Stretched film, metal laminated film, and film capacitor

Abstract

The purpose of the present invention is to provide a stretched film capable of imparting excellent safety performance to a capacitor element even under a high temperature environment.　In a stretched film according to the present invention, calculated in a 145°C environment from formula (1) ρV145°C = (SxV) / (DxA1) (1), a volume resistivity ρV145°C is 8.0x1014Ω•cm or greater, or ρV145°C / ρV40°C is 0.05 or greater (where in formula (1), ρV145°C is volume resistivity (Ω•cm) in a 145°C environment, S is an effective electrode area (cm2), V is an applied voltage (V), D is the thickness (cm) of the stretched film, and A1 is the detected value of the current value one minute after a voltage with a potential gradient of 100 V / µm is applied to the stretched film in a 145°C environment.

Description

Stretched films, metal laminated films, and film capacitors

[0001] The present invention relates to a stretched film formed from a polypropylene resin, a metal laminated film having the stretched film, and a film capacitor.

[0002] Stretched films primarily composed of polypropylene are used in film capacitor applications due to their excellent electrical properties. In electronic and electrical equipment, film capacitors made from stretched polypropylene are used, for example, as high-voltage capacitors, various switching power supplies, filter capacitors in converters and inverters, and smoothing capacitors. Film capacitors are also increasingly used in automobiles, such as electric vehicles and hybrid vehicles, where demand has been growing in recent years, for example, in inverters and converters that control drive motors.

[0003] Film capacitors, particularly automotive film capacitors, are increasingly being used in high-temperature environments. For example, in devices that control automotive drive motors (inverters, converters, etc.), the use of highly heat-resistant semiconductors (such as silicon carbide semiconductors) has increased in recent years. Consequently, capacitors used in these devices are required to have high heat resistance, such as 120°C or higher, preferably 130°C or higher. Conventional capacitors using polypropylene film are said to have an upper limit of operating temperature of about 110°C, and it is extremely difficult to stably maintain electrical insulation in high-temperature environments exceeding this.

[0004] One example of a resin film with high heat resistance is a film made of a resin composition containing a polyolefin mainly composed of polypropylene and a hydrogenated block copolymer, which is excellent in heat resistance and especially in its ability to block water vapor (Patent Document 1).

[0005] Japanese Patent Publication No. 2014-37532

[0006] Polypropylene-based resin films tend to exhibit a decrease in physical properties, such as reduced rigidity and reduced electrical insulation, as their operating temperature increases. In this regard, stretching a polypropylene-based resin film in at least one direction, preferably two directions, improves rigidity and electrical insulation, allowing these properties to be maintained even in high-temperature regions exceeding 110°C. However, at operating temperatures above 120°C, and even above 130°C, maintaining rigidity and electrical insulation becomes difficult even with a stretched film, and improving the long-term durability of the capacitor element is also challenging.

[0007] The present invention has been made in view of the above, and aims to provide a stretched film that can impart excellent safety performance to capacitor elements even in high-temperature environments. The present invention also aims to provide a metal laminated film and a film capacitor comprising the stretched film.

[0008] The inventors of this invention conducted extensive research to achieve the above objectives and, as a result, discovered that these objectives can be achieved by adjusting the volume resistivity characteristics of the stretched film, thus completing the present invention.

[0009] In other words, the present invention encompasses, for example, the subject matter described in the following sections: Section 1 A stretched film comprising a polypropylene resin, wherein the following formula (I) ρ Ｖ１４５℃ = (S × V) / (D × A １ ) (I) (In equation (I), ρ Ｖ１４５℃ Ω is the volume resistivity (Ω·cm) at a temperature of 145°C, and S is the effective electrode area (cm²). ２ ) where V is the applied voltage (V), D is the thickness of the stretched film (cm), A １ (This is the detected current value at 1 minute after applying a voltage with a potential gradient of 100 V / μm to a stretched film in a 145°C environment.) The volume resistivity ρ in a 145°C environment is calculated from this value. Ｖ１４５℃ 8.0 x 10 １４ A stretched film having a density of Ω·cm or greater. Item 2 A stretched film containing a polypropylene resin, wherein the following formula (I) ρＶ１４５℃ = (S × V) / (D × A １ )(I) (In formula (I), ρ Ｖ１４５℃ is the volume resistivity (Ω·cm) at 145°C, S is the effective electrode area (cm ２ ), V is the applied voltage (V), D is the thickness of the stretched film (cm), and A １ is the detected value of the current at the time when 1 minute has passed after applying a voltage with a potential gradient of 100 V / μm to the stretched film at 145°C), and the volume resistivity ρ at 145°C is calculated from this Ｖ１４５℃ and, the following formula (II) ρ Ｖ４０℃ = (S × V) / (D × A ２ )(II) (In formula (II), ρ Ｖ４０℃ is the volume resistivity (Ω·cm) at 40°C, S is the effective electrode area (cm ２ ), V is the applied voltage (V), D is the thickness of the stretched film (cm), and A ２ is the detected value of the current at the time when 1 minute has passed after applying a voltage with a potential gradient of 100 V / μm to the stretched film at 40°C), and the volume resistivity ρ at 40°C is calculated from this Ｖ４０℃ and, the ratio (ρ Ｖ１４５℃ / ρ Ｖ４０℃ ) is 0.05 or more, a stretched film. Item 3 The protrusion peak height Spk on at least one surface is 0.01 μm or more and 0.15 μm or less, the stretched film according to Item 1 or 2. Item 4 The arithmetic mean height Sa on at least one surface is 0.008 μm or more and 0.050 μm or less, the stretched film according to any one of Items 1 to 3. Item 5 The protrusion valley depth Svk on at least one surface is 0.01 μm or more and 0.06 μm or less, the stretched film according to any one of Items 1 to 4. Item 6 In X-ray diffraction intensity measurement, based on the half-width of the (110) plane derived from the α-crystal of isotactic polypropylene, the crystallite size obtained by the Scherrer formula is 105 Å or more, and the ratio of the crystallite size of the (110) plane to the crystallite size of the (040) plane ((110) plane crystallite size / (040) plane crystallite size) is 1.0 or more, the stretched film according to any one of Items 1 to 5. Item 7 In infrared absorption spectrum measurement, 880 - 890 cm－１ Absorption peaks are observed in the range, and at 1450 cm. －１ A stretched film according to any one of claims 1 to 6, having at least one of the shoulder peaks due to absorption in the vicinity. Claim 8 A stretched film according to any one of claims 1 to 7, wherein the polypropylene resin contains 55% by mass or more and 99% by mass of an isotactic polypropylene resin and 1% by mass or more and 45% by mass of a polymer having an alicyclic structure. Claim 9 A stretched film according to claim 8, wherein the polymer having an alicyclic structure contains two or more polymers with different glass transition temperatures. Claim 10 A stretched film according to claim 8 or 9, wherein the polymer having an alicyclic structure contains polymer B1 having an alicyclic structure with a glass transition temperature of 133°C or more and 155°C or less, and polymer B2 having an alicyclic structure with a glass transition temperature of 70°C or more and less than 133°C. Claim 11 A stretched film according to claim 10, wherein the mass ratio B2 / B1 of polymer B2 to polymer B1 is less than 0.85. Claim 12 A stretched film according to any one of claims 8 to 11, wherein the polymer having an alicyclic structure contains hydrogenated polystyrene. Item 13 The stretched film according to Item 12, wherein the hydrogenated polystyrene has an atactic structure and a hydrogenation rate of 95% or more. Item 14 The stretched film according to any one of Items 1 to 13, having a thickness of 1.8 μm or more and 10 μm or less, and a total light transmittance of 80% or more. Item 15 A metal laminated film having a metal layer on one or both sides of the stretched film according to any one of Items 1 to 14. Item 16 A film capacitor comprising the metal laminated film according to Item 15.

[0010] The stretched film of the present invention can provide capacitor elements with excellent safety performance even in high-temperature environments.

[0011] The results of the infrared absorption spectrum of the stretched film are shown, and (a) shows the infrared absorption spectrum measurement at 850–950 cm⁻¹. －１ (b) is within the range of 1400-1500 cm. －１ This indicates the range.

[0012] Embodiments of the present invention will be described in detail below. In this specification, the expressions "containing" and "including" include the concepts of "containing," "including," "substantially consisting of," and "consisting only of."

[0013] In the numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step can be arbitrarily combined with the upper or lower limit of a numerical range in another step. In the numerical ranges described in this specification, the upper or lower limit of a numerical range may be replaced with values ​​shown in the examples or values ​​that can be uniquely derived from the examples. Furthermore, in this specification, numbers connected by "~" mean a numerical range that includes the numbers before and after "~" as the lower and upper limits.

[0014] 1. Stretched Film The stretched film of the present invention includes the following stretched film A and stretched film B. Stretched film A: Formula (I) ρ Ｖ１４５℃ = (S × V) / (D × A １ ) (I) (In equation (I), ρ Ｖ１４５℃ Ω is the volume resistivity (Ω·cm) at a temperature of 145°C, and S is the effective electrode area (cm²). ２ ) where V is the applied voltage (V), D is the thickness of the stretched film (cm), A １ (This is the detected current value at 1 minute after applying a voltage with a potential gradient of 100 V / μm to a stretched film in a 145°C environment.) The volume resistivity ρ in a 145°C environment is calculated from this value. Ｖ１４５℃ 8.0 x 10 １４ It is Ω·cm or greater. Stretched film B: The following formula (I) ρ Ｖ１４５℃ = (S × V) / (D × A １ ) (I) (In equation (I), ρ Ｖ１４５℃ Ω is the volume resistivity (Ω·cm) at a temperature of 145°C, and S is the effective electrode area (cm²). ２ ) where V is the applied voltage (V), D is the thickness of the stretched film (cm), A １ (This is the detected current value at 1 minute after applying a voltage with a potential gradient of 100 V / μm to a stretched film in a 145°C environment.) The volume resistivity ρ in a 145°C environment is calculated from this value.Ｖ１４５℃ And, the following equation (II) ρ Ｖ４０℃ = (S × V) / (D × A ２ ) (II) (In equation (I), ρ Ｖ４０℃ Ω is the volume resistivity (Ω·cm) at a 40°C environment, and S is the effective electrode area (cm²). ２ ) where V is the applied voltage (V), D is the thickness of the stretched film (cm), A ２ (This is the detected current value at 1 minute after applying a voltage with a potential gradient of 100 V / μm to a stretched film in a 40°C environment.) The volume resistivity ρ in a 40°C environment is calculated from this value. Ｖ４０℃ and the ratio (ρ Ｖ１４５℃ / ρ Ｖ４０℃ ) is 0.05 or higher.

[0015] The stretched film A and the stretched film B of the present invention have high insulation resistance values ​​in high-temperature environments, and can provide excellent safety performance to capacitor elements even in high-temperature environments. For example, they can provide excellent safety performance to capacitor elements even in an environment of 135°C.

[0016] The stretched film A of the present invention has a volume resistivity ρ calculated from formula (I) above. Ｖ１４５℃ 8.0 x 10 １４ The volume resistivity ρ calculated from formula (I) of the stretched film A of the present invention is Ω·cm or greater. Ｖ１４５℃ 8.0 x 10 １４ When the resistance falls below Ω·cm, it becomes difficult to provide excellent safety performance to the capacitor element even in high-temperature environments, and the insulation resistance value in high-temperature environments also decreases.

[0017] The stretched film A of the present invention has a volume resistivity ρ Ｖ１４５℃ 1.0 × 10 １５ Preferably, it is Ω·cm or larger, and 1.1 × 10 １５ It is more preferable that it be Ω·cm or greater, and 1.2 × 10 １５ It is even more preferable that it be Ω·cm or greater. The stretched film A has a volume resistivity ρ at a 145°C environment. Ｖ１４５℃ For example, 1.0 × 10 １６ Preferably less than Ω·cm, and 7.0 × 10 １５Ω·cm or less is more preferable, and 5.0 × 10 １５ A value of Ω·cm or less is even more preferable.

[0018] Volume resistivity ρ of the stretched film A of the present invention Ｖ１４５℃ The value is 8.0 × 10 １４ The method for adjusting to Ω·cm or higher is not particularly limited, and for example, a method of producing stretched film A using a polypropylene resin containing isotactic polypropylene resin can be used. As described later, when stretched film A is produced using a polypropylene resin containing isotactic polypropylene resin and a polymer having an alicyclic structure, the volume resistivity ρ Ｖ１４５℃ The value is 8.0 × 10 １４ It becomes easier to adjust it to Ω·cm or higher. Also, the volume resistivity ρ depends on the manufacturing conditions of the stretched film A. Ｖ１４５℃ The value is 8.0 × 10 １４ It becomes easier to adjust it to Ω·cm or higher. For example, the volume resistivity ρ can also be adjusted depending on the melting temperature of the resin during manufacturing, the temperature of the cooling rolls such as metal drums, the stretching ratio, etc. Ｖ１４５℃ It is possible to adjust the value to a desired range.

[0019] The stretched film B of the present invention has a volume resistivity ρ calculated from formula (I). Ｖ１４５℃ And the volume resistivity ρ calculated from the above formula (II) Ｖ４０℃ The ratio of (ρ Ｖ１４５℃ / ρ Ｖ４０℃ ) is 0.05 or greater. Ｖ１４５℃ / ρ Ｖ４０℃ However, when the value falls below 0.05, it becomes difficult to provide the capacitor element with excellent safety performance even in high-temperature environments, resulting in a lower insulation resistance value in high-temperature environments.

[0020] The stretched film B of the present invention is ρ Ｖ１４５℃ / ρ Ｖ４０℃ It is preferable that it is 0.08 or higher, more preferably 0.10 or higher, even more preferably 0.11 or higher, even more preferably 0.15 or higher, and particularly preferably 0.2 or higher. The stretched film B is ρ Ｖ１４５℃ / ρ Ｖ４０℃However, for example, a value of 1.0 or less is preferred, a value of 0.8 or less is more preferred, and a value of 0.6 or less is even more preferred.

[0021] The ρ of the stretched film B of the present invention Ｖ１４５℃ / ρ Ｖ４０℃ The method for adjusting the value of to 0.05 or higher is not particularly limited, and for example, a method of producing stretched film B with a polypropylene resin containing isotactic polypropylene resin can be cited. As described later, when producing stretched film B using a polypropylene resin containing isotactic polypropylene resin and a polymer having an alicyclic structure, ρ Ｖ１４５℃ / ρ Ｖ４０℃ It becomes easier to adjust the value of to 0.05 or higher. Also, ρ is affected by the manufacturing conditions of stretched film B. Ｖ１４５℃ / ρ Ｖ４０℃ It becomes easier to adjust the value of to 0.05 or higher. For example, the melting temperature of the resin during manufacturing, the temperature of the cooling rolls such as the metal drum, the stretching ratio, etc., also affect ρ Ｖ１４５℃ / ρ Ｖ４０℃ It is possible to adjust the value to a desired range.

[0022] The above-described features of the stretched film B of the present invention may also be present in the stretched film A of the present invention. That is, the stretched film A of the present invention, like the stretched film B, ρ Ｖ１４５℃ / ρ Ｖ４０℃ However, it may be 0.05 or higher.

[0023] The following details the characteristics that the stretched film A and stretched film B of the present invention share in common. In the following description, stretched film A and stretched film B of the present invention will be collectively referred to as "the stretched film of the present invention."

[0024] In the stretched film of the present invention, it is preferable that the height Spk of the protruding peaks on at least one surface is 0.01 μm or more and 0.15 μm or less. In this case, the stretched film of the present invention can be provided with excellent safety performance by the capacitor element even in high-temperature environments. In the stretched film of the present invention, it is more preferable that the height Spk of the protruding peaks on at least one surface is 0.015 μm or more, more preferably 0.13 μm or less, and even more preferably 0.11 μm or less.

[0025] The stretched film of the present invention preferably has an arithmetic mean height Sa of at least one surface of 0.008 μm or more and 0.050 μm or less. In this case, the stretched film of the present invention can be provided with excellent safety performance by capacitor elements even in high-temperature environments. More preferably, the arithmetic mean height Sa of at least one surface of the stretched film of the present invention is 0.010 μm or more, more preferably 0.040 μm or less, and even more preferably 0.030 μm or less.

[0026] In the stretched film of the present invention, it is preferable that the depth Svk of the protruding valley portion on at least one surface is 0.01 μm or more and 0.06 μm or less. In this case, the stretched film of the present invention can be provided with excellent safety performance by the capacitor element even in high-temperature environments. In the stretched film of the present invention, it is more preferable that the depth Svk of the protruding valley portion on at least one surface is 0.015 μm or more, more preferably 0.055 μm or less, and even more preferably 0.050 μm or less.

[0027] The method for adjusting the surface peak height Spk, arithmetic mean height Sa, and trough depth Svk (hereinafter collectively referred to as "surface roughness characteristics") of the stretched film of the present invention is not particularly limited and can be broadly adopted from known methods. For example, a method of producing the stretched film using a polypropylene resin containing an isotactic polypropylene resin can be cited. When the stretched film is produced using a polypropylene resin containing an isotactic polypropylene resin and a polymer having an alicyclic structure, it becomes easier to adjust the surface roughness characteristics to a desired range.

[0028] Furthermore, the surface roughness characteristics of the stretched film can also be controlled by the manufacturing conditions of the stretched film. For example, when manufacturing the stretched film, the cooling temperature when cooling the molten resin with a cooling roll such as a metal drum makes it easier to adjust the surface roughness characteristics to a desired range. Generally, the surface that comes into contact with the cooling roll such as a metal drum becomes the roughened surface, and its surface roughness is greater than that of the surface that does not come into contact with the cooling roll such as a metal drum. Therefore, it is preferable that the surface of the stretched film of the present invention that comes into contact with the cooling roll has the above-mentioned surface roughness characteristics.

[0029] The stretched film of the present invention, by adjusting its volume resistivity to a specific range, can improve its safety function against dielectric breakdown (i.e., to provide superior safety performance to capacitor elements), and if the surface roughness characteristics are set within the predetermined range described above, the stretched film is also suitable for use as a capacitor material. In other words, the stretched film of the present invention possesses both the quality of safety performance and suitability as a capacitor material.

[0030] In the stretched film of the present invention, the crystallite size determined by Scherrer's formula based on the half-width of the (110) plane derived from the α-crystal of isotactic polypropylene, as measured by X-ray diffraction intensity, is preferably 105 Å or more (11.2 nm or more), and the ratio of the crystallite size of the (110) plane to the crystallite size of the (040) plane, "(110 plane) crystallite size / (040 plane) crystallite size", is preferably 1.0 or more. In this case, safety performance is easily improved, and the insulation resistance value in high-temperature environments tends to be high. Therefore, the polypropylene resin for forming the stretched film preferably contains at least isotactic polypropylene, as described below. In particular, in order to adjust the crystallite size to the above range, the polypropylene resin may contain a polymer having an alicyclic structure as described below, in addition to isotactic polypropylene.

[0031] The crystallite size of the stretched film of the present invention is preferably 112 Å or more, preferably 160 Å or less, more preferably 150 Å or less, still more preferably 145 Å or less, and particularly preferably 140 Å or less. The value of the (110) plane crystallite size / (040) plane crystallite size is more preferably 1.01 or more, preferably 1.2 or less, and more preferably 1.1 or less.

[0032] In the infrared absorption spectrum measurement of the stretched film of the present invention, there is preferably at least one of an absorption peak in the range of 880 to 890 cm －１ and a shoulder peak due to absorption around 1450 cm －１ . In this case, the security performance is likely to be improved, and the insulation resistance value under a high-temperature environment is likely to be high. In the infrared absorption spectrum measurement of the stretched film of the present invention, it is more preferable to have both an absorption peak in the range of 880 to 890 cm －１ and a shoulder peak due to absorption around 1450 cm －１ .

[0033] To have an absorption peak in the range of 880 to 890 cm －１ and / or a shoulder peak due to absorption around 1450 cm －１ , for example, the composition ratio of each component in the polypropylene-based resin for forming the stretched film may be adjusted. For example, since the characteristic peak of infrared absorption of the polymer having an alicyclic structure described later exists in the range of 880 to 890 cm －１ and / or around 1450 cm －１ , the polypropylene-based resin preferably contains a polymer component having the alicyclic structure. For example, the content ratio of the polymer component having the alicyclic structure described later in the polypropylene-based resin for forming the stretched film may be adjusted to 6% by mass or more, preferably 10% by mass or more.

[0034] The thickness of the stretched film of the present invention can be adjusted to an appropriate range depending on the application, and can be, for example, to the same range as the thickness of stretched films used in capacitor applications. For example, the stretched film of the present invention preferably has a thickness of 1.8 μm or more and 10 μm or less. The thickness of the stretched film was measured in accordance with JIS-C2330:2014, except that it was measured at 100 ± 10 kPa using a paper thickness gauge MEI-11 manufactured by Citizen Seimitsu Co., Ltd.

[0035] From the viewpoint of having high transparency, the stretched film of the present invention preferably has a total light transmittance of 80% or more. In particular, the stretched film of the present invention preferably has a thickness of 1.8 μm or more and 10 μm or less, and a total light transmittance of 80% or more. In this case, the stretched film of the present invention can be used particularly suitably for capacitor applications.

[0036] The stretched film of the present invention may have a single-layer structure or a multilayer structure in which multiple layers are laminated. If the stretched film has a multilayer structure, some or all of the layers may be different. In this case, at least one layer is a layer containing the polypropylene resin.

[0037] (Polypropylene Resin) Next, the polypropylene resin included in the stretched film of the present invention will be described. The stretched film of the present invention is formed using a polypropylene resin.

[0038] A wide variety of polypropylene resins can be included in the stretched film. Among these, it is preferable that the polypropylene resin contains at least an isotactic polypropylene resin and a heat-resistant resin having a high glass transition temperature, as this makes it easier to satisfy formula (1) and / or formula (2). The heat-resistant resin having a high glass transition temperature can be crystalline or amorphous, but an amorphous resin is preferable in order to better demonstrate the effect of having a high glass transition temperature. In particular, it is preferable that the polypropylene resin contains an isotactic polypropylene resin and a polymer having an alicyclic structure. In this case, it is possible to have a higher dielectric breakdown strength even in high-temperature environments of 120°C or higher, and the change in dielectric breakdown strength tends to be smaller.

[0039] As described above, in the stretched film of the present invention, the polypropylene resin is preferably a resin (so-called blended resin) that includes an isotactic polypropylene resin and a polymer having an alicyclic structure.

[0040] <Isotactic Polypropylene Resin> For the isotactic polypropylene resin, for example, known isotactic polypropylenes can be widely used.

[0041] The melt mass flow rate (MFR) of the isotactic polypropylene resin is preferably 0.5 g / 10 min or more and 6 g / 10 min or less, more preferably 1 g / 10 min or more and 5 g / 10 min or less, and even more preferably 1.5 g / 10 min or more and 4 g / 10 min or less, as measured at 230°C and 2.16 kgf. In this case, appropriate resin fluidity is obtained when stretching the film, and the stretchability is improved.

[0042] The melting point of the isotactic polypropylene resin is preferably 155°C or higher. In this case, the electrical insulation and stretchability at high temperatures are improved. The melting point is more preferably 160°C to 180°C, and even more preferably 164°C to 175°C.

[0043] The mesopentad fraction of the isotactic polypropylene resin is preferably 95 mol% or more and 99.9 mol% or less. A fraction of 95 mol% or more tends to improve the rigidity and electrical insulation of the stretched film of the present invention, while a fraction of 99.9 mol% or less tends to improve the stretchability. The mesopentad fraction is more preferably 96 mol% or more and 99.5 mol%, even more preferably 96 mol% or more and 99 mol%, and particularly preferably 97 mol% or more and 98 mol%.

[0044] The heptane-insoluble content (HI) of the isotactic polypropylene resin is preferably 94% by mass or more and 99.9% by mass or less. If it is 94% by mass or more, the rigidity and electrical insulation of the stretched film tend to improve, and if it is 99.9% by mass or less, the stretchability tends to improve. The heptane-insoluble content is more preferably 96% by mass or more and 99.5% by mass or less, even more preferably 97% by mass or more and 99.2% by mass or less, and particularly preferably 98% by mass or more and 99% by mass or less.

[0045] The number-average molecular weight (Mn) of the isotactic polypropylene resin is preferably between 30,000 and 70,000, and more preferably between 35,000 and 65,000. In this case, the rigidity, electrical insulation, and stretchability of the stretched film of the present invention tend to improve.

[0046] The weight-average molecular weight (Mw) of the isotactic polypropylene resin is preferably between 250,000 and 500,000, and more preferably between 300,000 and 450,000. In this case, the rigidity, electrical insulation, and stretchability of the stretched film of the present invention tend to improve.

[0047] The molecular weight distribution (Mw / Mn) of the isotactic polypropylene resin is preferably 3 or more and 12 or less, more preferably 5 or more and 10 or less, and even more preferably 5.5 or more and 9.5 or less. In this case, the rigidity, electrical insulation, and stretchability of the stretched film of the present invention are easily improved.

[0048] The z-average molecular weight (Mz) of the isotactic polypropylene resin is preferably between 700,000 and 3,000,000, and more preferably between 1,000,000 and 2,500,000. In this case, the rigidity, electrical insulation, and stretchability of the stretched film of the present invention tend to improve.

[0049] The Mz / Mw of the isotactic polypropylene resin is preferably 2 to 7, more preferably 2.5 to 6, and even more preferably 3 to 5. In this case, the rigidity, electrical insulation, and stretchability of the stretched film of the present invention tend to improve.

[0050] Isotactic polypropylene resin can be manufactured, for example, by known methods, or it can be obtained from the market.

[0051] Polymerization methods for obtaining isotactic polypropylene resins include, for example, gas-phase polymerization, bulk polymerization, and slurry polymerization. Polymerization may be a single-step polymerization using one polymerization reactor, or a multi-step polymerization using two or more polymerization reactors. Hydrogen or comonomers may also be added to the reactor as molecular weight modifiers during polymerization. Conventional known Ziegler-Natta catalysts or metallocene catalysts can be used as polymerization catalysts, and the polymerization catalysts may contain co-catalyst components or donors. The mesopentade fraction, melt mass flow rate, molecular weight, and molecular weight distribution of the polypropylene resin can be controlled by appropriately adjusting the polymerization catalyst and other polymerization conditions.

[0052] The polypropylene resin may contain one or more isotactic polypropylene resins.

[0053] Furthermore, when the polypropylene resin includes isotactic polypropylene resin, the X-ray diffraction intensity measurement of the stretched film reveals diffraction peaks from the (110) plane originating from the α-crystal of the isotactic polypropylene mentioned above.

[0054] <Polymers with Alicyclic Structures> Polymers with alicyclic structures are polymers that have alicyclic structures in their main chain or side chains. Typically, the alicyclic structure exists covalently bonded to the main chain or side chains.

[0055] An alicyclic structure is defined as comprising one or more saturated and / or unsaturated carbon ring structures that do not possess aromaticity. There may be two or more such carbon ring structures. The carbon ring structures may have branching aliphatic hydrocarbon structures. The carbon ring structures are bonded directly or via hydrocarbon chains to the hydrocarbon chains of the polymer backbone.

[0056] Examples of the aforementioned carbocyclic structures include cycloalkane structures such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane, as well as cycloalkene structures such as cyclopropene, cyclobutene, cyclopropene, cyclohexene, cycloheptene, and cyclooctene. Examples of bicyclic structures include bicyclic alkane structures such as bicycloundecane, and bicyclic alkene structures such as norbornene and norbornadiene, which can be suitably used. In particular, having a carbocyclic structure with 4 to 8 carbon atoms is preferred from the viewpoint of extensibility, having a monocyclic carbocyclic structure with 4 to 8 carbon atoms is more preferred, having a monocyclic cycloalkane carbocyclic structure with 4 to 8 carbon atoms is even more preferred, and having a cyclohexane structure is particularly preferred.

[0057] The main chain of a polymer having an alicyclic structure can be mainly composed of aliphatic hydrocarbons. The aliphatic hydrocarbons in the polymer main chain may have branches of aliphatic hydrocarbon structures and / or aromatic hydrocarbon structures. The main chain of a polymer having an alicyclic structure may further contain the alicyclic structure, but it is preferable that the main chain does not have an alicyclic structure, and that it is contained in the side chains, in order to easily maintain high dielectric breakdown strength even in high-temperature environments of 120°C or higher. Therefore, it is preferable that a polymer having an alicyclic structure is a polymer in which the side chain has an alicyclic structure.

[0058] A polymer having an alicyclic structure in its side chain may be a homopolymer whose constituent units are structures having an alicyclic structure in its side chain. For example, it may be a polyvinylcycloolefin obtained by homopolymerizing vinylcycloolefins. Examples of polyvinylcycloolefins include polyvinylcyclopropane, polyvinylcyclobutane, polyvinylcyclopentane, polyvinylcyclohexane, polyvinylcycloheptane, polyvinylcyclooctane, polyvinylcyclononane, polyvinylcyclodecane, polyvinylcycloundecane, and polyvinylcyclododecane. In the case of a homopolymer, it is preferable that rigidity and electrical insulation properties tend to be high in high-temperature environments. Among these, polyvinylcyclopentane, polyvinylcyclohexane, and polyvinylcycloheptane are preferred, with polyvinylcyclohexane being the most preferred.

[0059] Another example of a polymer having an alicyclic structure in its side chain is a hydrogenated block copolymer. The type of hydrogenated block copolymer is not particularly limited, and for example, known hydrogenated block copolymers can be broadly mentioned. A hydrogenated block copolymer can be, for example, a copolymer obtained by hydrogenating a block copolymer having at least a vinyl aromatic polymer block and a conjugated diene polymer block. That is, a hydrogenated block copolymer is a copolymer having at least a hydrogenated vinyl aromatic polymer block and a hydrogenated conjugated diene polymer block. Hydrogenated block copolymers will be described below.

[0060] ≪Hydrogenated Vinyl Aromatic Polymer Block≫ The hydrogenated vinyl aromatic polymer block contains constituent units derived from vinyl aromatic compounds, which have been hydrogenated. The hydrogenated vinyl aromatic polymer block contains 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass, constituent units derived from vinyl aromatic compounds. By having 50% by mass or more of constituent units derived from vinyl aromatic compounds, rigidity and electrical insulation properties in high-temperature environments are easily improved.

[0061] Examples of vinyl aromatic compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, vinyltoluene, 1-vinylnaphthalene, and 2-vinylnaphthalene. The vinyl aromatic compound is preferably selected from styrene and α-methylstyrene, and more preferably styrene.

[0062] The hydrogenated vinyl aromatic polymer block may consist of only one of the vinyl aromatic compounds, or it may consist of two or more. The hydrogenated vinyl aromatic polymer block may contain other constituent units other than those derived from the vinyl aromatic compounds. Examples of other constituent units include those derived from isoprene, butadiene, 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadiene, and the like.

[0063] The content of the vinyl hydrogenated aromatic polymer block is preferably 50% by mass or more and less than 100% by mass, relative to 100% by mass of the total of the vinyl hydrogenated aromatic polymer block and the hydrogenated conjugated diene polymer block. A content of 50% by mass or more tends to increase rigidity and electrical insulation at high temperatures. More preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

[0064] ≪Hydrogenated Conjugated Diene Polymer Block≫ The hydrogenated conjugated diene polymer block contains constituent units derived from a conjugated diene, which has been hydrogenated. The hydrogenated conjugated diene polymer block contains 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass of constituent units derived from a conjugated diene.

[0065] Examples of conjugated dienes include butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The conjugated diene is preferably selected from butadiene and isoprene, and more preferably butadiene.

[0066] The hydrogenated conjugated diene polymer block may contain structural units derived from a conjugated diene without side chains. Examples of conjugated dienes without side chains include butadiene, 1,3-pentadiene, and 1,3-hexadiene. Butadiene is preferred as the conjugated diene without side chains.

[0067] In hydrogenated conjugated diene polymer blocks, the bonding configuration of the conjugated dienes, i.e., the microstructure, is not particularly limited. For example, butadiene can have 1,2-bonds and 1,4-bonds. Isoprene can have 1,2-bonds, 3,4-bonds, and 1,4-bonds. Only one of these bonding configurations may be present, or two or more may be present. If two or more bonding configurations are present, the proportion of each configuration is not particularly limited.

[0068] Hydrogenated conjugated diene polymer blocks may contain other constituent units besides those derived from conjugated dienes. Examples of other constituent units include those derived from styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, vinyltoluene, 1-vinylnaphthalene, 2-vinylnaphthalene, and the like.

[0069] The content of the hydrogenated conjugated diene polymer block is preferably more than 0% by mass (e.g., 1% by mass or more) and 50% by mass or less, based on 100% by mass of the total of the hydrogenated vinyl aromatic polymer block and the hydrogenated conjugated diene polymer block. A content of 50% by mass or less is preferable because it tends to increase rigidity and electrical insulation at high temperatures. More preferably, it is 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

[0070] ≪Hydrogenation Rate≫ In the hydrogenated vinyl aromatic polymer block according to this embodiment, the hydrogenation rate of the aromatic ring of the hydrogenated vinyl aromatic polymer block is preferably 50 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, particularly preferably 90 mol% or more, and even more preferably 95 mol% or more. The hydrogenation rate may be 100 mol%. Furthermore, the hydrogenation rate of the carbon-carbon double bond derived from the conjugated diene in the hydrogenated conjugated diene polymer block is preferably 90 mol% or more, more preferably 95 mol% or more. The hydrogenation rate may be 100 mol%.

[0071] By setting the hydrogenation rate of the aromatic rings in the vinyl hydrogenated aromatic polymer block and / or the hydrogenation rate of the carbon-carbon double bonds derived from the conjugated diene in the hydrogenated conjugated diene polymer block within the above-mentioned range, the stretchability is improved, and the glass transition temperature (Tg) tends to be 100°C or higher, which is preferable.

[0072] ≪Bonding patterns of hydrogenated block copolymers≫ The bonding patterns of polymer blocks in hydrogenated block copolymers may be linear, branched, or radial, or a combination thereof.

[0073] For example, if we represent a hydrogenated vinyl aromatic polymer block as "X" and a hydrogenated conjugated diene polymer block as "Y", the bonding modes include diblock copolymers (X-Y), triblock copolymers (X-Y-X), tetrablock copolymers (X-Y-X-Y), and pentablock copolymers (X-Y-X-Y-X, or Y-X-Y-X-Y). From the viewpoint of ease of manufacture, the bonding modes are preferably diblock copolymers, triblock copolymers, or tetrablock copolymers.

[0074] Specific examples of hydrogenated block copolymers include hydrogenated block copolymers obtained by hydrogenating styrene-isoprene diblock copolymer (SI), styrene-butadiene diblock copolymer (SB), styrene-isoprene-styrene triblock copolymer (SIS), styrene-butadiene / isoprene-styrene triblock copolymer (SB / IS), and styrene-butadiene-styrene triblock copolymer (SBS), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), and styrene-butylene-butadiene-styrene copolymer (SBBS). Among these, hydrogenated block copolymers obtained by hydrogenating styrene-butadiene diblock copolymer (SB) are particularly preferred.

[0075] ≪Method for Producing Hydrogenated Block Copolymers≫ The method for producing hydrogenated block copolymers is not particularly limited, and known methods such as anionic polymerization can be used. Specifically, hydrogenated block copolymers can be produced by a polymerization reaction using an alkyllithium compound as an initiator to sequentially polymerize a vinyl aromatic compound and a conjugated diene; a method using an alkyllithium compound as an initiator to sequentially polymerize a vinyl aromatic compound and a conjugated diene, and then adding a coupling agent for coupling; or a method using a dilithium compound as an initiator to sequentially polymerize a conjugated diene, and then a vinyl aromatic compound, followed by a hydrogenation reaction.

[0076] Examples of alkyllithium compounds include methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and pentyllithium.

[0077] Examples of coupling agents include polyvalent epoxy compounds such as divinylbenzene, epoxidized 1,2-polybutadiene, epoxidized soybean oil, and 1,3-bis(N,N-glycidylaminomethyl)cyclohexane; halogen compounds such as dimethyldichlorosilane, dimethyldibromosilane, trichlorosilane, methyltrichlorosilane, tetrachlorosilane, and tetrachlorotin; ester compounds such as methyl benzoate, ethyl benzoate, phenyl benzoate, diethyl oxalate, diethyl malonate, diethyl adipate, dioctyl adipate, dimethyl phthalate, diethyl phthalate, dimethyl isophthalate, and dimethyl terephthalate; carbonate ester compounds such as dimethyl carbonate, diethyl carbonate, and diphenyl carbonate; and alkoxysilane compounds such as dimethyldimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, bis(trimethoxysilyl)hexane, and bis(triethoxysilyl)ethane.

[0078] Examples of dilithium compounds include naphthalenedithium and dilithiohexylbenzene.

[0079] The polymerization reaction is preferably carried out in the presence of a solvent. The solvent is not particularly limited as long as it is inert to the initiator and does not adversely affect the reaction. Examples include saturated aliphatic hydrocarbons such as hexane, cyclohexane, heptane, octane, and decane; and aromatic hydrocarbons such as toluene, benzene, and xylene. The polymerization reaction temperature is usually preferably 0 to 100°C, more preferably 30 to 90°C, even more preferably 40 to 80°C, and particularly preferably 50 to 80°C, from the viewpoint of microstructure control. The polymerization reaction time is preferably 0.5 to 50 hours, from the viewpoint of microstructure control.

[0080] Furthermore, Lewis bases may be used as co-catalysts during polymerization reactions. Examples of Lewis bases include ethers such as dimethyl ether, diethyl ether, and tetrahydrofuran; glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; and amines such as triethylamine, N,N,N',N'-tetramethylethylenediamine, and N-methylmorpholine. These Lewis bases may be used individually or in combination of two or more.

[0081] The hydrogenation reaction may be carried out immediately after the polymerization reaction, or it may be carried out after the block copolymer has been isolated following the polymerization reaction.

[0082] To isolate a block copolymer after a polymerization reaction, the polymerization reaction solution obtained after the polymerization reaction can be poured into a poor solvent for the block copolymer, such as methanol, to solidify the block copolymer. Alternatively, the polymerization reaction solution can be poured into hot water along with steam to remove the solvent by azeotropic removal (steam stripping), and then the block copolymer can be isolated by drying.

[0083] The hydrogenation reaction of block copolymers can be carried out, for example, by reacting them for 0.1 to 100 hours under conditions of a reaction temperature of 20 to 200°C and a hydrogen pressure of 0.1 to 20 MPa in the presence of a hydrogenation catalyst.

[0084] Examples of hydrogenation catalysts include Raney nickel; heterogeneous catalysts in which metals such as platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), and nickel (Ni) are supported on carriers such as carbon, alumina, and diatomaceous earth; Ziegler catalysts consisting of combinations of transition metal compounds (nickel octoate, nickel naphthenate, nickel acetylacetonate, cobalt octoate, cobalt naphthenate, cobalt acetylacetonate, etc.) and organoaluminum compounds such as triethylaluminum and triisobutylaluminum, or organolithium compounds; and metallocene catalysts consisting of combinations of bis(cyclopentadienyl) compounds of transition metals such as titanium, zirconium, and hafnium and organometallic compounds consisting of lithium, sodium, potassium, aluminum, zinc, or magnesium.

[0085] When the hydrogenation reaction is carried out immediately following the polymerization reaction, the hydrogenated block copolymer can be isolated by pouring the hydrogenation reaction solution into a poor solvent for the hydrogenated block copolymer, such as methanol, and allowing it to solidify, or by pouring the hydrogenation reaction solution into hot water with steam to remove the solvent by azeotrope (steam stripping), followed by drying.

[0086] <Polymers having an alicyclic structure in the main chain> In polymers having an alicyclic structure, the alicyclic structure may be present in the main chain. As polymers having an alicyclic structure in the main chain, known cycloolefin copolymers (so-called COCs) can be widely applied, for example. Specifically, a polymer in which an alkylene skeleton is the main chain and a part of the alkylene is replaced with an alicyclic structure can be given as an example. The alkylene skeleton may be, for example, an ethylene unit (-CH ２ -CH ２ -) is one example.

[0087] A specific example of a polymer having an alicyclic structure in its main chain is a polymer of norbornene and ethylene. In this case, the polymer having an alicyclic structure in its main chain is a polymer in which an alicyclic structure derived from norbornene is introduced into the polyethylene main chain. Polymers having an alicyclic structure in their main chain can be manufactured by known methods or obtained from commercially available products. Examples of commercially available polymers having an alicyclic structure in their main chain include the "Topas (registered trademark) COC" series from Polyplastics Co., Ltd., such as "COC6013F-04" (glass transition temperature Tg of 137°C) and "COC8007F-04" (Tg of 76°C).

[0088] <Preferred Embodiments of Polymers Having an Alicyclic Structure> As described above, polymers having an alicyclic structure may be homopolymers or copolymers. When the polymer having an alicyclic structure is a homopolymer, it is preferable that such polymer is a hydrogenated polymer, a so-called hydrogenated polymer. When the polymer having an alicyclic structure in its side chain is a hydrogenated polymer, a specific example is hydrogenated polystyrene (for example, polyvinylcyclohexane). The stereoregularity of the hydrogenated polystyrene may be isotactic, syndiotactic, or atactic, but in order to better demonstrate the effect of having a high glass transition temperature, it is more preferable that it be an atactic amorphous resin.

[0089] When the polymer having the alicyclic structure contains hydrogenated polystyrene, it is easier to impart excellent safety performance to the capacitor element even in high-temperature environments. Preferably, the hydrogenated polystyrene has an atactic structure and a hydrogenation rate of 95% or more.

[0090] When the polymer having an alicyclic structure is a copolymer, a block copolymer having at least a vinyl aromatic polymer block and a conjugated diene polymer block is preferred, and a hydrogenated block copolymer obtained by hydrogenating a styrene-butadiene diblock copolymer (SB) is particularly preferred.

[0091] The glass transition temperature (Tg) of a polymer having an alicyclic structure is preferably, for example, 100°C to 180°C. Setting the glass transition temperature to 100°C or higher tends to increase rigidity and electrical insulation at high temperatures, while setting it to 180°C or lower can improve stretchability. The glass transition temperature is more preferably 120°C to 165°C, more preferably 130°C to 160°C, and particularly preferably 140°C to 155°C.

[0092] In particular, polymers having an alicyclic structure preferably contain two or more polymers with different glass transition temperatures.

[0093] In this case, it is preferable that the polymer having an alicyclic structure includes polymer B1 having an alicyclic structure with a glass transition temperature of 133°C to 155°C and polymer B2 having an alicyclic structure with a glass transition temperature of 70°C to less than 133°C. In this case, heat resistance is improved by B1, and compatibility between polypropylene and B1 is increased by B2, resulting in a higher insulation resistance even in high-temperature environments of 120°C or higher. Hereinafter, polymer B1 having an alicyclic structure with a glass transition temperature of 133°C to 155°C will be abbreviated as "polymer B1", and polymer B2 having an alicyclic structure with a glass transition temperature of 70°C to less than 133°C will be abbreviated as "polymer B2".

[0094] The glass transition temperature of polymer B1 is preferably 135°C or higher. Furthermore, the glass transition temperature of polymer B2 is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher, and particularly preferably 110°C or higher.

[0095] The mass ratio of polymer B2 to polymer B1, B2 / B1 (where B2 represents the content (parts by mass) of polymer B2 in a polymer having an alicyclic structure, and B1 represents the content (parts by mass) of polymer B1 in a polymer having an alicyclic structure), is not particularly limited. For example, the mass ratio of polymer B2 to polymer B1, B2 / B1, is preferably less than 0.85. In this case, the insulation resistance value tends to be particularly high even in high-temperature environments of 120°C or higher. B2 / B1 is preferably 0.80 or less, more preferably 0.75 or less, even more preferably 0.70 or less, particularly preferably 0.65 or less, and also preferably 0.10 or more, more preferably 0.20 or more, even more preferably 0.25 or more, and particularly preferably 0.30 or more.

[0096] Even when the polymer having an alicyclic structure includes polymer B1 and / or polymer B2, it is preferable that both polymer B1 and polymer B2 are the aforementioned hydrogenated polystyrene, block copolymer, etc. For example, a combination can be given in which polymer B1 is hydrogenated polystyrene and polymer B2 is a block copolymer (for example, a hydrogenated block copolymer obtained by hydrogenating a styrene-butadiene diblock copolymer).

[0097] The Vicat softening point (1 kg, 50°C / hr) of polymers having an alicyclic structure is preferably between 100°C and 170°C. Setting the Vicat softening point above 100°C tends to increase rigidity and electrical insulation at high temperatures, while setting it below 170°C improves stretchability. A Vicat softening point of 120°C to 165°C is more preferable, 130°C to 160°C is even more preferable, and 140°C to 155°C is particularly preferable.

[0098] The glass transition temperature (Tg) and Vicat softening point of polymers having an alicyclic structure can be adjusted by the type of constituent unit having an alicyclic structure in the side chain, or by the type and ratio of one or more other constituent units.

[0099] The weight-average molecular weight (Mw) of the polymer having an alicyclic structure is preferably, for example, 50,000 to 400,000. In this case, the rigidity, electrical insulation, and stretchability of the stretched film of the present invention are easily improved.

[0100] The melt mass flow rate (MFR) of a polymer having an alicyclic structure is preferably 1 g / 10 min or more and 40 g / 10 min or less, more preferably 2 g / 10 min or more and 20 g / 10 min or less, and even more preferably 3 g / 10 min or more and 15 g / 10 min or less, as measured at 260°C and 2.16 kgf. In this case, appropriate resin fluidity is obtained when stretching the film, and the stretchability is easily improved.

[0101] Polymers having an alicyclic structure can be manufactured, for example, by known methods, or can be obtained from the market. An example of a commercially available product is ViviOn® (manufactured by USI Corporation).

[0102] Polypropylene resins may contain polymers having one or more alicyclic structures.

[0103] <Method for producing polymers having an alicyclic structure> The method for producing polymers having an alicyclic structure is not particularly limited and can be produced using known methods such as radical polymerization, ionic polymerization (anionic polymerization, coordination anionic polymerization, etc.), bulk polymerization, solution polymerization, suspension polymerization, etc. Specifically, polymers having an alicyclic structure can be produced by carrying out a polymerization reaction using known initiators such as alkyllithium compounds and dilithium compounds to sequentially polymerize monomers having an alicyclic structure (e.g., vinylcycloolefins); or by sequentially polymerizing monomers having an alicyclic structure and then adding a coupling agent to perform coupling.

[0104] In particular, polymers having an alicyclic structure in their side chains can be produced by polymerizing a monomer having an aromatic ring structure (e.g., styrene) by a known method, followed by a hydrogenation reaction. The hydrogenation reaction can be carried out, for example, by the method described later in the method for producing hydrogenated block copolymers.

[0105] When a hydrogenation reaction is carried out, the hydrogenation rate to the aromatic ring structure is preferably 50 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, particularly preferably 90 mol% or more, and even more preferably 95 mol% or more. The hydrogenation rate may also be 100 mol%. It is preferable to set the hydrogenation rate within the above range because it improves the stretchability while also tending to result in a glass transition temperature (Tg) of 100°C or higher.

[0106] A polymer having an alicyclic structure may be, for example, a copolymer having structural units with an alicyclic structure in their side chains and one or more other structural units. The copolymer may be a random copolymer or a block copolymer having at least two polymer blocks. From the viewpoint of stretchability, copolymers are preferred, and block copolymers are more preferred. Examples of other structural units include ethylene, propylene, butene, pentene, hexene, heptene, octene, etc., and may or may not have side chains. It may also contain both structural units with side chains and structural units without side chains. Examples of structural units with side chains include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc. The other structural units may be unsaturated hydrocarbons, but saturated hydrocarbons are preferred from the viewpoint of electrical insulation.

[0107] When a polymer having an alicyclic structure contains propylene as another constituent unit, the propylene content in the polymer is less than 50% by mass, preferably 20% by mass or less, and more preferably 10% by mass or less, based on 100% by mass of the polymer.

[0108] Polymers having an alicyclic structure can be obtained, for example, by polymerizing monomers having their respective constituent units using known methods. Furthermore, if the side chain has an aromatic ring structure, a polymer with an alicyclic structure in the side chain can be obtained by hydrogenation. Hydrogenation of polymers with aromatic ring structures in the side chain allows for the industrially inexpensive production of polymers with an alicyclic structure in the side chain.

[0109] When hydrogenating a polymer having an aromatic ring structure in its side chain, the polymer having an aromatic ring structure in its side chain may be a homopolymer or a copolymer. In the case of a copolymer, a block copolymer having at least a vinyl aromatic polymer block and a conjugated diene polymer block is preferred. By hydrogenating this, a hydrogenated block copolymer having at least a hydrogenated vinyl aromatic polymer block and a hydrogenated conjugated diene polymer block is obtained.

[0110] The following describes a hydrogenated block copolymer, which is one of the preferred embodiments of a method for producing a polymer having an alicyclic structure, and which comprises at least a hydrogenated vinyl aromatic polymer block and a hydrogenated conjugated diene polymer block.

[0111] <Polypropylene Resin> The polypropylene resin contained in the stretched film of the present invention preferably contains the isotactic polypropylene resin described above and the polymer having the alicyclic structure described above, more preferably containing the isotactic polypropylene resin and hydrogenated polystyrene (e.g., polyvinylcyclohexane), and even more preferably containing the isotactic polypropylene resin and hydrogenated polystyrene (polyvinylcyclohexane) having an atactic structure and a hydrogenation rate of 95% or more. Furthermore, the polypropylene resin contained in the stretched film of the present invention may contain the isotactic polypropylene resin and the block copolymer, or it may contain the isotactic polypropylene resin and the polymer B1 and the polymer B2.

[0112] When the polypropylene resin includes an isotactic polypropylene resin and a polymer having the aforementioned alicyclic structure, it is preferable that the isotactic polypropylene resin constitutes 55% to 99% by mass and the polymer having the alicyclic structure constitutes 1% to 45% by mass, based on the total mass of the polypropylene resin. In this case, the stretched film of the present invention is particularly likely to impart excellent safety performance to capacitor elements.

[0113] The polypropylene resin more preferably contains 60% by mass or more of isotactic polypropylene resin, even more preferably 65% ​​by mass or more, particularly preferably 70% by mass or more, more preferably 97% by mass or less, even more preferably 95% by mass or less, and particularly preferably 93% by mass or less.

[0114] The polypropylene resin more preferably contains 3% by mass or more of a polymer having an alicyclic structure, even more preferably 5% by mass or more, particularly preferably 7% by mass or more, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less. In these cases as well, the polymer having an alicyclic structure may preferably be, for example, hydride polystyrene (polyvinylcyclohexane) or the block copolymer, or the polymer having an alicyclic structure may include polymer B1 and polymer B2.

[0115] Polypropylene resins may include other resins besides isotactic polypropylene resins and polymers having an alicyclic structure. Examples of other resins include polyolefin resins and copolymer resins thereof, such as polyethylene, poly(1-butene), polyisobutene, poly(1-pentene), and poly(4-methyl-1-pentene), such as ethylene-propylene copolymers, propylene-butene copolymers, ethylene-butene copolymers, and ethylene-(4-methyl-1-pentene) copolymers, such as copolymers of α-olefins. Other examples include polystyrene resins, elastomers, polyvinyl resins, polyester resins, polyurethane resins, nylon resins, and copolymers thereof. Commercially available resins may be used as other resins, for example, Tuffmer® (manufactured by Mitsui Chemicals, Inc.) is an example of a copolymer of α-olefins and can be suitably used for the aforementioned purposes.

[0116] The polypropylene resin preferably contains 90% by mass or more of isotactic polypropylene resin and polymers having an alicyclic structure, more preferably 95% by mass or more, and even more preferably 99% by mass or less. The polypropylene resin also preferably does not contain any resins other than isotactic polypropylene resin and polymers having an alicyclic structure.

[0117] When the polypropylene resin includes isotactic polypropylene resin and polymers having an alicyclic structure, it is likely to satisfy formula (1) and / or formula (2).

[0118] When polypropylene resins contain isotactic polypropylene resin and polymers with alicyclic structures, they may exhibit a clear peak in the loss tangent (tanδ) in the region above 140°C. Such a peak is the main dispersion peak and may correspond to the glass transition temperature (Tg) of the polymer with an alicyclic structure (e.g., hydride polystyrene). This peak becomes clearer as the content of the polymer with an alicyclic structure (e.g., hydride polystyrene) increases. At the same time, the gentle bulge around 100°C present in polypropylene (100% polypropylene) (which may correspond to lattice relaxation in typical isotactic polypropylene) is lost with the addition of polymers with alicyclic structures because molecular mobility due to lattice relaxation is suppressed. That is, the loss tangent (tanδ) at 100°C becomes more easily satisfied with a value of 0.15 or less.

[0119] While we do not necessarily desire a restrictive interpretation, the fact that the loss tangent (tanδ) at 100°C is easily less than 0.15, or that there is a peak in the loss tangent (tanδ) in the region above 140°C, may indicate that the isotactic polypropylene resin and the polymer having an alicyclic structure have a phase-separated structure upon mixing. The structure consisting of the isotactic polypropylene resin and the polymer having an alicyclic structure is by no means a brittle phase-separated structure, and this can be judged from the fact that the film is not cloudy, that it maintains a high Tg (the presence of the aforementioned main dispersion peak), that the loss tangent (tanδ) at 100°C is small, that the lattice relaxation motion of polypropylene is contained (motion suppression effect), and that the temperature dependence of the storage modulus is small and flat with respect to temperature.

[0120] When a polypropylene resin contains isotactic polypropylene resin and polymers having an alicyclic structure, the presence of polymers having an alicyclic structure can be confirmed, for example, by changes in the infrared absorption spectrum. In particular, changes in the infrared absorption spectrum are more likely to occur when the polymer having an alicyclic structure contains hydrogenated polystyrene.

[0121] When the polypropylene resin contains isotactic polypropylene resin and polymers having an alicyclic structure, dynamic viscoelasticity measurements suggest that a "phase separation structure" is formed. By forming such a "phase separation structure," the relaxation motion (molecular chain motion) of polypropylene that occurs at high temperatures can be suppressed. As a result, the decrease in dielectric strength at high temperatures can be suppressed, and the stretched film of the present invention has high dielectric strength even in high-temperature environments of 120°C or higher, and moreover, the change in dielectric strength at high temperatures compared to room temperature (e.g., 25°C) is small.

[0122] When the polypropylene resin includes isotactic polypropylene resin and a polymer having an alicyclic structure, the stretched film of the present invention easily imparts excellent safety performance to capacitor elements.

[0123] While it is preferable in one embodiment that the polypropylene resin includes isotactic polypropylene resin and polymers having an alicyclic structure, the polypropylene resin may be composed of other resins, for example, propylene homopolymers such as syndiotactic polypropylene; copolymers of propylene and other olefins (e.g., ethylene, 1-butene, etc.) (the copolymer may be a random copolymer or a block copolymer having at least two polymer blocks); long-chain branched polypropylene; or polypropylene resin produced from plant-derived raw materials. In this case, the MFR, melting point, mesopentade fraction, heptane insoluble matter (HI), Mn, Mw, Mw / Mn, Mz, and Mz / Mw of the polypropylene resin can all be within the same range as the isotactic polypropylene resin described above.

[0124] (Other features of the stretched film of the present invention) The stretched film of the present invention can be obtained using the polypropylene resin described above. The stretched film of the present invention is stretched in at least one direction. Preferably, the stretched film of the present invention is a biaxially oriented film stretched in two directions. Preferably, such a biaxially oriented film is stretched in the MD (flow) direction and the TD (width) direction, respectively.

[0125] The stretched film of the present invention may also contain various additives, to the extent that the effects of the present invention are not impaired. Examples of additives include those found in stretched films used in known capacitor applications, such as antioxidants, necessary stabilizers such as chlorine absorbers and ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, and colorants.

[0126] Examples of antioxidants include hindered phenol antioxidants. Among hindered phenol antioxidants, examples of hindered phenol antioxidants having a carbonyl group include triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (trade name: Irganox 245), 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 259), pentaerythrultyl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1010), 2,2- Examples include o-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1035), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (trade name: Irganox 1076), and N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide) (trade name: Irganox 1098), but pentaerythrutyl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which has excellent heat resistance, is particularly preferred. All Irganox® products are manufactured by BASF Japan Ltd.

[0127] When the stretched film of the present invention contains an antioxidant, the amount is preferably 1,000 ppm by mass or more and 7,000 ppm by mass or less, and more preferably 2,000 ppm by mass or more and 6,000 ppm by mass or less, relative to the total mass of the stretched film. In general, the amount of the hindered phenol antioxidant remaining after the extrusion process during the stretched film formation process is 60 to 80% by mass of the above-mentioned content, as some of it is oxidized and decomposed during the extrusion process.

[0128] The stretched film of the present invention can be applied to capacitor applications, as well as various other applications such as packaging and separator applications. In particular, the stretched film of the present invention can be suitably used in capacitor applications, and is suitable for use in high-temperature environments of 120°C or higher, and is extremely suitable for small and high-capacitance capacitors (for example, 5 μF or more, preferably 10 μF or more, and even more preferably 20 μF or more).

[0129] The method for producing the stretched film of the present invention is not particularly limited. For example, the stretched film of the present invention can be produced by manufacturing a cast raw material sheet (unstretched film) using the polypropylene resin and then stretching the cast raw material sheet.

[0130] If the polypropylene resin includes an isotactic polypropylene resin and a polymer having an alicyclic structure, it can be obtained by mixing each resin in a predetermined ratio. For example, melt blending can be used as a mixing method. The polypropylene resin may be subjected to drying treatment or the like as needed.

[0131] The method for manufacturing the cast raw material sheet (unstretched film) is not particularly limited, and a wide range of known methods can be employed. For example, the cast raw material sheet can be manufactured by melt-kneading a polypropylene resin and then extruding it. As for the melt-kneading method, a single-screw type, twin-screw type, or multi-screw type melt-kneader can be used. The temperature during melt-kneading is preferably 200°C to 300°C, and more preferably 220°C to 280°C, considering the balance between suppressing resin degradation and the quality of the kneading. During melt-kneading, it is preferable to purge the kneader with an inert gas such as nitrogen in order to suppress resin degradation.

[0132] The extrusion molding method is not particularly limited; for example, a cast raw material sheet (unstretched film) can be obtained by extruding a molten and kneaded polypropylene resin into a film extruder. The extrusion molding method is not particularly limited, and known extrusion molding methods can be used. The molten and kneaded polypropylene resin may be filtered beforehand. The temperature during extrusion molding is not particularly limited, for example, 200 to 300°C, preferably 210 to 280°C, more preferably 215 to 270°C, and even more preferably 220 to 265°C.

[0133] The extruded, molten polypropylene resin can be cooled using a cooling roll such as a metal drum. The surface temperature of the cooling roll is, for example, 30 to 130°C, preferably 35 to 120°C, and more preferably 40 to 110°C. This yields a cast raw material sheet. The thickness of the cast raw material sheet is not particularly limited, but is, for example, 20 to 300 μm.

[0134] The stretched film of the present invention can be obtained by stretching a cast raw material sheet. The stretching method is not particularly limited, and examples include: a method of stretching the cast raw material sheet in the longitudinal direction (flow direction, MD) by heating it with a heating roll (longitudinal uniaxial roll stretching method); a method of stretching the cast raw material sheet in the transverse direction (width direction, TD) in an oven at a predetermined temperature (generally called a tenter) (transverse uniaxial stretching method); a method of performing transverse uniaxial stretching after longitudinal uniaxial roll stretching (sequential biaxial stretching method); a method of performing transverse uniaxial stretching after longitudinal uniaxial roll stretching, and then longitudinal uniaxial (roll or tenter method) stretching (multi-stage sequential biaxial stretching method); a method of sequentially stretching the cast raw material sheet longitudinally and transversely in a tenter at a predetermined temperature (tenter method sequential biaxial stretching method); a method of simultaneously stretching the cast raw material sheet longitudinally and transversely in a tenter (simultaneous biaxial stretching method); and so on. As for the stretching method, a method in which longitudinal uniaxial roll stretching is followed by transverse uniaxial stretching (sequential biaxial stretching method) is preferable because it provides excellent rigidity, electrical insulation, and stretchability of the stretched film.

[0135] One example of a sequential biaxial stretching method is to maintain a cast raw material sheet at a temperature of approximately 100 to 180°C (longitudinal stretching temperature), pass it between rolls with a speed difference to stretch it 3 to 7 times (longitudinal stretching ratio) in the flow direction, and immediately cool it to room temperature. After cooling, the stretched film is guided to a tenter and stretched at a stretching angle of 5 to 17° (transverse stretching angle) at a temperature of 150°C or higher (transverse stretching temperature) to approximately 3 to 11 times (transverse stretching ratio) in the width direction, after which it can be relaxed, heat-set, and wound up. The wound film can be aged in an atmosphere of approximately 20 to 45°C and then cut to the desired product width. The transverse stretching angle is defined as the angle between a straight line Lx connecting one edge Px in the width direction of the stretched film at the start of the transverse stretching process and the other edge Py (on the same side as Px) in the width direction of the stretched film at the end of the transverse stretching process, and a straight line Ly that starts at Px and is parallel to the extrusion direction.

[0136] The resulting stretched film may be subjected to corona treatment, electrostatic discharge treatment, heating treatment, etc. Appropriate implementation of corona treatment, electrostatic discharge treatment, heating treatment, etc. can improve passability to the vapor deposition process. The heating treatment temperature is preferably 20°C to 80°C, more preferably 25°C to 60°C, and even more preferably 30°C to 55°C. The heating treatment time is preferably 3 hours to 50 hours, and more preferably 6 hours to 30 hours.

[0137] 2. Metal Laminate Film / Film Capacitor The stretched film of the present invention may have a metal layer on one or both sides thereof. That is, a metal laminate film having a metal layer on one or both sides of the stretched film can be obtained using the stretched film of the present invention.

[0138] In a metal laminated film, the metal film can act as an electrode. Examples of the metal film include metal foil, paper with at least one side metallized, and plastic film with at least one side metallized. The metal can be a single metal such as zinc, lead, silver, chromium, aluminum, copper, and nickel, a mixture of several of these, or an alloy thereof. However, considering the environment, economy, and capacitor performance, zinc and aluminum are preferred.

[0139] The metal film can be formed, for example, by vacuum deposition and sputtering, and vacuum deposition is preferred from the viewpoint of productivity and economic efficiency. Vacuum deposition methods generally include the crucible method and the wire method.

[0140] The film resistance of the metal film is preferably about 1 to 100 Ω / □, more preferably 5 Ω / □ or higher, and even more preferably 10 Ω / □ or higher, from the viewpoint of the electrical characteristics of the capacitor. Furthermore, from the viewpoint of safety as a capacitor, the film resistance of the metal film is more preferably 50 Ω / □ or lower, and even more preferably 30 Ω / □ or lower. The film resistance of the metal film can be measured during metal deposition, for example, by the four-terminal method known to those skilled in the art. The film resistance of the metal film can be adjusted, for example, by adjusting the output of the evaporation source to adjust the evaporation rate. For the sake of clarity, in this specification, the unit "Ω / □" means "Ω / square".

[0141] When forming a metal film on one side of the film, an insulating margin is formed from one end of the film without deposition for a certain width, so that the film acts as a capacitor when wound. Furthermore, to strengthen the bond between the metal laminated film and the metallicon 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 is not particularly limited, but for example, 1 to 200 nm is preferred.

[0142] There are no particular restrictions on the margin pattern, and from the standpoint of improving characteristics such as the safety of the capacitor, patterns including so-called special margins such as fishnet patterns and T-margin patterns can be used. As for the method of forming the margin, any known method can be used without any restrictions, such as the tape method, which involves masking with tape during vapor deposition, or the oil method, which involves masking by applying oil.

[0143] The metal laminated film can be processed into the capacitor of the present invention, as described later, by winding it along the longitudinal direction of the film. Specifically, two metal laminated films are stacked as a pair, with the metal vapor-deposited film and polypropylene film alternately laminated and wound together. Then, a pair of metal-coated electrodes are formed on both end surfaces by thermal spraying to produce a film capacitor.

[0144] A capacitor can be manufactured using the above-mentioned metal laminated film for capacitors. As long as the capacitor includes the above-mentioned metal laminated film for capacitors, its other components are not particularly limited; for example, it can have a configuration similar to that of a known capacitor.

[0145] Since the capacitor described above is equipped with the stretched film of the present invention, it can have a high dielectric breakdown voltage, and moreover, the change in dielectric breakdown strength under high-temperature environments is small compared to the dielectric breakdown strength at room temperature (e.g., 25°C). Therefore, even when a voltage of, for example, 200 (Vdc / μm) is continuously applied to the capacitor at a high temperature of 135°C or higher, it will not short circuit and can maintain its insulation and capacitance for more than 500 hours. In other words, the capacitor does not short circuit at 135°C and exhibits little decrease in capacitance even under continuous voltage load.

[0146] The capacitor of the present invention, utilizing the stretched film of the present invention, is suitable for use in high-temperature environments and can be made into a small and high-capacitance capacitor (for example, 5 μF or more, preferably 10 μF or more, and even more preferably 20 μF or more). Therefore, the capacitor of the present invention can be used in electronic equipment, electrical equipment, etc., as a high-voltage capacitor; various switching power supplies; filter capacitors and smoothing capacitors for converters, inverters, etc. Furthermore, the capacitor of the present invention can be suitably used as an inverter capacitor and converter capacitor for controlling drive motors in electric vehicles, hybrid vehicles, etc., for which demand has been increasing in recent years.

[0147] In specifying the inventions contained herein, the components (properties, structures, functions, etc.) described in each embodiment of this disclosure may be combined in any way. That is, this disclosure encompasses all subject matter consisting of any combination of the combinatable components described herein.

[0148] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to the embodiments of these examples.

[0149] (1) Measurement Methods The various measurement methods are as follows:

[0150] (1-1) Mn, Mw, Mz, Mw / Mn, and Mz / Mw of isotactic polypropylene resin The number-average molecular weight (Mn), weight-average molecular weight (Mw), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mw) of isotactic polypropylene resin were measured using GPC (gel permeation chromatography) under the following conditions.

[0151] Specifically, a high-temperature GPC instrument with a built-in differential refractometer (RI), the HLC-8121GPC-HT model, manufactured by Tosoh Corporation, was used. Three TSKgel GMHHR-H(20)HT columns, also manufactured by Tosoh Corporation, were used in conjunction. Measurements were taken at a column temperature of 140°C, with trichlorobenzene flowing as the eluent at a flow rate of 1.0 ml / min. A calibration curve for the molecular weight M was created using standard polystyrene manufactured by Tosoh Corporation, and the measured values ​​were converted to the molecular weight of polypropylene using the Q-factor to obtain the number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz). The molecular weight distribution (Mw / Mn) was obtained using the Mw and Mn values. The molecular weight distribution (Mz / Mw) was also obtained using the Mz and Mw values.

[0152] (1-2) Mesopentad fraction of isotactic polypropylene resin The isotactic polypropylene resin was dissolved in a solvent and measured using a high-temperature Fourier transform nuclear magnetic resonance spectrometer (high-temperature FT-NMR) under the following conditions. High-temperature nuclear magnetic resonance (NMR) spectrometer: JEOL Ltd., high-temperature Fourier transform nuclear magnetic resonance spectrometer (high-temperature FT-NMR), JNM-ECP500 Observed nucleus: 13C (125 MHz) Measurement temperature: 135°C Solvent: Ortho-dichlorobenzene (ODCB: mixed solvent of ODCB and deuterated ODCB (mixing ratio = 4 / 1)) Measurement mode: Single pulse proton broadband decoupling Pulse width: 9.1 μsec (45° pulse) Pulse interval: 5.5 sec Number of integrations: 4,500 Shift reference: CH3 (mmmm) = 21.7 ppm The mesopentad fraction, which represents the degree of stereoregularity, was calculated as a percentage (%) from the integral intensity values ​​of each signal derived from combinations of five pentads (mmmm, mrrm, etc.) consisting of pentads arranged in the same direction ("meso (m)") and pentads arranged in opposite directions ("racemo (r)"). For the assignment of each signal derived from mmmm, mrrm, etc., spectral descriptions such as "T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988)" were consulted.

[0153] (1-3) Melt Mass Flow Rate (MFR) The melt flow rate (MFR) was measured in accordance with JIS K 7210-1:2014 using a melt indexer from Toyo Seiki Co., Ltd. Specifically, first, 4 g of raw material was inserted into a cylinder heated to the test temperature (230°C for isotactic polypropylene resin, and 260°C for polymers with an alicyclic structure), and preheated for 3.5 minutes under a load of 2.16 kgf. Then, the weight of the resin extruded from the bottom hole in 30 seconds was measured, and the MFR (g / 10 min) was determined. The above measurement was repeated three times, and the average value was taken as the measured value of MFR.

[0154] (1-4) Melting point and glass transition temperature The melting point and glass transition temperature were calculated using a Perkin-Elmer input-compensated DSC, DiamondDSC, following the procedure below. 5 mg of each resin was weighed out, packed into an aluminum sample holder, and set in the DSC apparatus. The temperature was increased from 30°C to 230°C at a rate of 20°C / min under a nitrogen flow, held at 230°C for 5 minutes, cooled to 30°C at a rate of 20°C / min, and held at 30°C for 5 minutes. The melting point and glass transition temperature were then determined from the DSC curve when the temperature was increased again to 230°C at a rate of 20°C / min. Specifically, the melting peak (the largest melting peak if multiple melting peaks are shown) as defined in JIS-K7121:1987 9.1(1) was used as the melting point, and the midpoint glass transition temperature as defined in JIS-K7121:1987 9.3(1) was used as the glass transition temperature.

[0155] (1-5) Heptane-insoluble content (HI) of polypropylene resin A sample of approximately 3 g was prepared for measurement by press-molding polypropylene resin to 10 mm x 35 mm x 0.3 mm. Next, approximately 150 mL of heptane was added and Soxhlet extraction was performed for 8 hours. The heptane-insoluble content was calculated from the sample mass before and after extraction.

[0156] (2) In order to prepare the polypropylene resin for obtaining the stretched raw material film, the following isotactic polypropylene resin and polymer having an alicyclic structure were prepared. [A1; Isotactic Polypropylene Resin A1] As isotactic polypropylene resin A1, an isotactic polypropylene resin "Prime Polypro (registered trademark); manufactured by Prime Polymer Co., Ltd." having the following physical properties was prepared. In addition, 3500 ppm by mass of "Irganox 1010" manufactured by BASF Japan Ltd. was pre-mixed into isotactic polypropylene resin A1 as an antioxidant. MFR: 3.5 g / 10 min (measurement temperature 230°C, 2.16 kgf) Melting point: 164°C Mesopentadione fraction: 98.6 mol% Heptane insoluble matter: 98.1 mass% Number average molecular weight (Mn): 49000 Weight average molecular weight (Mw): 390000 Z average molecular weight (Mz): 1,520000 Molecular weight distribution (Mw / Mn): 8.0 Molecular weight distribution (Mz / Mw): 3.9

[0157] [B1; Polymer B1 having an alicyclic structure] As polymer B1 having an alicyclic structure, hydrogenated polystyrene "Vivion® 0645; manufactured by USI Corporation" having the following physical properties was prepared. Glass transition temperature: 143°C (measured by DSC) MFR: 5.5 g / 10 min (measurement temperature 260°C, 2.16 kgf) Such polymer is a polymer having an alicyclic structure with a cyclohexane structure in the side chain, and the cyclohexane structure is formed by hydrogenation of the aromatic ring structure, with a hydrogenation rate of 99 mol% or more.

[0158] [B2; Polymer B2 having an alicyclic structure] As polymer B1 having an alicyclic structure, "Vivion® 1325; manufactured by USI Corporation" having the following physical properties was prepared. Glass transition temperature: 128°C MFR: 13 g / 10 min (measurement temperature 260°C, 2.16 kgf) Polymer B2 is a polymer having an alicyclic structure with a cyclohexane structure in its side chain, and is a hydrogenated block copolymer obtained by hydrogenating a styrene-butadiene diblock copolymer, and is not a hydrogenated polystyrene polymer. The cyclohexane structure is formed by hydrogenation of the aromatic ring structure derived from styrene, and the other structures are formed by hydrogenation of the carbon-carbon double bond derived from butadiene, with a hydrogenation rate of 99 mol% or more.

[0159] (Example 1) A biaxially oriented film was obtained according to the compounding and film-making conditions shown in Table 1. The isotactic polypropylene resin A1 and the polymer B1 having an alicyclic structure were compounded and mixed in amounts of 85% by mass and 15% by mass, respectively (i.e., A1:B1 = 85:15 by mass ratio) to prepare the raw material. After dry blending this raw material, it was supplied to a single-screw type film-making extruder (GM-50, L / D = 32, manufactured by GM Engineering Co., Ltd.) and melted at 265°C. The molten raw material was extruded using a T-die, and then wrapped around a metal drum maintained at a surface temperature of 101°C to solidify, thereby producing a cast raw material sheet (unstretched film) with a thickness of approximately 93 μm. The cast raw material sheet was then stretched 3.9 times in the flow direction at a temperature of 159.5°C, immediately cooled to room temperature, and then stretched 8.6 times in the transverse direction at a temperature of 165°C using a tenter to obtain a biaxially oriented film with an area stretching ratio of 33 times.

[0160] (Example 2) A biaxially oriented film was obtained in the same manner as in Example 1, except that the film was stretched 3.9 times in the flow direction and 8.7 times in the transverse direction, resulting in an area stretching ratio of 34 times.

[0161] (Example 3) A cast raw material sheet with a thickness of approximately 110 μm was prepared by changing the composition so that the isotactic polypropylene resin A1 and the polymer B1 having the alicyclic structure were blended in amounts of 90% by mass and 10% by mass, respectively (i.e., the mass ratio A1:B1 = 90:10). A biaxially oriented film was obtained in the same manner as in Example 1, except that the sheet was stretched 4.2 times in the flow direction and 8.6 times in the transverse direction to achieve an area stretching ratio of 36 times.

[0162] (Example 4) A biaxially oriented film was obtained in the same manner as in Example 3, except that the surface temperature of the metal drum was changed to 98°C, and the film was stretched 4.2 times in the flow direction and 8.8 times in the transverse direction, resulting in an area stretching ratio of 37 times.

[0163] (Example 5) An isotactic polypropylene resin A1 and an isotactic polypropylene resin A2 were used, and these resins were blended with the polymer B1 having the alicyclic structure in amounts of 55.2% by mass, 29.8% by mass, and 15% by mass, respectively (i.e., the mass ratio A1:A2:B1 = 55.2:29.8:15). In addition, the melting temperature of the raw materials was changed to 260°C and the surface temperature of the metal drum to 98°C to produce a cast raw material sheet with a thickness of approximately 80 μm. Furthermore, the sheet was stretched 3.4 times in the flow direction and 7.7 times in the transverse direction to obtain a biaxially oriented film in the same manner as in Example 1, except that the area stretching ratio was 27 times.

[0164] (Example 6) A biaxially oriented film was obtained in the same manner as in Example 1, except that the melting temperature of the raw material was changed to 260°C and the surface temperature of the metal drum to 95°C to produce a cast raw material sheet with a thickness of approximately 75 μm, and the sheet was stretched 3.5 times in the flow direction and 7.5 times in the transverse direction to obtain an area stretching ratio of 27 times.

[0165] (Example 7) A biaxially oriented film was obtained in the same manner as in Example 1, except that the isotactic polypropylene resin A1 and the polymer B1 having the alicyclic structure were blended in amounts of 95% by mass and 5% by mass, respectively (i.e., the mass ratio A1:B1 = 95:5), the surface temperature of the metal drum was changed to 100°C to produce a cast raw material sheet with a thickness of approximately 115 μm, and the sheet was stretched 4.7 times in the flow direction and 8.8 times in the transverse direction to obtain an area stretching ratio of 41 times.

[0166] (Example 8) An isotactic polypropylene resin A1 and polymers B1 and B2 having the alicyclic structure were blended in amounts of 86% by mass, 10% by mass, and 4% by mass, respectively (i.e., the mass ratio A1:B1:B2 = 86:10:4). The melting temperature of the raw materials was changed to 260°C and the surface temperature of the metal drum to 98°C to produce a cast raw material sheet with a thickness of approximately 117 μm. A biaxially oriented film was obtained in the same manner as in Example 1, except that it was stretched 4.2 times in the flow direction and 9.3 times in the transverse direction to achieve an area stretching ratio of 39 times.

[0167] (Example 9) An isotactic polypropylene resin A1 and polymers B1 and B2 having the alicyclic structure were blended in amounts of 84% by mass, 7.2% by mass, and 8.8% by mass, respectively (i.e., the mass ratio A1:B1:B2 = 84:7.2:8.8). The melting temperature of the raw materials was changed to 260°C and the surface temperature of the metal drum to 98°C to produce a cast raw material sheet with a thickness of approximately 117 μm. A biaxially oriented film was obtained in the same manner as in Example 1, except that it was stretched 4.2 times in the flow direction and 9.3 times in the transverse direction to achieve an area stretching ratio of 39 times.

[0168] (Comparative Example 1) Using only isotactic polypropylene resin A1 as the raw material, without using polymer B1 having the alicyclic structure, and changing the melting temperature of the raw material to 260°C and the surface temperature of the metal drum to 95°C, a cast raw material sheet with a thickness of approximately 115 μm was prepared in the same manner as in Example 1. A biaxially oriented film was obtained in the same manner as in Example 1, except that this cast raw material sheet was stretched five times in the flow direction and 7.9 times in the transverse direction at a temperature of 146°C, resulting in an area stretching ratio of 36 times.

[0169] (Comparative Example 2) An isotactic polypropylene resin A1 and the polymer B2 having the alicyclic structure were blended in amounts of 86% by mass and 14% by mass, respectively (i.e., the mass ratio A1:B2 = 86:14), and a cast raw material sheet with a thickness of approximately 123 μm was prepared by changing the surface temperature of the metal drum to 95°C. A biaxially oriented film was obtained in the same manner as in Example 1, except that it was stretched 4.7 times in the flow direction and 8.8 times in the transverse direction to achieve an area stretching ratio of 41 times.

[0170] (Evaluation Method) <Volume Resistivity> The measurement method of the volume resistivity was carried out according to the following procedure. However, in the following description, the measurement conditions not specifically described complied with JIS C 2139-3-1:2018. First, a jig for measuring volume resistivity (hereinafter simply referred to as "jig") was placed in a thermostatic bath at 145°C. The configuration of the jig for measuring volume resistivity was as follows. Also, a DC power supply and a DC ammeter were connected to each electrode of the jig. The jig had a main electrode (diameter 50 mm), a counter electrode (diameter 85 mm), and a ring-shaped guard electrode (outer diameter 80 mm, inner diameter 70 mm) surrounding the main electrode was used. Each electrode was made of copper plated with gold, and conductive rubber was attached to the surface in contact with the sample. The conductive rubber used was EC-60BL (W300) manufactured by Shin-Etsu Silicone Co., Ltd., and the shiny surface of the conductive rubber was attached so as to contact the copper plated with gold. Next, the stretched film (hereinafter also referred to as the sample) was set on the jig in the thermostatic bath. Specifically, the main electrode and the guard electrode were adhered to one surface of the stretched film, the counter electrode was adhered to the other surface, the stretched film and each electrode were adhered with a load of 5 kgf, and then left standing for 30 minutes. Then, a voltage was applied to the sample so that the potential gradient became 100 V / μm. After the voltage was applied, the current value at the time when 1 minute had elapsed was read, and the volume resistivity was calculated by the following formula. For the application of the voltage, a 2290-10 (DC power supply) manufactured by Keithley was used, and for the measurement of the current value, a 2635B (DC ammeter) manufactured by Keithley was used. The volume resistivity was calculated by the following formula. Volume resistivity = [(effective electrode area) × (applied voltage)] / [(thickness of the stretched film) × (current value)] Here, the effective electrode area was obtained by the following formula. (Effective electrode area) = π × [[[(diameter of the main electrode) + (inner diameter of the guard electrode)] / 2] / 2] ２ Here, let the effective electrode area be S (cm ２ ), the diameter of the main electrode be DM (cm), and the inner diameter of the guard electrode be DG (cm). Then, S = π × [{(DM + DG) ÷ 2} ÷ 2] ２ And the simplified form was the following formula. S = π × (DM + DG) ２ / 16 In this measurement, the effective electrode area was not defined as the area of ​​the main electrode, but rather as the portion of the space between the main electrode and the guard electrode that is the same distance from or closer to the main electrode. This enabled more accurate measurement of the current value. Furthermore, in this measurement, the volume resistivity ρ at 145°C was used. Ｖ１４５℃ ρ was calculated using the following formula I. Ｖ１４５℃ = (S × V) / (D × A １ ) (I) In equation (I), V is the applied voltage determined according to the thickness of the stretched film, in the range of V = 270 to 320 V (minimum value is 2.7 μm × 100 V / μm = 270 V, and maximum value is 3.2 μm × 100 V / μm = 320 V), and S is the effective electrode area, S = 28.27 cm². ２ D is the thickness of the stretched film (0.00027 to 0.00032 cm), and A １ This is the detected current value at 145°C after 1 minute, and the detected value A １ = 0.9 × 10 －８ ~8 x 10 －８ A was used.

[0171] Next, the sample was placed in a jig in a constant temperature bath at 40°C, and a load was applied to ensure close contact between the stretched film and each electrode. After standing for 30 minutes, a voltage was applied to the sample to achieve a potential gradient of 100 V / μm. The current value was read 1 minute after the voltage was applied, and the volume resistivity ρ at 40°C was determined. Ｖ４０℃ ρ was calculated from Equation II. Ｖ４０℃ = (S × V) / (D × A ２ ) (II) In equation (II), V is the applied voltage determined according to the thickness of the stretched film as described above, in the range of V = 270 to 320 V, and S is the effective electrode area, S = 28.27 cm². ２ D is the thickness of the stretched film (0.00027 to 0.00032 cm), and A ２ This is the detected current value at 40°C after 1 minute, and the detected value A ２ = 1 × 10 －９ ~9 x 10 －９ A was used.

[0172] <Evaluation of Surface Roughness Characteristics> The protruding peak height Spk, arithmetic mean height Sa, and protruding valley depth Svk of the stretched films obtained in the examples and comparative examples were measured as follows. A VertScan 2.0 (model: R5500GML) manufactured by Ryoka Systems Co., Ltd. was used as the optical interferometry non-contact surface shape measuring instrument. As a sample for measurement, the film was cut to an arbitrary size of about 20 cm square, and with the wrinkles sufficiently smoothed out, it was set on the measurement stage using an electrostatic contact plate or the like. Wave mode was used for measurement, and a 530 white filter and a 1×BODY microscope tube were applied, and observations were made for each field of view (470.92 μm × 353.16 μm) using a 10x objective lens. This operation was performed at five locations (total of 10 locations) at 1 cm intervals in both the flow direction and the width direction, starting from the center of the chill roll side surface of the target sample, and data was obtained. The data obtained from the above measurements was subjected to noise reduction using a median filter (3x3), followed by Gaussian filtering with a cutoff value of 30 μm to remove waviness components. This made it possible to appropriately measure the condition of the roughened surface. Next, analysis was performed using the "ISO parameters" in the "Bearing" plugin function of the "VS-Viewer" analysis software of "VertScan2.0". The arithmetic mean height Sa (μm), protruding peak height Spk (μm), and protruding valley depth Svk (μm) were determined as various surface roughness parameters specified in ISO 25178, and the average value of each value obtained at the above 10 locations was calculated. Measurements were taken on both the front and back surfaces, and the value from the larger surface was adopted for all parameters.

[0173] <Element Fabrication> An aluminum metal layer was formed on the polypropylene film described above using a vapor deposition apparatus (ULVAC, Inc., product name: EWE-060 roll-type vacuum vapor deposition apparatus) so that the surface resistivity of the metal film was 20 Ω / □. At this time, vapor deposition was performed using the oil margin method so that after slitting, an insulating groove (insulating margin: length 1 mm in the width direction) continuous in the longitudinal direction of the film was formed at one end in the width direction of the film. After slitting this film, a metallized film with a total width of 30 mm was obtained. The thickness of the metallized film was 3 μm.

[0174] Next, two metallized films were joined together. Using a 3KAW-N2 automatic winding machine manufactured by Kaito Manufacturing Co., Ltd., the joined metallized films were wound 970 times at a winding tension of 140-180g, a contact pressure of 200-255g, and a winding speed of 4m / s. The element wound with this winding was subjected to a load of 5.2kg / cm ２ The element was heat-treated at 135°C for 15 hours while being pressed. After that, zinc metal was sprayed onto the end faces of the element. The spraying conditions were a feed rate of 15 mm / s, a spraying voltage of 22 V, and a spraying pressure of 0.3 MPa, and the spraying was carried out to a thickness of 0.7 mm. A flat capacitor was thus obtained. Lead wires were soldered to the end faces of the flat capacitor. After that, the flat capacitor was sealed with epoxy resin. The epoxy resin was cured by heating at 90°C for 2.5 hours, followed by heating at 120°C for another 2.5 hours. The capacitance of the finished capacitor was 20 μF.

[0175] [Evaluation of element safety at 135°C] The capacitors obtained above were preheated at 135°C for 1 hour, and their capacitance was measured using a Keysight LCR meter E4980AL (initial capacitance). Next, a DC voltage of 280V was applied to the capacitors for 1 hour in a constant temperature chamber at 135°C. The capacitance of the capacitors after the voltage was applied was measured again, and the capacitance change rate before and after the test was calculated using the following formula: (Capacitance change rate) = [(Capacitance after voltage application) - (Initial capacitance)] / (Initial capacitance) × 100 (%) Then, the capacitors were returned to the constant temperature chamber, and the voltage was increased by 50V increments, and the capacitance change rate was measured repeatedly. The test was performed using five capacitors, and measurements were taken until the capacitance change rate reached -95% or less. Capacitors that short-circuited and lost insulation before the capacitance change rate reached -95% or less were considered defective, and further testing was not performed on them. Here, a short circuit failure was determined when the capacitor's resistance value fell below 10 kΩ. A Hioki Electric Corporation DSM-8104 super-insulation meter was used as the measuring device. The upper limit of the current measurement range of this device is 10 mA. When the current value at an applied voltage of 100 V exceeded the upper limit of the measurement range, the capacitor's resistance value was considered to be below 10 kΩ, and safety was evaluated according to the following evaluation criteria. ○: All of the five capacitors reached a capacitance change rate of -95% or less, and the resistance value was greater than 10 kΩ. △: Of the five capacitors, the resistance value fell below 10 kΩ before the capacitance change rate of one capacitor fell below -95%. ×: Of the five capacitors, the resistance value fell below 10 kΩ before the capacitance change rate of two or more capacitors fell below -95%.

[0176] [Insulation Resistance Values ​​at 120°C and 135°C] A heat-resistant cable was wired to a HIOKI DSM-8104 super insulation resistance meter so that it could be connected to a capacitor in a constant temperature bath. The applied voltage during measurement was set to 540V, the discharge time before measurement was 1 second, the discharge time after measurement was 10 seconds, and the measurement time was 1 minute. This measurement time is also the voltage application time. After preheating the capacitor in a constant temperature bath at 120°C for 1 hour and 30 minutes, the DSM-8104 super insulation resistance meter was connected in the constant temperature bath. After leaving it for 3 minutes until the temperature stabilized, the application of DC voltage and measurement of the insulation resistance value were started. The obtained value was taken as the insulation resistance value of the capacitor at 120°C. Subsequently, the temperature of the constant temperature bath was raised to 135°C and the capacitor was preheated for 1 hour. Then, the DSM-8104 super insulation resistance meter was connected, and the application of DC voltage and measurement of the insulation resistance value were performed in the same manner. The obtained value was taken as the insulation resistance value of the capacitor at 135°C.

[0177] <Film Thickness> The thickness of the stretched film was measured in accordance with JIS-C2330:2014, except that it was measured at 100 ± 10 kPa using a Citizen Seimitsu MEI-11 paper thickness gauge.

[0178] <X-ray Diffraction Intensity Measurement (XRD)> The X-ray diffraction intensity of the stretched film was measured using an XRD (wide-angle X-ray diffraction) device (manufactured by Rigaku Corporation) under the following conditions. Measurement device: Rigaku Corporation, X-ray diffractometer Mini-FLEX300 X-ray source: CuKα monometer wave (wavelength: 0.15418 nm) Irradiation output: 30 KV - 10 mA Scattering slit: 1.25 deg Receiving slit: 1.25 deg Scanning axis: 2θ / θ Scanning speed: 0.5 deg / min From the obtained data, the interplanar spacing values ​​d of the diffraction lines of the α-crystal (110) plane and (040) plane were calculated using an analysis computer and the integrated powder X-ray analysis software PDXL (Ver. 2.1.3.4) included as standard with the device.

[0179] <Infrared Absorption Spectrum Measurement (IR)> The infrared absorption spectrum of the stretched film was measured using a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation). A prism was placed in close contact with the stretched film (sample), and the absorbance spectrum against wavenumber was measured using the ATR method under the following conditions: Measurement device: JASCO Corporation, Fourier transform infrared spectrophotometer FT / IR-4000 ATR unit: ATR-PRO410-M Prism: ZnSe Incident angle: 45° Scanning range: 4000 cm －１ ~650cm －１ Integration number: Auto (121 times) Resolution: 4cm －１ Gain: Auto Aperture: Auto Scan Speed: Auto Filter: Auto

[0180] (Evaluation Results) Table 1 shows the manufacturing conditions for the stretched films obtained in each example and comparative example. In Table 1, A1 refers to isotactic polypropylene resin A1, A2 refers to "isotactic polypropylene resin A2", B1 refers to "polymer B1 having an alicyclic structure", and B2 refers to "polymer B2 having an alicyclic structure". Also in Table 1, the mirror metal roll temperature refers to the "surface temperature of the metal drum".

[0181] Table 2 shows the physical properties and evaluation results of the stretched films obtained in each example and comparative example. In Table 2, ρ Ｖ１４５℃ ρ is the volume resistivity of the stretched film under a 145°C environment. Ｖ４０℃ ρ is the volume resistivity of the stretched film in a 40°C environment. Ｖ１４５℃ / ρ Ｖ４０℃ This refers to the ratio of the volume resistivity of the stretched film at a 145°C environment to the volume resistivity of the stretched film at a 40°C environment.

[0182] Furthermore, in Table 2, the infrared absorption spectrum is 880–890 cm⁻¹. －１ Absorption peaks are observed in the range, and at 1450 cm. －１ If a shoulder peak due to absorption was observed in the vicinity, it was indicated as "present," and if not observed, it was indicated as "absent."

[0183] Table 1 shows the ρ under a 145°C environment. Ｖ１４５℃ 8.0 x 10 １４ Stretched film or ρ that is Ω·cm or larger Ｖ１４５℃ / ρ Ｖ４０℃ It was also found that stretched films with a ratio of 0.05 or higher exhibit high insulation resistance values ​​at 120°C and 135°C, and can provide excellent safety performance to capacitor elements.

[0184] Figure 1 shows the results of the infrared absorption spectrum of the stretched film, where (a) shows the infrared absorption spectrum measurement at 850–950 cm⁻¹. －１ (b) is within the range of 1400-1500 cm. －１ This indicates the range.

[0185] From Figure 1, the infrared absorption spectra of the stretched films obtained in Examples 1 to 7 were 880 to 890 cm⁻¹. －１ Absorption peaks are observed in the range, and at 1450 cm. －１ It can be seen that there is a shoulder peak due to absorption in the vicinity.

[0186]

[0187]

Claims

1. A stretched film containing a polypropylene resin, wherein the following formula (I) ρ Ｖ１４５℃ = (S × V) / (D × A １ ) (I) (In equation (I), ρ Ｖ１４５℃ Ω is the volume resistivity (Ω·cm) at a temperature of 145°C, and S is the effective electrode area (cm²). ２ ) where V is the applied voltage (V), D is the thickness of the stretched film (cm), A １ (This is the detected current value at 1 minute after applying a voltage with a potential gradient of 100 V / μm to a stretched film in a 145°C environment.) The volume resistivity ρ in a 145°C environment is calculated from this value. Ｖ１４５℃ 8.0 x 10 １４ A stretched film with dimensions of Ω·cm or greater.

2. A stretched film containing a polypropylene-based resin, wherein the volume resistivity ρ at 145 °C is calculated from the following formula (I): Ｖ１４５℃ = (S × V) / (D × A １ )(I) (In formula (I), ρ Ｖ１４５℃ is the volume resistivity (Ω·cm) at 145 °C, S is the effective electrode area (cm ２ ), V is the applied voltage (V), D is the thickness of the stretched film (cm), and A １ is the current value at the time point of 1 minute after applying a voltage to the stretched film at a potential gradient of 100 V / μm in an environment of 145 °C). The volume resistivity ρ Ｖ１４５℃ at 145 °C and the volume resistivity ρ Ｖ４０℃ calculated from the following formula (II): ２ = (S × V) / (D × A Ｖ４０℃ )(II) (In formula (II), ρ ２ is the volume resistivity (Ω·cm) at 40 °C, S is the effective electrode area (cm ２ ), V is the applied voltage (V), D is the thickness of the stretched film (cm), and A Ｖ４０℃ is the detected value of the current value at the time point of 1 minute after applying a voltage to the stretched film at a potential gradient of 100 V / μm in an environment of 40 °C). The ratio (ρ Ｖ１４５℃ / ρ Ｖ４０℃ ) of them is 0.05 or more. A stretched film.

3. The stretched film according to claim 1 or 2, wherein the height Spk of the protruding peaks on at least one surface is 0.01 μm or more and 0.15 μm or less.

4. The stretched film according to claim 1 or 2, wherein the arithmetic mean height Sa of at least one surface is 0.008 μm or more and 0.050 μm or less.

5. The stretched film according to claim 1 or 2, wherein the depth Svk of the protruding valleys on at least one surface is 0.01 μm or more and 0.06 μm or less.

6. The stretched film according to claim 1 or 2, wherein, in X-ray diffraction intensity measurement, the crystallite size determined by Scherrer's formula based on the full width at half maximum of the (110) plane derived from the α-crystal of isotactic polypropylene is 105 Å or more, and the ratio of the crystallite size of the (110) plane to the crystallite size of the (040) plane, "(110 plane) crystallite size / (040) plane crystallite size", is 1.0 or more.

7. In infrared absorption spectroscopy, 880–890 cm⁻¹ －１ Absorption peaks are observed in the range, and at 1450 cm. －１ The stretched film according to claim 1 or 2, having at least one of the shoulder peaks due to absorption in the vicinity.

8. The stretched film according to claim 1 or 2, wherein the polypropylene resin contains 55% by mass or more and 99% by mass or less isotactic polypropylene resin and 1% by mass or more and 45% by mass or less a polymer having an alicyclic structure.

9. The stretched film according to claim 8, wherein the polymer having the alicyclic structure comprises two or more polymers with different glass transition temperatures.

10. The stretched film according to claim 8, wherein the polymer having an alicyclic structure comprises polymer B1 having an alicyclic structure with a glass transition temperature of 133°C or more and 155°C or less, and polymer B2 having an alicyclic structure with a glass transition temperature of 70°C or more and less than 133°C.

11. The stretched film according to claim 10, wherein the mass ratio B2 / B1 of polymer B2 to polymer B1 is less than 0.

85.

12. The stretched film according to claim 8, wherein the polymer having the alicyclic structure contains hydrogenated polystyrene.

13. The stretched film according to claim 12, wherein the hydrogenated polystyrene has an atactic structure and a hydrogenation rate of 95% or more.

14. The stretched film according to claim 1 or 2, wherein the thickness is 1.8 μm or more and 10 μm or less, and the total light transmittance is 80% or more.

15. A metal laminated film having a metal layer on one or both sides of the stretched film according to claim 1 or 2.

16. A film capacitor comprising the metal laminated film described in claim 15.

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