JP4800891B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid electrolytic capacitor using a conductive polymer as an electrolyte and a method for manufacturing the same.

The electrolytic capacitor includes an anode made of a valve metal such as aluminum, tantalum, or niobium, and etching pits and fine holes are formed on the surface of the anode. An oxide film serving as a dielectric is formed on the surface of the anode.
Here, electrical extraction on the cathode side is performed by an electrolyte layer having conductivity. That is, the electrolyte layer is responsible for the true cathode in the electrolytic capacitor. Since the electrolyte layer functioning as a true cathode has a great influence on the electrical characteristics of the electrolytic capacitor, a number of methods for forming the electrolyte layer have been proposed.
Among such electrolytic capacitors, an electrolytic capacitor is disclosed in which a compound having a polyvinyl ether skeleton is dissolved in order to improve the withstand voltage (see, for example, Patent Document 1).
However, since the above electrolytic capacitor uses a liquid electrolyte, deterioration of impedance characteristics in the high frequency region is inevitable.

  On the other hand, some solid electrolytic capacitors use a conductive polymer such as polyethylenedioxythiophene (PEDOT), which is a polythiophene derivative, as an electrolyte. Compared with electrolytic capacitors using a liquid electrolyte, the impedance in a high frequency region is known. Excellent characteristics (see, for example, Patent Document 2).

In recent years, digitalization has progressed in various electronic devices and the like, and solid electrolytic capacitors are required to have low impedance, large capacity, and small size in a high frequency region. Various efforts are being made to meet these requirements.
For example, it has been studied to form a wound solid electrolytic capacitor by winding an anode foil and a cathode foil through a separator and holding the conductive polymer in the separator. Such a winding type solid electrolytic capacitor has an advantage that a wide electrode area can be secured. Aluminum or the like is used as the anode foil.

Conventionally, the above-described solid electrolytic capacitor is manufactured by the following method.
First, in the element manufacturing process, a capacitor element is manufactured in which the formed anode foil and cathode foil are wound through a separator made of paper fibers such as Manila paper.
Then, a restoration conversion in which a chemical conversion treatment is performed on the anode foil of the capacitor element thus manufactured, and a heat treatment in which the capacitor element is heated to a temperature of 200 ° C. or higher are performed.
Thereafter, chemical polymerization is performed in the holding layer forming step, and the conductive polymer is held in the separator layer of the capacitor element. In this way, a holding layer holding the conductive polymer is formed in the capacitor element.
In addition, said heat processing is performed in order to reduce the density of a separator layer by making paper fiber thin, and to reduce ESR (Equivalent Series Resistance; equivalent series resistance).

Thereafter, the capacitor element is housed in a bottomed and cylindrical outer case, the lead wires of the anode and the cathode are drawn out from through holes formed in the sealing rubber, and the opening of the outer case is sealed with the sealing rubber.
JP 2004-311579 A JP 2001-189242 A

As described above, when manufacturing a wound type solid electrolytic capacitor, the separator layer is subjected to heat treatment for the purpose of reducing ESR.
However, when such heat treatment is performed, the winding of the capacitor element is loosened, the withstand voltage is lowered, the leakage current is increased, and there is a possibility that problems such as short puncture occur in the aging process.
In addition to the above steps, when the capacitor element is subjected to heat treatment such as heat treatment in the chemical polymerization step, leakage current may increase due to thermal stress or mechanical stress applied to the electrode foil.

  In view of the above problems, an object of the present invention is to provide a solid electrolytic capacitor in which low ESR, low leakage current, and high withstand voltage are realized, and a method for manufacturing the same.

In order to solve the above problems, the present invention provides a solid electrolytic capacitor in which a conductive polymer is held in a capacitor element in which an anode foil and a cathode foil each having an anodized film formed on a surface thereof are wound through a separator. In
The capacitor element includes a conductive polymer and a compound having a polyvinyl ether skeleton represented by any one of the following chemical formula 1 and chemical formula 2 .

However, in each of Chemical Formula 1 and Chemical Formula 2, R ¹ represents substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl.
R ² and R ^{3 each} represent a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl. R ² and R ³ may be the same as or different from each other.
N represents a natural number of 500 or less. Here, when n is 2 or more, R ¹ may be the same or different from each other. R ² may be the same as or different from each other, and R ³ may be the same as or different from each other.

  In the present invention, the conductive polymer may be obtained by polymerizing aniline or a derivative thereof, pyrrole or a derivative thereof, or thiophene or a derivative thereof.

Further, the present invention provides a method for producing a solid electrolytic capacitor in which a conductive polymer is held in a capacitor element in which an anode foil and a cathode foil each having an anodized film formed on a surface thereof are wound via a separator.
The capacitor element is immersed in a solution obtained by mixing a compound having a polyvinyl ether skeleton represented by any one of the above chemical formula 1 and chemical formula 2 in a solution containing at least one of a monomer, an oxidant, and a dopant, and chemical polymerization A step of causing

The solid electrolytic capacitor of the present invention contains a compound having a polyvinyl ether skeleton together with a conductive polymer. Since the compound having the polyvinyl ether skeleton has an ether bond in the side chain, it has high solubility in a solvent such as methanol.
And, the oxide film of the aluminum electrode foil constituting the solid electrolytic capacitor causes a chemical reaction when the operating temperature of the electrolytic capacitor rises and the applied current or voltage increases, and deteriorates and the withstand voltage decreases. When the compound according to the present invention is present between the electrodes together with the conductive polymer, the ether-bonded oxygen atoms present in the structure are coordinated with the oxide film and are present on the surface of the electrode foil. It is considered that the withstand voltage of the solid electrolytic capacitor can be improved as a result.
By including the compound having the polyvinyl ether skeleton according to the present invention in the conductive polymer, it is possible to provide a solid electrolytic capacitor with reduced ESR, high withstand voltage, and low leakage current. Moreover, according to the manufacturing method of the solid electrolytic capacitor of this invention, it becomes possible to manufacture this solid electrolytic capacitor.

  Hereinafter, with reference to FIGS. 1-3, the solid electrolytic capacitor which is one Embodiment of this invention is demonstrated. FIG. 1 is an explanatory view of a capacitor element used in the solid electrolytic capacitor according to the present embodiment, FIG. 2 is an explanatory view showing a laminated structure of an anode, a separator, and a cathode of the solid electrolytic capacitor according to the present invention, and FIG. It is a process flow figure showing a manufacturing method of a solid electrolytic capacitor concerning this embodiment.

(Structure of solid electrolytic capacitor)
As shown in FIG. 1, a capacitor element 4 used in the solid electrolytic capacitor according to this embodiment includes an anode foil 1 and a cathode foil 3, and the anode foil 1 and the cathode foil 3 are interposed via a separator 2. It has a wound structure.
The anode foil 1 is formed of a valve metal such as aluminum. As shown in FIG. 2, the surface of the anode foil 1 is roughened by an etching process and an oxide film (not shown) is formed. Yes. The cathode foil 3 is made of aluminum or the like, like the anode foil 1, and the surface thereof is also roughened. The roughening may be performed by vapor deposition or coating instead of the etching process.

  A solid electrolyte made of a conductive polymer 7 is held on both surfaces of the separator 2. Thereby, a layer of the conductive polymer 7 is formed between the anode foil 1 and the cathode foil 3.

Here, as the conductive polymer 7, polyaniline or a derivative thereof, polypyrrole or a derivative thereof, or polythiophene or a derivative thereof can be used, and a typical example thereof is polyethylene dioxythiophene (PEDOT).
Such a conductive polymer 7 is produced by chemical polymerization of aniline or a derivative thereof, pyrrole or a derivative thereof, or thiophene or a derivative thereof.

  As shown in FIG. 1, lead tabs are connected to the anode foil 1 and the cathode foil 3, respectively, and lead wires 5 and 6 are drawn from the anode foil 1 and the cathode foil 3 through the lead tabs.

  The solid electrolytic capacitor configured as described above contains a compound having a polyvinyl ether skeleton together with a conductive polymer.

(Method for manufacturing solid electrolytic capacitor)
Next, with reference to FIGS. 1-3, the manufacturing method of the solid electrolytic capacitor to which this invention is applied is demonstrated.

First, in order to increase the effective surface area of the electrode, the surface of the aluminum foil or the like for forming the anode foil 1 and the cathode foil 3 is subjected to an etching process to be roughened.
Next, the roughened anode foil 1 is subjected to a chemical conversion treatment to form an oxide film. In the winding process (element manufacturing process), the lead wires 5 and 6 are connected to the anode foil 1 and the cathode foil 3 on which the oxide film is formed via the electrode tabs, respectively, and the anode foil 1 and the cathode foil 3 are connected. Are wound through a separator 2 to produce a cylindrical capacitor element 4.

  Next, in the repair chemical conversion step, chemical conversion treatment is performed on the anode foil 1 in the state of the capacitor element 4 to repair defects in the cut and oxide film of the anode foil 1.

  Next, when the separator 2 is made of natural fibers, it is preferable to perform heat treatment in order to reduce the density. When synthetic fibers are included, heat treatment may be omitted as appropriate. Then, the conductive polymer 7 is formed by impregnation of the monomer solution and chemical polymerization, and the conductive polymer 7 applied to the separator 2 is held (holding layer forming step). Here, in order to form the conductive polymer 7, thiophene or its derivative, aniline or its derivative, pyrrole or its derivative is chemically polymerized.

  Examples of the thiophene derivative include a thiophene derivative having at least one of a hydroxyl group, an acetyl group, a carboxyl group, an alkyl group, and an alkoxy group as a substituent at the 3-position, 3-position, 4-position or S-position of the thiophene skeleton, or 3 , 4-alkylenedioxythiophene. Examples of the aniline derivative include an aniline derivative having an aniline skeleton and having at least one substituent selected from an alkyl group, a phenyl group, an alkoxy group, an ester group, and a thioether group. Examples of the pyrrole derivative include a pyrrole derivative having at least one of a hydroxyl group, an acetyl group, a carboxyl group, an alkyl group, and an alkoxy group as a substituent at the 3-position, 3-position, 4-position or N-position of the pyrrole skeleton. it can.

  And when these thiophene or its derivative (s), aniline or its derivative (s), pyrrole or its derivative (s) are chemically polymerized by the method demonstrated below, the conductive polymer 7 is formed. In forming the conductive polymer 7, electrolytic polymerization may be combined.

  First, in the one-component method, a compound having a polyvinyl ether skeleton is added to a solution in which a monomer, a dopant and an oxidizing agent are mixed, or a solution in which a monomer and an oxidizing agent are mixed, and the capacitor element is impregnated. After pulling up from the solution, chemical polymerization is performed.

Next, in the two-component method, a capacitor solution is impregnated in a capacitor element, and subsequently, a mixed solution of a dopant and an oxidizing agent is impregnated in the capacitor element and chemically polymerized.
Alternatively, the capacitor element may be impregnated with a solution in which a monomer and a dopant are mixed, and then the capacitor element may be impregnated with a mixed solution of a monomer and an oxidant and chemically polymerized.
Furthermore, the capacitor element may be impregnated with the monomer solution, and then the capacitor element may be impregnated with a liquid obtained by mixing the dopant and the oxidizing agent and chemically polymerized.
Alternatively, the capacitor element may be impregnated with a solution in which a dopant and an oxidant are mixed, and then the monomer solution may be impregnated with the capacitor element and chemically polymerized.
In the above, the compound having a polyvinyl ether skeleton may be added to any solution.

  Next, in the three-component method, a capacitor element is impregnated with a liquid containing a dopant, subsequently, a monomer liquid is impregnated into the capacitor element, and finally, a liquid containing an oxidizing agent is impregnated into the capacitor element, and chemical polymerization is performed. Let it be done. At this time, the compound having a polyvinyl ether skeleton may be added to any solution.

In the present embodiment, the dopant is not particularly limited, but a sulfonic acid compound is preferable in order to obtain a solid electrolytic capacitor having good characteristics.
For example, 1,5-naphthalenedisulfonic acid, 1,6-naphthalenedisulfonic acid, 1-octanesulfonic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, 2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid Acid, 2-methyl-5-isopropylbenzenesulfonic acid, 4-octylbenzenesulfonic acid, 4-nitrotoluene-2-sulfonic acid, m-nitrobenzenesulfonic acid, n-octylsulfonic acid, n-butanesulfonic acid, n-hexane Sulfonic acid, o-nitrobenzenesulfonic acid, p-ethylbenzenesulfonic acid, p-chlorobenzenesulfonic acid, p-decylbenzenesulfonic acid, p-dodecylbenzenesulfonic acid, p-toluenesulfonic acid, p-nitrobenzenesulfonic acid, p-pentyl Benzenesulfonic acid, Tansulfonic acid, camphorsulfonic acid, dinonylnaphthalenesulfonic acid, acetylsulfonic acid, dodecylsulfonic acid, trichlorobenzenesulfonic acid, trifluoromethanesulfonic acid, hydroxybenzenesulfonic acid, butylnaphthalenesulfonic acid, benzenesulfonic acid, polyvinylsulfonic acid , Methanesulfonic acid, etc., and the salts include lithium salt, potassium salt, sodium salt, silver salt, copper salt, iron salt, aluminum salt, cerium salt, tungsten salt, chromium salt, manganese salt, tin salt, methyl Ammonium salt, dimethylammonium salt, trimethylammonium salt, tetramethylammonium salt, ethylammonium salt, diethylammonium salt, triethylammonium salt, tetraethylammonium salt, ethylmethylammonium Salt, diethylmethylammonium salt, dimethylethylammonium salt, triethylmethylammonium salt, trimethylethylammonium salt, diethyldimethylammonium salt, propylammonium salt, dipropylammonium salt, isopropylammonium salt, diisopropylammonium salt, butylammonium salt, dibutyl Ammonium salt, methylpropylammonium salt, ethylpropylammonium salt, methylisopropylammonium salt, ethylisopropylammonium salt, methylbutylammonium salt, ethylbutylammonium salt, tetramethylolammonium salt, tetra-n-butylammonium salt, tetra-sec- Butylammonium salt, tetra-t-butylammonium salt, piperidinium salt, pyrrolidinium Examples include salts, monoforinium salts, piperazinium salts, pyridinium salts, α-picolinium salts, β-picolinium salts, γ-picolinium salts, quinolinium salts, isoquinolinium salts, pyrrolinium salts, ammonium salts, and the like.

After the conductive polymer holding layer is formed by such a process, in the assembly process, the capacitor element 4 is housed in a bottomed cylindrical outer case, and the opening is sealed with a sealing rubber or the like.
Then, aging is performed. In the aging process, for example, a rated voltage is applied for 60 minutes under the condition of a temperature of 100 ° C. This completes the solid electrolytic capacitor.

(Main effects of this embodiment)
As described above, in this embodiment, the conductive polymer contains a compound having a polyvinyl ether skeleton.
Such a compound having a polyvinyl ether skeleton suppresses the chemical reaction of the electrode foil because the ether-bonded oxygen atoms existing in the structure coordinate with the aluminum oxide film and exist on the electrode surface, resulting in a solid The withstand voltage of the electrolytic capacitor can be improved.
Therefore, it is possible to provide a solid electrolytic capacitor capable of reducing leakage current and improving withstand voltage without impairing ESR.

[Example 1]
In Example 1, a cylindrical capacitor element is obtained by winding an anode foil (formation voltage 47V) and a cathode foil through a separator made of a single hemp paper.
Next, after immersing in an aqueous solution of diammonium adipate and applying a voltage of 47 V for 60 minutes as a restoration conversion process, the capacitor element was subjected to heat treatment at 300 ° C. for 90 minutes.
Next, a solution in which 3,4-ethylenedioxythiophene, iron (III) p-toluenesulfonate and compound A represented by the following chemical formula 3 are dissolved in n-butanol (monomer, oxidizing agent, compound A and After immersing the capacitor element in a weight ratio of butanol 1: 1: 0.01: 1), the PEDOT is formed by chemical polymerization by holding for 5 minutes at a temperature of 150 ° C.
The capacitor element thus obtained was housed in a bottomed cylindrical outer case, the opening was sealed with rubber packing or the like, and then aged to produce a solid electrolytic capacitor rated at 16V-220 μF.

[Example 2]
In Example 2, a cylindrical capacitor element is obtained by winding an anode foil (formation voltage 47V) and a cathode foil through a separator made of Manila hemp paper. Next, after carrying out the same repair conversion and heat treatment as in Example 1, 3,4-ethylenedioxythiophene, iron (III) p-toluenesulfonate, and compound B represented by the following chemical formula 4 are n -After the capacitor element is immersed in a solution dissolved in butanol (weight ratio of monomer, oxidizer, compound B and butanol 1: 1: 0.05: 1), it is kept at a temperature of 200 ° C. for 6 minutes for chemical polymerization. To form PEDOT.
The capacitor element thus obtained was housed in a bottomed cylindrical outer case, and a solid electrolytic capacitor having a rating of 16V-220 μF was produced in the same manner as in Example 1.

[Example 3]
In Example 3, the capacitor element produced in the same manner as in Example 1 was subjected to the same repair formation and heat treatment as in Example 1, and then represented by iron (III) p-toluenesulfonate and the following chemical formula 5. The capacitor element is immersed in a solution of compound C dissolved in n-butanol (weight ratio of oxidizer, compound C and butanol 2: 0.05: 3), and then held at a temperature of 150 ° C. for 10 minutes. Then, it is immersed in a solution of 3,4-ethylenedioxythiophene dissolved in methanol (weight ratio of monomer to methanol 1: 1), and kept at a temperature of 200 ° C. for 6 minutes. PEDOT is formed.
The capacitor element thus obtained was housed in a bottomed cylindrical outer case, and a solid electrolytic capacitor having a rating of 16V-220 μF was produced in the same manner as in Example 1.

[Example 4]
In Example 4, a capacitor element produced in the same manner as in Example 1 was subjected to the same repair formation and heat treatment as in Example 1, and then a solution in which iron (III) p-toluenesulfonate was dissolved in n-butanol ( After immersing the capacitor element in a weight ratio of oxidizer and butanol 2: 3), the butanol was evaporated by holding for 5 minutes at a temperature of 180 ° C., and then 3,4-ethylenedioxythiophene and the following chemical formula 6 A solution in which the compound D represented is dissolved in methanol (weight ratio of monomer, compound D and methanol 1: 0.01: 1) is immersed, and maintained at a temperature of 200 ° C. for 6 minutes, and then PEDOT is obtained by chemical polymerization. Form.
The capacitor element thus obtained was housed in a bottomed cylindrical outer case, and a solid electrolytic capacitor having a rating of 16V-220 μF was produced in the same manner as in Example 1.

(Conventional example 1)
In Conventional Example 1, a cylindrical capacitor element is obtained by winding an anode foil (formation voltage 47V) and a cathode foil through a separator made of a single hemp paper.
Next, after carrying out the repair conversion and heat treatment similar to those in Example 1, a solution (monomer and oxidizing agent) in which 3,4-ethylenedioxythiophene and iron (III) p-toluenesulfonate were dissolved in n-butanol. After the capacitor element is immersed in a 1: 1: 1) weight ratio of butanol, the PEDOT is formed by chemical polymerization while being held at a temperature of 150 ° C. for 5 minutes.
The capacitor element thus obtained was housed in a bottomed cylindrical outer case, and a solid electrolytic capacitor having a rating of 16V-220 μF was produced in the same manner as in Example 1.

(Conventional example 2)
In Conventional Example 2, a cylindrical capacitor element is obtained by winding an anode foil (formation voltage 47V) and a cathode foil through a separator made of Manila hemp paper.
Next, after carrying out the repair conversion and heat treatment similar to those in Example 1, a solution (monomer and oxidizing agent) in which 3,4-ethylenedioxythiophene and iron (III) p-toluenesulfonate were dissolved in n-butanol. After the capacitor element is immersed in a 1: 1: 1) weight ratio of butanol, the PEDOT is formed by chemical polymerization while being held at a temperature of 150 ° C. for 5 minutes.
The capacitor element thus obtained was housed in a bottomed cylindrical outer case, and a solid electrolytic capacitor having a rating of 16V-220 μF was produced in the same manner as in Example 1.

  The measurement results of the electrical characteristics of the solid electrolytic capacitors obtained by the manufacturing methods of Examples 1 to 4 and Conventional Examples 1 and 2 and the occurrence rate of short circuits are shown in Table 1 below. In Table 1, tan δ is a tangent of the loss angle of the capacitor, and LC (Leakage Current) is a leakage current value 2 minutes after application of the rated voltage.

As shown in Table 1, according to Examples 1 to 4 containing a compound having a polyvinyl ether skeleton in a conductive polymer, as compared with the conventional example not containing a compound having a polyvinyl ether skeleton, It can be seen that the electrical characteristics are improved and the occurrence rate of short circuit is reduced.
The above effect was the same both when a separator made of hemp paper single paper was used and when a separator made of Manila hemp paper was used.

[Other Examples]
In the above embodiment, PEDOT is used as a solid electrolyte, but it is confirmed that the same effect can be obtained when a known conductive polymer other than PEDOT (for example, polyaniline or polypyrrole) is used as the solid electrolyte. It was.
In the above embodiment, the one-liquid method and the two-liquid method are used. However, the same effect can be obtained when the two-liquid method and the three-liquid method other than the above-described examples are used. It was.

  Further, in the above embodiment, the solid electrolytic capacitor using aluminum as the anode has been described, but it was confirmed that the same effect can be obtained even when tantalum or niobium is used as the anode.

1 is a schematic perspective view of a solid electrolytic capacitor element according to an embodiment of the present invention. It is a schematic cross section of the laminated structure of the solid electrolytic capacitor of FIG. It is a process flow figure showing a manufacturing method of a solid electrolytic capacitor of Drawing 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode foil 2 Separator 3 Cathode foil 4 Capacitor element 5 Anode lead bar 6 Cathode lead bar 7 Conductive polymer

Claims (3)

In a solid electrolytic capacitor in which a conductive polymer is held in a capacitor element in which an anode foil and a cathode foil having an anodized film formed on the surface are wound through a separator,
A solid electrolytic capacitor characterized in that the capacitor element contains a compound having a polyvinyl ether skeleton represented by any one of the following chemical formula 1 and chemical formula 2 together with a conductive polymer.

However, in each of the above Chemical Formula 1 and Chemical Formula 2,
R1 represents substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl,
R2 and R3 are the same or different from each other and each represents a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl,
n represents a natural number of 500 or less,
When n is 2 or more, R1 may be the same or different from each other, R2 may be the same or different from each other, and R3 may be the same or different from each other Good. 2. The solid electrolytic capacitor according to claim 1 , wherein the conductive polymer is obtained by polymerizing aniline or a derivative thereof, pyrrole or a derivative thereof, or thiophene or a derivative thereof . In a method for producing a solid electrolytic capacitor in which a conductive polymer is held in a capacitor element in which an anode foil and a cathode foil having an anodized film formed on a surface are wound through a separator,
The capacitor element is immersed in a solution in which at least one of a monomer, an oxidant, and a dopant is mixed with a compound having a polyvinyl ether skeleton represented by any one of the following chemical formulas 1 and 2, and chemical polymerization is performed. The manufacturing method of the solid electrolytic capacitor characterized by including the process to make.

  However, in each of the above Chemical Formula 1 and Chemical Formula 2,
  R1 represents substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl,
  R2 and R3 are the same or different from each other and each represents a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl,
  n represents a natural number of 500 or less,
  When n is 2 or more, R1 may be the same or different from each other, R2 may be the same or different from each other, and R3 may be the same or different from each other Good.

Images