JP2002008221A - Polyester film for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for magnetic recording medium, particularly a ferromagnetic metallic thin film type magnetic tape which has both of both flatness and blocking and scraping resistances when the hardness and surface roughness of a coating layer under a ferromagnetic thin film are optimized, nearly free of dropout and excellent in running durability. SOLUTION: The polyester film for a magnetic recording medium is obtained by disposing a coating layer A on one side of a polyester film. The coating layer A consists essentially of (1) 30-88 wt.0/o acrylic-polyester resin, (2) 1-30 wt.% epoxy compound having two or more epoxy groups, (3) 1-20 Wt.% inert particles having 5-50 nm average particle diameter and (4) 10-50 wt.% surfactant. The molar ratio of the polyester component to the acrylic resin component in the acrylic-polyester resin is (1:9) to (5:5) and the amount of an epoxy- containing acrylic compound in the acrylic resin component is 3-30 mol%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a magnetic recording medium, and more particularly to a recording medium for recording digital data for digital video cassette tapes, data storage, etc., in which the magnetic layer is not scraped and has excellent dropout characteristics. The present invention relates to a polyester film useful as a base film of a ferromagnetic metal thin film type magnetic recording medium.

[0002]

2. Description of the Related Art Consumer digital video tapes put into practical use in 1995 have a metal magnetic thin film of Co provided on a base film by vacuum evaporation, and a diamond-like carbon film coated on the surface thereof. (Evaporation) Despite the flattened surface compared to tape,
Has good durability. The base film includes a polyester film, a polymer blend containing a water-soluble polyester copolymer adhered to at least one surface of the film, and a discontinuous film mainly composed of fine particles having a particle size of 5 to 50 nm. A polyester film having fine projections formed by the fine particles on the surface of a discontinuous film (for example, JP-B-63-57238) is used. This base film is a film having a smaller metal magnetic film-forming surface roughness than the Hi8ME base.

[0003]

However, in recent years,
In order to increase the recording capacity, it is necessary to flatten the tape more than ever. For this purpose, it is necessary to make the base film flatter.However, in the case of a conventional base film, blocking occurs when the film is wound, or the coating layer is shaved, and the shaved material adheres to the film and the magnetic recording medium There was a problem that could cause dropouts. An object of the present invention is to solve this problem and to provide a polyester film for a magnetic recording medium, which has both flatness, blocking resistance and abrasion resistance.

[0004]

The present invention has the following arrangement to attain the object. A film in which a film layer A is laminated on one side of a polyester film, wherein the film layer A has (1) an acrylic-polyester resin of 30% by weight to 88% by weight, and (2) two or more epoxy groups. 1 to 30% by weight of epoxy compound
In the following, the acryl is mainly composed of a component consisting of (3) 1% by weight to 20% by weight of inert particles having an average particle diameter of 5 nm to 50 nm and (4) 10% by weight to 50% by weight of a surfactant. The molar ratio of polyester component / acrylic resin component of the polyester resin is 1/9 or more and 5/5 or less, and the epoxy group-containing acrylic compound component in the acrylic resin component is 3 mol% with respect to the acrylic resin component;
A polyester film for a magnetic recording medium, wherein the content is at least 30 mol%.

In a preferred embodiment of the present invention, the surface roughness Ra of the coating layer A is 0.1 nm or more and 3 nm or less, and the surface (B
Surface roughness Ra of the surface is 2 nm or more and 10 nm or less, the polyester film is a film made of polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate, and the thickness of the film is less than 7 μm and 2 μm or more. That the surface of the coating layer A is the surface on which the ferromagnetic metal thin film layer of the magnetic layer is formed, and that the polyester film is used for a digital recording type magnetic tape. The present invention further includes a magnetic recording medium using the polyester film for a magnetic recording medium.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION <Polyester> The polyester constituting the film in the present invention may be any polyester which forms a high-strength film by molecular orientation. Among them, polyethylene terephthalate and polyethylene-2,6-naphthalenediene are preferred. Carboxylates are preferred. These include not only homopolymers, but also those in which 80% or more of their constituents are ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate. Ethylene terephthalate, ethylene-2,6
-As the polyester copolymer component other than naphthalenedicarboxylate, for example, diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylene glycol, 1,4-
Diol components such as cyclohexane dimethanol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, dicarboxylic acid components such as 5-sodium sulfoisophthalic acid,
Examples thereof include a trifunctional or higher functional polycarboxylic acid component such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid. The above polyester may be further mixed with at least one of an alkali metal salt derivative of sulfonic acid which is non-reactive with the polyester component and a polyalkylene glycol which is substantially insoluble in the polyester within a range not exceeding 5% by weight. Good. In any case, the content of the ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate component is preferably at least 80 mol%,
Further, it is preferably at least 90 mol%, particularly preferably at least 95 mol%.

<Inert Particles> In the present invention, the polyester constituting the film contains no inert particles,
Alternatively, even if it is contained, it is preferably contained in an amount of 0.5% by weight or less, more preferably 0.2% by weight. Examples of the inert particles include inert inorganic particles typified by calcium carbonate, aluminum oxide, silicon oxide, and titanium oxide, and fine particles of a heat-resistant polymer typified by a crosslinked silicone resin, a crosslinked polystyrene resin, and a crosslinked acrylic resin. Is mentioned. If the content exceeds 0.5% by weight, the electromagnetic conversion characteristics of the tape will deteriorate. In addition, when containing inert particles, the average particle size is 0.0
5 to 1.0 μm, preferably 0.2 to 0.5
μm is more preferred. When the average particle size exceeds 1.0 μm, the electromagnetic conversion characteristics deteriorate. On the other hand, when the average particle size is less than 0.05 μm, the particles tend to aggregate, which is not preferable.

The polyester film in the present invention may be a single-layer film or a multilayer film having two or more layers by coextrusion or the like. In the case of a multilayer film, the polyester forming the surface layer on the magnetic layer forming surface side does not substantially contain inert particles, or even if it does, does not exceed 0.1% by weight, and even 0.05%.
It is preferable that the amount does not exceed the weight%. The layer forming the opposite surface (nonmagnetic layer surface) has a thickness of 0.05 to 0.5.
It is preferred that it contains inert particles by weight, more preferably 0.1-0.3% by weight.

<Coating Layer A> In the present invention, the coating layer A laminated on one side of the polyester film comprises: (1) 30% by weight or more and 88% by weight or less of an acryl-polyester resin; and (2) two or more epoxy groups. (3) an average particle size of 5 n
a component consisting of 1% by weight to 20% by weight of inert particles having a particle size of m to 50 nm and (4) 10% to 50% by weight of a surfactant; The layer in which the molar ratio of the components is 1/9 or more and 5/5 or less, and the epoxy group-containing acrylic compound component in the acrylic resin component is 3 mol% or more and 30 mol% or less with respect to the acrylic resin component.

The proportion of the acrylic-polyester resin (1) in the coating layer A is 30% by weight to 88% by weight, preferably 40% by weight to 75% by weight. When the proportion is less than 30% by weight, the adhesion to the polyester film is reduced, and the coating layer is easily shaved. On the other hand, when the proportion exceeds 88% by weight, the component (2)
(3) The ratio of (4) decreases, and the tape properties and film layer A
Hinders the coatability of The polyester component in the component (1) ensures the adhesion between the coating layer and the polyester film, and the acrylic resin component ensures the abrasion resistance of the coating and the effect of suppressing oligomers in the base film.

The above-mentioned acryl-polyester resin is used to mean an acrylic-modified polyester resin or a polyester-modified acrylic resin. An acrylic resin component and a polyester resin component are bonded to each other. , Block types. Such an acrylic-polyester resin, for example, adds a radical initiator to both ends of the polyester to polymerize the acrylic monomer, or adds a radical initiator to the side chain of the polyester to polymerize the acrylic monomer. Alternatively, it can be produced by attaching a hydroxyl group to the side chain of the acrylic resin and reacting it with a polyester having an isocyanate group or a carboxyl group at the terminal.

The molar ratio of the polyester component / acrylic resin component of the acrylic-polyester resin is from 1/9 to 5
/ 5 or less, preferably 2/8 or more and 4/6 or less. If this ratio is less than 1/9, the adhesion of the coating layer A to the polyester film is insufficient, while if it exceeds 5/5, the abrasion resistance of the coating layer A and the effect of suppressing oligomers of the base film are inferior.

The polyester component constituting the acrylic-polyester resin comprises a polybasic acid component and a polyol component. Examples of the polybasic acid component include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2, 6
-Naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid, 5-sodium sulfoisophthalic acid and the like are preferred. These acid components are usually composed of two or more kinds, and may contain a small amount of an unsaturated polybasic acid component such as maleic acid, itaconic acid or the like and a hydroxycarboxylic acid component such as p-hydroxybenzoic acid. Further, as the polyol component, for example,
Ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) Glycol is preferred. These polyol components can be two or more kinds.

The above-mentioned polyester component can be produced by reacting the above-mentioned polybasic acid or its ester-forming derivative with the above-mentioned polyol or its ester-forming derivative by a conventional method.

The acrylic resin component constituting the acrylic-polyester resin must contain the epoxy group-containing acrylic compound component in an amount of 3 mol% to 30 mol%, preferably 7 mol%, based on the acrylic resin component. % Or more and 25 mol% or less. If this ratio is less than 3 mol%, the crosslinking density of the resin decreases, the shaving property deteriorates, blocking occurs when the film is wound, the film is cut when unwinding, and the surface is delaminated. As a result, the deposited layer formed thereon is roughened, resulting in deterioration of the electromagnetic conversion characteristics when used as a magnetic recording medium. On the other hand, if it exceeds 30 mol%, the background resin portion between the filler protrusions of the coating layer A becomes coarse, and the electromagnetic conversion characteristics deteriorate when used as a magnetic recording medium.

Preferred examples of the epoxy group-containing acrylic compound include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. Other components of the acrylic resin are not particularly limited, but preferably include alkyl methacrylate and alkyl acrylate. Examples of the alkyl group of the alkyl methacrylate and the alkyl acrylate include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group,
Examples include an ethylhexyl group and a cyclohexyl group.

In the present invention, the epoxy compound having two or more epoxy groups of the component (2) constituting the coating layer A is represented by the following chemical formula:

[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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And bisphenol A
And a water-soluble or water-dispersible epoxy compound of an addition condensate of the compound and epichlorohydrin.

The content of the epoxy compound (2) is from 1% by weight to 30% by weight, preferably from 2% by weight to 25% by weight.
% By weight or less. 1% by weight of epoxy compound
If the value is less than the above range, blocking tends to occur when the film is wound, and in that case, the film cannot be unwound smoothly.
On the other hand, if it exceeds 30% by weight, the film becomes hard, the surface roughness increases, and the electromagnetic conversion characteristics deteriorate.

In the present invention, the material of the inert particles of the component (3) constituting the coating layer A includes polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, methyl methacrylate copolymer crosslinked product, Any of organic substances such as polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine and silicone, and inorganic substances such as silica, alumina, titanium dioxide, kaolin, calcium carbonate, talc and graphite may be used.
Alternatively, core-shell particles having a multilayer structure composed of substances having different properties inside and outside the particles may be used.

The above inert particles are represented by the following formula:

[0037]

F = v / d ³ (where V is the volume of inert particles and d is the average particle size) The volume shape factor (f) defined by 0.1 to π /
6, and more preferably a substantially spherical or rugby ball-shaped elliptical sphere of 0.4 to π / 6.
For particles having a volume shape count (f) of less than 0.1, for example, flaky particles, the electromagnetic conversion characteristics are likely to deteriorate when used as a magnetic recording medium.

The inert particles (3) have an average particle size of 5 nm.
Not less than 50 nm, preferably not less than 10 nm and not more than 40 nm.
nm or less. When the average particle size is less than 5 nm,
When the magnetic recording medium is used, the running durability with the head is insufficient. On the other hand, when it exceeds 50 nm, the spacing with the head becomes large when the magnetic recording medium is used, and the electromagnetic conversion characteristics deteriorate. The ratio of the inert particles in the coating layer A is 1% by weight or more and 20% by weight or less, preferably 3% by weight or more and 10% by weight or less. When the proportion is less than 1% by weight, the running durability with the head is insufficient when the magnetic recording medium is used. On the other hand, when the proportion exceeds 20% by weight, particles are liable to fall off from the coating layer.

The height of the projections formed on the coating layer A with the above inert particles as nuclei is preferably 5 to 50 nm, more preferably 10 to 40 nm. If the height of the projection is less than 5 nm, the running durability with the head will be insufficient when the magnetic recording medium is used. On the other hand, if the height exceeds 50 nm, the spacing with the head will be large when the magnetic recording medium is used. In addition, the electromagnetic conversion characteristics decrease.

In the present invention, the surfactant of the component (4) constituting the coating layer A may be any of an anionic type, a cationic type and a nonionic type. preferable. As nonionic surfactants,
Ester type, ether type and alkyl phenol type are exemplified. As a specific example of such a surfactant, as a polyoxyethylene alkyl phenyl ether-based compound, a trade name of "Nonion NS-2" manufactured by NOF Corporation
30, "NS-240", "HS-220",
“HS-240”, a product name of Sanyo Chemical Co., Ltd.
"Nonipol 200", "Nonipol 400", "Nonipol 500", "Octapol 400"; trade names, manufactured by NOF Corporation, "Nonion E-230", "Nonpol E-230"
220, "K-230"; trade names, "Nonion S-15.4" and "S-40", manufactured by NOF Corporation as polyoxyethylene ester compounds of higher fatty acids.
And the like.

The proportion of the surfactant (4) in the coating layer A is from 10% by weight to 50% by weight, preferably 1% by weight.
5% by weight or more and 40% by weight or less. If the proportion is less than 10% by weight, the coatability deteriorates, and the running durability with the head becomes insufficient when used as a magnetic recording medium. On the other hand, if the proportion exceeds 50% by weight, particles easily fall off from the coating layer. Become.

In the present invention, if necessary, other components such as a stabilizer, a dispersant, a UV absorber, a thickener, and a release agent may be contained in the coating layer A as long as the effects of the present invention are not impaired. Etc. can be contained.

On the surface of the polyester film of the magnetic recording medium according to the present invention on the side opposite to the surface on which the film layer A is formed (the other surface: surface B), another film layer for the purpose of easy lubrication may be provided.

<Surface Roughness> The coating layer A in the present invention comprises:
It is preferable that the surface roughness Ra is 0.1 nm or more and 3 nm or less. It is difficult to make the surface roughness Ra less than 0.1 nm, and even if it is possible, the running property is impaired. On the other hand, when the surface roughness Ra exceeds 3 nm, the electromagnetic conversion characteristics deteriorate.

The surface roughness Ra of the other surface (B surface) is preferably 2 nm or more and 10 nm or less, more preferably 2 nm or more and 7 nm or less. This surface roughness R
When a is less than 2 nm, the handleability during the film forming process and the vapor deposition of the polyester film is extremely poor. On the other hand, if the surface roughness Ra exceeds 10 nm, the polyester film does not adhere sufficiently to the cooling can during vapor deposition, so that the heat load increases and oligomers are generated, which may cause a recording / reproducing error or cause vapor deposition. At times, the coating layer A is deformed by heat, and as a result, the deposited layer formed thereon is roughened to deteriorate the electromagnetic conversion characteristics.

<Thickness> It is particularly effective that the thickness of the polyester film of the magnetic recording medium in the present invention is less than 7 μm and not less than 2 μm. Such a magnetic recording medium polyester film is suitable for use as a base film of a magnetic recording medium comprising a ferromagnetic metal thin film layer, particularly when used as a base film for a digital video tape, because it exhibits excellent effects and is suitable. In addition, excellent effects can be exhibited in data storage tape applications, which is preferable.
If the film thickness is less than 2 μm, the film-forming stability during the production of the film is reduced, and even if the film can be produced, the rigidity of the tape is inferior.

<Magnetic Recording Medium> The magnetic recording medium according to the present invention is characterized in that a ferromagnetic metal thin film layer of a magnetic layer is provided on the above-mentioned film layer A of the polyester film. A well-known thing can be used for formation, and it does not specifically limit. The metal is preferably made of a ferromagnetic material of iron, cobalt, nickel, chromium, or an alloy thereof. For the formation of the metal thin film, a vacuum evaporation method, a sputtering method, or the like can be used. The thickness of the metal thin film layer is preferably from 100 to 300 nm.

<Backcoat Layer> The magnetic recording medium of the present invention comprises solid fine particles and a binder on the surface (surface B) opposite to the film layer A of the polyester film, and a solution containing various additives as necessary. A back coat layer formed by application may be provided. This solid particulate,
Known binders and additives can be used, and are not particularly limited. The thickness of the back coat layer is 0.3 to 1.5 μm.
m is preferable.

<Production Method of Film> The polyester film for a magnetic recording medium of the present invention can be obtained by a conventional polyester film (base film) production process comprising melt-molding, biaxial stretching and heat setting. The film can be manufactured by applying a coating solution for forming the film layer A on one surface of the film, drying the film, stretching the film in a perpendicular direction, and heat fixing the film. Known methods can be applied as a method for applying the coating liquid. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife method, an impregnation method, a curtain coating method, or the like can be used alone or in combination. The solid content of the coating solution is preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight. Stretching is at least 3 times or more in the uniaxial direction, 8 to 30 times in area magnification,
Furthermore, it is preferable to stretch 12 to 25 times.

[Method of measuring substances and method of evaluating effects]
The method for measuring the film characteristic value and the method for evaluating the effect in the present invention are as follows.

(1) Average Particle Diameter The average spherical diameter is determined by the equivalent spherical diameter of the particles at 50% by weight of all the particles determined by the light scattering method.

(2) Volume Shape Factor A photograph of each particle is taken with a scanning electron microscope at a magnification corresponding to the size of the particle, and the maximum diameter of the projected surface and the volume of the particle are calculated using an image analysis processor Luzex. Then, it is calculated by the following equation.

[0053]

F = V / d ³ (where f is the volume shape factor, and V is the volume of the particles (μ
m ³ ) and d represent the maximum diameter (μm) of the projection surface. )

(3) Height of projections Atomic force microscope Nano manufactured by Digital Instruments
Performed by Scope III. Using a J scanner, a 2 μm area is measured under the following conditions, and the height of each protrusion is measured from the AFM image. Deep needle: single crystal silicon nitride Scanning mode: tapping mode Number of pixels: 256 × 256 Scanning speed: 2.0 Hz Measurement environment: room temperature, in the air The height of the projection is defined by the height from the reference line to the top.
The height of the projections is an average value of 100 projections.

(4) Thickness of film layer A small piece of the film was fixedly formed with epoxy resin, and an ultrathin section (cut in parallel to the film flow direction) having a thickness of about 60 nm was prepared with a microtome. Is observed with an equivalent electron microscope (H-800, manufactured by Hitachi, Ltd.).
The layer thickness is determined from the boundary line of the layer.

(5) Surface roughness Ra According to JIS B0601, using a stylus type surface roughness meter (Surfcoder SE30FAT) manufactured by Kosaka Laboratory Co., Ltd., a stylus tip radius of 2 μm, measurement pressure of 30 mg, cutoff It is determined under the conditions of 0.08 mm and measurement length of 1.25 mm.
The measurement was performed four times, and the average value was shown.

(6) Unevenness of coating The coating layer was subjected to aluminum evaporation, and a coating having coating unevenness was evaluated as x, and an coating unevenness was evaluated as ○.

(7) Blocking The surface of the two films on which the coating layer A is formed and the other surface (B
Surface), and a 60 N under a load of 15 N / mm ²
After treating for 100 hours in an atmosphere of
The sheet was cut into a strip having a width of cm and evaluated by the peel strength (mN / 5 cm) at the point where a load was applied by a tensile tester. The evaluation is based on the following criteria from the value of the peel strength.
：: 0 to 70 △: 70 to 200 ×: 200 to rupture

(8) Production of Magnetic Tape and Characteristic Evaluation A cobalt-oxygen thin film having a thickness of 110 nm was formed on the film layer A of the polyester film by vacuum evaporation, and then formed on the cobalt-oxygen thin film layer by sputtering. Diamond-like carbon was formed to a thickness of 10 nm, and a fluorine-containing carboxylic acid-based lubricant was further provided in order. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone was provided to a thickness of 500 nm on the opposite surface, and the width was 8 mm and 6. It was slit to 35 mm and wound up on a commercially available reel to make a magnetic tape. For the electromagnetic conversion characteristics, the video S / N ratio is determined using a commercially available Hi8 type 8 mm video tape recorder, and the number of dropouts (DO) is determined using a commercially available digital video tape recorder with a built-in camera. For the measurement of S / N, a signal was supplied from a TV test signal generator, and a video noise meter was used. A commercially available standard Hi8ME tape was measured at zero decibel (dB).
To compare. ：: +2 dB or more compared to a commercial tape Δ: -2 dB or more to less than +2 dB compared to a commercial tape ×: Less than -2 dB compared to a commercial tape

The measurement of the number of DOs was performed using the 6.35 mm
After recording the tape with a commercially available camera-integrated digital video tape recorder, the tape is played back for one minute and the number of block-shaped mosaics appearing on the screen is counted.

The running durability is determined by measuring the S / N after repeating the recording and reproduction 700 times at 40 ° C. and 80% RH, and judging from the deviation from the initial value. ：: +0.0 dB or more with respect to the initial value Δ: -1.0 dB or more to less than +0.0 dB with respect to the initial value ×: less than -1.0 dB with respect to the initial value

[0062]

Next, the present invention will be further described based on examples.

[Example 1] Pellets of polyethylene-2,6-naphthalenedicarboxylate containing substantially no inert particles were dried at 170 ° C for 6 hours and then supplied to an extruder and melted at 305 ° C. . This molten polymer was filtered by a known method, extruded into a sheet from an extruder, and cooled and solidified on a casting drum to prepare an unstretched film. The unstretched film thus obtained was preheated at 120 ° C., further heated by a 900 ° C. infrared heater from 15 mm above between low-speed and high-speed rolls and stretched 3.7 times in the machine direction. Each of the aqueous solutions having the following compositions was applied to the film.

Composition of coating layer A: (1) 73% by weight of acrylic-polyester resin Polyester components: terephthalic acid (70 mol%), isophthalic acid (18 mol%), 5-sodium sulfoisophthalic acid (12 mol%) / Ethylene glycol (92 mol%), diethylene glycol (8 mol%) ・ Acrylic resin components: methyl methacrylate (80 mol%), glycidyl methacrylate (15 mol%), n-butyl acrylate (5 mol%) ・ Polyester component / Molar ratio of acrylic resin component = 3/7 (2) Epoxy compound: 2% by weight of polyfunctional epoxy compound (Toyo Polymer Co., Ltd. Mersi AD-65) (3) Fine particles of acrylic resin (average particle diameter 20 nm, volume) Shape factor 0.50) 5% by weight (4) Surfactant: NONION NS-240 manufactured by NOF Corporation 20% by weight ・ Thickness (after drying): 4.8 nm

Composition of coating layer B: (1) Copolyester 60% by weight 97% by mole of terephthalic acid / 1% by mole of isophthalic acid / 2% by mole of 5-sodium sulfoisophthalic acid // 60% by mole of ethylene glycol / diethylene Glycol 8 mol% (2) Silica particles (average particle size 60 nm) 10% by weight (3) Hydroxypropyl methyl cellulose 20% by weight (4) Nonionic NS-208.5 10% by weight manufactured by NOF Corporation Thickness (after drying): 15 nm

Subsequently, the mixture was supplied to a stenter, stretched 4.9 times in the horizontal direction at 150 ° C., and further stretched at 200 ° C. to 1.14.
The film was heat-treated while being stretched twice to obtain a biaxially oriented film having a thickness of 4.7 μm. Film layer A of this polyester film
Cobalt-oxygen thin film 110nm on the surface by vacuum evaporation
Formed with a thickness of Next, 10 n of diamond-like carbon was deposited on the cobalt-oxygen thin film layer by sputtering.
m. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone
0 nm, width 8 mm and 6.35 m by slitter
m and wound on a reel to produce a magnetic tape. Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

[Examples 2 to 5, Comparative Examples 1 to 9] Example 1
A polyester film and a magnetic tape were obtained in the same manner as in Example 1 except that the kind and ratio of the coating agent on the surface of the coating layer A were changed as shown in Table 1. The film properties are shown in Tables 1 and 2.

Example 6 In the production of the base film, the polyethylene-2,6-naphthalenedicarboxylate was changed to polyethylene terephthalate, the drying time of the pellets was 3 hours, the melt extrusion temperature was 295 ° C., and the film was stretched longitudinally. The preheating temperature and the magnification were set to 80 ° C. and 3.0 times, respectively, and the same coating solution as in Example 1 was applied. Further, the film was horizontally stretched 3.3 times at 105 ° C. and further 1.6 times at 210 ° C. The film was heat-treated while the other conditions were the same, and a film having a thickness of 6.4 μm was obtained in the same manner, and a magnetic tape was prepared in the same manner as in Example 1. Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

[Example 7] The procedure of Example 1 was repeated except that 0.03% by weight of spherical silica having an average particle size of 60 nm was contained in polyethylene-2,6-naphthalenedicarboxylate in the production of the base film of Example 1. In the same manner as in Example 1, a film having a thickness of 4.7 μm was obtained, and a magnetic tape was formed in the same manner as in Example 1. Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

Example 8 In the production of the base film of Example 1, raw material A, which is a polyethylene-2,6-naphthalenedicarboxylate containing substantially no inert particles, and substantially inert particles were used. The raw material B containing 0.3% by weight of silica having an average particle size of 300 nm in polyethylene-2,6-naphthalenedicarboxylate not containing was coextruded at a ratio of 5: 1 in thickness, and the other conditions were the same. Obtaining a 4.7 μm thick polyester film;
A magnetic tape was produced in the same manner as in Example 1. Tables 1 and 2 show the properties of the obtained polyester film and magnetic tape.

[0071]

[Table 1]

[0072]

[Table 2]

As is clear from Tables 1 and 2, the polyester film of the present invention has no coating unevenness, has excellent handling properties, and when used as a magnetic tape, has excellent electromagnetic conversion properties, dropout properties, and running durability. It becomes a tape.

[0074]

According to the present invention, flatness, blocking resistance and abrasion resistance are compatible by optimizing the hardness and surface roughness of the undercoat layer of the ferromagnetic thin film, and the dropout is extremely small. It is possible to provide a magnetic recording medium having excellent running durability, particularly a polyester film for a ferromagnetic metal thin film type magnetic tape.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/00 C08K 5/00 C08L 33/00 C08L 33/00 51/08 51/08 // (C08L 33 / 00 (C08L 33/00 63:00 63:00 Z 101: 00) 101: 00) (72) Inventor Hirofumi Murooka 3-37-19 Koyama, Sagamihara City, Kanagawa Prefecture F-term in Sagamihara Research Center, Teijin Limited (Reference) 4F100 AA20 AB01C AH02B AK25B AK41A AK41B AK42A AL01B BA02 BA03 BA07 BA10A BA10C BA13 BA16 CA18B CA23B DE01B EH46 EJ37 EJ38 EJ43 GB41 JG06C JK14B JK15 JL00 JM02B YY01B3 BG013BG033J023 DE136 DE146 DE236 DJ016 DJ036 DJ046 EU186 FA003 FA006 FD317 GS01 5D006 CB01 CB07 CB08

Claims (8)

[Claims] 1. A film layer A on one side of a polyester film.
Wherein the coating layer A is
(1) 30% by weight or more of acrylic-polyester resin 88
(2) 1% to 30% by weight of an epoxy compound having two or more epoxy groups, (3) 1% to 20% by weight of inactive particles having an average particle size of 5 nm to 50 nm, (4) 10% by weight or more of surfactant 5
0% by weight or less as a main component;
The molar ratio of the polyester component / acrylic resin component of the polyester resin is 1/9 or more and 5/5 or less, and the epoxy group-containing acrylic compound component in the acrylic resin component is 3 mol% or more and 30 mols with respect to the acrylic resin component. % Or less, a polyester film for a magnetic recording medium. 2. The polyester film for a magnetic recording medium according to claim 1, wherein the surface roughness Ra of the coating layer A is 0.1 nm or more and 3 nm or less. 3. The polyester film for a magnetic recording medium according to claim 1, wherein a surface roughness Ra of a surface (surface B) opposite to a surface on which the coating layer A is formed is 2 nm or more and 10 nm or less. 4. The polyester film as claimed in claim 1, wherein the polyester film is made of polyethylene terephthalate or polyethylene 2,6-naphthalenedicarboxylate.
The polyester film for a magnetic recording medium according to any one of the above. 5. The polyester film for a magnetic recording medium according to claim 1, wherein the thickness of the film is less than 7 μm and 2 μm or more. 6. The polyester film for a magnetic recording medium according to claim 1, wherein the surface of the coating layer A is a surface on which the ferromagnetic metal thin film layer of the magnetic layer is formed. 7. The polyester film for a magnetic recording medium according to claim 1, which is used for a digital recording type magnetic tape. 8. A magnetic recording medium using the polyester film for a magnetic recording medium according to claim 1.