JP2001323146A - Biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high quality biaxially oriented polyester film which is scratch-resistant on a surface thereof and is a little elimination of particles, and particularly for a magnetic recording medium, has excellent electro magnetic transducing characteristics, chipping resistance, scratch resistance or the like. SOLUTION: The biaxially oriented polyester film comprises a polyester (a polymer A) and a heat resistant thermoplastic resin (a polymer B) other than the polyester as resin components, the film containing inactive particles of 0.01-3 wt.% of an average particle diameter of 0.001-1.5 μm and having an extrapolation glass transition temperature (Tg-onset) of 90-150 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film.

Specifically, films for various industrial materials such as a magnetic recording medium, a capacitor, a thermal transfer ribbon, and a heat-sensitive stencil sheet are excellent in surface scratch resistance and little dropping of particles. More particularly, the present invention relates to a biaxially oriented polyester film which is very suitable as a base film for high-density magnetic recording media used for cassette tapes for digital recording.

[0003]

2. Description of the Related Art Polyester film enables continuous production of a large area film that cannot be obtained from other resin materials, and can impart strength, durability, transparency, flexibility, and surface characteristics. Utilizing these features, it can be used in large quantities for various industrial materials such as magnetic recording media, capacitors, thermal transfer ribbons, heat-sensitive stencil printing base paper, agriculture, packaging, and building materials. Used in various demanding fields.

[0004] Among them, polyester films containing various inorganic and organic particles are used in various fields from the viewpoint of surface design and the like, 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. To reduce the size and density of recording signals,
Smoothing of the film surface, especially the film surface on the magnetic surface side is required. In order to satisfy these requirements, the base film is required to have flatness by reducing the height of projections on the surface.

[0005] However, when the film surface is flat, the handling property is reduced, and in the film forming and processing steps, the friction with the roll is increased, which causes a problem that the film surface is easily damaged. In recent years, base films for high-density magnetic recording media are often formed using re-longitudinal / re-horizontal stretching for the purpose of increasing the elastic modulus. The problem is getting more serious. When a ferromagnetic metal thin film layer is provided on one surface of the base film to form a magnetic recording medium, the ferromagnetic metal thin film layer is provided on an ultra-flat surface, but the thickness of the ferromagnetic thin film layer is usually 0.04-0.5μ
Since the thickness of the ferromagnetic thin film is very thin, ie, about m, the surface of the base film becomes the surface shape of the ferromagnetic thin film as it is. For this reason, even a minute scratch on the film surface in a film forming process or a processing process becomes a large defect that deteriorates the quality such as the recording characteristics of the magnetic tape, and the base film is required to further reduce the scratch.

In order to solve these problems, not only are there no coarse projections, uniform and fine projections are provided at a high density to achieve both flatness and lubricity, but also to prevent scratches more than before. It is required to have a strong surface.

As a base film for a magnetic recording medium, conventionally, a base film having fine particles added and projections formed on the surface of the film (see, for example, JP-A-59-17162).
No. 3), 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), and a method of coating a discontinuous film containing fine particles on the film surface. (For example, JP-A-3-208639) is known.

However, when fine particles are used in a high concentration, the surface energy increases remarkably as the particle size of the particles decreases, and the surface of the particles is coated with a water-soluble polymer to suppress aggregation. Is required, for example, a processing method described in JP-A-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. Also, even if these methods are used, if the particle concentration becomes higher than a certain level, formation of coarse projections due to agglomeration is unavoidable, and in the film forming step and the processing step,
There is a problem that the coarse projections fall on the transport rolls and damage the film, and furthermore, when a magnetic tape is used, there is a problem that electromagnetic conversion characteristics are reduced, and scratches and shavings are generated due to repeated running.

In view of the above, there is known a method of forming uniform and fine projections on the surface without using particles by using fine crystals in a laminated portion (for example, Japanese Patent Application Laid-Open No. Hei 7-1696). However, in this method, since the unstretched film in which the surface layer is crystallized is stretched in the preheating step, process scratches on the stretching rolls become a problem, and further improvement is required for application to films for high-density magnetic recording tape. Is desired.

[0010] On the other hand, studies on the physical properties of a composition obtained by mixing a polyester and a thermoplastic resin are described in several documents. For example, it has been shown that, using polyethylene terephthalate (PET) as the polyester and polyetherimide (PEI) as the thermoplastic resin, the glass transition temperature increases as the weight fraction increases ( For example, "JOURNAL of APPLI
ED POLYMERCIENCE ”, 1993, 4
8, pp. 935-937, “Macromolecule
es ", 1995, 28, 2845-2851,
"POLYMER", 1997, 38, 4043-4
048 pages "). However, no studies have been made on the production of a film using the mixed resin of PET and PEI, and even less on the surface properties of the film.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a film having no coarse protrusions, uniform and fine protrusions at a high density, and exhibiting good affinity with the particles so that the particles are less likely to fall off. Therefore, by providing a biaxially oriented laminated polyester film capable of obtaining a magnetic recording medium having excellent surface scratch resistance and improved electromagnetic conversion characteristics, particularly when used as a base film for a magnetic recording medium. is there.

[0012]

Means for Solving the Problems Polyester (Polymer A) and a heat-resistant thermoplastic resin (Polymer B) other than polyester are used as resin components and have an average particle size of 0.001 to 0.001.
Containing 0.01 to 3% by weight of 1.5 μm inert particles;
And extrapolated glass transition temperature (Tg-onset) of 90 to 15
It is a biaxially oriented polyester film at 0 ° C.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer constituting the biaxially oriented polyester film of the present invention comprises a polyester (Polymer A) and a heat-resistant thermoplastic resin other than polyester (Polymer B).

In the biaxially oriented polyester film of the present invention, at least one of the film layers constituting the film must be biaxially oriented. If all the layers are non-oriented or uniaxially oriented, the characteristics of the present invention cannot be satisfied.

The polyester (Polymer A) used in the present invention is a polyester containing at least 70% by weight 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. It is.

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′-diphenylsulfondicarboxylic acid and the like can be used, and among them, terephthalic acid, Phthalic acid, 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. Only one of these acid components may be used.
More than one species may be used in combination. Preferably, terephthalic acid,
2,6-Naphthalenedicarboxylic acid and the like can be used, and terephthalic acid can be particularly preferably used. These acid components may be used alone or in combination of two or more.

As the diol component, 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-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, Triethylene glycol, polyalkylene glycol, 2,2′-bis (4′-β-hydroxyethoxyphenyl) propane and the like can be used,
Among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol,
Diethylene glycol or the like can be used, and particularly preferably, ethylene glycol can be used. One of these diol components may be used alone, or two or more thereof may be used in combination.

Among the polyesters (polymer A) used in the present invention, among the above, polyethylene terephthalate (PET) having ethylene terephthalate as a main constituent unit and / or ethylene-2,6-naphthalene dicarboxylate as a main constituent unit Poly (ethylene-2,6-naphthalenedicarboxylate) (P
EN) is preferable, and the above-mentioned polyethylene terephthalate (PET) is particularly preferable.

The polyester (polymer A) 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. Further, in addition to the acid component and the diol component, p-hydroxybenzoic acid,
Aromatic hydroxycarboxylic acids such as m-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid and p-aminophenol and p-aminobenzoic acid are further copolymerized in such a small amount that the effects of the present invention are not impaired. I can do it.

The heat-resistant thermoplastic resin (polymer B) used in the present invention is a heat-resistant thermoplastic resin other than polyester. When both the polymer A and the polymer B are polyester, a transesterification reaction occurs at the time of melt extrusion or the like, and fine projections are not formed on the surface, so that the effects of the present invention cannot be obtained.

The thermoplastic resin used as the heat-resistant thermoplastic resin (polymer B) in the present invention is not particularly limited as long as it is a heat-resistant thermoplastic resin having melt moldability and compatibility with polyester. Examples include a system resin (including polyetherimide), polysulfone, polyethersulfone, polyamideimide, polyetheretherketone, and polyarylate.

Among them, polyimide resin, polysulfone,
Thermoplastic resins selected from polyether sulfones are preferred. That is, the polyimide resin, polysulfone, and polyether sulfone have a glass transition temperature (Tg) of 150 ° C.
This is because the melting temperature is up to 350 ° C., the melt moldability is good, and the effects of the present invention such as scratch resistance and abrasion resistance are easily obtained. Glass transition temperature of polymer B is 150
If the temperature is lower than ° C, the surface is weak against abrasion or scratching, and the effect of the present invention may not be obtained. Also, 35
When the temperature exceeds 0 ° C., the melt moldability when the polymer A and the polymer alloy are used is deteriorated, or the polymer is not kneaded with the polymer A due to melting, and the surface projections become coarse.

Further, it is preferable that the polymer has good affinity with the polymers B and A of the present invention. Having good affinity here means, for example, using a polymer alloy composed of polymer A and polymer B, creating an unstretched or biaxially stretched film, and cross-section of the film with a transmission electron microscope at 30,000 to 50,000. When observed at a magnification of 10,000 times, a structure having a diameter of 200 nm or more not caused by additives such as externally added particles (for example, poorly dispersed polymer domains).
Is not observed. However, the method for determining the affinity between the polymer A and the polymer B is not particularly limited to this, and when a single glass transition point is observed by a temperature-modulated DSC (MDSC), good affinity is obtained. May be determined to exist.

The polyimide resin used as the heat-resistant thermoplastic resin (polymer B) in the present invention preferably contains, for example, a structural unit represented by the following general formula.

[0025]

Embedded image However, R1 in the formula is

[0026]

Embedded image

[0027]

Embedded image Represents one or more groups selected from aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, and R2 in the formula is

[0028]

Embedded image And one or more groups selected from aromatic hydrocarbon groups.

The preferred polyimide resin includes tetracarboxylic acid and / or an acid anhydride thereof,
Compounds obtained by dehydrating and condensing one or more compounds selected from the group consisting of aliphatic primary monoamines and / or aromatic primary monoamines, and / or aliphatic primary diamines and / or aromatic primary diamines Can be mentioned.

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-dicarboxyphenyl) 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 '-(p-phenylenedioxy) diphthalic acid, 4,4'
-(M-phenylenedioxy) diphthalic acid, 2,2'-bis [(2,3-dicarboxyphenoxy) phenyl] propane, etc. and / or acid anhydrides 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,
For example, o, m, p-phenylenediamine, tolylenediamine, xylenediamine and the like, and aromatic primary diamines having a hydrocarbon group of the aromatic primary diamine exemplified in these structural units are used.

As the above-mentioned polyimide resin, for example, polyetherimide containing an ether bond in a polyimide component, as shown by the following general formula, is particularly preferable from the viewpoint of melt moldability with polyester and handleability. preferable.

[0036]

Embedded image (Where 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; From the group consisting of alkylene groups having 2 to 20 carbon atoms, cycloalkylene groups having 2 to 20 carbon atoms, and polydiorganosiloxane groups chain-stopped with alkylene groups having 2 to 8 carbon atoms R ₃ and R ₄ are, for example, aromatic residues represented by the following formula groups:

[0037]

Embedded image Can be mentioned.

Among the above polyetherimides, from the viewpoints of compatibility with polyester (polymer A), cost, melt moldability, etc., they have a structural unit represented by the following formula:
A condensate of 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride with m-phenylenediamine or p-phenylenediamine is particularly preferred.

[0039]

Embedded image Or

[0040]

Embedded image (N is an integer of 2 or more, preferably an integer of 20 to 50) The polyether imide is "Ultem" (registered trademark).
It is available from GE Plastics under the trademark name.

The polyethersulfone used as the heat-resistant thermoplastic resin (polymer B) of the present invention has the following formula (PES1) in which an aromatic ring is bonded by one sulfonyl group and one or two ether groups. ), (PES
2) A polymer having at least one of (PES3) as a repeating unit, but other structural units may be copolymerized to some extent as long as the effects of the present invention are not impaired.
In that case, the other structural units to be copolymerized are 0.1 to 30.
mol% is preferred.

[0042]

Embedded image (N is an integer of 2 or more) The polysulfone used as the heat-resistant thermoplastic resin (polymer B) of the present invention is a polymer having a repeating unit represented by the following formula (PSF1), and includes, for example, a functional group such as an alkyl group. Other structural units may be copolymerized to some extent as long as the effects of the present invention are not impaired. In that case, the other structural units to be copolymerized are 0.1
~ 30 mol% is preferred.

[0043]

Embedded image (N is an integer of 2 or more) These heat-resistant thermoplastic resins (polymer B) may be used alone or in combination of two or more. further,
If necessary, the use of a compatibilizer is preferable because 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 added is 0.01 to 10%.
% By weight is preferred.

Among the combinations of the polymer A and the polymer B of the present invention, polyethylene terephthalate and polyetherimide, polyethylene terephthalate and polysulfone, poly (ethylene-2,6-naphthalenedicarboxylate) and polyetherimide, A combination of (ethylene-2,6-naphthalenedicarboxylate) and polysulfone, and a combination of poly (ethylene-2,6-naphthalenedicarboxylate) and polyethersulfone exhibit particularly preferable affinity. Further, among them, polyethylene terephthalate and polyetherimide are exemplified as the most preferable combination from the viewpoints of melt moldability, stability of the alloy in a molten state, and projection forming property when biaxially stretched.

The extrapolated glass transition onset temperature (Tg-onset) of the biaxially oriented polyester film of the present invention is 90 to 15
0 ° C. It is more preferably in the range of 95 to 130 ° C, and still more preferably in the range of 100 to 120 ° C. When the above-mentioned polyester and the heat-resistant thermoplastic resin are used and the extrapolated glass transition start temperature is within this range, it is considered to be caused by the fine dispersion state or the fine phase separation state of the polymer A and the polymer B on the film surface. Many very fine protrusions are formed, and it is thought that this is due to the difficulty in removing the fine protrusions or the polymer on the background, but the film surface becomes strong against scratches. In addition, the damage caused by the falling off of the particles is reduced as compared with the case where the polyester is used alone. When the extrapolated glass transition onset temperature is lower than 90 ° C., the domains of the polymer A and the polymer B when the film is stretched are both easily stretched, so that fine projections are hardly formed, and the film is used as a magnetic tape. In such a case, the dimensional stability due to heat is reduced, and it cannot be used. Also, 15
When the temperature is higher than 0 ° C., the stretchability and processing characteristics of the film are reduced.

The glass transition temperature (Tg) of the biaxially oriented polyester film of the present invention is not particularly limited, but is preferably one. Such a single glass transition temperature indicates that the polyester and the heat-resistant thermoplastic resin are compatible with each other. T when both are compatible
It is generally known that g exists between the Tg of polymer A and the Tg of polymer B. It should be noted that having a single glass transition temperature (Tg) means that ideally only one Tg is literally recognized and no other Tg or its equivalent is recognized at all,
Even if a gap similar to the heat flux other than the gap of the Tg is recognized, if the gap of the heat flux is 1/10 or less of the Tg, the gap is ignored and a single glass is used. It is regarded as having a dislocation point temperature (Tg).
Further, even if there is a shoulder of 5 mJ / mg or less near the glass transition temperature, it is regarded as having a single Tg.

The biaxially oriented polyester film of the present invention contains inert particles. Common particles are used as the inert particles, and are not particularly limited. For example,
Inorganic particles such as clay, mica, titanium oxide, calcium carbonate, kaolin, talc, wet or dry silica, colloidal silica, calcium phosphate, barium sulfate, aluminum silicate, alumina and zirconia, acrylic acids, styrene, divinylbenzene, etc. Organic particles as components, so-called internal particles, which are precipitated by a catalyst or the like added during the polyester polymerization reaction, can be used. Among them, polymer crosslinked particles, alumina particles, spherical silica particles, and aluminum silicate particles are particularly preferable. Further, when polyethylene terephthalate is used as the polymer A, crosslinked polymer particles, alumina particles, and aluminum silicate particles are particularly preferable because of excellent abrasion resistance and scratch resistance, and poly (ethylene-2,6-naphthalene diene) is used as the polymer A. When (carboxylate) is used, preferred examples thereof include crosslinked polymer particles, alumina particles, and spherical silica particles.

These particles can exert the effects of the present invention even when they contain only one kind. However, when alumina particles and polymer cross-linked particles or alumina particles and aluminum silicate particles are used in combination, In particular, it exhibits excellent abrasion resistance and scratch resistance.

The inert particles contained in the biaxially oriented polyester film of the present invention have an average particle size of 0.001 to 1.5.
μm, preferably 0.005 to 1 μm, more preferably 0.01 to 0.5 μm. When it is less than 0.001 μm, it is difficult to industrially produce such small-sized inert particles, and in addition, it does not play a role in forming film surface projections. If it exceeds 1.5 μm, it will easily fall off as a coarse projection or the electromagnetic conversion characteristics will be reduced.

The content of inert particles contained in the biaxially oriented polyester film of the present invention is 0.01 to 3% by weight, preferably 0.02 to 1% by weight, more preferably 0.05 to 0. 5% by weight. If the amount is less than 0.01% by weight, the film is not effective in running properties, abrasion resistance, scratch resistance and the like. If it exceeds 3% by weight, it is likely to aggregate to coarse projections and fall off.

The method of adding the heat-resistant thermoplastic resin (polymer B) to the polyester (polymer A) of the present invention is not particularly limited, but may be added before the polymerization of the polymer A, for example, before the esterification reaction. Alternatively, it may be added after the polymerization and before the melt extrusion. Further, the polymer A and the polymer B may be pelletized before use. In addition, at the time of pelletizing, once the polymer B1 has a high concentration (for example, 35 to 6).
(5% by weight, more preferably 40 to 60% by weight) is prepared and then further diluted with polymer A to adjust the concentration to a predetermined concentration, whereby the dispersibility between the polymers is improved. It shows a more preferable dispersion state as a polymer alloy, and is particularly preferable because the extrapolated glass transition onset temperature is easily controlled within the range of the present invention. Other methods for adjusting the polymer alloy to a more preferable dispersion state include, for example, a method of mixing using a tandem extruder, a method of finely dispersing the polymer B using two or more kinds of polyesters, and a method of mixing the polymer B with a pulverizer. Pulverized into a powder form and then mixed, a method of dissolving both in a solvent and mixing by coprecipitation, a method of dissolving one in a solvent and then mixing the other with the other, and the like. is not.

The biaxially oriented polyester film of the present invention may be a single layer or a laminated structure of at least two layers. In the case of taking a laminated structure, the film layer of the present invention may be used as a base layer portion or a laminated portion, but at least one surface layer is preferably composed of the film layer of the present invention. Among them, the film layer of the present invention is used as a base layer (the thickest layer).
A two-layer structure in which a film layer which plays a role of improving the running property and the handling property of the film on one side is thinly laminated is preferable because the electromagnetic conversion characteristics, the scratch resistance and the abrasion resistance are particularly excellent. One side of the film layer of the base layer is laminated with a film layer that plays a role of improving runnability and handling properties, and the film layer of the present invention is used to play a role of improving electromagnetic conversion characteristics and the like on the opposite surface layer. In the case of the A / B / C type three-layer laminated structure in which is laminated as a thin film, more excellent electromagnetic conversion characteristics can be obtained as compared with the two-layer laminated structure, but since three extruders are required, Production efficiency is inferior due to increased production troubles. Further, in the case of the above-mentioned laminated structure, two or more film layers satisfying the claims of the present invention may be used, or may be constituted only by the film layers of the present invention. The polymer used in the other layers of the film layer of the present invention is not particularly limited, but is preferably selected from the same polyester and heat-resistant thermoplastic resin as in the present invention. However, the content ratio of the polyester and the heat-resistant thermoplastic resin may be different. When the polymer of the film layer of the present invention is the same as the polymer of the other layer, when a laminated film is stretched, a difference in stretching stress between the film layers hardly occurs, so that cracks and peeling of the laminated portion are hardly generated.

When the film layer of the present invention is used in the laminated portion, there is no particular limitation, but the relationship between the average particle size d (nm) of the inert particles of the present invention and the laminated thickness t (nm) is 0. 2d
When ≦ t ≦ 10d, a projection with a uniform height is obtained, which is preferable.

The content of the heat-resistant thermoplastic resin (polymer B) of the present invention is not particularly limited, but is preferably 5 to 50% by weight.
Is preferably within the range. More preferably, 7 to
In the range of 40% by weight, more preferably 10 to 30%.
% By weight. Since the melt viscosities of the polyester (Polymer A) and the heat-resistant thermoplastic resin (Polymer B) are significantly different, if the content of Polymer A is less than 5% by weight, sufficient kneading is obtained by an extruder to finely disperse each other. In some cases, and the effect on the scratch resistance of the surface is small. On the other hand, if the content of the polymer B exceeds 50% by weight, it is difficult to carry out extrusion or stretching, or the domain of the polymer B due to fine dispersion or phase separation becomes too large, resulting in coarseness. Protrusions may form.

The sum of the Young's modulus in the longitudinal direction and the Young's modulus in the width direction of the biaxially oriented polyester film of the present invention is not particularly limited, but is preferably in the range of 10 to 25 GPa, more preferably 12 to 22 GPa, More preferably, it is 14 to 20 GPa. The sum of the Young's modulus is 10
If it is less than GPa, for example, when used for a magnetic recording medium or the like, the magnetic tape is likely to be stretched and deformed due to the tension received from the magnetic recording head and guide pins during traveling, and furthermore, the electromagnetic conversion characteristics (output characteristics) May adversely affect the practical use. 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 biaxially oriented polyester film of the present invention has a temperature of at least 100 ° C. in at least one of the longitudinal direction and the width direction.
The heat shrinkage at 30 minutes is not particularly limited, but from the viewpoint of elongation deformability and storage stability of the tape, is 0.01 to 0.01.
Preferably, it is 2.0%. More preferably, 0.
0.01 to 1.5%, and more preferably 0.01 to 1.5%.
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. In addition, temperature 100
If the heat shrinkage at 0.01 ° C. is less than 0.01%, the film may expand and wrinkles may occur.

The intrinsic viscosity of the biaxially oriented polyester film of the present invention is not particularly limited, but may be 0.50 to 2.0 in view of the stability of film processing and dimensional stability.
(Dl / g), more preferably 0.55 to 1.0 (dl / g).

The biaxially oriented polyester film of the present invention contains a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment, as long as the effects of the present invention are not impaired.
Organic lubricants such as dyes, fatty acid esters, and waxes may be added.

The use of the biaxially oriented polyester film of the present invention is not particularly limited, but it is preferably used for condensers, heat-sensitive transfer ribbons, heat-sensitive stencil printing paper, and the like. For a magnetic recording medium that requires Among them, for magnetic recording media, it is suitable for high-density magnetic recording tape, for example, a base film for data storage. The data recording capacity is preferably 30 GB (gigabyte) or more, more preferably 70 GB or more. , More preferably 1
00 GB or more.

The thickness of the biaxially oriented polyester film of the present invention is not particularly limited, but is preferably 1000 μm or less, and more preferably 0.5 to 500 μm. The film thickness may be appropriately determined according to the use and purpose, but is usually 1 to 15 μm for magnetic recording materials, 2 to 10 μm for data or digital video coating type magnetic recording media, and for data or digital video. For a vapor deposition type magnetic recording medium, the range is preferably 3 to 9 μm. Further, for capacitors, preferably 0.5 to 15 μm
Is applied, and the dielectric breakdown voltage and the dielectric characteristics are excellent in stability. A film having a thickness of 1 to 6 μm is preferably used for the thermal transfer ribbon, and high-definition printing can be performed without wrinkles at the time of printing, without causing uneven printing or overtransfer of ink. For use in heat-sensitive stencil paper, a film of 0.5 to 5 μm is preferably applied, and it has excellent low-energy perforation properties, and can change the perforation diameter according to the energy level. It also has excellent printability when performing color printing.

The biaxially oriented polyester film of the present invention is coated with a water-soluble film on the film surface for the purpose of imparting easy adhesion to the magnetic layer or inks or forming a discontinuous film having fine surface projections. You may coat | cover a hydrophilic polyester etc.

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

The magnetic layer is not particularly limited, but preferred examples thereof include a magnetic layer in which a ferromagnetic metal thin film or a ferromagnetic metal fine powder is dispersed in a binder, and a magnetic layer formed by coating a metal oxide. . As the ferromagnetic metal thin film,
Iron, cobalt, nickel and alloys thereof are preferred. The ferromagnetic metal fine powder used for the magnetic layer in which the ferromagnetic metal fine powder is dispersed in a binder is preferably a ferromagnetic hexagonal ferrite fine powder, iron, cobalt, nickel or an alloy thereof. 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 this protective film can further improve running durability and corrosion resistance. 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 to the lubricant applied on the hard carbon protective film, the surface of the hard carbon protective film may be surface-treated by 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 polyester film of the present invention is characterized in that, in the method for 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 film is formed. Is a method in which a molten polymer mixture of a polyester (polymer A) and a heat-resistant thermoplastic resin (polymer B) is discharged from a die by melt extrusion, and the molten polymer is cooled and solidified to form a sheet. At this time, although not particularly limited, it is preferable to use a vented twin-screw extruder as the extruder because the extrapolated glass transition temperature of the present invention can be easily controlled. The discharge time from the extruder to the die is preferably 30 seconds or more. If it is less than this, the dispersibility of the polymer A and the polymer B becomes poor, and the film properties may be reduced.

More specifically, although not particularly limited, the sheet-like molded product is stretched at a ratio of 1 to 10 times in the longitudinal direction and 1 to 10 times in the width direction, and then at 150 ° C.
It is preferable to heat-treat at a temperature of ~ 250 ° C.

More preferable 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. When the heat-resistant thermoplastic resin (polymer B) is added to the polyester (polymer A),
Although not particularly limited, before polymerization of the polyester, for example,
It may be added before the esterification reaction or after the polymerization and before the melt extrusion. Among them, it is preferable from the viewpoint of melt moldability that the polyester and the heat-resistant thermoplastic resin are pelletized before melt extrusion to obtain a master chip.

The biaxially oriented polyester film of the present invention may be stretched in the following manner. For example, the biaxially oriented polyester film may be stretched in the longitudinal direction and then stretched in the width direction. A simultaneous biaxial stretching method in which a longitudinal direction and a width direction are simultaneously stretched using a tenter or the like, and a method in which a sequential biaxial stretching method and a simultaneous biaxial stretching method are combined are included.

An example of the method for producing the biaxially oriented polyester film of the present invention will be described, but the present invention is not limited to this. Here, an example of a single-layer film using polyethylene terephthalate as the polyester (polymer A) and polyetherimide “Ultem” as the heat-resistant thermoplastic resin (polymer B) is shown. Manufacturing conditions differ depending on the plastic resin. In the case of a laminated film, the details of the manufacturing conditions are different.

First, according to a conventional method, bis-β-hydroxyethyl terephthalate (BH) is esterified from terephthalic acid and ethylene glycol, or transesterified between dimethyl terephthalate and ethylene glycol.
T). Next, while transferring this BHT to the polymerization tank,
Heat to 280 ° C. under vacuum to advance the polymerization reaction. 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 precrystallizing at a temperature of 180 ° C. or less,
The solid phase polymerization is carried out for 10 to 50 hours under a reduced pressure of about mHg.
As a method for incorporating particles into the polyester constituting the film, a method in which particles are dispersed in a predetermined ratio in ethylene glycol in a slurry form, and this ethylene glycol is polymerized with terephthalic acid is preferable. When the particles are added, for example, a water sol or an alcohol sol obtained at the time of synthesis of the particles is added without drying before 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 the number of particles, a master of high-concentration particles is prepared by the above method,
It is effective to adjust the content of the particles by diluting it with a polyester or a heat-resistant thermoplastic resin substantially free of particles or a mixture thereof during film formation.

Next, the polyethylene terephthalate pellets and the polyetherimide pellets are 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 from 50 to 300 sec-1, more preferably from 100 to 200 sec-1, and the residence time is preferably from 0.5 to 10 minutes, more preferably from 1 to 5 minutes. Further, when the chips are not compatible under the above kneading conditions, the obtained chips may be again introduced into a twin screw extruder and kneading and extrusion may be repeated until the chips are compatible.

The obtained pellets of the inert particles and the polyester containing polyetherimide are vacuum-dried at 180 ° C. for 3 hours or more, and then 280-320 ° C. under a nitrogen stream or vacuum so that the intrinsic viscosity does not decrease. Is supplied to an extruder heated to a predetermined temperature, and a film is formed by a conventional method. In addition, 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, a wire mesh, or the like in order to remove foreign substances and a deteriorated polymer. Further, if necessary, a gear pump may be provided in order to improve the quantitative supply property. Using an extruder, a sheet of a mixture of polyester and polyetherimide in a molten state 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 differs depending on the constitution of the polyester and the heat-resistant thermoplastic resin, and greatly differs in the case of the laminated constitution. For example, the case of a mixed polymer of polyethylene terephthalate and polyetherimide will be described. Unstretched film at 70-150 ° C
And stretched in one or two or more stages in the longitudinal direction by 1 to 10 times and cooled by a cooling roll group at 20 to 50 ° C. The longitudinal stretching speed is 1000 to 5
It is preferable to perform the reaction at a rate of 0000% / min, but there is no particular limitation. 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, and the stretching speed is 1000 to 20,000.
% / Min, and the temperature is preferably in the range of 80 to 150 ° C., but is not particularly limited. Further, if necessary, re-longitudinal stretching and / or re-lateral stretching are performed. As stretching conditions in that case, the stretching in the longitudinal direction is preferably performed at a temperature of 80 to 180 ° C., the stretching ratio is 1.1 to 2.0 times, and the stretching method in the width direction is preferably a method using a tenter. ,
The stretching is preferably performed at a magnification of 1.1 to 2.0 times, but is not particularly limited. The total stretching ratio is 1 to 1 in the longitudinal direction.
It is preferably 10 times 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 even more preferably, it is 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 23 ° C.
It is preferably performed at 0 ° C., more preferably at 180 to 220 ° C. for a time in the range of 0.2 to 30 seconds, but is not particularly limited.

[Methods for Measuring Physical Properties and Methods for Evaluating Effects] (1) Extrapolated Glass Transition Onset Temperature (Tg-onset), Glass Transition Temperature (Tg) A film sample was measured for specific heat using the following apparatus and conditions, and measured according to JIS K7121. Determined according to

Apparatus: Temperature-modulated DSC manufactured by TA Instrument 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 Temperature rise Step: 5K Sample weight: 5 mg Sample container: Open aluminum container (22 mg) Reference container: Aluminum open container (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 In the above measurement, two or more glass transition temperatures (or extrapolated glass transition start temperatures) were observed. In this case, the lowest glass transition temperature (or extrapolated glass transition onset temperature) is employed.

(2) Average Particle Diameter The cross section of the film obtained by incorporating the particles is observed at a magnification of 10,000 times or more using a transmission electron microscope (TEM). The thickness of the section of the TEM is about 100 nm, and measurement is performed in 100 or more visual fields 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 particles A value obtained by a method in which a solvent in which a polymer is dissolved and a particle is not dissolved is selected, the particles are centrifuged from the polymer, and the ratio of the particles to the total weight (% by weight) is obtained. Is the particle content.

(4) Content of Polyester (Polymer A) and Heat-Resistant Thermoplastic Resin (Polymer B) In a suitable solvent (for example, HFIP / deuterated chloroform) that dissolves both Polymer A and Polymer B, 1H
The nuclear NMR spectrum is measured. In the obtained spectrum, the absorption specific to polymer A and polymer B (for example, P
The peak area intensity of an aromatic proton of terephthalic acid for ET and an aromatic proton of bisphenol A for PEI) are determined, and the molar ratio of the blend 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 the polymer. The measurement conditions are, for example, the following conditions, but are not limited because they differ depending on the types of the polymer A and the polymer B.

Apparatus: BRUKER DRX-500 (Bruker) Solvent: HFIP / chloroform Observation frequency: 499.8 MHz Reference: TMS (0 ppm) Measurement temperature: 30 ° C. Observation width: 10 KHz Data point: 64 K acquisiton time: 4.952 Second pulse delay time: 3.048 seconds Number of integration: 256 times If necessary, composition analysis may be performed by a micro FT-IR method (Fourier transform micro infrared spectroscopy). In that case, it is determined from the ratio of the peak caused by the carbonyl group of the polyester (polymer A) to the peak caused by a substance other than the polyester. In order to convert the peak height ratio into a weight ratio, a calibration curve is prepared from a sample whose weight ratio is known in advance, and the ratio of the polyester (polymer A) to the total amount of the polyester (polymer A) and other substances is determined. . From this and the particle content, the ratio of the heat-resistant thermoplastic resin (polymer B) is determined. Further, if necessary, an X-ray microanalyzer may be used in combination.

(5) Film Lamination Thickness Using a transmission electron microscope (H-600 manufactured by Hitachi) at an accelerating voltage of 100 kV, the cross section of the film was subjected to an ultra-thin section method (R).
(UO4 staining), the interface is captured, and the lamination thickness is determined. The magnification is usually selected according to the thickness of the laminate to be determined, and is not particularly limited, but 10,000 to 100,000 times is appropriate.

If the interface cannot be detected by the above-mentioned microscopic observation, the secondary ion mass spectrometer (SIMS) is used to determine the highest concentration of particles in the film in the range from the surface layer to a depth of 3000 nm. Element or PE
The concentration ratio (M + / C +) of the element resulting from I and the carbon element of the polyester is defined as the particle concentration, and the depth is 3000 n from the surface.
The analysis in the thickness direction is performed up to m. In the surface layer, the particle (or element due to PEI) concentration is low due to the interface of the surface, and the particle (or element due to PEI) concentration increases as the distance from the surface increases. In the case of the film of the present invention, the concentration of the particle (or the element derived from PEI), which has once reached the maximum value, starts to decrease again. Based on this concentration distribution curve, the depth at which the concentration of the surface particles (or the element due to PEI) is の of the maximum value (this depth is deeper than the depth at which the maximum value is obtained) is obtained, and this is laminated. Thickness. The conditions are as follows.

1) Measuring apparatus Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany 2) Measurement conditions Primary ion species: O2 + 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 The particles contained most in the range from the surface layer to the depth of 3000 nm are organic polymers. In the case of particles, measurement by SIMS is difficult. Therefore, while etching from the surface, a depth profile similar to the above is measured by XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy) or the like, and the layer thickness is obtained.

(6) Young's modulus According to the method specified in JIS-Z-1702, at 25 ° C. using a strong tensile tester.
It was measured at 65% RH.

(7) Heat Shrinkage 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 100 ° C. The heat shrinkage was determined by the following formula. Heat shrinkage (%) = [(L0−L) / L0] × 100 L0: Mark line interval before heat treatment L: Mark line interval after heat treatment

(8) Intrinsic Viscosity The value calculated from the following formula from the solution viscosity measured at 25 ° C. in orthochlorophenol is used.

Ηsp / C = [η] + K [η] ² · C, where ηsp = (solution viscosity / solvent viscosity) −1, and 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 are measured using an Ostwald viscometer.

(8) Surface Roughness Ra The center line average roughness Ra was measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was an average value obtained by scanning 20 times in the film width direction and performing measurement.・ Stylus tip radius: 0.5m ・ Stylus load: 5mg ・ Measuring length: 1mm ・ Cutoff value: 0.08mm

(9) Electromagnetic conversion characteristics of magnetic tape (S /
N) A 200-nm-thick vapor-deposited layer of a cobalt-nickel alloy (Ni 20% by weight) was provided on the film of the present invention using a continuous vacuum vapor deposition device 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 this pancake was incorporated into a cassette to form a cassette tape.

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 measured at 0 dB (d) using a video noise meter.
Comparatively measured as B). The running conditions were 25 ° C, 6
0% RH.

If the electromagnetic conversion characteristic is 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: ◎ +1 dB or more, less than +3 dB: 未 満 less than +1 dB: × ：: excellent quality for high-density magnetic recording medium use, ：: usable for high-density magnetic recording medium use, ×: high This is an insufficient level for use in a density magnetic recording medium.

(10) Travelability with Magnetic Head Under an atmosphere of 20 ° C. and a relative humidity of 60%, a 1/2 inch wide guide pin (material: SUS, surface roughness Ra: 40 nm) was mounted on a guide pin having an outer diameter of 6 mmφ. Wind a tape-like film at an angle of 90 ° (entrance side tension: 50 g, running speed: 3.3 cm)
/ Sec, number of runs: 1) and the coefficient of friction μk was measured.

A film obtained by slitting a film into a tape having a width of 1/2 inch was measured at 25 ° C. and 6 ° C. using a tape running tester TBT-300 type (manufactured by Yokohama System Laboratory Co., Ltd.).
After running in a 5% RH atmosphere, the initial coefficient of friction was determined by the following equation (the film width was イ ン チ inch). In the case where the film had a laminated structure, the surface on the film layer side of the present invention was used as a measurement surface. μK = (2 / π) ln (T2 / T1) where T1 is the entrance tension and T2 is the exit tension. The μK value obtained by this measurement is a value that affects the runnability of the magnetic head when the film is used as a magnetic recording medium having a vapor-deposited magnetic layer. Become. The running property with the magnetic head is closely related to the damage of the film during running of the magnetic head.

(11) Abrasion resistance (scratch resistance during film running) Under an atmosphere of 50 ° C. and a relative humidity of 60%, a guide pin having an outer diameter of 6 mmφ (material: SUS, surface roughness: 0.2S) was used. ,
A 1/2 inch wide tape-like film was wound at a winding angle of 60 °, and repeatedly run (3 minutes × 5 times) under the conditions of an entrance tension of 35 g and a running speed of 100 m / min. After running, the shaved powder adhering to the surface of the guide pin was visually observed, and the scratches in the film were observed with a microscope, and the number of scratches having a width of 2 μm or more per tape width was examined. The measurement surface was evaluated on the same surface as the surface on which the traveling property was evaluated in the above (10).

No scratches or no scratches and no pin-adhered powder: ◎ 2 or more scratches and less than 5 scratches, and slight pin-adhered powders: ○ 5 or more scratches or pin A large amount of adhered powder: × ◎: Excellent quality for high-density magnetic recording media, ○: Usable for high-density magnetic recording media, ×: Insufficient level for high-density magnetic recording media It is.

(12) Scratch resistance of the film surface (scratch resistance in the film forming process) After two measurement surfaces (100 cm 2) of the film were superimposed and brought into close contact with each other by electrostatic force (applied voltage of 5.4 kv),
The number of coarse projections in which the Newton's ring generated by interference of light of the coarse projections between the two films was a single ring or more was measured. The light source used was a halogen lamp with a 564 nm band-pass filter. The shape of the coarse projection was observed using an optical microscope (x100), and the number of those having a flaw-like shape was counted and evaluated according to the following criteria.

Number of scratches 5/100 cm ² : ◎ Number of scratches 5/100 cm ² or more, less than 50/100 cm ² : ○ Number of scratches 50/100 cm ² or more: × ◎: High density magnetic recording medium Excellent quality for use, ：: usable for high-density magnetic recording media, ×: insufficient level for high-density magnetic recording media.

(13) Suitability for high-density magnetic recording medium Among the above-mentioned abrasion resistance, scratch resistance and electromagnetic conversion characteristics, ◎
When there are two or more but no ×, ◎, when ◎ is one or less, ×
A sample without any mark was marked with “O”, and a sample with at least one mark was marked with “x”.

A: Excellent quality for high-density magnetic recording medium use O: Usable for high-density magnetic recording medium use C: Insufficient level for high-density magnetic recording medium use

[0107]

Embodiments of the present invention will be described based on the following embodiments.

In the following, polyethylene terephthalate is PET, poly (ethylene-2,6-naphthalenedicarboxylate) is PEN, and polyetherimide is PE
I, PES for polyethersulfone, P for polysulfone
SF and polypropylene are abbreviated as PP. Where PE
As I, General Electric (G
E) "Ultem" 1010 with an intrinsic viscosity of 0.68
As PES, polyethersulfone having the above formula (PES1) as a repeating unit was used, and as PSF, polysulfone having the above formula (PSF1) as a repeating unit was used. In the case of a laminated structure of at least two layers, the respective film layers are denoted by reference numerals of A layer, B layer, and C layer. Among them, at least the layer A is a film layer corresponding to the present invention. In the layer thickness, the thickest layer is the above-described base layer portion, and the other layers are the laminated portions.

Example 1 PET pellets having an intrinsic viscosity of 0.85 (50% by weight) obtained by an ordinary method and General Elect
ric (GE) "Ultem" with an intrinsic viscosity of 0.68
1010 (hereinafter abbreviated as PEI) (50% by weight)
The mixture was supplied to a vented twin-screw kneading extruder of the same direction rotating at 0 ° C. to prepare a blended chip containing 50% by weight of “Ultem”.

Then, using two extruders, extruder A heated to 280 ° C. contained 20 parts by weight of the blended chips obtained by the above pelletizing operation and 2% by weight of alumina particles having an average particle size of 0.04 μm. 10 parts by weight of a PET chip to be mixed, 8 parts by weight of a PET chip containing 1% by weight of polymer crosslinked particles (crosslinked divinylbenzene particles) having an average particle diameter of 0.3 μm, and 62 parts by weight of a PET chip substantially containing no particles Supplied after vacuum drying for 3 hours at 280 ° C.
In the extruder B heated to a temperature of 2.5 mm, PET chips containing 20 parts by weight of the blended chips obtained by the above pelletizing operation and 2% by weight of spherical silica particles having an average particle diameter of 0.8 μm were used.
30 parts by weight of a PET chip containing 2 parts by weight of spherical silica particles having an average particle diameter of 0.3 μm and 47.5 parts by weight of a PET chip containing substantially no particles are vacuum-dried at 180 ° C. for 3 hours and then supplied. did. Thereafter, they were merged in a T-die (lamination ratio: 12/1), and were tightly cooled and solidified while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. to prepare a laminated unstretched film.

The unstretched film was stretched 3.2 times in the longitudinal direction at a temperature of 97 ° C. by a roll stretching machine, and then stretched 4.5 times in a width direction at a temperature of 103 ° C. using a tenter.
Further, it is re-stretched 1.6 times in the longitudinal direction at a temperature of 155 ° C. in a longitudinal direction by a roll-type stretching machine, and is re-transversally stretched 1.1 times in a width direction at a temperature of 195 ° C. using a tenter. Temperature 21
After a heat treatment at 0 ° C. for 10 seconds, a relaxation treatment of 2% was performed in the width direction to obtain a laminated biaxially oriented polyester film having a thickness of 6.5 μm.

The resulting biaxially oriented polyester film has a Young's modulus of 6.5 GPa in the longitudinal direction and 4.8 G in the width direction.
Pa, heat shrinkage 1.5% in longitudinal direction, 0.5 in width direction
%Met.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic characteristics, abrasion resistance, and scratch resistance.

Example 2 As shown in Table 1, the PEI content, particle type, particle size,
The particle content, the stretching ratio, and the like were changed, and a single layer was formed using one extruder. In the same manner as in Example 1, a biaxially oriented polyester film was obtained.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic characteristics, abrasion resistance, and scratch resistance.

Example 3 As shown in Table 1, PEI content, particle type, particle size,
The particle content, the stretching ratio, and the like were changed, and three extruders were used to form a three-layer laminate. In the same manner as in Example 1, a biaxially oriented polyester film was obtained.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic characteristics, abrasion resistance, and scratch resistance.

Example 4 As shown in Table 1, PEI content, particle type, particle size,
After changing the particle content and the like, and obtaining an unstretched film (three layers of A / B / C type) in the same manner as in Example 1, both ends of the unstretched film are gripped with clips, and linearly stretched. The film is guided to a simultaneous biaxial stretching tenter of a motor type, heated to a temperature of 103 ° C., and simultaneously biaxially stretched at an area stretching ratio of 12.25 times (longitudinal ratio: 3.5 times, horizontal ratio: 3.5 times). . Subsequently, the film temperature was set to 165 ° C., and the area stretching ratio was 2.56 times (longitudinal ratio: 1.6 times, horizontal ratio: 1.6 times).
Times) and re-stretching in two axes at the same time.
After a heat treatment for 1.5 seconds, a 1.5% relaxation treatment is performed in each of the vertical and horizontal directions to obtain a biaxially oriented polyester film having a thickness of 6.7 μm.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic characteristics, abrasion resistance, and scratch resistance.

Example 5 As shown in Table 1, 10% by weight of PSF and P
90% by weight of ET blend polymer (average particle size 0.03
0.03% by weight of the polymer crosslinked particles having a mean particle size of 0.03 wt.
A / B type two-layer oriented polyester film was obtained in the same manner as in Example 1 except that the polymer of the layer B was changed to PET.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic characteristics, abrasion resistance, and scratch resistance.

Example 6 As shown in Table 1, the polymer of the layer A was composed of 15% by weight of PES and P
EN 85% by weight of blend polymer (average particle size 0.2μ
m) and the B-layer polymer was changed to a blended polymer of PES and PEN, and an A / B type two-layer oriented polyester film was obtained in the same manner as in Example 1. In addition, the vertical and horizontal re-stretching was not performed.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic conversion characteristics, abrasion resistance, and scratch resistance.

Example 7 As shown in Table 1, 10% by weight of PEI and P
A blend polymer of 5% by weight of ES and 85% by weight of PEN (0.1% by weight of spherical silica particles having an average particle size of 0.25 μm and 0.5% by weight of alumina particles having an average particle size of 0.02 μm)
A / B type two-layer oriented polyester film was obtained in the same manner as in Example 1 except that the polymer of the B layer was changed to PEN. In addition, the vertical and horizontal re-stretching was not performed.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic conversion characteristics, abrasion resistance, and scratch resistance.

Example 8 As shown in Table 1, the polymer of the layer A was composed of 60% by weight of PEN and P
Blend polymer with EI 40% by weight (average particle size 0.2
μm spherical silica particles containing 0.2% by weight), and changing the polymer of the layer B to PEN.
An A / B type two-layer oriented polyester film was obtained. In addition,
Re-longitudinal and transverse stretching were not performed.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic characteristics, abrasion resistance, and scratch resistance.

Examples 9 to 11 As shown in Table 1, the A / B type two-layer oriented polyester film was obtained in the same manner as in Example 1 except that the particle type, particle size and content of the A layer were changed.

As shown in Table 2, the biaxially oriented polyester film had excellent characteristics as a base film for a magnetic recording medium, such as electromagnetic conversion characteristics, abrasion resistance, and scratch resistance.

COMPARATIVE EXAMPLE 1 Except that the polymer type of the A and B layers was only PET,
A laminated unstretched film was prepared in the same manner as in Example 1.
Then, in the same manner as in Example 1, a biaxially oriented polyester film having a thickness of 6.5 μm was obtained by a sequential biaxial stretching method.

As shown in Table 2, the properties of the biaxially oriented polyester film were inferior to films for magnetic recording media.

Comparative Example 2 The polymer type of the layer A was changed to PEN only, and the particle size, the particle type and the content of the inert particles were changed.
A biaxially oriented polyester film was obtained in the same manner as in Comparative Example 1 by an axial stretching method.

As shown in Table 2, the properties of this biaxially oriented polyester film were inferior to films for magnetic recording media.

Comparative Examples 3, 4, 5 As shown in Table 1, the content of PEI in the layer A, the particle size, the particle type and the content of the inactive particles, the polymer type and the lamination structure of the layers B and C were changed. Then, in the same manner as in Example 1, a biaxially oriented polyester film was obtained.

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 6 In the same manner as in Example 1, a biaxially oriented polyester film was obtained without containing particles as shown in Table 1.

As shown in Table 2, the properties of this biaxially oriented polyester film were inferior to films for magnetic recording media.

Comparative Example 7 The polymer in the layer A was a blend polymer of PET and PP (containing 0.4% by weight of alumina particles having an average particle size of 0.04), and the polymer in the layer B was PET. A biaxially oriented polyester film was obtained in the same manner as in Example 1 without stretching.

As shown in Table 2, the properties of the biaxially oriented polyester film were inferior to films for magnetic recording media.

Comparative Examples 8 and 9 In the same manner as in Example 1, as shown in Table 1, the particle type, the average particle diameter and the content of the inactive particles in the A layer were changed.
/ B type two-layer oriented polyester film was obtained.

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

[0142]

[Table 1]

[0143]

[Table 2]

[0144]

According to the present invention, biaxial orientation using a polymer alloy of polyester and a specific heat-resistant thermoplastic resin, with the average particle diameter and content of the particles contained therein and the glass transition onset temperature of the film within specific ranges. The polyester film is a base film which is excellent in running property and scratch resistance, and has extremely high industrial value.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08K 3/22 C08K 3/22 3/34 3/34 C08L 79/08 C08L 79/08 B 81/06 81 / 06 101/00 101/00 G11B 5/733 G11B 5/733 // B29K 67:00 B29K 67:00 105: 06 105: 06 B29L 9:00 B29L 9:00

Claims (8)

[Claims] A polyester (polymer A) and a heat-resistant thermoplastic resin (polymer B) other than polyester (polymer B) are used as resin components. A biaxially oriented polyester film containing 10% by weight and having an extrapolated glass transition onset temperature (Tg-onset) of 90 to 150 ° C. 2. The heat-resistant thermoplastic resin (polymer B)
Is a thermoplastic resin selected from the group consisting of a polyimide resin, polysulfone, and polyether sulfone. 3. The polyester according to claim 1, wherein the polyester (Polymer A) is polyethylene terephthalate having ethylene terephthalate as a main constituent unit.
Axial oriented polyester film. 4. The heat-resistant thermoplastic resin (polymer B)
The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the main component is polyetherimide. 5. The heat-resistant thermoplastic resin (polymer B)
Is contained in the film layer in an amount of 5 to 50% by weight.
The biaxially oriented polyester film according to any one of the above. 6. The biaxially oriented polyester according to claim 1, wherein the inert particles are at least one selected from polymer crosslinked particles, alumina particles, spherical silica particles, and aluminum silicate particles. the film. 7. A film comprising a film layer according to claim 1 as a base layer and at least one other layered layer.
Axis oriented laminated polyester film. 8. A magnetic recording medium comprising the biaxially oriented polyester film according to claim 1.