JP5806025B2 - High insulation film - Google Patents

Description

  The present invention relates to a highly insulating film containing a thermoplastic polyetherketone resin as a main component.

  In recent years, electronic devices have been downsized, and electronic components such as capacitors have been downsized accordingly. On the other hand, due to an increase in power to be handled, heat generation of the electronic device itself is increased, and there are advances in hybrid vehicles, electric vehicles, and the like, and electronic components that can be used in a high temperature environment are demanded. Therefore, high electrical insulation and high heat resistance have been required for films used for capacitors.

  As an electrically insulating film, particularly an electrically insulating film used as an insulator of a capacitor, a film made of polyethylene, polypropylene, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) or the like is well known. In recent years, for the purpose of increasing the heat resistance of capacitors, studies using other resins and studies for modifying these resins have been conducted. For example, in Patent Documents 1 and 2, the use of a thermoplastic polyetherketone film having excellent heat resistance for electrical insulation applications such as a capacitor has been studied.

  However, although the thermoplastic polyether ketone film is excellent in heat resistance, it has a drawback that it is slightly inferior in electrical insulation as compared with a polypropylene film or the like. In addition, a polypropylene film or the like has insufficient heat resistance, and a film having high heat resistance and electrical insulation is required.

JP 57-137116 A JP-A 61-37419 JP-A-1-205511

  An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a highly insulating film having excellent electrical insulation properties such as heat resistance and dielectric breakdown voltage. In particular, it is to provide a highly insulating film having excellent dielectric breakdown voltage characteristics even in a high temperature environment.

  As a result of diligent studies to solve the above problems, the present inventors have found that a biaxially stretched film using a thermoplastic polyetherketone resin as a main component has a water contact angle of 85 ° or more on at least one surface thereof. It was found that by providing a coating layer of 120 ° or less, a biaxially stretched film having excellent heat resistance and electrical insulation and excellent breakdown voltage characteristics even in a high temperature environment can be obtained, and the present invention has been achieved. did.

That is, the present invention relates to a biaxially stretched film having a thickness direction refractive index of 1.640 or less, the main component of which is a thermoplastic polyetherketone resin (A), and a surface water provided on at least one surface thereof. contact angle 85 ° or more, possess a coating layer is less than 120 °, in the machine direction and its perpendicular direction (lateral direction), the breaking strength (breaking strength 23) at 23 ° C. is at each 200MPa or more, highly insulating film breaking strength ratio of the breaking strength of (breaking strength 140) and 23 ° C. (breaking strength 140 / breaking strength 23) Ru least 0.7 Ah respectively at 140 ° C. is provided.

As a preferred embodiment of the present invention, the coating layer is at least one selected from the group consisting of a wax component, a silicone component and a fluorine compound, and is 41% by mass or more and 94% by mass or less based on the mass of the coating layer. A biaxially stretched film comprising a resin composition of a thermoplastic polyetherketone resin (A) and a resin component (B) having a glass transition temperature (Tg) of 180 ° C. or higher, and a resin component The content of (B) is in the range of 5 to 48% by mass based on the mass of the biaxially stretched film, the resin component (B) is a polyimide resin, and the biaxially stretched film is 1 An antioxidant (C) having a mass% weight loss temperature of 280 ° C. or higher is contained from 0.5% by mass to 8% by mass based on the mass of the biaxially stretched film, and the temperature is 150 ° C. for 30 minutes. Upon treatment, insulation in the direction this absolute value of the thermal shrinkage factor (transverse direction) is 1.0% or less, respectively, 23 ° C. and the breakdown voltage at 1 40 ℃ (BDV140) orthogonal machine direction and therewith At least one of ratio of breakdown voltage (BDV140 / BDV23) is 0.7 or more, electrical insulation, particularly for capacitors, and film thickness is 0.4 μm or more and less than 6.5 μm. It is preferable to further comprise one aspect, and these are included.

  ADVANTAGE OF THE INVENTION According to this invention, the highly insulating film excellent in heat resistance and electrical insulation can be provided. In particular, it is possible to provide a highly insulating film having excellent dielectric breakdown voltage characteristics in a high temperature environment. The highly insulating film of the present invention having such characteristics can be suitably used for electrical insulation used in a high temperature environment, and particularly for mobile objects, particularly automobile moving objects such as hybrid cars and electric cars. It can be suitably used for a capacitor, and its industrial value is extremely high.

The present invention will be described in detail below.
[Biaxially stretched film]
The biaxially stretched film in the present invention comprises a thermoplastic polyether ketone resin as a main component. Here, “main” means 51% by mass or more, preferably 59% by mass or more, more preferably 65% by mass or more, still more preferably 75% by mass or more, particularly preferably 92% by mass or more based on the biaxially stretched film. Represents a thermoplastic polyetherketone resin.

または

を単独で、あるいは該単位と他の構成単位からなるポリマーである。 <Thermoplastic polyether ketone resin (A)>
The thermoplastic polyetherketone resin (A) in the present invention is a structural unit.

Or

Is a polymer composed of the unit alone and other structural units.

等が挙げられる。上記構成単位において、Ａは直接結合、酸素、−ＣＯ−、−ＳＯ_２−または二価の低級脂肪族炭化水素基であり、Ｑ及びＱ’は同一であっても相違してもよく、−ＣＯ−または−ＳＯ_２−であり、ｎは０または１である。これらポリマーは、特公昭６０−３２６４２号公報、特公昭６１−１０４８６号公報、特開昭５７−１３７１１６号公報等に記載されている。 Examples of such other structural units include:

Etc. In the above structural unit, A is a direct bond, oxygen, —CO—, —SO ₂ — or a divalent lower aliphatic hydrocarbon group, and Q and Q ′ may be the same or different, CO— or —SO ₂ —, and n is 0 or 1. These polymers are described in JP-B-60-32642, JP-B-61-1486, JP-A-57-137116, and the like.

  As the thermoplastic polyetherketone resin (A) in the present invention, an embodiment containing the above formula [Chemical Formula 2] is preferable, and the content thereof is preferably 60, based on the mass of the thermoplastic polyetherketone resin (A). More than 66% by mass, more preferably 66% by mass or more, more preferably 75% by mass or more, and particularly preferably 80% by mass or more. By adopting such an embodiment, the electrical insulation is improved while maintaining the heat resistance. The effect can be enhanced, and the dielectric breakdown voltage characteristics in a high temperature environment can be further improved.

As described above, the thermoplastic polyether ketone resin (A) is known per se and can be produced by a method known per se.
Further, the thermoplastic polyetherketone resin (A) in the present invention has an apparent melt viscosity of 500 to 10,000 poise, more preferably 1000 to 5000 poise under the conditions of a temperature of 380 ° C. and an apparent shear rate of 1000 sec ^−1. A thing is preferable since it is excellent in film forming property.

<Antioxidant (C)>
In the present invention, the biaxially stretched film containing the thermoplastic polyetherketone resin (A) as a main constituent contains a specific amount of the antioxidant (C), so that the electrical characteristics are higher. can do.
Such an 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. Antioxidants include phenolic antioxidants and amine-based antioxidants, and secondary antioxidants include phosphorus-based antioxidants and sulfur-based antioxidants.

  Specific examples of the phenolic antioxidant include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, and 2-t-butyl-4-methoxy. Phenol, 3-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4- [4,6-bis (octylthio) -1,3,5-triazin-2-ylamino] phenol, n -Monophenol antioxidants such as octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2 , 2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl) 6-t-butylphenol), N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N′-hexane-1,6-diylbis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionamide], 3,9-bis [1,1-dimethyl-2- [β- (3-t-butyl-4-hydroxy-5] -Methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5.5] undecane and other bisphenol antioxidants, 1,1,3-tris (2-methyl-4-hydroxy- 5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, pentaerythritol tetrakis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], bis [3,3′-bis- (4′-hydroxy-3′-t-butylphenyl) butyric acid] glycol ester, 1,3,5-tris (3 ′, 5′-di-t-butyl-4′-hydroxybenzyl) -sec-triazine-2,4,6- (1H, 3H, 5H) trione, d-α- There may be mentioned polymer type phenolic antioxidants such as tocophenol.

Specific examples of amine-based antioxidants include alkyl-substituted diphenylamines.

  Specific examples of phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenylditridecyl) phos. Phyto, octadecyl phosphite, tris (nonylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10- (3,5-di- t-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, Tris (2,4-di-t-butylphenyl Phosphite, cyclic neopentanetetrayl bis (2,4-di-t-butylphenyl) phosphite, cyclic neopentanetetrayl bis (2,6-di-t-butyl-4-methylphenyl) phosphite 2,2′-methylenebis (4,6-di-t-butylphenyl) octyl phosphite and the like.

  Specific examples of the sulfur-based antioxidant include dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythritol. Tetrakis (3-lauryl thiopropionate), 2-mercaptobenzimidazole, etc. can be mentioned.

  The antioxidant in the present invention is preferably a primary antioxidant, and more preferably a phenolic antioxidant from the viewpoint that it is particularly excellent in corrosion resistance and can further enhance the effect of improving the dielectric breakdown voltage.

  The antioxidant (C) in the present invention preferably has a 1 mass% weight loss temperature of 280 ° C or higher. As a result, the thickness unevenness of the film can be made better, the in-plane variation of the electric insulation can be suppressed, and the electric insulation can be made better than simply adding an antioxidant. That is, the dielectric breakdown voltage can be increased. If the 1% by weight reduction temperature is too low, the amount of the antioxidant that is thermally decomposed during melt extrusion increases, and problems such as contamination of the process by such pyrolyzate and yellowing of the polymer are likely to occur. There is a tendency. And, such deteriorated products are likely to adhere to and accumulate on the die lip portion, which tends to cause streak-like irregularities on the film, and tends to reduce thickness unevenness, thereby tending to be poor in electrical insulation. It is in. Also, the stretchability tends to decrease. From such a viewpoint, the 1 mass% weight loss temperature of the antioxidant (C) is more preferably 300 ° C. or higher, further preferably 320 ° C. or higher, and particularly preferably 340 ° C. or higher. The antioxidant in the present invention preferably has a higher 1% by weight reduction temperature, but practically the upper limit is about 500 ° C. or less.

  Moreover, it is preferable that melting | fusing point of antioxidant (C) in this invention is 90 degreeC or more. 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 lower limit of the melting point of the antioxidant (C) is more preferably 100 ° C. or higher, further preferably 110 ° C. or higher, and particularly preferably 140 ° C. or higher. On the other hand, when the melting point of the antioxidant (C) is too high, the antioxidant (C) is hardly melted during melt extrusion, and the dispersion in the polymer tends to be poor. Thereby, problems such as the effect of adding the antioxidant (C) appear only locally. From such a viewpoint, the upper limit of the melting point of the antioxidant (C) is preferably 450 ° C. or less, more preferably 400 ° C. or less, still more preferably 380 ° C. or less, and particularly preferably 360 ° C. or less.

  A commercial item can also be used as it is as the above antioxidant (C). Examples of commercially available products include 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4. , 8,10-tetraoxaspirio [5-5] undecane (manufactured by Sumitomo Chemical Co., Ltd .: trade name SUMILIZER GA-80), 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 (Ciba Specialty Chemicals: Trade name IRGANOX1024), N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl) Le 4-hydroxyphenyl) propionamide] (Ciba Specialty Chemicals Inc., trade name Irganox 1098) and the like are preferably exemplified.

  The biaxially stretched film in the present invention preferably contains the antioxidant (C) in an amount of 0.5% by mass or more and 8% by mass or less based on the mass of the biaxially stretched film. By setting the content of the antioxidant (C) within the above numerical range, the dielectric breakdown voltage is excellent. When there is too little content of antioxidant (C), the addition effect of antioxidant is not enough and it exists in the tendency for the improvement effect of a dielectric breakdown voltage to fall. From such a viewpoint, the lower limit of the content of the antioxidant (C) is preferably 0.7% by mass or more, more preferably 1.0% by mass or more, and particularly preferably 1.5% by mass or more. On the other hand, when there is too much content, it exists in the tendency for antioxidant to aggregate in a film, the fault resulting from antioxidant tends to increase, and the improvement effect of a dielectric breakdown voltage becomes scarce. In addition, if the content is too high, the deterioration of the antioxidant tends to adhere to and accumulate on the extrusion die lip during high temperature melt extrusion, which causes streaky irregularities on the film, resulting in uneven thickness. It also becomes a factor that makes the effect of improving the breakdown voltage poor. Also, the stretchability tends to decrease. From such a viewpoint, the upper limit of the content of the antioxidant (C) is preferably 7% by mass or less, more preferably 5% by mass or less, and particularly preferably 3% by mass or less.

  One type of the antioxidant (C) as described above may be used alone, or two or more types may be used in combination. When two or more types are used in combination, an embodiment using two or more types of primary antioxidants may be used, an embodiment using two or more types of secondary antioxidants may be used, or one or more types of primary antioxidants and 1 Two or more kinds of secondary antioxidants may be used in combination. For example, it can be expected to prevent both primary oxidation and secondary oxidation by using two types of antioxidants, a primary antioxidant and a secondary antioxidant, in combination. In the present invention, an embodiment in which a primary antioxidant is used alone or an embodiment in which two or more kinds of primary antioxidants are used is preferable from the viewpoint that the effect of improving the dielectric breakdown voltage can be further increased. An embodiment using a single antioxidant or an embodiment using two or more phenolic antioxidants is preferred.

<Inert particles>
The biaxially stretched film in the present invention preferably contains inert particles as long as the effects of the invention are not impaired in order to improve the handleability of the highly insulating film. In order for the film to contain an inert particle, for example, it is preferable that the thermoplastic polyether ketone resin contains the inert particle in advance. In addition, a known method such as addition of inert particles in the step of melt-extruding the thermoplastic polyetherketone resin can be employed.

  Examples of the inert particles include inorganic particles containing elements of Periodic Tables IIA, IIB, IVA, and IVB (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide (silica), etc.). And organic particles made of a polymer having high heat resistance such as a crosslinked silicone resin, a crosslinked polystyrene resin, and a crosslinked acrylic resin. Among these, inorganic particles are preferable for reasons such as high heat resistance, and silica particles are particularly preferable.

  The average particle size of the inert particles is preferably 0.01 μm or more and 3 μm or less, more preferably 0.05 μm or more and 2 μm or less, and particularly preferably 0.1 μm or more and 1 μm or less. The content is preferably 0.01% by mass or more and 3.0% by mass or less, more preferably 0.03% by mass or more and 2.0% by mass or less, and particularly preferably 0.00% by mass or less based on the mass of the biaxially stretched film. It is 05 mass% or more and 1.0 mass% or less. By adopting the above average particle size and content, the handling properties can be improved more efficiently, and the mechanical properties of the biaxially stretched film (breaking strength, breaking elongation, Young's modulus, etc.) And electrical characteristics (such as dielectric breakdown voltage) are not reduced excessively.

The inert particles in the present invention preferably have a spherical shape, and when the ratio of the major axis to the minor axis (major axis / minor axis) of the inert particles is defined as the particle size ratio, the particle size ratio Is preferably 1.20 or less, more preferably 1.10 or less, particularly preferably 1.05 or less, and the handling property can be further improved.
Such inert particles can be used in combination of two or more kinds having different types and average particle diameters, and are preferable from the viewpoint of improving handling properties. In addition, it is easier to achieve both handleability and dielectric breakdown voltage in such a manner.

<Other additives>
The thermoplastic polyether ketone resin in the present invention may be blended with a resin such as polyarylene polyether, polysulfone, polyarylate, polyester, or polycarbonate for the purpose of improving fluidity. In addition, for the purpose of improving heat resistance and other properties, resin components having a high glass transition temperature (Tg) described later, such as polyimide resins, polyarylate resins, polyether sulfone resins, polysulfone resins, etc. You may blend. Further, additives such as a stabilizer and an ultraviolet absorber may be contained.

(High Tg resin component (B))
In this invention, it is preferable to contain the resin component (B) whose glass transition temperature (Tg) is high, Preferably Tg is 180 degreeC or more. By adding such a high Tg resin component (B), the effect of improving heat resistance and electrical insulation can be further increased. Moreover, the improvement effect of the dielectric breakdown voltage in a high temperature environment can be heightened. When Tg of the resin component (B) is less than 180 ° C., the effect of improving electrical insulation tends to be reduced. From such a viewpoint, the Tg of the resin component (B) is preferably 190 ° C. or higher, more preferably 200 ° C. or higher, and further preferably 210 ° C. or higher. If the Tg of the resin component (B) is too high, the difference from the Tg of the thermoplastic polyetherketone resin (A) tends to be too large, and the compatibility and kneadability at the time of melting tend to deteriorate. is there. From such a viewpoint, the Tg of the resin component (B) is preferably 300 ° C. or lower, more preferably 260 ° C. or lower, and further preferably 230 ° C. or lower. Moreover, it is preferable that this resin component (B) is non-crystalline from a compatible and kneadable viewpoint.

  Examples of the resin constituting the resin component (B) include polyarylate resins, polyimide resins, polyether sulfone resins, and polysulfone resins. Among them, more excellent heat resistance, electrical insulation, phase From the viewpoint of obtaining solubility and kneadability, a polyimide resin is preferable.

  Such a polyimide resin is a melt-formable polymer containing a cyclic imide group and is not particularly limited as long as it can meet the object of the present invention, but is an aliphatic, alicyclic or aromatic ether unit. A polyetherimide containing a cyclic imide group as a repeating unit is preferred. For example, polyether imides described in U.S. Pat. Nos. 4,141,927, 2,262,678, 2,606,912, 2,606,914, 2,596,565, 2,596,656, and 2,598,478 are disclosed. No. 2598536, Japanese Patent No. 2599171, Japanese Patent Laid-Open No. 9-48852, Japanese Patent No. 2565556, Japanese Patent No. 2564636, Japanese Patent No. 2564537, Japanese Patent No. 2563548, Japanese Patent No. 2563547, Japanese Patent No. 2558341, Japanese Patent No. 2558341 Examples include polymers described in Japanese Patent Nos. 2558339 and 28345580.

Moreover, structural units other than cyclic imide and ether units, for example, aromatic, aliphatic, alicyclic ester units, oxycarbonyl units and the like may be contained in the main chain of polyimide.
In the present invention, specific examples of the polyetherimide that can be preferably used as a high Tg resin component include polymers represented by the following general formula.

（ただし、上記式中、Ｒ_１は、６〜３０個の炭素原子を有する２価の芳香族または脂肪族残基であり、Ｒ_２は、６〜３０個の炭素原子を有する２価の芳香族残基、２〜２０個の炭素原子を有するアルキレン基、２〜２０個の炭素原子を有するシクロアルキレン基、及び２〜８個の炭素原子を有するアルキレン基で連鎖停止されたポリジオルガノシロキサン基からなる群より選択された２価の有機基である。）

(Wherein R ₁ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, and R ₂ is a divalent aromatic having 6 to 30 carbon atoms. Group residues, alkylene groups having 2 to 20 carbon atoms, cycloalkylene groups having 2 to 20 carbon atoms, and polydiorganosiloxane groups chain-terminated with alkylene groups having 2 to 8 carbon atoms A divalent organic group selected from the group consisting of:

As said R < ₁ >, R < ₂ >, the aromatic residue shown by the following formula group can be mentioned, for example.

  In the present invention, the glass transition temperature (Tg) is preferably 300 ° C. or lower, more preferably 260 ° C. or lower, from the viewpoints of compatibility / kneading properties with the thermoplastic polyether ketone resin (A), cost, and melt moldability. More preferably, a polyetherimide at 230 ° C. or lower is preferable, and 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylene having a structural unit represented by the following formula Most preferred are condensates with diamine or p-phenylenediamine, and copolymers and modified products thereof. This polyetherimide is manufactured by GE Plastics, for example, and can be exemplified by what is known under the trade name of ““ Ultem ”1000, 5000, and 6000 series”.

または

Or

  The content of the resin component (B) is preferably 5 to 48% by mass based on the mass of the biaxially stretched film. When the content is in the above numerical range, the effect of improving heat resistance and electrical insulation can be increased, and the effect of improving the dielectric breakdown voltage in a high temperature environment can be increased. If the content is too small, the effect of improving heat resistance and electrical insulation tends to be reduced. From such a viewpoint, the content of the resin component is preferably 8% by mass or more, and more preferably 14% by mass or more. Moreover, when there is too much content, it will become easy to fracture | rupture at the time of film forming, and it exists in the tendency for film forming property (stretchability) to worsen. From such a viewpoint, the content of the resin component (B) is preferably 35% by mass or less, and more preferably 25% by mass or less.

<Coating layer>
The highly insulating film of the present invention has a coating layer having a water contact angle of 85 ° or more and 120 ° or less on at least one surface thereof. By having such a coating layer, the dielectric breakdown voltage can be increased. The reason for this is not clear, but it is considered that the presence of a thin coating layer between the biaxially stretched film and the electrode can alleviate charge concentration and improve the dielectric breakdown voltage. Further, when a coating layer that is a thin layer having a surface energy smaller than that of the biaxially stretched film is present, the coating layer is peeled off from the biaxially stretched film even when electric discharge occurs, and the biaxially stretched film that is a dielectric It is considered that the breakdown voltage is prevented and breakdown voltage is improved as a result. That is, in the present invention, when the water contact angle on the surface of the coating layer is in the above numerical range, the coating layer peels off from the film at the same time as voltage is applied and discharge occurs, and only the peeled coating layer is destroyed, It is considered that the breakdown voltage is improved as a result without being broken.

  For this reason, if the water contact angle of the coating layer is too low, the coating layer is difficult to peel off from the film even if a discharge occurs, and since the peeling is incomplete, the dielectric breakdown of the coating layer is induced and the dielectric breakdown of the film occurs. Therefore, the effect of improving the dielectric breakdown voltage by the coating layer cannot be obtained. Moreover, when the water contact angle of the coating layer is in the above range, it is possible to improve the slipping property and improve the winding property, and it is also possible to improve the heat resistance as seen by shear stress described later.

  From such a viewpoint, the water contact angle on the surface of the coating layer is preferably 86 ° or more, more preferably 88 ° or more, still more preferably 90 ° or more, and particularly preferably 95 ° or more. On the other hand, when the water contact angle is high, the coating layer tends to be peeled off from the film. Therefore, even when discharge occurs, only the easily peeled coating layer is broken, and the film is hardly broken down. However, if the water contact angle on the surface of the coating layer becomes too high, the adhesiveness with the metal layer formed on the capacitor becomes low, and particularly when the water contact angle exceeds 120 °, the adhesion with the metal layer is reduced. It tends to be inferior in performance and difficult to function as a capacitor. From such a viewpoint, the water contact angle on the surface of the coating layer needs to be 120 ° or less, preferably 115 ° or less, more preferably 110 ° or less, and further preferably 105 ° or less.

  In order to achieve the value of the surface water contact angle as described above, for example, a component that can reduce the surface energy after forming the coating layer, such as a wax component, a silicone component, or a fluorine component, is contained in the coating layer. Good. Moreover, the water contact angle in the coating layer surface can also be adjusted by adjusting these content and the thickness of a coating layer. Preferably, it is an embodiment in which the components described later are contained in the content described later. Of the wax component, silicone component, and fluorine component, the wax component and silicone component are particularly preferred.

  The type of the coating layer in the present invention is not particularly limited as long as the above-described surface water contact angle is achieved, but at least one selected from the group consisting of a wax component, a silicone component and a fluorine component is used as the mass of the coating layer. The content is preferably 41% by mass or more and 94% by mass or less. Here, the content indicates the total content of the wax component, the silicone component, and the fluorine component in the coating layer. When the coating layer contains at least one of these components in the above content, the surface energy of the coating layer can be easily made smaller than the surface energy of the film, and the water contact angle on the surface of the coating layer can be reduced. The numerical range can be achieved more easily. When the content is too small, the water contact angle tends to be difficult to increase. From such a viewpoint, the content of the above components is more preferably 51% by mass or more, and particularly preferably 65% by mass or more. On the other hand, if the content is large, the contact angle tends to increase, so that it tends to be preferable from the viewpoint of peeling of the coating layer, but if it is too much, it becomes difficult to form a uniform coating layer, for example, Defects in the coating layer such as missing coating are likely to occur, or the coating layer is easily peeled off from the film, and these improve the dielectric breakdown voltage improvement effect. In addition, when manufacturing a capacitor, the releasability of the coating layer is too high and the metal layer easily peels off, and the metal layer is easily detached during processing into a capacitor such as winding, resulting in a defective capacitor. May occur. From such a viewpoint, the content is more preferably 90% by mass or less, and particularly preferably 85% by mass or less.

(Wax component)
Examples of the wax component include synthetic waxes such as polyolefin waxes and ester waxes, and natural waxes such as carnauba wax, candelilla wax and rice wax. Examples of polyolefin waxes include polyethylene wax and polypropylene wax. Examples of ester waxes include ester waxes composed of aliphatic monocarboxylic acids having 8 or more carbon atoms and polyhydric alcohols, and specific examples thereof include sorbitan tristearate, pentaerythritol triplet. Nate, glycerin tripalmitate and polyoxyethylene distearate are exemplified. Among these waxes, it is preferable to use a polyolefin-based wax because the contact angle defined by the present invention is easily satisfied. Particularly preferred is polyethylene wax.
In addition, the wax is preferably water-soluble or water-dispersible from the viewpoint of exhibiting good dispersibility in the coating layer and thereby improving the dielectric breakdown voltage.

(Silicone component)
The silicone component is preferably a silicone composition mainly formed from a silicone compound having a reactive group. Here, “mainly” means, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more in the silicone component. By setting it as such an aspect, the improvement effect of a dielectric breakdown voltage can be made high. The silicone compound having no reactive group may be contained in the silicone component. However, if the content is too large (for example, 30% by mass or more in the silicone component), the formation of the vapor deposition layer is not possible. Difficult to evaluate as a capacitor. Therefore, the silicone compound having no reactive group is preferably 20% by mass or less, more preferably 10% by mass or less, in the silicone component.

  Examples of the silicone compound include polydimethylsiloxane in which a methyl group may be substituted with another alkyl group or a phenyl group. By using this, the effect of improving the breakdown voltage can be further increased. Can be high. Examples of the reactive group preferably include a hydrogen group, a vinyl group (including vinyl alkyl groups such as an allyl group), and a hydroxyl group. That is, as the silicone compound having a reactive group, polydimethylsiloxane having these reactive groups is particularly preferable. In the polydimethylsiloxane having such a reactive group, the reactive group has two or more reactive groups in the molecule and is usually directly bonded to a silicon atom. Then, due to heat applied at the time of forming the coating layer, preferably using a catalyst such as platinum or palladium, an addition reaction occurs in the hydrogen group and the vinyl group, or a condensation reaction occurs in the hydrogen group and the hydroxyl group, and curing is performed. Reaction occurs to form a crosslinked structure, resulting in a silicone composition.

The silicone compound may be a mixture of silicone compounds having different types of reactive groups. Such a silicone compound preferably has a molecular weight of 1,000 to 500,000. If it is less than 1000, the cohesive force of the coating film may be reduced and the coating layer may be easily lost. If it exceeds 500,000, the viscosity becomes high and handling may be difficult.
From the viewpoint of easy handling of the coating liquid for forming the coating layer and good dispersibility in the coating layer, thereby enhancing the effect of improving the dielectric breakdown voltage, the silicone compound and polydimethylsiloxane are water-soluble or It is preferably water-dispersible.

  In the present invention, the silicone compound is preferably used in combination with a silane coupling agent. Such a silane coupling agent is a silane compound having a hydrolyzable group directly bonded to a silicon atom, and preferably having a reactive group described later. The silane compound having a reactive group has a hydrolyzable group directly bonded to a silicon atom, and is selected from an organic group containing an amino group, an organic group containing an epoxy group, and an organic group containing a carboxylic acid group It is preferable to use one containing at least one group. The hydrolyzable group is an organic group that generates a silanol group by hydrolysis and reaction, such as an alkoxy group or a halogen group, such as a methoxy group or an ethoxy group.

  For example, specific examples of reactive groups in such silane compounds include organic groups containing amino groups such as primary amino groups such as 3-aminopropyl group, 3-amino-2-methyl-propyl group, and 2-aminoethyl group. Examples thereof include organic groups having primary and secondary amino groups, such as alkyl groups, N- (2-aminoethyl) -3-aminopropyl groups, and N- (2-aminoethyl) -2-aminoethyl groups. . Examples of the organic group containing an epoxy group include glycidoxyalkyl groups such as γ-glycidoxypropyl group, β-glycidoxyethyl group, γ-glycidoxy-β-methyl-propyl group, and 2-glycidoxycarbonyl-ethyl. And a glycidoxycarbonylalkyl group such as a 2-glycidoxycarbonyl-propyl group. Examples of organic groups that generate silanol groups by hydrolysis include alkoxy groups such as methoxy group, ethoxy group, butoxy group, and 2-ethylhexyloxy group, β-methoxyethoxy group, β-ethoxyethoxy group, and butoxy-β-ethoxy group. Such as alkoxy-β-ethoxy group, acetoxy group, propoxy group and the like, N-alkylamino group such as methylamino group, ethylamino group and butylamino group, N, N-dialkylamino group such as dimethylamino group and diethylamino group And heterocyclic groups containing nitrogen such as imidazole group and pyrrole group.

  Preferred silane coupling agents in the present invention include those having three methoxy groups as hydrolyzable groups, γ-glycidoxypropyl groups as reactive groups, and three ethoxy groups as hydrolyzable groups. Are bonded to form a reactive group and have a γ-glycidoxypropyl group. By adding such a silane coupling agent, the crosslinking density of the silicone compound thin film can be increased. When the coating film rigidity is increased, breakage of the film due to discharge can be further suppressed, and the dielectric breakdown characteristics are improved.

(Fluorine component)
Examples of the fluorine component include a polymer using a fluoroethylene monomer and a polymer using a fluorinated alkyl (meth) acrylate monomer. Examples of (co) polymers using fluoroethylene monomers include (co) polymers such as tetrafluoroethylene, trifluoroethylene, difluoroethylene, monofluoroethylene, and difluorodichloroethylene.

(Other additives)
In addition, the coating layer may contain a surfactant, a crosslinking agent, a lubricant and the like.
The surfactant is used for the purpose of increasing the wettability of the coating liquid for forming the coating layer on the film or improving the stability of the coating liquid. For example, polyoxyethylene-fatty acid ester, sorbitan fatty acid Examples include anionic and nonionic surfactants such as esters, glycerin fatty acid esters, fatty acid metal soaps, alkyl sulfates, alkyl sulfonates, and alkyl sulfosuccinates. It is preferable that 1-60 mass% of surfactant is contained on the basis of the mass of an application layer.

  Moreover, the addition of a crosslinking agent is preferred because the cohesive force of the coating layer can be improved. Examples of the crosslinking agent include epoxy compounds, oxazoline compounds, melamine compounds, and isocyanate compounds, and other coupling agents can also be used. It is preferable that the addition amount of a crosslinking agent is 5-30 mass% on the basis of the mass of an application layer.

  Furthermore, the coating layer of the present invention is inert to the components forming the coating layer for the purpose of further improving the handleability of the resulting highly insulating film or preventing blocking between the films. Fine particles can be added. Such fine particles are preferably organic or inorganic inert fine particles, such as calcium carbonate, calcium oxide, aluminum oxide, kaolin, silicon oxide, zinc oxide, silica particles, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, crosslinked particles. Examples thereof include silicone resin particles.

  The thickness of the coating layer is preferably 0.005 to 0.5 μm, more preferably 0.005 to 0.2 μm, and still more preferably 0.02 to 0.1 μm as the thickness after drying. By setting the thickness of the coating layer within this range, when peeling and causing dielectric breakdown, energy of a larger voltage can be lost, and the effect of improving the dielectric breakdown voltage can be enhanced. When the thickness of the coating layer is less than the lower limit value, the effect of improving the dielectric breakdown voltage may not be sufficiently exhibited. Moreover, even if the thickness of the coating layer is increased to an extent that exceeds the upper limit value, a further effect of improving the dielectric breakdown voltage may not be obtained.

<Metal layer>
The highly insulating 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.

[Production method of highly insulating film]
The highly insulating film of the present invention has a machine axis direction (hereinafter sometimes referred to as a longitudinal direction, a longitudinal direction or MD) and a direction (hereinafter referred to as a lateral direction or a width direction) orthogonal to the machine axis direction and the thickness direction. Alternatively, the coating layer may be formed on a biaxially stretched film stretched in the biaxial direction. By biaxially stretching the film forming the coating layer in this way, mechanical properties (breaking strength, breaking elongation, Young's modulus, etc.) are improved, and it is also highly suitable for electrical insulation, especially for capacitors. Heat resistance and electrical insulation can be expressed, and a high dielectric breakdown voltage can be expressed in a high temperature environment. Such biaxial stretching may be either simultaneous biaxial stretching or sequential biaxial stretching. However, sequential biaxial stretching is preferable from the viewpoint of making thickness unevenness better, and the order of stretching is longitudinal stretching first. Then, it is preferable to carry out the transverse stretching to improve the thickness unevenness and from the viewpoint of productivity.
Hereinafter, the manufacturing method of the biaxially stretched film in this invention is demonstrated.

<Extrusion process>
The pellets of the mixture of the thermoplastic polyetherketone resin (A) and the resin (B) as necessary are put into an extruder, and heated and melted at a temperature of (Tm + 20) ° C. or higher and (Tm + 90) ° C. or lower to form a sheet. After extrusion, it is cooled and solidified by bringing it into contact with a cooling roll to obtain an unstretched film. Here, Tm is a melting point (unit: ° C.) of a resin mixture composition of a thermoplastic polyetherketone resin (A) obtained by a differential scanning calorimeter (DSC) and a resin (B) mixed as necessary. Represents.
In order to make the film contain a high Tg resin component (B), an antioxidant (C) and other additives, for example, a thermoplastic polyetherketone resin before the pellets are put into an extruder. The method of previously containing a high Tg resin component (B), antioxidant (C), and other additives is preferable. In addition, a known method such as adding an antioxidant or the like in the step of melt-extruding the thermoplastic polyetherketone resin after putting the pellets into the extruder can be employed.

<Extension process>
Subsequently, the obtained unstretched film is stretched biaxially in the machine direction and the transverse direction.
Stretching in the longitudinal direction (hereinafter sometimes referred to as longitudinal stretching) is performed at a temperature (Tg−10) ° C. to (Tg + 45) ° C. and a magnification of 1.5 to 5.0 times. The stretching temperature is preferably (Tg) ° C. or more and (Tg + 30) ° C. or less, and the stretching ratio is preferably 2.0 times or more and 4.0 times or less, more preferably 2.4 times or more and 3.5 times or less. is there.
In the present invention, as described later, an unstretched sheet, such an unstretched sheet, preferably a uniaxially stretched film uniaxially stretched in the longitudinal direction, by applying a coating liquid for forming a coating layer, It is preferable to form a coating layer.

  Stretching in the transverse direction (hereinafter sometimes referred to as transverse stretching) is performed at a temperature (Tg + 10) ° C. to (Tg + 40) ° C. and a magnification of 2.5 to 5.0 times. The stretching temperature is preferably (Tg + 15) ° C. or more and (Tg + 30) ° C. or less, and the stretching ratio is preferably 2.5 times or more and 3.5 times or less. Here, Tg represents the glass transition temperature (unit: ° C.) of the thermoplastic polyetherketone resin (A) required by DSC. In addition to the thermoplastic polyetherketone resin (A), the resin component (B), etc. Represents a melting point (unit: ° C.) of the resin composition in the case where the resin composition is mixed as necessary.

  By making the stretching conditions (stretching temperature and stretching ratio) in the longitudinal direction and the transverse direction as described above, the effect of improving heat resistance and electrical insulation can be enhanced. Moreover, the dielectric breakdown voltage in a high temperature environment can be further increased. Moreover, a thickness spot can be made into a more favorable range. Increasing the draw ratio tends to increase heat resistance and electrical insulation. Further, the thickness unevenness tends to be improved. Also, the Young's modulus and breaking strength in the same direction tend to increase. If the stretching temperature is too low, film breakage tends to occur, and thickness unevenness tends to be worsened.On the other hand, if the stretching temperature is too high, so-called flow stretching tends to occur, and thickness unevenness tends to be worsened. There is a tendency to be inferior in electrical insulation.

  Here, in the present invention, in order to make the electrical insulation better, it is preferable to carry out transverse stretching by dividing it into a plurality of temperature regions, with the temperature of the first region and the temperature of the final region, It is preferable to set a temperature difference of 3 ° C. or more and 60 ° C. or less. If the temperature difference is too large or too small, the effect of improving electrical insulation tends to be low. If the temperature difference is too small, for example, when the transverse stretching temperature is medium, the stretching stress tends to be low at the stretching start portion and the stretching stress tends to be high at the stretching end portion (final region). It is likely that the thickness becomes large and variation tends to occur, or the thickness unevenness of the film tends to deteriorate, and the effect of improving electrical insulation tends to decrease. On the other hand, if the temperature difference is too large, it is likely that local temperature fluctuations and temperature variations are likely to occur because the temperature changes greatly in the adjacent area, and the thickness unevenness tends to deteriorate. And the effect of improving the electrical insulation tends to be low. From such a viewpoint, the lower limit of the temperature difference is more preferably 5 ° C. or more, more preferably 10 ° C. or more, particularly preferably 17 ° C. or more, and the upper limit of the temperature difference is more preferably 50 ° C. or less, and 40 ° C. or less. More preferably, 30 ° C. or less is particularly preferable, and more preferable electrical insulation can be obtained.

  In the transverse stretching step, in order to create a temperature difference between the first region and the final region, a temperature difference may be provided between the zone entrance (first region) and the outlet (final region) in one stretching zone. Alternatively, two or more continuous stretching zones having different temperatures may be provided, and a temperature difference may be provided between the first stretching zone (first region) and the last stretching zone (final region). Here, the zone indicates one area divided by a shutter or the like in a tenter or the like. In any case, it is preferable to further divide between the first region and the final region and increase the temperature from the first region toward the final region, and it is particularly preferable to increase the gradient so as to be linear. For example, in the case of two or more continuous stretching zones having different temperatures, it is preferable to further provide one or more stretching zones between the first stretching zone and the last stretching zone, and one or more stretching zones are provided. More preferably. Setting the total number of stretching zones to 13 or more is disadvantageous in terms of equipment costs.

  The draw ratio should be such that the value obtained by dividing the film width immediately after leaving the final area by the film width immediately before entering the first area is the target draw ratio, and the film width is increased step by step. It is preferable to increase the gradient so that the gradient is linear. In the case where the machine direction and the transverse direction are drawn simultaneously, the drawing temperature is similarly divided into a plurality of stages, and a temperature difference is provided between the first stage temperature and the final stage temperature.

  Furthermore, in the present invention, in the above stretching conditions, the area stretching ratio (longitudinal stretching ratio × lateral stretching ratio) is preferably 5 times or more, more preferably 6 times or more, and 7 times or more. It is more preferable to make the thickness unevenness better. If the area stretch ratio is too high, the film tends to break, and the upper limit is preferably 25 times or less, more preferably 20 times or less, and particularly preferably 15 times or less.

<Heat setting process>
Next, the film biaxially stretched as described above is heat-treated and heat-set. The heat setting is performed at a temperature of (Tg + 27) ° C. or more and (Tm) ° C. or less, preferably (Tg + 60) ° C. or more and (Tm−20) ° C. or less, more preferably (Tg + 90) ° C. or more and (Tm−30) ° C. or less. The time is 1 second to 10 minutes, preferably 2 seconds to 5 minutes, preferably 3 to 120 seconds, more preferably 5 to 60 seconds. Heat setting is divided into two or more steps, such as a heat treatment that is continuously performed after the stretching process when forming a biaxially stretched film and a heat treatment that is performed separately after the formation of a biaxially stretched film. May be.
By setting the heat setting conditions (heat setting temperature and heat setting time) as described above, the effect of improving heat resistance and electrical insulation can be enhanced. Moreover, a thickness spot can be made into a more favorable range. Further, the thermal shrinkage rate can be set in a numerical range preferably defined by the present invention. If the heat setting temperature is too high, the effect of improving heat resistance and electrical insulation tends to be low, and thickness unevenness tends to be poor. On the other hand, if it is too low, the heat shrinkage rate tends to be high.

<Thermal relaxation treatment>
Next, the film heat-fixed as described above is preferably subjected to heat relaxation treatment in the width direction in order to adjust the heat shrinkage rate. Specifically, the temperature is 180 ° C. or more and 320 ° C. or less, and the relaxation rate is 1% or more. It is preferable to perform a heat relaxation treatment of 7% or less. When the relaxation rate is too high, the thermal shrinkage rate tends to be low, but the flatness of the film tends to be inferior. On the other hand, if it is too low, the thermal shrinkage tends to increase. From such a viewpoint, the relaxation rate is more preferably 2% or more and 6% or less.

<Coating and drying of coating layer>
In the present invention, the coating layer is a coating solution for forming a coating layer obtained by blending each component constituting the coating layer described above, applied to the surface of the film where the coating layer is to be formed, dried, and necessary. To cure and form. In addition, this coating liquid can be diluted using a suitable solvent, and a density | concentration and a viscosity can be adjusted. As such a solvent, water is preferably used from the viewpoint of ease of handling, and thus each component is preferably water-soluble or water-dispersible.

  The coating layer may be formed by a so-called in-line method formed during film production or a so-called off-line method formed after film production. From the viewpoint of productivity and the viewpoint that a stronger coating layer can be obtained, it is preferable to employ an in-line method. In the in-line method, in the film production process, it may be applied to an unstretched sheet, may be applied to a uniaxially stretched film uniaxially stretched in the longitudinal or lateral direction, or may be applied biaxially stretched in the longitudinal and lateral directions. It may be applied to an axially stretched film (including those that have undergone orientation crystallization and those that have not been completed), but from the viewpoint of adhesion between the film and the coating layer, it is applied to an unstretched sheet or a uniaxially stretched film. It is preferable to do.

  Specifically, in the case of simultaneous biaxial stretching, it is preferable to apply a coating solution to an unstretched sheet before stretching. In the case of sequential biaxial stretching, the coating liquid may be applied in a stage before stretching in the first axial direction, or after stretching in the first axial direction and in the second axial direction. You may apply | coat a coating liquid in the step before performing. Among these, it is easy to suppress the occurrence of scratches by applying the coating liquid in the stage after stretching in the first axial direction and before stretching in the second axial direction. It is preferable because there is a heat treatment fixing that advances the process, and the structure of the coating layer is easily stabilized.

  Moreover, it is preferable that the coating film obtained by apply | coating a coating liquid is dried to some extent until it enters into the following process. For example, when stretching is performed after coating, if the coating film is not sufficiently dried, temperature fluctuations are likely to occur in the film during stretching, and unevenness occurs in the stretching, resulting in poor film thickness irregularities.

  The coating film may be dried independently after application of the coating liquid, or may be performed continuously from the coating process by providing a drying process before the stretching process, and a preheating process in the stretching process may be applied. You may divert as a drying process of a film | membrane. The lower limit of the drying temperature is 60 ° C. or higher, preferably 70 ° C. or higher, more preferably 80 ° C. or higher. The upper limit is preferably 175 ° C. or lower, more preferably 155 ° C. or lower, still more preferably 135 ° C. or lower, and the drying time is 0.1 minutes or more and 10 minutes or less are preferable. If the drying temperature is too high or the drying time is too long, the crystallization of the film will proceed before stretching, the stretching stress will increase and the stretchability will decrease, and there will be many breaks during stretching. If the drying temperature is too low or the drying time is too short, the coating liquid tends to be insufficiently dried, and the diluting solvent remains in the coating film even in the stretching process. However, the evaporation occurs, stretch spots tend to occur, and the film thickness spots tend to deteriorate.

  Further examination of these reveals that the drying temperature is more strongly dependent on the drying time, and as a result, the value of [drying temperature (° C.) × drying temperature (° C.) × drying time (minutes)] is obtained. It is preferably 1000 or more, more preferably 3000 or more, further preferably 8000 or more, preferably 100,000 or less, more preferably 70,000 or less, and more preferably 30,000 or less. It turned out to be even better.

Here, the drying temperature is expressed as an average of the first temperature and the last temperature in the drying process when the coating film drying process exists apart from the stretching process. In the case where there is a drying process in succession to the application of the coating, it is expressed as an average of the initial temperature of the drying process and the temperature of the last part of the drying process (the initial temperature of the stretching process). The preheating part before a extending process may become a drying process.
Thus, the highly insulating film of the present invention can be obtained.

[Characteristics of highly insulating film]
<Film thickness>
The thickness of the highly insulating film of the present invention is preferably 0.3 μm or more and 250 μm or less. When the film thickness is too thin, the film tends to break during film formation, and the production efficiency tends to deteriorate. On the other hand, when the film thickness is too thick, the stretching stress tends to increase, and it tends to be difficult to increase the stretching ratio, and as a result, the thickness unevenness tends to deteriorate. Further, the effect of improving heat resistance and electrical insulation tends to be reduced. From such a viewpoint, the lower limit of the high insulating film thickness is more preferably 0.5 μm or more, further preferably 0.8 μm or more, and particularly preferably 1.2 μm or more. On the other hand, the upper limit of the thickness of the highly insulating film is preferably 128 μm or less, more preferably 50 μm or less, still more preferably 13 μm or less, and particularly preferably 5.5 μm or less. Moreover, when using for a capacitor | condenser use, 0.4-6.5 micrometers is preferable, 0.5-3.5 micrometers is preferable, and it can be set as a favorable electrical property.

  The thickness of the coating layer is preferably 0.005 to 0.5 μm, more preferably 0.005 to 0.2 μm, and still more preferably 0.02 to 0.1 μm as the thickness after drying. By setting the thickness of the coating layer within this range, when peeling and causing dielectric breakdown, energy of a larger voltage can be lost, and the effect of improving the dielectric breakdown voltage can be enhanced. When the thickness of the coating layer is less than the lower limit value, the effect of improving the dielectric breakdown voltage may not be sufficiently exhibited. Moreover, even if the thickness of the coating layer is increased to an extent that exceeds the upper limit value, a further effect of improving the dielectric breakdown voltage may not be obtained.

<Thick spots>
The highly insulating film of the present invention preferably has a thickness unevenness of 10% or less, and can improve the electrical insulating effect. When thickness unevenness deteriorates, in-plane variation in electrical insulation tends to increase, and as a result, the effect of improving electrical insulation and dielectric breakdown voltage characteristics tends to decrease. From such a viewpoint, the thickness unevenness is preferably 9% or less, more preferably 6% or less, and further preferably 3% or less. The lower limit of the thickness unevenness is preferably as small as possible. Ideally, the thickness unevenness is 0%, but actually it is about 0.1% or more.
In order to make the thickness unevenness within the above numerical range, the stretching condition may be the above-described embodiment. In particular, it is important that the transverse stretching conditions are divided into the above-described embodiments, that is, divided into a plurality of temperature regions.

  Moreover, in order to keep the thickness unevenness of a highly insulating film favorable, it can also mention preferably that the content in a film does not deteriorate easily. This is because when the contents such as antioxidants and other additives are easily deteriorated at high temperatures or the weight is easily reduced, these deteriorated substances are deposited on the extrusion die lip during melt extrusion. This is because adhesion tends to occur, and the effect of this tends to cause streak irregularities on the film. Similarly, even when the content of contents such as antioxidants and other additives is too large, they tend to aggregate, tend to precipitate and adhere with an extrusion die lip, and tend to deteriorate thickness spots. is there. Therefore, in order to achieve the thickness spots, adjusting the 1% by weight reduction temperature and content of the antioxidant (C), adjusting the type and blending amount of the high Tg resin component (B), stretching The range defined by the present invention may be set by adjusting the conditions.

<Glass transition temperature (Tg)>
The biaxially stretched film in the present invention preferably has a glass transition temperature (Tg) of 135 ° C. or higher and lower than 180 ° C. When Tg is in the above numerical range, it is easy to maintain the rigidity of the film even in a high temperature environment, and it can be more suitably used for an automobile capacitor. Further, the effect of improving the heat resistance is increased, and as a result, the dielectric breakdown voltage in a high temperature environment can be increased. From such a viewpoint, the lower limit of Tg is more preferably 145 ° C. or more, further preferably 150 ° C. or more, and the upper limit of Tg is more preferably 175 ° C. or less, further preferably 165 ° C. or less. A temperature of not higher than ° C is particularly preferred. In particular, when the above-described resin component (B) is contained, the lower limit of Tg is preferably 145 ° C. or higher, and more preferably 150 ° C. or higher. The glass transition temperature (Tg) is achieved by adjusting the type and blending amount of the polyether ketone and the resin component (B).

<Dielectric breakdown voltage>
The highly insulating film of the present invention preferably has a breakdown voltage (BDV23) at 23 ° C. of 330 kV / mm or more. When BDV23 is in the above numerical range, it can be suitably used for a condenser of a hybrid vehicle. When the BDV 23 is low, when used for a capacitor of a hybrid vehicle, a short circuit occurs in the capacitor due to a large current, and problems such as destruction of the capacitor are likely to occur. From such a viewpoint, BDV23 is more preferably 350 kV / mm or more, further preferably 380 kV / mm or more, and particularly preferably 410 kV / mm or more.

  In addition, the highly insulating film of the present invention preferably has a high dielectric breakdown voltage under a high temperature environment, and the ratio of the dielectric breakdown voltage (BDV130) to BDV23 at 130 ° C. (BDV130 / BDV23) is 0.7 or more. It is preferably 0.85 or more. When this ratio is in the above numerical range, it means that it exhibits electrical insulation equivalent to room temperature even in a high temperature environment, and can be suitably used for a capacitor of a hybrid vehicle. If the ratio is too small, it means that the electrical insulation is lowered in a high temperature environment, and it is difficult to apply to a use used in a high temperature environment such as a capacitor for a hybrid vehicle. From such a viewpoint, the ratio is more preferably 0.90 or more, and further preferably 0.95 or more. The BDV 130 is preferably 280 kV / mm or more, more preferably 330 kV / mm or more, and further preferably 390 kV / mm or more.

  BDV23 and BDV130 as described above may be provided with the coating layer defined in the present invention in the thermoplastic polyetherketone resin (A), and further mixed with the above-mentioned high Tg resin component (B) or antioxidant. It can be further enhanced by adding the agent (C) or by further stretching under the above-mentioned specific conditions.

<Break strength>
The high insulating film of the present invention preferably has a breaking strength (breaking strength 23) at 23 ° C. of 200 MPa or more in each of the longitudinal direction and the transverse direction. When the breaking strength 23 is in the above numerical range, the film becomes stiff and the flexibility is improved, and it can be more suitably used for electrical insulation such as for capacitors. From such a viewpoint, the breaking strength 23 is more preferably 220 MPa or more, further preferably 250 MPa or more, and particularly preferably 270 MPa or more.

  The high insulating film of the present invention has a ratio of breaking strength (breaking strength 130) and breaking strength 23 at 130 ° C. (breaking strength 130 / breaking strength 23) of 0.7 in each of the longitudinal direction and the transverse direction. The above is preferable. When the ratio is 0.7 or more, it means that mechanical characteristics equivalent to normal temperature are expressed even in a high temperature environment, and more particularly for electrical insulation such as a capacitor used in a high temperature environment. It can be used suitably. When the ratio is less than 0.7, that is, when the breaking strength is greatly reduced when a high temperature environment is used, when used in applications exposed at high temperatures, such as for a hybrid vehicle capacitor, Destruction tends to occur easily in a high temperature environment. From such a viewpoint, the ratio of the breaking strength 130 / breaking strength 23 in each of the longitudinal direction and the transverse direction is preferably 0.8 or more, more preferably 0.85 or more, and 0.90. More preferably, it is more preferably 0.93 or more. The breaking strength 130 is preferably 140 MPa or more, more preferably 250 MPa or more, and further preferably 300 MPa.

  In order to make the said ratio into the said numerical range, it can achieve by adjusting extending | stretching conditions (a draw ratio, extending | stretching temperature, etc.). Further, in order to increase the breaking strength at 130 ° C., the thermoplastic polyetherketone resin (A) is preferably used with a high Tg resin component, and the above-described stretching conditions, heat setting conditions, etc. are determined according to the resin composition. It can be achieved by adjusting.

<Heat shrinkage>
In the highly insulating film of the present invention, it is preferable that the absolute values of the heat shrinkage in the vertical and horizontal directions after heat treatment at a temperature of 150 ° C. for 30 minutes are both 1.0% or less. The absolute value of the heat shrinkage rate is more preferably 0.7% or less, and particularly preferably 0.5% or less. In other words, the heat shrinkage rate is preferably closer to 0. When the thermal contraction rate is in the above numerical range, the thermal dimensional stability is excellent, and the workability is excellent, such as warpage and curling are difficult to occur during processing.
In order to make the heat shrinkage ratio as described above, the thermoplastic polyetherketone resin (A) may be used as the main component constituting the biaxially stretched film, and the film may be produced under the production conditions described above. In particular, increasing the draw ratio tends to increase the heat shrinkage rate, increasing the heat setting temperature tends to decrease the heat shrinkage rate, and increasing the relaxation rate tends to decrease the heat shrinkage rate. It is important to adjust.

<Refractive index>
In the highly insulating film of the present invention, the upper limit of the refractive index in the thickness direction of the biaxially stretched film is 1.640 or less. Moreover, it is preferable that the minimum of a refractive index is 1.570 or more.
When the refractive index is in the above numerical range, the effect of improving insulation can be enhanced. If the refractive index in the thickness direction is too low, the stretchability of the film tends to be inferior. On the other hand, if the refractive index is too high, the insulating improvement effect tends to be low. From such a viewpoint, the lower limit of the refractive index in the thickness direction is more preferably 1.590 or more, further preferably 1.600 or more, particularly preferably 1.605 or more, and the upper limit of the refractive index in the thickness direction is 1. 634 or less is more preferable, 1.628 or less is more preferable, and 1.622 or less is particularly preferable. The refractive index in the thickness direction can be achieved by adjusting the film forming conditions such as the type and blending amount of the resin component (B) and stretching conditions.

(Surface roughness)
In the highly insulating film of the present invention, the center line average surface roughness Ra of the surface of the coating layer on at least one side thereof is preferably 7 nm or more and 89 nm or less. By making the center line average surface roughness Ra within the above numerical range, the effect of improving the winding property can be enhanced. 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. From such a viewpoint, the center line average surface roughness Ra is preferably 10 nm or more, more preferably 15 nm or more, and particularly preferably 17 nm or more. On the other hand, when the center line average surface roughness Ra is too high, the slipping property tends to be too high, and the effect of improving the winding property, such as end face misalignment during winding, becomes low. From such a viewpoint, the center line average surface roughness Ra is more preferably 79 nm or less, further preferably 69 nm or less, particularly preferably 59 nm or less, and most preferably 29 nm or less.

In the highly insulating film of the present invention, the 10-point average roughness Rz of the surface of the coating layer on at least one side thereof is preferably 200 nm or more and 3000 nm or less. By setting the 10-point average roughness Rz within the above numerical 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 up as a roll, and the effect of improving the winding property such that the film is liable to slip 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. From such a viewpoint, 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. 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 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.
Ra and Rz as described above can be achieved by employing inert fine particles defined by the present application.

[Usage]
The highly insulating film of the present invention is excellent in heat resistance and electrical insulation, and can be suitably used for electrical insulation that requires excellent dielectric breakdown voltage characteristics even in a high temperature environment. In particular, it can be suitably used for applications that require higher heat resistance and electrical insulation characteristics (dielectric breakdown voltage), such as those for capacitors such as those for moving bodies, particularly for hybrid vehicles, electric vehicles, and fuel vehicles. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited only to these Examples. Each characteristic value was measured by the following method. Moreover, unless otherwise indicated, the part and% in an Example mean a mass part and mass%, respectively.

(1) Elongation at break, strength at break The room was adjusted to a temperature of 23 ° C. and a humidity of 60% RH using a Tensilon UCT-100 model manufactured by Orientec Co., Ltd., using a test piece obtained by cutting the film into a length of 150 mm × 10 mm. , The tensile test was carried out at a chuck distance of 100 mm, a tensile speed of 20 mm / min, and a chart speed of 50 mm / min. From the elongation at break to 23 ° C., the elongation at break (break elongation 23), and from the stress at break to 23 ° C. The breaking stress (breaking stress 23) was determined. Note that the longitudinal direction breaking elongation and breaking stress are those in which the longitudinal direction (MD) of the film is the measuring direction, and the transverse direction breaking elongation and breaking stress are the measuring direction in the transverse direction (TD) of the film. It is what. Each breaking elongation and breaking stress were measured 10 times, and the average value was used.
The breaking elongation (breaking elongation 140) and breaking stress (breaking stress 140) in a temperature atmosphere of 140 ° C. are set in a chamber set in a temperature atmosphere of 140 ° C. and a chuck portion of the test piece and Tensilon. It determined by performing said tension test after leaving still for 2 minutes.

(2) Glass transition temperature (Tg) and melting point (Tm)
About 10 mg of a sample for a resin sample and about 20 mg of a sample for a film sample are sealed in an aluminum pan for measurement and attached to a differential calorimeter (TA Instruments, trade name: DSC2920 Modulated), and 25 ° C. to 20 ° C. The temperature was raised to 370 ° C. at a rate of / min, held at 370 ° C. for 3 minutes, then taken out, immediately transferred onto ice and rapidly cooled. The pan was again attached to the differential calorimeter, and the glass transition temperature (unit: ° C) and melting point (unit: ° C) were measured by increasing the temperature from 25 ° C to 20 ° C / min.

(3) Heat shrinkage rate In a oven set at a temperature of 150 ° C., the film was marked in the longitudinal and transverse directions, and a 30 cm long film whose exact length was measured in advance was placed under no load for 30 minutes. Take out after holding treatment, return to room temperature, and then read the change in dimensions. From the length (L ₀ ) before the heat treatment and the dimensional change (ΔL) due to the heat treatment, the thermal shrinkage rates in the vertical direction and the horizontal direction were obtained from the following formula (1).
Thermal contraction rate (%) = (ΔL / L ₀ ) × 100 (1)

(4) Dielectric breakdown voltage (BDV)
It was measured according to the method shown in JIS C 2151. The sample was prepared by aluminum vapor deposition according to JIS C 2151. Using a DC withstand voltage tester in an atmosphere of 23 ° C. and 50% relative humidity, the upper electrode is a brass cylinder with a diameter of 25 mm, the lower electrode is an aluminum cylinder with a diameter of 75 mm, and the pressure is increased at a pressure increase rate of 100 V / second. The voltage when the film was broken and short-circuited was read. The obtained voltage was divided by the film thickness to obtain a dielectric breakdown voltage (BDV23, unit: kV / mm) at 23 ° C.
The measurement was carried out 41 times, and the median value of the 21 points was taken as the measured value of the dielectric breakdown voltage except for the larger value of 10 points and the smaller value of 10 points.
Measurement of dielectric breakdown voltage (BDV130) at 130 ° C. is performed by setting an electrode and a sample in a hot air oven, connecting to a power source with a heat-resistant cord, and starting the pressure increase in one minute after putting the sample in the oven at 130 ° C. Measured in the same manner as above.

(5) Stretchability Judgment was made as follows according to the number of breaks that occurred during the production of a high-insulation film of 1 million meters.
Stretchability ◎: Less than 1 break per 100,000 m film formation Stretchability ○: 1 to less than 100,000 breakage per 100,000 m stretchability △: 2 breaks per 100,000 m film formation ~ Less than 4 times Stretchability x: Breakage per 100,000 m film formation 4 times to less than 8 times Stretchability XX: Breakage more than 8 times per 100,000 m film formation

(6) Film thickness and thickness unevenness The thickness of the highly insulating film was measured uniformly at 10 points in a 0.5 m section using an electronic micrometer in the vertical and horizontal directions, and the average thickness (unit: μm) ) Was calculated. In addition, the ratio (percentage) of the difference between the maximum thickness (unit: μm) and the minimum thickness (unit: μm) to the average thickness (unit: μm) of the measured length is obtained, and the thickness variation (unit:%) ). The thickness variation in the vertical direction and the horizontal direction was taken as the respective measured values.
In addition, the thickness of the coating layer was determined by embedding a sample piece of the obtained highly insulating film in a visible light curable resin and curing it by exposure to visible light at room temperature. An ultra-thin slice having a thickness of about 70 to 100 μm was prepared using, and the cross section of the coating layer was observed and measured using a transmission electron microscope.

(7) Refractive index It measured by 23 degreeC65% RH using the Abbe refractometer which used sodium D line | wire (589 nm) as the light source, and made the refractive index of thickness direction nZ.

(8) 1% by mass reduction temperature When a thermogravimetric analyzer was used, the temperature was increased from room temperature to 600 ° C. under a temperature increase of 20 ° C./min in nitrogen gas, and the mass reduction amount reached 1% by mass. The temperature was defined as a 1% by weight reduction temperature.

(9) Surface roughness of the film (centerline average surface roughness (Ra))
Measurement length (Lx) 1 mm, sampling pitch 2 μm, cut-off using a non-contact type three-dimensional roughness meter (Kosaka Laboratories, ET-30HK) with a semiconductor laser with a wavelength of 780 nm and an optical stylus with a beam diameter of 1.6 μm Under the conditions of 0.25 mm, thickness direction enlargement magnification of 10,000 times, lateral direction enlargement magnification of 200 times, and the number of scanning lines of 100 (therefore, the Y-direction measurement length Ly = 0.2 mm), Measure the protrusion profile on the surface. 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.

(10) Water contact angle On the surface of the coating layer of the film, measurement was performed 5 times using a Kyowa Interface Science contact angle meter (model: CA-A), and the water contact angle (°) with the average value. It was.
In addition, the measurement is performed by slowly dropping 0.2 mL of distilled water from a height of 5 mm onto the surface of the coating layer with a syringe, leaving it for 30 seconds, and then its contact angle (angle formed by the tangent line between the coating layer surface and the droplet). Was observed with a CCD camera and measured. And the same operation was repeated 5 times and the average value was used.

(11) Rewindability In the film production process, the film is wound up into a roll of 500 mm width and 5000 m at a speed of 170 m / min, and the roll form obtained and the end face deviation at the end face of the roll are rated as follows. did.
[Rolling appearance]
A: There are no pimples on the surface of the roll, and the winding shape is good.
B: There are 1 to 4 pimples (protruding bulges) on the surface of the roll, and the winding shape is almost good.
C: There are 4 or more and less than 10 pimples (protruding bulges) on the surface of the roll, and the wound form is somewhat poor, but it can be used as a product.
D: There are 10 or more pimples (protruding protrusions) on the surface of the roll, the winding shape is poor, and it cannot be used as a product.
[Edge misalignment]
(Double-circle): The end surface shift | offset | difference in a roll end surface is less than 0.5 mm, and is favorable.
○: The end face deviation at the end face of the roll is 0.5 mm or more and less than 1 mm, which is almost good.
(Triangle | delta): The end surface shift | offset | difference in a roll end surface is 1 mm or more and less than 2 mm, and although it is a little inferior, it can be used as a product.
X: The end face deviation at the end face of the roll is 2 mm or more, which is inferior and cannot be used as a product.
XX: The end face shift increases during roll winding, and a 5000 m roll cannot be created.

[Reference Example 1] (Adjustment of coating liquid 1)
As the adjustment of the coating liquid 1, the following release formation, surfactant and cross-linking agent were dispersed in water so that the weight of the solid component was 5% by mass in the weight ratio shown in Table 1, and the emulsion aqueous solution was prepared. Created.
Mold release component: Polyethylene wax (trade name: U3, manufactured by Takamatsu Yushi Co., Ltd., an emulsion of polyethylene wax, and the amount of polyethylene wax in the emulsion is described to be the content of the mold release component in Table 1. .)
Surfactant: Polyoxyalkylene alkyl ether (product name L950, manufactured by Lion Corporation)
・ Crosslinking agent: Zirconyl ammonium carbonate

[Reference Examples 2 to 4] (Adjustment of coating liquids 2 to 4)
As shown in Table 1, the same operation as in Reference Example 1 was repeated except that the content of polyethylene wax was changed and the binder resin a having the following composition was changed to the content shown in Table 1.
<Binder resin a>: Acrylic modified polyester / polyester component: 50 mol% terephthalic acid / 45 mol% isophthalic acid / 5 mol% 5-sodium sulfoisophthalic acid / 75 mol% ethylene glycol / 25 mol% diethylene glycol
Acrylic component: 90 mol% methyl methacrylate / 10 mol% glycidyl methacrylate
Polyester resin component / acrylic resin component repeating unit molar ratio = 3/7

[Reference Example 5] (Adjustment of coating liquid 5)
As the adjustment of the coating liquid 5, the following release formation, surfactant, and crosslinking agent were dispersed in water so that the weight of the solid component was 5% by weight to prepare an aqueous emulsion solution. In addition, about the silicone compound, after previously mixing with surfactant, it added to the coating liquid.
-Mold release component: Carboxy modified silicone (trade name X22-3701E manufactured by Shin-Etsu Chemical Co., Ltd.)
Surfactant: Polyoxyethylene (n = 8.5) lauryl ether (trade name NAROACTY N-85, manufactured by Sanyo Chemical Co., Ltd.)
・ Crosslinking agent: Oxazoline (trade name Epocros WS-300, manufactured by Nippon Shokubai Co., Ltd.)

  Coating solutions 1 to 5 in Table 1 were prepared in Reference Examples 1 to 5, respectively, and binder resin a means the acrylic-modified polyester of Reference Examples 2 to 4 above.

[Comparative Example 1]
Polyetheretherketone resin as thermoplastic polyetherketone resin (A) (manufactured by Victrex: Polyetheretherketone 381G, Tg: 142 ° C., Tm: 343 ° C.), as inert particles, as inert fine particles A, 0.4 parts by mass of spherical silica particles having an average particle size of 0.3 μm, a relative standard deviation of 0.16, and a particle size ratio of 1.09 (being 0.4% by mass in 100% by mass of the obtained biaxially stretched film) And 0.1 part by mass of spherical silicone resin particles having an average particle size of 1.2 μm, a relative standard deviation of 0.15, and a particle size ratio of 1.10 as inert fine particles B (in 100% by mass of the obtained biaxially stretched film) And then dried at 160 ° C. for 4 hours, melt extruded at 380 ° C. with an extruder, cast onto a casting drum maintained at 80 ° C., and And create a thin film.
Next, biaxially stretched sequentially in the machine direction and then in the transverse direction under the following conditions, and further heat-set and heat-relaxed to obtain a biaxially stretched film having a thickness of 3 μm.
That is, an unstretched film was stretched 2.6 times in the machine direction (machine axis direction) at 155 ° C. and then led to a tenter, followed by a preheating start portion temperature of 95 ° C. and a preheating end portion temperature (stretch start portion temperature). ) Preheating for 20 seconds in a process at 145 ° C., followed by stretching 2.7 times in the transverse direction (direction perpendicular to the machine axis direction and the thickness direction). At that time, the stretching speed in the transverse direction was set to 5000% / min. Further, the stretching temperature in the transverse direction was 145 ° C. for the first stage, 150 ° C. for the second stage, and 160 ° C. for the third stage (final stage). Thereafter, the film was heat-fixed at 245 ° C. for 25 seconds, and further subjected to a 3% relaxation treatment in the transverse direction while cooling to 180 ° C., to obtain a biaxially stretched film having a thickness of 3.0 μm and wound into a roll.
The properties of the obtained biaxially stretched film are shown in Table 2.

[Examples 1 to 4, Comparative Example 2]
In Comparative Example 1, after stretching an unstretched film in the machine direction (machine axis direction), coating liquids 1 to 5 (5% by mass water dispersion) containing the components listed in Table 1 on one surface of the film after longitudinal stretching. High-insulating film having a thickness of 3 μm in the same manner as in Comparative Example 1 except that the coating layer was applied so that the final coating layer thickness was 40 nm and then led to a tenter. Got. Table 2 shows the characteristics of the obtained highly insulating film.

[Examples 5 to 15, Comparative Examples 3 and 4]
As shown in Table 3, the thermoplastic polyetherketone resin (A) was changed to a mixture of thermoplastic polyetherketone, resin component (B), and antioxidant. The same operation as in Example 1 was repeated except that the extrusion amount and the coating amount were adjusted so that the thickness of the film and the coating layer obtained by changing the film forming conditions was 3 μm and 40 nm, respectively.

Here, as resin component (B), PEI in Table 3 uses polyetherimide resin (manufactured by General Electric, Ultem 1010, Tg: 217 ° C.), and as an antioxidant, C1 is 3,9- Bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspirio [5 -5] Undecane (manufactured by Sumitomo Chemical Co., Ltd .: trade name SUMILIZER GA-80, 1 mass% weight loss temperature 348 ° C, melting point 120 ° C, compound represented by the following formula [Chemical Formula 8]), C2 is a hindered phenol antioxidant IRGANOX 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd., 1% by weight weight loss temperature 310 ° C., melting point 120 ° C., compound represented by the following formula [Chemical Formula 9]), 3 is 2,2′-methylenebis (6-t-butyl-4-methylphenol) (manufactured by Sumitomo Chemical Co., Ltd .: trade name SUMILIZER MDP-S, 1 mass% weight loss temperature 205 ° C., melting point 128 ° C., the following formula: ] (The mixing ratio is shown in Table 3).
Note that Comparative Example 3 is not stretched.
The properties of the obtained film are shown in Table 3.

  The highly insulating film of the present invention is excellent in electrical insulation and heat resistance, exhibits a high dielectric breakdown voltage, and can be suitably used as a capacitor film for electrical insulation of a mobile body, particularly for a hybrid vehicle. .

Claims (9)

A biaxially stretched film having a refractive index in the thickness direction of 1.640 or less, the main component of which is the thermoplastic polyetherketone resin (A), and a water contact angle on the surface of at least one surface thereof is 85 °. above, possess a coating layer is less than 120 °, in the machine direction and its perpendicular direction (lateral direction), the breaking strength (breaking strength 23) at 23 ° C. is at each 200MPa or more, the breaking strength at 140 ° C. (breaking strength 140) and highly insulating film ratio (tensile strength 140 / breaking strength 23) Ru der each 0.7 or more and the breaking strength at 23 ° C..   The said coating layer contains at least 1 sort (s) chosen from the group which consists of a wax component, a silicone component, and a fluorine compound in the range of 41 to 94 mass% on the basis of the mass of a coating layer. Highly insulating film as described. The biaxially stretched film is composed of a resin composition of a thermoplastic polyetherketone resin (A) and a resin component (B) having a glass transition temperature (Tg) of 180 ° C. or higher, and the content of the resin component (B) is , the two based on the weight of the biaxially stretched film, the high dielectric film according to any one of 5 to 48% by weight in the range der Ru claim 1 or 2.   The highly insulating film according to claim 3, wherein the resin component (B) is a polyimide resin.   The biaxially stretched film contains 0.5 mass% or more and 8 mass% or less of the antioxidant (C) having a 1 mass% weight loss temperature of 280 ° C or higher based on the mass of the biaxially stretched film. The high insulating film of any one of -4.   The absolute value of the heat shrinkage rate in the machine axis direction and the direction orthogonal to the machine axis direction (lateral direction) when heat-treated at a temperature of 150 ° C for 30 minutes is 1.0% or less, respectively. Highly insulating film as described. The high insulation property according to any one of claims 1 to 6 , wherein a ratio (BDV140 / BDV23) of a breakdown voltage (BDV140) at 140 ° C to a breakdown voltage (BDV23) at 23 ° C is 0.7 or more. the film. The highly insulating film according to any one of claims 1 to 7 , which is used for electrical insulation. The highly insulating film according to claim 8 , wherein the electrical insulation is for a capacitor and the film thickness is 0.4 μm or more and less than 6.5 μm.