JP2018152440A - Separator for solid electrolytic capacitor or hybrid electrolytic capacitor, and solid electrolytic capacitor or hybrid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor which enable the achievement of further ESR reduction.SOLUTION: A separator for an aluminum electrolytic capacitor is shaped in the form of a sheet, and is to be interposed between a pair of electrodes. The sheet has a binding density in a range (0.00005-0.00025 μm) and a fiber filling rate in a range (15.0-45.0%), includes at least a fibrillated cellulose as a sheet material, and has a rate of fibrillation of the sheet in a range (5.0-15.0%).SELECTED DRAWING: None

Description

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

  In recent years, the performance of electronic devices such as personal computers (hereinafter referred to as “PCs”), home-use game machines, and automobile electrical equipment has been remarkably advanced, and at the same time, downsizing of these devices has been strongly demanded. Yes. For this reason, there is a growing need for downsizing of components mounted on electronic circuit boards and the like used for these.

An aluminum electrolytic capacitor using a conductive polymer as a cathode material (hereinafter referred to as “solid electrolytic capacitor”) has better ESR (equivalent series resistance) characteristics than an aluminum electrolytic capacitor using an electrolyte as a cathode material. Therefore, it can be miniaturized by reducing the number of people and is used in personal computers and game machines.
In addition, in a personal computer or the like, there is a demand for higher speed and higher functionality of the CPU, and the operating frequency is further increased.

  Although the conduction mechanism of an aluminum electrolytic capacitor using an electrolytic solution is ionic conduction, the conduction mechanism of a solid electrolytic capacitor is electronic conduction and exhibits high conductivity. That is, since the responsiveness to discharge 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.

  Recently, conductive polymer hybrid aluminum electrolytic capacitors (hereinafter referred to as “hybrid electrolytic capacitors”) using both conductive polymers and electrolytes as cathode materials have been marketed by capacitor manufacturers. It has also been used for automotive electrical equipment applications where low ESR characteristics and absence of short circuit defects are essential requirements.

  As a method of holding the conductive polymer as the 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 a prepolymerized conductive polymer. is there.

  When polymerizing a conductive polymer in a capacitor element, the capacitor element is impregnated with a solution containing a monomer and an oxidant (hereinafter referred to as “polymerization solution”), and then heated and dried to polymerize the conductive polymer. A layer is formed in the capacitor element.

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

  In any case of the polymerization liquid and the dispersion liquid, the quality of the conductive polymer layer is determined to determine the ESR characteristics of the solid electrolytic capacitor and the hybrid electrolytic capacitor.

  So far, for example, the techniques described in Patent Documents 1 to 5 have been disclosed as separators for solid electrolytic capacitors and hybrid electrolytic capacitors.

  Patent Document 1 proposes a separator having a porosity of 85% or more after the thermal decomposition loss of the separator, and describes that the storage rate of the solid electrolyte is increased. By using the separator described in Patent Document 1, the electrical characteristics can be improved.

  Patent Document 2 describes a separator having a porosity of 60 to 86% by adjusting the density of the separator based on the specific gravity of the separator, and is excellent in carrying property of the conductive polymer. A separator has been proposed. It is said that a solid electrolytic capacitor having a low ESR can be provided by using this separator.

  Furthermore, Patent Document 3 proposes a microporous membrane made of cellulose fibers. In particular, a technique for obtaining a separator by casting a finely-treated cellulose fiber is disclosed, and a cellulose fiber having a fiber diameter of 1 μm or more is contained in an amount of 5% by weight or more based on the total weight of the cellulose fiber. It is described that the volume resistivity of the separator can be controlled. By using this separator, it can cope with an electrochemical element satisfactorily.

  Patent Document 4 describes a separator containing 0.1% or more of an ion-exchangeable substance in the separator, and it is said that ion conduction can be made smooth. It is said that the internal resistance of the capacitor can be reduced by using this separator.

  Patent Document 5 describes a separator that contains fibers made of a semi-aromatic polyamide resin and is well-familiar with a conductive polymer. By using the separator described in Patent Document 5, aluminum electrolysis can be performed. It is said that the ESR of the capacitor can be reduced.

JP 2004-193402 A JP 2011-228320 A JP 2014-210987 A JP 2004-47914 A JP 2004-165593 A

  In the capacitors described in Patent Documents 1 and 2, it is recognized that the storage rate and supportability of the conductive polymer are important for lowering the ESR of the solid electrolytic capacitor. And porosity are used. However, in recent years, there has been an increasing demand for ESR reduction in capacitors having good ESR using a separator as disclosed in Patent Documents 1 and 2.

  In the capacitors described in Patent Documents 3 and 4, the ionic conduction of the separator is smoothed or the volume resistivity is controlled. However, the conduction mechanism of the solid electrolytic capacitor is not ionic conduction in the electrolytic solution. In such separators, the ESR reduction effect was not a satisfactory result.

  In Patent Document 5, a separator containing a semi-aromatic polyamide resin as a synthetic fiber is proposed. It is described that this separator is well-familiar with the conductive polymer polymerization solution and has good impregnation properties. Moreover, although it is described that ESR can be reduced by using this separator, in recent years, there is an increasing demand for further ESR reduction.

  Thus, as a separator for reducing the ESR of an aluminum electrolytic capacitor, a separator having a good chemical affinity with an electrolytic solution or a polymerized liquid or dispersion of a conductive polymer, a porosity, etc. Although controlled separators have been proposed, in recent years, further reduction in ESR has been demanded for aluminum electrolytic capacitors, and further conventional ESR reduction effects have also been demanded for these conventional separators.

  This invention is made | formed in view of the said subject, and it aims at providing the separator for aluminum electrolytic capacitors and the aluminum electrolytic capacitor which implement | achieved further reduction of ESR.

As a means for solving the above-described problems and achieving the above-described object, an embodiment of the invention according to the present invention has the following configuration, for example.
That is, a separator for an aluminum electrolytic capacitor that is formed into a sheet shape and interposed between a pair of electrodes, wherein the sheet has a connectivity density in a range of (0.00005 to 0.00025 μm ⁻³ ), The filling rate is (15.0-45.0%).

For example, the sheet material includes at least fibrillated fibers, and the fibrillation rate of the sheet is (5.0 to 15.0%).
Further, for example, the fibrillated fiber includes fibrillated cellulose.

Alternatively, for example, an aluminum electrolytic capacitor is characterized in that the above-described separator for an aluminum electrolytic capacitor is interposed between a pair of electrodes.
For example, a conductive polymer is used as the cathode of the pair of electrodes.

  By using the separator of the present invention for an aluminum electrolytic capacitor, ESR can be greatly reduced.

It is the figure which showed the model of the connectivity in the separator of one Embodiment which concerns on this invention. It is the figure which showed the calculation method of the connectivity of the spherical form in this Embodiment. It is the figure which showed the calculation method of the connectivity of the donut shape in this Embodiment. It is the figure which showed the calculation method of the connectivity of the pig nose shape in this Embodiment. It is the figure which showed the model of the fibril which concerns on this Embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The inventors of the present invention diligently studied about reduction of ESR. As a result, it was found that it is necessary to continuously form an electron conduction path inside the separator in order to further reduce the ESR of the capacitor.
In order to continuously form the electron conduction path inside the separator, it has been found that it is important to have a separator internal structure in which the conductive polymer layer that becomes the electron conduction path is continuously formed inside the separator. .

  In general, in an aluminum electrolytic capacitor, a polymer solution or dispersion of a conductive polymer sucks up the fiber surface by utilizing the capillary phenomenon of a separator as a holding body. By heating and drying this, a conductive polymer layer serving as an electron conduction path is formed on the fiber surface constituting the separator. For this reason, it turned out that it is important to control the internal structure of a separator.

  For this reason, an electron conduction path | route can be formed continuously by controlling the internal structure of a separator and forming the fiber structure like the continuous mesh inside a separator. In an aluminum electrolytic capacitor using a separator in which the electron conduction path is continuously formed, ESR can be further reduced.

  In the embodiment according to the present invention, attention is paid to the continuity of the fiber structure such as the mesh inside the separator and the gap between the fibers, and the structure has a connectivity density and a fiber filling rate within a certain range.

The separator of the present embodiment is an aluminum electrolytic capacitor separator interposed between a pair of electrodes, and the connectivity density of the separator is in the range of (0.00005 to 0.00025 μm ⁻³ ). Is preferred. More preferably, it is in the range of (0.00009 to 0.00018 μm ⁻³ ).

Furthermore, it is preferable that the filling rate of the fiber is in the range of (15.0 to 45.0%).
In the present embodiment, the internal structure of the separator is controlled by the connectivity density and the fiber filling rate. That is, the continuity of the fiber structure such as the mesh inside the separator and the gap between the fibers are controlled.

  The porosity and porosity proposed for conventional separators are values calculated from the true specific gravity and density of the separator, and do not take into account the internal structure of the separator. For this reason, even if the porosity and porosity are the same, the internal structure of the separator may be different.

  Even if the fiber has a space inside or does not have a space, the fiber may contain a different kind of substance in the fiber. Since the porosity and porosity used conventionally are values calculated from the true specific gravity of the fiber material constituting the separator and the density of the separator, the porosity and porosity and the space existing inside the separator are It did not necessarily match the volume.

That is, there are cases where there are pores that are not in direct contact with the electrolytic solution or the conductive polymer, or there are cases where it is not appropriate to calculate the porosity from only the specific gravity of the material constituting the fiber used in the separator.

In the embodiment of the present invention, in order to eliminate these elements and directly measure the internal structure of the separator, the connectivity density and the fiber filling rate are employed instead of the conventional porosity and porosity. It was decided to.
In other words, in this embodiment, the connectivity density of the separator and the fiber filling rate that greatly affect the formation of a continuous fiber structure such as a mesh inside the separator, and the continuity of the electron conduction path that determines the ESR characteristics of the capacitor are used. Used as a measure index.

When the connectivity density exceeds 0.00025 μm ⁻³ , the connectivity of the fiber structure inside the separator becomes too high, so that the separator internal structure becomes excessively dense and impregnated using the capillary phenomenon. In some cases, the polymerization liquid or dispersion liquid is not sucked up and the electron conduction path cannot be formed continuously. Even if the separator is forcibly impregnated with a polymer solution or dispersion liquid of a conductive polymer by decompression treatment or the like, uneven formation of the conductive polymer layer after polymerization and drying may occur, In some cases, the conductive polymer layer cannot be formed without a break.

When the connectivity density is less than 0.00005 μm ⁻³ , the continuity of the fiber structure inside the separator is lowered, and the continuity of the conductive polymer layer formed through the fibers may be lowered. Thereby, in any case, the electron conduction path formed through the fiber structure of the separator between the electrode foils cannot be continuously formed, and the ESR cannot be sufficiently reduced.

When the fiber filling ratio exceeds 45.0%, the gap between the fibers becomes excessively narrow, so that the electron conduction path is continuous for the same reason as when the connectivity density exceeds 0.00025 μm ^−3. It may not be formed. Further, when the fiber filling rate is less than 15.0%, the gap between the fibers is excessively wide, so that the force of the conductive polymer polymerization solution and dispersion sucking up between the fibers due to the capillary phenomenon is weakened. For this reason, in any case, formation of a continuous conductive polymer layer is insufficient, and ESR cannot be sufficiently reduced.

ESR can be reduced by setting the connectivity density of the separator in the range of (0.00005 to 0.00025 μm ⁻³ ) and the fiber filling rate in the range of (15.0 to 45.0%).
When both connectivity density and fiber filling rate, or one of them does not satisfy the above range, even if either one satisfies the above range, the electron conduction path cannot be formed continuously for the above reasons. , ESR cannot be reduced sufficiently.

For example, the connectivity density of the separator and the fiber filling rate can be calculated by three-dimensional image analysis using X-ray micro CT.
The connectivity density referred to here is connectivity per unit volume. Furthermore, the connectivity here is the maximum number of times that an object can be cut without being divided into two.

  In the present embodiment, in the X-ray micro CT, an X-ray transmission image of the separator is taken from all directions of 360 degrees, and a reconstruction calculation is performed from the obtained transmission image to generate a cross-sectional image group. The connectivity is calculated by building a 3D model of the separator from the reconstructed cross-sectional image group and analyzing the continuity of the fibers inside the separator.

For example, as in the example shown in FIG. 1, in the case of a sphere filled with contents, the object is divided by one cutting, and thus the connectivity is 0 (FIG. 2). In the donut shape, the object is divided by two cuts, so the connectivity is 1 (FIG. 3), and in the pig nose shape, the connectivity is 2 (FIG. 4). In the case of a more complicated lotus root, the connectivity is 8.
2 to 4 are diagrams more specifically illustrating the connectivity calculation method in the case of the spherical shape, the donut shape, and the pig nose shape shown in FIG.

The higher the connectivity, the higher the connectivity density per unit volume, and the higher the continuity of the structure like the fiber network inside the separator.
Further, the fiber filling rate here is a value obtained by dividing the fiber volume calculated by analyzing a 3D model imaged and reconstructed using X-ray micro CT and multiplying it by the separator volume and multiplying by 100.

And the connectivity density of a separator and the filling rate of a fiber can be made into the said range by controlling the fibrillation rate of a separator in the range of (5.0-15.0%), for example.
When the fibrillation rate is less than 5.0%, the connectivity density or filling rate may be lower than the above range, and when the fibrillation rate exceeds 15.0%, the connectivity density or filling rate exceeds the above range. There is a case.

Here, the fibrillation rate is a value obtained by dividing the fibril area constituting the separator by the total area of the fibrils and the fibers that generated the fibrils and multiplying by 100.
Furthermore, the fibril here is, for example, a whisker-like thread-like body that is thinner than the original fiber that is generated when the fiber is treated with a mechanical external force or the like, as shown in FIG.

For example, by using fibrillated fibers, the fibrillation rate of the separator can be in the above range.
Examples of the means for fibrillation of fibers include beating treatment. There is no particular limitation on the equipment used for beating the fibers. In general, a beater, a conical refiner, a disc refiner, a high-pressure homogenizer, and the like can be given.

  Each fiber used in the present embodiment may be beaten alone or mixed before paper making, or may be beaten after mixing. Moreover, as long as a desired fibrillation rate can be obtained, the fibers are not limited to beaten fibers, and fibers manufactured to have a fibrillar structure such as synthetic pulp may be used.

  The fiber type of the fibrillated fiber is not particularly limited, and natural fiber or synthetic fiber can be used. Among these, cellulose fibers are preferable from the viewpoint of hydrophilicity and mechanical strength due to the action of hydroxyl groups, and natural cellulose fibers are more preferable from the viewpoint of affinity for conductive polymers.

In consideration of the necessity at the time of forming the separator and the mechanical strength at the time of handling, binder fibers can be used.
However, it is only necessary to be able to control the connectivity density of the separator and the filling rate of the fibers within the above ranges, and the method is not limited to the method using the fibrillated fibers.

As the thickness and density of the separator of the present embodiment, those satisfying desired characteristics of the aluminum electrolytic capacitor can be employed without any particular limitation. In general, a separator having a thickness and density of about 20 to 70 μm and a density (0.20 to 0.60 g / cm ³ ) is used, but the separator according to the present embodiment falls within this range. It is not limited.

  In the present embodiment, a wet nonwoven fabric formed using a papermaking method was employed as the separator sheet. The paper making format of the separator is not particularly limited as long as the connectivity density and fiber filling rate of the separator can be satisfied, and paper making formats such as long net paper, short net paper, and circular net paper can be used. A plurality of layers formed by the above may be combined. In addition, when making paper, additives such as a dispersant, an antifoaming agent, and a paper strength enhancer may be added as long as the impurity content does not affect the capacitor separator.

  Further, after the paper layer is formed, processing such as paper strength enhancement processing, lyophilic processing, calendar processing, embossing processing, and the like may be performed. If the desired connectivity density and filling rate can be satisfied, the coating amount for paper strength enhancement processing and hydrophilic processing is not particularly limited, but for example, up to about 5% by mass affects the connectivity density and filling rate. It is hard to give.

In the aluminum electrolytic capacitor of the present embodiment, the separator having the above configuration is used as a separator, a separator is interposed between a pair of electrodes, and a conductive polymer is used as a cathode material.
By adopting the above configuration, the separator of the present embodiment contributes to the formation of a continuous electron conduction path. Then, by using this separator for an aluminum electrolytic capacitor using a conductive polymer as a cathode material, an aluminum electrolytic capacitor having a low ESR can be obtained.

[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.
〔thickness〕
As defined in “JIS C 2300-2“ Electrical cellulose paper-Part 2: Test method ”5.1 Thickness”, “5.1.1 Measuring instrument and measuring method a When using an external micrometer” Using a micrometer, the thickness of the separator was measured by the method of folding it into 10 sheets as described in “5.1.3 When measuring thickness by folding paper”.

〔density〕
The density of the absolutely dried separator was measured by the method defined in Method B of “JIS C 2300-2“ Electric Cellulose Paper—Part 2: Test Method ”7.0 A Density”.
[Fibrillation rate]
The value of fibrillation measured using kajaaniFiberLab (Metso Automation Co., Ltd.) was defined as the fibrillation rate.

[Porosity]
The porosity of the separator was determined by the following formula.
(Separator's true specific gravity-separator density) / Separator's true specific gravity x 100 (%)
[Connectivity density and filling rate]
Separation density of the separator and fiber filling ratio are as follows: skyscan 1272 (manufactured by Bruker), tube voltage 50 kV, tube current 200 μA, resolution 0.7 μm, exposure time 1100 ms, rotation step 0.2 degree, irradiation method is step It was measured by the and shoot method and calculated by three-dimensional image analysis.

[Production process of solid electrolytic capacitor]
Using the separator of each example, comparative example, and each conventional example, rated voltage 6.3V electrostatic capacity 470 μF, diameter 10.0 mm × height 8.0 mm, rated voltage 50 V, electrostatic capacity 33 μF, diameter 10 mm × high Two types of solid electrolytic capacitors having a thickness of 10.0 mm were produced.

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

  Here, about the capacitor | condenser element using the separator of Examples 2 and 7 mentioned later and the cellulose fiber of a comparative example of 100 mass%, heat processing was performed for 280 degreeC and 1 hour. However, the heat treatment temperature and time are not limited to these conditions.

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

[Production process of hybrid electrolytic capacitor]
Using the separators of Examples, Comparative Examples, and Conventional Examples described later, a rated voltage of 16 V, a capacitance of 470 μF, a diameter of 10.0 mm × a height of 10.5 mm, a rated voltage of 80 V, a capacitance of 39 μF, and a diameter of 10. Two types of hybrid electrolytic capacitors of 0 mm × height 10.0 mm were produced.

A specific manufacturing method is as follows.
A capacitor element was produced by winding with a separator so that the anode foil and the cathode foil subjected to the etching treatment and oxide film formation treatment were not in contact with each other. The produced capacitor element was dried after the re-chemical conversion treatment.

In the case of a hybrid electrolytic capacitor having a rated voltage of 16 V, the capacitor element is impregnated with a conductive polymer polymerization solution, heated and polymerized, and the solvent is dried to form a conductive polymer.
In the case of a hybrid electrolytic capacitor with a rated voltage of 80 V, a conductive polymer is formed by impregnating a capacitor element with a conductive polymer dispersion, followed by heating and drying.

  Subsequently, the capacitor element was impregnated with a driving electrolyte, the capacitor element was put in a predetermined case, the opening was sealed, and aging was performed to obtain respective hybrid electrolytic capacitors.

[Evaluation method for aluminum electrolytic capacitors]
The specific performance evaluation of the aluminum electrolytic capacitor of the present embodiment was performed under the following conditions and method.
[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.

〔Example〕
Hereinafter, specific examples of the separator according to the embodiment of the present invention will be described.

[Example 1]
The separator of Example 1 was made into a circular mesh paper using a raw material in which 30% by mass of fibrillated cellulose fibers having a fibrillation rate of 8.3%, 35% by mass of acrylic fibers, and 35% by mass of polyester fibers were mixed. Got.
The completed separator of Example 1 has a thickness of 40 μm, a density of 0.20 g / cm ³ , a porosity of 85.2%, a connectivity density of 0.00005 μm ⁻³ , a filling rate of 22.0%, and fibrillation. The rate was 6.0%.

[Example 2]
Circular paper making was performed using 100% by mass of fibrillated cellulose fibers beaten to a fibrillation rate of 15.6% to obtain a separator of Example 2.
The separator of Example 2 has a thickness of 70 μm, a density of 0.60 g / cm ³ , a porosity of 60.0%, a connectivity density of 0.00025 μm ⁻³ , a filling rate of 40.5%, and a fibrillation rate of 13.8%.

Example 3
Circular separator paper making was performed using 50% by mass of fibrillated cellulose fibers and 50% by mass of aramid fibers beaten to a fibrillation rate of 11.0% to obtain a separator of Example 3.
The separator of Example 3 has a thickness of 20 μm, a density of 0.30 g / cm ³ , a porosity of 79.6%, a connectivity density of 0.00008 μm ⁻³ , a filling rate of 15.0%, and a fibrillation rate of It was 10.3%.

Example 4
Circular paper making was performed using 50% by mass of fibrillated cellulose fiber, which was beaten to a fibrillation rate of 11.1%, 15% by mass of acrylic fiber, and 35% by mass of polyvinyl alcohol fiber to obtain the separator of Example 4. .
The separator of Example 4 has a thickness of 35 μm, a density of 0.45 g / cm ³ , a porosity of 67.1%, a connectivity density of 0.00020 μm ⁻³ , a filling rate of 45.0%, and a fibrillation rate of It was 10.3%.

Example 5
Circular separator paper making was performed using 40% by mass of fibrillated cellulose fibers, 30% by mass of nylon fibers, and 30% by mass of polyester fibers beaten to a fibrillation rate of 6.5%, whereby a separator of Example 5 was obtained.
The separator of Example 5 has a thickness of 25 μm, a density of 0.38 g / cm ³ , a porosity of 73.4%, a connectivity density of 0.00012 μm ⁻³ , a filling rate of 27.0%, and a fibrillation rate of It was 5.0%.

Example 6
Example 6 A circular paper was made using 80% by mass of fibrillated cellulose fibers beaten to a fibrillation rate of 16.4% and 20% by mass of fibrillated aramid fibers beaten to a fibrillation rate of 16.4%. A separator was obtained.
The separator of Example 6 has a thickness of 30 μm, a density of 0.43 g / cm ³ , a porosity of 70.9%, a connectivity density of 0.00022 μm ⁻³ , a filling rate of 38.0%, and a fibrillation rate of It was 15.0%.

Example 7
Circular paper making was performed using 100% by mass of fibrillated cellulose fibers beaten to a fibrillation rate of 7.2% to obtain a separator of Example 7.
The separator of Example 7 has a thickness of 50 μm, a density of 0.35 g / cm ³ , a porosity of 76.7%, a connectivity density of 0.00009 μm ⁻³ , a filling rate of 23.5%, and a fibrillation rate of It was 6.6%.

Example 8
The separator of Example 8 was coated with 5% by mass of polyacrylamide after circular mesh paper making using 70% by mass of fibrillated cellulose fibers beaten to 13.0% and 30% by mass of nylon fibers. Got.
The separator of Example 8 has a thickness of 40 μm, a density of 0.40 g / cm ³ , a porosity of 72.7%, a connectivity density of 0.00018 μm ⁻³ , a filling rate of 33.3%, and a fibrillation rate of It was 12.5%.

[Reference example]
After making a circular mesh paper using 40% by mass of fibrillated cellulose fibers beaten to a fibrillation rate of 8.7% and 60% by mass of nylon fibers, 15% by mass of polyacrylamide is applied, and the separator of the reference example is formed. Obtained.
The thickness of the separator of the reference example is 35 μm, the density is 0.28 g / cm ³ , the porosity is 82.5%, the connectivity density is 0.00008 μm ⁻³ , the filling rate is 44.8%, and the fibrillation rate is 7 0.0%.

[Comparative example]
Circular mesh papermaking was performed using 100% by mass of fibrillated cellulose fibers beaten to a fibrillation rate of 20.1% to obtain a separator of Comparative Example 1.
The separator of Comparative Example 1 has a thickness of 60 μm, a density of 0.45 g / cm ³ , a porosity of 70.0%, a connectivity density of 0.00023 μm ⁻³ , a filling rate of 60.3%, and a fibrillation rate of 19.0%.

[Conventional example 1]
A separator manufactured by a method similar to the method described in Example 1 of Patent Document 1 was produced and used as the separator of Conventional Example 1.
The separator of Conventional Example 1 contains 100% by mass of aramid fibers, the thickness is 40 μm, the density is 0.14 g / cm ³ , the porosity is 90.3%, the connectivity density is 0.00002 μm ⁻³ , and the filling rate is The fibrillation rate was 15.0% and 0.0%.

[Conventional example 2]
A separator manufactured by the same method as that described in Example 2 of Patent Document 2 was prepared, and the separator of Conventional Example 2 was obtained.
The separator of Conventional Example 2 contains 50% by mass of fibrillated cellulose fibers and 50% by mass of acrylic fibers beaten to a fibrillation rate of 23.7%, a thickness of 30 μm, a density of 0.45 g / cm ³ , and a porosity. Was 66.4%, the connectivity density was 0.00030 μm ⁻³ , the filling rate was 43.0%, and the fibrillation rate was 22.3%.

[Conventional example 3]
A separator manufactured by the same method as that described in Example 1 of Patent Document 5 was produced, and the separator of Conventional Example 3 was obtained.
The separator of Conventional Example 3 contains 70% by mass of nylon fiber and 30% by mass of polyvinyl alcohol fiber, the thickness is 40 μm, the density is 0.27 g / cm ³ , the porosity is 79.7%, and the connectivity density is 0. 0.00006 μm ⁻³ , the filling rate was 12.5%, and the fibrillation rate was 0.0%.

Aluminum electrolytic capacitors produced using the separators of the examples, reference examples, comparative examples, and conventional examples are a solid electrolytic capacitor having a rated voltage of 6.3 V for a low voltage and a solid electrolytic capacitor having a rated voltage of 50 V for a high voltage. A capacitor was produced.
Moreover, a capacitor having a rated voltage of 16V for low voltage and a capacitor having a rated voltage of 80V for high voltage were produced as hybrid electrolytic capacitors.

  Table 1 shows the raw materials and post-processing of each separator of Examples 1 to 8, Reference Example, Comparative Example, and Conventional Examples 1 to 3 of the present embodiment described above. Table 2 shows the performance evaluation results.

Hereinafter, evaluation results will be described in detail for each example, reference example, comparative example, and each conventional example.
As can be seen from Table 2, the solid electrolytic capacitor having the rated voltage of 6.3 V using the separators of Examples 1 to 8 has a low ESR of 18 to 24 mΩ. A solid electrolytic capacitor having a rated voltage of 50 V using the separator also has a low ESR of 25 to 34 mΩ.

  In addition, the ESR is as low as 22 to 29 mΩ in the hybrid electrolytic capacitor with the rated voltage of 16 V using the separators of Examples 1 to 8. A hybrid electrolytic capacitor having a rated voltage of 80 V using the separator also has a low ESR of 33 to 44 mΩ.

The separators of Examples 1 to 8 had a connectivity density of 0.00005 to 0.00025 μm ⁻³ , a filling rate of 15.0 to 45.0%, and a fibrillation rate of 5.0 to 15.0%.
From this, the separator of this embodiment controls the continuity of the fiber structure like the mesh inside the separator and the gap between the fibers, so that the electron conduction path between the electrode foils can be continuously formed. It becomes possible, and it turns out that it contributes to low ESR in a solid electrolytic capacitor and a hybrid electrolytic capacitor.

The separator of the reference example has a connectivity density of 0.00008 μm ⁻³ , a filling rate of 44.8%, and a fibrillation rate of 7.0%. The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of the reference example have slightly higher ESR than the respective examples.

  Details are unknown, but because the polyacrylamide coating amount is as high as 15% by mass and the majority of the surface of the fibrillated cellulose fiber is covered with polyacrylamide, the affinity with the conductive polymer has decreased. It is believed that there is. And it can be estimated from the comparison between Example 8 and the reference example that the affinity is not affected if the coating amount is 5% by mass or less.

The separator of the comparative example has a connectivity density of 0.00023 μm ⁻³ , a filling rate of 60.3%, and a fibrillation rate of 19.0%.
The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of the comparative example have higher ESR than the respective examples and reference examples. This is because the fibrillation rate is high, the filling rate is high, and the gap between fibers is excessively narrow, and the formation of the conductive polymer layer inside the separator is insufficient. It is thought that.

The separator of Conventional Example 1 is a separator manufactured in the same manner as the separator described in Example 1 of Patent Document 1, and has a connectivity density of 0.00002 μm ⁻³ , a filling rate of 15.0%, and a fibrillation rate of 0. 0.0%.
The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Conventional Example 1 have higher ESR than the respective Examples and Reference Examples.

  This is because the separator of Conventional Example 1 has a high porosity of 90.3%, but because the connectivity density is low due to the low fibrillation rate, the continuity between the fibers is low, and the fibers are formed through the fibers. It is thought that this is because the continuity of the conductive polymer layer is lowered and the electron conduction path cannot be continuously formed.

The separator of Conventional Example 2 is a separator produced in the same manner as the separator described in Example 2 of Patent Document 2, and has a connectivity density of 0.00030 μm ^-3 , a filling rate of 43.0%, and a fibrillation rate of 22 .3%.
The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Conventional Example 2 have higher ESR than the respective Examples and Reference Examples. This is because the separator of Conventional Example 2 has a high fibrillation rate, and the connectivity density is high. Therefore, the continuity of the fiber structure becomes too high, the separator internal structure becomes excessively dense, and the conductive polymer polymerization solution and dispersion impregnated using the capillary phenomenon cannot be sucked up. Therefore, it is considered that this is because the electron conduction path could not be formed continuously.

  From comparison between Conventional Examples 1 and 2 and each example, it can be seen that controlling the porosity of the separator does not necessarily reduce the ESR of the capacitor.

The separator of Conventional Example 3 is a separator manufactured in the same manner as the separator described in Example 1 of Patent Document 5, and has a connectivity density of 0.00006 μm ⁻³ , a filling rate of 12.5%, and a fibrillation rate of 0. 0.0%.
The solid electrolytic capacitor and the hybrid electrolytic capacitor using the separator of Conventional Example 3 have higher ESR than the respective Examples and Reference Examples. This is because the separator of Conventional Example 3 has a low fibrillation rate and a low filling rate. For this reason, it is considered that the reason is that the electron conduction path could not be continuously formed even in the separator of Conventional Example 3 having good affinity with the conductive polymer.
From the comparison between Conventional Example 3 and each example, it can be seen that just because the separator has a high affinity with the conductive polymer, the ESR of the capacitor cannot always be reduced.

As described above, according to the embodiment of the present invention, the connectivity density of the separator is in the range of (0.00005 to 0.00025 μm ⁻³ ), and the fiber filling rate is (15.0 to 4.5). 0.0%) and the fibrillation rate within the range of (5.0 to 15.0%), the internal structure of the separator can be controlled, and the electron conduction path can be formed continuously. Become. That is, it can contribute to the reduction of ESR of the aluminum electrolytic capacitor.

  In addition, since the separator contains cellulose fibers, the affinity of the separator for the conductive polymer is increased, and the separator can be sufficiently filled with the conductive polymer. The ESR of the capacitor can be further reduced.

  As described above, the separator of the present embodiment is controlled to a structure in which the fiber structure that is the internal structure of the separator is formed like a continuous mesh and the gap between fibers is appropriately maintained. The separator of this embodiment having such a structure is a separator that has been proposed so far, with a controlled porosity or porosity, and a separator that focuses on the affinity with an electrolyte or a conductive polymer. Clearly different.

  In this embodiment, since the internal structure of the separator that directly contributes to the formation of a continuous electron conduction path is controlled, the polymer liquid and dispersion of the conductive polymer are the fibers of the formed separator. The conductive polymer layer is formed on the fiber surface by being impregnated through the structure, polymerized and dried. This conductive polymer layer can be formed continuously by controlling the connectivity density of the separator and the fiber filling rate. That is, the electron conduction path can be continuously formed, and ESR can be reduced. Therefore, it can contribute to the low ESR of the aluminum electrolytic capacitor using the separator of the present embodiment.

  Furthermore, since it is possible to reduce the conductive polymer while maintaining the ESR, it is possible to contribute to the cost reduction by reducing the man-hour of the capacitor and the amount of the member used.

Claims (5)

A separator for an aluminum electrolytic capacitor molded into a sheet and interposed between a pair of electrodes,
The aluminum electrolytic capacitor characterized in that the sheet has a connectivity density in the range of (0.00005 to 0.00025 μm ⁻³ ) and a fiber filling ratio in the range of (15.0 to 45.0%). Separator for use. Including at least fibrillated fibers as a material of the sheet,
The separator for an aluminum electrolytic capacitor according to claim 1, wherein the fibrillation rate of the sheet is in the range of (5.0 to 15.0%).   The separator for an aluminum electrolytic capacitor according to claim 2, wherein the fibrillated fiber contains fibrillated cellulose.   An aluminum electrolytic capacitor comprising the aluminum electrolytic capacitor separator according to any one of claims 1 to 3 interposed between a pair of electrodes.   The aluminum electrolytic capacitor according to claim 4, wherein a conductive polymer is used as a cathode of the electrode.