JP5501002B2 - Method for producing metallized film for film capacitor - Google Patents

Description

  The present invention relates to a method for producing a metallized film for a film capacitor in which an electrode film made of a metal is formed on the surface of a film-like substrate made of a dielectric.

  The film capacitor is formed by laminating or winding a metallized film in which an electrode film made of metal is formed on the surface of a film-like substrate made of dielectric. Here, in recent years, film capacitors have been increasingly used in hybrid electric vehicles. The film capacitors have a higher electrostatic capacity and a smaller size, and further have self-recovery properties (the dielectric film is broken and the electrode film is broken). When the short circuit occurs, the electrode film partially disappears due to the short circuit current and the insulation recovery function is required. Therefore, thinning of the electrode film of the metallized film for film capacitors is progressing, and an electrode film whose film thickness is reduced from the current 10Ω / □ to about 30Ω / □ in terms of sheet resistance is required. .

  However, in film capacitors used in high-temperature and high-humidity environments such as for hybrid electric vehicles, as the electrode film thickness becomes thinner, the resistance value of the electrode film increases and the effective area decreases due to deterioration over time. As a result, there is a problem that the capacitance of the film capacitor is reduced and the quality of the product is deteriorated.

  By the way, conventionally, as a method for producing a metallized film for a film capacitor, a method of forming an electrode film on a plasma-treated surface of a film-like substrate after performing a plasma treatment on the surface of the film-like substrate is known ( For example, see Patent Documents 1 and 2). In this case, the adhesion between the film-like substrate and the electrode film is improved, and the electrode film can be made thinner while ensuring the current resistance.

  Moreover, when this inventor tested, it turned out that the metallized film manufactured by the said method can suppress aged deterioration to some extent in high temperature, high humidity. However, it has not yet been possible to sufficiently suppress deterioration over time when the electrode film is thinned.

JP 2008-115417 A JP 2007-300126 A

  In view of the above, the present invention has as its object to provide a method for producing a metallized film for a film capacitor that can sufficiently suppress deterioration over time under high temperature and high humidity even if the electrode film is thinned. Yes.

  In order to solve the above-mentioned problems, a method for producing a metallized film for a film capacitor according to the present invention comprises a plasma step before performing plasma treatment on the surface of a film-like substrate made of a dielectric, and a plasma-treated surface of the film-like substrate. A film forming step of forming an electrode film made of metal, and a plasma step after performing plasma treatment on the surface of the electrode film.

  According to the present invention, by performing the pre-plasma step, impurities such as moisture are removed from the film-like substrate, and the adhesion of the electrode film formed on the film-like substrate in the subsequent film-forming step is improved. Therefore, even if the electrode film is made thinner, film cracking is less likely to occur and natural oxidation is suppressed. Furthermore, in the present invention, the surface of the electrode film is modified by performing a post-plasma process. As a result, even if the electrode layer is thinned, an increase in the resistance value of the electrode film due to aging under high temperature and high humidity can be sufficiently suppressed. Therefore, by using the metallized film produced by the method of the present invention, a high-quality film capacitor having high capacitance and high self-recovery property and excellent durability under high temperature and high humidity is obtained. be able to.

  Note that the plasma treatment in the post-plasma process is desirably performed in an atmosphere containing at least one of oxygen and nitrogen as the atmosphere gas. According to this, a modified layer made of metal oxide or metal nitride is formed on the surface of the electrode film, and the durability under high temperature and high humidity is further improved.

  In the present invention, a first and second pair of unwinding and winding rollers, a cooling drum for winding a film-like substrate between both unwinding and winding rollers, and a film-like base in the vacuum chamber. A film forming unit disposed so as to face the peripheral surface portion of the cooling drum around which the material is wound, between the cooling drum and the first unwinding roller, and between the cooling drum and the second unwinding winding Using a vacuum wind-up film forming apparatus that houses at least one of the plasma generating units disposed between and a roller, a film-like base material is transferred from the first wind-up roll to the second wind-up roll. The plasma generating unit is operated while carrying out the pre-plasma process, and then the film-like substrate is conveyed from the second unwinding roller to the first unwinding roller. The film forming unit is operated to perform the film forming process, and then the first unwinding and winding roller While conveying the film-shaped substrate into et second winding Demakito roller, it is desirable to perform post-plasma process by operating the plasma unit.

  Further, when a metallized film is produced using a vacuum winding film forming apparatus as described above, a pair of slit-like openings through which the film-like substrate passes and an atmosphere gas inlet are provided as a plasma generation unit. It is desirable to use a box having a pair of cathode electrodes arranged so as to face each other with a film-like substrate interposed therebetween. According to this, in the plasma process before and after, the plasma treatment is also performed on the surface (back surface) opposite to the surface of the film-shaped substrate forming the electrode film, and impurities are removed from the back surface of the film-shaped substrate. The Therefore, it is possible to prevent the electrode film from being contaminated with impurities when the film-like base material is wound around each unwinding and winding roller and the back surface of the fill-like base material comes into contact with the electrode film.

Sectional drawing which shows the vacuum winding film-forming apparatus used for implementation of the manufacturing method of embodiment of this invention. The expanded sectional view of the part of the plasma generation unit of the apparatus of FIG. The typical sectional view of a metallized film.

  FIG. 1 shows a vacuum winding film forming apparatus for producing a metallized film for a film capacitor. The metallized film is obtained by forming an electrode film b made of a metal such as aluminum on the surface of a film-like substrate a as shown in FIG. The film-like substrate a is made of a dielectric material such as polyethylene terephthalate (PET), polyethylene (PEN), polypropylene (PP), and has a thickness of 1 to 10 μm.

The vacuum winding film forming apparatus includes a vacuum chamber 1 having a plurality of exhaust ports 1a, 1b, 1c connected to a vacuum pump (not shown) such as an oil diffusion pump. The vacuum chamber 1, the first and the second pair of winding Demakito roller 2 _1, 2 _2, a double winding Demakito roller 2 _1, 2 ₂ cooling drum 3 located between the cooling drum 3 And a plurality of guide rollers 4 positioned between the unwinding and winding rollers 2 ₁ and 2 ₂ are accommodated. Then, in a state where the film-like substrate a is wound around the peripheral surface of the cooling drum 3 at a predetermined holding angle, the first and second unwinding and winding rollers 2 ₁ and 2 ₂ are changed from one to the other. I am trying to carry it. The peripheral surface of the cooling drum 3 is cooled by a cooling medium flowing through the cooling drum 3.

A film forming unit 5 is disposed in the vacuum chamber 1 so as to face the peripheral surface portion of the cooling drum 3 around which the film-shaped substrate a is wound. Further, the cooling drum 3 and the first unwinding winding are arranged. plasma unit 6 is arranged between the intake roller 2 _1. Further, an eddy current sensor 7 for measuring the film thickness of the electrode film b is provided in the vacuum chamber 1, and a partition plate that partitions the space in which the film forming unit 5 is arranged from other spaces in the vacuum chamber 1. 8 is provided.

  The film forming unit 5 is of an EB vapor deposition type in which a metal material such as aluminum housed in a crucible 51 is heated and evaporated by an electron beam 52 a from an electron gun 52. In addition, as the film-forming unit 5, it is also possible to use a device other than the EB vapor deposition method such as a resistance heating vapor deposition method, an induction heating vapor deposition method, or a sputtering method.

  As shown in FIG. 2, the plasma generating unit 6 is opposed to a conductive box 61 having a pair of slit openings 61a and 61b through which the film-like substrate a passes, with the film-like substrate a interposed therebetween. In this way, a pair of cylindrical cathode electrodes 62, 62 are arranged. Then, an atmospheric gas is introduced into the box 61 from a gas inlet 63 formed therein, a direct current or an alternating current is applied to the cathode electrode 62, and the plasma p is generated by discharging in the atmospheric gas, thereby producing a film. Plasma treatment for irradiating the substrate a and the electrode film b with electrons and ions is performed.

As the atmospheric gas, Ar (argon), _{O 2} (oxygen), _{N 2} (nitrogen), the He (helium), CF ₄ (carbon tetrafluoride), CO ₂ (carbon dioxide), CH ₄ (methane) , One kind of gas selected from C ₂ H ₂ (acetylene) or two or more kinds of mixed gases can be used. In addition, a magnet (not shown) is arranged inside or around the cathode electrode 62 to cause magnetron discharge or penning discharge in an atmospheric gas, but the discharge type is not limited to this. Further, the cathode electrode 62 may be flat.

Making the metallized film is first while conveying the film-shaped substrate a from the first winding Demakito roller 2 ₁ to the second winding Demakito roller 2 ₂ actuates the plasma unit 6 Then, a pre-plasma process is performed to perform plasma treatment on the surface of the film-like substrate a. Then, the second winding Demakito roller 2 ₂ while conveying the first winding Demakito roller 2 ₁ to the film-form substrate a, by operating the film forming unit 5, the film-form substrate a A film forming process for forming the electrode film b on the plasma processing surface is performed. Then, while conveying the film-shaped substrate a from the first winding Demakito roller 2 ₁ to the second winding Demakito roller 2 _2, by operating the plasma generating unit 6, the surface of the electrode film b After performing the plasma treatment, a plasma process is performed. In the film forming step, the electrode film b having a predetermined film thickness is formed by monitoring the film thickness of the electrode film b by the eddy current sensor 7 and adjusting the substrate transport speed.

Incidentally, also arranged plasma unit between the cooling drum 3 and the second winding Demakito roller 2 _2, the first winding Demakito roller 2 ₁ to the second winding Demakito roller 2 ₂ while conveying the film-form substrate a, the plasma generating unit 6 which is disposed between the cooling drum 3 and the first winding Demakito roller 2 _1, a deposition unit 5, and the cooling drum 3 second winding Demakito roller 2 ₂ is actuated and the plasma unit disposed between, it is conceivable to perform before continuously the plasma process and the deposition process and post-plasma process. However, in order to reduce the thickness of the electrode film b, it is necessary to considerably increase the substrate conveyance speed during the film formation process, and on the other hand, the film-shaped substrate a is not damaged in the front and rear plasma processes. In order to perform the required plasma treatment with a sufficient strength, the substrate conveyance speed must be reduced. Therefore, it is necessary to perform the pre-plasma process, the film-forming process, and the post-plasma process separately as described above, and change the substrate conveyance speed in each process. When the film forming unit 5 is of the EB vapor deposition type, the film-like substrate a is charged. Therefore, during the film forming process, the plasma generation unit 6 is operated to perform the charge removal process.

  According to this embodiment, by performing the pre-plasma process, impurities such as moisture are removed from the film-shaped substrate a, and the adhesion of the electrode film b formed on the film-shaped substrate a in the subsequent film-forming process. Will improve. Therefore, even if the electrode film b is thinned, film cracking is difficult to occur, and natural oxidation is suppressed. Furthermore, the surface of the electrode film b is modified by performing a post-plasma process. As a result, even if the film thickness of the electrode layer b is reduced to about 10 nm, an increase in the resistance value of the electrode film b due to aging under high temperature and high humidity can be sufficiently suppressed. Therefore, by using the metallized film manufactured as in the present embodiment, a high-quality film capacitor having high capacitance and high self-recovery property and excellent durability under high temperature and high humidity is obtained. be able to. In particular, when the post-plasma process is performed in an atmosphere containing at least one of oxygen and nitrogen as an atmospheric gas, a modified layer made of a metal oxide or metal nitride is formed on the surface of the electrode film b, and the high temperature and high humidity Durability is further improved.

Further, in the post-plasma process, will be a film-shaped substrate a is conveyed through the first winding Demakito roller 2 ₁ to the second winding Demakito roller 2 ₂ to the cooling drum 3, the film formation Cooling of the film-like substrate a heated in the process can be promoted by the cooling drum 3. Therefore, after the post-plasma process, the waiting time for cooling required to take out the metallized film from the vacuum chamber 1 can be shortened, and productivity is improved.

In this embodiment, since the plasma generation unit 6 has a pair of cathode electrodes 62 and 62 facing each other with the film-like substrate a interposed therebetween, the electrode film b is formed in the front and rear plasma processes. Plasma treatment is also performed on the surface (back surface) opposite to the surface of the film-shaped substrate a to remove impurities from the back surface of the film-shaped substrate a. Therefore, when the film-like base material a is wound around the first and second unwinding and winding rollers 2 ₁ and 2 ₂ and the back surface of the fill-like base material a comes into contact with the electrode film b, the electrode film b Can be prevented from being contaminated with impurities.

Incidentally, in this embodiment, it is arranged plasma unit 6 between the cooling drum 3 and the first winding Demakito roller 2 _1, without charging the film forming step, unnecessary subsequent neutralization process If it is, it may be disposed plasma unit between the cooling drum 3 and the second winding Demakito roller 2 _2. Also, the between the cooling drum 3 and the first winding Demakito roller 2 _1, the plasma unit is disposed on both the between the cooling drum 3 and the second winding Demakito roller 2 _2, prior The plasma process and the post-plasma process may be performed by both plasma generation units, respectively, the pre-plasma process may be performed by one plasma generation unit, and the post-plasma process may be performed by the other plasma generation unit.

Example 1
Using a vacuum take-up the film deposition apparatus shown in FIG. 1, the vacuum chamber 1 after evacuated to 4.7 × 10 -3 ^Pa, the second winding Demakito roller from the first winding Demakito roller 2 ₁ 2 ₂ film-form substrate a (material PP, thickness 12 [mu] m, width 220 mm) while conveying at a speed of 3.0 m / min, while introducing oxygen as an atmospheric gas at 300sccm flow rate into the plasma generation unit 6, A direct current voltage was applied to the cathode electrode 62, and a pre-plasma process was performed on the surface of the fill substrate a under the conditions of current 0.1A and voltage 250V. Then, while conveying the film-shaped substrate a the second winding Demakito roller 2 ₂ to the first winding Demakito roller 2 _1, aluminum materials (purity 99 in the crucible 51 of the deposition unit 5. 9%) is heated with an electron beam 52a having a power of 5.8 kW, the pressure during film formation is 1.0 to 1.4 × 10 ⁻² Pa, the distance between the cooling drum 3 and the crucible 51 is 275 mm, and the substrate tension is 24. A film forming step of forming an electrode film b made of an aluminum material on the plasma-treated surface of the film-like substrate a was performed under the conditions of 5N and the peripheral surface temperature of the cooling drum 3 of 20 ° C. The film thickness of the electrode film b was adjusted to 20 nm and 10 nm by monitoring with the eddy current sensor 7 and adjusting the substrate transport speed. The substrate conveyance speed was about 48 m / min when the electrode film b having a thickness of 20 nm was formed, and about 80 m / min when the electrode film b having a thickness of 10 nm was formed. In the film forming step, the plasma generation unit 6 performed a charge removal process. Finally, while the film-shaped substrate a from the first winding Demakito roller 2 ₁ to the second winding Demakito roller 2 ₂ is conveyed at a speed of 3.0 m / min, the atmospheric gas into the plasma generating unit 6 As a result, nitrogen is introduced at a flow rate of 300 sccm, a direct current voltage is applied to the cathode electrode 62, a plasma process is performed on the surface of the electrode film b under conditions of current 0.1A and voltage 230V, and then a metallized film is formed. The sample was manufactured.

  In addition, a sample in which only the film forming process was performed under the same conditions as described above in the same batch, a sample in which the pre-plasma process and the film forming process were performed under the same conditions as described above, and the same conditions as described above. A sample was manufactured in which a film process and a post-plasma process were performed. And in order to accelerate the deterioration under high temperature and high humidity, each sample is put in a constant temperature and humidity furnace, maintained at a temperature of 40 ° C. and a humidity of 90% for 30 days, and the sheet resistance value Rs of each sample is Changes were measured. Rs was measured by the four probe method. The results when the thickness of the electrode film b is 20 nm are shown in Table 1 below, and the results when it is 10 nm are shown in Table 2 below.

Table 1

Table 2

  From the comparison between Table 1 and Table 2, it can be seen that the increase in Rs due to aging under high temperature and high humidity becomes more prominent as the electrode film b is made thinner. When the thickness of the electrode film b was reduced to 10 nm, in the sample in which the pre-plasma process and the post-plasma process were omitted, Rs increased by 104.1% in 30 days. In the sample in which the post-plasma process was omitted, Rs increased by 55.1% in 30 days, and in the sample in which the pre-plasma process was omitted, Rs increased by 53.9% in 30 days. On the other hand, in the sample which performed both the pre-plasma process and the post-plasma process, Rs rose only 26.4% in 30 days. Therefore, it can be seen that by performing the pre-plasma step and the post-plasma step, the aging deterioration under high temperature and high humidity can be sufficiently suppressed even if the electrode film b is thinned.

  As is apparent from Table 2, when the electrode film b is thinned, the sample subjected to the pre-plasma process has a significantly lower Rs immediately after the film formation than the sample omitting the pre-plasma process. This is because impurities are removed from the surface of the film-like substrate a in the pre-plasma process, the adhesion of the electrode film b is improved, and an increase in Rs due to film cracking is suppressed.

(Example 2)
As in Example 1, after performing a plasma process on the surface of the film-like base material a (material PP, thickness 5 μm, width 200 mm) by the plasma generation unit 6, A film forming process for forming an electrode film b made of an aluminum material on the plasma processing surface of the material a was performed, and finally, a plasma process was performed after the plasma generation unit 6 performed plasma processing on the surface of the electrode film b. The pressure at the time of film formation is 5.0 to 6.0 × 10 ⁻³ Pa, the distance between the cooling drum 3 and the crucible 51 is 280 mm, and the electrode is monitored by the eddy current sensor 7 to adjust the substrate conveyance speed. The thickness of the film b was set to 10 nm. The pre-plasma process and the post-plasma process were performed by introducing atmospheric gas at a flow rate of 300 sccm and applying direct current to the cathode electrode 62 under conditions of a current of 0.4 A and a voltage of 250 to 300 V. As an atmospheric gas used in the pre-plasma process and the post-plasma process, a sample using argon, a sample using oxygen, a sample using nitrogen, a sample using helium, and carbon tetrafluoride are used. And a sample using carbon dioxide. Moreover, the sample which performed only the film-forming process on the same conditions as the above as a comparative example was also created.

  Thereafter, each sample was placed in a constant temperature and humidity oven, maintained at a temperature of 40 ° C. and a humidity of 90% for 30 days, and the change in the sheet resistance value Rs of each sample was measured. Rs was measured by the four probe method. The results are shown in Table 3 below.

Table 3

  The rate of change in Rs is lower than that obtained by omitting the pre-plasma process and the post-plasma process, regardless of which of the above gases is used as the atmospheric gas. The rate of increase of Rs after 30 days is over 80% when argon, carbon tetrafluoride, and carbon dioxide are used, whereas 42.2% when nitrogen is used. In this case, it is significantly reduced to 33.4%. This is because a modified layer made of aluminum oxide or aluminum nitride is formed on the surface of the electrode film b, and the durability under high temperature and high humidity is further improved. This shows that the plasma treatment in the post-plasma process is preferably performed in an atmosphere containing at least one of oxygen and nitrogen as the atmosphere gas.

a ... film-like substrate, b ... electrode film, 1 ... vacuum chamber, 2 ₁ ... first unwinding and winding roller, 2 ₂ ... second unwinding and winding roller, 3 ... cooling drum, 5 ... film formation Unit: 6 ... Plasma generating unit, 61 ... Box, 61a, 61b ... Slit-like opening, 62 ... Cathode electrode, 63 ... Gas inlet.

Claims (3)

In the vacuum chamber, a first and second pair of unwinding and winding rollers, a cooling drum for winding the film-like substrate between both unwinding and winding rollers, and a cooling drum for winding the film-like substrate At least between the film-forming unit disposed so as to face the peripheral surface portion, between the cooling drum and the first unwinding roller, and between the cooling drum and the second unwinding roller. Using a vacuum winding film forming apparatus containing a plasma generating unit arranged on one side,
The plasma generating unit is operated while conveying the film-like substrate from the first unwinding roller to the second unwinding roller, and the surface of the film-like substrate made of a dielectric is subjected to plasma treatment. Perform pre-plasma process ,
Next, the film forming unit is operated while conveying the film-like base material from the second unwinding and winding roller to the first unwinding and winding roller, and the plasma-treated surface of the film-like base material is made of metal. Execute the film forming process to form the electrode film,
Next, a plasma process is performed after the plasma generating unit is operated while the film-like base material is conveyed from the first unwinding roller to the second unwinding roller to perform plasma treatment on the surface of the electrode film. The manufacturing method of the metallized film for film capacitors characterized by performing these.   2. The method for producing a metallized film for a film capacitor according to claim 1, wherein the plasma treatment in the post-plasma process is performed in an atmosphere containing at least one of oxygen and nitrogen as an atmosphere gas. As the plasma generating unit, a pair of cathodes is disposed so as to face each other with a film-like substrate sandwiched in a box having a pair of slit-like openings through which the film-like substrate passes and a gas introduction port for introducing atmospheric gas. The method for producing a metallized film for a film capacitor according to claim 1 or 2, wherein an electrode is used.

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