JP7020033B2 - Orientation film - Google Patents

Description

The present invention relates to an alignment film composed of a polycarbonate resin and a crystalline resin, and more particularly to an alignment film having a particularly high breakdown voltage by using a polycarbonate resin having a specific molecular weight band.

Conventionally, a film condenser is manufactured by a method of laminating a film such as a uniaxially oriented polycarbonate film, a biaxially oriented polyester film, or a biaxially oriented polypropylene film and a metal thin film such as an aluminum foil, and winding or laminating them. In recent years, with the demand for miniaturization of electric or electronic circuits, the miniaturization and mounting of film capacitors have been progressing, and in addition to the thinning of the film used and the improvement of electrical characteristics, further heat resistance is required. It has come to be. Further, in automobile applications, the range of use is expanding not only in the driver's cab but also in the engine room, and in addition to electrical characteristics, a film capacitor suitable for an environment at a higher temperature is required.

In response to such a requirement, Patent Documents 1 to 3 propose a method of using a polymer film having excellent heat resistance and electrical properties. For example, in Patent Document 1, in a polymer alloy film containing a two-component resin, a dispersed structure having a structural period or an interparticle distance of a dispersed phase of less than 0.001 to 0.01 μm is formed. It is taught. Further, Patent Document 2 teaches a method for forming a dispersed phase of a resin having a reactive functional group in various thermoplastic resins. Further, Patent Document 3 discloses a method for forming a dispersed phase containing polyester and / or polycarbonate in a matrix phase containing polyester and / or polycarbonate. Although all the documents show methods for producing a film using a plurality of resins, it is still difficult to stably exhibit high insulation performance.

Japanese Unexamined Patent Publication No. 2004-231907 Japanese Unexamined Patent Publication No. 2009-203410 Japanese Unexamined Patent Publication No. 2014-62260

The present invention has been made in view of the above background art, and an object of the present invention is to provide an alignment film made of a polycarbonate resin and a crystalline resin having a high dielectric breakdown voltage and high heat resistance.

As a result of diligent studies to achieve the above object, the present inventors set the mixing ratio of the polycarbonate resin and the crystalline resin in the range of 50:50 to 95: 5 in the alignment film composed of the polycarbonate resin and the crystalline resin. Further, an alignment film having a polycarbonate resin having a viscosity average molecular weight of 25,000 to 30,000 or less is provided.

Although the alignment film of the present invention uses an amorphous polycarbonate resin, it can be mixed with a crystalline resin and molecularly oriented to achieve high productivity and high film thickness control. Further, by using a highly heat-resistant polycarbonate resin in a specific molecular weight range, high productivity and high dielectric breakdown voltage can be achieved, and it can be suitably used as a base film for a film capacitor.

The alignment film of the present invention is an alignment film in which the weight ratio of the high molecular weight polycarbonate resin to the crystalline resin described later is in the range of 50:50 to 95: 5. Further, the alignment film of the present invention may contain an antioxidant and a filler described later, which can be said to be a preferred embodiment of the present invention. Hereinafter, each constituent component constituting the alignment film of the present invention will be described.

<Polycarbonate resin>
As the monomer used for the polymerization of the polycarbonate resin in the present invention, those known per se can be adopted. For example, as a typical example of the dihydric phenol compound, 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol) can be used. A), hydroquinone, resorcinol, 4,4'-biphenol, 1,1-bis (4 hydroxyphenyl) ethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4) -Hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3, 3,5-trimethylcyclohexane, 2,2-bis (4-hydroxyphenyl) pentane, 4,4'-(p-phenylenediisopropyridene) diphenol, 4,4'-(m-phenylenediisopropyridene) di Examples thereof include phenol, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, and bis (4-hydroxyphenyl) sulfoxide. These may be used alone or in combination of two or more. Of these, 2,2-bis (4-hydroxyphenyl) propane is preferable.

In addition to the above, in the present invention, a trivalent or higher-valent polyvalent phenol compound having a branched structure or a derivative thereof can also be used. Typical examples are 1,1,1-tris (4-hydroxyphenyl) ethane, 4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptene-2,4,6-dimethyl- 2,4,6-tri (4-hydroxyphenyl) heptane, 1,3,5-tri (4-hydroxyphenyl) benzene, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylpheno- Le, Tetra (4-hydroxyphenyl) methane, Trisphenol, Bis (2,4-dihydroxyphenylphenyl) ketone, Fluoroglucin, Fluorogluside, Isanthine bisphenol, 1,4-bis (4,4-dihydroxytriphenylmethyl) benzene , 4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) pentene, 3,3-bis (4-hydroxyaryl) oxyindole, 5-chloroisatin, 5,7-dichloroisatin, 2, 4,4-Trihydroxybenzophenone, 2,2,4,4-tetrahydroxybenzophenone, 2,4,4-trihydroxydiphenyl ether, 2,2,4,4-tetrahydroxydiphenyl ether, 2,4,4-trishydroxy Phenyl-2-propane, 2,2-bis (2,4-dihydroxy) propane, 2,2,4,4-tetrahydroxydiphenylmethane, 1- [α-methyl-α- (4-hydroxyphenyl) ethyl]- 4- [α, α-bis (4-hydroxyphenyl) ethyl] benzene, α, α', α ”-tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, 2,2-bis [ 4,4-Bis (4-hydroxyphenyl) cyclohexyl] -propane, 2,6-bis (2-hydroxy-5-isopropyrobenzyl) -4-isopropylphenol, bis [2-hydroxy-3- (2-hydroxy) -5-isopropyrobenzyl) -5-methylphenyl] methane, tris (4-hydroxyphenyl) phenylmethane, 2,4,7-trihydroxyflaban, 2,4,4-trimethyl-2,4,7-tri Examples thereof include hydroxyflavan, 1,3-bis (2,4-dihydroxyphenylisopropyl) benzene, 5-bromoisatin, trimeritic acid, pyromeritic acid, benzophenone tetracarboxylic acid and acid chlorides thereof. These may be used alone. , Two or more types may be used together.

In the present invention, the monohydric phenols (terminal terminators) used as the molecular weight regulator may have any structure and are not particularly limited. For example, p-tert-butylphenol, p-tert-octylphenol, p-cumylphenol, 4-hydroxybenzophenone, phenol and the like can be mentioned. Of these, p-tert-butylphenol is preferable. It is desirable that these monohydric phenols are introduced at least 5 mol%, preferably at least 10 mol% or more of these monohydric phenols with respect to all the terminals of the obtained polycarbonate resin, and monovalent phenols may be used alone or in two kinds. The above may be mixed and used. The monohydric phenols can be added by dissolving the solid and / or melt, or the solid and / or melt in an alkaline aqueous solution or an organic solvent.

The viscosity average molecular weight of the polycarbonate resin used in the present invention is in the range of 25,000 to 30,000. The range of 25500 to 29500 is particularly preferable, and the range of 26000 to 29000 is more preferable. When the viscosity average molecular weight is in the above range, the dielectric breakdown voltage can be surprisingly suppressed to a high degree and fluctuation.

The viscosity average molecular weight of the polycarbonate resin is obtained by inserting the specific viscosity (ηsp) obtained from a solution of 0.7 g of the polycarbonate resin in 100 ml of methylene chloride at 20 ° C into the following equation.
ηsp / c = [η] +0.45 × [η] ² c (however, [η] is the limit viscosity)
[Η] = 1.23 × 10 ^-4 M ^0.83
c = 0.7

<Crystalline resin>
The crystalline resin used in the present invention is not particularly limited, but a polyester resin is preferable because of its mixability with the polycarbonate resin and heat resistance characteristics. The polyester resin is composed of, for example, an acid component such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid, and a diol component. Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-diphenyldicarboxylic acid. Acids, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid and the like can be used, and among them, terephthalic acid, phthalic acid and 2,6-naphthalenedicarboxylic acid can be used. .. As the alicyclic dicarboxylic acid component, for example, cyclohexanedicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecandionic acid and the like can be used. Only one kind of these acid components may be used, or two or more kinds thereof may be used in combination. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. , 1,6-Hexanediol, 1,2-Cyclohexanedimethanol, 1,3-Cyclohexanedimethanol, 1,4-Cyclohexanedimethanol, Diethylene glycol, Triethylene glycol, Polyalkylene glycol, 2,2'-Bis (4) '-Β-Hydroxyethoxyphenyl) propane or the like can be used. Of these, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be preferably used, and 1,4-cyclohexanedimethanol and the like can be particularly preferably used. Only one kind of these diol components may be used, or two or more kinds thereof may be used in combination.

The crystalline resin used in the present invention is particularly preferably compatible with the polycarbonate resin, and is mainly composed of cyclohexanedimethylene terephthalate from the viewpoints of compatibility with the polycarbonate resin, mechanical strength, productivity, handleability and the like. It is preferably at least one selected from the group consisting of polyester as a component and modified products thereof, and particularly from the group consisting of polyester containing 1,4-cyclohexanedimethylene terephthalate and the like as a main component and modified products thereof. It is preferably at least one selected. The main constituents referred to here are preferably 30 mol% or more, more preferably 50 mol% or more, and particularly preferably 70 mol% or more, based on the number of moles of the repeating structural unit. Further, as the copolymerization component, an isophthalic acid component is preferable.

In the present invention, the weight ratio of the polycarbonate resin to the crystalline resin needs to be in the range of 50:50 to 95: 5. If the ratio of the crystalline resin is larger than this, the effect of improving the dielectric breakdown voltage of the obtained film is reduced, which is not preferable. On the other hand, if the ratio of the crystalline resin is too small, the crystallinity of the obtained film is low and the thickness unevenness at the time of film formation tends to be large, which is not preferable because fracture defects are likely to occur. From this point of view, the weight ratio of the polycarbonate resin to the crystalline resin is more preferably 55:45 to 92: 8, more preferably 60:40 to 90:10, and particularly preferably 65:35 to 88:12. be.

<Antioxidant>
The alignment 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 peroxide to prevent oxidation. Examples of the primary antioxidant include a phenol-based antioxidant and an amine-based antioxidant, and examples of the secondary antioxidant include a phosphorus-based antioxidant and a sulfur-based antioxidant. Among these, it is preferable to use a primary antioxidant and a secondary antioxidant in combination, and in particular, it is preferable to add a larger amount of the primary antioxidant, and the weight ratio of the primary antioxidant to the secondary antioxidant is 10. The range of 1 to 10: 5 is preferable.

Specific examples of the phenolic antioxidant are 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-triazine-2-ylamino] phenol, n Examples thereof include monophenolic antioxidants such as -octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate. In addition, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 4,4'-thiobis (3-methyl-6). -T-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), N, N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl ] Hydradin, 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] bisphenol-based antioxidants such as undecane Agents are mentioned. In addition, 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 Examples thereof include high molecular weight phenolic antioxidants such as 6- (1H, 3H, 5H) trione and d-α-tocophenol.

Specific examples of the phosphorus-based antioxidant include triphenylphosphite, diphenylisodecylphosphite, phenyldiisodecylphosphite, and 4,4'-butylidene-bis (3-methyl-6-t-butylphenylditridecyl) phos. Fight, Octadecylphosphite, Tris (nonylphenyl) phosphite, diisodecylpentaerythritol 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 neopentanetetraylbis (2,4-di-t-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6- Examples thereof include di-t-butyl-4-methylphenyl) phosphite and 2,2'-methylenebis (4,6-di-t-butylphenyl) octylphosphite.

Specific examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, disstearyl-3,3'-thiodipropionate, and pentaerythritol. Examples thereof include tetrakis (3-laurylthiopropionate) and 2-mercaptobenzimidazole.

Further, it is preferable that the antioxidant has a thermal decomposition temperature of 250 ° C. or higher. The higher the thermal decomposition temperature, the higher the effect of improving the dielectric breakdown voltage at high temperatures. If the thermal decomposition temperature is too low, the antioxidant itself will be thermally decomposed during melt extrusion, and problems such as process contamination and polymer coloring are likely to occur. 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 likely to be thermally decomposed and preferably has a high thermal decomposition temperature, but in reality, the upper limit thereof is about 500 ° C. or lower. The pyrolysis temperature in the present invention is a temperature at which the weight is reduced by 5% when measured at a heating rate of 20 ° C./min using a thermogravimetric measuring device.

Further, the melting point of the antioxidant is preferably 40 ° C. or higher. If the melting point is too low, the antioxidant will melt faster than the polymer during melt extrusion and the polymer will tend to slip in the screw feed portion of the extruder. As a result, the supply of the polymer becomes unstable, and problems such as deterioration of the thickness unevenness of the film occur. From this point of view, the melting point of the antioxidant is more preferably 50 ° C. or higher, still more preferably 100 ° C. or higher, and particularly preferably 150 ° C. or higher. On the other hand, if the melting point of the antioxidant is too high, the antioxidant tends to be difficult to melt during melt extrusion, and the dispersion in the polymer tends to be poor. As a result, there arises a problem that the effect of adding the antioxidant is expressed only locally. From this point of view, the melting point of the antioxidant is preferably 300 ° C. or lower, more preferably 280 ° C. or lower, still more preferably 260 ° C. or lower, and particularly preferably 240 ° C. or lower.

As the above-mentioned antioxidant, a commercially available product can be used as it is. Examples of commercially available products include pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals, trade name IRGANOX1010), N, N'-. Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1024), n-octadecyl-β- (4'-hydroxy-3) ', 5'-di-t-butylphenyl) propionate (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1076), N, N'-hexane-1,6-diylbis [3- (3,5-di-t) -Butyl-4-hydroxyphenyl) propionamide] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1098), 3,9-bis [1,1-dimethyl-2- [β- (3-t-butyl-4) -Hydroxy-5-methylfienyl) propionyloxy] ethyl] 2, 4, 8, 10-tetraoxaspiro [5, 5] -undecane (manufactured by Adeca: trade name Adecastab AO-80) and the like are preferably mentioned.

The content of the antioxidant is preferably 0.001% by mass or more and less than 2.0% by mass based on the mass of the alignment film. By containing the antioxidant in the above numerical range, the effect of improving the dielectric breakdown voltage can be enhanced. If the content of the antioxidant is too low, the effect of adding the antioxidant is not sufficient, the effect of improving the dielectric breakdown voltage is low, and the thermal deterioration product derived from the thermoplastic amorphous resin described later is present. Occur. From such a viewpoint, the content of the antioxidant is more preferably 0.001% by mass or more, further preferably 0.01% by mass or more, and particularly preferably 0.1% by mass or more. On the other hand, if the content is too high, the antioxidant tends to aggregate in the biaxially stretched film, and the defects caused by the antioxidant tend to increase, and such defects tend to improve the dielectric breakdown voltage. The effect is low. From such a viewpoint, the content of the antioxidant is more preferably 1.8% by mass or less, and particularly preferably 1.6% by mass or less.

<Other additives>
The alignment film of the present invention contains other resin components different from the thermoplastic amorphous resin in order to further improve the moldability, mechanical characteristics, surface properties, etc., as long as the object of the present invention is not impaired. , Antistatic agents, colorants, weather resistant agents and the like can be added. Further, the Inactive particles such as inorganic particles and organic particles may be used in combination in a small amount regardless of the shape of the particles as long as the object of the present invention is not impaired.

<Film characteristics>
(Film thickness)
The thickness of the oriented film of the present invention is not particularly limited, but it is particularly preferable that the thickness of the oriented film is 0.1 μm or more and less than 20 μm because the effect of the present invention is more likely to be obtained as the film becomes thinner. It is more preferably 0.2 μm or more and less than 18 μm, and particularly preferably 0.3 μm or more and less than 16 μm. Further, by setting the film thickness as described above, a capacitor having a high capacitance can be obtained.

(Differential scanning calorimetry)
The alignment film of the present invention preferably does not have a glass transition temperature Tg of less than 120 ° C. observed at the first temperature rise in differential scanning calorimetry (DSC).

When the glass transition temperature (Tg) is present in a relatively low temperature region of less than 120 ° C., the thermal deformation start temperature of the obtained film is low, the heat resistance is low, and the usable region is greatly limited. For example, in order to use it as a film for a large capacitor such as that used in a power control unit of an automobile, it is desirable that the glass transition temperature does not exist below 120 ° C. From such a viewpoint, the alignment film of the present invention preferably has a glass transition temperature Tg of 120 ° C. or higher observed on the lowest temperature side observed by the first temperature rise in differential scanning calorimetry (DSC). Further, it is preferably 123 ° C. or higher. The glass transition temperature in the present invention is defined as the intersection of the tangent line and the extension line of the baseline at the point of the maximum gradient of the curve.

The alignment film of the present invention has a melting peak Tm of 220 ° C. or higher obtained by the differential scanning calorimetry observed at the first temperature rise, and the crystal melting enthalpy ΔHm of the melting peak is 0.01 to 20 J / g. It is preferable from the viewpoint of stretchability and productivity during film formation. When the melting peak temperature (Tm) is lower than this or the crystal melting enthalpy (ΔHm) is small, the heat resistance tends to decrease even if the film is further crystallized. The upper limit of the melting peak temperature (Tm) is preferably 290 ° C. or lower. If the melting peak temperature (Tm) is higher than this or the crystal melting enthalpy (ΔHm) is larger than the above-mentioned upper limit, it becomes difficult to process because an excessive amount of heat is required during heat processing, and the resin temperature also increases. Since it becomes expensive, it may cause deterioration of the resin.

(Relative permittivity)
The alignment film of the present invention preferably has a relative permittivity of at least 2.0. If the relative permittivity is smaller than this, the capacitance will be small when used as an insulating material such as a capacitor film, which is not preferable. By setting a larger relative permittivity, a larger capacitance is obtained. can do. The preferable relative permittivity is 2.2 or more, and more preferably 2.5 or more. The upper limit of the relative permittivity is not particularly limited, but is preferably 3 or less.

(Dielectric breakdown voltage (BDV))
The alignment film of the present invention preferably has a breakdown voltage (BDV) of 400 kV / mm or more at 25 ° C. The fact that the breakdown voltage is in the above numerical range means that it has excellent characteristics that can be used even at a high voltage. The dielectric breakdown voltage is more preferably 450 kV / mm or more, still more preferably 500 kV / mm or more.

<Manufacturing method of alignment film>
The alignment film of the present invention can be basically obtained by a method known conventionally or accumulated in the art. Hereinafter, the manufacturing method for obtaining the oriented film of the present invention will be described in detail. The alignment 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 a polycarbonate resin, a crystalline resin and various additives is heated, melted and kneaded to prepare an unstretched sheet. Specifically, the resin composition is heated and melted at a temperature equal to or higher than the melting point (Tm, unit: ° C.) (Tm + 50 ° C.), extruded into a sheet, and cooled and solidified to obtain an unstretched sheet. Before forming the unstretched sheet, either a pellet-shaped composition may be prepared once and then remelted to form a sheet, or an unstretched sheet may be directly prepared.

Next, this unstretched sheet is biaxially stretched. The stretching may be performed simultaneously in the vertical direction (machine axial direction) and the horizontal direction (direction perpendicular to the mechanical axial direction and the thickness direction), or may be sequentially stretched in any order. For example, in the case of sequential stretching, first, at a temperature of uniaxially (glass transition temperature (Tg, unit: ° C.) -10 ° C. of the resin composition) or more (Tg + 70 ° C.), 2.8 times or more and 5.8 times or less. It is preferably stretched at a magnification of 2.9 times or more and 5.4 times or less, more preferably 3.0 times or more and 5.0 times or less, and then has a temperature of Tg or more (Tg + 80 ° C.) or less in a direction orthogonal to the uniaxial direction. 2.8 times or more and 5.9 times or less, preferably 2.9 times or more and 5.5 times or less, more preferably 3.0 times or more and 5.1 times or less, and further preferably 3.1 times or more and 4.9 times. Stretch at a magnification of 2 times or less. Further, the area stretching ratio (= longitudinal stretching ratio × lateral stretching ratio) is preferably 8.0 times or more in order to obtain a film having the above-mentioned plane orientation coefficient. When the area stretch ratio is low, the heat resistance becomes inferior, which is not preferable. From this, the area stretch ratio is more preferably 8.5 times or more, further preferably 9.0 times or more, and particularly preferably 9.5 times or more. Further, if the area stretching ratio becomes too high, breakage is likely to occur during film formation / stretching, which is not desirable. From such a viewpoint, the area stretch ratio is preferably 20 times or less, more preferably 18 times or less, further preferably 17 times or less, and particularly preferably 16 times or less.

In the present invention, the coating layer is formed by applying a coating liquid for forming a coating layer to an unstretched sheet or a uniaxially stretched film in which the unstretched sheet is preferably uniaxially stretched in the vertical direction. It may be formed.

Then, it is preferable to heat-fix at a temperature of (Tg + 40 ° C.) to Tm. The heat fixing temperature is preferably 160 ° C. or higher and 260 ° C. or lower, more preferably 165 ° C. or higher and 255 ° C. or lower, and further preferably 170 ° C. or higher and 250 ° C. or lower. If the heat fixing temperature is too high, film breakage is likely to occur and thickness unevenness is likely to be exacerbated, especially when a film having a thin film thickness is produced. If the relaxation treatment is performed at a temperature 20 ° C. to 90 ° C. lower than the heat fixing temperature, if necessary, after the heat fixing, the dimensional stability is further improved.

Hereinafter, the present invention will be further described with reference to Examples. Each characteristic value is measured by the following method, and unless otherwise specified, parts and% mean parts by weight and% by weight, respectively.
(1) Content of antioxidant The components and content of the antioxidant were specified by ^{1 1} H-NMR measurement and ¹³ C-NMR measurement. At that time, when the antioxidant was reacting with the resin, the content of the antioxidant was determined by the content converted to the original antioxidant. In addition, if the antioxidant that has not reacted with the polymer and the antioxidant that has reacted with the polymer are mixed and multiple peak positions are detected even when focusing on the same hydrocarbon chain, the total value of them is used. The content was determined.
(2) Film thickness A film thickness was measured at 10 points with a stylus pressure of 30 g using an electronic micrometer (trade name "K-312A type" manufactured by Anritsu Co., Ltd.), and the average value was taken as the thickness.
(3) Glass transition temperature (Tg), melting enthalpy (ΔHm), melting peak temperature (Tm)
A 10 mg sample was measured at a heating rate of 20 ° C./min using a differential scanning calorimetry device (TA Instruments 2100 DSC).
(4) Relative Permittivity Using the obtained alignment film, aluminum vapor deposition was performed according to JIS C2151, and the relative permittivity at 25 ° C. at 1 KHz was determined using an LCR meter (HEWLETT PACKAD 4284A).
(5) Dielectric breakdown voltage (BDV)
Using the obtained alignment film, it was measured at a step-up rate of 0.1 kV / sec using ITS-6003 manufactured by Tokyo Seiden Co., Ltd. in accordance with the flat plate electrode method among the DC tests described in JIS standard C2151. , The voltage at the time of breakdown was measured as the dielectric breakdown voltage. The measurement was performed at n = 50, the average value was defined as the breakdown voltage, and the standard deviation (%) with respect to the mean value was defined as the variation in the breakdown voltage. The measurement was carried out at room temperature of 25 ° C.
(6) TEM observation (dispersion structure of structural period)
Using the obtained alignment film, polycarbonate was stained by an iodine staining method, and then an ultrathin section was cut out and observed with a transmission electron microscope at a magnification of 100,000 times. When the structural period and the formation of the dispersed structure could not be confirmed, it was judged to be compatible.

[Example 1]
(Preparation of resin composition)
For each raw material shown in Table 1, melt extrusion pelletization was carried out using a vent type twin-screw extruder at the component ratio shown in Table 1.
(Formation of alignment film)
The obtained pellets were dried at 110 ° C. for 7 hours, then fed to an extruder, melted at 280 ° C., extruded from a die slit and then cooled and solidified on a casting drum cooled to 90 ° C. to form an unstretched sheet. Created.
This unstretched sheet is stretched 3.0 times in the vertical direction (machine axis direction) at 140 ° C., subsequently guided to a tenter, and then 3.5 in the lateral direction (direction perpendicular to the machine axis direction and the thickness direction). It was double stretched. The temperature of the lateral stretching was divided into four equal parts, the temperature of the first stage was 130 ° C, and the temperature of the final stage was 145 ° C. Then, the film was heat-fixed at 180 ° C. for 9 seconds, and further subjected to a 3% relaxation treatment in the lateral direction while cooling to 120 ° C. to obtain a biaxially oriented film having a thickness of 3.0 μm, which was wound into a roll. The characteristics of the obtained film are shown in Table 1.

[Examples 2 to 8, Comparative Examples 1 to 4]
The same operation as in Example 1 was repeated except for the changes as shown in Table 1. The evaluation results of the obtained alignment film are shown in Table 1.

Each symbol in Table 1 is as follows.
-PC1: Aromatic polycarbonate resin (polycarbonate resin powder having a viscosity average molecular weight of 28500 made from bisphenol A and carbonyl chloride by a conventional method, Panlite K-1285WP (product name) manufactured by Teijin Limited).
-PC3: Aromatic polycarbonate resin (polycarbonate resin powder having a viscosity average molecular weight of 23700 made from bisphenol A and carbonyl chloride by a conventional method, Panlite L-1250WP (product name) manufactured by Teijin Limited).
PC2: Aromatic polycarbonate resin powder having a viscosity average molecular weight of 26200 prepared by mixing the PC1 and the PC3 at a blending ratio of 50:50).
-PC4: Aromatic polycarbonate resin (polycarbonate resin powder having a viscosity average molecular weight of 30300 made from bisphenol A and carbonyl chloride by a conventional method, Panlite K-1300WP (product name) manufactured by Teijin Limited).
PCTA: Copolymer of 1,4-cyclohexylene methylene terephthalate (88 mol%) and 1,4-cyclohexylene methylene isophthalate (12 mol%) (manufactured by SK Chemials: trade name SKYpura1631).
-PCT: 1,4-Cyclohexylene methylene terephthalate (manufactured by SK Chemials: trade name SKYpura0502)
-Irg1010: Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1010)
-P-EPQ: Phosphorus-based antioxidant (manufactured by Clariant Chemicals, trade name: Hostanox P-EPQ)
-Silica: true spherical silica particles, average particle size 1.5 μm (manufactured by Nippon Shokubai Co., Ltd .: trade name KEP150)

Since the alignment film of the present invention can stably develop a particularly high dielectric breakdown voltage, it can be suitably used as an insulating material such as a base film for a film capacitor.

Claims (10)

An alignment film composed of a polycarbonate resin and a crystalline resin, wherein the crystalline resin is a polyester resin having cyclohexylene methylene terephthalate as a main repeating unit, and the weight ratio of the polycarbonate resin to the crystalline resin is 50:50 to 95 :. An alignment film in the range of 5, further characterized in that the viscosity average molecular weight of the polycarbonate resin is in the range of 25,000 to 30,000. The oriented film according to claim 1, wherein the melting peak Tm obtained by differential scanning calorimetry is 220 ° C. or higher, and the crystal melting enthalpy ΔHm of the melting peak is 0.01 to 20 J / g. The alignment film according to any one of claims 1 and 2, wherein the glass transition temperature Tg obtained by differential scanning calorimetry does not exist below 120 ° C. The alignment film according to any one of claims 1 to 3, which has a thickness of 0.1 to 20.0 μm . The alignment film according to any one of claims 1 to 3, wherein the thickness is 0.1 μm or more and less than 20.0 μm. The alignment film according to any one of claims 1 to 5 , wherein the polycarbonate resin and the crystalline resin are compatible with each other when measured with a scanning microscope. The oriented film according to any one of claims 1 to 6, which contains a primary antioxidant and a secondary antioxidant as an antioxidant. The alignment film according to any one of claims 1 to 7, wherein a filler having an average particle size of 0.05 μm or more and 5 μm or less is blended. The alignment film according to any one of claims 1 to 8, wherein the relative permittivity at 25 ° C. is at least 2.0 and the dielectric breakdown strength is at least 400 V / μm. The alignment film according to any one of claims 1 to 9, which is used for a capacitor.