JP2000043216A - Biaxially oriented polyethylene-2,6-naphthalate film for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene-2,6-naphthalate film for a magnetic recording medium solved in the point of issue possessed by a conventional polyethylene-2,6-naphthalate film and improved in delamination resistance while holding high elastic modulus. SOLUTION: A film layer is formed to at least the single surface of a biaxially oriented film comprising copolymerized polyethylene-2,6-naphthalate wherein 2,6-naphthalenedicarboxylic acid is a main dicarboxylic acid component and ethylene glycol is a main glycol component and 0.1-10 mol.% (with respect to the total amt. of the total carboxylic acid component) of an isophthalic acid component is contained as a copolymerizing component and the content of a diethylene glycol component is 3 mol.% (with respect to glycol total amt. of the total glycol component). The film layer is a coating film formed from a water soluble or water dispersible resin containing inert particles with an average particle size of 5-100 nm and has 1×106-1×109/mm2 of projections caused by inert particles on the surface thereof and the surface center line average roughness of the film layer is 0.1-2 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium. More specifically, it has excellent elasticity and delamination resistance,
And a biaxially oriented polyethylene-2 for magnetic recording media having excellent electromagnetic conversion characteristics and running durability when used as a magnetic recording medium.
6-Related to naphthalate film.

[0002]

2. Description of the Related Art Polyesters represented by polyethylene terephthalate are widely used today in applications such as fibers, films or resin molded products because of their excellent physical and chemical properties. In particular, in the field of magnetic recording such as audio tape, video tape, computer tape and floppy disk, which has been remarkably developed in recent years, a biaxially oriented film of polyethylene terephthalate is suitably used as a base film.

[0003] However, with recent advances in miniaturization, weight reduction, and high performance of electric and electronic equipment, the characteristics required for base films have become increasingly severe.
For example, in the magnetic recording field, long-time recording, miniaturization,
It is necessary to reduce the thickness of the base film in order to reduce the weight, but at the same time, it is important to maintain the stiffness of the film with a higher elastic modulus. For this reason, when the thickness of the base film is very thin, the elasticity of the base film using the conventional polyethylene terephthalate is sometimes insufficient.

[0004] In contrast to polyethylene terephthalate film, polyethylene-2,6-naphthalate film has excellent mechanical properties, heat resistance, chemical properties and high Tg and is preferably used in the above applications. However,
Polyethylene-2,6-naphthalate film has a drawback of lower tear strength (poor delamination resistance) than ordinary polyethylene terephthalate film. In particular, when a stretching treatment is involved as in the case of a biaxially oriented film, the tear strength of an intermediate product or a final product in the molding process often decreases. For this reason, in the film forming process of the sequential biaxially stretched film of, for example, polyethylene-2,6-naphthalate, the film is frequently broken and the product cannot be obtained, or even if the product is obtained, it is vulnerable to tearing in a specific direction. There was a problem of becoming a film.

[0005] Particularly, in the case of a film having a smooth surface in which high density of magnetic recording is to be achieved, blocking tends to occur when the film is wound in a roll state. If the blocking roll film has poor delamination resistance, it may break when unwinding, or even if it does not break, it will locally transfer the substance to the surface where the polyethylene-2,6-naphthalate film comes into contact by local blocking, and it will be applied to the tape. There is also a problem that a drop-out occurs when you do.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional polyethylene-2,6-naphthalate film and to improve the delamination resistance while maintaining a high elastic modulus. To provide polyethylene-2,6-naphthalate for magnetic recording media.

[0007]

According to the present invention, it is an object of the present invention to provide 2,6-naphthalenedicarboxylic acid as a main dicarboxylic acid component, ethylene glycol as a main glycol component, and an isophthalic acid component as a copolymerization component. Is 0.1 to 10 mol% (based on the total amount of all dicarboxylic acid components), and the content of the diethylene glycol component is 3
A film layer is formed on at least one surface of a biaxially oriented film composed of copolymerized polyethylene-2,6-naphthalate of not more than mol% (based on the total amount of all glycol components), and the film layer has an average particle size of 5%. a coating comprising a water-soluble resin or water dispersible resin containing inert particles of ~ 100 nm, 1 × on the surface due to the inert particles 10 ⁶ to 1 × 1
0 ⁹ / mm ² of has a projection, and a magnetic recording medium for biaxially oriented polyethylene-2,6-naphthalate, wherein the center line average roughness of said coating surface is 0.1~2nm Achieved by film. Hereinafter, the present invention will be described.

[Polyethylene-2,6-naphthalate Copolymer] In the present invention, the main dicarboxylic acid component constituting the polyethylene-2,6-naphthalate copolymer is naphthalenedicarboxylic acid, and the main glycol component is ethylene glycol.

Here, the main dicarboxylic acid component means 80 mol% or more, preferably 90 mol% or more based on the total amount of all dicarboxylic acid components, and the main glycol component means 80 mol% or more based on the total amount of all glycol components. % Or more, preferably 90 mol% or more.

In the present invention, the polyethylene-2,6-naphthalate copolymer contains an isophthalic acid component as a copolymer component in an amount of 0.1 to 0.1% based on the total amount of all dicarboxylic acid components. l-10
It is copolymerized so as to account for mol%.

The isophthalic acid component is preferably copolymerized by using a compound represented by the following general formula in a copolymer production reaction.

[0012]

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(In the formula, R represents hydrogen or a lower alkyl group.) In the above general formula, R is hydrogen, a methyl group, an ethyl group,
It is a lower alkyl group such as a propyl group and a butyl group.

The copolymerization amount of this isophthalic acid component is 0.1% based on the total amount of all dicarboxylic acid components. If the amount is less than 1 mol%, the delamination resistance of the film will not be improved, and if it exceeds 10 mol%, the crystallinity of the film will be impaired and the film will have poor mechanical strength. The copolymerization amount of the isophthalic acid component is preferably 0.5 to
It is 8 mol%, and more preferably 1 to 7 mol%.

Preferred examples of the compound represented by the above general formula include isophthalic acid and dimethyl isophthalate.

In the present invention, the copolymerized polyethylene
In 2,6-naphthalate, the copolymerization amount of the diethylene glycol component needs to be 3 mol% or less (based on the total glycol component).

The diethylene glycol component is not added in the form of diethylene glycol or its ester-forming derivative as a copolymer component during the production of the copolymer, but is a copolymer produced as a by-product during the production reaction. is there.

When the total copolymerization amount of the diethylene glycol component exceeds 3 mol%, the effect of improving the delamination resistance of the film is increased, but the crystallinity is impaired, so that the mechanical strength is greatly reduced. become. The total copolymerization ratio of the diethylene glycol component is preferably 2.
It is at most 5 mol%, more preferably at most 2 mol%. In order to suppress the by-product of diethylene glycol during the production reaction, the ratio of the molar amount of ethylene glycol to be added to the molar amount of dicarboxylic acid is preferably 2.0 to 3.0. The shorter the time required for the transesterification reaction, the better.

The copolymerized polyethylene-2,6-naphthalate may contain other copolymerized components as impurities in addition to the copolymerized components of the isophthalic acid component and the diethylene glycol component, but these components are effective for delamination resistance. However, do not enter a large amount to greatly reduce the Young's modulus. The amount is preferably not more than 3 mol%, preferably not more than 1 mol%, more preferably not more than 0.1 mol% with diethylene glycol.

Examples of copolymer components as impurities include:
Compounds having two ester-forming functional groups, such as oxalic acid, adipic acid, phthalic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, terephthalic acid, 2-potassium sulfoterephthalate Acid, 2,7-naphthalenedicarboxylic acid,
1,4-cyclohexanedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, phenylindanedicarboxylic acid,
Diphenyl ether dicarboxylic acid; oxycarboxylic acid such as p-oxyethoxybenzoic acid; propylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 6-hexanediol, 1,2-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,4-cyclohexane dimethanol, p-xylylene glycol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol sulfone , Triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol, neopentyl glycol and the like.
These can also be used as an ester-forming derivative in the copolymer production reaction.

The copolymerized polyethylene-2,6-naphthalate is obtained by blocking a terminal hydroxyl group and / or a carboxyl group partially or entirely with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. It may be modified with a very small amount of an ester-forming compound having three or more functional groups such as glycerin and pentaerythritol within a range where a substantially linear polymer can be obtained.

[Additives] Copolymerized polyethylene of the present invention
2,6-Naphthalate has additives such as dyes, pigments,
A stabilizer, a lubricant, an ultraviolet absorber, a flame retardant, and the like can be contained as desired.

The biaxially oriented film comprising the copolymerized polyethylene-2,6-naphthalate of the present invention may have a single-layer structure or a multilayer structure composed of two or more layers by co-extrusion. The inert particles contained therein are
The average particle size is 200 nm or less, preferably 130 nm or less, and the content is 0 to 0.1% by weight, preferably 0 to
~ 0.06% by weight. When the average particle size is larger than 200 nm, or when the content is larger than 0.1% by weight, the electromagnetic conversion characteristics as a high-density magnetic recording medium are hindered. Such inert particles include, for example, spherical silica, porous silica, calcium carbonate, silica alumina,
Examples include inorganic particles such as alumina, titanium dioxide, kaolin clay, barium sulfate, and zeolite, or organic particles such as silicon resin particles and cross-linked polystyrene particles. Inorganic particles are preferably synthetic, rather than natural, for reasons such as uniform particle size,
Inorganic particles of any crystal morphology, hardness, specific gravity, and color can be used.

The inert particles to be added to the film may be a single component selected from those exemplified above, or a multi-component containing two or more components.

The timing of adding the inert particles is not particularly limited as long as it is a stage until the copolymer polyethylene-2,6-naphthalate is formed. For example, the inert particles may be added at the polymerization stage. May be added.

[Coating layer] Copolyethylene-2,6-
The biaxially oriented film made of naphthalate has a film layer on at least one surface, but as a water-soluble resin or a water-dispersible resin constituting the film, an acrylic resin, a polyester resin, an acryl-ester resin, an alkyd resin, a phenol resin, Examples thereof include an epoxy resin, an amino resin, a polyurethane resin, a vinyl acetate resin, and a vinyl chloride-vinyl acetate copolymer. Acrylic resins, polyester resins, and acryl-polyester resins are preferred from the viewpoints of the adhesion of the core layer to the polyester resin, the retention of protrusions, and the ease of sliding. These may be a homopolymer or a copolymer, and may be a mixture. These water-dispersible resins are preferable.

The water-soluble or water-dispersible acrylic resin is, for example, an acrylate ester (alcohol residues such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl). Butyl group, 2
-Ethylhexyl group, cyclohexyl group, phenyl group,
Benzyl group, phenylethyl group, etc.); methacrylic acid ester (the alcohol residue is the same as above);
Hydroxy-containing monomers such as -hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide; Amide group-containing monomers such as N-methylol methacrylamide, N, N-dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-phenylacrylamide; N, N-diethylaminoethyl acrylate, N, N -Amino group-containing monomers such as diethylaminoethyl methacrylate; glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ester A sulfonic acid group such as styrenesulfonic acid, vinylsulfonic acid and salts thereof (eg, sodium salt, potassium salt, ammonium salt, etc.) or a salt thereof, containing one or more epoxy group-containing monomers such as ter as a main component; A monomer containing a carboxyl group or a salt thereof such as crotonic acid, itaconic acid, acrylic acid, maleic acid, fumaric acid and salts thereof (eg, sodium salt, potassium salt, ammonium salt, etc.); maleic anhydride Acid, monomers containing anhydrides such as itaconic anhydride; other vinyl inocyanates;
Allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleate monoester, alkyl fumarate monoester, acrylonitrile, methacrylonitrile, alkyl itaconate monoester, vinylidene chloride, vinyl acetate, vinyl chloride And the like are preferably made from a combination containing at least one kind of monomer as an auxiliary component.
Further, those containing 50 mol% or more of components of (meth) acrylic monomers such as acrylic acid derivatives and methacrylic acid derivatives are preferable, and those containing components of methyl methacrylate and ethyl methacrylate are particularly preferable. .

The water-soluble or water-dispersible acrylic resin can be self-crosslinked with a functional group in the molecule, or can be crosslinked with a crosslinking agent such as a melamine resin or an epoxy compound.

The acid component constituting the water-soluble or water-dispersible polyester resin includes, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4 ´―
Diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2-potassium sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid Examples thereof include polycarboxylic acids such as acid and monopotassium trimellitate. Examples of the hydroxy compound component include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p- Xylylene glycol,
Bivalent such as ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethyl sulfonate, potassium dimethylolpropanoate, etc. Hydroxy compounds can be exemplified. A polyester resin can be prepared from these compounds by a conventional method. From the viewpoint of producing an aqueous coating composition, it is preferable to use an aqueous polyester resin containing a 5-sodium sulfoisophthalic acid component or a carboxylate group. Such a polyester resin can be a self-crosslinking type having a functional group in the molecule, or can be crosslinked using a curing agent such as a melamine resin or an epoxy resin.

In the present invention, the water-soluble or water-dispersible acrylic-polyester resin is used in the sense that it contains an acrylic modified polyester resin and a polyester-modified acrylic resin, and the acrylic resin component and the polyester resin component are bonded to each other. And includes, for example, a graft type, a block type, and the like. Acrylic-polyester resin, for example, by adding a radical initiator to both ends of the polyester resin to polymerize the acrylic monomer,
Add a radical initiator to the side chain of the polyester resin to polymerize the acrylic monomer, or add a hydroxyl group to the side chain of the acrylic resin and react with a polyester having an isocyanate group or a carboxyl group at the end to form a comb. It can be produced by using a polymer or the like.

Examples of the material of the inert particles to be blended in the coating layer include polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride. ,
Organic materials such as polyacrylonitrile and benzoguanamine resin, silica, alumina, titanium dioxide, kaolin,
Any of inorganic materials such as talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, barium sulfate and the like may be used.

Further, core-shell type particles having a multilayer structure composed of substances having different properties inside and outside may be used.

The inert particles have an average particle size of 5 to 100 nm,
Preferably it is 10 to 50 nm. Further, those having a uniform particle size distribution are preferred. If the average particle size is less than 5 nm, the slipperiness deteriorates. On the other hand, if the average particle size exceeds 100 nm, the particles will fall off and the abrasion resistance will deteriorate. In addition, the spacing with the magnetic head is increased, and it is difficult to provide a magnetic recording medium of a high-density recording type.

The inert particles have a surface projection frequency of 1 in the coating layer.
It is contained in the coating layer so as to exhibit an amount of × 10 ⁶ to 1 × 10 ⁹ / mm ² . This surface projection frequency is 1 × 10
^If it is less than ⁶ pieces / mm ² , the running durability of a magnetic recording medium will be insufficient. On the other hand, when it exceeds 1 × 10 ⁹ pieces / mm ² , the electromagnetic conversion characteristics are adversely affected. The preferred frequency of surface projections is 1 × 10 ⁶ to 1 × 10 ⁸ / mm ² , more preferably 2 × 10 ^{6 to} 5 × 10 ⁷ / mm ² , particularly preferably 3 × 10 ^{6 to} 3 × 10 ⁷ / mm ² . a mm ^2.

The coating layer is formed by applying a coating liquid containing inert particles and a water-soluble or water-dispersible resin to at least one surface of the above-mentioned film made of copolymerized polyethylene-2,6-naphthalate, and drying. Can be formed. At this time, the film may be a biaxially oriented film, a uniaxially oriented film or an unstretched film. In the latter case, after the application of the coating liquid, a stretching treatment for forming a biaxially oriented film is performed.

The coating solution has a solid content of 0.2 to 10% by weight, more preferably 0.5 to 5% by weight, particularly 0.7 to 3% by weight.
It is preferred that If necessary, other components such as a surfactant, a stabilizer, a dispersant, a UV absorber, a thickener, and the like can be added to the coating liquid as long as the effects of the present invention are not impaired.

Center line average roughness Ra of the surface on which the coating layer is formed
Is 0.1 to 2 nm, more preferably 0.5 to 1.5 nm
It is. When Ra exceeds 2 nm, the electromagnetic conversion characteristics deteriorate particularly when a metal thin film type magnetic recording medium is used.
On the other hand, when Ra is less than 0.1 nm, slipperiness is extremely deteriorated, running durability is insufficient, and tape squeezes due to sticking to the magnetic head, which makes it difficult to be put to practical use.

The copolymerized polyethylene-2,6-naphthalate film of the present invention may or may not have a coating layer on the surface opposite to the surface on which the above-mentioned coating layer is formed. When it has (coating layer B), it may be the same as the above-mentioned coating layer or a different coating layer.

[Production of Film] The biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium of the present invention can be produced according to a conventionally known method.

For example, when the copolymer polyethylene-2,6-naphthalate film is a single layer, first, the copolymer polyethylene-2,6-naphthalate is heated at a temperature from the polymer melting point (Tm: ° C.) to (Tm + 70) ° C. After extruding into a film, the mixture is rapidly cooled and solidified at 10 to 90 ° C. to obtain an unstretched film. Thereafter, the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) to
At a temperature of (Tg + 70) ° C. (Tg: glass transition temperature of polymer), the film is stretched at a magnification of 2.5 to 8.0 times, preferably 3.0 to 7.5 times, and then a coating layer is formed. The coating solution to be applied is applied to a film, and thereafter, at a temperature of Tg to (Tg + 70) ° C. in a direction perpendicular to the above direction, a magnification of 2.5 to 8.0 times, preferably 3.0 to 7.5 times. Stretch. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. That is, two, three, four
Step stretching or multi-step stretching may be performed. The total stretching ratio is usually 9 times or more as an area stretching ratio, preferably 12 to 35.
And more preferably 15 to 32 times. Subsequently, the biaxially oriented film was moved from (Tg + 70) to (Tm-1).
0) Excellent dimensional stability is provided by heat set crystallization at a temperature of 0 ° C, for example, 180 to 250 ° C. The heat setting time is preferably 1 to 60 seconds.

[Young's Modulus of Film] The biaxially oriented polyethylene-2,6-naphthalate film for magnetic recording media of the present invention has a Young's modulus in the transverse direction of 6.9 from the viewpoint of output characteristics.
The sum of the Young's modulus in the vertical direction and the horizontal direction is 12.7 or more.
GPa or more is preferable.

[Magnetic Recording Medium] The biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium of the present invention is prepared by depositing iron, iron, or the like on the surface of a film layer by a method such as vacuum deposition, sputtering, or ion plating. Form a ferromagnetic metal thin film layer composed of cobalt, chromium or an alloy or oxide containing these as a main component, and on the surface,
Applications and, if necessary, diamond-like carbon (DL
C) and the like, and a fluorinated carboxylic acid-based lubricating layer is sequentially provided, and a known back coat layer is further provided on the surface of the coating layer B, so that output in the short wavelength region, S / N, C / N
Thus, a vapor-deposited magnetic recording medium for high-density recording with excellent electromagnetic conversion characteristics such as low dropout and error rate can be obtained. This vapor-deposited type electromagnetic recording medium includes a Hi8 for recording an analog signal, a digital video cassette recorder (DVC) for recording a digital signal, 8 mm data, and a DDSIV.
It is extremely useful as a tape medium for use.

[0043]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. The measuring method used in the present invention is as follows. "Parts" means parts by weight.

(1) Average particle size of particles (average particle size: 0.0
6μm or more) Shimadzu CP-50 Centrifugal Particle Size Analyzer (Centrifugal Particle)
It is measured using a Size Analyzer). From the integrated curve of particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, the particle size “equivalent sphere diameter” corresponding to 50 mass percent is read, and this value is defined as the above average particle size. ("Granularity measurement technology" published by Nikkan Kogyo Shimbun, 1975, p. 242
247).

(2) Average particle size of ultrafine particles (average particle size:
(Less than 0.06 μm) Particles having an average particle diameter of less than 0.06 μm forming small projections are
It is measured using a light scattering method. That is, Nicom Instruments Inc. (NicompInst)
devices Inc. NICOMP MO manufactured by
DEL 270 SUBMICRON PARTICL
50% by weight of all particles as determined by E Sizer
At the point indicated by "Equivalent spherical diameter".

(3) Surface roughness of the film (center line average roughness: Ra) The center line average roughness (Ra) is measured according to JIS-B601. In the present invention, it is measured and measured under the following conditions using a stylus type surface roughness meter (SURFCORDER SE, 30C) manufactured by Kosaka Laboratory Co., Ltd. (A) Tip radius of the stylus: 2 μm (b) Measurement pressure: 30 mg (c) Cut-off: 0.08 mm (d) Measurement length: 8.0 mm (e) How to summarize data: Repeated measurement of the same sample six times The center line average roughness (Ra) is determined as an average using the remaining five data except for the largest value.

(4) Number of Particle Protrusions Using a SEM (scanning electron microscope, T-300 manufactured by JEOL), the surface of the laminated film was magnified 30,000 times at an angle of 0 °.
, And the number of granular projections is counted, and the average value is calculated as the number of projections per piece / mm ² by area conversion.

(5) Transfer foreign matter tension: 1.7 × 10 ⁶ kg / m ² , contact pressure 1.5 × 10 ⁷
A film roll slit at a size of 300 mm × 5000 m under the condition of kg / m ² was cut into 10 ⁻⁵ torr ×
Under a vacuum of 3 hours, the film is pierced by removing the air between the films, then the roll is cut open to sample the polyester film of the core, and the polyester film is inclined on the surface of the film layer by vacuum evaporation. An aluminum thin film was formed at an angle of 45 ° to a thickness of 0.2 μm, and observed under a transmission microscope at a magnification of 4000 × 1 cm ^2, and the maximum length of the non-deposited portion due to the shadow of the projection (projection height) (Corresponding to the above) is counted for the number of transmitted light of 0.2 mm or more. (That is, the height is 0.2 mm / 400
= Count the frequency of coarse transfer foreign particles of 0.5 μm or more. )

The evaluation is performed according to the following criteria. ○: less than 20 / cm ² delta: 20 / cm ² or more, less than 50 / cm ² ×: 50 or more / cm ²

(6) Content of diethylene glycol (DEG) The polymer was decomposed using hydrazine hydrate and quantified by gas chromatography. For gas chromatography, Model 263-70 manufactured by Hitachi, Ltd. was used.

(7) Young's Modulus The film is cut into a sample having a width of 10 mm and a length of 15 cm, and the distance between the chucks is set to 100 mm. The film is pulled at a pulling speed of 10 mm / min and a chart speed of 500 mm / min using an Instron universal tensile tester. The Young's modulus is calculated from the tangent at the rising portion of the obtained load-elongation curve.

(8) Crease Delamination Whitening A film is cut out to a size of 40 mm × 40 mm, folded into two pieces by hand, sandwiched between a pair of flat metal plates, and then pressed at a predetermined pressure of 10 (kgf / cm) by a press machine. ² )
Press for 20 seconds. After pressing, return the folded film to the original state by hand, and apply a pressure of 4 (kgf / cm ² ) for 20 minutes.
Press for seconds. Thereafter, a sample is taken out, the width (μm) of the whitened portion appearing on the fold is measured, and the average of the maximum value and the minimum value is defined as the fold delamination whitening width.

This value is used as an index indicating the likelihood of delamination (delamination) of the film. A smaller value indicates that delamination is less likely to occur.

The evaluation is performed according to the following criteria. ；: Delami whitening width less than 30 μm △: Delami whitening width 30 μm or more, less than 35 μm ×: Delami whitening width 35 μm or more

(9) Production of Magnetic Tape and Evaluation of Characteristics The surface of the coating layer was coated with 100% cobalt by vacuum evaporation.
Are formed to a thickness of 0.02 μm (each layer thickness is about 0.1 μm), and a diamond-like carbon (DLC) film and a fluorine-containing carboxylic acid-based lubricating layer are sequentially provided on the surface thereof. Further, a back coat layer having the following composition is applied to the surface of the coating layer B and dried.

The thickness of the back coat layer after drying is 0.8 μm.
m. Backcoat layer composition: carbon black 100 parts thermoplastic polyurethane 60 parts isocyanate compound 18 parts (Nippon Polyurethane Industry Co., Ltd. Coronate L) silicone oil 0.5 parts methyl ethyl ketone 250 parts

After that, the slit was cut into an 8 mm width to obtain a commercially available 8 mm.
mm video cassette. Next, the properties of the tape are measured using the following commercially available equipment. Equipment used: 8mm video tape recorder: EDV manufactured by Sony Corporation
-6000 C / N measurement: Noise meter manufactured by Shibasoku Co., Ltd.

C / N Measurement A signal having a recording wavelength of 0.5 μm (frequency of about 7.4 MHz) is recorded, and the ratio of the value of the reproduced signal between 6.4 MHz and 7.4 MHz is defined as the C / N of the tape. The C / N of the 8 mm video evaporation tape is represented by OdB and expressed as a relative value. : 0 dB or more Δ: -3 or more, less than 0 dB ×: less than -3 dB

Dropout (D / O) Measurement Using a dropout counter, 15 μs / 18 d
The number per minute is measured in B. : Less than 20 pieces / minute △: 20 to 50 pieces / minute, 20 pieces / minute or more, less than 50 pieces / minute ×: 50 pieces / minute or more

C./N after measuring 500 times of recording and reproduction at a running speed of 85 cm / min with a tape at 40 ° C. and 80% RH.
The deviation from the initial value is determined based on the following criteria. ◎: +0.0 dB or more with respect to the initial value: -1.0 dB or more with respect to the initial value, +0.0 dB
Less than ×: less than -1.0 dB from the initial value

Example 1 Transesterification of 99 parts of dimethyl naphthalene-2,6-dicarboxylate, 0.8 part of dimethyl isophthalate (1 mol% based on the total amount of all dicarboxylic acid components) and 60 parts of ethylene glycol After transesterification according to a conventional method using 0.03 parts of manganese acetate tetrahydrate as a catalyst, 0.23 parts of trimethyl phosphate was added to substantially terminate the transesterification reaction.

Then, 0.024 part of antimony trioxide was added, and a polymerization reaction was subsequently carried out at a high temperature and a high vacuum by a conventional method to obtain an intrinsic viscosity of 0.61 dl / g and a DEG copolymerization amount of 1.1.
A mole% of a polyethylene-2,6-naphthalate copolymer was obtained.

The polyethylene-2,6-naphthalate copolymer pellets were dried at 170 ° C. for 6 hours, fed to an extruder hopper, and melted at a melting temperature of 310 ° C.
The resulting product was extruded through a slit die having a surface temperature of 60 ° C. onto a rotary cooling drum to obtain an unstretched film. The unstretched film thus obtained is preheated at 120 ° C., and 900 ° C. from 15 mm above between low-speed and high-speed rolls.
The film is stretched 4.75 times in the machine direction by heating with an IR heater. Then, a water-soluble coating solution having the following composition is applied to each film, and then supplied to a stenter. 4.8 times. The obtained biaxially oriented film was heat-set at a temperature of 200 ° C. for 5 seconds and relaxed in the width direction by 0.5% at a temperature of 190 ° C. to obtain a biaxially oriented film having a thickness of 7.5 μm. Table 1 shows the results.

Coating layer (magnetic layer formation surface) Resin; Copolymerized polyester (terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // ethylene glycol / bisphenol A / propion oxide 2 mol adduct = 97/1/2) // 60/40) 80 parts ・ Inert particles; 5 parts of acrylic particles (average particle size: 40 nm) ・ Surfactant; Inion NS-240 15 manufactured by NOF Corporation
Part ・ Thickness (after drying); 10 nm Coating layer B (the other side) ・ Resin: Acrylic-modified polyester SH5 made by Takamatsu Yushi
51A 70 parts-Inert particles; 20 parts of silica particles (average particle size: 60 nm)-Surfactant: NONION NS-208.5 manufactured by NOF Corporation
10 parts ・ Thickness (after drying); 30nm

Example 2 Example 1 was repeated except that the copolymerization amount of dimethyl isophthalate, the particles containing the polyethylene-2,6-naphthalate copolymer, and the particles contained in the coating layer were changed as shown in Table 1. A biaxially oriented film was obtained in the same manner as described above. Table 1 shows the results.

Example 3 The same procedure as in Example 1 was carried out except that the copolymerization amount of dimethyl isophthalate, the stretching ratio in the longitudinal and transverse directions, the resin of the coating layer and the particles contained were changed as shown in Table 1. Then, a biaxially oriented film was obtained. Table 1 shows the results.

Example 4 Two kinds of polyethylene-2,6-naphthalate copolymers shown in Table 1 were each used in 170
After drying at 6 ° C for 6 hours, the temperature was 310 ° C using two extruders.
And polymer A; polymer B = 5: 1 using a 1 mm slit-shaped multi-manifold type coextrusion die.
And a biaxially oriented film was obtained in the same manner as in Example 1 except that the resin of the coating layer was changed as shown in Table 1. Table 1 shows the results.

Comparative Example 1 A biaxially oriented film was obtained in the same manner as in Example 1 except that dimethyl isophthalate was not copolymerized. Table 1 shows the results.

Comparative Example 2 A biaxially oriented film was obtained in the same manner as in Example 1 except that 1 mol% of dimethyl terephthalate was copolymerized instead of dimethyl isophthalate. Table 1 shows the results.

Comparative Example 3 Diethylene glycol (DE
A biaxially oriented film was obtained in the same manner as in Example 1 except that 2.5 parts of G) were added. Table 1 shows the results.

Comparative Example 4 A biaxially oriented film was obtained in the same manner as in Example 1 except that the frequency of protrusions of the coating layer was changed as shown in Table 1. Table 1 shows the results.

Comparative Example 5 A biaxially oriented film was obtained in the same manner as in Example 1, except that the particles containing the polyethylene-2,6-naphthalate copolymer were changed as shown in Table 1. Table 1 shows the results.

[0073]

[Table 1]

[0074]

According to the present invention, the conventional polyethylene
Solving the problems of 2,6-naphthalate film,
It is possible to provide a polyethylene-2,6-naphthalate for a magnetic recording medium having improved delamination resistance while maintaining a high elastic modulus.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) B29K 67:00 B29L 9:00 (72) Inventor Toshifumi Osawa 3-37-19 Koyama, Sagamihara-shi, Kanagawa 4F100 AA20C AA20H AK01B AK25B AK25H AK41A AK41B AK41C AK41D AK41J AL06C AR00E BA03 BA04 BA05 BA06 BA07 BA10A BA10B BA10C BA10E BA13 CC01B DD01 DE01B38 J01 DE07B01 J01 DE01B38 J01 DE01B38 YY00B YY00H 4F210 AA26E AB11 AB17 AB19 AG01 AG03 AH38 QC06 QD08 QG01 QW07 4J029 AA03 AB04 AB07 AC02 AE03 AE11 AE12 AE18 BA02 BA03 BA04 BA05 BA08 BA10 BB06A BD07A BF09 BF18 CC03 CB25 CB26 CB18 CB25 CB26 FC35 FC36 HA01 HB01 HB03A HB06 JA093 JA123 JA203 JA293 JE053 JE182 JE223 JF14 3 JF163 JF223 JF323 KH01 KH08 5D006 CB01 CB05 CB07 CB08 FA00

Claims (7)

[Claims] 1. A 2,6-naphthalenedicarboxylic acid as a main dicarboxylic acid component, an ethylene glycol as a main glycol component, and an isophthalic acid component as a copolymer component in an amount of 0.1 to 10 mol% (based on the total amount of all dicarboxylic components). ) Having a diethylene glycol component content of 3
A film layer is formed on at least one surface of a biaxially oriented film composed of copolymerized polyethylene-2,6-naphthalate of not more than mol% (based on the total amount of all glycol components), and the film layer has an average particle size of 5%. A coating film made of a water-soluble resin or a water-dispersible resin containing inactive particles having a particle size of 1 to 10 nm, and a surface of 1 × 10 ⁶ to 1 × 10 ⁶ due to the inactive particles.
^A biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium, having ⁹ projections / mm ² and a center line average roughness of the coating surface of 0.1 to 2 nm. . 2. The magnetic recording medium according to claim 1, wherein the water-soluble resin or the water-dispersible resin forming the coating layer is at least one resin selected from the group consisting of an acrylic resin, a polyester resin, and an acryl-polyester resin. Biaxially oriented polyethylene-2,6-naphthalate film. 3. The inert particles contained in the biaxially oriented film have an average particle diameter of 200 nm or less and a content of 0 to 3.
2. The biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium according to claim 1, wherein the content is 0.1% by weight. 4. The film according to claim 1, wherein the biaxially oriented film is a film composed of at least two or more coextruded layers of an A layer and a B layer, wherein the A layer has a coating layer on a side not in contact with another layer. Item 6. Biaxially oriented polyethylene for a magnetic recording medium according to Item 1.
2,6-naphthalate film. 5. The layer B comprises 2,6-naphthalenedicarboxylic acid as a main dicarboxylic acid component, ethylene glycol as a main glycol component, and an isophthalic acid component as a copolymer component in an amount of 0.1 to 10 mol% (total dicarboxylic acid component). 5. A magnetic recording medium according to claim 4, comprising a copolymerized polyethylene-2,6-naphthalate having a diethylene glycol component content of not more than 3 mol% (based on the total amount of all glycol components). Biaxially oriented polyethylene-2,6-naphthalate film. 6. The film has a transverse Young's modulus of 6.9 G.
The sum of the Young's modulus in the vertical direction and the horizontal direction is 12.7 G or more.
The biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium according to any one of claims 1 to 4, which is not less than Pa. 7. A magnetic recording medium comprising a biaxially oriented polyethylene-2,6-naphthalate film for a magnetic recording medium according to claim 1 and a magnetic recording layer provided on the film layer.