JPH08306588A - Solid-state electrolytic capacitor and manufacturing method - Google Patents

Abstract

PURPOSE: To provide a solid-state electrolyte with high electrolytic conduction and good adhesiveness to a dielectric film, by using a solid-state electrolyte, as a complex, made up of a conductive polymer of pentagonal heterocyclic complex with conjugated double bonds in the main chain and a polymeric electrolyte represented in a given formula. CONSTITUTION: A porous dielectric oxide film 3 that is oxidized in electrolysis is formed on a surface of an anode made of aluminum valve metal. Then, a solid-state electrolyte 6, as a complex, made up of conductive polymer of pentagonal heterocyclic complex with conjugated double bonds in the main chain and a polymeric electrolyte represented by a given formula, where X and Y are hydrogen atoms or an alkyl group with carbon number of 10 or below, Z is -OSO3 or -SO3 , a and b are zero or an integral number of 10 or below, Q is a methyl group, and n is a positive integral number of 3 or above is put in contact with the dielectric oxide film 3. After a cathode 4 made of metal foil like aluminum foil is provided, these members are sealed with a resin 7 to complete a solid-state electrolytic capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor having a good performance using a composite of a conductive polymer and a polymer electrolyte as a solid electrolyte, and a method for producing the same.

[0002]

2. Description of the Related Art A conventional solid electrolytic capacitor, for example, an aluminum electrolytic capacitor, has an aluminum oxide layer, which is a dielectric material, provided on an etched porous aluminum foil having a large specific surface area to form an electrolytic paper between it and a cathode foil. It is well known that the structure is impregnated with a liquid electrolyte, but the liquid electrolyte is not preferable because it causes problems such as liquid leakage. Attempts have been made to replace the layers with solid electrolytes. Such a solid electrolytic capacitor has a structure in which a solid electrolyte is adhered to a film-forming metal such as aluminum having an anodized film or tantalum.The solid electrolyte of this type of solid electrolytic capacitor is mainly composed of manganese nitrate. Manganese dioxide formed by pyrolysis is used. However, due to the high heat required for this thermal decomposition and the oxidizing action of the generated NO _x gas, the metal oxide film such as aluminum or tantalum, which is a dielectric, may be damaged.
As a result, the withstand voltage is lowered, the leakage current is increased, and the dielectric characteristics are deteriorated, which is a very serious drawback. Further, such a solid electrolytic capacitor also has a drawback that a process of re-formation is required.

In order to make up for these drawbacks, a method of forming a solid electrolyte layer without applying high heat, that is, a method of using a highly conductive organic semiconductor material as a solid electrolyte has been proposed.
For example, JP-A-52-79255 and JP-A-58-1
Japanese Patent Publication No. 7609 describes a solid electrolytic capacitor containing 7,7,8,8-tetracyanoquinodimethane (hereinafter abbreviated as TCNQ) as a main component. Further, a solid electrolytic capacitor using a complex salt of Nn-propylisoquinoline and 7,7,8,8-tetracyanoquinodimethane is known.

[0004]

However, these TCNQ complex salt compounds have poor adhesion to the anodized film,
Since the electric conductivity is insufficient as 10 ⁻³ to 10 ⁻² S · cm ⁻¹ , the solid electrolytic capacitor using this has the problem that the capacitance value of the capacitor is small and the dielectric loss is large. Stability is poor and reliability is low. Therefore, an object of the present invention is to solve these problems of the prior art, and to provide a solid electrolytic capacitor using an organic semiconductor having high conductivity and good adhesion to a dielectric film as a solid electrolyte, and a method for manufacturing the same. It is in.

Further, the above-mentioned conventional solid electrolytic capacitor has a problem that the manufacturing cost of the whole solid electrolytic capacitor is high because the price of TCNQ is high. Therefore, another object of the present invention is to provide a solid electrolytic capacitor which uses a conductive polymer compound which is inexpensive and has good performance as a solid electrolyte.

[0006]

The present invention has been made to achieve the above object, and the gist thereof is to provide a conductive polymer comprising a hetero five-membered ring compound having a conjugated double bond in the main chain and the following. There is provided a solid electrolytic capacitor characterized by using a complex with a polymer electrolyte represented by the general formula (1) as a solid electrolyte and a method for producing the same.

Embedded image (However, X, Y is a hydrogen atom or an alkyl group having 10 or less carbon atoms, Z is -OSO ₃ ^-, or -SO ₃ ^- and is,
a, b is 0 or 10 less positive integer, Q is a methylene group (-CH ₂ -), n is an positive integer of 3 or more. )

[0007]

The present invention will be described in detail below. FIG. 1 is a vertical sectional view of a solid electrolytic capacitor of the present invention. aluminum,
An electrolytically oxidized porous dielectric oxide film 3 is provided on the surface of an anode 2 made of a valve metal such as tantalum or niobium, and a solid electrolyte 6 made of a composite of a conductive polymer and a polymer electrolyte as described above is provided on the porous dielectric oxide film 3. Are in contact with each other, and a part of this solid electrolyte enters the pores of the dielectric oxide film 3. Further, after providing the cathode 4 of a metal foil such as aluminum, it is sealed with a resin 7. Further, 1 indicates an anode lead wire and 5 indicates a cathode lead wire.

In the present invention, the conductive polymer used in the solid electrolyte is a hetero five-membered ring compound having a conjugated double bond in the main chain, and specific examples thereof include polyfuran, polypyrrole, polyselenophene and polythiophene. And derivatives thereof.

Next, the polyelectrolyte complexed with the conductive polymer has a number average molecular weight of 500 or more and contains at least one sulfoxyl anion in the molecule and is represented by the following general formula. To be

[Chemical 4] (However, X, Y is a hydrogen atom or an alkyl group having 10 or less carbon atoms, Z is -OSO ₃ ^-, or -SO ₃ ^- and is,
a, b is 0 or 10 less positive integer, Q is a methylene group (-CH ₂ -), n is an positive integer of 3 or more. ) For example, polyvinyl sulfonate anion having a number average molecular weight of 500 or more, polyallyl sulfonate anion and the like can be mentioned.

The amount of the above-mentioned polymer electrolyte to be complexed with the conductive polymer is not particularly limited, but usually the conductive polymer 100 is used.
The amount of the polymer electrolyte is 1 to 500 parts by weight, preferably 2 to 200 parts by weight, particularly preferably 4 to 100 parts by weight, based on parts by weight.

There are various possible methods for producing a composite of a conductive polymer and a polymer electrolyte. Usually, the conductive polymer is chemically or electrochemically produced by a known method in the presence of the polymer electrolyte. It is obtained by synthesizing At this time, the polymer electrolyte is preferably dissolved in the polymerization solution, but it may be in a non-dissolved slurry state.

For the anode of the solid electrolytic capacitor according to the present invention, a metal foil of aluminum, tantalum, niobium or the like or a sintered body of these metal powders is used. In the case of a metal foil, the surface is etched to have pores. The metal foil or the sintered body is subjected to electrode oxidation in, for example, a solution of ammonium borate to form a thin layer of a dielectric on the metal foil or the sintered body. The composite of the conductive polymer and the polyelectrolyte according to the present invention comes into contact with the thin layer of the dielectric and partly penetrates into the pores.

Next, for attaching a composite of a conductive polymer and a polymer electrolyte to a thin dielectric layer, for example, (i)
A method of directly polymerizing a monomer of a conductive polymer on a dielectric thin layer in the presence of a polyelectrolyte, (ii) by dispersing or dissolving a composite of a preliminarily synthesized conductive polymer and a polyelectrolyte in a solvent Examples include a method of coating a thin dielectric layer,
It is not necessarily limited to these.

[0014]

The present invention will be described in detail with reference to the following examples. Example 1 Aluminum foil having a thickness of 100 μm (purity 99.99%)
Is used as an anode, and the surface of the foil is electrochemically etched by alternately using direct current and alternating current, and the average pore diameter is 2 μm.
Then, a porous aluminum foil having a specific surface area of 12 m ² / g was obtained. The etched aluminum foil was then immersed in a solution of ammonium borate to electrochemically form a thin layer of dielectric on the aluminum foil in the solution. Next, a solution prepared by dissolving 70 g of polyvinyl potassium sulfate and 20 g of ferric chloride in 500 cc of distilled water was applied onto this aluminum dielectric, and the vapor of pyrrole was contacted with this for about 1 hour to form a polypyrrole / polyvinyl sulfate composite. The body was formed. After sufficiently washing with distilled water and drying, an aluminum foil was used as the cathode and the resin was sealed to form a solid electrolytic capacitor. The conductivity of the solid electrolyte is 0.2S
It was cm ^-1 .

Comparative Example 1 A solid electrolytic capacitor was prepared in which manganese dioxide was used as a solid electrolyte and an aluminum foil was used as a cathode on an aluminum foil having the same dielectric layer as in Example 1.

Table 1 collectively shows the characteristic values of the solid electrolytic capacitors obtained in the above examples.

[Table 1] As is clear from Table 1, the solid electrolytic capacitor according to the present invention has a smaller dielectric loss and leakage current than the conventional solid electrolytic capacitor using manganese dioxide as an electrolyte, and can produce a high withstand voltage solid electrolytic capacitor. it can. Further, the value of capacity × rated voltage of the solid electrolytic capacitor according to the present invention is larger than that of a solid electrolytic capacitor using manganese dioxide, and a large capacity can be obtained with the same shape.

[0017]

The solid electrolytic capacitor of the present invention has extremely high practicability and has the following advantages as compared with the conventionally known solid electrolytic capacitors. Since the electrolyte layer can be formed without heating at a high temperature, there is no damage to the anodic oxide film, and there is no need to perform anodic oxidation (reformation) for repair. Therefore, the rated voltage can be several times higher than conventional ones. The size can be reduced to obtain a capacitor having the same capacity and rated voltage. Since the conductive compound has good adhesion to the dielectric film,
(I) Leakage current is small, and (ii) High breakdown voltage capacitors can be manufactured. Since the electrolyte has a sufficiently high electric conductivity of 10 ⁻² to 10 ² S · cm ⁻¹ , it is not necessary to provide a conductive layer such as graphite, which simplifies the process and is advantageous in cost. Good high frequency characteristics.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a specific example of a solid electrolytic capacitor according to the present invention.

[Explanation of symbols]

 1 Anode Lead Wire 2 Anode 3 Dielectric Oxide Film 4 Cathode 5 Cathode Lead Wire 6 Solid Electrolyte 7 Resin

Claims (2)

[Claims] 1. A composite of a conductive polymer composed of a hetero five-membered ring compound having a conjugated double bond in the main chain and a polymer electrolyte represented by the following general formula is used as a solid electrolyte. Solid electrolytic capacitor. Embedded image (However, X, Y is a hydrogen atom or an alkyl group having 10 or less carbon atoms, Z is -OSO ₃ ^-, or -SO ₃ ^- and is,
a, b is 0 or 10 less positive integer, Q is a methylene group (-CH ₂ -), n is an positive integer of 3 or more. ) 2. A conductive polymer monomer composed of a hetero five-membered ring compound having a conjugated double bond in its main chain is polymerized on a dielectric thin layer in the presence of a polymer electrolyte represented by the following general formula. A method for producing a solid electrolytic capacitor, characterized in that it is attached. Embedded image (However, X, Y is a hydrogen atom or an alkyl group having 10 or less carbon atoms, Z is -OSO ₃ ^-, or -SO ₃ ^- and is,
a, b is 0 or 10 less positive integer, Q is a methylene group (-CH ₂ -), n is an positive integer of 3 or more. )