CN100473691C - Biaxially oriented film - Google Patents

Abstract

An object of the present invention is to provide a thin biaxially oriented film excellent in dimensional stability against humidity changes, a magnetic recording medium and a film capacitor using the film. The present invention relates to a biaxially oriented film, which is a single-layer or laminated biaxially oriented film comprising an aromatic polyester (a) and a polyolefin (b) having a melting point of 230-280° C., the polyolefin ( b) The proportion, based on the total weight of the film, is in the range of 2-60% by weight, and the film thickness is in the range of 1-10 μm.

Description

biaxially oriented film

technical field

The present invention relates to a thin biaxially oriented film having excellent dimensional stability against humidity changes. More specifically, it relates to a thin biaxially oriented film having excellent withstand voltage characteristics. Furthermore, the present invention relates to a biaxially oriented film suitable for use as a magnetic recording medium or as a base film of a thin film capacitor.

Background technique

Since polyester films have excellent thermal and mechanical properties, they are used in various applications such as magnetic recording media, capacitors, flexible substrates, optical members, food packaging, and decoration.

In magnetic recording media, especially magnetic recording media for storing data, the requirements for the characteristics of the base film are also becoming stricter along with the increase in capacity and density of magnetic tapes. Magnetic recording media for storing data using a linear track system such as QIC, DLT, and high-capacity super DLT and LTO have very narrow track pitches in order to achieve high data capacity. Therefore, when a dimensional change occurs in the width direction of the magnetic tape, a track shift is caused, so that there is a problem that an error occurs. These dimensional changes include dimensional changes due to changes in temperature and humidity, and dimensional changes due to time-dependent shrinkage in the width direction that occurs when repeated operations are performed under high tension and high temperature and high humidity. When this dimensional change is large, a track shift occurs and an error occurs during electromagnetic switching. In addition, for convenience of description, the advancing direction during continuous film production may be referred to as the film-forming direction, continuous film-forming direction, longitudinal direction, longitudinal direction, or MD direction, and the in-plane direction of the film perpendicular to the film-forming direction may be referred to as the transverse or horizontal direction. widthwise.

In order to solve such dimensional changes, Japanese Unexamined Publication No. 5-212787 discloses a biaxially oriented polyethylene 2,6-naphthalene dicarboxylate film, whose longitudinal Young's modulus (EM) and transverse Young's modulus The amount (ET), the ratio of the two Young's moduli (ET/EM) are specified within a specific range, and the longitudinal shrinkage rate, the longitudinal temperature expansion rate (αt), and the longitudinal humidity expansion coefficient (αh ). In addition, International Publication No. 99/29488 pamphlet discloses a biaxially oriented polyester film in which the thermal expansion coefficient αt (×10 ^-6 /°C) in the transverse direction, the humidity expansion coefficient αh (×10 -6 /°C) in the transverse direction ^{, 6} /%RH) and the lateral shrinkage rate P (ppm/g) relative to the load when the load is loaded in the longitudinal direction are specified within a specific range. In addition, International Publication No. 00/76749 pamphlet discloses a biaxially oriented polyester film in which the dimensional change in the width direction, the thermal expansion coefficient αt(×10 ^-6 /°C), the humidity expansion coefficient αh (×10 ^-6 /%RH) in the transverse direction, and the transverse contraction rate P (ppm/g) relative to the load when a load is applied in the longitudinal direction are specified within specific ranges.

However, the methods proposed in these publications are realized by setting the stretching conditions and the subsequent heat setting treatment conditions within specific ranges. For example, the time-dependent shrinkage in the width direction when a load is applied in the longitudinal direction can be achieved by increasing the The Young's modulus in the longitudinal direction can be improved, but on the other hand, from the perspective of polymer properties and film forming properties, the higher the Young's modulus in the longitudinal direction, the smaller the upper limit of the Young's modulus in the transverse direction. As a result, temperature and humidity The dimensional change caused by the change becomes larger, etc., and cannot be solved fundamentally.

In addition, capacitors are manufactured by a method in which a thermoplastic resin film such as polyethylene terephthalate or polypropylene is laminated with a metal thin film such as aluminum foil, and then wound or laminated. In recent years, along with the demand for miniaturization of electric or electronic circuits, film capacitors have also been miniaturized and packaged, and further heat resistance has been demanded in addition to electrical characteristics. In addition, in automotive applications, not only in the cab, but also in the engine room, there is a demand for a film capacitor suitable for dimensional stability at higher temperatures and high humidity in addition to electrical characteristics.

Therefore, for the purpose of solving the heat resistance of the film for capacitors, JP-A-2000-173855 discloses a method of using polyethylene 2,6-naphthalene dicarboxylate film for the purpose of improving its electrical characteristics , proposed methods to control the crystallization state, limit viscosity, etc. However, in this method, there is a limit to further improvement of electrical characteristics because of the polar polymer.

On the other hand, syndiotactic polystyrene polymers are known as thermoplastic resins excellent in electrical properties. However, syndiotactic polystyrene-based polymers are more difficult to form into films than polyester resins, and the obtained films are also prone to cracking. Therefore, it is necessary to improve the workability in producing capacitors.

International Publication No. 97/32223 proposes films comprising syndiotactic polystyrene and polyethylene 2,6-naphthalate. However, these films are optical materials for controlling optical properties such as reflectance and transmittance, and are substantially uniaxially oriented films.

In addition, JP-A-08-176329 and the like propose a void-containing polyester film in which a syndiotactic polystyrene as a void-developing agent is blended into a polyester resin, and discloses that the stretching temperature The following content shows that the degree of deformation of syndiotactic polystyrene affects the appearance of voids. However, as the thickness of the film becomes thinner, the impact of voids on various properties becomes greater. Therefore, in applications requiring thin film thicknesses, various properties necessary for those applications, such as mechanical properties such as Young's modulus, etc. characteristics and withstand voltage characteristics may be degraded.

In addition, as a film in which syndiotactic polystyrene and polyester are laminated, JP-A-8-48008 describes a laminated film in which the ratio of the syndiotactic polystyrene layer is 70% or more.

In addition, Japanese Unexamined Patent Application Publication No. 2000-326467 proposes a multilayer laminated film comprising a layer comprising polyethylene 2,6-naphthalate and a layer comprising syndiotactic polystyrene. It is formed by stacking more than 11 layers alternately. However, these films are intended to selectively reflect light of a specific wavelength through light interference caused by a difference in refractive index between layers.

Contents of the invention

An object of the present invention is to provide a thin biaxially oriented film having excellent dimensional stability against humidity changes.

Another object of the present invention is to provide a thin biaxially oriented film having excellent withstand voltage characteristics.

In addition, another object of the present invention is to provide a biaxially oriented film suitable for use as a magnetic recording medium or a base film of a thin film capacitor.

As a result of earnest studies by the present inventors to solve the above-mentioned problems, it was found that by using a single-layer or laminated biaxially oriented film using an aromatic polyester and a polyolefin having a melting point of 230-280° C. in a specific ratio, Even if the thickness is thin, the mechanical properties can be maintained, and the dimensional change against the humidity change can be reduced, so that the present invention has been completed.

That is, the present invention is a biaxially oriented film which is a single-layer or laminated biaxially oriented film comprising an aromatic polyester (a) and a polyolefin (b) having a melting point of 230-280° C.,

The proportion of the polyolefin (b) is in the range of 2-60% by weight based on the total weight of the film, and the film thickness is in the range of 1-10 μm.

In addition, the present invention includes a magnetic recording medium and a film capacitor using the biaxially oriented film described above.

Although the biaxially oriented film of the present invention is thin, its dimensional change with respect to a change in humidity is within the prescribed range. Therefore, the biaxially oriented film of the present invention can be suitably used as a base film of a magnetic recording medium.

In addition, since the magnetic recording medium of the present invention is less likely to cause a track shift and is excellent in high density and high capacity, it is particularly suitable as a magnetic recording medium for storing data.

In addition, the biaxially oriented film of the present invention has a dimensional change with respect to a change in humidity within a prescribed range, and has excellent withstand voltage characteristics. Therefore, the biaxially oriented film of the present invention can be suitably used as a base film of a thin film capacitor.

In addition, the film capacitor of the present invention is suitable as a film capacitor for electrical and electronic equipment and automotive parts that is thin, has excellent withstand voltage characteristics, and requires miniaturization and heat resistance.

Detailed ways

(biaxially oriented film)

The biaxially oriented film of the present invention is a single-layer film or a laminated film, and specific examples of the configuration described below are given. The biaxially oriented film of the present invention comprises an aromatic polyester (a) and a polyolefin (b) having a melting point of 230-280° C., and the proportion of the polyolefin (b) is based on the total weight of the film, It needs to be in the range of 2-60% by weight. When the content of the polyolefin (b) is less than the lower limit, the improvement of the dimensional stability against humidity changes is insufficient. In addition, when the content of polyolefin (b) exceeds the upper limit, the resulting biaxially oriented film is a film lacking in mechanical properties. The preferred proportion of polyolefin (b) is 3-55% by weight, more preferably 3-50% by weight, further preferably 5-50% by weight, particularly preferably 5-30% by weight. When the content of the polyolefin (b) is less than the lower limit, in addition to insufficient improvement in dimensional stability against changes in humidity, the withstand voltage characteristics may not be sufficiently improved. In addition, when the proportion of the polyolefin (b) exceeds 50% by weight, it may become difficult to form a stretched film.

The biaxially oriented film of the present invention needs to have a film thickness in the range of 1-10 μm, preferably 2-10 μm, more preferably 2-7 μm, particularly preferably 3-7 μm. When its thickness exceeds the upper limit, the film thickness is too thick, for example, in the case of a magnetic recording medium, the tape length contained in the cartridge becomes short, and a sufficient magnetic recording capacity cannot be obtained. In addition, when used in a capacitor, miniaturization of the capacitor becomes difficult. On the other hand, when it is less than the lower limit, film breakage often occurs during film production due to the thin film thickness, and the winding property of the film tends to be poor.

(aromatic polyester (a))

The aromatic polyester (a) in the present invention is a polymer obtained by polycondensation of a diol and an aromatic dicarboxylic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, and 4,4'-biphenyldicarboxylic acid. Diol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol. Among these polymers, polyethylene terephthalate and polyethylene 2,6-naphthalene dicarboxylate are preferable, and polyethylene 2,6-naphthalene dicarboxylate is particularly preferable from the viewpoint of mechanical properties and heat resistance. diester.

The polyester resin in the present invention may be a single polyester resin, or any one selected from a copolymer with other polyesters and a mixture of two or more polyesters, but from the perspective of mechanical properties From the viewpoint of heat resistance, polyester resin alone is preferable. The other components in the copolymer or mixture are preferably 10 mol% or less, more preferably 5 mol% or less, based on the number of moles of repeating structural units. Examples of copolymerization components include glycol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, Dicarboxylic acid components such as 5-sodiosulfoisophthalic acid.

The intrinsic viscosity of the polyester resin in the present invention is preferably 0.40 or more at 35° C. in o-chlorophenol, and more preferably 0.40 to 0.80. When the intrinsic viscosity is less than 0.4, cutting tends to occur frequently during film formation, and the strength of the molded product is insufficient. On the other hand, when the intrinsic viscosity exceeds 0.8, the yield during polymerization decreases.

The melting point of the polyester resin in the present invention is preferably 200-300°C, more preferably 240-300°C, particularly preferably 260-290°C. When the melting point is less than the lower limit, the heat resistance of the polyester film may not be sufficient. In addition, when the melting point exceeds the upper limit, mixing with polyolefin (b) may become difficult.

The dielectric constant of the polyester resin in the present invention is preferably 2.7-3.4 at 23° C. and 1 MHz. This dielectric constant is a property inherent in polyester resins.

(Polyolefin (b))

The polyolefin (hereinafter sometimes referred to as polyolefin (b)) in the present invention is a polyolefin having a melting point of 230-280°C. Examples of the polyolefin include poly-3-methylbutene-1, poly-4-methylpentene-1, polyvinyl tert-butane, 1,4-trans-poly-2,3-di Methylbutadiene, polyvinylcyclohexane, polystyrene, polymethylstyrene, polydimethylstyrene, polybutylstyrene, etc. Among these polyolefins, styrenic polymers having a syndiotactic structure (hereinafter sometimes referred to as syndiotactic styrenic polymers) are preferable from the viewpoint of heat resistance and mechanical properties.

The syndiotactic styrene-based polymer in the present invention is a polystyrene with a syndiotactic structure in the stereochemical structure, and the tacticity measured by the nuclear magnetic resonance method ( ¹³ C-NMR method) is a diad. (2 structural units) is 75% or more, preferably 85% or more, and pentads (5 structural units) are 30% or more, preferably 50% or more.

Examples of the syndiotactic styrene-based polymer include polystyrene, poly(methylstyrene), poly(ethylstyrene), and poly(propylstyrene) as poly(alkylstyrene). , poly(butylstyrene), poly(phenylstyrene), among these substances, polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly( p-tert-butylstyrene). The syndiotactic styrenic polymer in the present invention may be used alone or in combination of two or more.

In addition, the weight average molecular weight of the syndiotactic styrene polymer in the present invention is preferably 10,000 or more, more preferably 50,000 or more. When the weight average molecular weight is less than the lower limit, heat resistance and mechanical properties are insufficient. On the other hand, the upper limit of the weight average molecular weight is preferably 500,000 or less. When the upper limit is exceeded, film-forming property may be poor.

The polyolefin in the present invention preferably has a melting point of 240-275°C. When the melting point is lower than the lower limit, mixing with the aromatic polyester (a) is difficult, and the heat resistance of the obtained biaxially oriented film may be insufficient. In addition, when the melting point exceeds the upper limit, mixing with aromatic polyester is also difficult.

The dielectric constant of the polyolefin in the present invention is preferably less than 3.0 at 23°C and 1 MHz, more preferably in the range of 2.2-2.9. When the dielectric constant exceeds the upper limit, the withstand voltage characteristics of the biaxially oriented film may not be sufficiently improved. In addition, when the dielectric constant is less than the lower limit, polyolefin often lacks processability.

The polyolefin in the present invention preferably has a dielectric loss of less than 0.001. Here, the dielectric loss is represented by a dielectric tangent (tan δ) under the conditions of 23° C. and 1 MHz. When the dielectric loss is 0.001 or more, the insulating properties are lowered, and the withstand voltage characteristics of the obtained biaxially oriented film may not be sufficiently improved.

(single layer film)

The biaxially oriented film of the present invention includes a monolayer film as a preferred embodiment. The monolayer film is preferably formed of the thermoplastic resin composition (c) which is a mixture of aromatic polyester (a) and polyolefin (b). In the single-layer film, the ratio of the aromatic polyester (a) to the polyolefin (b) is based on the weight of the thermoplastic resin composition (c) forming the film, and the aromatic polyester (a) is 40-98 % by weight, polyolefin (b) is 2-60% by weight. The content of the aromatic polyester (a) is preferably 45-97% by weight, more preferably 50-97% by weight, still more preferably 50-95% by weight, particularly preferably 70-95% by weight. When the content of the aromatic polyester is less than the lower limit, the obtained biaxially oriented film will be a film lacking in mechanical properties. In addition, when it is less than 50% by weight, stretched film forming may not be sufficiently improved. On the other hand, when the content of the aromatic polyester exceeds the upper limit, the improvement of dimensional stability against humidity changes may not be sufficient, and the withstand voltage characteristics may be insufficient.

In addition, in the thermoplastic resin composition (c), the content of polyolefin (b) is preferably 3-55% by weight, more preferably 3-50% by weight, further preferably 5-50% by weight, particularly preferably 5-50% by weight. 30% by weight. When the content of the polyolefin (b) is less than the lower limit, the improvement of the dimensional stability against changes in humidity may not be sufficient, and the withstand voltage characteristics may not be sufficient. On the other hand, when the content of the polyolefin (b) exceeds the upper limit, the obtained biaxially oriented film becomes a film lacking in mechanical properties. Moreover, when it exceeds 50 weight%, stretching film formation may become difficult.

(laminated film)

(Biaxially oriented film (X))

The biaxially oriented film of the present invention includes a laminated film as a preferred embodiment. The biaxially oriented film is preferably a biaxially oriented film (X) composed of a film layer A and a film layer B comprising an aromatic polyester (a) laminated on at least one side thereof, and the film layer A is composed of A thermoplastic resin composition (c') of a mixture of an aromatic polyester (a) and a polyolefin (b) is formed. In the film layer A, the ratio of the aromatic polyester (a) to the polyolefin (b) is preferably in the following range based on the weight of the thermoplastic resin composition (c') forming the film layer A. That is, in the thermoplastic resin composition (c'), the aromatic polyester (a) is 5-95% by weight, preferably 7-93% by weight, more preferably 10-90% by weight, particularly preferably 50-90% by weight %, polyolefin (b) is in the range of 5-95 wt%, preferably 7-93 wt%, more preferably 10-90 wt%, particularly preferably 10-50 wt%. In the thermoplastic resin composition (c'), when the content of the aromatic polyester (a) exceeds the upper limit, or the content of the polyolefin (b) is less than the lower limit, the intended effect of improving dimensional stability against changes in humidity is insufficient. . On the other hand, when the content of the aromatic polyester (a) is less than the lower limit, or the content of the polyolefin (b) exceeds the upper limit, the resulting biaxially oriented film will be poor in mechanical properties. When the content of the aromatic polyester (a) exceeds 50% by weight, particularly excellent film forming property is obtained, and the adhesiveness with the film layer B becomes high.

In addition, the thickness of the film layer A is preferably in the range of 5-95%, more preferably 7-93%, and particularly preferably 10-90% of the thickness of the laminated film. When the thickness of the film layer A is less than the lower limit, the effect of improving the dimensional stability against humidity changes is insufficient. On the other hand, when the thickness of the film layer A exceeds the upper limit, the obtained biaxially oriented film becomes a film lacking in mechanical properties.

The film layer B may contain basically aromatic polyester (a), and may contain other thermoplastic resins, such as polyolefin (b), within the range that does not impair the purpose of the present invention. The content of the aromatic polyester (a) in the film layer B is preferably 90% by weight or more, more preferably 95% by weight or more, based on the weight of the film layer B.

The polyolefin (b) in the biaxially oriented film (X) is present in an amount of 2-60% by weight, preferably 3-55% by weight, more preferably 3-50% by weight, based on the weight of the laminated film , more preferably in the range of 5-50% by weight, particularly preferably in the range of 5-30% by weight. When the amount of the polyolefin (b) is less than the lower limit, the effect of improving the dimensional stability against changes in humidity may be lacking, and the withstand voltage characteristics may be insufficient. On the other hand, when the polyolefin (b) is present in an amount exceeding the upper limit, the obtained biaxially oriented film tends to be a film lacking in mechanical properties. Moreover, when it exceeds 50 weight%, stretching film formation may become difficult.

Biaxially oriented film (X), as a preferable layer structure, exemplifies: i) a two-layer structure in which layer B is laminated on one surface of layer A; ii) layer B is laminated on both surfaces of layer A 3-layer structure; iii) a multi-layer structure in which at least 4 layers of film layer A and film layer B are laminated based on the total number of layers. In the case of the three-layer structure of ii), the curl resistance is further improved. In addition, in the case of the multilayer structure of iii), even if film layers containing different resins are laminated, film formation can be performed without deterioration of the process due to interlayer detachment or the like. In the case of the multilayer structure of iii), the total number of layers is preferably 8 or more, more preferably 16 or more, and particularly preferably 32 or more. The upper limit is not particularly limited, but from the viewpoint of preventing the complexity of the process, it is About 500 layers, preferably 250 layers. Here, the film layer A and the film layer B are preferably laminated alternately, but film layers made of other resins may be laminated within the range not impairing the object of the present invention. In the case of the multilayer structure of iii), the thickness of each layer of the film layer A is preferably in the range of 0.02-1.5 μm, more preferably in the range of 0.04-1.0 μm, on the other hand, the thickness of each layer of the film layer B is preferably in the range of 0.02-1.5 μm, more preferably in the range of 0.04-1.0 μm. When the thickness of each layer of the film layer A or the film layer B is less than the lower limit, it is necessary to stack too many layers, and the process is likely to be complicated. On the other hand, when the thickness of each layer of the film layer A or the film layer B exceeds the upper limit, delamination between layers sometimes occurs. Their thicknesses can be measured by cutting the laminated film in the thickness direction with a microtome or the like to obtain ultrathin slices, and observing the ultrathin slices with a transmission electron microscope.

(Biaxially oriented film (Y))

As another preferred embodiment of the laminated film, a biaxially oriented film ( Y).

In the biaxially oriented film (Y), the film layer B contains the aromatic polyester (a), and other resins may be mixed or copolymerized within the range that does not impair the object of the present invention. The content of the aromatic polyester (a) in the film layer B is preferably 90% by weight or more, more preferably 95% by weight or more, based on the weight of the film layer B.

In the biaxially oriented film (Y), the film layer C contains polyolefin (b), and other resins may be mixed or copolymerized within the range that does not impair the object of the present invention. The content of the polyolefin (b) in the film layer C is preferably 90% by weight or more, more preferably 95% by weight or more, based on the weight of the film layer C.

The polyolefin (b) in the biaxially oriented film (Y) is present in an amount of 2-60% by weight, preferably 3-55% by weight, more preferably 3-50% by weight, based on the weight of the laminated film , more preferably in the range of 5-50% by weight, particularly preferably in the range of 5-30% by weight. When the amount of the polyolefin (b) is less than the lower limit, the effect of improving the dimensional stability against changes in humidity may be lacking, and the withstand voltage characteristics may be insufficient. On the other hand, when the polyolefin (b) is present in an amount exceeding the upper limit, the obtained biaxially oriented film tends to be a film lacking in mechanical properties. Moreover, when it exceeds 50 weight%, stretching film formation may become difficult.

Biaxially oriented film (Y), as a preferable layer structure, exemplifies: i) a two-layer structure in which layer B is laminated on one surface of layer C; ii) layer B is laminated on both surfaces of layer C 3-layer structure; iii) a multi-layer structure in which at least 4 layers of film layer C and film layer B are laminated based on the total number of layers. In the case of the three-layer structure of ii), the curl resistance is further improved. In addition, in the case of the multilayer structure of iii), even if film layers containing different resins are laminated, film formation can be performed without deterioration of the process due to interlayer detachment or the like. In the case of the multilayer structure of iii), the total number of layers is preferably 8 or more, more preferably 16 or more, and particularly preferably 32 or more. The upper limit is not particularly limited, but from the viewpoint of preventing the complexity of the process, it is About 500 layers, preferably 250 layers. Here, the film layer B and the film layer C are preferably laminated alternately, but film layers made of other resins may be laminated within a range that does not impair the purpose of the present invention. In the case of the multilayer structure of iii), the thickness of each layer of the film layer B is preferably in the range of 0.02-1.5 μm, more preferably in the range of 0.04-1.0 μm. On the other hand, the thickness of each layer of the film layer C is preferably in the range of 0.02-1.5 μm, more preferably in the range of 0.04-1.0 μm. When the thickness of each layer of the film layer B or the film layer C is less than the lower limit, a very large number of layers need to be stacked, and the process is likely to be complicated. On the other hand, when the thickness of each of the film layer B or the film layer C exceeds the upper limit, delamination between layers sometimes occurs. Their thicknesses can be measured by cutting the laminated film in the thickness direction with a microtome or the like to obtain ultrathin slices, and observing the ultrathin slices with a transmission electron microscope.

The biaxially oriented film in the present invention includes, as specific examples, the above-mentioned single-layer film and laminated film, and specific examples of the laminated film include biaxially oriented film (X), biaxially oriented film ( Y), a layer structure suitable for further required properties can be used according to the application. Among these layer structures, a single-layer film or a biaxially oriented film (X) is preferable from the viewpoint of layer peeling. In particular, in the case of a single-layer film, the excellent dimensional stability against humidity changes due to the polyolefin (b) and the excellent mechanical properties due to the aromatic polyester (a) can be exhibited by using it as a mixture. properties and film-forming properties. In addition, in the case of the single-layer film of the present invention, even if the compounding amount of the polyolefin (b) is small, it can have the same withstand voltage characteristics as the polyolefin (b). In addition, in the case of a biaxially oriented film (X), in the case of a two-layer structure, by further laminating the film layer B, the excellent mechanical properties and film-forming properties due to the aromatic polyester (a) are likely to be exhibited. In addition, the three-layer structure of the biaxially oriented film (X) is preferable from the viewpoint of curl resistance.

(Dispersion state of film layer comprising thermoplastic resin composition)

The film layer comprising the thermoplastic resin composition (c) or thermoplastic resin composition (c') of the present invention is formed using a mixture of aromatic polyester (a) and polyolefin (b), preferably polyolefin (b) is island-shaped dispersed. Here, the "island-like dispersed shape" may be any shape such as spherical, elliptical, or rod-like. In the present invention, many rod-like dispersed shapes elongated in the MD direction are observed, and the average length in the MD direction is more preferably 20 μm or less. The above-mentioned average length is obtained by observing the thickness section of the obtained film parallel to the MD direction with an optical microscope (OPTPHOT-2 manufactured by Nikon Corporation) at a magnification of 200, and measuring the MD direction of 100 dispersed phases containing olefin (b). length to find the average length.

The average length in the MD direction is more preferably 15 μm or less, particularly preferably 10 μm or less. When the average length exceeds the upper limit, the film may be easily broken in the stretching step of the film. In addition, as the thickness of the film becomes thinner, the influence of the size of the dispersed phase becomes significant, and the film is easily broken during the stretching step of the film.

As a method of making the average length in the MD direction 20 μm or less, there are physical methods using a kneading method, chemical methods using a compatibilizing agent, and the like. It is more preferable to further contain a compatibilizing agent in the thermoplastic resin composition (c) or thermoplastic resin composition (c') from the viewpoint that it can be processed by existing equipment.

Here, the compatibilizing agent includes, in addition to the usual definition of a compatibilizing agent, an agent having a function of reducing the size of the dispersed phase containing the polyolefin (b). It is not particularly limited as long as it is a compatibilizing agent having such a function, for example, one having an intermediate solubility parameter (hereinafter sometimes abbreviated as SP value) between the aromatic polyester (a) and the polyolefin (b) thermoplastic amorphous resin (d). The SP values of the aromatic polyester (a) and polyolefin (b) are determined according to the type of resin used and the copolymerization component. For example, among the aromatic polyesters (a), the SP value of polyethylene terephthalate calculated by the Fedor method (hereinafter abbreviated as the Fedor method) is 23.6 (MJ/m ³ ) ^0.5 , poly 2, Ethylene-6-naphthalate was 24.8 (MJ/m ³ ) ^0.5 (Fedor method), and among polyolefins (b), polystyrene was 20.7 (MJ/m ³ ) ^0.5 (Fedor method).

Examples of the thermoplastic amorphous resin (d) include acrylic copolymerized polyolefins and vinyloxazoline copolymerized polyolefin resins. Among these copolymers, the monomer constituting the olefin component is more preferably styrene. Moreover, in this copolymer, acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate are mentioned as a monomer which comprises an acrylic acid component. The thermoplastic amorphous resin (d) may further introduce an epoxy group in order to enhance the compatibility effect.

The thermoplastic amorphous resin (d) is preferably contained in an amount of 0.1 to 10% by weight based on the weight of the thermoplastic resin composition (c) or thermoplastic resin composition (c'). The content of the thermoplastic amorphous resin (d) is more preferably 0.2 to 5% by weight, particularly preferably 0.3 to 3% by weight. When the content is less than the lower limit, since the effect as a compatibilizing agent is not exhibited, the average length of the polyolefin (b) is not in the desired range, and film forming property may be poor. On the other hand, when the content exceeds the upper limit, gelation may occur due to a crosslinking reaction.

The film layer comprising the thermoplastic resin composition (c) or thermoplastic resin composition (c') of the present invention preferably has no voids. Here, the term "voids" refers to voids generated at the interface between the aromatic polyester (a) forming the matrix phase and the polyolefin (b) forming the island phase. The voids can be obtained by observing at 200 magnifications using an optical microscope (OPTPHOT-2 manufactured by Nikon Corporation) in the same manner as the method for obtaining the average length of the polyolefin (b). In addition, "having no voids" means that among 100 dispersed phases containing polyolefin (b) in the observation with the above-mentioned optical microscope, the number of dispersed phases in which voids are observed around the dispersed phase is 10 or less , more preferably five or less states.

When voids exist, the film may be easily broken in the film stretching step. In addition, as the film thickness becomes thinner, voids become defects, and mechanical properties and withstand voltage properties may be lowered.

In order not to have voids, it is preferable to select a polyolefin (b) having a Tg lower than the glass transition point (Tg) of the aromatic polyester (a), and the stretching temperature of the film is the Tg of the aromatic polyester (a) above. In addition, among polyolefins, resins having compatibility parameters close to those of aromatic polyesters are preferably used. In addition, voids can also be eliminated by containing a compatibilizing agent.

(inert particles)

The biaxially oriented film of the present invention can contain inert particles in the film, such as inorganic particles (such as kaolin, aluminum oxide, titanium oxide, calcium carbonate, silica, etc.), fine particles containing polymers with high heat resistance such as cross-linked silicone resin, cross-linked polystyrene, cross-linked acrylic resin particles, and the like.

When containing inert particles, the average particle size of the inert particles is preferably 0.001 to 5 μm, and the inert particles are preferably contained in an amount of 0.01 to 10% by weight based on the total weight of the film.

When used in a magnetic recording medium, the preferred average particle size and content of the inert particles are exemplified as follows for a single-layer film or a laminated film.

That is, when the single-layer film is used as a magnetic recording medium, the average particle diameter of the inert particles is preferably 0.01-1.0 μm, more preferably 0.03-0.8 μm, particularly preferably 0.05-0.6 μm. In addition, the content of the inert particles is preferably 0.01-1.0 wt%, more preferably 0.03-0.8 wt%, particularly preferably 0.05-0.5 wt%, based on the weight of the thermoplastic resin composition (c). In addition, the inert particles contained in the film may be a single-component system or a multi-component system, but it is preferable to use a two-component system or a Inert particles of the multi-component system with more than one component system. The adjustment of the surface roughness (WRa) of the film surface may be performed by appropriately selecting the average particle diameter and the addition amount of the inert particles from the above range.

When a biaxially oriented film (X) or a biaxially oriented film (Y) is used as a laminated film for a magnetic recording medium, the average particle diameter of the inert particles is preferably 0.01-0.8 μm, more preferably 0.02-0.6 μm, Particularly preferred is 0.03-0.4 μm. In addition, the content of the inert particles is at most 0.5% by weight, preferably 0.4% by weight, if the surface on the flat side does not contain inert particles, or even if it contains inert particles, relative to the weight of the film layer forming the surface on the flat side. Preferably it is 0.3% by weight. On the other hand, the surface on the rough side contains preferably 0.01-1.0% by weight, more preferably 0.03-0.8% by weight, particularly preferably 0.05-0.6% by weight of inert particles based on the weight of the film layer forming the surface. In the case of a laminated structure of four or more layers, the film layer having the same composition as the film layer forming the rough side surface may contain the same inert particles as the rough side surface layer. In addition, the inert particles contained in the film may be a single-component system or a multi-component system, but especially in the polymer on the non-magnetic layer side, it is possible to combine the electromagnetic conversion characteristics of the tape and the windability of the film. From this point of view, it is preferable to contain inert particles of a two-component system or a multi-component system of two or more components. The adjustment of the surface roughness (WRa) of the film surface may be performed by appropriately selecting the average particle diameter and the addition amount of the inert particles from the above range. In addition, in the case of a single-layer film, the roughness of one surface and the other cannot be easily changed, but when it is a laminated film, the roughness of one surface and the other can be easily changed, and it is easy to obtain electromagnetic conversion at the same time. The advantages of characteristics and travelability of the film.

(additive)

The biaxially oriented film in the present invention may contain a small amount of ultraviolet absorbers, antioxidants, antistatic agents, light stabilizers, and heat stabilizers as needed.

In addition, the biaxially oriented film in the present invention may contain a phosphorus compound. As the above-mentioned phosphorus compound, if it is a phosphorus compound that functions as a heat stabilizer, the type is not particularly limited. Among the phosphorus compounds, triethyl phosphonic acid acetate is particularly preferable.

The preferred content of the phosphorus compound is 20-300ppm, more preferably 30-250ppm, particularly preferably 50-200ppm, based on the molar concentration of phosphorus in the phosphorus compound relative to the total dicarboxylic acid components of the polyester. When the content of the phosphorus compound is less than the lower limit, the transesterification catalyst is not completely deactivated, and sometimes the thermal stability is poor and the mechanical properties are lowered. On the other hand, when the content of the phosphorus compound exceeds the upper limit, thermal stability may be poor and mechanical properties may be lowered.

(Humidity expansion coefficient in the width direction)

In the biaxially oriented film of the present invention, the humidity expansion coefficient αh in the width direction of the film is preferably in the range of 0.1×10 ^-6 to 13×10 ^-6 /%RH. More preferably, αh is in the range of 0.5×10 ^-6 to 11×10 ^-6 /%RH, particularly preferably in the range of 0.5×10 ^-6 to 10×10 ^-6 /%RH.

When αh is less than the lower limit, the polyolefin (b) is excessively present, and the film formability may be lowered, and the mechanical properties may also be lowered. On the other hand, when the upper limit is exceeded, the film is stretched due to changes in humidity, and when used for magnetic recording media, track shifting, etc. are sometimes caused. In addition, when used for film capacitors, these high-humidity Capacitor characteristics may not be sufficient for applications required by the environment. Such αh is achieved by increasing the Young's modulus in the measurement direction by stretching and by mixing polyolefin. When the film is not stretched in the width direction, the Young's modulus in the width direction is low, so even if polyolefin is mixed, the humidity expansion coefficient in the above range cannot be obtained.

(Temperature expansion coefficient in the width direction)

In the biaxially oriented film of the present invention, the temperature expansion coefficient αt in the width direction of the film is preferably in the range of -10×10 ^-6 to +15×10 ^-6 /°C. αt is preferably in the range of -8×10 ^-6 to +10×10 ^-6 /°C, particularly preferably in the range of -5×10 ^-6 to +5×10 ^-6 /°C. When αt is less than the lower limit, it shrinks, and when it exceeds the upper limit, the film is stretched due to changes in humidity, and when it is used for magnetic recording media, it sometimes causes track deviation. In the case of capacitors, the characteristics of capacitors may not be sufficient for applications required in high-temperature environments such as engine rooms of automobiles. Such αt is achieved by increasing the Young's modulus in the measurement direction by stretching, and by keeping the polyolefin content below the above-mentioned upper limit. In the case of not stretching in the width direction, the temperature expansion coefficient in the above-mentioned range cannot be obtained even if polyolefin is mixed because the Young's modulus in the width direction is low.

(Young's modulus)

The biaxially oriented film of the present invention preferably has a Young's modulus of 5 GPa or more in both the film forming direction (MD direction) and the width direction (hereinafter sometimes referred to as the transverse direction or TD direction) of the film. When either Young's modulus is less than the lower limit, even if the dimensional change due to humidity change is small, it may not withstand the load applied as a magnetic recording medium or may deform due to temperature and humidity changes. In addition, it is preferable that the sum of the Young's moduli in the film-forming direction and the width direction is at most 22 GPa. When the sum of the Young's modulus in the film-forming direction and the Young's modulus in the width direction exceeds the upper limit, the stretching ratio becomes excessively high during film forming, and film breakage often occurs, resulting in a markedly low product yield. The upper limit of the sum of the Young's modulus in the film forming direction and the width direction is preferably 20 GPa or less, more preferably 18 GPa or less.

When providing a magnetic tape of a linear track system, it is preferable that the Young's modulus in the film forming direction is larger than the Young's modulus in the width direction from the viewpoint of reducing the elongation in the film forming direction. Preferred Young's modulus, the Young's modulus in the film-forming direction is larger than the Young's modulus in the width direction, the Young's modulus in the film-forming direction is more than 6GPa, preferably more than 7GPa, particularly preferably more than 8GPa, and the Young's modulus in the width direction The Young's modulus is 5 GPa or more, more preferably 6 GPa or more, particularly preferably 7 GPa or more. In addition, from the viewpoint of minimizing the elongation in the width direction, it is preferable that the Young's modulus in the width direction is larger than the Young's modulus in the film forming direction. Preferred Young's modulus, the Young's modulus in the width direction is larger than the Young's modulus in the film-forming direction, and the Young's modulus in the width direction is 7 GPa or more, preferably 8 GPa or more, particularly preferably 9 GPa or more, and the film-forming direction The Young's modulus is 5 GPa or more, more preferably 6 GPa or more, particularly preferably 7 GPa or more. In addition, from the viewpoint of reducing the elongation in the film-forming direction and the width direction, the difference between the Young's modulus in the film-forming direction and the Young's modulus in the width direction is 2 GPa or less, particularly preferably 1 GPa or less. The Young's modulus is 6 GPa or more, preferably 7 GPa or more, particularly preferably 8 GPa or more, and the width direction Young's modulus is 6 GPa or more, more preferably 7 GPa or more, particularly preferably 8 GPa or more.

(dielectric breakdown voltage)

The biaxially oriented film of the present invention preferably has a breakdown voltage exceeding 400 V/µm. The dielectric breakdown voltage is more preferably 410 V/μm or higher, still more preferably 460 V/μm or higher, particularly preferably 470 V/μm or higher. When the dielectric breakdown voltage is below the lower limit, the electrical characteristics when used in a capacitor may be insufficient. Here, the dielectric breakdown voltage is a value measured with a direct current of 160 V/s using an apparatus ITS-6003 manufactured by Tokyo Seiden Co., Ltd. in accordance with the flat electrode method described in JIS C2151.

(heat resistance temperature)

The biaxially oriented film of the present invention preferably has a heat resistance temperature of 110° C. or higher. The heat resistance temperature is more preferably 115°C or higher, particularly preferably 120°C or higher. When the heat resistance temperature is lower than the lower limit, the heat resistance when used in a capacitor may be insufficient. Here, the heat resistance temperature is a temperature defined by a temperature that can withstand 20,000 hours based on the temperature index of IEC60216, plotting the relationship between the time and temperature of the half-life of the dielectric breakdown voltage and the Arrhenius curve.

(coating layer)

The biaxially oriented film of the present invention may have a coating film layer (hereinafter sometimes referred to as coating layer) on at least one surface of the outermost layer. This coating layer is obtained by coating a coating agent containing a binder resin and a solvent on a biaxially oriented film. As the binder resin, various thermoplastic resins or thermosetting resins can be used, such as polyester, polyimide, polyamide, polyesteramide, polyolefin, polyvinyl chloride, poly(meth)acrylate , polyurethane and polystyrene, and their copolymers and mixtures. Among these binder resins, polyester copolymers are particularly preferable. Examples of the solvent include organic solvents such as toluene, ethyl acetate, and methyl ethyl ketone, and mixtures thereof, and water may also be used.

The coating film layer in the present invention may further contain a crosslinking agent, a surfactant, and inert particles as coating film forming components. Polyalkylene oxide is mentioned as this surfactant.

The coating layer in the present invention, in addition to the above-mentioned components, can further contain other resins such as melamine resins, soft polymers, fillers, heat stabilizers, weather-resistant stabilizers, anti-aging agents, marking agents (Labeling agent) ), antistatic agent, slip agent, anti-adhesive agent, anti-halation agent, dyestuff, pigment, natural oil, synthetic oil, wax, emulsifier, curing agent and flame retardant, etc., its compounding ratio does not damage the present invention The scope of purpose is appropriately selected.

In the present invention, the method of laminating the coating layer on the biaxially oriented film may be any of the following methods: a method of coating and drying at least one side of a biaxially oriented film; A method in which a coating agent is applied to a film, dried, stretched, and heat-treated if necessary. Here, the so-called stretchable film is an unstretched film, a uniaxially stretched film, or a biaxially stretched film, and among these films, it is particularly preferable that the film is extruded in the direction (longitudinal direction) of the film. Monoaxially stretched longitudinally stretched film.

In addition, when applying a coating agent on a film, it is preferable to apply in a clean atmosphere, that is, to apply in a film forming step, so that the adhesion of the coating film to the film is improved. In a normal coating process, that is, when a film thermally fixed after biaxial stretching is coated in a process separated from the production process of the film, dust, dust, and the like are likely to be involved.

As the method of coating the coating agent on the film, known arbitrary coating methods can be used, for example, roll coating, gravure coating, roll brushing, spraying, air knife coating, dipping and coating can be used alone or in combination. Curtain coating method.

(surface layer)

The biaxially oriented film of the present invention may be a laminate in which other layers are further laminated on at least one surface for the purpose of imparting other functions.

For example, in the case of a magnetic recording medium, in order to make the magnetic layer side a flatter surface, a polyester film layer substantially free of inert particles can be laminated on the magnetic layer side surface of the biaxially oriented film of the present invention. . In addition, in order to make the running surface (non-magnetic layer) side a surface with better running properties, it is possible to laminate the biaxially oriented film of the present invention on the non-magnetic layer side surface of the biaxially oriented film containing relatively large and large amounts of inert particles. Polyester film layer. Such a laminated film is preferable in terms of obtaining both electromagnetic conversion characteristics and film windability when used as a magnetic recording medium.

In addition, when used in a film capacitor, for example, for the purpose of further improving self-healing properties (Self-ring properties), at least one side of the biaxially oriented film may further have a layer D containing an oxygen atom-containing compound. . The ratio of oxygen atoms to carbon atoms on the surface as measured by X-ray photoelectron spectroscopy is preferably 10% or more, more preferably 15% or more. When the (oxygen atom/carbon atom) ratio is less than the lower limit, the self-healing property at the time of voltage application may become poor. Examples of compounds containing oxygen atoms include cellulose and SiO ₂ . In the case of cellulose, the binder component of the above-mentioned coating film layer contains cellulose in the range of 5 to 50% by weight, and can be laminated by coating. In the case of SiO ₂ , any method of vacuum evaporation, ion plating, or sputtering can be used for lamination.

In addition, the thickness of the layer D containing the compound containing an oxygen atom is preferably 30% or less with respect to the total thickness of the film. When it is thicker than 30%, electrical characteristics such as capacitance, dielectric tangent temperature, and frequency characteristics may become poor. The lower limit of the thickness is not particularly limited, but when it is thinner than 0.005 μm, it may be difficult to obtain the effect of improving self-healing properties.

(surface roughness WRa)

The biaxially oriented film of the present invention preferably has a surface roughness WRa (center plane average roughness) suitable for the application depending on the application.

For example, in the case of being used for a magnetic recording medium, the surface roughness WRa (center plane average roughness) of one surface of the biaxially oriented film is preferably 1-10 nm, more preferably 2-10 nm, particularly preferably 2-8 nm . When the surface roughness WRa is greater than 10 nm, the surface of the magnetic layer becomes rough, and it tends to be difficult to obtain satisfactory electromagnetic conversion characteristics. On the other hand, when the surface roughness WRa is less than 1 nm, because the surface is too flat, the sliding on the transfer roll or calender becomes poor, wrinkles occur, and the magnetic layer cannot be coated smoothly in some cases. apply the calender.

In addition, the surface roughness WRa of the other surface may be the same as the above-mentioned WRa or larger than the above-mentioned WRa, and is preferably 5-20 nm, more preferably 6-15 nm, and particularly preferably 8-12 nm. When the surface roughness WRa of the other surface exceeds the upper limit, the unevenness of the advancing surface side surface is transferred to the magnetic layer side surface, and the magnetic layer side surface becomes rough, and satisfactory electromagnetic conversion characteristics may not be obtained. On the other hand, when the surface roughness WRa is less than the lower limit, the surface is too flat, the sliding on a transfer roll or a calender deteriorates, wrinkles occur, and the magnetic layer cannot be applied smoothly in some cases. In the case of a biaxially stretched laminated film, it is preferable to make the two surfaces have different surface forms from the viewpoint that the electromagnetic conversion characteristics and running properties can be adjusted more easily.

The surface roughness WRa can be adjusted by including inert particles in the film, or by surface treatment for forming fine unevenness, such as coating treatment of a paint.

In addition, when used in a film capacitor, the surface roughness WRa (average center surface roughness) of the biaxially oriented film is preferably 1-150 nm, more preferably 10-120 nm, particularly preferably 30-100 nm. When the surface roughness WRa is greater than the upper limit, when processed into a capacitor, the protrusion of the film is too large, and the dielectric characteristics may be unstable due to the action of air interposed between the films, and the dielectric breakdown voltage is likely to decrease due to the action of the protrusion. . On the other hand, when the surface roughness WRa is less than the lower limit, the film is too flat, which may cause workability in the metal vapor deposition process, film winding process, deformation in the capacitor heat treatment process, pressing process, adhesion between films, etc. Possibility of failure, as a result, the variation in capacitor capacity may become large.

(film making method)

The biaxially oriented film of the present invention is preferably produced by the following method.

When the biaxially oriented film of the present invention is a single-layer film, the above-mentioned aromatic polyester (a) and polyolefin (b) are used as raw materials and extruded into a sheet in a molten state. Manufactured using known film-making methods such as the tenter method and inflation method, for example: mixing a predetermined amount of aromatic polyester (a) and polyolefin (b), drying, and extruding to 300°C The method of feeding out of the machine and forming into a sheet form from a T-die.

Preferably, it can be extruded at a temperature from the melting point (Tm: °C) of the aromatic polyester to (Tm+70) °C, quenched and solidified to form an unstretched film, and then the unstretched film can be processed in a single Stretch in the axial direction (longitudinal or transverse) to a specified ratio at a temperature of (Tg-10) to (Tg+70)°C, and then stretch in a direction perpendicular to the above-mentioned stretching direction (the first step is longitudinal) , the second step is the transverse direction) at the temperature of Tg ~ (Tg + 70) ° C stretching to the specified ratio, and then use the method of heat treatment to manufacture. At this time, the stretching ratio, stretching temperature, heat treatment conditions, etc. are selected and determined according to the characteristics of the above-mentioned film. The areal stretch ratio is preferably 6 to 35 times, preferably 6 to 25 times in the case of a capacitor, and more preferably 7 to 16 times. In addition, in the case of magnetic recording media, it is preferably 15 to 35 times, more preferably 20 to 30 times. The heat fixing temperature can be determined from the range of 190-250°C, and the processing time can be determined from the range of 1-60 seconds. In particular, when heat resistance is required, in order to improve dimensional stability under high temperature conditions, it is preferable to perform heat setting in the range of 210 to 240°C. By performing such heat fixing treatment, the thermal shrinkage rate at 200°C of the obtained biaxially oriented film can be -3.5-3.5%, more preferably -3-3%, particularly preferably 0-3%. When the thermal shrinkage rate is within these ranges, the film is less likely to be wrinkled when processed into a capacitor. In addition, in order to suppress the thermal shrinkage rate, an annealing treatment may be further performed in an off-line process by annealing at a temperature atmosphere of 50-80° C. after heat treatment at 150-220° C. for 1-60 seconds.

In addition to the sequential biaxial stretching method described above, a simultaneous biaxial stretching method may also be used. In addition, in the sequential biaxial stretching method, the number of stretches in the longitudinal direction and the transverse direction is not limited to one time, and the longitudinal-lateral stretching can be performed through several stretching treatments, and the number of times is not limited. For example, in the case of magnetic recording media, if it is desired to further improve the mechanical properties, the above-mentioned biaxially oriented film before the heat setting treatment is heat-treated at a temperature of (Tg+20) to (Tg+70)°C, and then Stretching in the longitudinal or transverse direction at a temperature 10-40°C higher than the heat treatment temperature, and then further stretching in the transverse or longitudinal direction at a temperature 20-50°C higher than the stretching temperature, preferably longitudinal comprehensive stretching The stretching ratio is 3.0-7.0 times, and the comprehensive stretching ratio in the transverse direction is 3.0-6.0 times.

In the case of producing a two-layer or three-layer laminated film, a coextrusion method is mentioned. Preferably, the raw materials constituting each layer are laminated in a mold by a co-extrusion method in a molten state and then extruded into a sheet, or two or more molten polyesters are extruded from a die and then laminated, quenched and solidified to form The unstretched film is laminated, followed by biaxial stretching and heat treatment under the same method and conditions as in the case of the single-layer film to form a laminated biaxially oriented film.

When producing a laminated film having four or more layers, it can be produced by, for example, the simultaneous multilayer extrusion method using a feedblock proposed in paragraph 0028 of JP-A-2000-326467. That is, after drying the aromatic polyester (a) constituting the film layer B, the thermoplastic resin composition (c') constituting the film layer A, or the polyolefin (b) constituting the film layer C, the Extruder supply, using a feed block, for example, alternately layer each melt, expand and extrude in a die to make a laminated unstretched film, and then proceed with the same method and conditions as in the case of a single-layer film Biaxial stretching and heat treatment form a laminated biaxially oriented film.

In addition, when providing a coating layer, it is preferable to coat a desired coating liquid on one side or both sides of the above-mentioned unstretched film or uniaxially stretched film.

(magnetic recording medium)

According to the present invention, there is provided a magnetic recording medium comprising the above biaxially oriented film of the present invention as a base film and having a magnetic layer on one surface thereof.

As a magnetic recording medium, as long as the above-mentioned biaxially oriented film of the present invention is used as a base film, it is not particularly limited, for example, magnetic tapes for storing data in a linear track system such as QIC, DLT, and high-capacity S-DLT or LTO. wait. In addition, since the dimensional change of the base film due to changes in temperature and humidity is extremely small, even if the track pitch is narrowed to ensure high capacity of the magnetic tape, it is a magnetic recording medium suitable for high density and high capacity that hardly causes track deviation.

(film capacitor)

According to the present invention, there is provided a film capacitor comprising the biaxially oriented film of the present invention as a base film and having a metal layer on at least one surface thereof. The material of the metal layer is not particularly limited, and examples thereof include aluminum, zinc, nickel, chromium, tin, copper, and alloys thereof. In addition, when layer D containing a compound containing an oxygen atom is provided to improve self-healing property, examples of the constitution of the thin film capacitor include base film/layer D/metal layer, layer D/base film/metal layer.

The film capacitor is not particularly limited as long as the above-mentioned biaxially oriented film of the present invention is used as a base film. For example, it is used in electrical and electronic applications requiring miniaturization, in cabs of automotive applications, and in engine compartments requiring heat resistance and moisture resistance. Used in electrical equipment, etc. In addition, since the dimensional change of the base film due to changes in temperature and humidity is extremely small, and the heat resistance and withstand voltage characteristics expressed by dielectric breakdown voltage are excellent, further miniaturization of film capacitors is possible. In addition, high temperature and high Suitable for use in humidity.

Example

The present invention will be described below based on examples. The respective characteristic values and evaluation methods were measured and evaluated by the following methods. In addition, the parts and % in an Example mean parts by weight and % by weight, respectively.

(1) Melting point, glass transition point

10 mg of aromatic polyester (a) or polyolefin (b) was enclosed in an aluminum dish for measurement, and measured using a differential calorimeter DSC2920 manufactured by TAinstruments Co., Ltd. from 25°C to 300°C at a heating rate of 20°C/min , the respective melting points (melting point of aromatic polyester (a): Tma, melting point of polyolefin (b): Tmb) and glass transition points (glass transition point of aromatic polyester (a): Tga , glass transition point of polyolefin (b): Tgb).

(2) Average particle size of inert particles

The measurement was performed using a CP-50 centrifugal particle size analyzer (Centrifugal Particle Size Analyzer) manufactured by Shimadzu Corporation. The particle diameter corresponding to 50% by mass (masspercent) was read from the cumulative curve of the particle diameter of each particle calculated based on the obtained centrifugal sedimentation curve and the amount thereof, and this value was regarded as the above-mentioned average particle diameter.

(3) Humidity expansion coefficient (αh)

Cut the film sample into a length of 15mm and a width of 5mm, and make the width direction the measurement direction, place it in a TMA3000 made by Vacuum Engineering, and keep the humidity at 30% RH and the humidity at 70% RH in a nitrogen atmosphere at 30°C. , measure the sample length at that time, and calculate the humidity expansion coefficient by the following formula (1). In addition, the measurement direction is the longitudinal direction of a sample, it carried out about 10 samples, and made the average value into αh.

αh=(L ₇₀ −L ₃₀ )/(L ₃₀ ×ΔH). ···(1)

Among them, L ₃₀ : sample length at 30% RH (mm)

L ₇₀ : Sample length at 70% RH (mm)

ΔH: 40(=70-30)%RH.

(4) Temperature expansion coefficient (αt)

The film sample was cut into length 15mm, width 5mm, and made the width direction become the measurement direction, placed in TMA 3000 manufactured by Vacuum Engineering, pre-treated at 60°C for 30 minutes under nitrogen atmosphere (0%RH), and then used Cool down to room temperature. Thereafter, the temperature was raised from 25°C to 70°C at 2°C/min, the sample length at each temperature was measured, and the temperature expansion coefficient (αt) was calculated from the following formula (2). In addition, the measurement direction is the longitudinal direction of a sample, it measures 10 times, and uses the average value.

αt={(L ₆₀ -L ₄₀ )/(L ₄₀ ×ΔT)}+0.5×10 ^-6 ··(2)

Among them, L ₄₀ : sample length at 40°C (mm)

L ₆₀ : Sample length at 60°C (mm)

ΔT: 20(=60-40)℃

0.5×10 ^-6 : The temperature expansion coefficient of quartz glass.

(5) Young's modulus

Cut the film into a sample with a width of 10mm and a length of 15cm, and set the chuck interval to 100mm. Tensile with a tensile speed of 10mm/min and a recording paper speed of 500mm/min using an inward-facing universal tensile tester. The obtained load- The Young's modulus was calculated from the tangent to the rising portion of the elongation curve.

In addition, the measurement direction is the longitudinal direction of a sample, Young's modulus was measured 10 times, and the average value was used.

(6) Surface roughness (WRa)

Using a non-contact three-dimensional roughness meter (NT-2000) manufactured by WYKO Co., Ltd., under the conditions of a measurement magnification of 25 times and a measurement area of 246.6 μm×187.5 μm (0.0462 mm ² ), the surface analyzer built in the roughness meter was used. Software, use the following formula (3) to calculate the center surface roughness (WRa). In addition, the measurement was repeated 10 times, and the average value was used.

$\mathrm{<span\; class="notranslate">\; wxya</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; jk</span>}}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Z</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

in,

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Z</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; jk</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

Here, Zjk is the height on the three-dimensional roughness graph at the j-th and k-th positions in each direction when the measurement direction (246.6 μm) and the direction perpendicular to it (187.5 μm) are M-divided and N-divided respectively .

(7) The thickness of each layer

The laminated film was cut into triangles, fixed in an embedding capcell, and embedded with epoxy resin. Cut with a microtome (ULTRACUT-S) in a direction parallel to the film-forming direction and the thickness direction to form slices of a film with a thickness of 50 nm. Then, using a transmission electron microscope, it was observed at an accelerating voltage of 1000 kV, and photographed at a magnification of 10,000 times to 100,000 times, and the thickness of each layer was measured from the photographs.

(8) Dispersion and porosity of olefin (b)

Using an optical microscope (OPTPHOT-2 manufactured by Nikon Corporation), the thickness section parallel to the MD direction of the film sample was observed at 200 magnifications, and the lengths in the MD direction of 100 dispersed phases containing olefin (b) were measured to obtain the average length.

In addition, the voids around the dispersed phase containing olefin (b) at that time were observed, and the number of dispersed phases in which voids occurred among the 100 dispersed phases containing olefin (b) was calculated, and judged by the following criteria.

◯: The number of dispersed phases having voids is 10 or less.

×: More than 10 dispersed phases having voids.

(9) Heat resistance

Using a film sample, an Arrhenius curve was drawn for the relationship between the half-life time of the breakdown voltage and the temperature according to the temperature index of IEC60216, and the temperature that can withstand 20,000 hours was obtained.

(10) Dielectric constant

Using a thermoplastic resin, the dielectric constant at 23°C and 1 MHz was measured in accordance with JIS C2151.

(11) Dielectric loss

Using a thermoplastic resin, the dielectric loss at 23°C and 1 MHz was measured in accordance with JIS C2151.

(12) Dielectric breakdown voltage

Using a film sample, the dielectric breakdown voltage was measured with a direct current of 160 V/s using the ITS-6003 manufactured by Tokyo Seiden Co., Ltd. according to the flat electrode method described in JIS C2151.

(13) Film curling

The film samples were sampled to 30 mm in length x 200 mm in width and 200 mm in length x 30 mm in width, respectively, and were visually judged by the following criteria in the state of being naturally placed on a flat plate.

◯: Curl is hardly seen.

Δ: Curl is slightly observed.

×: Curl is conspicuous.

(14) Peel resistance

On one side of the sample film, six vertical and horizontal lines were drawn at intervals of 2 mm using a cutter, and 25 checkerboards were produced. Then, a 24 mm wide adhesive tape (manufactured by Nichipan Co., Ltd., trade name: ゼロテ-プ (registered trademark)) was pasted on both sides of the sample film, and after the adhesive tape on the side with the checkerboard was peeled off sharply at a peeling angle of 180 degrees, the peeled surface was observed. Evaluation was performed on the following criteria.

◯: There is no peeled area, and the adhesion between layers is good.

Δ: The peeled area is less than 20%, and the adhesion between layers is poor.

×: The peeling area is 20% or more, and the adhesion between layers is extremely poor.

(15) Film-forming properties

The state at the time of film formation was observed, and the following criteria were used for classification.

：在进行制膜时，没有切断等的问题，能连续制膜12小时以上。

: During film formation, there is no problem such as cutting, and film formation can be continued for more than 12 hours.

◯: Conditions capable of film formation are narrowly limited, but extra long rolls can be used.

×: Continuous film forming property is poor, and film forming can only be performed for an extremely short time.

(16) track offset

Using an LTO1 driver manufactured by Hi-LetsutoPatsuka-do Co., Ltd., recording was performed at a temperature and humidity of 10°C and 10% RH, and then reproduced at a temperature and humidity of 30°C and 80% RH, and the effect caused by changes in temperature and humidity was measured. The amount of track offset of the tape relative to the head.

The smaller the absolute value of these offset widths, the better.

(17) Moisture resistance of capacitors

Using the 4192A LF IMPEDANCEANALYZER manufactured by Hey-LetsutoPatsuka-do Co., Ltd., apply a voltage of 100V (DC) at 60°C and 95%RH, and perform aging for 500 hours to measure the capacitance change rate in the capacitor, using the following Benchmark evaluation. Here, the capacitance change rate is represented by ΔC/C (%), where C is the capacitance before aging, and ΔC is an absolute value obtained by subtracting the capacitance before aging from the capacitance after aging.

◯: ΔC/C (%) is 5 or less.

×: ΔC/C (%) exceeds 5.

<Comparative example>

Dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol were transesterified by a conventional method in the presence of manganese acetate, and then triethyl phosphonic acid acetate was added. Next, antimony trioxide was added and polycondensed by a conventional method to obtain a polyethylene 2,6-naphthalate resin (intrinsic viscosity (o-chlorophenol, 35° C.) 0.62, hereinafter abbreviated as PEN). The results of measuring the concentration of each element in the resin by atomic absorption method are: Mn=50ppm, Sb=300ppm, P=50ppm. In addition, in the PEN, in the polymerization stage, based on the weight of the resin composition, 0.02% by weight of siloxane particles with an average particle size of 0.5 μm, 0.3% by weight of silicone particles with an average particle size of 0.1 μm were added in advance. Silicon oxide particles.

After the obtained PEN was dried at 180°C for 6 hours, it was supplied to an extruder heated to 300°C, extruded using a T-shaped extrusion die, and the surface roughness was 0.3S, and the surface temperature was kept at 60°C. It was quenched and solidified on a drum to obtain an unstretched film. The unstretched film was preheated at 75°C, heated between low-speed and high-speed rolls from 14 mm above with an infrared heater with a surface temperature of 830°C, stretched to 5.1 times in the film-forming direction of the film, and quenched , and then supplied to a tenter, and stretched 4.8 times in the transverse direction at 125°C. Further, after heat-setting at 240° C. for 10 seconds, a 1.0% relaxation treatment was performed in the lateral direction at 120° C. to obtain a biaxially oriented film having a thickness of 4.5 μm. The Young's modulus of the obtained film was 8 GPa in the longitudinal direction and 6.5 GPa in the transverse direction.

On the other hand, the composition shown below was put into a ball mill, and after kneading and dispersion for 16 hours, 5 parts by weight of an isocyanate compound (Desumoglu L manufactured by Bayer Co., Ltd.) was added and high-speed shear dispersion was carried out for 1 hour to obtain magnetic paint.

The composition of magnetic paint:

Acicular Fe particles 100 parts by weight

Vinyl chloride-vinyl acetate copolymer 15 parts by weight

(Esretsu 7A manufactured by Sekisui Chemical Co., Ltd.)

Thermoplastic polyurethane resin 5 parts by weight

Chromium oxide 5 parts by weight

Carbon black 5 parts by weight

Lecithin 2 parts by weight

Fatty acid ester 1 part by weight

Toluene 50 parts by weight

Methyl ethyl ketone 50 parts by weight

Cyclohexanone 50 parts by weight

The magnetic paint was coated on one side of the above-mentioned PEN film so that the coating thickness reached 0.5 μm, and then, orientation treatment was performed in a DC magnetic field of 2,500 Gauss, and after heating and drying at 100° C., multi-roll calendering treatment (wire pressure 2000N/cm, temperature 80°C), and winding was performed. The coil obtained by this winding was left to stand in the oven of 55 degreeC for 3 days.

Furthermore, a back coat paint having the following composition was applied to the other surface of the PEN film in a thickness of 1 μm, dried, and cut to 12.65 mm (= 1/2 inch) to obtain a magnetic tape.

Composition of back coat paint:

Carbon black 100 parts by weight

Thermoplastic polyurethane resin 60 parts by weight

Isocyanate compound 18 parts by weight

(Corone-to-L manufactured by Japan Polyuretan Industry Co., Ltd.)

Silicone oil 0.5 parts by weight

Methyl ethyl ketone 250 parts by weight

Toluene 50 parts by weight

Table 1 and Table 5 show the properties of the obtained biaxially oriented film and magnetic tape.

<Example 1>

The PEN of Comparative Example 1 was changed to a thermoplastic resin composition (c1) obtained by uniformly blending 90% by weight of PEN and 10% by weight of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC). The stretching ratio was adjusted to obtain a biaxially oriented film having a Young's modulus of 8 GPa in the longitudinal direction, a Young's modulus of 6.5 GPa in the transverse direction, and a thickness of 4.5 μm. In addition, in the thermoplastic resin composition (c1), at the polymerization stage of PEN, based on the weight of the thermoplastic resin composition (c1), 0.02% by weight of siloxane particles with an average particle diameter of 0.5 μm, 0.3% by weight of silica particles having an average particle diameter of 0.1 μm.

The same operation as that of Comparative Example 1 was repeated for the obtained biaxially oriented film to prepare a magnetic tape.

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

<Example 2>

Instead of the thermoplastic resin composition (c1), a thermoplastic resin composition (c2) obtained by changing the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) from 10% by weight to 30% by weight was used. ), and the stretch ratio was changed, and the same operation as in Example 1 was repeated except that.

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

<Example 3>

Instead of the thermoplastic resin composition (c1), a thermoplastic resin composition (c3) obtained by changing the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) from 10% by weight to 50% by weight was used. ), and the stretch ratio was changed, and the same operation as in Example 1 was repeated except that.

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

<Example 4>

The same operation as in Example 2 was repeated except that the stretch ratio was changed to obtain a biaxially oriented film having a longitudinal Young's modulus of 8 GPa, a transverse Young's modulus of 8 GPa, and a thickness of 4.5 μm.

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

<Example 5>

The same operation as in Example 2 was repeated except that the stretch ratio was changed to obtain a biaxially oriented film having a longitudinal Young's modulus of 5.5 GPa, a transverse Young's modulus of 12 GPa, and a thickness of 4.5 μm.

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

<Example 6>

Instead of the thermoplastic resin composition (c1), a thermoplastic resin composition (c4) was used in which the content of PEN was changed from 90% by weight to 89% by weight, and 1% by weight of The epoxy group-containing acrylic copolymer polystyrene (made by Toagosei Co., Ltd., Alphon UG-4070, SP value 21.5 (Fedor method)) of the epoxy-based reagent was formed, and the same procedure as in Example 1 was repeated except that operate. In addition, the SP value of PEN was 24.8 (Fedor method), and the SP value of syndiotactic polystyrene was 20.7 (Fedor method).

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

<Example 7>

Instead of the thermoplastic resin composition (c2), a thermoplastic resin composition (c5) was used in which the content of PEN was changed from 70% by weight to 69% by weight, and 1% by weight of The oxazoline group-containing polystyrene (manufactured by Nippon Shokubai Co., Ltd., Epocross RPS-1005, SP value 22.2 (Fedor method)) of the active agent forms, except that, repeat the same operation as Example 2 . In addition, the SP value of PEN was 24.8 (Fedor method), and the SP value of syndiotactic polystyrene was 20.7 (Fedor method).

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

<Comparative example 2>

Instead of the thermoplastic resin composition (c1), a thermoplastic resin composition (c6) obtained by changing the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) from 10% by weight to 70% by weight was used. ), and the stretch ratio was changed, and the same operation as in Example 1 was repeated except that.

Table 1 shows the properties of the obtained biaxially oriented film and magnetic tape.

Table 1

unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative example 1 Comparative example 2 film thickness μm 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Proportion of polyolefin Wt% 10 30 50 30 30 10 30 0 70 compatibility reagent Wt% 1 1 Young's modulus Film direction Width direction GPaGPa 8.06.5 8.06.5 8.06.5 8.08.0 5.512 8.06.5 8.06.5 8.06.5 8.06.5 temperature expansion coefficient ppm/°C 7 7 8 -2 -8 7 7 7 8 humidity expansion coefficient ppm/%RH 11 9 6 6 4 11 9 12 4 track offset ppm 862 705 548 367 100 870 705 940 391 Film forming ◎ ○ ○ ○ ○ ◎ ◎ ◎ x

<Embodiment 8>

Dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol were transesterified by a conventional method in the presence of manganese acetate, and then triethyl phosphonic acid acetate was added. Next, antimony trioxide was added and polycondensed by a conventional method to obtain polyethylene 2,6-naphthalate resin (PEN). The results of measuring the concentration of each element in the resin by atomic absorption method are: Mn=50ppm, Sb=300ppm, P=50ppm.

Combination of thermoplastic resins obtained by uniformly blending 90% by weight of the obtained PEN (intrinsic viscosity: 0.62) and 10% by weight of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) The product (c7) was dried at 180° C. for 6 hours, then supplied to an extruder heated to 300° C., and molded into a sheet form from a 290° C. mold. Further, the sheet was cooled and solidified on a cooling drum with a surface temperature of 60° C. to obtain an unstretched film, which was introduced into a roller group heated to 140° C. and stretched at a rate of 3.6 times in the longitudinal direction (longitudinal direction). After stretching, it is cooled in a roll set at 60°C.

Next, the longitudinally stretched film was introduced into a tenter while holding both ends of the longitudinally stretched film with clips, and the transverse stretching was carried out at 4.0 times in the direction perpendicular to the longitudinal direction (transverse direction) in an atmosphere heated to a maximum temperature of 150°C. stretch. Then, heat setting was performed at 220° C. for 5 seconds in a tenter, and 1% heat relaxation was performed at 200° C., and then uniformly and slowly cooled to room temperature to obtain a biaxially oriented film with a thickness of 5 μm. The Young's modulus of the obtained film was 6.0 GPa in the longitudinal direction and 6.5 GPa in the transverse direction.

500 angstroms of aluminum was vacuum-deposited on one side of the obtained biaxially oriented film, and wound into a 4.5 mm wide tape to form a tape roll. The obtained strip coils are overlapped and wound to obtain the wound body, then pressed at 150°C and 1 MPa for 5 minutes, flame-sprayed metal coatings on both ends to make external electrodes, and welded on the metal-sprayed coatings to form external electrodes. wound film capacitors.

Table 2 shows the properties of the aromatic polyester (a) and polyolefin (b) used, and the properties of the obtained biaxially oriented film and capacitor.

<Example 9>

Instead of the thermoplastic resin composition (c7), a thermoplastic resin composition (c8) obtained by changing the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) from 10% by weight to 30% by weight was used. ), except that, the same operation as in Example 8 was repeated.

Table 2 shows the properties of the obtained biaxially oriented film and film capacitor.

<Example 10>

Instead of the thermoplastic resin composition (c7), a thermoplastic resin composition (c9) obtained by changing PEN to polyethylene terephthalate (PET) was used, dried at 170°C for 3 hours, and then supplied to the Extruder at 280°C, molded at 290°C into sheet. Further, the sheet was cooled and solidified on a cooling drum with a surface temperature of 20°C to obtain an unstretched film, which was introduced into a roller group heated to 90°C and stretched 3.6 times in the longitudinal direction (longitudinal direction). Afterwards, cool in a roll set at 20°C.

Next, the longitudinally stretched film was introduced into a tenter while holding both ends of the longitudinally stretched film with clips, and the transverse stretching was carried out at 4.0 times in the direction perpendicular to the longitudinal direction (transverse direction) in an atmosphere heated to a maximum temperature of 120°C. stretch. Then, heat setting was performed at 220° C. for 5 seconds in a tenter, and 1% heat relaxation was performed at 200° C., and then uniformly and slowly cooled to room temperature to obtain a biaxially oriented film with a thickness of 5 μm.

Table 2 shows the properties of the aromatic polyester (a) and polyolefin (b) used, and the properties of the obtained biaxially oriented film and film capacitor.

<Comparative example 3>

The same operation as in Example 8 was repeated except that 100% by weight of PEN was used instead of the thermoplastic resin composition (c7) and no syndiotactic polystyrene was used.

Table 2 shows the properties of the obtained biaxially oriented film and film capacitor.

<Comparative example 4>

The same operation as in Example 10 was repeated except that instead of the thermoplastic resin composition (c9), 100% by weight of PET was used and no syndiotactic polystyrene was used.

Table 2 shows the properties of the obtained biaxially oriented film and film capacitor.

<Comparative example 5>

A thermoplastic resin composition (c10) obtained by changing the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) from 10% by weight to 90% by weight instead of the thermoplastic resin composition (c7). , except that, the same operation as in Example 8 was repeated.

Table 2 shows the properties of the obtained biaxially oriented film and film capacitor.

Table 2

unit Example 8 Example 9 Example 10 Comparative example 3 Comparative example 4 Comparative Example 5 film thickness μm 5.0 5.0 5.0 5.0 5.0 5.0 Proportion of polyolefin Wt% 10 30 10 90 Aromatic Polyester (a) Type Melting Point (Tma) Glass Transition Point (Tga) ℃℃ PEN270120 PEN270120 PET26075 PEN270120 PET26075 PEN270120 Polyolefin (b) melting point (Tma) glass transition point (Tgb) dielectric constant dielectric loss ℃℃ 270932.60.0002 270932.60.0002 270932.60.0002 ———— ———— 270932.60.0002 temperature expansion coefficient ppm/°C 7 7 7 7 7 8 humidity expansion coefficient ppm/%RH 11 9 11 12 12 2 Dielectric breakdown voltage V/μm 460 480 410 400 450 490 heat resistance ℃ 120 120 95 120 95 120 gap - ○ ○ x - - - Film forming - ◎ ◎ x ◎ ◎ x Humidity Resistance of Capacitors - ○ ○ ○ x x ○

<Example 11>

Instead of thermoplastic resin composition (c7), use thermoplastic resin composition (c11), this thermoplastic resin composition (c11) is to change the content of PEN from 90% by weight to 89% by weight, and add 1% by weight of The oxazoline group-containing polystyrene (manufactured by Nippon Shokubai Co., Ltd., Epocles RPS-1005, SP value 22.2 (Fedor method)) of the active agent is formed, and the film thickness is changed from 5.0 μm to 3.0 μm, Except for this, the same operation as in Example 8 was repeated. In addition, the SP value of PEN was 24.8 (Fedor method), and the SP value of syndiotactic polystyrene was 20.7 (Fedor method).

Table 3 shows the properties of the obtained biaxially oriented film.

<Example 12>

Instead of the thermoplastic resin composition (c11), the content of PEN was changed from 89% by weight to 79% by weight, and the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) was changed from 10% by weight to 10% by weight. Except having changed % into the thermoplastic resin composition (c12) of 20 weight%, the operation similar to Example 11 was repeated.

Table 3 shows the properties of the obtained biaxially oriented film.

<Example 13>

Instead of the thermoplastic resin composition (c11), a thermoplastic resin composition (c13) in which the type of syndiotactic polystyrene was changed to 10 mol% methylstyrene copolymerized syndiotactic polystyrene was used. The same operation as in Example 11 was repeated except that a water-soluble coating solution having the following composition was coated on one side of the uniaxially stretched film as layer D, and the thickness after stretching and drying was 20 nm.

(Composition of coating layer)

Binder resin A: isophthalic acid copolymerized PEN 50wt%

Binder resin B: 40% by weight of hydroxypropyl cellulose (Nippon Soda Co., Ltd. HPC-SL)

Surfactant: 10% by weight of alkyl nonylphenyl ether

Table 3 shows the properties of the obtained biaxially oriented film.

In addition, the film laminate obtained by vapor-depositing aluminum with a thickness of 600 angstroms on one side of the obtained film sample was cut into a square with a side of 1 cm, and two sheets were superimposed and sandwiched in a rubber plate with a side of 2 cm. A load of 2 kg was applied. In this state, a voltage was applied to the film laminate to cause dielectric breakdown, and self-healing properties were observed.

<Example 14>

Instead of the thermoplastic resin composition (c12), a thermoplastic resin composition (c13) in which the content of PEN was changed from 79% by weight to 80% by weight and the content of the compatibilizing agent was changed from 1% by weight to 0% by weight was used, Except for this, the same operation as in Example 12 was repeated.

An attempt was made to obtain a biaxially oriented film with a thickness of 3.0 μm, but very many breakages occurred during production.

<Comparative example 6>

In place of the thermoplastic resin composition (c11), the content of PEN was changed from 89% by weight to 100% by weight, and the same procedure as in Example 11 was repeated except that no syndiotactic polystyrene and a compatibilizing agent were used. operation.

Table 3 shows the properties of the obtained biaxially oriented film.

table 3

unit Example 11 Example 12 Example 13 Example 14 Comparative example 6 film thickness μm 3.0 3.0 3.0 3.0 3.0 Proportion of polyolefin Wt% 10 20 10 20 - compatibility reagent Wt% 1 1 1 — - Aromatic Polyester (a) Type Melting Point (Tma) Glass Transition Point (Tga) ℃℃ PEN270120 PEN270120 PEN270120 PEN270120 PEN270120 Polyolefin (b) Type Melting point (Tma) Glass transition point (Tgb) Dielectric constant Dielectric loss ℃℃ SPS270932.60.0002 SPS270932.60.0002 PMS-SPS247952.60.0002 SPS270932.60.0002 ———— temperature expansion coefficient ppm/°C 7 7 7 7 7 humidity expansion coefficient ppm/%RH 11 10 11 10 12 Dielectric breakdown voltage V/μm 460 480 460 — 380 heat resistance ℃ 120 120 120 — 120 Average length of dispersed phase μm 10 15 9 30 — Film forming — ◎ ◎ ◎ x ◎

<Example 15>

Dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol were transesterified by a conventional method in the presence of manganese acetate, and then triethyl phosphonic acid acetate was added. Next, antimony trioxide was added and polycondensed by a conventional method to obtain a polyethylene 2,6-naphthalate resin (a) (hereinafter abbreviated as PEN (a)). The results of measuring the concentration of each element in PEN (a) by atomic absorption method are: Mn=50ppm, Sb=300ppm, P=50ppm.

25% by weight of the obtained PEN (a) (intrinsic viscosity (o-chlorophenol, 35°C) is 0.62) and 75% by weight of syndiotactic polystyrene (b) (Idemitsu Petrochemical Co., Ltd. Co., Ltd., grade: 130ZC) obtained thermoplastic resin composition (c'1) and PEN (a) were dried at 180°C for 6 hours, and then supplied to an extruder heated to 300°C. Channel-type co-extrusion die, laminated extrusion in the mold, so that the thermoplastic resin composition (c'1) becomes the film layer A, PEN (a) becomes the film layer B, and then the surface roughness is 0.3S, the surface temperature It was rapidly cooled and solidified on a casting drum kept at 60° C. to obtain an unstretched film. Film layer A was extruded in contact with the casting drum, and in the PEN constituting film layer B, 0.15% by weight of silica with an average particle size of 0.3 μm was added in advance, based on the weight of the layer, Particles, 0.1% by weight of silica particles with an average particle diameter of 0.1 μm, in addition, in the thermoplastic resin composition (c'1) constituting the film layer A, in the polymerization stage, based on the weight of the layer, 0.1% by weight of silica particles having an average particle diameter of 0.1 μm was added.

Except having changed the draw ratio of this unstretched film, the same operation as Comparative Example 1 was repeated, and the biaxially oriented laminated film was obtained. The Young's modulus of the obtained film was 8 GPa in the longitudinal direction and 6.5 GPa in the transverse direction. The thicknesses of layer A and layer B in the laminated film were adjusted according to the discharge amount, and the thickness of layer A was 4 μm and that of layer B was 2 μm.

The same operation as that of Comparative Example 1 was repeated for the obtained biaxially oriented laminated film to obtain a magnetic tape.

In addition, the magnetic paint is formed on the surface of the film layer A of the biaxially oriented laminated film, and the back coating paint is formed on the surface of the film layer B of the biaxially oriented laminated film.

In addition, the ratio (% by weight) of the polyolefin was determined from the specific gravity of the PEN film of 1.36 g/cm ³ and the specific gravity of the syndiotactic polystyrene film of 1.04 g/cm ³ .

Table 4 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 16>

Instead of the thermoplastic resin composition (c'1), a thermoplastic resin composition ( c'2), and the draw ratio was changed, and the operation similar to Example 15 was repeated.

Table 4 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Examples 17-19>

Instead of the thermoplastic resin composition (c'1), a thermoplastic resin composition ( c'3), and the draw ratio was changed, and the operation similar to Example 15 was repeated.

Table 4 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 20>

In the PEN constituting the film layer B, in the polymerization stage, 0.1% by weight of silica particles with an average particle diameter of 0.1 μm is added in advance, and in addition, instead of the thermoplastic resin composition (c'1) constituting the film layer A, use The content of PEN (a) was changed from 25% by weight to 24% by weight, and 1% by weight of oxazoline-containing polystyrene (manufactured by Nippon Shokubai Co., Ltd., Epocles RPS-1005) was added as a compatibilizing agent. ) thermoplastic resin composition (c'4), in addition, in the polymerization stage, 0.15% by weight of silica particles with an average particle size of 0.3 μm, 0.1% by weight of silica particles with an average particle size of 0.1 μm were added in advance. For silicon particles, the same operation as in Example 15 was repeated except for this.

In addition, the magnetic paint is formed on the surface of the film layer B of the biaxially oriented laminated film, and the back coating paint is formed on the surface of the film layer A of the biaxially oriented laminated film.

Table 4 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 21>

Instead of the thermoplastic resin composition (c'4), the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) was changed from 75% by weight to 10% by weight, and a compatibilizing agent was used. The type of epoxy group-containing acrylic copolymer polystyrene (Toagosei Co., Ltd., アルフオン UG-4070) thermoplastic resin composition (c'5) was replaced, and the draw ratio was changed. The same operation as in Example 20.

Table 4 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 22>

Instead of the thermoplastic resin composition (c'4), a thermoplastic resin composition (c'4) in which the content of syndiotactic polystyrene (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) was changed from 75% by weight to 30% by weight was used. '6), and the stretch ratio was changed, and the same operation as in Example 20 was repeated.

Table 4 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 23>

Instead of the 2-layer structure of layer A/layer B, a 3-layer structure of layer B/layer A/layer B was used, and the thickness of each layer after biaxial stretching was changed to 1.0 μm/4.0 μm/ The same operation as in Example 22 was repeated except that the stretching ratio was changed to 1.0 μm.

Table 5 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Comparative example 7>

Instead of PEN (a), the content of the syndiotactic polystyrene (made by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) of the thermoplastic resin composition (c'1) was changed from 75% by weight to 70% by weight. Except for the thermoplastic resin composition (c'7), the operation similar to the comparative example 1 was repeated.

Table 5 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Comparative example 8>

The unstretched film obtained in Example 23 was stretched 5.1 times in the film-forming direction of the film to obtain a uniaxially oriented film stretched only in the film-forming direction.

Table 5 shows the properties of the obtained uniaxially oriented film.

Table 4

table 5

<Comparative example 9>

The same operation as in Comparative Example 1 was repeated except that the film thickness after biaxial stretching was changed from 4.5 μm to 6.0 μm.

Table 6 and Table 7 show the properties of the obtained biaxially oriented film and magnetic tape.

<Example 24>

Intrinsic viscosity (o-chlorophenol, 35°C) of 0.62, 0.62, As the resin of the film layer B, a polyethylene 2,6-naphthalate resin (PEN) having a melting point (Tm) of 269° C. and dried at 160° C. for 5 hours was used. In addition, an intrinsic viscosity (o-chlorophenol, 35° C.) was prepared as an additive containing 0.02% by weight of siloxane particles with an average particle diameter of 0.5 μm and 0.3% by weight of silica particles with an average particle diameter of 0.1 μm. PEN dried at 160°C for 5 hours with a melting point (Tm) of 0.62 and a melting point (Tm) of 269°C and syndiotactic polystyrene (B) dried at 100°C for 3 hours (manufactured by Idemitsu Petrochemical Co., Ltd., grade : 130ZC) in a weight ratio of 50:50, adding 0.02% by weight of siloxane particles with an average particle size of 0.5 μm and 0.3% by weight of silica particles with an average particle size of 0.1 μm, thermoplastic The resin composition (c'8) is used as the resin of the film layer A. These film layer A and film layer B polymers are supplied to the extruder to be melted, and after the film layer B polymer is branched into 25 layers, and the film layer A polymer is branched into 24 layers, use such as A layer and A multi-layer feeder device such that layer B is alternately stacked is merged, and it is introduced into a mold while maintaining its stacked state, and poured on a casting drum to make the total number of alternately stacked layers A and B. It is a laminated unstretched sheet of 49 layers. At this time, the extrusion ratio of the polymers of the B layer and the A layer was adjusted to 8:2, and they were laminated so that the two surface layers were the B layer. In addition, the laminated unstretched sheet extruded from the die was quenched and solidified on a casting drum with a surface roughness of 0.3S and a surface temperature maintained at 60° C. to form an unstretched film.

Except for changing the draw ratio of this laminated unstretched film, the same operation as Comparative Example 1 was repeated to obtain a biaxially oriented laminate with a Young's modulus in the longitudinal direction of 8 GPa and a Young's modulus in the transverse direction of 6.5 GPa. membrane. The thickness of film layer A and film layer B in the laminated film is adjusted by the discharge volume. The thickness of each layer of film layer B is 0.192 μm, and the total is 4.8 μm. The thickness of each layer of film layer A is 0.050 μm. The total thickness of layers A was 1.2 μm.

The same operation as in Comparative Example 1 was repeated to obtain a magnetic recording medium.

In addition, the ratio (% by weight) of the polyolefin was determined from the specific gravity of the PEN film of 1.36 g/cm ³ and the specific gravity of the syndiotactic polystyrene film of 1.04 g/cm ³ .

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 25>

In Example 24, the inert particles contained in the resins of the film layer A and the film layer B were changed to 0.1% by weight of silica particles with an average particle diameter of 0.1 μm, and the thermoplastic resin composition (c'8) was changed to In addition to changing the thermoplastic resin composition (c'9) of a mixture of PEN and syndiotactic polystyrene in a weight ratio of 40:60, and changing the stretching ratio and the discharge amount of each layer, the same process was repeated. The same operation as in Example 24 obtained a longitudinal Young's modulus of 8 GPa, a transverse Young's modulus of 6.5 GPa, a thickness of each layer of the film layer B of 0.168 μm, and a total thickness of the film layer B of 4.2 μm. A biaxially oriented laminated film in which the thickness of each layer is 0.075 μm and the total thickness of the film layers A is 1.8 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 26>

In Example 24, the thermoplastic resin composition (c'8) was changed to the thermoplastic resin composition (c'10) which is a mixture of PEN and syndiotactic polystyrene (B) in a weight ratio of 60:40 , and changed the stretching ratio and the discharge amount of each layer, except that, repeat the same operation as in Example 24, and obtain the Young's modulus in the longitudinal direction of 8GPa, the Young's modulus in the transverse direction of 6.5GPa, the film layer B per A biaxially oriented laminated film in which the thickness of one layer is 0.120 μm, the total thickness of film layer B is 3.0 μm, the thickness of each layer of film layer A is 0.125 μm, and the total thickness of film layer A is 3.0 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 27>

In Example 24, the stretching ratio, the discharge amount of each layer, and the number of layers were changed, and the film layer B was 9 layers, the film layer A was 8 layers, and the film layer B was arranged at both ends. The same operation as in Example 24, the Young's modulus in the longitudinal direction was 8GPa, the Young's modulus in the transverse direction was 6.5GPa, the thickness of each layer of the film layer B was 0.333 μm, and the total thickness of the film layer B was 3.0 μm. A biaxially oriented laminated film in which the thickness of each layer A is 0.375 μm and the total thickness of the film layers A is 3.0 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 28>

In Example 24, the stretching ratio and the discharge amount and the number of layers of each layer were changed, and the film layer B was 49 layers, the film layer A was 48 layers, and the film layer B was arranged at both ends. The same operation as in Example 24 obtained a longitudinal Young's modulus of 8 GPa, a transverse Young's modulus of 6.5 GPa, a thickness of each layer of the film layer B of 0.037 μm, and a total thickness of the film layer B of 1.8 μm. A biaxially oriented laminated film in which the thickness of each layer A is 0.088 μm and the total thickness of the film layers A is 4.2 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 29>

In Example 26, except that the draw ratio and the discharge amount of each layer were changed, the same operation as in Example 24 was repeated to obtain a bilayer with a Young's modulus in the longitudinal direction of 8 GPa and a Young's modulus in the transverse direction of 8 GPa. Axially oriented laminated film.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 30>

In Example 26, except that the draw ratio and the discharge amount of each layer were changed, the same operation as in Example 24 was repeated to obtain a film with a Young's modulus in the longitudinal direction of 5.5 GPa and a Young's modulus in the transverse direction of 12 GPa. Biaxially oriented laminated film.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Comparative Example 10>

In Example 24, the inert particles contained in the resin of film layer A and film layer B were changed to 0.02% by weight of siloxane particles with an average particle size of 1.2 μm and 0.4% by weight of siloxane particles with an average particle size of 0.1 μm. Silica particles, changing the thermoplastic resin composition (c'8) to a thermoplastic resin composition (c'11) consisting only of syndiotactic polystyrene (b), and changing the draw ratio and each layer In addition, the same operation as in Example 24 was repeated, and the Young's modulus in the longitudinal direction was 8GPa, the Young's modulus in the transverse direction was 6.5GPa, the thickness of each layer of the film layer B was 0.072μm, and the film layer A biaxially oriented laminate film in which the total thickness of B is 1.8 μm, the thickness of each layer of film layer A is 0.175 μm, and the total thickness of film layer A is 4.2 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 6 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

Table 6

<Example 31>

Intrinsic viscosity (o-chlorophenol, 35°C) of 0.62, 0.62, As the resin of the film layer B, polyethylene 2,6-naphthalate resin (PEN) having a melting point (Tm) of 269° C. was used. In addition, syndiotactic polystyrene (Idemitsu Petrochemical Co., Ltd.) to which 0.02% by weight of siloxane particles with an average particle diameter of 0.5 μm and 0.3% by weight of silica particles with an average particle diameter of 0.1 μm were added was prepared. System, grade: 130ZC) as the resin of the film layer C. After drying the polymer of film layer B at 160° C. for 3 hours and drying the polymer of film layer C at 100° C. for 3 hours, they were supplied to an extruder for melting, and the polymers of film layer B were branched into 25 layers. After the polymer of film layer C is branched into 24 layers, they are merged using a multi-layer feeder device such that layers B and C are alternately laminated, introduced into the mold while maintaining the laminated state, and poured into On the casting drum, a laminated unstretched sheet having a total of 49 layers in which layers B and C were alternately laminated was produced. At this time, the extrusion ratio of the polymers of the B layer and the C layer was adjusted to 9:1, and they were laminated so that the two surface layers were the B layer. In addition, the laminated unstretched sheet extruded from the die was rapidly cooled and solidified on a casting drum with a surface roughness of 0.3S and a surface temperature maintained at 60° C. to form an unstretched film.

Except for changing the draw ratio of this laminated unstretched film, the same operation as Comparative Example 1 was repeated to obtain a biaxially oriented laminate with a Young's modulus in the longitudinal direction of 8 GPa and a Young's modulus in the transverse direction of 6.5 GPa. membrane. The thickness of film layer B and film layer C in the laminated film is adjusted by the discharge volume. The thickness of each layer of film layer B is 0.216 μm, which is 5.4 μm in total, and the thickness of each layer of film layer C is 0.025 μm, which is a total of The thickness is 0.6 μm.

In addition, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

In addition, the ratio (% by weight) of the polyolefin was determined from the specific gravity of the PEN film of 1.36 g/cm ³ and the specific gravity of the syndiotactic polystyrene film of 1.04 g/cm ³ .

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 32>

In Example 31, the inert particles contained in the resin of the film layer B and the film layer C were changed to 0.1% by weight of silica particles with an average particle diameter of 0.1 μm, and the stretching ratio and the discharge rate of each layer were changed. In addition, the same operation as in Example 31 was repeated, and the Young's modulus in the longitudinal direction was 8GPa, the Young's modulus in the transverse direction was 6.5GPa, the thickness of each layer of the film layer B was 0.168 μm, and the film layer B was obtained. A biaxially oriented laminated film with a total thickness of 4.2 μm, a thickness of each layer of the film layer C of 0.075 μm, and a total thickness of the film layer B of 1.8 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 33>

In Example 31, except that the stretch ratio and the discharge amount of each layer were changed, the same operation as in Example 31 was repeated, and the Young's modulus in the longitudinal direction was 8 GPa, and the Young's modulus in the transverse direction was 6.5 GPa. A biaxially oriented laminate film in which the thickness of each layer of film B is 0.120 μm, the total thickness of film layers B is 3.0 μm, the thickness of each layer of film C is 0.125 μm, and the total thickness of film layers B is 3.0 μm .

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 34>

In Example 31, the stretching ratio, the discharge amount of each layer, and the number of layers were changed, and the film layer B was 9 layers, the film layer C was 8 layers, and the film layer B was arranged at both ends. The same operation as in Example 31, the Young's modulus in the longitudinal direction was 8GPa, the Young's modulus in the transverse direction was 6.5GPa, the thickness of each layer of the film layer B was 0.533 μm, and the total thickness of the film layer B was 4.8 μm. A biaxially oriented laminate film in which the thickness of each layer C is 0.15 μm and the total thickness of the film layers C is 1.2 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 35>

In Example 31, the stretching ratio and the discharge amount and the number of layers of each layer were changed, and the film layer B was 49 layers, the film layer C was 48 layers, and the film layer B was arranged at both ends. The same operation as in Example 31 obtained a longitudinal Young's modulus of 8 GPa, a transverse Young's modulus of 6.5 GPa, a thickness of each layer of the film layer B of 0.073 μm, and a total thickness of the film layer B of 3.6 μm. A biaxially oriented laminated film in which the thickness of each layer C is 0.050 μm and the total thickness of the film layers C is 2.4 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 36>

Except that the draw ratio and the discharge amount of each layer were changed, the same operation as in Example 32 was repeated to obtain a biaxially oriented laminated film having a Young's modulus in the longitudinal direction of 8 GPa and a Young's modulus in the transverse direction of 8 GPa.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Example 37>

Except for changing the draw ratio and the discharge amount of each layer, the same operation as in Example 32 was repeated to obtain a biaxially oriented laminated film with a Young's modulus in the longitudinal direction of 5.5 GPa and a Young's modulus in the transverse direction of 12 GPa. .

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

<Comparative Example 11>

In Example 31, the inert particles contained in the resin of the film layer B were changed to 0.02% by weight of siloxane particles with an average particle size of 1.2 μm and 0.4% by weight of silica particles with an average particle size of 0.1 μm. , and changed the stretching ratio and the discharge amount of each layer, except that, the same operation as in Example 31 was repeated, and the Young's modulus in the longitudinal direction was 8GPa, and the Young's modulus in the transverse direction was 6.5GPa. A biaxially oriented laminated film in which the thickness of one layer is 0.072 μm, the total thickness of film layer B is 1.8 μm, the thickness of each layer of film layer C is 0.175 μm, and the total thickness of film layer C is 4.2 μm.

Moreover, the same operation as Comparative Example 1 was repeated to obtain a magnetic recording medium.

Table 7 shows the properties of the obtained biaxially oriented laminated film and magnetic tape.

Table 7

unit Example 31 Example 32 Example 33 Example 34 Example 35 Example 36 Example 37 Comparative Example 9 Comparative Example 11 layer structure - multi-layer multi-layer multi-layer multi-layer multi-layer multi-layer multi-layer single layer multi-layer film thickness μm 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 Each layer B μm 0.216 0.168 0.120 0.533 0.073 0.168 0.168 - 0.072 Tier B Total μm 5.4 4.2 3.0 4.8 3.6 4.2 4.2 6.0 1.8 Each layer C μm 0.025 0.075 0.125 0.150 0.050 0.075 0.075 - 0.175 Tier C Total μm 0.6 1.8 3.0 1.2 2.4 1.8 1.8 - 4.2 layers - Layer B - 25 25 25 9 49 25 25 - 25 Layer C - twenty four twenty four twenty four 8 48 twenty four twenty four - twenty four all layers - 49 49 49 17 97 49 49 - 49 Proportion of polyolefin weight% 8 25 43 16 34 25 25 0 64 Young's modulus Film direction GPa 8.0 8.0 8.0 8.0 8.0 8.0 5.5 8.0 8.0 Width direction GPa 6.5 6.5 6.5 6.5 6.5 8.0 12 6.5 6.5 temperature expansion coefficient ppm/°C 7 7 8 7 7 -2 -8 7 8 humidity expansion coefficient ppm/%RH 11 9 6 10 7 6 4 12 4 track offset ppm 862 705 548 783 626 367 100 940 391 Film forming - ◎ ◎ ○ ◎ ◎ ○ ◎ ◎ x

<Example 38>

As the inert particles, the average particle diameter of 0.1% by weight was changed to spherical silica of 0.3 μm, except that, the same method as Comparative Example 1 was used to obtain polyethylene 2,6-naphthalate resin (PEN ). The obtained PEN (intrinsic viscosity: 0.62) was dried at 180°C for 6 hours, and then supplied to an extruder heated to 300°C. On the other hand, syndiotactic polystyrene as polyolefin (b) was (manufactured by Idemitsu Petrochemical Co., Ltd., grade: 130ZC) was supplied to another extruder heated to 280°C, and the PEN layer B and the syndiotactic polystyrene layer C were alternately melted inside the mold. 49 layers represented by B/C/B...B/C/B are laminated, and the laminated structure is maintained and molded into a sheet shape. Further, the sheet was cooled and solidified with a cooling drum with a surface temperature of 60°C, and the unstretched film thus obtained was introduced into a roll group heated to 140°C, stretched 3.6 times in the longitudinal direction (longitudinal direction), and then stretched with a 60°C cooling drum. The roll pack is cooled.

Next, the longitudinally stretched film was introduced into a tenter while holding both ends of the longitudinally stretched film with clips, and the transverse stretching was carried out at 4.0 times in the direction perpendicular to the longitudinal direction (transverse direction) in an atmosphere heated to a maximum temperature of 150°C. stretch. Then, heat setting was performed at 220°C for 5 seconds in a tenter, and then 1% heat relaxation was performed at 200°C, and then uniformly and slowly cooled to room temperature to obtain a biaxially oriented laminated film with a thickness of 5 μm. . The average thickness of each layer was 0.1 μm.

The proportion (% by weight) of polyolefin was determined from the specific gravity of the PEN film of 1.36 g/cm ³ and the specific gravity of the syndiotactic polystyrene film of 1.04 g/cm ³ .

Table 8 shows the properties of the aromatic polyester (a) and polyolefin (b) used and the properties of the obtained biaxially oriented laminated film.

<Example 39>

Except changing the laminated structure from 49 layers to a 5-layered structure represented by B/C/B/C/B, the same operation as in Example 38 was repeated to obtain a biaxially oriented laminated film with a thickness of 5 μm. . The average thickness of each layer was 1 μm.

Table 8 shows the properties of the obtained biaxially oriented laminated film.

<Example 40>

Except changing the laminated structure of the PEN layer B and the syndiotactic polystyrene layer C from 49 layers to 2 layers represented by B/C, the same operation as in Example 38 was repeated, and a thickness of 5 μm was obtained. biaxially oriented laminated film. The average thickness of each layer was 3 μm for the B layer and 2 μm for the C layer.

Table 8 shows the properties of the obtained biaxially oriented laminated film. Although the film of this example was satisfactory in heat resistance and dielectric breakdown voltage, curling occurred, and delamination was observed on the film.

<Comparative Example 12>

Except that the laminated structure was changed to one layer of PEN layer B, and the syndiotactic polystyrene layer C was not laminated, the same operation as in Example 38 was repeated to obtain a biaxially oriented laminated film with a thickness of 5 μm. .

Table 8 shows the properties of the obtained biaxially oriented laminated film.

<Comparative Example 13>

The polyethylene 2,6-naphthalate resin of Comparative Example 12 was changed to a polyethylene terephthalate resin, and after drying at 170° C. for 3 hours, it was supplied to an extruder heated to 280° C. Formed into sheets from a mold at 290°C. Further, the sheet was cooled and solidified with a cooling drum with a surface temperature of 20°C, and the unstretched film thus obtained was introduced into a roll group heated to 90°C, stretched 3.6 times in the longitudinal direction (longitudinal direction), and then stretched with a 20°C cooling drum. The roll pack is cooled.

Next, the longitudinally stretched film was introduced into a tenter while holding both ends of the longitudinally stretched film with clips, and the transverse stretching was carried out at 4.0 times in the direction perpendicular to the longitudinal direction (transverse direction) in an atmosphere heated to a maximum temperature of 120°C. stretch. Then, heat setting was performed at 220° C. for 5 seconds in a tenter, and 1% heat relaxation was performed at 200° C., and then uniformly and slowly cooled to room temperature to obtain a biaxially oriented film with a thickness of 5 μm.

Table 8 shows the properties of the aromatic polyester (a) used and the properties of the obtained biaxially oriented film.

Table 8

unit Example 38 Example 39 Example 40 Comparative Example 12 Comparative Example 13 film thickness μm 5.0 5.0 5.0 5.0 5.0 Proportion of polyolefin Wt% 43 34 34 - - Aromatic Polyester (a) Type Melting Point (Tma) . ℃ PEN270 PEN270 PEN270 PEN270 PET260 Polyolefin (b) melting point (Tmb) dielectric constant dielectric loss ℃ 2702.60.0002 2702.60.0002 2702.60.0002 ——— ——— temperature expansion coefficient ppm/°C 7 7 7 7 7 humidity expansion coefficient ppm/%RH 6 7 7 12 12 Dielectric breakdown voltage V/μm 500 480 460 400 450 heat resistance ℃ 120 120 120 120 95 membrane curl ○ ○ x ○ ○

Claims (23)

1. A biaxially oriented film which is a single-layer or laminated biaxially oriented film formed of an aromatic polyester (a) and a polyolefin (b) having a melting point of 230-280 ℃, characterized in that:

the aromatic polyester (a) is polyethylene terephthalate or polyethylene 2, 6-naphthalate;

the polyolefin (b) is a syndiotactic styrene polymer, and accounts for 2-60 wt% of the total weight of the film;

the film thickness is in the range of 1-10 μm.

2. The biaxially oriented film according to claim 1, which is a single layer film formed of a thermoplastic resin composition (c) of an aromatic polyester (a) and a polyolefin (b).

3. The biaxially oriented film according to claim 1, which is a laminate film comprising at least 1 layer of a film layer A comprising a thermoplastic resin composition (c) of an aromatic polyester (a) and a polyolefin (B), and at least one surface of the film layer A being laminated with a film layer B comprising an aromatic polyester (a).

4. The biaxially oriented film according to claim 3, wherein the film layer A is formed of a thermoplastic resin composition (c') comprising 5 to 95% by weight of the aromatic polyester (a) and 5 to 95% by weight of the polyolefin (b), and the thickness of the film layer A is in the range of 5 to 95% with respect to the thickness of the laminate film.

5. The biaxially oriented film according to claim 1, which is a laminate film, at least 1 layer of which is a film layer C comprising a polyolefin (B), and at least one side of which is laminated a film layer B comprising an aromatic polyester (a).

6. The biaxially oriented film of claim 1, wherein the aromatic polyester (a) is polyethylene 2, 6-naphthalate.

7. The biaxially oriented film of claim 1, wherein polyolefin (b) has at least any 1 characteristic of a dielectric constant of less than 3.0 and a dielectric loss of less than 0.001.

8. The biaxially oriented film according to claim 2 or 3, wherein the polyolefin (b) in the film layer formed of the thermoplastic resin composition (c) is dispersed in islands, and the average length in the MD direction thereof is 20 μm or less.

9. The biaxially oriented film of claim 8, wherein the thermoplastic resin composition (c) further comprises 0.1 to 10% by weight, based on the weight of the thermoplastic resin composition, of a thermoplastic amorphous resin (d) having a solubility parameter between the aromatic polyester (a) and the polyolefin (b).

10. The biaxially oriented film according to claim 9, wherein the thermoplastic amorphous resin (d) is an acrylic copolymerized polyolefin or a vinyl oxazoline copolymerized polyolefin-based resin.

11. The biaxially oriented film according to claim 3, wherein the film comprises 3 layers each comprising a film layer A and a film layer B laminated on both sides thereof.

12. A biaxially oriented film according to claim 3, which film laminates a film layer a and a film layer B having a total number of layers of at least 4.

13. A biaxially oriented film according to claim 5, which comprises 3 layers each comprising a film layer B laminated on both sides of a film layer C.

14. The biaxially oriented film of claim 5, which film laminates film layer C and film layer B having a total number of layers of at least 4.

15. The biaxially oriented film of claim 1, wherein the moisture expansion coefficient in the width direction of the film is 0.1 x 10^-6～13×10^-6Range of%/RH%.

16. The biaxially oriented film of claim 1, wherein the film has a temperature expansion coefficient in the width direction of-5 x 10^-6～15×10^-6Range of%/° c.

17. The biaxially oriented film according to claim 1, wherein the Young's modulus in both the film formation direction and the width direction of the film is 5GPa or more, and the total of both is at most 22 GPa.

18. A biaxially oriented film according to any one of claims 1 or 15 to 17, which is used as a base film for a magnetic recording medium.

19. A magnetic recording medium comprising the biaxially oriented film according to claim 1 or any one of claims 15 to 17 and a magnetic layer provided on one side thereof.

20. The biaxially oriented film according to claim 1, wherein the dielectric breakdown voltage is more than 400V/μm, and the heat resistance temperature is 110 ℃ or more.

21. The biaxially oriented film according to any one of claim 1, 15 or 20, which is used as a base film of a film capacitor.

22. A film capacitor comprising the biaxially oriented film according to claim 1, 15 or 20 and a layer D containing an oxygen atom-containing compound provided on at least one surface of the biaxially oriented film, wherein the thickness of the layer D is 30% or less of the total thickness of the film, the ratio of oxygen atoms to carbon atoms on the surface of the layer D as measured by X-ray photoelectron spectroscopy is 10% or more,

23. a film capacitor comprising the biaxially oriented film according to claim 1, 15 or 20 and a metal layer provided on at least one side thereof.