JP2001076974A - Electrolytic solution for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic solution whose high temperature service life characteristics and overvoltage characteristics are satisfactory. SOLUTION: In this electrolytic solution, organic carboxylic acid, such as 1,6-decanoic carboxylic acid or the salt, is doped to an electrolytic solution obtained by dissolving one or more kinds of polyhydric alcohol complex compound of nitric acid obtained from nitric acid and polyhydric alcohol or the salt by 5-40 wt.% of the total amount of nitric acid in a solvent with ethylene glycol as main components. Thus, an electrolytic capacitor whose voltage resistance is made high and whose service life characteristics and overvoltage characteristics are satisfactory can be obtained by using the electrolytic solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for electrolytic capacitors, and more particularly to an electrolytic solution for medium and high pressures.

[0002]

2. Description of the Related Art An electrolytic solution for an electrolytic capacitor uses a valve metal having an insulating oxide film formed on the surface such as aluminum or tantalum for an anode electrode, and uses the oxide film layer as a dielectric material. An electrolyte for forming an electrolyte layer is brought into contact with the surface of the substrate, and a current collecting electrode usually called a cathode is arranged.

As described above, the electrolytic solution for an electrolytic capacitor directly contacts the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric of the electrolytic capacitor and the collector cathode, and the resistance of the electrolytic solution is inserted in series with the electrolytic capacitor. Therefore, the characteristics of the electrolytic solution are a major factor affecting the characteristics of the electrolytic capacitor.

[0004] In the prior art of electrolytic capacitors, since an electrolysis solution for medium and high pressures can obtain a relatively high spark voltage, an organic carboxylic acid such as sebacic acid or azelaic acid is used using ethylene glycol as a solvent. In some cases, however, since these have low solubility, crystals tend to precipitate at low temperatures, and the disadvantage of deteriorating the low-temperature characteristics of the capacitor cannot be avoided. Furthermore, Japanese Patent Publication No. 60-1
There is an example using butyloctane diacid as a solute as shown in Japanese Patent No. 3296, and an example using 5,6-decanedicarboxylic acid as a solute as shown in Japanese Patent Publication No. 63-15738. Electrolyte solutions using these organic carboxylic acids or salts thereof have high sparking voltage and conductivity, and high solubility, and thus have good low-temperature characteristics.

[0005]

However, in these electrolytes, the esterification reaction proceeds between the hydroxyl group of ethylene glycol and the carboxyl group of the organic carboxylic acid, and the conductivity decreases due to the decrease of ions. Tanδ of the electrolytic capacitor increases. Moreover,
The organic carboxylic acid forms a complex with aluminum on the surface of the electrode foil, resulting in a decrease in the effective area of the electrode foil, and a phenomenon that the capacitance decreases. For this reason, there is a problem that the life characteristics of the electrolytic capacitor at high temperatures are not sufficient.

Furthermore, in recent years, electronic equipment using a switching power supply has been widely used in ordinary households, and there has been an increasing demand for safety of aluminum electrolytic capacitors.
In order to improve the safety of this electrolytic capacitor, it is desired to improve the overvoltage characteristics of the electrolytic capacitor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a medium-to-high pressure electrolytic solution having good high-temperature life characteristics, that is, good tan δ and capacitance characteristics, and good overvoltage characteristics.

[0008]

In order to solve the above-mentioned problems, an electrolytic solution for an electrolytic capacitor of the present invention comprises a polyhydric boric acid obtained from boric acid and a polyhydric alcohol in a solvent mainly composed of ethylene glycol. 1,6-Decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1 in an electrolytic solution in which at least one alcohol complex compound or a salt thereof is dissolved. , 9-Decanedicarboxylic acid, 7,9-dimethyl-7,9-dimethoxycarbonyl-1,11-dodecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid, sebacine At least one organic carboxylic acid compound selected from acids and azelaic acids, or a salt thereof, in an amount of 5 to 4 times the total amount of boric acid. Characterized in that the addition by weight%.

Further, the polyhydric alcohol in the polyhydric alcohol complex compound of boric acid in the electrolytic solution may be erythritol,
It is a sugar alcohol selected from arabbit, adnit, sorbit, mannitol, dursit, and tarit.

[0010] One or more polyoxyalkylene polyhydric alcohol ether compounds obtained by polymerizing ethylene oxide and / or propylene oxide with a polyhydric alcohol are added to the electrolyte solution. It is characterized by the following.

[0011] Further, one or more aromatic nitro compounds are added to the electrolyte.

Further, the electrolyte has a general formula:

Embedded image Wherein R ₁ and R ₂ each represent an alkyl group having 1 to 18 carbon atoms or a hydrogen atom which may be the same or different, and at least one is alkyl. And one or more phosphorous acids are added.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolytic solution for an electrolytic capacitor of the present invention mainly comprises a polyhydric alcohol complex compound of boric acid or a salt thereof (hereinafter referred to as polyhydric alcohol complex compounds of boric acid) obtained from boric acid and a polyhydric alcohol. Solute. Examples of the polyhydric alcohol in the polyhydric alcohol complex compound of boric acid include ethylene glycol, propylene glycol, trimethylolpropane, trimethylolethane, pentaerythritol, polyvinyl alcohol, and the like. Sugar alcohols such as petite, octit, nonit, desit, dodecit and the like can be mentioned.

Here, the polyhydric alcohol complex compounds of boric acid are obtained by synthesizing boric acid and polyhydric alcohol. When mixing and preparing an electrolytic solution, boric acid and polyhydric alcohol are added to ethylene glycol. It can also be obtained by mixing quantitatively, dissolving by heating, and synthesizing in an electrolytic solution. In the latter case,
Since the formation of polyhydric alcohol complex compound of boric acid involves the formation of water (3 moles of water per mole of boric acid), water is removed by heating and stirring in an open system as necessary.

And 1,6-decanedicarboxylic acid,
5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1,9
-Decanedicarboxylic acid, 7,9-dimethyl-7,9-dimethoxycarbonyl-1,11-dodecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid, sebacic acid,
At least one or more organic carboxylic acid compounds or salts thereof (hereinafter, organic carboxylic acids) selected from azelaic acid are added in an amount of 5 to 40% by weight, preferably 10 to 25% by weight of the total amount of the boric acid. Here, the total amount of boric acid refers to the total amount of boric acid used at that time, although the polyhydric alcohol complex compounds of boric acid are prepared from boric acid and polyhydric alcohol, as described above.

The above-mentioned electrolytic solution of the present invention has a high spark voltage, a high-temperature life characteristic, that is, good stability of electric conductivity, capacitance characteristic and leakage current characteristic at high temperature, and also has good overvoltage characteristic. It is. The reason is presumed to be as follows.

The polyalcohol complex compound of boric acid, which is obtained from boric acid and polyhydric alcohol, which is the main solute of the electrolytic solution of the present invention, has an electric conductivity by an esterification reaction with ethylene glycol like an organic carboxylic acid. There is no such thing as lowering. Further, since a complex with aluminum is not formed, the capacitance does not decrease, and the life characteristics at high temperatures are good. Here, if only boric acid is used, there is a problem that the electrical conductivity decreases and the leakage current increases in a high temperature test, but polyhydric alcohol complex compounds of boric acid do not have such a disadvantage. It is because boric acid which became borate anion in the electrolyte is taken in the anodic oxide film at high temperature and the concentration of borate anion in the electrolyte decreases,
The conductivity of the electrolytic solution decreases, and furthermore, the borate anion incorporated in the oxide film reacts with the oxide film, dissolving the oxide film and increasing the leakage current. However, since the polyhydric alcohol complex compounds of boric acid of the present invention have a large molecular size, they are not taken into the oxide film, so that the conductivity does not decrease and the leakage current increases. It is considered that this is due to the absence of any.

Since the above-mentioned organic carboxylic acids are added in an amount of 5 to 40% by weight based on the total amount of the boric acid, the ability of the electrolyte to repair the oxide film, ie, the chemical conversion, is improved, and the spark voltage and the leakage current are improved. Since the characteristics are improved and good chemical conversion properties are maintained for a long time, the leakage current characteristics in the life test are further improved.

Further, the above-mentioned electrolytic solution has excellent overvoltage characteristics when an overvoltage is applied to the electrolytic capacitor, that is, excellent safety. Normally, when an overvoltage is applied to a capacitor, an anodic oxidation reaction occurs, the current increases, and heat generation and generation of hydrogen gas occur. Here, in the conventional electrolytic solution using an organic carboxylic acid, the anodic oxidation reaction is slow at the beginning when an overvoltage is applied, and the reaction becomes explosive on the way.
Since a large current flows due to the explosive reaction, the possibility of occurrence of a short circuit increases. However, in the electrolytic solution of the present invention containing the polyhydric alcohol complex compound of boric acid as a main solute, when an overvoltage is applied, the anodic oxidation reaction proceeds from the beginning, the current increases, and heat is generated and hydrogen gas is generated. Occurs, and due to this heat generation and generated gas,
Since the safety valve operates and the electrolytic solution evaporates to be in an open state, high safety can be achieved. Although the reason is not clear in the electrolytic solution of the present invention, by adding an organic carboxylic acid in the range of 5 to 40% by weight of the total amount of boric acid, the overvoltage characteristic does not decrease.

In the electrolyte of the present invention, the organic carboxylic acid contains 5 to 40% by weight, preferably 10 to 25% by weight of the total amount of the boric acid.
Although it is added by weight%, since the situation is as described above, if it is less than this range, the effect of improving the leakage current characteristics during the initial and life tests is reduced. If the ratio exceeds this range, the spark voltage decreases, and the conductivity decreases due to the decrease in anions due to the esterification reaction of organic carboxylic acids with ethylene glycol during the life test, so that the life characteristics deteriorate.

The content of the solute comprising the polyhydric alcohol complex compound of boric acid and the organic carboxylic acid in the electrolyte is 3 to 50% by weight, preferably 5 to 20% by weight.
It is. Below this range, the ion concentration is low, and above this range, the mobility of ions decreases due to an increase in the viscosity of the electrolyte, resulting in a significant decrease in conductivity.

Then, ammonia gas is injected and added to the electrolyte solution thus formed to adjust the pH, whereby the electrolyte solution of the present invention is formed.

Here, as the polyhydric alcohol in the polyhydric alcohol complex compound of boric acid, a sugar alcohol having a cis-position hydroxyl group such as erythritol, arabbit, adnit, sorbit, mannitol, dursit, and tarit is used. It is possible to suppress a decrease in conductivity at a high temperature. This is presumably because when a sugar alcohol having a cis-position hydroxyl group is used, the two hydroxyl groups at the cis-position combine with boric acid to form a more stable boric acid complex compound at high temperatures. Although the reason is not clear, the spark voltage can be increased. Here, among these sugar alcohols having a hydroxyl group at the cis position, mannitol is the most preferable. The content of the sugar alcohol having a cis-position hydroxyl group is in the range of 0.4 to 3.0, preferably 1.0 to 2.0, by weight, based on 1 of boric acid. Below this range, the conductivity at high temperatures will increase, and beyond this range the initial conductivity will decrease.

The salts of the polyhydric alcohol complex compound of boric acid and the salts of the organic carboxylic acid compounds in the present invention include ammonium salts, amine salts, quaternary ammonium salts and quaternary ammonium salts of cyclic amidine compounds. Examples of the amine constituting the amine salt include primary amines (methylamine, ethylamine, propylamine, butylamine,
Ethylenediamine, monoethanolamine, etc., secondary amines (dimethylamine, diethylamine, dipropylamine, ethylmethylamine, diphenylamine, diethanolamine, etc.), tertiary amines (trimethylamine, triethylamine, tributylamine, 1,8-diazabicyclo (5, 4,0) -undecene-7, triethanolamine and the like. Of these, ammonium salts are preferred.

Although the solvent is mainly composed of ethylene glycol, a protic polar solvent, an aprotic solvent or water may be added for the purpose of improving low-temperature characteristics and reducing specific resistance. Protic polar solvents include monohydric alcohols (methanol, ethanol, propanol,
Butanol, hexanol, cyclohexanol, cyclopentanol, benzyl alcohol, etc.), polyhydric alcohols and oxy alcohol compounds (propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, 1,3-butanediol, methoxypropylene glycol, etc.), etc. Is raised. As aprotic solvents, amides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N
-Dimethylformamide, N-methylacetamide, hexamethylphosphoric amide, etc.), lactones, cyclic amides, carbonates (γ-butyrolactone, N-
Representative examples include methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate), nitriles (acetonitrile) oxides (dimethylsulfoxide and the like).

As described above, the electrolytic solution of the present invention has a high spark voltage, stable characteristics of the electrolytic solution at high temperatures, and
The overvoltage characteristics are also good. Therefore, by using the electrolytic solution of the present invention, an electrolytic capacitor having a high withstand voltage, a good life characteristic such as a change in dielectric loss at a high temperature, a change in capacitance, a change in leakage current, and a good overvoltage characteristic can be obtained. Obtainable.

Then, a non-ionic surfactant, a polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide to a polyhydric alcohol are added to the electrolytic solution, whereby the electrolytic solution is The spark voltage can be improved. This makes it possible to reduce the short-circuit rate at the time of re-chemical formation, and it becomes suitable as an electrolyte for a high-voltage capacitor. In addition, since the nonionic surfactant has a property of foaming during impregnation, considering the workability at the time of impregnation, polyoxyalkylene polyoxyalkylene obtained by polymerizing ethylene oxide and / or propylene oxide with a polyhydric alcohol is used. Dihydric alcohol ether compounds are preferred.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene alkyl ether, and polyoxyethylene of glycerin fatty acid ester. Ether, polyoxyethylene ether of sorbitan fatty acid ester, polyoxyethylene ether of sorbitol fatty acid ester, fatty acid ester of polyethylene glycol, hydrophilic silicone oil and the like.

The polyhydric alcohol of the polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide with the polyhydric alcohol includes ethylene glycol, propylene glycol,
Glycerin, pentaerythritol, sorbit, polyglycerin, trimethylolpropane, trimethylolethane and the like can be mentioned. Of these, glycerin,
Pentaerythritol, sorbit, polyglycerin,
Trimethylolpropane and trimethylolethane are preferred.

The addition amount of the nonionic surfactant and polyoxyalkylene polyhydric alcohol ether compound is 0.1%.
-15% by weight, preferably 0.5-10% by weight. Below this range, the effect decreases, and beyond this range,
Conductivity decreases. Here, the polyoxyalkylene polyhydric alcohol ether compound has an average molecular weight of 1
In the case of 000 or more, the effect is high, so the addition amount may be small.

Further, by adding an aromatic nitro compound to the electrolytic solution, an increase in the internal pressure of the capacitor can be suppressed, and the life characteristics of the capacitor can be improved. This is considered to be due to a reduction reaction of the nitro group with the hydrogen gas generated inside the capacitor. The addition amount of the aromatic nitro compound is 0.01
To 7.0% by weight, preferably 0.1 to 5.0% by weight. If it is less than this range, the effect decreases, and if it exceeds this range, the conductivity of the electrolytic solution decreases.

Specific examples of the aromatic nitro compound include nitrophenol, dinitrophenol, nitrobenzoic acid, nitrotoluene, dinitrotoluene, nitroxylene, nitrobenzene, dinitrobenzene, nitrobenzyl alcohol, nitroacetophenone, nitroanisole, dimethoxynitrobenzene, and nitrobenzene. Examples include aniline, nitrophenetol, nitrophthalic acid, 2- (nitrophenoxy) ethanol and the like.

Further, by adding an acidic alkyl phosphate compound represented by the formula (2), phosphoric acid, and phosphorous acid to the electrolytic solution, it is possible to suppress an increase in leakage current at a high temperature of the capacitor. This seems to be due to the effect of these additives on hydration deterioration of the anodic oxide film generated when the capacitor is left for a long time. The addition amount of phosphoric acid or phosphorous acid is 0.01 to 1.0% by weight, preferably 0.1 to 0.5% by weight. The amount of the acidic alkyl phosphate compound to be added is 0.01 to 5.0% by weight, preferably 0.1 to 3.0% by weight. If it is less than this range, the effect decreases, and if it exceeds this range, the spark voltage decreases.

[0034]

Embodiments of the present invention will be described below.

Tables 1 to 3 show the composition of the electrolytic solution for the electrolytic capacitor, the spark voltage, and the conductivity for the example of the present invention, the conventional example, and the comparative example. is there. Here, the preparation of the electrolytic solution was performed by a conventional method, and the pH was adjusted by injecting ammonia gas. The spark voltage is a value measured using a capacitor element (rating: 550 V-120 μF) at room temperature by passing a constant current of 10 mA. The aliphatic carboxylic acid A in the table is
1,7-octanedicarboxylic acid (51%), 7-methyl-7-methoxycarbonyl-1,9-decanedicarboxylic acid (14%), 7,9-dimethyl-7,9-dimethoxycarbonyl-1,11- Dodecanedicarboxylic acid (13
%), 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid (22%).

Table 4 shows the initial characteristics of an electrolytic capacitor of 450 V-180 μF using the electrolytes of Examples, Conventional Examples, and Comparative Examples in Tables 1 to 3 and 105 ° C. Shows the characteristics after 2000 hours with the rated voltage applied.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

As is clear from Tables 1 to 3,
The electrolytic solution of the present invention has a higher spark voltage than that of the conventional electrolytic solution, and an electrolytic solution having excellent conductivity characteristics is obtained.

As is clear from (Table 4), the electrolytic capacitors of Examples 1 to 7 using the electrolytic solution of the present invention
Compared with the electrolytic capacitor of Conventional Example 2 mainly composed of an organic acid, the change in tan δ after 2000 hours is small, the capacity decrease is small, and the life characteristics are excellent. Further, the electrolytic capacitor of Comparative Example 1 to which no organic carboxylic acid was added had a large initial leakage current, and even in a life test, a valve was opened due to gas generation due to an increase in leakage current. It can be seen that the electrolyte solution provided good leakage current characteristics in the initial and life tests. The amount of the organic carboxylic acid added is 10 to 25% by weight of the total amount of boric acid.
And the amount of the solute added is 5 to 2
Example 1, which is within the range of 0% by weight, obtained the best results in both initial and life characteristics.

Then, overvoltage characteristics were evaluated using an electrolytic capacitor using the electrolytic solution having the composition of Examples 1 and 2. In addition, as a conventional example 4, ethylene glycol 93,
An electrolyte having a composition of water 2,1,6-decanedicarboxylic acid 5, and ethylene glycol 83, boric acid 5, mannite 7, and 1,6-decanedicarboxylic acid 5 as Comparative Example 2 was used. Further, for each of the electrolytes, the amount of the ammonia gas to be injected and added was adjusted so that the spark voltages became equal. In the test, 20 electrolytic capacitors rated at 450 V-180 μF using an anode foil having a formation voltage of 674 V were used, and the short-circuit occurrence rate when applying an overvoltage of 650 V DC and 10 A was investigated. The results are shown in (Table 5).

[0044]

[Table 5]

As is clear from Table 5, in the conventional example 4 using the organic carboxylic acid, the short-circuit rate was 20%.
However, in Examples 1 and 2, no short circuit was observed. Further, the amount of the organic carboxylic acid to be added is 100 times the amount of boric acid contained in the polyhydric alcohol complex compound of boric acid.
Short-circuiting also occurred in the comparative example in which the weight% was added. As described above, it can be seen that an electrolytic capacitor having good overvoltage characteristics is obtained by using the polyhydric alcohol complex compound of boric acid of the present invention as a main solute and adding an organic carboxylic acid to the electrolytic solution. As described above, by the synergistic effect of the polyhydric alcohol complex compounds of boric acid, which is the main solute of the present invention, and the added organic carboxylic acids, the withstand voltage is high, the change in tan δ and the capacitance during the high-temperature life test, and Thus, an electrolytic solution capable of obtaining an electrolytic capacitor with a small increase in leakage current and excellent overvoltage characteristics is realized.

Next, an example using a sugar alcohol having a cis-position hydroxyl group will be described. (Table 6) and (Table 7) show the compositions, spark voltages, and conductivities of the electrolyte solutions of the examples and comparative examples. The preparation of the electrolyte is the same as before. Also,
Table 8 shows the initial characteristics of the electrolytic capacitors of 450 V-220 μF using the electrolytes of Examples and Comparative Examples in Tables 6 and 7, and the values of 2000 when the rated voltage was applied at 105 ° C. The characteristics after time are shown.

[0047]

[Table 6]

[0048]

[Table 7]

[0049]

[Table 8]

As is clear from Tables 6 to 8,
In the electrolytic capacitors using the electrolytic solutions of Examples 8 to 12,
Compared with the electrolyte solution for electrolytic capacitors using the electrolyte solutions of Example 13 and Conventional Example 2 using ethylene glycol which is a sugar alcohol having no cis-position hydroxyl group, the spark voltage was higher and the spark voltage was higher after the life test. It can be seen that the change in tan δ is small and the life characteristics at higher temperatures are excellent.

Next, examples of the electrolytic solution using the nonionic surfactant and the polyoxypolyhydric alcohol ether compound of the present invention will be described. (Table 9) and (Table 10) show the electrolyte composition, spark voltage and conductivity characteristics of the examples and comparative examples.

[0052]

[Table 9]

[0053]

[Table 10]

As is clear from (Table 9) and (Table 10), Examples 14 to 18 using the surfactant and the like of the present invention were used.
In these electrolytic solutions, the spark voltage was improved as compared with Examples 19 and 20 in which these were not used. By using these electrolytic solutions, it was possible to obtain an electrolytic capacitor having a low short-circuit rate during re-chemical formation. Can be. Among these, Example 15 using polyoxyethylene glycerin having a degree of polymerization of 1000 or more had the highest spark voltage and obtained good results.

Next, examples using the aromatic nitro compound of the present invention will be described. (Table 11) and (Table 12) show the compositions of the electrolyte solutions of Examples and Comparative Examples. Also, (Table 13) shows the change in the height of the product of the 400 V-220 μF electrolytic capacitor using these electrolytes at 105 ° C. for 2000 hours.

[0056]

[Table 11]

[0057]

[Table 12]

[0058]

[Table 13]

As is clear from Tables 11 to 13, Example 21 using the aromatic nitro compound of the present invention was used.
Nos. 25 to 25 do not use these, the product height dimensional change after 2000 hours is small, the internal pressure rise of the capacitor is suppressed, and the life characteristics are improved as compared with Examples 26 and 27 and Conventional Example 2. .

Next, examples using the acidic alkyl phosphate compound represented by formula (2) of the present invention, phosphoric acid, and phosphorous acid will be described. (Table 14) and (Table 15) show the composition of the electrolytic solution of the example and the comparative example, and (Table 16) shows the electrolytic capacitor of 400 V-220 μF at 105 ° C. of 1000 using these electrolytic solutions. The properties after standing for a time were shown.

[0061]

[Table 14]

[0062]

[Table 15]

[0063]

[Table 16]

As can be seen from Tables 14 to 16, in Examples 28 to 31 using the phosphoric acid or the like of the present invention,
Compared with Examples 32 and 33 and Conventional Example 2 which do not use these, the leakage current after leaving at high temperature is kept low, and the life characteristics are improved. Among them, the electrolyte composition of Example 28 has the best values for both the rate of change in capacitance and the increase in leakage current.

[0065]

As described above, the electrolytic solution of the present invention is obtained by dissolving at least one polyhydric alcohol complex compound of boric acid obtained from a polyhydric alcohol of boric acid in a solvent mainly composed of ethylene glycol. An electrolytic solution to which an organic carboxylic acid is added in an amount of 5 to 40% by weight of the total amount of boric acid, which has a high spark voltage, good high-temperature long-life characteristics, and good overvoltage characteristics. Therefore, by using the electrolytic solution of the present invention, the withstand voltage is high, the capacity change after the life test,
It is possible to obtain an electrolytic capacitor having a low tan δ change and a low leakage current change, good life characteristics, and good overvoltage characteristics.

Further, as the polyhydric alcohol of the polyhydric alcohol complex compound of boric acid in the electrolytic solution, erythritol,
When a sugar alcohol having a cis-position hydroxyl group selected from among arabbit, adnit, sorbit, mannitol, dursit, and tarrit is used, the stability of electric conductivity at a high temperature and the spark voltage are further improved.

When a polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide with a polyhydric alcohol is added to the electrolytic solution, Can be further increased, and the re-formability of the electrolytic capacitor is improved, which is suitable for a high-voltage electrolytic capacitor.

Further, when an aromatic nitro compound is added to the electrolytic solution, gas generation inside the capacitor is suppressed, and the life characteristics of the electrolytic capacitor are improved.

When an acidic alkyl phosphate ester, phosphoric acid, or phosphorous acid represented by the following chemical formula (2) is added to the electrolytic solution, deterioration of the anodic oxide film can be suppressed. Can be suppressed from increasing.

Claims (5)

[Claims] 1. A 1,6-decanedicarboxylic acid solution obtained by dissolving at least one polyhydric alcohol complex compound of boric acid or a salt thereof obtained from boric acid and a polyhydric alcohol in a solvent mainly composed of ethylene glycol. Acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-
Methyl-7-methoxycarbonyl-1,9-decanedicarboxylic acid, 7,9-dimethyl-7,9-dimethoxycarbonyl-1,11-dodecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1 At least one or more organic carboxylic acid compounds or salts thereof selected from 14,14-tetradecanedicarboxylic acid, sebacic acid and azelaic acid in an amount of 5 to 40% by weight of the total amount of boric acid
Electrolyte solution for electrolytic capacitors added. 2. The polyhydric alcohol in the polyhydric alcohol complex compound of boric acid according to claim 1, wherein the polyhydric alcohol is a cis-position sugar alcohol selected from erythritol, arabit, adnit, sorbit, mannitol, dursit, and tarit. Electrolyte for electrolytic capacitors. 3. The electrolysis according to claim 1, wherein at least one polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide with a nonionic surfactant or polyhydric alcohol is added. Electrolyte for capacitors. 4. The method according to claim 1, wherein at least one aromatic nitro compound is added.
The electrolytic solution for an electrolytic capacitor according to claim 1. 5. A compound of the general formula: (Wherein, R ₁ and R ₂ each represent an alkyl group having 1 to 18 carbon atoms, which may be the same or different, or a hydrogen atom, and at least one of them is alkyl.) The electrolytic solution for an electrolytic capacitor according to claim 1, wherein one or more phosphorous acids are added.