Dielectric film for capacitors, metallized film for capacitors, and capacitors

Abstract

To provide a dielectric film for a capacitor in which leakage current in a high temperature environment is reduced.SOLUTION: A dielectric film for a capacitor contains at least an amorphous thermoplastic resin containing an aromatic ring in a main chain as a main component, and 1 mass% or more and 8 mass% or less of an olefinic resin as an accessory component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a dielectric film for capacitors, a metallized film for capacitors, and a capacitor. [Background technology]

[0002] Conventionally, capacitors utilizing resin films have been used in electronic and electrical equipment, for example, as high-voltage capacitors, various switching power supplies, filter capacitors and smoothing capacitors in converters and inverters. In such capacitors, the resin film is used as a dielectric film for capacitors, and the capacitor is constructed by, for example, (i) creating a so-called "metallized film" on which a conductive layer such as a metal layer is provided by methods such as metal deposition, vacuum plating such as sputtering, coating and drying of a metal-containing paste, or pressing metal foil or metal powder onto the dielectric film; or (ii) laminating a dielectric film without a conductive layer such as a metal layer with another conductive material such as metal foil or a metallized film with a metal layer provided by a method similar to (i). Dielectric films for capacitors are also used as capacitors for inverter power supply equipment that controls drive motors in electric vehicles and hybrid vehicles, for which demand has been increasing in recent years.

[0003] In the applications mentioned above, capacitors used in automobiles, for example, are operated in high-temperature environments, so dielectric films for capacitors are required to have high dielectric breakdown strength even in high-temperature environments. Furthermore, in recent years, the required temperature for automotive applications has risen compared to the past, and the required temperature exceeds 120°C, sometimes reaching 150°C.

[0004] For example, Patent Document 1 discloses a plastic film capacitor in which a film mainly composed of an aromatic polyethersulfone resin having high heat resistance is used as a dielectric thin film. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 60-68505 [Overview of the project] [Problems that the invention aims to solve]

[0006] Generally, the dielectric breakdown strength of polymer resins is temperature-dependent, and as the test temperature increases, the dielectric breakdown strength tends to decrease. Therefore, as mentioned above, capacitors used in high-temperature environments require dielectric films for capacitors that have high dielectric breakdown strength in high-temperature environments.

[0007] Traditionally, it was believed that if a dielectric film for capacitors had high dielectric breakdown strength (voltage resistance), it could be used under high potential gradients even after being processed into a capacitor. However, the voltage resistance expected from the dielectric film does not always match the voltage resistance after processing into a capacitor element, and under high potential gradients of several hundred V / μm, the capacitor element may experience thermal runaway (smoke and fire).

[0008] It is generally known that dielectric films manufactured from polymer resins exhibit decreased electrical insulation and increased leakage current as the temperature rises. In other words, dielectric films with high leakage currents have a large amount of self-heating (multiplication of voltage and current), resulting in a large temperature rise relative to the ambient temperature. This leads to a vicious cycle where decreased electrical insulation increases leakage current, further increasing heat generation, thus increasing the likelihood of thermal runaway (smoke and fire) in the capacitor.

[0009] To prevent thermal runaway in such capacitors, heat dissipation countermeasures are necessary in high-temperature environments, such as derating the voltage applied to the capacitor to suppress leakage current (heat generation) and providing an auxiliary mechanism for forced cooling of the capacitor. In addition, derating of frequency, time, and ambient temperature may also be necessary in some cases.

[0010] Also, depending on the type of dielectric film, under a high potential gradient, a phenomenon occurs where the electrical insulation deviates from Ohm's law, deviating from the proportional relationship between voltage and current (constant resistance value, i.e., constant electrical insulation) shown by Ohm's law, and the current shifts to a region proportional to the square of the voltage. That is, the electrical insulation under a high potential gradient cannot be inferred from the electrical insulation evaluated under a low potential gradient. Furthermore, as a method for evaluating electrical insulation, volume resistivity can be cited, but there are many cases where the measurement remains at a potential gradient of about several tens of V / μm, and it is insufficient as a method for inferring electrical insulation under a high potential gradient such as several hundreds of V / μm due to the aforementioned reasons.

[0011] Under such circumstances, the main object of the present invention is to provide a dielectric film for a capacitor with reduced leakage current in a high-temperature environment.

Means for Solving the Problems

[0012] The inventors of the present invention conducted intensive studies to solve the above problems. As a result, it was found that a dielectric film for a capacitor containing an amorphous thermoplastic resin containing an aromatic ring in the main chain as a main component and a predetermined amount of an olefin resin as a sub-component has reduced leakage current in a high-temperature environment. The present invention was completed by further studies based on such findings.

[0013] That is, the present invention includes the following. Item 1. A dielectric film for a capacitor containing at least an amorphous thermoplastic resin containing an aromatic ring in the main chain as a main component and an olefin resin of 1% by mass or more and 8% by mass or less as a sub-component. Item 2. The dielectric film for a capacitor according to Item 1, having a thickness of 1 μm or more and 9 μm or less. Item 3. The dielectric film for a capacitor according to Item 1 or 2, having a dielectric breakdown strength of 300 V DC / μm or more in a 150°C environment. Item 4. The dielectric film for a capacitor according to any one of Items 1 to 3, having a surface roughness Sa of 0.004 μm or more and 0.020 μm or less. Item 5. The dielectric film for a capacitor according to any one of Items 1 to 4, wherein the amorphous thermoplastic resin containing an aromatic ring in the main chain is at least one selected from the group consisting of polysulfone, polyethersulfone, polyphenylsulfone, polycarbonate, polyarylate, polyetherimide, and polyamideimide. Item 6. The dielectric film for a capacitor according to any one of Items 1 to 5, wherein the amorphous thermoplastic resin containing an aromatic ring in the main chain is polysulfone. Item 7. The dielectric film for a capacitor according to any one of Items 1 to 6, wherein the olefin resin is at least one selected from the group consisting of polypropylene, polyethylene, polymethylpentene, cycloolefin polymer, and cycloolefin copolymer. Item 8. The dielectric film for a capacitor according to any one of Items 1 to 7, wherein the olefin resin is at least one of polypropylene and polyethylene. Item 9. A metallized film for a capacitor having a metal film on one or both sides of the dielectric film for a capacitor according to any one of Items 1 to 8. Item 10. A capacitor including the dielectric film for a capacitor according to any one of Items 1 to 9.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a dielectric film for a capacitor with reduced leakage current in a high-temperature environment. Since the leakage current of the dielectric film for a capacitor of the present invention is reduced in a high-temperature environment, it can have a high dielectric breakdown strength in a high-temperature environment. Further, according to the present invention, it is also possible to provide a metallized film for a capacitor and a capacitor using the dielectric film for a capacitor.

Modes for Carrying Out the Invention

[0015] The dielectric film for capacitors according to this embodiment is characterized by comprising, at least, an amorphous thermoplastic resin containing aromatic rings in its main chain as a main component, and an olefin-based resin in an amount of 1% to 8% by mass as a secondary component.

[0016] The dielectric film for capacitors according to this embodiment has such a configuration, which reduces leakage current in high-temperature environments. Because the dielectric film for capacitors according to this embodiment has reduced leakage current in high-temperature environments, it has high dielectric breakdown strength in high-temperature environments (for example, dielectric breakdown strength of 300V in a 120°C environment). DC The thickness must be greater than or equal to / μm, and the dielectric breakdown strength at 300V in a 150°C environment. DC It can have a thickness of 1 / μm or more and can be suitably used in capacitors used in high-temperature environments.

[0017] The dielectric film for capacitors according to this embodiment, the metallized film for capacitors utilizing the dielectric film for capacitors, and the capacitors will be described in detail below. In this specification, the "~" in numerical ranges means greater than or equal to and less than or equal to. That is, the notation α~β means α or greater and β or less, or β or greater and α or less, and the range includes α and β. In this specification, unless otherwise specified, "mass%" indicating the content of each component indicates the percentage of content when the dielectric film for capacitors is set to 100 mass%.

[0018] Furthermore, in the dielectric film for capacitors of this disclosure, "main component" refers to the component that is present in the largest quantity among the components contained in the dielectric film for capacitors, and the main component is an amorphous thermoplastic resin containing aromatic rings in the main chain. Also, in the dielectric film for capacitors, "minor components" refer to components other than the main component among the components contained in the dielectric film for capacitors.

[0019] 1. Dielectric film for capacitors The dielectric film for capacitors according to this embodiment comprises, at least, an amorphous thermoplastic resin containing aromatic rings in its main chain as a main component, and an olefin-based resin in an amount of 1% to 8% by mass as a secondary component.

[0020] In this embodiment, "amorphous thermoplastic resin" refers to a resin that, when measured using a differential scanning calorimeter (DSC), has a glass transition temperature (Tg) but does not have a clear endothermic peak (melting point) associated with dissolution. Specific examples of amorphous thermoplastic resins containing aromatic rings in the main chain include polysulfone, polyethersulfone, polyphenylsulfone, polycarbonate, polyarylate, polyetherimide, and polyamideimide. The amorphous thermoplastic resin contained in the dielectric film for capacitors may be one type or two or more types.

[0021] From the viewpoint of easily enhancing the charge storage performance due to its relatively high dielectric constant, amorphous thermoplastic resins having structural units represented by the formula -[O-Ph-SO2-Ph]- in the main chain are preferred.

[0022] The formula -[O-Ph-SO2-Ph]- is represented as follows in chemical formula (structural formula).

[0023] [ka]

[0024] Particularly preferred examples of amorphous thermoplastic resins include polysulfone-based resins (polysulfone, polyethersulfone, polyphenylsulfone) having the above-mentioned structural units.

[0025] There are no particular restrictions on the polysulfone resin used; known resins can be used, and commercially available products can also be used. Examples of commercially available polysulfones include BASF's Ultrazone® brand (e.g., Ultrazone® S6010, Ultrazone® S3010, Ultrazone® S2010) and Solvey's Udel® brand (e.g., Udel® P-1700, Udel® P-3500LCD). Examples of commercially available polyethersulfones include BASF's Ultrazone® brand (e.g., Ultrazone® E3010, Ultrazone® E2010) and Solvey's Veradel® brand (e.g., Veradel® 3200, Veradel® 3300PREM, Veradel® A-301). Examples of commercially available polyphenylsulfones include BASF's Ultrasone® brand (e.g., Ultrasone® P3010, Ultrasone® P2010) and Solvey's Radel® brand (e.g., Radel® R-5100, Radel® R-5500).

[0026] The glass transition temperature (Tg) of the polysulfone resin can be, for example, 170 to 230°C, preferably 175 to 225°C, more preferably 180 to 200°C, and even more preferably 185 to 195°C. The mass-average molecular weight of the polysulfone is not particularly limited, but can be, for example, around 30,000 to 100,000, preferably around 35,000 to 80,000.

[0027] In this embodiment, the mass-average molecular weight of the resin can be measured using a gel permeation chromatography (GPC) device.

[0028] There are no particular restrictions on the type of polycarbonate used; known types can be used, and commercially available products can also be used. Examples of commercially available polycarbonates include Teijin Limited's product name Panlite (registered trademark) (e.g., Panlite (registered trademark) K-1300Y), Mitsubishi Engineering Plastics Corporation's product name Yupiron (registered trademark) (e.g., Yupiron (registered trademark) E-2000), and Novarex (registered trademark) (e.g., Novarex (registered trademark) 7030R).

[0029] The glass transition temperature (Tg) of the polycarbonate can be in the range of 130°C to less than 200°C, but is preferably 140 to 165°C, more preferably 145 to 160°C, and even more preferably 145 to 155°C. The weight-average molecular weight of the polycarbonate is not particularly limited, but is, for example, about 10,000 to 60,000, preferably about 20,000 to 40,000.

[0030] In the dielectric film for capacitors according to this embodiment, the content of amorphous thermoplastic resin containing aromatic rings in the main chain is sufficient if it is included as a main component, but is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90.5% by mass or more, particularly preferably 91.5% by mass or more, and most preferably 93% by mass or more. On the other hand, is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. Preferred ranges include approximately 60-99% by mass, 60-98% by mass, 60-97% by mass, 70-99% by mass, 70-98% by mass, 70-97% by mass, 80-99% by mass, 80-98% by mass, 80-97% by mass, 90.5-99% by mass, 90.5-98% by mass, 90.5-97% by mass, 91.5-99% by mass, 91.5-98% by mass, 91.5-97% by mass, 93-99% by mass, 93-98% by mass, and 93-97% by mass.

[0031] The dielectric film for capacitors according to this embodiment further comprises an olefin resin. The olefin resin is a minor component and is included in an amount of 1% to 8% by mass. The dielectric film for capacitors according to this embodiment mainly comprises an amorphous thermoplastic resin containing aromatic rings in the main chain, and further contains 1 to 8% by mass of an olefin resin, thereby exhibiting the effect of reducing leakage current in high-temperature environments.

[0032] From the viewpoint of effectively reducing leakage current in high-temperature environments, preferred olefin resins include polypropylene, polyethylene, polymethylpentene, cycloolefin polymers, and cycloolefin copolymers, with polypropylene and polyethylene being more preferred. The olefin resin contained in the dielectric film for capacitors may be one type or two or more types.

[0033] Preferred properties for olefin resins include, for example, the following:

[0034] (1) Polypropylene For example, it is preferable that the product has few impurities. As an indicator of impurities, the ash content is preferably 100 ppm or less, more preferably 60 ppm or less, and particularly preferably 20 ppm or less. The lower limit of the ash content is 0 ppm, 10 ppm or more, 15 ppm or more, etc. Examples of products with low ash content include Prime Polymer's product name F135A, and Borealis AG (headquartered in Austria)'s product names Borclean® HC300BF and HC318BF. As an indicator of impurities, the total chlorine content is preferably 10 ppm or less, more preferably 5 ppm or less, and particularly preferably 1 ppm or less. The lower limit of the total chlorine content is 0 ppm, 0.3 ppm or more, 0.5 ppm or more, etc. Examples of products with low total chlorine content include Prime Polymer's product name F135A, and Borealis AG (headquartered in Austria)'s product names Borclean® HC300BF and HC318BF. Furthermore, a low MFR (230°C, 2.16kg) is also preferable. While there are no particular restrictions on MFR, it should be 6g / 10min or less, 3g / 10min or less, or 1g / 10min or less. An example of a product with a low MFR is Novatec® PP EA9HD manufactured by Nippon Polypropylene Co., Ltd.

[0035] (2) Polyethylene For example, a low MFR (190°C, 2.16 kg) is also desirable. There are no particular restrictions on the MFR, but it should be 6 g / 10 min or less, 3 g / 10 min or less, or 1 g / 10 min or less. An example of a product with a low MFR is Hi-zex® 7000F manufactured by Prime Polymer Co., Ltd.

[0036] In the dielectric film for capacitors according to this embodiment, the content of olefin resin is preferably 1.5% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more. On the other hand, it is preferably 7.5% by mass or less, more preferably 7% by mass or less, and even more preferably 6.5% by mass or less. Preferred ranges include approximately 1.5 to 7.5% by mass, approximately 1.5 to 7.0% by mass, approximately 1.5 to 6.5% by mass, approximately 2.0 to 7.5% by mass, approximately 2.0 to 7.0% by mass, approximately 2.0 to 6.5% by mass, approximately 3.0 to 7.5% by mass, approximately 3.0 to 7.0% by mass, and approximately 3.0 to 6.5% by mass.

[0037] The dielectric film for capacitors according to this embodiment may contain other resins different from amorphous thermoplastic resins and olefin resins that have aromatic rings in their main chain, as long as they do not hinder the effects of the present invention. Such other resins are preferably thermoplastic resins different from those mentioned above.

[0038] Other specific examples of amorphous thermoplastic resins include amorphous polystyrene, acrylic resin, ABS resin, polyphenylene ether, polyarylate, polyamide-imide, polyether-imide, and thermoplastic amorphous polyimide.

[0039] Other specific examples of crystalline thermoplastic resins include polyvinyl alcohol, syndiotactic polystyrene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyamide, polyether ether ketone, polyacetal, liquid crystal polymer, thermoplastic crystalline polyimide, and fluororesin.

[0040] If the dielectric film for the capacitor according to this embodiment contains other resins, the content of these resins may be 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. The other resins contained in the dielectric film for the capacitor may be one type or two or more types.

[0041] The dielectric film for the capacitor according to this embodiment may be single-layer or multi-layer, but is preferably single-layer.

[0042] The dielectric film for capacitors according to this embodiment may or may not contain an antiblocking agent. When the dielectric film for capacitors contains an antiblocking agent, the antiblocking agent content is preferably 0.3% by mass or more, more preferably 0.5% by mass or more. On the other hand, it is preferably 1.5% by mass or less, more preferably 1.1% by mass or less, and even more preferably 0.7% by mass or less. Preferred ranges include approximately 0.3 to 1.5% by mass, approximately 0.3 to 1.1% by mass, approximately 0.3 to 0.7% by mass, approximately 0.5 to 1.5% by mass, approximately 0.5 to 1.1% by mass, and approximately 0.5 to 0.7% by mass. Furthermore, when the dielectric film for capacitors does not substantially contain an antiblocking agent, the antiblocking agent content is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0% by mass.

[0043] The average particle size of the antiblocking agent is, for example, about 0.1 to 5 μm, preferably about 0.5 to 2.5 μm, and more preferably 0.7 to 1.5 μm. When the dielectric film for the capacitor according to this embodiment contains an antiblocking agent, known antiblocking agents can be used, such as silica and calcium carbonate. Commercially available antiblocking agents can also be used. As silica, synthetic amorphous silica is preferred because it is easier to obtain a preferred particle size. The shape of the silica is not particularly limited, and may be, for example, spherical silica consisting of a single particle, or amorphous silica forming secondary and tertiary particles from a plurality of primary particles, but spherical silica consisting of a single particle is preferred. Since impurities (e.g., lower alcohols) contained in synthetic amorphous silica during synthesis may adversely affect the dielectric strength, it is preferable to reduce the impurity content by calcination treatment. As calcium carbonate, light calcium carbonate is preferred because it is easier to obtain a preferred particle size.

[0044] The thickness of the dielectric film for the capacitor according to this embodiment is, for example, 15 μm or less, and from the viewpoint of reducing the volume of the capacitor and increasing the capacitance, it is preferably 12 μm or less, more preferably 9 μm or less, even more preferably 8 μm or less, and even more preferably 5 μm or less. Dielectric breakdown strength (V DC From the viewpoint of further improving winding suitability, the lower limit of the thickness of the dielectric film for capacitors according to this embodiment is, for example, 1 μm or more, preferably 1.8 μm or more, and more preferably 2.0 μm or more.

[0045] The relationship between dielectric film thickness, capacitor volume, and capacitance is explained in detail below. The thinner the dielectric film, the greater the capacitance per unit volume. More specifically, the capacitance C of a flat plate capacitor is expressed as follows, using the dielectric constant ε, electrode area S, and dielectric thickness d (thickness d of the dielectric film for the capacitor). C = εS / d

[0046] In the case of a film capacitor, the thickness of the electrodes is more than three orders of magnitude thinner than the thickness of the dielectric film. Therefore, if we ignore the volume of the electrodes, the volume V of the capacitor can be expressed as follows. V=Sd

[0047] Therefore, from the two equations above, the capacitance C / V per unit volume can be expressed as follows. C / V = ε / d 2

[0048] Here, the dielectric constant ε is determined by the material used. As can be seen from the above equation, unless the material is changed, the capacitance per unit volume (C / V) improves inversely proportional to the square of the thickness of the dielectric film for the capacitor as the thickness of the film is reduced.

[0049] The above explanation is idealized for ease of understanding. In reality, the capacitance per unit volume (C / V) varies depending on the area due to factors such as the presence of small air gaps between the films, the influence of the fringe effect at the electrode ends, and the fact that it is a wound capacitor. However, generally speaking, it can be understood that the capacitance per unit volume (C / V) is determined by the thickness of the dielectric film.

[0050] Therefore, it is preferable to make the thickness of the dielectric film as thin as possible within the range that reduces leakage current in high-temperature environments.

[0051] The thickness of the dielectric film for capacitors is measured using an outside micrometer (Mitutoyo Corporation high-precision digital micrometer MDH-25MB) in accordance with JIS K 7130:1999 Method A.

[0052] In evaluating the reduction of the dielectric film for capacitors according to this embodiment, it is preferable that the following relationship (A) is satisfied in the high-temperature environment. By satisfying the following relationship (A), it can be evaluated that the leakage current of the dielectric film for capacitors in a high-temperature environment (150°C environment) is suitably reduced.

[0053] <Evaluation of leakage current reduction> In a dielectric film for capacitors, a dielectric breakdown test was conducted under a 150°C atmosphere. The test start voltage was 0V, the boost rate was 100V / s, and dielectric breakdown was defined as the point when the current value exceeded 5mA. The test time and leakage current value were recorded at 0.1-second intervals from the start of the test. The time immediately before dielectric breakdown (t), the current value measured immediately before dielectric breakdown (I), the test elapsed time at 80% of the test time (t80), and the leakage current value at the test elapsed time (t80) (I80) satisfy the relationship shown in equation (A) below. Equation (A): |I-I80%| / (t-t80%)≦1

[0054] Also, from the perspective of the breakdown strength in a high-temperature environment, the breakdown strength of the dielectric film for capacitors according to this embodiment at 120°C is preferably 300 V DC / μm or more, 310 V DC / μm or more, more preferably 350 V DC / μm or more, further 380 V DC / μm or more, further 400 V DC / μm or more, particularly 420 V DC / μm or more. Note that there is no upper limit to the breakdown strength of the dielectric film for capacitors according to this embodiment at 120°C, and for example, 600 V DC / μm can be mentioned. The breakdown strength at 120°C is the value measured by the following measurement method.

[0055] (Breakdown strength at 120°C and 150°C environments) Prepare a measuring device according to 17.2.2 (flat electrode method) of JIS C2151:2006. However, as the lower electrode, instead of the elastic body described in 17.2.2 of JIS C2151:2006, conductive rubber (E12S10 manufactured by Starwa Electric Co., Ltd.) is used as the electrode, and the winding of aluminum foil is not performed. The measurement environment is inside a forced circulation oven with a set temperature of 120°C. The electrodes and the film are used after being temperature-adjusted in the same oven for 30 minutes. The voltage rise starts from 0 V and is at a rate of 100 V / second, and the time when the current value exceeds 5 mA is defined as the breakdown time. The number of breakdown voltage measurements is 20 times. The breakdown voltage value V DC is divided by the thickness (μm) of the film, and the average value of 16 points excluding the top 2 points and the bottom 2 points among the 20 calculation results is taken as the breakdown strength (V DC / μm).

[0056] Also, from the perspective of the breakdown strength in a high-temperature environment, the breakdown strength of the dielectric film for capacitors according to this embodiment at 150°C is preferably 300 V DC / μm or more, 310 V DC / μm or more, more preferably 350 V DC / μm or more, further 380 V DC / μm or larger, and also 400V DC / μm or larger, especially at 420V DC Examples include a thickness of / μm or greater. There is no upper limit to the dielectric breakdown strength of the capacitor dielectric film according to this embodiment at a 150°C environment, but for example, 600V DC The unit is given as / μm. Dielectric breakdown strength in a 150°C environment is performed and calculated in the same manner as in a 120°C environment, except that the measurement environment is a forced-circulation oven at a set temperature of 150°C.

[0057] It should be noted that, although both 120°C and 150°C environments are "high-temperature" environments, the load on dielectric breakdown strength typically differs significantly. According to the present invention, even under the high load of 150°C, higher dielectric breakdown strength can be exhibited and / or maintained.

[0058] Furthermore, the dielectric breakdown strength of the capacitor dielectric film according to this embodiment at a 23°C environment is preferably 300V. DC / μm or more, 310V DC / μm or larger, more preferably 350V DC / μm or larger, and also 380V DC / μm or larger, and also 400V DC / μm or larger, especially at 420V DC Examples include a thickness of / μm or greater. There is no upper limit to the dielectric breakdown strength of the capacitor dielectric film according to this embodiment at a 23°C environment, but for example, 650V DC One example is / μm. Dielectric breakdown strength in a 23°C environment is calculated by performing the same measurement as at 120°C, but not in a forced-circulation oven at a set temperature of 120°C, but in a glove box filled with dry air at 23°C and 0% relative humidity.

[0059] The surface roughness Sa of the dielectric film for capacitors according to this embodiment is 0.004 to 0.020 μm, preferably 0.006 to 0.018 μm, and more preferably 0.008 to 0.016 μm. The method for measuring the surface roughness Sa is as described in the examples.

[0060] The dielectric film for the capacitor according to this embodiment may be an unstretched film or a stretched film. If the dielectric film for the capacitor is a stretched film, it may be a uniaxially stretched film or a biaxially stretched film.

[0061] As described above, the dielectric film for the capacitor according to this embodiment may be single-layer or multi-layer. A single-layer film is preferable because it makes it easier to reduce the film thickness.

[0062] Furthermore, the dielectric film for capacitors according to this embodiment may be laminated on a substrate formed from a metal foil such as aluminum foil or another dielectric film for capacitors, but preferably it is not formed on a substrate and is manufactured as a standalone dielectric film for capacitors according to this embodiment (preferably, after film formation, it is wound onto a core by itself to form a winding body) and used in the manufacture of the metallized film for capacitors or capacitors described later.

[0063] The dielectric film for capacitors according to this embodiment may contain additives. The additives are not particularly limited, as long as they do not hinder the effects of the present invention, and additives used in known dielectric films for capacitors can be used. Examples of additives include antioxidants, necessary stabilizers such as chlorine absorbers, lubricants (different from the antiblocking agents such as silica and calcium carbonate mentioned above), plasticizers, flame retardants, colorants, and the like. The dielectric film for capacitors according to this embodiment may contain such additives in amounts that do not adversely affect the dielectric film for capacitors of this embodiment. It is preferable that the dielectric film for capacitors according to this embodiment does not use spherical crosslinked polymer resin particles such as silicone resin.

[0064] The "antioxidant" is not particularly limited as long as it can be used to obtain the dielectric film for the capacitor of this embodiment. The antioxidant is generally used for two purposes. One purpose is to suppress thermal degradation and oxidative degradation in the extruder, and the other purpose is to suppress degradation during long-term use as a capacitor film and to contribute to improving capacitor performance.

[0065] The "chlorine absorbent" is not particularly limited as long as it does not impair the effects of the present invention. Using a chlorine absorbent helps to capture trace amounts of chlorine contained in the resin due to polymerization catalysts, etc., thereby suppressing the chlorination of the metal vapor-deposited film described later and improving the performance of the capacitor. Examples of chlorine absorbents include metal soaps such as calcium stearate.

[0066] The "lubricant" is not particularly limited as long as it does not impair the effects of the present invention. Examples of lubricants include primary amides (such as stearic acid amide), secondary amides (such as N-stearyl stearate amide), ethylenebisamides (such as N,N'-ethylenebisstearate amide), and various waxes such as polyethylene wax.

[0067] The "plasticizer" is not particularly limited as long as it does not impair the effects of the present invention. Examples of plasticizers include bis(2-ethylhexyl) phthalate.

[0068] The "flame retardant" is not particularly limited as long as it does not impair the effects of the present invention. Examples of flame retardants include halogen compounds, aluminum hydroxide, magnesium hydroxide, phosphates, borates, antimony oxides, and the like.

[0069] The "coloring agent" is not particularly limited as long as it does not impair the effects of the present invention. Examples of coloring agents include inorganic coloring agents such as titanium dioxide, carbon black, talc, chromium compounds, and zinc sulfide, as well as organic coloring agents such as azo, quinacridone, and phthalocyanine.

[0070] The dielectric film for capacitors of this embodiment exhibits reduced leakage current in high-temperature environments, making it extremely suitable for use in high-temperature environments and for small, and even high-capacitance (for example, 5 μF or more, preferably 10 μF or more, and even more preferably 20 μF or more) capacitors.

[0071] The dielectric film for capacitors of this embodiment can be manufactured by forming a resin composition into a film, which at least includes, as a main component, an amorphous thermoplastic resin containing aromatic rings in its main chain, and as a secondary component, 1% by mass or more and 8% by mass or less of an olefin resin.

[0072] Details of amorphous thermoplastic resins and olefin resins containing aromatic rings in the main chain are as described above.

[0073] Furthermore, there are no particular limitations on the method for forming the resin composition into a film, and known film forming methods can be employed. For example, a method can be used in which the resin composition supplied to an extruder is heated to a melted state, filtered, extruded into a film using a T-die, and solidified by contact with a roll set to a predetermined surface temperature. After forming into a film, the dielectric film for capacitors of this embodiment can be wound around a core to form a winding body (film roll).

[0074] There are no particular restrictions on the method of mixing the resin composition, but methods such as dry blending the resin composition pellets using a mixer or the like, or supplying the resin composition pellets to a kneader and melt-kneading them to obtain a blended resin are acceptable.

[0075] There are no particular restrictions on mixers or kneaders, and kneaders can be single-screw, twin-screw, or multi-screw types. Furthermore, in the case of twin-screw or multi-screw types, either co-rotating or staggered rotation kneading types are acceptable.

[0076] In the case of blending by melt kneading, there are no particular restrictions on the kneading temperature as long as good kneading is achieved, but generally, it is in the range of 230 to 400°C, preferably 280 to 380°C, and more preferably 290 to 350°C. To suppress degradation during the kneading and mixing of the resin, the kneader may be purged with an inert gas such as nitrogen.

[0077] The extrusion temperature and the surface temperature of the cooling roll when forming the resin composition into a film from a molten state are adjusted as appropriate. For example, the extrusion temperature can be around 230 to 400°C, preferably 280 to 380°C, and more preferably 290 to 350°C. For example, the surface temperature of the cooling roll can be around 80 to 230°C, preferably 120 to 190°C, and more preferably 130 to 170°C.

[0078] The following provides specific examples of the preparation of resin pellets and the supply of resin pellets to the extruder.

[0079] (Preparation of resin pellets) The moisture content of the main component in the resin pellets should be adjusted to 0.02% or less, preferably 0.01% or less, and even more preferably 0.005% or less. The lower limit of moisture content is 0%. If the moisture content exceeds 0.02%, the molten resin extruded from the T-die is prone to slight foaming, and fine resin droplets adhere to the T-die outlet. If the accumulation of resin droplets continues, the deposits may come into contact with the molten resin extruded from the T-die outlet, impairing the film formation stability. The moisture content of the main component can be adjusted by drying in a resin pellet dryer at 130-150°C for 3-5 hours. Dry air is generally circulated in the resin pellet dryer, but a dry inert gas (e.g., nitrogen gas) may also be circulated to suppress oxidative degradation. In addition, only the main component may be dried in the resin pellet dryer, or the secondary components may be mixed in the desired ratio beforehand. The path for transferring the dried resin pellets to the extruder is preferably a sealed system that is isolated from the outside air. If the pathway is an open system, the resin pellets may absorb moisture from the air when exposed to the outside air, resulting in a higher moisture content. For transporting the resin pellets, airflow using dry air from which moisture has been removed beforehand is preferable, and airflow using a dry, inert gas is even more preferable.

[0080] (Feeding resin pellets to the extruder) Resin pellets can be temporarily stored in a storage facility between the resin pellet dryer and the extruder. The storage facility is preferably filled with dry air, and more preferably with dry inert gas. The storage facility may also be heated using a heater. Heating is preferable to soften the resin pellets, as it reduces the amount of resin powder generated by collisions between the pellets. The temperature inside the storage facility is 50-150°C, preferably 60-140°C, and more preferably 70-130°C. The storage facility may be a pellet hopper connected to the extruder.

[0081] Continuous film formation can be improved by suppressing thermal and oxidative degradation of resin pellets. Thermal degradation can be suppressed by setting the extruder and T-die temperatures low within a range where the discharge of molten resin is stable. Oxidative degradation can be suppressed by using an inert gas (e.g., nitrogen gas) for drying and conveying the resin pellets. Since olefin resins, which are minor components, are more susceptible to thermal and oxidative degradation than the main component, continuous film formation can also be improved by reducing the addition rate of olefin resins.

[0082] When solidifying a molten resin composition in contact with a cooling roll, known methods such as air knives, electrostatic pinning, elastic roll nips, metal roll nips, and elastic metal roll nips can be used for adhesion.

[0083] In this embodiment, when the dielectric film for the capacitor is a stretched film, the resin composition is formed into a film, and then the film is further stretched. The stretching ratio is not particularly limited, but is approximately 1.1 to 4.0 times in the MD direction and approximately 1.1 to 4.0 times in the TD direction. As mentioned above, the stretched film may be a uniaxially stretched film or a biaxially stretched film. In the case of biaxial stretching, it may be simultaneous biaxial stretching or sequential biaxial stretching.

[0084] The temperature during stretching is adjusted as appropriate according to the glass transition temperature (Tg) of the amorphous thermoplastic resin containing aromatic rings in the main chain. Examples of stretching temperatures include 100 to 270°C, preferably around 220 to 260°C.

[0085] The temperature used for relaxation (loosening) after stretching is not particularly limited, but is, for example, 100 to 220°C, preferably 150 to 200°C. The relaxation (loosening) rate is not particularly limited, but is, for example, 1 to 10%, preferably 2 to 6%. Keeping the temperature and relaxation rate within the above ranges is preferable as it makes it easier to suppress thermal shrinkage of the film.

[0086] 2. Metallized film for capacitors The metallized film for capacitors according to this embodiment has a metal film on one or both sides of the dielectric film for capacitors according to this embodiment.

[0087] The dielectric film for capacitors in this embodiment can have a metal film attached to one or both sides as electrodes for processing into a capacitor. Such electrodes are not particularly limited as long as they can produce the capacitor targeted by the present invention, and electrodes commonly used in the manufacture of capacitors can be used.

[0088] Since capacitors are increasingly required to be smaller and lighter, it is preferable to form electrodes directly on one or both sides of the dielectric film for the capacitor in this embodiment (metallization) to create a metallized film. As a method for metallizing the surface of the dielectric film for the capacitor in this embodiment, a metal layer (electrode) is provided by methods such as metal deposition, vacuum plating such as sputtering, coating and drying of a metal-containing paste, or pressing metal foil or metal powder onto the film. Among these, vacuum deposition and sputtering are preferred to meet the increasing demand for miniaturization and weight reduction of capacitors, and vacuum deposition is preferred from the viewpoint of productivity and economic efficiency. Examples of vacuum deposition methods include the crucible method and the wire method, but there are no particular limitations as long as the capacitor intended for this invention can be obtained, and the most suitable method can be selected as appropriate.

[0089] The metals used for the electrodes can be individual metals such as zinc, lead, silver, chromium, aluminum, copper, and nickel, as well as mixtures of several of these metals and alloys thereof. However, considering environmental factors, economic efficiency, and capacitor performance, zinc and aluminum are preferred.

[0090] From the standpoint of the electrical characteristics of the capacitor, the film resistance of the metal vapor-deposited film is preferably around 1 to 100 Ω / □. Within this range, a higher value is desirable from the standpoint of self-healing characteristics, and a film resistance of 5 Ω / □ or higher is more preferable, and 10 Ω / □ or higher is even more preferable. Furthermore, from the standpoint of safety as a capacitor, a film resistance of 50 Ω / □ or less is more preferable, and 30 Ω / □ or less is even more preferable.

[0091] When forming electrodes (metal vapor-deposited films) by vacuum deposition, the film resistance can be measured during deposition, for example, by a method known to those skilled in the art. Since the film resistance of a metal vapor-deposited film is correlated with the light transmittance, the film resistance can be adjusted, for example, by adjusting the output of the evaporation source to control the evaporation rate using the light transmittance as an indicator.

[0092] When forming a metal vapor-deposited film on one side of the dielectric film for the capacitor in this embodiment, an insulating margin is formed without vapor deposition for a certain width from one end of the film so that it becomes a capacitor when the film is wound. Furthermore, in order to strengthen the bond between the metallized film for the capacitor and the metallion electrode, it is preferable to form a heavy edge structure at the end opposite the insulating margin. The film resistance of the heavy edge is usually about 1 to 8 Ω / □, and preferably about 1 to 5 Ω / □. The thickness of the metal film of the heavy edge is not particularly limited, but is preferably 1 to 200 nm.

[0093] There are no particular restrictions on the deposition pattern (margin pattern) of the metal deposition film to be formed, but from the viewpoint of improving characteristics such as the safety of the capacitor, it is preferable to form the fuse as a pattern that includes so-called special margins such as a fishnet pattern or a T-margin pattern. Forming the metal deposition film with a deposition pattern that includes special margins on at least one side of the dielectric film for the capacitor of this embodiment is preferable because it improves the safety of the resulting capacitor and is effective in suppressing capacitor failure and short circuits.

[0094] Any known method can be used without limitation to form the margin, such as the tape method, which involves masking with tape during vapor deposition, or the oil method, which involves masking by applying or transferring oil.

[0095] A protective layer may be provided on the metallized film of this embodiment for the purpose of physically protecting the metal vapor-deposited film, preventing moisture absorption, preventing oxidation, etc. Preferably, silicone oil or fluorine oil can be used as the protective layer.

[0096] The metallized film of this embodiment can be processed into a capacitor of this embodiment, which will be described later.

[0097] 3. Capacitor The capacitor according to this embodiment includes the dielectric film and / or metallized film for the capacitor of this embodiment.

[0098] In such a capacitor, the film of the present invention can be used as a dielectric film for capacitors, for example, by (i) using the aforementioned metallized film, or (ii) laminating the film of the present invention without electrodes with other conductors (for example, metal foil, the film of the present invention with one or both sides metallized, paper with one or both sides metallized, and other plastic films).

[0099] In the process of manufacturing the capacitor, a film winding process is performed. For example, two pairs of metallized films of this embodiment are overlapped and wound so that the metal film in the metallized film of this embodiment and the dielectric film for capacitors of this embodiment are alternately laminated, and furthermore, so that the insulating margins are on opposite sides. In this case, it is preferable to overlap the pairs of metallized films of this embodiment by 1 to 2 mm. Alternatively, an unmetallized dielectric film for capacitors may be laminated with other conductive materials such as metal foil or other metallized films. The winding machine used is not particularly limited, and for example, an automatic winding machine 3KAW-N2 manufactured by Kaito Manufacturing Co., Ltd. can be used. The film winding process is not limited to the above method, and other methods may be used, for example, by alternately laminating and winding the film of this embodiment that has been double-sided coated and an uncoated film of this embodiment (which is 2 to 3 mm narrower than the film of this embodiment that has been double-sided coated).

[0100] When manufacturing flat-type capacitors, the resulting winding is usually pressed after winding. Pressing promotes winding tightness and element formation of the capacitor. The optimal pressure applied to control and stabilize the interlayer gap varies depending on the thickness of the dielectric film for the capacitor in this embodiment, but for example, it is 2 to 20 kg / cm². 2 That is the case.

[0101] Next, a capacitor is fabricated by spraying metal onto both ends of the wound material to create metallized electrodes.

[0102] The capacitor is subjected to a further predetermined heat treatment. Specifically, in this embodiment, the capacitor is subjected to a heat treatment (hereinafter sometimes referred to as "thermal aging") at a temperature of 80 to 265°C for 1 hour or more, in an atmosphere or under vacuum, within a range that does not exceed the Tg of the amorphous thermoplastic resin, which is the main component.

[0103] In the above process of heat-treating the capacitor, the heat treatment temperature is preferably in the range of 10°C to 100°C lower than the Tg of the amorphous thermoplastic resin containing aromatic rings in the main chain, and is 15°C to 8°C. A temperature 0°C lower is more preferable. By performing heat treatment at the above temperature, the effect of thermal aging can be obtained. Specifically, the gaps between the films constituting the capacitor based on the metallized film of this embodiment are reduced, and corona discharge is suppressed. Alternatively, the strain (internal stress) in the dielectric film for the capacitor is eliminated. As a result, it is thought that the dielectric strength is improved. If the heat treatment temperature is lower than the predetermined temperature, the above effect of thermal aging cannot be sufficiently obtained. On the other hand, if the heat treatment temperature is higher than the predetermined temperature, thermal decomposition or oxidative degradation may occur in the dielectric film for the capacitor.

[0104] Methods for applying heat treatment to the capacitor may be appropriately selected from known methods, including, for example, methods using a constant temperature bath under a vacuum atmosphere or methods using high-frequency induction heating. Specifically, it is preferable to use a method using a constant temperature bath.

[0105] The heat treatment time is preferably 1 hour or more, and more preferably 10 hours or more, in order to obtain mechanical and thermal stability, but it is more preferably 72 hours or less in order to prevent molding defects such as heat wrinkles and mold formation.

[0106] Lead wires are typically attached to the metallicon electrodes of a heat-aged capacitor. The method of attachment is not particularly limited, but can be done by welding, ultrasonic welding, or soldering. Furthermore, to provide weather resistance and especially to prevent humidity degradation, it is preferable to enclose the capacitor in a case and pot the inside of the case with epoxy resin.

[0107] As described above, the dielectric film for capacitors of this embodiment exhibits reduced leakage current in high-temperature environments, making it extremely suitable for use in high-temperature environments, small size, and high capacitance (for example, 5 μF or more, preferably 10 μF or more, and even more preferably 20 μF or more) capacitors. In other words, the capacitor of this embodiment, utilizing the dielectric film for capacitors of this embodiment, can be used in high-temperature environments, is small, and has high capacitance. Therefore, the capacitor of this embodiment can be used as a high-voltage capacitor, a filter capacitor and smoothing capacitor in various switching power supplies, converters and inverters, etc., used in electronic equipment and electrical equipment. Furthermore, the capacitor of this embodiment can also be suitably used as a capacitor for inverter power supply equipment that controls drive motors in electric vehicles and hybrid vehicles, for which demand has been increasing in recent years. [Examples]

[0108] The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to the examples. Unless otherwise specified, parts and % refer to "parts by mass" and "mass%", respectively.

[0109] [Measurement Method and Evaluation Method] The various measurement and evaluation methods used in the examples and comparative examples are as follows:

[0110] (1) Film thickness Measurements were taken using an outside micrometer (Mitutoyo Corporation, high-precision digital micrometer MDH-25MB) in accordance with JIS K 7130:1999 Method A.

[0111] (2) Surface roughness Sa The arithmetic mean height Sa is a value measured according to the ISO-25178 standard as follows: A non-contact optical interferometry surface shape measuring instrument, "VertScan® 2.0 (model: R5500GML)" manufactured by Ryoka Systems Co., Ltd., is used. As a sample for measurement, a piece of film is cut to an arbitrary size of approximately 10 cm square, and with the wrinkles fully smoothed out, The sample is set on the measurement stage using an electrostatic contact plate or similar. First, the WAVE mode is used for measurement, a 530 white filter and a 1×BODY microscope tube are applied, and a 10x objective lens is used to measure one field of view (470.92 μm × 353.16 μm). The obtained data is subjected to fourth-order surface correction, noise reduction processing using a median filter (3×3), and then Gaussian filtering with a cutoff value of 30 μm. This ensures that the roughened surface condition can be measured appropriately. Next, the "ISO parameter" in the "bearing" plugin function of the "VS-Viewer" analysis software of "VertScan2.0" is used to perform the analysis and determine Sa (μm). This operation is performed at five locations on the chill roll side surface of the target sample, at 1 cm intervals in the flow direction, starting from the center in both the flow direction and width direction, and the average value of each obtained value is calculated.

[0112] (3) Dielectric breakdown strength (Dielectric breakdown strength and leakage current test in a 150°C environment) A measuring device conforming to JIS C2151:2006 17.2.2 (Platform electrode method) was prepared. A TOS-9301 manufactured by Kikusui Electronics Co., Ltd. was used as the dielectric breakdown voltage measuring device, and a DRM620DD manufactured by Advantec Toyo Co., Ltd. was used as the forced-circulation oven. The upper electrode was a 25mm diameter brass metal cylinder with a 2mm radius rounded edge (contact area with film was 3.5cm²). 2The weight shall be 200g. For the lower electrode, conductive rubber (E12S10 manufactured by Seiwa Electric Co., Ltd.) shall be used as the electrode instead of the elastic material described in JIS C2151:2006 17.2.2, and no aluminum foil wrapping shall be performed. The measurement environment was a forced-circulation oven set at a temperature of 150°C, and the electrode and film were used after being conditioned in the oven for 30 minutes. The voltage rise was set to start from 0V and increase at a rate of 100V / sec, and dielectric breakdown was defined as the point when the current value exceeded 5mA, with the dielectric breakdown voltage V DC The following was recorded. From the start of the test until dielectric breakdown occurred, the test time and leakage current value were recorded at 0.1-second intervals. The time immediately before dielectric breakdown (t), the current value measured immediately before dielectric breakdown (I), the test elapsed time at 80% of the test time (t80), and the leakage current value at the test elapsed time (t80) (I80) were determined. When calculating t80 for t, the value was rounded to two decimal places. Also, "immediately before dielectric breakdown" refers to the value observed 0.1 seconds before dielectric breakdown, since measurements were recorded at 0.1-second intervals. Here, the unit of time t is seconds, and the unit of current I is μA. Dielectric breakdown voltage was measured 20 times, and the dielectric breakdown voltage value V DC Divide this by the film thickness (μm), and take the average of the 16 results obtained by excluding the top 2 and bottom 2 from the 20 calculation results. The dielectric breakdown strength (V) is calculated from this average. DC ( / μm) The leakage current test was deemed satisfactory if it satisfied equation (A). Equation (A): |I-I80%| / (t-t80%)≦1

[0113] (Dielectric breakdown strength at 120°C) The measurement environment was a forced-circulation oven set to a temperature of 120°C, but the procedure and calculation were the same as for dielectric breakdown strength in a 150°C environment.

[0114] (4) Continuous membrane properties Films were formed under the conditions described in each example, and the continuous film-forming capability was evaluated based on the film length that could be formed without breakage, according to the following criteria. ○: The film deposition length is 1000m or more, and the continuous film deposition capability is very high. △: The film deposition length is 500m or more but less than 1000m, indicating high continuous film deposition capability. ×: The film deposition length is less than 500m, and the continuous film deposition capability is low.

[0115] (5) Winding suitability A roll of film material was obtained under the conditions described in each example. The roll of film material was slit to a width of 620 mm using a slitting machine to obtain a film winding. 100 m was pulled out from the slitting winding, and the wrinkle condition of the 620 mm x 100 m film was checked, and the winding suitability was evaluated according to the following criteria. ○: No wrinkles are visible. △: There are three or fewer wrinkles, and the length of each wrinkle is 3m or less, so there are no practical problems. ×: There are four or more wrinkles, or the length of each wrinkle is longer than 3m.

[0116] [Example 1] (A) Polysulfone resin [PSU, manufactured by BASF Japan Ltd.: trade name Ultrazone® S6010] and (B) Polypropylene [PP, manufactured by Borealis AG (headquarters: Austria): trade name Borclean® HC300BF] were weighed and mixed in the mixing ratio (mass ratio) shown in Table 1, and the dry blend was supplied to an extruder. After melting at a resin temperature of 310°C, it was passed through a 45 μm mesh filter and extruded using a T-die. It was then pressed into contact with a mirror-finish metal roll (cooling roll) with a surface temperature maintained at 150°C using an air knife to form a film. The ends of the obtained unstretched dielectric film for capacitors were slit and wound up on a winding machine to obtain a dielectric film roll for capacitors. The thickness of the obtained dielectric film for capacitors was 5.0 μm as shown in Table 1, by adjusting the extrusion amount and take-up speed to obtain the unstretched dielectric film for capacitors of Example 1.

[0117] [Examples 2-8 and Comparative Examples 1-3] Except for the mixing ratio (mass ratio) of (A) polysulfone resin and (B) polypropylene being as shown in Table 1, unstretched dielectric films for capacitors were obtained in the same manner as in Example 1, for Example 2-8 and Comparative Example 1-3, respectively.

[0118] [Examples 9-15 and Comparative Examples 4-5] Unstretched dielectric films for capacitors, Examples 9-15 and Comparative Examples 4-5, were obtained in the same manner as in Example 1, except that silica particles (manufactured by Nippon Shokubai Co., Ltd.: trade name SeaHostar (registered trademark) KE-S100 (spherical fine particles with an average particle diameter of 1.0 μm)) were used as the antiblocking agent, and the mixing ratio (mass ratio) of (A) polysulfone resin, (B) polypropylene, and antiblocking agent (A and B agents) was as shown in Table 1.

[0119] [Examples 16-19] Except for using "Polypropylene [PP, manufactured by Daehan Oil & Chemical Co., Ltd. (headquarters: South Korea): product name S800]" instead of "Polypropylene [PP, manufactured by Borealis AG (headquarters: Austria): product name Borclean (registered trademark) HC300BF]" as (B) polypropylene, and setting the blending ratio (mass ratio) of (A) polysulfone resin and (B) polypropylene as shown in Table 2, unstretched dielectric films for capacitors of Examples 16-19 were obtained in the same manner as in Example 1.

[0120] [Examples 20-25 and Comparative Example 6] Except for using "Polypropylene [PP, manufactured by Daehan Oil & Chemical Co., Ltd. (headquarters: South Korea): product name S802M]" instead of "Polypropylene [PP, manufactured by Borealis AG (headquarters: Austria): product name Borclean (registered trademark) HC300BF]" as (B) polypropylene, and setting the blending ratio (mass ratio) of (A) polysulfone resin and (B) polypropylene as shown in Table 2, unstretched dielectric films for capacitors were obtained in the same manner as in Example 1, for Examples 20-25 and Comparative Example 6.

[0121] [Examples 26-29] Except for using "Polypropylene [PP, manufactured by Nippon Polypropylene Co., Ltd. (headquarters: Japan): product name Novatec (registered trademark) EA9HD]" instead of "Polypropylene [PP, manufactured by Borealis AG (headquarters: Austria): product name Borclean (registered trademark) HC300BF]" as (B) polypropylene, and setting the blending ratio (mass ratio) of (A) polysulfone resin and (B) polypropylene as shown in Table 2, unstretched dielectric films for capacitors of Examples 26-29 were obtained in the same manner as in Example 1.

[0122] [Examples 30-35 and Comparative Example 7] Except for using polyethylene [PE, manufactured by Prime Polymer Co., Ltd., Japan: product name Hyzex® 7000F] instead of polypropylene [PP, manufactured by Borealis AG (headquarters: Austria): product name Borclean® HC300BF] as the olefin resin, and (A) the mixing ratio (mass ratio) of the polysulfone resin and polyethylene as shown in Table 2, unstretched dielectric films for capacitors were obtained in the same manner as in Example 1, for Examples 30-35 and Comparative Example 7.

[0123] [Table 1]

[0124] [Table 2]

[0125] The dielectric films for capacitors in Examples 1 to 35 each contain, at least, an amorphous thermoplastic resin containing aromatic rings in the main chain as the main component, and an olefin-based resin in an amount of 1% to 8% by mass as a secondary component. The dielectric films for capacitors in Examples 1 to 35 exhibit reduced leakage current in high-temperature environments and high dielectric breakdown strength in high-temperature environments.

Claims

1. At a minimum, it comprises an amorphous thermoplastic resin containing aromatic rings in its main chain as the main component, and an olefin resin in an amount of 1% to 8% by mass as a secondary component. The amorphous thermoplastic resin containing an aromatic ring in the main chain is at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone. A dielectric film for capacitors, wherein the olefin resin is at least one of polypropylene and polyethylene.

2. A dielectric film for a capacitor according to claim 1, wherein the thickness is 1 μm or more and 9 μm or less.

3. The dielectric breakdown strength at a 150°C environment is 300V. DC A dielectric film for a capacitor according to claim 1 or 2, wherein the thickness is 1 / μm or more.

4. A dielectric film for a capacitor according to claim 1 or 2, wherein the surface roughness Sa is 0.004 μm or more and 0.020 μm or less.

5. The dielectric film for a capacitor according to claim 1 or 2, wherein the amorphous thermoplastic resin containing aromatic rings in the main chain is polysulfone.

6. A metallized film for capacitors, having a metal film on one or both sides of the dielectric film for capacitors according to claim 1 or 2.

7. A capacitor comprising a dielectric film for a capacitor according to claim 1 or 2.

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