Electrolytic capacitor element and electrolytic capacitor

Abstract

The present invention provides an electrolytic capacitor element 1 which comprises: a valve-acting metal base material 10 that comprises a core part 11 which is formed of a metal foil and a porous part 12 which is formed along the surface of the metal foil 11; a dielectric layer 13 that is formed on the porous part 12; a solid electrolyte layer 14 that is formed on the dielectric layer 13; and a conductive layer 16 that is formed on the solid electrolyte layer 14. With respect to this electrolytic capacitor element 1, the conductive layer 16 comprises a carbon layer 16; the carbon layer 16 contains a carbon filler 40 and a scale-like insulating inorganic filler 50; and in a cut surface obtained by cutting the electrolytic capacitor element 1 in a direction that is perpendicular to a main surface of the metal foil 10, the average of the acute angles θ among the angles between the longitudinal direction of a cross-section of the insulating inorganic filler 50 present in the carbon layer 16 that is formed on the main surface of the metal foil 10 and the longitudinal direction of a cross-section of the metal foil 10 is 0° to 45°.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor element and an electrolytic capacitor.

Background Art

[0002] Patent Document 1 includes a capacitor element including an anode body, a dielectric layer covering at least a part of the anode body, a solid electrolyte layer covering at least a part of the dielectric layer, and a cathode lead-out layer covering at least a part of the solid electrolyte layer. The cathode lead-out layer includes a conductive carbon layer covering at least a part of the solid electrolyte layer and a silver paste layer covering at least a part of the carbon layer. The carbon layer includes carbon particles and silver, and an electrolytic capacitor is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electrolytic capacitor described in Patent Document 1, a metal foil such as aluminum is used as the anode body. When moisture enters an electrolytic capacitor including a metal foil, the metal foil is corroded, and LC failure (leakage current failure) becomes a problem. In particular, moisture may reach the metal foil through the carbon layer, and it has been desired to prevent the intrusion of moisture through this path.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide an electrolytic capacitor element and an electrolytic capacitor capable of preventing corrosion of a metal foil due to intrusion of moisture.

Means for Solving the Problems

[0006] The electrolytic capacitor element of the present invention includes a valve-acting metal substrate having a core portion made of a metal foil and a porous portion formed along the surface of the metal foil, a dielectric layer formed on the porous portion, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer. The conductive layer includes a carbon layer, and the carbon layer includes a carbon filler and a flaky insulating inorganic filler. Among the angles formed by the longitudinal direction of the cross-section of the insulating inorganic filler present in the carbon layer formed on the main surface of the metal foil and the longitudinal direction of the cross-section of the metal foil at a cut surface obtained by cutting the electrolytic capacitor element in a direction perpendicular to the main surface of the metal foil, the average value of the acute angles is 0° or more and 45° or less.

[0007] The electrolytic capacitor of the present invention includes a laminate in which a plurality of the electrolytic capacitor elements of the present invention are stacked, an anode external electrode, and a cathode external electrode.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide an electrolytic capacitor element and an electrolytic capacitor that can prevent corrosion of the metal foil due to intrusion of moisture.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the electrolytic capacitor element and the electrolytic capacitor of the present invention will be described. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied without changing the gist of the present invention. In addition, a combination of two or more of the individual desirable configurations of the present invention described below is also the present invention.

[0011] The electrolytic capacitor element of the present invention includes a valve-acting metal substrate having a core portion made of a metal foil and a porous portion formed along the surface of the metal foil, a dielectric layer formed on the porous portion, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer. The conductive layer includes a carbon layer, and the carbon layer includes a carbon filler and a flaky insulating inorganic filler. In a cross-sectional view obtained by cutting the electrolytic capacitor element in a direction orthogonal to the main surface of the metal foil, among the angles formed by the longitudinal direction of the cross-section of the insulating inorganic filler present in the carbon layer formed on the main surface of the metal foil and the longitudinal direction of the cross-section of the metal foil, the average value of the acute angles is 0° or more and 45° or less.

[0012] FIG. 1 and FIG. 2 are perspective views schematically showing an example of a laminate in which a plurality of electrolytic capacitor elements are laminated. In FIG. 1, a first end face E101, which is a cathode-side end face, is shown in the front, and in FIG. 2, a second end face E102, which is an anode-side end face, is shown in the front.

[0013] The laminate 100 has a first main surface M101 and a second main surface M102 that face each other in the stacking direction (T direction), a first end face E101 and a second end face E102 that face each other in the length direction (L direction) orthogonal to the stacking direction, and a first side face S101 and a second side face S102 that face each other in the width direction (W direction) orthogonal to the stacking direction and the length direction.

[0014] Moisture may penetrate into the laminate 100. The direction of moisture penetration focused on in this specification is the direction indicated by the arrows in FIGS. 1 and 2. In this specification, attention is paid to preventing corrosion of the metal foil due to moisture penetration from the first end face E101, the second end face E102, the first side face S101, or the second side face S102 of the laminate.

[0015] Moisture penetration into the laminate 100 can occur in situations such as during storage of the laminate and during storage after forming external electrodes on the laminate to form an electrolytic capacitor.

[0016] FIG. 3 is a cross-sectional view schematically showing an example of a laminate in which a plurality of electrolytic capacitor elements are laminated, and is an LT-plane cross-sectional view cut along a plane along the length direction (L direction) and the lamination direction (T direction) of the laminate. FIG. 3 is also a cross-sectional view taken along line A-A of FIG. 1. In FIG. 3, the directions in which moisture enters from the first end face E101 and the second end face E102 of the laminate 100 are also indicated by arrows.

[0017] With reference to FIG. 3, the configuration of the electrolytic capacitor element and the configuration of the laminate will be described. The electrolytic capacitor element 1 shown in FIG. 3 includes a valve-acting metal substrate 10 having a core portion 11 made of a metal foil and a porous portion 12 formed along the surface of the metal foil, a dielectric layer 13 formed on the porous portion 12, a solid electrolyte layer 14 formed on the dielectric layer 13, and a conductive layer 16 formed on the solid electrolyte layer 14. The core portion 11 of the valve-acting metal substrate 10 is drawn out to the second end face E102 of the laminate 100 and constitutes the anode-side end face. The core portion 11 is connected to the anode external electrode at the second end face E102 of the laminate 100.

[0018] The valve-acting metal substrate is made of a valve-acting metal showing a so-called valve action. Examples of the valve-acting metal include a single metal such as aluminum, tantalum, niobium, titanium, zirconium, or an alloy containing these metals. Among these, aluminum or an aluminum alloy is preferable.

[0019] The core portion constituting the valve-acting metal substrate is a metal foil. The porous portion includes an etching layer formed on the surface of the valve-acting metal substrate and a porous layer formed by printing and sintering on the surface of the valve-acting metal substrate. When the valve-acting metal is aluminum or an aluminum alloy, an etching layer is preferable, and when it is titanium or a titanium alloy, a porous layer is preferably used.

[0020] The dielectric layer formed on the surface of the porous portion is porous, reflecting the surface state of the porous portion, and has a fine uneven surface shape. The dielectric layer is preferably composed of the oxide film of the valve action metal.

[0021] Also, from the viewpoint of improving the manufacturing efficiency, as the valve action metal substrate with the dielectric layer formed on the surface, a formed foil that has been subjected to a forming treatment in advance may be used.

[0022] Examples of the material constituting the solid electrolyte layer include conductive polymers having skeletons such as pyrroles, thiophenes, and anilines. Examples of the conductive polymer having a thiophene skeleton include PEDOT [poly(3,4-ethylenedioxythiophene)], and PEDOT:PSS obtained by complexing with polystyrene sulfonic acid (PSS) as a dopant may also be used.

[0023] The solid electrolyte layer is formed, for example, by forming a polymer film such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer using a treatment liquid containing a monomer such as 3,4-ethylenedioxythiophene, or by applying a dispersion liquid of a polymer such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer and drying it. After forming the solid electrolyte layer for the inner layer that fills the pores (recesses), it is preferable to form the solid electrolyte layer for the outer layer that covers the entire dielectric layer.

[0024] The solid electrolyte layer can be formed in a predetermined region by applying the above treatment liquid or dispersion liquid on the dielectric layer by means such as sponge transfer, screen printing, spray coating, dispenser coating, inkjet printing, etc. The thickness of the solid electrolyte layer is preferably 2 μm or more and preferably 20 μm or less.

[0025] The conductive layer includes a carbon layer. The conductive layer may be only a carbon layer, or may be a composite layer in which a silver layer is provided on the carbon layer. FIG. 3 shows a configuration in which only the carbon layer 16 is used as the conductive layer 16.

[0026] FIG. 3 shows a cathode foil 21 provided on the conductive layer 16. The cathode foil 21 is preferably a metal foil, and is preferably made of at least one metal selected from the group consisting of aluminum, copper, silver, and alloys mainly composed of these metals. The cathode foil 21 is drawn out to the first end face E101 and constitutes the cathode-side end face. The cathode foil 21 is connected to the cathode external electrode at the first end face E101 of the laminate 100.

[0027] The valve-acting metal substrate 10 has porous portions 12 on both sides of the core portion 11, a dielectric layer 13 is formed on the surface of each porous portion 12, and a solid electrolyte layer 14 is provided on the dielectric layer 13. A conductive layer 16 and a cathode foil 21 are provided on the solid electrolyte layer 14. By repeatedly providing this configuration, a plurality of electrolytic capacitor elements 1 are laminated, and a laminate 100 whose outer periphery is sealed with a sealing material 130 is formed.

[0028] The carbon layer contains a carbon filler and a flaky insulating inorganic filler. Further, in a cross-sectional view obtained by cutting the electrolytic capacitor element in a direction perpendicular to the main surface of the metal foil, among the angles formed by the longitudinal direction of the cross-section of the insulating inorganic filler present in the carbon layer formed on the main surface of the metal foil and the longitudinal direction of the cross-section of the metal foil, the average value of the acute angles is 0° or more and 45° or less. Hereinafter, the specific matters of this invention will be described.

[0029] FIG. 4 is an enlarged cross-sectional view schematically showing an example of the carbon layer. FIG. 4 shows an enlarged cross-sectional view of the carbon layer in a cross-sectional view obtained by cutting the electrolytic capacitor element in a direction perpendicular to the main surface of the metal foil. The carbon layer 16 contains spherical carbon fillers 40 and flaky insulating inorganic fillers 50. The direction parallel to the main surface of the metal foil is indicated by an arrow L in FIG. 4. Among the angles formed by the longitudinal direction of the cross-section of one flaky insulating inorganic filler 50 shown in FIG. 4 and the longitudinal direction of the cross-section of the metal foil, the acute angle is indicated by θ in FIG. 4. The angles indicated by θ in FIG. 4 are determined for the scaly insulating inorganic fillers shown in the electron microscope image taken on the cut surface cut in a direction orthogonal to the main surface of the metal foil, and when the average value is taken, the value is 0° or more and 45° or less. If the angle formed by the longitudinal direction of the cross section of the scaly insulating inorganic filler and the longitudinal direction of the cross section of the metal foil on the above-mentioned cut surface is within the range of the specific matters of this invention, the angle formed three-dimensionally by the flat surface of the insulating inorganic filler and the main surface of the metal foil also becomes smaller. That is, the scaly insulating inorganic filler is in an oriented state with respect to the main surface of the metal foil.

[0030] FIG. 5 is a schematic diagram showing how the maze effect is exhibited by the scaly insulating inorganic filler. Since the carbon layer 16 exists between the cathode foil 21 and the core 11 of the valve action metal substrate, FIG. 5 schematically shows only the cathode foil 21, the core 11 of the valve action metal substrate, and the carbon layer 16 therebetween. Then, consider the case where moisture enters in the direction indicated by the arrow with respect to the carbon layer 16, that is, from the first end face E101 and the second end face E102 of the laminate.

[0031] FIG. 5 schematically shows a case where, in the carbon layer 16, the angle formed between the longitudinal direction of the cross section of the flaky insulating inorganic filler 50 and the longitudinal direction of the cross section of the metal foil is 0°. When the flaky insulating inorganic filler is oriented in this way, moisture that has entered the carbon layer 16 from the first end face E101 and the second end face E102 of the laminate is prevented from moving in the laminating direction of the carbon layer 16 and reaching the cathode foil 21 or the core 11. The moisture cannot pass through the flaky insulating inorganic filler 50, and in order for the moisture to reach the cathode foil 21 or the core 11, it has to bypass the flaky inorganic filler. Therefore, it becomes difficult for the moisture to reach the cathode foil 21 or the core 11, and corrosion of the cathode foil 21 or the core 11 by the moisture is prevented. In FIG. 5, the direction of moisture intrusion from the end face of the laminate is indicated by an arrow, and it is shown that the diffusion of this moisture in the laminating direction is prevented. Similarly, it is also possible to prevent the moisture that has entered from the side face of the laminate from diffusing in the laminating direction. The effect of preventing the moisture that has entered from the end face or side face of the laminate from diffusing in the laminating direction by arranging the flaky insulating inorganic filler is called the maze effect.

[0032] Since the electrolytic capacitor element of the present invention includes a flaky insulating inorganic filler whose longitudinal direction of the cross section is oriented in a specific direction (0° or more and 45° or less) with respect to the longitudinal direction of the cross section of the metal foil, the maze effect is exhibited, and corrosion of the metal foil due to moisture intrusion from the end face or side face of the laminate can be prevented.

[0033] FIG. 6 is a perspective view schematically showing the shape of the flaky insulating inorganic filler. The flaky insulating inorganic filler 50 has a relatively wide plane with respect to its thickness. When the thickness of the flaky insulating inorganic filler 50 is t, the maximum length is length l, and the maximum width is width w, it is preferable that the product of the length and the width (l×w) is large with respect to the thickness t. Specifically, it is preferable that (l×w) / t≧4. Also, it is preferable that (l×w) / t≦400. In FIG. 6, the thickness t, length l, and width w of the flaky insulating inorganic filler 50 are indicated by double-headed arrows t, double-headed arrows l, and double-headed arrows w, respectively. The value of the product (l×w) of the length and width is larger than the area of the plane of the insulating inorganic filler, but when considering the ratio of the area of the plane of the insulating inorganic filler to the thickness, it is used as an approximate value of the area. Also, for the length l and width w, the longer dimension is defined as the length l and the shorter dimension is defined as the width w. The ratio of the length l to the thickness t is preferably (l / t)≧2. Also, it is preferably (l / t)≦20. The ratio of the width w to the thickness t is preferably (w / t)≧2. Also, it is preferably (w / t)≦20.

[0034] The length l of the flaky insulating inorganic filler is preferably 1 μm or more. Also, it is preferably 20 μm or less. The width w of the flaky insulating inorganic filler is preferably 1 μm or more. Also, it is preferably 20 μm or less.

[0035] In addition, each dimension of the flaky insulating inorganic filler observed in the electron microscope image taken on the cut surface cut in a direction perpendicular to the main surface of the metal foil is determined as the average value of the dimensions of 10 or more fillers existing in the image for the flaky insulating inorganic filler contained in the carbon layer. The ratio of each dimension is also determined as the ratio of the average values of each dimension.

[0036] Also, when the shape of the filler observed in the electron microscope image taken on the cut surface cut in a direction perpendicular to the main surface of the metal foil is a rectangular shape with one direction being long, like the flaky insulating inorganic filler 50 shown in FIG. 4, the dimension of the long side is defined as the length l and the dimension of the short side is defined as the thickness t. For a filler with a ratio of the length l to the thickness t of (l / t)≧2, even if the width w is unknown, it may be regarded as a flaky filler.

[0037] Also, the thickness of the carbon layer (double-headed arrow T in FIG. 4) 16The ratio (l / T 16 ) of the length l of the flaky insulating inorganic filler to the dimension shown by 16 ) is preferably (l / T

[0038] ≧0.05. The flaky insulating inorganic filler is made of an insulating material. Examples of the insulating material include those having a volume resistivity as a material of 1×10 10 Ω·cm or more. The whole filler may be an insulating material, or it may be a material in which an insulating film is formed on the surface of a conductor such as metal to become an insulating material. Examples of the latter include materials in which a passive film (aluminum oxide film) is formed on the surface of aluminum. Specific examples include ceramics or glass which are insulating materials. Examples of ceramics include silica, alumina, zirconia, aluminum nitride, silicon nitride, cordierite, mullite, yttria, etc. In particular, it is preferably at least one material selected from the group consisting of silica, alumina, and glass.

[0039]

[0040] As the carbon filler contained in the carbon layer, those usually used as materials contained in the carbon layer of an electrolytic capacitor can be used, and its shape is not particularly limited. FIG. 4 shows a spherical carbon filler 40 as an example of the carbon filler. The carbon filler may be a flaky carbon filler. FIG. 7 is an enlarged cross-sectional view schematically showing another example of the carbon layer. FIG. 7 shows a state in which a flaky carbon filler 45 is contained in the carbon layer 16 instead of the spherical carbon filler 40 shown in FIG. 4. When the carbon filler is a flaky carbon filler, among the angles formed by the longitudinal direction of the cross-section of the flaky carbon filler and the longitudinal direction of the cross-section of the metal foil on the cut surface cut in a direction perpendicular to the main surface of the metal foil, the acute angle is preferably 0° or more and 45° or less. When the above conditions are satisfied, the maze effect is also exhibited by the flaky carbon filler, and corrosion of the metal foil due to intrusion of moisture from the end face or side face of the laminate can be further prevented.

[0041] In the carbon layer, the ratio of the weight of the flaky insulating inorganic filler to the total weight of the carbon filler and the flaky insulating inorganic filler ((weight of the flaky insulating inorganic filler) / (weight of the carbon filler + weight of the flaky insulating inorganic filler)) is preferably 0.01 or more and 0.5 or less. By containing a flaky insulating inorganic filler in the carbon layer so that the above ratio is 0.01 or more, corrosion of the metal foil is sufficiently prevented. As a result, the long-term reliability of the electrolytic capacitor can be improved. On the other hand, by containing a carbon filler which is a conductive filler so that the above ratio is 0.5 or less, the resistance value of the carbon layer can be lowered. As a result, the ESR of the electrolytic capacitor can be lowered.

[0042] The carbon layer may or may not contain a non-flaky insulating inorganic filler separately from the flaky insulating inorganic filler. When the carbon layer contains a non-flaky insulating inorganic filler, the weight ratio thereof is preferably 5% or less of the flaky insulating inorganic filler.

[0043] The carbon layer may further contain a metal filler, and examples of the material of the metal filler include silver, copper, aluminum, etc. Since the metal filler itself may be subject to galvanic corrosion by moisture, it is preferably not contained in the carbon layer.

[0044] Next, as an example of the electrolytic capacitor element and laminate of the present invention, an example of a form different from the forms shown in FIGS. 1, 2, and 3 will be described. FIG. 8 is an LT-plane cross-sectional view schematically showing another example of a laminate in which a plurality of electrolytic capacitor elements are laminated.

[0045] The electrolytic capacitor element 2 shown in FIG. 8 includes a valve-action metal substrate 10 having a core portion 11 made of a metal foil and a porous portion 12 formed along the surface of the metal foil, a dielectric layer 13 formed on the porous portion 12, a solid electrolyte layer 14 formed on the dielectric layer 13, and a conductive layer 16 formed on the solid electrolyte layer 14. The conductive layer 16 is composed of a carbon layer 16a and a silver layer 16b. In the laminate 200, a plurality of electrolytic capacitor elements 2 are laminated, and the outer periphery thereof is sealed with an outer package 220. The outer package 220 includes a first outer package 221 and a second outer package 222 that seal the periphery of the electrolytic capacitor element 2. The second outer package 222 is located on the outermost periphery of the laminate 200 and forms the first main surface M201, the second main surface M202, the first side surface (not shown in FIG. 7: S201), and the second side surface (not shown in FIG. 7: S202) of the laminate 200.

[0046] At the second end face E202 of the laminate 200, the core portion 11 of the valve-action metal substrate 10 is drawn out, which constitutes the anode-side end face of the laminate 200. The core portion 11 is connected to the anode external electrode at the second end face E202 of the laminate 200. In the vicinity of the anode-side end face of the valve-action metal substrate 10, a mask layer 242, which is an insulating member, is provided.

[0047] A current collector electrode 230 is provided on the first end face E201 of the laminate 200 and is electrically connected to the cathodes of the plurality of electrolytic capacitor elements 2. As shown in FIG. 8, the current collector electrode 230 is exposed on the first end face E201 of the laminate 200 and constitutes the cathode-side end face of the laminate 200. The current collector electrode 230 is connected to the cathode external electrode at the first end face E201 of the laminate 200.

[0048] In the electrolytic capacitor element 2 shown in FIG. 8, the dielectric layer 13, the solid electrolyte layer 14, and the conductive layer 16 are also provided on the side surface and one end surface of the valve-acting metal substrate 10. Then, in the cross section obtained by cutting the electrolytic capacitor element in a direction perpendicular to the main surface of the metal foil, among the angles formed by the longitudinal direction of the cross section of the flaky insulating inorganic filler present in the carbon layer formed on the side surface and one end surface of the metal foil and the longitudinal direction of the cross section of the metal foil, the average value of the acute angles is 45° or more and 90° or less.

[0049] First, the “carbon layer formed on one end surface of the metal foil” will be described. The region of interest is the region surrounded by region B in FIG. 8, which is the region near the end surface on the cathode side of the metal foil. Note that since there is no carbon layer in the region near the end surface on the anode side of the metal foil, it is not taken into consideration. FIG. 9 is an enlarged cross-sectional view schematically showing the region surrounded by region B in FIG. 8.

[0050] “One end surface of the metal foil” is the end surface of the core part made of the metal foil, and FIG. 9 shows the position of the first end surface 11e1 of the metal foil, which is the end surface of the core part 11. On the first end surface 11e1 of the metal foil, a porous part 12, a dielectric layer 13, a solid electrolyte layer 14, and a conductive layer 16 are formed along its surface. The conductive layer 16 is composed of a carbon layer 16a and a silver layer 16b.

[0051] The “carbon layer formed on one end surface of the metal foil” is the region surrounded by region C in FIG. 9. The carbon layer 16a contains flaky insulating inorganic fillers 50 and flaky carbon fillers 45. The longitudinal direction of the cross section of the metal foil (the direction parallel to the main surface of the metal foil) is indicated by an arrow L in FIG. 9. Among the angles formed by the longitudinal direction of the cross section of one flaky insulating inorganic filler 50 present in the carbon layer (region C) formed on one end surface of the metal foil and the longitudinal direction of the cross section of the metal foil, the acute angle is indicated by φ in FIG. 9. The angles indicated by φ in Fig. 9 are respectively determined for the scaly insulating inorganic fillers shown in the electron microscope image taken on the cross-section cut in the direction orthogonal to the main surface of the metal foil, and when taking the average value, the value is 45° or more and 90° or less.

[0052] When the orientation of the scaly insulating inorganic fillers contained in the carbon layer is like this, it is possible to prevent, by the maze effect, the moisture that has entered from the first end face E201 of the laminate 200 from moving in the thickness direction of the carbon layer 16a formed on one end face of the metal foil and reaching the core part 11.

[0053] Also, among the angles formed by the longitudinal direction of the cross-section of one scaly insulating inorganic filler 50 present in the carbon layer formed on the main surface of the metal foil and the longitudinal direction of the cross-section of the metal foil, the acute angle is indicated by θ in Fig. 9. Similar to the aspect described with reference to Fig. 4, this angle is 0° or more and 45° or less.

[0054] Fig. 9 shows an aspect in which the carbon layer 16a contains scaly carbon fillers 45. Also for the scaly carbon fillers 45 present in the carbon layer (region C) formed on one end face of the metal foil, it is preferable that the acute angle among the angles formed by the longitudinal direction of the cross-section of the scaly carbon fillers 45 and the longitudinal direction of the cross-section of the metal foil is 45° or more and 90° or less. With this configuration, it is possible to more effectively prevent the corrosion of the metal foil due to the moisture that has entered from the first end face of the laminate.

[0055] Subsequently, the "carbon layer formed on the side surface of the metal foil" will be described. Fig. 10 is a WT plane cross-sectional view schematically showing an example of a laminate in which a plurality of electrolytic capacitor elements are laminated. The regions of interest are the region surrounded by region D and the region surrounded by region E in Fig. 10. Regions D and E are regions in the vicinity of the side surface of the metal foil. Region D is a region in the vicinity of the second side surface 11s2 of the metal foil, and region E is a region in the vicinity of the first side surface 11s1 of the metal foil. FIG. 11 is an enlarged cross-sectional view schematically showing the region surrounded by region D in FIG. 10.

[0056] The "side surface of the metal foil" is the side surface of the core portion made of the metal foil, and FIG. 11 shows the position of the second side surface 11s2 of the metal foil, which is the side surface of the core portion 11. On the second side surface 11s2 of the metal foil, a porous portion 12, a dielectric layer 13, a solid electrolyte layer 14, and a conductive layer 16 are formed along its surface. The conductive layer 16 is composed of a carbon layer 16a and a silver layer 16b.

[0057] The "carbon layer formed on the side surface of the metal foil" is the region surrounded by region F in FIG. 11. The carbon layer 16a contains flaky insulating inorganic fillers 50 and flaky carbon fillers 45. Among the angles formed by the longitudinal direction of the cross-section of one flaky insulating inorganic filler 50 existing in this region and the longitudinal direction of the cross-section of the metal foil, the acute angle is indicated by φ in FIG. 11. The angle indicated by φ in FIG. 11 is determined for each of the flaky insulating inorganic fillers shown in the electron microscope image taken on the cross-section cut in the direction perpendicular to the main surface of the metal foil, and when the average value is taken, the value is 45° or more and 90° or less.

[0058] When the orientation of the flaky insulating inorganic fillers contained in the carbon layer is like this, the moisture that has penetrated from the second side surface S202 of the laminate 200 can be prevented from reaching the core portion 11 by moving in the thickness direction of the carbon layer 16a formed on the second side surface of the metal foil due to the maze effect.

[0059] The carbon layer formed on the first side surface 11s1 of the metal foil can also have the same configuration as the carbon layer formed on the second side surface 11s2 of the metal foil, and the same effect can be exerted on the moisture that has penetrated from the first side surface S201 of the laminate 200.

[0060] The electrolytic capacitor of the present invention includes a laminate in which a plurality of electrolytic capacitor elements of the present invention are stacked, an anode external electrode, and a cathode external electrode. FIG. 12 is a perspective view schematically showing an example of an electrolytic capacitor. In the electrolytic capacitor 300 shown in FIG. 12, an anode external electrode 320 is provided on the second end face E102 of the laminate 100 (see FIGS. 1, 2, and 3), and a cathode external electrode 330 is provided on the first end face E101. The structures of the anode external electrode and the cathode external electrode are not particularly limited as long as they are structures conventionally used for the external electrodes of electrolytic capacitors. As the structures of the anode external electrode and the cathode external electrode, a structure formed by arbitrarily combining layers such as a sputtered film and / or a vapor-deposited film, a resin electrode layer, and a plated layer can be used.

[0061] When manufacturing the electrolytic capacitor element and the electrolytic capacitor of the present invention, a carbon filler and a flaky insulating inorganic filler are blended into a carbon paste, which is a material for forming a carbon layer. The carbon paste may contain a resin component such as an epoxy resin or a phenol resin.

[0062] A carbon layer can be formed by applying a carbon paste on the solid electrolyte layer by a method such as coating or dipping. When obtaining the structure of the laminate 100 shown in FIG. 3, it is preferable to form a carbon layer by applying a carbon paste on the solid electrolyte layer. The carbon paste can be applied by screen printing, sponge transfer, spray coating, dispenser coating, inkjet printing, or the like. In screen printing, it is preferable to apply a carbon paste to which shear stress (shearing stress) is applied to the carbon paste in one direction with a squeegee. In this way, it becomes easy to orient the flaky insulating inorganic filler in a state close to parallel to the printing surface. In addition, when the compounding amounts of the carbon filler and the flaky insulating inorganic filler contained in the carbon paste are reduced, the flaky insulating inorganic filler is likely to be oriented in a direction close to parallel to the printing surface during drying.

[0063] When obtaining the structure of the laminate 200 shown in FIG. 8, it is preferable to form a carbon layer by immersing an element in which a dielectric layer and a solid electrolyte layer are formed on a valve-acting metal substrate in a carbon paste.

[0064] For steps other than the formation of the carbon layer, a method conventionally used in manufacturing an electrolytic capacitor element and an electrolytic capacitor can be employed.

Explanation of Symbols

[0065] 1, 2 Electrolytic capacitor element 10 Valve-acting metal substrate 11 Core part (metal foil) 11e1 One end face of the metal foil (the first end face) 11s1 The first side face of the metal foil 11s2 The second side face of the metal foil 12 Porous part 13 Dielectric layer 14 Solid electrolyte layer 16 Conductive layer (carbon layer) 16a Carbon layer 16b Silver layer 21 Cathode foil 40 Carbon filler (spherical) 45 Carbon filler (flaky) 50 Flaky insulating inorganic filler 100 Laminate M101 First main face M102 Second main face E101 First end face E102 Second end face S101 First side face S102 Second side face 130 Sealing material 200 Laminate M201 First main face The second main surface of M202 The first end surface of E201 The second end surface of E202 The first side surface of S201 The second side surface of S202 The exterior body 220 The first exterior body 221 The second exterior body 222 The current collecting electrode 230 The mask layer 242 The electrolytic capacitor 300 The anode external electrode 320 The cathode external electrode 330

Claims

1. A valve-acting metal substrate having a core portion made of a metal foil and a porous portion formed along the surface of the metal foil, a dielectric layer formed on the porous portion, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer, wherein the conductive layer includes a carbon layer, the carbon layer includes a carbon filler and a flaky insulating inorganic filler, in a cross-sectional plane obtained by cutting the electrolytic capacitor element in a direction perpendicular to the main surface of the metal foil, an average value of acute angles among angles formed by a longitudinal direction of a cross-section of the insulating inorganic filler present in the carbon layer formed on the main surface of the metal foil and a longitudinal direction of the cross-section of the metal foil is 0° or more and 45° or less. An electrolytic capacitor element.

2. The dielectric layer, the solid electrolyte layer, and the conductive layer are also provided on a side surface and one end surface of the valve-acting metal substrate, in a cross-sectional plane obtained by cutting the electrolytic capacitor element in a direction perpendicular to the main surface of the metal foil, an average value of acute angles among angles formed by a longitudinal direction of a cross-section of the insulating inorganic filler present in the carbon layer formed on the side surface and one end surface of the metal foil and a longitudinal direction of the cross-section of the metal foil is 45° or more and 90° or less. The electrolytic capacitor element according to Claim 1.

3. The electrolytic capacitor element according to Claim 1 or 2, wherein the carbon filler includes a flaky carbon filler.

4. The electrolytic capacitor element according to Claim 1 or 2, wherein the insulating inorganic filler is at least one selected from the group consisting of silica, alumina, and glass.

5. An electrolytic capacitor including a laminate in which a plurality of the electrolytic capacitor elements according to Claim 1 or 2 are laminated, an anode external electrode, and a cathode external electrode.

Images