JPH0821518B2 - Method of manufacturing electrolytic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an electrolytic capacitor using a conductive polymer as a solid electrolyte.

2. Description of the Related Art Conventionally, as an electrolytic capacitor using a conductive polymer, an Al ₂ O ₃ dielectric layer is provided on an aluminum surface, and is further formed on the aluminum surface, as described in JP-A-64-900517, for example. As the solid electrolyte layer, an electrolytically polymerized film of pyrrole monomer, thiophene monomer or the like is formed.

However, in order to obtain a high polymer by polymerization from a monomer, in addition to the problem that the electrolytic polymerization step requires a long time,
There is a problem that the electrolytically polymerized electrolytically polymerized film is peeled off from the electrode, and the peeling causes an electrical defect to cause a loss.

Therefore, an object of the present invention is to provide an electrolytic capacitor having excellent impedance characteristics.

Means for Solving the Problems In order to achieve the above object, the present invention provides an electrolytic capacitor characterized in that an electropolymerized film of π-electron conjugated oligomer is formed on a porous surface electrode having a conductive nucleus. Configure

Action Since the polymer thin film of the present invention is an electrolytic polymerization method using an oligomer as a raw material, a film having a high degree of polymerization can be formed in a shorter time than in the case of using a monomer.

This is because the oligomer has a lower oxidation-reduction potential than the monomer, so that the polymerization rate is faster and the reaction is easier.

Further, in the electrolytic capacitor of the present invention, since the polymer thin film of the electrolyte layer has a high degree of polymerization, the conductivity is also high and the dopant does not move even when a current is applied for a long time, so that the low impedance characteristic can be maintained.

Example The present invention prepares a polymer thin film by immersing an electrode in the welding of π-electron conjugated oligomer and electropolymerizing on the electrode.

Examples of the π-electron conjugated oligomers include thiophene oligomers, pyrrole oligomers, benzene oligomers, furan oligomers, carbazole oligomers, pyrene oligomers, azulene oligomers, N-vinylcarbazole oligomers and fluorenone oligomers. Of these, thiophene oligomers, pyrrole oligomers and benzene oligomers are preferable from the viewpoint of film-forming property.

As an example of a method for producing an oligomer, for example, thiophene trimer can be synthesized by reacting 1 mol of 2,5-dibromothiophene with 2 mol of 2-cenylmagnesium bromide.

Thus, the π-electron conjugated oligomer can be easily synthesized by, for example, a dehalogenation reaction between a dibromo derivative and a Grignard reagent, a Friedel-Crafts reaction, or the like.

 The average degree of polymerization of the oligomer is preferably 3-10.

If the average degree of polymerization is 2 or less, formation of a high degree of polymerization film in a short time cannot be expected, and if 10 or more, it is difficult to dissolve in an organic solvent.
This is because a uniform film cannot be formed.

The electrolytic capacitor of the present invention comprises an electrode (anode) having a porous surface having conductive nuclei, an electrolytic polymerized film and a cathode.

As an example of a porous surface electrode having conductive nuclei, aluminum is subjected to chemical conversion treatment to roughen the surface and
_{For example, a 2} O ₃ film is formed, and manganese dioxide fine particles are further formed thereon.

 Next, the present invention will be described with reference to specific examples.

Example 1 5 g of thiophene trimer (thiophene trimer) and 2 g of tetra-n-butylammonium perchlorate were dissolved in 300 ml of nitrobenzene to prepare a reaction solution.

The electrode used was an indium oxide (ITO) glass electrode for the anode and a platinum plate for the cathode, and the anode current density was 30 mA at ² mA / cm ² .
A polymer thin film was obtained on the anode by conducting electric current for minutes to carry out electrolytic polymerization.

Example 2 A polymer thin film was similarly obtained by replacing thiophene trimer in Example 1 with thiophene pentamer (pentamer of thiophene).

Example 3 5 g of pyrrole trimer (trimer of pyrrole) and 2 g of tetra-n-butylammonium perchlorate were dissolved in 300 ml of acetonitrile to prepare a reaction solution.

An ITO glass electrode was used as an electrode and a platinum plate was used as a cathode. Electrodes were polymerized by applying current at an anode current density of ² mA / cm ² for 30 minutes to obtain a polymer thin film on the anode.

Example 4 A polymer thin film was obtained in the same manner as in Example 3 except that the pyrrole trimer was replaced with pyrrole pentamer (pentamer of pyrrole).

Example 5 5 g of benzene trimer (trimer of benzene) and 2 g of tetra-n-butylammonium perchlorate were dissolved in 300 ml of propylene carbonate to prepare a reaction solution.

An ITO glass electrode was used as an electrode and a platinum plate was used as a cathode. Electrodes were polymerized by applying current at an anode current density of ² mA / cm ² for 30 minutes to obtain a polymer thin film on the anode.

Example 6 In Example 5, the polymer thin film was similarly obtained by replacing benzene trimer with benzene pentamer (pentamer of benzene).

Example 7 An aluminum foil was subjected to a chemical conversion treatment to be roughened, and manganese dioxide fine particles were further formed on the aluminum foil to form a porous surface electrode having conductive nuclei.

Using this as an anode, and using a platinum plate as the cathode, the solution of Example 1 was used, and current was applied at an anode current density of ² mA / cm ² for 10 minutes to carry out electrolytic polymerization to obtain a polymer thin film on the anode.

This electrode foil (5 × 15 mm ² ) was folded, and lead wires were attached to the polymer film and aluminum foil to make an electrolytic capacitor element.

Example 8 An electrolytic capacitor was prepared by using the pyrrole trimer solution of Example 3 in Example 7.

Example 9 An electrolytic capacitor was prepared by using the benzene trimer solution of Example 5 in Example 7.

Comparative Example 1 A polymer thin film was obtained in the same manner as in Example 3 except that the pyrrole trimer was changed to the pyrrole monomer.

Comparative Example 2 An electrolytic capacitor was prepared in the same manner as in Example 7 except that the pyrrole monomer solution was used.

The polymer films of Examples 1 to 6 and Comparative Example 1 were 2 × 20.
The electrical conductivity was measured by the four-terminal method while cutting it into mm ² and applying a constant current of 1 mA.

The results and the polymerization rate are shown in Table 1. The polymerization rate is the film formation rate (μm / m when polymerized at a current density of ² mA / cm ²
in).

As is clear from Table 1, the polymerization method of the present invention has a polymerization rate three times or more as high as that of the comparative example, so that the film formation time can be reduced to one third or less.

Further, the higher conductivity of the polymer thin film of the present invention as compared with the comparative example is considered to be because the polymer thin film having a high degree of polymerization was obtained.

Table 2 shows the impedance characteristics of the electrolytic capacitors of Examples 7 to 9 and Comparative Example 2.

As is clear from Table 2, the electrolytic capacitor of the comparative example shows a change in impedance after 1000 hours of energization.
Although it was 50% or more, the rate of change in impedance of the electrolytic capacitor of the present invention was within 5%.

EFFECTS OF THE INVENTION As described above, an electrolytic capacitor in which an electrolytically polymerized film of a π-electron conjugated oligomer is formed on a porous surface electrode having a conductive nucleus according to the present invention has a solid property even when energized for a long time with excellent frequency characteristics. There is an effect that the electrolyte can maintain low impedance characteristics for a long time.

 Thus, the present invention is of great industrial value.

Claims (1)

[Claims] 1. After roughening an aluminum foil, fine particles of manganese dioxide are formed on the aluminum foil, and the aluminum foil is used as an anode, and at least the thiophene oligomer, the pyrrole oligomer or the benzene oligomer is formed on the anode. A method for producing an electrolytic capacitor, comprising forming an electrolytically polymerized film of one π-electron conjugated oligomer.