JPH0754788B2 - Electrolytic capacitor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor obtained by impregnating an electrolytic paper interposed between an anode foil and a cathode foil with a predetermined electrolytic solution, and particularly to a short circuit defective rate thereof. And the improvement of impedance characteristics, and the impregnation property of the electrolytic solution.

Conventional Technology and Its Deficiencies Generally, electrolytic capacitors, particularly aluminum electrolytic capacitors, are formed by winding electrolytic paper between an anode aluminum foil and a cathode aluminum foil, and then immersing the electrolytic paper in a predetermined electrolytic solution. It is manufactured by impregnating it with electrolyte and sealing it. The electrolyte is usually made by using ethylene glycol, dimethylformamide, etc. as a solvent, and by dissolving organic acid salts such as boric acid or ammonium adipate, ammonium hydrogen maleate, etc. in these solvents and making it penetrate from both ends of the capacitor element. is doing.

Since the conventional aluminum electrolytic capacitors as described above have electrolytic paper impregnated with an electrolytic solution, the impedance characteristics as a capacitor, especially the equivalent series resistance (abbreviated as ESR below)
Since it is high and it may deteriorate during use, the resistance value of the electrolytic solution is usually lowered, the electrolytic paper is thinned or the density is reduced, and the material of the electrolytic paper is made from ordinary wood kraft pulp. Special materials such as Manila hemp pulp and esparto pulp are being changed.

However, lowering the resistance value of the electrolytic solution causes corrosiveness to the aluminum foil, and thinning the electrolytic paper or lowering the density increases the short-circuit failure rate when winding it around the capacitor element. Even if no short circuit occurs, the short defect rate after being commercialized and put on the market is high.

Therefore, in order to reduce the short-circuit defect rate, the thickness of electrolytic paper should be increased, the density should be increased, and in the case of the same density, JIS P 8121 shall indicate the degree of beating of the raw material pulp.
It is known that if the value of CSF (Canadian Standard Freeness) is reduced, the pulp fibers become finer due to fibrillation, and the resulting electrolytic paper becomes denser, which is good for improving the short-circuit failure rate. Also for these items
The effect on ESR is that when the electrolytic paper is thickened, the ESR deteriorates linearly, and when the density is increased, the ESR deteriorates quadratically.However, it was found that the CSF value has almost no effect. ing. That is, in order to improve the ESR, it is necessary to make the electrolytic paper thin and reduce its density, contrary to the improvement of the short circuit defect rate.

Therefore, in order to achieve the objectives of both the improvement of short-circuit defect rate and the improvement of ESR at the same time, it is necessary to reduce the value of CSF in order to improve the short-circuit defect rate, considering that the CSF value does not affect ESR. Must be assumed. Therefore, it is ideal to make electrolytic paper with a low density and low density CSF. However, when an electrolytic paper is produced from pulp composed of natural cellulose such as ordinary kraft pulp, Manila hemp pulp, and esparto pulp,
If the value of CSR is made small, hydrogen bonds that act between fibers increase due to fibrillation, so the density of electrolytic paper always increases. Therefore, when electrolytic paper of the same thickness is made with the same paper machine, the CSF value of high-density paper is smaller than that of low-density paper. As a result, if a low density electrolytic paper is used to improve the ESR of the electrolytic capacitor, the CSF value will increase,
While the short-circuit defect rate increases, when the value of CSF is small, the density becomes higher and the ESR becomes worse.As a result, it is difficult to improve both the short-circuit defect ratio and ESR at the same time. there were.

Therefore, the applicant previously provided JP-A-61-29118 as an electrolytic capacitor in which the causal relationship between the short-circuit defect rate and the ESR is reversed and both are improved at the same time. This is obtained by passing the electrolytic paper 1 shown in FIG. 1 between the cotton roll 3 and the engraving roll 2 by secondary processing after paper making,
As shown in FIG. 2, an appropriate number of convex portions 4 are formed on one surface of the electrolytic paper 1, and concave portions 5 are formed on the other surface so as to correspond to the convex portions 4.
The electrolytic paper 1 is characterized in that its thickness is substantially increased to T2 from the thickness T1 at the time of paper making and the density is lowered. Therefore, even if the raw pulp is beaten sufficiently to reduce the short-circuit defect rate and the CSF value is reduced, the density of the electrolytic paper can be reduced and the thickness can be increased by the secondary processing. Can be improved at the same time.

Furthermore, the applicant previously provided Japanese Patent Application No. 61-250479 with electrolytic paper for electrolytic capacitors in which electrolytic paper contains cellulose fibers introduced with an organic substituent by a chemical reaction to remarkably increase the degree of swelling in an electrolytic solution. is doing. According to this electrolytic paper, the density and thickness are maintained so that a short circuit failure does not occur during the element winding process, and the element is wound without impairing the short circuit failure and impregnated with the electrolytic solution, and then the electrolytic paper swells with respect to the electrolytic solution. Since the degree of swelling is remarkably higher than that of conventional swelling, the fibers that make up the electrolytic paper expand and the gap between the fibers increases, which can substantially reduce the density of the electrolytic paper and reduce the ESR. be able to. Moreover, since the element is wound, the short-circuit defect rate does not increase.

Problems to be Solved by the Invention However, the above-mentioned Japanese Patent Laid-Open No. SHO 61-62, which performs secondary processing after papermaking
In order to sufficiently reduce the ESR in the electrolytic capacitor according to -29118, the electrolytic paper 1 that has been subjected to the secondary processing is removed from the state in which it is wound between the anode aluminum foil 6 and the cathode aluminum foil 7 shown in FIG. It is necessary to swell in the electrolytic solution to at least the thickness T2 after the secondary processing as shown in FIG. For example, electrolytic paper with a thickness T1 of 20 μm during papermaking is subjected to secondary processing by embossing, and thickness T2 after secondary processing.
Even if a 40 μm electrolytic paper is used, if the electrolytic paper itself does not swell in the electrolytic solution to a thickness of at least 40 μm ES
R does not decrease enough. On the contrary, when the degree of swelling of the electrolytic paper is insufficient and does not swell up to the thickness T2 after the secondary processing, the electrolytic solution is not uniformly impregnated into the electrolytic paper and the ESR
Not only does not decrease, but also an excessive amount of electrolytic solution stays between the irregularities of the electrolytic paper formed by the secondary processing and both electrodes. When a mechanical shock is applied to the electrolytic capacitor, the electrolytic solution retained between the concavo-convex portion of the electrolytic paper and the both electrodes is removed by, for example, centrifuging the extra electrolytic solution attached to the element impregnated with the electrolytic solution in a batch process. In such a case, it easily leaks from the element, resulting in poor impregnation of the electrolytic solution, and the capacitance of the electrolytic capacitor is significantly reduced.

Therefore, the increase in thickness due to the secondary processing needs to be limited to the range in which the electrolytic paper 1 can swell. Electrolytic paper made from wood pulp or Manila hemp pulp as a raw material for an electrolytic solution containing ethylene glycol or dimethylformamide, which is generally used today, as a main solvent, and other solvents such as water and methyl cellosolv if necessary. The degree of swelling is about 50%, and the electrolytic paper swells to a thickness of about 1.5 times even when impregnated with the electrolytic solution. Also, change the thickness of the base electrolytic paper
To swell more than 1.5 times and smooth the ESR reducing effect, use an electrolytic solution having a greater swelling effect on electrolytic paper than dimethylformamide or ethylene glycol, for example, an electrolytic solution containing a large amount of dimethyl sulfoxide. Was needed. If dimethyl sulfoxide is used in the electrolytic solution, the degree of swelling of the electrolytic paper can be made 100% or more, and the base electrolytic paper can be swollen in the electrolytic solution to a thickness twice or more. However, dimethyl sulfoxide is a sulfur compound, and when it is mixed in a large amount in the electrolytic solution, corrosion of the electrolytic capacitor is likely to occur, and since its melting point is 18.5 ° C, the low temperature characteristics of the electrolytic capacitor are significantly deteriorated. For these reasons, an electrolytic solution containing dimethyl sulfoxide has been proposed but cannot be used in reality. Therefore, the thickness of electrolytic paper whose thickness has increased due to secondary processing must be 150% or less of the thickness of the base electrolytic paper after paper making. The effect of processing was faint.

Therefore, even if the thickness exceeds 150% by the secondary processing, if the electrolytic paper swells by the increased thickness and the irregularities due to the secondary processing can be eliminated, the ESR will be further improved and reduced. Is something that can be done.

In addition, an electrolytic solution was developed by using γ-butyrolactone, which has a low viscosity and low toxicity, as a solvent, and has been developed into an electrolytic solution using ethylene glycol, which has poor electrical properties at low temperatures, or dimethylformamide, which has strong toxicity, as a solvent. It is used instead. This γ-butyrolactone-based electrolytic solution has good low-temperature characteristics and working characteristics, but ESR
Was extremely bad. This is because γ-butyrolactone is less hydrophilic than other conventional electrolytic solutions, so that the cellulose fibers after being impregnated with the electrolytic solution hardly swell, and the substantial density of the electrolytic paper is hardly reduced. by. Therefore, in the case of the electrolytic capacitor according to Japanese Patent Application Laid-Open No. 61-29118, the electrolytic paper 1 having a small CSF value and fibers strongly bonded to each other by hydrogen bonding is subjected to secondary processing to increase the thickness and decrease the density. Γ-
When an electrolytic solution containing butyrolactone as a solvent is used, the electrolytic paper 1 hardly swells up to the thickness T2 after the secondary processing and causes the above-mentioned adverse effect, and the ESR is not improved but rather deteriorated. Therefore, the electrolytic solution using γ-butyrolactone as a solvent is substantially thicker than that at the time of papermaking by the secondary processing according to JP-A-61-29118, and is not suitable for electrolytic capacitors using electrolytic paper having a low density. Could not be used.

On the other hand, by including a cellulose fiber having an organic substituent introduced therein, the degree of swelling of electrolytic paper is remarkably improved.
According to No. 61-250479, the electrolytic paper can be swollen even with an electrolytic solution containing γ-butyrolactone as a solvent, and the ESR can be improved without affecting the short-circuit defective rate. However, since the electrolytic paper is a device wound by being interposed between the anode foil and the cathode foil,
Even though it has the ability to swell, it cannot swell beyond the distance between the anode foil and the cathode foil. Therefore, if a wide space where the electrolytic paper can swell can be secured, the swelling can further improve and reduce the ESR.

Therefore, the present invention solves the problems of the above-mentioned conventional examples, and even if the thickness after secondary processing is 150% or more of the electrolytic paper after papermaking, the electrolytic solution is sufficient, even if γ-butyrolactone is the solvent. Even if it is, an electrolytic paper capable of swelling to at least the thickness after secondary processing, that is, an electrolytic capacitor using an electrolytic paper that can sufficiently secure the range of swelling by secondary processing is provided. It is what

Means for Solving the Problems In an electrolytic capacitor formed by impregnating an electrolytic paper interposed between an anode foil and a cathode foil with a predetermined electrolytic solution, the electrolytic paper is formed on one surface by secondary processing after papermaking. By using an embossed paper in which a proper number of convex portions are formed and concave portions are formed on the other surface corresponding to the convex portions, the thickness thereof is substantially thicker than that at the time of papermaking, and the density is reduced. Along with at least the thickness after the secondary processing with respect to the electrolytic solution by containing a fiber introduced with an organic substituent by an etherification reaction of a hydroxyl group contained in the cellulose fiber, an esterification reaction or an acetalization reaction It is intended to provide an electrolytic capacitor characterized in that the degree of swelling is increased so as to swell. The secondary processing after papermaking referred to in the present invention is the processing after the paper layer is formed by a method such as handmaking or mechanical papermaking, specifically, the fiber dispersion is poured into a net to form the paper layer. Processing is performed after formation.

Effect According to the present invention having the above-mentioned configuration, by using the embossed paper in which the uneven portion is formed on the electrolytic paper by the secondary processing after papermaking, a raw material having a small CSF, and a thick electrolytic paper having a low density is obtained. In addition, since it contains cellulose fibers introduced with an organic substituent, the degree of swelling with respect to the impregnated electrolytic solution is remarkably increased, and the electrolytic paper swells reliably to the thickness after secondary processing Since the target density is lowered, both the short circuit failure and the ESR can be simultaneously improved and reduced. Therefore, compared to conventional electrolytic paper that only has secondary processing,
Even if the range in which the thickness increases due to the secondary processing is increased, the thickness can be easily swelled to the thickness after the secondary processing, there is no leakage of the electrolytic solution due to insufficient swelling, and the ESR can be further improved and reduced. Moreover, since it hardly swells, it can also be used in an electrolytic solution using γ-butyrolactone as a solvent, which could not be used in the electrolytic paper of the conventional secondary processing only,
ESR can be improved by taking advantage of the characteristics of an electrolytic solution using γ-butyrolactone as a solvent, which has good low-temperature characteristics and workability. Furthermore, in contrast to the conventional electrolytic paper that only contains cellulose fibers introduced with organic substituents, the thickness of the electrolytic paper is increased by secondary processing to allow the electrolytic paper to swell sufficiently between the anode foil and the cathode foil. Since it can be secured as widely as possible, the ESR can be further improved and reduced.

That is, the present invention is capable of increasing the degree of the secondary processing and the range of effectiveness and increasing the degree of the degree of swelling, and improves both the ESR and the short-circuit defect rate at a higher level. It can be realized at the same time.
Further, according to the present invention, the wettability and the holding property of the electrolytic paper with respect to the electrolytic solution are improved, and the amount of the impregnated electrolytic solution is necessarily increased. Capacitor can be obtained.

Examples The configuration of the electrolytic capacitor according to the present invention and various examples will be described below.

The present invention discloses an electrolytic paper of the group proposed by the applicant in Japanese Patent Application No. 61-250479, which contains a fiber in which an organic substituent is introduced into a cellulose fiber to increase the degree of swelling in an electrolytic solution.
As proposed in No. 8, by forming a suitable number of convex parts on one side by secondary processing and forming concave parts on the other side corresponding to the convex parts, the thickness is made 150% or more of that at the time of papermaking. Also constitutes an electrolytic capacitor using electrolytic paper that can be swollen to the thickness after secondary addition by being impregnated with an electrolytic solution.

The material of the electrolytic paper used in the present invention is mainly composed of cellulose, specifically, softwood, wood pulp fiber obtained from hardwood, Manila hemp, red hemp, non-wood pulp fiber obtained from sigil hemp and esparto grass, bis. Examples thereof include regenerated cellulose fibers such as course lace and cupra lace. These cellulose fibers contain many hydroxyl groups (OH), and the fibrils constituting the fibers are strongly bonded by the hydrogen bond formed between the hydroxyl groups. Even when such a cellulose fiber is dipped in a solvent having a low hydrophilicity such as γ-butyrolactone, the solvent cannot penetrate into the hydrogen bond portion formed between the fibrils, so that the fiber hardly swells. In addition, even in electrolytic paper composed of cellulose fibers, the paper is not simply formed by the entanglement of the fibers, but hydrogen bonds are formed at the contact parts where the fibers are entangled, and this force also bonds the fibers. Has been done.

Therefore, in the present invention, the various electrolytic solutions described above are introduced into the cellulose fiber, particularly, an organic substituent that is easily compatible with γ-butyrolactone as a solvent is introduced, and if the electrolytic solution can easily penetrate into hydrogen bonding portions formed between fibrils or between fibers. As a result, the fibers themselves are swollen by the electrolytic solution, and at the same time, the binding force between the fibers in the electrolytic solution is weakened to increase the swelling of the electrolytic paper in the electrolytic solution.

As the chemical reaction for introducing the organic substituent, an etherification reaction, an esterification reaction or an acetalization reaction of the hydroxyl group contained in the cellulose fiber is used to facilitate the reaction. In addition, in the chemical reaction for introducing the organic substituent, it is necessary that the cellulose fiber retains the same fiber morphology as that before the reaction even after the reaction, and does not excessively dissolve in the electrolytic solution. Therefore, the chemical reaction for introducing these organic substituents is carried out under conditions that are reduced as compared with the reaction for producing a general cellulose derivative, and in the hydroxyl group substitution reaction, one of the hydroxyl groups contained in cellulose is Reaction conditions are preferred in which only parts are replaced. For example, most of the hydroxyl groups, such as 50% or more, are substituted (substitution degree DS =
1.5 or more), the resulting fiber may be brittle, or the fiber form may not be retained, and electrolytic paper may not be formed. Furthermore, when an electrolytic capacitor is manufactured using such fibers, most of the fibers are dissolved when the electrolytic paper is immersed in the electrolytic solution, causing a short circuit failure of the obtained electrolytic capacitor and the viscosity of the electrolytic solution. It also means that the ESR increases with the increase.

Substituents to be introduced into cellulose fibers are chlorine CL, bromine
Substituents that do not contain elements that cause corrosion of electrolytic capacitors such as Br and iodine I may be used, but if a substituent with a large proportion of carbon such as an alkyl group or an allyl group having 8 or more carbon atoms is introduced, the cellulose fiber becomes extremely hydrophobic. As a result, the strength of the electrolytic paper decreases, which may cause a trouble during the element winding process. In addition, the proportion of carbon is low, and the carboxyl group (-CO
It is not preferable to introduce a substituent having a dissociative polar group such as OH) or a sulfonic acid group (—SO ₃ H) because the swelling property decreases. Therefore, it is necessary to select the organic substituent introduced depending on the degree of polarity or hydrophilicity of the electrolytic solution. Preferably a hydroxyl group to an alkyl group, an ether group,
An organic substituent having one or more kinds such as an amino group, a nitrile group, an amide group, an imide group or a carbonyl group bonded thereto, and a substituent having an appropriate polarity is desirable. The particularly preferable chemical reaction examples are shown below.

(A) Esterification reaction (1) Reaction with acid chloride (2) Reaction with acid anhydride (3) Reaction with isocyanate (Note) R indicates any of CH ₃ , C ₂ H ₅ , and C ₃ H ₇ .

CELL indicates a cellulose chain.

(B) Etherification reaction (4) Reaction with halogenated alkyl group CELL-OH + RCL → CELL-OR (5) Reaction with dialkylsulfuric acid (Note) R indicates any of CH ₃ , C ₂ H ₅ , and C ₃ H ₇ .

CELL indicates a cellulose chain.

(6) Reaction with alkylene oxide (Note) R indicates any of H, CH ₃ , and C ₂ H ₅ . n represents an integer of 1 or more. CELL indicates a cellulose chain.

(7) Reaction with a benyl compound (Note) R indicates any of CN, CONH ₂ , OC ₂ H ₅ , COCH ₃ , and COC ₂ H ₅ .

CELL indicates a cellulose chain.

(C) Acetalization reaction (8) Reaction with aldehyde (Note) R represents any one of CH ₃ , C ₂ H ₅ , C ₃ H ₇ , and C ₄ H ₉ .

CELL indicates a cellulose chain.

As described above, it is preferable that a part of the hydroxyl group (OH) in the cellulose is replaced with the above-mentioned substitution device by utilizing the esterification reaction (A), the etherification reaction (B), and the acetalization reaction (C).
Further, the electrolytic paper used in the present invention does not need to be a paper composed only of cellulose fibers introduced with an organic substituent, and ordinary cellulose fibers or polypropylene fibers, polyester fibers, polyethylene synthetic pulp, polypropylene synthetic pulp, vinylon fibers, It may be a mixture of chemical fibers such as polyvinyl alcohol fibers and cellulose fibers introduced with an organic substituent. In the case of regenerated cellulosic fibers such as viscose rayon, cupra rayon or acetate, before being spun into fibers, organic substituents are introduced into the fibers at the raw material or manufacturing stage to form fibers.
You may make paper. Furthermore, regenerated cellulose films such as cellophane can introduce organic substituents by the same reaction as fibers, and similarly, the degree of swelling increases in the electrolytic solution. It can be used as.

It is preferable that the fibers introduced with the organic substituents as described above are appropriately beaten to form a base electrolytic paper in order to reduce the short circuit defective rate. As for the degree of beating, the CSF value is 700 when the thickness of the base electrolytic paper after papermaking is 50 to 60 μm.
ml or less, CSF value of 650 ml or less for 40 to 50 μm,
In case of 30-40μm, the value of CSF is 600ml or less, 20-30μ
When the value is m, the CSF value is 550 ml or less, and when it is 10 to 20 μm, the CSF value is 500 ml or less. Further, it is preferable that the thickness of the electrolytic paper as a base for papermaking is 60 μm or less and the density is 0.4 g / cm ³ or more.

In the present invention, the electrolytic paper of the group containing the cellulose fiber introduced with the organic substituent thus obtained is subjected to secondary processing after papermaking to form an appropriate number of convex portions on one surface, and the convex portion on the other surface. By forming recesses corresponding to the parts, an electrolytic paper having a substantially thicker thickness and a lower density than that at the time of papermaking can be obtained. The secondary processing after papermaking referred to in the present invention is the processing after the paper layer is formed by a method such as handmaking or mechanical papermaking, specifically, the fiber dispersion is poured into a net to form the paper layer. Processing is performed after formation.
Therefore, after the paper layer formed after papermaking is dried to form a base electrolytic paper, the base electrolytic paper is separately subjected to secondary processing by a processing machine to form an uneven portion for use in the present invention. Electrolytic paper may be obtained, on the other hand, secondary processing is performed in a wet paper state immediately after paper making to form a paper layer, and after forming irregularities on a paper machine, the wet paper is dried to obtain the present invention. The electrolytic paper used may be obtained. When the unevenness is formed by secondary processing in the wet paper state, it is difficult to measure the thickness and the density in the wet paper state. Therefore, the paper layer before and after the secondary processing was dried. After that, the degree of increase in thickness and the degree of decrease in density are measured. Further, the shape and arrangement of the concavo-convex portion forming the electrolytic paper are not particularly limited as long as the thickness of the electrolytic paper after the secondary processing can be substantially maintained at the time of winding the element.

The secondary processing method is not limited as long as it is a method capable of forming a convex portion and a concave portion, but a method capable of forming a convex portion and a concave portion by a single process such as embossing or creping is preferable.
Therefore, a method of forming projections and depressions through an embossing roll of the base electrolytic paper after papermaking, and further pressing a doctor knife against the wet paper in the press roll part of the paper machine, creping was performed in the wet paper state. A method such as post-drying is suitable.

The increase in thickness due to this secondary processing is preferably 10-300% of the thickness of the base electrolytic paper, and the amount of increase in thickness due to secondary processing is the thickness due to the swelling of the base electrolytic paper in the electrolytic solution. It is necessary not to exceed the increase in size. This is because if the increase in the thickness of the base electrolytic paper due to swelling in the electrolyte is less than the increase in the thickness due to the secondary processing, the electrolyte may leak from the capacitor element.

In addition, when the concave portion does not correspond to the convex portion,
It is also possible to increase the thickness by forming only a convex part on one side of the base electrolytic paper by laminating or laminating ultra-low density paper of 0.1 to 0.2 g / cm ³ and thickness of about 10 μm or paper with thread Is. Even when such uneven portions do not correspond or when only convex portions are formed, the electrolytic paper is substantially thickened, and the distance between the anode foil and the cathode foil is wide enough so that the electrolytic paper can swell sufficiently. Therefore, it is effective in improving the short-circuit defect rate and ESR.

Below, various examples of the electrolytic capacitor according to the present invention, comparative examples and the characteristics of the electrolytic capacitor such as its ESR and short circuit failure rate, and the results of measuring the swelling degree of the used electrolytic paper are shown. Each measured value of each sample was measured by the following measuring method and apparatus.

(1) Method for producing electrolytic capacitor Electrolytic paper is interposed between the tabbed anode foil and cathode foil so that both electrodes do not come in contact with each other and wound to form an electrolytic capacitor element, which is then impregnated with a predetermined electrolytic solution. By encapsulating it in a case and aging it with a normal method of 50 WV, 22
A 0 μm 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 C 2301 (electrolytic capacitor paper).

Swelling degree The swelling degree is obtained by stacking 10 sheets of electrolytic paper to make a test piece, and measuring its thickness with a dial thickness gauge (A μm), and then using γ-butyrolactone or a predetermined solvent or a predetermined electrolytic solution for the test piece. Soak for exactly 30 minutes. Then, the test piece was taken out, and the thickness was measured with a dial thickness gauge (B μm) in a wet state. For the dial thickness gauge, use a probe with a diameter of 10 mm.
The degree of swelling was calculated by the following formula.

(3) Evaluation Method of Electrolytic Capacitors Short Circuit Failure Rate After winding electrolytic paper with anode foil and cathode foil to form an electrolytic capacitor element, conduction by short circuit between both electrodes was confirmed with a tester without impregnating electrolytic solution. .
Short defect rate is inspected for 500-1000 elements,
The ratio of the short elements to the total number of elements was calculated.

ESR (Equivalent Series Resistance) The ESR of an electrolytic capacitor is LC at a frequency of 100HZ at a temperature of -40 ° C.
Measured by R meter.

Amount of Leakage of Electrolyte Solution After impregnating the electrolytic capacitor element with the electrolyte solution, the element was placed in a centrifuge and centrifuged to separate and remove the electrolyte solution easily leaking from the element. The weight difference between the elements before and after the centrifugation was measured and used as the amount of electrolyte leaked from the elements.

Example 1 100 kg of Manila hemp pulp was immersed in 0.5 m ^{3 of a} 2% NaOH aqueous solution, 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 the alkali-treated pulp, and the mixture was slowly stirred at 20 ° C. for 2 hours to cyanoethylate the hemp pulp. This cyanoethylated Manila hemp pulp was thoroughly washed with ion-exchanged water, beaten up to 270 ml of CSF with a beader, and further paper-made with a cylinder paper machine using ion-exchanged water as a water, thickness 27.9 μm, density 0.653 g / A cm ³ -based electrolytic paper was obtained.

Next, the electrolytic paper of this base is subjected to secondary processing with an embossing machine combining an engraving roll and a cotton roll to form a convex portion on one surface and a concave portion corresponding to the convex portion on the other surface. An electrolytic paper having a thickness of 50.2 μm and a density of 0.385 g / cm ³ was obtained. Then, 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 Ω · cm (20 ° C).

Comparative Example 1 An aluminum electrolytic capacitor was manufactured by using the electrolytic paper having a thickness of 29.7 μm and a density of 0.653 g / cm ³ obtained in Example 1 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 200 Ω · cm (20 ° C).

(Comparative Example 2) The cyanoethylated Manila hemp pulp obtained by treating in the same manner as in Example 1 was thoroughly washed with ion-exchanged water and then with a beater.
The CSF was beaten to 680 ml, and ion-exchanged water was used as water for papermaking with a cylinder paper machine.
An electrolytic paper having the same density and a thickness of 50.7 μm and a density of 0.389 g / cm ³ was obtained.

Then, using this electrolytic paper, an aluminum electrolytic capacitor was manufactured. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone to increase the specific resistance.
It is adjusted to 200 Ω · cm (20 ° C).

(Comparative Example 3) Manila hemp pulp was thoroughly washed with ion-exchanged water, beaten to 280 ml of CSF with a beater, and further ion-exchanged water was used as water for papermaking with a cylinder paper machine to give a thickness of 29.5 μm.
A base electrolytic paper having a density of 0.650 g / cm ³ was obtained.

Next, the electrolytic paper of this base was secondarily processed by an embossing machine combining the same engraving roll and cotton roll as in Example 1 to form a convex portion on one surface and the convex portion on the other surface. Correspondingly formed recesses, thickness 49.7μm, density 0.386g
An electrolytic paper having the same thickness and the same density as in Example 1 having a density of / cm ³ 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 to obtain a specific resistance of 200.
It is adjusted to Ω · cm (20 ° C).

(Example 2) 100 kg of softwood wood pulp was immersed in 0.5 m ^{3 of a} 2% NaOH aqueous solution, and then squeezed with a screw press to remove excess NaOH aqueous solution to a pulp concentration of 40%. The alkali-treated pulp was placed in a stainless steel pressure resistant container, and the air in the container was replaced with nitrogen gas. Then 1,2-butylene oxide 5
Put 0 kg in a container and seal it, let it react at 90 ℃ for 60 minutes,
Softwood wood pulp was hydroxybutylated. After thoroughly washing the hydroxybutylated softwood wood pulp with ion-exchanged water, use a double disc refiner to remove CSF 5 ml.
The solution was beaten to the following conditions and further paper-made with a Fourdrinier paper machine using ion-exchanged water to obtain a base electrolytic paper having a thickness of 20.4 μm and a density of 0.855 g / cm ³ .

Next, this base electrolytic paper was subjected to secondary processing with an embossing machine combining an engraving roll and a cotton roll to form a convex portion on one surface and a concave portion corresponding to the convex portion on the other surface. An electrolytic paper having a thickness of 50.6 μm and a density of 0.345 g / cm ³ was obtained. An aluminum electrolytic capacitor according to the present invention was manufactured using this electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of dimethylformamide 50% and ethylene glycol 50% to obtain a specific resistance of 200 Ω · c.
It is adjusted to m (20 ℃).

Comparative Example 4 An aluminum electrolytic capacitor was manufactured by using the electrolytic paper having a thickness of 20.4 μm and a density of 0.855 g / cm ³ obtained in Example 2 as the electrolytic paper as it was without secondary processing. The impregnated electrolytic solution was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol to adjust the specific resistance to 200 Ω · cm (20 ° C).

(Comparative Example 5) Hydroxybutylated softwood wood pulp obtained by treating in the same manner as in Example 2 was thoroughly washed with ion-exchanged water, and then unbeaten (CSF700 ml) using ion-exchanged water as water to make a cylinder paper. Papermaking was carried out by a machine to obtain electrolytic paper having substantially the same thickness as in Example 2, the same density as 50.1 μm and a density of 0.348 g / cm ³ .

Then, using this electrolytic paper, an aluminum electrolytic capacitor was manufactured. The impregnated electrolytic solution was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol to obtain a specific resistance of 200 Ω · cm.
It is adjusted to (20 ℃).

Comparative Example 6 After softwood wood pulp was thoroughly washed with ion-exchanged water,
The mixture was beaten with a double disc refiner to a CSF of 5 ml or less, and further paper-made with a Fourdrinier paper machine using ion-exchanged water as water to obtain a base electrolytic paper having a thickness of 20.2 μm and a density of 0.848 g / cm ³ . Next, the electrolytic paper of this base was subjected to secondary processing by an embossing machine combining the same engraving roll and cotton roll as in Example 2 to form a convex portion on one surface and the convex portion on the other surface. Correspondingly formed recesses, thickness 49.8 μm, density 0.
344 g / cm ³ of electrolytic paper having substantially the same thickness and density as in Example 2 was obtained.

Then, using this electrolytic paper, an aluminum electrolytic capacitor was manufactured. The impregnated electrolytic solution was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol to obtain a specific resistance of 200 Ω · cm.
It is adjusted to (20 ℃).

Example 3 100 kg of acetic anhydride was added to 20 kg of Manila hemp pulp and reacted at 120 ° C. for 2 hours while stirring to acetylate the Manila hemp pulp. This acetylated Manila hemp pulp was centrifuged, taken out from the reaction solution, thoroughly washed with ion-exchanged water, beaten to CSF 530 ml with a beater, and further paper-made with a cylinder paper machine using ion-exchanged water as water, Thickness 40.4
A base electrolytic paper having a thickness of μm and a density of 0.509 g / cm ³ was obtained.

Then, the base is processed with an embossing machine that combines an electrolytic paper with an engraving roll and a cotton roll to form a convex portion on one surface and a concave portion corresponding to the convex portion on the other surface,
An electrolytic paper having a thickness of 50.1 μm and a density of 0.410 g / cm ³ was obtained. Then, 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 200 Ω · cm (20 ° C).

Comparative Example 7 An aluminum electrolytic capacitor was manufactured by directly using the electrolytic paper having a thickness of 40.4 μm and a density of 0.509 g / cm ³ obtained in Example 3 as the electrolytic paper without secondary processing. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the specific resistance to 200 Ω · cm (20 ° C).

(Comparative Example 8) Acetylated Manila hemp pulp obtained by treating in the same manner as in Example 3 was thoroughly washed with ion-exchanged water, and then CSF6 was added with a beader.
It was beaten to 70 ml, and further ion-exchanged water was used as water for papermaking with a cylinder paper machine to obtain an electrolytic paper having substantially the same thickness as in Example 3, a density of thickness 50.4 μm, and a density of 0.406 g / cm ^3. It was Next, an aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide to obtain a specific resistance of 200.
It is adjusted to Ω · cm (20 ° C).

(Comparative Example 9) Manila hemp pulp was thoroughly washed with ion-exchanged water, beaten to a CSF of 530 ml with a beater, and further ion-exchanged water was used as water for papermaking with a cylinder paper machine to give a thickness of 40.5 μm.
A base electrolytic paper having a density of 0.507 g / cm ³ was obtained. Then, this base electrolytic paper was processed by an embossing machine combining the same engraving rolls and cotton rolls as in Example 3 to form convex portions on one surface and corresponding to the convex portions on the other surface. forming a recess to give thickness 50.2Myuemu, example 3 and substantially the same thickness of the density of 0.408 g / cm ^3, the electrolytic paper of the same density. An aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the specific resistance to 200 Ω · cm (20 ° C).

Example 4 100 kg of Manila hemp pulp was immersed in 0.5 m ^{3 of a} 5% NaOH aqueous solution, and then pressed with a screw press to remove excess NaOH aqueous solution to a pulp concentration of 40%. 70 kg of acrylonitrile was added to the alkali-treated pulp, and the mixture was slowly stirred at 20 ° C. for 2 hours to cyanoethylate the hemp pulp. This cyanoethylated Manila hemp pulp was thoroughly washed with ion-exchanged water and then beaten to 460 ml of CSF with a beater. Next, paper was made using ion-exchanged water with a cylinder paper machine equipped with a doctor blade on the press roll portion. When making this paper, press the doctor blade against the wet paper with the press roll, crepe the wet paper on the paper machine, and then dry it to obtain a base electrolytic paper with a thickness of 40.2 μm and a density of 0.304 g / cm ^3. Obtained. The thickness of the electrolyte obtained by papermaking under the same conditions without pressing the doctor blade and without creping was 29.4μ.
m, density 0.413 g / cm ³ , which is equivalent to the base electrolytic paper.

Then, 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 Ω · cm (20 ° C).

(Comparative Example 10) A thickness of 29.4 μm obtained without creping in Example 4,
An aluminum electrolytic capacitor was manufactured by directly using the electrolytic paper having a density of 0.413 g / cm ³ as the electrolytic paper without secondary processing. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone to obtain a specific resistance of 200.
It is adjusted to Ω · cm (20 ° C).

(Comparative Example 11) Cyanoethylated Manila hemp pulp obtained by treating in the same manner as in Example 4 was thoroughly washed with ion-exchanged water, and then washed with a beater.
It was beaten to 690 ml of CSF and further paper-made with a cylinder paper machine using ion-exchanged water as water to obtain an electrolytic paper having substantially the same thickness as Example 4, a thickness of 40.6 μm and a density of 0.301 g / cm ³ . .

Then, using this electrolytic paper, an aluminum electrolytic capacitor was manufactured. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone to increase the specific resistance.
It is adjusted to 200 Ω · cm (20 ° C).

(Comparative Example 12) Manila hemp pulp was thoroughly washed with ion-exchanged water and then beaten with a beader to 450 ml of CSF. Then, a cylinder paper machine equipped with a doctor blade on the press roll portion was used to make paper using ion-exchanged water as water. In this papermaking process, a doctor blade was pressed against the wet paper web with a press roll, the wet paper web was creped on the paper machine, and then dried.
Thickness of 40.5μm and density of 0.303g / c
An m ³ -based electrolytic paper was obtained. The thickness of the electrolytic paper obtained by making paper under the same conditions without pressing the doctor blade and without creping is 29.8 μm and the density is 0.413 g / cm ³ , which is equivalent to the basic electrolytic paper. It is a thing.

An aluminum electrolytic capacitor was manufactured using this electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone to give a specific resistance of 200Ω.
・ Adjusted to cm (20 ℃).

The electrolytic paper obtained by using the electrolytic paper of the base before secondary processing used in Examples 1, 2, 3, 4 and Comparative Examples 3, 6, 9, 12 obtained as described above was used as an electrolytic solution and other electrolytic solutions. The swelling degree was measured by immersing it in a solvent. The results are shown in Table 1 together with the thickness and density of the base electrolytic paper before secondary processing.

Table 1 shows the thickness, density, and swelling degree of the electrolytic solution of the base before secondary processing, which have substantially the same thickness and the same density, in Examples and Comparative Examples. ,
Nos. 3 and 4 are those containing cellulose fibers introduced with an organic substituent to increase the degree of swelling in an electrolytic solution, and Comparative Examples 3, 6, 9 and 12 are ordinary electrolytic papers.

Comparative Example 3 has a swelling degree of 53.6% with respect to dimethylformamide, which has been often used as a solvent for an electrolytic solution, and 38.6% with respect to ethylene glycol. for that reason,
In order to improve ESR only by conventional secondary processing, it is necessary to keep the range of increase in thickness by secondary processing within the range of this swelling, and within this range, a sufficient effect is exhibited. However, 0.1% was added to the electrolytic solution in which ammonium borodisalicylate was dissolved in γ-butyrolactone, which has been attracting attention recently, and the specific resistance was adjusted to 200 Ω · cm (20 ° C).
As a result, not only does the swelling hardly occur and the ESR does not decrease due to the secondary processing, but also an excessive amount of electrolyte stays and leaks between the uneven parts and the electrodes that do not swell. In addition, even with γ-butyrolactone alone, the swelling rate is 0.1%, which is almost non-swelling. Therefore, Comparative Example 3 cannot be used for an electrolytic solution containing γ-butyrolactone as a solvent.

On the other hand, in Example 1, the swelling degree was remarkably increased to 76.0% with respect to the electrolytic solution, and the density of the electrolytic paper was substantially reduced.
Further, it also remarkably swelled in the same manner as 75.2% with respect to only γ-butyrolactone which is the solvent of the electrolytic solution. Therefore, according to Example 1, even when an electrolytic paper having a thickness greater than that at the time of paper making by secondary processing is used for an electrolytic solution using γ-butyrolactone as a solvent, the electrolytic solution causes swelling and uneven portions. ESR can be improved and reduced since the

53.6% to 118.4% for dimethylformamide
%, The degree of swelling also increases remarkably with respect to the solvent of other electrolytes, such as increasing the degree of swelling. The range in which the thickness increases due to secondary processing can be expanded to this increased range. It is a thing. This is exactly the same in the corresponding Example 2 and Comparative Example 6, Example 3 and Comparative Example 9 and Example 4 and Comparative Example 12, respectively. Therefore, the electrolytic paper of the base before the secondary processing according to the example containing the cellulose fiber having the organic substituent introduced, the swelling degree is remarkable as compared with the comparative example which is the electrolytic paper of the conventional group. As a result, the density after impregnation with the electrolytic solution is substantially reduced.

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

In Table 2, Example 1 contains the cellulose fiber introduced with the organic substituent according to the present invention to increase the degree of swelling and to increase the thickness and reduce the density by the secondary processing after paper making, Compared with Comparative Example 3 having substantially the same thickness and the same density only in the secondary processing, the good short-circuit defect rate of 0.8% was maintained, and the ESR was greatly reduced from 1.76Ω to 0.51Ω. Then, according to Example 1, since the uneven portion formed on the electrolytic paper by swelling completely disappeared and became the thickness after the secondary processing, the leakage amount of the electrolytic solution was changed from 0.35 g of Comparative Example 3 to 0.04 g. is decreasing.

In Comparative Example 1, the base electrolytic paper before secondary processing of Example 1 was used as it was, and it had a high density of 0.653 g / cm ³ , but it was as thin as 29.7 μm, so the short-circuit failure rate was 3.6%. It has a large size and has a sufficient swelling capacity by containing a cellulose fiber introduced with an organic substituent, but since it is as thin as 29.7 μm, there is not a sufficient gap between the anode foil and the cathode foil for swelling. Therefore, the ESR is 0.22Ω. In contrast,
According to Example 1 in which Comparative Example 1 was subjected to secondary processing so that the thickness thereof was substantially thicker than that at the time of papermaking and the density was reduced,
The short-circuit defect rate was reduced to 0.8%, and the ESR was remarkably improved to 0.51Ω because the swelling gap was sufficiently taken as the thickness increased.

On the other hand, in Comparative Example 2, papermaking was carried out in Example 1 without secondary processing.
ESR is 0.48, which is lower than that in Example 1, but has a short circuit failure rate of 5.7.
%, Which is extremely poor, the ESR and the short-circuit defect rate are not well balanced, and the short-circuit defect rate is sacrificed, which is not practical. This is 0.389 g only with papermaking
This is because it is necessary to make paper with the CSF value of 680 ml, which is almost unbeaten in order to achieve a low density of / cm ³ . On the other hand, according to Example 1, the thickness was increased from 29.7 μm at the time of paper making to 50.2 μm by the secondary processing, and as a result, the density was also reduced from 0.653 g / cm ³ to 0.385 g / cm ^3. Because
Since the degree of beating can be increased to 270 ml, the short-circuit failure rate can be dramatically reduced by 0.8% along with ESR.

Therefore, according to the first embodiment of the present invention, the electrolytic paper can be surely swelled to the thickness after the secondary processing, the ESR can be improved, and the swelling can be made, as compared with the case where only the secondary processing is performed. Both the short-circuit defect rate and ESR can be improved and reduced at a high level at the same time as compared with the case of only one.

This is true even in the relationship between Example 2 and Comparative Examples 2, 3, 4 and Example 3 and Comparative Examples 7, 8 and 9 which are in the same relationship as Example 1 and Comparative Examples 1, 2 and 3. It is represented as data.

On the other hand, Example 4 also contains the organic substituent-introduced cellulose fiber of the present invention to increase the degree of swelling and to increase the thickness and reduce the density by secondary processing after papermaking. Examples 1, 2 and 3 are examples in which the specific secondary processing method is different. That is, Example 1,
2 and 3 are obtained by forming a paper layer on a paper machine and then drying it to obtain a base electrolytic paper, which is then subjected to secondary processing with an embossing machine that is a combination of an engraving roll and a cotton roll.
In Example 4, when the wet paper web was used, a doctor blade was pressed against the press roll to perform crepe processing on a paper machine and then dried. Comparative Example 12 corresponding to Example 4 showing only the secondary processing is also subjected to the same crepe processing.

Also in this Example 4, the short-circuit failure rate was 15.8% as compared with Comparative Example 10 in which the base electrolytic paper before secondary processing was used as it was.
To 6.3%, the ESR is improved and decreased from 0.54Ω to 0.43Ω, and the same result as the relationship between Example 1 and Comparative Examples 1, 2 and 3 described above is shown as a numerical value. Therefore, it is clearly shown as data that the secondary processing method in the present invention is not limited as long as it is a method capable of forming a convex portion and a concave portion.

Effects of the Invention According to the present invention described in detail above, by using an embossed paper as an electrolytic paper by secondary processing after papermaking, a raw material having a small CSF as compared with an electrolytic paper of the same density by papermaking alone, a low It is possible to obtain a thick electrolytic paper with a high density, and since it contains cellulose fibers introduced with organic substituents, the degree of swelling with respect to the impregnated electrolytic solution is significantly increased. Sufficient swelling up to the later thickness and a decrease in the actual density, resulting in a short defect rate and ES
Both R can be improved and reduced at the same time. Therefore, compared with the conventional electrolytic paper only secondary processing, even if the range of increase in thickness by secondary processing is large, it can easily swell to the thickness after secondary processing, and due to insufficient swelling ESR can be improved and reduced without leakage of electrolyte. Further, since it hardly swells, it can be used in an electrolytic solution using γ-butyrolactone as a solvent, which could not be used in conventional electrolytic papers only for secondary processing, and has good low temperature characteristics and workability. ESR can be improved by taking advantage of the characteristics of the electrolytic solution using γ-butyrolactone as a solvent. Furthermore, in contrast to the conventional electrolytic paper that only contains cellulose fibers introduced with organic substituents, the thickness of the electrolytic paper is increased by secondary processing to allow the electrolytic paper to swell sufficiently between the anode foil and the cathode foil. Since it can be secured as widely as possible, the ESR can be further improved and reduced.

That is, the present invention is capable of increasing the degree of the secondary processing and the range of effectiveness and increasing the degree of the degree of swelling, and improves both the ESR and the short-circuit defect rate at a higher level. It can be realized at the same time.
Further, according to the present invention, the wettability and the holding property of the electrolytic paper with respect to the electrolytic solution are improved, and the amount of the impregnated electrolytic solution is necessarily increased. Capacitor can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embossing method, FIG. 2 is an explanatory view showing an electrolytic paper after embossing, FIG. 3 is an explanatory view showing an element winding state before impregnation with an electrolytic solution, and FIG. It is explanatory drawing which shows the element winding state after liquid impregnation.

Claims (1)

[Claims] 1. An electrolytic capacitor comprising an electrolytic paper interposed between an anode foil and a cathode foil impregnated with a predetermined electrolytic solution, wherein the electrolytic paper has a convex portion on one surface by secondary processing after papermaking. By forming an appropriate number, by using the embossed paper in which the concave portion is formed on the other surface corresponding to the convex portion, the thickness is substantially thicker than at the time of paper making, and the density is reduced, By swelling to at least the thickness after the secondary processing with respect to the electrolytic solution by containing a fiber introduced with an organic substituent by an etherification reaction, an esterification reaction or an acetalization reaction of the hydroxyl group contained in the cellulose fiber The electrolytic capacitor is characterized by increasing the degree of swelling.