JP3265431B2 - Solid electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller, thinner and lighter, there has been a demand for smaller capacitors used in circuits.

An aluminum electrolytic capacitor used as a relatively large-capacity capacitor has conventionally used an electrolytic solution, has a poor high-frequency characteristic, and has a possibility of liquid leakage. It was difficult.

[0004] Recently, the use of a conductive complex of 7,7,8,8-tetracyanoquinodimethane instead of an electrolytic solution has made it possible to solidify an electrolytic capacitor and greatly improve high-frequency characteristics. . However, this complex has a problem in solder heat resistance, and it has been difficult to make a chip component.

[0005] More recently, a solid electrolytic capacitor using polypyrrole, which is a conductive polymer, has been proposed and put into practical use (Japanese Patent Application Laid-Open No. 63-158829). In this capacitor, a conductive pre-coat layer is formed on an anodic oxide film as an insulator, and a conductive polypyrrole layer is formed thereon by electrolytic polymerization. Further, in order to simplify the manufacturing process, there has been proposed a method in which a solvent-soluble polyaniline is used instead of polypyrrole, and a conductive polymer layer is provided by a coating method (Japanese Patent Laid-Open No. 3-3551).
6).

[0006] These capacitors have good performance due to low high-frequency impedance and excellent heat resistance. However, a common problem is that the use of an electron conductive polymer in the solid electrolyte causes the anode to have a negative electrode. Poor ability to re-oxidize defective portions of the oxide film to reduce leakage current (hereinafter referred to as self-healing action), which may require time for aging after capacitor formation and poor product yield. Having.

An object of the present invention is to solve the above problems in a capacitor using a conductive polymer as a solid electrolyte,
An object of the present invention is to provide a solid electrolytic capacitor having excellent high-frequency characteristics, high reliability, and excellent self-healing properties.

[0008]

The solid electrolytic capacitor of the present invention comprises a homopolymer of (A) polyaniline and (B) an alkylene oxide monomer on a derivative oxide film formed on a film-forming metal. At least one selected from the group consisting of a block copolymer, a random copolymer and a crosslinked product obtained by crosslinking them; and (C) an anion of a protic acid, an alkali metal salt, an alkaline earth metal salt, and Do at least one selected from the group consisting of other organic salts Ri, wherein component (a) the
The component (B) is molecularly dispersed to form a polymer alloy,
By forming a solid electrolyte layer of a conductive polymer composition while creating.

In the conductive polymer composition used as a solid electrolyte in the solid electrolytic capacitor of the present invention, the component (A) and the component (B) are molecularly dispersed to form a polymer alloy, and the component (C) Is doped.

In this conductive polymer composition,
When the component (A) is doped with the component (C), the component has high conductivity, and when the component (B) is doped with the component (C), the component has ion conductivity. Therefore, when both the component (A) and the component (B) are doped with the component (C), the conductive polymer composition becomes an electron-ion mixed conductor. When such a conductive polymer composition is used as a solid electrolyte, the property of electron conductivity mainly contributes to electrical conductivity, and the property of ion conductivity contributes to rapid self-healing property.

In the present invention, the addition of the component (C) to the component (A), the component (B), or the complex of the component (A) and the component (B) is referred to as "doping".
That.

The polyaniline as the component (A) used in the present invention is prepared by dispersing or dissolving aniline in a solvent such as water or methanol, and then adding ammonium persulfate, hydrogen peroxide, or carbon dioxide in the presence of a protic acid such as sulfuric acid or hydrochloric acid. It can be easily obtained by adding an oxidizing agent such as manganese and polymerizing to obtain a doped polyaniline, which is further subjected to a dedoping treatment with a base such as ammonia or sodium hydroxide. Furthermore, reduced polyaniline obtained by treating undoped polyaniline with a reducing agent such as hydrazine, phenylhydrazine, or hydrazine hydrochloride can also be suitably used.

The alkylene oxide polymer or the crosslinked product thereof as the component (B) is a homopolymer, a block copolymer, a random copolymer or a crosslinked product obtained by crosslinking the alkylene oxide monomer. Usually, a polymer obtained by the addition (ring-opening) polymerization reaction of an alkylene oxide to an active hydrogen compound as described below, or a polymer obtained by subjecting the polymer to a crosslinking reaction using an appropriate crosslinking agent. is there.

Examples of the active hydrogen compound include monohydric alcohols such as methanol and ethanol, ethylene glycol,
Dihydric alcohols such as propylene glycol and 1,4-butanediol, polyhydric alcohols such as glycerin, trimethylolpropane, sorbitol, sucrose, polyglycerin, monoethanolamine, ethylenediamine, diethylenetriamine, 2-ethylhexylamine, hexa Examples include amines such as methylene diamine, and phenolic active hydrogen-containing compounds such as bisphenol A and hydroquinone.

Examples of the alkylene oxide monomer include ethylene oxide, propylene oxide, 1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, and 1,2-epoxyoctane. , 1,2-epoxynonane or the like having 2 to 9 carbon atoms
Α-olefin oxide, and α having 10 or more carbon atoms
Any of olefin oxide, styrene oxide and the like can be used, but ethylene oxide, propylene oxide and 1,2-epoxybutane are particularly preferable.

In the polymerization reaction, a basic catalyst such as sodium methoxide, sodium hydroxide, potassium hydroxide, lithium carbonate, triethylamine, potassium-t-butoxide and an acidic catalyst such as perchloric acid and boron trifluoride are used. Particularly, a basic catalyst is preferably used.

The number average molecular weight of the alkylene oxide polymer is preferably from 100 to 20,000.

Examples of the method of crosslinking the alkylene oxide polymer include isocyanate crosslinking and ester crosslinking.

As the crosslinking agent used for each crosslinking, in the case of isocyanate crosslinking, for example, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI) , 4,4 '
-Diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate, lysine ester triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, 1,6,11-undecane triisocyanate, 1,3,6- Hexamethylene triisocyanate, triphenylmethane diisocyanate, tris (isocyanatephenyl) thiophosphate, bicycloheptane triisocyanate, buret-bonded HMD
I, isocyanurate-bonded HMDI, trimethylolpropane TDI 3 mol adduct, or a mixture thereof. In the case of ester crosslinking, for example, malonic acid, succinic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, phthalic acid Polycarboxylic acids such as acid, isophthalic acid, terephthalic acid, itaconic acid, trimellitic acid, pyromellitic acid, and dimer acid; monomethyl ester, dimethyl ester, monoethyl ester, diethyl ester, monopropyl ester of these polycarboxylic acids; Lower alkyl esters such as dipropyl ester, monobutyl ester and dibutyl ester; and acid anhydrides of the above-mentioned polycarboxylic acids.

When the isocyanate crosslinking is carried out, the reaction is carried out, for example, by mixing an isocyanate and an alkylene oxide polymer in an NCO / OH equivalent ratio of 1.5 to 0.5, at a temperature of 80 to 150.degree. Perform for 5 hours.

In the case of performing ester cross-linking, the reaction (eg, esterification reaction or transesterification reaction)
Is, for example, a mixture of an alkylene oxide polymer and a polycarboxylic acid, a lower alkyl ester thereof, or an acid anhydride thereof at a functional ratio of 1: 2 to 2: 1 and a temperature of 120 to 120.
２５０250 ° C., 10 ^{-4 -10} Torr.

In the present invention, the conductive polymer composition used as the solid electrolyte layer includes, for example, a component (A) and a component (B) which are common solvents such as dimethyl sulfoxide, dimethylformamide, and N-methyl-2- It is obtained by dissolving in pyrrolidone or the like to form a complex composed of the component (A) and the component (B), and then doping the composite with the component (C). However, as for the method of doping the component (C), various embodiments are possible as described later.
It can be carried out either before or after the formation of the complex.

When undoped polyaniline which has not been reduced is used as the component (A), a complex is formed by the above-described method, and then a protic acid such as perchloric acid, sulfuric acid, paratoluenesulfonic acid or the like is used. By immersing the composite in the component (C), the component (C) can be doped.

Furthermore, in the conductive polymer composition used in the present invention, since an alkylene oxide polymer or a cross-linked product thereof is compounded as the component (B), an alkali metal salt or an alkaline earth metal salt is used. It is possible to dope the component (B) by using it as the component C). These salts can be doped into the component (B) either before or after the formation of the complex of the component (A) and the component (B).

In the case where the alkylene oxide polymer is used as the component (B) and the component (C) is doped before forming the complex, acetone, methanol, tetrahydrofuran or the like may be used.
A method of using a common solvent for the component (B) and the component (C), mixing them, and then distilling off the solvent can be used. The crosslinked product of the alkylene oxide polymer is
When the component (C) is doped as a component, the component (C) can be dissolved in the above-mentioned solvent, and the component (B) can be immersed in the solution.

When the component (C) is doped after the formation of the complex, the complex can be immersed in a solution of the component (C).

An alkali metal salt doped into the component (B),
Alkaline earth metal salts or organic salts are not particularly limited, for example, lithium iodide, lithium chloride, lithium perchlorate, lithium thiocyanate, lithium tetrafluorofluoride, lithium trifluoromethanesulfonate, sodium iodide, thiocyanic acid Sodium, sodium bromide,
Alkali metal salts or alkaline earth metal salts such as magnesium perchlorate and calcium perchlorate, or organic salts such as ammonium adipate, ammonium benzoate and ammonium azelate are preferred.

As described above, the method for producing the conductive polymer composition as the solid electrolyte layer of the present invention has a high degree of freedom. The ratio of the component (A) in this conductive polymer composition is from 20 to 9
It is 8% by weight, preferably 50 to 95% by weight. Also,
The proportion of the component (B) is 2 to 80% by weight, preferably 5 to 5%.
0% by weight. The ratio of the component (C) to the composite of the component (A) and the component (B) is preferably 0.01 to 20% by weight.

As the anode of the solid electrolytic capacitor of the present invention, an anode obtained by forming a dielectric film by oxidation on a valve metal such as aluminum or tantalum is preferably used.

As a method of manufacturing the solid electrolytic capacitor of the present invention, a composite solution of the component (A) and the component (B) is prepared in advance by the above-mentioned method, and then impregnated or coated on the dielectric oxide film. It is preferable to use a method in which a film is formed by heating or the like to form a film, and then the component (C) is doped.

[0031]

EXAMPLES Examples of the synthesis of polyaniline are shown below.

Synthesis Example 1 (Synthesis of undoped polyaniline) In a 1-liter four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping funnel, 20 g of aniline, 18 ml of hydrochloric acid,
And 250 ml of water were added. After cooling to 0 ° C., a solution of 49 g of ammonium persulfate dissolved in 120 g of water was dropped from the dropping funnel over 4 hours. After stirring for 1 hour after the completion of the dropwise addition, the precipitated solid was separated by filtration, washed with water, and then washed with methanol until the filtrate became transparent. Then, this solid was dispersed in 500 ml of 4N aqueous ammonia and stirred for 4 hours. After completion of the stirring, the solid was separated by filtration, washed with water until the filtrate became neutral, and then washed with methanol until the filtrate became transparent. The filtered solid was dried under vacuum to obtain 10.2 g of dark brown undoped polyaniline. It was soluble in N-methyl-2-pyrrolidone.

Synthesis Example 2 (Synthesis of reduced polyaniline) 2 g of the undoped polyaniline obtained in Synthesis Example 1 was
It was dissolved in 98 g of methyl-2-pyrrolidone, and 0.8 g of phenylhydrazine was added to this solution. After the completion of the reaction, the precipitate was reprecipitated with acetone, and the precipitated solid was separated by filtration, washed with acetone, and dried to give gray title polyaniline 1.6.
g was obtained.

Next, a synthesis example of an alkylene oxide polymer will be described.

Synthesis Example 3 (Synthesis of alkylene oxide polymer B-2) Using 212 g of diethylene glycol as a starting material, 12 g of potassium hydroxide as a catalyst and 1,8 of ethylene oxide
After reacting 94 g and 1,894 g of propylene oxide in a 5-liter autoclave at 120 ° C. for 8 hours, desalting and purification were carried out, and the number average molecular weight was 4,000.
3,980 g of an ethylene oxide-propylene oxide random copolymer (calculated from the hydroxyl value) was obtained.

Synthesis Example 4 (Synthesis of alkylene oxide polymer B-4) Using 184 g of glycerin as a starting material, 12.0 g of potassium hydroxide as a catalyst, and 3,816 g of ethylene oxide
Was reacted in a 5 liter autoclave at 130 ° C. for 4 hours, followed by desalting and purification, and the number average molecular weight was 2,2.
3,940 g of an ethylene oxide homopolymer having a molecular weight of 000 (calculated from the hydroxyl value) was obtained.

Synthesis Example 5 (Synthesis of alkylene oxide polymer B-6) Starting from 92 g of glycerin, 10 g of potassium hydroxide was used as a catalyst, and 2,454 g of ethylene oxide and 2,454 g of propylene oxide were mixed in a 10-liter autoclave at 120 g. After reacting at 8 ° C. for 8 hours, desalting and purification were performed to obtain 4,990 g of an ethylene oxide-propylene oxide random copolymer having a number average molecular weight of 5,000 (calculated from a hydroxyl value).

Synthesis Example 6 (Synthesis of alkylene oxide polymer B-7) Using 92 g of glycerin as a starting material, 21 g of potassium hydroxide as a catalyst and 1,382 g of ethylene oxide and 5,526 g of propylene oxide in a 10-liter autoclave, After reacting at 8 ° C. for 8 hours, desalting and purification were performed to obtain 6,990 g of an ethylene oxide-propylene oxide random copolymer having a number average molecular weight of 7,000 (calculated from a hydroxyl value).

Table 1 shows examples of alkylene oxide polymers which can be used in the present invention.

[0040]

[Table 1]

[0041] Alkylene oxide polymers obtained in the de-doped polyaniline 0.9g obtained in Example 1 Synthesis Example 1 Synthesis Example 4 (B-4) 0.1g
Was dissolved in 9.0 g of N-methyl-2-pyrrolidone to obtain a homogeneous solution. An anode foil (an anode area of 1 cm ² , a liquid volume of 1) was formed by forming a dielectric oxide film layer on a roughened aluminum foil having a thickness of 50 μm and attaching an anode lead to the solution.
μF) was soaked for 3 minutes.

After lifting the anode foil, it was dried at 150 ° C. for 10 minutes to remove the solvent. By this operation, a blue-violet thin film was formed on the anode foil.

Next, this anode foil was immersed in an aqueous solution containing 10% of paratoluenesulfonic acid and 10% of ammonium adipate for 5 hours. After immersion, washing with water, further washing with methanol, and drying at 80 ° C. for 3 hours, a cathode lead was attached using a silver paste to obtain a solid electrolytic capacitor.

Applying a direct current of 20 V to this capacitor,
The time required for the leakage current to become 1 μA or less, the capacity, and the equivalent series resistance at 100 kHz were measured.

Example 2 0.8 g of the undoped polyaniline obtained in Synthesis Example 1, 0.05 g of lithium perchlorate, 0.2 g of the alkylene oxide polymer (B-7) obtained in Synthesis Example 6, and 2,4- Tolylene diisocyanate was added so that the NCO / OH equivalent ratio became 1, to obtain a homogeneous solution. Thereafter, a thin film was formed on the anode foil in the same manner as in Example 1, and then this anode foil was immersed in a 10% aqueous solution of p-toluenesulfonic acid for 5 hours.

Further, a solid electrolytic capacitor was obtained in the same manner as in Example 1, and the performance was evaluated.

Example 3 A solid electrolytic capacitor was obtained in exactly the same manner as in Example 1 except that the alkylene oxide polymer was changed to B-2 obtained in Synthesis Example 3. The performance of this capacitor was evaluated in the same manner as in Example 1.

Example 4 0.5 g of the undoped polyaniline obtained in Synthesis Example 1 and 0.5 g of the alkylene oxide polymer (B-6) obtained in Synthesis Example 5
A solid electrolytic capacitor was obtained in exactly the same manner as in Example 1 except for using. The performance of this capacitor was evaluated in the same manner as in Example 1.

Comparative Example 1 1.0 g of the undoped polyaniline obtained in Synthesis Example 1 was dissolved in 9.0 g of N-methyl-2-pyrrolidone to obtain a homogeneous solution. After a thin film was formed on the anode foil using this solution in the same manner as in Example 1, the anode foil was immersed in a 10% aqueous solution of p-toluenesulfonic acid for 5 hours. Thereafter, a solid electrolytic capacitor was obtained in exactly the same manner as in Example 1.

The performance of this capacitor was evaluated in the same manner as in Example 1.

Comparative Example 2 Alkylene oxide polymer (B-4) obtained in Synthesis Example 4
1.0 g and 0.05 g of lithium perchlorate were dissolved in methyl ethyl ketone, and 2,4-tolylene diisocyanate was added so that the NCO / OH equivalent ratio became 1, to obtain a uniform solution. The same anode foil as that used in Example 1 was immersed in this solution, and the solvent was distilled off and cross-linked at 80 ° C. for 3 hours to form a colorless and transparent thin film on the anode foil. A cathode lead was attached to this anode foil using a silver paste to obtain a solid electrolytic capacitor. The performance of this capacitor was evaluated in the same manner as in Example 1.

Table 2 shows the evaluation results of the performance of the solid electrolytic capacitors in Examples 1 to 4 and Comparative Examples 1 and 2.

[0053]

[Table 2]

[0054]

The solid electrolytic capacitor of the present invention has an excellent self-healing property, a low high-frequency impedance and an unprecedented high performance.

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein (A) polyaniline, (B) a homopolymer of an alkylene oxide monomer, a block copolymer, a random copolymer and At least one selected from the group consisting of crosslinked products obtained by crosslinking them, and (C) selected from the group consisting of anions of protonic acids, alkali metal salts, alkaline earth metal salts and other organic salts Ri Do at least one, the component (a) the
The component (B) is molecularly dispersed to form a polymer alloy,
The solid electrolytic capacitor, characterized in that to form a solid electrolyte layer of a conductive polymer composition while creating.