JP6740213B2 - Electrode material for aluminum electrolytic capacitor and manufacturing method thereof - Google Patents

Description

The present invention relates to an electrode material for aluminum electrolytic capacitors and a method for manufacturing the same.

Aluminum electrolytic capacitors are widely used in various fields because they can be obtained at low cost and have high capacity. Generally, an aluminum foil is used as an electrode material for an aluminum electrolytic capacitor.

The surface area of the aluminum foil can be increased by performing an etching process to form etching pits. Then, an oxide film is formed by anodizing the surface thereof, which functions as a dielectric. Therefore, an aluminum foil for an electrolytic capacitor (anode foil) can be manufactured according to the application by etching the aluminum foil and anodizing the surface of the aluminum foil at various voltages according to the voltage used. ..

In the aluminum foil etching process, the etching process is performed so that optimum etching pits corresponding to the anodic oxidation voltage are formed. Specifically, it is necessary to form a thick oxide film for medium- and high-voltage capacitor applications. Therefore, in order to prevent the etching pits from being filled with a thick oxide film, the etching pit shape is made into a tunnel type by mainly performing DC etching, and the thickness is processed according to the anodizing voltage. On the other hand, for low voltage capacitor applications, fine etching pits are required, and sponge-like etching pits are mainly formed by AC etching.

In the etching process, a hydrochloric acid aqueous solution obtained by adding sulfuric acid, phosphoric acid, nitric acid or the like to hydrochloric acid is mainly used. However, since hydrochloric acid has a large environmental load, it is desired to develop a method for increasing the surface area of aluminum foil that does not rely on etching treatment.

In this regard, Patent Document 1 proposes an aluminum electrolytic capacitor characterized by using an aluminum foil having fine aluminum powder adhered to the surface thereof.

However, in this document, since aluminum powder or the like is attached to the aluminum foil by plating and/or vapor deposition, it cannot be said to be sufficient as a substitute for at least a thick etching pit for use in capacitors for medium and high voltages. ..

Further, Patent Document 2 discloses an electrode material for an aluminum electrolytic capacitor, wherein the electrode material is made of at least one sintered body of aluminum and an aluminum alloy. It has been confirmed that a capacitance equal to or higher than that of the conventional etched foil can be obtained.

However, although the electrode material disclosed in Patent Document 2 exhibits excellent performance for use in capacitors for medium and high voltages, when used in a low voltage region, it can exhibit performance superior to that obtained by conventional etching treatment. Not not.

Patent Document 3 discloses that at least one kind of powder of aluminum and aluminum alloy is burned through electrically insulating particles in order to exert a performance higher than that of an electrode material obtained by a conventional etching process even when used in a low pressure region. Disclosed is an electrode material for an aluminum electrolytic capacitor, which has a bonded sintered layer.

JP-A-2-267916 JP 2008-98279 JP International Publication No. 2015/019987

In the aluminum electrolytic capacitor electrode material of Patent Document 3, since the sintered aluminum powder is scaly aluminum flakes having a high aspect ratio, high electrostatic capacity can be exhibited. On the other hand, when manufacturing a capacitor, there is a process of winding the anode foil and cathode foil, which are the electrode materials for aluminum electrolytic capacitors, into a cylindrical element by inserting a separator between both electrode foils (winding). A force may be applied in a direction in which the formed aluminum powder and the base aluminum foil are separated from each other. Therefore, an electrode material for an aluminum electrolytic capacitor, which does not cause cracking or peeling in the manufacturing process and has higher adhesion between the aluminum base material and the sintered layer while maintaining the high capacitance as described above, is desirable. ..

The present inventors, as a result of intensive research to solve the above problems, one or both sides of the aluminum substrate, at least one selected from the group consisting of aluminum and aluminum alloy having a specific aspect ratio In the case of laminating the first layer and the second layer, which are the sintered bodies of the powder of 1., it was found that the above problems can be solved, and further studies were conducted to complete the present invention.

The present invention includes the following subjects, for example.
Item 1. On one side or both sides of the aluminum base material, at least a first layer and a second layer,
The aluminum base material and the first layer are in contact with each other, the first layer and the second layer are in contact with each other,
The first layer and the second layer are sintered layers containing at least one powder selected from the group consisting of aluminum and aluminum alloys, the aspect ratio of the powder contained in the first layer is A1, the second layer When the aspect ratio of the powder contained in A2 is A2, A2/A1 is 10 to 1000,
Electrode material for aluminum electrolytic capacitors.
Item 1a. The electrode material for an aluminum electrolytic capacitor according to Item 1, wherein A1 is 1 or more and 10 or less.
Item 1b. The electrode material for an aluminum electrolytic capacitor according to Item 1 or Item 1a, wherein A2 is greater than 10 and 1000 or less.
Item 2. Item 2. The electrode material for an aluminum electrolytic capacitor according to Item 1, Item 1a, or Item 1b, wherein the second layer is a sintered layer further containing electrically insulating particles.
Item 3. Item 3. The electrode material for an aluminum electrolytic capacitor according to any one of Items 1 and 2, wherein the powder contained in the first layer has an average particle size of 1 μm or more and 50 μm or less.
Item 4. Item 4. The electrode material for an aluminum electrolytic capacitor according to any one of Items 1 to 3, wherein the first layer has an average thickness of 1 μm or more and 50 μm or less.
Item 5. Item 5. The electrode material for an aluminum electrolytic capacitor according to any one of Items 1 to 4, wherein the density of the powder in the first layer is 5% by volume or more and 60% by volume or less.
Item 6. Item 6. The electrode material for an aluminum electrolytic capacitor according to any one of Items 1 to 5, wherein the electrically insulating particles have an average particle size of 0.01 µm or more and 10 µm or less.
Item 7. Item 7. The electrode material for an aluminum electrolytic capacitor according to any one of Items 1 to 6, wherein a weight ratio of contents of the powder and the electrically insulating particles in the second layer is 1:2 to 200:1. ..
Item 8. Item 8. The electrode material for an aluminum electrolytic capacitor according to any one of Items 1 to 7, which has the first layer and the second layer subjected to anodizing treatment.
Item 9. (1) A first step of forming at least one kind of powder of aluminum and an aluminum alloy, the first film comprising a paste composition containing the powder on one side or both sides of an aluminum base material,
(2) A second step of forming at least one powder of aluminum and an aluminum alloy, the second coating comprising a paste composition containing the powder on the surface of the first coating; and (3) the first coating. Including a third step of sintering the coating and the second coating, does not include an etching step, the aspect ratio of the powder contained in the first coating is A1, the aspect ratio of the powder contained in the second coating is A2 and Then, the ratio A2/A1 is 10 to 1000, and a method for manufacturing an electrode material for an aluminum electrolytic capacitor.
Item 10. Item 10. The method according to Item 9, wherein the paste composition in the second step further contains electrically insulating particles.
Item 11. Item 11. The production method according to Item 9 or 10, further comprising a fourth step of subjecting the sintered first film and second film to anodizing treatment.

The electrode material according to the present invention, while maintaining a high electrostatic capacity, suppresses the occurrence of cracks and peeling during the winding process, and has high adhesion between the aluminum base material and the sintered layer.

It is a scanning electron microscope (SEM) image of the partial cross section of the electrode material for aluminum electrolytic capacitors (Example 7) by one Embodiment of this invention.

Aluminum Electrode Capacitor Electrode Material The present invention relates to an aluminum electrolytic capacitor electrode material. The electrode material of the present invention has at least a first layer and a second layer on one surface or both surfaces of an aluminum base material, the aluminum base material and the first layer are in contact with each other, and the first layer and the second layer are in contact with each other. The first and second layers are sintered layers containing at least one kind of powder selected from the group consisting of aluminum and aluminum alloys, and the aspect ratio of the powder contained in the first layer is A1 and Second. When the aspect ratio of the powder contained in the layer is A2, the ratio A2/A1 is 10 to 1000. Hereinafter, at least one kind of powder selected from the group consisting of aluminum and aluminum alloys may be simply referred to as “Al powder”.

The electrode material of the present invention comprises at least the first layer and the second layer on one side or both sides of the aluminum base material. When the first layer and the second layer are provided on both sides of the aluminum base material, it is preferable that the respective layers are symmetrically arranged with the aluminum base material interposed therebetween. By providing the first layer and the second layer symmetrically, the stress applied to the electrode material can be uniformly dispersed over the entire surface, and the shape of the electrode material can be more stabilized.

In addition, the electrode material of the present invention may appropriately include another layer on the surface of the second layer opposite to the first layer. For example, an anodized film (specifically, an aluminum oxide film) can be preferably provided.

Hereinafter, the electrode material of the present invention will be described for each constitution.

Aluminum Base Material As the aluminum base material, for example, pure aluminum or aluminum alloy can be used. The aluminum alloy includes an aluminum alloy containing other alloy elements in the necessary range. The pure aluminum also includes aluminum containing an unavoidable impurity element. More specifically, the aluminum base material has, for example, as its composition, silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn). ), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni) and boron (B) at least one alloying element is added within the necessary range, or an alloying element above is inevitable. Aluminum, which is included as a specific impurity element, is also included.

The thickness of the aluminum base material is not particularly limited as long as it can form the electrode material, and can be, for example, 5 μm or more and 100 μm or less. The thickness of the aluminum substrate is more preferably 10 μm or more and 50 μm or less in order to improve the strength of the electrode material and the capacity efficiency per total thickness. In particular, an aluminum foil can be preferably used as the aluminum base material.

As the above-mentioned aluminum base material, one manufactured by a known method can be used. For example, when the aluminum base material is an aluminum foil, a molten metal of aluminum or an aluminum alloy having the above-mentioned predetermined composition is prepared, the ingot obtained by casting this is appropriately homogenized, and then this An aluminum foil can be obtained by subjecting the ingot to hot rolling and cold rolling. The aluminum foil may be a soft foil.

In addition, intermediate annealing treatment may be performed at 50° C. or higher and 500° C. or lower, particularly 150° C. or higher and 400° C. or lower during the cold rolling process. Further, after the above cold rolling step, annealing treatment may be performed at 150° C. or higher and 650° C. or lower, particularly 350° C. or higher and 550° C. or lower to obtain a soft foil.

First Layer The electrode material of the present invention includes a first layer on one side or both sides of an aluminum base material so as to be in contact with the base material.

The first layer is a sintered layer containing at least one powder selected from the group consisting of aluminum and aluminum alloys. The aspect ratio of the particles of the powder is preferably 1 or more and 10 or less.

When the first layer contains aluminum powder, for example, aluminum powder having an aluminum purity of 99.8% by weight or more is preferable. When the first layer contains aluminum alloy powder, for example, silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn) Powders of alloys containing one or more of elements such as titanium, titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), boron (B) and zirconium (Zr) are preferable. The content of each of these elements in the aluminum alloy is, for example, preferably 1% by weight or less, and more preferably 0.5% by weight or less. When these elements are contained in aluminum as unavoidable impurities, the content of each of these elements is preferably 100 ppm by weight or less, and particularly preferably 50 ppm by weight or less.

The shape of the particles of the Al powder contained in the first layer is not particularly limited, and any of spherical shape, irregular shape, scale shape, fibrous shape and the like can be preferably used. Particularly, powder composed of spherical particles is preferable.

The particles of the Al powder contained in the first layer preferably have an aspect ratio (average particle diameter/average thickness) of 1 or more and 10 or less. In particular, when the shape of the particles is irregular, scale-like (flake-like) or fibrous, the aspect ratio is preferably 1 or more and 10 or less. By setting the aspect ratio of the Al powder contained in the first layer within the above range, the adhesiveness between the first layer and the second layer described below and the adhesiveness between the first layer and the aluminum base material become higher. It is possible to preferably suppress the occurrence of peeling or cracking of the first layer and/or the second layer in the winding step of the electrode material for an aluminum electrolytic capacitor of the present invention.

The average thickness of the Al powder particles contained in the first layer is preferably 0.1 μm or more and 50 μm or less, and more preferably 0.1 μm or more and 10 μm or less. By setting it in such a range, the adhesiveness with the aluminum base material becomes higher, and peeling or cracking of the sintered layer can be suppressed.

In the present specification, the average thickness of each particle is a value measured by observing the particle with a scanning electron microscope (SEM). For example, regarding the particles of the Al powder contained in the first layer (or the second layer), before sintering, the powder is appropriately mixed with a resin or solvent to form a coating film, and a cross-sectional observation of this coating film is performed by SEM. Done in. In addition, after the sintering, the cross section of the sintered layer is observed by SEM. In these observations, the minimum diameter of each powder particle is taken as the thickness of the particle, the thickness of 50 particles is measured at random, and the arithmetic mean thereof is taken as the average thickness of the particles.

The Al powder particles contained in the first layer preferably have an average particle size of 1 μm or more and 50 μm or less, more preferably 1 μm or more and 30 μm or less, and further preferably 1 to 15 μm. By setting it in such a range, the adhesion with the aluminum base material becomes higher, and peeling or cracking of the sintered layer in the winding step of the obtained electrode material can be suppressed.

In addition, the average particle size of each particle in the present specification is an average particle size D ₅₀ value obtained by measuring the particle size distribution on a volume basis by a laser diffraction/scattering method. A particle size distribution measuring device can be used for the measurement, and more specifically, for example, Microtrac MT3300EX II (manufactured by Nikkiso Co., Ltd.) can be used. However, the average particle diameter of the Al powder particles after sintering is a value measured by observing the cross section of the sintered body in both the first layer and the second layer with a scanning electron microscope. Specifically, the cross section of the sintered layer is observed by SEM, the maximum diameter of each powder particle is taken as the particle diameter of the particle, the particle diameter of 50 particles is measured at random, and the arithmetic mean of these is calculated as the particle diameter. The average particle size of Note that the powder after sintering may be partially melted or in a state where powder particles are connected to each other, but a portion having a substantially circular shape can be approximately regarded as particles.

As the Al powder contained in the first layer and the second layer described later, one manufactured by a known method can be used. For example, the atomization method, melt spinning method, rotating disk method, rotating electrode method, rapid solidification method and the like can be mentioned, but the atomization method, particularly the gas atomization method is preferable for industrial production. That is, it is desirable to use the powder obtained by atomizing the molten metal.

The thickness of the first layer is not particularly limited, and generally, the average thickness is preferably 1 μm or more and 50 μm or less, and particularly preferably 1 μm or more and 15 μm or less. By setting it within such a range, it is possible to obtain an electrode material for an aluminum electrolytic capacitor having a larger capacitance per unit volume.

The average weight of the first layer is, for example, preferably 1 g/m ² or more and 75 g/m ² or less, and more preferably 1 g/m ² or more and 20 g/m ² or less. By setting it within such a range, it is possible to obtain an electrode material for an aluminum electrolytic capacitor having a larger capacitance per unit volume. The average weight means the weight per 1 m ² .

The density (volume filling rate) of the first layer is, for example, preferably 5% by volume or more and 60% by volume or less, and more preferably 40% by volume or more and 60% by volume or less. By setting it in such a range, it is possible to have a high electrostatic capacity as an electrode material while maintaining high adhesion between the aluminum base material and the second layer described later. The density value is calculated using the specific gravity of Al powder.

Second Layer The electrode material of the present invention includes a second layer so as to be in contact with the first layer. When the first layer is formed on both sides as described, it is preferable to provide the second layer on one side or both sides, and to provide it on both sides.

The second layer is a sintered layer containing at least one powder selected from the group consisting of aluminum and aluminum alloys. The aspect ratio of the particles of the powder is preferably more than 10 and 1000 or less.

As the at least one powder selected from the group consisting of aluminum powder and aluminum alloy contained in the second layer, those listed above can be used.

The shape of the particles of the Al powder contained in the second layer is not particularly limited, and for example, any of irregular shape, scale shape, fibrous shape and the like can be preferably used. In particular, powder composed of scale-like particles is preferable.

The particles of the Al powder contained in the second layer preferably have an aspect ratio (average particle size/average thickness) of more than 10 and 1000 or less, and more preferably 100 to 1000. In the case of this range, the electrode material having the above structure can obtain a higher capacitance than the electrode material obtained by the conventional etching treatment even in the low pressure region.

The average thickness of the particles of the Al powder contained in the second layer is preferably 0.01 μm or more and 80 μm or less, and more preferably 0.01 μm or more and 1 μm or less. By setting it within such a range, an electrode material having a higher capacitance can be obtained.

The Al powder contained in the second layer preferably has an average particle size of 1 μm or more and 80 μm or less. In particular, when the average particle size of the powder is 1 to 10 μm, the obtained electrode material can be suitably used as an electrode material for an aluminum electrolytic capacitor for low voltage applications of 100 V or less.

The second layer in the electrode material of the present invention may further contain electrically insulating particles.

As the electrically insulating particles, particles capable of suppressing over-sintering of the powders by interposing a spacer between the powders during the sintering of the Al powder, and ensuring an effective surface area and a capacitance of the electrode material can be used. preferable. As such electrically insulating particles, for example, metal compound particles are preferable, and metal oxide particles, metal nitride particles and the like are more preferable. Specifically, particles of at least one metal compound selected from the group consisting of alumina, titania, zirconia, and silica are preferable.

These particles have electric insulation and high melting point (for example, about 2000 ℃), they do not sinter themselves with Al powder, and they can act as spacers during sintering of Al powder. It is preferable in that there is no possibility of adversely affecting the electric characteristics of.

The average particle size of the electrically insulating particles is not limited, but is preferably 0.01 to 10 μm, and more preferably 0.1 to 0.5 μm. By setting it within such a range, an electrode material particularly suitable for low voltage applications of 100 V or less can be obtained. The average particle size of the electrically insulating particles is a value measured by the same method as the Al powder particles.

The weight ratio of the Al powder and the electrically insulating particles contained in the second layer is not limited, but for example, the Al powder: the electrically insulating particles = 1: 2 to 200: 1 is preferable, It is more preferably 1:2 to 100:1, and particularly preferably 3:1 to 10:1. As the volume ratio of the Al powder and the electrically insulating particles contained in the second layer, it is preferable that the Al powder: the electrically insulating particles = 3:4 to 300:1, and 3:4 to. It is more preferably 150:1, and particularly preferably 9:2 to 15:1. The volume (ratio) is calculated from the specific gravity of each particle.

By setting the content ratio (weight ratio, volume ratio) within such a range, it is easy to secure the effective surface area of the electrode material.

The shape of the second layer is not particularly limited, and generally the average thickness is preferably 5 μm or more and 1000 μm or less, and particularly preferably 5 μm or more and 50 μm or less. By setting it in such a range, it is possible to obtain an electrode material for an aluminum electrolytic capacitor having higher adhesion.

The average thickness of the first layer and the second layer is measured as follows. The thickness of the sintered body (including the first layer and the second layer) at any 10 points is measured with a micrometer, and the average value is taken as the average thickness of the sintered body. Then, in a scanning electron microscope cross-sectional photograph (three pieces photographed arbitrarily) of about 200 times that the cross section of the sintered body is all within the photographing range, visual judgment is made at each interface of the base material, the first layer, and the second layer. Then, a straight line is drawn to determine the thickness ratio of each sintered layer, the average thickness of the sintered body is multiplied by each ratio to calculate the thickness of each sintered layer, and the calculated values for the three photographs are averaged. And the average thickness of the first layer and the second layer.

The electrode material of the present invention can be used as an electrode without etching treatment. Further, the surfaces of the first layer and the second layer may be further anodized to be used as an electrode. In particular, the electrode material of the present invention can be preferably used as an electrode foil.

For example, an anode foil using the electrode material of the present invention and a cathode foil are laminated with a separator interposed therebetween and wound to form a capacitor element, and the capacitor element is impregnated with an electrolytic solution and contains an electrolytic solution. An electrolytic capacitor is obtained by housing the capacitor element in an outer case and sealing the case with a sealing body.

Manufacturing method of aluminum electrolytic capacitor material The manufacturing method of the electrode material for aluminum electrolytic capacitor of the present invention,
(1) A first step of forming a first film made of a paste composition containing at least one powder selected from the group consisting of aluminum and aluminum alloys on one side or both sides of an aluminum base material,
(2) a second step of forming on the surface of the first coating a second coating made of a paste composition containing at least one powder selected from the group consisting of aluminum and aluminum alloys; and (3) the above Including a third step of sintering the one film and the second film, without including an etching step, the aspect ratio of the powder contained in the first film is A1, the aspect ratio of the powder contained in the second film is A2. Then, A2/A1 is characterized by 10 to 1000.
More preferably, the method for producing an electrode material for an aluminum electrolytic capacitor of the present invention,
(1) A first step of forming a first film made of a paste composition containing at least one powder selected from the group consisting of aluminum and aluminum alloys on one side or both sides of an aluminum base material,
(2) At least one kind of powder selected from the group consisting of aluminum and aluminum alloys, where A2 is the aspect ratio of the powder and A1 is the aspect ratio of the powder contained in the first coating. A second step of forming on the surface of the first coating a second coating made of a paste composition containing a powder in which /A1 is 10 to 1000, and (3) sintering the first coating and the second coating. It is characterized in that it includes a third step of performing and does not include an etching step.

Hereinafter, each step will be described separately.

<First step>
In the first step, a first film made of a paste composition containing at least one powder selected from the group consisting of aluminum and aluminum alloys is formed on one side or both sides of the aluminum base material. The particles of the powder preferably have an aspect ratio of 1 or more and 10 or less.

As the composition (component) of aluminum and aluminum alloy, those listed above can be used. As the powder, for example, pure aluminum powder having an aluminum purity of 99.8% by weight or more is preferably used.

In addition to the Al powder, the paste composition may contain a resin binder, a solvent, a dispersion medium, a sintering aid, a surfactant, etc., if necessary. Any of these may be publicly known or commercially available. In particular, it is preferable to use at least one of a resin binder and a solvent for use as a paste-like composition, whereby a film can be formed efficiently.

The resin binder is not limited, and examples thereof include carboxy-modified polyolefin resin, vinyl acetate resin, vinyl chloride resin, vinyl chloride vinyl acetate copolymer resin, vinyl alcohol resin, butyral resin, vinyl fluoride resin, acrylic resin, polyester resin, urethane. Resin, epoxy resin, urea resin, phenol resin, acrylonitrile resin, cellulose resin, paraffin wax, polyethylene wax, and other synthetic resins; wax, tar, glue, natural resin such as lacquer, pine resin, beeswax, or wax is preferably used. it can. Cellulose resin is preferable, and ethyl cellulose is particularly preferable.

Depending on the molecular weight, the type of resin, etc., these resin binders include those that volatilize when heated and those that remain with Al powder due to thermal decomposition, and are used properly according to the desired electrical characteristics such as capacitance. can do.

In addition, a known solvent or dispersion medium can be used. For example, in addition to water, organic solvents such as ethanol, toluene, ketones and esters can be used. Esters are preferable, acetic acid esters are more preferable, and butyl acetate is particularly preferable.

Although not particularly limited, when the paste is prepared using ethyl cellulose and butyl acetate, for example, the paste can be prepared by mixing Al powder with a solution of ethyl cellulose dissolved in butyl acetate. At this time, the weight ratio of the solution to the Al powder is preferably about 1:1 to 5, more preferably about 1:1.5 to 3.

When forming the film, the film can be formed by applying a paste composition, for example. More specifically, for example, a coating can be formed by applying using a coating method such as roller, brush, spray, dipping or the like. In addition, the film can be formed by a known printing method such as silk screen printing.

The first coating is formed on one side or both sides of the aluminum base material. When it is formed on both sides, it is preferable to arrange the coating symmetrically with the aluminum base material sandwiched therebetween.

The thickness of the first coating is not limited, but it is preferable that the sintered layer obtained after sintering has an average thickness of 1 μm or more and 50 μm or less, and particularly 1 μm or more and 15 μm or less.

The first coating is preferably dried at a temperature within the range of 20 to 300° C. for 10 minutes or more.

<Second step>
In the second step, a second film made of a paste composition containing at least one powder selected from the group consisting of aluminum and aluminum alloys is formed on the surface of the first film. In that case, [aspect ratio of at least one powder selected from the group consisting of aluminum and aluminum alloy contained in the second coating]/[at least selected from the group consisting of aluminum and aluminum alloy contained in the first coating] The aspect ratio of one kind of powder] is adjusted to fall within the range of 10 to 1000.

The powder contained in the second coating preferably has an aspect ratio of more than 10 and 1000 or less.

As the composition (component) of at least one powder selected from the group consisting of aluminum and aluminum alloys, those listed above can be used. For example, it is preferable to use pure aluminum powder having an aluminum purity of 99.8% by weight or more.

The paste composition may further include electrically insulating particles. As the electrically insulating particles, those listed above can be used.

In addition to the Al powder and the electrically insulating particles, the paste composition may contain a resin binder, a solvent, a dispersion medium, a sintering aid, a surfactant, etc., if necessary. Any of these may be publicly known or commercially available. In particular, it is preferable to use at least one of a resin binder and a solvent for use as a paste-like composition, whereby a film can be formed efficiently.

The resin binder, solvent and dispersion medium are not limited, and those listed above can be used.

When forming the second coating, the coating can be formed by applying a paste composition, for example. More specifically, for example, a coating can be formed by applying using a coating method such as roller, brush, spray, dipping or the like. In addition, the film can be formed by a known printing method such as silk screen printing.

The thickness of the second coating is not limited, but it is preferable that the second coating is formed so that the average thickness of the sintered layer obtained after sintering is 5 to 1000 μm, particularly 5 to 50 μm.

The second coating is preferably dried at a temperature within the range of 20 to 300° C. for 10 minutes or more.

<Third step>
In the third step, the coating is sintered at a temperature of 400 to 660°C to form a sintered layer.

The sintering temperature is 400 to 660°C, preferably 450 to 600°C. Although the sintering time varies depending on the sintering temperature and the like, it can usually be appropriately determined within the range of about 5 to 24 hours.

The sintering atmosphere is not particularly limited and may be, for example, a vacuum atmosphere, an inert gas atmosphere, an oxidizing gas atmosphere (atmosphere), a reducing atmosphere, or the like, but a vacuum atmosphere or a reducing atmosphere is particularly preferable. Is preferred. The pressure condition may be normal pressure, reduced pressure or increased pressure.

After the second step, prior to the third step, it is preferable to perform a heat treatment (degreasing treatment) in advance in a temperature range of 100 to 600° C. for a holding time of 5 hours or longer. The heat treatment atmosphere is not particularly limited, and may be, for example, a vacuum atmosphere, an inert gas atmosphere, or an oxidizing gas atmosphere. The pressure condition may be normal pressure, reduced pressure or increased pressure.

The first coating is sintered to form the first layer, and the second coating is sintered to form the second layer.

<4th step>
In the third step, a laminate including the aluminum base material, the first layer, and the second layer is obtained. The laminate can be used as the electrode material of the present invention. That is, the laminate obtained in the third step can be used as an electrode material without being subjected to etching treatment. In addition, an anodized film (specifically, an aluminum oxide film) can be formed by subjecting the laminated body to an anodizing treatment as a fourth step, and a laminated body further including the anodized film is also included in the present invention. It can be used as an electrode material.

Conditions for the anodizing treatment are not particularly limited, and known anodizing treatment can be performed. For example, by applying a current of 10 mA/cm ² or more and 40 mA/cm ² or more for 5 minutes or more in a boric acid solution or ammonium adipate aqueous solution with a concentration of 0.01 mol or more and 5 mol or less and a temperature of 30° C. or more and 100° C. or less. ,It can be carried out.

As the manufacturing method of the present invention, before forming the second coating, the first coating is dried and sintered, the second coating is formed on the layer obtained by sintering the first coating, and further sintering is performed. You can also

The electrode material of the present invention can exhibit excellent performance even when used in a capacitor for low voltage of 100 V or less, and thus can be suitably used for applications of aluminum electrolytic capacitors for low voltage, and an anodizing treatment step, It is possible to suppress the occurrence of cracks and peeling of the sintered layer in the capacitor manufacturing process and the like.

In addition, in this specification, "comprising" includes "consisting essentially of" and "consisting of." is also included including "consisting essentially of" and "consisting of".

Example 1
Both sides of a 20 μm aluminum base material (99.99 wt% or more high-purity aluminum foil) with a paste in which aluminum powder with an average particle diameter of 3 μm (99.99 wt% or more high-purity aluminum particles, aspect ratio 1) is uniformly dispersed. Was applied to and dried to form a first film.

Aluminum powder with an average particle diameter of 5 μm (99.99% by weight or more of high-purity aluminum particles, aspect ratio 100) and alumina particles with an average particle diameter of 0.01 μm in a weight ratio of 10:1 (volume ratio of 15:1) The uniformly dispersed paste was applied onto the first coating on both sides and dried to form the second coating.

The paste used was prepared by preparing a solution containing 10% by weight of ethyl cellulose in butyl acetate, and mixing the solution and aluminum particles in a weight ratio of 1:2. Moreover, the application of the paste was performed using a coating machine.

This was sintered and the electrode material was produced. By sintering, the first coating became the first layer and the second coating became the second layer. The average thickness, weight and density of the first layer on one side were 5 μm, 7 g/m ² and 52% by volume, respectively. The average thickness of the second layer on one surface was 50 μm.

Further, an anodic oxidation treatment was carried out using an aqueous solution of ammonium adipate. The conditions of the anodic oxidation treatment were such that the concentration of the aqueous solution was 0.3 mol, the temperature was 60° C., a current of 25 mA/cm ² was applied up to a predetermined voltage, and then a constant voltage was applied for 10 minutes.

The average particle size of the particles of each powder used was measured by the laser diffraction/scattering method (dispersion medium: isopropyl alcohol). Specifically, the measurement was performed using a particle size distribution measuring device (Microtrac MT3300EX II manufactured by Nikkiso Co., Ltd.).

The average thickness of the first layer and the second layer was measured as follows. The thickness of the sintered body (including the first layer and the second layer) at any 10 points is measured with a micrometer, and the average value is taken as the average thickness of the sintered body. Then, in a scanning electron microscope cross-sectional photograph (three pieces photographed arbitrarily) of about 200 times that the cross section of the sintered body is all within the photographing range, visual judgment is made at each interface of the base material, the first layer, and the second layer. Then, a straight line is drawn to determine the thickness ratio of each sintered layer, the average thickness of the sintered body is multiplied by each ratio to calculate the thickness of each sintered layer, and the calculated values for the three photographs are averaged. And the average thickness of the first layer and the second layer. The same applies to the following.

The aspect ratio is a value represented by (average particle size/average thickness). The same applies to the following.

Moreover, the average thickness of the particles of each powder used was a paste obtained by mixing each powder at a weight ratio of 1:2 to a solution containing 10% by weight of ethyl cellulose (acting as a binder) in butyl acetate to form a coating film, This is a value obtained by observing the cross section of the coating film by SEM, measuring the thickness (minimum diameter) of 50 particles selected at random, and averaging the measured values. The same applies to the following.

Comparative example 1
An electrode material was prepared in the same manner as in Example 1 except that the first coating and the first layer were not formed (therefore, the second layer was in contact with the aluminum base material), and anodization treatment was performed.

Test example 1
Capacitance measurement and winding test were carried out using the anodized electrode material at each voltage of 2.5, 5, 10, and 100 V.

The capacitance measurement was carried out after the anodizing treatment in a similar solution by making a test piece having a projected area of 5 cm ² face the electrode material (liquid temperature was 30° C.).

For the winding test, the winding method of JIS Z 2248 was referred to. Specifically, a test piece was prepared from the anodized electrode material so that the width was 10 mm, and the diameter of the shaft (round bar) was Φ1, 5, or 10 mm, and the test piece was 180°. It was manually bent until it became, and it was visually judged whether or not peeling of the first layer and/or the second layer occurred. The case where the peeling occurred was rejected, and the case where the peeling did not occurred was accepted. In the table showing the results, the pass is indicated by “◯” and the fail is indicated by “x”. Those that passed can be judged to have excellent adhesion of each layer. It should be noted that the higher the voltage during the anodizing treatment, the thicker the oxide film formed, so that peeling is more likely to occur in the winding test.

The following capacitance measurement and winding test were also performed in the same procedure.

Table 1 shows the capacitance and winding test results of the electrode materials of Example 1 and Comparative Example 1. In the following, each voltage of 2.5, 5, 10, and 100 V in each table indicates the voltage at the time of anodizing treatment.

Comparing the cases where the anodizing treatment is performed at the same voltage, the electrode material of Example 1 including the first layer has a smaller diameter than the electrode material of Comparative Example 1 not including the first layer. It was possible to wind the rod.

Example 2
An electrode material was prepared in the same manner as in Example 1 except that aluminum powder having an average particle diameter of 10 μm (high-purity aluminum particles of 99.99% by weight or more, aspect ratio 25) was used in the formation of the second coating, and the anode was prepared. Oxidation treatment was performed.

Comparative example 2
An electrode material was prepared and anodized in the same manner as in Example 2 except that the first coating and the first layer were not formed (the second layer was in contact with the aluminum base material).

Table 2 shows the capacitance and winding test results of the electrode materials of Example 2 and Comparative Example 2.

Comparing the cases where the anodizing treatment is performed at the same voltage, the electrode material of Example 2 including the first layer has a smaller diameter than the electrode material of Comparative Example 2 including no first layer. It was possible to wind the rod.

Example 3
In the formation of the second coating, an electrode material was prepared in the same manner as in Example 1 except that aluminum powder having an average particle size of 10 μm (high-purity aluminum particles of 99.99% by weight or more, aspect ratio 1000) was used, and an anode was prepared. Oxidation treatment was performed.

Comparative example 3
An electrode material was prepared and anodized in the same manner as in Example 3 except that the first coating and the first layer were not formed (the second layer was in contact with the aluminum base material).

Table 3 shows the capacitance and winding test results of the electrode materials of Example 3 and Comparative Example 3.

Comparing the cases where the anodizing treatment is performed at the same voltage, the electrode material of Example 3 including the first layer has a smaller diameter than the electrode material of Comparative Example 3 including no first layer. It was possible to wind the rod.

Example 4
In the formation of the first coating, an electrode material was prepared in the same manner as in Example 1 except that aluminum powder having an average particle size of 5 μm (high-purity aluminum particles of 99.99% by weight or more, aspect ratio 10) was used, and an anode was prepared. Oxidation treatment was performed.

The average thickness, average weight and density of the first layer on one side were 1 μm, 1.3 g/m ² and 48% by volume, respectively.

Table 4 shows the capacitance and the winding test results of the electrode materials of Example 4 and Comparative Example 1.

Comparing the cases where the anodizing treatment is performed at the same voltage, the electrode material of Example 4 including the first layer has a smaller diameter than the electrode material of Comparative Example 1 not including the first layer. It was possible to wind the rod.

Example 5
In the formation of the first coating, an electrode material was prepared in the same manner as in Example 1 except that aluminum powder having an average particle size of 15 μm (99.99% by weight or more of high-purity aluminum particles, aspect ratio 1) was used, and an anode material was prepared. Oxidation treatment was performed.

The average thickness, average weight and density of the first layer on one surface were 15 μm, 3 g/m ² and 7% by volume, respectively.

Table 5 shows the capacitance and winding test results of the electrode materials of Example 5 and Comparative Example 1.

Comparing the cases where the anodizing treatment is performed at the same voltage, the electrode material of Example 5 including the first layer has a smaller diameter than the electrode material of Comparative Example 1 not including the first layer. It was possible to wind the rod.

Example 6
In the formation of the first coating, an electrode material was prepared in the same manner as in Example 1 except that aluminum powder having an average particle size of 30 μm (high-purity aluminum particles of 99.99% by weight or more, aspect ratio 1) was used, and an anode was prepared. Oxidation treatment was performed.

The average thickness, average weight and density of the first layer on one side were 50 μm, 75 g/m ² and 55% by volume, respectively.

Table 6 shows the capacitance and winding test results of the electrode materials of Example 6 and Comparative Example 1.

Comparing the cases where the anodizing treatment is performed at the same voltage, the electrode material of Example 6 including the first layer has a smaller diameter than the electrode material of Comparative Example 1 not including the first layer. It was possible to wind the rod.

Comparative Example 4
Aluminum etched foil with an average thickness of 120 μm (2.5, 5, 10V)
Aluminum etched foil with an average thickness of 110 μm (100 V)
The capacitance of the electrode material of Example 6 and the aluminum etched foil of Comparative Example 4 were evaluated. Table 7 shows the capacitance per 1 μm of thickness.

Since the thickness of the first layer is large, the thickness of the electrode material itself is large. Therefore, it is considered that the electrode material anodized at 100 V had a lower capacitance efficiency per volume than the etched foil.

Example 7
In the formation of the first coating, an electrode material was prepared in the same manner as in Example 1 except that aluminum powder having an average particle diameter of 1 μm (high-purity aluminum particles of 99.99% by weight or more, aspect ratio 1) was used, and an anode was prepared. Oxidation treatment was performed.

The average thickness, average weight and density of the first layer on one side were 1 μm, 1.6 g/m ² and 60% by volume, respectively.

Table 8 shows the capacitance and winding test results of the electrode materials of Example 7 and Comparative Example 1 above.

Comparing the cases where the anodic oxidation treatment is performed at the same voltage, the electrode material of Example 7 including the first layer has a smaller diameter than the electrode material of Comparative Example 1 not including the first layer. It was possible to wind the rod.

Examples 8-1 to 8-4
In forming the second coating, an electrode material was prepared and anodized in the same manner as in Example 1 except that the weight ratio of aluminum powder and alumina particles was as follows.

Comparative Examples 5-1 to 5-4
An electrode material was prepared and anodized in the same manner as in Examples 8-1 to 8-4, except that the first film and the first layer were not formed (the second layer was in contact with the aluminum base material). The treatment was carried out.

Table 10 shows the capacitance and winding test results of the electrode materials of Examples 8-1 to 8-4 and Comparative Examples 5-1 to 5-4 according to the above test method. However, the voltage during the anodizing treatment was 5 V.

In any of the electrode materials of Examples 8-1 to 8-4, compared with the electrode materials of Comparative Examples 5-1 to 5-4, which have the same configuration except for the first layer, respectively, the adhesion of the anodic oxide film It was highly effective (see especially the results for Φ5 mm).

Examples 9-1 to 9-4
In forming the second coating, an electrode material was prepared and anodized in the same manner as in Examples 8-1 to 8-4, except that the average particle diameter of the alumina particles was 0.5 μm.

Comparative Examples 6-1 to 6-4
An electrode material was prepared and anodized in the same manner as in Examples 9-1 to 9-4 except that the first coating and the first layer were not formed (thus the second layer was in contact with the aluminum base material). The treatment was carried out.

Table 12 shows the capacitance and winding test results of the electrode materials of Examples 9-1 to 9-4 and Comparative Examples 6-1 to 6-4. However, the voltage during the anodizing treatment was 5 V.

Any of the electrode materials of Examples 9-1 to 9-4, respectively, compared to the respective electrode materials of Comparative Examples 6-1 to 6-4, which have the same configuration except the first layer, adhesion of the anodic oxide film It was highly effective (see especially the results for Φ5 mm).

10: Aluminum electrolytic capacitor electrode material
11: First layer
12: Second layer
13: Aluminum base material (aluminum foil)

Claims (13)

On one side or both sides of the aluminum base material, at least a first layer and a second layer,
The aluminum base material and the first layer are in contact with each other, the first layer and the second layer are in contact with each other,
The first layer and the second layer is a sintered layer containing at least one powder selected from the group consisting of aluminum and aluminum alloys, the aspect ratio of the powder particles contained in the first layer is A1, the second layer. When the aspect ratio of the powder particles contained in A2 is A2, A2/A1 is 10 to 1000,
Electrode material for aluminum electrolytic capacitors. The electrode material for an aluminum electrolytic capacitor according to claim 1, wherein A1 is 1 or more and 10 or less. The electrode material for an aluminum electrolytic capacitor according to claim 1 , wherein A2 is greater than 10 and 1000 or less. The electrode material for an aluminum electrolytic capacitor according to claim 1, wherein an average particle diameter of the powder particles contained in the first layer is 1 μm or more and 50 μm or less. The electrode material for an aluminum electrolytic capacitor according to claim 1, wherein the average thickness of the first layer is 1 μm or more and 50 μm or less. The electrode material for an aluminum electrolytic capacitor according to claim 1, wherein a density of the powder in the first layer is 5% by volume or more and 60% by volume or less. The electrode material for an aluminum electrolytic capacitor according to claim 1, wherein the second layer is a sintered layer that further contains electrically insulating particles. The electrode material for an aluminum electrolytic capacitor according to claim 7, wherein an average particle diameter of the electrically insulating particles is 0.01 μm or more and 10 μm or less. The electrode material for an aluminum electrolytic capacitor according to claim 7, wherein the weight ratio of the contents of the powder and the electrically insulating particles in the second layer is 1:2 to 200:1. The electrode material for an aluminum electrolytic capacitor according to claim 1, which has the first layer and the second layer which have been subjected to anodization treatment. (1) A first step of forming a first film made of a paste composition containing at least one powder selected from the group consisting of aluminum and aluminum alloys on one side or both sides of an aluminum base material,
(2) a second step of forming on the surface of the first coating a second coating made of a paste composition containing at least one powder selected from the group consisting of aluminum and aluminum alloys; and (3) the above Including a third step of sintering the one film and the second film, without including an etching step, the aspect ratio of the powder contained in the first film is A1, the aspect ratio of the powder contained in the second film is A2. Then, A2/A1 is 10-1000, The manufacturing method of the electrode material for aluminum electrolytic capacitors characterized by the above-mentioned. The manufacturing method according to claim 11, wherein the paste composition in the second step further contains electrically insulating particles. The manufacturing method according to claim 11 or 12, further comprising a fourth step of performing anodizing treatment after the third step.

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