KR20010013411A - Solid electrolytic capacitor and process for producing the same - Google Patents

Abstract

A capacitor element (10) fabricated by winding an anode foil (1) and a cathode foil (2) via a separator (3) is impregnated with a 3,4- ethylenedioxythiophene and an oxidizing agent to form poly(ethylenedioxythiophene) by polymerization. A nonwoven fabric composed chiefly of a synthetic fiber is used as a separator, enabling a solid electrolyte to be favorably formed without being reacted with the oxidizing agent. Preferably, the capacitor element is dipped in water at 80 to 100 °C for 1 to 10 minutes to dissolve and remove the binder in the separator in order to preclude adverse effects on the electric characteristics caused by the binder. The oxidizing agent is used at a concentration in excess of 40 % by weight with respect to the solvent, so that the degree of polymerization is high and a dense and homogeneous solid electrolytic layer is formed. To form the electrolytic layer, the capacitor element is impregnated with a monomer solution prepared by mixing 3,4-ethylenedioxythiophene and a volatile solvent at a volume ratio of 1:1 to 1:3. Then, the capacitor element is heat-treated and impregnated with a solution of oxidizing agent to form a dense and homogenous solid electrolytic layer.

Description

Solid Electrolytic Capacitor and Method for Manufacturing the Same {Solid Electrolytic Capacitor and Process for Producing the Same}

(1) The material of the conventional solid electrolyte layer

The electrolytic capacitor is composed of a metal for valve fabrication such as tantalum and aluminum, and forms an oxide film as a dielectric on the surface of the anode electrode with fine holes or etching pits, and withdraws the electrode from the oxide film layer.

And the electrode extraction from an oxide film layer is performed by the electroconductive electrolyte layer. Therefore, in the electrolytic capacitor, the electrolyte layer is responsible for the intrinsic cathode. For example, in an aluminum electrolytic capacitor, the liquid electrolyte is used as the intrinsic electrode, and the cathode electrode is merely responsible for the electrical connection between the liquid electrolyte and the external terminals.

The electrolyte layer that functions as an intrinsic cathode is desired to have adhesion to the oxide film layer, compactness, uniformity, and the like. In particular, the adhesion inside the micropores or etching pits of the anode electrode has a great influence on the electrical properties, and various electrolyte layers have been proposed in the past.

Since the solid electrolytic capacitor is ion conductive, a solid electrolyte having conductivity instead of a liquid electrolyte lacking impedance characteristics in the high frequency region is used. Among them, manganese dioxide or 7,7,8,8-tetracyanoquinomethane ( TCNQ) complexes are known.

Among these, a solid electrolyte layer made of manganese dioxide is produced by immersing an anode element made of tantalum sintered body in an aqueous solution of manganese nitrate and thermally decomposing at a temperature of about 300 ° C to 400 ° C. The capacitor using such a solid electrolyte layer tends to break the oxide film layer when thermally decomposing manganese nitrate, and therefore, the leakage current tends to increase, and the specific resistance of manganese dioxide itself is also high. Thus, a characteristic that is sufficiently satisfactory in impedance characteristics can be obtained. Was difficult.

In addition, the lead wire was also damaged by heat treatment, and it was necessary to separately install a connection external terminal as a subsequent step.

On the other hand, as a solid electrolytic capacitor using a TCNQ complex, what is described in Unexamined-Japanese-Patent No. 83-191414 is known, The TCNQ complex is heat-melted, immersed and apply | coated to an anode electrode, and the solid electrolyte layer is formed. This TCNQ complex has high conductivity and can obtain good results in frequency characteristics and temperature characteristics.

However, the TCNQ complex is close to its melting point and decomposition point and, depending on the temperature control, has a property of transferring to the insulator in a short time after melting. Remarkable characteristic fluctuations occur due to the solder heat when mounting on a printed board.

(2) Application of conductive polymer

In addition, in order to solve the problems of manganese dioxide or TCNQ complex as described above, it has recently been attempted to use a conductive polymer such as polypyrrole as a solid electrolyte layer.

Although the conductive polymer represented by polypyrrole is mainly produced by the chemical oxidation polymerization method (chemical polymerization) or the electrolytic oxidation polymerization method (electrolytic polymerization), it was difficult to form a film with a strong strength by chemical polymerization.

On the other hand, in electrolytic polymerization, it is necessary to apply a voltage to an object to form a film, and therefore, it is difficult to apply it to an anode electrode for an electrolytic capacitor having an oxide film layer as an insulator on the surface. For example, a method of forming an electrolyte layer by electrolytic polymerization using a conductive polymer film chemically polymerized with an oxidant as a precoating layer, and then using the precoating layer as an electrode has been proposed (Japanese Patent Laid-Open No. 88-173313). Publication No. 88-158829: Manganese dioxide as a precoat layer).

However, since the precoating layer is formed in advance, the manufacturing process is complicated, and in electrolytic polymerization, since a solid electrolyte layer is generated in the vicinity of the external electrode for polymerization disposed on the coating surface of the anode electrode, electroconductivity having a uniform thickness over a wide range It was very difficult to continuously produce a polymer film.

Thus, a thin anode electrode and a cathode electrode are wound around the partition wall to form a so-called wound capacitor element, and an electrolyte layer made of a conductive polymer membrane produced only by chemical polymerization by immersing a monomer such as pyrrole and an oxidant in the capacitor element. It was attempted to form.

Such winding type capacitor elements are well known in aluminum electrolytic capacitors. However, it is expected to keep the conductive polymer layer as a partition to avoid the complexity of electrolytic polymerization and to increase the capacity by a thin electrode having a large surface area.

In addition, it was expected that by using the wound capacitor element, the electrodes and the partition walls of both poles were maintained at a constant tension force, contributing to the adhesion between the electrodes of the both poles and the electrolyte layer.

However, when the condenser element is impregnated with the mixed solution of the monomer and the oxidizing agent, the polymerization reaction of the monomer and the oxidant proceeds rapidly, so that no solid electrolyte layer is formed to the inside of the condenser element, so that the expected electrical characteristics can be obtained. It turned out that there was no.

Thus, attempts have been made to lower the polymerization temperature of the solution during the reaction, and some good electrical characteristics have been obtained, but there is a problem that only the breakdown voltage characteristics are insufficient.

In addition, in the case of chemical polymerization at low temperature, in addition to the need for strict temperature control, there is a problem that the manufacturing apparatus is complicated, resulting in high product cost.

(3) Conception about polyethylene dioxythiophene

On the other hand, the examination of various conductive polymers continues, and the reaction speed is slow, and the technique focusing on the polyethylene dioxythiophene (PEDT) excellent in adhesiveness with the oxide film layer of a positive electrode (Unexamined-Japanese-Patent No. 90-15611) This exists.

Applicant noticed that the polymerization reaction rate of this polyethylenedioxythiophene is slow, and the present invention is immersed in a mixed solution in which a monomer and an oxidant solution are mixed in a condenser element wound around a cathode electrode foil and a cathode electrode foil through a partition wall. The invention (Japanese Patent Application No. 96-131374) which filed the polyethylenedioxythiophene which is a solid electrolyte in the capacitor | condenser element by the chemical polymerization reaction of the monomer and oxidant which arises slowly is filed.

(4) challenges to be solved

However, even if the mixed solution which mixed the monomer and the oxidant solution was impregnated using the partition used for the normal electrolytic capacitor in order to produce polyethylenedioxythiophene, the ESR characteristic of the obtained solid electrolytic capacitor is not satisfactory, and an electrostatic The variation in capacity or lifetime characteristics is also large. This is considered to be because the use of ordinary barrier ribs is unsuitable for producing polyethylene dioxythiophene, and the impregnation conditions of the monomer and the oxidant for the capacitor element are not sufficient. This point will be described below.

First, in the case of producing polyethylenedioxythiophene, since ferric p-toluenesulfonic acid or the like is used as the oxidizing agent, chemical reactions occur in partitions such as manilages used in ordinary electrolytic capacitors, thereby oxidizing the oxidizing agent. In addition to damage to the wall, it may also cause an accident such as a short circuit caused by damage to the partition wall.

On the other hand, although it is also possible to use glass paper etc. as a partition, it is difficult to make thin glass paper of 80-200 micrometers of normal thickness to the same extent as partitions of 40 micrometers-thick manilaji etc., and bending strength Is slightly fragile, making it difficult to downsize the product. In addition, since the glass paper is non-hydrophilic, it is difficult to produce a dense and uniform conductive polymer layer, that is, a solid electrolyte layer, which may adversely affect the electrical properties of the product.

On the other hand, it is considered that it is difficult to produce a sufficiently dense and uniform solid electrolyte layer inside the condenser element simply by simply impregnating the mixed solution in which the monomer and the oxidant solution are mixed. In particular, when the mixed solution in which the monomer and the oxidant solution are mixed is impregnated, the polymerization reaction of the mixed solution proceeds over time, so that the mixed solution is impregnated in the condenser element in parallel with the polymerization reaction. Therefore, it is thought that the solid electrolyte layer produced | generated easily becomes nonuniform by hardening on the way, etc. without penetrating into the capacitor element inside. In addition, in order to predict the case where the mixed solution hardens in this way, in order to immerse the mixed solution again, the mixed solution is continuously impregnated. This continuous impregnation of the mixed solution is a waste of material and time. Many reduce productivity.

(5) Purpose of the invention

The present invention has been proposed in order to solve the above problems, and its object is to improve the impregnation conditions of the monomer and the oxidant on the partition wall or the capacitor element used in the wound capacitor element, thereby making it compact and uniform inside the capacitor element. It is to provide a solid electrolyte layer made of a conductive polymer, excellent in electrical characteristics, and a large capacity solid electrolytic capacitor. Moreover, it is providing the manufacturing method which can manufacture such excellent solid electrolytic capacitor efficiently and is excellent in productivity.

<Start of invention>

In order to solve the above problems, in the present invention, 3,4-ethylenedioxythiophene and an oxidizing agent are impregnated into a capacitor element wound between the positive electrode foil and the negative electrode foil via a partition wall, and the polyethylene deoxytiation is carried out by a chemical polymerization reaction. It is to provide an improved solid electrolytic capacitor as the solid electrolytic capacitor which produces the offen, and at the same time, to provide an improved method for producing such a solid electrolytic capacitor.

The present invention is to provide a solid electrolytic capacitor using a nonwoven fabric mainly composed of synthetic fibers in a partition for improving the partition. This nonwoven fabric is suitably a nonwoven fabric obtained by mixing vinylon fibers or vinylon fibers with glass fibers, polyester fibers, nylon fibers, rayon fibers, and paper fibers. The partition wall mainly composed of such synthetic fibers does not react with the oxidizing agent and has affinity for the solvent. Thus, the monomer and the oxidizing agent easily penetrate to the inside of the wound capacitor, thereby obtaining a dense and uniform solid electrolyte layer. Moreover, since such a partition is thin and rich in flexibility compared to glass paper having a thickness of 80 to 200 µm, the amount of winding per volume of the electrode foil and the partition is increased as a result.

By the way, when the nonwoven fabric which mainly uses the synthetic fiber as mentioned above is used as a partition, it turned out that the target capacitance characteristic or heat resistance becomes difficult to be obtained. The reason is not clear, but it was thought that the binder in the nonwoven fabric had some effect. Based on these considerations, the present invention provides a method for producing a solid electrolytic capacitor for improving the partition wall, wherein the capacitor element after winding is immersed in water of 80 ° C to 100 ° C for 1 to 10 minutes to dissolve and remove the binder in the partition wall. A method of impregnating, 4-ethylenedioxythiophene and an oxidizing agent is provided. In this method, after dissolving and removing the binder in a partition, the said capacitor | condenser element may be dried at 80 to 120 degreeC, and 3, 4- ethylene dioxythiophene and an oxidizing agent may be impregnated after that. It is more preferable to repeat the series of processes which consist of the process of removing a binder in water mentioned above, and the drying process following this at least 2 times or more.

The present invention then provides a method for impregnating 3,4-ethylenedioxythiophene and an oxidizing agent in a concentration exceeding 40% by weight with respect to the solvent in terms of improving the impregnation conditions of the monomer and the oxidizing agent. The solvent used here is suitably butanol, and an oxidizing agent is suitably selected from ferric p-toluenesulfonic acid, ferric dodecylbenzenesulfonic acid, and ferric chloride. When the oxidizing agent of 40 weight% or less is used with respect to a solvent, sufficient ESR characteristic is not acquired, but ESR characteristics can be improved remarkably by using an oxidizing agent of concentration exceeding 40 weight% with respect to a solvent.

The present invention also relates to the improvement of the impregnation conditions of the monomer and the oxidant, and to provide a method of impregnating a constituent of 3,4-ethylenedioxythiophene in the capacitor element and then impregnating the oxidant in the capacitor element. According to this method, since the monomer first impregnated and distributed in the condenser element and the later impregnated oxidant are chemically polymerized in the condenser element, a dense and uniform solid electrolyte layer can be produced inside the wound condenser element. . More suitably, the monomer is diluted with a volatile solvent and then heat treated to impregnate the oxidant solution. In this case, the diluted monomer can be impregnated uniformly in the condenser element, and the volatile solvent can be volatilized by subsequent heat treatment, whereby a higher quality solid electrolyte layer can be produced.

In this case, since the heat treatment time is completed in a short time, the productivity is also excellent.

The volatile solvent used in this method is suitably selected from hydrocarbons, ethers, esters, ketones, alcohols and nitrogen compounds. Such materials are sufficiently dissolved in the monomers to promote uniform impregnation of the monomers, and at the same time, they do not cause adverse effects on the electrode foil made of aluminum or the like. In particular, methanol, ethanol, acetone and the like are more suitable because of their low price and relatively easy handling. In addition, when the monomer solution which mixed the monomer and the volatile solvent is impregnated as it is in the process of impregnating a monomer solution in a capacitor element, since a volatile solvent may volatilize after mixing, a composition may change with time, suitably Impregnates the monomer and the volatile solvent separately. In this case, the monomer solution with a small change in composition can be impregnated into the capacitor element. In addition, by impregnating the monomer solution in which the monomer and the volatile solvent are mixed at a volume ratio of 1: 1 to 1: 3, the monomer can be uniformly impregnated with the capacitor element, thereby producing a high quality solid electrolyte layer. In this case, it is also necessary to use the minimum required volatile solvent, which does not reduce productivity.

The present invention relates to a method for producing a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor using a conductive polymer as an electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded perspective view showing an example of a solid electrolytic capacitor produced by the present invention, and Fig. 2 is an enlarged cross sectional view showing a positive electrode foil having a solid electrolyte layer produced by the present invention.

<Best form for carrying out invention>

EMBODIMENT OF THE INVENTION Hereinafter, the best form for implementing this invention is demonstrated concretely with reference to drawings.

(1) basic manufacturing process

1 shows a solid electrolytic capacitor manufactured by the present invention, and is basically produced in the following order.

First, the anode electrode foil (anode foil) 1 and the cathode electrode foil (anode foil) 2 formed of a metal for valve manufacture such as aluminum and having an oxide film layer formed thereon are wound through a partition wall 3. The capacitor element 10 is formed. The condenser element 10 is impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent to produce a solid electrolyte layer 5 made of polyethylene dioxythiophene by a chemical polymerization reaction in the condenser element 10. . This solid electrolyte layer 5 is held by the partition 3.

More specifically, the anode foil 1 is made of a metal for valve fabrication such as aluminum, and as shown in Fig. 2, the surface thereof is roughened by an electrochemical etching treatment in an aqueous chloride solution, and a plurality of etching pits ( 8) is formed. In addition, an oxide film layer 4 serving as a dielectric is formed on the surface of the positive electrode foil 1 by applying a voltage in an aqueous solution such as ammonium borate. In addition, the cathode foil 2 is made of aluminum or the like as the anode foil 1, and only the etching treatment is performed on the surface thereof.

The lead wires 6 and 7 for connecting each electrode to the outside are connected to the anode foil 1 and the cathode foil 2 by well-known means, such as stitching and ultrasonic welding. The lead wires 6 and 7 are made of aluminum or the like, and constitute a connection part of the positive electrode foil 1 and the negative electrode foil 2 and an external connection part which is responsible for electrical connection with the outside. It is derived from the end face of.

Here, the dimensions of both electrode foils 1 and 2 are arbitrary in accordance with the specifications of the solid electrolytic capacitor to be manufactured, and the partition 3 is also slightly larger in width depending on the dimensions of both electrode foils 1 and 2. You may use one.

In addition, 3, 4- ethylene dioxythiophene can be obtained by the well-known manufacturing method disclosed by Unexamined-Japanese-Patent No. 90-15611. As the oxidizing agent, ferric p-toluenesulfonic acid dissolved in butanol is used.

(2) solid electrolytic capacitors with improved partitions

One form of the partition wall improved by the present invention is a nonwoven fabric mainly composed of vinylon fibers, and in another form, by mixing vinylon fibers with paper fibers such as glass fibers, polyester fibers, nylon fibers, rayon fibers, and manila The obtained nonwoven fabric can also be used. In addition, as such a nonwoven fabric, the thing of 6-36 g / m <^2> , fiber diameters 5-30 micrometers, 30-150 micrometers in thickness, and 0.2-0.5 g / cm <^3> in density is used specifically ,.

This improved partition wall is about the same thickness as the partition wall thickness of 40 μm used in conventional electrolytic capacitors, and does not react chemically with the oxidant and has affinity for the solvent of the oxidant. It is possible to improve the volumetric efficiency of the condenser element without impairing the permeability. Therefore, the size and capacity of the solid electrolytic capacitor can be realized.

In addition, when manufacturing the solid electrolytic capacitor which has such an improved partition, a winding type capacitor | condenser element is formed using this partition, and this capacitor | condenser element is immersed for 1 minute-10 minutes in 80 degreeC-100 degreeC water, After dissolving and removing the binder, the condenser element is dried at 80 ° C to 120 ° C, and then 3,4-ethylenedioxythiophene and an oxidizing agent are impregnated.

By this method, since the binder in the nonwoven fabric used as a partition can be dissolved and removed, the phenomenon of the electrostatic capacitance which arises due to a binder can be prevented. Therefore, the characteristic of a capacitor can be improved.

Hereinafter, the concrete manufacturing process of the solid electrolytic capacitor which has such an improved partition, and the Example of the solid electrolytic capacitor obtained by it are demonstrated concretely, comparing with a comparative example.

(2-1) Comparison of Improved Bulkheads and Glass Paper

First, a solid electrolytic capacitor (Example 1) having an improved partition wall according to the present invention and a solid electrolytic capacitor (Comparative Example 1) having a partition wall made of glass paper were compared.

<Example 1>

The positive electrode foil 1 and the negative electrode foil 2 described above were wound through a partition 3 made of a nonwoven fabric mainly composed of vinylon fibers having a thickness of 50 µm and a basis weight of 12 g / m 2, as shown in FIG. 1. The capacitor element 10 was formed. Here, the diameter dimension of the capacitor | condenser element 10 was 4 (phi), the longitudinal dimension was 7 mm, the rated voltage was 16 WV and the rated capacitance was 10 microF.

And the binder in the partition 3 was dissolved and removed by immersing this capacitor element 10 in 100 degreeC water for 5 minutes. This process can be repeated several times at regular intervals as needed.

Subsequently, the condenser element 10 was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent. As the oxidizing agent, ferric p-toluenesulfonic acid dissolved in butanol was used as described above. In addition, the compounding ratio of 3, 4- ethylene dioxythiophene and an oxidizing agent can be 1: 5, for example.

Subsequently, the capacitor element 10 impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent is left to polymerize by being left to stand for 2 to 15 hours at a polymerization temperature of 25 ° C to 150 ° C to form a solid electrolyte layer made of polyethylenedioxythiophene ( 5) was generated.

In this case, the polymerization temperature and the stand-by time range, although the capacitance, tan δ, and impedance characteristics of the solid electrolytic capacitors produced increased as the polymerization temperature increased, the leakage current characteristics tended to deteriorate. Therefore, it can change arbitrarily within the said range according to the specification of the capacitor | condenser element 10 to manufacture.

After the solid electrolyte layer 5 is formed in the partition 3 interposed between the positive electrode foil 1 and the negative electrode foil by the above process, the outer periphery of this capacitor element 10 is covered with a solid electrolyte A capacitor was obtained.

<Comparative Example 1>

The fresh positive electrode foil 1 and the negative electrode foil 2 were wound up through a partition wall made of glass paper having a thickness of 150 μm and a basis weight of 20 g / m 2, thereby obtaining a capacitor element as shown in FIG. 1. The capacitor element was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent under the same conditions as in Example 1 to form a solid electrolyte layer made of polyethylenedioxythiophene, and then the outer cover was covered with a rated voltage of 16 WV and rated electrostatic A solid electrolytic capacitor with a capacity of 10 μF was obtained.

<Comparison of Initial Characteristics>

When the initial characteristic was measured about the solid electrolyte capacitor of Example 1 and Comparative Example 1 as mentioned above, the result as shown in following Table 1 was obtained. In addition, "capacity appearance rate" shows the ratio with respect to the rated electrostatic capacity of the measured electrostatic capacity.

120 Hz (μF) capacitance Capacity Prevalence (%) tan δ 120 Hz (%) ESR100 KHz (Ω) Leakage Current 20 V (μA) Comparative Example 1 8.6 86.0 1.8 0.065 0.23 Example 1 9.4 94.0 1.8 0.070 0.15

As can be seen from Table 1, in the solid electrolytic capacitor of Example 1 using a 50 μm-thick bulkhead composed of nonwoven fabric mainly composed of vinylon fibers, Comparative Example 1 and a partition of 150 μm-thickness made of glass paper were used. In contrast, nearly equivalent characteristics were obtained. Therefore, it was clear that the volume efficiency of Example 1 which used the partition thickness of 1/3 of the comparative example 1 improved significantly compared with the comparative example 1.

(2-2) Comparison of the Effect of Binders

<Example 2>

In the same manner as in Example 1 described above, the positive electrode foil 1 and the negative electrode foil 2 were wound through a partition 3 made of a nonwoven fabric mainly composed of vinylon fibers having a thickness of 50 μm and a basis weight of 12 g / m 2. The element 10 was formed. Then, the capacitor element 10 was immersed in water at 100 ° C. for 5 minutes to dissolve and remove the binder in the partition, and then the capacitor element 10 was dried at 100 ° C. for 10 minutes.

The capacitor element 10 was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent under the same conditions as in Example 1 to produce a solid electrolyte layer made of polyethylenedioxythiophene, and then coated with an exterior resin to give a rated voltage of 6.3. A solid electrolytic capacitor having a WV and a rated capacitance of 33 µF was obtained.

<Example 3>

The step of immersing the condenser element 10 formed in the same manner as in Example 2 in water at 100 ° C. for 5 minutes to dissolve and remove the binder in the partition wall and drying the condenser element 10 at 100 ° C. for 10 minutes. The series of processes made was repeated twice. Then, the capacitor element 10 was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent under the same conditions as in Example 1 to produce a solid electrolyte layer made of polyethylenedioxythiophene, and then coated with an exterior resin to provide a rated voltage. A solid electrolytic capacitor of 6.3 WV and a rated capacitance of 33 μF was obtained.

<Comparative Example 2>

In the same manner as in Example 1 described above, the positive electrode foil 1 and the negative electrode foil 2 were wound around a partition 3 made of a nonwoven fabric mainly composed of vinylon fibers having a thickness of 50 μm and a basis weight of 12 g / m 2, to condenser elements. (10) was formed. Then, the condenser element 10 is impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent under the same conditions as in Example 1 without performing a step of dissolving and removing the binder in water or a subsequent drying step. After producing the solid electrolyte layer made of citofene, the exterior resin was coated to obtain a solid electrolytic capacitor having a rated voltage of 6.3 WV and a rated capacitance of 33 µF.

<Comparison of Initial Characteristics>

When the initial characteristic was measured about Example 2, Example 3, and Comparative Example 2 mentioned above, the result as shown in following Table 2 was obtained. In addition, as mentioned above, "capacitance appearance rate" shows the ratio with respect to the rated capacitance of the measured capacitance.

120 Hz (μF) capacitance Capacity Prevalence (%) tan δ 120 Hz (%) ESR100 KHz (Ω) Leakage Current 20 V (μA) Comparative Example 2 28.1 85.2 6.1 0.035 5.10 Example 2 31.5 95.5 5.1 0.045 4.45 Example 3 32.8 99.4 6.2 0.037 1.50

As can be seen from Table 2, the capacity appearance rate of the solid electrolytic capacitors of Example 1 and Example 3 without the binder was higher than that of Comparative Example 2 without the binder, and the influence of the nonwoven binder made of synthetic fibers This was reduced. In other words, when the nonwoven fabric mainly composed of synthetic fibers is used as the partition wall as described above, the target capacitance characteristics or heat resistance become difficult to be obtained. Therefore, the target capacitance characteristics or heat resistance can be obtained by removing the binder. I thought it was.

In addition, as apparent from the comparison between Example 2 and Example 3, the capacity appearance rate of Example 3, in which a series of processes consisting of a process of dissolving and removing a binder in water and a subsequent drying process, is repeated twice, is a series of processes. Was higher than the capacity appearance rate of Example 2, which was used only once. This indicates that the effects of the binder can be lessened by repeating the series of processes two or more times.

(2-3) Modification

The specific manufacturing process using the improved partition is not limited to the above-described manufacturing process but may be appropriately modified. In addition, the nonwoven fabric which comprises a partition is not limited to the said Examples 1-3, The nonwoven fabric of arbitrary types which mainly use a synthetic fiber can be used suitably. The thickness of the nonwoven fabric can be appropriately selected, but from the viewpoint of downsizing and large capacity, the thickness of the nonwoven fabric is preferably about 50 µm or less, as in Examples 1 to 3 above. Capacitors of the same rating could be obtained in size.

(3) Preparation method using improved concentration of oxidant

In one embodiment of the production method according to the present invention, ferric p-toluenesulfonic acid dissolved in butanol as a solvent was used. In this case, it has been found that good results are obtained when the oxidizing agent is at a concentration exceeding 40% by weight relative to butanol. Although the reason is not clear, it was thought that the high concentration of the oxidizing agent accelerated the chemical polymerization reaction to increase the polymerization degree, and consequently, the conductivity of the solid electrolytic material was improved.

Here, the distribution of the oxidant to butanol in a concentration exceeding 40% by weight was due to the fact that sufficient capacitance characteristics and ESR characteristics were not obtained at 40% by weight or less. In addition, the substantial upper limit is about 60% by weight, and the oxidizing agent exceeding this becomes remarkably difficult to synthesize. Therefore, the target characteristic is obtained, and distribution of 50 weight%-55 weight% was preferable as a range which is also easy to synthesize | combine.

In addition, the ratio of butanol to ferric p-toluenesulfonic acid in the oxidizing agent may be arbitrary, but a mixing ratio of 1: 3 to 1:15 is suitable.

Hereinafter, the specific manufacturing process of the solid electrolytic capacitor using this improved concentration of oxidizing agent, and the Example of the solid electrolytic capacitor obtained by this are demonstrated concretely, comparing with a comparative example.

(3-1) Manufacturing Process

The positive electrode foil 1 and the negative electrode foil 2 described above were wound through a partition 3 made of a nonwoven fabric mainly composed of vinylon fibers as described above to form a capacitor element 10 as shown in FIG. 1. . Here, the diameter of the condenser element 10 was 4 ψ, the longitudinal size was 7 mm, the rated voltage was 6.3 WV, and the rated capacitance was 33 μF.

Subsequently, the capacitor element 10 was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent to produce a solid electrolyte layer 5 made of polyethylenedioxythiophene. Here, as the oxidizing agent, six different ratios (40% by weight: Comparative Example 3, 44% by weight: Example 4, 48% by weight: Example 5, 52% by weight: Example 6, 56% by weight) with respect to butanol: Example 7, 60 wt%: Ferric p-toluenesulfonic acid dissolved in Example 8) was used. In addition, the compounding ratio of 3, 4- ethylene dioxythiophene and an oxidizing agent was 1: 5.

After the solid electrolyte layer 5 is formed in the partition 3 formed between the positive electrode foil 1 and the negative electrode film 2 by the above process, the outer periphery of this capacitor element 10 is covered with a solid electrolyte. A capacitor was obtained.

(3-2) Change of Characteristics by Concentration of Oxidizer

As described above, six types of solid electrolytic capacitors (Examples 4 to 8 and Comparative Example 3) obtained by using different concentrations of oxidants were investigated. The same result was obtained.

As can be seen from Table 3, in Comparative Example 3 using an oxidizing agent in which 40% by weight of ferric p-toluenesulfonic acid was dissolved in a solvent, sufficient ESR characteristics were not obtained, and the rated capacitance was 30.6 μF. For 33 μF), only 93% of the dose appeared. On the other hand, it was understood that in Examples 4 to 8 using an oxidizing agent having a concentration exceeding 40% by weight, the ESR characteristics were remarkably improved, and the solid electrolyte in the condenser element was densely and uniformly produced.

Concentration of oxidant 120 Hz (μF) capacitance ESR100 KHz (Ω) Comparative Example 3 40 wt% 30.6 0.079 Example 4 44 wt% 32.2 0.039 Example 5 48 wt% 33.0 0.029 Example 6 52 wt% 33.4 0.024 Example 7 56 wt% 33.5 0.025 Example 8 60 wt% 32.8 0.024

(3-3) Modification

The specific manufacturing process using the improved concentration of the oxidizing agent is not limited to the above-described manufacturing process but may be appropriately modified. In addition, the specific density | concentration of an oxidizing agent is not limited to the said Examples 4-8, It can select suitably if it is concentration exceeding 40 weight% with respect to a solvent.

(4) a manufacturing method comprising an improved solid electrolyte layer production process

In one aspect of the production method according to the present invention, when producing a solid electrolyte layer, the capacitor element is impregnated with a monomer solution obtained by mixing 3,4-ethylenedioxythiophene and a volatile solvent, followed by heat treatment of the capacitor element, Thereafter, the capacitor element was impregnated with the oxidant solution.

In addition, as a method of impregnating the condenser element 10 with a monomer solution obtained by mixing 3,4-ethylenedioxythiophene and a volatile solvent, or impregnating an oxidant solution after heat treatment, known means, for example, pressure reduction. Acupuncture method, pressure impregnation method, etc. can be used.

As the volatile solvent, a material selected from hydrocarbons, ethers, esters, ketones, alcohols and nitrogen compounds was used. More specifically, pentane, hexane, etc. can be used as hydrocarbons, and tetrahydrofuran, dipropyl ether, etc. can be used as ethers. Moreover, ethyl formate, ethyl acetate, etc. can be used as ester, and acetone, methyl ethyl ketone, etc. can be used as ketone. Moreover, methanol, ethanol, propanol, etc. can be used as alcohol, and acetonitrile etc. can be used as a nitrogen compound.

Among the above volatile materials, in particular, it is preferable to use methanol, ethanol, acetone and the like as described above. In addition, since water is hardly dissolved in 3,4-ethylenedioxythiophene, it is not preferable to use water as a volatile solvent.

According to the above manufacturing method, the following actions are obtained.

That is, since the amount of 3,4-ethylenedioxythiophene which is a monomer is overwhelmingly small compared to the oxidizing agent, when only this monomer is impregnated in the capacitor element 10, the variation in the amount of monomer in the capacitor element 10 is likely to occur. In this method, the monomer can be uniformly impregnated with the condenser element 10 by diluting the monomer with a volatile solvent such as methanol, ethanol or acetone. In this case, although it is also possible to impregnate the condenser element 10 with the monomer solution which mixed the monomer and the volatile solvent as it is, in this method, the monomer solution which changes little with time especially by impregnating the monomer and volatile solvent separately, especially. Can be impregnated into the capacitor element.

In addition, the volatile solvent can be volatilized by heat-treating the condenser element 10 in which the monomer and the volatile solvent are impregnated.

Therefore, by impregnation of the oxidant solution, the oxidant solution and the monomer uniformly impregnated in the condenser element 10 are chemically polymerized to form a solid, compact polyethylene dioxythiophene inside the wound condenser element 10. The electrolyte layer 5 could be produced.

Moreover, since the heat processing time was short, productivity was excellent. Moreover, productivity was further improved by using methanol, ethanol, acetone, etc. which are cheap and comparatively easy to handle as a volatile solvent.

(4-1) Manufacturing Process

The above-mentioned positive electrode foil 1 and negative electrode foil 2 were wound through a partition 3 made of a nonwoven fabric mainly composed of vinylon fibers as described above, thereby forming a capacitor element 10 as shown in FIG. 1. . Here, the rated voltage of the capacitor | condenser element 10 was 20 WV, and the rated capacitance was 10 microF.

Subsequently, this capacitor element 10 was subjected to an improved solid electrolyte layer generation step. First, a monomer solution obtained by mixing 3,4-ethylenedioxythiophene and a volatile solvent in a volume ratio of 1: 1 to 1: 3 was impregnated. Specifically, 3,4-ethylenedioxythiophene and a volatile solvent were impregnated into the capacitor element 10. And the volatile solvent was volatilized by heat-processing the capacitor | condenser element 10 in which the monomer solution was impregnated in this way.

Then, the solid electrolyte layer 5 which consists of polyethylene dioxythiophene was produced by the chemical polymerization reaction with the said monomer solution which penetrated the partition 3 by impregnating the oxidizing agent solution in the capacitor element 10. As the oxidizing agent, ferric p-toluenesulfonic acid dissolved in butanol was used. In this case, the ratio of butanol and ferric p-toluenesulfonic acid may be arbitrary, but 40 to 60% of the solution was used as an example. And the compounding ratio of 3, 4- ethylene dioxythiophene and an oxidizing agent suited the range of 1: 3-1: 6.

After the solid electrolyte layer 5 was formed in the partition 3 between the positive electrode foil 1 and the negative electrode foil by the above process, the outer periphery of this capacitor element 10 was coat | covered and the solid electrolyte capacitor was obtained. .

(4-2) Comparison of Solid Electrolyte Layer Generation Processes

Hereinafter, specific details of the improved solid electrolyte layer generating process as described above and examples of the solid electrolytic capacitor obtained thereby will be described in detail with reference to a comparative example.

First, Table 4 below shows five examples 9 to 13 as an improved solid electrolyte layer generation process and three comparative examples 4 to 6 as a comparative solid electrolyte layer generation process.

Referring to each example shown in Table 4, Example 9 according to the present invention is an example in which an oxidizing agent is impregnated after a monomer impregnation treatment and a heat treatment of about a few minutes. Examples 10 to 13 are examples in which a monomer is impregnated using a volatile solvent such as acetone or methanol, followed by heat treatment for about a few minutes, followed by impregnation of an oxidizing agent. The difference is in the volume ratio.

In addition, Comparative Examples 5 and 6 are examples which are left to stand at room temperature without using a volatile solvent, and differ in the time from monomer impregnation to oxidizer impregnation. In addition, the comparative example 4 is an example which applied the technique which impregnates the liquid mixture of the monomer and oxidizing agent which concerns on a prior art.

Comparative Example 4 Impregnation of monomer / oxidant mixture solution Comparative Example 5 Monomer impregnation → 15 minutes after oxidizer solution impregnation Comparative Example 6 Monomer impregnation → 80 minutes after oxidizer solution impregnation Example 9 Monomer impregnation → heat treatment → oxidant solution impregnation Example 10 Monomer: Acetone = 1: 1 solution impregnation → heat treatment → oxidant solution impregnation Example 11 Monomer: Acetone = 1: 2 solution impregnation → heat treatment → oxidant solution impregnation Example 12 Monomer: Methanol = 1: 1 solution impregnation → heat treatment → oxidant solution impregnation Example 13 Monomer: Methanol = 1: 2 solution impregnation → heat treatment → oxidant solution impregnation

(4-3) Comparison of Initial Characteristics

Moreover, when initial characteristic was measured about each of Examples 9-13 and Comparative Examples 4-6 mentioned above, the result shown in Table 5 was obtained.

As can be seen from the results shown in Table 5, Examples 9 to 13 according to the present invention showed good values compared to Comparative Examples 4 to 6 with respect to all characteristics of the capacitance, tan δ and equivalent series resistance (ESR). In addition, Comparative Examples 5 and 6 showed better values than Comparative Example 4, but Comparative Example 6 requires a long time from monomer impregnation to oxidizer impregnation, and compared with Examples 9 to 13 in which heat treatment was performed for a short time of about several minutes. Productivity was low.

Capacitance (μF) tan δ ESR100KHz (Ω) Comparative Example 4 9.44 0.042 0.111 Comparative Example 5 10.3 0.032 0.093 Comparative Example 6 10.3 0.024 0.092 Example 9 10.1 0.036 0.077 Example 10 10.4 0.033 0.076 Example 11 10.4 0.034 0.063 Example 12 10.2 0.034 0.060 Example 13 10.3 0.030 0.054

(4-4) Modification

Specific manufacturing processes may be appropriately selected, including improved solid electrolyte layer production processes. In addition, the details of the solid electrolyte layer formation process are not limited to the above Examples 9 to 13, the type of volatile solvent can be appropriately selected, and the volume ratio of monomer and volatile solvent is 1: 1 to 1: 3. It can select suitably in range. In addition, in Examples 9 to 13, the monomer solution in which the monomer and the volatile solvent were mixed was impregnated in the condenser element. However, it is also possible to impregnate the monomer and the volatile solvent separately. Can be impregnated Moreover, the kind of oxidizing agent or its solvent, its ratio, etc. can also be selected suitably.

(5) another embodiment

In addition, this invention is not limited to the said form or Example, In addition, various modifications are possible within the scope of this invention.

For example, in the above-described aspect of the manufacturing method using an improved concentration of the oxidizing agent or in the above-described aspect of the manufacturing method including the improved solid electrolyte layer production process, the improved partitions are used, respectively. The effect is also obtained, but a superior effect has been obtained by carrying out a production process comprising an improved solid electrolyte layer production process using an improved concentration of oxidant. In other words, by carrying out a manufacturing method including an improved solid electrolyte layer production process using an improved partition and an improved concentration of oxidant, synergistic effects by respective features have been obtained. On the contrary, only by having any one of these characteristics, a certain effect according to the characteristic was acquired.

As described above, the present invention first uses a nonwoven fabric mainly composed of synthetic fibers as an improved partition wall. The nonwoven fabric includes vinylon fibers or vinylon fibers and glass fibers, polyester fibers, nylon fibers, rayon fibers, and paper fibers. It is a nonwoven fabric obtained by mixing.

Such a partition wall is about the same thickness as a partition wall having a thickness of about 40 µm such as manilages used in a conventional electrolytic capacitor, and does not react chemically with an oxidant and has affinity for a solvent of the oxidant. Therefore, the volumetric efficiency of a capacitor | condenser element can be improved, without impairing the permeability of the monomer or oxidizing agent to be impregnated, and a miniaturization or large capacity | capacitance of a solid electrolytic capacitor can be realized.

Further, the capacitor element wound using the partition wall is immersed in water at 80 ° C to 100 ° C for 1 minute to 10 minutes to dissolve and remove the binder in the partition wall, or thereafter, by drying the capacitor element at 80 ° C to 120 ° C, It is possible to dissolve and remove the binder in the partition wall, thereby preventing the reduction of the capacitance generated due to the binder.

In addition, in the present invention, by using an oxidizing agent having a concentration of more than 40% by weight with respect to the solvent as an improved oxidizing agent, it is possible to produce a dense and uniform solid electrolyte layer inside the condenser element, and as a result, ESR characteristics This excellent solid electrolytic capacitor can be obtained.

In addition, in the present invention, as an improved solid electrolyte layer generating process, by impregnating a monomer in a capacitor element and then impregnating an oxidizing agent, a dense and uniform solid electrolyte layer can be produced inside the wound capacitor element, and as a result, The electrical characteristics are excellent and a large capacity solid electrolytic capacitor can be obtained.

In particular, in the typical manufacturing method according to the present invention, after impregnating a capacitor solution in which a monomer and a volatile solvent are mixed into a capacitor element, heat treating the capacitor element, and then impregnating the capacitor element with an oxidant solution, Since a solid electrolyte layer of high quality can be produced, a solid electrolytic capacitor having higher electrical characteristics can be produced. This production method is particularly excellent in productivity and very practical because only a few minutes of heat treatment can be used and inexpensive and easy to handle volatile solvents can be used.

Claims (16)

A solid electrolytic capacitor in which 3,4-ethylenedioxythiophene and an oxidizing agent are impregnated in a capacitor element wound around a cathode electrode foil and a cathode electrode foil through a partition wall to produce polyethylenedioxythiophene by a chemical polymerization reaction. A solid electrolytic capacitor comprising a nonwoven fabric mainly composed of synthetic fibers. The solid electrolytic capacitor according to claim 1, wherein the barrier rib is made of vinylon fibers or nonwoven fabric obtained by mixing vinylon fibers with glass fibers, polyester fibers, nylon fibers, rayon fibers, and paper fibers. In the manufacturing method of the solid electrolytic capacitor which produces | generates polyethylene dioxythiophene by chemical polymerization reaction by impregnating 3, 4- ethylene dioxythiophene and an oxidizing agent in the capacitor element which wound the positive electrode foil and the negative electrode foil through the partition. Using a nonwoven fabric mainly composed of synthetic fibers in the partition wall, and immersing the condenser element wound using the partition wall in water of 80 ° C to 100 ° C for 1 minute to 10 minutes to dissolve and remove the binder in the partition wall. And after this step, the capacitor element is impregnated with the 3,4-ethylenedioxythiophene and an oxidizing agent. 4. The method for producing a solid electrolytic capacitor according to claim 3, wherein the partition wall is made of vinylon fiber or nonwoven fabric obtained by mixing vinylon fiber and glass fiber, polyester fiber, nylon fiber, rayon fiber and paper fiber. The method of claim 3, further comprising the step of drying the condenser element at 80 ° C to 120 ° C after the step of dissolving and removing the binder, after which the condenser element is impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent. The manufacturing method of the solid electrolytic capacitor characterized by the above-mentioned. The method for producing a solid electrolytic capacitor according to claim 5, wherein the partition wall is made of vinylon fibers or nonwoven fabric obtained by mixing vinylon fibers with glass fibers, polyester fibers, nylon fibers, rayon fibers, and paper fibers. The method of manufacturing a solid electrolytic capacitor according to claim 5, wherein a series of steps comprising a step of dissolving and removing the binder and a step of drying the capacitor element are repeated two or more times. In the manufacturing method of the solid electrolytic capacitor which produces | generates polyethylene dioxythiophene by chemical polymerization reaction by impregnating 3, 4- ethylene dioxythiophene and an oxidizing agent in the capacitor element which wound the positive electrode foil and the negative electrode foil through the partition. And impregnating an oxidizing agent in a concentration exceeding 40% by weight with respect to the solvent as the oxidizing agent. The method for producing a solid electrolytic capacitor according to claim 8, wherein the solvent is butanol. The method for producing a solid electrolytic capacitor according to claim 8, wherein the oxidant is selected from ferric p-toluenesulfonic acid, ferric dodecylbenzenesulfonic acid, and ferric chloride. In the manufacturing method of the solid electrolytic capacitor which produces | generates polyethylene dioxythiophene by chemical polymerization reaction by impregnating 3, 4- ethylene dioxythiophene and an oxidizing agent in the capacitor element which wound the positive electrode foil and the negative electrode foil through the partition. And a process of impregnating a monomer consisting of 3,4-ethylenedioxythiophene in the capacitor element and a step of impregnating the monomer with the oxidizing agent after the step of impregnating the monomer. In the manufacturing method of the solid electrolytic capacitor which produces | generates polyethylene dioxythiophene by chemical polymerization reaction by impregnating 3, 4- ethylene dioxythiophene and an oxidizing agent in the capacitor element which wound the positive electrode foil and the negative electrode foil through the partition. And impregnating a capacitor solution in which the capacitor element is mixed with 3,4-ethylenedioxythiophene and a volatile solvent, heat treating the capacitor element after the impregnation of the monomer solution, and an oxidizing agent in the capacitor element after the heat treatment step. It has a process to impregnate a solution, The manufacturing method of the solid electrolytic capacitor characterized by the above-mentioned. The method for producing a solid electrolytic capacitor according to claim 12, wherein a material selected from hydrocarbons, ethers, esters, ketones, alcohols, and nitrogen compounds is used as the volatile solvent. The method for producing a solid electrolytic capacitor according to claim 13, wherein a material selected from methanol, ethanol and acetone is used as the volatile solvent. The method for producing a solid electrolytic capacitor according to claim 12, wherein 3,4-ethylenedioxythiophene and a volatile solvent are impregnated separately during the impregnation of the monomer solution. The solid electrolytic capacitor according to claim 12, wherein in the step of impregnating the monomer solution, a monomer solution obtained by mixing 3,4-ethylenedioxythiophene and a volatile solvent in a volume ratio of 1: 1 to 1: 3 is impregnated. Method of preparation.