JP3668255B2 - Method for producing electrode foil for electrolytic capacitor - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for producing an electrode foil for an electrolytic capacitor. More specifically, the present invention relates to a method for manufacturing a cathode foil that contributes to a reduction in size and capacity of electrolytic capacitors.
[0002]
[Prior art]
As an electrode for an electrolytic capacitor, an electrode obtained by etching an aluminum foil to increase the surface area is generally used. Enlarging the surface area of the electrode is indispensable for increasing the capacitance of the capacitor, and it is required to further increase the surface area of the electrode in order to increase the size and capacity. However, the expansion of the surface area of the aluminum foil by etching is approaching its limit due to a decrease in the strength of the aluminum foil.
[0003]
On the other hand, in Japanese Patent Application Laid-Open No. 56-29669, a porous metal film is formed by allowing a valve metal vapor such as aluminum or tantalum to enter a substrate at an incident angle of 30 degrees or more, preferably 80 to 85 degrees. It has been proposed to obtain an electrolytic capacitor electrode foil with an increased surface area. In JP-A-59-167909, a porous film is formed by depositing a valve metal such as aluminum, tantalum, titanium, niobium or zirconium on a base such as an aluminum foil in an inert gas such as argon, It has been proposed to increase the surface area of the electrode and increase the dielectric constant.
[0004]
These techniques have a great effect on increasing the capacitance per apparent unit area of the electrolytic capacitor.
[0005]
[Problems to be solved by the invention]
However, these technologies still have the following problems.
[0006]
(1) In order to obtain a sufficient surface area expansion effect, it is necessary to increase the thickness of the valve metal film to 1 to 20 μm, which is problematic in terms of productivity, and valve metals other than aluminum are high melting point materials. For this reason, if a relatively thick film as described above is to be formed, the substrate is subject to thermal damage during vapor deposition, and the flatness tends to be impaired.
[0007]
(2) In the method of depositing the valve metal in an inert gas, increasing the pressure in the vacuum chamber can provide a large surface area, that is, a large capacitance even with the same film thickness, but if the pressure in the vacuum chamber is increased, There is a problem that the film deposition rate decreases. Especially in a large-scale production machine using a straight-ahead electron beam gun, the evaporation source and the substrate cannot be made very close, so the decrease in the film deposition rate accompanying the increase in the pressure in the vacuum chamber is significant, resulting in a significant reduction in productivity. Come on.
[0008]
(3) Porous metal films deposited in an inert gas and expanded in surface area to a certain extent are finer due to hydrates and oxides produced by reaction with electrolytes, especially in high-temperature atmospheres, when converted to capacitors. The hole is easily blocked, and the surface area is easily reduced, that is, the capacitance is easily reduced.
[0009]
The present invention was devised in view of the above-mentioned drawbacks of the prior art. The object of the present invention is to provide excellent stability of characteristics, a great effect in increasing capacitance, and thermal damage during production. It is an object to provide an electrode foil for an electrolytic capacitor excellent in productivity.
[0010]
[Means for Solving the Problems]
The object of the present invention is achieved by the following configurations.
[0011]
That is, the capacitance of the electrode foil for an electrolytic capacitor was measured in an electrolytic solution in which a metal thin film was formed on at least one surface of a substrate by a vacuum deposition method and 25% of tetraethylammonium phthalate was dissolved in γ-butyrolactone. An electrode foil for an electrolytic capacitor having a ratio A / B between A and a capacitance B of the electrode foil for an electrolytic capacitor measured in a 10% aqueous solution of ammonium borate in the range of 0.3 to 0.8 is manufactured. In the method, the substrate is moved along a cylindrical drum, an evaporation source is disposed on the opposite side of the drum through a mask having an opening, and an initial incident angle when the metal deposition is incident on the substrate, That is, a normal line is established on the substrate surface at a point where a straight line connecting the center of the vapor deposition source and the end on the upstream side of the mask opening with respect to the substrate traveling direction is incident on the substrate, and a straight line connected to the normal line is formed. Angle, 90 degrees, the final incident angle, i.e. make the center of the evaporation source, the normal to the substrate surface at a point where a straight line connecting the end on the downstream side of the mask opening to the substrate travel direction is incident on the substrate, the normal The angle formed by the straight line previously connected is -90 to -45 degrees, and the same direction as the incident direction of the metal vapor from the nozzle provided in the vicinity of the vapor deposition source or between the vapor deposition source and the vapor incident area on the substrate. An inert gas is supplied toward the surface of the electrolytic capacitor.
[0012]
As the substrate used in the present invention, aluminum foil, metal foil other than aluminum foil, metal foil other than aluminum, plastic film, paper, and the like can be used, but from the viewpoint of low leakage current and high mechanical strength. Adoption of aluminum foil, aluminum alloy foil or plastic film is preferred. These metal foils are preferably roughened by etching, sandblasting, etc. in terms of increasing the surface area, and in the point of increasing productivity by omitting the process, the manufactured state remains flat. Preferably there is. The thickness of the metal foil is preferably in the range of 5 to 100 μm from the relationship between mechanical strength and occupied volume.
[0013]
Examples of the plastic film include polyesters such as polyethylene terephthalate and polycarbonate, polyolefins such as polypropylene, polyarylene sulfides such as polyphenylene sulfide, polyamides, aromatic polyamides, and polyether ketones. And terephthalates or polyimides, but polyethylene terephthalate or polypropylene is preferred in terms of electrical characteristics and price. From the viewpoint of mechanical stability and strength, these plastics are preferably biaxially stretched into a film. The thickness of the plastic film is preferably in the range of 1 to 50 μm from the relationship between mechanical strength and occupied volume.
[0014]
When the metal thin film of the present invention is formed only on one side of a non-conductive substrate such as a plastic film, the surface opposite to the side on which these films are formed needs to be metallized. Metallization of a plastic film is performed by forming a metal film by vapor deposition or sputtering. The metal film is preferably an aluminum film or a zinc film because the higher the conductivity, the smaller the dielectric loss, which is preferable. The thickness of the metal film is preferably in the range of 0.03 to 0.15 μm because the thicker the film, the better the conductivity, while the thinner the film, the easier it is to self-heal. Prior to metallization, the non-conductive substrate may be subjected to pretreatment such as heat treatment and easy adhesion treatment by various cleaning treatments. Titanium, zirconium, tantalum, niobium, hafnium, etc. are not highly conductive. Therefore, when these metal or alloy films are formed on a non-conductive substrate, the non-conductive substrate may be metallized in advance. This is preferable in that the dielectric loss can be reduced.
[0015]
The metal thin film referred to in the present invention is preferably made of at least one metal selected from a group of so-called valve metals such as aluminum, titanium, zirconium, tantalum, niobium, hafnium or an alloy thereof, but cobalt, chromium, nichrome, Metals such as silver, copper, iron, zinc, and alloys thereof can also be used. Titanium is preferable because it is effective in increasing the capacitance. The purity of the metal or alloy thin film is preferably 99.8% or more, more preferably 99.9% or more in order to reduce the leakage current.
[0016]
The metal thin film may contain oxygen, nitrogen, carbon, hydrogen or the like as long as the characteristics are not impaired.
[0017]
In order to reduce the cost in order to suppress thermal damage to the substrate, the metal thin film should be thin, while the A / B value of the present invention is in the range of 0.3 to 0.8. In order to increase the electrostatic capacity, it is preferable that the film thickness is larger. Therefore, the thickness is more preferably selected from the range of 0.05 to 0.5 μm , particularly preferably from 0.2 to 0.4 μm.
[0018]
For the formation of the metal thin film, a vacuum vapor deposition method is adopted because the thin film can be formed at high speed .
[0019]
In vacuum deposition, metal deposition in order to increase the capacitance of the metal thin film directing insert the inert gas in a region that is incident to the substrate. Examples of the inert gas, argon, neon, krypton, other rare gases such as helium, hydrocarbons, nitrogen or hydrogen can also be employed, also can be employed a mixture of these gases. Examples of the hydrocarbon include methane, ethane, propane, ethylene, propylene, acetylene and the like. In order to obtain the electrode foil for an electrolytic capacitor of the present invention, the use of argon or krypton is preferable because a gas that hardly reacts with the elements constituting the metal thin film and has a large molecular radius is great.
[0020]
The electrode foil for an electrolytic capacitor of the present invention is an electrode foil for an electrolytic capacitor in which a metal thin film is formed on at least one side of a substrate, and measured in an electrolytic solution in which 25% of tetraethylammonium o-phthalate is dissolved in γ-butyrolactone. The ratio A / B between the capacitance A of the electrolytic capacitor electrode foil and the capacitance B of the electrolytic capacitor electrode foil measured in a 10% aqueous solution of ammonium borate is 0.3 to 0.8. It is important to be in range. The electrolytic solution is prepared by weight concentration. In addition, it is permissible for an electrolytic solution in which 25% of tetraethylammonium o-phthalate is dissolved in γ-butyrolactone to contain 1% or less of water due to moisture absorption.
[0021]
When A / B is less than 0.3, the decrease in the electrostatic capacity when the electrolytic capacitor is operated at a high temperature increases. That is, the heat resistance of the electrolytic capacitor is poor. On the other hand, if an attempt is made to make a metal thin film with A / B exceeding 0.8, the structure of the metal thin film is not so fine that the metal thin film must be made thick in order to obtain a predetermined capacitance. That is, the productivity is lowered and the substrate is easily damaged during vapor deposition, and the flatness is easily impaired. In view of heat resistance and productivity of the electrolytic capacitor and thermal damage, A / B is more preferably in the range of 0.35 to 0.7.
[0022]
Electrode capacitor electrode foils with a small capacitance are likely to increase the A / B value. On the other hand, in order to obtain a small and large capacity electrolytic capacitor, the electrolytic capacitor electrode foil has a certain capacitance or more. It must be. It is preferable that the value of A / B is in the range of 0.3 to 0.8 and the capacitance A is 200 μF / cm ² or more. Electrolytic capacitors produced using electrode foils for electrolytic capacitors having an electrostatic capacity A of 200 μF / cm ² or more are more compact and larger in capacity, but the capacitance tends to decrease greatly when used at high temperatures. It is particularly effective. More preferably, the capacitance A is 300 μF / cm ² or more.
[0023]
In order to obtain the electrode foil for an electrolytic capacitor of the present invention, it is preferable that the metal vapor is incident on the substrate at a specific initial incident angle and final incident angle in vacuum deposition.
[0024]
Hereinafter, the incident angle of the vapor to the substrate will be described with reference to FIG.
[0025]
A normal line 13 is set on the drum surface at a point 12 where a straight line 11 connecting the center 5 of the evaporation source and the downstream end 10 of the mask 3 in the substrate traveling direction is incident on the drum (substrate). An angle β formed by the normal 13 and the straight line 11 is an initial incident angle. Depending on the positional relationship among the mask 3, the drum 1, and the evaporation source 2, the initial incident angle may be upstream or downstream in the substrate traveling direction with respect to the normal line standing on the drum surface. Regarding the positive and negative of the incident angle, a negative value is set when the angle formed by the normal line 13 and the straight line 11 is on the upstream side in the substrate traveling direction, and a positive value is set when the angle is on the downstream side. A normal line 9 is set on the drum surface at a point 8 where a straight line 7 connecting the center 5 of the evaporation source and the upstream end 6 of the mask 4 in the substrate traveling direction enters the drum. The angle α formed by the normal 9 and the straight line 7 is the final incident angle. Depending on the positional relationship among the mask 4, the drum 1, and the evaporation source 2, the final incident angle may be a negative value or a positive value.
[0026]
In order to obtain an electrode foil for an electrolytic capacitor having an A / B value in the range of 0.3 to 0.8 of the present invention, the initial incident angle is 0 to 90 degrees and the final incident angle is -90 to -45. Use a combination of degrees . Further, the incident area of the vapor to the substrate has an opening between the downstream end 10 in the substrate traveling direction of the mask 3 and the upstream end 6 in the substrate traveling direction of the mask 4 in order to effectively retain the inert gas to be directed. Except for this, it is preferably a substantially sealed structure. That is, the lower side of the incident area of the vapor on the substrate is blocked by the masks 3 and 4, the upper side is blocked by the drum 1, and the side is blocked by a partition wall that is not shown in FIG. It is preferable.
[0027]
Although an example of the manufacturing method of the electrode foil for electrolytic capacitors of this invention is shown below with reference to FIG. 1, it is not limited to this.
[0028]
FIG. 1 is a schematic view of a vacuum deposition apparatus provided with a long substrate traveling system. A long base traveling system comprising an unwinding shaft 15, a cylindrical cooling drum 16, and a winding shaft 17 is installed in the vacuum chamber 14. An aluminum foil substrate 18 having a predetermined thickness is installed in the substrate running system. The vacuum chamber 14 is divided into an upper tank 19 in which an unwinding shaft and a winding shaft are stored, and a lower tank 20 in which an evaporation source 21 is stored by partition walls 22 and 23 and masks 24 and 25, and an exhaust port 26. And 27 are each evacuated. The mask 24 on the upstream side in the substrate traveling direction and the mask 25 on the downstream side in the substrate traveling direction are installed so that the initial incident angle and the final incident angle of vapor from the evaporation source to the substrate are predetermined angles. The inside of the lower tank is evacuated to 5 × 10 ⁻⁵ Torr or less, the valve 33 is opened, and the nozzle 34 installed in the vicinity of the evaporation source passes through the partition walls 22 and 23, the masks 24 and 25, and the vapor incident area surrounded by the cooling drum 16. Argon gas is directed and the pressure in the lower tank is adjusted to a predetermined pressure. The evaporation source is an electron beam heater, which is filled with a titanium ingot 30. While the substrate is running, the titanium ingot is melted and evaporated to deposit a titanium thin film having a predetermined thickness on the substrate at a predetermined deposition rate. Similarly, a titanium thin film is deposited on the other surface of the substrate.
[0029]
As a metal evaporation source, an induction heater, a resistance heater, a laser heater, or the like can be used, but it is preferable to use an electron beam heater in order to evaporate a refractory metal at a high speed. It is permissible to perform ion plating by radiating high-frequency power between these evaporation sources and the substrate. Further, these evaporation sources do not need to be directly under the drum, and a suitable position may be appropriately selected from the viewpoint of material use efficiency.
[0030]
In order to obtain the electrode foil for an electrolytic capacitor of the present invention, an inert gas is supplied from the nozzle 34 provided near the evaporation source or between the evaporation source and the vapor incident area to the vapor substrate toward the vapor incident area. insert directing. The vapor flow from the evaporation source generally has a high concentration directly above the evaporation source, and the concentration rapidly decreases as it moves away from directly above. That is, the generation rate of the thin film is high immediately above the evaporation source, and the generation rate rapidly decreases as the distance from the upper side is increased. A nozzle is provided in the vicinity of the evaporation source or between the evaporation source and the vapor incident region on the substrate, and an inert gas is supplied to the vapor incident region on the substrate in a distribution close to the vapor concentration distribution. Compared with the case where the inert gas is supplied from a direction different from the vapor incident direction, such as the nozzles 29 and 32 shown in FIG. 1, the fine structure in the depth direction of the metal thin film becomes more uniform, and as a result, A / There is an effect of controlling the value of B in the range of 0.3 to 0.8. It is more preferable to install the nozzle in the vicinity of the evaporation source because the concentration distribution of the vapor flow and the inert gas can be made closer. At this time, in order to give the gas ejected from the nozzle a strong directionality, the length of the nozzle is preferably 5 times or more the nozzle diameter. It is preferable to provide a plurality of nozzles in the drum width direction in order to improve the uniformity in the width direction of the metal thin film formed.
[0031]
In order to obtain the electrode foil for an electrolytic capacitor of the present invention, it is preferable that the pressure in the lower tank is set in the range of 4 × 10 ⁻⁴ Torr to 1 × 10 ⁻² Torr. When the pressure in the lower tank exceeds 1 × 10 ⁻² Torr, the resulting metal thin film structure becomes too fine and the A / B value becomes less than 0.3. When the pressure in the lower tank is 4 × 10 ⁻⁴ Torr or less, the capacitance A per unit area of the metal thin film is 200 μF / cm ² or more although the A / B value is in the range of 0.3 to 0.8. It cannot be increased, which is not preferable in terms of productivity and miniaturization of the electrolytic capacitor.
[0032]
When the metal thin film is formed while introducing nitrogen gas or oxygen gas into the lower tank, there is an advantage that the capacitance can be particularly increased, but the value of A / B tends to be less than 0.3. Heat-treating the metal thin film formed while introducing nitrogen gas or oxygen gas into the lower tank in the atmosphere at 100 ° C. to 200 ° C. for about 30 minutes to 5 hours increases the value of A / B to 0.3 Is preferable in the range of 0.8 to 0.8. The heat treatment is effective not only when the metal thin film is formed while introducing nitrogen gas or oxygen gas into the lower tank, but also generally has an effect of increasing the value of A / B, but reduces the capacitance of the metal thin film.
[0033]
Prior to the formation of the metal thin film, pretreatment such as heat treatment and various cleaning treatments is appropriately permitted for the purpose of improving the adhesion between the substrate and the metal thin film.
[0034]
Although the details of the operation of the present invention are not clear, it is assumed as follows.
[0035]
It is considered that a 10% aqueous solution of ammonium borate has a lower viscosity than an electrolytic solution in which 25% of tetraethylammonium o-phthalate is dissolved in γ-butyrolactone, and is likely to enter a fine hole (gap) of the metal thin film. Therefore, a 10% aqueous solution of ammonium borate enters a narrower hole, and the capacitance is measured to that extent. The difference in capacitance measured using the two electrolytes is presumed to be a value suggesting the fineness and amount of the holes in the metal thin film. If the amount of pores is too small, for example, hydrates or oxides generated by reaction with the electrolyte will easily block the pores, resulting in a decrease in surface area, that is, a decrease in capacitance. It is done. On the other hand, when trying to enlarge the fine holes of the metal thin film, there is a problem that the thickness of the metal thin film has to be increased, which impairs productivity and makes the substrate susceptible to thermal damage during production.
[0036]
[Measurement method and evaluation method of characteristics]
(1) Capacitance measurement method A sample in which a metal thin film is formed on both sides of a substrate is cut out, and the sample is sandwiched and fixed between two holders having 20 mm × 20 mm openings. Two samples fixed to the holder are prepared and fixed so as to be parallel in the electrolytic solution. Using two samples as electrodes, the electrostatic capacity at 120 Hz was measured with an LCR meter (AG-4311 manufactured by Ando Electric Co., Ltd.). One half of the measured value was defined as the capacitance per unit area.
[0037]
When the electrolytic solution is a solution obtained by dissolving 25% of tetraethylammonium o-phthalate in γ-butyrolactone, the capacitance value per unit area is capacitance A, and the electrolytic solution is in a 10% aqueous solution of ammonium borate. The capacitance value per unit area at this time was defined as capacitance B. It is important that the value of A / B is in the range of 0.3 to 0.8.
[0038]
(2) Evaluation of heat resistance The electrode foil of the present invention is wound together with an anode foil and a separator and impregnated with a driving electrolyte. Subsequently, it enclosed with the metal can and produced the electrolytic capacitor. The electrolytic capacitor was stored in an oven at 110 ° C. for 1000 hours while applying a rated voltage, and the heat resistance was evaluated based on the rate of decrease in capacitance due to storage at high temperature. It shows that heat resistance is so good that the fall of an electrostatic capacitance is small. The evaluation of heat resistance also serves as an accelerated life test, and the better the heat resistance, the longer the life.
[0039]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[0040]
Example A long flat aluminum foil substrate having a thickness of 22 μm was attached to a vacuum deposition apparatus equipped with the long substrate running system of FIG. The masks 24 and 25 were adjusted so that the initial incident angle was 40 degrees and the final incident angle was −40 degrees . After filling the electron beam heater 21 with the titanium ingot 30, the inside of the vacuum chamber 14 is evacuated from the exhaust ports 26 and 27, and the lower tank 20 is closed by the partition walls 22 and 23, the masks 24 and 25, and the cooling drum 16. the inner pressure 5 × 10 ^- was below 5 Torr. Then valves 33 and argon gas 0.2 l / min supplied toward the entrance region to the substrate of the steam through a nozzle 34, the pressure inside the lower chamber 1 × 10 ^- was adjusted to ³ Torr. While running the substrate, the titanium ingot was melted and evaporated to form a 0.4 μm thick titanium thin film on the aluminum foil at a deposition rate of 1.5 μm / min. When forming the titanium thin film, the cooling drum 16 was water-cooled. Similarly, a titanium thin film was formed on the other surface of the aluminum foil substrate.
[0041]
The electrolytic capacitor electrode foil thus obtained had a capacitance A of 340 μF / cm ² and a capacitance B of 760 μF / cm ² . Therefore, A / B = 0.45.
[0042]
This electrolytic capacitor electrode foil was used as a cathode, and a capacitor element was produced by winding it with a 90 μm-thick anode foil on which an anodized film was formed, via a separator. This capacitor element was impregnated with a driving electrolytic solution consisting of 74% γ-butyrolactone, 25% o-tetraethylammonium phthalate, and 1% water, and sealed in a metal can to produce an electrolytic capacitor having a rating of 10 V · 8200 μF.
[0043]
The electrolytic capacitor was stored in an oven at 110 ° C. for 1000 hours while applying a voltage of 10V. The capacitance after storage was only 3.6% lower than that before storage, and the heat resistance was good.
[0044]
Without performing the heat resistance evaluation test, the electrolytic capacitor of Example 1 stored at room temperature for 1000 hours was disassembled, and the cathode foil was taken out. The cathode foil was ultrasonically cleaned in acetone, and the capacitance was measured. The electrostatic capacity A was 337 μF / cm ² , the electrostatic capacity B was 710 μF / cm ² , and A / B = 0.47.
[0045]
Example 2
Argon gas was supplied at 0.7 liters / minute, the pressure in the lower tank was adjusted to 7 × 10 ⁻³ Torr, and a titanium thin film having a thickness of 0.2 μm was formed. A titanium thin film was formed on an aluminum foil substrate.
[0046]
Thus obtained capacitance A of the electrode foil for electrolytic capacitors is, 350μF / cm ^2, the capacitance B was 920μF / cm ^2. Therefore, A / B = 0.38.
[0047]
Using this electrolytic capacitor electrode foil as a cathode, an electrolytic capacitor having a rating of 10 V · 8200 μF was produced in the same manner as in Example 1.
[0048]
The electrolytic capacitor was stored in an oven at 110 ° C. for 1000 hours while applying a voltage of 10V. The capacitance after storage was only 4.0% lower than that before storage, and the heat resistance was good.
[0049]
Comparative Example 1
The same as in Example 1 except that argon gas was supplied at 1.4 liters / min, the pressure in the lower tank was adjusted to 1.3 × 10 ⁻² Torr, and a titanium thin film having a thickness of 0.1 μm was formed. Thus, a titanium thin film was formed on the aluminum foil substrate.
[0050]
The electrolytic capacitor electrode foil thus obtained had a capacitance A of 320 μF / cm ² , a capacitance B of 1330 μF / cm ² , and A / B = 0.24.
[0051]
Using this electrolytic capacitor electrode foil as a cathode, an electrolytic capacitor having a rating of 10 V · 8200 μF was produced in the same manner as in Example 1.
[0052]
The electrolytic capacitor was stored in an oven at 110 ° C. for 1000 hours while applying a voltage of 10V. The capacitance after storage was greatly reduced to 10.4% compared to before storage, and the heat resistance was poor.
[0053]
【The invention's effect】
The present invention relates to an electrode foil for an electrolytic capacitor in which a metal thin film is formed on at least one surface of a substrate, and the electrode for an electrolytic capacitor measured in an electrolytic solution in which 25% of tetraethylammonium phthalate is dissolved in γ-butyrolactone. By making the ratio of the capacitance of the foil and the capacitance of the electrode foil for an electrolytic capacitor measured in a 10% aqueous solution of ammonium borate within a predetermined range, the productivity is reduced and the capacitance is reduced. A small electrolytic capacitor with excellent heat resistance and long life was obtained.
[Brief description of the drawings]
FIG. 1 is an example of a vacuum deposition apparatus for producing an electrode foil for an electrolytic capacitor according to the present invention.
FIG. 2 is an example of a vacuum vapor deposition apparatus for producing an electrode foil for an electrolytic capacitor according to the present invention, and is an explanatory view of an incident angle of a metal vapor to a substrate.
[Explanation of symbols]
1: substrate 2: evaporation sources 3 and 4: mask for shielding metal vapor α: final incident angle β: initial incident angle 18: substrate 21: evaporation sources 28, 31 and 33: gas supply valves 29, 32 and 34: Nozzle

Claims (2)

A capacitance A of the electrode foil for an electrolytic capacitor measured in an electrolytic solution in which a metal thin film is formed on at least one surface of the substrate by vacuum deposition and 25% of tetraethylammonium phthalate is dissolved in γ-butyrolactone; A method for producing an electrode foil for an electrolytic capacitor having a ratio A / B with a capacitance B of the electrode foil for an electrolytic capacitor measured in a 10% aqueous solution of ammonium borate in the range of 0.3 to 0.8. The substrate is moved along a cylindrical drum, a deposition source is disposed on the opposite side of the drum through a mask having an opening, and an initial incident angle, that is, deposition is performed when metal deposition is incident on the substrate. A normal line is established on the substrate surface at a point where a straight line connecting the center of the source and the end upstream of the mask opening with respect to the substrate traveling direction is incident on the substrate, and an angle formed by the normal line and the straight line previously connected, 0 to 90 degrees Final angle of incidence, i.e. make the center of the evaporation source, the normal to the substrate surface at a point where a straight line connecting the end on the downstream side of the mask opening to the substrate travel direction is incident on the substrate, connecting in the normal and previously The angle formed by the straight line is -90 to -45 degrees, and is not directed toward the same direction as the incident direction of the metal vapor from a nozzle provided in the vicinity of the vapor deposition source or between the vapor deposition source and the vapor incident area on the substrate. A method for producing an electrode foil for an electrolytic capacitor, comprising supplying an active gas.   2. The method for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein the thickness of the metal thin film is 0.2 to 0.4 [mu] m.

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