JP6820673B2 - Electrolytic capacitors and electrolytic solutions for electrolytic capacitors - Google Patents

Description

The present invention relates to an electrolytic capacitor soldered to a circuit board and an electrolytic solution for an electrolytic capacitor.

A conventional capacitor has a structure in which an anode and a cathode are immersed in an electrolytic solution containing a carboxylic acid, a base, and an organic solvent.

High voltage is applied to some capacitors used in power supply circuits of automobiles, power supply circuits of lighting devices using LEDs, and the like. When a high voltage is applied to a capacitor having a conventional configuration, the oxide film formed on the surface of the anode may be damaged. If the oxide film of the anode is damaged, the anode and the cathode may be short-circuited and cannot be used as a capacitor. If it cannot be used as a capacitor, the operation of the power supply circuit may become unstable or stop working.

Therefore, a capacitor used in a circuit to which such a high voltage is applied can withstand use even when a high voltage is applied (in the following description, it may be referred to as a high withstand voltage) and has a long life. It is required to be. By increasing the thickness of the oxide film of the anode in the capacitor, it is possible to suppress damage to the oxide film of the anode when a high voltage is applied, that is, to increase the withstand voltage of the capacitor.

Japanese Unexamined Patent Publication No. 2013-45920

However, if the thickness of the oxide film on the anode of the capacitor is increased, the distance between the anode and the cathode is increased, so that the capacitance of the capacitor is reduced. Therefore, it is possible to increase the capacitance by increasing the facing area between the anode and the cathode, but the capacitor becomes large. In recent years, there has been an increasing demand for miniaturization of the circuit itself in the power supply circuit of an automobile and the power supply circuit of a lighting device, but it becomes difficult to miniaturize the circuit when the capacitor becomes large for high withstand voltage.

An object of the present invention is to provide an electrolytic capacitor that operates stably even when a high voltage is applied without increasing the size.

In order to achieve the above object, the electrolytic capacitor of the present invention has a container, a capacitor element housed in the container, and an electrolytic solution housed in the container and impregnated with the capacitor element. The capacitor element has an anode and a cathode arranged to face each other, and an oxide film is formed on the surface of the anode facing the cathode, and the side of the oxide film facing the cathode. A conductive polymer layer is formed in the above, and the electrolytic solution is characterized by using a solvent, an acid, and a base having a base dissociation constant of 10 or more.

According to this configuration, since the electrolytic solution uses a weak base having a pKb constant of 10 or more, the conductivity of the electrolytic solution is low, so that the oxide film is damaged even when used in a circuit to which a high voltage is applied. Hateful. In addition, by forming a conductive polymer layer on the cathode side of the oxide film, the low conductivity of the electrolytic solution due to the use of weak bases is compensated, and the equivalent series resistance (ESR) of the capacitor is suppressed from increasing. doing.

Since a weak base having a pKb constant of 10 or more is used in the electrolytic solution, damage to the conductive polymer layer due to the base is suppressed. From these facts, it is possible to obtain an electrolytic capacitor that operates stably in a high voltage state for a long period of time. With such a configuration, it is not necessary to thicken the oxide film or increase the facing area of the anode and the cathode, so that the size is equivalent to that of the conventional capacitor. That is, the electrolytic capacitor of the present invention can operate stably for a long period of time in a circuit to which a high voltage is applied without increasing the size.

As the bases used in the electrolytic solution of the electrolytic capacitor having the above configuration, acetanilide (chemical formula CH ₃ CONHC ₆ H ₅ ), urea (chemical formula CO (NH ₂ ) ₂ ), caffeine (chemical formula C ₈ H ₁₀ O ₂ N ₄ ) and α − Naphthylamine (chemical formula C ₁₀ H ₇ NH ₂ ) can be mentioned.

In order to achieve the above object, the electrolytic solution for an electrolytic capacitor of the present invention is characterized by using a solvent, an acid, and a base having a base dissociation degree of 10 or more.

Acetanilide (chemical formula CH ₃ CONHC ₆ H ₅ ), urea (chemical formula CO (NH ₂ ) ₂ ), caffeine (chemical formula C ₈ H ₁₀ O ₂ N ₄ ) and α are used as the bases used in the electrolytic solution for the electrolytic capacitor having the above configuration. − Naphthylamine (chemical formula C ₁₀ H ₇ NH ₂ ) can be mentioned.

According to the present invention, it is possible to provide an electrolytic capacitor that operates stably even when a high voltage is applied, without increasing the size.

It is a side sectional view which shows the electrolytic capacitor of embodiment of this invention. It is a perspective view which shows the capacitor element of the electrolytic capacitor of embodiment of this invention. It is sectional drawing which includes the anode and the cathode of a capacitor element. It is a graph which shows the high withstand voltage of an electrolytic capacitor. It is a graph which shows the high withstand voltage of an electrolytic capacitor. It is a table which shows the evaluation of the base used in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 2, its pKb constant and high withstand voltage. It is a graph which shows the relationship between the time passage of an electrolytic capacitor and ESR.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing an electrolytic capacitor of one embodiment. The electrolytic capacitor 1 has a capacitor element 10 housed in an outer case 2 made of bottomed tubular aluminum or the like having an opening 2a on one surface. The opening 2a of the outer case 2 is sealed by a rubber sealing member 3. The outer case 2 and the sealing member 3 are containers.

FIG. 2 shows an exploded perspective view of the capacitor element. The capacitor element 10 is formed by winding a strip-shaped anode foil 11 and a cathode foil 12 in a columnar shape with a separator 13 such as electrolytic paper interposed therebetween. The end of the anode foil 11 or the cathode foil 12 is fixed by the winding stop tape 14. Lead wires 21 and 22 are attached to the anode foil 11 and the cathode foil 12 via lead tabs 21a and 22a, respectively. The lead wires 21 and 22 form the terminals of the anode and cathode.

Next, a main part of the present invention will be described. The electrolytic solution stored in the outer case 2 is a liquid containing an acid, a base, and a solvent. As a result of diligent research, the inventor of the present invention uses an electrolytic capacitor 1 even if a base having a base dissociation constant (pKb constant: a constant indicating the strength of the base) of 10 or more is used as the base contained in the electrolytic solution. We obtained the finding that the withstand voltage of This finding will be described below.

The pKb constant is a constant indicating the strength of the base. The larger the pKb constant, the lower the basicity. A solution prepared by dissolving a base having a large pKb constant as a solute in a solvent has low conductivity, and when used as an electrolytic solution of an electrolytic capacitor, the equivalent series resistance (ESR) of the electrolytic capacitor becomes large. Therefore, in a conventional electrolytic capacitor, a solution prepared by dissolving a base having a large pKb constant as a solute in a solvent is considered unsuitable as an electrolytic solution and has not been adopted.

The inventor of the present application may use a base having a large pKb constant as the solute of the electrolytic solution in the electrolytic capacitor in which the conductive polymer layer 16 is provided on the cathode side of the oxide film 15 of the anode foil 11 of the electrolytic capacitor 1. I thought that the conductive polymer layer 16 could prevent the ESR of the electrolytic capacitor from becoming high. Therefore, the configuration of the capacitor element 10 is as follows.

FIG. 3 is a cross-sectional view including an anode and a cathode of the capacitor element. The surface of the anode foil 11 on the cathode foil 12 side is subjected to unevenness treatment. Then, as shown in FIG. 3, an oxide film 15 is formed on the surface of the anode foil 11 that has been subjected to the unevenness treatment on the cathode foil 12 side. Further, a conductive polymer layer 16 is formed on the surface of the oxide film 15 on the cathode 12 side.

The anode foil 11 is formed of a valve acting metal such as aluminum, tantalum, niobium, and titanium. The cathode foil 12 faces the anode foil 11 via the separator 13 and is made of aluminum, tantalum, niobium, titanium, or the like. As the conductive polymer layer 16, for example, polyethylene dioxythiophene, polypyrrole, polythiophene, polyaniline, or derivatives thereof are used.

The capacitor element 10 (anode foil 11, cathode foil 12, separator 13, oxide film 15, and conductive polymer layer 16) of the electrolytic capacitor 1 is housed inside the outer case 2. The outer case 2 houses the capacitor element 10 impregnated with the electrolytic solution.

The electrolytic solution is a solvent in which acids and bases, which are solutes, are dissolved. Examples of the solvent include, but are not limited to, γ-butyrolactone, sulfolane, ethylene glycol and a mixture thereof. Examples of the acid include, but are not limited to, o-phthalic acid, adipic acid, and borodisalicylic acid. Examples of the base include, but are not limited to, substances having a pKb constant of 10 or more, such as acetanilide, urea, caffeine, and α-naphthylamine.

The characteristics of the electrolytic capacitor 1 according to the present invention having the above configuration were evaluated. As a characteristic evaluation test, the high withstand voltage of the electrolytic solution of the electrolytic capacitor 1 was measured (test 1), and further, the ESR due to time change was measured in order to measure the life of the electrolytic capacitor 1 (test 2). First, Examples 1 to 6 having the configuration according to the present invention were prepared as the samples tested. In addition, Comparative Examples 1 to 4 were also prepared for comparison with each of the examples according to the present invention. First, each Example and Comparative Example will be described.

(Example 1)
The electrolytic capacitor of Example 1 has a completed dimension (external dimension of the electrolytic capacitor 1 in the state of being housed in the outer case 2) of φ10 mm × H10.5 mm. First, the anode foil 11 and the cathode foil 12 having a dielectric film were wound around the anode foil 12 via a separator 13 such as electrolytic paper to prepare a capacitor element 10 having a rating of 250 (V) -6.8 (μF).

Next, the electrolytic solution is a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane as a solvent, о-phthalic acid (acid) and acetoanilide (chemical formula, CH ₃ CONHC ₆ H ₅ : base), etc. It is produced by adding 5 parts by weight of a mixture and stirring it to dissolve it. The pKb constant of acetanilide is 13.38 (> 10).

Then, the capacitor element 10 was immersed in the electrolytic solution kept at 25 ° C. for 10 seconds to impregnate the capacitor element 10 with the electrolytic solution. Next, the capacitor element 10 impregnated with the electrolytic solution was housed in the aluminum outer case 2 and the outer case 2 was sealed to prepare the electrolytic capacitor of Example 1.

(Example 2)
The electrolytic capacitor of Example 2 has the same configuration as the electrolytic capacitor of Example 1 except that urea (chemical formula, CO (NH ₂ ) ₂ ) is used as a base constituting the electrolytic solution. Therefore, detailed description of the common part will be omitted. In Example 2, as the electrolytic solution, 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of о-phthalic acid (acid) and urea (base) was added. , Melted by stirring to produce. The pKb constant of urea is 12.50 (> 10).

(Example 3)
The electrolytic capacitor of Example 3 has the same configuration as the electrolytic capacitor of Example 1 except that caffeine (chemical formula, C ₈ H ₁₀ O ₂ N ₄ ) is used as a base constituting the electrolytic solution. Therefore, detailed description of the common part will be omitted. In Example 3, as the electrolytic solution, 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of о-phthalic acid (acid) and caffeine (base) was added. It is produced by melting by stirring. The pKb constant of caffeine is 13.38 (> 10).

(Example 4)
The electrolytic capacitor of Example 4 has the same configuration as the electrolytic capacitor of Example 1 except that α-naphthylamine (chemical formula, C ₁₀ H ₇ NH ₂ ) is used as a base constituting the electrolytic solution. Therefore, detailed description of the common part will be omitted. In Example 4, the electrolytic solution is 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of о-phthalic acid (acid) and α-naphthylamine (base). It is produced by adding and melting by stirring. The pKb constant of α-naphthylamine is 10.07 (> 10).

(Example 5)
The capacitor element 10 was manufactured in the same process as in Example 1. Then, the condenser element 10 is immersed in a dispersion liquid (concentration: about 3% by mass) in which polyethylene oxyofene particles are dispersed in water at 25 ° C. under a reduced pressure of 89 (kPa) for 1 minute, and the dispersion liquid is placed in the condenser element 10. Impregnated. Next, the capacitor element was dried in a drying oven at 125 ° C. to form the conductive polymer layer 16.

Then, the capacitor element 10 was immersed in the electrolytic solution kept at 25 ° C. for 10 seconds to impregnate the capacitor element 10 with the electrolytic solution. Next, the capacitor element 10 impregnated with the electrolytic solution was housed in the aluminum outer case 2, and the outer case 2 was sealed.

Next, the electrolytic capacitor of Example 5 was prepared by aging at about 125 ° C. for about 1 hour while applying a voltage 1.15 times the rated voltage.

In Example 5, о-phthalic acid (acid) and acetoanilide (chemical formula, CH ₃ CONHC ₆ H ₅ : base) are mixed in equal amounts with a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane as a solvent. It is produced by adding 5 parts by weight of the product and stirring it to dissolve it. The pKb constant of acetanilide is 13.38 (> 10). That is, the electrolytic capacitor of Example 5 has a configuration in which the conductive polymer layer 16 is added to the configuration of the electrolytic capacitor of Example 1.

(Example 6)
The electrolytic capacitor of Example 6 has the same configuration as the electrolytic capacitor of Example 5 except that urea (chemical formula, CO (NH ₂ ) ₂ ) is used as a base constituting the electrolytic solution. Therefore, detailed description of the common part will be omitted. In Example 6, as the electrolytic solution, 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of о-phthalic acid (acid) and urea (base) was added. , Melted by stirring to produce. The pKb constant of urea is 12.50 (> 10).

(Comparative Example 1)
The electrolytic capacitor of Comparative Example 1 uses triethylamine (chemical formula, (C ₂ H ₅ ) ₃ N) as a base constituting the electrolytic solution. Other configurations were the same as in Example 1. Therefore, detailed description of the common part will be omitted. In Comparative Example 1, as the electrolytic solution, 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of о-phthalic acid (acid) and triethylamine (base) was added. , Melted by stirring to produce. The pKb constant of triethylamine is 3.25 (<10).

(Comparative Example 2)
The electrolytic capacitor of Comparative Example 2 uses pyridine (chemical formula, C ₅ H ₅ N) as a base constituting the electrolytic solution. Other configurations were the same as in Example 1. Therefore, detailed description of the common part will be omitted. In Comparative Example 2, as the electrolytic solution, 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of о-phthalic acid (acid) and pyridine (base) was added. , Melted by stirring to produce. The pKb constant of pyridine is 8.37 (<10).

(Comparative Example 3)
The electrolytic capacitor of Comparative Example 3 uses triethylamine (chemical formula, (C ₂ H ₅ ) ₃ N) as a base constituting the electrolytic solution. Other configurations were the same as in Example 5. Therefore, detailed description of the common part will be omitted. In Comparative Example 3, as the electrolytic solution, 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of о-phthalic acid (acid) and triethylamine (base) was added. , Melted by stirring to produce. The pKb constant of triethylamine is 3.25 (<10).

(Comparative Example 4)
The electrolytic capacitor of Comparative Example 4 uses borodisalicylic acid as the acid constituting the electrolytic solution and trimethylamine (chemical formula, (CH ₃ ) ₃ N) as the base. Other configurations were the same as in Example 5. In Comparative Example 4, as the electrolytic solution, 5 parts by weight of a mixture (solvent) of 50 parts by weight of γ-butyrolactone and 45 parts by weight of sulfolane mixed in equal amounts of borodisalicylic acid (acid) and trimethylamine (base) was added. It is produced by melting by stirring. Therefore, detailed description of the common part will be omitted. The pKb constant of trimethylamine is 4.26 (<10).

The following two tests were performed on the electrolytic capacitors 1 of each of the examples and comparative examples prepared as described above, and comparisons were made.

(Test 1)
As described above, when an electrolytic capacitor is used in a power supply circuit of an automobile or a power supply circuit of LED lighting, it is used in a circuit to which a high voltage (for example, 250V) is applied, so that it can withstand a high voltage with respect to the electrolytic capacitor. The demand for performance (high pressure resistance) increases. As Test 1, the high withstand voltage performance (performance to withstand high voltage) of the electrolytic capacitor was measured.

Therefore, in Test 1, the voltage applied between the cathode and the anode terminals was increased while supplying a current of 10 mA to the electrolytic capacitor in an atmosphere of 125 ° C., and the anode foil 11 and the cathode foil at that time were increased. The voltage between 12 was measured. The high withstand voltage performance of the electrolytic capacitor is affected by the withstand voltage of the electrolytic solution. Therefore, in order to evaluate the pressure resistance of the electrolytic solution, a test was conducted using the electrolytic capacitors of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 not provided with the conductive polymer layer 16. The test results are shown in FIG. FIG. 4 is a graph showing the high withstand voltage of the electrolytic capacitor. In FIG. 4, the vertical axis is voltage (V) and the horizontal axis is time (seconds).

As shown in FIG. 4, in the first and second embodiments, the voltage (measured voltage) between the cathode and the anode increases with the passage of time, in other words, as the voltage applied to the terminal increases. Is rising. Then, the voltage has risen further beyond 300 (V). It can be seen that the electrolytic capacitors of Examples 1 and 2 have a high withstand voltage. It can be seen that the electrolytic solutions used in Examples 1 and 2 are suitable as electrolytic solutions for electrolytic capacitors having a high voltage rating of 250 V (high voltage).

On the other hand, in Comparative Example 1, the measured voltage shows the same behavior as in Example 1 and Example 2 until about 100 seconds after the start of the test. After that, the rise of the measured voltage becomes slow from around 150 seconds, rises to about 160 (V), and then falls. This is because the conductivity of triethylamine, which is the base of the electrolytic solution of Comparative Example 1, is high, so that a current flows through the triethylamine, that is, the electrolytic solution due to a voltage increase, and the current becomes a leakage current between the anode and the cathode. Therefore, it is considered that the voltage between the anode and the cathode has dropped. It can be seen that the electrolytic capacitor of Comparative Example 1 does not have a high withstand voltage, that is, the electrolytic solution of Comparative Example 1 is not suitable as an electrolytic solution of an electrolytic capacitor having a rating of 250 V (high voltage).

Further, in Comparative Example 2, the measured voltage starts to decrease after rising to about 280 (V) (after about 320 seconds have passed), and then drops to about 220 (V) to 240 (V). There is. Comparative Example 2 has a higher withstand voltage than Comparative Example 1, but if it exceeds about 1.1 times the rated voltage 250 (V) of the electrolytic capacitor 1, the withstand voltage becomes smaller than 250 (V). Therefore, in consideration of safety, the electrolytic solution shown in Comparative Example 2 is not preferable as an electrolytic solution for an electrolytic capacitor having a rated voltage of 250 (V). That is, the electrolytic solution of Comparative Example 2 is not suitable for an electrolytic capacitor that requires a high withstand voltage (about 250 V) as in the present invention. The electrolytic solution used in Comparative Example 2 can be used as an electrolytic solution for an electrolytic capacitor in which the rated voltage is suppressed (for example, about 200 (V)).

In addition, Test 1 was also performed on Examples 3 and 4 which do not have a conductive polymer layer. The results are shown in FIG. 5 together with Example 1. FIG. 5 is a graph showing the high withstand voltage of the electrolytic capacitor. As shown in FIG. 5, in the third and fourth embodiments, the voltage rises above 300 (V) as in the first embodiment. Then, it reaches the upper limit at about 330 (V) and drops a little, but it is flat at a voltage value exceeding 300 (V). That is, it can be said that the electrolytic capacitors shown in Examples 3 and 4 have a withstand voltage of about 300 (V) or more. Then, it can be seen that the electrolytic solutions used in Examples 3 and 4 are suitable as the electrolytic solution of the electrolytic capacitor 1 having a high withstand voltage (rated 250V) according to the present invention.

The above tests are summarized in FIG. FIG. 6 is a table showing the evaluation of the bases used in Examples 1 to 4 and Comparative Examples 1 to 2 and their pKb constants and high withstand voltage. The leftmost column of FIG. 6 shows Examples 1 to 4 and Comparative Examples 1 to 2 in order from the top. The second column from the left is the type of base used in each example, the next column is the pKb constant, and the rightmost column is the evaluation of high withstand voltage. Regarding the evaluation of high withstand voltage, those having high withstand voltage are indicated by "○", those that can be used conditionally are indicated by "Δ", and those that are not appropriate are indicated by "x".

As described above, the electrolytic capacitors of Examples 1 to 4 can withstand a voltage of 300 (V) or more, which is 1.2 times the rated voltage of 250 (V), that is, have high withstand voltage. (High withstand voltage). Therefore, in FIG. 6, the evaluation of Examples 1 to 4 was designated as “◯”. As shown in FIG. 6, the pKb constant of α-naphthylamine, which is the base used in Example 4, is 10.07, which is the smallest among the bases used in Examples 1 to 4.

On the other hand, in Comparative Example 1, the maximum value of the measured voltage is about 160 (V), which does not reach the rating of 250 (V) of the electrolytic capacitor. Therefore, the evaluation of the high withstand voltage of the electrolytic capacitor of Comparative Example 1 was set to "x".

Further, in Comparative Example 2, the measured voltage was measured up to about 280 (V), which is higher than the rating of 250 (V), but the measured voltage is subsequently lower than the rated voltage of 250 (V). For example, when used in a circuit that does not exceed the rating, the electrolytic capacitor of Comparative Example 2 can be used, but the performance cannot be guaranteed when the voltage exceeds the rating. The electrolytic capacitor of Example 2 can be used as a capacitor with a high withstand voltage under the condition that the rating is not exceeded, and the evaluation of the high withstand voltage is set to “Δ”. The pKb constant of pyridine, which is the base used in Comparative Example 2, is 8.37.

From the above, it can be seen that the high withstand voltage of the electrolytic capacitor is related to the pKb constant of the base contained in the electrolytic solution. It was found that it is difficult to use an electrolytic solution containing pyridine having a pKb constant of 8.37 as a base as an electrolytic solution for a required high withstand voltage (250 V) electrolytic capacitor. On the other hand, it was found that the electrolytic solution containing α-naphthylamine having a pKb constant of 10.07 can be used as the electrolytic solution of the required high withstand voltage (250 V) electrolytic capacitor. That is, from the above test results, it was found that by using an electrolytic solution containing a base having a pKb constant of 10 or more, safety can be ensured and a high withstand voltage electrolytic capacitor can be manufactured.

(Test 2)
Electrolytic capacitors with high withstand voltage are often used, for example, in power supply circuits for compressors used in automobiles and electric appliances, power supply circuits for lighting devices using LEDs, and the like. Then, the electrolytic capacitor used in the power supply circuit is required to maintain the performance assumed at the time of design for a long period of time, that is, to have a long life.

Equivalent direct current resistance (ESR) is one of the indexes for measuring the performance of electrolytic capacitors. In the electrolytic capacitor, the larger the ESR, the larger the decrease in the discharge voltage. That is, a capacitor with a small ESR has high performance. Further, in a general electrolytic capacitor, the ESR tends to increase as the usage time increases. When the ESR increases, the amount of heat generated when energized increases, which causes deterioration (deterioration) of the performance of the capacitor. It is said that a capacitor with a small increase in ESR due to time change can maintain its performance for a long period of time. That is, it can be said that the smaller the ESR of the electrolytic capacitor, the more the decrease in the discharge voltage is suppressed and the higher the performance, and the smaller the increase of the ESR with the passage of time (use time), the longer the life.

Therefore, as test 2, a test for measuring the ESR of the electrolytic capacitor was performed. The details of Test 2 are as follows. In Test 2, a rated voltage of 250 V was applied to the electrolytic capacitors of Example 5, Example 6, Comparative Example 3 and Comparative Example 4 provided with the conductive polymer layer at an ambient temperature of 135 ° C., and electrolysis was performed at regular time intervals. The ESR of the capacitor at 100 kHz was measured. The test results are shown in FIG. FIG. 7 is a graph showing the relationship between the passage of time of the electrolytic capacitor and ESR. In the graph shown in FIG. 7, the vertical axis is ESR (mΩ / 100 kHz) and the horizontal axis is time (Hrs). The graph is a semi-logarithmic graph with a logarithmic scale on the vertical axis.

As shown in FIG. 7, the ESRs of Example 5 and Example 6 immediately after the start of the test are about 20 mΩ and about 60 mΩ, respectively, which are low values. The ESRs of Examples 5 and 6 increase slightly with the passage of time and stabilize at about 40 mΩ and about 100 mΩ, respectively. That is, in Examples 5 and 6, the decrease in the discharge voltage due to ESR is suppressed, and the decrease in the discharge voltage is suppressed for a long period of time.

It is considered that the reason why the ESR is kept low is that the low conductivity of the electrolytic solution due to the use of the base having a large pKb constant is compensated by the conductive polymer layer 16 provided on the anode foil 11. Be done. Further, the increase in ESR with the passage of time is suppressed because the pKb constant of the base contained in the electrolytic solution is small, that is, it is a weak base, so that the oxide film 15 and the conductive polymer layer 16 are less likely to deteriorate. It is thought that this is the reason.

On the other hand, the ESRs of Comparative Example 3 and Comparative Example 4 immediately after the start of the test were 30 mΩ and 20 mΩ, respectively, which are low values. It is considered that the electrolytic solution containing a base having a low pKb constant has high conductivity, and as a result, the ESR is low. Further, in Comparative Example 3, the ESR increased sharply from around 1000 hours (Hrs) and in Comparative Example 4 from around 3500 hours (Hrs). This is because in Comparative Example 3 and Comparative Example 4, the pKb constant is small, that is, a strong base is used. Therefore, when the elapsed time is long, the oxide film 15 and the conductive polymer layer 16 of the electrolytic capacitor are formed by the base. It is probable that the ESR increased due to the deterioration.

That is, in the electrolytic capacitor having the configuration of the present invention, even if a base having a large pKb constant, which has not been used in the past because it causes an increase in ESR, is used in the electrolytic solution, the ESR can be kept low and the elapsed time can be suppressed. The increase in ESR due to the above can also be suppressed.

Like the electrolytic capacitor according to the present invention, in an electrolytic capacitor having a structure in which the oxide film 15 of the anode foil 11 is covered with the conductive polymer layer 16 and impregnated with the electrolytic solution, the pKb constant of the base contained in the electrolytic solution is used. It was found that an electrolytic capacitor having a high withstand voltage and a long life can be obtained by setting the value to 10 or more.

1 Electrolytic capacitor 2 Exterior case (container)
3 Sealing member 10 Capacitor element 11 Anode foil 12 Cathode foil 13 Separator 14 Unwinding tape 15 Oxidation film 16 Conductive polymer layer 21, 22 Lead wire 21a, 22a Lead tab

Claims (7)

With the container
The capacitor element housed in the container and
It has an electrolytic solution that is stored in the container and impregnated in the capacitor element.
The capacitor element has an anode and a cathode arranged at intervals, and has an anode and a cathode.
An oxide film is formed on the surface of the anode on the cathode side, and a conductive polymer layer is formed on the side of the oxide film facing the cathode.
The electrolytic solution uses a solvent, an acid, and a base.
An electrolytic capacitor characterized in that an amine having a base dissociation degree of more than 12.50 is used as the base. With the container
The capacitor element housed in the container and
It has an electrolytic solution that is stored in the container and impregnated in the capacitor element.
The capacitor element has an anode and a cathode arranged at intervals, and has an anode and a cathode.
An oxide film is formed on the surface of the anode on the cathode side, and a conductive polymer layer is formed on the side of the oxide film facing the cathode.
The electrolytic solution uses a solvent, an acid, and a base having a base dissociation degree of 10 or more.
An electrolytic capacitor using acetanilide (chemical formula CH3CONHC6H5) as the base. With the container
The capacitor element housed in the container and
It has an electrolytic solution that is stored in the container and impregnated in the capacitor element.
The capacitor element has an anode and a cathode arranged at intervals, and has an anode and a cathode.
An oxide film is formed on the surface of the anode on the cathode side, and a conductive polymer layer is formed on the side of the oxide film facing the cathode.
The electrolytic solution uses a solvent, an acid, and a base having a base dissociation degree of 10 or more.
An electrolytic capacitor characterized by using caffeine (chemical formula C8H10O2N4) as the base. An electrolytic solution for a capacitor used in the electrolytic capacitor according to claim 1 .
An electrolytic solution for an electrolytic capacitor using an amine having a base dissociation degree of more than 12.50 as the base. An electrolytic solution for a capacitor used in the electrolytic capacitor according to claim 1 .
An electrolytic solution for an electrolytic capacitor, characterized in that acetanilide (chemical formula CH3CONHC6H5) is used as the base. An electrolytic solution for a capacitor used in the electrolytic capacitor according to claim 1 .
An electrolytic solution for an electrolytic capacitor, characterized in that caffeine (chemical formula C8H10O2N4) is used as the base. An electrolytic solution for a capacitor used in the electrolytic capacitor according to any one of claims 1 to 3 .
An electrolytic solution for an electrolytic capacitor, which comprises using any one of γ-butyrolactone, sulfolane, or a mixture thereof as the solvent.

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