JP2001326137A - Film capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film capacitor which is improved in insulation resistance and breakdown voltage characteristic, without lowering the productivity and mechanical strength of the capacitor and causes little variation in capacitance, a method of manufacturing the capacitor, and a metallized film for capacitor used for the capacitor. SOLUTION: The film capacitor is provided with a capacitor element, formed by winding the metallized film for capacitor obtained by forming a metallic layer on a polyester-based film. A crystallized polyester film, having a center- line average height Ra of 30-70 nm and a strength of 25 kg/mm2 in the lengthwise direction, is used as the polyester-based film. At manufacturing of the film capacitor, the winding speed of the metallized film is adjusted to 500-3,000 rpm and the heat-pressing temperature, pressure, and duration of the film are respectively adjusted to ranges of 80-150 deg.C, 500-3,000 kPa, and 5-15 minutes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film capacitor and a method for manufacturing the same, and more particularly, to a polyester film used for a film capacitor having a predetermined center line average roughness Ra and a longitudinal strength. By using a crystallized film, and further reducing the winding speed, and the heat press temperature, pressure, and time to predetermined values, without reducing productivity and mechanical strength,
The present invention relates to a film capacitor having excellent insulation resistance and voltage resistance and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a film capacitor as shown in the sectional view of FIG. 1 has been known. The method of manufacturing this film capacitor will be described. First, a metallized film for a capacitor is formed by laminating a metal layer 2 on a polyester-based film 1 by vapor deposition or the like. I do. Next, after the capacitor element is heat-pressed at a predetermined temperature and pressure for a predetermined time, zinc and the like are welded to both sides of the capacitor element to form first and second external electrodes 3.

[0003] Thus, as shown in FIG.
A film capacitor is manufactured in which the metal layer 2 of the odd-numbered capacitor film is connected to the first external electrode 3a and the metal layer 2 of the even-numbered capacitor film is connected to the second external electrode 3b. Is done. In addition, the metal layer 2 of the odd-numbered capacitor film and the second external electrode 3
b, the insulating portion 21 where the metal layer 2 is not formed
However, when the metal layer 2 is formed on the film, the insulating portion 21 may be formed simultaneously by an oil margin method, a tape margin method, or the like, or once the metal layer 2 is formed on the film. After being formed on the entire surface, the film 1 may be formed by performing trimming on the film 1 using a laser or the like.

As shown in FIG. 2, heat press is performed by pressing the capacitor element 5 while heating it with a press plate 6. When a polyester film such as polyethylene terephthalate is used as the film, usually, the temperature of the heat press is about 80 to 150 ° C., the pressure is about 500 to 3000 kPa, and the press time is about 5 to 15 minutes.

The purpose of the heat press is to use a capacitor element 5
Eliminating air remaining inside the capacitor element 5
By securing the strength of itself and bonding the metallized films for capacitors that have been overlapped by winding more strongly, it is possible to prevent moisture from entering the inside of the film capacitor, The purpose is to improve the mechanical properties against the factors.

[0006] If heat pressing is not performed or is insufficient, for example, when an AC voltage is applied to a film capacitor, corona discharge occurs due to air existing between the films. Corona discharge oxidizes the metal layer formed on the film, and may cause a change in the capacity of the film capacitor, a decrease in insulation resistance, and the like.

On the other hand, the heat press increases the distortion between the films, and causes wrinkles 4 inside the capacitor element 5 as shown in FIG. This is considered to have occurred because the film did not have adequate slip properties during winding. Further, the wrinkles 4 reduce the mechanical strength of the film capacitor, and lower the insulation resistance and withstand voltage characteristics of the film capacitor. Further, when the film is compressed by the Maxwell stress between the electrodes generated at the time of applying a voltage and the mechanical balance cannot be maintained, the film is crushed and dielectric breakdown occurs.

Therefore, distortion and wrinkles 4 between films when the capacitor element is heat-pressed are reduced.
In order to optimize the adhesion between the films, generally, the temperature, pressure, and time of the pressing conditions are appropriately adjusted (ie, by parameterizing) to optimize the heat press, Alternatively, when winding a metallized film for a capacitor, a method has been used in which the winding speed is adjusted to reduce the tension applied to the film during winding as much as possible.

[0009]

However, in order to optimize the adhesion between the films by appropriately adjusting the time and the like of the heat press, there is no means other than selection under a condition of a lower temperature or a lower pressure. . In this case, the pressing operation takes a long time, and therefore the productivity is remarkably reduced, which leads to an increase in cost. Furthermore, there is a problem that the mechanical strength of the capacitor element cannot be sufficiently secured because the adhesion between the films is not enough due to the low temperature and the low pressure.

On the other hand, when the winding speed is adjusted to reduce the winding tension as much as possible, for example, the film is disturbed at the time of winding, for example, the film meanders at the time of winding. There is a problem in that the picking speed must be reduced, and the productivity is significantly reduced, leading to an increase in cost.

The present inventors have made intensive efforts to solve the above problems, and as a result, as shown in FIG. 3, which is a schematic view of a photograph of a cross section of a polyester film, the polyester used in a film capacitor. The present inventors have found that the amorphous portion 7 which may be present in the system film lowers the mechanical strength of the film capacitor and also causes a large decrease in the insulation resistance and the withstand voltage, thereby completing the present invention. Furthermore, when a polyester film having such a center line average roughness and length strength within a predetermined range is used, a winding speed substantially equal to or higher than a winding speed in a case where heat pressing is not performed without causing turbulence. The present invention was completed by finding that the metallized film could be wound at a speed, and that the temperature and pressure of the pressing conditions were reduced and the pressing for a long time was not required.

That is, an object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to improve the insulation resistance and the withstand voltage without lowering the productivity and the mechanical strength and to change the capacitance. And a method of manufacturing the same, and a metallized film for a capacitor used in the film capacitor.

[0013]

A film capacitor according to the present invention, which solves the above-mentioned problems, comprises a capacitor element formed by winding a metallized film for a capacitor in which a metal layer is formed on a polyester film, and a capacitor element. A first external electrode and a second external electrode sandwiched from both sides, wherein the polyester film is made of crystallized polyester, and the center line average roughness Ra of the polyester film is
Is not less than 30 nm and not more than 70 nm, and the strength in the length direction of the polyester film is 25 kg / mm ² .

A method for manufacturing a film capacitor according to the present invention, which solves the above-mentioned problems, comprises a winding step of winding a metallized film for a capacitor, which is formed by laminating a metal layer on a polyester film, to form a capacitor element; A pressing step of heat-pressing the element, and an external electrode forming step of forming first and second external electrodes on both sides of the pressed capacitor element, wherein the polyester film is made of crystallized polyester, and the polyethylene terephthalate film Has a center line average roughness Ra of 30 nm or more and 70 nm or less, and a strength in the length direction of 25 k
g / mm ² and the winding speed is 500 rpm or more and 30
00 rpm or less and the temperature of the heat press is 80
℃ 150 ℃ below, the pressure of the heat press,
The pressure is 500 kPa or more and 3000 kPa or less, and the heat press time is 5 minutes or more and 15 minutes or less.

Another method of manufacturing a film capacitor according to the present invention that solves the above-mentioned problems is to laminate a metallized film for a capacitor, which is formed by laminating a metal layer on a polyester film, by winding it around a rotating flat plate. A polyester-based film including a laminating step of forming a capacitor element by heating, a pressing step of heat-pressing the capacitor element, and an external electrode forming step of forming first and second external electrodes on both side surfaces of the pressed capacitor element. Is made of crystallized polyester, the center line average roughness Ra of the polyethylene terephthalate film is 30 nm or more and 70 nm or less, and the strength in the length direction is 25 kg.
/ Mm ² or more, the rotation speed of the flat plate is 20 rpm to 100 rpm or less, and the temperature of the heat press is
It is 80 to 150 ° C., the pressure of the heat press is 500 to 3000 kPa, and the heat press time is 5 to 15 minutes.

In the length direction of the polyester film,
It is preferable that the metal layer and the insulating portion are formed in parallel.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. As shown in FIG. 4 showing a cross-sectional view of the film capacitor according to the present invention, in the film capacitor according to the present invention, a metal layer 10 is formed on a polyester film 9 made of polyethylene terephthalate (hereinafter referred to as “PET”) or the like. A capacitor element formed by laminating a plurality of metallized films for a capacitor, and a first external electrode 11a and a second external electrode 11b sandwiching the capacitor element.

In producing a capacitor element,
Two polyester films 1 each having a metal layer 2 laminated on only one surface may be wound, and a polyester film 1 having a metal layer 2 laminated on both surfaces and a plain polyester film having no metal layer laminated. 1 may be wound.

The metal layer 10 of the odd-numbered capacitor film is electrically connected to the first external electrode 11a, while the metal layer 10 of the even-numbered capacitor film is connected to the second external electrode 11b. ing. Then, the metal layer 10 of the odd-numbered capacitor film and the second external electrode 1
1b, and between the metal layer 10 of the even-numbered capacitor film and the first external electrode 11a are both insulated by the insulating portion 22 where the metal layer 10 is not formed.

Originally, as shown in FIG. 3, the polyester molecules of the polyester film consist of a crystalline portion 8 and an amorphous portion 7, and the polyester film used in the present invention is shown in FIG. Thus, it consists of crystallized polyester. That is, the polyester molecules of the polyester film consist only of crystal parts. Such a polyester film can be obtained, for example, from Toray Industries, Inc. under the trade name (model number) "Lumirror".
As shown in FIG. 5, the crystal part 13 is formed by changing a crystalline part 13 which is already crystalline from the time of film formation and a part which was originally an amorphous part 7. Both of them include the pseudo-crystalline portion 12.

As described above, in the present invention, since the polyester molecules do not have the amorphous portion 7, the mechanical strength of the film capacitor can be maintained or improved as compared with the conventional film capacitor. Along with
Similarly, the insulation resistance and the withstand voltage can be maintained or improved.

Next, a method for obtaining the film capacitor according to the present invention from the polyester molecules of such a polyester film will be described in detail.

First, the center line average roughness Ra is not less than 30 nm and not more than 70 nm, and the intensity in the length direction is 2 nm.
A polyester film having a weight of 5 kg / mm ² or more is prepared. The center line average roughness Ra is JIS B 060
According to No. 1, it can be measured by a surface roughness measuring device obtained from Tokyo Seimitsu Co., Ltd. under the trade name “Surfcom”. In addition, as a polyester-type film, a polyethylene terephthalate film and a polyethylene naphthalate film are preferable because they are easily available.

When the center line average roughness Ra is less than 30 nm, the overlapping films after winding become too close to each other, causing the capacitor element to wrinkle, and this wrinkling tends to cause dielectric breakdown. Very large. On the other hand, when the center line average roughness Ra exceeds 70 nm, the film surface is rough, so that not only the adhesion between the overlapping films after winding is very poor, but also air tends to remain between the films. Corona discharge, which is a cause of the change in the capacity and the decrease in insulation resistance, is likely to occur. Further, for the same reason, there is a disadvantage that the obtained film capacitor is easily deformed by external force.

In particular, the larger the value of the center line average roughness Ra, the worse the adhesion between the overlapping films after winding and the more air tends to remain between the films.
The value of the center line average roughness Ra is more preferably 30 nm or more and 50 nm or less.

If the strength in the length direction is less than 25 kg / mm ² , the strength is insufficient, and the tendency to wrinkle during heat pressing is very large. Further, as compared with a film capacitor prepared using a film having a strength in the length direction of 25 kg / mm ² or more, a film formed using a film having a strength in the length direction of less than 25 kg / mm ^2. Capacitors have poor insulation resistance and withstand voltage.

Next, such a polyester film is wound to form a capacitor element. In addition, the term “winding” used in this specification indicates that the film is rotated and wound. Therefore, the core used when winding the film may be rod-shaped (in this case, a so-called “rolled film capacitor” is obtained) or may be flat ( If
A so-called "laminated film capacitor" is obtained.

In the present invention, the speed at which the film is wound, that is, the winding speed is 500 rpm or more and 3000 rpm or less when a wound type film capacitor is obtained. When the winding speed is less than 500 rpm, productivity is significantly reduced, which leads to a problem that the cost is increased. On the other hand, when the winding speed exceeds 3000 rpm, there is a problem that wrinkles and winding disorder occur.

The lamination speed for obtaining a laminated film capacitor, that is, the rotation speed of a flat plate when winding a metallized film around a rotating flat plate is 20 rpm.
m or more and 100 rpm or less. The rotation speed of the flat plate is 20
When the rotation speed is lower than rpm, productivity is remarkably reduced, and there is a problem that the cost is increased. On the other hand, when the rotation speed of the flat plate exceeds 100 rpm,
There is a problem that wrinkles and winding disorder occur.

Next, as shown in FIG. 2, the capacitor element is subjected to a heat press. The temperature of the heat press applied to the capacitor element is from 80 ° C to 150 ° C. When the temperature of the heat press is lower than 80 ° C., the overlapping films do not sufficiently adhere to each other, and corona discharge, which may cause a change in the capacity of the film capacitor and a decrease in insulation resistance, is likely to occur between the films. Would. On the other hand, the temperature of the heat press is 150 ° C.
When it exceeds, the polyester-based film cannot withstand such high heat, and the withstand voltage may be reduced. In addition, ensure the mechanical strength of the capacitor element,
In order to prevent the withstand voltage of the capacitor from being lowered, the temperature of the heat press is not less than 80 ° C and not more than 150 ° C.
The following is preferred.

The pressure applied to the capacitor element during heat pressing is 500 kPa or more and 3000 kPa or less. When the pressure of the heat press is less than 500 kPa, there is a possibility that it is difficult to secure the mechanical strength of the finally obtained capacitor. On the other hand, when the pressure of the heat press exceeds 3000 kPa, a large mechanical stress is applied to the film,
There is a possibility that a problem that the insulation resistance and the withstand voltage of the capacitor is reduced may occur.

The time for heat pressing is from 5 minutes to 15 minutes. If the time for heat pressing is less than 5 minutes, the films do not adhere sufficiently, and corona discharge is likely to occur in the obtained film capacitor.
On the other hand, when the time for heat pressing exceeds 15 minutes, there is a possibility that productivity may be remarkably reduced and cost may be increased.

Finally, as shown in FIG. 4, first and second external electrodes 11 are formed by spraying zinc or the like on both side surfaces of the capacitor element subjected to the heat press. In this way, as shown in FIG. 4, the metal layer 10a of the odd-numbered capacitor film is connected to the first external electrode 11a, and the metal layer 10b of the even-numbered capacitor film is connected to the first external electrode 11a. 2 A film capacitor connected to the external electrode 11b is created.

Usually, in order to obtain a large number of film capacitors from one film, heat-pressed capacitor elements are cut into so-called unit capacitor elements, and first and second external electrodes are provided on both end surfaces thereof. 11 is formed. Examples of the metal used for the external electrode 11 include tin and zinc or alloys thereof. In addition, as a method of forming the external electrode 11, a method of spraying these metals can be used.

As before, between the metal layer 10 of the odd-numbered capacitor film and the second external electrode 11b and between the metal layer 10 of the even-numbered capacitor film and the first external electrode 11a. Is provided with an insulating portion 22 on which the metal layer 10 is not formed.
The metal layer 10 is formed in parallel with the metal layer 10, and when the metal layer 10 is formed on the film 9, the metal layer 10 may be formed simultaneously as a margin by an oil margin method, a tape margin method, or the like. After forming the film, the film may be formed by trimming the film with a laser or the like. The method for forming the metal layer 10 on the film 9 is not particularly limited, and examples thereof include an electron beam evaporation method (EB evaporation method), a high frequency evaporation method (RF evaporation method), a resistance heating evaporation method, and a sputter evaporation method. Can be mentioned. The metal used as the metal layer 10 is not particularly limited, and for example, aluminum, copper, zinc, or the like can be used.

The lead wire of the formed film capacitor is welded to the external electrode 11 in the same manner as a normal film capacitor. Of course, an exterior may be provided around the film capacitor as needed. Examples of the exterior method include a resin exterior method of covering the film capacitor with an insulating powder exterior resin such as an epoxy resin, and polycarbonate (P).
C), after inserting into a plastic case made of polybutylene terephthalate (PBT), etc., epoxy resin,
A case exterior method of injecting a urethane resin or the like may be used.

[0037]

The present invention will be described in more detail with reference to the following examples, which are only used to illustrate the present invention described in the claims. In no way should the following examples be used to limit the invention described in the claims.

(Example 1) A 4 μm thick PET film 9 made of crystallized polyethylene terephthalate was
Aluminum 10 was deposited by an evaporation method. At the time of vapor deposition, the insulating portion 22 was formed in parallel with the longitudinal direction of the PET film 9 by a tape margin method. The center line average roughness Ra of the PET film 9 used in Example 1
Is 30 nm and the strength in the length direction is 25 kg / mm ²
Met.

Next, PET on which aluminum 10 was deposited
The film 9 was wound at a speed of 1000 rpm to form the capacitor element 5. Next, this capacitor element 5
As shown in FIG. 2, at a temperature of 100 ° C. and a pressure of 980 KP
Heat-pressed for 5 minutes under the condition of a. In this example, since the PET film 9 was individually wound, there was no need to cut the capacitor element into unit capacitors after heat pressing.

Then, zinc was sprayed on both sides of the heat-pressed capacitor element to form first and second external electrodes 11. Lastly, a lead wire was welded to each of the first and second external electrodes 11, and a powder resin sheathing with an epoxy resin was performed to form a film capacitor.

(Example 2) Center line average roughness Ra is 30
nm and a strength in the length direction of 30 kg / mm ² was used. After winding the PET film 9 at a speed of 1000 rpm, a temperature of 10
A film capacitor was prepared in the same manner as in Example 1, except that the film was heat-pressed at 0 ° C. and a pressure of 980 KPa for 5 minutes.

(Embodiment 3) Center line average roughness Ra is 50
nm and a strength in the length direction of 30 kg / mm ² was used. After winding the PET film 9 at a speed of 1000 rpm, a temperature of 10
A film capacitor was prepared in the same manner as in Example 1, except that the film was heat-pressed at 0 ° C. and a pressure of 980 KPa for 5 minutes.

(Example 4) Center line average roughness Ra is 70
nm and a strength in the length direction of 30 kg / mm ² was used. After winding the PET film 9 at a speed of 1000 rpm, a temperature of 10
A film capacitor was prepared in the same manner as in Example 1, except that the film was heat-pressed at 0 ° C. and a pressure of 980 KPa for 5 minutes.

Comparative Example 1 A PET film having a thickness of 4 μm in which crystallized polyethylene terephthalate and non-crystallized polyethylene terephthalate were mixed was used.
The center line average roughness Ra of the T film is 20 nm,
Example 1 was repeated except that the strength in the length direction was 20 kg / mm ² and that the PET film was wound at a speed of 1000 rpm and then heat-pressed at a temperature of 100 ° C. and a pressure of 980 KPa for 5 minutes. A film capacitor was prepared in the same manner as described above.

Comparative Example 2 A PET film having a thickness of 4 μm in which crystallized polyethylene terephthalate and amorphous polyethylene terephthalate were mixed was used.
The center line average roughness Ra of the T film is 20 nm,
Example 1 was repeated except that the strength in the length direction was 30 kg / mm ² and that the PET film was wound at a speed of 1000 rpm and then heat-pressed at a temperature of 100 ° C. and a pressure of 980 KPa for 5 minutes. A film capacitor was prepared in the same manner as described above.

Comparative Example 3 A 4 μm thick PET film in which crystallized polyethylene terephthalate and non-crystallized polyethylene terephthalate were mixed was used.
The center line average roughness Ra of the T film is 30 nm,
Example 1 was repeated except that the strength in the length direction was 20 kg / mm ² and that the PET film was wound at a speed of 1000 rpm and then heat-pressed at a temperature of 100 ° C. and a pressure of 980 KPa for 5 minutes. A film capacitor was prepared in the same manner as described above.

Comparative Example 4 A 4 μm thick PET film in which crystallized polyethylene terephthalate and amorphous polyethylene terephthalate were mixed was used.
The center line average roughness Ra of the T film is 50 nm,
Example 1 was repeated except that the strength in the length direction was 20 kg / mm ² and that the PET film was wound at a speed of 1000 rpm and then heat-pressed at a temperature of 100 ° C. and a pressure of 980 KPa for 5 minutes. A film capacitor was prepared in the same manner as described above.

Comparative Example 5 A 4 μm thick PET film in which crystallized polyethylene terephthalate and non-crystallized polyethylene terephthalate were mixed was used.
The center line average roughness Ra of the T film is 70 nm,
Except that the strength in the length direction was 20 kg / mm ² and that the PET film 9 was wound at a speed of 1000 rpm and then heat pressed at a temperature of 100 ° C. and a pressure of 980 KPa for 5 minutes. A film capacitor was prepared in the same manner as in Example 1.

Comparative Example 6 A 4 μm thick PET film in which crystallized polyethylene terephthalate and non-crystallized polyethylene terephthalate were mixed was used.
The center line average roughness Ra of the T film is 90 nm,
Except that the strength in the length direction is 20 kg / mm ² and that the PET film 9 was wound at a speed of 1000 rpm, and then heat pressed at a temperature of 100 ° C. and a pressure of 980 KPa for 5 minutes. A film capacitor was prepared in the same manner as in Example 1.

Comparative Example 7 A 4 μm thick PET film in which crystallized polyethylene terephthalate and non-crystallized polyethylene terephthalate were mixed was used.
The center line average roughness Ra of the T film is 90 nm,
Example 1 was repeated except that the strength in the length direction was 30 kg / mm ² and that the PET film was wound at a speed of 1000 rpm and then heat-pressed at a temperature of 100 ° C. and a pressure of 980 KPa for 5 minutes. A film capacitor was prepared in the same manner as described above.

Here, for convenience, each condition of Examples 1 to 4 and Comparative Examples 1 to 7 is summarized in Table 1.

[0052]

[Table 1]

(Characteristics of Each Capacitor)
4 and Comparative Examples 1 to 7 will be described. The capacitance of each of these film capacitors was 0.47 μF, and the rated voltage was 250 V.

PET used in each example and each comparative example
The cross-sectional structure of the film was observed with a scanning electron microscope (STM) Akashi Beam Technology DS-130S. PE constituting the film capacitors of Examples 1 to 4
In the T film, no wrinkles were observed as shown in FIG. On the other hand, in the PET films constituting the film capacitors of Comparative Examples 1 to 4, as shown in FIG. 3, an amorphous portion 7 and a crystalline portion 8 exist, and the amorphous portion 7 Was composed.

As a result, the film was made of crystallized polyethylene terephthalate, had a center line average roughness Ra of 30 nm or more and 70 nm or less, and had a longitudinal strength of
It has been found that when a metallized PET film of 5 kg / mm ² or more is used, no wrinkling occurs even when the film is wound at the winding speed and heat pressed to obtain a capacitor without heat pressing.

Further, each of the obtained film capacitors of Examples 1 to 4 and Comparative Examples 1 to 7 was subjected to a DC step-up breakdown test.
The DC breakdown voltage value, the insulation resistance value, the AC corona starting voltage value, and the element deformation failure rate were measured or calculated by applying to an insulation resistance value measurement test, an AC corona initiation voltage measurement test, and an element deformation failure rate test. . Hereinafter, each test method and the test results will be described.

(DC step-up breakdown test) In the DC step-up breakdown test, a DC voltage was gradually applied to the obtained film capacitor at a rate of 100 V / sec. Was used as the breakdown voltage. The test results are shown in FIG. FIG. 6 is a graph showing the average value of the DC breakdown voltage value with respect to the center line average roughness Ra of the film. Incidentally, in this study, a film capacitor, except for film capacitors obtained in Example 4 (i.e., strength in the longitudinal direction is 20 Kg / mm ² or 30 Kg / mm ² at which ones) were used 12 respectively.

FIG. 6 shows that if the center line average roughness Ra of the PET film is 30 nm or more, the DC breakdown voltage value becomes 1
000 V or more, and has excellent withstand voltage, whereas when a PET film having a center line average roughness Ra of 20 nm is used, the DC breakdown voltage value is remarkably reduced, and the withstand voltage is inferior. Is understood. When the center line average roughness Ra is the same, the strength in the length direction is 20%.
Than is kg / mm ^2, the strength in the longitudinal direction is 30Kg
It is also understood that the DC breakdown voltage value is higher when the value is / mm ² .

(Insulation Resistance Value Measurement Test) The insulation resistance value measurement test was performed by using a high insulation resistance meter (YOKOGAWA-HEWLETTPACKACK) specified in JIS C 1303 by the insulation resistance measurement method specified in JIS C 5102. It was measured. The test results are shown in FIG.
FIG. 7 is a graph showing the maximum value and the minimum value of the insulation resistance value with respect to the strength in each length direction. In FIG. 7, white circles are average values. In this test, 12 film capacitors each having a center line average roughness of the PET film 9 of 30 nm (that is, the film capacitors obtained in Examples 1 and 2 and Comparative Example 1) were used.

As can be understood from FIG.
25kg / mm ^TwoIf it is more than
Average insulation resistance is 1 × 10¹¹About Ω and its roses
Even though it is at most about 10 times smaller,
On the other hand, the strength in the length direction of the PET film is 20 kg /
mm^Two, The average insulation resistance value is 1 × 10^{1 0}
Ω, and the strength in the length direction of the PET film is 2
5kg / mm^TwoInsulation resistance is inferior to the above case
In addition, the variation in insulation resistance is about 1000 times
And as a product manufactured in large quantities,
Difficult to maintain quality. The length of the film
The higher the direction strength, the higher the average insulation resistance value.
It is also understood that

(AC Corona Starting Voltage Measurement Test) The AC corona starting voltage measurement test is performed by using a corona measuring device manufactured by Ando Electric Co., Ltd., which can measure the amount of charge and the degree of occurrence of corona discharge of an insulator. A when the voltage is detected
It was measured by setting the C corona onset voltage. The test results are shown in FIG. FIG. 8 is a graph showing the average value of the AC corona onset voltage value with respect to the center line average roughness Ra of the PET film. In this test, 12 film capacitors obtained in Examples 2 to 4 and Comparative Examples 1 to 7 were used.

As can be understood from FIG. 8, when the center line average roughness Ra of the film is 70 nm or less, the AC corona starting voltage value is 250 V or more, and therefore, when a relatively high voltage is applied. However, it is understood that corona discharge hardly occurs. On the other hand, when the center line average roughness Ra of the film is 90 nm or more, the AC corona starting voltage value is about 150 V, and it is understood that corona discharge easily occurs even at a relatively low voltage. It is also understood that the larger the center line average roughness Ra of the film, the smaller the AC corona onset voltage value. In addition, even if the strength in the length direction of the film is different, A
It is also understood that the C corona onset voltage value is not affected.

(Element deformation defect rate test) The element deformation defect rate test is performed by applying a load of 1.5 kg of a push bull gauge to the pressed capacitor element for 10 seconds and confirming whether the capacitor is deformed or cracked. did. The test results are shown in FIG. FIG. 9 is a graph showing a defect rate of element deformation with respect to the center line average roughness Ra of the PET film. In this test, each of the film capacitors obtained in Examples 2 to 4 and Comparative Examples 1 to 7 was 100
0 were used.

As can be understood from FIG. 9, when the center line average roughness Ra of the film is 70 nm or less, the defective rate of element deformation is extremely small, and therefore, the mechanical strength is high. On the other hand, the center line average roughness Ra of the film
Is 90 nm or more, the defect rate of element deformation is 5%.
It can be seen that it is above 0% and therefore the mechanical strength is significantly lower. It is also understood that the greater the center line average roughness Ra of the film, the lower the mechanical strength.
It is also understood that the difference in the strength in the longitudinal direction of the film does not affect the AC corona starting voltage value.

[0065]

According to the present invention, a film capacitor which is excellent in insulation resistance and withstand voltage and has a small change in capacitance without reducing productivity and mechanical strength, a method of manufacturing the same, and a capacitor used therefor A metallized film is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a conventional film capacitor.

FIG. 2 is a diagram showing how a heat press is applied to a capacitor element 5;

FIG. 3 is a schematic view of a photograph of a cross section of a polyester film in a conventional film capacitor.

FIG. 4 is a sectional view of a film capacitor according to the present invention.

FIG. 5 is a schematic view of a photograph of a cross section of a polyester film in the film capacitor according to the present invention.

FIG. 6 is a diagram showing test results of a DC boost breakdown test.

FIG. 7 is a diagram showing a test result of an insulation resistivity measurement test.

FIG. 8 is a diagram showing a test result of an AC corona starting voltage measurement test.

FIG. 9 is a diagram showing test results of an element deformation defect rate test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Polyester film 2 ... Metal layer 21, 22 ... Insulation part 3 ... External electrode 4 ... Wrinkle 5 ... Capacitor element 6 ... Press plate 7 ... Amorphous part 8 ... Crystalline part 9 ... Polyester film (PET film) DESCRIPTION OF SYMBOLS 10 ... Metal layer 11 ... External electrode 12 ... Pseudo crystalline part 13 ... Crystal part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) H01G 4/30 311 H01G 4/30 311Z 4/32 301B 4/32 301 311Z 311 C08L 67:00 // C08L 67:00 H01G 4/24 321C 321E (72) Inventor Shigeka Matsuoka 1006 Ojidoma, Kadoma-shi, Osaka F-term in Matsushita Electric Industrial Co., Ltd. F-term (reference) 5E082 AB03 AB05 EE07 EE11 EE23 EE37 FF05 FG06 FG36 GG10 GG11 GG27 JJ04 JJ22 LL35 MM22 MM24 PP05 PP06 PP07 PP09 PP10

Claims (6)

[Claims] 1. A capacitor element formed by winding a metallized film for a capacitor in which a metal layer is formed on a polyester-based film, and a first external electrode and a second external electrode sandwiching the capacitor element from both sides. The polyester film is made of crystallized polyester, the center line average roughness Ra of the polyester film is 30 nm or more and 70 nm or less, and the strength in the length direction of the polyester film is 2
A film capacitor having a weight of 5 kg / mm ² . 2. The film capacitor according to claim 1, wherein the metal layer and the insulating portion are formed in parallel with a length direction of the polyester film. 3. A winding step of winding a metallized film for a capacitor formed by laminating a metal layer on a polyester-based film to form a capacitor element; a pressing step of heat-pressing the capacitor element; An external electrode forming step of forming first and second external electrodes on both side surfaces of the film capacitor, wherein the polyester film is made of crystallized polyester, and the center line of the polyethylene terephthalate film is The average roughness Ra is 30 nm or more and 70 nm or less, the strength in the length direction is 25 kg / mm ² , the winding speed is 500 rpm or more and 3000 rpm or less, and the temperature of the heat press is 80 ° C. or more. 150 ° C. or less, and the pressure of the heat press is 500 kPa More than 3000
The method of manufacturing a film capacitor, wherein the heat press time is 5 minutes or more and 15 minutes or less. 4. The method according to claim 3, wherein the metal layer and the insulating portion are formed in parallel in a length direction of the polyester film. 5. A laminating step of forming a capacitor element by laminating a metallized film for a capacitor formed by laminating a metal layer on a polyester-based film around a rotating flat plate; and heat-pressing the capacitor element. And forming an external electrode on both sides of the pressed capacitor element, wherein the polyester film is made of crystallized polyester. The center line average roughness Ra of the polyethylene terephthalate film is 30 nm or more and 70 nm or less, the longitudinal strength is 25 kg / mm ² or more, and the rotation speed of the flat plate is 20 rpm to 100 rpm or less. The temperature of the heat press is 80 ° C. or more and 150 ° C. or less There, the pressure of the heat press, 500kPa more than 3000
The method of manufacturing a film capacitor, wherein the heat press time is 5 minutes or more and 15 minutes or less. 6. The method for manufacturing a film capacitor according to claim 3, wherein the metal layer and the insulating portion are formed in parallel with a length direction of the polyester-based film.