JP2001291643A - Electrolyte solution for driving electrolytic capacitor, and electrolytic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte solution which is to be used in an electrolytic capacitor which has a low impedance characteristic and satisfactory frequency characteristic even at a low-temperature condition, and where a reaction of the electrolyte solution with an electrode metal can be suppressed for a long time on account of its stability, even at a high-temperature condition and whose service life is long due to less change with time lapse. SOLUTION: This electrolyte solution contains a polyacrylamide or its derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolytic solution for an electrolytic capacitor and an electrolytic capacitor using the same. More specifically, the present invention has low impedance characteristics, maintains good frequency characteristics even under low temperature conditions, and has a stable electrolyte solution even at high temperature conditions, and the reaction with the electrode metal is suppressed for a long time. , Little change in characteristics over time,
Further, the present invention relates to an electrolytic solution for driving an electrolytic capacitor capable of exhibiting extremely stable capacitor characteristics and excellent life characteristics from a low temperature to a high temperature, and an electrolytic capacitor using the same. The electrolytic capacitor of the present invention is useful as an aluminum electrolytic capacitor and other electrolytic capacitors.

[0002]

2. Description of the Related Art Capacitors are one of general electric components, and are widely used in various electric and electronic products, mainly for power supply circuits and noise filters for digital circuits. Capacitors are broadly classified into electrolytic capacitors and other capacitors (ceramic capacitors, film capacitors, etc.).

[0003] There are various types of electrolytic capacitors currently used, examples of which are an aluminum electrolytic capacitor and a wet tantalum electrolytic capacitor. The present invention can provide a remarkable effect even when applied to any type of electrolytic capacitor, but an aluminum electrolytic capacitor can be expected to have a particularly excellent effect. The invention will be described with reference to a type of electrolytic capacitor.

In a conventional aluminum electrolytic capacitor, typically, after a high-purity aluminum foil is etched to increase its surface area, an anode foil having a film formed on the surface of the aluminum foil by anodization, It can be manufactured by using an etched cathode foil. Then, the obtained anode foil and cathode foil are arranged to face each other, and furthermore, a structure in which a separator (separating paper) is interposed between the foils to form an element having a structure, and this element is wound up Is impregnated with the electrolytic solution. The element impregnated with the electrolytic solution is housed in a case (generally made of aluminum) and sealed with an elastic sealing member to complete an electrolytic capacitor. It should be noted that there is an electrolytic capacitor other than such a wound structure.

In the above electrolytic capacitor,
The characteristics of the electrolytic solution play a major factor in determining the performance of the electrolytic capacitor. In particular, with the recent miniaturization of electrolytic capacitors, anode foil or cathode foil has come to be used with a high etch sig magnification, and the resistivity of the capacitor body has increased. In addition, a highly conductive material having a small resistivity (specific resistance) is always required.

A conventional electrolytic solution for an electrolytic capacitor is a solvent composed of ethylene glycol (EG) as a main solvent and water to about 10% by weight, and a carboxylic acid such as adipic acid or benzoic acid as an electrolyte. Or, a solution obtained by dissolving an ammonium salt thereof is generally used. In such an electrolytic solution, the specific resistance is about 1.5 Ω · m (150 Ω · cm).

On the other hand, in a capacitor, it is required to lower the impedance (Z) in order to sufficiently exhibit its performance. The impedance is determined by various factors. For example, the impedance decreases as the electrode area of the capacitor increases. Therefore, as the size of the capacitor increases, the impedance is naturally reduced. In addition, there is an approach for reducing the impedance by improving the separator. Nevertheless, particularly in a small-sized capacitor, the specific resistance of the electrolytic solution is a major controlling factor of the impedance.

Recently, a low-specific-resistance electrolytic solution using an aprotic organic solvent, for example, GBL (γ-butyrolactone) or the like, has also been developed (for example, JP-A-62-14).
5713, JP-A-62-145714 and JP-A-62-145715). However, capacitors using this aprotic electrolyte are
The impedance is much lower than that of a solid capacitor using an electronic conductor having a specific resistance of 1.0 Ω · cm or less.

Further, the aluminum electrolytic capacitor has poor low-temperature characteristics due to the use of an electrolytic solution, and the ratio of the impedance at −40 ° C. to the impedance at 20 ° C. at 100 kHz: Z (−40 ° C.) / Z (20 ℃) is about 4
In fact, it is quite large, 0. In view of such a current situation, an aluminum electrolytic capacitor having a low impedance, a low equivalent series resistance (ESR), excellent low-temperature characteristics, and a small change with time in high-temperature conditions is provided. It is desired to do.

Furthermore, water used as a part of the solvent in the electrolytic solution of the aluminum electrolytic capacitor is a chemically active substance for aluminum constituting the anode foil and the cathode foil. The characteristics of the capacitor are remarkably degraded by the reaction, and the pressure inside the capacitor is increased by the hydrogen gas generated at the time of the reaction, causing abnormal appearance.

An electrolytic solution having a high concentration of water is chemically active, and is a capacitor component other than the electrolytic solution such as an aluminum electrode and a separator (in the present specification, such a component is referred to as a “capacitor element”). On the other hand, the attack of ions in the electrolytic solution becomes extremely large, so that there is a problem that the stability of the capacitor is significantly impaired under high temperature conditions.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. The first object of the present invention is to provide an electrolytic capacitor having a low impedance and a low E.C. S. R. To provide an electrolytic solution for driving an electrolytic capacitor, which has both the excellent characteristics that these characteristics change little even under low-temperature conditions and the characteristics that the characteristics are very stable and have little change over time even under high-temperature conditions. is there.

It is another object of the present invention to provide an electrolytic capacitor using the electrolytic solution of the present invention, particularly an aluminum electrolytic capacitor.

[0014]

According to one aspect of the present invention, there is provided an electrolytic solution for driving an electrolytic capacitor, comprising polyacrylamide or a derivative thereof. In another aspect, the present invention resides in an electrolytic capacitor comprising the electrolytic solution for driving an electrolytic capacitor of the present invention.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolytic solution for driving an electrolytic capacitor of the present invention contains at least an electrolyte and a solvent in which the electrolyte is dissolved. As a solvent for dissolving the electrolyte, an organic solvent or a water-organic solvent-based solvent, that is, a solvent having a high water concentration consisting of a mixture of an organic solvent and water is preferably used.

As the organic solvent, a protic solvent or an aprotic solvent can be used alone or in combination of two or more. If necessary, one or more of the protic solvents and one or more of the aprotic solvents may be used in any combination. Suitable proton solvents include, for example, alcohol compounds. Further, specific examples of the alcohol compound that can be advantageously used here are not limited to those listed below, but include methyl alcohol,
Monohydric alcohols such as ethyl alcohol, propyl alcohol and butyl alcohol, dihydric alcohols (glycols) such as ethylene glycol, diethylene glycol, triethylene glycol and propylene glycol, and trihydric alcohols such as glycerin can be mentioned. Also,
Examples of suitable aprotic solvents include, but are not limited to, lactone compounds such as γ-butyrolactone, propylene carbonate, tetrahydrofuran, acetonitrile, dimethylformamide, nitrobenzene, and other intramolecularly polarized compounds. Can be mentioned.

In the practice of the present invention, when one or more solvents selected from the group consisting of the protic solvent group and the aprotic solvent group are used as the solvent, more specifically, one kind of the protic solvent is used. May be used, one kind of aprotic solvent may be used, plural kinds of protic solvents may be used, plural kinds of aprotic solvents may be used, or 1 At least one kind of protic solvent and 1
A mixed system of two or more aprotic solvents may be used.

In the electrolytic solution of the present invention, a water-organic solvent-based solvent can be used as a solvent instead of using an organic solvent alone as described above. Particularly, in the case of the present invention, it is distinguished from the conventional electrolytic solution in that a relatively large amount of water is preferably used in combination. In the present invention, by using such a water-organic solvent-based solvent, the freezing point of the solvent is lowered, thereby improving the specific resistance characteristics of the electrolyte at low temperatures, and the ratio between the low temperature and the normal temperature is improved. Good low-temperature characteristics indicated by a small difference in resistance can be realized.

More specifically, taking as an example the case where ethylene glycol is used as the organic solvent, the protonic organic solvent has a boiling point of about 198 ° C. and a melting point of −198 ° C.
About 13 ° C. The temperature range required for the capacitor is
Generally, since the temperature is −40 ° C. to 85 ° C. to 105 ° C., the electrolyte using this solvent has a margin in characteristics at a high temperature, but has a remarkable electric characteristic due to an increase in viscosity and solidification of the electrolyte at a low temperature. descend. In the present invention, in the electrolytic solution, while using an organic solvent having an excellent temperature characteristic alone or in a mixture of plural kinds, when an organic solvent having a relatively high freezing point is used, water is added by adding water to an organic solvent. By using a solvent-based solvent, the freezing point of the solvent can be lowered, and electrical characteristics at low temperatures can be secured. Since the water-organic solvent-based electrolyte has a very high electrolyte dissolving ability and ion mobility, it can realize a much lower specific resistance than conventional electrolytes. Further, at low temperatures, since the characteristics of the solvent are improved, an electrolytic solution having an unprecedented epoch-making characteristic that the difference in specific resistance between low temperature and normal temperature is small. Therefore, an electrolytic capacitor using such an electrolytic solution can naturally have good temperature characteristics reflecting the characteristics of the electrolytic solution.

The content of water in the solvent in the electrolytic solution is as follows:
Although there is no particular limitation, it is preferable that water is in the range of 0 to 90% by mass (wt%) in the solvent. Water may not be added when the organic solvent alone has good temperature characteristics, but it is recommended to add water when slight or significant improvement in characteristics is expected. Since the amount of water added at this time varies depending on the organic solvent, the lower limit is not limited. When the amount of water added is 90% by mass or more, the temperature characteristics of water are greatly reflected in the electrolytic solution. At a low temperature, the specific resistance increases significantly due to solidification, and at a high temperature, the electrolytic solution is scattered at a high vapor pressure. No good characteristics can be obtained with respect to temperature. When the characteristics of the electrolytic solution are improved by adding water, the more preferable water content in the water-organic solvent-based solvent is 3%.
The water content is in the range of 0 to 80% by mass, and the most preferable water content is in the range of 45 to 80% by mass.

The electrolytic solution of the present invention is prepared by using the above-mentioned organic solvent or a water-organic solvent-based solvent, and as an additive of the electrolytic solution, a polyacrylamide which is a water-soluble polymer or a polyacrylamide thereof. It is necessary to add a derivative. The polyacrylamide or derivative thereof added here can be represented by the following general formula.

[0022]

Embedded image

In the above formula, R may be the same or different and represents a hydrogen atom or a substituted or unsubstituted lower alkyl group having 1 to 4 carbon atoms, for example, a methyl group, And n is a positive integer, preferably an integer necessary to give a molecular weight of 100 to 2,000,000. It is preferred that all R's in the formula are hydrogen atoms.

Polyacrylamide or a derivative thereof is a polymer compound that is very soluble in water, but generally has a property of being hardly soluble in an organic solvent. When this polyacrylamide or a derivative thereof is added to an electrolyte comprising an organic solvent or a water-organic solvent system according to the present invention, although it has not been expected at all in the studies so far, it has been confirmed that even under low-temperature conditions, The frequency characteristics are maintained, the electrolytic solution is stable even under high temperature conditions, the reaction with the electrode metal is suppressed for a long time, and therefore, the characteristics change with time and the life is long. In fact, although the life of an electrolytic capacitor using an electrolyte solution to which polyacrylamide is not added is at most 4,000 to 5,000 hours (at 105 ° C.), an electrolyte solution to which polyacrylamide or a derivative thereof is added is used. In the case of a capacitor that has been
It can be extended to about 00 to 10,000 hours (about twice). In addition, the electrolytic solution to which polyacrylamide or a derivative thereof is added exhibits extremely stable capacitor characteristics from a low temperature to a high temperature, and can sufficiently satisfy the temperature acceleration condition of 2 × / 10 ° C. in the Arrhenius chemical reaction.

It is considered that the remarkable effect as described above largely depends on the fact that polyacrylamide or a derivative thereof has an action of uniformly dispersing ions in the electrolytic solution. Due to this action, concentration of ions in the electrolytic solution, which occurs when the reaction is expanded, can be inhibited, so that even under a high temperature condition, the suppression of the activity and the deterioration of the electrolyte solution can be maintained for a long time. Further, under a low temperature condition, the conductivity can be maintained by lowering the solidification temperature of the solution.

As described above, the molecular weight of polyacrylamide or a derivative thereof is preferably in the range of 100 to 2,000,000. That is, in the practice of the present invention, polyacrylamide or a derivative thereof can be widely used from a relatively low molecular weight (oligomer) to a high molecular weight depending on a desired effect or the like. For example, a dimer of polyacrylamide having a molecular weight of about 144 or a trimer having a higher molecular weight can be advantageously used.

The amount of polyacrylamide or a derivative thereof can be widely varied depending on the desired effect and the like, but is usually 0.05 to 5.0% based on the total amount of the solvent of the electrolytic solution. It is preferably in the range of 0% by mass, more preferably 0.1 to 2.0% by mass.
Range. An addition amount of about 10.0% by mass is not preferable because it causes gelation of the electrolytic solution.

In the practice of the present invention, the method of including polyacrylamide or a derivative thereof (hereinafter collectively referred to as "polyacrylamide") in the electrolytic solution is not particularly limited, and the desired effect can be obtained. As far as possible, various methods can be adopted. The following describes some of the preferred methods. 1. Direct addition of polyacrylamide Polyacrylamide can be added directly to the electrolyte. In the case where a water-organic solvent-based solvent is used and the ratio of water in the solvent used is high, solid polyacrylamide may be added to the electrolytic solution and dissolved with stirring.

2. Addition of Polyacrylamide Aqueous Solution In many cases, after polyacrylamide is dissolved in water in advance to obtain an aqueous solution of several% to several tens%, the aqueous solution can be added to the electrolytic solution. This method is the easiest when handling polyacrylamide and is a method for reducing external contamination and errors.

3. Addition of polyacrylamide while paying attention to the viscosity of the electrolytic solution When polyacrylamide is used by dissolving it in the electrolytic solution, it is necessary to pay attention to the viscosity of the electrolytic solution caused by adding the polyacrylamide. Since the electrolytic solution targeted by the present invention has a low resistance, that is, a highly conductive electrolytic solution, it is not preferable that the movement of ions involved in conductivity is hindered by an increase in solution viscosity. In the case of a polymer-containing electrolytic solution, the aggregation of the polymer (salting out) may occur due to the interaction with the electrolyte ions in the solution. Solution preparation is required. For these reasons, the molecular weight and the amount of polyacrylamide to be added to the electrolytic solution have the appropriate ranges as described above.

4. Addition of low molecular weight polyacrylamide For an electrolytic solution using a water-organic solvent solvent having a small water ratio, it is preferable to add low molecular weight polyacrylamide from the relationship between the molecular weight and solubility of polyacrylamide. . Of course, this method can also be used for an electrolytic solution using a water-organic solvent-based solvent having a large water ratio.

5. Other Methods of Adding Polyacrylamide Polyacrylamide may be impregnated or applied to a capacitor element before being impregnated with an electrolytic solution, or may be dispersed in an adhesive for fixing the element. Regardless of which method is adopted, polyacrylamide can be gradually moved (migrated) into the electrolytic solution from the contact portion between such a capacitor element and the electrolytic solution. Alternatively, the capacitor element impregnated with the electrolyte may be impregnated with a solution of polyacrylamide, or else the polyacrylamide may be supplied to the electrolyte by applying a solution of polyacrylamide to the outside of such a capacitor element. Is also possible.

6. Dissolving Polyacrylamide by Changing Solvent Ability of Solvent In the case of dissolving polyacrylamide in an electrolytic solution, a plurality of solvents can be combined, and dissolution can be performed in a state where the solubility of the solvent is largely changed. For example, an electrolytic solution using a ternary solvent of methanol / ethylene glycol / water is one example.

7. Dissolving polyacrylamide in the presence of a surfactant When dissolving polyacrylamide in an electrolytic solution, a surfactant (for example, an ionic surfactant such as dodecyl sulfate or a nonionic surfactant such as a polyether derivative) is used. (A surfactant) is effective. 8. Addition of polydispersed polyacrylamide It is also effective when the molecular weight distribution is wide, that is, when polydispersed polyacrylamide is added. Polydispersed polyacrylamide has high solubility in an electrolytic solution.

9. Depends on the breakage of the polymer chain of polyacrylamide Polyacrylamide having a molecular weight that is difficult to dissolve in the electrolytic solution is supplied in advance to the capacitor element, and when the capacitor element is impregnated with the electrolytic solution to produce a capacitor, the polyacrylamide is electrolyzed. When left in the solution, the polymer molecular chains are cut and become dissolved in the electrolytic solution. This dissolution is affected by the solvent of the electrolyte solution (the more water, the more easily the polymer molecular chains are broken), the type of electrolyte, and the ambient temperature (the higher the ambient temperature, the more easily the polymer molecular chains are broken).

As the electrolyte in the electrolytic solution of the present invention,
Organic acids, particularly preferably carboxylic acids or salts thereof, and inorganic acids or salts thereof are used. These electrolyte components may be used alone or in combination of two or more. Examples of carboxylic acids that can be used as the electrolyte component include, but are not limited to, those listed below, formic acid, acetic acid, propionic acid,
Butyric acid, p-nitrobenzoic acid, monocarboxylic acids represented by salicylic acid and benzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid,
It includes dicarboxylic acids represented by phthalic acid and azelaic acid, and carboxylic acids having a functional group such as a hydroxyl group such as citric acid, sebacic acid, and oxybutyric acid can also be used. Of course, such a carboxylic acid derivative may be used if necessary.

Examples of inorganic acids that can also be used as the electrolyte component are not limited to those listed below, but include phosphoric acid, phosphorous acid, hypophosphorous acid, boric acid, and sulfamic acid. Etc. are included. If necessary, a derivative of such an inorganic acid may be used. Further, as a salt of a carboxylic acid or an inorganic acid as described above,
A variety of commonly known salts can be used. Examples of suitable salts include, but are not limited to, the ammonium salts, sodium salts, potassium salts, amine salts, alkyl ammonium salts, and the like. Among such salts, it is more preferable to use an ammonium salt.

In addition, when an inorganic acid or a salt thereof is used as the electrolyte in the practice of the present invention, a decrease in the freezing point of the electrolyte can be expected, which can contribute to further improvement of the low-temperature characteristics of the electrolyte. When an inorganic acid or a salt thereof is used, when a nitro compound is used as an additive, the ability to absorb hydrogen gas derived from the nitro compound can be maintained for a long period of time.

According to the study of the present inventors, when an electrolyte such as an inorganic acid or a salt thereof is used in combination with an electrolyte such as the carboxylic acid or a salt thereof described above, they are used alone. As compared with the case, the life of the electrolytic capacitor can be significantly extended. further,
In conventional electrolytic capacitors, inorganic acid-based electrolytes have been mainly used for medium to high voltage (160 to 500 volt) type electrolytic capacitors due to problems such as electrical conductivity. When used in combination, it can also be used advantageously in low voltage (less than 160 volt) type electrolytic capacitors.

The amount of the electrolyte used in the electrolytic solution of the present invention depends on various characteristics such as the characteristics required for the electrolytic solution and the finally obtained capacitor, the type and composition and amount of the solvent used, and the type of the electrolyte used. The optimal amount can be appropriately determined according to the factors. For example, as described above, when using an inorganic acid-based electrolyte in combination with a carboxylic acid-based electrolyte, the content of the inorganic acid-based electrolyte in the mixed electrolyte can be changed in a wide range, Usually, it is preferred that the content be in the range of about 0.1 to 15% by mass based on the total amount of the electrolyte.

Further, the electrolytic solution of the present invention comprises (1) a chelating compound, (2) a saccharide, (3) hydroxybenzyl alcohol and / or L-glutamic acid diacetate or a salt thereof, and (4) gluconic acid and It is preferable to add additives such as (or) gluconolactone and (5) a nitro compound as needed. These additives may be used alone or in any combination of two or more additives.

Hereinafter, each additive will be described. (1) Chelate compounds Chelate compounds such as ethylenediaminetetraacetic acid (ED
TA), trans-1,2-diaminocyclohexane-
N, N, N ′, N′-tetraacetic acid monohydrate (CyDTA),
Dihydroxyethylglycine (DHEG), ethylenediaminetetrakis (methylenephosphonic acid) (EDTP
O), diethylenetriamine-N, N, N ', N ",
N "-pentaacetic acid (DTPA), diaminopropanol tetraacetic acid (DPTA-OH), ethylenediamine diacetic acid (ED
DA), ethylenediamine-N, N'-bis (methylenephosphonic acid) hemihydrate (EDDPO), glycol etherdiaminetetraacetic acid (GEDTA), hydroxyethylethylenediaminetriacetic acid (EDTA-OH) and the like. Generally, the chelate compound is preferably added in the range of 0.01 to 3% by mass. Such a chelate compound can be used for aluminum (A
l) Prolonging the life of the capacitor by suppressing the hydration reaction of the electrode foil, improving the low-temperature characteristics of the electrolytic capacitor (since the solvent has a composition close to the antifreeze state, the change in impedance between normal temperature and low temperature is small), corrosion resistance The effect such as improvement of can be brought about.

(2) Sugars Sugars such as glucose, fructose, xylose, galactose and the like. Sugars are generally from 0.01 to 5
It is preferable to add in the range of mass%. Such saccharides can suppress the hydration reaction of the Al electrode foil of the low-impedance capacitor, prolong the life of the capacitor, suppress the decomposition and activation of electrolytes such as carboxylic acids by adding saccharides,
Effects such as improvement of the low temperature characteristics of the electrolytic capacitor (since the solvent has a composition close to the antifreeze state, the change in impedance between normal temperature and low temperature becomes small) can be obtained.

(3) Hydroxybenzyl alcohol Hydroxybenzyl alcohol, for example, 2-hydroxybenzyl alcohol, L-glutamic acid diacetic acid or a salt thereof. Generally, this additive is preferably added in the range of 0.01 to 5% by mass. Such additives are:
Prolonging the life of the capacitor by suppressing the hydration reaction of the Al electrode foil of the low impedance capacitor, and improving the low temperature characteristics of the electrolytic capacitor (since the solvent has a composition close to the antifreeze state, the change in impedance between room temperature and low temperature is small) And other effects.

(4) Gluconic acid and / or gluconolactone The electrolytic solution of the present invention may contain gluconic acid, gluconolactone or the like, if necessary, alone or in combination. Additives of this type are generally present in the range of 0.01 to 5
It is preferable to add in the range of mass%. When gluconic acid or gluconolactone is added to the electrolyte solution of the present invention, the effects of the present invention such as longer life of the electrolytic capacitor, improvement of low-temperature characteristics, and excellent hydrogen gas absorption effect can be obtained. In addition, a remarkable effect such as improvement in corrosion resistance can be further obtained.

(5) Nitro compound The electrolytic solution of the present invention may contain nitrophenol,
For example, containing at least one nitro compound selected from a compound group such as p-nitrophenol, nitrobenzoic acid, for example, p-nitrobenzoic acid, dinitrobenzoic acid, nitroacetophenone, for example, p-nitroacetophenone, nitroanisole. Can be.

In the present invention, when the above-mentioned nitro compound group is used, a particularly remarkable hydrogen gas absorbing effect can be obtained. From the experience of the present inventors, it is understood that this effect is largely due to the fact that the substituent contained in each nitro compound exhibits the hydrogen gas absorbing effect at different timings. The nitro compound used here has a function of suppressing the element from being corroded by the action of a halogenated hydrocarbon used for washing the printed circuit board, for example, trichloroethane (in other words, a halogen trapping action). Can have.

When the above-mentioned nitro compound is added to the electrolytic solution of the present invention, a specific composition effective for the effect of the present invention is employed in the electrolytic solution itself. Although possible hydrogen gas absorbing effects and halogen scavenging effects can be achieved, more preferable effects can be expected when two or more nitro compounds are used in combination. In general,
It is recommended to use a mixture of the two nitro compounds. In addition, the nitro compound is usually preferably used by adding it in an amount of 0.01 to 5% by mass based on the total amount of the electrolytic solution. If the added amount of the nitro compound is less than 0.01% by mass, the intended effect can hardly be obtained, and if it exceeds 5% by mass, the expected effect can be further improved. In some cases, other characteristics may be adversely affected.

To further explain the use of the nitro compound, the absorption of hydrogen gas generated during the reaction between aluminum and water can be explained by the fact that the nitro compound alone is used as described in the description of the prior art. The absorption effect tends to decrease as the content of water increases, and this absorption effect tends to decrease when the electrolytic solution is placed in a high-temperature environment. However, such problems arising from the single use of nitro compounds can be solved by using two or more nitro compounds in combination as in the present invention. In fact, in the case of the electrolyte solution of the present invention, by using a plurality of types of nitro compounds,
The hydrogen gas absorption capacity was able to be maintained for a much longer time than the conventional single use.

The excellent effect of the present invention on the absorption of hydrogen gas was also confirmed in relation to the electrolyte used together. In a conventional electrolytic solution, a method has been adopted in which only one type of nitro compound is added to only a carboxylic acid-based electrolyte, or only one type of nitro compound is added to only an inorganic acid-based electrolyte. But,
When the content of water in the solvent is large, a satisfactory hydrogen gas absorbing effect cannot be obtained by the above-described method, and an electrolyte in which a carboxylic acid-based electrolyte and an inorganic acid-based electrolyte are mixed. The same was true for the electrolyte, but in the case of the electrolyte of the present invention (using only one type of nitro compound), surprisingly, even in such a carboxylic acid-based / inorganic acid-based mixed electrolyte, the conventional single electrolyte was used. The hydrogen gas absorption capacity was able to be maintained for a much longer period than use.

Furthermore, in addition to the above-mentioned additives, the electrolytic solution of the present invention may further contain additives commonly used in the field of aluminum electrolytic capacitors or other electrolytic capacitors. Suitable conventional additives include, for example, mannitol, silane coupling agents, water-soluble silicones, polymer electrolytes, and the like. The electrolytic solution of the present invention can be prepared by mixing and dissolving the above-described various components in an arbitrary order, and basically using a conventional technique as it is or by modifying it. Can be. For example, after preparing a solvent having a high water concentration which is a mixture of an organic solvent and water, it is easily prepared by dissolving an electrolyte, polyacrylamide or a derivative thereof and optional additives as necessary in the obtained solvent. can do. Further, as described above, polyacrylamide or a derivative thereof can be introduced into the electrolytic solution by using various methods, and therefore, the embodiment of the present invention has a large degree of freedom.

According to the present invention, there is provided a capacitor element formed of an electrolytic capacitor, preferably an anode foil and a cathode foil which are arranged to face each other, and a separator paper interposed therebetween. Also provided is an electrolytic capacitor comprising an electrolyte. The electrolytic capacitor of the present invention is more preferably an aluminum electrolytic capacitor, and most preferably, an anode foil composed of an aluminum foil and an anodic oxide film on the surface of the aluminum foil, and a cathode foil composed of an aluminum foil. A capacitor element formed by winding the surfaces so as to face each other with a separator therebetween, an electrolytic solution of the present invention, a case containing the capacitor element and the electrolytic solution, and an elastic sealing body sealing an opening of the case; An aluminum electrolytic capacitor comprising:

In the electrolytic capacitor of the present invention, since the electrolytic solution of the present invention is used, many remarkable effects, such as improvement in low-temperature characteristics by an organic solvent or a mixed solvent of an organic solvent and water, are obtained. It is possible to achieve long life by adding polyacrylamide or a derivative thereof, stable capacitor characteristics from low to high temperatures, and long life and low impedance by suppressing the hydration reaction by using a specific electrolyte. it can. In addition, it has sufficient characteristics as a chip capacitor compatible with reflow.

The aluminum electrolytic capacitor of the present invention
Preferably, an anode foil having the surface of the etched aluminum foil anodized and a cathode foil made of the etched aluminum foil are wound so that both surfaces face each other via a separator. The capacitor element and the electrolytic solution formed as described above are housed in a case, and the opening of the case in which the capacitor element is housed is sealed with an elastic sealing body. FIG. 1 is a cross-sectional view showing an example of the electrolytic capacitor of the present invention, and FIG.
FIG. 2 is a perspective view showing a capacitor element of the electrolytic capacitor shown in FIG. 1, particularly with a part thereof enlarged in a thickness direction. In addition,
The example shown is an electrolytic capacitor with a winding structure,
The electrolytic capacitor of the present invention can be modified or improved within the scope of the present invention. For example, the electrolytic capacitor of the present invention is an electrolytic capacitor having an oxide film on both electrode foils constituting the electrolytic capacitor, and an electrolytic capacitor having an electrode foil having a functional material such as a silane coupling agent on the surface. It may be a capacitor. Needless to say, an electrolytic capacitor other than the wound structure is also included.

The illustrated electrolytic capacitor 10 is an aluminum electrolytic capacitor, and has a structure in which a capacitor element 1 impregnated with an electrolytic solution is housed in a metal case 4 and the opening of the case 4 is closed with a sealing body 3. . Further, the capacitor element 1 housed in the metal case is in the form of a wound sheet laminate 20. Laminate 20
As shown in the figure, an aluminum oxide film 22
, An aluminum foil (cathode) 23, a first separator (separator) 24, and a second separator (separator) 25 sandwiched between these electrodes. . The first separator 24 and the second separator 25 may be the same or different. The capacitor element 1 is impregnated with an electrolytic solution.

The electrolytic capacitors shown in FIGS. 1 and 2 can be manufactured, for example, as follows. At first,
Using a high-purity aluminum foil as a raw material, etching the surface to increase the surface area, then anodizing the surface of the aluminum foil and applying an oxide film over the entire surface, A cathode foil having a surface area increased by etching is produced. Next, the obtained anode foil and cathode foil are arranged to face each other, and a separator (separation paper) is interposed between the foils to form a laminate, and an element having a structure in which the laminate is wound up, That is, a capacitor element is manufactured. Subsequently, the obtained capacitor element is impregnated with an electrolytic solution, and the capacitor element impregnated with the electrolytic solution is placed in a case (generally made of aluminum) as described above.
And the opening of the case is closed with a sealing body.
In addition, two lead wires are inserted into the lead wire through-holes of the sealing body, and they are completely sealed so that the electrolyte does not leak.

To further explain the electrolytic capacitor according to the present invention, the aluminum foil used as the anode foil and the cathode foil is preferably a high-purity aluminum foil having a purity of 99% or more. The anode foil can be preferably formed by electrochemically etching an aluminum foil, anodizing to form an oxide film on the surface, and then attaching an electrode lead tab. Further, the cathode foil can be formed by etching the aluminum foil and then attaching a lead tab for leading the electrode.

A capacitor element can be obtained by winding the anode foil and the cathode foil formed as described above, with the surfaces of both being opposed to each other via the above-mentioned separator paper. The separator paper used for producing the capacitor element is not particularly limited, but is preferably a paper produced from a naturally-occurring cellulose material, for example, manila hemp or vegetation pulp. For such a separator paper, for example, paper produced by using a pulp of a plant as a raw material and subjecting the raw pulp to a dust removing step, a washing step, a beating step, a paper making step, and the like can be advantageously used. In addition, the use of paper derived from synthetic fibers is also possible.

The sealing body used in the electrolytic capacitor of the present invention is a material as long as its material is high in hardness, has a suitable rubber elasticity, is impermeable to electrolyte, and has good airtightness as a sealing body. , Can be formed from a variety of conventional materials. Suitable sealing material is, for example, natural rubber (NR), styrene-butadiene rubber (S
BR), ethylene-propylene terpolymer (EP
T) and elastic rubbers such as isobutylene / isoprene rubber (IIR). It is also preferable to use isobutylene-isoprene rubber (IIR) because the airtightness is high and the electrolyte does not permeate as vapor. In particular, I having better heat resistance
IR, for example, sulfur vulcanization, quinoid vulcanization, resin vulcanization,
It is more preferable to use IIR such as peroxide vulcanization.

Further, in practicing the present invention, in place of the above-mentioned sealing material, a resin material plate (for example, a fluororesin plate such as a PTFE plate) having airtightness and sufficiently high strength may be used. Hybrid materials bonded with rubber can also be used advantageously.

[0061]

Next, the present invention will be further described with reference to examples.
It goes without saying that the examples given here are intended to illustrate the invention, but not to limit it. Example 1 An aluminum electrolytic capacitor having a wound structure was manufactured according to the following procedure.

First, an aluminum foil was electrochemically etched to form an oxide film on the surface, and then a lead tab for leading out an electrode was attached to produce an aluminum anode foil. Next, another aluminum foil was also subjected to an electrochemical etching treatment, and a lead tab for extracting an electrode was settled to form an aluminum cathode foil. Subsequently, a capacitor element was formed by winding a separator (isolation paper) between the anode foil and the cathode foil. Then, the capacitor element is impregnated with an electrolytic solution having a composition shown in Table 1 below, and then housed in a bottomed aluminum case so that a lead tab for extracting an electrode comes out of the case. It sealed with the elastic sealing body, and produced the electrolytic capacitor (10WV-1,000microF) of a winding structure.

Next, the impedance at low temperature (−40 ° C.) and the impedance at room temperature (20 ° C.) of the electrolytic capacitor manufactured as described above were measured at a frequency of 120 Hz, and the ratio of each measured value was measured. The impedance ratio (Z ratio) expressed as The measured values as shown in Table 1 below were obtained. further,
In order to evaluate the life characteristics of the electrolytic capacitor, the capacity, ta
For each of nδ and leakage current (LC, current value one minute after applying a rated voltage of 10 V), initial characteristics (characteristic values immediately after the production of the capacitor) and a load test (105 ° C.
, And a characteristic value was measured at room temperature (25 ° C.). The capacity and tan δ were measured at a frequency of 120 Hz.
The measured values as shown in Table 1 below were obtained. Examples 2 to 8 The procedure described in Example 1 was repeated, but in the case of this example, the composition of the electrolytic solution used was changed as shown in Table 1 below. The content of polyacrylamide in Example 7 was determined by disassembling the capacitor after completion of the capacitor test and measuring the amount of polyacrylamide dissolved in the electrolytic solution to obtain a content of about 0.05 mass with respect to the solvent. %. The results obtained by the property test are summarized in Table 1 below. Comparative Examples 1 to 6 The procedure described in Example 1 was repeated, but in the case of this example, for comparison, the composition of the electrolytic solution used was changed as shown in Table 1 below. The results obtained by the property test are summarized in Table 1 below.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

As understood from the test results described in Table 1 above, in Comparative Examples 1, 2, and 4, 105 ° C.
After 3,000 hours, the capacity greatly decreases, and tan δ
Increased significantly. On the other hand, in Examples 1, 2, and 4 to which polyacrylamide was added according to the present invention, the characteristics were very stable, and both the capacity and the tan δ were small, so that good characteristics were maintained.

Further, in Comparative Examples 3, 5 and 6, 105
The explosion-proof valve was activated at 3000 ° C. for 3,000 hours, resulting in a capacitor failure. In contrast, in Examples 3 and 5 to 8,
Very good properties were confirmed.

[0069]

As described above, when the electrolytic solution of the present invention is used, it has low impedance characteristics, excellent low temperature characteristics represented by the impedance ratio (Z ratio) between low temperature and normal temperature, and low temperature conditions. To provide an electrolytic capacitor that maintains good frequency characteristics even under high temperatures, has a stable electrolytic solution even under high temperature conditions, suppresses the reaction with the electrode metal for a long time, has a small change with time, and has a long life, especially an aluminum electrolytic capacitor. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one example of the electrolytic capacitor of the present invention.

FIG. 2 is a perspective view showing a configuration of a capacitor element of the electrolytic capacitor of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Capacitor element 2 ... Lead wire 3 ... Sealing body 4 ... Case 10 ... Electrolytic capacitor 13 ... Cylindrical projection 14 ... Curl

Claims (6)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor, comprising polyacrylamide or a derivative thereof. 2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the polyacrylamide or a derivative thereof has a molecular weight in a range of 100 to 2,000,000. 3. The method according to claim 1, wherein the polyacrylamide or the derivative thereof is contained in an amount of 0.05 to 5.
3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the electrolytic solution is contained in a range of 0% by mass. 4. A method comprising: a solvent comprising an organic solvent containing 0 to 90% by mass of water; and at least one electrolyte selected from the group consisting of a carboxylic acid or a salt thereof and an inorganic acid or a salt thereof. Any one of claims 1 to 3,
An electrolytic solution for driving an electrolytic capacitor according to item 9. 5. The electrolytic solution for driving an electrolytic capacitor according to claim 4, wherein the organic solvent is a protic solvent, an aprotic solvent or a mixture thereof. 6. An electrolytic capacitor comprising the electrolytic solution according to claim 1. Description: