JP2665243B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an electrolytic solution for an electrolytic capacitor, and more particularly, to a method of adding a compound having a unique structure to an electrolytic solution, and particularly to the improvement of the withstand voltage of an electrolytic capacitor. Related to the improvement of

[Conventional technology]

Electrolytic capacitors are small, large-capacity, inexpensive and have excellent characteristics such as smoothing of rectified output, and are one of the important components of various electric and electronic devices. Generally, the surface is changed to an oxide film by electrolytic oxidation. Aluminum film as anode,
The oxide film is formed as a dielectric material with an electrolytic solution interposed between the oxide film and the collector cathode.

Since the electrolytic capacitor is used while constantly regenerating the dielectric oxide film while performing a chemical reaction during use, the steady state of the chemical reaction that occurs between the aluminum electrode with the oxide film on the surface and the electrolyte solution It is important to stabilize the performance that the state is maintained and the aluminum oxide film serving as the dielectric is kept well.

In a chemical reaction that proceeds during the use of an electrolytic capacitor, the electrolyte forms an ionic conductor that is a medium for the transfer of ions. At the interface between the electrolyte and the electrode, the charge moves due to the progress of the electrode reaction, the oxidation reaction proceeds on the anode surface, the reduction reaction proceeds on the cathode surface, and ions move in the electrolyte solution, which is the ion conductor. Electric current flows. Therefore, the specific resistance, which is the reciprocal of the electric conductivity of the electrolytic solution, reflects the characteristics of the electrolytic solution, which is an ionic conductor, in a chemical reaction that proceeds during use of the electrolytic capacitor. A phenomenon in which the electrochemical state fluctuates as a result of a change in the physical properties of a dielectric material due to an increase in the load voltage of a capacitor and a high voltage load resulting in a temporal change in dielectric constant is called scintillation. Can be used as a measure of the withstand voltage of the capacitor as a scintillation voltage (spark voltage), and the higher the scintillation voltage (spark voltage), the higher the withstand voltage of the capacitor.

Other indexes of the capacitor characteristics include capacitance (Cap), dielectric loss tangent (tan δ), and leakage current (LC). The tangent of the loss angle, that is, the dielectric loss tangent, which is the difference between the phase of the charging current and the phase of the external electric field, is used as a measure of the power consumption of the capacitor. A smaller value indicates that the power consumption is smaller. Leakage current, which is a current that flows when the charge reaches a certain value after the start of charging, is due to steady movement of the charge carrier of the dielectric, and ions generated by dissociation of impurities in the dielectric form the main component of the charge carrier. It is believed that the magnitude of the leakage current reflects the stability of the electrochemical state of the dielectric.

In the conventional general electrolytic solution for electrolytic capacitors,
The withstand voltage of the electrolyte has been uniquely defined mainly depending on the characteristics of the main solute. That is, once the solvent and the solute to be used are determined, the voltage range in which the produced electrolytic capacitor can be used is automatically specified, and it has been extremely difficult to achieve a higher withstand voltage. On the other hand, if the type of solvent or solute is changed by focusing only on the improvement of the withstand voltage, the other characteristics are usually reduced even if the withstand voltage is improved. It has been desired to increase the withstand voltage without deteriorating.

Compounds of silicon and titanium are generally used as a surfactant or a coupling agent for bonding a metal to a polymer. In particular, titanium is a metal that can also be used as a capacitor electrode, and capacitors using an alloy with aluminum have been studied. It has been found that apart from the cost aspect, characteristics are superior to aluminum alone. . Therefore, as a result of continuing study on the possibility of applying a titanium compound to an electrolytic solution for an electrolytic capacitor, it was found that the spark voltage was significantly increased by adding a specific titanium compound to the electrolytic solution.

[Problems to be solved by the invention]

The present invention adds a compound having a unique structure to the electrolytic solution, thereby increasing the withstand voltage without deteriorating the characteristics of the electrolyte, reducing defects such as short circuits, and further having a composition having a particularly large withstand voltage inherently. An object of the present invention is to enable use of an electrolyte at a higher voltage.

[Means for solving the problem]

According to the present invention, in an electrolyte for driving an aluminum electrolytic capacitor, the following formula is contained in a molecule: (Wherein, n is an integer) wherein a compound having a titanium polymer structure is added.

It is preferable that the compound having a titanium polymer structure be a compound having a titanium polymer structure modified by introducing a substituent capable of imparting solvent solubility.

Since the inorganic polymer, titanium polymer, is generally insoluble in solvents, it is preferred to modify it to the following structure: In the formula, n and m are integers, and R represents a substituent capable of imparting solvent solubility. When performing an organic modification to impart solvent solubility to these modified titanium polymers, the ratio of the organic portion may be larger than that of the inorganic portion. Therefore, Although the skeleton is not always the main chain in the molecular chain, functionally this structure is essential.

Substituent capable of imparting the solvent solubility can be classified into an organic group and an inorganic group, for example R ^- alkyl group, a hydrocarbon group such as methylene group, substituent such as the following may be included .

1) Examples of organic groups -R'-OH alcohol modified -R'-COOH carboxyl modified -Fluorine modified with ₃ CF groups in the molecule -R'-CONH amide modification -R'-NH ₂ amino modification —C _X H _2X-1 Olefill Modification 2) Examples of Inorganic Groups B Boron (C ₂ B ₁₀ H ₁₀ ) Carboranes Titanium polymer is, for example, “Kenjiro Meguro, Miyoko Oc.
hi, IV th International Congress of Surface Active
Agent (Brussels), 4th (1964), pages 199 to 207 ".

The compound having a titanium polymer structure of the present invention can be added to all kinds of electrolytic solutions for electrolytic capacitors, and the addition concentration is preferably 0.1 to 30% by weight, more preferably 1 to 10% by weight.

[Action]

It is not clear how the addition of the compound having the titanium polymer structure disclosed in the present invention acts on the aluminum oxide film dielectric in the electrolytic solution.

However, it is presumed that the compound having a titanium polymer structure of the present invention having the above-mentioned unique chemical structure has a specific action of suppressing the fluctuation of the electrochemical state when a high voltage is applied to the electrolytic capacitor. This effect is
The observable form is most greatly reflected in the spark voltage lowering effect when the load voltage increases with time.

In general Although the polymer is an inorganic polymer that is hardly soluble in a solvent, a substituent such as the above-mentioned organic group or inorganic group can be introduced to impart solvent solubility. Since such a polymer has a lyophobic portion and a lipophilic portion, it acts as a surfactant, causing a peculiar phenomenon at the interface between the aluminum foil and the paste (electrolyte solution), which is presumed to increase the withstand voltage. .

〔The invention's effect〕

According to the present invention, by adding a compound having a titanium polymer structure in the molecular chain to the electrolytic solution for the electrolytic capacitor, the withstand voltage is increased without deteriorating the characteristics of the electrolyte, and defects such as short circuits are reduced. Further, it is possible to use an electrolytic solution having a composition having particularly high withstand voltage at a higher voltage.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

An etched foil having an area of 30 × 2000 mm was formed in a boric acid solution at 380 V, and this was used as an anode foil, which was wound with paper and a cathode foil to obtain an element. The rating of this element is 250V, 470μ
F, the size was 30φ × 40. This element was impregnated with an electrolytic solution having the composition shown in Table 1 and re-formed. The titanium polymer was synthesized according to the above-mentioned document of Kenjiro Megro et al., And the organic group was polyethylene oxide. Table 1 also shows the measured values of the specific resistance and the spark voltage.

As can be seen from Table 1, the electrolytic solution for an electrolytic capacitor to which the titanium polymer of the present invention has been added has a higher specific resistance value and a higher spark voltage as compared with the electrolyte solution without the addition. FIG. 1 shows the scintillation curves of the electrolytic capacitors using the electrolytic solutions of Example 1 and Comparative Example 1.

For the electrolytic capacitors using the electrolytes of Examples 1 and 2 and Comparative Examples 1 and 2, a long-time operation test at a high temperature was performed as shown in Table 2.

Although the electrolytic capacitor according to the present invention showed stable values in all of the capacitance (Cap), the dielectric loss tangent (tanδ), and the leakage current (LC) even when used at 110 ° C. for 1000 hours, the conventional capacitor A short failure occurred in the electrolytic capacitor, and the test could not be continued.

[Brief description of the drawings]

FIG. 1 is a scintillation curve of an electrolytic capacitor prepared using an electrolytic solution to which a titanium polymer according to the present invention is added and a conventional electrolytic solution to which no titanium polymer is added. The rating of the element is 250 V, 470 μF.

Claims (2)

(57) [Claims] In an electrolytic solution for driving an aluminum electrolytic capacitor, the following formula is contained in a molecule: (Wherein n is an integer) a compound having a titanium polymer structure of the formula (I), wherein: 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the compound having a titanium polymer structure is a compound having a titanium polymer structure modified by introducing a substituent capable of imparting solvent solubility.