WO2015199184A1

WO2015199184A1 - Stretched film

Info

Publication number: WO2015199184A1
Application number: PCT/JP2015/068369
Authority: WO
Inventors: 正紀羽田; 吉田　哲男
Original assignee: 帝人株式会社
Priority date: 2014-06-27
Filing date: 2015-06-25
Publication date: 2015-12-30
Also published as: CN106459448B; CN106459448A

Abstract

Provided is a syndiotactic polystyrene–based resin alignment film having excellent windability and shaving resistance, or a stretched film that is suitable for use in particular as a film capacitor and has excellent particle dispersibility, dielectric breakdown characteristics, shaving resistance, and handling properties including windability. Specifically, the stretched film comprises a resin composition that contains a syndiotactic styrene–based polymer and also contains porous particles having an average particle diameter of 0.5–5.0 µm, the content of the porous particles being 0.01–3 mass% relative to the mass of the resin composition. The stretched film satisfies either of the following conditions: (1) the resin composition contains a silicone oil, with the content of the silicone oil being 0.1–3 mass% relative to the mass of the porous particles; or (2) the porous particles are porous silica particles having an average particle diameter A of 0.5–5 µm and a di-n-butylamine adsorption (DBA) value of 200 millimoles/kg or less.

Description

Stretched film

The first aspect of the present invention relates to an oriented film composed of a styrene polymer having a syndiotactic structure, and more specifically, a stretched film composed of a styrene polymer having a syndiotactic structure with improved winding and scraping properties. It is about.

The second aspect of the present invention relates to a stretched film made of a resin composition with improved dispersibility of porous silica particles. More specifically, handling properties such as winding property, abrasion resistance, and dielectric breakdown characteristics made of a resin composition with improved dispersibility of porous silica particles in a polystyrene resin having a syndiotactic structure have been improved. In particular, the present invention relates to a stretched film suitable for a film capacitor.

Conventionally, a film capacitor is manufactured by a method in which a film such as a biaxially oriented polyethylene terephthalate film or a biaxially oriented polypropylene film and a metal thin film such as an aluminum foil are overlapped and wound or laminated. In recent years, with the demand for miniaturization of electric or electronic circuits, film capacitors have also been miniaturized and mounted, and further heat resistance has been demanded in addition to electrical characteristics. In automotive applications, the range of use extends not only in the cab, but also in the engine room. In addition to electrical characteristics, film capacitors that are suitable for environments with higher temperatures and higher humidity are required. Yes.

In response to this requirement, Japanese Patent Application Laid-Open Nos. 2-143951, 3-124750, 5-200858 and International Publication No. 2008/156210 have synergy excellent in heat resistance and electrical characteristics. A method using an tactic polystyrene film has been proposed. However, since it is difficult to form a film as compared with a conventionally used polyester film and the film is easily torn, an improvement in handling at the time of producing a capacitor is also demanded. As a method for improving the film forming property and handling property, a powder filler is generally added to the resin. However, in the case of a normally used powder filler, when a syndiotactic polystyrene resin is used as a film, the winding is performed. It has been difficult to achieve both take-off and wear resistance.

In response to such demands, Japanese Patent Application Laid-Open No. 2000-173855 uses a polyethylene-2,6-naphthalenedicarboxylate film having higher heat resistance than a polyethylene terephthalate film or a polypropylene film. A method for improving electrical characteristics by controlling viscosity or the like has been proposed. However, since polyethylene-2,6-naphthalenedicarboxylate is a polar polymer, there is a limit to improving the electrical characteristics.
Japanese Patent Laid-Open No. 2-143851 Japanese Patent Laid-Open No. 3-124750 Japanese Patent Laid-Open No. 5-200858 International Publication No. 2008/156210 Pamphlet JP 2000-173855 A

The first aspect of the present invention has been made in view of the above-described background art, and an object thereof is to provide a stretched film of a syndiotactic polystyrene resin that is excellent in winding property and abrasion resistance.

The second aspect of the present invention has been made in view of the above-described background art, and its purpose is excellent in particle dispersibility in a polystyrene resin having a syndiotactic structure, handling properties such as winding property, and abrasion resistance. Another object of the present invention is to provide a stretched film that is excellent in dielectric breakdown characteristics (dielectric breakdown voltage, variation thereof) and can be suitably used particularly for a film capacitor.

It should be noted that the stretched film in the present invention can be said to be an oriented film in which molecular chains are oriented by stretching, and is hereinafter sometimes referred to as an oriented film in the first invention.

The present inventors diligently studied various inert particles in order to achieve the above object. At that time, porous particles capable of suppressing the generation of voids were examined for polyester and the like, but syndiotactic polystyrene resin did not provide the same effect as polyester film. However, surprisingly, when porous particles were used in combination with silicone oil, it was found that the above problems could be solved, and the first invention was reached.

Thus, according to the first aspect of the present invention, the resin composition comprising a syndiotactic styrene polymer, porous particles having an average particle size of 0.5 to 5.0 μm and silicone oil, The content is in the range of 0.01% by mass to 3% by mass based on the mass of the resin composition, and the content of silicone oil is 0.1-3% by mass based on the mass of the porous particles. A stretched film having a range (hereinafter referred to as an oriented film in the first invention) is provided.

In addition, as a result of intensive investigations to achieve the above object, the present inventors have found that a resin composition in which porous silica particles having specific surface characteristics are blended in a polystyrene-based resin having a syndiotactic structure includes the particles. Stretched film with excellent dispersibility, small voids when formed into a stretched film after dilution with a base resin as necessary, and good handling, dielectric breakdown, and abrasion resistance for film capacitors Has been found to be easily obtained, and has reached the second aspect of the present invention.

Thus, according to the second present invention, a resin composition comprising a polystyrene-based resin having a syndiotactic structure and porous silica particles having an average particle diameter A of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less. The stretched film is a stretched film having a content of the porous silica particles of 0.01% by mass or more and 3% by mass or less based on the amount of the resin composition material.

As described above, according to the present invention, the first and second aspects of the present invention are provided. Specifically, it comprises a resin composition comprising a styrene polymer having a syndiotactic structure and porous particles having an average particle size of 0.5 to 5.0 μm, and the content of the porous particles is the same as that of the resin composition. A range of 0.01% by weight to 3% by weight based on the weight,
(1) The resin composition contains silicone oil, and the silicone oil content is in the range of 0.1 to 3% by mass based on the mass of the porous particles, or (2) the porous particles are There is provided a stretched film characterized by satisfying any one of porous silica particles having an average particle diameter A of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less.

The stretched film of the first aspect of the present invention has a high degree of winding property and wear resistance in the obtained oriented film while using a polystyrene polymer having a syndiotactic structure excellent in electrical characteristics and heat resistance. Can be made.

Moreover, according to the first aspect of the present invention, an oriented film having a high dielectric breakdown voltage and a small standard deviation can be obtained, and it can be suitably used as a base film for a film capacitor that is extremely thin and difficult to handle. .

Since the stretched film of the second present invention contains a specific amount of porous silica particles having a specific particle size and a specific surface property in a polystyrene-based resin having a syndiotactic structure excellent in heat resistance and electrical properties, The dispersibility of the particles is extremely good, the voids generated due to the particles are small, the handleability, the dielectric breakdown characteristics, and the abrasion resistance are excellent, and it is particularly suitable for a film capacitor.

First, the oriented film of the first invention will be described.

The oriented film of the present invention comprises a resin composition comprising a styrene polymer having a syndiotactic structure, porous particles having an average particle size of 0.5 to 5.0 μm, and silicone oil.

The polystyrene resin having a syndiotactic structure in the present invention (hereinafter sometimes referred to as “syndiotactic polystyrene resin” or “SPS”) is used as a main chain formed of carbon-carbon bonds. The side chain has a three-dimensional structure in which phenyl groups and substituted phenyl groups are alternately positioned in opposite directions. In general, tacticity is quantified by an isotope carbon nuclear magnetic resonance method ( ¹³ C-NMR method). Specifically, it can be indicated by the abundance ratio of a plurality of consecutive structural units, for example, a dyad in the case of two, a triad in the case of three, a pentad in the case of five. In the present invention, the polystyrene-based resin having a syndiotactic structure is polystyrene, poly (alkyl) having a syndiotacticity of 75% or more, preferably 85% or more, or 30% or more, preferably 50% or more, of pentad. Styrene), poly (halogenated styrene), poly (alkoxystyrene), poly (vinyl benzoate), polymers in which a part of these benzene rings are hydrogenated, mixtures thereof, or structural units thereof. The copolymer containing is designated. Here, poly (alkyl styrene) includes poly (methyl styrene), poly (ethyl styrene), poly (propyl styrene), poly (butyl styrene), poly (phenyl styrene), and the like. ) Include poly (chlorostyrene), poly (bromostyrene), poly (fluorostyrene) and the like. Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene).

Among these, preferred polystyrene resins include polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (p-tertiarybutylstyrene), poly (p-chlorostyrene), and poly (m- Chlorostyrene), poly (p-fluorostyrene), and a copolymer of styrene and p-methylstyrene. Among them, polystyrene is preferable.

Further, in the case where the polystyrene resin in the present invention is used as a copolymer containing a copolymer component, as its comonomer, in addition to the above-mentioned polystyrene resin monomer, ethylene, propylene, butene, hexene, octene. Olefin monomers such as diene monomers such as butadiene and isoprene, cyclic diene monomers, polar vinyl monomers such as methyl methacrylate, maleic anhydride, and acrylonitrile.

The weight average molecular weight of this syndiotactic polystyrene resin is preferably 1.0 × 10 ⁴ to 3.0 × 10 ⁶ , more preferably 5.0 × 10 ⁴ to 1.5 × 10 6. ⁶ , particularly preferably 1.1 × 10 ⁵ to 8.0 × 10 ⁵ . By setting the weight average molecular weight to 1.0 × 10 ⁴ or more, preferably 5.0 × 10 ⁴ or more, and particularly preferably 1.1 × 10 ⁵ or more, the strength and elongation characteristics are excellent and the heat resistance is further improved. A molded product such as a film can be obtained. Further, when the weight average molecular weight is 3.0 × 10 ⁶ or less, preferably 1.5 × 10 ⁶ or less, particularly preferably 8.0 × 10 ⁵ or less, the stretching tension is in a suitable range, and at the time of film formation, etc. Breakage and the like are less likely to occur.

The porous particles contained in the oriented film of the present invention must have an average particle size of 0.5 to 5 μm, preferably 0.8 to 2.5 μm. When this average particle diameter is less than 0.5 μm, the slipping property of the film is insufficient, and the winding property and handling property become insufficient. On the other hand, when it exceeds 5 μm, the diameter of voids formed around the particles by stretching or the like becomes large, which is not preferable. The content of the particles is 0.01 to 3% by mass, more preferably 0.02 to 1% by mass, particularly preferably 0.05 to 0.5% by mass, based on the amount of the resin composition substance. There is a need to. If this content is less than the lower limit, the slipping property is insufficient and the winding property becomes poor. On the other hand, if the upper limit is exceeded, the abrasion resistance becomes insufficient, and the dielectric breakdown characteristics and film-forming stretchability are impaired.

In view of the above, the porous particles used in the present invention preferably have an average particle size of 0.5 to 5 μm, more preferably 0.8 to 2.5 μm. The porous particles used in the present invention may further have a compressibility (at 0.2 gf load: measured by a micro compression test MCTM-200 manufactured by Shimadzu Corporation) of 20 to 90%, particularly 50 to 85%. preferable. When this value is less than the lower limit, for example, when it is a stretched film, the effect of improving the abrasion resistance is poor. On the other hand, if the upper limit is exceeded, for example, when a stretched film is formed, the particles are crushed and protrusion formation is insufficient, and the effect of improving the winding property is reduced. When the compression ratio is in the above-described appropriate range, the particles are appropriately deformed by the stress at the time of processing into a stretched film or the like, and it becomes easy to achieve both high winding properties and wear resistance.

As such porous particles, particles known per se can be used, and porous silica particles are particularly preferred. The production method of the porous silica particles is not particularly limited, and a known method produced by a conventionally known method such as a sol-gel method or a precipitation method can be used. Among them, those having a pore volume in the range of 0.4 to 2.5 ml / g, particularly 1.2 to 1.8 ml / g are preferable, and those having an average pore diameter in the range of 5 to 25 nm. Is preferred.

The oriented film of the present invention further uses silicone oil as described above. The content of the silicone oil is in the range of 0.1 to 3% by mass, preferably 0.2 to 2.0% by mass, based on the mass of the porous particles. When the content of the silicone oil is less than the lower limit, the dispersibility of the porous particles is deteriorated to form coarse aggregated particles, resulting in poor film-forming stretchability and poor abrasion resistance. On the other hand, when the upper limit is exceeded, silicone oil may bleed out on the surface of the film and contaminate the processing process.

The silicone oil referred to here is a silicone compound having a dialkylsiloxane component as a main repeating unit, and has a linear structure having a siloxane bond of 2000 or less. For example, polysiloxane side chain, dimethylpolysiloxane having all methyl groups at the ends, methylphenyl polysiloxane having a part of the polysiloxane side chain having a phenyl group, and methyl having a part of the side chain of the polysiloxane having hydrogen Examples thereof include straight silicone oils such as hydrogen polysiloxane, and other modified silicone oils in which an organic group is introduced at the side chain and terminal. Organic groups introduced into the modified silicone oil include monoamine groups, diamine groups, amino groups, epoxy groups, alicyclic epoxy groups, mercapto groups, carboxyl groups, polyether groups, aralkyl groups, fluoroalkyl groups, and long-chain alkyl groups. Higher fatty acid ester groups, higher fatty acid amide groups, methacrylic groups, carboxyl groups, phenol groups, silanol groups and the like. Of these, dimethylpolysiloxane is preferred because of its excellent heat resistance.

The method of blending the silicone oil into the film is not particularly limited, but the method of directly dropping or applying to the porous particles, spraying with a spray, etc., and stirring in a mixer or the like is selectively applied to the surface of the porous particles. The silicone oil is preferable because it is easy to be present.

The porous particles subjected to the silicone oil adhesion treatment may be added at the polymerization stage of the resin material, or may be added to the resin material obtained by polymerization by a melt-kneading method, and there is no particular limitation. For example, the resin material is first charged into a melt kneader such as a method of melt kneading by supplying the porous particle powder and the resin material from the same supply port of the melt kneader, or a biaxial kneading extruder with a vent. Alternatively, a method may be used in which the porous particles are added to the melted portion of the resin material and melt kneaded. Among them, a method is preferable in which the particles to which the silicone oil is adhered and the resin pellets or resin powder are mixed in advance and then fed into a vented twin-screw kneading extruder. According to such a method, since the particles are attached to the surface of the resin pellets or resin powder, when the crushing progresses inside the kneader, the contact distance between the particles and the resin is extremely small, so that the dispersibility is high. It is estimated that it will further improve.

As a twin screw kneading extruder with a vent, a particle addition port is provided in a full flight part of a screw arranged inside a vented twin screw kneading extruder, and a feed blade and a return blade for kneading and dispersing particles are provided. It is preferable to use a device in which at least one rotor segment having at least one rotor segment is provided downstream from the addition port in the axial direction of the screw. Here, the vent line is for removal of by-products from the resin. Further, the vented twin-screw kneading extruder preferably has 1 to 3 rotor segments. If there is no rotor segment, the kneading dispersibility of the particles will be reduced, and if the rotor segment exceeds three locations, the propulsive force of the resin will be reduced and venting will be likely to occur. Moreover, it is preferable to have a kneading disk for supplementing the kneading dispersion of the porous particles.

In the oriented film of the present invention, the number of coarse aggregated particles having a maximum length of 25 μm or more in the film is preferably 10 or less per 1 m ² , more preferably 5 / m ² or less, and particularly preferably 3 / m ² or less. If the number of coarse agglomerated particles is larger than the upper limit, uneven projections are generated on the surface of the film, which is inappropriate because a winding shift is deteriorated and workability is lowered when a wound film is formed. Moreover, it becomes a starting point of a fracture | rupture in a film forming extending | stretching process, and since a drawability becomes unstable, it is not preferable.

In the oriented film of the present invention, particles B different from the porous particles can be added in addition to the porous particles as long as the object of the present invention is not impaired. The particles B in the present invention preferably play a role of forming smaller protrusions because the porous particles described above form relatively large protrusions. From such a viewpoint, the particle B is preferably smaller in particle size than the above-described porous particles, and particles that are less likely to aggregate due to the smaller particle size are preferable. The average particle diameter A of the particles B is preferably 0.01 μm or more and less than 0.5 μm. More preferably, it is 0.1 μm or more and less than 0.4 μm. If the average particle diameter A is less than the lower limit, sufficient slipperiness cannot be obtained, which is not preferable. On the other hand, if the average particle diameter A exceeds the upper limit, the abrasion resistance deteriorates, which is not preferable.

The content of the particles B in the present invention is preferably 0.5% by weight or less based on the mass of the oriented film. When the content is increased, the dielectric breakdown voltage may be lowered because the frequency of voids due to particles increases. From such a viewpoint, it is more preferably 0.5% by weight or less, and particularly preferably 0.2% by weight or less.

Various kinds of particles B can be used, and spherical particles having a small specific surface area are preferable. In addition, the spherical shape in the present invention means a shape in which the ratio of the maximum major axis to the area circle equivalent diameter is 1.5 or less, preferably 1.2 or less, when image analysis is performed on the particle shape. Specific particles are not particularly limited, and are known per se (1) silicon dioxide (including hydrate, silica sand, quartz and the like); (2) alumina in various crystal forms; (3) SiO ₂ Silicates containing 30% by weight or more of components (for example, amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), warm asbestos, zircon, fly ash, etc.); (4) Mg Oxides of Zn, Zn, Zr, and Ti; (5) sulfates of Ca and Ba; (6) phosphates of Li, Ba, and Ca (including monohydrogen and dihydrogen salts); (7) Benzoates of Li, Na, and K; (8) terephthalates of Ca, Ba, Zn, and Mn; (9) Mg, Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co, And Ni titanates; (10) Ba and Pb chromium (11) Carbon (eg, carbon black, graphite, etc.); (12) Glass (eg, glass powder, glass beads, etc.); (13) Carbonate of Ca and Mg; (14) Fluorite; (15) (16) Crosslinked organic particles (silicone, polystyrene particles, etc.), but from the viewpoint of obtaining good slipping and abrasion resistance, spherical silica particles, spherical alumina particles, and crosslinked organic particles Furthermore, those composite particles are preferable, and spherical silicone particles are particularly preferable. When spherical silicone resin particles are used as the particles B, the heat resistance becomes particularly high due to a synergistic effect when polyphenylene ether is used in combination as a thermoplastic amorphous resin described later.

An oriented film of the present invention comprises a resin composition comprising the above-mentioned styrenic polymer having a syndiotactic structure, porous particles having an average particle size of 0.5 to 5.0 μm, and silicone oil, which is at least uniaxially oriented. Preferably, it is an oriented film in which molecular chains are oriented by stretching in biaxial directions.

Incidentally, the resin composition in the present invention preferably contains the following thermoplastic amorphous resin Y. The thermoplastic amorphous resin Y here is preferably a thermoplastic amorphous resin having a glass transition temperature Tg determined by DSC (differential scanning calorimeter) having a Tg higher than SPS. When such a thermoplastic amorphous resin Y is blended with SPS, not only the glass transition temperature Tg as a mixture increases, but also the heat resistance improves, and the dielectric breakdown voltage at a high temperature increases. Moreover, the thermal dimensional stability of the oriented film becomes good, and the stretchability can also be improved. From such a viewpoint, the glass transition temperature Tg of the thermoplastic amorphous resin Y is preferably 150 ° C. or higher, more preferably 180 ° C. or higher, and particularly preferably 200 ° C. or higher. The higher the glass transition temperature Tg of the thermoplastic amorphous resin Y to be blended, the greater the effect of improving the above effects such as thermal dimensional stability. Considering melt extrusion or the like, the substantial upper limit is preferably 350 ° C., more preferably 300 ° C.

Preferred examples of the thermoplastic amorphous resin Y include aromatic polyethers such as polyphenylene ether and polyetherimide, polycarbonate, polyarylate, polysulfone, polyethersulfone, and polyimide. Among these, it is easy to improve stretchability, and because it has a synergistic effect when combined with an antioxidant, not only heat resistance and dimensional stability, but also dielectric breakdown voltage is further improved. Particularly preferred. Examples of the polyphenylene ether resin used here include conventionally known resins such as poly (2,3-dimethyl-6-ethyl-1,4-phenylene ether) and poly (2-methyl-6-chloromethyl-1). , 4-phenylene ether), poly (2-methyl-6-hydroxyethyl-1,4-phenylene ether), poly (2-methyl-6-n-butyl-1,4-phenylene ether), poly (2-ethyl-6-isopropyl-1,4-phenylene ether), poly (2-ethyl-6-n-propyl-1,4-phenylene ether), poly (2,3,6-trimethyl-1) , 4-phenylene ether), poly (2- (4′-methylphenyl) -1,4-phenylene ether), poly (2-bromo-6-phenyl-1,4-phenylene ether), poly 2-methyl-6-phenyl-1,4-phenylene ether), poly (2-phenyl-1,4-phenylene ether), poly (2-chloro-1,4-phenylene ether), poly (2 -Methyl-1,4-phenylene ether), poly (2-chloro-6-ethyl-1,4-phenylene ether), poly (2-chloro-6-bromo-1,4-phenylene ether), Poly (2,6-di-n-propyl-1,4-phenylene ether), poly (2-methyl-6-isopropyl-1,4-phenylene ether), poly (2-chloro-6-methyl-) 1,4-phenylene ether), poly (2-methyl-6-ethyl-1,4-phenylene ether), poly (2,6-dibromo-1,4-phenylene ether), poly (2,6 -Dichloro-1,4-phenyle Homopolymers such as ether), poly (2,6-diethyl-1,4-phenylene ether), poly (2,6-dimethyl-1,4-phenylene ether), and copolymers thereof Can be mentioned. Further, those modified with a modifying agent such as maleic anhydride or fumaric acid are also preferably used. Furthermore, a copolymer obtained by graft copolymerization or block copolymerization of a vinyl aromatic compound such as styrene with the polyphenylene ether is also used. Of these, poly (2,6-dimethyl-1,4-phenylene ether) is particularly preferred.

The intrinsic viscosity of the polyphenylene ether resin is preferably in the range of 0.2 to 0.8 dl / g, more preferably in the range of 0.3 to 0.6 dl / g when measured at 30 ° C. in chloroform. When the intrinsic viscosity is less than 0.2 dl / g, the mechanical strength of the resulting resin composition may be lowered. On the other hand, when it exceeds 0.8 dl / g, the fluidity of the resulting resin composition is lowered, and the processing during melt molding into a film or the like tends to be difficult. Two or more types of polyphenylene ether resins may be used in combination, and in this case, those having different intrinsic viscosities may be mixed to obtain a desired intrinsic viscosity.

The oriented film of the present invention preferably contains 5% by mass or more and 48% by mass or less of the above thermoplastic amorphous resin Y with respect to the mass of the oriented film. By blending the amount of the thermoplastic amorphous resin Y in the above range, the heat resistance is excellent and the effect of improving the dielectric breakdown voltage can be increased. That is, the dielectric breakdown voltage at high temperatures can be increased. When the content is too small, the heat resistance tends to be inferior, the effect of improving the dielectric breakdown voltage tends to be low, and the effect of improving the stretchability is poor. From such a viewpoint, the content of the thermoplastic amorphous resin Y is more preferably 8% by mass or more, further preferably 11% by mass or more, and particularly preferably 20% by mass or more. Moreover, when there is too much content, it exists in the tendency for the crystallinity of SPS to fall easily, and it exists in the tendency for the heat resistance of a film to be inferior. From such a viewpoint, the content of the thermoplastic amorphous resin Y is more preferably 45% by mass or less, further preferably 40% by mass or less, and particularly preferably 35% by mass or less.

Of course, the oriented film of the present invention may further use other resins in addition to the SPS and the thermoplastic amorphous resin Y as long as the object of the present invention is not impaired.

<Antioxidant>
The oriented film of the present invention preferably contains an antioxidant. The antioxidant may be either a primary antioxidant that captures the generated radicals to prevent oxidation, or a secondary antioxidant that decomposes the generated peroxides to prevent oxidation. Examples of the primary antioxidant include phenol-based antioxidants and amine-based antioxidants, and examples of the secondary antioxidant include phosphorus-based antioxidants and sulfur-based antioxidants. Of these, primary antioxidants are preferred, and phenolic antioxidants are particularly preferred.

Further, it is preferable that the antioxidant has a thermal decomposition temperature of 250 ° C. or higher. When the thermal decomposition temperature is high, the effect of improving the dielectric breakdown voltage at a high temperature becomes high. If the thermal decomposition temperature is too low, the antioxidant itself is thermally decomposed at the time of melt extrusion, which tends to cause problems such as contamination of the process and yellowing of the polymer. From such a viewpoint, the thermal decomposition temperature of the antioxidant is more preferably 280 ° C. or higher, further preferably 300 ° C. or higher, and particularly preferably 320 ° C. or higher. The antioxidant in the present invention is preferably less susceptible to thermal decomposition and preferably has a higher thermal decomposition temperature, but in reality, the upper limit is about 500 ° C. or less.

The melting point of the antioxidant is preferably 90 ° C. or higher. If the melting point is too low, the antioxidant melts faster than the polymer during melt extrusion, and the polymer tends to slip at the screw supply portion of the extruder. As a result, the supply of the polymer becomes unstable, and problems such as the uneven thickness of the film occur. From such a viewpoint, the melting point of the antioxidant is more preferably 120 ° C. or higher, further preferably 150 ° C. or higher, and particularly preferably 200 ° C. or higher. On the other hand, when the melting point of the antioxidant is too high, the antioxidant becomes difficult to melt during melt extrusion, and the dispersion in the polymer tends to be poor. Thereby, problems such as the effect of adding the antioxidant appear only locally. From such a viewpoint, the melting point of the antioxidant is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, further preferably 220 ° C. or lower, and particularly preferably 170 ° C. or lower.

As the above antioxidants, commercially available products can be used as they are. Commercially available products include, for example, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1010), N, N′— Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1024), N, N′-hexane-1,6-diylbis [ 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1098) is preferred.

The content of the antioxidant is preferably 0.1% by mass or more and 5% by mass or less based on the mass of the oriented film. By containing the antioxidant in a content within the above numerical range, the effect of improving the dielectric breakdown voltage can be increased. When the content of the antioxidant is too small, the effect of adding the antioxidant is not sufficient, and the effect of improving the dielectric breakdown voltage tends to be low. From such a viewpoint, the content of the antioxidant is more preferably 0.2% by mass or more, further preferably 0.5% by mass or more, and particularly preferably 0.7% by mass or more. On the other hand, when the content is too high, the antioxidant tends to aggregate in the biaxially stretched film, and the defects due to the antioxidant tend to increase. Less effective. From such a viewpoint, the content of the antioxidant is more preferably 3% by mass or less, further preferably 2% by mass or less, and particularly preferably 1.5% by mass or less.

These antioxidants may be used alone or in combination of two or more.

<Other additives>
The oriented film of the present invention contains other resin components different from the thermoplastic amorphous resin Y, for example, in order to further improve the moldability, mechanical properties, surface properties, etc., as long as the object of the present invention is not impaired. Or additives such as antistatic agents, colorants, weathering agents and the like can be added. In addition, porous particles and inert particles other than the above-described particle B may be used in a small amount as long as the object of the present invention is not impaired.

<Metal layer>
The oriented film of the present invention becomes a capacitor by, for example, laminating a metal layer on at least one side. The material of the metal layer is not particularly limited, and examples thereof include aluminum, zinc, nickel, chromium, tin, copper, and alloys thereof. Further, these metal layers may be slightly oxidized. Moreover, since a metal layer can be formed easily, it is preferable that a metal layer is a vapor deposition type metal layer formed by the vapor deposition method.

Further, in laminating the metal layer, by further providing a metal layer on the surface of the coating layer of the present invention, the base material layer and the metal layer have an appropriate adhesive force, such as winding in film capacitor production. When processing is performed, the metal layer does not peel off, and the function as a capacitor is exhibited. Furthermore, at the same time, the coating layer and the metal layer have moderate adhesion, and even if a discharge occurs, the coating layer with a small surface energy is peeled off from the film first, and only the metal layer and the coating layer are destroyed. It is not destroyed, thereby not being short-circuited, and the effect of improving the dielectric breakdown voltage can be increased.

<Film characteristics>
(Refractive index in the thickness direction)
The oriented film of the present invention preferably has a refractive index in the thickness direction of 1.575 or more and 1.635 or less. By setting the refractive index in the thickness direction within the above numerical range, the dielectric breakdown voltage can be further increased. In addition, the frequency of film breakage in the film manufacturing process is reduced, and productivity is easily improved. From such a viewpoint, the refractive index in the thickness direction is preferably 1.620 or less, more preferably 1.615 or less, and particularly preferably 1.610 or less. On the other hand, when the refractive index in the thickness direction is too low, the dielectric breakdown voltage tends to be low.

Also, the highly insulating film of the present invention increases the frequency of film breakage in the capacitor manufacturing process, and the productivity of the capacitor tends to decrease. Furthermore, the thickness unevenness of the film tends to deteriorate, and it becomes difficult to obtain a capacitor with stable quality. From such a viewpoint, the refractive index in the thickness direction is preferably 1.590 or more, more preferably 1.595 or more, and particularly preferably 1.600 or more.

The refractive index in the thickness direction as described above can be adjusted according to the stretching conditions of the film.

(Film thickness)
Although the thickness of the oriented film of the present invention is not particularly limited, it is particularly preferably 0.4 μm or more and less than 6.5 μm because the effects of the present invention are more likely to become thinner. More preferably, it is 0.4 μm or more and less than 6.0 μm, and particularly preferably 0.5 μm or more and less than 3.5 μm. Further, by setting the film thickness as described above, a capacitor having a high capacitance can be obtained.

(Void rate)
The oriented film of the present invention preferably contains substantially no voids around the porous particles. In the present invention, “substantially not containing a void” means containing a void that does not contain a void, does not cause particle dropout, or contains a void that does not lower the dielectric breakdown voltage. That is, when the void ratio described later is measured, it means that the void ratio is 50% or less, particularly preferably 30% or less. When the void ratio exceeds the upper limit, the filler falls off during processing, and not only the process contamination but also the surface roughness changes, resulting in problems in winding the film roll.

(Dielectric breakdown voltage (BDV))
The oriented film of the present invention preferably has a dielectric breakdown voltage (BDV) at 120 ° C. of 450 kV / mm or more. The fact that the dielectric breakdown voltage is in the above numerical range means that the dielectric breakdown voltage is excellent even at a high temperature. The dielectric breakdown voltage is more preferably 500 kV / mm or more, and further preferably 520 kV / mm or more.

The standard deviation of the oriented film of the present invention is preferably 40 kV / mm or less, more preferably 30 kV / mm or less, and still more preferably 20 kV / mm or less.

The oriented film of the present invention has a high average value of dielectric breakdown voltage by using specific porous particles, and can reduce the standard deviation of the material. When used as an electrical insulating material such as a capacitor, Reliability can be increased. That is, since the standard deviation of the breakdown voltage can be reduced, a decrease in the minimum value of the breakdown voltage is suppressed, and the average value of the breakdown voltage is increased.

<Film production method>
The oriented film of the present invention can basically be obtained by a method conventionally known or accumulated in the art. Hereinafter, the production method for obtaining the oriented film of the present invention will be described in detail. The oriented film of the present invention may be a uniaxially oriented film or a biaxially oriented film, but is preferably a biaxially oriented film from the viewpoint of the balance between productivity and physical properties. Hereinafter, a biaxially oriented film will be described as an example.

First, as described above, a resin composition containing SPS, porous particles, and silicone oil is heated and melted to prepare an unstretched sheet. Specifically, the resin composition is heated and melted at a temperature not lower than the melting point (Tm, unit: ° C.) and not higher than (Tm + 50 ° C.), extruded into a sheet, cooled and solidified to obtain an unstretched sheet. The intrinsic viscosity of the obtained unstretched sheet is preferably in the range of 0.35 to 0.9 dl / g.

Next, this unstretched sheet is stretched biaxially. Stretching may be performed simultaneously in the machine direction (machine axis direction) and the transverse direction (direction perpendicular to the machine axis direction and the thickness direction) or sequentially in any order. For example, in the case of successive stretching, first, in a uniaxial direction (glass transition temperature (Tg, unit: ° C.) − 10 ° C.) to (Tg + 70 ° C.) or less at a temperature of 3.2 to 5.8 times, Preferably, the film is stretched at a magnification of 3.3 times to 5.4 times, more preferably 3.4 times to 5.0 times, and then a temperature of Tg or more (Tg + 80 ° C.) in a direction perpendicular to the uniaxial direction. 3.8 times to 5.9 times, preferably 4.0 times to 5.5 times, more preferably 4.1 times to 5.1 times, and even more preferably 4.2 times to 4.9 times. Stretch at a magnification of less than double. Furthermore, the area stretching ratio (= longitudinal stretching ratio × lateral stretching ratio) is preferably 12.0 times or more in order to obtain a film having the above-described plane orientation coefficient. If the area stretch ratio is low, the heat resistance becomes poor, which is not preferable. Therefore, the area stretch ratio is more preferably 13.0 times or more, further preferably 13.5 times or more, and particularly preferably 14.0 times or more. On the other hand, if the area stretch ratio is too high, breakage tends to occur during film formation and stretching, which is not desirable. From such a viewpoint, the area stretch ratio is preferably 22 times or less, more preferably 20 times or less, still more preferably 18 times or less, and particularly preferably 17 times or less.

In the present invention, the coating layer is formed by applying a coating solution for forming a coating layer on an unstretched sheet or a uniaxially stretched film obtained by uniaxially stretching the unstretched sheet in the longitudinal direction. It may be formed.

Next, heat setting is performed at a temperature of (Tg + 70 ° C.) to Tm. The heat setting temperature is 200 ° C. or higher and 260 ° C. or lower, preferably 225 ° C. or higher and 255 ° C. or lower, and more preferably 235 ° C. or higher and 250 ° C. or lower. When the heat setting temperature is too high, film breakage is likely to occur particularly when a film having a thin film thickness is produced, and the thickness unevenness is deteriorated. If relaxation treatment is performed at a temperature lower than the heat setting temperature by 20 ° C. to 90 ° C. as necessary after heat setting, the dimensional stability is improved.

Next, the stretched film of the second invention will be described.
<Stretched film>
The stretched film of the second aspect of the invention includes a syndiotactic polystyrene resin (hereinafter sometimes referred to as SPS) and porous silica particles having an average particle diameter A of 0.5 to 5.0 μm. It consists of a resin composition.

The polystyrene resin having a syndiotactic structure used here can be said to be the same as described in the first aspect of the present invention.

The porous silica particles contained in the stretched film of the present invention can be said to be the same as described in the first aspect of the present invention unless otherwise specified. Unlike the first aspect of the present invention, since it has a specific specific surface area and DBA value, silicone oil may not be used in combination.

The porous silica particles used in the second present invention are required to have a DBA value (di-n-butylamine adsorption amount) of 200 mmol / kg or less, preferably 100 mmol / kg or less. When the DBA value exceeds 200 mmol / kg, not only the dispersion of the porous silica particles in the resin composition is deteriorated, but also voids are easily generated between the resin and the particles when formed into a stretched film. This is not preferable. The DBA value here is the amount of di-n-butylamine adsorbed when the porous silica particles are treated with a toluene solution of di-n-butylamine (the amount of adsorbed di-n-butylamine per milligram of particles). It is.

The production method of the porous silica particles is not particularly limited, and the surface of the porous silica particles produced by a conventionally known method such as a sol-gel method or a precipitation method is treated with, for example, an alkylalkoxysilane compound or a silazane compound. Thus, it can be easily obtained by modifying the silanol group on the particle surface. When there are many silanol groups on the particle surface, the affinity with a polystyrene resin having a syndiotactic structure is lowered, and the dispersibility of the particles in the resin composition is lowered. In addition, voids are likely to be generated between the resin and the particles when formed into a stretched film, and when the activity of the particle surface is increased and blended into the resin material, problems such as particle re-aggregation occur. It becomes easy to do.

The porous silica particles are preferably aggregated particles in which primary particles are aggregated, and more preferably, the primary particle diameter is 0.01 to 0.1 μm and the pore volume is 0.5 to 2. It is preferably in the range of 0 ml / g, and the average pore diameter is preferably in the range of 5 to 25 nm. By satisfying such requirements, it is considered that the diameter of voids formed around the particles is reduced by moderately deforming the particles due to stress during processing into a stretched film or the like.

The stretched film of the second invention described above has particles having an average particle size A of 0.01 μm or more and less than 0.5 μm (hereinafter referred to as inactive particles C) in addition to the porous silica particles described above. It is preferable to contain a certain). By containing such inactive particles C, the stretched film can have good slipping property while maintaining a high dielectric breakdown voltage, and a stretched film excellent in winding property can be obtained. When the average particle diameter A of the inert particles C is too small, the effect of improving the slipping property tends to be lowered, and the effect of improving the winding property is also lowered. On the other hand, if it is too large, the height of the low protrusions on the film surface becomes too high, thereby making the slipping property too high, and the winding property is lowered such that end face deviation is likely to occur during winding. In addition, voids in the film tend to increase, resulting in low abrasion resistance and dielectric breakdown voltage. From such a viewpoint, the average particle diameter A of the inert particles C is preferably 0.05 μm or more and less than 0.5 μm, more preferably 0.1 μm or more and less than 0.5 μm, particularly preferably 0.2 to 0.4 μm. It is. The average particle diameter A of the inert particles C is preferably smaller than the average particle diameter A of the porous silica particles, and the difference is preferably 0.2 μm or more.

Such inert particles C are preferably spherical particles having a particle size ratio (major axis / minor axis) of 1.0 to 1.3. The particle size ratio is more preferably 1.0 to 1.2, particularly preferably 1.0 to 1.1. When the particle size ratio is in the above numerical range, the effect of improving the winding property and the effect of improving the dielectric breakdown voltage can be further increased.

Such inert particles may be either organic particles or inorganic particles. Examples of the organic particles include polymer resin particles such as polystyrene resin particles, silicone resin particles, acrylic resin particles, styrene-acrylic resin particles, divinylbenzene-acrylic resin particles, polyester resin particles, polyimide resin particles, and melamine resin particles. Can be mentioned. Among these, silicone resin particles and polystyrene resin particles are preferable from the viewpoint of excellent slipperiness and abrasion resistance, and spherical silicone resin particles and spherical polystyrene resin particles are particularly preferable as described above. Examples of the inorganic particles include particles (1) to (15) exemplified for the particles B described in the first aspect of the present invention. Of these, calcium carbonate particles and silica particles are preferable, and silica particles are particularly preferable from the viewpoint of excellent slipperiness and abrasion resistance. Such inorganic particles are preferably spherical as described above, and spherical silica particles are particularly preferred.

Most preferable as the inert particles C are spherical silicone resin particles. When spherical silicone resin particles are used as the inert particles, the heat resistance becomes particularly high due to a synergistic effect when polyphenylene ether is used in combination as a thermoplastic amorphous resin described later.

The content of the inert particles C is preferably 0.01 to 3% by mass, more preferably 0.05 to 2% by mass, and further preferably 0.1 to 0.5% by mass in 100% by mass of the resin composition. %, Particularly preferably 0.1 to 0.3% by mass or less. By containing such inert particles in the above range, the handleability of the film can be improved while maintaining a high dielectric breakdown voltage.

In addition, when melt-molding a resin composition containing no inert particles into a film, the inert particles are added as they are or as master chips so that the content of the inert particles in the resulting film is in the above range. It doesn't matter.

It is preferable that the stretched film of the second present invention further contains a thermoplastic amorphous resin. The thermoplastic amorphous resin here can be said to be the same as that described in the first aspect of the present invention.

In addition, in the stretched film of the second invention, other resins may be used in combination with the SPS and the thermoplastic amorphous resin as long as the object of the invention is not impaired.

It is preferable that the stretched film of the second invention further contains an antioxidant. As the antioxidant, the same thing as described in the first aspect of the present invention can be said.

The stretched film of the second aspect of the present invention is a resin component different from the thermoplastic amorphous resin, for example, in order to further improve the film forming property, the mechanical properties, the surface property, etc., within the range not impairing the object of the present invention. Or additives such as antistatic agents, colorants, weathering agents and the like can be added. Further, inert particles other than the above-mentioned particles may be used in a small amount as long as the object of the present invention is not impaired.

The stretched film of the second invention can be said to have the same refractive index in the thickness direction and coarse agglomerated particles having a maximum length of 25 μm or more present in the film as described in the first invention.

It is preferable that the stretched film of the second invention has substantially no void around the porous silica particles. Here, “substantially no void” is the same as described in the first aspect of the present invention. If the void ratio exceeds 50%, particles fall off during processing, and not only process contamination but also the surface roughness changes, resulting in poor handling of the film roll. In addition, the dielectric breakdown voltage decreases and the variation tends to increase (dielectric breakdown characteristics tend to deteriorate).

The thickness of the stretched film of the second invention is not particularly limited, but it is particularly preferably 0.4 to 6.5 μm because the effects of the invention are more likely to be obtained as the thickness is reduced. More preferably, it is 0.4 to 6.0 μm, and particularly preferably 0.5 to 3.5 μm. By using such a film thickness, a capacitor having a high capacitance can be obtained.

The stretched film of the second invention preferably has a dielectric breakdown voltage (BDV) at 120 ° C. of 450 V / μm or more. The fact that the breakdown voltage satisfies such a requirement means that the breakdown voltage is excellent even at a high temperature. The breakdown voltage is more preferably 500 V / μm or more, and further preferably 520 V / μm or more.

The standard deviation of the dielectric breakdown voltage is preferably 40 V / μm or less, more preferably 30 V / μm or less, and still more preferably 20 V / μm or less. If this standard deviation satisfies this requirement, it means that the local breakdown voltage drop is small (variation is small), and it increases the reliability of the material when used as an electrical insulation material such as a capacitor. Can do.

The stretched film of the second aspect of the present invention preferably has a center line average surface roughness Ra of 7 to 89 nm on at least one side. When the center line average surface roughness Ra is within this range, the effect of improving the winding property can be increased. Moreover, blocking resistance improves and the external appearance of a roll can be made favorable. When the center line average surface roughness Ra is too low, the slipping property tends to be too low, and the effect of improving the winding property is lowered. On the other hand, if it is too high, the slipping property tends to be too high, and the effect of improving the winding property becomes low, such as the occurrence of end face misalignment during winding. From such a viewpoint, the lower limit of the centerline average surface roughness Ra is more preferably 11 nm or more, further preferably 21 nm or more, and particularly preferably 31 nm or more. The upper limit of the center line average surface roughness Ra is more preferably 79 nm or less, still more preferably 69 nm or less, and particularly preferably 59 nm or less.

Further, the stretched film of the second invention preferably has a 10-point average roughness Rz of 200 to 3000 nm on at least one side thereof. When the 10-point average roughness Rz is within this range, the effect of improving the winding property can be increased. When the 10-point average roughness Rz is too low, the air release property tends to be low when the film is wound as a roll, and the effect of improving the winding property such that the film is liable to skid is reduced. In particular, when the film thickness is thin, the film loses its elasticity, so that the air release property tends to be further lowered, and the effect of improving the winding property is further reduced. On the other hand, when the 10-point average roughness Rz is too high, the number of coarse protrusions tends to increase, and the effect of improving the dielectric breakdown voltage is reduced. From such a viewpoint, the lower limit of the 10-point average roughness Rz is more preferably 600 nm or more, further preferably 1000 nm or more, and particularly preferably 1250 nm or more. Further, the upper limit of the 10-point average roughness Rz is more preferably 2600 nm or less, further preferably 2250 nm or less, and particularly preferably 1950 nm or less.

<Film production method>
The stretched film of the second invention described above can be produced by the same production method as described in the first invention except that the silicone oil need not be added.

<Resin composition>
The resin composition preferably used for the production of the stretched film of the second invention is obtained by melting and mixing porous silica particles with the above-mentioned syndiotactic polystyrene resin.

The average particle diameter B of the porous silica particles used here is preferably in the range of 0.5 to 5 μm, particularly 0.8 to 3.0 μm. When this average particle size is less than 0.5 μm, the average particle size A of the porous silica particles in the film when melt-formed into a film or the like becomes small and the slipping property is insufficient, so that the winding property and handling property are insufficient. Tends to be insufficient. On the other hand, when the thickness exceeds 5 μm, the diameter of voids formed around the particles by stretching or the like tends to increase when melt-molding into a film or the like. The content of the particles is 0.01 to 10% by mass, preferably 0.5 to 5.0% by mass based on the amount of the resin composition material. If the content is less than 0.01% by mass, the slidability of the molded product after being formed into a film or the like is insufficient, and the handleability becomes insufficient. On the other hand, when it exceeds 10% by mass, the dispersion of the particles in the resin composition is deteriorated, which is not preferable. When the resin composition is melt-molded as it is and formed into a film or the like, the content of the particles is 0.01 to 3% by mass, further 0.02 to 1% by mass, particularly 0.05, as described above. It is preferably in the range of 0.5% by mass. On the other hand, in the case of diluting with a base resin or the like to form a melt film, a resin composition having a high content, for example, 0.5 to 10% by mass is used. What is necessary is just to dilute so that content of may become said range.

Furthermore, the DBA value of the porous silica particles needs to be 200 mmol / kg or less, preferably 100 mmol / kg or less as described above. When the DBA value exceeds 200 mmol / kg, not only the dispersion of the porous silica particles in the resin composition is deteriorated, but also voids are easily generated between the resin and the particles when formed into a stretched film. This is not preferable.

The compressibility of the porous silica particles is preferably in the range of 20 to 90%, particularly 50 to 85% as described above. When the compression ratio is within this range, it is considered that the diameter of the void formed around the particles is reduced by moderately deforming the particles due to the stress at the time of processing into a stretched film.

As described above, the resin composition preferably contains a thermoplastic amorphous resin, particularly a polyphenylene ether resin. When the resin composition is melt-molded as it is and formed into a film or the like, the thermoplastic amorphous resin content is 48 mass% or less, and more preferably in the range of 5 to 48 mass%, based on the mass of the resin composition. It is preferable that By doing so, it is possible to obtain a stretched film having excellent heat resistance and a high breakdown voltage, that is, an improved breakdown voltage at a high temperature. When the content is too small, the heat resistance improving effect tends to be low, the dielectric breakdown voltage improving effect tends to be low, and the stretchability improving effect is poor. From such a viewpoint, the content of the thermoplastic amorphous resin is more preferably 8% by mass or more, further preferably 11% by mass or more, and particularly preferably 20% by mass or more. Moreover, when there is too much content, it exists in the tendency for the crystallinity of SPS to fall easily, and it exists in the tendency for the heat resistance of a film to fall. From such a viewpoint, the content of the thermoplastic amorphous resin is more preferably 45% by mass or less, further preferably 40% by mass or less, and particularly preferably 35% by mass or less. On the other hand, the resin composition is used as a masterbatch and does not contain porous silica particles, for example, a base resin such as a syndiotactic polystyrene resin or a masterbatch containing other additives is melt-kneaded and diluted. In the case of using a resin composition having a high polyphenylene ether resin content, for example, a content of 20 to 80% by mass, it is diluted so that the content in the resin composition molded into a film is within the above range. do it.

The mixing method of the porous silica particles and the resin material is not particularly limited, and may be added at the polymerization stage of the resin material, or may be added by a method of melt-kneading the resin material obtained by polymerization. May be. For example, the particle powder and the resin material may be supplied from the same supply port of the melt kneader and melt kneaded, or the resin material is first put into a melt kneader such as a biaxial kneading extruder with a vent. Alternatively, a method of adding the particles to the portion where the resin material is melted may be used. Of these, a method is preferable in which the particles and resin pellets or resin powder are mixed in advance and then fed into a vented twin-screw kneading extruder. According to such a method, since the particles are attached to the surface of the resin pellets or resin powder, when the crushing progresses inside the kneader, the contact distance between the particles and the resin is extremely small, so that the dispersibility is high. It is estimated that it will further improve.

<Condenser>
The stretched film of the present invention described above can obtain a capacitor by, for example, laminating a metal layer on at least one side. The material of the metal layer is not particularly limited, and examples thereof include aluminum, zinc, nickel, chromium, tin, copper, and alloys thereof. Further, these metal layers may be slightly oxidized. Moreover, since a metal layer can be formed easily, it is preferable that a metal layer is a vapor deposition type metal layer formed by the vapor deposition method. In addition, when laminating the metal layer, by providing a coating layer in advance, the stretched film layer (base material layer) and the metal layer can have an appropriate adhesive force, and processing such as winding in the production of film capacitors. In the case of applying, the metal layer is not peeled off and the function as a capacitor is exhibited. Furthermore, at the same time, the coating layer and the metal layer have moderate adhesion, and even if a discharge occurs, the coating layer with a small surface energy is peeled off from the film first, and only the metal layer and the coating layer are destroyed. It is not destroyed, thereby not being short-circuited, and the effect of improving the dielectric breakdown voltage can be increased.

Hereinafter, the present invention will be further described by examples. Each characteristic value was measured by the following method.
(1) Film thickness Using an electronic micrometer (trade name “K-312A type” manufactured by Anritsu Corporation), the film thickness was measured at a needle pressure of 30 g.
(2) Average particle diameter (2-1) Average particle diameter A
For the average particle size A in the film, the film surface was treated with a plasma reactor to expose the particles, and a gold thin film deposition layer was formed on the surface with a thickness of 200 to 300 mm by a gold sputtering apparatus. Next, observation was performed at a magnification of 15,000 using a scanning electron microscope, and the area equivalent particle diameter (Di) of 110 particles was obtained with Luzex 500 manufactured by Japan Regulator Co., Ltd. The number average of these area equivalent particle diameters (Di) excluding the five area equivalent particle diameters (Di) of the maximum and minimum diameters (Di) was defined as the average particle diameter A of the particles.

(2-2) Average particle diameter B
The average particle size B before being added to the polymer was determined on the basis of volume distribution using ethanol as a dispersion medium and using a laser diffraction particle size distribution analyzer SALD-2000J manufactured by Shimadzu Corporation.
(3) Particle compression rate For porous particles before being added to the polymer, a micro compression test MCTM-200 (maximum load 1 gf, minimum load 0.2 gf) manufactured by Shimadzu Corporation was used, and the load load rate was 0.0725 gf / sec. Under the conditions, n = 5 particles having the same particle size as the average particle size were prepared, the compression rate at a load of 0.2 gf was measured, and the average value thereof was calculated as the particle compression rate.
(4) The contents of porous particles, other particles, silicone oil, thermoplastic amorphous resin Y, and antioxidant were measured by the methods described later.

Porous particles and other particles: Select the solvent in which the obtained oriented film dissolves the resin but does not dissolve the particles, dissolve the sample, centrifuge the particles from the resin, and the ratio of the particles to the sample weight The particle content was defined as (% by weight). Moreover, when other particles were included, the respective contents were determined from the abundance ratio of the individual particles.

Silicone oil: The components of silicone oil and the amount of each component were identified by using a cryoprobe (high-sensitivity probe) by 32 times of integration by 1H-NMR measurement and ¹³ C-NMR measurement.

Thermoplastic Amorphous Resin Y: The components and the amount of each component of the thermoplastic amorphous resin Y were specified by ¹ H-NMR measurement and ¹³ C-NMR measurement.

Antioxidant: The components of the antioxidant and the amount of each component were identified by ¹ H-NMR measurement and ¹³ C-NMR measurement. In the case of N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide] (registered trademark Irg1098), tert-butyl-4- The peak intensity due to hydrogen due to the hydrocarbon chain between the hydroxyphenyl and the amide bond was measured. Based on the NMR measurement results, when the stabilizer reacted with the resin, the content converted to the original stabilizer was determined. In addition, if a polymer and an unreacted stabilizer are mixed with a stabilizer that has reacted with a polymer and a plurality of peak positions are detected even when focusing on the same hydrocarbon chain, the content is calculated from the total value of them. Asked.
(5) Film-forming stretchability Under the conditions of each example and comparative example, the polymer is supplied to an extruder and the volatile components are generated when melt-extruded through a die, and the film is formed in the film-drawing process. The sex was evaluated according to the following criteria.

◎: There is no coarse agglomerate during polymer melt extrusion, and the film forming process can be produced without breaking. ○: Coarse agglomerate is seen during polymer melt extrusion, but it can be produced without breaking. △: Coarse agglomeration during polymer melt extrusion. Some are broken, but breakage sometimes occurs and stable production cannot be achieved. ×: Coarse aggregates are remarkable at the time of polymer melt extrusion, or breakage occurs frequently and cannot be produced. (6) Filter pressurization Japan PALL H-250 (opening 25 μm) When the resin containing porous fine particles A is converted by discharge amount (kg) / filter area (cm ² ) with a sintered (grain) type filter) and filtered at an extrusion temperature of 300 ° C. and 5 kg / cm ² The filter pressure difference (ΔP: unit is MPa) increased from the initial pressure when 100 kg of was filtered was evaluated according to the following criteria.

◎: There is no pressure increase of the filter during polymer melt extrusion, and the resin can be extruded stably.

○: The pressure of the filter temporarily increases during polymer melt extrusion, but the resin can be extruded stably.

Δ: The pressure of the filter gradually increases during polymer melt extrusion, and the resin cannot be extruded stably for a long period of time. .

X: The pressure of the filter suddenly increased during polymer melt extrusion, and it was not possible to extrude in a short time.
(7) Refractive index in the thickness direction The refractive index (Nz) in the thickness direction was measured at 23 ° C. and 65% RH using an Abbe refractometer using sodium D line (589 nm) as a light source. A higher refractive index in the thickness direction means that molecular chains are oriented in the plane direction of the film.
(8) Number of coarse aggregated particles The film sample was magnified 20 times with transmitted illumination using a universal projector, and the number of particles having a maximum length of 25 μm or more contained in 1 m ² area was counted.
(9) Void ratio The film was cut with a microtome along the thickness direction and the width direction, and the cut surface was 20,000 times with Hitachi Scanning Electron Microscope S-4700, and the porosity in the film on the cut surface The silica particles and the voids around them were observed, and the diameter of the cross section of each particle and the void cross section around each particle was determined for 10 particles, and the void ratio of each particle was calculated by the following formula.
Void ratio = ((void diameter around particle−particle diameter) / void diameter around particle) × 100
The average of the void ratio was calculated for 10 particles to obtain the average void ratio, and it was evaluated whether or not the void was substantially present in the film.
◯: There is substantially no void (average void ratio is 30% or less)
Δ: substantially free of voids (average void ratio is more than 30%, 50% or less)
X: Void is substantially present (average void ratio exceeds 50%)
(10) Surface roughness (Ra and Rz)
Measurement length (Lx) 1 mm, sampling pitch 2 μm, cut-off using a non-contact type 3D roughness meter (manufactured by Kosaka Laboratory, ET-30HK) with a semiconductor laser with a wavelength of 780 nm and an optical stylus with a beam diameter of 1.6 μm The protrusion profile on the film surface was measured under the conditions of 0.25 mm, thickness direction magnification 10,000 times, lateral direction magnification 200 times, and the number of scanning lines 100 (thus, the measurement length Ly in the Y direction was 0.2 mm). . When the roughness curved surface was represented by Z = f (x, y), the value obtained by the following formula was defined as the center line average surface roughness (Ra, unit: nm) of the film.

Also, in the projection profile on the film surface obtained by the above Ra, take 5 points from the highest peak (Hp) and 5 points from the lower valley (Hv), and 10 points average roughness by the following formula

(Rz, unit: nm) was determined.
(11) Winding property In the film production process, the film was wound up into a roll having a width of 550 mm and a width of 6000 m at a speed of 100 m / min.

A: The surface roughness is uniform over the entire film surface, and the roll roll is good. B: Due to the influence of coarse aggregated particles in the film, 1 to less than 5 pimples (protruding bulges) are seen on the roll surface. Almost good
C: There are many coarse aggregates in the film, and 5 or more pimples (protruding protrusions) are seen on the surface of the roll, resulting in poor appearance.
D: Film end face misalignment of roll occurs, winding shape failure (12) Dielectric breakdown voltage (BDV) and variation Using the obtained biaxially oriented film (stretched film sample), flat plate among DC tests described in JIS standard C2151 In accordance with the electrode method, measurement was performed at a boosting rate of 0.1 kV / sec using ITS-6003 manufactured by Tokyo Seiden Co., Ltd., and the voltage at breakdown was measured as the dielectric breakdown voltage. The measurement was performed at n = 50, the average value was the breakdown voltage, and the standard deviation was the variation in breakdown voltage. The measurement was performed at room temperature of 25 ° C.
(13) Scratch resistance A film cut to 1/2 inch in width and 400 mm in length is run on a stainless guide pin (surface roughness: Ra of 40 nm) using a film running tester, The travel speed was 20 mm / second and the distance of 200 mm was reciprocated twice (winding angle 90 °, outlet tension 50 g). After running, the amount of adhering particles was observed at a magnification of 100 times with a Hitachi scanning electron microscope S-4700 at the film contact portion of the guide pin and the guide pin contact surface of the film, and the determination was made according to the following criteria. The smaller the accumulation width of the shaved particles, the better the shaving resistance.
○: Less than 0.20 mm Δ: 0.20 mm or more and less than 0.50 mm x: 0.50 mm or more (14) Anti-blocking property The film was cut into a 100 mm square and superimposed so that the total thickness was 20 μm or more. (A single film having a thickness of 20 μm or more is used as a single sheet), and a laminate was produced that was sandwiched between upper and lower sheets of aluminum foil of the same size. The laminate was subjected to thermocompression bonding with a hot press. The pressing conditions were a press temperature of 125 ° C., a press pressure of 5 MPa, and a press time of 30 minutes. After crimping, the laminate was heat treated in an oven at 150 ° C. for 30 minutes, and the peel strength between the cooled laminate film and aluminum foil was measured. The peel force was measured using a tensile tester under the condition of a tensile speed of 300 mm / min, and the blocking property was determined from the measurement result according to the following criteria.

○: Peeling almost naturally or the average peeling force is 1.0 mN / mm or less.

Δ: Partially blocked, but average peel force exceeds 1.0 mN / mm and is 3.0 mN / mm or less.

X: Blocking is performed as a whole, and the average peeling force exceeds 3.0 mN / mm.
(15) DBA value of porous silica particles (adsorption amount of di-n-butylamine)
A sample of 250 mg dried at 105 ° C. for 2 hours is precisely weighed, 50 ml of 1/500 N-DBA solution (petroleum benzine solvent) is added thereto, and the mixture is allowed to stand at 20 ° C. for 2 hours. To 25 ml of this supernatant, add 5 ml of chloroform and 2 to 3 drops of crystal violet indicator, and titrate with a 1 / 100N-perchloric acid solution (acetic anhydride solvent) until the purple color turns blue. To do. Separately, it was blanked to obtain Bml, and the DBA value was calculated by the following formula.

DBA value (mmol / kg) = 80 (AB) f
Where f is the titer of 1 / 100N-perchloric acid solution (see R. Meyer; Kautschuku. Gummi., 7 [8], 180-182 (1954))
[Example 1]
(Silicon oil adhesion treatment of porous silica particles)
Silicone oil (manufactured by Shin-Etsu Silicone, wire) with respect to 100 parts by mass of porous silica particles (average particle size = 2.7 μm, compressibility = 66%, pore volume = 1.5 ml / g, average pore size = 10 nm) After spraying 1 part by mass of sprayed dimethylpolysiloxane, KF-96-100CS, the mixture was placed in a mixer and stirred.
(Melting and kneading treatment of resin material and porous silica particles)
Two feed blades and two return blades for the rotor disk are installed in the ventilated twin-screw kneading extruder KTX-46 made by Kobe Steel Co., Ltd., which has a vacuum vent at the resin inlet and two locations, and further downstream of the rotor segment. A kneading disk is arranged on the side, and a resistance part with a reverse full-flight screw is arranged just downstream of the kneading disk. 30 parts by weight of (2,6-dimethyl-1,4-phenylene) ether (inherent viscosity measured in chloroform is 0.32 dl / g, glass transition temperature is 210 ° C.) and a weight-average molecular weight of 3 as polystyrene resin .0 × a 10 ^{^5,} 13 C-NMR polystyrene 70 quality to be an almost perfect syndiotactic structure is observed on In addition, 0.1 part by mass of the above-mentioned silicone oil-adhered porous silica particles with respect to the total amount of these resins, and pentaerythritol tetrakis [3- (3,5-di-t-butyl-) as an antioxidant (C1). 4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1010, melting point 120 ° C., thermal decomposition temperature 335 ° C.) Mixing and dispersing the mixture at a ratio of 2 parts by mass, supplying 35 parts by mass / Hr The resin was introduced at a speed from a resin inlet, and melt extruded from a die hole into a strand at a barrel temperature of 270 ° C. and a screw rotation speed of 250 rpm. Thereafter, the resin was cooled with a cooling bath, and then cut with a letterer to obtain a resin composition chip having a major axis of about 4 mm, a minor axis of about 4 mm, and a length of about 3 mm.
(Oriented film production)
The obtained resin composition was dried at 120 ° C. for 7 hours, then fed to an extruder, melted at 300 ° C., extruded from a die slit, solidified by cooling on a casting drum cooled to 50 ° C., and unstretched Created a sheet.

This unstretched sheet was stretched 3.5 times in the longitudinal direction (machine axis direction) at 140 ° C., and subsequently led to a tenter, and then 4.5 times in the lateral direction (direction perpendicular to the machine axis direction and the thickness direction). The film was stretched twice. At that time, the stretched portion was divided into four equal zones, and the stretching speed in the transverse direction was set to 5000% / min. Further, the stretching temperature in the transverse direction was also divided into four equal parts, and the first stage temperature was 126 ° C. and the final stage temperature was 145 ° C. Thereafter, the film was heat-fixed at 250 ° C. for 9 seconds, and further subjected to a 2% relaxation treatment in the transverse direction while cooling to 180 ° C. to obtain a biaxially oriented film having a thickness of 2.5 μm and wound into a roll. The properties of the obtained film are shown in Table 1.

[Examples 2 to 20, Comparative Examples 1 to 7]
The same operation as in Example 1 was repeated except that the changes were made as described in Tables 1 to 3. The evaluation results of the obtained oriented film are shown in Tables 1 and 2 for Examples and Table 3 for Comparative Examples.

In Tables 1 to 3, porous silica means porous silica particles, spherical silicone means crosslinked silicone resin particles, and nonporous silica means spherical silica particles. In Table 1, Irg1010 is pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1010), and Irg1098 is N, N '-Bis 3- (3'5' di-t-butyl-4'-hydroxyphenyl) propionyl hexamethylenediamine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1098), Irg565 is 2,4-bis (n- Octylthio) -6- (4′-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX565). PPE in Tables 1 and 2 means poly (2,6-dimethyl-1,4-phenylene) ether (inherent viscosity measured in chloroform is 0.32 dl / g, glass transition temperature is 210 ° C.) PC means bisphenol A type polycarbonate (Idemitsu Petrochemical, Idemitsu Polycarbonate A300, glass transition temperature is 145 ° C.). Further, in the column of average particle diameter in the film in Table 3, “-*” means that the aggregation of the particles was large and the measurement of the average particle diameter was stopped.

[Synthesis Example 1]
A 22 wt% sodium silicate aqueous solution and a 37 wt% sulfuric acid aqueous solution were reacted using a mixing nozzle to obtain a silica hydrosol. The silica hydrosol gelled in about 7 minutes to obtain a silica hydrogel. This silica hydrogel was roughly crushed to a diameter of about 10 mm, hydrothermally treated at 90 ° C. and pH 9.0 for 5 hours, and then washed with water. Next, the silica hydrogel washed with water is subjected to a first step of drying for 60 minutes using a vibration fluidized bed (trade name “vibration fluid phase apparatus VUA-15 type” manufactured by Chuo Kako Co., Ltd.), and then dried to a moisture content of 7%. Got. Thereafter, a second step of adding water to the dried silica is performed to obtain a silica adjusted to a water content of 37%, and then a third step of drying for 2 hours in the vibrating fluidized bed is performed again. A gel silica having a water content of 1% was obtained. This dried silica is pulverized using a jet mill, and 100 parts of the resulting silica is charged into a vibrating fluidized bed, and 12 parts of n-octyltriethoxysilane is sprayed while being vibrated and flowed with dehumidified air, flowing for 30 minutes. Mixed. Then, it was immediately put into a constant temperature and humidity chamber maintained at a temperature of 25 ° C. and a humidity of 90%, and a surface-treated silica powder was obtained by maintaining for 72 hours. Again, it was pulverized using a jet mill for silica dispersion. Table 4 shows the characteristic values of the obtained silica powder 1 (porous silica particles 1).

[Synthesis Examples 2, 3, 5]
The same treatment as in Synthesis Example 1 was performed except that the average particle size was adjusted by changing the jet mill conditions. Table 4 shows the characteristic values of the obtained silica powders 2, 3, and 5.

[Synthesis Example 4]
The same treatment as in Synthesis Example 1 was performed except that the amount of n-octyltriethoxysilane added was changed. The characteristic values of the obtained silica powder 4 are shown in Table 4.

[Synthesis Example 6]
To make the particle size small, the same as Synthesis Example 1 except that after the first jet mill treatment, silica is made into 10% slurry with distilled water and a wet grinding step of a sand grinder (dyno mill, capacity 5 L) is added. Was done. The characteristic values of the obtained silica powder 6 are shown in Table 4. Since this silica powder had an average particle size of too small as 0.3 μm, the compression rate could not be measured.

[Synthesis Example 7]
The same treatment as in Synthesis Example 1 was performed, except that the surface treatment with n-octyltriethoxysilane was not performed. The characteristic values of the obtained silica powder 7 are shown in Table 4.

[Reference Example 1]
Two feed blades and two return blades for the rotor disk are installed in the ventilated twin-screw kneading extruder KTX-46 made by Kobe Steel Co., Ltd., which has a vacuum vent at the resin inlet and two locations, and further downstream of the rotor segment. A kneading disk is arranged on the side, and a polyphenylene ether resin (hereinafter abbreviated as PPE) is introduced from the resin inlet using equipment in which a resistance part with a reverse feed full flight screw is arranged immediately downstream of the kneading disk. Mitsubishi Engineering Plastics Iupiace PX-100L (Tg210 ° C) is 40 parts by mass, and a syndiotactic polystyrene resin (hereinafter sometimes abbreviated as SPS) is 55.8 masses of Idemitsu Kosan Zarek 60ZC. As an antioxidant, Ciba Specialty Chemicals Inc. The Ganokkusu 1010 was 0.2 part by weight mixture turned.

Furthermore, 4 parts by mass of the silica powder 1 described above as porous silica particles was added from the middle part of the twin-screw kneading extruder (downstream part of the kneading disk), and mixed and dispersed. At this time, the mixture feed amount was 35 parts by mass / Hr, the barrel temperature was 270 ° C., and the screw rotation speed was 250 rpm. Thereafter, the resin was cooled with a cooling bath, and then cut with a letterer to obtain a resin composition chip having a major axis of about 4 mm, a minor axis of about 4 mm, and a length of about 3 mm. The obtained resin composition chip is shown in Table 4.

[Reference Examples 2 to 5, Reference Comparative Examples 1 to 3]
A resin composition chip was obtained in the same manner as in Reference Example 1 except that the usage ratios of the porous silica particles, PPE, and SPS used were as shown in Table 3. The results are also shown in Table 4.

[Reference Example 6]
In addition to the porous silica particles, 4 parts by mass of spherical silicone resin particles having an average particle size B of 0.3 μm were used, and the same as in Reference Example 1 except that the use ratio of SPS was as shown in Table 1. A resin composition chip was obtained. The results are also shown in Table 4.

[Reference Comparative Example 4]
A resin composition chip was obtained in the same manner as in Reference Example 1 except that spherical silica particles (non-porous) having an average particle size B of 2.0 μm were used instead of the porous silica particles used. The results are also shown in Table 4.

[Example 21]
Resin composition chip (master chip A) obtained in Reference Example 1, polyphenylene ether resin (Mitsubishi Engineering Plastics Iupiace PX-100L), syndiotactic polystyrene resin (Zarek 60ZC made by Idemitsu Kosan), polyphenylene ether After drying master chips containing 5% by weight of Irganox 1010 manufactured by Ciba Specialty Chemicals as an antioxidant in resin (Iupiace PX-100L manufactured by Mitsubishi Engineering Plastics), a film having the composition shown in Table 5 was obtained. These were mixed at a ratio and supplied to an extruder, melted at 300 ° C., extruded from a die slit, and cooled and solidified on a casting drum cooled to 50 ° C. to prepare an unstretched sheet. In addition, since antioxidant was partly scattered in the film forming process of the film, the antioxidant content in the mixture of raw materials was increased so that the content in the film was 1% by weight.

This unstretched sheet was stretched 3.5 times in the longitudinal direction (machine axis direction) at 140 ° C., and subsequently led to a tenter, and then 4.5 times in the lateral direction (direction perpendicular to the machine axis direction and the thickness direction). The film was stretched twice. At that time, the transverse stretching speed was 5000% / min, the transverse stretching temperature was divided into four equal parts, the first stage temperature was 126 ° C., and the final stage temperature was 145 ° C. Thereafter, the film was heat-fixed at 250 ° C. for 9 seconds, and further subjected to a 2% relaxation treatment in the transverse direction while cooling to 180 ° C. to obtain a biaxially stretched film having a thickness of 2.5 μm and wound into a roll. Table 4 shows the properties of the obtained film.

[Examples 22 to 24, 26, 29, 30, 33 to 37, Comparative Examples 8 to 10, 12, and 13]
Using a master chip as described in Tables 5-7, and so that the composition of the film obtained is as described in Tables 5-7, polyphenylene ether resin, polycarbonate resin, syndiotactic polystyrene resin and antioxidant The same operation as in Example 21 was repeated except that the contained master chip was used in combination. The evaluation results of the obtained stretched film are shown in Tables 5 to 7. In Examples 25 and 26, a syndiotactic polystyrene resin (Idemitsu Kosan Zarek 60ZC) containing 5% by weight of Irganox 1010 was used as an antioxidant-containing master chip.

[Examples 25, 27, 28, 31, 32, Comparative Example 11]
First, a polyphenylene ether resin, a polystyrene resin having a syndiotactic structure, porous silica particles and an antioxidant were mixed in the same manner as in Reference Example 1 so that the composition of the resulting film was as shown in Tables 5-7. A resin composition chip was obtained. The obtained resin composition was dried and formed into a film in the same manner as in Example 21 to obtain a biaxially stretched film. The evaluation results of the obtained stretched film are shown in Tables 5 to 7.

PC in Tables 5 to 7 is a bisphenol A type polycarbonate (Idemitsu Petrochemicals Idemitsu Polycarbonate A300, glass transition temperature 145 ° C.).

In Tables 5 to 7, Irg1010 is pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1010). Irg1098 is N, N′-bis-3- (3′5′di-t-butyl-4′-hydroxyphenyl) propionylhexamethylenediamine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1098), and Irg565 is 2,4. -Bis (n-octylthio) -6- (4'-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 565).

The oriented film of the first aspect of the present invention is particularly suitable as a base film for a film capacitor because it is excellent in abrasion resistance and winding property.

In addition, the stretched film of the second aspect of the present invention is excellent in particle dispersibility and has a small void diameter caused by the particles, so that it has excellent wear resistance, handleability, and dielectric breakdown characteristics (dielectric breakdown voltage and variations thereof). In particular, it can be suitably used as a film capacitor.

Claims

It comprises a resin composition comprising a styrene polymer having a syndiotactic structure and porous particles having an average particle size of 0.5 to 5.0 μm, and the content of the porous particles is 0 based on the mass of the resin composition. In the range of not less than 01% by mass and not more than 3% by mass,
(1) The resin composition contains silicone oil, and the silicone oil content is in the range of 0.1 to 3% by mass based on the mass of the porous particles, or (2) the porous particles are A stretched film characterized by satisfying any of the following: porous silica particles having an average particle diameter A of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less.
It comprises a resin composition comprising a styrenic polymer having a syndiotactic structure, porous particles having an average particle size of 0.5 to 5.0 μm and silicone oil, and the content of the porous particles is the mass of the resin composition. 2. The stretched film according to claim 1, wherein the content of the silicone oil is in the range of 0.1 to 3% by mass based on the mass of the porous particles in a range of 0.01% by mass to 3% by mass as a standard. .
A stretched film comprising a polystyrene resin having a syndiotactic structure and a porous silica particle having an average particle diameter A of 0.5 to 5 μm and a DBA value of 200 mmol / kg or less, 2. The stretched film according to claim 1, wherein the content of the porous silica particles is 0.01 to 3% by mass based on the amount of the resin composition material.
The stretched film according to any one of claims 1 to 3, wherein the resin composition contains a thermoplastic amorphous resin.
The stretched film according to any one of claims 1 to 3, comprising a thermoplastic amorphous resin in an amount of 5% by mass to 48% by mass with respect to the mass of the film.
The stretched film according to any one of claims 1 to 3, wherein the refractive index in the thickness direction is from 1.575 to 1.635.
The stretched film according to any one of claims 1 to 3, comprising an antioxidant in an amount of 0.1% by mass to 5% by mass with respect to the mass of the film.
The stretched film according to any one of claims 1 to 3, wherein the thermal decomposition temperature of the antioxidant is 250 ° C or higher.
The stretched film according to any one of claims 1 to 3, wherein the compressibility of the porous particles or the porous silica particles is in the range of 20 to 90%.
The stretched film according to any one of claims 1 to 3, comprising particles having an average particle diameter of 0.01 µm or more and less than 0.5 µm in a range of 0.01 mass% or more and 3 mass% or less.
The stretched film according to any one of claims 1 to 3, wherein the number of coarse aggregated particles having a maximum length of 25 µm or more contained in the film is 10 or less per 1 m 2 .
The stretched film according to any one of claims 1 to 3, wherein a void ratio represented by the following formula (1) generated around the porous particles or porous silica particles contained in the film is 50% or less.
Void ratio = ((void diameter around particle−particle diameter) / void diameter around particle) × 100 (1)
(1) Void ratio = ((void diameter around particles−particle diameter) / void diameter around particles) × 100
The stretched film according to any one of claims 1 to 3, which is used for a capacitor.