JP2019102649A - Separator for solid electrolytic capacitor or hybrid electrolytic capacitor, and solid electrolytic capacitor or hybrid electrolytic capacitor - Google Patents

Abstract

To provide a separator for an aluminum electrolytic capacitor, achieving a reduction in ESR and an improvement in capacitance furthermore in comparison with conventional examples, and an aluminum electrolytic capacitor.SOLUTION: A separator for an aluminum electrolytic capacitor is interposed between a pair of electrodes and is made of cellulose fibers and synthetic fibers. The separator contains 40-80 mass% of the cellulose fibers and 20-60 mass% of the synthetic fibers, and has a porosity of 65-85% and a compression impregnation rate of 30% or more. An aluminum electrolytic capacitor including a separator interposed between a pair of electrodes includes, as the separator, the separator for an aluminum electrolytic capacitor.SELECTED DRAWING: None

Description

  The present invention relates to a separator for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor using the separator.

  Recently, the performance of electronic devices such as personal computers (hereinafter referred to as "PCs"), home-use game consoles and automobile electrical equipment has been significantly improved, and at the same time, miniaturization of these devices etc. There is. Therefore, there is an increasing need for miniaturization of parts mounted on electronic circuit boards and the like used for these.

  An aluminum electrolytic capacitor (hereinafter referred to as "solid electrolytic capacitor") using a conductive polymer as a cathode material has better ESR (equivalent series resistance) characteristics than an aluminum electrolytic capacitor using an electrolytic solution as a cathode material. Due to the fact that the number can be reduced by reducing the number, it is used in personal computers and game machines. In addition, in personal computers and the like, it is required to increase the speed and functionality of the CPU, and the operating frequency is further increased.

  The conduction mechanism of the aluminum electrolytic capacitor using the electrolytic solution is ion conduction, but the conduction mechanism of the solid electrolytic capacitor is electron conduction and exhibits high conductivity. That is, since the response to release the stored electrons is good, the ESR characteristic is low, and there is a merit as a capacitor used around the CPU in the power supply circuit.

  In recent years, conductive polymer hybrid aluminum electrolytic capacitors (hereinafter referred to as "hybrid electrolytic capacitors"), which use a conductive polymer and an electrolytic solution as cathode materials, have been marketed by capacitor manufacturers. It has also been used in automotive electrical equipment applications where low ESR characteristics and no short circuit defects are essential requirements.

  As a method of holding the conductive polymer which is a cathode material in the capacitor element, there are a method of polymerizing the conductive polymer in the capacitor element and a method of impregnating the capacitor element with the conductive polymer polymerized in advance. is there.

  In the case of polymerizing a conductive polymer in a capacitor element, a solution containing a monomer and an oxidizing agent (hereinafter referred to as "polymer solution") is impregnated into the capacitor element, heated, dried and polymerized to form a conductive polymer. A layer is formed in the capacitor element.

  When impregnating a conductive polymer that has been polymerized in advance, a suspension (hereinafter referred to as a "dispersion liquid") in which the conductive polymer is dispersed in water is impregnated into a capacitor element, heated and dried, and then conductive. A polymer layer is formed in the capacitor element.

  In either case of the polymerization liquid or the dispersion liquid, the quality of the formation state of the conductive polymer layer inside the capacitor element determines the characteristics of the solid electrolytic capacitor and the hybrid electrolytic capacitor.

  In particular, in recent years, with the progress of electrification of automobiles, the number of Electronic Control Units (hereinafter referred to as "ECUs"), which are electronic control devices for controlling various functions of automobiles, tends to increase. Furthermore, due to an increase in products installed in the vehicle compartment, such as car navigation systems and airbag systems, ECUs and the like that were conventionally mounted in the vehicle compartment will be expelled out of the vehicle exterior, and with the miniaturization of boards There is also a need to implement the highest density mounting in the limited space. For this reason, the parts to be mounted are also required to be downsized and to have high functionality. In order to meet these requirements, further reduction in ESR and improvement in capacitance are required also in solid electrolytic capacitors and hybrid electrolytic capacitors, which are one of the components mounted in ECUs and the like.

  Until now, the technique described, for example in patent documents 1-8 is disclosed as a separator for solid electrolytic capacitors and hybrid electrolytic capacitors.

JP, 2015-15312, A Unexamined-Japanese-Patent No. 2004-165593 JP 2004-235293 A JP, 2013-197297, A JP, 2011-228320, A JP, 2016-115730, A JP, 2013-246926, A JP, 2013-157230, A

  Patent Document 1 contains 35% by weight or more of pulp made of seed wool fibers such as cotton linters or the like having an α-cellulose content of 94% or more, dissolved pulp, or mercerized pulp. A separator having a low swelling ratio to the electrolyte has been proposed. By using this separator, there is disclosed a technology for providing an aluminum electrolytic capacitor in which the electrolyte impregnation property is significantly improved and the impedance characteristic is improved.

  However, the separator as disclosed in Patent Document 1 is composed only of cellulose fibers, and when impregnated with a polymer or dispersion of a conductive polymer used in a solid electrolytic capacitor, the cellulose fibers are gradually decomposed under acidic conditions Therefore, the decrease in mechanical strength of the separator may be remarkable, or the reaction of the cellulose fiber with the oxidizing agent of the polymerization liquid may inhibit the polymerization of the conductive polymer. For this reason, when the mechanical strength of the separator is lowered, the short failure of the solid electrolytic capacitor may be increased, or the ESR of the solid electrolytic capacitor may be deteriorated.

  Temporarily, in order to avoid the fall of the mechanical strength with respect to the polymerization liquid of the conductive polymer, and the dispersion liquid of the separator of patent document 1, when synthetic fiber is mix | blended, a cellulose fiber is intervened by the synthetic fiber being interposed between cellulose fibers. By inhibiting the hydrogen bond between each other, the mechanical strength of the separator may be reduced, and there may be a problem that breakage or the like may occur at the time of forming the separator or at the time of forming the capacitor element.

  Patent Document 2 proposes a separator containing fibers made of a semi-aromatic polyamide resin and having a good compatibility with a conductive polymer. By using this separator, there is disclosed a technology for providing a solid electrolytic capacitor having improved electrolyte retention and improved ESR characteristics of an aluminum electrolytic capacitor.

  However, in recent years, even in a solid electrolytic capacitor using a separator having good compatibility with a conductive polymer as disclosed in Patent Document 2, further reduction in ESR and improvement in capacitance are required, and the separator is required to be used. There is a demand for further improvement of the impregnation.

  Further, Patent Document 3 proposes a separator having a non-fibrillated organic fiber and a fibrillated polymer having a melting point or a thermal decomposition temperature of 250 ° C. or more as a synthetic fiber and having a water absorption speed of 5 mm / min or more. There is. In Patent Document 3, by using a very thin fibrillated polymer having a large aspect ratio, the number of fibers in the separator is significantly increased, and at the same time, the frequency of entanglement between fibrils and other fibers is increased to achieve compactness. Discloses a technique for forming a non-woven fabric with small pores. And, by using this separator, the formation of the conductive polymer in the solid electrolytic capacitor becomes uniform, and a technology for providing a low resistance solid electrolytic capacitor is disclosed.

  However, a solid electrolytic capacitor using a separator having a high water absorption rate as described in Patent Document 3 exhibits low ESR characteristics, but as described above, since the separator is dense and the pores are small, the polymer electrolyte of conductive polymer or It is difficult to further improve the impregnation of the dispersion, which makes it difficult to further reduce the ESR and improve the capacitance of the solid electrolytic capacitor. If the density of the separator of Patent Document 3 is lowered to increase the proportion of non-fibrillated organic fibers for the purpose of reducing ESR and improving the capacitance, the density of the separator will be lowered. The burrs and the like of the foil easily penetrate the separator, and the solid electrolytic capacitor using this separator has a high short failure rate.

  Patent Document 4 proposes a separator in which the ratio of fiber orientation is 2.0 or less. By using this separator, the liquid absorption degree of the polymer and the dispersion liquid of the conductive polymer from the lateral direction of the separator is improved. By using this separator, an electrolytic capacitor having an improved ESR and capacitance. A technology for providing

  However, there is a limit to reducing the ratio of fiber orientation, so it is difficult to further reduce the ESR and improve the capacitance of the solid electrolytic capacitor.

  Furthermore, Patent Document 5 describes a separator comprising solvent-spun cellulose fibers having a modified freeness of 0 to 250 ml and synthetic short fibers, and adjusting the density of the separator based on the specific gravity of the separator to obtain pores. Separators having a rate of 60 to 86% have been proposed. A solvent-spun cellulose fiber having a modified freeness of 0 to 250 ml has a thin fiber diameter and high uniformity, so a conductive polymer is uniformly formed on the separator, and this separator is excellent in the carrying property of the conductive polymer. Discloses a technique for providing a solid electrolytic capacitor with reduced ESR.

  However, the separator as in Patent Document 5 has very high compactness, and it is difficult to further improve the impregnating property of the polymerization liquid or dispersion liquid of the conductive polymer. For this reason, also in the solid electrolytic capacitor using the separator of Patent Document 5 having a good supporting property of the conductive polymer, further reduction of ESR and improvement of electrostatic capacity are required in recent years.

  Here, when the composition of the synthetic short fiber is increased for the purpose of reducing the fineness of the separator and reducing the ESR and improving the capacitance, the fineness is low, and the burrs of the electrode foil, etc. Is likely to penetrate the separator, and the solid electrolytic capacitor using this separator has a high short failure rate.

  Further, Patent Document 6 proposes a separator having a high liquid retention rate and a high compression liquid retention rate among separators made of synthetic fibers and synthetic pulp. Since this separator is excellent in the ability to hold an electrolytic solution, there is disclosed a technology for providing an electric double layer capacitor with low internal resistance by using this separator.

  However, Patent Document 6 is a separator in view of the fact that the electrolytic solution is released when the separator is compressed at the time of crimping after the electrolytic solution impregnation. That is, although the separator of Patent Document 6 has good retention of the electrolytic solution after completion of the capacitor, it does not improve the impregnatability at the time of production of the capacitor. Further, the separator of Patent Document 6 is a separator for an electric double layer capacitor, and the electrolyte used is different from that of the solid electrolytic capacitor. For this reason, if this separator is temporarily applied to a solid electrolytic capacitor, the impregnating property to a polymer solution or dispersion liquid of a conductive polymer is poor, and a solid electrolytic capacitor using such a separator has a reduced ESR and The improvement effect of the capacitance was not a satisfactory result.

  Furthermore, in Patent Document 7, in a separator comprising synthetic short fibers and cotton pulp as essential components, the modified freeness of cotton pulp is 90 to 160 ml, and the length weighted average fiber length is 0.80 to A separator having good electrolytic solution permeability of 1.20 mm and excellent in compactness has been proposed.

  Patent Document 7 controls the length-weighted average fiber length and modified freeness by highly refining intrinsically long cotton lint pulp. For this reason, the cotton pulp becomes soft due to internal and external fibrillation, and the interstices inside and between the fibers are clogged to significantly improve the compactness and strength of the separator. On the other hand, the internal porosity of the separator is also reduced due to the increase in the compactness of the separator, so the impregnation of the conductive polymer polymerization liquid or dispersion liquid can not be improved more than a certain level. For this reason, there is also a limit to improving the impregnation property of the polymerization liquid and the dispersion liquid of the solid electrolytic capacitor using this separator, and it is difficult to further reduce the ESR and improve the electrostatic capacity of the solid electrolytic capacitor. Here, when the blending ratio of the synthetic short fiber is increased in order to improve the impregnation property of the polymerization liquid and the dispersion liquid of the conductive polymer, the fineness is lowered and the burrs of the electrode foil and the like easily penetrate the separator. Thus, the solid electrolytic capacitor using this separator has a high short circuit failure rate.

  Furthermore, Patent Document 8 proposes a separator which is composed of cellulose fibers and alkali-resistant synthetic fibers and in which the cellulose fibers contain dissolved pulp, and which can suppress the property deterioration after long-term storage. It is done.

  However, Patent Document 8 is an alkaline battery separator, and when it is used for a solid electrolytic capacitor, the thickness is large, and there may be a case where it can not meet the demand for miniaturization as described above. If the separator of Patent Document 8 is made to have a thickness required for downsizing of a solid electrolytic capacitor, the reduction in thickness reduces the amount of deposited fibers and weakens the mechanical strength of the separator. As a result, at the time of forming the separator or forming the capacitor element, there arises a problem that breakage or the like occurs. Here, when the blending of polyvinyl alcohol fibers conventionally used as a binder for an alkaline battery separator is increased in order to strengthen the mechanical strength of the separator, the polyvinyl alcohol fibers form a gap between fibers constituting the separator. As a result, the impregnation property of the polymerization liquid or dispersion liquid of the conductive polymer is deteriorated, and the solid electrolytic capacitor using such a separator has the effect of reducing the ESR and improving the capacitance. It was not a satisfactory result.

  A separator consisting only of cotton linter pulp, dissolving pulp and mercerized pulp is a polymer liquid of a conductive polymer although its impregnating ability is high because its constituent fibers are bulky fibers or fibers with high rigidity. And there is a problem that the resistance to the dispersion is weak, and there is a problem that when synthetic fibers are blended to solve the problem, the mechanical strength becomes weak.

  In order to blend synthetic fibers and improve mechanical strength, it is conceivable to increase the thickness, blend binder fibers, highly beat cellulose fibers, etc. In any case, it is possible to improve mechanical strength. In exchange for this, problems such as the inability to meet the demand for miniaturization and a decrease in the impregnation of the polymer and dispersion liquid of the conductive polymer occur, and the ESR is further reduced in recent years and the capacitance is improved in recent years. It can not meet the demand.

  As described above, the conventional separator has all the resistance to the polymerization liquid or dispersion liquid of the conductive polymer, the mechanical strength, and the thickness required for the solid electrolytic capacitor, and the polymerization liquid or dispersion liquid of the conductive polymer And the inability to meet the further reduction of ESR and the improvement of capacitance, which are required in recent years.

  The present invention has been made in view of the above problems, and maintains mechanical strength at a thickness required for a solid electrolytic capacitor while having resistance to a polymerization liquid or a dispersion liquid of a conductive polymer, and It is an object of the present invention to provide an aluminum electrolytic capacitor separator and an aluminum electrolytic capacitor, which realize further reduction of ESR and improvement of electrostatic capacity by improving the impregnating property of a polymerization liquid or dispersion liquid of a conductive polymer. .

  The present invention has, for example, the following configuration as a means for solving the problems described above and achieving the above object.

  That is, the present invention is a separator for an aluminum electrolytic capacitor, which is interposed between a pair of electrodes, and the separator comprises cellulose fiber and synthetic fiber, and 40 to 80% by mass of the cellulose fiber, the synthetic fiber 20 to 60% by mass, and the porosity is 65 to 85%, and the compression impregnation rate is 30% or more.

  And For example, the said separator contains a total of 10-50 mass% of unbeaten cellulose fibers selected from at least one or more among unbeaten cotton linter pulp, unbeaten mercerized pulp, and unbeaten dissolving pulp as the cellulose fiber It is characterized by

  Furthermore, for example, the separator is characterized in that it contains 10 to 70% by mass of beaten cellulose fiber. Also, for example, the thickness of the separator is 20 to 100 μm.

  The aluminum electrolytic capacitor of the present invention is characterized in that the above-mentioned separator for an aluminum electrolytic capacitor is used as a separator. The aluminum electrolytic capacitor is characterized in that a conductive polymer is used as a cathode material.

  The separator of the present invention maintains mechanical strength at a thickness required for a solid electrolytic capacitor while having resistance to a polymerization liquid or dispersion liquid of a conductive polymer, and also in a state where the separator is compressed, The internal structure of the separator can be controlled so as to appropriately maintain the gap between the fibers, and the impregnation property of the polymerization liquid or dispersion liquid of the conductive polymer can be improved.

  Moreover, the aluminum electrolytic capacitor of the present invention can uniformly form the conductive polymer layer up to the inside of the capacitor element even in the compressed state by using the above-mentioned separator. Thereby, the ESR of the solid electrolytic capacitor can be greatly reduced, and the electrostatic capacitance can be greatly improved.

It is a figure which shows the model of the modal method used for the threshold value decision at the time of binarizing the picked-up image of the separator which concerns on this invention.

  In a separator for an aluminum electrolytic capacitor, mechanical strength is maintained at a thickness required for a solid electrolytic capacitor while having resistance to a polymer solution or a dispersion liquid of the conductive polymer, and a polymer solution of the conductive polymer In order to improve the impregnation of dispersion and dispersion, and to further reduce the ESR of the capacitor and to improve the capacitance, the separators originally possessed from the time of separator formation to the time of use for separators consisting of cellulose fibers and synthetic fibers It is important to form the conductive polymer layer uniformly to the inside of the capacitor element when the internal structure is maintained and the polymerizing liquid or dispersion liquid of the conductive polymer is impregnated.

  The inventors of the present invention conducted intensive studies on the reduction of ESR and the improvement of capacitance, and as a result, in a separator containing a cellulose fiber and a synthetic fiber, when a polymerization liquid or a dispersion liquid of a conductive polymer is impregnated. It is necessary to form the conductive polymer layer uniformly to the inside of the capacitor element, and for that purpose, it has an internal structure capable of impregnating the polymerization liquid or dispersion liquid of the conductive polymer to the inside of the separator, Even when the separator between the two electrode foils is compressed from the time of formation of the separator to the time of use, the polymerization liquid or dispersion liquid of the conductive polymer is uniformly impregnated to the inside of the separator by maintaining the above internal structure. I found that it was important.

  On the other hand, conventional separators with high impregnatability do not take into account the above-mentioned separator's impregnation in the compressed state, and simply improve the separator's impregnation in the non-compressed state, or compress after electrolyte impregnation. And improve the difficulty of releasing the electrolyte solution. In such a conventional separator, the fibers are softened by beating, and the bulkiness and rigidity of the fibers are reduced. Therefore, a capacitor element is formed by the separators, and a polymerization liquid or a dispersion liquid of a conductive polymer is impregnated. In such a case, although the amount of retention of the conductive polymer is large, the conductive polymer layer can not be uniformly formed up to the inside of the capacitor element, and the ESR reduction and the capacitance improvement required recently achieved can be achieved. Can not.

  Therefore, in the separator for an aluminum electrolytic capacitor of the present invention, the compression impregnation ratio, which is the impregnating property of the separator in a compressed state, is improved, which directly affects the ESR and capacitance of the solid electrolytic capacitor. The

Hereinafter, an embodiment of the present invention will be described in detail.
When the capacitor element is formed by sandwiching and winding a separator between the electrodes, the separator is compressed by both electrode foils. Even in a separator having a high water absorption rate or liquid absorption degree, a separator having a controlled porosity, and a separator having a high electrolyte solution retention rate, in such a compressed state, the conductive polymer is uniformly formed to the inside of the capacitor element I could not do that.

  Furthermore, the conventional separator having a high compression retention rate improves the difficulty of releasing the electrolyte when it is compressed after being impregnated with the electrolyte, and does not take into consideration the impregnation in the compressed state. In other words, the impregnation in the compressed state can not be achieved by the conventional compression retention rate as disclosed in Patent Document 6. For this reason, as in the case of the above-mentioned separator, there were cases in which the conductive polymer could not be formed uniformly to the inside of the capacitor element. The reason for this is that the conventional separators proposed so far can not retain the internal structure originally possessed by the separator in the compressed state, and the gap between the fibers inside the separator may become excessively narrow, It is mentioned that the polymerization liquid or dispersion liquid of the above was not impregnated to the inside of the separator.

  Therefore, the separator according to the embodiment of the present invention is configured to secure a predetermined compression impregnation rate. That is, the separator according to the present embodiment is a separator for an aluminum electrolytic capacitor interposed between a pair of electrodes, and the separator comprises cellulose fiber and synthetic fiber, and 40 to 80% by mass of the cellulose fiber, The synthetic fiber is contained at 20 to 60% by mass, and the porosity is 65 to 85%, and the compression impregnation rate is 30% or more.

  The separator according to the present embodiment reduces the ESR of the solid electrolytic capacitor and improves the capacitance by setting the compression impregnation rate to 30% or more. The compression impregnation rate of the separator is more preferably 50% or more, and still more preferably 60% or more. On the other hand, if the compression impregnation rate is less than 30%, the conductive polymer layer can not be formed uniformly up to the inside of the element when forming the capacitor element, so that the ESR of the capacitor can not be reduced and the capacitance can not be improved.

  The term “compression impregnation rate” refers to an impregnation rate calculated from the ratio of the total area of the separator before impregnation and the area of the impregnated portion, by immersing the dispersion in the conductive polymer dispersion while the separator is compressed. It is used as an index to measure the impregnation.

Specifically, a separator test piece is cut into a circle (800 mm ² ), and while the entire surface of the separator test piece is weighted at 7 kN / m ² , a conductive polymer aqueous dispersion (solid content concentration: 2.0 mass%) Immerse and impregnate the separator test piece with the aqueous dispersion for 30 seconds. After passing for 30 seconds, the separator test piece was taken out in a weighted state, and after taking it out, the separator test piece was not put on weight, and the taken out separator test piece was completely removed of the solvent in a hot air dryer. The dried separator test piece clearly differs in color from the portion into which the conductive polymer has penetrated and the portion not penetrated. Using this, the area of the impregnated part of the conductive polymer and the area of the non-impregnated part of the separator test piece taken out are measured by image analysis by the mode method using a digital microscope, and the impregnation occupies the total area The proportion of the area of the part was calculated as the compression impregnation rate.

The image analysis by the modal method was performed as follows.
First, the separator test piece after impregnation and drying is photographed with a digital microscope, and the brightness of the photographed image (hereinafter referred to as "brightness") is distributed to 256 gradations from 0 to 255 by image processing. The frequency of occurrence of each luminance was calculated to obtain a luminance value histogram of this image. Next, as shown in FIG. 1, a threshold value between the valleys of the bimodal peak of the dark portion (hereinafter referred to as "impregnated portion") and the light portion (hereinafter referred to as "unimpregnated portion") of the luminance value histogram. Were binarized by converting the luminance from 256 gradations to two gradations. And the area of the impregnation part of the dispersion liquid of a conductive polymer and the area of the non-impregnated part were computed from the image which binarized. For example, when the luminance value 150 is binarized using the threshold value, the section widths 0 to 150 of the luminance value are counted as the impregnated portion, and the section widths 151 to 255 of the luminance value are counted as the non-impregnated section. In addition, ring photography was used in the case of photography with a digital microscope.

  The compression impregnation ratio is 100 after dividing the area of the impregnated portion of the conductive polymer of the separator test piece obtained by the image analysis by the total area of the separator test piece (the sum of the area of the impregnated portion and the area of the non-impregnated portion). It is a doubled value. With such a compression impregnation rate, it is possible to check the impregnation in the loaded state of the separator, and it is possible to appropriately determine the impregnation of the separator in the compressed state after element winding.

In the embodiment of the present invention, the reason for focusing on the impregnation property at the compression impregnation rate is as follows.
Even in the case where the impregnation property is good as in the conventional separator, the impregnation of the polymer solution or dispersion liquid of the conductive polymer becomes good, the capacity appearance ratio of the capacitor is improved, and the ESR is also reduced. However, as described above, in recent years, further reduction of ESR and improvement of capacitance are required, and in order to meet this, not only the impregnating property as in the past but also the impregnating property in the compressed state is It turned out to be important.

For example, a separator having a compression load of 30% or more at a load of 7 kN / m ² , which is a stronger load than applied to the separator after element winding, can be said to be a separator having higher impregnation. When the impregnation property in such a compressed state is high, the conductive polymer layer can be uniformly formed to the inside of the element at the time of producing the capacitor element.

  That is, by using the separator having a high compression impregnation rate according to the embodiment of the present invention, the conductive polymer layer can be formed uniformly to the entire surface between the capacitor electrode foil and the electrode foil, and the ESR characteristics and Capacitance characteristics can be improved.

  Moreover, the porosity of the separator of this Embodiment is 65 to 85%, and 70 to 80% is more preferable. When the porosity is less than 65%, the interstices of the fibers inside the separator become excessively dense, and the polymerization liquid or dispersion liquid of the conductive polymer to be impregnated using capillary phenomenon does not absorb, and the separator is compressed. The impregnation rate may be less than 30%.

  On the other hand, when the porosity exceeds 85%, the gap between the fibers is excessively large, and the capillary action causes the polymer solution or dispersion liquid of the conductive polymer to absorb the fibers so weakly that the separator is compressed. The impregnation rate may be less than 30%. Furthermore, since the compactness is low, burrs and the like of the electrode foil may easily penetrate the separator, and the short failure rate may increase.

  In any case, the conductive polymer layer can not be formed uniformly to the inside of the capacitor element, and the ESR characteristic and the capacitance characteristic may not be improved. Furthermore, there are cases where the short failure rate can not be reduced.

  There is a cellulose-made separator as a separator used for a solid electrolytic capacitor. Cellulose is a polymer having a large number of hydroxyl groups, and a separator made of cellulose fiber has high mechanical strength due to hydrogen bonding of the hydroxyl groups. However, the oxidizing agent of the polymerization liquid of the conductive polymer is consumed by the hydroxyl group of cellulose to inhibit the polymerization of the conductive polymer. At the same time, the strength of the separator is reduced by the decomposition and deterioration of the cellulose.

  For this reason, a cellulose separator is usually used after being carbonized. The carbonization treatment of the cellulose separator improves the resistance of the separator to the oxidizing agent, and the porosity of the separator is further increased by the carbonization, so that the impregnation property of the polymerization liquid or dispersion liquid of the conductive polymer is also increased. It is because it can be improved.

  However, such heat in the carbonization step of the separator causes thermal deterioration of the cellulose fibers, and the thermal deterioration lowers the mechanical strength of the separator. In addition, since cellulose fibers are gradually decomposed under acidic conditions, if a polymer solution of a conductive polymer containing an oxidizing agent or a dispersion of a conductive polymer exhibiting acidity is impregnated into a capacitor element, the mechanical properties of the separator are obtained. The decrease in strength is remarkable. The decrease in mechanical strength of the separator may increase the short circuit failure rate of the capacitor.

  In order to avoid the decrease in mechanical strength under acidic conditions of such a cellulose separator, in the present embodiment, a separator in which cellulose fibers and synthetic fibers are blended is used.

  Specifically, by containing 40 to 80% by mass of cellulose fibers in the separator, the affinity of the conductive polymer of the separator to the polymerization liquid or dispersion of the separator due to the action of the hydroxyl group and the mechanical strength of the separator are improved. There is. The content of cellulose fiber is preferably 50% by mass or more. When the content of the cellulose fiber is less than 40% by mass, that is, the content of the synthetic fiber exceeds 60% by mass, the affinity of the conductive polymer of the separator to the polymerization liquid or dispersion of the separator by the action of the hydroxyl group decreases. The conductive polymer layer can not be formed uniformly to the inside of the capacitor element, and the ESR can not be reduced and the capacitance can not be improved.

  In addition, when synthetic fibers inhibit hydrogen bonding between cellulose fibers, the mechanical strength of the separator is reduced, and winding defects such as breakage of the separator occur in the capacitor element winding step, burrs of electrode foil, etc. It becomes easy to penetrate the separator, and the short circuit failure rate of the capacitor may increase.

  On the other hand, when the content of the cellulose fiber is more than 80% by mass, that is, the content of the synthetic fiber is less than 20% by mass, the acid resistance and the oxidation resistance of the separator are reduced, and the polymerization liquid or dispersion of the conductive polymer The decrease in the mechanical strength of the separator after solution impregnation may increase the short circuit failure rate of the capacitor.

  Furthermore, by containing 20 to 60% by mass of synthetic fibers, the acid resistance and the oxidation resistance of the separator can be improved, and the decrease in mechanical strength of the separator due to the polymerization liquid or the dispersion liquid of the conductive polymer can be suppressed. When the content of synthetic fibers is less than 20% by mass, that is, the content of natural fibers such as cellulose fibers exceeds 80% by mass, as described above, the short failure rate of the capacitor may increase. Also, even when the content of synthetic fiber is more than 60% by mass, that is, the content of natural fiber such as cellulose fiber is less than 40% by mass, the ESR of the solid electrolytic capacitor can not be reduced similarly, and the capacitance In some cases, improvement can not be achieved, or winding defects such as breakage of the separator may occur in the capacitor element winding process.

  There are no particular restrictions on the fiber type of the synthetic fiber used in the separator of this embodiment, and it is possible to select from, for example, nylon fiber, polyester fiber, acrylic fiber, aramid fiber, etc. Even fibrillated fibers are fibrillated. No fibers may be used, and these fibers may be combined. Among these, nylon fibers are preferable from the viewpoint of the affinity to the polymerization liquid or dispersion liquid of the conductive polymer.

  In addition, as the cellulose fibers used in the separator of the present embodiment, unbeaten cellulose fibers selected from at least one or more of unbeaten cotton linter pulp, unbeaten mercerized pulp, and unbeaten dissolved pulp are used as a total of 10 to a separator. By containing 50% by mass, even in the compressed state of the separator, the gaps between the fibers in the separator can be appropriately maintained, and the conductive polymer layer can be formed uniformly to the inside of the capacitor element.

  Here, cotton linter pulp refers to a pulp consisting of only short fibers remaining in seeds after long fibers (lint) are taken from cotton seeds. The mercerized pulp refers to a pulp made of fibers obtained by immersing cellulose fibers in a sodium hydroxide solution and then washing with water. And, unlike dissolved pulp for ordinary papermaking, dissolved pulp refers to a pulp of high cellulose purity which has been further subjected to a refining treatment.

  Cotton linter pulp, mercerized pulp, and solution pulp are bulky and rigid in themselves as compared to other cellulose pulp and ordinary paper pulp. For this reason, even when the separator containing these pulps is in a compressed state, the gaps of the separator are maintained to improve the compression impregnation rate.

  Furthermore, it is preferable to use these cellulose fibers as unbeaten cellulose fibers so as not to impair the bulkiness and rigidity described above. In this embodiment, the degree of the beating process of the cellulose fiber is managed by the Canadian Standard Freeness (hereinafter referred to as “CSF” and the details will be described later), but it is not limited thereto. There is no problem even with methods such as measurement of fiber length with a fiber length measuring machine or a microscope.

  In addition, the value of CSF was made into the range of 500-800 ml for the purpose of not losing the bulkiness and rigidity which the fiber itself has as mentioned above in this Embodiment.

  When the total content of unbeaten cotton linter pulp, unbeaten mercerized pulp, and unbeaten dissolved pulp is less than 10% by mass as unbeaten cellulose fibers, the internal structure of the separator is maintained in a compressed state of the separator And the gaps between the fibers become excessively narrow. Therefore, the polymerization liquid and the dispersion liquid of the conductive polymer can not be sufficiently impregnated to the inside of the capacitor element.

  In addition, when the total content of unbeaten cotton linter pulp, unbeaten mercerized pulp and unbeaten dissolving pulp is more than 50% by mass as unbeaten cellulose fibers, the formation is likely to be uneven, and polymerization of the conductive polymer The liquid or the dispersion can not be formed uniformly to the inside of the capacitor element. In addition, mechanical strength of the separator may be reduced, and winding defects such as breakage of the separator may occur in the capacitor element winding process.

  The unbeaten cotton linter pulp, the unbeaten mercerized pulp, and the unbeaten dissolving pulp are bulky and have high rigidity as described above, and thus the compression impregnation rate of the separator can be easily improved. However, since these unbeaten cellulose fibers have high rigidity of the fibers, the degree of freedom in shape at the time of sheet formation is low. That is, in the sheet containing the unbeaten cotton linter pulp, the unbeaten mercerized pulp, and the unbeaten dissolving pulp, the formation is likely to be uneven, and the mechanical strength of the sheet is also likely to be low. Furthermore, since the separator of the present embodiment contains synthetic fibers, the sheet strength may be reduced.

  For this reason, the mechanical strength of a separator can be improved and a texture can be made uniform by containing 10-70 mass% of beaten cellulose fibers as a cellulose fiber used for a separator of this embodiment to a separator. It is considered that this is because the beaten cellulose fiber having a high degree of freedom moves so as to fill in the uneven portion of the sheet from sheet formation to completion. Therefore, although the separator of the present embodiment originally contains many fibers which are uneven in formation and also decreases in mechanical strength, it can have sufficient mechanical strength and uniform formation as the separator. .

  The beatable cellulose fiber material is not particularly limited, and for example, it is possible to use a chemical pulp for papermaking which is digested and extracted from wood or non-wood by a sulfate (kraft) method, a sulfite method, or an alkali method. It may be the same material as the beaten cellulose fiber, or may be a different material. Among them, jute pulp, sisal pulp, manila pulp and regenerated cellulose, rayon and lyocell are preferable as natural cellulose from the viewpoint of mechanical strength of separator and impregnation property of polymerization liquid and dispersion liquid of conductive polymer.

  Note that "beaten cellulose fiber" refers to a treatment in which mechanical shear force is applied to cellulose fibers in the presence of water, and in the present embodiment, as described above, the mechanical strength is sufficient as a separator. The value of CSF was set in the range of 0 to 400 ml for the purpose of achieving uniform formation. Here, with regard to the one to be beaten, it is possible to form a sheet by mixing the ones to be beaten alone, or to form the sheet simultaneously by beating the mixed one. There is no particular limitation on equipment used for refining the fiber, and generally, a beater, conical refiner, disc refiner, high-pressure homogenizer, etc. may be mentioned.

  Furthermore, if a desired compression impregnation rate can be secured, a binder fiber such as polyvinyl alcohol fiber can be used in consideration of the necessity for forming the separator and the mechanical strength at the time of handling.

  The thickness of the separator of the present embodiment is preferably in the range of 20 to 100 μm. When the thickness is smaller than 20 μm, the mechanical strength is weakened, and the separator is easily broken at the time of forming the separator or at the time of forming a capacitor. In addition, since the distance between the electrodes becomes short, burrs and the like of the electrode foil easily penetrate the separator, and the short resistance is also lowered. If the thickness is greater than 100 μm, the size reduction required for the solid electrolytic capacitor may not be achieved.

Moreover, it is preferable that the density of the separator of this Embodiment is the range of 0.20-0.600 g / cm < ³ >. If the density is lower than 0.200 g / cm ³ , the mechanical strength is weakened, and the separator is easily broken at the time of forming the separator or at the time of forming a capacitor. In addition, since the compactness is reduced, the short resistance is also reduced. On the other hand, if the density is higher than 0.600 g / cm ³ , the impregnating property of the polymerization liquid or dispersion liquid of the conductive polymer is lowered.

  Furthermore, the separator according to the present embodiment preferably has a tensile strength of 7.0 N / 15 mm or more. If the tensile strength is lower than 7.0 N / 15 mm, the separator is likely to break at the time of forming the separator or at the time of forming a capacitor. In addition, burrs of the electrode foil and the like easily penetrate the separator, and the short resistance is also reduced.

  For the separator of the present embodiment, a wet non-woven fabric formed using a papermaking method was adopted. The papermaking type of the separator is not particularly limited as long as the compression impregnation ratio of the separator can be satisfied, and a papermaking type such as Fourdrinier papermaking, Fourdrinier papermaking, or Circle papermaking can be used, and a layer formed by these papermaking methods A plurality of these may be combined. In addition, when making paper, additives such as a dispersant, an antifoaming agent, a paper strengthening agent and the like may be added as long as the content of impurities does not affect the separator for capacitors.

  Furthermore, after the paper layer is formed, processing such as paper strengthening processing, lyophilic processing, calendering, embossing may be performed. There is no particular limitation on the coating amount such as paper strengthening processing and hydrophilic processing as long as the desired compression impregnation rate can be satisfied, but for example, the application amount up to about 15% by mass affects the compression impregnation rate. Hateful.

  The separator of the present embodiment adopting the above configuration has sufficient mechanical strength and compactness in the thickness required for the solid electrolytic capacitor while having resistance to the polymerization liquid and dispersion liquid of the conductive polymer. . And, even in the compressed state, the internal structure of the separator can be properly maintained, and the conductive polymer layer can be formed uniformly to the inside of the separator when impregnated with the polymer liquid or dispersion liquid of the conductive polymer. . Therefore, by using this separator for an aluminum electrolytic capacitor using a conductive polymer as a cathode material, it is possible to obtain an aluminum electrolytic capacitor with reduced ESR and improved capacitance.

  On the other hand, the aluminum electrolytic capacitor according to the embodiment of the present invention uses the separator having the above configuration as the separator, interposes the separator between the pair of electrodes, and uses the conductive polymer as the cathode material.

[Method of measuring characteristics of separator and aluminum electrolytic capacitor]
Specific measurement of each characteristic of the separator and the aluminum electrolytic capacitor of the present embodiment was performed under the following conditions and methods.

[CSF]
CSF is “JIS P 812 1-2“ Pulp-Freeness test method-Part 2: Canadian standard freeness method ”(ISO 5 267-2“ Pulps-Determination of drainability-Part 2: 'Canadian Standard' freeness method ”) It measured according to "."

〔thickness〕
In "5.1.1 Measuring instrument and measuring method a when using an outer micrometer" defined in "JIS C 2300-2" Cellulose paper for electricity-Part 2: Test method "5.1 Thickness" Using a micrometer, the thickness of the separator was measured by a method of folding on 10 sheets in "5.1.3 When folding paper to measure thickness".

〔density〕
The density of the dry-dried separator was measured by the method defined in Method B of “JIS C 2300-2“ Cellulose Paper for Electricity—Part 2: Test Method ”7.0A Density”.

〔Tensile strength〕
The tensile strength of the separator in the longitudinal direction was measured by the method defined in “JIS C 2300-2“ Cellulose paper for electricity-Part 2: Test method 8 tensile strength and elongation ”.

[Void ratio]
The porosity of the separator was determined by the following equation (1).
(True specific gravity of separator-separator density) / true specific gravity of separator × 100 (%) ... (1)

[Compression liquid retention rate]
Take a test piece of 30 mmφ in size, and measure the mass before immersion. The product was immersed in a propylene carbonate solution for 10 minutes and compressed for 30 seconds with a pressure of 5 MPa by a press, and then its mass was measured, and the compression retention rate was determined using the following formula (2). This test was performed four times, and the average value was determined, and the unit was expressed in%.
Compression retention ratio (%) = [(W2-W1) / W1] x 100 (2)
Here, W1 is a mass before immersion, and W2 is a mass after immersion compression.

[Compression impregnation rate]
The compression impregnation rate of the separator is obtained by cutting out a separator having a fixed area, immersing the separator in an aqueous dispersion of a conductive polymer at 20 ° C. while being weighted at 7 kN / m ² , and using the aqueous dispersion in the separator test piece for 30 seconds. After impregnating, removing the load, and drying the test piece, an image taken with ring illumination is binarized by a mode method using a digital microscope (VHX-6000: manufactured by Keyence Corporation), and conductive polymer From the area of the impregnated part and the area of the non-impregnated part, the compression impregnation rate was calculated by the following equation (3). The impregnation of the conductive polymer was performed at room temperature of 20 ° C. under an environment of relative humidity of 65%.
Compression impregnation rate (%) = [W1 / (W1 + W2)] × 100 (3)
Here, W1 is the impregnated part area (mm ² ), and W2 is the non-impregnated part area (mm ² ).

[Manufacturing process of solid electrolytic capacitor]
Rated voltage 6.3 V, diameter 8.0 mm × height 7.0 mm, rated voltage 50 V, diameter 8.0 mm × height 10.0 mm using the separators of each example, each comparative example, and each conventional example Two types of solid electrolytic capacitors were produced.

A specific method for producing a solid electrolytic capacitor is as follows.
A capacitor element was produced by winding with a separator interposed so that the anode foil and the cathode foil subjected to the etching treatment and the oxide film formation treatment do not come in contact with each other. The produced capacitor element was dried after the reconversion treatment.

  In the case of a solid electrolytic capacitor with a rated voltage of 6.3 V, the capacitor element was impregnated with a conductive polymer solution, heated and polymerized, and the solvent was dried to form a conductive polymer layer. In the case of a solid electrolytic capacitor with a rated voltage of 50 V, the capacitor element was impregnated with the conductive polymer dispersion, and then heated and dried to form a conductive polymer layer. Then, the capacitor element was placed in a predetermined case, the opening was sealed, and then aging was performed to obtain each solid electrolytic capacitor.

[Production process of hybrid electrolytic capacitor]
Two types of rated voltage 16 V, diameter 10.0 mm × height 10.5 mm, rated voltage 80 V, diameter 8.0 mm × height 10.0 mm using the separators of each example, each comparative example, and each conventional example The hybrid electrolytic capacitor of

The specific preparation method is as follows.
A capacitor element was produced by winding with a separator interposed so that the anode foil and the cathode foil subjected to the etching treatment and the oxide film formation treatment do not come in contact with each other. The produced capacitor element was dried after the reconversion treatment.

  In the case of a hybrid electrolytic capacitor with a rated voltage of 16 V, the capacitor element is impregnated with a conductive polymer solution, heated and polymerized, and the solvent is dried to form a conductive polymer layer. In the case of a hybrid electrolytic capacitor with a rated voltage of 80 V, after impregnating the capacitor element with the conductive polymer dispersion, the conductive polymer layer is formed by heating and drying. Then, the above-mentioned capacitor element was impregnated with a driving electrolytic solution, the capacitor element was put in a predetermined case, the opening was sealed, and aging was performed to obtain each hybrid electrolytic capacitor.

[ESR]
The ESR of the produced capacitor element was measured using an LCR meter under conditions of a temperature of 20 ° C. and a frequency of 100 kHz.

[Capacitance]
The capacitance was determined by the method of “4.7 Capacitance” specified in “JIS C 5101-1“ Fixed capacitors for electronic devices Part 1: General rules by item ””.

[Short defect rate]
The short-circuit failure rate is calculated by counting the number of short-circuit failures generated during aging using a wound capacitor element, dividing the number of short-circuit failure elements by the number of capacitor elements subjected to aging, and shorting with a percentage It was taken as the defect rate.

<Examples>
Hereinafter, specific examples and the like of the separator according to the embodiment of the present invention will be described.

Example 1
Using a raw material obtained by mixing 20% by mass of cotton linter pulp (500 ml of CSF), 20% by mass of lyocell fiber (50 ml of CSF), and 60% by mass of nylon fiber, circular papermaking was performed to obtain a separator of Example 1.
The completed separator of Example 1 has a thickness of 30 μm, a density of 0.250 g / cm ³ , a tensile strength of 7.0 N / 15 mm, a porosity of 82.5%, a compression retention of 240%, and compression impregnation. The rate was 37%.

Example 2
Using a raw material obtained by mixing 10% by mass of cotton linter pulp (700 ml of CSF), 70% by mass of sisal pulp (10 ml of CSF), and 20% by mass of acrylic fiber, circular papermaking was performed to obtain a separator of Example 2.
The completed separator of Example 2 had a thickness of 20 μm, a density of 0.300 g / cm ³ , a tensile strength of 24.5 N / 15 mm, a porosity of 79.1%, a compression retention of 190%, and compression impregnation The rate was 35%.

[Example 3]
Using a raw material obtained by mixing 30% by mass of mercerized bamboo pulp (600 ml of CSF), 15% by mass of jute pulp (300 ml of CSF), and 55% by mass of nylon fiber, circular net papermaking was performed to obtain a separator of Example 3.
The completed separator of Example 3 has a thickness of 100 μm, a density of 0.502 g / cm ³ , a tensile strength of 17.6 N / 15 mm, a porosity of 65.0%, a compression retention of 220%, and compression impregnation. The rate was 30%.

Example 4
After making a circular net paper making using the raw material which mixed 15 mass% of dissolved kraft pulp (CSF 700 ml), 50 mass% of rayon fiber (CSF 100 ml), and 35 mass% of polyester fiber, coat 15 mass% of polyacrylamide, The separator of Example 4 was obtained.
The completed separator of Example 4 has a thickness of 50 μm, a density of 0.218 g / cm ³ , a tensile strength of 18.6 N / 15 mm, a porosity of 85.0%, a compression retention of 200%, and compression impregnation. The rate was 31%.

[Example 5]
Using a raw material obtained by mixing 40% by mass of cotton linter pulp (800 ml of CSF), 10% by mass of jute pulp (0 ml of CSF), and 50% by mass of nylon fiber, circular net papermaking was performed to obtain a separator of Example 5.
The completed separator of Example 5 has a thickness of 40 μm, a density of 0.350 g / cm ³ , a tensile strength of 7.8 N / 15 mm, a porosity of 75.9%, a compression retention of 170%, and compression impregnation. The rate was 52%.

[Example 6]
Using a raw material obtained by mixing 25% by mass of cotton linter pulp (700 ml of CSF), 40% by mass of jute pulp fiber (250 ml of CSF), and 35% by mass of nylon fiber, circular papermaking was performed to obtain a separator of Example 6.
The completed separator of Example 6 had a thickness of 60 μm, a density of 0.437 g / cm ³ , a tensile strength of 37.2 N / 15 mm, a porosity of 70.0%, a compression retention of 200%, and compression impregnation. The rate was 70%.

[Example 7]
Using a material obtained by mixing 30% by mass of cotton linter pulp (750 ml of CSF), 30% by mass of manila hemp pulp (300 ml of CSF), and 40% by mass of nylon fiber, circular net papermaking was performed to obtain a separator of Example 7.
The completed separator of Example 7 had a thickness of 35 μm, a density of 0.274 g / cm ³ , a tensile strength of 11.8 N / 15 mm, a porosity of 80.0%, a compression retention of 180%, and compression impregnation. The rate was 50%.

Example 8
Using a raw material obtained by mixing 50 mass% of cotton linter pulp (650 ml of CSF), 20 mass% of jute pulp (400 ml of CSF), and 30 mass% of aramid fiber, circular net papermaking was performed to obtain a separator of Example 8.
The finished separator of Example 8 has a thickness of 45 μm, a density of 0.400 g / cm ³ , a tensile strength of 14.7 N / 15 mm, a porosity of 72.8%, a compression retention of 180%, and compression impregnation. The rate was 60%.

Comparative Example 1
Using a raw material obtained by mixing 15 mass% of cotton linter pulp (700 ml of CSF), 15 mass% of jute pulp (350 ml of CSF), and 70 mass% of acrylic fiber, circular net papermaking was performed to obtain a separator of Comparative Example 1.
The completed separator of Comparative Example 1 has a thickness of 30 μm, a density of 0.305 g / cm ³ , a tensile strength of 7.4 N / 15 mm, a porosity of 76.1%, a compression retention of 200%, and compression impregnation. The rate was 15%.

Comparative Example 2
Using a raw material obtained by mixing 42 mass% of cotton linter pulp (500 ml of CSF), 42 mass% of lyocell fiber (50 ml of CSF), and 16 mass% of nylon fiber, circular papermaking was performed to obtain a separator of Comparative Example 2.
The completed separator of Comparative Example 2 has a thickness of 35 μm, a density of 0.280 g / cm ³ , a tensile strength of 34.3 N / 15 mm, a porosity of 81.1%, a compression retention of 210%, and compression impregnation. The rate was 35%.

Comparative Example 3
Using a raw material obtained by mixing 15 mass% of cotton linter pulp (300 ml of CSF), 30 mass% of jute pulp (0 ml of CSF), and 55 mass% of acrylic fiber, circular net papermaking was performed to obtain a separator of Comparative Example 3.
The completed separator of Comparative Example 3 has a thickness of 50 μm, a density of 0.488 g / cm ³ , a tensile strength of 17.6 N / 15 mm, a porosity of 63.1%, a compression retention of 180%, and compression impregnation. The rate was 17%.

Comparative Example 4
Using a raw material obtained by mixing 12 mass% of cotton linter pulp (700 ml of CSF), 32 mass% of sisal hemp pulp (500 ml of CSF), and 56 mass% of aramid fibers, circular net papermaking was performed to obtain a separator of Comparative Example 4.
The completed separator of Comparative Example 4 has a thickness of 40 μm, a density of 0.200 g / cm ³ , a tensile strength of 6.7 N / 15 mm, a porosity of 86.1%, a compression retention of 170%, and compression impregnation. The rate was 16%.

Comparative Example 5
Using a raw material obtained by mixing 5 mass% of cotton linter pulp (CSF 600 ml), 75 mass% of hemp hemp pulp (100 ml CSF), and 20 mass% of nylon fiber, circular net papermaking was performed to obtain a separator of Comparative Example 5.
The completed separator of Comparative Example 5 has a thickness of 45 μm, a density of 0.350 g / cm ³ , a tensile strength of 44.1 N / 15 mm, a porosity of 76.3%, a compression retention of 210%, and compression impregnation. The rate was 21%.

Comparative Example 6
Using a raw material in which 55 mass% of cotton linter pulp (650 ml of CSF), 15 mass% of jute pulp (200 ml of CSF), and 30 mass% of polyester fiber were mixed, circular net papermaking was performed to obtain a separator of Comparative Example 6.
The completed separator of Comparative Example 6 has a thickness of 60 μm, a density of 0.425 g / cm ³ , a tensile strength of 15.2 N / 15 mm, a porosity of 71.0%, a compression retention of 170%, and compression impregnation. The rate was 25%.

Comparative Example 7
Using a raw material obtained by mixing 40 mass% of cotton linter pulp (700 ml of CSF), 5 mass% of rayon fiber (10 ml of CSF), and 55 mass% of nylon fiber, circular net papermaking was performed to obtain a separator of Comparative Example 7.
The completed separator of Comparative Example 7 has a thickness of 55 μm, a density of 0.350 g / cm ³ , a tensile strength of 5.9 N / 15 mm, a porosity of 75.6%, a compression retention of 220%, and compression impregnation. The rate was 27%.

Comparative Example 8
Using a material obtained by mixing 30% by mass of cotton linter pulp (700 ml of CSF), 30% by mass of jute pulp (300 ml of CSF), and 40% by mass of aramid fiber, circular net papermaking was performed to obtain a separator of Comparative Example 8.
The completed separator of Comparative Example 8 has a thickness of 15 μm, a density of 0.435 g / cm ³ , a tensile strength of 11.8 N / 15 mm, a porosity of 70.2%, a compression retention of 230%, and compression impregnation. The rate was 40%.

[Conventional Example 1]
The separator manufactured by the method similar to the method as described in Example 3 of patent document 3 was produced, and was used as the separator of Conventional Example 1.
The separator of Conventional Example 1 contains 5% by mass of cotton linter pulp (0 ml of CSF), 30% by mass of fibrillated aramid fiber (0 ml of CSF), and 65% by mass of polyester fiber, and has a thickness of 45 μm and a density of 0.356 g / cm ^3, a tensile strength of 7.4 N / 15 mm, porosity of 74.4% and the compressibility solution holding ratio is 200%, compression impregnation rate was 10%.

[Conventional Example 2]
The separator manufactured by the method similar to the method as described in Example 6 of patent document 5 was produced, and it was set as the separator of the prior art example 2.
The separator of Conventional Example 2 contains 10% by mass of cotton linter fiber (CSF 20 ml), 30% by mass of solvent-spun cellulose (CSF 0 ml) and 60% by mass of acrylic fiber, and has a thickness of 35 μm and a density of 0.314 g / cm. ^{3 The} tensile strength was 11.8 N / 15 mm, the porosity was 76.0%, the compression and holding ratio was 170%, and the compression impregnation ratio was 15%.

[Conventional Example 3]
The separator manufactured by the method similar to the method as described in Example 2 of patent document 7 was produced, and it was set as the separator of the prior art example 3. FIG.
The separator of Conventional Example 3 contains 50% by mass of cotton lint pulp (10 ml of CSF) and 50% by mass of nylon fiber, the thickness is 30 μm, the density is 0.550 g / cm ³ , and the tensile strength is 19.6 N / The void ratio was 61.8%, the compression retention ratio was 190%, and the compression impregnation ratio was 12%.

Conventional Example 4
The separator manufactured by the method similar to the method as described in Example 1 of patent document 8 was produced, and it was set as the separator of the prior art example 4.
The separator of Example 4 contains 50% by mass of dissolved kraft pulp (CSF 350 ml), 40% by mass of vinylon fibers, and 10% by mass of polyvinyl alcohol fibers, and has a thickness of 97 μm and a density of 0.346 g / cm ³ . The tensile strength was 39.2 N / 15 mm, the porosity was 74.9%, the compression water retention rate was 210%, and the compression impregnation rate was 20%.

  The aluminum electrolytic capacitors manufactured using the separators of the above-described respective embodiments, comparative examples, and conventional examples are a solid electrolytic capacitor with a rated voltage of 6.3 V for low voltage and a solid electrolytic capacitor with a rated voltage of 50 V for high voltage. A capacitor was produced. Further, as a hybrid electrolytic capacitor, a capacitor with a rated voltage of 16 V for low voltage and a capacitor with a rated voltage of 80 V for high voltage were manufactured.

  Table 1 shows the raw material and mixing | blending of each separator of said Examples 1-8, Comparative Examples 1-8, and Conventional Examples 1-4, and Table 2 shows the evaluation result of each separator single-piece | unit. Moreover, Table 3 shows the performance evaluation result of a solid electrolytic capacitor, and Table 4 shows the performance evaluation result of a hybrid electrolytic capacitor.

  Hereinafter, evaluation results will be described in detail for each example, each comparative example, and each conventional example.

  From Tables 3 and 4, the solid electrolytic capacitors with a rated voltage of 6.3 V using the separators of Examples 1 to 8 have low ESR of 8 to 12 mΩ, high electrostatic capacitance of 530 to 650 μF, and a short failure rate of It is understood that it is as low as 0.0%. The solid electrolytic capacitor with a rated voltage of 50 V using the same separator also has a low ESR of 10 to 20 mΩ, a high electrostatic capacitance of 50 to 70 μF, and a low short failure rate of 0.0%. Furthermore, a hybrid electrolytic capacitor with a rated voltage of 16 V using the same separator also has a low ESR of 10 to 17 mΩ, a high electrostatic capacitance of 330 to 450 μF, and a short failure rate of 0.0%. Furthermore, a hybrid electrolytic capacitor with a rated voltage of 80 V using the same separator also has a low ESR of 20 to 30 mΩ, a high electrostatic capacitance of 38 to 60 μF, and a short failure rate of 0.0%.

  The compression impregnation rate of the separators of Examples 1 to 8 was 30 to 70%. From this, even in the compressed state, the separator of this embodiment can be highly impregnated, and can form the conductive polymer layer uniformly to the inside of the capacitor element. That is, since the conductive polymer layer can be formed all the way between the capacitor electrode foil surface and the electrode foil, it is possible to improve the ESR characteristics and the capacitance characteristics.

  Furthermore, it can be seen from Example 4 that if the coating amount of polyacrylamide is about 15% by mass, the compression impregnation rate is not affected.

In the separator of Comparative Example 1, the content of cellulose fibers is as low as 30% by mass, and the content of synthetic fibers is as high as 70% by mass. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 1 have a high ESR and a low electrostatic capacitance as compared with each example. This is because the separator of Comparative Example 1 has a low content of cellulose fibers and a high content of synthetic fibers, so the affinity of the conductive polymer of the separator with the polymerization liquid or dispersion liquid due to the action of the hydroxyl group is lowered. The reason is considered to be that the conductive polymer layer could not be formed uniformly to the inside of the capacitor element. From the comparison of each Example and Comparative Example 1, it is understood that the content of the cellulose fiber is preferably 40% by mass or more, and the content of the synthetic fiber is preferably 60% by mass or less.

  In the separator of Comparative Example 2, the content of cellulose fibers is as high as 84% by mass, and the content of synthetic fibers is as low as 16% by mass. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 2 have a high short circuit failure rate as compared with the respective examples. This is because the separator of Comparative Example 2 has a large content of cellulose fibers and a small content of synthetic fibers, so the separator is low in acid resistance and oxidation resistance, and the separator and the dispersion liquid of the conductive polymer are used. It is considered that the cause is a decrease in the mechanical strength of From the comparison of each Example and Comparative Example 2, the content of cellulose fiber is preferably 80% by mass or less, and the content of synthetic fiber is preferably 20% by mass or more.

  The separator of Comparative Example 3 has a low porosity of 63.1%. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 3 have a high ESR and a low electrostatic capacitance as compared with the respective examples. This is because the separator of Comparative Example 3 has a low porosity, so that the interstices of the fibers inside the separator become excessively dense, and the polymer liquid or dispersion liquid of the conductive polymer impregnated by capillary action is absorbed Since the conductive polymer layer can not be formed up to the inside of the capacitor element without raising the temperature, it is considered that the ESR characteristic and the capacitance characteristic can not be improved. From the comparison of each Example and Comparative Example 3, it is understood that the porosity of the separator is preferably 65% or more.

  The separator of Comparative Example 4 has a high porosity of 86.1%. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 4 have a high ESR, a low electrostatic capacity, and a high short failure rate, as compared with the respective examples. This is because the separator of Comparative Example 4 has a high porosity, so that the gap between the fibers is excessively wide, and the force by which the polymerization liquid or dispersion of the conductive polymer absorbs the fibers is weak due to the capillary phenomenon. . From this, it is considered that the conductive polymer layer can not be formed uniformly to the inside of the capacitor element, so that the ESR characteristic and the capacitance characteristic can not be improved. Furthermore, the CSF value of the beaten cellulose raw material is 500 ml, the mechanical strength of the separator is weak, and the compactness is also low, so it is considered that the burrs of the electrode foil easily penetrate the separator and the short defect rate becomes high. . From the comparison of each Example and Comparative Example 4, the value of CSF of the beaten cellulose raw material is preferably 400 ml or less, the tensile strength of the separator is preferably 7.0 N / 15 mm or more, and the porosity is 85% or less.

  In the separator of Comparative Example 5, the content of unbeaten cellulose fiber is as low as 5% by mass, and the content of beatable cellulose fiber is as high as 75% by mass. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 5 have a high ESR and a low electrostatic capacitance as compared with the respective examples. This is because the separator of Comparative Example 5 has a low content of unbeaten cellulose fibers and a high content of beatable cellulose fibers, so the gap between the fibers constituting the separator is narrow, and the separator is further compressed. The internal structure of the separator can not be maintained, and the gap between the fibers is excessively narrowed, so that the polymerization liquid or dispersion liquid of the conductive polymer can not be sufficiently impregnated to the inside of the capacitor element. Is considered to be the cause. From the comparison of each Example and Comparative Example 5, it is understood that the content of unbeaten cellulose fiber is preferably 10% by mass or more, and the content of beatable cellulose fiber is preferably 70% by mass or less.

  The separator of Comparative Example 6 has a high content of unbeaten cellulose fibers of 55% by mass. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 6 have a high ESR and a low electrostatic capacitance as compared with each example. This is because the separator of Comparative Example 6 has a large content of unbeaten cellulose fiber, the formation of the separator becomes nonuniform, and the polymerization liquid or dispersion liquid of the conductive polymer is uniformly formed to the inside of the capacitor element. It is considered to be the cause of failure. From the comparison of each Example and Comparative Example 6, it is understood that the content of unbeaten cellulose fiber is preferably 50% by mass or less.

  The separator of Comparative Example 7 has a content of beating cellulose fiber as low as 5% by mass. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 7 have a high ESR, a low electrostatic capacity, and a high short failure rate, as compared with the examples. This is because, in the separator of Comparative Example 7, the content of the beatable cellulose fiber is as low as 5% by mass, the formation of the separator becomes uneven, and the polymerization liquid or dispersion liquid of the conductive polymer is uniformly formed inside the capacitor element In addition to being unable to do this, it is considered that the reason is that the tensile strength is low and burrs of the electrode foil and the like easily penetrate the separator. From the comparison of each Example and Comparative Example 7, the content of the beaten cellulose fiber is preferably 10% by mass or more, and it is understood that the tensile strength of the separator is preferably 7.0 N / 15 mm or more.

  The separator of Comparative Example 8 is as thin as 15 μm. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Comparative Example 8 have a high short circuit failure rate as compared with the respective examples. This is because the separator of Comparative Example 8 is thin and the distance between the electrodes is short, so that burrs of the electrode foil and the like easily penetrate the separator and the short resistance is lowered. Conceivable. From the comparison of each Example and Comparative Example 8, it is understood that the thickness of the separator is preferably 20 μm or more.

  As compared with the performance of the solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Conventional Example 1, each example has a low ESR and a high capacitance. This is because in the separator of Conventional Example 1, the content of cotton linter pulp, which is a cellulose fiber, is as low as 5% by mass, and in the compressed state of the separator, the gaps between the fibers inside the separator become excessively narrow. It is presumed that the cause is that the polymerization liquid or dispersion liquid of the conductive polymer could not be sufficiently impregnated to the inside of the capacitor element. From the comparison of each example and the conventional example 1, it is understood that the content of cellulose fiber is preferably 40 to 80% by mass, and the content of cotton linter pulp is preferably 10% by mass or more.

  Furthermore, the CSF of cotton linter pulp contained in the separator of Conventional Example 1 was 0 ml, and the denseness of the separator was high, and the impregnating property of the polymerization liquid or dispersion liquid of the conductive polymer was insufficient. From this, 10 to 50% by mass in total of one or more unbeaten cellulose fibers selected from unbeaten cotton linter pulp, unbeaten mercerized pulp, and unbeaten dissolving pulp in the range of CSF 500 to 800 ml as cellulose fibers in a separator By containing 10 to 70% by mass of beatable cellulose fiber in the range of 0 to 400 ml of CSF, the impregnation property of the polymerization liquid or dispersion liquid of the conductive polymer is improved while maintaining the compactness of the separator. It can be seen that

  As compared with the performance of the solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Conventional Example 2, each example has a low ESR and a high capacitance. This is because the separator of Conventional Example 2 has a low CSF of cotton linter pulp as low as 20 ml, and the bulkiness and rigidity possessed by fibers are impaired by beating, so that the internal structure inherent in the separator can not be maintained in the compressed state. It is considered that the reason is that the infiltration of the polymer solution and the dispersion solution of the conductive polymer is insufficient because the gaps between the fibers inside become excessively narrow.

  Compared with the performances of the solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Conventional Example 3, each example has a low ESR and a high capacitance. This is because the separator of Conventional Example 3 has a low porosity of 61.8%, the interstices of the fibers inside the separator become excessively fine, and the polymerizing liquid of the conductive polymer impregnated with the capillary phenomenon or the like Since the dispersion does not absorb and the conductive polymer layer can not be formed up to the inside of the capacitor element, it is considered that the ESR characteristic and the capacitance characteristic can not be improved. Furthermore, the CSF of cotton lint pulp contained in the separator of Conventional Example 3 was 10 ml, and the denseness of the separator was high, and the impregnatability of the polymerization liquid or dispersion liquid of the conductive polymer was insufficient.

  As compared with the performance of the solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Conventional Example 4, each example has a low ESR and a high capacitance. This is because the separator of Conventional Example 4 does not contain unbeaten cellulose, and therefore the gap between the fibers inside the separator becomes excessively narrow in the compressed state of the separator, whereby the polymerization liquid of the conductive polymer is obtained. It is presumed that the cause is that the dispersion could not be sufficiently impregnated to the inside of the capacitor element.

  From the comparison of each example and Comparative Example 3 and Comparative Example 4, it is understood that the porosity of the separator is preferably in the range of 65 to 85%. Further, from the comparison of Example 3 and Example 4 with Example 6 and Example 7, it is understood that the range of 70 to 80% of the porosity is more preferable.

  And from the comparison of each example and each comparative example and each conventional example, the compression immersion ratio of the separator is preferably 30% or more, and further, from Examples 5 and 7 and Example 8, the compression impregnation rate of the separator 50% or more is more preferable, and 60% or more is more preferable.

  From the comparison of each example, each comparative example, and each conventional example, although it is Example 1 that the compression liquid retention rate of the separator is the highest, the ESR and capacitance of each rated voltage of the solid electrolytic capacitor and the hybrid electrolytic capacitor Does not show the best characteristics.

  Similarly, from the comparison of each example, each comparative example, and each conventional example, it is the compression impregnation rate that most greatly affects the ESR and capacitance of each rated voltage of the solid electrolytic capacitor and the hybrid electrolytic capacitor. I understand.

  As described above, the separator of the present embodiment has sufficient mechanical strength and compactness in the thickness required for the solid electrolytic capacitor while having resistance to the polymerization liquid and dispersion liquid of the conductive polymer. Even in the compressed state, the internal structure of the separator can be properly maintained.

  That is, when the separator of this embodiment is impregnated with the polymerization liquid or dispersion liquid of the conductive polymer, the internal structure of the separator is controlled so that the conductive polymer layer can be formed uniformly to the inside of the separator. The separator has excellent properties which are clearly different from conventionally proposed separators with high water absorption speed or liquid absorption degree, separators with controlled porosity, and separators with high electrolyte holding ratio and high compression holding ratio.

  Further, the aluminum electrolytic capacitor of the present embodiment using the above-mentioned separator can uniformly form the conductive polymer layer up to the inside of the capacitor element even in the compressed state, so the ESR in the solid electrolytic capacitor can be obtained. The capacitance can be greatly reduced and the capacitance can be greatly improved.

Claims (6)

  It is a separator for aluminum electrolytic capacitors which intervenes between a pair of electrodes, and the separator consists of cellulose fiber and a synthetic fiber, contains 40-80 mass% of the cellulose fiber, and 20-60 of the synthetic fiber. A separator for an aluminum electrolytic capacitor, containing: mass%, having a porosity of 65 to 85%, and a compression impregnation ratio of 30% or more.   The cellulose fibers include unbeaten cellulose fibers selected from at least one or more of unbeaten cotton linter pulp, unbeaten mercerized pulp, and unbeaten dissolved pulp, and the unbeatable cellulose fibers are added to the separator in total. The separator for an aluminum electrolytic capacitor according to claim 1, containing 10 to 50% by mass.   The separator for an aluminum electrolytic capacitor according to claim 1 or 2, wherein 10 to 70% by mass of beated cellulose fiber is contained as the cellulose fiber.   The thickness is 20-100 micrometers, The separator for aluminum electrolytic capacitors of any one of Claims 1-3 characterized by the above-mentioned.   An aluminum electrolytic capacitor in which a separator is interposed between a pair of electrodes, wherein the separator for an aluminum electrolytic capacitor according to any one of claims 1 to 4 is used as the separator. .   The aluminum electrolytic capacitor according to claim 5, wherein a conductive polymer is used as the cathode.