JP2012255213A - Aluminum material for electrolytic capacitor electrode, electrode material for electrolytic capacitor, and aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that the etching characteristics of an aluminum material, with respect to the conventional aluminum material for an electrolytic capacitor electrode, are not satisfactory, and to provide an aluminum material for an electrolytic capacitor electrode having excellent etching characteristics, an electrode material for an electrolytic capacitor, and an aluminum electrolytic capacitor.SOLUTION: The aluminum material for the electrolytic capacitor has a Pb content of 0.3-2.5 mass ppm, and a Lab-based lightness index (L value) of the aluminum material after evaluation etching under predetermined conditions, measured by a predetermined method, of a value satisfying at least either 25-56 for a pretreatment time of 30 seconds or 27-58 for a pretreatment time of 45 seconds.

Description

  The present invention relates to an aluminum material for electrolytic capacitor electrodes, an electrode material for electrolytic capacitors, and an aluminum electrolytic capacitor.

  In this specification, the term “aluminum” is used to include alloys thereof, and aluminum materials include foils and plates and molded bodies using these.

  An aluminum material generally used as an electrode material for an aluminum electrolytic capacitor is subjected to electrochemical or chemical etching treatment to increase the effective area of the aluminum material for the purpose of increasing the capacitance.

  In the manufacture of aluminum materials for electrolytic capacitor anodes that generate tunnel-like pits by direct current etching, it is common to perform final annealing in an inert atmosphere or vacuum at a temperature of around 500 ° C in order to develop a cubic texture of aluminum. Is. The final annealing is performed in a process after the cold rolling. Moreover, you may implement annealing as needed in order to raise the cube orientation occupation rate after the last annealing in the middle of a cold rolling process. The annealing in the middle of the cold rolling process is referred to as intermediate annealing, and is generally performed in an inert atmosphere such as nitrogen or argon.

  Since the characteristics of the oxide film on the surface of the aluminum material after the final annealing are particularly related to the formation of pits at the initial stage of electrolytic etching, studies on the oxidation treatment on the surface of the aluminum material are being conducted. Trace elements contained in the aluminum material also affect the etching characteristics of the aluminum material. In particular, Pb concentrates on the surface of the aluminum material during the final annealing and activates the surface to affect the initial pit formation and surface solubility. In addition, it is important to optimize the content of Cu because it affects the amount of aluminum material dissolved and the initial pit formation during electrolytic etching.

Patent Document 1 discloses a step of removing a surface layer of an aluminum foil, a step of heat oxidation under conditions of a temperature of 40 to 350 ° C., a dew point of 0 to 80 ° C., and a time of 30 to 1800 seconds after the removal, and heat oxidation. Subsequently, it is disclosed that by performing a step of annealing in a non-oxidizing atmosphere, the oxide film on the surface of the aluminum foil after annealing can be thinned and quickly dissolved and removed in an etching solution.
Patent Document 2 describes the concentrations of Cu and Pb.

JP-A-7-201673 JP 2000-239773 A

  However, in Patent Document 1, although the capacitance is improved by heating in an oxidizing atmosphere, there is no description regarding trace elements contained in aluminum materials such as Pb and Cu.

  Further, in Patent Document 2, the concentration of Pb and Cu is defined, and it is described that hot rolling, cold rolling, intermediate annealing, finish rolling, and final annealing may be performed by a conventionally known method. Although the amount of precipitation of Fe and Si is shown as the characteristics of the aluminum foil after the final annealing, a sufficient capacitance improvement effect is obtained because the characteristics evaluation of the foil after the final annealing is insufficient Not.

  The present invention has been made in view of such a technical background, and in the conventional aluminum material for electrolytic capacitor electrodes, the problem that the etching characteristics of the aluminum material are insufficient is solved, and the etching characteristics are improved. It is an object of the present invention to provide an excellent aluminum material for an electrolytic capacitor electrode, and further to provide an electrode material for an electrolytic capacitor using the aluminum material and an aluminum electrolytic capacitor.

  In order to solve the above-mentioned problems, the present inventors have completed the present invention by making the composition of the aluminum material for electrolytic capacitor electrodes and the etching characteristics for evaluation appropriate.

  That is, the aluminum material for electrolytic capacitor electrodes, the electrode material for electrolytic capacitors, and the aluminum electrolytic capacitor of the present invention have the following configurations.

(1) The lightness index (L value) in the Lab system measured by the method shown below of the aluminum material after the etching for evaluation shown below with a Pb content of 0.3 mass ppm to 2.5 ppm by mass is pre-treated. An aluminum material for electrolytic capacitor electrodes satisfying at least one of 25 to 56 when the time is 30 seconds, or 27 to 58 when the pretreatment time is 45 seconds.
[Etching method for evaluation]
As a pretreatment, the aluminum material is immersed in a 2 mol / L phosphoric acid solution at 50 ° C for 30 or 45 seconds, then washed with water, and DC electrolytic etching for 3 seconds at a current density of 0.4 A / cm ^{2 in the} electrolyte shown below. Wash with water and dry.

Electrolyte composition: hydrochloric acid 1.0 mol / L, sulfuric acid 2.7 mol / L, aluminum sulfate 1.0 mol / L (added as aluminum sulfate hydrated water)
Electrolyte temperature: 82 ℃
A carbon electrode is installed as a counter electrode on both sides of the aluminum material, with a distance of 17 mm from the aluminum material, and double-sided etching (current density is the value per projected area)
[Measurement method of lightness index (L value) by Lab system]
Optical conditions: 45-n (condition a described in JIS Z 8722 5.3.1)
Color measurement condition: C light 2 ° field of view Sample placement condition: The normal of the surface including the optical path at the center of the light bundle, and the sample normal so that the rolling direction is perpendicular to the normal contained in the sample surface Place and measure.

(2) The electrolytic capacitor electrode according to item 1 above, wherein the lightness index (L value) satisfies both 25 to 56 when the pretreatment time is 30 seconds and 27 to 58 when the pretreatment time is 45 seconds. Aluminum material.

(3) The aluminum material for electrolytic capacitor electrodes as described in (1) or (2) above, containing 10 ppm by mass to 150 ppm by mass of Cu.

(4) The aluminum material for electrolytic capacitor electrodes as recited in any one of the aforementioned Items 1 to 3, wherein the aluminum material has an aluminum purity of 99.9% by mass or more.

(5) The aluminum material for electrolytic capacitor electrodes according to any one of the preceding items 1 to 4, which is used as an anode material for medium pressure or high pressure.

(6) An electrode material for an electrolytic capacitor, wherein the aluminum material according to any one of items 1 to 4 is etched.

(7) The electrode material for an electrolytic capacitor as described in 6 above, wherein at least a part of the etching is performed by direct current electrolytic etching.

(8) The electrode material for electrolytic capacitors as described in (6) or (7) above, which is further subjected to chemical conversion treatment.

(9) The electrode material for electrolytic capacitors as described in 8 above, which is used as an anode material.

(10) An aluminum electrolytic capacitor characterized in that the electrolytic capacitor electrode material according to (8) or (9) is used.

  According to the invention described in the preceding item (1), the lightness index (L value) in the Lab system measured by a predetermined method of the aluminum material after the evaluation etching under a predetermined condition has a pretreatment time of 30 seconds. 25 to 56 or less, or 27 to 58 or less when the pretreatment time is 45 seconds, so that the solubility of the surface layer of the aluminum material at the time of etching is uniform and excellent in etching characteristics, and thus electrostatic It can be made of an aluminum material for electrolytic capacitor electrodes having a large capacity.

  According to the invention described in item (2) above, the lightness index (L value) satisfies both 25 and 56 when the preprocessing time is 30 seconds, and 27 and 58 when the preprocessing time is 45 seconds. Therefore, the aluminum material for electrolytic capacitor electrodes can be made further excellent in etching characteristics.

  According to the invention described in the above item (3), since it contains 10 mass ppm or more and 150 mass ppm or less of Cu, it can be formed as an aluminum material for electrolytic capacitor electrodes having further excellent etching characteristics.

  According to the invention described in item (4) above, since the aluminum purity of the aluminum material is 99.9% by mass or more, deterioration of etching characteristics due to impurities can be prevented.

  According to the invention described in the above item (5), the anode material for intermediate pressure or high pressure excellent in etching characteristics can be obtained.

  According to the invention described in item (6), the electrode material for an electrolytic capacitor having a large capacitance can be obtained by etching.

  According to the invention described in item (7) above, since at least a part of the etching is performed by direct current electrolytic etching, a large number of deep and thick tunnel-like pits are generated, and electrolysis having a large capacitance is performed. Capacitor electrode material can be used.

  According to the invention described in item (8), since chemical conversion treatment is further performed after etching, an electrode material for an electrolytic capacitor suitable as an anode material can be obtained.

  According to the invention described in item (9) above, it can be formed as an anode material for electrolytic capacitors having a high electrostatic capacity.

  According to the invention described in item (10) above, an aluminum electrolytic capacitor having a high capacitance can be obtained.

It is a perspective view for demonstrating the arrangement conditions of the sample for L value measurement.

1 Aluminum material 4 Beam bundle 5 Central optical path

  The inventor of the present application, in the aluminum material for electrolytic capacitor electrodes, the Pb content of the aluminum material is 0.3 mass ppm or more and 2.5 mass ppm or less, and the aluminum material after the final annealing is pretreated for a predetermined time, after being immersed in an acid, If the brightness index (L value) of the foil obtained by time electrolytic etching (etching for evaluation) is within a certain range, pretreatment, primary etching (formation of tunnel-like pits by electrolytic etching), secondary etching (tunnel-like) It has been found that the capacitance of the aluminum material subjected to chemical conversion treatment is improved as necessary after performing the treatment of increasing the diameter of the pits and increasing the area.

  The L value measurement of the etched foil for evaluation can be used as an evaluation method for the aluminum material after the final annealing. When the L value of the aluminum material after the etching for evaluation is low, it means that there is little generation of etch pits, or etch pits are concentrated locally. In addition, when the L value is too large, melting of the aluminum surface is prioritized over pit generation. Therefore, if the L value is too small, the pit dispersibility is poor, and if it is too large, the aluminum material is lost due to the surface dissolution, so the inventors of the present application set the etching conditions for evaluation for evaluating the etch pit dispersibility and the surface solubility. We have studied and have come up with an appropriate range of L values for improving capacitance.

  It was also found that the capacitance is further improved by optimizing the Cu concentration that affects the amount of aluminum material dissolved and the initial pit formation during electrolytic etching.

  Below, the aluminum material for electrolytic capacitors is demonstrated in detail.

  The purity of the aluminum material is not particularly limited as long as it is within the range used for the electrolytic capacitor electrode, but the purity is preferably 99.9% by mass or more, particularly preferably 99.95% by mass or more. In the present invention, for convenience, the aluminum purity of the aluminum material is a value obtained by subtracting the total concentration (mass%) of Fe, Si and Cu from 100 mass%.

  Pb is concentrated on the surface of the aluminum material at the time of final annealing and greatly affects the formation of etch pits. When tunnel-like etch pits are generated by a direct current etching method, if Pb is too small, etch pit dispersibility is poor, and if it is too large, surface dissolution of the aluminum material increases. In the present invention, the Pb content is defined as 0.3 mass ppm or more and 2.5 mass ppm or less in order to exert the effect of improving the etching characteristics by heating the aluminum material in the oxidizing atmosphere. Further, the Pb content is preferably 0.4 mass ppm or more and 1.8 mass ppm or less, and particularly preferably 0.5 mass ppm or more and 1.2 mass ppm or less.

  Further, in order to further improve the dispersibility of etch pits, it is preferable that Cu of 10 mass ppm or more and 150 mass ppm or less is contained. If the Cu content is less than 10 ppm by mass, the dispersibility of the etch pits may be insufficient, and if it exceeds 150 ppm by mass, the loss of dissolution of the aluminum material during electrolytic etching may increase and the capacitance may decrease. is there. Further, the Cu content is preferably 15 ppm or more and 100 ppm or less.

  Etching for evaluation of the aluminum material after final annealing and L value measurement are performed as follows.

As a pretreatment, the aluminum material was immersed in an aqueous solution of phosphoric acid at 50 ° C. and 2 mol / L for 30 seconds or 45 seconds, washed with water, and subjected to direct current electrolytic etching for 3 seconds at a current density of 0.4 A / cm ^{2 in the} electrolyte solution shown below. Washing with water and drying to obtain an aluminum material for L value measurement.

Electrolyte composition: hydrochloric acid 1.0 mol / L, sulfuric acid 2.7 mol / L, aluminum sulfate 1.0 mol / L (added as aluminum sulfate hydrated water)
Electrolyte temperature: 82 ℃
A carbon electrode is installed as a counter electrode on both sides of the aluminum material with a distance of 17 mm from the aluminum material, and double-sided etching is performed (current density is the value per projected area of the aluminum material). The projected area of the aluminum material is the same as the cross-sectional area when the intermediate portion in the thickness direction of the aluminum material is cut in parallel with the surface of the aluminum material.

  Next, the lightness index (L value) according to the Lab system of the aluminum material for L value measurement subjected to the etching for evaluation is measured by the following method.

Optical conditions: 45-n (condition a described in JIS Z 8722 5.3.1)
Color measurement condition: C light 2 ° field of view Sample arrangement condition: As shown in FIG. 1, the aluminum material 1 as a sample is a normal line of a surface including the optical path 5 at the center of a light beam 4 for measurement, Measurement is performed by arranging the normal line Y included in the sample surface and the rolling direction X of the sample (aluminum material) 1 to be perpendicular to each other. In FIG. 1, reference numeral 2 denotes a light source (light emitting unit) that illuminates the sample 1 with a measuring beam, and 3 denotes a light receiving unit that receives reflected light from the sample 1.

  The Hunter color difference, that is, the color difference (ΔE) in the Lab system is calculated by the following equation.

ΔE = [(Δa) ² + (Δb) ² + (ΔL) ² ] ^1/2
Here, Δa, Δb, and ΔL are differences between a, b, and L of the two colors.

    The relationship between L, a, b and tristimulus values X, Y, Z is as follows.

L = 10Y ^1/2
a = 17.5 (1.02XY) / Y ^1/2
b = 7.0 (Y-0.847 Z) / Y ^1/2
In the present invention, the lightness index (L value) of the aluminum material after the above-described etching for evaluation is at least one of 25 to 56 when the pretreatment time is 30 seconds, and 27 to 58 when the pretreatment time is 45 seconds. Is defined as satisfying When the pretreatment time is 30 seconds, if the L value is less than 25, the dispersibility of the etch pits is poor, and if it exceeds 56, the surface dissolution is large and the number of etch pits is small. Electric capacity decreases. The reason why the L value when the preprocessing time is 45 seconds is defined as described above is the same as that when the preprocessing time is 30 seconds. Furthermore, when the L value satisfies both of 25 to 56 when the pretreatment time is 30 seconds and 27 to 58 when the pretreatment time is 45 seconds, the electrostatic capacity is further increased, which is preferable.

  When the pretreatment time is 30 seconds, the range of the L value is more preferably 30 to 53, and particularly preferably 33 to 45.

  When the pretreatment time is 45 seconds, the range of the L value is more preferably 30 to 55, and particularly preferably 40 to 53.

  Furthermore, it is preferable that the L value satisfies both of 30 and 53 or less when the pretreatment time is 30 seconds, and 30 or more and 55 or less when the pretreatment time is 45 seconds, and in particular, the pretreatment time is 30 seconds. It is preferable to satisfy both of 33 to 45 in the case, and 40 to 53 in the case where the pretreatment time is 45 seconds.

  Below, an example of the manufacturing method of the aluminum material for electrolytic capacitor electrodes is shown.

  As an example of the manufacturing method, it is carried out in the order of adjustment of melting components of aluminum material, slab casting, hot rolling, cold rolling, cold rolling including finish cold rolling (low pressure rolling), and final annealing, and after cold rolling. A method of performing heating in an oxidizing atmosphere before final annealing can be exemplified. In addition, it is preferable to perform washing before heating in an oxidizing atmosphere after completion of cold rolling. Moreover, in the middle of the cold rolling process, intermediate annealing is performed as necessary in order to increase the cube orientation occupation ratio after the final annealing. A tensile strain may be applied instead of the finish cold rolling. The method for imparting tensile strain is not particularly limited, but the method described in WO2004 / 003248A1 can be applied.

  As the cleaning liquid used for cleaning the aluminum material, an organic solvent, water to which a surfactant is added, an alkaline aqueous solution, or an acidic aqueous solution can be used. A mixture of a water-soluble organic solvent and water may also be used.

  When removing the aluminum material surface layer by washing, at least one of an alkaline aqueous solution and an acidic aqueous solution is used. In addition, a single cleaning solution may be used, and after an alkaline aqueous solution is used, the cleaning may be performed using an acidic aqueous solution.

  The organic solvent used for washing is not particularly limited, but examples include alcohols, diols, aromatic hydrocarbons such as toluene and xylene, alkane hydrocarbons, cyclohexane, ketones, ethers, esters, petroleum products, etc. It is done.

Examples of the alcohol include methanol (CH ₃ OH), ethanol (C ₂ H ₅ OH), 1-propanol (CH ₃ CH ₂ CH ₂ OH), 2-propanol (CH ₃ CH (OH) CH ₃ ), 1-butanol (CH ₃ CH ₂ CH ₂ CH ₂ OH), 2-butanol (CH ₃ CH ₂ CH (OH) CH ₃ ), 1-pentanol (CH ₃ CH ₂ CH ₂ CH ₂ CH ₂ OH), 2 -Pentanol (CH ₃ CH ₂ CH ₂ CH (OH) CH ₃ ) and the like are mentioned, and those represented by C _n H _{2n + 1} OH (n = 1 to 10 natural number) are preferred. An alicyclic compound such as cyclohexanol can also be used.

Examples of the diol include 1,2-ethanediol (HOCH ₂ CH ₂ OH), 1,2-propanediol (CH ₃ CH (OH) CH ₂ OH), 1,3-propanediol (HOCH ₂ CH ₂ CH ₂ OH).

Examples of the alkane hydrocarbons include pentane (C ₅ H ₁₂ ), hexane (C ₆ H ₁₄ ), heptane (C ₇ H ₁₆ ), octane (C ₈ H ₁₈ ), nonane (C ₉ H ₂₀ ), decane (C ₁₀ H ₂₂₎ which like is represented by C _n H _{2n + 2} include (a natural number of n = 5 to 15) are preferred. Moreover, application of alicyclic hydrocarbons such as cyclohexane is also possible.

Examples of the ketone include acetone (CH ₃ COCH ₃ ), 2-butanone (CH ₃ COC ₂ H ₅ ), 3-pentanone (CH ₃ CH ₂ COCH ₂ CH ₃ ), 3-methyl-2-butanone (CH ₃ COCH (CH ₃ ) ₂ ) and the like can be exemplified, and those represented by R1COR2 (R1 and R2: aliphatic hydrocarbon groups, and the total number of carbon atoms of R1 and R2 is 8 or less) are preferable. In addition, cyclic ketones such as cycloheticanone (C ₆ H ₁₀ O) may be used.

Examples of the ether include a substance represented by R1-O—R2 (R1 and R2: aliphatic hydrocarbon groups, and the total number of carbon atoms of R1 and R2 is 8 or less), 2-methoxyethanol (CH ₃ OCH ₂ CH ₂ OH), 2-ethoxyethanol (CH ₃ CH ₂ OCH ₂ CH ₂ OH), 2-butoxyethanol (CH ₃ CH ₂ CH ₂ CH ₂ OCH ₂ CH ₂ OH) 2- (2-ethoxy) ethoxy Also included are glycol ethers such as ethanol (CH ₃ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ OH).

Examples of the ester include acetate represented by CH ₃ COOR (R: an aliphatic hydrocarbon group having 1 to 5 carbon atoms).

  Examples of petroleum products include industrial gasoline (JIS K 2201), automotive gasoline (JIS K 2202), aviation gasoline (JIS K 2206), kerosene (JIS K 2203), light oil (JIS K 2204), petroleum ether (JIS K 8593), petroleum benzine (JIS K 8594), ligroin (JIS K 8937), kerosene and the like.

  The surfactant contained in the cleaning liquid obtained by adding a surfactant to water is not particularly limited, and an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used.

  As the anionic surfactant, sulfate ester salts and sulfonate salts can be used.

As the sulfate ester salt, R-OSO ₃ Na (R = saturated hydrocarbon group having 8 to 18 carbon atoms or unsaturated hydrocarbon group having one double bond) can be used, specifically sodium dodecyl sulfate. (C ₁₂ H ₂₅ OSO ₃ Na), sodium hexadecyl sulfate (C ₁₆ H ₃₃ OSO ₃ Na), sodium stearyl sulfate (C ₁₈ H ₃₇ OSO ₃ Na), sodium oleyl sulfate (C ₁₈ H ₃₅ OSO ₃ Na), etc. It can be illustrated.

The sulfonate is R-SO ₃ Na (R = saturated hydrocarbon group having 8 to 18 carbon atoms or unsaturated hydrocarbon group having one double bond) or sodium dodecylbenzenesulfonate (C ₁₂ H ₂₅ -C ₆ H ₄ -SO ₃ Na) and other R-SO ₃ Na (R: an alkylbenzyl group in which the alkyl group is a saturated hydrocarbon group having 8 to 14 carbon atoms or an unsaturated hydrocarbon group having one double bond) Can be used.

As a cationic surfactant, a quaternary ammonium salt represented by RN ⁺ (CH ₃ ) ₃ · Cl ⁻ (R = saturated hydrocarbon group having 8 to 16 carbon atoms) can be used.

As a nonionic surfactant, RO-(-CH ₂ CH ₂ O) _n H (R = saturated hydrocarbon group having 8 to 16 carbon atoms or unsaturated hydrocarbon group having one double bond, n = 6 -14) or _{RO - (- CH 2 CH 2} O) n H (R = alkyl group is an alkyl phenyl group which is unsaturated hydrocarbon group having one saturated hydrocarbon group or a double bond having 8 to 12 carbon atoms , N = 6 to 14), and a polyethylene glycol type nonionic surfactant can be exemplified. In addition, what has more n than the said range may be contained in the nonionic surfactant by the molar ratio of 50% or less.

  At least one of the above surfactants can be added to water and used as a cleaning liquid. A surfactant having a surfactant whose carbon number is less than the above range may be added in a molar ratio of 50% or less. In addition, when an anionic surfactant and a cationic surfactant are mixed in water, a precipitate is generated. Therefore, it is preferable to avoid mixing.

  The addition concentration of the surfactant is not particularly defined, but is preferably not less than the critical micelle concentration in order to exert the cleaning effect.

  Examples of the alkali in the alkaline aqueous solution used for washing include sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium orthosilicate, sodium metasilicate, trisodium phosphate and sodium carbonate, and were selected from these alkalis. One or more types can be dissolved in water and used as a cleaning solution.

  As the acid in the acidic aqueous solution used for washing, one or more selected from acids containing hydrochloric acid, sulfuric acid, nitric acid, and phosphorus elements are used. Examples of the acid containing phosphorus element include orthophosphoric acid (hereinafter referred to as phosphoric acid), pyrophosphoric acid, metaphosphoric acid, and polyphosphoric acid. Perchloric acid and hypochlorous acid may also be used.

  The surface layer removal amount of the aluminum material by the alkaline aqueous solution or the acidic aqueous solution is adjusted by adjusting the alkali or acid concentration, the temperature of the alkaline or acidic aqueous solution, and the contact time between the aluminum material and the alkaline or acidic aqueous solution. The Further, for the purpose of enhancing the cleaning effect of the aluminum material surface layer, a surfactant or a chelating agent may be added to the cleaning liquid.

  The removal amount of the aluminum material surface layer by the washing is preferably an average value of 1 nm or more and 500 nm or less per one side of the aluminum material. If the surface layer removal amount is less than 1 nm on average, there is a risk of insufficient removal of the oxide film on the aluminum material surface layer. If the surface layer is removed more than 500 nm, the formation of etch pit nuclei on the aluminum material surface layer is suppressed. As a result, the etching characteristics are poor and the capacitance may be reduced. A particularly preferable surface layer removal amount by washing is 1.5 nm or more and 200 nm or less, more preferably 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less per one surface of the aluminum material.

Although the aluminum surface layer oxide film and metal aluminum have different densities, the surface layer removal amount D (nm) of the aluminum material in this application is the mass loss E (g / cm ² ) per unit surface area due to cleaning and the aluminum. Using the density of 2.7 g / cm ³ , D (nm) = E × 10 ⁷ /2.7.

  A method for contacting the cleaning liquid with the aluminum material is not particularly limited, and examples include immersion, contact of the aluminum material with the surface of the cleaning liquid, and spraying.

  The heating method in the oxidizing atmosphere is not limited, and examples thereof include blast heating and radiation heating. Moreover, the form of the aluminum material to be heated is not particularly limited, and batch heating may be performed in a state where the coil is wound around the coil, or winding may be performed after the coil is rewound and continuously heated.

  The heating temperature of the aluminum material in the oxidizing atmosphere is preferably 50 to 400 ° C. When the heating temperature is less than 50 ° C., the solubility of the aluminum material surface layer at the time of etching the aluminum material after the final annealing becomes non-uniform. When the heating temperature exceeds 400 ° C., the surface oxide film of the aluminum material becomes too thick, so that the etching characteristics of the aluminum material after the final annealing deteriorate. The heating temperature of the particularly preferable aluminum material is 70 to 350 ° C.

  The heating time is preferably 3 seconds or more and 72 hours or less. If the heating time is less than 3 seconds, the solubility of the aluminum material surface layer becomes uneven when etching the aluminum material after the final annealing, and if the heating time exceeds 72 hours, the dissolution uniformity of the aluminum material surface layer is almost It will not change, and the cost will increase due to energy consumption during heating. A particularly preferable heating time is 10 seconds to 48 hours, particularly 70 seconds to 48 hours.

Appropriate conditions for the heating temperature and time in the oxidizing atmosphere are selected depending on the heating method. For example, when the aluminum material is heated in the state of being wound as a coil, it is preferably heated at 50 ° C. to 280 ° C. for 30 minutes to 72 hours. In addition, the heating time t (hour) when heating the aluminum material with the coil unwound or cut into a sheet is 10 / (1.44 × x ^1.5 ), where the heating temperature is x (° C.). ≦ t ≦ 72 is preferable, and 10 / (1.44 × x ^1.5 ) ≦ t ≦ 48 is more preferable.

  The oxygen concentration in heating the aluminum material in an oxidizing atmosphere is preferably 0.1% by volume or more. If the oxygen concentration is less than 0.1% by volume, the surface of the aluminum material may not be sufficiently oxidized during heating. The oxygen concentration is particularly preferably 1% by volume or more, particularly preferably 5% by volume or more, and air can be suitably used as the oxidizing atmosphere.

  The treatment atmosphere in the final annealing of the aluminum material is not particularly limited, but it is preferable to heat in an atmosphere with less moisture and oxygen so as not to increase the thickness of the oxide film. Specifically, it is preferable to heat in an inert gas such as argon or nitrogen or in a vacuum of 0.1 Pa or less. Moreover, hydrogen gas can also be suitably used as the atmosphere for final annealing.

  The cubic occupancy ratio of the aluminum material after the final annealing is preferably 90% or more.

  The method of final annealing is not particularly limited, and batch annealing may be performed in a state of being wound around the coil, and the coil may be rewound and continuously annealed, and then wound on the coil, and at least batch annealing and continuous annealing may be performed. Any one of them may be performed a plurality of times.

  Although the temperature and time during annealing are not particularly limited, for example, when performing batch annealing, it is preferable to perform annealing at 450 to 600 ° C. for 10 minutes to 50 hours. If the temperature is less than 450 ° C. and the time is less than 10 minutes, a surface on which etch pits are uniformly generated may not be obtained. On the other hand, when the annealing temperature exceeds 600 ° C., the aluminum material is likely to be adhered, and even if annealing is performed for more than 50 hours, the surface expansion effect by etching is saturated, and the heat energy cost is increased. In particular, it is preferably annealed at 460 to 570 ° C. for 20 minutes to 40 hours.

  The temperature raising rate / pattern is not particularly limited, and may be raised at a constant rate, may be stepped up and cooled while repeating the temperature raising and temperature holding, and is 450 to 600 ° C. in the annealing process. It may be annealed in the temperature range for a total of 10 minutes to 50 hours.

  Processes and process conditions other than those specified in the present invention are not particularly limited, and may be performed according to a conventional method. Moreover, the manufacturing method of an aluminum material is changed suitably according to the relationship with the etching conditions of an aluminum material.

  The thickness of the aluminum material for electrolytic capacitor electrodes obtained after the final annealing is not particularly defined. Those having a thickness of 200 μm or less, referred to as foil, and those having a thickness larger than that are also included in the present invention.

  The aluminum material that has undergone final annealing is subjected to an etching process in order to improve the surface expansion ratio. Etching conditions are not particularly limited, but preferably a direct current etching method is employed. By the direct current etching method, the portion that becomes the nucleus of the etch pit promoted in the annealing is deeply and thickly etched to generate a large number of tunnel-like pits, thereby realizing a high capacitance.

  After the etching treatment, a chemical conversion treatment is preferably performed to obtain an anode material. In particular, it is preferably used as an electrolytic capacitor electrode material for medium pressure and high pressure, but it does not preclude use as a cathode material. Moreover, the electrolytic capacitor using this electrode material can realize a large capacitance.

  Capacitance may be measured in accordance with a conventional method. For example, a chemically treated etched foil is measured at 120 Hz using a stainless steel plate as a counter electrode in an 80 g / L ammonium borate aqueous solution at 30 ° C. It can be illustrated.

  Examples of the present invention and comparative examples are shown below.

Aluminum slabs containing Fe, Si, Cu, and Pb listed in Table 1 were prepared. A plate obtained by hot rolling an aluminum slab was cold-rolled and subjected to intermediate annealing at 260 ° C. for 18 hours in a nitrogen atmosphere, followed by finish cold-rolling to obtain an aluminum material.
Example 1
The aluminum material after finish cold rolling of composition 6 in Table 1 is washed with n-hexane, heated in air at 240 ° C for 6 hours, and further subjected to final annealing in argon at 540 ° C for 16 hours. To obtain an aluminum material for electrolytic capacitor electrodes.
Example 2
The aluminum after finish cold rolling of composition 6 in Table 1 was washed with 40 ° C., 0.2 mass% sodium hydroxide aqueous solution, 10 nm of the aluminum material surface layer was removed, and then heated in air at 200 ° C. for 6 hours. Furthermore, final annealing at 540 ° C. for 12 hours was performed in argon, to obtain an aluminum material for electrolytic capacitor electrodes.
Example 3
An aluminum material for electrolytic capacitor electrodes was obtained in the same manner as in Example 2 except that the composition of the aluminum material was composition 7 in Table 1.
Examples 4 to 20
After cleaning the aluminum material after finish cold rolling of compositions 1 to 13 in Table 1 using an acidic aqueous solution, an alkaline aqueous solution or an organic solvent, heating in an oxidizing atmosphere and final annealing in argon were carried out and evaluated. Aluminum materials for electrolytic capacitor electrodes having different L values after etching were obtained.
Comparative Examples 1 to 3
After cleaning the cold-rolled aluminum material of composition 3, composition 14, and composition 15 in Table 1, final annealing was performed in argon without heating in an oxidizing atmosphere to obtain an aluminum material for electrolytic capacitor electrodes. Obtained.

The aluminum material obtained in each of the above Examples and Comparative Examples was etched for evaluation by the following method, and the lightness index (L value) in the Lab system was measured by the method described below.
[Etching method for evaluation]
As a pretreatment, the aluminum material was immersed in a 2 mol / L phosphoric acid aqueous solution at 50 ° C for 30 seconds or 45 seconds, washed with water, and then subjected to DC electrolytic etching for 3 seconds at a current density of 0.4 A / cm ^{2 in the} electrolyte shown below. The aluminum material which was washed with water, dried and etched for evaluation was obtained.

Electrolyte composition: hydrochloric acid 1.0 mol / L, sulfuric acid 2.7 mol / L, aluminum sulfate 1.0 mol / L (added as aluminum sulfate hydrated water)
Electrolyte temperature: 82 ℃
A carbon electrode is installed as a counter electrode on both sides of the aluminum material, with a distance of 17 mm from the aluminum material, and double-sided etching (current density is the value per projected area)
[Measurement Method of Lightness Index (L Value) by Lab System for Aluminum Material Etched for Evaluation]
The measurement was performed under the following conditions using SC-3-CH manufactured by Suga Test Instruments Co., Ltd.

Optical conditions: 45-n (condition a described in JIS Z 8722 5.3.1)
Color measurement condition: C light 2 ° field of view Sample measurement part: Circle with a diameter of 30 mm Sample installation method: Normal of the surface including the optical path at the center of the light bundle, the normal contained in the sample surface, and the rolling direction Place the sample so that is vertical.

  Table 2 shows the measured brightness index (L value).

The aluminum material after the final annealing obtained in each of the above Examples and Comparative Examples was immersed in a phosphoric acid aqueous solution at 50 ° C. and 2 mol / L for 30 seconds or 45 seconds as a pretreatment for etching, and then washed with water. DC electrolytic etching is performed for 120 seconds at a current density of 0.4 A / cm ^{2 in the} same electrolytic solution as the evaluation etching performed for index (L value) measurement to form tunnel-like pits. It was immersed in a solution at 90 ° C. having the same liquid composition to thicken the etch pit. The obtained etched foil was subjected to chemical conversion treatment according to the EIAJ standard at a chemical conversion voltage of 270 V to obtain a sample for measuring capacitance.

  Table 2 shows the relative capacitance when the capacitance of the pretreatment 30 seconds and 45 seconds of Comparative Example 1 is taken as 100.

  As described above, the Pb content is 0.3 mass ppm or more and 2.5 mass ppm or less, and the lightness index (L value) in the Lab system measured by the above-described method of the aluminum material after the above-described evaluation etching is pre-processed. By satisfying at least one of 25 to 56 when the time is 30 seconds, or 27 to 58 when the pretreatment time is 45 seconds, an aluminum material for electrolytic capacitor electrodes having excellent etching characteristics can be obtained. it can.

  In addition, the example in which the Cu content is 10 ppm or more and 150 ppm or less has a higher capacitance than the example in which the Cu content is less than 10 ppm or more than 150 ppm.

  On the other hand, since Comparative Example 1 has a lightness index (L value) outside the range specified in the present application, the capacitance is lower than that of the example. In Comparative Example 2, the Pb content and the L value are less than the lower limits specified in the present invention, and in Comparative Example 3, the Pb content and the L value exceed the upper limits specified in the present invention.

Claims (10)

The lightness index (L value) in the Lab system measured by the method shown below of the aluminum material after etching for evaluation shown below having a Pb content of 0.3 mass ppm to 2.5 mass ppm, the pretreatment time is 30 An aluminum material for electrolytic capacitor electrodes satisfying at least one of 25 to 56 in the case of seconds, or 27 to 58 in the case of a pretreatment time of 45 seconds.
[Etching method for evaluation]
As a pretreatment, the aluminum material is immersed in a 2 mol / L phosphoric acid solution at 50 ° C for 30 or 45 seconds, then washed with water, and DC electrolytic etching for 3 seconds at a current density of 0.4 A / cm ^{2 in the} electrolyte shown below. Wash with water and dry.
Electrolyte composition: hydrochloric acid 1.0 mol / L, sulfuric acid 2.7 mol / L, aluminum sulfate 1.0 mol / L (added as aluminum sulfate hydrated water)
Electrolyte temperature: 82 ℃
A carbon electrode is installed as a counter electrode on both sides of the aluminum material at a distance of 17 mm from the aluminum material, and double-sided etching (current density is the value per projected area of the aluminum material)
[Measurement method of lightness index (L value) by Lab system]
Optical conditions: 45-n (condition a described in JIS Z 8722 5.3.1)
Color measurement condition: C light 2 ° field of view Sample placement condition: The normal of the surface including the optical path at the center of the light bundle, and the sample normal so that the rolling direction is perpendicular to the normal contained in the sample surface Place and measure.   The aluminum material for electrolytic capacitor electrodes according to claim 1, wherein the lightness index (L value) satisfies both of 25 to 56 when the pretreatment time is 30 seconds and 27 to 58 when the pretreatment time is 45 seconds. .   The aluminum material for electrolytic capacitor electrodes according to claim 1 or 2, comprising Cu of 10 mass ppm to 150 mass ppm.   The aluminum material for electrolytic capacitor electrodes according to any one of claims 1 to 3, wherein the aluminum material has an aluminum purity of 99.9% by mass or more.   The aluminum material for electrolytic capacitor electrodes according to any one of claims 1 to 4, which is used as an anode material for medium pressure or high pressure.   An electrode material for an electrolytic capacitor, wherein the aluminum material according to any one of claims 1 to 4 is etched.   The electrode material for electrolytic capacitors according to claim 6, wherein at least a part of the etching is performed by direct current electrolytic etching.   The electrode material for electrolytic capacitors according to claim 6 or 7, further subjected to chemical conversion treatment.   The electrode material for electrolytic capacitors according to claim 8, which is used as an anode material.   An aluminum electrolytic capacitor, wherein the electrolytic capacitor electrode material according to claim 8 or 9 is used.

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