JPH08227829A - Aluminum foil for electrolyc capacitor electrode - Google Patents

Abstract

PURPOSE: To provide the aluminum foil for an electrolytic capacitor electrode, which can stably obtain the electrode foil (especially an anode foil for a high voltage) having the high electrostatic capacitance. CONSTITUTION: The aluminum impurity of this aluminum foil for an electrolytic capacitor is 99.9wt.% or more. Furthermore, the elements of 0.0010-0.0100wt.% of Fe, 0.0015-0.0150wt.% of Si and 0.0001-0.0050wt.% of Cu and other inevitable impurity elements are contained. The amount of the deposition of Fe is specified to the range of 10-70% of the content of Fe. With respect to the amount of the deposition of Fe, errors and the like are not generated by a thermal phenol dissolution method, and the amount is accurately measured. It is preferable that the amount of deposition of Si is specifed in the range of 5-50% with respect to the content of Si. It is preferable that the amount of deposition of Cu is specified in the range of 1-20% with respect to the sum of the amounts of deposition of Fe, Si and Cu.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum foil for an electrolytic capacitor electrode, which can obtain an electrode foil for an electrolytic capacitor having a high electrostatic capacity (particularly, a high voltage anode foil).

[0002]

2. Description of the Related Art Conventionally, in order to manufacture an electrode foil for an electrolytic capacitor, an aluminum foil for an electrolytic capacitor electrode is subjected to an etching treatment to form a large number of fine holes (etching pits) on the foil surface. The surface area of is being expanded. This expansion of the surface area is the most effective method for increasing the capacitance of the electrode foil for electrolytic capacitors. Therefore, in order to obtain an electrode foil for an electrolytic capacitor having a high capacitance, it is necessary to manufacture using an aluminum foil for an electrolytic capacitor electrode having good etching characteristics. On the other hand, as the etching treatment, various etching methods are adopted so that etching pits suitable for the withstand voltage used can be obtained. For example, for high voltage anode foil,
It is preferable that a tunnel-shaped etching pit is formed, and a DC etching method is adopted as an etching method suitable for this.

One of the means for improving the electrostatic capacity of the high voltage anode foil is to increase the density of the tunnel-shaped etching pits. To increase the density of tunnel-shaped etching pits, it is necessary to form tunnel-shaped etching pits vertically from the aluminum foil surface in the depth direction, and the diameter of one etching pit must not be blocked by the withstand voltage film. It is to be the diameter of. In order to form etching pits perpendicularly to the depth direction from the surface of the aluminum foil, it is necessary to increase the proportion of crystal grains having a cubic orientation in all the crystal grains of the aluminum foil before direct current etching. That is, the foil surface is (10
It is advisable to form a large number of crystal structures parallel to the (0) plane (this is called a crystal grain having a cubic orientation) with respect to all the crystal grains in the aluminum foil. For the crystal grains having such a cubic orientation, the conditions for homogenization treatment, hot rolling, primary cold rolling, intermediate annealing, secondary cold rolling and final annealing during the production of aluminum foil should be appropriately selected. According to this, a large amount can be formed in the aluminum foil. In particular, a large amount can be formed by reducing the secondary cold rolling to a low rolling rate or by setting the temperature of final annealing to a relatively high temperature.

The production rate of crystal grains having this cubic orientation is governed by the solid solution / precipitation state of impurities. For example, in Japanese Examined Patent Publication No. 3-63333, the precipitation amount of either Fe or Si in an aluminum foil is
It is taught that when the content is regulated to 10 to 70%, the etching characteristics are improved. Japanese Patent Publication No. 3-61333 does not specify the principle of improving the etching characteristics, but eventually, many crystal grains having a cubic orientation are generated depending on the precipitation state of impurities, and the etching characteristics are improved. It is presumed that it is based on the principle. However, in this prior art, the precipitation amount of Fe or Si is measured by the electric resistance method, and there are the following defects. (I) In the electric resistance method, the electric resistance value increases or decreases due to the influence of all the elements precipitated in the aluminum foil, and it is extremely difficult to measure the precipitation amount of only Fe or the precipitation amount of only Si. there were. Therefore, if the aluminum foil contains only Fe or Si, other Cu, Zn,
When an element such as Mn is contained, the amount of precipitation of only Fe or Si cannot be actually measured. (I
i) Regarding the amount of decrease in electric resistance value due to the amount of precipitation of Fe or Si, a definite value is not known. Therefore, it is actually difficult to know the precipitation amount of Fe or Si by increasing or decreasing the electric resistance value. In addition, S measured at 20 ° C.
Regarding the decrease amount of the electric resistance value due to the precipitation amount of i (or the increase amount of the electric resistance value due to the solid solution amount of Si), the value has not been determined yet (Publication “Light Metal”, 1985, Vol. 35, No. 3).
See No. 162-167, entitled "Effects of Silicon, Iron, and Silicon Coexistence on Recrystallization of Aluminum," especially page 163, left column, lines 5-8. ). That is, it is practically impossible to know the precipitation amount of Fe or Si in the aluminum foil containing various impurity elements by the electric resistance method.
Therefore, it is practically impossible to manufacture an aluminum foil for electrolytic capacitor electrodes by which the electrode foil for electrolytic capacitor having high capacitance can be stably obtained by the method described in Japanese Patent Publication No. 3-61333. Met.

[0005]

Therefore, the inventor of the present invention
Various studies were conducted by adopting a method capable of measuring the amount of each element deposited in the aluminum foil. As a result, the aluminum foil in which Fe is deposited at a constant ratio with respect to the content of Fe has good etching characteristics (particularly, tunnel-like etching pit generation characteristics) and has a high capacitance. The inventors have found that a capacitor electrode foil (in particular, a high voltage anode foil) can be stably manufactured, and have reached the present invention. Furthermore, with respect to the Si content, Si
Aluminum foil in which a certain proportion is deposited, or F
Even for aluminum foil in which Cu is deposited at a constant ratio with respect to the total amount of deposited e, Si, and Cu, the etching characteristics are improved, and the electrode foil for electrolytic capacitors having high capacitance is stabilized. They have found that they can be manufactured and have reached the present invention.

[0006]

That is, according to the present invention, the aluminum purity is 99.9% by weight or more, and Fe: 0.
0010 to 0.0100% by weight, Si: 0.0015 to
0.0150% by weight, Cu: 0.0001 to 0.005
It is characterized by containing 0% by weight and other unavoidable impurity elements, and the precipitation amount of Fe measured by the hot phenol dissolution method is regulated in the range of 10 to 70% with respect to the Fe content. The present invention relates to an aluminum foil for electrolytic capacitor electrodes. In addition to the above-mentioned conditions, the amount of deposited Si is regulated within the range of 5 to 50% relative to the content of Si, the aluminum foil for electrolytic capacitor electrodes, or the amount of deposited Cu is Fe, The present invention relates to an aluminum foil for electrolytic capacitor electrodes, which is regulated in the range of 1 to 20% with respect to the total amount of deposited Si and Cu.

First, the premise of the present invention is that the aluminum purity of the electrolytic capacitor electrode aluminum foil is 99.9% by weight or more.
If the purity is less than 99.9% by weight, the amount of impurities becomes relatively large, and no matter how the precipitation amount of each Fe, Si and / or Cu is regulated, the existence of precipitates due to other impurity elements However, over-dissolution tends to occur during etching, and the surface area cannot be sufficiently expanded. Further, when the impurities are excessively contained, the generation ratio of crystal grains having a cubic orientation becomes small, or the growth of crystal grains having a cubic orientation cannot be achieved, and it becomes difficult to obtain tunnel-shaped etching pits. Therefore, it is difficult to obtain an aluminum foil for an electrolytic capacitor electrode having good etching characteristics, and it is difficult to obtain an electrode foil for an electrolytic capacitor having a high capacitance, which is not preferable.

Fe is contained in the aluminum foil for electrolytic capacitor electrodes in an amount of 0.0010 to 0.0100% by weight, preferably 0.0015 to 0.0040% by weight. If the Fe content is less than 0.0010% by weight, the aluminum foil becomes highly pure and expensive, which is not preferable.
Further, the amount of Fe becomes too small, and it becomes difficult to precipitate Fe within the range regulated in the present invention. On the other hand, when the Fe content exceeds 0.0100% by weight, it is easy to set the Fe precipitation amount within the range regulated in the present invention, but the absolute Fe precipitation amount increases and the cubic orientation becomes relatively large. It is not preferable because the proportion of the crystal grains having γ is reduced and the proportion of the tunnel-shaped etching pits is reduced. Furthermore, since the absolute amount of precipitated Fe is large, overdissolution tends to occur during etching, and it becomes difficult to obtain an electrode foil for an electrolytic capacitor having a high electrostatic capacity, which is not preferable.

In the aluminum foil for electrolytic capacitor electrodes, Si is contained in an amount of 0.0015 to 0.0150% by weight,
It is preferably contained in an amount of 0.0015 to 0.0050% by weight. If the Si content is less than 0.0015% by weight, the aluminum foil becomes highly pure and expensive, which is not preferable. On the other hand, when Si exceeds 0.0150% by weight, the absolute amount of precipitated Si increases and overmelting easily occurs during etching, which makes it difficult to obtain an electrode foil for electrolytic capacitors with high capacitance. Not preferable.

Further, the aluminum foil for electrolytic capacitor electrodes contains 0.0001 to 0.0050% by weight of Cu. If the Cu content is less than 0.0001% by weight, the amount of Cu becomes too small and the etching characteristics tend to deteriorate, which is not preferable. On the other hand, when Cu exceeds 0.0050% by weight, the absolute amount of precipitated Cu increases and overmelting easily occurs during etching, making it difficult to obtain an electrode foil for electrolytic capacitors with high capacitance. Not preferable. The aluminum foil for electrolytic capacitor electrodes according to the present invention may contain other impurity elements such as Zn and Mn.

In the aluminum foil for electrolytic capacitor electrodes according to the present invention, Fe is deposited at a constant quantitative ratio with respect to the Fe content. That is, with respect to the Fe content,
The Fe precipitation amount is 10 to 70%, preferably 20 to 50%.
If this amount of precipitation is less than 10%, the starting point of etching is reduced, and many etching pits are not formed,
It becomes difficult to obtain an electrode foil for an electrolytic capacitor having a high capacitance. On the other hand, if the precipitation amount of Fe is less than 10%, the formation ratio of crystal grains having a cubic orientation decreases, and it becomes difficult to form many tunnel-shaped etching pits, which is not preferable. On the contrary, the total amount of precipitation is 70
If it exceeds%, over-dissolution occurs during etching, the surface area cannot be sufficiently expanded, and it becomes difficult to obtain an electrode foil for an electrolytic capacitor having high capacitance. In addition, the leakage current tends to increase after the chemical conversion treatment, which is not preferable.

Further, in the present invention, it is preferable to control the amount of Si deposited in the range of 5 to 50% with respect to the content of Si. If the amount of Si deposited is less than 5%, the starting point of etching is reduced, and the etching characteristics tend to be deteriorated. On the other hand, when the amount of Si deposited exceeds 50%, there are too many Si deposits, and overdissolution tends to occur.
It tends to be impossible to increase the surface area. Also, Si
If there are too many precipitates, it may hinder the growth of crystal grains having a cubic orientation, or the leakage current tends to increase after the chemical conversion treatment. Note that Si may be precipitated alone or in the form of Al—Fe—Si compound. Therefore, whether it is in the form of an Al-Fe-Si-based compound, elemental Si, or both are present, in short, S of the total weight of the precipitated Si element is
Indicates the ratio to the i content.

Further, in the present invention, the amount of Cu deposited is 1 to the total amount of Fe, Si and Cu deposited.
It is preferable to regulate it in the range of 20%, particularly 1 to 10
It is more preferable to regulate the content in the range of%. Cu is an element that easily forms a solid solution in aluminum, and when it forms a solid solution, the natural electrode potential of the aluminum matrix increases, and the etching characteristics improve. However, Cu
If the solid solution amount of Cu is too large, it may cause overdissolution at the time of etching, or may hinder the growth of crystal grains having a cubic orientation, and it tends to be difficult to increase the surface area. Is preferred. Also, C
Since the u precipitate itself exhibits a noble potential, even if there are many Cu precipitates, overdissolution may occur. Therefore, the amount of Cu deposited is preferably regulated to 20% or less.

In the present invention, the amounts of Fe, Si and Cu deposited are measured by the hot phenol dissolution method described below. The basic idea of the hot phenol dissolution method is as follows. That is, when the aluminum foil is dissolved in phenol heated to about 443 K, aluminum other than the precipitate and each element dissolved in the aluminum are easily dissolved. After that, the undissolved precipitate was filtered through a filter having an appropriate pore size, the precipitate collected on the filter was dissolved in a hydrochloric acid solution, and this solution was quantitatively analyzed to obtain Fe, Si, The amount of individual precipitation of Cu is measured. The specific measurement method when the hot phenol dissolution method is adopted is as follows. First, the aluminum foil prepared by various methods is cut into a proper size and collected, and the impurities attached during the cutting are removed by a suitable pretreatment method. This removal method includes:
For example, a method of washing with a sodium hydroxide solution, ethanol or the like is adopted. Then, a certain volume of phenol is weighed and heated to 443 to 453 K while refluxing so that it does not evaporate and decrease. The prepared aluminum foil is put into this heated phenol to dissolve the aluminum and each element that forms a solid solution in the aluminum. After that, phenol coagulates at a temperature of about 313K, so a certain amount of benzyl alcohol was added to the phenol, and while maintaining the liquid state, the aluminum-dissolved phenol was filtered using a filter with an appropriate pore size. To do. Then, the precipitate collected on the filter is dissolved with a hydrochloric acid solution having a constant concentration. This solution is analyzed by a method such as an atomic absorption method or an ICP emission analysis method to measure the content of each element. As described above, the amounts of Fe, Si and Cu deposited in the prepared aluminum foil can be obtained. And the precipitation amount of each element,
It is possible to calculate the precipitation ratio of Fe, Si, and Cu in the present invention by using the content of each element contained in the aluminum foil.

The particle size distribution can be determined by collecting each precipitate on the filter by the hot phenol dissolution method. That is, the precipitate collected on the filter is observed with a scanning electron microscope, and the result is image-analyzed to obtain the particle size distribution. Then, when the present inventor studied this particle size distribution, when the number of precipitates of 2 μm or less accounted for 50% or more of the total number of precipitates, the etching characteristics tended to be improved. . 2 μm
When the number of the following precipitates is less than 50% of the whole, it is considered that the etching starting point is reduced and the etching characteristics are deteriorated. When manufacturing an anode foil for electrolytic capacitor high voltage, it is required to form a large number of tunnel-shaped etching pits having an appropriate diameter according to the withstand voltage used on the foil surface. It is preferably as small as possible. That is, a precipitate having a size of more than 2 μm causes the formation of tunnel-shaped etching pits having a relatively large diameter at the time of etching, and the pit density tends to decrease, which may make it difficult to form a large number of tunnel-shaped etching pits. There is.

Further, in the present invention, the average crystal grain size in the aluminum foil is preferably 0.02 to 5 mm. Etching pits are often formed from crystal grain boundaries at the initial stage of etching, and therefore, the smaller the crystal grain size, the more etching pits are formed, which contributes to the increase in surface area. That is, if the average crystal grain size exceeds 5 mm, the pit density becomes low, many etching pits are not formed, and the surface area tends not to be sufficiently expanded. However, if the crystal grain size is too small, the formed etching pits coalesce with each other and fall out, resulting in a decrease in the surface area. That is, when the average crystal grain size is less than 0.02 mm, the surface area tends to gradually decrease. The average crystal grain size is JIS G
Measurement is repeated several times by the method specified in 0501 (Cutting method of grain size test method for copper alloy products), and the average value is calculated.

Further, there is a relationship between the size of crystal grains and the generation rate of crystal grains having a cubic orientation, in general, the larger the crystal grain size, the lower the production rate of crystal grains having a cubic orientation. . That is, as the crystal grain before the final annealing is larger, the grain size of the crystal grain other than the crystal grain having the cubic orientation is also large, so that the growth of the crystal grain having the cubic orientation is hindered in the final annealing step. In the present invention, the crystal grains having a cubic orientation are 6 with respect to all the crystal grains.
It preferably accounts for 0% or more. If the proportion of crystal grains having a cubic orientation is less than 60%, the proportion of formation of tunnel-shaped etching pits tends to decrease, and the capacitance tends not to become sufficiently high. Recently, electrolytic capacitor anode foils used in disposable cameras and the like tend to prioritize low cost over high capacitance. Therefore, even for aluminum foil for electrolytic capacitor electrodes,
In many cases, there is no problem even if crystal grains having a cubic orientation are not produced at a high rate. It has also been reported that the presence of some crystal grains other than those having a cubic orientation has better overvoltage characteristics after chemical conversion treatment [Publication "Summary of the 87th Autumn Meeting of the Japan Institute of Light Metals". "A paper by Masaaki Fukuchi (Hokkaido Vocational Ability Development Junior College) entitled" Fine Texture of Aluminum Foil for Electrolytic Capacitors "on pages 285-286]. Therefore,
The proportion of crystal grains having a cubic orientation is generally 60%.
The above is preferable, but needless to say, it may be less than that.

As described above, the aluminum foil for electrolytic capacitor electrodes according to the present invention in which the amount of Fe deposited is regulated within a predetermined range, or the present invention in which the amount of Si and Cu deposited is further regulated within a predetermined range, if desired. As a method for producing such an aluminum foil for electrolytic capacitor electrodes, for example, after casting an aluminum ingot at a predetermined speed, homogenization treatment is performed at an appropriate temperature, and hot rolling or intermediate annealing is performed at a predetermined temperature. That method can be mentioned. In particular, by adjusting the temperature and time of homogenization treatment, the temperature and time of hot rolling, and the temperature and time of intermediate annealing and final annealing, the precipitation amount of Fe or the precipitation amount of Si and Cu can be controlled within a predetermined range. Can be regulated. When the aluminum foil for electrolytic capacitor electrodes thus obtained is subjected to an etching treatment under predetermined conditions, a large number of fine tunnel-shaped etching pits are formed on the foil surface, resulting in a high electrostatic capacitance with a large surface area. Thus, a capacitor electrode foil can be obtained. And this electrolytic capacitor electrode foil can be suitably used especially as a high voltage anode foil.

[0019]

【Example】

Example 1 Thickness 400 mm, Al purity 99.99% by weight, Fe:
0.0015% by weight, Si: 0.0020% by weight, C
u: 0.0030% by weight, and an aluminum ingot containing other unavoidable impurity elements was prepared. This aluminum ingot was subjected to homogenization treatment under the condition of 803K × 18Ks (530 ° C. × 5 hours). After that, hot rolling start temperature 7
83 K (510 ° C), hot rolling finish temperature 613 K (34
Hot rolling was performed at 0 ° C. Then, after performing a primary cold rolling by a conventional method, 503 K × 36 Ks (230 ° C. ×
Intermediate annealing was performed for 10 hours). Then, after performing secondary cold rolling by a conventional method, after degreasing and washing with an alkaline solution containing a surfactant, 803K × 54Ks (530
Final annealing was performed in a nitrogen atmosphere under the conditions of (° C. × 15 hours) to obtain a 0.1 mm thick aluminum foil for electrolytic capacitor electrodes.

Example 2 The intermediate annealing conditions were 523 K × 72 Ks (250 ° C. × 20).
An aluminum foil for an electrolytic capacitor electrode having a thickness of 0.1 mm was obtained in the same manner as in Example 1 except that the time was changed.

Example 3 The same method as in Example 1 was used except that the hot rolling was omitted, the homogenization treatment was performed, and then the material was gradually cooled and the primary cold rolling was performed until a predetermined thickness was obtained. An aluminum foil for an electrolytic capacitor electrode having a thickness of 0.1 mm was obtained.

Comparative Example 1 Between the hot rolling and the primary cold rolling, 633 K × 18 Ks
An aluminum foil for an electrolytic capacitor electrode having a thickness of 0.1 mm was obtained in the same manner as in Example 1 except that the intermediate annealing was inserted under the condition of (360 ° C. × 5 hours).

Comparative Example 2 The conditions for homogenization treatment were 873 K × 18 Ks (600 ° C. × 5
An aluminum foil for an electrolytic capacitor electrode having a thickness of 0.1 mm was obtained in the same manner as in Example 1 except that the time was changed.

The amounts of Fe, Si and Cu deposited on the five types of aluminum foil for electrolytic capacitor electrodes obtained by the methods of Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the hot phenol dissolution method, and The ratio of each precipitation amount described in 1 was determined. Further, the proportion of the deposits of 2 μm or less in each aluminum foil for electrolytic capacitor electrode was also obtained. The results are shown in Table 1. Further, the number of crystal grains having a cubic orientation with respect to the total number of crystal grains (cubic orientation ratio) and the average grain size were measured, and the results are shown in Table 1.
It was shown to. The cubic orientation ratio was measured by measuring the aluminum foil sample with hydrochloric acid: nitric acid: hydrofluoric acid = 50: 4.
After immersing in a solution having a volume ratio of 7: 3 for 15 seconds to reveal a crystal structure, the crystal structure was measured with an image analyzer.

Then, each aluminum foil for electrolytic capacitor electrode was subjected to etching treatment and chemical conversion treatment under the following conditions, and the electrostatic capacity (μF / cm ² ) was measured under the following conditions. [Etching process]: 348K (75 ° C) (5.3w
t. % HCl + 6.4 wt. % AlCl ₃ 6H ₂ O + 6.
9 wt. % H ₂ SO ₄ ) solution, the aluminum foil for electrolytic capacitor electrodes is dipped to obtain a current density of DC 0.2 A / cm
² for 400 sec. It was made to flow and the etching process was performed. [Chemical conversion treatment]: The aluminum foil after the etching treatment was cut into a size of 1 cm in width and 5 cm in length, and this one sheet was cut at a liquid temperature of 353 K (80 ° C.) (9 wt.% Boric acid + 0.1 wt.
% Ammonium pentaborate) aqueous solution and subjected to chemical conversion treatment under the conditions of 370 V for 30 minutes with sus 304 as the counter electrode. [Capacitance]: Electrode foil subjected to chemical conversion treatment (size width 1 cm x
One piece (length: 5 cm) has a weight of 7 wt. %
The counter electrode was immersed in an aqueous solution of ammonium pentaborate, and the counter electrode was used as an etched aluminum foil having a capacitance of 40,000 μF or more, and the capacitance (μF / cm ² ) was measured using an LCR meter in a 120 Hz series equivalent circuit. . In addition,
The electrostatic capacity (%) shown in Table 1 is 0.009% by weight of Fe, 0.001% by weight of Si, 0.005% by weight of Cu, and a purity of 99.99 containing other unavoidable impurity elements.
% Aluminum ingot was used and the aluminum foil obtained by the same method as in Example 1 was subjected to the above-mentioned etching treatment and chemical conversion treatment, and the electrostatic capacity was set to 100%, and a relative comparison was made. It was obtained in. In the aluminum foil used as the reference sample, the ratio of the precipitation amount of Fe to the content of Fe was 50%, the ratio of the precipitation amount of Si to the content of Si was 15%, and Fe, Si and C were used.
The ratio of the amount of Cu deposited to the total amount of u deposited is 5%,
The ratio of deposits of 2 μm or less to the total number of deposits is 9
0%, cubic orientation ratio 95%, average crystal grain size 0.5
mm.

[0026]

[Table 1]

Examples 4 to 7 Aluminum ingot No. 1 having the elemental composition shown in Table 2
In the same manner as in Example 1, except that 4 is used, a thickness of 0.1
An aluminum foil for an electrolytic capacitor electrode having a thickness of mm was obtained.

Examples 8 and 9 Aluminum ingots Nos. 3 and 4 (thickness 400 mm) having the elemental compositions shown in Table 2 were prepared. This aluminum ingot was subjected to a homogenization treatment under the conditions of 793 K × 36 Ks (520 ° C. × 10 hours). After that, the hot rolling start temperature is 743K (470 ° C) and the hot rolling end temperature is 543K (2
Hot rolling was performed at 70 ° C. Then, the hot-rolled sheet was subjected to primary intermediate annealing under the conditions of 653 K × 18 Ks (380 ° C. × 5 hours), and then subjected to primary cold rolling by a conventional method. After that, 523K × 36Ks (250 ° C ×
Secondary intermediate annealing was performed under the condition of 10 hours). Then, after performing secondary cold rolling by a conventional method, after degreasing and washing with an alkaline solution containing a surfactant, 803K × 54K
Final annealing was performed in a nitrogen atmosphere under the condition of s (530 ° C x 15 hours) to obtain an aluminum foil for electrolytic capacitor electrodes having a thickness of 0.1 mm.

Comparative Example 3 An aluminum ingot No. 5 having the elemental composition shown in Table 2 was used, and the homogenization treatment conditions were 793 K × 90 Ks.
(520 ° C. × 25 hours), and the same conditions as in Example 1 except that the hot rolling conditions were a hot rolling start temperature of 753 K (480 ° C.) and a hot rolling end temperature of 523 K (250 ° C.). An aluminum foil for an electrolytic capacitor electrode having a thickness of 0.1 mm was obtained.

Comparative Example 4 Ingot No. 2 having the elemental composition shown in Table 2
(Thickness 400 mm) was prepared. This aluminum ingot was subjected to homogenization treatment under the conditions of 873K × 18Ks (600 ° C. × 5 hours). After that, hot rolling start temperature 853
K (580 ° C.) hot rolling finish temperature 523 K (250
Hot rolling was performed at (.degree. C.). Then, after performing primary cold rolling by a conventional method, 523K × 18Ks (250 ° C. × 5
Intermediate annealing was performed. Then, after performing secondary cold rolling by a conventional method, after degreasing and cleaning with an alkaline solution containing a surfactant, 803K × 54Ks (530 ° C ×
15 hours) under the nitrogen atmosphere in the final annealing,
An aluminum foil for an electrolytic capacitor electrode having a thickness of 0.1 mm was obtained.

Comparative Example 5 The same method as in Example 8 was used except that the aluminum ingot No. 6 having the elemental composition shown in Table 2 was used, and the thickness was 0.1 m.
An aluminum foil for an electrolytic capacitor electrode of m was obtained.

[0032]

[Table 2]

With respect to the nine types of aluminum foil for electrolytic capacitor electrodes obtained by the methods according to Examples 4 to 9 and Comparative Examples 3 to 5, the amounts of Fe, Si and Cu deposited were measured by the hot phenol dissolution method, The ratio of each precipitation amount described in 3 was obtained. Further, the proportion of the deposits of 2 μm or less in each aluminum foil for electrolytic capacitor electrode was also obtained. The results are shown in Table 3. Further, the number of crystal grains having a cubic orientation with respect to the total number of crystal grains (cubic orientation ratio) and the average grain size were measured, and the results are shown in Table 3.
It was shown to. Then, each aluminum foil for electrolytic capacitor electrodes was subjected to etching treatment and chemical conversion treatment under the same conditions as in Example 1 to obtain a capacitance (μF / cm ² ).
Was measured and the results are shown in Table 3 by the same evaluation method as in Example 1.

[0034]

[Table 3]

As is clear from the results of Examples 1 to 9 and Comparative Examples 1 to 5 described above, the aluminum foil for electrolytic capacitor electrodes in which the precipitation amount of Fe is regulated within a specific range is used and the etching treatment is performed. It can be seen that the formed electrode foil has a high capacitance. Although the aluminum foil for electrolytic capacitor electrodes obtained by the method according to Examples 6 to 9 has a low capacitance, the aluminum foil used as a standard for relative evaluation is 9
9.99% Al purity, whereas Al purity is 9
Despite the low purity of 9.97% or less,
It can be seen that the capacitance is relatively high. In addition, Example 6
As is clear from a comparison between Example and Example 8, Si and C
It can be seen that the capacitance is higher when the deposition amount of u is regulated within a specific range. On the other hand, Comparative Examples 1, 2,
In the aluminum foil for electrolytic capacitor electrodes obtained by the methods according to 4 and 5, since the amount of Fe deposited is not regulated within a specific range, an electrode foil with high capacitance cannot be obtained. In addition, the aluminum foil for electrolytic capacitor electrodes obtained by the method according to Comparative Example 3 had an excessively high impurity element content,
Even if the amount of e deposited is regulated within a specific range, it is not possible to obtain an electrode foil having a high capacitance. It is presumed that this is because there are too many impurities to cause overdissolution during etching. The aluminum foil for electrolytic capacitor electrodes obtained by the method according to Examples 1 to 9 was anodized in a 2% aqueous solution of ammonium hydrogen phosphate, and the leakage current of each foil was measured. There was no problem.

[0036]

As described above, in the aluminum foil for electrolytic capacitor electrodes according to the present invention, the precipitation amount of Fe contained in the foil is regulated within a specific range.
By performing the etching process, it is possible to stably obtain an electrode foil having a high capacitance. Furthermore, when the amount of each precipitate of Si or Cu is regulated within a specific range,
It is possible to more stably obtain an electrode foil having a high capacitance.
In addition, when the size and number of each precipitate are specified in a specific range, or when the size of the average crystal grain size in the aluminum foil and the cubic orientation ratio are specified in a specific range, it is more stable and high static. An effect that an electrode foil having a capacitance can be obtained is obtained.

Claims (5)

[Claims] 1. The aluminum purity is 99.9% by weight or more, and Fe: 0.0010 to 0.0100% by weight,
Si: 0.0015 to 0.0150% by weight, Cu: 0.
F, which contains 0001 to 0.0050% by weight and other unavoidable impurity elements and is measured by a hot phenol dissolution method
The aluminum foil for electrolytic capacitor electrodes, wherein the amount of e deposited is regulated in the range of 10 to 70% with respect to the content of Fe. 2. The aluminum foil for an electrolytic capacitor electrode according to claim 1, wherein the amount of Si deposited measured by the hot phenol dissolution method is regulated within the range of 5 to 50% with respect to the Si content. 3. The deposition amount of Cu measured by the hot phenol dissolution method is regulated within the range of 1 to 20% with respect to the total deposition amount of Fe, Si and Cu. Aluminum foil for electrolytic capacitor electrodes. 4. The number of precipitates of 2 μm or less accounts for 50% or more of the total number of precipitates.
The aluminum foil for an electrolytic capacitor electrode according to any one of 1. 5. The average crystal grain size is 0.02 to 5 mm, and the crystal grains having a cubic orientation account for 60% or more of all the crystal grains, and are present. An aluminum foil for an electrolytic capacitor electrode according to the item 1.