 μm.

  The resin spheres or the fine particles 2 conforming to the resin spheres may be arranged by being naturally placed on the surface of the aluminum material 1 without being accompanied by an artificial bonding force such as adhesion, fusion, or welding, They may be placed and arranged by a method involving an artificial bonding force such as adhesion, fusion, or welding.

Further, as a method for arranging the resin spheres or the fine particles 2 based on the resin spheres, a dry adhesion method such as electrostatic coating, or an adhesion method for generating colloidal crystals from a suspension may be adopted. An adhesion method that forms as a colloidal crystal from a suspension is desirable in that it provides the best regularity of etch pits.
Furthermore, when the above-described arranged resin spheres or fine particles 2 conforming to the resin spheres are artificially welded to the aluminum surface as described above, the fine particles 2 are subjected to glass transition as shown in FIGS. It is also effective to heat the material more than the point and fix it to the surface of the natural oxide film of the aluminum material 1 and perform anodizing treatment as shown in FIG.

  In addition, as a pretreatment for anodizing treatment, for the purpose of reducing unevenness due to rolling streaks formed by rolling and improving the adhesion of the resin spheres or fine particles 2 conforming to the resin spheres to the surface of the aluminum material 1, You may perform the smoothing process by chemical polishing, mechanical polishing, etc.

The type and conditions of the anodizing treatment are not particularly limited, and a known treatment method or treatment conditions may be adopted. Preferably, the surface of the aluminum material is formed using an electrolyte solution having a pH of 4 to 8. It is desirable in that a barrier-type film can be formed without generating pores. Such electrolytes with pH 4-8 include hydrochloric acid, sulfuric acid, nitric acid, boric acid, adipic acid, tartaric acid, phosphoric acid, citric acid, malonic acid, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and Those containing one or more of these compounds can be mentioned, and this makes it possible to more easily and stably form an anodized film around the fine particles 2.
The anodized film 3 formed by the anodizing treatment serves to prevent the aluminum base from being exposed except for the portion where the resin spheres or fine particles 2 conforming to the resin spheres were present.
For this reason, the thickness of the anodized film 3 is such that the resin spheres or fine particles 2 conforming to the resin spheres can sufficiently mask the surface of the aluminum material 1 and remain on the surface of the aluminum material 1 when the fine particles are removed. Therefore, it is preferable that the thickness is 0.02 μm or more. Further, the fine particles 2 for masking the surface of the aluminum material 1 may be arranged in one or more layers on the surface of the aluminum material. However, when the thickness of the layer of the laminated particles is small, there may be a region where masking is not satisfied locally. For this reason, the thickness of the layer of the laminated particles is desirably 3 or more.
After the anodizing treatment, as shown in FIG. 1C, FIG. 1D, or FIG. 2D, the resin spheres or fine particles 2 conforming to the resin spheres and the anodized film 3 are removed sequentially or simultaneously.
The removal of the resin sphere or the fine particle 2 conforming to the resin sphere may be generally performed by dissolving the resin sphere or the fine particle 2 conforming to the resin sphere. What is necessary is just to select a melt | dissolution liquid suitably according to the kind of microparticles | fine-particles 2 according to a resin ball or a resin ball. For example, when the resin sphere is made of PS (polystyrene), toluene or the like may be used. Further, depending on the material of the resin sphere, other acids and alkalis, particularly “weak acid” and “weak alkali” may be selected. By removing the resin spheres or the fine particles 2 conforming to the resin spheres, the fine particle removal region 4 is formed in the anodized film 3 as shown in FIG.

Next, the anodized film 3 is removed sequentially in the thickness direction or simultaneously with the resin spheres or the fine particles 2 conforming to the resin spheres. As the removal method, a chemical or electrochemical method using an acid or an alkaline solution is used. Examples of the method of dissolving by (1) or removing by a dry method such as dry etching can be given.
By removing the anodic oxide film 3 uniformly in the thickness direction over the entire surface of the aluminum material 1, the anodic oxide film 3 is rapidly reduced inside the thin particle removal region 4 having a thin thickness. As a result, the thin anodic oxide film remains or the aluminum base is exposed, and the anodic oxide film 3 remains in the surrounding area. That is, as shown in FIG. 1 (d) and FIG. 2 (d), fine concave portions 6 are formed in the region where the resin spheres or fine particles 2 conforming to the resin spheres were present. In addition, the thin anodic oxide film 3 may remain on the bottom of all the fine recesses 6, the aluminum base 5 may be exposed on the bottom of all the fine recesses 6, or some of the fine recesses 6 may be exposed. The aluminum substrate 5 may be exposed only at the bottom of the substrate. The exposed aluminum substrate may be coated with a natural oxide film.

Further, the resin sphere or the removal of the fine particles 2 according to the resin sphere and the removal of the anodized film 3 or the exposure of the aluminum substrate may be performed in the same process by dry etching.
The fine concave portions 6 have an average equivalent circle diameter of 0.01 to 10 μm at the bottom, and the fine concave portions 6 are dispersed at a density of 10 ⁴ to 10 ⁸ pieces / mm ^2. The total area ratio to the surface of 1 is preferably 1 to 80%. When the fine concave portion 6 has an equivalent circle diameter of less than 0.01 μm, the surrounding anodic oxide film is reduced extremely thinly when the fine particle masking is removed, making it difficult to uniformly distribute the etch pits. For this reason, the capacitance ratio cannot be sufficiently increased. On the other hand, if it exceeds 10 μm, the interval between the regions of the adjacent fine particles contacting the aluminum material surface becomes excessively large, and the dispersion interval of the etch pits becomes excessively large, so that the capacitance ratio cannot be sufficiently increased. A particularly preferable size of the fine recess 6 is 0.05 to 5.0 μm in equivalent circle diameter.
If the density of the fine recesses 6 is less than 10 ⁴ pieces / mm ² , the etch pit interval may be excessively large and the capacitance ratio may not be sufficiently increased. If the density exceeds 10 ⁸ pieces / mm ² , masking may be performed. When it is removed, the surrounding anodic oxide film also decreases extremely thinly, making it difficult to uniformly disperse etch pits, and the capacitance ratio may not be sufficiently increased.
If the total area ratio of the fine recesses 6 is less than 1%, the fine recesses 6 are dispersed in a rough state, and the number of etch pits may be reduced. On the other hand, if the area ratio exceeds 80%, the number of etch pits increases excessively, and tunnels due to the etch pits are combined, so that there is a possibility that a sufficient area expansion rate cannot be obtained. A particularly preferable total area ratio of the fine recesses 6 is 15 to 40%.

  After forming the fine recesses 6 as described above, preferably, as shown in FIG. 2 (e), the bottom of the fine recesses 6 is an ellipse or polygonal 1 having an average equivalent circle diameter of 0.01 to 0.50 μm. If a porous oxide film 7 in which more than one pore is dispersed is formed, it becomes a starting point for generation of etch pits more reliably. The porous oxide film 7 may be thicker than the anodic oxide film around the fine recess 6. However, the anodized film inside each pore forming the porous layer is thinner than the surrounding anodized film.

  Such a porous oxide film 7 can be formed by performing the second anodic oxidation treatment following the first anodic oxidation treatment.

  This second anodic oxidation treatment is performed using an electrolytic solution containing oxalic acid, phosphoric acid, sulfuric acid and one or more of these compounds, or an electrolytic solution capable of forming a porous oxide film according to the electrolytic solution. It may be carried out at a voltage equal to or lower than that of the anodizing treatment.

Here, the reason why the pores of the porous oxide film 7 preferably have an average equivalent circle diameter of 0.01 to 0.50 μm is that the pores are excessively small when the average pore diameter is less than 0.01 μm. It is hard to become the starting point of the etch pit. If the equivalent circle diameter exceeds 0.50 μm on average, the anodic oxide film thickness inside the pores may increase excessively, making it difficult to form preferential etch pits. A particularly preferable pore size is an equivalent circle diameter of 0.05 to 0.20 μm on average.
In the second anodic oxidation treatment, 0.05 M oxalic acid electrolyte is preferably used, and the current density is 0.1 mA / cm ² .
More preferably, the aluminum material is applied to the bottom of the fine recess 6 without or after the second anodic oxidation treatment, as shown in FIG. 1 (e) (e ′) or FIG. 2 (f). It is preferable to form a depressed hole 8 having a depth of 0.01 μm or more inward in the thickness direction. FIG. 1 (e) shows the case where the hole 8 is formed with the aluminum substrate 5 exposed on the bottom surface of the fine recess 6, and FIG. 1 (e ′) shows the anode on the bottom surface of the fine recess 6. The case where the hole 8 is formed in the state where the oxide film remains is shown. Such a hole 8 can be formed by chemical etching after the first or second anodizing treatment. The preferred conditions for this chemical etching are etching using 0.5 wt.% Phosphoric acid or 2.0 M sulfuric acid, and the preferred treatment condition is 0.5 wt.% Phosphoric acid solution within 1 hour. Soaking.

  Plan views of the aluminum material in a state in which the depressed hole 7 is formed are shown in FIGS. 1 (f) and 2 (g).

  The aluminum material for electrolytic capacitor electrodes according to the present invention is used as an electrode material for electrolytic capacitors after being etched for improving the surface expansion ratio. The etching treatment conditions are not particularly limited, but it is preferable that at least a part of the etching is direct current electrolytic etching.

  The aluminum material produced according to the present invention can be used as a cathode material or an anode material. However, the aluminum material can be used as an anode material in that it has a large effective area even when a voltage-resistant film is formed by a chemical conversion treatment after etching. Is suitable. Furthermore, among anode materials, it is suitable for medium and high pressure electrolytic capacitor electrode materials.

The chemical conversion treatment after the etching can be performed by various methods. The conditions for the chemical conversion treatment are not particularly limited. For example, using an electrolytic solution containing at least one of oxalic acid, adipic acid, boric acid, phosphoric acid, sodium silicate, etc., the electrolytic solution concentration is 0.05 mass% to 20 mass%, the temperature is 0 ° C to 90 ° C, The current density is 0.1 mA / cm ^{2 to} 1 A / cm ² , and the voltage is set in accordance with the conversion voltage of the aluminum material to be processed. More preferably, the electrolyte concentration is 0.1 wt% to 15 wt%, temperature of 20 ° C. to 70 ° C., a current density of ^{1mA / cm 2 ~100mA / cm 2} , the chemical conversion time is in the range of 30 minutes It is better to select the conditions.

  After the chemical conversion treatment, for example, a phosphoric acid immersion treatment for improving water resistance, a heat treatment for strengthening the film, or an immersion treatment in boiling water can be performed as necessary.

  The electrolytic capacitor using the electrode material manufactured as described above can realize a large capacitance. The type and manufacturing method of the electrolytic capacitor are not particularly limited. For example, a capacitor element in which an anode material and a cathode material each having a lead tab electrically connected thereto are wound or laminated via a separator is used for driving. The manufacturing method which impregnates electrolyte solution and uses it as an aluminum electrolytic capacitor can be mentioned.

(Example 1)
A plurality of soft aluminum materials having a thickness of 99.99% and 99.9% purity and having a thickness of 100 μm were prepared by an ordinary method including intermediate annealing, subsequent light cold rolling, and high temperature annealing.
Next, as shown in Table 1, on the surface of each aluminum material, the average diameter (sphere equivalent diameter) was set variously, electrostatically applied fine particles of Si oxide (fine particle adhesion array method A), or The number of formed particles in the thickness direction of the fine particles was changed to 1 to 3 layers by an adhesion method (fine particle adhesion arrangement method B) in which PS fine particles or PP fine particles were produced as a colloidal crystal from the suspension. The fine particles were fixed by changing the conditions to heating below the glass transition temperature (X) or heating above the glass transition temperature (Y). In addition, some were not heated.
Next, an anodizing treatment was performed by a constant current electrolysis method using a 0.5 mol / l boric acid-0.05 mol / l borax aqueous solution at a liquid temperature of 20 ° C. and a current density of 1.0 A / m ^2. A .05 μm anodic oxide film was coated.

  Next, the Si-oxide particles were removed by dissolving caustic soda, and the resin balls made of PS using toluene, and then immersed in a 1% by weight Na0H aqueous solution at 50 ° C. for a predetermined time to dissolve the coating in order to remove fine particles. A fine recess was formed in the region.

Table 1 shows the bottom surface state of the fine recesses, the average value of equivalent circle diameters, the dispersion density of the fine recesses, and the area ratio. In the surface state of the bottom of the fine recess, the anodic oxide film marked with ○ indicates that the anodized film remains, and the aluminum substrate marked with ◯ is aluminum. The case where the substrate is exposed is shown.
Furthermore, chemical etching was performed to form a depressed hole at the bottom of the fine recess. The chemical etching was performed by immersing in a 0.5 wt.% Phosphoric acid solution for 30 minutes.
Moreover, the depth of the formed hole was as shown in Table 1.
Next, electrolytic etching was performed on each obtained aluminum material. Etching is performed using a mixed solution of 1.0 mol / l HC1 and 3.5 mol / l H ₂ SO ₄ , and after performing an immersion treatment at a liquid temperature of 75 ° C. for 30 sec, a current density of 0.2 A / cm ^2. For 120 sec. Furthermore, chemical etching was performed at 90 ° C. for 900 seconds with the liquid having the same composition, washed with water and dried to complete the etching.

Next, after performing a chemical conversion treatment in a boric acid bath 500V, the capacitance was measured. The results are shown in Table 1.
The electrostatic capacity was relatively evaluated with an aluminum material (comparative example) having a purity of 99.99% not adhering fine particles as 100.

  The fine particle diameter, the equivalent circle diameter of the fine recesses, and the dispersion density were measured by observing the foil surface before etching with a scanning electron microscope and performing image analysis.

From Table 1, it can be seen that the product of the present invention has an increased capacitance.
(Example 2)
A plurality of soft aluminum materials having a thickness of 99.99% and 99.9% purity and having a thickness of 100 μm were prepared by an ordinary method including intermediate annealing, subsequent light cold rolling, and high temperature annealing.
Next, as shown in Table 1, fine particles were formed on the surface of each aluminum material by an adhesion method (fine particle adhesion arrangement method B) in which PS fine particles having an average diameter (sphere equivalent diameter) of 1 μm were produced from the suspension as colloidal crystals. The number of formed particles in the thickness direction was made to be 1 to 5 layers. The fine particles were fixed by heating (X) below the glass transition temperature or heating (Y) above the glass transition temperature. In addition, some were not heated.
Next, each aluminum material was anodized with the electrolytic solution conditions shown in Table 2 and an electrolytic solution consisting of pH to form an anodized film.

  Next, the resin balls made of PS are dissolved and removed using toluene, and subsequently immersed in a 5% by mass phosphoric acid aqueous solution at 50 ° C. for a predetermined time, so that the film is sequentially dissolved to form fine recesses in the fine particle removal region. did.

  Table 2 shows the bottom surface state of the fine recesses, the average value of the equivalent circle diameter, the dispersion density of the fine recesses, and the area ratio. In the surface state of the bottom of the fine recess, the anodic oxide film marked with ○ indicates that the anodized film remains, and the aluminum substrate marked with ◯ is aluminum. The case where the substrate is exposed is shown.

Further, chemical etching was performed under the conditions shown in Table 2 to form a depressed hole at the bottom of the fine recess. The depth of the formed hole was as shown in Table 1.
Next, electrolytic etching was performed on each obtained aluminum material. Etching is performed using a mixed solution of 1.0 mol / l HC1 and 3.5 mol / l H ₂ SO ₄ , and after performing an immersion treatment at a liquid temperature of 75 ° C. for 30 sec, a current density of 0.2 A / cm ^2. For 120 sec. Furthermore, chemical etching was performed at 90 ° C. for 900 seconds with the liquid having the same composition, washed with water and dried to complete the etching.

Next, after performing a chemical conversion treatment in a boric acid bath 500V, the capacitance was measured. The results are shown in Table 2.
The electrostatic capacity was relatively evaluated with an aluminum material (comparative example) having a purity of 99.99% not adhering fine particles as 100.

  The fine particle diameter, the equivalent circle diameter of the fine recesses, and the dispersion density were measured by observing the foil surface before etching with a scanning electron microscope and performing image analysis.

From Table 2, it can be seen that the product of the present invention has increased capacitance.
(Example 3)
A plurality of soft aluminum materials having a thickness of 99.99% and having a purity of 99.99% and prepared by a conventional method including intermediate annealing, subsequent light cold rolling, and high temperature annealing were prepared.
Next, as shown in Table 3, an adhesion method (particulate adhesion array method B) for producing PS fine particles having various average diameters (equivalent sphere diameters) from the suspension as colloidal crystals on the surface of each aluminum material. Thus, the number of formed particles in the thickness direction of the fine particles was adhered so as to be one layer. The fine particles were fixed by changing the conditions to heating below the glass transition temperature (X) or heating above the glass transition temperature (Y). In addition, some were not heated.
Next, an anodizing treatment was performed by a constant current electrolysis method using a 0.5 mol / l boric acid-0.05 mol / l borax aqueous solution at a liquid temperature of 20 ° C. and a current density of 1.0 A / m ^2. A .05 μm anodic oxide film was coated.

  Next, the resin balls made of PS were dissolved and removed using toluene, and subsequently immersed in a 1% by mass Na0H aqueous solution at 50 ° C. for a predetermined time, and the film was sequentially dissolved to form fine recesses in the fine particle removal region.

  Table 1 shows the bottom surface state of the fine recesses, the average value of equivalent circle diameters, the dispersion density of the fine recesses, and the area ratio.

Next, a second anodic oxidation treatment was performed on some aluminum materials. The second anodizing treatment condition was 0.05 M oxalic acid and 0.1 mA / cm ² .

For the aluminum material subjected to the second anodic oxidation treatment, the average equivalent circle diameter of the porous oxide film formed on the bottom of the fine recess and the average equivalent circle diameter of the pores formed on the porous oxide film The values were as shown in Table 3.
Furthermore, chemical etching was performed to form a depressed hole at the bottom of the fine recess. Chemical etching was performed by immersing in a 0.5 wt.% Phosphoric acid solution for 30 minutes.
Moreover, the depth of the formed hole was as shown in Table 3.
Next, electrolytic etching was performed on each obtained aluminum material. Etching is performed using a mixed solution of 1.0 mol / l HC1 and 3.5 mol / l H ₂ SO ₄ , and after performing an immersion treatment at a liquid temperature of 75 ° C. for 30 sec, a current density of 0.2 A / cm ^2. For 120 sec. Furthermore, chemical etching was performed at 90 ° C. for 900 seconds with the liquid having the same composition, washed with water and dried to complete the etching.

Next, after performing a chemical conversion treatment in a boric acid bath 500V, the capacitance was measured. The results are shown in Table 1.
The electrostatic capacity was relatively evaluated assuming that an aluminum material (comparative example) having a purity of 99.99% not adhering fine particles shown in Sample 1-11 of Table 1 was 100.

  The fine particle diameter, the equivalent circle diameter of the fine recesses, and the dispersion density were measured by observing the foil surface before etching with a scanning electron microscope and performing image analysis.

From Table 3, it can be seen that the product of the present invention has increased capacitance.
Example 4
A plurality of soft aluminum materials having a mass ratio of 99.99% purity or 99.9% purity and having a thickness of 100 μm were prepared by an ordinary method including intermediate annealing, subsequent light cold rolling, and high temperature annealing.
Next, as shown in Table 4, fine particles of silica (SiO ₂ ) with various average diameters (sphere equivalent diameters) set on the surface of each aluminum material by electrostatic coating (particulate adhesion array method A) By the adhesion method (fine particle adhesion arrangement method B) in which PS fine particles are generated as a colloidal crystal from the suspension, the fine particles are adhered so that the number of formed particles in the thickness direction is 1 to 4 layers. The fine particles were fixed by changing the conditions to heating below the glass transition temperature (X) or heating above the glass transition temperature (Y). In addition, some were not heated.
Next, each aluminum material was anodized under the processing conditions shown in Table 4 to form an anodized film.

  Next, the resin balls made of PS were dissolved and removed using toluene, and subsequently immersed in a 1% by mass Na0H aqueous solution at 50 ° C. for a predetermined time, and the film was sequentially dissolved to form fine recesses in the fine particle removal region.

  Table 4 shows the bottom surface state of the fine recesses, the average value of the equivalent circle diameter, the dispersion density of the fine recesses, and the area ratio.

  Next, the second anodic oxidation treatment was performed on some aluminum materials under the conditions shown in Table 4.

For the aluminum material subjected to the second anodic oxidation treatment, the average equivalent circle diameter of the porous oxide film formed on the bottom of the fine recess and the average equivalent circle diameter of the pores formed on the porous oxide film The values are shown in Table 4.
Further, chemical etching was performed under the conditions shown in Table 4 to form a depressed hole at the bottom of the fine recess. The depth of the formed hole was as shown in Table 4.
Next, electrolytic etching was performed on each obtained aluminum material. Etching is performed using a mixed solution of 1.0 mol / l HC1 and 3.5 mol / l H ₂ SO ₄ , and after performing an immersion treatment at a liquid temperature of 75 ° C. for 30 sec, a current density of 0.2 A / cm ^2. For 120 sec. Furthermore, chemical etching was performed at 90 ° C. for 900 seconds with the liquid having the same composition, washed with water and dried to complete the etching.

Next, after performing a chemical conversion treatment in a boric acid bath 500V, the capacitance was measured. The results are shown in Table 1.
The electrostatic capacity was relatively evaluated assuming that an aluminum material (comparative example) having a purity of 99.99% not adhering fine particles shown in Sample 1-11 of Table 1 was 100.

  The fine particle diameter, the equivalent circle diameter of the fine recesses, and the dispersion density were measured by observing the foil surface before etching with a scanning electron microscope and performing image analysis.

  From Table 4, it can be seen that the product of the present invention has increased capacitance.

It is typical sectional drawing for demonstrating the manufacturing method of the aluminum material which concerns on one Embodiment of this invention. It is typical sectional drawing for demonstrating the other example of the manufacturing method of the aluminum material which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum material 2 Fine particle 3 Anodized film 5 Aluminum base exposed part 6 Fine recessed part 7 Porous type oxide film 8 Recessed hole

Claims (20)

  An anodized film is formed on the surface of the aluminum material, and the average equivalent circle diameter is 0.01 to 10 μm, and an anodized film thinner than the surroundings remains on the bottom, or the aluminum base is exposed. An aluminum material for electrolytic capacitor electrodes, wherein a large number of fine recesses are formed in a dispersed state. ^2. The aluminum material for electrolytic capacitor electrodes according to claim 1, wherein the fine concave portions are dispersed at a density of 10 ⁴ to 10 ⁸ pieces / mm ² and the total area ratio is 1 to 80%.   3. The aluminum material for electrolytic capacitor electrodes according to claim 1, wherein a hole having a depth of 0.01 μm or more is formed at the bottom of the fine recess inward in the thickness direction of the aluminum material. After the anodizing treatment with the fine particles that form the masking part arranged and attached to the aluminum material surface, the location of the fine particles can be reduced by reducing the thickness of the anodized film following or simultaneously with the removal of the fine particles. It has a circle equivalent diameter of 0.01 to 10 μm, and an anodic oxide film thinner than the surrounding area remains on the bottom, or a large number of fine recesses with an aluminum substrate exposed are formed in a dispersed state. A method for producing an aluminum material for electrolytic capacitor electrodes.   The method for producing an aluminum material for electrolytic capacitor electrodes according to claim 4, wherein at least one layer of fine particles serving as the masking portion is arranged and adhered.   6. The method for producing an aluminum material for electrolytic capacitor electrodes according to claim 4, wherein the fine particles have a sphere equivalent diameter and an average size of 0.03 to 20 [mu] m.   7. The aluminum material for electrolytic capacitor electrodes according to claim 4, wherein the fine particles are resin spheres having an equivalent sphere diameter and an average size of 0.03 to 20 μm formed from a suspension as colloidal crystals. Production method.   The method for producing an aluminum material for electrolytic capacitor electrodes according to claim 7, wherein the resin sphere is heated to a glass transition point or higher to adhere to the surface of the aluminum material.   The method for producing an aluminum material for electrolytic capacitor electrodes according to any one of claims 4 to 8, wherein the anodizing treatment is performed using an electrolytic solution having a pH of 4 to 8.   As electrolyte, hydrochloric acid, sulfuric acid, nitric acid, boric acid, adipic acid, tartaric acid, phosphoric acid, citric acid, malonic acid, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and one of those compounds The method for producing an aluminum material for electrolytic capacitor electrodes according to claim 9, wherein a material containing at least a seed is used. The aluminum material in which the fine concave portion is formed is subjected to chemical etching to form a hole having a depth of 0.01 μm or more inward in the thickness direction of the aluminum material at the bottom of the fine concave portion. The manufacturing method of the aluminum material for electrolytic capacitor electrodes as described in any one of. An anodized film is formed on the surface of the aluminum material, and the average equivalent circle diameter is 0.01 to 10 μm, and an anodized film thinner than the surroundings remains on the bottom, or the aluminum base is exposed. And a porous oxide film in which one or more pores having an average equivalent circle diameter of 0.01 to 0.50 μm are dispersed at the bottom of the fine recesses. An aluminum material for electrolytic capacitor electrodes. The aluminum material for electrolytic capacitor electrodes according to claim 12, wherein the fine recesses are dispersed at a density of 10 ⁴ to 10 ⁸ pieces / mm ² , and the total area ratio is 1 to 80%.   The aluminum material for electrolytic capacitor electrodes according to claim 12 or 13, wherein a hole having a depth of 0.01 µm or more is formed at a bottom portion of the fine recess toward the inside in the thickness direction of the aluminum material. After the first anodic oxidation treatment with the fine particles serving as masking portions arranged and attached to the surface of the aluminum material, the thickness of the anodic oxide film is reduced following or simultaneously with the removal of the fine particles. It has an average equivalent circle diameter of 0.01 to 10 μm at the location where it exists, and a thin anodic oxide film remains on the bottom, or a large number of fine recesses with an aluminum substrate exposed are formed in a dispersed state. Subsequently, a second anodic oxidation treatment is performed, and a porous oxide film containing pores having an average equivalent circle diameter of 0.01 to 0.50 μm is formed on the bottom of the fine recesses. A method of manufacturing the material. The second anodic oxidation treatment is performed using an electrolytic solution containing one or more of oxalic acid, phosphoric acid, sulfuric acid and their compounds, or an electrolytic solution capable of forming a porous oxide film according to the electrolytic solution. The method for producing an aluminum material for electrolytic capacitor electrodes according to claim 15, wherein the method is carried out at a voltage equal to or lower than that of the anodizing treatment. The aluminum material on which the porous oxide film is formed is subjected to chemical etching to form a hole having a depth of 0.01 μm or more inward in the thickness direction of the aluminum material at the bottom of the fine recess. The manufacturing method of the aluminum material for electrolytic capacitor electrodes of description.   Aluminum comprising the aluminum material for electrolytic capacitor electrodes according to claims 1 to 3 and 12 to 14, wherein the aluminum material has a purity of 99.9% by mass or more and a (100) crystal orientation density of 97% or more. Electrode capacitor electrode material.   The electrode material for an aluminum electrolytic capacitor according to claim 18, which is used as an anode material.   An aluminum electrolytic capacitor in which the electrode material according to claim 19 is used.

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