JP4555204B2 - Aluminum cathode foil for electrolytic capacitors - Google Patents

Description

The present invention relates to an aluminum cathode foil for electrolytic capacitor.

As a method for producing an aluminum cathode foil for an electrolytic capacitor that obtains a high capacitance, a technique of depositing Ti on an aluminum substrate is known (for example, see Non-Patent Document 1).
As a typical manufacturing method thereof, a method of depositing fine particles of Ti on a roughened aluminum substrate in an inert gas atmosphere such as argon (for example, see Patent Documents 1, 2, and 3), an atmosphere A method of obtaining a TiN film by using nitrogen as a gas and ionizing by an anodic arc vapor deposition method (see, for example, Patent Documents 4 and 5). When depositing Ti, the incident angle on the base material is changed to make it porous. A method for generating a Ti or TiN film (see, for example, Patent Documents 6 and 7) is disclosed.

However, the cathode foil (hereinafter referred to as Ti vapor-deposited foil) obtained by vapor-depositing Ti or TiN on an aluminum base material has an oxide film that gradually grows on the surface of Ti even though high capacitance is obtained. For this reason, there is a problem in that the decrease in capacitance (change over time) is large (see, for example, Non-Patent Document 1).
On the other hand, an electric double layer capacitor uses an electrode foil (hereinafter referred to as a carbon coated foil) having a very large real surface area (hereinafter referred to as a carbon coated foil) in which carbon fine particles and activated carbon are coated on an aluminum substrate (for example, referred to as carbon coated foil). Non-Patent Document 1).

Since carbon itself is chemically stable and does not produce an oxide film, it is an ideal material as a cathode material for electrolytic capacitors, and the manufacturing method by coating is inexpensive, has high productivity, and is industrially superior. Yes.
Japanese Patent No. 1674572 Japanese Patent No. 1636763 Japanese Patent No. 1631296 Japanese Patent No. 2687299 Japanese Patent No. 2864477 Japanese Patent No. 3168588 Japanese Patent No. 3475193 By Isaya Nagata, “Electrolytic Cathode Aluminum Electrolytic Capacitor”, Nippon Electric Storage Co., Ltd., February 24, 1997, P344-345, P20-23

  However, since the electrolytic solution for driving the electrolytic capacitor usually contains moisture, when a slight reverse voltage is applied by charging / discharging or the like, in the case of a carbon coating foil, the carbon coating material and the aluminum base material In the meantime, an oxide film of aluminum is generated to be in an insulating state, and there is a problem that it cannot be used as an aluminum cathode foil for electrolytic capacitors.

  As described above, both the Ti vapor-deposited foil and the carbon-coated foil are insufficient in terms of characteristics as an aluminum cathode foil for electrolytic capacitors, although a high capacitance can be obtained.

In view of the above problems, an object of the present invention is to provide an aluminum cathode foil for an electrolytic capacitor that has a high capacitance and has little change with time in capacitance.

In order to solve the above problems, in the aluminum cathode foil for an electrolytic capacitor according to the present invention, any one of Ti, Zr, Hf, V, Nb, Ta, Mo, or W is formed on the surface of the roughened aluminum material. The metal film is formed , a carbon film is formed on the surface of the metal film, and carbon fine particles are fixed on the surface of the carbon film .

  In the present invention, Ti, Zr, Hf, V, Nb, Ta, Mo, and W can be used as the metal film. Among these metals, Zr, Hf, V, Nb, Ta, and Mo other than Ti are used. , W has a high melting point and is relatively expensive, so that Ti has the advantage that it is most easily handled industrially.

According to the present invention, the high capacitance can be obtained, it is possible to suppress the change with time in electrostatic capacity is extremely valuable as an aluminum cathode foil for electrolytic capacitor.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

[ Reference Example ] Fixing of carbon fine particles on a metal film FIG. 1 is a schematic diagram showing a contact state between carbon fine particles and an aluminum substrate in a carbon coating foil, and an insulating oxide film generated when a chemical conversion treatment is performed. It is.
FIG. 2 is a schematic view showing a bonding state of a roughened aluminum base material, a Ti film, and carbon fine particles in the cathode foil according to the present invention.

In the aluminum cathode foil for electrolytic capacitors according to the reference example of the present invention, any metal film of Ti, Zr, Hf, V, Nb, Ta, Mo, or W is formed on the surface of the roughened aluminum material. A large number of carbon fine particles are fixed on the upper layer side of the metal film.

  In the manufacturing process of such an aluminum cathode foil for electrolytic capacitors, a metal film of Ti, Zr, Hf, V, Nb, Ta, Mo, or W is deposited on the surface of the roughened aluminum material by vapor deposition or the like. A metal film forming process to be formed, and a carbon fine particle fixing process in which carbon fine particles dispersed in an organic binder are applied to the upper layer side of the metal film and then heat treatment is performed.

In the reference example of the present invention, first, aluminum is used as a base material, but this purpose is that the base material of the cathode foil of the electrolytic capacitor does not react with the driving electrolyte, and in the assembly and use of the electrolytic capacitor. It has a rich track record. As described later, the aluminum used as the base material is superior in terms of the bonding strength between Ti and carbon, as will be described later.

Next, in the reference example of the present invention, first, a metal film such as a Ti film is formed by vapor deposition or the like, and then, a carbon fine particle dispersed in an organic binder is applied. The purpose is to chemically join aluminum and carbon fine particles through the metal.

  The problem with carbon-coated foils based on aluminum is that the adhesion between aluminum and carbon is due to the van der Waals force caused by the binder contained in the coating material, and the ability to produce an oxide film produced when aluminum is oxidized. In other words, it is weaker than the ion binding force. Further, the carbon coating material (carbon fine particles + binder) does not completely cover the aluminum base material, and the driving electrolyte solution partially permeates the interface between the aluminum base material and the carbon coating material.

  For this reason, as shown in FIG. 1, in the carbon coating foil provided with the carbon fine particles 2 and the binder 3 on the surface of the aluminum substrate 1, when a voltage is applied in a driving electrolyte containing moisture, the aluminum substrate An insulating oxide film 4 is generated and expanded on the surface. At this time, since the stress due to expansion exceeds the van der Waals binding force by the binder contained in the coating material, the carbon coating material is peeled off as shown in FIG. Electrolyte permeation, generation of an oxide film, and generation of new stress occur repeatedly in a chain, and the electrical contact is eventually cut off.

  However, in this embodiment, as shown in FIG. 2, a metal film such as a Ti film 7 is deposited on the surface of the roughened aluminum base 6, so that metal atoms such as Ti atoms and the base aluminum are react. At the interface, as shown by an alloy layer of Ti and aluminum (FIG. 2, reference numeral 10), alloy bonding occurs, and as described later, when the organic binder applied on the metal film is heat-treated. , Carbonized to change to carbon 8 to form a metal and a conductive carbide (conductive compound layer 9 of Ti and carbonized binder) to be chemically bonded.

  In this case, the larger the bonding area between the Ti film and the carbon, the smaller the influence of oxidation by the driving electrolyte solution, so the aluminum base material is an etching foil that has been chemically and electrochemically roughened, It is preferable to use a mechanically roughened aluminum material.

  In addition, as shown in FIG. 2, it is desirable that the metal film such as a Ti film also has a uniform film shape by a method such as increasing the degree of vacuum at the time of vapor deposition or ionizing by applying an electric field. In particular, good results can be obtained by improving the contact with the roughened aluminum material.

Furthermore, in the reference example of the present invention, the heat treatment is performed, and the object is to chemically bond the carbon fine particles 2 and the Ti film 7 shown in FIG.

  As the organic binder used for the carbon coating material, for example, a phenolic resin diluted with an organic solvent is used.

  When preparing an electrode for an electric double layer capacitor, the heat treatment is performed at a temperature at which the binder is slightly carbonized and conductive, and the binder itself can maintain adhesion with aluminum, more specifically, 200 to 300. It is carried out at a relatively low temperature of about ° C.

  However, in the case of this embodiment, the organic binder is completely carbonized, and the purpose is to bond by a chemical reaction between the generated carbon and a metal such as Ti. Therefore, an oxidation reaction of the carbon coating material or a metal film such as a Ti film It is better to perform the heat treatment at a high temperature within a range where no oxidation or nitridation occurs. Specifically, an optimum condition may be found within a range of 300 to 450 ° C.

Forming a carbon film on Embodiment] metal film, in the form status of implementation of the fine carbon particles fixing invention, carbon coating is formed on the surface of the metal film of Reference Example, the number on the surface of the carbon film Carbon fine particles are fixed. That is, in the aluminum cathode foil for electrolytic capacitor according to the shape condition of the present invention, Ti the roughened surface of the aluminum material, Zr, Hf, V, Nb , Ta, Mo or of W,, any A metal film is formed, a carbon film is formed on the surface of the metal film, and the carbon fine particles are fixed on the surface of the carbon film.

In such a method for producing an aluminum cathode foil for electrolytic capacitors, in the production method according to the reference example , a carbon film is formed on the upper layer side of the metal film after the metal film forming step and before the carbon fine particle fixing step. A carbon layer forming step is performed.
That is, in the manufacturing process of the aluminum cathode foil for electrolytic capacitors, any metal film of Ti, Zr, Hf, V, Nb, Ta, Mo, or W is deposited on the surface of the roughened aluminum material by vapor deposition or the like. A metal film forming step to be formed; a carbon layer forming step for forming a carbon film on the upper layer side of the metal film; and a coating of carbon fine particles dispersed in an organic binder on the surface of the carbon film, followed by heating. And a carbon fine particle fixing step for performing the treatment.

  As described above, in this embodiment, after a metal film such as a Ti film is first deposited, a carbon film is deposited, and a carbon fine particle dispersed in an organic binder is applied and heat-treated. The reaction between carbon atoms and a metal film such as a Ti deposited film can be promoted, and chemical bonding can be made more complete.

  Hereinafter, based on an Example, this invention is demonstrated in detail.

[ Reference Examples 1-1 to 1-10] Examination of Ti vacuum deposition and carbon fine particle fixing First, in the metal film forming step, a coil obtained by slitting a commercially available cathode etching foil to a width of 10 cm was set in a vacuum deposition apparatus, After vacuuming to a vacuum degree of 5 × 10 −4 Torr (0.065 Pa), Ti is deposited on one side under the conditions shown in Table 1.
Next, in the carbon fine particle fixing step, a carbon coating material using a commercially available phenol resin binder is applied to the surface on which Ti is vapor-deposited to a thickness of about 10 μm, and then heat-treated to produce an aluminum cathode foil for an electrolytic capacitor. did.

(Comparative Example 1)
An aluminum cathode foil for electrolytic capacitors was produced in the same manner as in Example 1-1 except that a smooth foil having a thickness of 0.5 mm was used instead of the etching foil.

(Conventional example 1)
Using the same etching foil as in Example 1-1, Ti was evaporated at ² g / m ^{2 in} a vacuum degree of 5 × 10 ⁻⁴ Torr, and carbon coating and heat treatment were not performed, and an aluminum cathode foil for an electrolytic capacitor was produced.

(Conventional example 2)
The same 0.5 μm-thick smooth foil as in Comparative Example 1 was used, vapor deposition was not performed, carbon coating was performed in the same manner as in Example 1-1, and heat treatment was performed at 200 ° C. for 30 minutes to produce an aluminum cathode foil for electrolytic capacitors.

(Conventional example 3)
The same etching foil as in Example 1-1 was used, vapor deposition was not performed, carbon coating was performed in the same manner as in Example 1-1, and heat treatment was performed at 200 ° C. for 30 minutes to produce an aluminum cathode foil for an electrolytic capacitor.

  Evaluation of the aluminum cathode foil for electrolytic capacitors thus manufactured was performed for the following two items.

  The first item of evaluation is to measure the capacitance of the center part of the cathode foil left for 1 day and the cathode foil left for 3 months in a room temperature atmosphere with a humidity of 35% according to the JEITA method. From the capacitance change rate A (the value obtained by subtracting the capacitance value after standing for 3 months from the capacitance value after standing for 1 day, divided by the capacitance value after standing for 1 day, and so on). Evaluation was performed.

The second item of evaluation is chemical formation by applying a cathode foil left at room temperature in a normal atmosphere of 35% humidity after production for 1 day in ammonium adipate at 20 g / dm ² at 65 ° C. for 0.5 V for 5 minutes. The capacitance of the center portion of the cathode foil left to stand for 1 day in a normal humidity of 35% post-humidity and the cathode foil formed by applying 0.5 V for 5 minutes was measured according to the JEITA method, and the capacitance Rate of change B (a value obtained by subtracting a capacitance value after application of 0.5 V for 5 minutes from a capacitance value after being left for 1 day divided by a capacitance value after being left for 1 day, and so on) Was evaluated.

In addition, the commercially available etching foil for cathodes was used for 3 months after the production and had a stable capacity, and the capacitance was about 80 μF / cm ² .

  Table 1 shows the results calculated for the capacity change rates A and B.

As shown in Table 1, the Ti-deposited foil of Conventional Example 1 (deposited Ti fine particles on the cathode etching foil) has a large capacitance change with time (capacitance change rate A), while Conventional Examples 2, 3 The carbon coated foil has a large capacity change (capacity change rate B) after chemical conversion. On the other hand, Reference Examples 1-1 to 1-10 show a change with time in capacitance (capacitance change rate A) close to that of the carbon coated foil, and a change in capacitance after formation (capacitance change rate B) is also shown. Greatly improved.

As the thickness of the deposited Ti film increases, the capacitance change rate tends to decrease, but the capacitance decreases at 2 μm or more ( Reference Example 1-5). In Reference Examples 1-1 to 1-10 In the used etching foil for cathodes, it is estimated that the etched surface is smoothed, and an optimum value may be set as appropriate depending on the substrate to be used.

Similarly, in the carbon coating materials used in Reference Examples 1-1 to 1-10, the capacity change (capacitance change rate B) after chemical conversion is small at 300 ° C. or more at which carbonization is considered to start. When the temperature is higher than or equal to ° C., the electrostatic capacity is decreasing, and it is considered that the carbon coating material is oxidized, and this tendency is presumed to change depending on the properties of the carbon coating material used.

[ Reference Examples 2-1 to 2-10] Examination of Ti Sputtering and Carbon Fine Particle Fixation in Argon First, in the metal film forming step, a coil obtained by slitting a commercially available cathode etching foil into a width of 10 cm was used as a DC sputtering apparatus. After setting and evacuating to a vacuum degree of 5 × 10 −4 Torr (0.065 Pa), argon was introduced so as to be 5 × 10 −2 Torr (6.5 Pa), and Ti was formed on one side under the conditions shown in Table 2. Sputter.
Next, in the carbon fine particle fixing step, a carbon coating material using a commercially available phenol resin binder is applied to the surface on which Ti is sputtered to a thickness of about 10 μm, and then heat-treated to produce an aluminum cathode foil for an electrolytic capacitor. did.

(Conventional example 4)
Using the same etching foil as in Reference Example 2-1, after evacuating to a vacuum degree of 5 × 10 −4 Torr, argon was introduced so as to be 5 × 10 −2 Torr, Ti was deposited at 2 g / m 2, carbon coating and The aluminum cathode foil for electrolytic capacitors was produced without performing heat treatment.

As shown in Table 2, also in Reference Examples 2-1 to 2-9, the capacitance change with time (capacity change rate A), which is close to the carbon coated foil, is shown, and the capacity change after formation (capacitance change rate B). Has also been improved.

Comparing Reference Example 1-1 and Reference Example 2-4, with the same Ti film thickness, it is determined that sputtering has a smaller capacitance change rate B and better Ti coverage. Then, since it is difficult to increase the thickness of the Ti film, a method such as ion plating may be used to increase the thickness of the Ti film.

[Examples 3-1 to 3-10] Examination of Ti vapor deposition, carbon vapor deposition, and carbon fine particle fixing First, in the metal film forming step, a coil obtained by slitting a commercially available cathode etching foil into a width of 10 cm is set in a vacuum vapor deposition apparatus. After vacuuming to a vacuum degree of 5 × 10 ⁻⁴ Torr (0.065 Pa), Ti is deposited on one side under the conditions shown in Table 3.
Next, in the carbon layer forming step, carbon was vapor-deposited on one side of the Ti vapor deposition surface under the condition of a degree of vacuum of 5 × 10 ⁻⁴ Torr (0.065 Pa).
Next, in the carbon fine particle fixing step, a carbon coating material using a commercially available phenolic resin binder is applied to the surface on which Ti and carbon are vapor-deposited to a thickness of about 10 μm, and then heat treatment is performed to obtain an aluminum for electrolytic capacitors. A cathode foil was prepared, and the capacitance and the rate of change in capacity were evaluated.

  As shown in Table 3, also in Examples 3-1 to 3-10, the capacitance change with time (capacity change rate A), which is close to the carbon coated foil, is shown, and the capacitance change after formation (capacitance change rate B). There have also been significant improvements.

  In addition, when carbon deposition is performed, there is a tendency that the capacity change (capacity change rate B) at the time of chemical conversion is improved as compared with the case where carbon deposition is not performed.

[Examples 4-1 to 4-17, 3-1, 3-4, 3-6] Examination of metal vapor deposition, carbon vapor deposition, and carbon fine particle fixing First, in the metal film forming step, a commercially available etching foil for cathode is 10 cm. The coil slitted to the width is set in a vacuum vapor deposition apparatus, vacuumed to a vacuum degree of 5 × 10 ⁻⁴ Torr (0.065 Pa), and then a metal film such as Ti is vapor-deposited on one side under the conditions shown in Table 4.
Next, in the carbon layer forming step, carbon was vapor-deposited on one side on the metal film.
Next, in the carbon fine particle fixing step, a carbon coating material using a commercially available phenol resin binder is applied to a thickness of about 10 μm on each metal film and the surface on which the carbon film is deposited, and then heat treatment is performed. An aluminum cathode foil for electrolytic capacitors was prepared and the capacitance and the rate of change in capacitance were evaluated.

  As shown in Table 4, Examples 4-1 to 4-17, 3-1, 3-4, and 3-6 also show a change with time in capacitance (capacitance change rate A) that is close to the carbon coated foil. Also, the capacity change (capacitance change rate B) after chemical conversion is improved.

  In the above examples, the capacity change rate B of Ta, Mo, and W shows a slightly worse overall trend, but the melting point of these metals is very high, so the uniformity of the deposited film is poor and the particles are formed into particles. If the uniformity of the vapor-deposited film is improved, it is presumed that a result that is not much different from the case where the Ti film is vapor-deposited can be obtained.

It is a schematic diagram which shows the insulating oxide film produced | generated when the contact condition of the carbon microparticles | fine-particles and aluminum base material in a carbon application | coating foil and a chemical conversion treatment are performed. It is a schematic diagram which shows the joining condition of the roughened aluminum base material, Ti film | membrane, and carbon microparticles | fine-particles with the cathode foil which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum base material 2 Carbon fine particle 3 Binder 4 Insulating oxide film 5 Peeled binder 6 Roughened aluminum base material 7 Ti vapor deposition film 8 Carbonized binder 9 Conductive compound layer 10 of Ti and carbonized binder 10 Ti And aluminum alloy layer

Claims (1)

A metal film of Ti, Zr, Hf, V, Nb, Ta, Mo, or W is formed on the surface of the roughened aluminum material,
An aluminum cathode foil for electrolytic capacitors , wherein a carbon film is formed on the surface of the metal film, and carbon fine particles are fixed on the surface of the carbon film .

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