JPH065472A - Electrode material for electrolytic capacitor and its manufacture - Google Patents

Abstract

(57) [Abstract] [Purpose] The purpose is to stabilize the quality by reducing the change with time of the capacitance of the electrode material for electrolytic capacitors. According to the electrode material for an electrolytic capacitor of the present invention, a conductive metal vapor deposition layer is formed on the surface of a base material, and an oxide film having a thickness of 20 to 100 angstrom is formed on the surface layer of the conductive metal layer. It is characterized by being. Further, in such a method for producing an electrolytic capacitor electrode material, during the vapor deposition process of the conductive metal on the surface of the base material,
Alternatively, it is preferable to form the oxide film having the above-mentioned thickness immediately after the vapor deposition process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode material used for electrolytic capacitors such as aluminum having a conductive metal vapor deposition layer formed on a base material.

[0002]

2. Description of the Related Art As an electrode material for a large capacitance electrolytic capacitor, in order to increase the capacitance, conductive metal particles such as titanium are vapor-deposited on various base materials such as an aluminum etching foil to obtain a large surface area. The expanded version is widely used.

[0003]

However, there is a problem in that the capacitance of such an electrode material changes with time between the time when it is manufactured and the time when it is incorporated into a capacitor.

For example, FIG. 4 shows a state in which the capacitance of an electrode material in which titanium is vapor-deposited on an aluminum etching foil is changed with time while the electrode material is stored in the atmosphere. . When the capacitance changes with time in this manner, the capacitance varies depending on the period from the manufacturing of the electrode material to the incorporation into the capacitor, and it is very difficult to guarantee the quality of the electrode material and the capacitor.

The present invention aims to solve the above problems by providing an electrode material for an electrolytic capacitor, which has a small change in electrostatic capacitance over time and a stable quality, and a method for producing the same.

[0006]

As a result of various experiments and studies conducted by the inventor in order to achieve the above-mentioned object, it was found that the change in the capacitance with time showed that a conductive metal vapor-deposited layer formed on a substrate, such as titanium. It was found that this is due to the fact that the oxidation of the surface layer of the vapor deposition layer progresses and the thickness of the oxide film increases with time.
Moreover, it has been found that when the oxide film grows and reaches a certain thickness, the growth rate thereafter becomes extremely slow or almost stops.

The electrolytic capacitor electrode material of the present invention was made on the basis of such findings, and a conductive metal vapor deposition layer is formed on the surface of a base material, and the conductive metal vapor deposition layer has a surface layer. An oxide film having a thickness of 20 to 100 angstrom is formed.

When the oxide film is formed on the surface of the conductive metal vapor deposition layer, ions such as oxygen are prevented from entering the conductive metal vapor deposition layer, and the growth of the oxide film is slowed down to give an electrostatic charge. It is presumed that it hinders the change in capacity over time. However, if the thickness of such an oxide film is less than 20 Å, the rate of change in capacitance when incorporated in an electrolytic capacitor is 20 because ions easily pass through and the conductive metal vapor deposition layer oxidizes quickly. %, And practicality is poor. If it exceeds 100 angstroms, the rate of change in capacitance decreases, but the capacitance itself decreases, making it difficult to secure the capacitance required for the electrode material and the capacitor. poor.

The base material used in the present invention may be an aluminum foil, an aluminum alloy foil, or the like, and the surface of which is roughened by etching or the like.
Titanium, aluminum, tantalum, niobium, zirconium, silicon and the like can be used as the metal forming the vapor deposition layer. Further, the oxide film may be a crystalline film or an amorphous film such as a hydratable film, and any of them can exhibit the effect of preventing a change in capacitance. The method for forming the oxide film of these metals is not particularly limited, and examples thereof include heating in various oxidizing atmospheres, annealing, and chemical conversion treatment. The thickness of the oxide film is 20
In order to obtain -100 angstrom, the oxidation treatment temperature is preferably 300 ° C or lower.

Further, in such a method for producing an electrode material for electrolytic capacitors, it is preferable to form an oxide film having the above-mentioned thickness during or immediately after vapor deposition of a conductive metal on the surface of a substrate. This is preferable in that an electrode material with a small change in electric capacity can be manufactured early.

[0011]

In the electrode material for electrolytic capacitors of the present invention,
On the surface of the conductive metal vapor deposition layer formed on the surface of the base material, the conductive metal is oxidized to form an oxide film having a thickness of 20 to 100 angstroms. Ions such as oxygen do not easily pass through this oxide film,
It is considered that the number of ions reaching the surface of the conductive metal vapor deposition layer is drastically reduced and the growth of the oxide film becomes extremely slower than when the oxide film is not formed or when the oxide film is thin. As a result, the capacitance of the electrode material for the electrolytic capacitor is prevented from changing, and the quality is stable.

Furthermore, by forming an oxide film of the above-mentioned thickness during or immediately after the vapor deposition of the conductive metal on the surface of the base material, an electrode material with a small change in capacitance can be manufactured at an early stage. .

[0013]

EXAMPLES Next, specific examples of the present invention will be described.

In each of the following Examples and Comparative Examples, a coil-shaped aluminum etching foil having a purity of 99.8% was used as a base material, and the base material was heated at a temperature of 30 ° C. in a vacuum chamber of 1 × 10 ⁻³ Torr. While carrying along the lower peripheral surface of the base roll held in the above, while winding, titanium vapor deposition is performed on the base material carried along the base roll to form a titanium vapor deposition film of 2.0 μm in thickness. It was formed continuously.
Using this as a basic sample, in Examples 1 to 5 and Comparative Example 1, the surface of the vapor deposition film of this basic sample was oxidized under the conditions described below to form a titanium oxide film. In addition, Comparative Example 2,
In No. 3, no oxidation treatment was performed.

Example 1 After the completion of vapor deposition, Ar gas having a dew point of 10 ° C. was filled in a vacuum chamber, and the basic sample was rewound at a substrate roll temperature of 30 ° C. and a winding speed of 1 m / min.

(Example 2) After the completion of vapor deposition, Ar gas having a dew point of 10 ° C was enclosed in a vacuum chamber, and the substrate was rewound at a winding temperature of 100 ° C and a winding speed of 1 m / min.

(Embodiment 3) After completion of vapor deposition, subsequently, 30 vol% O ₂ gas was added to Ar gas having a dew point of 10 ° C. and enclosed in a vacuum chamber at a substrate roll temperature of 30 ° C. and a winding speed of 1 m / min. It was rewound.

(Embodiment 4) After completion of vapor deposition, subsequently, 30 vol% O ₂ gas was added to Ar gas having a dew point of 10 ° C. and sealed in a vacuum chamber, and the basic sample was heated to a base roll temperature of 100
Rewinding was carried out at ℃ and a winding speed of 1 m / min.

(Embodiment 5) The basic sample wound in a coil shape is taken out from the vacuum chamber, and then 30 minutes in a heating furnace.
After raising the temperature to 0 ° C and reaching 300 ° C, the dew point is 30 ° C and O ₂
It heated in the atmosphere of concentration 30% for 10 hours.

Comparative Example 1 The above basic sample was immersed in a mixed solution of 1000 ml of dimethylformamide + 56 ml of phosphoric acid, and
The chemical conversion treatment was performed for 20 minutes under conditions of 0 ° C., current density of 10 mA / cm ² (direct current), and applied voltage of 7V.

(Comparative Examples 2 and 3) Two basic samples which were not subjected to oxidation treatment were designated as Comparative Examples 2 and 3. However, some titanium oxide film was naturally formed on the surface of the titanium vapor-deposited film without positive oxidation treatment.

In the above Examples and Comparative Examples, the capacitance and the thickness of the titanium oxide film were measured immediately after the oxidation treatment (however, immediately after the titanium vapor deposition in Comparative Examples 2 and 3) and after the capacitance deterioration treatment. At the same time, the rate of change in capacitance was obtained and used as a capacitance deterioration test. Details of these measurement methods and test methods are shown below, and the measurement results are shown in Table 1.

(Measurement of Capacitance) Two test pieces of 20 mm × 50 mm square are dipped in a 10 wt% ammonium borate solution facing each other at an interval of 10 mm, and the capacitance at 120 Hz is measured by an LCR meter. Was measured.

(Measurement of film thickness) The film thickness of the oxide film was measured by ESCA.

(Capacitance deterioration test) As deterioration processing,
A 1000 ml beaker was filled with ion-exchanged water kept at 90 ° C., and the two test pieces were dipped to promote deterioration. Then, after 180 minutes, the test piece was pulled up and the capacitance and the film thickness were measured by the above-mentioned methods.
Then, the rate of change in capacitance was obtained by the following formula and used as a guideline for the rate of deterioration.

Capacitance change rate (%) = {(a)-
(B)} / (b) × 100 (b): Capacitance (μF / cm ² ) immediately after oxidation treatment or titanium vapor deposition (b): Capacitance (μF / cm ² ) after deterioration treatment The reason why the immersion time was 180 minutes was as follows.

FIG. 1 shows that the test piece of the above basic sample is immersed in ion exchanged water at 90 ° C. immediately after titanium deposition and is withdrawn every 30 minutes to obtain capacitance and film thickness of titanium oxide film. Is the result of measurement. As is apparent from FIG. 1, the film thickness and the electrostatic capacitance became stable values after the immersion time of 180 minutes, and the growth of the titanium oxide film became extremely slow, and almost no change was observed even after immersion for 180 minutes or more. Not considered. Therefore, the immersion time in the capacitance deterioration treatment was set to 180 minutes.

[0028]

[Table 1] Here, referring to FIG. 2, focusing on the relationship between the film thickness and the capacitance of the titanium oxide film immediately after the oxidation treatment, if there is a titanium oxide film with a thickness of at least 20 Å,
It can be seen that the capacitance variation rate of the capacitor satisfies ± 20% which is practically allowable. Further, referring to FIG. 3, taking out only those having a film thickness of 20 Å or more and focusing on the relationship between the film thickness and the capacitance, the film thickness of 1
It can be seen that the capacitance level (300 μF / cm ² ) of the existing aluminum etching foil is satisfied in the range of 00 Å or less. From FIG. 2 and FIG. 3, when the thickness of the titanium oxide film is in the range of 20 to 100 angstroms, it has a sufficient capacitance and the rate of change of the capacitance is stable, and the quality as an electrode material is stable. You can see that

In Comparative Example 1, an oxide film having a thickness of 100 angstroms or more is formed and deviates from the scope of the present invention. However, this does not mean that the oxidation treatment method by chemical conversion treatment is not appropriate, but only the film thickness. Needless to say, such a method can be adopted as the oxidation treatment method if the chemical conversion treatment conditions are changed so that the film thickness is in the range of 20 to 100 angstroms.

[0030]

EFFECT OF THE INVENTION The electrode material for electrolytic capacitors of the present invention has a small decrease in electrostatic capacity over time, can realize stable product quality, and can also stabilize the quality of capacitors. It's easy.

When the electrode material for an electrolytic capacitor of the present invention is used as an anode, since an oxide film is formed, the amount of electrolysis in the chemical conversion treatment step for forming a dielectric is small and productivity is improved. Can be improved. Furthermore, when the voltage used as the capacitor is low, the oxide film can be used as the dielectric film, so that the chemical conversion treatment step can be omitted and the manufacturing process of the electrode material can be a dry process. Such a dry process is significant not only for improving productivity by omitting the drainage treatment step but also for preventing destruction of the natural environment by drainage.

According to the second aspect of the present invention, by forming an oxide film having the above-mentioned film thickness on the surface of the base material during the vapor deposition treatment of the conductive metal or immediately after the vapor deposition treatment, the capacitance change can be suppressed. A small amount of electrode material can be manufactured early, and the manufacturing time of the electrode material can be shortened.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an immersion time and a capacitance in a deterioration process.

FIG. 2 is a graph showing the relationship between the titanium oxide film thickness and the capacitance change rate in the oxidation treatment.

FIG. 3 is a graph showing the relationship between the titanium oxide film thickness and the capacitance immediately after the oxidation treatment.

FIG. 4 is a graph showing the change with time of the capacitance of an electrode material in the atmosphere.

Claims (2)

[Claims] 1. A conductive metal vapor deposition layer is formed on the surface of a base material, and an oxide film having a thickness of 20 to 100 angstrom is formed on the surface of the conductive metal vapor deposition layer. Electrode material for electrolytic capacitors. 2. Forming an oxide film having a thickness of 20 to 100 angstroms on the surface of the conductive metal vapor deposition layer by performing an oxidation treatment at the same time as or immediately after the vapor deposition of the conductive metal on the surface of the base material. A method for producing an electrode material for a characteristic electrolytic capacitor.