JP3478726B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor and a manufacturing method thereof, and more particularly to a manufacturing method for easily realizing a small-sized and large-capacity capacitor excellent in frequency characteristics and capacitor characteristics such as heat resistance and humidity resistance.

[0002]

2. Description of the Related Art In recent years, with the digitization of electrical equipment,
Also for capacitors, small capacitors, large capacitors, and low impedance in a high frequency region are required. Conventionally, capacitors used in the high frequency region include plastic capacitors, mica capacitors, and monolithic ceramic capacitors, but these capacitors have a large shape and it is difficult to increase the capacity.

On the other hand, as a large-capacity capacitor, there is an aluminum dry electrolytic capacitor or an electrolytic capacitor such as an aluminum or tantalum solid electrolytic capacitor.

In these capacitors, since the oxide film serving as a dielectric is extremely thin, a large capacity can be realized. On the other hand, since the oxide film is easily damaged, it is a true cathode for repairing it. For example, in an aluminum dry-type capacitor, an etched anode and cathode aluminum foil is wound around a separator and a liquid electrolyte is impregnated into the separator to be used. Since this liquid electrolyte has ionic conductivity and high specific resistance, it has a problem that loss is large and impedance frequency characteristics and temperature characteristics are significantly deteriorated. In addition, liquid leakage and evaporation are unavoidable, and there is a problem that the capacity decreases and the loss increases with the passage of time.

Further, in the tantalum solid electrolytic capacitor,
Since manganese oxide is used as an electrolyte, the problems of temperature characteristics and changes in capacity, loss, etc. over time are improved, but since the specific resistance of manganese oxide is relatively high, the frequency characteristics of loss and impedance are It was inferior to ceramic capacitors or film capacitors.

In addition, in the tantalum solid electrolytic capacitor, when forming an electrolyte made of manganese oxide,
The step of thermally decomposing at a temperature of about 300 ° C. after immersion in a manganese nitrate solution needs to be repeated several times to ten times, and the forming step is complicated.

Therefore, in recent years, after forming a conductive polymer such as a metal, a conductive metal oxide, or polypyrrole on the dielectric film, the conductive polymer such as polypyrrole is formed by electrolytic polymerization through the conductive layers. A solid electrolytic capacitor formed of a conductive polymer has been proposed (JP-A-63-1).
58829, JP-A-63-173313 and JP-A-1-253226). Furthermore, 3 and 4
A solid electrolytic capacitor has been proposed in which a conductive polymer polythiophene having a substituent at the position is formed by chemical polymerization (Japanese Patent Publication No. 2-15611).

Further, a large-capacity film capacitor is proposed in which a conductive polymer layer is sequentially formed by chemical polymerization and electrolytic polymerization after forming a dielectric made of an electrodeposited polyimide thin film on an etched aluminum foil to form an electrode. (Abstracts of the 58th Conference of the Electrochemical Society of Japan, pp. 251-252 (199
1 year)).

[0009]

However, when an electrolytically polymerized polymer is formed via a conductive pyrolytic metal oxide such as manganese oxide, the dielectric film is damaged by heat. However, in order to obtain a high withstand voltage capacitor, it is necessary to perform chemical conversion again before electrolytic polymerization and to repair it, which has a problem that the process becomes more complicated.

Further, in a tantalum solid electrolytic capacitor, an electrolyte made of manganese oxide is repeatedly formed by thermal decomposition, and chemical conversion is required each time to repair the film damage that has occurred, which makes the process more complicated. Had a problem.

In addition, when a conductive polymer layer is formed by chemical polymerization with polypyrrole, the polymerization rate is high at around room temperature, so that the polymerization is performed while penetrating deep into the pores of the etched aluminum foil and the tantalum sintered body. As a result, the etch pits and the pores of the sintered body were partially blocked, and it was difficult to form a conductive polymer layer having a high filling rate.

This problem can be solved by lowering the polymerization temperature, but when water is used as the medium, there is a limit because it freezes at around 0 degrees Celsius.

Although this problem can be solved by reducing the concentration of the pyrrole monomer, a new problem arises that the number of times of repeating polymerization required for coating increases.

Furthermore, when a thiophene having an alkoxy substituent at the 3- and 4-positions as shown in the following (Chemical Formula 2) is dissolved in an organic solvent in which it is dissolved and is formed by chemical polymerization, the Compared with thiophene, it is easier to polymerize due to the effect of the donating alkoxy group,
The polymerization rate is slower than in the case of pyrrole, and it takes a long time for the polymerization, or in order to shorten the polymerization time, the polymerization temperature is raised or the concentration of the thiophene derivative and the oxidant in the solution is increased. Was necessary.

[0015]

[Chemical 2]

Many organic solvents are flammable, and in consideration of mass production by the electrolytic polymerization method, strict measures are required to prevent ignition due to electric sparks.

When the concentration of the thiophene derivative and the concentration of the oxidizing agent are increased, the viscosity of the liquid is increased, and a conductive polymer layer having a high coverage is formed on the surface of the capacitor element having fine pores. There was a problem that it became difficult.

[0018] Furthermore, higher thiophene derivative concentration and oxidizer concentration, when using a low-boiling solvent, large polymerization solution composition variation due to solvent volatilization, is difficult to proceed the polymerization reaction in the steady state, stable electrical There is also a problem that it is difficult to obtain a conductive polymer having conductivity and environmental stability.

Further, in the case of chemical polymerization, there is a problem that after the solvent is volatilized, an excessive oxidizing agent and a residue of the polymerization reaction are formed in a film form on the surface of the dielectric, which makes it extremely difficult to dissolve and remove it.

Furthermore, as shown in (Chemical Formula 2), 3,
Since thiophene having an alkoxy substituent at the 4-position has extremely low water solubility, it was virtually impossible to polymerize a conductive polymer in an aqueous medium to produce a capacitor.

The present invention solves each of the problems in the prior art described above. It is possible to easily obtain a solid electrolytic capacitor having a high capacity achievement rate and high heat resistance and humidity resistance, and a small capacity and a large capacity, and a high capacity achievement rate. Moreover, it is an object to easily obtain a film capacitor having high heat resistance and humidity resistance.

[0022]

DISCLOSURE OF THE INVENTION The present invention provides a thiophene represented by the chemical formula 2 in at least one of a pair of electrodes provided facing each other, a dielectric layer provided between the electrodes, and the electrode. The conductive polymer layer containing a thiophene derivative as a repeating unit, which is a method for producing a capacitor having a conductive polymer layer containing a derivative as a repeating unit, is an aqueous medium in which an anionic surfactant coexists. The manufacturing method of forming by chemical polymerization in a system is suitable.

The conductive polymer layer containing the thiophene derivative shown in the chemical formula 2 as a repeating unit is chemically polymerized by using a transition metal salt as an oxidizing agent in an aqueous medium in which an anionic surfactant coexists. The manufacturing method of forming is more preferable.

As the transition metal salt, any one can be used as long as it can polymerize the thiophene derivative represented by (Chemical Formula 2), but an iron salt is preferably used.

The thiophene derivative is not limited as long as it is substituted at the 3- and 4-positions with a dioxyalkylene group, but 3,4-ethylenedioxythiophene is preferably used.

Since this thiophene derivative has extremely low solubility in water, a production method in which it is emulsified with an anionic surfactant, dispersed in water and subjected to chemical polymerization is suitable.

Since the thiophene derivative is highly hydrophobic,
By stirring in an aqueous medium together with the anionic surfactant, it is incorporated into the micelle formed by the surfactant.

Since the polymerization reaction takes place in micelles in which the polymerizable monomer is concentrated, it is likely to proceed at a relatively low temperature as in the case of other emulsion polymerization, and a polymer having a high degree of polymerization can be easily obtained.

It was confirmed that even in the electrolytic polymerization, by emulsifying with an anionic surfactant, the polymerization proceeds smoothly and the obtained PEDOT has high electric conductivity and environmental stability.

Therefore, the conductive polymer containing the obtained thiophene derivative as a repeating unit is characterized by high yield and high electric conductivity.

As the anionic surfactant, a sulfonic acid surfactant is preferably used, and more preferably, a sulfonic acid surfactant having an aromatic ring having a bulky structure that is difficult to dope is preferably used. To be done.

In emulsion polymerization, since the surfactant anion exists near the obtained polymer, this anion is preferentially incorporated as a dopant.

Since the bulk of the surfactant anion is large, it is possible to easily obtain a conductive polymer containing a thiophene derivative as a repeating unit, which is excellent in heat resistance and humidity resistance with suppressed dedoping.

Furthermore, this chemical polymerization is carried out by using a phenol derivative such as P-nitrophenol, P-cyanophenol, m-hydroxybenzoic acid, m-hydroxyphenol, m-nitrophenol or a nitrobenzene derivative such as nitrobenzoic acid and nitrobenzyl alcohol. Can also be carried out in a system in which is added to an aqueous medium containing the thiophene derivative shown in Chemical formula 2 or an aqueous medium containing an oxidizing agent.

With the thiophene derivative shown in (Chemical Formula 2), the polymerization reaction is promoted by this, and the number of repetitions of polymerization required for forming the conductive polymer layer on the dielectric surface of the capacitor can be greatly reduced. Therefore, the capacitor can be easily manufactured.

By the above manufacturing method, it is possible to easily obtain a solid electrolytic capacitor having a high capacity achievement rate and a high heat resistance and moisture resistance, and to easily form a film capacitor having a small capacity and a high capacity achievement rate and a high heat resistance and humidity resistance. Obtainable.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention according to claim 1 of the present invention comprises: a step of disposing a pair of electrodes facing each other; a step of forming a dielectric layer between the electrodes; In the above, a step of preparing the thiophene derivative shown in (Chemical Formula 2), a step of preparing an anionic surfactant aqueous solution, and 0.1 mol / l or more and 0.25 mol / l of the thiophene derivative in the anionic surfactant aqueous solution. Step of emulsifying and dispersing at a concentration of 1 or less, and step of preparing an oxidant
When, and a polymerization <br/> forming by chemical polymerization of a conductive polymer layer in an aqueous medium containing as a repeating unit the thiophene derivative, wherein the polymerization step, the dielectric between the electrodes
A pair of electrodes a layer is formed, in a manufacturing method of a solid electrolytic capacitor, wherein said switch thiophene derivative is a step of impregnating alternately and aqueous medium containing the oxidizing agent and emulsified and dispersed water medium is there.

As described above, in the capacitor whose dielectric is composed of the oxide film of the valve metal, the conductive polymer functions as an electrolyte which also serves as a true cathode, while in the capacitor which is composed of a polymer thin film, It functions as a simple electrode.
Further, the conductive polymer layer containing the thiophene derivative represented by (Chemical Formula 2) as a repeating unit exhibits high electric conductivity and excellent environmental stability because the bulky anion dissociated from the anionic surfactant is ( This is because it is incorporated into the conductive polymer containing the thiophene derivative shown in Chemical formula 2). As a result, it is possible to realize a capacitor having excellent high frequency characteristics and heat and humidity resistance . Furthermore, comprising the step of further providing an oxidizing agent, Ri preferably der that the polymerization is carried out in chemical polymerization, also a pair of electrodes dielectric layer formed between the electrodes, thiophene derivative represented by the formula 2 It is preferable that the conductive polymer layer containing the thiophene derivative as a repeating unit is polymerized in an aqueous medium by alternately impregnating the emulsified and dispersed aqueous medium with the aqueous medium containing the oxidizing agent.

Here, for example, in order to be competitive with the transition metal salt anion used as the oxidizing agent, the surfactant anion is incorporated as a dopant in the conductive polymer containing the thiophene derivative shown in Chemical formula 2. A conductive polymer having high electric conductivity and excellent environmental stability can be obtained.

[0040]

Further, by emulsifying the thiophene derivative represented by the surfactant (Formula 2), since the thiophene derivative is incorporated into the surfactant micelles at higher concentrations, the polymerization reaction in which progresses, compares The polymerization can be carried out at extremely low temperatures. The conductive polymer layer containing the thiophene derivative shown in (Chemical Formula 2) as a repeating unit exhibits high electrical conductivity and excellent environmental stability because the bulky anion dissociated from the anionic surfactant is This is because it is incorporated into the conductive polymer containing the thiophene derivative shown in (4). As a result, it is possible to realize a capacitor having excellent high frequency characteristics and heat and humidity resistance .

[0042]

According to a second aspect of the present invention, a step of disposing a pair of electrodes facing each other, a step of forming a dielectric layer between the electrodes, and a step of forming a dielectric layer between the electrodes The step of preparing the thiophene derivative shown, the step of preparing an anionic surfactant aqueous solution, the step of dissolving the phenol derivative or nitrobenzene or its derivative in the anionic surfactant aqueous solution, the thiophene derivative, the phenol derivative Or nitro
Benzene or 0.1 mol / l or more on 0.25mol derivative thereof is dissolved anionic surfactant aqueous solution /
Prepare a step of emulsifying and dispersing at a concentration of 1 or less and an oxidizing agent
And a conductive polymer layer containing the thiophene derivative as a repeating unit is chemically polymerized in an aqueous medium.
Comprising a polymerization step, said polymerization step, induced between the electrodes
A method for manufacturing a solid electrolytic capacitor, which comprises a step of alternately impregnating a pair of electrodes on which an electric layer is formed with an aqueous medium in which the thiophene derivative is emulsified and dispersed and an aqueous medium containing the oxidant. Is.

As described above, by polymerizing the thiophene derivative represented by the chemical formula (2) in a system in which a phenol derivative or nitrobenzene or its derivative is allowed to coexist, the polymerization rate is increased, and the conductive polymer layer can be formed with a small number of polymerization repetitions. Can be formed. Although this mechanism is not clear, it is considered that the interaction of the thiophene derivative shown in (Chemical Formula 2) with the phenol derivative and the nitrobenzene derivative exerts an effect of promoting a polymerization reaction which is an electrophilic substitution reaction. This makes it possible to easily realize a capacitor having excellent high-frequency characteristics and heat and humidity resistance . Also, the step of preparing an oxidant
It is preferable that the polymerization is performed by chemical polymerization, and a pair of electrodes having a dielectric layer formed between the electrodes is formed into an aqueous medium in which the thiophene derivative shown in Chemical formula 2 is emulsified and dispersed, and an oxidizing agent. It is preferable that the conductive polymer layer containing the thiophene derivative as a repeating unit is polymerized and formed in an aqueous medium by alternately impregnating it with an aqueous medium containing

[0045]

Here, as described in claim 3 , it is preferable that the thiophene derivative represented by (Chemical Formula 2) is 3,4-ethylenedioxythiophene.

Further, as described in claim 4 , it is desirable that the anionic surfactant is a sulfonic acid surfactant.

Further, as described in claim 5 ,
It is preferable to use a transition metal salt as the oxidant, and it is also preferable to use a trivalent iron salt as described in claim 6 .

Further, as described in claim 7 , the dielectric layer may be an oxide film of a valve metal forming one of the electrodes.

In this case, as described in claim 8 , it is preferable that the valve metal is aluminum or tantalum.

[0051]

[0052] Moreover, as claimed in claim 9, wherein the conductive polymer layer is preferably formed adjacent the dielectric layer.

[0053] Furthermore, as in claim 10, a phenol derivative nitrophenol, cyanophenol, hydroxybenzoic acid, hydroxyphenol or acetoacetic phenol or a combination thereof der Turkey are preferred.

Further, as described in claim 11 , it is preferable that the nitrobenzene derivative is nitrobenzyl alcohol or nitrobenzoic acid, or a combination thereof.

[0055]

Embodiments of the present invention will be described in detail below. (Embodiment 1) In Embodiment 1, first, a solution of 5 ml of phosphoric acid dissolved in 1000 ml of water is used for a 2 x 1.4 x 0.9 mm ³ tantalum sintered body, and 40 V is applied at about 90 ° C. By applying, an oxide film dielectric film was formed by anodic oxidation. When this structure was regarded as a capacitor and the capacity in the chemical conversion liquid was measured, 18.
It was 0 μF.

Further, using this constitution, 3,4-ethylenedioxythiophene (EDOT) 0.1 mol / l
And an aromatic sulfonic acid surfactant, sodium alkylnaphthalene sulfonate (average molecular weight 338) 0.7
After dipping in 5% by weight of a 25 ° C. monomer-dispersed aqueous medium for 5 minutes, dipping in a 65 ° C. oxidant aqueous solution containing ferric sulfate 0.75 mol / l for 120 minutes to add polyethylenedioxythiophene (PEDOT). Formed.

Immersion of the capacitor element in the monomer-dispersed aqueous medium and the oxidizing agent aqueous solution was repeated until the surface was coated with PEDOT. The number of repetitions required for coating is 2
It was 0 times.

Here, as the EDOT, the one commercially available from Bayer AG of Germany was used, but the EDOT may be synthesized by a general production method. For example, Polymer
Alternatively, the method disclosed in p. 1347 of Vol. 35, No. 7 (1994) may be used. By this treatment, a conductive layer made of polyethylenedioxythiophene (PEDOT) which was predominantly doped with alkylnaphthalenesulfonate ion was formed on the tantalum sintered body on which the dielectric film was formed.

Here, FIG. 1 shows changes in the yield and electrical conductivity of PEDOT obtained when the amount of sodium alkylnaphthalene sulfonate added was changed. As shown in FIG. 1, it can be seen that the PEDOT yield and the electrical conductivity are increased by gradually adding the sodium alkylnaphthalene sulfonate. It is considered that this is due to the fact that PEDOT is doped with an alkylnaphthalenesulfonate ion.
On the other hand, when a sulfonate having no surface activity was added, the yield of PEDOT and the electrical conductivity did not increase significantly up to this point.

Therefore, it was also found that the addition of a sulfonate having a surfactant action has the effect of further accelerating the polymerization rate and increasing the yield.

It was confirmed from the elemental analysis that the polymerization product did not substantially contain iron. On the tantalum sintered body on which the PEDOT layer is formed,
A cathode was formed with a carbon layer and a silver paint layer, and a cathode lead was attached on it to obtain a total of 10 capacitor elements. Further, the device was packaged with an epoxy resin, and further subjected to an aging treatment by applying 13 V at 125 ° C. to complete a capacitor. These 10
For each element, capacitance at 1 kHz, loss factor,
And the impedance at 400 kHz were measured, and the rate of change in capacity and loss coefficient after a load heat resistance test performed by applying 10 V at 125 ° C. were measured, and their average values are shown in (Table 1) below.

[0063]

[Table 1]

(Embodiment 2) In Embodiment 2, in place of PEDOT in Embodiment 1, a conductive polymer poly (3) containing a thiophene derivative similarly represented by Chemical Formula 2 as a repeating unit is also used. , 4- (1,2-propylene) dioxythiophene) (PPDOT) was used, and 10 capacitor elements configured in the same manner as in Embodiment 1 were completed.

With respect to these ten elements, the capacitance at 1 kHz, the loss coefficient, and the 4
The impedance at 00 kHz and the rate of change in capacity and loss coefficient after a load heat resistance test performed by applying 10 V at 125 ° C. were each measured, and the average values thereof are shown in the above (Table 1).

As can be seen from Table 1, the capacitor characteristics and heat resistance similar to those of the first embodiment can be realized also in the present embodiment. This has the same physical properties as the PEDOT layer in the present embodiment,
This is because the conductive polymer PPDOT layer doped with the anion of the surfactant sodium naphthalenesulfonate is formed.

As described above, also in the present embodiment, it is possible to efficiently obtain a capacitor having a high capacity achievement rate, a low loss and a high frequency impedance characteristic, and further having high heat resistance.

Similar results were obtained with the other thiophene derivatives shown in the chemical formula (2).

Comparative Example 1 Next, for comparison, Comparative Example 1
As a result, 10 capacitors were completed under the same conditions as in Embodiment 1 except that the polypyrrole layer was formed using a pyrrole monomer instead of EDOT.

The number of times of immersion in the monomer-dispersed aqueous medium and the oxidizing agent aqueous solution required for coating the polypyrrole was 8 times. As with the first embodiment, the capacitance, loss coefficient, and
Impedance at Hz, 10V at 125 ° C
The rate of change in capacity and the loss coefficient after the load heat resistance test performed by applying the voltage were measured, and their average values are shown in the above (Table 1).

Examining the results of the first embodiment and this comparative example, the initial capacitor characteristics and heat resistance are the same as those of the first embodiment.
It can be seen that the capacitor obtained in step 1 is superior.
That is, in the case of Comparative Example 1, the coating with the conductive polymer layer can be realized with a small number of times of repeated polymerization, but the rapid progress of the polymerization prevents the permeation of the polymerization solution into the inside of the sintered body and the capacity does not become sufficiently large. It is considered to be a thing.

Further, it is considered that as a result of rapid progress of polymerization, polypyrrole having a skeleton structure with high regularity cannot be obtained, resulting in a decrease in electrical conductivity, resulting in an increase in loss coefficient. It is considered that this lowers the environmental stability of polypyrrole and also lowers the heat resistance.

From the above, EDOT is emulsified by using sodium alkylnaphthalene sulfonate, which is an anionic surfactant, in an aqueous medium, and PEDOT is polymerized to form a capacitor having excellent capacitor characteristics and heat resistance. It turned out to be possible.

Comparative Example 2 Next, for comparison, Comparative Example 2
As an attempt to manufacture 10 capacitors under the same conditions as in Embodiment 1, except that sodium alkylnaphthalene sulfonate was not added. The capacitor element immersion treatment in the monomer-dispersed aqueous medium and the oxidizing agent aqueous solution was repeated 40 times or more, but the surface could not be completely covered with the PEDOT layer. It is considered that this is because when EDOT is not emulsified, the solubility in water is extremely low, and thus the progress of polymerization is slow.

From the above, it was found that by emulsifying EDOT with sodium alkylnaphthalene sulfonate, PEDOT having high electric conductivity was easily obtained in an aqueous medium and the capacitor characteristics and heat resistance could be improved.

(Third Embodiment) In the third embodiment, sodium dodecylbenzene sulfonate, which is also an aromatic sulfonic acid surfactant, is used instead of sodium alkylnaphthalene sulfonate in the first embodiment. Except for the above, 10 capacitor elements configured in the same manner as in the first embodiment were completed.

With respect to these 10 elements, the capacitance at 1 kHz, the loss coefficient, and the 4
The impedance at 00 kHz and the rate of change in capacity and loss coefficient after a load heat resistance test performed by applying 10 V at 125 ° C. were each measured, and the average values thereof are shown in the above (Table 1). As can be seen from (Table 1), it can be seen that also in the present embodiment, the same capacitor characteristics and heat resistance as those of the first embodiment can be realized. This is because the present embodiment also has a conductive layer composed of a PEDOT layer, sodium dodecylbenzenesulfonate acts as a surfactant, and PEDOT is doped with anions dissociated from the surfactant. is there.

As described above, also in the present embodiment, it is possible to efficiently obtain a capacitor having a high capacity achievement rate, a low loss, a high frequency impedance characteristic, and a high heat resistance.

(Fourth Embodiment) In the fourth embodiment, ten tantalum sintered bodies of the first embodiment are used under the same conditions as the first embodiment except that an etched aluminum foil electrode is used instead of the tantalum sintered body. The capacitor was completed and the same characteristic evaluation was performed, and the results are shown in (Table 1) above.

Here, the concrete production of the etched aluminum electrode foil was carried out as follows. First, 4 x 10 mm
A polyimide tape having a width of 1 mm was attached to both sides of the etched aluminum foil of No. ² so as to be divided into 3 mm and 6 mm portions. Next, the anode lead of the 4 × 3 mm ² portion of the aluminum etched foil 1 was attached, and the 4 × 6 mm ² portion of the aluminum etched foil was applied with a 3% ammonium adipate aqueous solution at 50 V at about 70 ° C. Then, an oxide film dielectric layer was formed by anodic oxidation.

Here, this structure is regarded as a capacitor,
When the capacity in the chemical conversion solution was measured, it was 4.92 μF. Further, using this structure, PEDOT was formed in the same manner as in the first embodiment. The number of repetitions required for coating was 18.

Comparative Example 3 Next, for comparison, Comparative Example 3
As a result, 10 capacitors were completed under the same conditions as in Embodiment 1 except that the polypyrrole layer was formed using a pyrrole monomer instead of EDOT. The number of repetitions of dipping in the aqueous solution of the monomer dispersion and the aqueous solution of the oxidant required for coating the polypyrrole was 5 times.

With respect to these 10 elements, the capacitance at 1 kHz, the loss coefficient, and the 4
The impedance at 00 kHz and the rate of change in capacity and loss coefficient after a load heat resistance test performed by applying 10 V at 125 ° C. were each measured, and the average values thereof are shown in the above (Table 1).

When the results of the first embodiment and this comparative example are examined, the initial capacitor characteristics and heat resistance are the same as those of the first embodiment.
It can be seen that the capacitor obtained in step 1 is superior.
That is, in the case of Comparative Example 1, the coating with the conductive polymer layer can be realized with a small number of repetitions of polymerization, but the polymerization liquid rapidly prevents the polymerization liquid from penetrating into the inside of the sintered body and the capacity does not become sufficiently large. It is considered to be a thing.

Further, as a result of rapid progress of polymerization, polypyrrole having a skeleton structure with high regularity cannot be obtained, so that the electric conductivity is lowered, resulting in an increase in loss coefficient. It is also considered that this lowers the environmental stability of polypyrrole and also lowers the heat resistance.

From the above, EDOT is emulsified with anionic surfactant sodium alkylnaphthalene sulfonate in an aqueous medium to polymerize PEDOT to produce a capacitor having excellent capacitor characteristics and heat resistance. It turned out to be possible.

Comparative Example 4 Next, for comparison, Comparative Example 4
As an attempt to manufacture 10 capacitors under the same conditions as in Embodiment 1, except that sodium alkylnaphthalene sulfonate was not added.

The capacitor element immersion treatment in the monomer-dispersed aqueous medium and the oxidizing agent aqueous solution was repeated 40 times or more, but the surface could not be completely covered with the PEDOT layer. It is considered that this is because when EDOT is not emulsified, the solubility in water is extremely low, and thus the progress of polymerization is slow.

From the above, it was found that by emulsifying EDOT with sodium alkylnaphthalene sulfonate, PEDOT having high electric conductivity was easily obtained in an aqueous medium and the capacitor characteristics and heat resistance could be improved.

(Fifth Embodiment) In the fifth embodiment, in the structure of the fourth embodiment, an aluminum smooth foil of 20 mm × 20 mm is used instead of the etched aluminum foil, and an oxide film dielectric is additionally formed. Instead of using an electrode having a polyimide dielectric layer made of a polyimide thin film having a thickness of 0.5 μm formed on one surface by spin coating, a total of 10 capacitors were formed under substantially the same conditions as in the fourth embodiment. It was made.

These were evaluated in the same manner as in Embodiment 1, and the results are shown in (Table 1) above. Note that, also in this embodiment, when each conductive polymer shown in Embodiment 2 is used instead of PEDOT, and / or when sodium dodecylbenzenesulfonate is used instead of sodium alkylnaphthalenesulfonate. Also, similar results were obtained.

Comparative Example 5 Next, for comparison, Comparative Example 5
As a result, 10 capacitors were completed under the same conditions as in Embodiment 1 except that the polypyrrole layer was formed using a pyrrole monomer instead of EDOT.

The number of repetitions of immersion in the aqueous solution of the monomer dispersion and the aqueous solution of the oxidant required for coating the polypyrrole was 3 times. As with the first embodiment, the capacitance, loss coefficient, and
Impedance at Hz, 10V at 125 ° C
The rate of change in capacity and the loss coefficient after the load heat resistance test performed by applying the voltage were measured, and their average values are shown in the above (Table 1).

When the results of the fifth embodiment and this comparative example are examined, the initial capacitor characteristics and heat resistance are the same as those of the fifth embodiment.
It can be seen that the capacitor obtained in step 1 is superior.
That is, in the case of Comparative Example 5, the coating with the conductive polymer layer can be realized with a small number of times of repeated polymerization, but as a result of rapid progress of the polymerization, polypyrrole having a skeleton structure with high regularity cannot be obtained, so that the electrical conductivity is reduced. Is expected to decrease, resulting in an increase in the loss coefficient. Further, it is considered that polypyrrole having a skeleton structure with low regularity is formed, so that environmental stability is also lowered and heat resistance is also lowered.

From the above, EDOT is emulsified by using sodium alkylnaphthalene sulfonate which is an anionic surfactant in an aqueous medium and PEDOT is polymerized to form a capacitor having excellent capacitor characteristics and heat resistance. It turned out to be possible.

Comparative Example 6 Next, for comparison, Comparative Example 6
As an attempt to manufacture 10 capacitors under the same conditions as in Embodiment 1, except that sodium alkylnaphthalene sulfonate was not added.

The capacitor element immersion treatment in the monomer-dispersed aqueous medium and the oxidizing agent aqueous solution was repeated 40 times or more, but the surface could not be completely covered with the PEDOT layer. It is considered that this is because when EDOT is not emulsified, the solubility in water is extremely low, and thus the progress of polymerization is slow.

From the above, it was found that by emulsifying EDOT with sodium alkylnaphthalene sulfonate, PEDOT having high electric conductivity was easily obtained in an aqueous medium and the capacitor characteristics and heat resistance could be improved.

Although the case where polyimide is used as the polymer serving as the dielectric has been described, any material other than polyimide may be used as long as it is a polymer material for the dielectric capable of forming a thin film. Then, the case where the polyimide film serving as the dielectric is formed on the aluminum smooth foil by spin coating has been described, but the polyimide film may be formed on the surface of the etched aluminum foil by, for example, electrodeposition, and also in the third embodiment. A polymer dielectric can be applied.

(Embodiment 6) In the present embodiment, in the structure of Embodiment 1, the oxidant solution is further added with 0.0
Ten capacitor elements were completed in the same manner as in Embodiment 1 except that 5 mol / l of p-nitrophenol was added.

These were evaluated in the same manner as in Embodiment 1, and the results are shown in (Table 1) above. Note that P
The number of repetitions of dipping the capacitor element in the monomer-dispersed aqueous medium and the oxidizing agent aqueous solution required for the EDOT coating was 16 times.

By adding p-nitrophenol, ED
In the case of OT, the improvement in electric conductivity was not clearly observed, but it was confirmed that the polymerization rate was accelerated to the extent that pores were not blocked.

Here, FIG. 2 shows the effect on the yield of PEDOT obtained when the amount of p-nitrophenol added was changed. As shown in FIG. 2, by increasing the amount of p-nitrophenol added, PEDO
It can be seen that the yield of T is increasing.

The p-nitrophenol is PEDOT.
It was confirmed from elemental analysis that it was not incorporated into the sample. PED obtained by adding P-nitrophenol
OT showed a tendency to suppress deterioration of electric conductivity when left in high temperature air. Then, as can be seen from (Table 1), the capacitor of the present embodiment exhibits substantially the same capacitor characteristics as the capacitors of the first and second embodiments, and is further excellent in heat resistance. Was done.

Therefore, in this embodiment, the high capacity achievement rate, the low loss and the high frequency impedance characteristics are excellent,
Not only can a capacitor with high heat resistance be realized, but by adding p-nitrophenol to the polymerization solution, P
It can be said that the capacitor was able to be realized more efficiently and practically because the polymerization reaction to EDOT was promoted and the yield increased while maintaining good permeability of PEDOT into the sintered body.

Also in Embodiments 2 to 5, the same effect was obtained by adding p-nitrophenol to the polymerization solution in addition to the anionic surfactant.

(Embodiment 7) In Embodiment 7, p-nitrophenol in Embodiment 5 is replaced by p-nitrophenol.
10 capacitors were prepared in the same manner as in Embodiment 5 except that cyanophenol (A), m-hydroxybenzoic acid (B), m-hydroxyphenol (C) and m-nitrophenol (D) were added. Completed

The same evaluations as those of the first embodiment were carried out on these, and the results are shown in (Table 1) above. (Table 1)
As will be understood from the above, the capacitor according to the present embodiment also exhibited results similar to the capacitor characteristics and heat resistance of the sixth embodiment. Therefore, it can be said that also in the present embodiment, it is possible to efficiently obtain a capacitor element having a high capacity achievement rate, low loss, high frequency impedance characteristics, and high heat resistance.

Also in Embodiments 2 to 5, the same effect was obtained by adding the above phenol compound to the polymerization solution in addition to the anionic surfactant.

(Embodiment 8) Embodiment 8 is the same as Embodiment 1 except that the same concentration of cupric sulfate is used in place of ferric sulfate in Embodiment 1. 10 capacitor elements configured as described above were completed.

These were evaluated in the same manner as in Embodiment 1, and the results are shown in (Table 1) above. (Table 1)
As can be understood from the above, the capacitor according to the present embodiment also exhibited a practically acceptable result, although it was slightly inferior to the capacitor characteristics and heat resistance of the first embodiment. Therefore, it can be said that also in the present embodiment, it is possible to efficiently obtain a capacitor element having a high capacity achievement rate, low loss, high frequency impedance characteristics, and high heat resistance.

In Embodiments 2 to 7 as well, the same effect was obtained by adding the above phenol compound to the polymerization solution in addition to the anionic surfactant.

(Ninth Embodiment) In this embodiment, ten capacitors are formed in the same manner as in the fourth embodiment except that the PEDOT is formed by electrolytic polymerization instead of chemical polymerization in the fourth embodiment. Completed

The same evaluations as those in the fourth embodiment were carried out on these, and the results are shown in the above-mentioned (Table 1). Here, the conditions of the electrolytic polymerization of the present embodiment are shown. EDOT concentration is 0.25 mol / l, supporting electrolyte and surfactant,
The sodium alkylnaphthalene sulfonate had a concentration of 0.
1 mol / l, emulsify the aqueous medium containing these, PE
The element on which the DOT layer is formed is dipped, the electrode for electropolymerization made of stainless steel is brought into contact, and a voltage of 3.0 V is applied between the electrode for electropolymerization and the second electrode for electropolymerization provided apart from the electrode for electropolymerization. The electropolymerized polypyrrole layer is formed through the PEDOT layer.

In order to impart conductivity to the etched aluminum foil capacitor element on which the anodized film is formed, 3
After being immersed in a 0% aqueous solution of manganese nitrate, it was heated at about 250 ° C. for 30 minutes to form a pyrolytic manganese dioxide layer in advance. Also in this case, since the bulky surfactant anion is doped, PE excellent in electrical conductivity and environmental stability is obtained.
DOT is obtained.

Therefore, as can be understood from (Table 1), the capacitor according to the present embodiment is also the same as the capacitor according to the fourth embodiment.
The results are similar to those of the capacitor characteristics and heat resistance. Therefore, also in the present embodiment, a capacitor element having a high capacity achievement rate, excellent loss characteristics, and high heat resistance can be obtained.

In Embodiments 1 to 9, only the sulfate ion was described as the polyvalent anion, but a transition metal polyvalent acid salt other than the sulfate salt should be used so that other polyvalent anions can be doped. You can also

In Embodiments 1 to 9, only the case where an aromatic sulfonic acid-based surfactant is used as the anionic surfactant is described, but other sulfonic acid surfactants may be used. Further, an anionic surfactant other than sulfonic acid can be used.

In the first to ninth embodiments, only the case where iron (III) and copper (II) are used as the transition metals has been described, but transitions having a redox potential capable of oxidizing other pyrroles are described. Metals can be used as well and the invention is not limited to that type.

In the first to ninth embodiments, only the case where the valve metal is aluminum or tantalum has been described.
In addition, zirconium, niobium, hafnium, titanium and their intermetallic compounds can be used.

In the embodiments, only the case where the conductive polymer layer is formed on only one side of the capacitor has been described. However, when the dielectric exists alone without being supported by another, It is also possible to form capacitors on both sides to manufacture a capacitor.

[0122]

As described above, the present invention relating to the method for producing a capacitor includes a conductive polymer containing the thiophene derivative shown in (Chemical Formula 2) as a repeating unit, containing the thiophene derivative and an anionic surfactant. By forming by polymerization in an aqueous medium, at least one of the electrodes provided facing each other of the capacitor is constituted. By using a conductive polymer containing a thiophene derivative monomer having a slow polymerization rate, it is possible to form a conductive polymer layer with a high coverage without blocking the pores on the electrode surface,
A capacitor with a high capacity achievement rate can be obtained. Also, by adding a sulfonic acid type surfactant, it is possible to introduce a dopant having a large molecular size in an aqueous medium, and the electric conductivity and thermal stability of the polymer are improved, so that the loss coefficient and impedance characteristics are excellent. It has a unique effect that a capacitor can be obtained and the heat resistance is improved.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of added surfactant, the electrical conductivity, and the yield of a conductive polymer containing a thiophene derivative represented by (Chemical Formula 2) as a repeating unit in Embodiment 1 of the present invention.

FIG. 2 is a graph showing the relationship between the amount of p-nitrophenol added and the yield of a conductive polymer containing a thiophene derivative represented by (Formula 2) as a repeating unit in Embodiment 6 of the present invention.

Front page continuation (72) Inventor Matsue Yasue 3-10-1, Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. (56) Reference JP-A-9-293639 (JP, A) JP-A 9-74050 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01G 9/02

Claims (11)

(57) [Claims] 1. A step of disposing a pair of electrodes facing each other,
A dielectric layer forming step of forming a dielectric layer between the electrodes,
Between the electrodes, a step of preparing a thiophene derivative represented by (Chemical Formula 1), a step of preparing an anionic surfactant aqueous solution, and a step of preparing the thiophene derivative in the anionic surfactant aqueous solution by 0.1 mol / l or more 0 0.25 mol
A step of dispersing emulsifying with / l concentrations below, to prepare an oxidizing agent
Comprising a that step, and a polymerization step of forming by chemical polymerization of a conductive polymer layer in an aqueous medium containing as a repeating unit the thiophene derivative, the Polymerization step, a dielectric layer is formed between the electrodes A method of manufacturing a solid electrolytic capacitor, comprising a step of alternately impregnating the pair of electrodes with a water medium in which the thiophene derivative is emulsified and dispersed and a water medium containing the oxidant. [Chemical 1] 2. A step of disposing a pair of electrodes facing each other,
A dielectric layer forming step of forming a dielectric layer between the electrodes,
Between the electrodes, a step of preparing a thiophene derivative shown in Chemical formula 1, a step of preparing an anionic surfactant aqueous solution, and a step of dissolving a phenol derivative or nitrobenzene or a derivative thereof in the anionic surfactant aqueous solution. When, the thiophene derivative, the phenol
Solution or nitrobenzene or its derivative dissolved in an anionic surfactant solution 0.1 mol
A step of emulsifying and dispersing at a concentration / l or 0.25 mol / l, the polymerization formed by chemical polymerization in an aqueous medium a conductive polymer layer comprising the steps of preparing an oxidizing agent, as a repeating unit the thiophene derivative comprising a step of, said heavy
The bonding step includes a pair of electrodes having a dielectric layer formed between the electrodes.
Method for producing a solid electrolytic capacitor characterized in that pole, the thiophene down derivative is a step of impregnating alternately and aqueous medium containing the oxidizing agent and emulsified and dispersed water medium. 3. A solid conductive according to claim 1 or 2, wherein the thiophene derivative is 3,4-ethylenedioxythiophene
Solution capacitor manufacturing method. Wherein the anionic surfactant is according to any one of claims 1 is a sulfonic acid type surfactant 3
Manufacturing method of solid electrolytic capacitor. 5. The method according to claim 1, wherein a transition metal salt is used as the oxidizing agent .
Method for producing a solid body electrolytic capacitor according to any one of al 4. 6. A transition metal salt is a trivalent iron salt according to claim 5
A method for producing the solid electrolytic capacitor described. 7. The dielectric layer is, the manufacturing method of solid electrolytic capacitor according to any one of claims 1 to 6 which is an oxide film of the valve metal constituting one of the electrodes. 8. The method for producing a solid electrolytic capacitor according to claim 7 , wherein the valve metal is aluminum or tantalum. 9. The conductive polymer layer, a solid electrolytic capacitor <br/> capacitors method according to any one of claims 1 to 8 adjacent to the dielectric layer. 10. The method for producing a solid electrolytic capacitor according to claim 2 , wherein the phenol derivative is nitrophenol, cyanophenol, hydroxybenzoic acid, hydroxyphenol or acetophenol, or a combination thereof. 11. The method for producing a solid electrolytic capacitor according to claim 2 , wherein the nitrobenzene derivative is nitrobenzyl alcohol or nitrobenzoic acid.