JP2001226502A - Biaxially oriented film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a high quality biaxially oriented film having minute protrusions in a high density homogeneously on the surface of the film and excellent in electromagnetic transducing characteristics, traveling durability, traveling characteristics of the magnetic head, or the like, used for a magnetic recording medium. SOLUTION: The biaxially oriented film comprises a polymer alloy essentially comprising a thermoplastic resin except a polyester (polymer 1) and a polyester (polymer 2), and 1-90 millions of minute protrusions having a protrusion height of 2-50 nm on at least one surface thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a polyester film which has greatly improved the quality, especially the surface properties, of a conventional polyester film.
It relates to an axially oriented film.

[0002] Specifically, it is very suitable for magnetic recording media, in particular, for base tapes for magnetic tapes for data storage and digital video tapes requiring high-density recording, and for capacitors, thermal transfer, etc. The present invention relates to a biaxially oriented polyester film which is also suitable as a film for various industrial materials such as a ribbon or a heat-sensitive stencil sheet.

[0003]

2. Description of the Related Art A polyester film is capable of continuous production of a large-area film which cannot be obtained from other materials, and can impart strength, durability, transparency, flexibility and surface characteristics. Taking advantage of its features, it can be used for various industrial materials such as magnetic recording media, capacitors, thermal transfer ribbons, heat-sensitive stencil printing paper, agriculture, packaging,
It is used in various fields in large demand such as for building materials.

Among them, they are used in various fields from the viewpoint of ease of surface design, and are particularly useful as base films for magnetic recording media. Polyester films are often used as biaxially stretched films to improve mechanical properties, thermal properties, electrical properties, and the like. For magnetic recording media, in particular, in recent years, miniaturization of recording signals has been demanded in order to reduce the weight and size of equipment and to record for a long time. In order to reduce the size and density of recording signals, it is necessary to smooth the film surface, especially the film surface on the magnetic surface side. Furthermore, the drive side is also improving its performance, such as adopting an MR head, but the demand for smoothing the base film surface, such as the absence of coarse protrusions that damage the MR head, is becoming increasingly severe. Has become.

[0005] However, when the surface becomes smooth, not only the handleability is reduced, but also when used as a magnetic tape, the coefficient of friction between the film surface and the magnetic head is increased, so that the tape running property is reduced or the tape surface is deteriorated. In this case, there is a problem that the durability of the magnetic head is lowered and the magnetic head is easily worn.

For this reason, conventionally, a method of coating a polyester film in which a thin layer containing particles for forming surface protrusions is laminated on a base layer (for example, JP-A-2-77431), or a discontinuous film containing fine particles is coated. (For example, JP-A-3-208639) is known.

However, when fine particles are used at a high concentration, the surface energy increases remarkably as the particle size of the particles decreases, so that the surface of the particles is coated with a water-soluble polymer to suppress aggregation. Is required, for example, Japanese Patent Application Laid-Open No. 9-300563 is known. However, there are problems such as a problem of thermal deterioration of the coating film, a decrease in productivity, and an increase in cost. Even if these methods are used, if the particle concentration becomes higher than a certain level, formation of coarse projections due to aggregation cannot be avoided,
It has been difficult to form uniform fine projections at a high density by the particles.

For this reason, as a method for forming uniform and fine projections on the surface without using particles, a method utilizing fine crystals in a laminated portion is known (for example, Japanese Patent Laid-Open No. 7-169).
No. 6). However, in this method, since the unstretched film in which the surface layer is crystallized in the preheating step is stretched, there is a problem such as a process scratch in a stretching roll, and a problem remains when applied to a high-density magnetic recording tape. Is the current situation.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium having a base film for a magnetic recording medium, particularly when used as a base film for a magnetic recording medium, because of its high density of uniform fine projections on its surface. By providing a biaxially oriented film suitable as a base film for a high-density magnetic recording tape, having excellent characteristics and high durability of a film surface with respect to a magnetic head and characteristics that hardly deteriorate the durability of a magnetic head such as an MR head. is there.

[0010]

An object of the present invention is to provide a polymer alloy having thermoplastic resin (polymer 1) other than polyester and polyester (polymer 2) as essential components, and having at least one surface having a protrusion height of 2 to 2. This is achieved by a biaxially oriented film characterized by having 1 to 90 million fine protrusions / mm ^{2 of} 50 nm.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below.

The biaxially oriented film of the present invention comprises a thermoplastic resin other than polyester (polymer 1) and a polymer alloy containing polyester (polymer 2) as essential components.

The polymer alloy referred to in the present invention is a polymer multi-component system, and may be a block copolymer obtained by copolymerization or a polymer blend obtained by mixing. However, this does not apply when polymer particles such as polystyrene particles and polymethyl methacrylate particles are externally added.

When the polymer 1 and the polymer 2 of the present invention are formed into a polymer alloy, the polymer having a small content becomes a very small domain and is finely dispersed in the polymer having a large content. It is considered that when the polymer alloy is biaxially stretched, it reflects the difference in stretchability between these two different polymer domains, but uniform and fine projections are formed on the film surface at high density.

The polyester (Polymer 2) of the present invention comprises
It is a polyester containing 70% by weight or more of a polyester unit composed of an acid component such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol component.

Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,
2,6-Naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid and the like can be used, and among them, terephthalic acid, Phthalic acid and 2,6-naphthalenedicarboxylic acid can be used. As the alicyclic dicarboxylic acid, for example, cyclohexanedicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. These acid components may be used alone or in combination of two or more. Preferably, terephthalic acid, 2,6-naphthalenedicarboxylic acid, or the like can be used, and particularly preferably, terephthalic acid can be used. These acid components may be used alone or in combination of two or more.

The diol component includes, for example, ethylene glycol, 1,2-propanediol, 1,3
-Propanediol, neopentyl glycol, 1,3
-Butanediol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,2
-Cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,4-cyclohexane dimethanol, diethylene glycol, triethylene glycol,
Polyalkylene glycol, 2,2′-bis (4′-β
-Hydroxyethoxyphenyl) propane and the like, among which ethylene glycol,
1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be used, and particularly preferably, ethylene glycol can be used. These diol components may be used alone or in combination of two or more.

As the polyester (polymer 2) of the present invention, among the above, polyethylene terephthalate (PE)
T) and poly (ethylene-2,6-naphthalenedicarboxylate) (PEN) are particularly preferred.

The polyester (Polymer 2) includes:
Other compounds such as monofunctional compounds such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, 2,4-dioxybenzoic acid, lauryl alcohol and phenyl isocyanate may be copolymerized. Furthermore, in addition to the acid component and the diol component, p-hydroxybenzoic acid, m
Aromatic hydroxycarboxylic acids such as -hydroxybenzoic acid and 2,6-hydroxynaphthoic acid and p-aminophenol and p-aminobenzoic acid are further copolymerized in such a small amount that the effect of the present invention is not impaired. be able to.

The thermoplastic resin (Polymer 1) of the present invention comprises:
Thermoplastic resin other than polyester. When a polyester is used as the polymer 2, the glass transition temperature, etc.
It is considered that the reason is that the thermal properties of the polymers are close to each other, but during biaxial stretching, a difference in effective stretchability between the two polymers is hardly generated, and it is difficult to generate fine protrusions by the polymer of the present invention. Not preferred.

The polymer 1 of the present invention is preferably a polymer having a higher glass transition temperature (Tg) than the polymer 2. When the Tg of the polymer 1 is higher, fine projections are easily formed during stretching, and the abrasion resistance of the fine projections tends to be improved.

The polymer 1 of the present invention preferably has good affinity with the polymer 2. To have good affinity here means that, for example, a polymer alloy composed of polymer 1 and polymer 2 is used,
When an axially stretched film is prepared and the cross section of the film is observed with a transmission electron microscope at a magnification of 30,000 to 500,000 times, a structure having a diameter of 200 nm or more not caused by additives such as externally added particles (for example, poor dispersion) Polymer domains) are not observed. However, the method of determining the affinity between the polymer 1 and the polymer 2 is not particularly limited to this, and when a single glass transition point is observed by a temperature-modulated DSC (MDSC), a good affinity is determined. May be determined to exist.

As the polymer 1 of the present invention, polyimide (including polyether imide), polysulfone, and polyether are preferred from the viewpoint of exhibiting good affinity for polyester and forming fine projections when biaxially stretched. Sulfone is preferably exemplified. These thermoplastic resins may be used alone or in combination of two or more.

As described above, since the thermoplastic resin (Polymer 1) and polyester (Polymer 2) of the present invention have an appropriate affinity, they have good melt moldability and handleability, and are suitable as a polymer alloy. When stretched axially, two different
Uniform and fine projections can be formed at high density on the film surface due to the difference in the stretching properties of the kinds of polymers.

If necessary, it is preferable to use a compatibilizer in combination, since the dispersion diameter can be controlled. In this case, the type of the compatibilizer differs depending on the type of the polymer, but the amount of addition is preferably 0.01 to 10% by weight.

As the polymer 1 of the present invention, among the above, polyimide is particularly preferred. The polyimide may have any melt-molding property, and for example, preferably contains a structural unit represented by the following general formula.

[0027]

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However, R _{1 in} the formula is

[0029]

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[0030]

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Represents one or more groups selected from the group consisting of an aliphatic hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group, and R _{2 in} the formula is

[0032]

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And one or more groups selected from aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups.

The preferred polyimide is a group consisting of a tetracarboxylic acid and / or an acid anhydride thereof, an aliphatic primary monoamine and / or an aromatic primary monoamine, and / or an aliphatic primary diamine and / or an aromatic primary diamine. And compounds obtained by dehydrating and condensing one or more compounds selected from the group consisting of:

Examples of the tetracarboxylic acid and / or its acid anhydride include ethylene tetracarboxylic acid,
1,2,3,4-butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, pyromellitic acid, 1,2,3
4-benzenetetracarboxylic acid, 3,3 ', 4,4'-
Biphenyltetracarboxylic acid, 2,2 ′, 3,3′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 2,2 ′, 3,3′-benzophenonetetracarboxylic acid, Bis (2,3-dicarboxyphenyl) methane, bis (3,4-dicarboxyphenyl) methane, 1,1′-bis (2,3-dicarboxyphenyl) ethane, 2,2′-bis (3 4-dicarboxyphenyl) propane, 2,2′-bis (2,3
-Dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) ether, bis (2,3-dicarboxyphenyl) ether, bis (3,4-dicarboxyphenyl) sulfone, bis (2,3-di Carboxyphenyl) sulfone, 2,3,6,7-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid,
2,3,6,7-anthracenetetracarboxylic acid, 1,
2,7,8-phenanthrenetetracarboxylic acid, 3,
4,9,10-perylenetetracarboxylic acid, 4,4′-
(P-phenylenedioxy) diphthalic acid, 4,4′-
(M-phenylenedioxy) diphthalic acid, 2,2′-bis [(2,3-dicarboxyphenoxy) phenyl] propane, and / or an acid anhydride thereof are used.

As the aliphatic primary monoamine, for example,
A saturated or unsaturated linear, branched or alicyclic monoamine having 2 to 22 carbon atoms is used, and specifically, ethylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine,
Decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, eicosylamine, heneicosylamine, docosylamine, cyclohexylamine, methylcyclohexyl Amines, dimethylcyclohexylamine, diethylcyclohexylamine and structural isomers thereof are used.

As the aromatic primary monoamine, for example,
Unsubstituted or alkyl-substituted primary anilines having 1 to 22 carbon atoms are used. Specific examples include aniline, toluidine, ethylaniline, propylaniline, butylaniline, pentylaniline, hexylaniline, heptylaniline, octylaniline, and nonylaniline. , Decylaniline, undecylaniline, dodecylaniline, tridecylaniline, tetradecylaniline, pentadecylaniline, hexadecylaniline, heptadecylaniline, octadecylaniline, nonadecylaniline, eicosylaniline, heneicosylaniline, docosylaniline And their structural isomers and the like.

As the aliphatic primary diamine, for example, a primary diamine bonded by a methylene group having 1 to 12 carbon atoms or a diamine having an alicyclic group is used. Specifically, ethylene diamine, trimethylene diamine, tetramethylene Diamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine,
Undecamethylenediamine, dodecamethylenediamine,
1,3-bisaminocyclohexane, diaminodicyclohexylmethane, m-xylenediamine, structural isomers thereof and the like are used.

Examples of the aromatic primary diamine include benzidine, dimethylbenzidine, diaminodiphenylmethane, diaminoditolylmethane, diaminodiphenylethane, diaminodiphenylpropane, diaminodiphenylbutane, diaminodiphenylether, diaminodiphenylsulfone, diaminodiphenylbenzophenone,
o, m, p-phenylenediamine, tolylenediamine,
Xylene diamines and the like, and aromatic primary diamines having a hydrocarbon group of the exemplified aromatic primary diamine in the structural unit are used.

The above-mentioned polyimide may be any polyimide having a good affinity for the polyester. However, from the viewpoint of melt moldability with the polyester and handleability, for example, as shown in the following general formula, a polyimide composition Polyetherimides containing ether linkages in the components are particularly preferred.

[0041]

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(Wherein R ₃ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms; R ₄
Is a divalent aromatic residue having 6 to 30 carbon atoms, 2
Alkylene groups having -20 carbon atoms, cycloalkylene groups having 2-20 carbon atoms, and 2-8
Selected from the group consisting of polydiorganosiloxane groups chain terminated with an alkylene group having 10 carbon atoms
Is a valence organic group. R ₃ and R ₄ are, for example, aromatic residues represented by the following formula groups:

[0043]

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The following can be mentioned.

In the present invention, the polyester (polymer 2)
From the viewpoints of affinity with, cost, melt moldability, etc., 2,2-bis [4- having a structural unit represented by the following formula
A condensate of (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylenediamine or p-phenylenediamine is preferred.

[0046]

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Or

[0048]

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(N is an integer of 2 or more, preferably 20 to 5
(Integer of 0) This polyetherimide is "Ultem" (registered trademark).
Available from GE Plastics.

The polyethersulfone used as the polymer 1 is a polymer having a repeating unit represented by the following formula in which an aromatic ring is bonded by one sulfonyl group and one or two ether groups, and other structural units May be copolymerized to some extent.

[0051]

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(N is an integer of 2 or more)

[0053]

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(N is an integer of 2 or more)

[0055]

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(N is an integer of 2 or more) The polysulfone used as the polymer 1 is a polymer having a repeating unit represented by the following formula. For example, the polysulfone may contain a functional group such as an alkyl group. It may be copolymerized to some extent.

[0057]

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(N is an integer of 2 or more) The affinity between the polymer 1 and the polymer 2 of the present invention greatly differs depending on the combination of the polymer 1 and the polymer 2. Among the above, polyethylene terephthalate, polyetherimide, polyethylene terephthalate And polysulfone, poly (ethylene-2,6-naphthalenedicarboxylate) and polyetherimide, poly (ethylene-
Combinations of 2,6-naphthalenedicarboxylate) and polysulfone, and poly (ethylene-2,6-naphthalenedicarboxylate) and polyethersulfone exhibit particularly preferred affinity. Among them, melt moldability,
From the viewpoint of the stability of the alloy in the molten state and the formation of protrusions when biaxially stretched, polyethylene terephthalate and polyetherimide are exemplified as the most preferable combination.

In the present invention, the timing of adding the thermoplastic resin (Polymer 1) to the polyester (Polymer 2) is as follows.
It may be added before the polymerization of the polymer 2, for example, before the esterification reaction, or may be added after the polymerization. Before melt extrusion, polymer 1 and polymer 2 may be mixed and pelletized. Further, at the time of pelletizing, once a master pellet containing a high concentration of the polymer 1 (for example, 35 to 65% by weight, more preferably 40 to 60% by weight) is prepared, and further diluted with the polymer 2, When a method of adjusting the concentration to a predetermined concentration is used, the dispersibility of the polymers is improved, and the polymer alloy of the present invention may exhibit a more preferable dispersion state.

Other methods for adjusting the polymer alloy of the present invention to a more preferable dispersion state include, for example, a method of mixing using a tandem extruder, and a method of finely dispersing the polymer 2 using two or more kinds of polyesters. A method in which the polymer 2 is pulverized into a powder by a pulverizer and then mixed, a method in which both are dissolved in a solvent and mixed by coprecipitation,
A method in which one is dissolved in a solvent to form a solution and then mixed with the other is also exemplified, but not limited thereto.

The biaxially oriented film of the present invention has a projection height of 2 to 50 nm, preferably 10 to 50 nm, on at least one surface.
40 nm, more preferably 15 to 30 nm of fine projections of 1,000,000 to 90,000,000 / mm ² , preferably 300
It has from 10 to 60 million pieces / mm ² , more preferably from 5 to 20 million pieces / mm ² . When the protrusion height is less than 2 nm, the protrusion is too low and does not contribute to the improvement of the film running property, which is not preferable. Is not preferred because it reduces the On the other hand, if the projection density is less than 1,000,000 / mm ^2, it is not preferable because it cannot sufficiently contribute to improving the running performance.
If it is larger than 10,000,000 / mm ² , even if it is fine projections, the electromagnetic conversion characteristics of a magnetic tape may deteriorate, which is not preferable.

Further, at least a part of the surface projections of the biaxial film of the present invention may not be caused by inert particles (externally added particles or internally precipitated particles) but may be caused by a polymer alloy. preferable. That is, it is preferable that at least a part of the projection is made of polymer 1 or polymer 2. More preferably, 30
% Or more, more preferably 60% or more is preferably caused by a polymer alloy.

The inert particles referred to in the present invention are inorganic or organic particles having an average particle size of about 10 nm to 1 μm.
A polymer which does not cause a chemical reaction in the polymer of the present invention or does not adversely affect magnetic recording due to electromagnetic influence. The inert particles include titanium oxide, calcium carbonate, kaolin, talc, wet or dry silica, colloidal silica, calcium phosphate, barium sulfate, inorganic particles such as alumina and zirconia, acrylic acids, styrene, silicone, imide, etc. Organic particles, particles precipitated by a catalyst or the like added during the polyester polymerization reaction (so-called internal particles), surfactants, and the like.

The mechanism of the formation of protrusions due to the polymer alloy has not been elucidated in detail. However, when the polymer alloy is biaxially stretched, unevenness is generated due to the difference in stretchability between polymer 1 and polymer 2. It is believed that there is. When a large number of protrusions are generated using inert particles, coarse protrusions are inevitably generated due to agglomeration of the particles, and the coarse protrusions cause a decrease in electromagnetic conversion characteristics, dropout, and a decrease in durability of the magnetic head. Is not preferred. In addition, protrusions caused by the polymer alloy,
This is thought to be because the affinity between the polymer constituting the projection and the surrounding polymer is good. It is preferable because of high wear resistance. Here, a method for confirming whether or not the surface protrusions are caused by the polymer alloy is, for example, etching the target protrusions in the thickness direction of the film with an appropriate solvent to form the protrusions. When the substance remains as an insoluble substance, it is assumed that the substance is caused by inert particles, and when the substance does not remain, it is caused by a polymer alloy. Observation is made, for example, of a method in which inactive particles are not observed up to a certain depth below the protrusions, where the protrusions are caused by a polymer alloy, and the like. However, the method is not limited thereto. Also, two or more methods may be used in combination as appropriate.

In the biaxially oriented film of the present invention, the number of protrusions having a protrusion height of 50 nm or more is 3,000 / mm ² on the surface on the side of layer A.
The following is preferred. Further, it is more preferable that the number of coarse projections exceeding the projection height of 30 nm is 3000 / mm ² or less. The number of coarse projections is more preferably 15
00 pieces / mm ² or less, more preferably 500 pieces / mm ²
It is as follows. This is because, when used as a magnetic tape, the protrusions having a protrusion height of 50 nm or more not only deteriorate the electromagnetic conversion characteristics, but also damage the MR head if the drive uses an MR head. This is because running durability may be deteriorated.

The content of the polymer 2 is preferably in the range of 5 to 50% by weight in the polymer alloy. More preferably, it is in the range of 5 to 40% by weight, and more preferably, it is in the range of 25 to 40% by weight. In general, the melt viscosities of polymer 1 and polymer 2 are greatly different. If the content of polymer 2 is less than 5% by weight, it may be difficult to sufficiently finely disperse the polymer 2 in an extruder. When the domain becomes coarse, the surface protrusion may become coarse. Conversely, if fine dispersion is achieved by kneading, the domain is too small due to the low content, and a desirable surface projection cannot be formed, for example, a projection of an effective size cannot be obtained. On the other hand, if the content of the polymer 2 is more than 50% by weight, it becomes difficult to carry out extrusion and stretching, which may cause problems in film formation and processing such as film breakage and die streaks during extrusion. Or the domain of the polymer 2 due to fine dispersion or microphase separation becomes too large, and the projections may become coarse.

The content of the thermoplastic resin (polymer 1) of the present invention is preferably in the range of 5 to 50% by weight.
More preferably, it is in the range of 25 to 40% by weight, and more preferably, it is in the range of 25 to 40% by weight. In general, the melt viscosities of polymer 1 and polymer 2 are greatly different, so that if the content of polymer 1 is less than 5% by weight, it may be difficult to obtain sufficient kneading with an extruder and finely disperse each other. In some cases, when the domains of the polymer 1 are coarse, the surface protrusions may be coarse. Conversely, if fine dispersion is achieved by kneading, the domain is too small due to the low content, and a desirable surface projection cannot be formed, for example, a projection of an effective size cannot be obtained. On the other hand, if the content of the polymer 1 exceeds 50% by weight, it is difficult to carry out extrusion and stretching, which may cause troubles in film formation and processing such as film breakage and die streaks during extrusion. Or the domain of the polymer 2 due to fine dispersion or microphase separation becomes too large, and the projections may become coarse.

The biaxially oriented film of the present invention may be a single layer. However, in order to simultaneously impart different characteristics such as good film running properties or good winding characteristics and good electromagnetic conversion characteristics to the film, the biaxially oriented film of the present invention may be used. It is preferable to have a laminated structure of at least two or more layers using a film layer having fine projections (referred to as an A layer) as at least one outermost layer. That is, it is a film in which the A layer is laminated on at least one outermost layer of the base layer portion (called the B layer), and the fine projections of the present invention are formed on the surface of the A layer. The layer A in the biaxially oriented film of the present invention is a film layer having a flat surface used as a magnetic surface when used for a magnetic recording medium. The base layer (layer B) is generally the thickest layer in the film, and mainly has strength,
This layer functions to maintain dimensional stability. Also, 2
At the time of layer lamination, good runnability can also be obtained by giving the layer B a relatively rough surface. At this time, the polymer used for the base layer (B layer) is preferably the polyester (Polymer 2) used for the A layer or the polymer alloy of the polymer 2 and the polymer 1 used for the A layer. When the layer A and the layer B contain the same polyester (polymer 2), and when the film in which the layer B and the layer A are laminated is stretched, the polyester of the layer B and the layer A (polymer 2) are the same under the same stretching conditions. It can be stretched as follows. Therefore, the domains of the polyester (polymer 2) existing in the layer A due to fine dispersion or microphase separation are easily stretched, and the difference in stretchability between the polyester (polymer 2) and the thermoplastic resin (polymer 1) is different. It is easy to develop and surface projections can be easily formed. In this case, if the thickness of the layer A is 20% or less (more preferably 15% or less, particularly preferably 10% or less) of the thickness of the entire film, the film-forming property is good and the effect of the present invention is more excellent. Is preferable. Also, when used as a laminated film,
When the thickness of the layer A is 0.01 to 5 μm, the film-forming properties are good and the effects of the present invention are further improved, which is preferable. A
The thickness of the layer is preferably 0.03 to 2 μm, more preferably 0.05 to 1 μm.

In the case of a laminated structure, it is preferable to laminate the layer A with a small amount of oligomer bleed out, since good oligomer deterrence against the oligomer generated from the layer B can be obtained.

When forming a laminated structure, the content W _A (% by weight) of the polymer 1 in the layer _A and the content W _B (% by weight) of the polymer 1 in the layer _B satisfy the following relationship. preferable.

[0071] _{0 ≦ W B ≦ 40,5 ≦ W} A ≦ 50,10 ≦ W
_A -W More preferably _{B ≦ 40, 0 ≦ W B} ≦ 25,25 ≦ W A ≦ 50,10 ≦ W A -W B ≦ 4
0.

In the case of a laminated structure, when the content of the polymer 1 in the base layer (layer B) is more than 40% by weight, the moldability deteriorates, and troubles in film formation and processing such as film breakage occur. It may cause, which is not preferable. Also, A
When the difference obtained by subtracting the content of the polymer 1 in the base layer portion from the content of the polymer 1 in the layer is less than 10% by weight, the stretchability between the domains of the polymer 2 and the polymer 1 in the A layer during biaxial stretching. Since it is difficult to express the difference between them, it is difficult to form the surface projections of the present invention, which is not preferable. When the difference obtained by subtracting the content of the polymer 1 in the base layer from the content of the polymer 1 in the layer A is larger than 40% by weight, the difference in the melt viscosity between the base layer polymer and the laminate polymer is large during co-extrusion. It is not preferable because troubles in film formation and processing are apt to occur, such as difficulty in uniform lamination due to excessive formation.

The sum of the Young's modulus in the longitudinal direction and the Young's modulus in the width direction of the biaxially oriented film of the present invention is preferably in the range of 10 to 25 GPa, more preferably 12 to 22 GPa.
GPa, more preferably 14 to 20 GPa. If the sum of the Young's modulus is less than 10 GPa, for example, when the magnetic tape is used for a magnetic recording medium or the like, the magnetic tape is easily stretched and deformed due to the tension received from a magnetic recording head or a guide pin during traveling. The conversion characteristics (output characteristics) may be adversely affected and may not be practically usable. In addition, a film having a sum of Young's modulus exceeding 25 GPa may be industrially difficult to produce, or the tear resistance and dimensional stability of the film may be significantly reduced.

When the inactive particles are not substantially contained in the layer A, the projections are fine and uniform, and the number of coarse projections is small, so that particularly good electromagnetic conversion characteristics are obtained and the magnetic head is less damaged. Therefore, it is preferable. In this case, "substantially does not contain inert particles" means that the inert particles in the layer A are not contained at all, or even if they are contained,
This refers to the case where the average particle size is smaller than 10 nm or the case where the content of inert particles is smaller than 0.001% by weight.

The layer A may contain a small amount of inert particles. In this case, the smoothness, abrasion resistance, scratch resistance and the like of the film surface are improved. Furthermore, when the film has a laminated structure of two or more layers, and the layer A contains inert particles, the edge damage resistance is particularly good. On the other hand, as compared with the case where no inert particles are contained, there is a demerit that the electromagnetic conversion characteristics are reduced and the magnetic head is easily damaged. At this time, as the inert particles added to the layer A, the above-mentioned inert particles can be used.
The inert particles may be used alone or in combination of two or more. When used for a magnetic recording medium, the average particle size d of the inert particles is preferably 0.01 to 2 μm, and more preferably 0.01 to 1 μm. The content is 0.001 to 2% by weight, preferably 0.01 to 1% by weight from the viewpoint of edge damage resistance. In this case, the thickness t of the A layer is preferably 0.1 to 10 times the average particle size d of the inert particles,
More preferably, it is 0.2 to 5 times.

It is preferable to add inert particles to the B layer for the purpose of improving abrasion resistance, running properties, handling properties and the like. However, the amount of addition is preferably as small as possible in order to suppress the formation of coarse projections and transfer to the A layer due to the added particles. If inert particles are added, 0.
001 to 10% by weight is preferred. The average particle size is 1
nm-1 μm is preferred.

The most preferred laminated structure of the biaxially oriented film of the present invention is a laminated structure of at least three layers of A layer / B layer / C layer in which different films are laminated on both sides of the base layer (B layer). That is, the A layer is laminated on one outermost layer of the base layer portion (referred to as the B layer), and the C layer is laminated on the opposite outermost layer, and the fine projections of the present invention are formed on the surface of the A layer. It is a formed film. In the case of a two-layer structure of the A layer / B layer, the B layer preferably contains inert particles having a relatively large average particle size in order to obtain the running property and the handling property as described above. However, when the layer A is a thin film, the surface of the layer A becomes rough due to the influence of inert particles in the layer B, and the electromagnetic conversion characteristics may be deteriorated. On the other hand, in the case of the three-layered layer A / layer B / layer C, the base layer (layer B) was a smooth layer containing substantially no inert particles, and the layer C contained inert particles. The running surface may have a relatively rough surface. In this case, the surface of the layer A is not roughened by the inert particles of the layer C by sandwiching the smooth base layer portion (layer B) therebetween, and the electromagnetic conversion characteristics and running properties of the magnetic tape are obtained. Are preferable because they can be compatible at a higher level.

The amount of the inert particles added to the layer C is as follows:
0.001 to 10% by weight is preferred. Further, the average particle size is preferably from 1 nm to 1 μm.

When the biaxially oriented film of the present invention has a three-layer structure of layer A / layer B / layer C, the surface roughness R of layer A
a _A is preferably 0.2～10Nm, more preferably 0.5 to 5 nm, more preferably from 1 to 3 nm. A
When the surface roughness Ra _{A of the} layer is smaller than 0.2 nm, friction with a process roll or the like becomes too large in a film forming and processing step, and the layer is easily scratched. The sex worsens. When the surface roughness Ra A of the layer _A is larger than 10 nm, the electromagnetic conversion characteristics when used as a magnetic tape are deteriorated, so that the layer _A may not be suitable as a high-density magnetic recording medium.

The surface roughness Ra _C of the C layer is preferably larger than the surface roughness Ra _A of the A layer. When the surface roughness Ra _C of the C layer is smaller than the surface roughness Ra _A of the A layer, the coefficient of friction on both sides of the film becomes very large,
In the processing step, handling properties such as transportability may be reduced, and it may be difficult to wind up as a roll.

The surface roughness Ra _C of the C layer is preferably 1 to 30 nm, more preferably 5 to 15 nm, and further preferably 6 to 10 nm. C layer surface roughness Ra _C 15 nm
If it is smaller, handling properties such as transportability in the film forming and processing steps are reduced, and when used as a magnetic tape, the running properties with respect to the guide pins are deteriorated. Also,
When the surface roughness Ra _C of the C layer is larger than 30 nm, the projections may be transferred to the flat A layer side on the opposite surface when wound on a roll, and the A layer may be rough.

The thickness of the layer C is preferably 0.01 μm to 2 μm, more preferably 0.1 μm to 1.5 μm, and further preferably 0.2 to 1 μm.

The biaxially oriented film of the present invention may contain a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment, a dye, a fatty acid ester, a wax, etc. within a range not to impair the present invention. Organic lubricants and the like may be added.

The sum of the Young's modulus in the longitudinal direction and the Young's modulus in the width direction of the biaxially oriented film of the present invention is preferably in the range of 10 to 25 GPa, more preferably 12 to 22 GPa.
GPa, more preferably 14 to 20 GPa. If the sum of the Young's modulus is less than 10 GPa, for example, when the magnetic tape is used for a magnetic recording medium or the like, the magnetic tape is easily stretched and deformed due to the tension received from a magnetic recording head or a guide pin during traveling. The conversion characteristics (output characteristics) may be adversely affected, and may not be practically usable. In addition, a film having a sum of Young's modulus exceeding 25 GPa may be industrially difficult to produce, or the tear resistance and dimensional stability of the film may be significantly reduced.

The heat shrinkage of the biaxially oriented film of the present invention in at least one of the longitudinal direction and the width direction at a temperature of 100 ° C. for 30 minutes is from 0.01 to 2 from the viewpoints of elongation deformability and storage stability of the tape. It is preferably 0.0%. More preferably, it is 0.01 to 1.5%, and still more preferably, it is 0.01 to 1.0%. If the heat shrinkage at a temperature of 100 ° C. exceeds 2.0%, the dimensional stability may be easily impaired. For example, in the case of a magnetic recording medium, a film processing step such as applying a magnetic layer of a base film is performed. Thermal deformation of the tape due to heat history and frictional heat between the magnetic tape and the magnetic recording head during running, the tape tends to be thermally deformed, the durability of the film surface is poor, and the storage stability of the tape is deteriorated Sometimes.
If the heat shrinkage at a temperature of 100 ° C. is less than 0.01%, the film may expand and wrinkles may occur.

The intrinsic viscosity of the polymer alloy comprising the polyester (Polymer 2) and the thermoplastic resin (Polymer 1) of the present invention is 0.55 to 0.55 from the viewpoint of the stability of the film forming process and the mixing property with the thermoplastic resin. It is preferably in the range of 3.0 (dl / g), more preferably 0.6 (dl / g).
0 to 2.0 (dl / g). In addition, the intrinsic viscosity of the film after film formation is preferably in the range of 0.50 to 2.0 (dl / g), more preferably from the viewpoints of stability of film forming process and dimensional stability. 0.55-
1.0 (dl / g).

The biaxially oriented film of the present invention is preferably used for magnetic recording materials, capacitors, heat-sensitive transfer ribbons, heat-sensitive stencil sheets, and the like. Particularly preferably, it is used as a magnetic recording medium for data storage or the like that requires a uniform and fine surface form. For magnetic recording media, it is suitable for high-density magnetic recording tapes, for example, base films for data storage. The data storage capacity of the data storage is preferably 30 GB (gigabyte) or more, more preferably 70 GB (gigabyte).
B or more, more preferably 100 GB or more.

The thickness of the biaxially oriented film of the present invention is 10
00 μm or less, more preferably 0.5 to 5 μm.
It is in the range of 00 μm. It can be appropriately determined according to the application and purpose, but usually 1 to 15 μm for magnetic recording materials, and 2 to 15 μm for data or digital video coating type magnetic recording media.
The thickness is preferably in the range of 3 to 9 μm for a data or digital video evaporation type magnetic recording medium. Also,
For capacitors, a film of preferably 0.5 to 15 μm is applied, which results in excellent breakdown voltage and stable dielectric properties. For thermal transfer ribbon applications, preferably a film of 1 to 6 μm is applied, without wrinkles when printing, without causing uneven printing or over-transfer of ink,
High-definition printing can be performed. For use in heat-sensitive stencil paper, a film of preferably 0.5 to 5 μm is applied,
It also has excellent low-energy perforation properties, can change the perforation diameter in accordance with the energy level, and has excellent printability when performing color printing in multiple versions.

The biaxially oriented film of the present invention may be further laminated with another polymer layer, for example, a polyolefin, polyamide, polyvinylidene chloride and acrylic polymer directly or via a layer such as an adhesive.

The biaxially stretched film of the present invention may be subjected to any processing such as heat treatment, molding, surface treatment, laminating, coating, printing, embossing, and etching, if necessary. When used as a magnetic recording medium, a magnetic layer may be formed.

Preferred examples of the magnetic layer include a magnetic layer in which a ferromagnetic metal thin film or a ferromagnetic metal fine powder is dispersed in a binder, a magnetic layer formed by coating a metal oxide, and the like.
As the metal used for the ferromagnetic metal thin film, iron, cobalt, nickel, an alloy thereof, and the like are preferable. Further, as the ferromagnetic metal fine powder used in the magnetic layer formed by dispersing the ferromagnetic metal fine powder in a binder, a ferromagnetic hexagonal ferrite fine powder, or a powder composed of iron, cobalt, nickel or an alloy thereof. preferable. The binder is preferably a thermoplastic resin, a thermosetting resin, a reactive resin, or a mixture thereof.

The magnetic layer may be formed by kneading the magnetic powder with a binder such as a thermosetting, thermoplastic or radiation-curable coating and coating and drying; a metal or alloy vapor deposition, sputtering, and ion plating. For example, any of the dry methods of directly forming a magnetic metal thin film layer on a base film can be adopted.

In the magnetic recording medium of the present invention, a protective film may be provided on the ferromagnetic metal thin film, and the running durability and corrosion resistance can be further improved by this protective film. Examples of the protective film include oxide protective films such as silica, alumina, titania, zirconia, cobalt oxide, and nickel oxide; nitride protective films such as titanium nitride, silicon nitride, and boron nitride; silicon carbide, chromium carbide, and boron carbide. Examples of the protective film include a carbon protective film made of carbon such as a carbide protective film, graphite, and amorphous carbon.

The carbon protective film is a carbon film made of an amorphous, graphite, diamond structure or a mixture thereof formed by a plasma CVD method, a sputtering method or the like, and is particularly preferably a hard carbon film generally called diamond-like carbon. is there.

For the purpose of further improving the adhesion with the lubricant to be provided on the hard carbon protective film, the surface of the hard carbon protective film may be subjected to surface treatment with oxidizing or inert gas plasma.

In the present invention, in order to improve the running durability and corrosion resistance of the magnetic recording medium, it is preferable to add a lubricant or a rust inhibitor to the magnetic film or the protective film.

The method for producing a biaxially oriented film of the present invention comprises:
In a method of producing a film in which a molten polymer is discharged from a die by melt extrusion using an extruder, and a molten polymer is cooled and solidified and formed into a sheet, at least one polyester and a thermoplastic resin are discharged from the die by melt extrusion and melted. The polymer is cooled and solidified to form a sheet.
More specifically, the sheet-like molded product is moved in the longitudinal direction by 1 to 1
It is preferable that the film is stretched 0 times and 1 to 10 times in the width direction, and then heat-treated at a temperature of 150 ° C. to 250 ° C.

More preferred conditions are 2 to 9 in the longitudinal direction.
And stretched in the width direction at a magnification of 2 to 9 times.
The heat treatment is performed at a temperature of 0 to 230 ° C, and more preferably, the film is stretched at a magnification of 3 to 8 times in the longitudinal direction and 3 to 8 times in the width direction, and then heat-treated at a temperature of 180 to 220 ° C. That is.

[0099] The biaxially oriented film of the present invention may be stretched in the following manner. For example, a sequential biaxial stretching method combining stretching in one direction, such as a method of stretching in the longitudinal direction and then stretching in the width direction, or a simultaneous biaxial tenter. And the like, a simultaneous biaxial stretching method in which the film is stretched simultaneously in the longitudinal direction and the width direction, and a method in which the sequential biaxial stretching method and the simultaneous biaxial stretching method are combined.

Hereinafter, an example of the method for producing a biaxially oriented film of the present invention will be described, but the present invention is not limited thereto. Here, polyethylene terephthalate is used as the polyester (polymer 2) of the layer A polymer, and polyether imide is used as the thermoplastic resin (polymer 1).
An example of a laminated film using "Ultem" is shown, but the production conditions are different depending on the polyester (polymer 2) or thermoplastic resin (polymer 1) used, and the lamination structure.
In the case of a single layer film, the details of the manufacturing conditions are different.

First, bis-β-hydroxyethyl terephthalate (BHT) is obtained by esterifying terephthalic acid and ethylene glycol or by transesterifying dimethyl terephthalate and ethylene glycol according to a conventional method. Next, while transferring the BHT to the polymerization tank, the polymerization reaction is advanced by heating to 280 ° C. under vacuum. Here, a polyester having an intrinsic viscosity of about 0.5 is obtained. The obtained polyester is subjected to solid-state polymerization in a pellet form under reduced pressure. In the case of solid phase polymerization, after preliminarily crystallizing at a temperature of 180 ° C. or less,
The solid phase polymerization is carried out at a temperature of about 250 ° C. under a reduced pressure of about 1 mmHg for 10 to 50 hours. In addition, when particles are contained in the polyester constituting the film, a preferred method is to disperse the particles in ethylene glycol at a predetermined ratio in the form of a slurry, and polymerize the ethylene glycol with terephthalic acid. When adding particles, for example,
If the water sol or alcohol sol obtained during the synthesis of the particles is once added without drying, the particles have good dispersibility. It is also effective to directly mix the water slurry of the particles with predetermined polyester pellets and knead the polyester with a vented twin-screw extruder. As a method of adjusting the content and number of particles, a master of high concentration particles is prepared by the above method, and the content is adjusted by diluting it with a polyester substantially free of particles during film formation. Is effective.

Next, the polyethylene terephthalate pellets and the polyetherimide pellets were mixed at a predetermined ratio and supplied to a vented twin-screw extruder heated to 270 to 300 ° C. I do. The shear rate at this time is preferably 50 to 300 sec ^-1 , more preferably 100 to 200 sec ^-1 , and the residence time is 0.5 to 1 sec.
The condition is preferably 0 minutes, more preferably 1 to 5 minutes. Further, when the chips are not compatible under the above conditions, the obtained chips may be again introduced into the twin-screw extruder and the extrusion may be repeated until the chips are compatible.

The obtained polyetherimide-containing polyester pellets were vacuum-dried at 180 ° C. for 3 hours or more, and then extruded at 280 to 320 ° C. under a nitrogen stream or vacuum so as not to lower the intrinsic viscosity. The film is supplied to a machine and formed into a film by a conventional method. Also,
It is preferable to use various filters, for example, a filter made of a material such as a sintered metal, a porous ceramic, a sand, or a wire mesh, in order to remove foreign matters, a deteriorated polymer, unmelted substances, and the like in the polymer. Particularly, in the case of the layer A and the three-layer laminated structure, the polymer of the layer C is preferably exemplified by filtering the polymer with a fiber sintered stainless steel metal filter having a cut of 1.2 μm or less. More preferably,
It is a filter of 0.8 μm or less. Further, if necessary, it is preferable to pass through two or more filter portions and filter in two or more stages, because unmelted matter can be removed more effectively. Most preferably, a sand filter, 1.2μ
A method of filtering in three stages by sequentially using an m-cut fiber sintered stainless metal filter and a 0.8 μm cut fiber sintered stainless metal filter is exemplified.

The filter having a cut size of 1.2 μm refers to a filter having a filtration accuracy of 1.2 μm, and the filter accuracy refers to the maximum particle size of glass beads transmitted through a filter medium according to the method of JIS-B8356. . Further, if necessary, a gear pump may be provided in order to improve the quantitative supply property. Using two or more extruders, a manifold, or a merging block, a sheet obtained by laminating a molten polyester or a mixture of polyester and polyimide is extruded from a slit die, and cooled on a casting roll to form an unstretched film.

Next, this unstretched film is biaxially stretched,
Biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. here,
A sequential biaxial stretching method in which stretching is performed first in the longitudinal direction and then in the width direction is used. The stretching temperature varies depending on the constituent components of the lamination. For example, the intermediate layer is made of polyethylene terephthalate in a three-layer structure, and is 80% of the thickness of the entire film.
The above is an explanation of the case where the outermost layer is made of a mixed polymer of polyethylene terephthalate and polyetherimide. The unstretched film is heated by a group of heating rolls at 80 to 150 ° C., stretched 1 to 10 times in one or two or more stages in the longitudinal direction, and cooled by a group of cooling rolls of 20 to 50 ° C. The longitudinal stretching speed is 1000 to 50
It is preferably performed in the range of 000% / min. Subsequently, as a stretching method in the width direction, for example, a method using a tenter is generally used. The stretching ratio in the width direction is 1 to 10 times, the stretching speed is 1000 to 20000% / min, and the temperature is 80 to 15.
It is preferable to carry out in the range of 0 ° C. If necessary,
Re-longitudinal stretching and / or re-lateral stretching are performed. As the stretching conditions in that case, the stretching in the longitudinal direction is performed at a temperature of 80 to 180.
As a stretching method in the width direction, a method using a tenter is preferable, and a temperature of 80 to 18 is used.
It is preferable to carry out at 0 ° C. and a stretching ratio of 1.1 to 2.0 times.
The total stretching ratio is preferably 1 to 10 times in the longitudinal direction and 1 to 10 times in the width direction. More preferably,
It is 2 to 9 times in the longitudinal direction and 2 to 9 times in the width direction, and more preferably 3 to 8 times in the longitudinal direction and 3 to 8 times in the width direction. Subsequently, the stretched film is heat-treated under tension or while relaxing in the width direction. The heat treatment temperature in this case is
150 ° C to 250 ° C, preferably 170 to 230 ° C,
More preferably at 180 to 220 ° C. for a time of 0.2 to
It is preferable to carry out within 30 seconds.

[Method for Measuring Physical Properties and Method for Evaluating Effect] (1) Height and Number of Projections on Surface Using an atomic force microscope (AFM), measurement is performed 10 times at different locations under the following conditions.

Apparatus: NanoScope III AFM (manufactured by Digital Instruments) Cantilever: silicon single crystal Scanning mode: tapping mode Scanning range: 5 μm × 5 μm Scanning speed: 0.5 Hz Measurement environment: temperature 25 ° C., relative humidity 55% From flat surface The number of protrusions in the range of 2 to 50 nm is measured, and the average thereof is converted to the number per 1 mm ² . In addition, the number of protrusions having a size of 50 nm or more is measured, and the average is converted to the number per 1 mm ² .

Similarly, the number of protrusions whose height is larger than 30 nm and the number of protrusions whose height is larger than 50 nm are measured and converted to the number per 1 mm ² . In this case, the scanning range is 30 μm × 30 μm. However, the scanning range is changed as needed.

(2) Average particle size of the particles: The cross section of the film was measured by using a transmission electron microscope (TEM).
Observe at a magnification of 10,000 times or more. TEM section thickness is about 10
Measure to 100 nm or more at different locations. The average particle diameter d of the particles is determined from the weight average diameter (equivalent circle equivalent diameter).

(3) Content of Polymer 1, Polymer 2, and Inactive Particles Both Polymer 1 and Polymer 2 are dissolved in a suitable solvent that dissolves them, and the ¹ H nucleus NMR (nuclear magnetic resonance) spectrum is measured. . Suitable solvents will depend on the type of polymer, for example, hexafluoroisopropanol (HF
IP) / deuterated chloroform is used. In the obtained spectrum, the peak area intensity of the absorption peculiar to the polymer 1 and the polymer 2 (for example, the absorption of an aromatic proton of terephthalic acid for PET and the absorption of an aromatic proton of bisphenol A for PEI) is determined. The molar ratio between polymer 1 and polymer 2 is calculated from the ratio and the number of protons. Further, the weight ratio is calculated from the formula weight corresponding to the unit unit of each polymer. The measurement conditions are, for example, the following conditions, but are not limited because they vary depending on the type of polymer.

Apparatus: BRUKER DRX-500 (Bruker) Solvent: HFIP / chloroform Observation frequency: 499.8 MHz Reference: TMS (tetramethylsilane) (0 pp
m) Measurement temperature: 30 ° C. Observation width: 10 KHz Data point: 64 K acquisiton time: 4.952 seconds pulse delay time: 3.048 seconds Number of accumulations: 256 times If necessary, the microscopic FT-IR method (Fourier transform) (Microscopic infrared spectroscopy). In that case, it is determined from the ratio of the peak due to the carbonyl group of the polyester to the peak due to other substances. In addition,
In order to convert the peak height ratio into a weight ratio, a calibration curve is prepared in advance using a sample whose weight ratio is known, and the polyester ratio with respect to the total amount of the polyester and other substances is determined. The PEI ratio is determined from this and the inert particle content. Further, if necessary, an X-ray microanalyzer may be used in combination.

Regarding the content of the inert particles, a solvent that can dissolve the polymer 1 and the polymer 2 but not the inert particles is selected, the polymer 1 and the polymer 2 are dissolved, and the inert particles are centrifuged. And the weight percentage was determined.

(4) Lamination Thickness Using a transmission electron microscope (H-600, manufactured by Hitachi), the cross section of the film was measured by an ultra-thin section method (R) at an acceleration voltage of 100 kV.
uO ₄ staining). From the observation result of the interface, the thickness of each layer is determined. As the magnification, an appropriate magnification is selected according to the thickness of the laminated layer to be determined, but 10,000 to 100,000 times is appropriate.

A secondary ion mass spectrometer (SIM)
S) can be measured using a surface depth of 300
The concentration ratio (M ⁺ / C ⁺ ) of the element resulting from the highest concentration of particles (or PEI) of the inert particles in the film in the range of 0 nm to the carbon element of the polyester is determined from the surface to a depth of 3000 nm. Analysis by SIMS in the vertical direction.
In the surface layer, the element concentration due to the inert particles (or PEI) is low, and the element concentration due to the inert particles (or PEI) increases as the distance from the surface increases. In the case of the film of the present invention, the element concentration caused by the inert particles (or PEI) which has once reached a maximum value starts to decrease again.
In this concentration distribution curve, the inert particles (or PE
The depth at which the element concentration caused by I) is reduced to half of the maximum value is defined as the lamination thickness. The conditions are as follows.

I) Measuring apparatus Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany ii) Measurement conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12 KV Primary ion current: 200 nA Raster Area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 5.0 × 10 ⁻⁹ Torr E-GUN: 0.5 KV-3.0 A Inactive particles contained most in the range from the surface layer to a depth of 3000 nm Is organic polymer particles, it is difficult to measure by SIMS.
(X-ray photoelectron spectroscopy), IR (infrared spectroscopy) and the like can be used to measure the same depth profile as above to determine the lamination thickness.

(5) Young's modulus Measured using an Instron type tensile tester according to the method specified in ASTM-D882. The measurement was performed under the following conditions.

Measuring device: Automatic film strength and elongation measuring device “Tensilon AMF / RTA-100” manufactured by Orientec Co., Ltd. Sample size: width 10 mm × test length 100 mm, tensile speed: 200 mm / min Measurement environment: temperature 23 ° C. , Humidity 65% RH (6) Heat shrinkage rate Measured according to JIS-C2318.

Sample size: width 10 mm, mark interval 200
mm Measurement conditions: temperature 100 ° C., processing time 30 minutes, no load state 100 ° C. Heat shrinkage was determined by the following formula.

Heat shrinkage (%) = [(L ₀ −L) / L ₀ ] × 100 L ₀ : Marking line interval before heat treatment L: Marking line interval after heat treatment (7) Electromagnetic conversion of magnetic tape Characteristics (S / N) A 200-nm-thick deposited layer of a cobalt-nickel alloy (Ni 20% by weight) was provided on the film of the present invention using a continuous vacuum deposition apparatus in the presence of a trace amount of oxygen. Further, after forming a carbon protective film on the surface of the vapor deposition layer by a known means,
It was slit to a width of 8 mm to prepare a pancake. Next, a length of 200 m from the pancake was incorporated into a cassette, and a cassette tape was prepared.

Using a commercially available Hi8 VTR, video S /
The N ratio was determined. For the measurement of the S / N ratio, a signal was supplied from a TV test signal generator, and a commercially available standard Hi8ME tape was attached to a 0 dB (d) using a video noise meter.
Comparative measurement was performed as B). The running conditions were 25 ° C, 6
0% RH.

If the electromagnetic conversion characteristics are 0 dB or more compared to a commercially available Hi8ME tape, the digital recording VT
This is a level that can be sufficiently used as an R tape. Evaluation was made according to the following criteria.

+3 dB or more: 0 dB or more, less than +3 dB: 未 満 Less than 0 dB: × Here, ○ indicates an excellent level for high recording density magnetic recording medium use, and △ indicates high level use for high recording density magnetic recording medium use. A possible level, and x means a level that can be used for high recording density magnetic recording media.

(8) Drop-out The number of drop-outs (DO) was determined using the above-deposited cassette tape and a commercially available camera-integrated digital video tape recorder (DVC).

The number of DOs was measured by recording the produced DVC tape with a commercially available digital video tape recorder with a built-in camera, playing it back for one minute, and counting the number of block mosaics that appeared on the screen. The running conditions were 25 ° C. and 60% RH.

30 or less: 50 or less: △ 51 or more: × Here, ○ indicates an excellent level for use in high-density magnetic recording media, and △ indicates use in high-density magnetic recording media. A possible level, and x means a level that can be used for high recording density magnetic recording media.

(9) Running Durability of Magnetic Tape After running the magnetic tape 200 times at 25 ° C. and 60% RH, the S / N ratio and the number of DOs were measured and evaluated according to the following criteria.

○: S / N ratio reduction is 1 dB or less,
And the dropout increase is 30 or less.

Δ: The decrease in the S / N ratio is 2 dB or less,
In addition, the number of dropouts is 50 or less.

X: The decrease in the S / N ratio is larger than 2 dB, or the increase in the dropout is more than 50.

Here, ○ indicates a level excellent for use in a high recording density magnetic recording medium, Δ indicates a level usable for a high recording density magnetic recording medium, and X indicates a level usable for a high recording density magnetic recording medium. Means that it is at a usable level.

(10) Coefficient of friction μK (head running property) A tape running property tester TBT-300 type (manufactured by Yokohama System Laboratory Co., Ltd.) is used by slitting a film into a tape having a width of 1/2 inch. Then, the film was run in an atmosphere of 60 ° C. and 80% RH, and the initial coefficient of friction was determined by the following equation (the film width was イ ン チ inch). The measurement surface was the surface on the side of layer A.

ΜK = (2 / π) ln (T ₂ / T ₁ ) where T ₁ is the incoming tension and T ₂ is the outgoing tension. The guide diameter is 6mmφ, the guide material is SUS27 (surface roughness 0.2S), the winding angle is 90 °, and the running speed is 3.3c.
m / sec. When the μK in the longitudinal direction of the film obtained by this measurement is 0.7 or less, the head running property is good (○), and when it exceeds 0.7, the head running property is poor (×).
It was determined. This μK is a critical point that determines the running property of the magnetic head when the film is used as a magnetic recording medium having a vapor-deposited magnetic layer.

(11) Intrinsic Viscosity The value calculated from the following formula based on the solution viscosity measured at 25 ° C. in orthochlorophenol is used. That is, η _sp / C = [η] + K [η] ² · C, where η _sp = (solution viscosity / solvent viscosity) −1, C is the weight of dissolved polymer per 100 ml of solvent (g / 100 ml,
Normally 1.2), K is the Haggins constant (0.343)
It is. The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

(12) Proportion of protrusions caused by polymer The protrusions to be measured were placed on polymer 1 in the direction of the film thickness.
The projections are observed at a magnification of 10,000 to 100,000 by a scanning electron microscope (SEM) while etching with a solvent (for example, HFIP / chloroform, which differs depending on the type of the polymer) that dissolves the polymer 2 together. When the substance forming the projection remains as an insoluble substance, the substance forming the projection is determined to be inert particles (I). When there is substantially no insoluble matter remaining, the cause of formation of the protrusion is polymer 1 or polymer 2
(II). With this method, 20 visual fields are observed with a visual field area of 25 μm ² , and the average value of II / (I + II) is obtained.

If necessary, the cross section of the film surface layer is observed with a transmission electron microscope (TEM) at a magnification of 10,000 to 500,000 (for 100 projections), and it is checked whether or not there is any cause under the projections. The method was used in combination.

(13) Average dispersion diameter of polymer 1 Apparatus: Transmission electron microscope (H-7100FA manufactured by Hitachi)
Condition): Acceleration voltage 100 kV Sample preparation: Ultra-thin section method Sample thickness: 50 nm Image analysis: A negative of a transmission electron micrograph of each sample is scanned with a dedicated scanner (Image Pro, manufactured by Planetron).
Plus). afterwards,
Dedicated software (Leafscan 45 Plug manufactured by Nippon Cytex Corporation)
-In), image analysis was performed, and the circle equivalent diameter of the high contrast component was randomly observed at 100 points, and the average value was defined as the average dispersion diameter.

(14) Glass transition temperature (Tg) The specific heat was measured by the following apparatus and under the conditions described in JIS K71.
21.

Apparatus: Temperature modulation D manufactured by TA Instrument
SC Measurement conditions: Heating temperature: 270 to 570K (RCS cooling method) Temperature calibration: Melting point of high-purity indium and tin Temperature modulation amplitude: ± 1K Temperature modulation cycle: 60 seconds Heating step: 5K Sample weight: 5mg Sample container: Aluminum Open container made of aluminum (22 mg) Reference container: Open container made of aluminum (18 mg) The glass transition temperature was calculated by the following equation.

Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2 (15) Comprehensive evaluation The above-mentioned head running property, electromagnetic conversion characteristics, dropout,
In the evaluation of the running durability of the magnetic tape, when all the items are ○ or when △ is one and all the remaining items are ○, the film has excellent characteristics as a base film for a high-density magnetic recording medium ( ○), and two or more △ or ×
Those having one or more were judged to be difficult to use as a base film for a high-density magnetic recording medium (x).

[0140]

Embodiments of the present invention will be described based on the following embodiments. In addition, for each polymer, in principle, the polymer corresponding to the A layer is denoted by A, the polymer corresponding to the B layer is denoted by B, and the others are denoted by C, but there are some exceptions.

Example 1 PET having an intrinsic viscosity of 0.85 (PE
T) pellets (50% by weight) and General El
"Ultem" 1010 (50% by weight) with an intrinsic viscosity of 0.68 manufactured by ectric (GE) Co., Ltd. was supplied to a vented twin-screw extruder of the same direction rotating type heated to 290 ° C. To prepare a blend chip (II) containing 50% by weight.

Next, using three extruders, pellets of polyethylene terephthalate (PET) (B1) substantially containing no particles were vacuum-dried at 180 ° C. for 3 hours in an extruder B heated to 280 ° C. Supplied later, 290 ° C
The extruder A heated to 40 ° C. was charged with 40 parts by weight of the blended chips obtained by the above pelletizing operation and P having an intrinsic viscosity of 0.65.
60 parts by weight of ET chips (A1) were supplied after vacuum drying at 180 ° C. for 3 hours, and extruder C heated to 280 ° C.
Has a spherical silica particle having an average particle size of 0.17 μm
% By weight and spherical silica particles having an average particle diameter of 0.3 μm
5% by weight polyethylene terephthalate (PE
T) The pellet of (C1) was supplied after vacuum drying at 180 ° C. for 3 hours. Then, the polyester composition (B1)
Are combined in a T-die so that three layers of the polyester composition (A1) and the polyester composition (C1) become the outermost layer in the base layer portion (lamination thickness ratio A1 / B1 / C1 =
(1/10/1), while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C., tightly cooling and solidifying to form a laminated unstretched film.

This unstretched film was stretched 3.4 times at 105 ° C. in one step in the longitudinal direction by a roll-type stretching machine, and further 3.4 mm at 95 ° C. in the width direction using a tenter.
It was stretched twice. Subsequently, the film was stretched 1.8 times at a temperature of 140 ° C. in two steps in the longitudinal direction with a roll-type stretching machine, and then stretched 1.5 times at a temperature of 190 ° C. in the width direction using a tenter. After a heat treatment at a temperature of 210 ° C. for 10 seconds under a constant length, a relaxation treatment of 2% was performed in the width direction to obtain a biaxially oriented film having a thickness of 5 μm.

The properties of this laminated polyester film are as follows:
As shown in Table 2, there were few dropouts and excellent characteristics such as electromagnetic conversion characteristics and running durability as base films for magnetic recording media.

Examples 2 and 3 In the same manner as in Example 1, the biaxially oriented film was obtained by changing the polyetherimide content (A2, A3) as shown in Table 1. In Example 3, an A layer was also provided on the opposite side of the B layer instead of the C layer, and a three-layer A3 / B1 / A3 layer was formed.

As shown in Table 2, the characteristics of this biaxially oriented film were as follows: dropout was small,
It had excellent characteristics such as running durability as a base film for a magnetic recording medium.

Example 4 In the same manner as in Example 1, as shown in Table 1, the polymer of Layer A was prepared by mixing 20% by weight of polyether sulfone (PES) and 80% by weight of poly (ethylene 2,6-naphthalenedicarboxylate). A blend polymer (containing 0.05% by weight of spherical silica particles having an average particle diameter of 0.3 μm) (A4), and a B-layer polymer of poly (ethylene 2,6-naphthalenedicarboxylate) (an average particle diameter of 0.17 μm) (B4) was changed to (B4) containing 0.3% by weight of spherical silica particles and 0.05% by weight of spherical silica particles having an average particle diameter of 0.3 μm, and the unstretched film (A / After obtaining the B-type two-layer laminate), both ends of the unstretched film are gripped with clips and guided to a simultaneous biaxial stretching tenter of a linear motor type, the film temperature is heated to 100 ° C., and the area stretching ratio is 1
Simultaneous biaxial stretching is performed at 2.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was raised to 150 ° C., and the film was stretched simultaneously and biaxially at an area stretching ratio of 1.96 times (longitudinal ratio: 1.4 times, lateral ratio: 1.4 times). After a heat treatment at 10 ° C. for 10 seconds, a 2% relaxation treatment was performed in each of the longitudinal and transverse directions to obtain a biaxially oriented film having a thickness of 5 μm.

As shown in Table 2, the characteristics of the biaxially oriented film are as follows: dropout is small,
It had excellent characteristics such as running durability as a base film for a magnetic recording medium.

Example 5 In the same manner as in Example 4, as shown in Table 1, the polymer of Layer A was a blend polymer of 10% by weight of polysulfone (PSF) and 90% by weight of poly (ethylene 2,6-naphthalenedicarboxylate). After changing to (A5), a biaxially oriented film was obtained by the same stretching method as in Example 1.

As shown in Table 2, the properties of the biaxially oriented film are as follows: dropout is small,
It had excellent characteristics such as running durability as a base film for a magnetic recording medium.

Example 6 Polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.85 and obtained by a conventional method (50% by weight, Tg
81 ° C) and General Electric (GE)
"Ultem" 1010 (50
% By weight, Tg 216 ° C.) to a co-rotating vented twin-screw extruder heated to 290 ° C.
A blend chip (II) containing 50% by weight of EI was prepared.

Next, film formation was performed using three extruders. The extruder B heated to 280 ° C. was charged with polyethylene terephthalate (PET) pellets (B6) having an intrinsic viscosity of 0.62 and containing substantially no inert particles at 180 ° C.
And dried under vacuum for 3 hours. In extruder A heated to 290 ° C., a mixed raw material (A6) comprising 70 parts by weight of the blended chips obtained by the above pelletizing operation and 30 parts by weight of PET chips having an intrinsic viscosity of 0.65 was vacuum dried at 180 ° C. for 3 hours. Supplied after. Extruder C heated to 280 ° C. has an intrinsic viscosity of 0.3% by weight of spherical silica particles having an average particle diameter of 0.17 μm and 0.05% by weight of spherical silica particles having an average particle diameter of 0.3 μm. .62 polyethylene terephthalate (PET) pellets (C6)
Supplied after vacuum drying at 0 ° C. for 3 hours. Thereafter, the polyester composition (B6) is joined to the base layer in a T-die so that the polyester composition (A6) and the polyester composition (C6) become the outermost layers, and an electrostatic charge is applied to a cast drum having a surface temperature of 25 ° C. Is applied while cooling, and solidifies
Layer laminated unstretched film (lamination thickness ratio A6 / B6 / C6 =
0.07 / 5/1).

The unstretched film was stretched 3.4 times at 105 ° C. in one step in the longitudinal direction by a roll type stretching machine, and further 3.4 mm at 95 ° C. in the width direction using a tenter.
It was stretched twice. Subsequently, the film was re-stretched 1.3 times at a temperature of 140 ° C. in two steps in the longitudinal direction using a roll-type stretching machine, and re-stretched 1.8 times at a temperature of 190 ° C. in the width direction using a tenter. After a heat treatment at 210 ° C. for 10 seconds under a constant length, a 2% relaxation treatment was performed in the width direction to obtain a biaxially oriented film having a thickness of about 6.1 μm. The film thickness of each layer is as follows: layer A 0.07 μm, layer B
The layer was 5 μm and the C layer was 1 μm.

As shown in Table 2, this biaxially oriented film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Example 7 In the same manner as in Example 6, as shown in Table 1, the polymer of the layer A and the layer C were not changed, and the same polyethylene terephthalate 90% by weight as the polymer of the layer B was used for the layer A. And a 10% by weight polyetherimide blend polymer (B7) to obtain a biaxially oriented film. The film thickness of each layer was 0.1 μm for layer A, 5 μm for layer B, and 1 μm for layer C.

As shown in Table 2, this biaxially oriented film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as base films for magnetic recording media.

Example 8 In the same manner as in Example 6, as shown in Table 1, the polymer of Layer A was a blend polymer of 50% by weight of polyetherimide and 50% by weight of polyethylene terephthalate (average particle size: 0.0%).
(Containing 0.3% by weight of 15 μm spherical silica particles)
After changing to (B8) and using one extruder to obtain a single-layer unstretched film, a biaxially oriented film was obtained in the same manner as in Example 4. The film thickness was 6.2 μm.

As shown in Table 2, this biaxially oriented film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Example 9 The procedure of Example 7 was repeated, except that the polymer in the layer A was changed to a blend polymer (A9) of 15% by weight of polyetherimide and 85% by weight of polyethylene terephthalate. A biaxially oriented film of about 6.1 μm was obtained. The film thickness of each layer is as follows: A layer 0.15 μm, B layer 5
μm and the C layer was 1 μm.

As shown in Table 2, this biaxially oriented film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Comparative Examples 1 and 2 A laminated unstretched film was prepared in the same manner as in Example 1 except that in the three-layer laminate, all three layers were made of polyethylene terephthalate (PET).

Next, in the same manner as in Example 1, a laminated polyester film having a thickness of 5 μm was obtained by successive biaxial stretching.

As shown in Table 2, this biaxially oriented film was inferior as a film for magnetic recording media.

Comparative Example 3 In the same manner as in Example 1, the biaxially oriented film was obtained by changing the polyetherimide content of the layer A as shown in Table 1 (A7).

Table 2 shows the properties of this polyester film.
As shown in Table 2, the film was inferior as a film for use in a magnetic recording medium.

Comparative Example 4 In the same manner as in Example 1, polypropylene (10% by weight)
And a polyethylene terephthalate (90% by weight) blend chip (A8). Using an extruder, an unstretched film was obtained without performing lamination.

The unstretched film was stretched 3.4 times at a temperature of 100 ° C. in one step in a longitudinal direction by a roll-type stretching machine, and further, 4.3 mm at a temperature of 95 ° C. in a width direction using a tenter.
The film was stretched twice to obtain a biaxially stretched film.

As shown in Table 2, this biaxially oriented film was inferior as a film for magnetic recording media.

Comparative Examples 5 to 8 In the same manner as in Example 6, as shown in Table 1, the type of polymer in the layer A, the content of polyetherimide, the average particle size and content of the inert particles, and the type of polymer in the layer B By changing the above, a biaxially oriented film was obtained. The film thickness of each layer was A
Layer 0.07 μm, B layer 5 μm, C layer 1 μm, Comparative Example 6
Is A layer 1 μm, B layer 5 μm, C layer 1 μm, Comparative Example 7
Is A layer 1 μm, B layer 5 μm, and Comparative Example 8 is A layer 0.1 μm.
m, the B layer was 5 μm, and the C layer was 1 μm.

As shown in Table 2, this biaxially oriented film was inferior as a film for magnetic recording media.

Comparative Example 9 In the same manner as in Example 4, as shown in Table 1, the average particle size and the content of the inactive particles in the A layer were changed, and the B layer was made of polyethylene (2) substantially containing no particles. , 6-naphthalenedicarboxylate), and changing the layer C to the same composition as the layer B in Example 4 to obtain a biaxially oriented film having a thickness of 5 μm. The film thickness of each layer is A layer 1 μm, B layer 3 μm, C layer 1 μm
m.

As shown in Table 2, this biaxially oriented film was inferior as a film for magnetic recording media.

[0173]

[Table 1]

[0174]

[Table 2]

[0175]

The biaxially oriented film, which uses the polymer alloy of the polyester and the specific thermoplastic resin disclosed in the present invention and regulates the height and the number of the fine protrusions on the surface,
It is an excellent base film in terms of electromagnetic characteristics, running durability, and running performance of a magnetic head, and its industrial value is extremely high.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 5/733 G11B 5/733 // (C08L 67/00 (C08L 67/00 101: 00) 101: 00 ) B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 9:00 9:00

Claims (18)

[Claims] 1. A microalloy comprising a thermoplastic alloy other than polyester (polymer 1) and a polymer alloy containing polyester (polymer 2) as essential components, and having at least one surface having fine projections having a height of 2 to 50 nm of 1,000,000 to 1,000,000. A biaxially oriented film having 90 million pieces / mm ² . 2. The biaxially oriented film according to claim 1, wherein polymer 1 has a higher glass transition temperature than polymer 2. 3. The polymer 1 is polyimide, polysulfone,
3. The biaxially oriented film according to claim 1, which is at least one kind of thermoplastic resin selected from polyether sulfone. 4. The biaxially oriented film according to claim 3, wherein the polymer 1 is a polyimide. 5. The biaxially oriented film according to claim 4, wherein the polymer 1 is a polyetherimide. 6. The layer comprising polymer 1 and polymer 2 containing 1 to 50% by weight of polymer 1.
The biaxially oriented film according to any one of the above. 7. A biaxially oriented film comprising the film (A layer) according to claim 1 laminated on at least one outermost layer of a base layer (B layer). 8. The biaxially oriented film according to claim 7, wherein the base layer (layer B) is made of polyester. 9. The method according to claim 1, wherein the base layer (B layer) is formed of polymer 1 or
The biaxially oriented film according to claim 7, comprising a polymer alloy containing polymer 1 and polymer 2 as essential components. 10. The biaxially oriented film according to claim 7, wherein the number of projections having a height of 50 nm or more on the surface on the side of the layer A is 3000 or less / mm ² . 11. The biaxially oriented film according to claim 1, wherein at least a part of the fine projections is made of polymer 1 or polymer 2. 12. The biaxially oriented film according to claim 7, wherein the layer A contains substantially no inert particles. 13. The layer A contains 0.001-2% by weight of inert particles having an average particle diameter of 0.01-0.5 μm.
12. The biaxially oriented film according to any one of 11. 14. The biaxially oriented film according to claim 1, wherein the sum of the Young's modulus in the longitudinal direction and the Young's modulus in the width direction is 10 to 25 (GPa).
14. The biaxially oriented film according to any one of 13). 15. The biaxially oriented film according to claim 1, wherein at least one of the longitudinal direction and the width direction has a heat shrinkage of 0.01 to 2.0% at 100 ° C. for 30 minutes. Biaxially oriented film. 16. A magnetic recording medium comprising the biaxially oriented film according to claim 1 and a magnetic layer provided on at least one surface. 17. The method according to claim 1, wherein the magnetic layer is a ferromagnetic metal thin film.
7. The magnetic recording medium according to 6. 18. The magnetic recording medium according to claim 16, wherein the magnetic layer comprises a ferromagnetic metal fine powder dispersed in a binder.