JP2016082053A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor having high reliability.SOLUTION: An electrolytic capacitor has a capacitor element which is provided with an anode body having a dielectric layer formed therein, electrically conductive polymer covering the surface of a part of the dielectric layer, and electrolytic liquid containing non-aqueous solvent and a glycerin compound. The non-aqueous solvent contains γ-butyrolactone, and the glycerin compound is at least one kind selected from the group consisting of glycerin and polyglycerol. The content of the glycerin compound in the electrolytic solution is preferably equal to 5 wt% or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor having high reliability.

  Along with the digitization of electronic devices, capacitors used therefor are required to have small size, large capacity, and low equivalent series resistance (ESR) in a high frequency region.

  As a small-sized, large-capacity, low-ESR capacitor, an electrolytic capacitor using a conductive polymer such as polypyrrole, polythiophene, polyfuran, or polyaniline as a cathode material is promising. For example, an electrolytic capacitor has been proposed in which a conductive polymer layer is provided as a cathode material on an anode foil (anode body) on which a dielectric layer is formed.

  In Patent Document 1, an element including a separator is impregnated with a dispersion of a conductive polymer to form a conductive solid layer, and then impregnated with an electrolytic solution to include the conductive solid layer and the electrolytic solution. A method for manufacturing an electrolytic capacitor has been proposed.

JP 2008-010657 A

  In recent years, electrolytic capacitors have been used not only in electronic equipment but also in automotive electrical equipment. In particular, since electrolytic capacitors used in automobile electrical equipment are used for a long period of time in a high temperature environment, the electrolytic capacitors are required to have higher reliability over a longer period than before. Then, an object of this invention is to provide the electrolytic capacitor which has further high reliability.

One aspect of the present invention is a capacitor element including an anode body in which a dielectric layer is formed;
A conductive polymer covering a surface of at least a part of the dielectric layer;
An electrolyte solution containing a non-aqueous solvent and a glycerin compound,
The non-aqueous solvent includes γ-butyrolactone,
The glycerin compound relates to an electrolytic capacitor which is at least one selected from the group consisting of glycerin and polyglycerin.

  According to the present invention, an electrolytic capacitor having high reliability can be obtained.

It is a cross-sectional schematic diagram of the electrolytic capacitor which concerns on one Embodiment of this invention. It is the schematic for demonstrating the structure of the capacitor | condenser element in the electrolytic capacitor of FIG.

  Embodiments of the electrolytic capacitor of the present invention will be described below with reference to the drawings as appropriate. However, the following embodiments do not limit the present invention.

≪Electrolytic capacitor≫
FIG. 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present invention. FIG. 2 is a schematic developed view of a part of the capacitor element included in the electrolytic capacitor.

  In FIG. 1, an electrolytic capacitor includes a capacitor element 10 including an anode body 21 on which a dielectric layer is formed and a conductive high layer that covers (or adheres to at least a part of) the surface of at least a part of the dielectric layer. It includes molecules (not shown) and an electrolyte solution (not shown). And the capacitor | condenser element 10 is accommodated in the exterior case with electrolyte solution in the state in which at least one part surface of the dielectric material layer was covered with the conductive polymer. The exterior case includes a bottomed case 11 that houses the capacitor element 10 therein, an insulating sealing member 12 that closes the opening of the bottomed case 11, and a seat plate 13 that covers the sealing member 12. The vicinity of the open end of the bottomed case 11 is drawn inward, and the open end is curled so as to be crimped to the sealing member 12.

  For example, the capacitor element 10 as shown in FIG. 2 is called a wound body. The capacitor element 10 includes an anode body 21 connected to the lead tab 15A, a cathode body 22 connected to the lead tab 15B, and a separator 23. The anode body 21 and the cathode body 22 are wound through a separator 23. The outermost periphery of the capacitor element 10 is fixed by a winding tape 24. FIG. 2 shows a state where a part of the capacitor element 10 is unfolded before stopping the outermost periphery.

The anode body 21 includes a metal foil roughened so that the surface has irregularities, and a dielectric layer is formed on the metal foil having irregularities.
In the electrolytic capacitor, the conductive polymer is attached so as to cover at least a part of the surface of the dielectric layer formed on the anode body 21. However, the present invention is not limited to this, and the anode body 21 and the cathode body 22 It may be attached at any position between. For example, the conductive polymer covers at least part of the surface of the dielectric layer formed on the anode body 21, and further, at least one part of the surface of the cathode body 22 and / or the surface of the separator 23. The part may be covered. In an electrolytic capacitor, generally, a conductive polymer (specifically, a film containing a conductive polymer) covering at least a part of the surface of an anode body, a cathode body, a separator, or the like is used as a conductive polymer layer. May be called.

Below, the structure of the electrolytic capacitor which concerns on embodiment of this invention is demonstrated in detail.
The capacitor element includes an anode body on which a dielectric layer is formed. The conductive polymer attached to the surface of the dielectric layer functions as a practical cathode material. The capacitor element may further include a cathode body and / or a separator as necessary.

(Capacitor element)
(Anode body)
As an anode body, the metal foil with which the surface was roughened is mentioned, for example. Although the kind of metal which comprises metal foil is not specifically limited, From the point that formation of a dielectric material layer is easy, it is preferable to use the alloy which contains valve action metals, such as aluminum, a tantalum, niobium, or a valve action metal.

  The roughening of the metal foil surface can be performed by a known method. By roughening, a plurality of irregularities are formed on the surface of the metal foil. The roughening is preferably performed, for example, by etching a metal foil. The etching treatment may be performed by, for example, a direct current electrolytic method or an alternating current electrolytic method.

(Dielectric layer)
The dielectric layer is formed on the surface of the anode body (specifically, the surface of the roughened metal foil).
Although the formation method of a dielectric material layer is not specifically limited, It can form by performing a chemical conversion treatment of metal foil. The chemical conversion treatment may be performed, for example, by immersing the metal foil in a chemical conversion solution such as an ammonium adipate solution. In the chemical conversion treatment, a voltage may be applied in a state where the metal foil is immersed in the chemical conversion liquid as necessary.

  Usually, from the viewpoint of mass productivity, a roughening treatment and a chemical conversion treatment are performed on a metal foil formed of a large valve metal or the like. In that case, the anode body 21 is prepared by cutting the foil after processing into a desired size.

(Cathode)
Similarly to the anode body, a metal foil may be used for the cathode body 22. The type of metal is not particularly limited, but it is preferable to use a valve action metal such as aluminum, tantalum, or niobium or an alloy containing the valve action metal. If necessary, the surface of the metal foil may be roughened.
The surface of the cathode body 22 may be provided with a chemical conversion film, or a metal (different metal) different from the metal constituting the cathode body or a non-metal film may be provided. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon.

(Separator)
As the separator 23, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, polyamide (for example, an aromatic polyamide such as aliphatic polyamide or aramid) may be used.

  The capacitor element 10 can be produced by a known method. For example, the capacitor element 10 may be manufactured by superposing the anode body 21 and the cathode body 22 with the separator 23 interposed therebetween. A winding body as shown in FIG. 2 may be formed by winding the anode body 21 and the cathode body 22 through the separator 23. At this time, by winding the lead tabs 15A and 15B while winding them, the lead tabs 15A and 15B may be planted from the wound body as shown in FIG.

The material of the lead tabs 15A and 15B is not particularly limited as long as it is a conductive material. The surface of the lead tabs 15A and 15B may be subjected to chemical conversion treatment. Moreover, the part which contacts the sealing body 12 of lead tab 15A, 15B and the connection part with lead wire 14A, 14B may be covered with the resin material.
The material of the lead wires 14A and 14B connected to each of the lead tabs 15A and 15B is not particularly limited, and a conductive material or the like may be used.

  Of the anode body 21, the cathode body 22, and the separator 23, the end portion of the outer surface of the wound body (the cathode body 22 in FIG. 2) is fixed with a winding tape 24. When the anode body 21 is prepared by cutting a large-sized metal foil, in order to provide a dielectric layer on the cut surface of the anode body 21, the capacitor element in a state such as a wound body is further formed. Processing may be performed.

(Conductive polymer)
Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polythiophene vinylene, and the like. These may be used alone or in combination of two or more, or may be a copolymer of two or more monomers.

  In the present specification, polypyrrole, polythiophene, polyfuran, polyaniline and the like mean polymers having a basic skeleton of polypyrrole, polythiophene, polyfuran, polyaniline and the like, respectively. Accordingly, polypyrrole, polythiophene, polyfuran, polyaniline and the like can also include respective derivatives. For example, polythiophene includes poly (3,4-ethylenedioxythiophene) and the like.

  The conductive polymer may contain a dopant. A polyanion can be used as the dopant. Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacryl sulfonic acid, poly (2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, poly Anions such as acrylic acid can be mentioned. Of these, polyanions derived from polystyrene sulfonic acid are preferred. These may be used alone or in combination of two or more. These may be a single monomer polymer or a copolymer of two or more monomers.

  Although the weight average molecular weight of a polyanion is not specifically limited, For example, it is 1,000-1,000,000. Such a conductive polymer containing a polyanion is easily dispersed homogeneously in a liquid solvent, and easily adheres uniformly to the surface of the dielectric layer.

  The conductive polymer may be attached to at least a part of the surface of the dielectric layer in the anode body 21 so as to cover the dielectric layer, but is preferably attached so as to cover as many regions as possible. When the capacitor element includes a cathode body and / or a separator, the conductive polymer may be attached not only to the surface of the surface of the dielectric layer but also to the surface of the cathode body and / or the separator. That is, the conductive polymer may be in contact with the separator and / or the cathode body.

  The conductive polymer includes a step (first step) of impregnating a capacitor element including an anode body on which a dielectric layer is formed with a first treatment liquid containing the conductive polymer, and a first step if necessary. Then, it can be made to adhere by passing through the process (2nd process) which makes a capacitor | condenser element impregnate a 2nd process liquid. Through the first step or the first and second steps, the conductive polymer is attached to the surface of the dielectric layer. The method for manufacturing an electrolytic capacitor may include a step (third step) of removing at least a part of the solvent component contained in the first processing liquid after the first step, and the first processing liquid after the second step. And / or a step of removing at least a part of the solvent component contained in the second treatment liquid (fourth step) may be included.

(I) Step of impregnating the capacitor element (winding body) 10 with the first treatment liquid (first step)
The impregnation of the first treatment liquid into the capacitor element 10 is not particularly limited as long as the first treatment liquid can be applied to at least the anode body (particularly, at least the dielectric layer). For example, the capacitor element is immersed in the first treatment liquid. Alternatively, the first treatment liquid may be injected into the capacitor element. The impregnation may be performed under atmospheric pressure, but may be performed under reduced pressure, for example, in an atmosphere of 10 to 100 kPa, preferably 40 to 100 kPa. Impregnation may be performed under ultrasonic vibration as necessary. Although the impregnation time depends on the size of the capacitor element 10, it is, for example, 1 second to 5 hours, preferably 1 minute to 30 minutes. Through this step, the first treatment liquid is applied to the capacitor element 10.

  The first treatment liquid may include a conductive polymer and a liquid solvent. The first treatment liquid may be either a solution in which a conductive polymer is dissolved in a liquid solvent or a dispersion liquid in which a conductive polymer is dispersed in a liquid solvent. In the dispersion, the conductive polymer is dispersed in the liquid solvent in the form of particles. As the dispersion, a conductive polymer containing a dopant is obtained by polymerizing a raw material of a conductive polymer (for example, a precursor of a monomer and / or oligomer of a conductive polymer) in a liquid solvent in the presence of a dopant. You may use what is obtained by producing | generating this particle | grain. Also, a dispersion obtained by polymerizing a raw material of a conductive polymer in a liquid solvent to produce particles of the conductive polymer, or a conductive polymer synthesized in advance in a liquid solvent Those obtained by dispersing the particles may be used.

  The liquid solvent of the first treatment liquid may contain a first solvent, and may contain a first solvent and a solvent other than the first solvent. The liquid solvent contained in the first treatment liquid may contain a plurality of different first solvents. For example, the first solvent may occupy 30% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more of the liquid solvent of the first treatment liquid.

  The first solvent is not particularly limited, and may be water or a non-aqueous solvent. The non-aqueous solvent is a general term for liquids excluding water and liquids containing water, and includes organic solvents and ionic liquids. Especially, it is preferable that a 1st solvent is a polar solvent. The polar solvent may be a protic solvent or an aprotic solvent.

  Examples of protic solvents include methanol, ethanol, propanol, butanol, ethylene glycol (EG), propylene glycol, polyethylene glycol, diethylene glycol monobutyl ether, glycerol, 1-propanol, butanol, polyglycerol, and other alcohols, formaldehyde, and water. Etc.

  Examples of the aprotic solvent include amides such as N-methylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, esters such as methyl acetate, methyl ethyl ketone, and γ-butyrolactone (γBL). Ketones, ethers such as 1,4-dioxane, sulfur-containing compounds such as dimethyl sulfoxide and sulfolane, and carbonate compounds such as propylene carbonate.

  Of these, the first solvent is preferably a protic solvent. In particular, the first solvent is preferably water. In this case, the handleability of the first treatment liquid and the dispersibility of the conductive polymer are improved. Moreover, since water has a low viscosity, it can be expected that the contact property between the conductive polymer and the second treatment liquid is improved in the second step, which is a subsequent step. When the first solvent is water, the water preferably occupies 50% by mass or more of the liquid solvent of the first treatment liquid, more preferably 70% by mass or more, and particularly preferably 90% by mass or more.

  The particles of the conductive polymer dispersed in the dispersion are the median diameter (hereinafter simply referred to as the median diameter by the dynamic light scattering method). It is preferable that it is 0.01-0.5 micrometer. The particle diameter of the conductive polymer can be adjusted by polymerization conditions, dispersion conditions, and the like.

  The concentration of the conductive polymer (including the dopant or polyanion) in the first treatment liquid is preferably 0.5 to 10% by mass. The first treatment liquid having such a concentration is suitable for adhering an appropriate amount of the conductive polymer, and is easy to be impregnated into the capacitor element 10 and is advantageous in improving productivity.

(Ii) Step of impregnating the capacitor element with the second treatment liquid (second step)
In the second step, the capacitor element to which the first processing liquid is applied is impregnated with the second processing liquid. The second step is an optional step.

  In the second step, it is preferable that the second treatment liquid is impregnated with at least a part of the liquid solvent (such as the first solvent) of the first treatment liquid remaining in the capacitor element (particularly, the anode body). The capacitor element including the anode body in a state where the liquid solvent remains has extremely high permeability of the second processing liquid. Therefore, when a 2nd process liquid is provided to the capacitor | condenser element in such a state, a 2nd process liquid can be osmose | permeated further inside. Such an effect is easily obtained particularly when the process is performed with at least water remaining. Therefore, it is preferable to use a liquid solvent containing at least water as the first solvent for the first treatment liquid. When a liquid solvent containing water is used as the first solvent, the stability of the first treatment liquid is also increased, which is advantageous from this viewpoint.

  In the capacitor element used in the second step, the residual amount of the liquid solvent is preferably 5% by mass or more (for example, 5 to 100% by mass), and 20% by mass or more (for example, 20 to 100% by mass). Or it is more preferable that it is 50 mass% or more (for example, 50-100 mass%). When the remaining amount of the liquid solvent is in such a range, the second treatment liquid is easily mixed in the conductive polymer and the capacitor element in the second step, so that the conductive polymer is applied to the surface of the dielectric layer. It becomes easier to adhere more uniformly.

  The remaining amount of the liquid solvent is the mass of the liquid solvent contained in the capacitor element used in the second step with respect to the mass of the liquid solvent contained in the first treatment liquid impregnated in the capacitor element in the first step. It is a ratio (mass%).

  A solvent (second solvent) is used as the second treatment liquid. The impregnation of the capacitor element with the second processing liquid can be performed according to the case of the first processing liquid. Examples of the second solvent include a polar solvent and a nonpolar solvent. Examples of the nonpolar solvent include hydrocarbon, ethyl acetate, diethyl ether and the like.

As the second solvent, a polar solvent is preferable. Examples of the polar solvent include an aprotic solvent in addition to the protic solvent exemplified for the first solvent.
Examples of the aprotic solvent include those exemplified for the first solvent, amides, lactones such as γBL, cyclic ethers such as 1,4-dioxane, sulfones such as dimethyl sulfoxide and sulfolane, and propylene carbonate. A cyclic carbonate etc. are mentioned. The second treatment liquid may contain one type of second solvent, or may contain two or more types of second solvent.

Examples of protic solvents include water, alcohols (specifically, polyol compounds such as alkanols such as methanol and ethanol, glycols (EG, PEG, etc.), glycerols (glycerol, polyserine, etc.), diethylene glycol monobutyl ether, etc. Protic organic solvents such as glycol monoethers are preferred.
The at least one second solvent is preferably a protic solvent, and the second treatment liquid may be a mixture of a protic solvent and an aprotic solvent. When using a plurality of second solvents, for example, a combination of a polyol compound having three or more hydroxyl groups per molecule and a polar solvent (protic organic solvent and / or aprotic solvent) other than the polyol compound. Also good. As the protic organic solvent, alcohols other than polyol compounds (specifically, alkanols and glycols), glycol monoethers and the like are preferable.

(Iii) Step of removing the solvent component (third step, fourth step)
After the first step, the solvent component remaining in the capacitor element can be removed in the third step. Further, after the second step, the solvent component remaining in the capacitor element may be removed in the fourth step. In the third step or the fourth step, at least part of the solvent component may be removed, and all of the solvent component may be removed. By removing the solvent component in the fourth step, the conductive polymer can be more uniformly attached to the surface of the dielectric layer.
The solvent component here refers to the liquid solvent contained in the first treatment liquid and the second solvent contained in the second treatment liquid. Among these, it is preferable to remove at least a part of the first solvent and / or the second solvent (particularly the first solvent) in the fourth step.

In each of the third step and the fourth step, the solvent component can be removed by evaporation under heating, may be removed under atmospheric pressure, or may be removed under reduced pressure as necessary. Good. The temperature at which the solvent component is removed may be equal to or higher than the boiling point of the first solvent (or the second solvent). The removal of the solvent component may be performed, for example, at a plurality of stages having different temperatures (for example, two stages or three stages or more) or may be performed while raising the temperature.
In this way, the conductive polymer adheres between the anode body 21 and the cathode body 22 (particularly the surface of the dielectric layer), and the capacitor element 10 to which the conductive polymer is attached is manufactured.

  The conductive polymer is preferably attached so as to cover at least part of the surface of the dielectric layer. At this time, the conductive polymer may adhere not only to the surface of the dielectric layer but also to the surfaces of the cathode body 22 and / or the separator 23. Also, a first step (i) of impregnating the capacitor element 10 including the anode body 21 having a dielectric layer with the first treatment liquid, and a solvent component (a liquid solvent such as the first solvent) is removed after the first step. Three steps (optional step), a second step (ii) for impregnating the capacitor element with the second treatment liquid, and a second step for removing the solvent component (liquid solvent such as the first solvent and / or the second solvent) after the second step. You may repeat at least 1 process selected from the group which consists of 4 processes (iv) (optional process) twice or more as needed. A process selected from these processes may be repeated twice or more as a series of processes. For example, after the first step is repeated a plurality of times, another step may be performed, and the first step, the third step, and the second step as necessary may be repeated a plurality of times as a series of steps. From the viewpoint of easily increasing the coverage of the conductive polymer with respect to the dielectric layer, it is advantageous to repeat at least the first step a plurality of times.

  All the solvent components may be removed from the capacitor element 10 obtained in the second step or the fourth step. Further, the capacitor element 10 obtained in the second step or the fourth step may be in a state where the solvent component remains. When the solvent component remains, the function of repairing the dielectric layer can be further improved. Further, since the remaining solvent component exists between the conductive polymer particles, the electrolytic solution easily permeates between the conductive polymer particles when the capacitor element is impregnated with the electrolytic solution. Therefore, the function of repairing the dielectric layer by the electrolytic solution can be easily obtained. By increasing the repair function of the dielectric layer, it is possible to effectively suppress a short circuit even when the guaranteed lifetime of the electrolytic capacitor has passed.

(Electrolyte)
The electrolytic solution includes a nonaqueous solvent containing γBL and at least one glycerol compound selected from the group consisting of glycerol and polyglycerol. Further, the electrolytic solution may further contain an ionic substance (solute) or may not contain a solute. As the ionic substance, a glycerin compound and / or a substance that dissolves in a non-aqueous solvent is used.

  When the electrolytic solution contains γBL, the impregnation property of the electrolytic solution into the capacitor element can be enhanced despite the use of a glycerin compound having a relatively high viscosity. When the electrolytic solution contains a glycerin compound, the conductive polymer can be swollen. Therefore, the conductive polymer can be present at every corner of the plurality of irregularities formed by roughening the anode foil. As a result, in addition to being able to reduce ESR at the beginning of charge / discharge, low ESR can be maintained even when the electrolytic capacitor is used for a long period of time, and high reliability is obtained.

  In addition, electrolyte solution refers to the electrolyte solution (solvent component) accommodated in the assembled electrolytic capacitor (specifically, in the exterior case). The electrolytic solution also includes a solvent component remaining in the electrolytic capacitor during the manufacturing process of the electrolytic capacitor. As such a solvent component, a solvent component contained in the first treatment liquid and / or the second treatment liquid (for example, a liquid medium and / or the first solvent and the second treatment liquid contained in the first treatment liquid). A second solvent).

  The polyglycerin includes, for example, 2 to 20 (preferably 2 to 12, 2 to 10, or 2 to 6) glycerin units. As polyglycerol, diglycerol, triglycerol, etc. are also preferable.

  The glycerin compound has a high affinity for the conductive polymer and is likely to exist stably between the particles of the conductive polymer. Further, the glycerin compound has low volatility. Therefore, when the electrolytic solution contains a glycerin compound, the electrolytic solution can be easily held around the dielectric layer, the film repairability of the dielectric layer can be enhanced, and the effect of suppressing leakage current can be enhanced. Therefore, even when the guaranteed lifetime of the electrolytic capacitor has passed, the short circuit can be effectively suppressed.

The content of the glycerin compound in the electrolytic solution is, for example, 5% by mass or more, and may be 10% by mass or more or 20% by mass or more. The content of the glycerin compound in the electrolytic solution may be, for example, 50% by mass or less, preferably 30% by mass or less. These lower limit values and upper limit values can be arbitrarily combined. 5-50 mass% or 10-30 mass% may be sufficient as content of the glycerol compound in electrolyte solution, for example.
When the content of the glycerin compound in the electrolytic solution is in the above range, higher reliability is obtained.

  In the electrolytic capacitor, the mass of the glycerin compound contained in the electrolytic solution may be 2 to 100 times or 3 to 80 times the mass of the conductive polymer impregnated in the capacitor element. Good. When the mass ratio is in such a range, the effect of swelling the conductive polymer is easily obtained.

  The non-aqueous solvent may include a non-aqueous solvent (organic solvent and / or ionic liquid) other than γBL. An organic solvent (an organic solvent other than γBL) is preferably used. Such a non-aqueous solvent desirably has a high boiling point, and examples of the high boiling non-aqueous solvent include an ionic liquid and / or a high boiling organic solvent. The boiling point of the non-aqueous solvent is, for example, higher than 100 ° C., preferably 150 ° C. or higher, and more preferably 200 ° C. or higher. Examples of the organic solvent include the organic solvent exemplified for the first solvent of the first treatment liquid, the second solvent exemplified for the second treatment liquid, and the like. A non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types.

  As the non-aqueous solvent, it is preferable to use one that dissolves the glycerin compound (or one that is miscible or compatible with the glycerin compound). Examples of such non-aqueous solvents include protic organic solvents, and among aprotic solvents, amides, lactones, cyclic ethers, sulfones, and cyclic carbonates. As the protic organic solvent, alcohols other than glycerol (specifically, alkanol, glycol), glycol monoethers, and the like are preferable. Of the non-aqueous solvents, at least one selected from the group consisting of glycols, lactones, sulfones, and cyclic carbonates is preferred. The non-aqueous solvent may contain at least one selected from the group consisting of EG, sulfolane, and PC together with γ-BL.

  Such an aprotic solvent and a protic organic solvent have high affinity with a glycerin compound, and can be uniformly mixed with the glycerin compound. Therefore, when such a solvent is used, it is easy to infiltrate the electrolytic solution between the conductive polymer particles.

  As the solute, anion and cation salts are used, and an organic salt in which at least one of the anion and cation is an organic substance is preferable. Organic salts include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono 1,2,3,4-tetramethylimidazolinium phthalate, mono 1,3-dimethyl-2-ethyl imidazole phthalate Examples include linium. Solutes may be used singly or in combination of two or more.

  The impregnation of the electrolytic solution into the capacitor element 10 is not particularly limited and can be performed by a known method. For example, the capacitor element may be immersed in the electrolytic solution, or the electrolytic solution may be injected into a container containing the capacitor element. The impregnation of the electrolytic solution into the capacitor element may be performed under reduced pressure (for example, 10 to 100 kPa) as necessary.

(Other)
The capacitor element 10 may be sealed. More specifically, the capacitor element 10 is first housed in the bottomed case 11 so that the lead wires 14A and 14B are positioned on the upper surface of the bottomed case 11 that opens. As a material of the bottomed case 11, a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy thereof can be used.

  Next, the sealing member 12 formed so that the lead wires 14 </ b> A and 14 </ b> B penetrate is disposed above the capacitor element 10, and the capacitor element 10 is sealed in the bottomed case 11. The sealing member 12 may be an insulating material. As the insulating substance, an elastic body is preferable, and among them, silicone rubber, fluorine rubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber (hypalon rubber, etc.), butyl rubber, isoprene rubber and the like having high heat resistance are preferable.

  Next, lateral drawing is performed in the vicinity of the open end of the bottomed case 11, and the open end is crimped to the sealing member 12 for curling. And the electrolytic capacitor as shown in FIG. 1 is completed by arrange | positioning the seat board 13 in a curl part. Then, you may perform an aging process, applying a rated voltage.

  In the above embodiment, the wound type electrolytic capacitor has been described. However, the scope of the present invention is not limited to the above, and other electrolytic capacitors, for example, a chip type electrolytic capacitor using a metal sintered body as an anode body. The present invention can also be applied to a capacitor or a multilayer electrolytic capacitor using a metal plate as an anode body.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
A wound type electrolytic capacitor (diameter: 6.3 mm, length: 5.8 mm) having a rated voltage of 35 V and a rated capacitance of 47 μF as shown in FIG. 1 was prepared and evaluated by the following procedure.

(1) Production of electrolytic capacitor (Preparation of anode body having dielectric layer)
Etching was performed on an aluminum foil having a thickness of 100 μm to roughen the surface of the aluminum foil. Thereafter, a dielectric layer was formed on the surface of the aluminum foil by a chemical conversion treatment using an ammonium adipate aqueous solution to prepare an anode body having the dielectric layer.

(Preparation of cathode body)
An aluminum foil having a thickness of 50 μm was etched to roughen the surface of the aluminum foil to prepare a cathode body.

(Production of capacitor element (winding body))
An anode lead tab and a cathode lead tab were connected to the anode body and the cathode body, and the anode body and the cathode body were wound through a separator while winding the lead tab to obtain a capacitor element. An anode lead wire and a cathode lead wire were connected to the ends of each lead tab protruding from the capacitor element. Then, chemical conversion treatment was performed again on the manufactured capacitor element, and a dielectric layer was formed on the cut end portion of the anode body. Next, the end of the outer surface of the capacitor element was fixed with a winding tape.

(Impregnation of the first treatment liquid)
A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid as a dopant in ion-exchanged water (first solvent). While stirring the obtained mixed solution, ferric sulfate and sodium persulfate (oxidant) dissolved in ion-exchanged water were added to perform a polymerization reaction. After the reaction, the reaction solution obtained was dialyzed to remove unreacted monomers and excess oxidant, and poly 3,4-ethylenedioxythiophene (PEDOT) doped with about 5% by mass of polystyrene sulfonic acid. A dispersion liquid (first treatment liquid) was obtained.
The obtained first treatment liquid was impregnated into the capacitor element for 5 minutes. Subsequently, the solvent component was removed by heating the capacitor element at 150 ° C. for 20 minutes.
In this way, a capacitor element having a conductive polymer attached thereto was produced.

(Impregnation with electrolyte)
Next, the capacitor element was impregnated with an electrolytic solution under reduced pressure. As an electrolytic solution, a solution containing γBL: glycerin: phthalic acid mono (ethyldimethylamine) (solute) = 50: 25: 25 (mass ratio) was used.

(Capacitor element sealing)
The capacitor element impregnated with the electrolytic solution was accommodated in an outer case as shown in FIG. 1 and sealed to produce an electrolytic capacitor. Similarly, a total of 300 electrolytic capacitors were produced.

(2) Performance Evaluation (a) Capacitance and ESR Value Capacitance (μF) and ESR value (mΩ) were measured as initial characteristics of the electrolytic capacitor. Specifically, the initial capacitance (μF) at a frequency of 120 Hz was measured for the electrolytic capacitor using an LCR meter for 4-terminal measurement. Further, an ESR value (mΩ) at a frequency of 100 kHz of the electrolytic capacitor was measured using an LCR meter for measuring four terminals.
As an acceleration test, the capacitance (μF) and ESR value (mΩ) after leaving the electrolytic capacitor for 4000 hours at 125 ° C. were also measured in the same manner as in the case of the above initial characteristics.
The electrostatic capacity and ESR value were measured for 120 electrolytic capacitors selected at random, and the average value was calculated.

<< Comparative Example 1 >>
An electrolytic capacitor was produced in the same manner as in Example 1 except that a solution containing γBL: mono (ethyldimethylamine) phthalate (solute) = 75: 25 (mass ratio) was used as the electrolytic solution. Evaluation was performed.

Example 2
Except that a solution containing γBL: sulfolane: glycerin: phthalic acid mono (ethyldimethylamine) (solute) = 25: 25: 25: 25 (mass ratio) was used as the electrolytic solution in the same manner as in Example 1. An electrolytic capacitor was prepared and performance evaluation was performed.

Example 3
An electrolytic capacitor was prepared in the same manner as in Example 1 except that a solution containing γBL: glycerin: mono (ethyldimethylamine) (solute) = 70: 5: 25 (mass ratio) was used as the electrolytic solution. Fabricated and evaluated for performance.
The results of Examples and Comparative Examples are shown in Table 1.

  As shown in Table 1, in the examples, the capacitance can be secured and the ESR can be kept low even after the acceleration test. On the other hand, in Comparative Example 1, the capacitance decreased and the ESR increased after the acceleration test.

  The present invention can be used for an electrolytic capacitor using a conductive polymer as a cathode material.

  10: capacitor element, 11: bottomed case, 12: sealing member, 13: seat plate, 14A, 14B: lead wire, 15A, 15B: lead tab, 21: anode body, 22: cathode body, 23: separator, 24 : Winding tape

Claims (5)

A capacitor element including an anode body on which a dielectric layer is formed;
A conductive polymer covering a surface of at least a part of the dielectric layer;
An electrolyte solution containing a non-aqueous solvent and a glycerin compound,
The non-aqueous solvent includes γ-butyrolactone,
The electrolytic capacitor, wherein the glycerin compound is at least one selected from the group consisting of glycerin and polyglycerin.   The electrolytic capacitor according to claim 1, wherein the content of the glycerin compound in the electrolytic solution is 5% by mass or more.   The electrolytic capacitor according to claim 1, wherein the polyglycerol includes 2 to 12 glycerol units.   The electrolytic capacitor according to claim 1, wherein the non-aqueous solvent further includes at least one selected from the group consisting of ethylene glycol, propylene carbonate, and sulfolane. The capacitor element includes a cathode body and a separator,
The separator is interposed between the anode body and the cathode body,
The electrolytic capacitor according to claim 1, wherein the conductive polymer is in contact with the separator and the cathode body.

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