JPS63226020A - Electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to an electrolytic capacitor in which electrolytic paper interposed between an anode foil and a cathode foil is impregnated with a predetermined electrolyte, and particularly relates to its short-circuit failure rate and impedance characteristics. The present invention relates to improvements in both of the above, as well as in the impregnating properties of the electrolyte.

In general, electrolytic capacitors, and aluminum electrolytic capacitors in particular, are formed by interposing electrolytic paper between an anode aluminum foil and a cathode aluminum foil to form a winding, and then immersing the electrolytic paper in a predetermined electrolytic solution for electrolysis. It is manufactured by impregnating it with liquid and sealing it. The electrolytic solution usually uses ethylene glycol, dimethylformamide, etc. as a solvent, and is made by dissolving boric acid or an organic acid salt such as ammonium adipate or ammonium hydrogen maleate in these solvents and infiltrating it from both ends of the capacitor element. are doing.

Conventional aluminum electrolytic capacitors such as those mentioned above have electrolytic paper impregnated with an electrolytic solution, so the impedance characteristics as a capacitor, especially the equivalent series resistance (hereinafter abbreviated as ESR), are high, and there is a risk of deterioration during use. Therefore, in addition to lowering the resistance of the electrolytic solution or making the electrolytic paper thinner or less dense, the material of the electrolytic paper can be changed from ordinary wood craft pulp to special materials, such as Manila hemp pulp or esparto. A change is being made to pulp, etc.

However, lowering the resistance value of the electrolytic solution may cause corrosion to the aluminum foil, and making the electrolytic paper thinner or lower in density may increase the short-circuit failure rate when it is wound around a capacitor element. However, even if there is no short-circuit, the short-circuit failure rate will be high after the product is commercialized and put on the market.

Therefore, in order to reduce the short-circuit defect rate, the thickness of the electrolytic paper should be increased, the density should be increased, and if the density is the same, the JIS standard that indicates the degree of beating of the pulp that is the raw material.
C3F (Canadian 5
It is known that by decreasing the value of standard freeass, the pulp fibers become finer due to fibrillation, and the resulting electrolytic paper becomes finely dense, which is good for improving the short-circuit defect rate. In addition, the ES of these items
The effect on R is that when the electrolytic paper is made thicker, ESR increases in a linear manner.
It has been found that increasing the density deteriorates the ESR in a quadratic manner, while the C8F value has almost no effect. That is, in order to improve ESR, it is necessary to make the electrolytic paper thinner and lower its density, contrary to improving the short-circuit failure rate.

Therefore, in order to simultaneously achieve the objectives of improving the short failure rate and improving ESR, it is necessary to reduce the value of C8F in order to improve the short failure rate, considering that the value of C8F does not affect ESR. It is necessary to assume that Therefore, it would be ideal to make low-density electrolytic paper from a raw material with a low C8F value. However, when electrolytic paper is made from natural cellulose pulp such as ordinary kraft pulp, Manila hemp pulp, and esparto pulp, if the C3F value is reduced, the hydrogen bonds between fibers will increase due to fibrillation. Therefore, the density of electrolytic paper always tends to be high. Therefore, when electrolytic paper of the same thickness is made using the same paper machine, the C8F value of the paper with high density is smaller than the value of C8F of the paper with low density. As a result, the ES of electrolytic capacitor
If you use low-density electrolytic paper to improve R, C3
As the value of F increases, the short failure rate increases, while when the value of C5F becomes small, the density increases and the ESR worsens, making it difficult to improve both the short failure rate and ESR. It was difficult to achieve both at the same time.

Therefore, the applicant has previously provided an electrolytic capacitor in Japanese Patent Laid-Open No. 61-29118 which reverses the causal relationship between the short-circuit failure rate and ESR and improves both simultaneously. In the secondary processing after paper making, for example, by passing the electrolytic paper 1 shown in FIG. A suitable number of portions 4 are formed, and concave portions 5 are formed on the other side corresponding to the convex portions 4, and the thickness is substantially thicker to T2 than the thickness TI at the time of paper making, and the density is lowered. It is characterized by using the electrolytic paper 1 that has been Therefore, even if the raw material pulp is sufficiently beaten to reduce the CSF number 11N in order to improve the short-circuit defect rate, it is possible to lower the density and increase the thickness of the electrolytic paper through secondary processing. E
SR can also be improved at the same time.

Furthermore, the applicant has previously provided electrolytic paper for electrolytic capacitors in Japanese Patent Application No. 61-250479, in which electrolytic paper contains cellulose fibers into which organic substituents have been introduced through a chemical reaction, thereby significantly increasing the degree of swelling with respect to an electrolytic solution. are doing. According to this electrolytic paper, the density and thickness are maintained so that short-circuits do not occur during the element winding process, the element is wound without short-circuits, and after being impregnated with electrolyte, the electrolytic paper swells in the electrolyte. Since the degree of swelling is significantly higher than that of conventional swelling, the fibers that implant the electrolytic paper expand, and the gaps between the fibers become larger, which can substantially lower the density of the electrolytic paper and reduce ESRJ. can be done. Moreover, since the process is performed after the element is wound, the short-circuit failure rate does not increase.

However, in the aforementioned Unexamined Patent Application Publication No. 6, which involves secondary processing after paper making,
ESR in the electrolytic capacitor according to No. 1-29118
In order to sufficiently reduce the electrolytic paper 1, the secondary processed electrolytic paper 1 is wrapped between the anode aluminum foil 6 and the cathode aluminum foil 7 shown in FIG. 3 and impregnated with an electrolytic solution as shown in FIG. Therefore, it is necessary to swell in the electrolytic solution to at least the thickness T2 after secondary processing. For example, the thickness T1 during paper making is 20μ
Even if secondary processing by embossing is performed on electrolytic paper of 500 m, and the thickness T2 after the secondary processing is 40 μm, the electrolytic paper itself will swell in the electrolytic solution and become at least 40 μm thick. Otherwise, the ESR will not be reduced sufficiently. On the other hand, if the degree of swelling of the electrolytic paper is insufficient and it does not swell to the thickness T2 after secondary processing, the entire amount of electrolyte will not be uniformly impregnated into the electrolytic paper, and not only will the ESR not decrease, but the second Excess electrolyte remains between the concave and convex portions of the electrolytic paper formed by the subsequent processing and the two electrodes. If the electrolytic capacitor is subjected to mechanical shock, the electrolytic solution that remains between the uneven parts of the electrolytic paper and the two electrodes can be removed by centrifugation, for example, to remove excess electrolytic solution that has adhered to elements that have been impregnated with electrolytic solution in batch processing. It easily leaks out of the element at times, resulting in poor electrolyte impregnation.
The capacitance of the electrolytic capacitor will be significantly reduced.

Therefore, the increase in thickness due to secondary processing must be kept within a range that allows the electrolytic paper 1 to swell.

Electrolytic paper made from wood pulp or Manila hemp pulp for electrolytic solutions that use the currently commonly used ethylene glycol or dimethylformamide as the main solvent, with other solvents such as water and methylcellosolve mixed as needed. The degree of swelling is about 50%, and electrolytic paper only swells to about 1.5 times its thickness even if it is impregnated with an electrolytic solution. In addition, in order to swell the thickness of the electrolytic paper to 1.5 times or more and increase the ESR reduction effect, use an electrolytic solution 5, such as dimethyl sulfoxide, which has a greater swelling effect on the electrolytic paper than dimethylformamide or ethylene glycol. It was necessary to use an electrolytic solution containing a large amount of. If dimethyl sulfoxide is used as an electrolyte, the degree of swelling of electrolytic paper can be reduced to 10
0% or more, and the base electrolytic paper can be swollen to twice the thickness or more in the electrolytic solution.

However, dimethyl sulfoxide is a sulfur compound, and if added to the electrolyte in large quantities, it tends to cause corrosion of electrolytic capacitors, and its melting point is 18.5°C, so it significantly deteriorates the low-temperature characteristics of electrolytic capacitors.
For these reasons, electrolytic solutions containing dimethyl sulfoxide have been proposed, but cannot be used in practice. Therefore, the thickness of the electrolytic paper increased by secondary processing is 150% of the thickness of the basic electrolytic paper after paper making.
% or less, but if it greatly exceeds 150%, the above-mentioned disadvantages will occur and the effect of secondary processing will be weakened.

Therefore, even if the thickness exceeds 150% due to secondary processing, if the electrolytic paper can swell by the increased thickness and eliminate the unevenness caused by secondary processing, ESR can be further improved and reduced. It is something that can be done.

Furthermore, recently, an electrolytic solution using γ-butyrolactone as a solvent, which has low viscosity and low toxicity, has been developed. It is used instead. Although this electrolytic solution using γ-butyrolactone as a solvent has good low-temperature characteristics and work characteristics, it has an ESR
was extremely bad. This is because γ-butyrolactone is less hydrophilic than other conventional electrolytes, so the cellulose fibers hardly swell after being impregnated with the electrolyte, and the actual density of the electrolytic paper hardly decreases. by. Therefore, in the case of the electrolytic capacitor according to JP-A No. 61-29118, the electrolytic paper 1, which has a small C8F value and whose fibers are strongly bonded to each other through hydrogen bonding, is made thicker and has a lower density through secondary processing. Therefore, if an electrolytic solution containing γ-butyrolactone as a solvent is used, the electrolytic paper 1 will not swell to the thickness T2 after secondary processing, and the above-mentioned disadvantage will occur, but the ESR will not improve. Instead of getting better, it actually got worse. Therefore γ−
An electrolytic solution using butyrolactone as a solvent is disclosed in Japanese Patent Application Laid-open No. 61-29.
It could not be used in an electrolytic capacitor using electrolytic paper which was made substantially thicker and lower in density than when the paper was made due to the secondary processing according to No. 118.

On the other hand, according to the above-mentioned Japanese Patent Application No. 61-250479, the degree of swelling of electrolytic paper is significantly increased by incorporating cellulose fibers into which organic substituents have been introduced.

The electrolytic paper can also be swollen in an electrolytic solution using γ-butyrolactone as a solvent, and the ESR can be improved without affecting the short-circuit failure rate. However, since electrolytic paper is interposed between the anode foil and the cathode foil and wound around the element, although it has the ability to swell, it cannot swell beyond the distance between the anode foil and the cathode foil. . Therefore, if a wide interval can be secured in which the electrolytic paper can swell, the ESR can be further improved or reduced by swelling.

Therefore, the present invention solves the above-mentioned problems of the conventional example, and even if the thickness after secondary processing is 150% or more of the electrolytic paper after papermaking, the electrolytic solution can be sufficiently used, even if the electrolytic solution uses γ-butyrolactone as a solvent. The purpose of the present invention is to provide an electrolytic capacitor using electrolytic paper that can swell to at least the thickness after secondary processing, that is, a sufficient swelling range during secondary processing. That is.

In an electrolytic capacitor comprising electrolytic paper interposed between an anode foil and a cathode foil impregnated with a predetermined electrolytic solution, the electrolytic paper is formed on one side by secondary processing after paper making. By forming an appropriate number of convex portions on the surface and forming concave portions corresponding to the convex portions on the other side, the thickness is substantially thicker and the density is lower than that during paper making, and the cellulose fibers are The present invention provides an electrolytic capacitor characterized in that the degree of swelling is increased by containing fibers into which organic substituents have been introduced through a chemical reaction, so that the capacitor swells in the electrolytic solution at least to the thickness after the secondary processing. That is. In the present invention, secondary processing after papermaking refers to processing after forming a paper layer by hand or machine papermaking, or specifically, by pouring a fiber dispersion onto a screen to form a paper layer. Processing is performed after forming.

1. According to the present invention having the above configuration, by forming uneven portions on electrolytic paper through secondary processing after paper making, it is possible to obtain low density and thick electrolytic paper using a raw material with a small CSF.
Moreover, since it contains cellulose fibers with organic substituents introduced, the degree of swelling with respect to the electrolytic solution impregnated is significantly increased, and the electrolytic paper reliably swells to the thickness after secondary processing, reducing its actual density. Therefore, both short circuit defects and ESR can be improved and reduced at the same time. Therefore, compared to conventional electrolytic paper that undergoes only secondary processing, even if the range of increase in thickness due to secondary processing is increased, it can be easily swollen to the thickness after secondary processing, and due to insufficient swelling. There is no electrolyte leakage, and ESR can be further improved and reduced. Furthermore, because it hardly swells, it can be used in electrolytes using γ-butyrolactone as a solvent, which could not be used in conventional electrolytic paper that only undergoes secondary processing, and has good low-temperature properties and workability. The ESR can be improved by taking advantage of the characteristics of an electrolytic solution using a certain γ-butyrolactone as a solvent. Furthermore, compared to the conventional electrolytic paper that only contains cellulose fibers with organic substituents introduced, the thickness of the electrolytic paper is increased through secondary processing, and the gap between the anode foil and the cathode foil is sufficiently expanded so that the electrolytic paper swells. Since it can be secured as widely as possible, ESR can be further improved and reduced.

That is, the present invention can expand the degree and effective range of the secondary processing and increase the degree of swelling, thereby improving both ESR and short defect rate at a higher level. They can be realized simultaneously. Furthermore, according to the present invention, the wettability and retention of the electrolytic paper with respect to the electrolytic solution are improved, and the amount of electrolytic solution impregnated is also inevitably increased, so drying up of the electrolytic solution is prevented and the electrolytic paper has a long service life. You can get a capacitor.

The structure and various embodiments of the electrolytic capacitor according to the present invention will be described below.

The present invention utilizes an electrolytic paper based on cellulose fibers proposed in Japanese Patent Application No. 61-250479, which contains fibers with organic substituents to increase the degree of swelling with respect to an electrolytic solution. As proposed in the above issue, by forming an appropriate number of convex portions on one side by secondary processing and forming concave portions corresponding to the convex portions on the other side, the thickness can be reduced to 150 mm at the time of paper making.
% or more, an electrolytic capacitor is constructed using electrolytic paper that can be easily swollen to the thickness after secondary heating by impregnating it with an electrolytic solution.

The material of the electrolytic paper used in the present invention is mainly composed of cellulose, and specifically, wood pulp fibers obtained from coniferous trees and hardwoods, non-wood pulp fibers obtained from Manila hemp, red hemp, sisal hemp, esparto-based fibers, etc. Examples include regenerated cellulose fibers such as coarse rayon and cupra rayon. These cellulose fibers contain many hydroxyl groups (OH), and the fibrils constituting the fibers are strongly bonded by hydrogen bonds formed between the hydroxyl groups. Even when such cellulose fibers are immersed in a solvent with poor hydrophilicity such as γ-butyrolactone, the solvent cannot penetrate into the hydrogen bonds formed between the fibrils, so the fibers hardly swell. Even in electrolytic paper composed of
Hydrogen bonds are formed at the contact areas where the fibers intertwine, and this force also bonds the fibers together.

Therefore, the present invention introduces into the cellulose fibers an organic substituent that is compatible with the various electrolytic solutions, especially γ-butyrolactone as a solvent, thereby making it easier for the electrolytic solution to penetrate into the hydrogen bonds formed between fibrils or between fibers. This causes the fibers themselves to swell with the electrolytic solution and weakens the bond between the fibers in the electrolytic solution, thereby increasing the swelling of the electrolytic paper in the electrolytic solution.

As a chemical reaction for introducing an organic substituent, all reactions caused by cellulose can be used, such as graft polymerization reaction to cellulose and substitution reaction of hydroxyl groups in cellulose, but in particular, esterification reaction of hydroxyl groups contained in cellulose can be used. It is suitable to use an etherification reaction or an acetalization reaction because the reaction can be easily carried out. Furthermore, when introducing an organic substituent using graft polymerization, it is desirable that the reaction be such that the by-produced homopolymer can be easily removed. In addition, in the chemical reaction for introducing an organic substituent, it is necessary that the cellulose fibers maintain the same fiber morphology as before the reaction even after the reaction is completed, and that they do not dissolve excessively in the electrolytic solution.

Therefore, the chemical reactions for introducing these organic substituents are carried out under conditions that are milder than those for producing general cellulose derivatives, and in the hydroxyl substitution reaction, only one of the hydroxyl groups contained in cellulose is used. Reaction conditions such that only moieties are substituted are preferred. For example, when most of the hydroxyl groups, such as 50% or more, are substituted (W conversion degree DS=1.5 or more).

The resulting fibers may be brittle or may not retain their fiber shape, making it impossible to form electrolytic paper. Furthermore, when an electrolytic capacitor is manufactured using such fibers, most of the fibers dissolve when the electrolytic paper is immersed in an electrolytic solution, causing short-circuit defects in the resulting electrolytic capacitor or due to the viscosity of the electrolytic solution. This also means that the ESR increases with the increase.

Introduced into cellulose fibers. As a substituent, chlorine CL,
Any substituent may be used as long as it does not contain elements that cause corrosion of electrolytic capacitors such as bromine, Br, and iodine.

When a substituent with a high carbon content such as an alkyl group having 8 or more carbon atoms or an allyl group is introduced, the cellulose fiber becomes extremely hydrophobic, which reduces the strength of the electrolytic paper and may cause trouble during the element winding process. In addition, the proportion of carbon is small, and carboxyl group (-C00H), sulfonic acid group (-8
Introducing a substituent having a dissociative polar group such as O3H) is undesirable because the swelling property decreases. Therefore, the organic substituent to be introduced should be selected depending on the degree of polarity or hydrophilicity of the electrolytic solution. is necessary. Preferably, a hydroxyl group, ether group, amino group, nitrile group,
The organic substituent is preferably an organic substituent to which one or more of amide groups, imido groups, carbonyl groups, etc. are bonded, and has appropriate polarity.Particularly preferred chemical reaction examples are shown below.

(A) Esterification reaction (1) Reaction with acid chloride CELL -OH+ RCOCL → CELL -
0-C-R(2) Reaction with acid anhydride CELL -OH+ RN = C= O→ CEL
L -0-C-R (Note) R is CH3, C2H5, C3H
, indicates either.

CELL indicates a cellulose chain.

(B) Etherification reaction (4) Reaction with alkyl halide CELL -OH+ RCL-) CELL -0-R(
5) Reaction with dialkyl sulfuric acid (Note) R indicates any of CH3, C, 2H5, or C3H7.

CELL indicates a cellulose chain.

(6) Reaction with alkylene oxide (Note) R represents H, CH3, or C2H5. n is 1
Indicates an integer greater than or equal to CELL indicates a cellulose chain.

(7) Reaction with vinyl compounds (Note) R is CN, C0NF+2.0c2), C0C)
Indicates either +3, COC, or 2115.

CELL indicates a cellulose chain.

(C) Acetalization reaction (8) Reaction with aldehyde OH (Note) R represents any of CH3, C2H5, C3H7, and C4H9.

CELL indicates a cellulose chain.

As mentioned above, it is preferable to use (A) esterification reaction, (B) etherification reaction, and (C) acetalization reaction to replace a part of the hydroxyl groups (OH) in cellulose with the above-mentioned substituents; The electrolytic paper used in the present invention is composed only of cellulose fibers into which organic substituents have been introduced, and does not need to be a filter paper.
It may be a mixture of ordinary cellulose fibers or chemical fibers such as polypropylene fibers, polyester fibers, polyethylene synthetic pulp, polypropylene synthetic pulp, vinylon fibers, polyvinyl alcohol fibers, and cellulose fibers into which organic substituents have been introduced. In addition, for regenerated cellulose fibers such as viscose rayon, cupra rayon, or acetate, before spinning into fibers,
The fibers may be made into paper by introducing organic substituents into the raw materials or during the production stage.

Furthermore, regenerated cellulose films such as cellophane can also be introduced with organic substituents through a reaction similar to that of fibers, and their degree of swelling increases in an electrolytic solution in the same way. It can also be used as electrolytic paper.

It is preferable that the fiber into which organic substituents have been introduced as described above be moderately beaten to form a basic electrolytic paper in order to reduce the short-circuit defect rate. Regarding the degree of beating, when the thickness of the electrolytic paper after papermaking is 50 to 60 μm, the value of C8F is 700 m1 or less.

In the case of 40-50μm, the C3F value is 650m1 or less, and in the case of 30-40μm, the C5F value is 600m1.
1 or less, if the thickness is 20~'30um, the C8F value is 5.
In the case of 50 m1 or less, 10 to 20 μm, it is appropriate that the C8F value is 500 m1 or less. Further, it is preferable that the thickness of the electrolytic paper to be paper-made is 60 μm or less and the density is 0.4 g/cd or more.

In the present invention, an appropriate number of convex portions are formed on one side of the electrolytic paper containing cellulose fibers into which organic substituents have been introduced by secondary processing after papermaking, and the convex portions are formed on the other side. By forming recesses corresponding to the areas, electrolytic paper is obtained which is substantially thicker and has lower density than when the paper is made. In the present invention, secondary processing after papermaking refers to processing after forming a paper layer by hand or machine papermaking, or specifically, by pouring a fiber dispersion onto a screen to form a paper layer. Processing is performed after forming.

Therefore, after drying the paper layer formed after paper making to form a basic electrolytic paper, this basic electrolytic paper is subjected to secondary processing using a separate processing machine to form uneven portions and used in the present invention. Alternatively, electrolytic paper may be obtained by performing secondary processing on the wet paper immediately after paper making and forming a paper layer, forming irregularities on a paper machine, and then drying the wet paper. It is also possible to obtain electrolytic paper for use. In addition, when performing secondary processing to form uneven parts in this wet paper state, it is difficult to measure the thickness and density in the wet paper state, so dry the paper layer before and after the secondary processing. After that, measure the degree of increase in thickness and decrease in density. Further, the shape and arrangement of the uneven portions forming the electrolytic paper are not particularly limited as long as the thickness of the electrolytic paper after secondary processing can be substantially maintained during winding of the element.

The method of secondary processing is not limited as long as it can form the convex part and the concave part, but it is preferable to use a method such as embossing or crepe processing that can form the convex part and the four parts in one process.
Therefore, we developed a method in which the base electrolytic paper after papermaking was passed through an embossing roll to form convex and concave parts, and a doctor knife was pressed against the wet paper in the press roll section of the paper machine to crepe the wet paper. A method of post-drying is suitable.

The increase in thickness due to this secondary processing is preferably 10 to 300% of the thickness of the base electrolytic paper, and the amount of increase in thickness due to secondary processing is the thickness due to swelling of the base electrolytic paper in the electrolytic solution. It is necessary that the amount of increase in This is because if the amount of increase in thickness of the base electrolytic paper due to swelling in the electrolytic solution is less than the amount of increase in thickness due to secondary processing, the electrolyte will leak out from the capacitor element.

In addition, if the concave portions do not correspond to the convex portions, or if ultra-low density paper with a density of 0.1 to 0.2 g/crl and a thickness of about 10 μm is laminated or laminated, or paper with threads is used, the base electrolytic paper is It is also possible to increase the thickness by forming only a convex portion on one surface. Even when such uneven portions do not correspond or when only convex portions are formed, the electrolytic paper becomes substantially thicker, and the distance between the anode foil and the cathode foil is ensured to be wide enough to allow the electrolytic paper to swell sufficiently. Therefore, it is effective in improving the short-circuit failure rate and ESR.

Below are shown various examples and comparative examples of electrolytic capacitors according to the present invention, and the results of measuring the characteristics of the electrolytic capacitors such as ESR and short-circuit failure rate, and the swelling degree of the electrolytic paper used. In addition, each measurement value of each sample was performed by the following measurement method and apparatus.

(1) Manufacturing method for electrolytic capacitors Electrolytic paper is interposed between tabbed anode foil and cathode foil so that the two electrodes do not come into contact with each other, and after winding up to form an electrolytic capacitor element, impregnating it with a predetermined electrolytic solution. 50WV by the usual method of enclosing it in a case and aging it.
, a 220μm aluminum dry electrolytic capacitor was manufactured.

(2) Evaluation method of electrolytic paper ■Thickness, density, and tensile strength Thickness, density, and tensile strength were measured by the method specified in JIS C2301 (electrolytic capacitor paper).

■ Swelling degree The degree of swelling is determined by stacking 10 sheets of electrolytic paper to make a test piece, and measuring its thickness with a dial thickness gauge (Aμm).Then, the test piece is soaked in γ-butyrolactone, a specified solvent, or a specified electrolyte. Soak for exactly 30 minutes. Thereafter, the test piece was taken out and its thickness was measured using a dial thickness gauge (8 μm) while it remained wet. A dial thickness gauge with a measuring tip having a diameter of 10 cm was used, and the degree of swelling was determined using the following formula.

(3) Evaluation method for electrolytic capacitors ■Short-circuit failure rate After winding electrolytic paper together with anode foil and cathode foil to form an electrolytic capacitor element, use a tester to check continuity due to a short between the two electrodes without impregnating them with electrolyte. did.

The short-circuit failure rate was determined by inspecting 500-1000 devices and determining the ratio of short-circuit devices to the total number of devices.

■ESR (Equivalent Series Resistance) The ESR of an electrolytic capacitor is 1000H7 at a temperature of -40℃.
It was measured by an LCR meter at the frequency of .

■Amount of Electrolyte Leakage After the electrolytic capacitor element was impregnated with electrolyte, the element was placed in a centrifugal separator and centrifuged to separate and remove the electrolyte that easily leaked from the element. The difference in weight of the element before and after centrifugation was measured, and was determined as the amount of electrolyte leaked from the element.

(Example 1) 100 kg of Manila hemp pulp was mixed with 2% NaOH aqueous solution 0,5
After being immersed in rn', the pulp was squeezed using a screw press to remove excess NaOH aqueous solution to give a pulp concentration of 40%. 70 kg of acrylonitrile is added to this alkali-treated pulp.
was added and reacted for 2 hours with slow stirring at 20°C to cyanoethylate Manila hemp pulp. After thoroughly washing this cyanoethylated Manila hemp pulp with ion-exchanged water, it was beaten with a beater to 270 ml of CSF.
Further, paper was made using a cylinder paper machine using ion-exchanged water as water to obtain electrolytic paper having a thickness of 27.9 pm and a density of 0.653 g 10 J.

Next, this basic electrolytic paper is subjected to secondary processing using an embossing machine that combines an engraving roll and a cotton roll to form convex portions on one side and concave portions corresponding to the convex portions on the other side. An electrolytic paper having a thickness of 50.2 μm and a density of 0.385 g/aj was obtained. Using this electrolytic paper, an aluminum electrolytic capacitor according to the present invention was manufactured. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusting the specific resistance to 200Ω·ell (20°C).

(Comparative Example 1) Thickness 29.7 μm and density 0.653 g/
An aluminum electrolytic capacitor was manufactured by using the aj-based electrolytic paper as an electrolytic paper without secondary processing. The impregnated electrolyte was made by dissolving ammonium borodisalicylate in γ-butyrolactone, and the specific resistance was adjusted to 200Ω・C1.
1 (20°C).

(Comparative Example 2) Cyanoethylated Manila hemp pulp obtained by the same treatment as in Example 1 was thoroughly washed with ion-exchanged water, and then beaten with a beater to C5C3F68O, and further made into a circular mesh using ion-exchanged water as water. Paper was made using a paper machine, and the thickness and density were approximately the same as in Example 1, with a thickness of 50.7 μm and a density of 0.389.
An electrolytic paper of g/c+J was obtained.

Next, an aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusting the resistivity to 200Ω・ell (20°C) (Comparative Example 3) Manila hemp pulp was thoroughly soaked in ion-exchanged water. After washing, it is beaten with a beater to C8C8F28O, and then paper is made with a cylinder paper machine using ion-exchanged water as water to a thickness of 2.
An electrolytic paper having a diameter of 9.5 μm and a density of 0.650 g/cd was obtained.

Next, this basic electrolytic paper was subjected to secondary processing using an embossing machine that combined an engraving roll and a cotton roll exactly the same as in Example 1 to form convex portions on one side and the convex portions on the other side. A recess is formed corresponding to the thickness of 49.7 μm and a density of 0.
．． Electrolytic paper having approximately the same thickness and density as Example 1 of 386 g/cd was obtained. An aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusting the specific resistance to 200Ω·ell (20°C).

(Example 2) 100 kg of coniferous wood pulp was immersed in 0.5 m' of 2% NaOH aqueous solution, and then squeezed with a screw press to remove excess NaOH aqueous solution to give a pulp concentration of 40%.
And so. This alkali-treated pulp was placed in a stainless steel pressure container, and the air in the container was replaced with nitrogen gas. Next, 50 kg of 1,2-butylene oxide was placed in the container, which was sealed, and reacted at 90° C. for 60 minutes to hydroxybutylate the softwood pulp. After washing this hydroxybutylated coniferous wood pulp thoroughly with ion-exchanged water.

With a double disc refiner, 5 ml of CSF
The paper was beaten to a thickness of 20.4 μm and a density of 0°855 g using ion-exchanged water as water.
/cd group electrolytic paper was obtained.

Next, this basic electrolytic paper is subjected to secondary processing using an embossing machine that combines an engraving roll and a cotton roll to form convex portions on one side and concave portions corresponding to the convex portions on the other side. An electrolytic paper having a thickness of 50.6 μm and a density of 0°345 g/cd was obtained. Using this electrolytic paper, an aluminum electrolytic capacitor according to the present invention was manufactured. The impregnated electrolyte is 50% dimethylformamide and 50% ethylene glycol.
ammonium hydrogen maleate was dissolved in a mixed solvent with 200 Ω·CI+ (20° C.).

(Comparative Example 4) Thickness 20.4 μm and density 0.855 g/
An aluminum electrolytic capacitor was manufactured by using cj-based electrolytic paper as an electrolytic paper without secondary processing. The impregnated electrolyte solution was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol, and adjusting the specific resistance to 200Ω・1 (at 20℃).
).

(Comparative Example 5) Hydroxybutylated coniferous wood pulp obtained by the same treatment as in Example 2 was thoroughly washed with ion-exchanged water, and then unbeaten (C8F16Oml) was made into cylinder paper using ion-exchanged water as water. Make paper using a machine.

Almost the same thickness as Example 2, thickness 50.1 μm with the same density,
Electrolytic paper with a density of 0.348 g/cj was obtained.

Next, an aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol, and adjusting the specific resistance to 200.
It was adjusted to Ω・1 (20°C).

(Comparative Example 6) After thoroughly washing the coniferous wood pulp with ion-exchanged water,
It was refined in a double disc refiner to -C8F 5ml or less, and then made into paper using a Fourdrinier paper machine using ion-exchanged water to a thickness of 20.2 μm and a density of 0.848 g/cd.
An electrolytic paper based on this was obtained.

Next, this basic electrolytic paper was subjected to secondary processing using an embossing machine that combined an engraving roll and a cotton roll exactly the same as in Example 2 to form convex portions on one side.

A concave portion is formed on the other surface corresponding to the convex portion, and the thickness is 49 mm.
．． Almost the same as Example 2 with a density of 8 μm and a density of 0.344 g/cd.
Electrolytic paper with the same thickness and density was obtained.

Next, an aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol, and adjusting the specific resistance to 200.
It was adjusted to Ω·am (20°C).

(Example 3) Add 100Q of acetic anhydride to 20 kg of Manila hemp pulp,
The Manila hemp pulp was acetylated by reacting at 120° C. for 2 hours with stirring. This acetylated Manila hemp pulp was centrifuged, taken out from the reaction solution, thoroughly washed with ion-exchanged water, beaten with a beater to 530 ml of CSF, and then made into paper using a cylinder paper machine using ion-exchanged water as water. , thickness 40.4μm, density 0.509g/cj
An electrolytic paper based on this was obtained.

Next, this basic electrolytic paper is processed with an embossing machine that combines an engraving roll and a cotton roll to form convex portions on one side and concave portions corresponding to the convex portions on the other side,
Electrolytic paper with a thickness of 50.1 μm and a density of 0.410 g/ctl was obtained. Using this electrolytic paper, an aluminum electrolytic capacitor according to the present invention was manufactured. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the specific resistance to 200Ω·01 (20′C).

(Comparative Example 7) Thickness 40.4 μm and density 0.509 g/
An aluminum electrolytic capacitor was manufactured by using ctj-based electrolytic paper as electrolytic paper without secondary processing. The impregnated electrolyte solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the specific resistance to 200Ω.
(Comparative Example 8) Ji/Ji [After the acetylated Manila hemp pulp obtained by the same treatment as in 3 was sufficiently washed with ion-exchanged water.

The paper was beaten to C8C3F67O with a beater, and then made with a cylinder paper machine using ion-exchanged water as water, and the paper was approximately the same as Example 3, with a thickness of 50.4 μm and a density of 0.
．． 406g/c11? Electrolytic paper was obtained. Next, an aluminum electrolytic capacitor was manufactured using this electrolytic paper. In addition,
The impregnated electrolyte was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the resistivity to 200Ω・el.
(Comparative Example 9) Manila hemp pulp was thoroughly washed with ion-exchanged water and then beaten with a beater to C5C3F33O.

Furthermore, paper was made using a cylinder paper machine using ion-exchanged water as water to a thickness of 40.5 μm and a density of 0.507 g/ctl.
An electrolytic paper based on this was obtained. Next, this basic electrolytic paper was prepared in Example 3.
An embossing machine that combines the same engraving roll and cotton roll is used to form a convex part on one side, and a concave part corresponding to the convex part on the other side. ．．
Electrolytic paper having approximately the same thickness and density as Example 3 with a thickness of 2 μm and a density of 0° and 408 g/cd was obtained. An aluminum electrolytic capacitor was then manufactured using this electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the specific resistance to 200Ω・Cl1 (20
(Example 4) 100 kg of Manila hemp pulp was immersed in a 5% NaOH aqueous solution 0.5rrI3, and then squeezed with a screw press to remove excess NaOH aqueous solution to a pulp concentration of 40.
%. 70 kg of acrylonitrile was added to this alkali-treated pulp and reacted at 20° C. with slow stirring for 2 hours to cyanoethylate Manila hemp pulp. This cyanoethylated Manila hemp pulp was thoroughly washed with ion-exchanged water and then beaten with a beater to a CSF of 460 ml. Next, paper was made using ion-exchanged water using a cylinder paper machine with a doctor blade attached to the press roll. When making this paper, a doctor blade is pressed against the wet paper using the press roll part, and the wet paper is creped on the paper machine and then dried to form electrolytic paper with a thickness of 40.2 μm and a density of 0°304 g/cd. I got it. In addition, the thickness of the electrolytic paper obtained by making the paper under the same conditions without pressing the doctor blade and without creping was 29.4 μm and the density was 0.413 g/aJ, which is equivalent to the basic electrolytic paper. It is something to do.

Using this electrolytic paper, an aluminum electrolytic capacitor according to the present invention was manufactured. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusting the specific resistance to 200 Q-am (20° C.).

(Comparative Example 10) Thickness 29.4p obtained without crepe processing in Example 4
An aluminum electrolytic capacitor was manufactured by using a base electrolytic paper with a density of 0.413 g/crl as an electrolytic paper without secondary processing. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusting the specific resistance to 200Ω·CI (20° C.).

(Comparative Example 11) Cyanoethylated Manila hemp pulp obtained by the same treatment as in Example 4 was thoroughly washed with ion-exchanged water, then beaten with a beater to 690 ml of CSF, and further ion-exchanged water was used as water for use. The paper was made using a circular mesh paper machine, and the thickness was approximately the same as in Example 4. The thickness was 40.6 μm, and the density was 0.
．． Electrolytic paper of 301 g/cd was obtained.

Next, an aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusting the resistivity to 200 Ω・cn (20'C) (Comparative Example 12). After washing, the mixture was beaten with a beater to 450 ml of C8F.

Next, paper was made using ion-exchanged water as water using a cylinder paper machine with a doctor blade attached to the press roll. When making this paper, a doctor blade was pressed against the wet paper using the press roll part, and the wet paper was creped on the paper machine and then dried.
An electrolytic paper having a size of 0.5 μm and a density of 0.303 glctl was obtained. In addition, the thickness of electrolytic paper obtained by making paper under the same conditions without applying a doctor blade and without creping was 29.
It has a diameter of 8 μm and a density of 0.413 g/c+d, which corresponds to the basic electrolytic paper.

An aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium borodisalicylate in γ-butyrolacone and adjusting the resistivity to 200.
It was adjusted to Ω·cn (20°C).

Example 1.2.3.4 and Comparative Example 3 obtained as above
．． The degree of swelling was measured by immersing the electrolytic paper used in 6.9.12 in the electrolytic solution used and the solvent used in other electrolytic solutions. The results are shown in Table 1 along with the thickness and density of the basic electrolytic paper before secondary processing.

Untreated: Comparative Example 3, 6.9.12 Table 1 shows the thickness, density, and swelling in response to electrolytic solution of the electrolytic paper before secondary processing, which has approximately the same thickness and density in the above Examples and Comparative Examples. Example 1.2.3,
Comparative Example 3.6 contains cellulose fibers introduced with organic substituents to increase the degree of swelling with respect to the electrolytic solution.
．． 9 and 12 are ordinary electrolytic paper.

Comparative Example 3 has a degree of swelling of 53.6% with respect to dimethylformamide, which is conventionally widely used as a solvent for electrolytic solutions, and a degree of swelling of 38.6% with respect to ethylene glycol. Therefore, in order to improve ESR only by conventional secondary processing, it is necessary to keep the range in which the thickness increases due to secondary processing to be below this swelling range, and sufficient effects are exhibited within this range. However, in an electrolytic solution in which ammonium borodisalicylate is dissolved in γ-butyrolactone, which has been attracting attention recently, and the resistivity is adjusted to 200Ω・em (20°C), it hardly swells at 0.1%. Not only does the ESR not decrease due to secondary processing, but excess electrolyte remains between the uneven portions that do not swell and the electrodes and leaks out. Also, 0.0% for γ-butyrolactone alone.
It hardly swells at 1%. Therefore, Comparative Example 3 cannot be used in an electrolytic solution using γ-butyrolactone as a solvent.

On the other hand, in Example 1, the degree of swelling was significantly increased to 76.0% with respect to the electrolytic solution, and the density of the electrolytic paper was substantially reduced. Furthermore, the swelling was remarkable at 75.2% even when only γ-butyrolactone, which is the solvent of the electrolytic solution, was used. Therefore, according to Example 1, even if electrolytic paper is used that has been made thicker than during papermaking through secondary processing, it will swell with the electrolytic solution and cause irregularities. Since the ESR is eliminated, the ESR can be improved or reduced.

Furthermore, 53.6% to 1 for dimethylformamide
The degree of swelling increases significantly even when the same size of the electrolyte solvent is used, which increases the degree of swelling to 18.4%, and the range in which the thickness increases due to secondary processing is expanded to this increased range. It is something that can be done. This is the corresponding example 2
The same holds true for Comparative Example 6, Example 3 and Comparative Example 9, and Example 4 and Comparative Example I2. Therefore, the degree of swelling of the base electrolytic paper before secondary processing according to the example containing cellulose fibers into which organic substituents have been introduced is significantly higher than that of the comparative example that is the conventional base electrolytic paper. This results in a substantial decrease in density after electrolyte impregnation.

Next, Table 2 shows the measurement results of ESR, short-circuit failure rate, and electrolyte leakage of the electrolytic capacitors of Examples 1 to 4 and Comparative Examples 1 to 12.

Secondary processing + increasing degree of swelling: Examples 1, 2, 3.
4.Those with only increased swelling degree: Comparative Examples 1, 2, 4
,5,7,8,10. I only undergoes subsequent processing
: Comparative example 3e L 9. + 2 In Table 2, Example I contains cellulose fibers introduced with organic substituents according to the present invention to increase the degree of swelling, and is made thicker and has a lower density through secondary processing after papermaking. can be,
Compared to Comparative Example 3, which was only subjected to secondary processing and had the same thickness and density, it maintained a good short defect rate of 0.8%.
The ESR has been significantly reduced from 1.76Ω to 0.51Ω. According to Example 1, the uneven portions formed on the electrolytic paper due to swelling completely disappear and the thickness becomes the same as that after secondary processing, so the leakage amount of the electrolytic solution is reduced from 0.35 g in Comparative Example 3 to 0.5 g. It has decreased to 0.04g.

Comparative Example 1 uses the basic electrolytic paper of Example 1 before secondary processing, and has a high density of 0.653 g/c+J, but is thin at 29.7 μm.

The short-circuit failure rate is as high as 3.6%, and even though the cellulose fiber contains organic direct substituent groups and has sufficient swelling ability, it is thin at 29.7 μm, making it difficult to bond between the anode foil and the anode foil. ESR because there is not enough space for swelling between
The resistance is also 1.22Ω. On the other hand, according to Example 1, in which Comparative Example 1 was subjected to secondary processing to make the paper substantially thicker and lower in density than when paper was made, the short defect rate was 0.8%. The ESR is significantly improved to 0.51 Ω because the swelling gap is sufficient to compensate for the drop in thickness and the increase in thickness.

On the other hand, Comparative Example 2 is the same as Example 1 by paper making without secondary processing.
It has approximately the same thickness and the same density, and because the degree of swelling is increased by introducing an organic substituent, the ESR is 0.48, which is lower than Example 1, but the short failure rate is is extremely bad at 5.7%.

There is no balance between ESR and short-circuit failure rate, and the short-circuit failure rate is sacrificed, which is impractical. This is 0゜389g/c+1 due to paper making only.
? In order to achieve a low density, the C8F value was set to 680 ml.
This is because the paper must be made in an almost unbeaten state. On the other hand, according to Example 1, the thickness was increased from 29°7 μm when paper was made to 50.2 μm through secondary processing, and as a result, the density was also increased from Q, 653 g/cj to 0.38 μm.
Since it is reduced to 5 g/cd, the degree of beating can be increased to 270 m1, and the short defect rate can be significantly reduced by 0.8% as well as the ESR.

Therefore, according to Example 1 of the present invention, the electrolytic paper can be reliably swollen to the thickness after secondary processing, and the ESR can be improved, and the swelling Both the short-circuit defect rate and ESR can be improved and reduced at a high level at the same time compared to the case where only the short-circuit failure rate and ESR are improved.

This is also clearly seen in the relationships between Example 2 and Comparative Examples 2, 3.4, and Example 3 and Comparative Examples 7, 8.9, which have the same relationship as Example I and Comparisons 1 and 2.3. It is expressed as data.

On the other hand, Example 4 also contains cellulose fibers into which the organic substituent according to the present invention has been introduced to increase the degree of swelling and to increase the thickness and lower the density through secondary processing after paper making. , Example 1.2.3 shows an example in which the specific secondary processing method is different. That is, Example 1
．． In contrast to Example 2.3, a paper layer was formed using a paper machine and then dried to obtain a basic electrolytic paper, which was then subjected to secondary processing using an embossing machine that combined an engraving roll and a cotton roll. No. 4 is a wet paper that was pressed against a doctor blade by a press roll, crepe-processed on a paper machine, and then dried. Further, Comparative Example 12, which corresponds to Example 4 and shows an example of only secondary processing, was also subjected to the same crepe processing.

In Example 4, the short defect rate was 15% compared to Comparative Example 10 in which the basic electrolytic paper was used as it was before secondary processing.
．． From 8% to 6.3%, ESR from 0°54Ω to 0.4
Numerical results are exactly the same as the relationship between Example 1 and Comparative Examples 1 and 2.3, such as an improved reduction of 3Ω. Therefore, the data clearly shows that the method of secondary processing in the present invention is not limited as long as it can form convex portions and concave portions.

According to the present invention, which has been explained in detail above, by forming irregularities on the electrolytic paper through secondary processing after papermaking, it is possible to use a raw material with a lower C3F content than electrolytic paper of the same density produced only by papermaking. It is possible to obtain a thick electrolytic paper with a low density, and since it contains cellulose fibers into which organic substituents have been introduced, the degree of swelling with respect to the electrolyte impregnated with it is significantly increased. Since it reliably swells to the thickness after the next processing and the substantial density is lowered, both the short failure rate and ESR can be improved and reduced at the same time. Therefore, compared to conventional electrolytic paper that undergoes only secondary processing, even if the range of increase in thickness due to secondary processing is increased, it can be easily swollen to the thickness after secondary processing, and due to insufficient swelling. There is no electrolyte leakage, etc., and ESR can be further improved and reduced. Furthermore, because it hardly swells, it can be used in electrolytes that use γ-butyrolactone as a solvent, which could not be used in conventional electrolytic paper that only undergoes secondary processing, and has good low-temperature properties and workability. It is possible to improve the ESR by taking advantage of the characteristics of an electrolytic solution using γ-butyrolactone as a solvent. Furthermore, compared to the conventional electrolytic paper that only contains cellulose fibers with organic substituents introduced, the thickness of the electrolytic paper is increased through secondary processing, and the gap between the anode foil and the cathode foil is sufficiently expanded so that the electrolytic paper swells. Since it can be secured as widely as possible, ESR can be further improved and reduced.

That is, the present invention can expand the degree and effective range of the secondary processing and increase the degree of swelling, thereby reducing both ESR and short failure rate at a higher level. Improvements can be made at the same time. Furthermore, according to the present invention, the wettability and retention of the electrolytic paper with respect to the electrolytic solution are improved, and the amount of electrolytic solution impregnated is also inevitably increased, so drying up of the electrolytic solution is prevented and the life of the paper is extended. You can get an electrolytic capacitor.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the embossing method, FIG. 2 is an explanatory diagram showing the electrolytic paper after embossing, and FIG. 3 is an explanatory diagram showing the state of winding of the element before being impregnated with electrolyte. FIG. 4 is an explanatory diagram showing the state of winding of the element after being impregnated with electrolyte.

Claims (1)

[Claims] In an electrolytic capacitor formed by impregnating electrolytic paper interposed between an anode foil and a cathode foil with a predetermined electrolytic solution, the electrolytic paper is formed with an appropriate number of convex portions on one side by secondary processing after papermaking, By forming concave portions on the other side corresponding to the convex portions, the thickness is substantially thicker than that during paper making, and
In addition to lowering the density, the degree of swelling is increased so that the cellulose fibers swell to at least the thickness after the secondary processing in the electrolytic solution by containing fibers in which organic substituents are introduced by chemical reaction. Features of electrolytic capacitors.