JP3288940B2 - Laminated film for magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laminated film for a magnetic recording medium. More specifically, it is suitable for use as a base material for high-density magnetic recording media, which has excellent winding properties, slipperiness, and handling properties, and has excellent electromagnetic conversion properties, dropout properties, running properties of magnetic layers, and durability. And a thermoplastic resin laminated film.

[0002]

2. Description of the Related Art In recent years, remarkable progress has been made in increasing the density of magnetic recording. For example, a ferromagnetic metal thin film in which a ferromagnetic metal thin film is formed on a nonmagnetic support by a physical deposition method such as vacuum evaporation or sputtering or a plating method. Development and commercialization of a magnetic recording medium or a thin-layer coating type magnetic recording medium in which a needle-like magnetic powder such as a metal powder or an iron oxide powder is applied to a thickness of 2 μm or less is in progress.

Examples of the former include, for example, Co-deposited tape (Japanese Patent Application Laid-Open No. 54-147010), Co-Cr
Perpendicular magnetic recording medium made of an alloy (Japanese Patent Laid-Open No. 52-1347)
No. 06) is disclosed. Examples of the latter include, for example, high-density magnetic recording using an ultra-thin layer coating type medium (Technical Report of the Institute of Electronics and Communication Engineers MR94-78 (1995-0)
2)) and the like are disclosed.

Conventional coating type magnetic recording media (magnetic recording media obtained by mixing a magnetic powder in an organic polymer binder and coating on a non-magnetic support) have a low recording density and a long recording wavelength. While the thickness of the magnetic layer is as thick as about 2 μm or more, the metal thin film formed by thin film forming means such as vacuum evaporation, sputtering or ion plating is as thin as 0.2 μm or less. In the case of an ultra-thin layer coating type medium, although a nonmagnetic underlayer has been proposed,
A coating type magnetic layer having a thickness of 0.13 μm has been proposed and is very thin.

For this reason, in the high-density magnetic recording medium described above, the surface condition of the non-magnetic support greatly affects the surface properties of the magnetic recording layer. The surface state of the magnetic support is directly expressed as irregularities on the surface of the magnetic recording layer, which causes noise in the reproduced signal. Therefore, it is desirable that the surface of the nonmagnetic support is as smooth as possible.

[0006] On the other hand, from the viewpoint of handling such as film formation of a base film (non-magnetic support), transport / scratching, winding and unwinding in a processing step, if the film surface is too smooth, the film-to-film mutual contact will occur. The slip property deteriorates, a blocking phenomenon occurs, the shape when rolled around the roll (roll formation) deteriorates, and the product yield decreases, and the product manufacturing cost increases. Therefore, it is desirable that the surface of the base film is rough to some extent in terms of manufacturing cost.

[0007] As described above, the surface of the nonmagnetic support is required to be smooth from the viewpoint of electromagnetic conversion characteristics, and is required to be rough from the viewpoint of handling properties and film cost.

Further, in the case of a vapor-deposited metal thin film type magnetic recording medium, there is a problem in running the metal thin film surface as a problem when actually used. In the case of a coating type magnetic recording medium in which a magnetic substance powder is mixed into an organic polymer bander and applied to a base film, a lubricant is dispersed in the binder to improve the running property of the magnetic surface. However, in the case of a vapor-deposited metal thin film type magnetic recording medium, such measures cannot be taken, and it is extremely difficult to maintain stable running properties. have.

Therefore, in order to supply a base film for a high-density recording medium of excellent quality at low cost, it is necessary to simultaneously satisfy the above contradictory properties.

As a specific method for this purpose, a method of applying a specific coating agent to the film surface to form a discontinuous film (Japanese Patent Publication No. 3-80410, Japanese Patent Application Laid-Open No. Sho 60-180839).
No., JP-A-60-180838, JP-A-60-180
No. 837, JP-A-56-16937, JP-A-58-6
No. 8223), a method for forming a continuous film (Japanese Patent Laid-Open No.
-194772, JP-A-5-210833), a method of forming a different surface on the front and back by a technique such as co-extrusion (JP-A-2-21083).
No. 214657, Japanese Patent Publication No. 7-80282) and a method using + or + as a combination (Japanese Patent Laid-Open No. 3-73409) has been proposed.

[0011]

However, in the conventional method for forming a discontinuous film or a continuous film, although problems such as film-to-film slip and blocking can be solved, fine methods are not included in the film. It is difficult to uniformly disperse the inert particles, and coarse projections due to aggregated particles are likely to occur. As a result, there has been a problem that the quality as a magnetic tape is not stable, such as deterioration of electromagnetic conversion characteristics. Agglomerated particles are more likely to be scraped off by contact with various guide rolls used in the film forming process than monodispersed particles, adhere to and accumulate on the base film to form projections, and when magnetic tape is formed, dropouts are formed. There are also issues that cause it.

On the other hand, inorganic particles have high hardness and are hard to be deformed, so they are excellent in cleaning properties of a magnetic head. Also, although fine particles of various sizes can be easily produced, they have poor affinity with a polymer and particles are not easily removed. Tend to occur. On the other hand, although the organic particles have excellent affinity with the polymer, the hardness is lower than that of the inorganic particles, and the entire particles are deformed by heat or mechanical friction. There was a problem of deterioration.

[0013] Furthermore, the thermal load on the tape is increasing more and more as the equipment (hardware) to be used is miniaturized and the density is increased. In particular, in a high-density magnetic recording medium, the pitch of the magnetic recording tracks is very narrow, around 10 μm, so that a dimensional change of the base film due to the heat history leads to a shift of the tracks, which causes a problem that electromagnetic conversion characteristics are deteriorated.

It is an object of the present invention to provide a high-density magnetic recording medium, particularly a vapor-deposited metal thin film type magnetic recording medium, which solves the above-mentioned drawbacks of the prior art and has excellent abrasion resistance and winding property in a film forming process. In this case, it is an object of the present invention to provide a laminated film having excellent electromagnetic conversion characteristics, dropout characteristics, reduced output, and running durability.

[0015]

SUMMARY OF THE INVENTION The present invention substantially on at least one surface of the polyethylene-2,6-naphthalene dicarboxylate layer A containing no inert particles, the average particle diameter d _B is 5 to 100 nm, the volume Shape factor is 0.1 to π / 6
And a coating layer B made of a water-soluble acrylic resin containing inert particles B having a core-shell type structure in which the outside is more flexible than the inside of the particles.
Wherein the ambient temperature is 80 ° C.
, The dimensional displacement L _M (%) in the film longitudinal direction and the dimensional displacement L _T (%) in the width direction satisfy the following formula (1) when the temperature is changed from 20 ° C. to 20 ° C .; _B (nm)
And the thickness t _B (nm) of the coating layer B satisfy the following expression (2), and the frequency of surface protrusions of the coating layer B due to the inert particles is 1 × 10 ⁶ to 1 × 10 ⁸ / mm ² der is, between the atoms
Surface roughness A of coating layer B measured by force microscope (AFM)
Ra _B (nm) and 10-point average roughness ARz _B (nm) are lower
A laminated film for a magnetic recording medium, which satisfies the expressions (3) and (4) at the same time .

[0016]

Equation 3] _{│L T -L M │ ≦ 8.0 ×} 10 -4 ...... (1) 0.05 ≦ t B / d B ≦ 0.8 ...... (2) 0.7 ≦ ARa B ≦ 2 ... (3) 10 ≦ ARz _B ≦ 100 (4)

The layer A of the laminated film according to the present invention comprises polyethylene-2,6-naphthalenedicarboxylate. The polyethylene-2,6-naphthalenedicarboxylate may be a homopolyester or a copolyester. In the case of a copolyester, examples of the copolymerization component include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyoxyethylene glycol, p-xylene glycol, and 1,4-cyclohexanedimethanol, adipic acid, sebacic acid, and phthalic acid. And other dicarboxylic acid components such as isophthalic acid, terephthalic acid, and 5-sodium sulfoisophthalic acid; and oxycarboxylic acid components such as p-oxyethoxybenzoic acid. The amount of the copolymer component is 2
It is preferably at most 0 mol%, more preferably at most 10 mol%.

Further, a trifunctional or higher polyfunctional compound such as trimellitic acid or pyromellitic acid may be copolymerized. In this case, the polymer can be copolymerized in a substantially linear amount, for example, 2 mol% or less.

In the present invention, it is necessary that the layer A contains substantially no particles. Here, the term "substantially free of particles" does not include externally added particles or internally precipitated particles that form projections on the film surface, but, for example, has a lubricating effect that may be caused by a catalyst necessary for polymerizing the polymer. It means that even a very small amount of particles that do not substantially exhibit may be contained. For example, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, and an antistatic agent can be contained as necessary, except for particles that form surface projections.

In the laminated film of the present invention, the relationship between the dimensional displacement L _M (%) in the film longitudinal direction and the dimensional displacement L _T (%) in the width direction when the environmental temperature is changed from 80 ° C. to 20 ° C. is as follows. Equation (1) needs to be satisfied.

[0021]

Equation 4] _{│L T -L M │ ≦ 8.0 ×} 10 -4 ...... (1) the value of │L _T -L _M │ exceeds 8.0 × 10 ^-4, when the magnetic tape In this case, the magnetic recording track is displaced at a high temperature, causing a decrease in electromagnetic conversion characteristics.

The water-soluble resin constituting the coating layer B in the present invention means a water-soluble organic resin and a water-dispersible organic resin, and includes a water-soluble alkyd resin, phenol resin, epoxy resin, amino resin, polyurethane resin, vinyl acetate resins, vinyl chloride - can be exemplified vinyl acetate copolymer, adhesion to the thermoplastic resin layer a, the protrusion retaining property, in view of lubricity, a water-soluble acrylic resin
is there. The water-soluble acrylic resin may be a homopolymer or a copolymer, or may be a mixture.

The water-soluble acrylic resin includes, for example, acrylic acid esters (alcohol residues such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, Ethylhexyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); methacrylic acid ester (alcohol residue is the same as above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl Hydroxy-containing monomers such as acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-
Amide group-containing monomers such as methylol acrylamide, N-methylol methacrylamide, N, N-dimethylol acrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-phenylacrylamide; N, N-diethylaminoethyl acrylate; Amino group-containing monomers such as N, N-diethylaminoethyl methacrylate; epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether; styrene sulfonic acid, vinyl sulfonic acid, and salts thereof (eg, sodium salt, potassium Such as crotonic acid, itaconic acid, acrylic acid, maleic acid, fumaric acid, and the like. (E.g., a monomer containing a carboxyl group or a salt thereof such as a sodium salt, a potassium salt, or an ammonium salt); a monomer containing an anhydride such as maleic anhydride or itaconic anhydride; other vinyl isocyanate, allyl isocyanate, styrene, Vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester,
Alkyl fumaric acid monoester, acrylonitrile,
(Meth) acrylic monomers such as acrylic acid derivatives and methacrylic acid derivatives, which are made from a combination of monomers such as methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate and vinyl chloride Is preferably contained in an amount of 50 mol% or more, particularly preferably a component containing a methyl methacrylate component.

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

[0025]

[0026]

Particles that are softer on the outside than on the inside used for the coating layer B in the present invention (hereinafter referred to as shell core particles)
B means particles having a multilayer structure in which each of the inside and the outside is composed of substances having different properties. In this case, the multilayer means two or more layers, and may have a property continuously changing in the radial direction. The outer portion of the particles (hereinafter referred to as a shell portion) has a function of reacting with the film base after being coated on the film, or having a function of reacting, melting, softening or deforming by heat treatment to adhere to the film base. The core (hereinafter, referred to as a core) is assumed to have a function as a so-called particle that gives the film an appropriate sliding property and an optimal spacing with the magnetic head together with the shell. From the viewpoint of the division of functions between the shell part and the core part, the shell part is required to have excellent affinity with the film base and to have appropriate physical, chemical, and thermal characteristics at the film forming heat treatment temperature. The core portion is required not to be deformed by mechanical friction or the like and to have a relatively high hardness relative to the shell portion or the base film.

Examples of the material of the core of the shell core particles B include polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate, 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, and barium sulfate may be used.

The material of the shell portion is generally preferably a thermoplastic resin, particularly preferably an acrylic resin, a polyester resin, or the like. Further, in order to increase the affinity with the film base, the film base may have an arbitrary ratio in the molecule. It is preferable to introduce a functional group having a reactivity or affinity with, specifically, a carboxyl group, a hydroxyl group, a glycidyl group, an amide group, an epoxy group, an isocyanate group, or the like. These functional groups may be used alone or in combination of two or more in some cases. The glass transition temperature (hereinafter referred to as Tg) of the shell portion is preferably 80 ° C. or lower, more preferably 20 ° C. or lower.
C or lower is good. When the Tg exceeds 80 ° C., the shell core particles fall off from the film. By using a polymer having such a composition in the shell portion, excellent abrasion resistance can be exhibited.

The volume shape factor (f) of the shell core particle B defined by the following equation is 0.1 to π / 6 (0.524).

[0031]

F = V / d ³ Here, V represents the volume (μm ³ ) of the shell core particles, and d represents the maximum particle size (μm) of the particle projection surface.

The volume shape factor f is preferably 0.3 to π / 6, and more preferably a substantially sphere of 0.4 to π / 6 or a rugby ball-shaped elliptical sphere. When the volume shape factor f is smaller than 0.1, for example, in the case of flaky particles, the magnetic properties of the thin film magnetic layer deteriorate.

The average particle size (d _B ) of the shell core particles B is 5
１００100 nm, preferably 10-50 nm. Further, those having a uniform particle size distribution are preferred. If the average particle size is less than 5 nm, the sliding property and the abrasion resistance deteriorate, and a blocking phenomenon occurs when the film is wound into a roll. 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, making it difficult to provide a high-density magnetic recording medium.

The agglomeration rate of the shell core particles B in the coating layer B (as will be described later in the measurement item (6) of the examples) is preferably 10% or less, more preferably 5% or less. When the agglomeration rate exceeds 10%, the properties of the particle aggregates as abnormal projections become remarkable, and the particles are liable to fall off, which tends to adversely affect the performance as a magnetic tape.

The shell core particles B are contained in the coating layer B such that the frequency of surface protrusions of the coating layer B is 1 × 10 ⁶ to 1 × 10 ⁸ particles / mm ² . If the frequency of the surface protrusions is less than 1 × 10 ⁶ / mm ² , the running durability of the magnetic recording medium is insufficient. On the other hand, when it exceeds 1 × 10 ⁸ / mm ² , the electromagnetic conversion characteristics are adversely affected. The preferred frequency of the surface projections is 2 × 10 ^{6 to} 5 × 10 ⁷ / mm ² , more preferably 3.0 × 10 ^{6 to} 3.0 × 10 ⁷ / mm ² .

The ratio of the average particle diameter d _B of the coating layer the layer thickness t _B (nm) and the shell core particles B of B (t _B / d _B) is 0.05
-0.8, preferably 0.08-0.6, more preferably 0.1-0.5. This ratio (t _B / d _B ) is 0.8
If the ratio exceeds the above range, the effect of forming the projections of the shell core particles B is reduced, and the running durability of the magnetic recording medium is insufficient.
On the other hand, when it is smaller than 0.05, particles on the surface of the laminated film are scraped off by contact with the guide roll in the film forming process, resulting in insufficient running durability, or the scraped particles adhere to and deposit on the film and drop. Cause an increase in out.

The shell core particles B can be produced, for example, by a method in which a polymerizable monomer in the shell is emulsion-polymerized in a system in which the particles in the core are present and the particle surface of the core is coated. Is not limited by the manufacturing method.

In the present invention, the coating layer B is made of polyethylene-
The coating solution containing the above-mentioned shell core particles and a water-soluble resin, preferably a water-soluble coating solution, is applied to at least one surface of the 2,6-naphthalenedicarboxylate layer A and dried. The solid content concentration of this coating solution is 0.2 to 10% by weight, further 0.5 to 5% by weight, particularly 0.7 to 3% by weight.
It is preferable that And this coating liquid, preferably a water-soluble coating liquid, as long as the effect of the present invention is not impaired, other components as desired, for example, a surfactant, a stabilizer,
Dispersants, UV absorbers, thickeners and the like can be added.

The coating is preferably performed on the polyethylene-2,6-naphthalenedicarboxylate film before the final stretching, and the film is preferably stretched in at least one axial direction after the coating. Before or during this stretching, the coating film is dried. Among them, the coating is preferably performed on an unstretched film or a longitudinal (uniaxial) stretched film. The application method is not particularly limited, and examples thereof include a roll coating method and a die coating method.

Atomic force microscope (AF) of the surface of the coating layer B
M), the surface roughness ARa _B (nm) is 0 . 7-2.
5 nm. Also, 10-point average roughness ARz _B (nm)
Is 10 to 100 nm, more preferably 15 to 70 n
m, particularly preferably 20 to 40 nm. This ARa
_{If B} is excessively large , or if ARz _B exceeds 100 nm, the electromagnetic conversion characteristics deteriorate particularly when a metal thin-film magnetic recording medium is used. On the other hand, ARa _B is excessive
If small, or when ARz _B is less than 10nm is insufficient or running durability slip properties are significantly deteriorated,
It tends to stick to the magnetic head and cause squealing of the tape, making it impossible to put it to practical use.

In the present invention, in order to impart the winding property of the laminated film, the coating layer containing the inert particles C on the surface of the polyethylene-2,6-naphthalenedicarboxylate layer A which is not in contact with the coating layer B. C is preferably provided.

The coating layer C may be formed as a coating layer.
Further, it may be formed by a co-extrusion method described later. Coating layer C
Is a coating layer, the inert particles C consist of a single particle or two or more types of particles having different sizes. The average particle size of the largest particle in the case of two or more particles is 20 to 200 n.
m, preferably 30 to 100 nm. The content of the inert particles C in the coating layer C is 3 to 50% by weight, preferably 5% by weight.
３０30% by weight. If the average particle size of the particles C is less than 20 nm or the content is less than 3% by weight, the film cannot be sufficiently rolled, and the film can be unsatisfactorily transported in the film forming step.
In addition, blocking easily occurs. On the other hand, when the average particle size exceeds 200 nm, the particles easily fall off the coating film. Further, when the content of the inert particles C in the coating layer C exceeds 50% by weight, the strength of the coating layer C itself is reduced and the coating layer C is easily chipped.

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

As the resin containing the inert particles C and forming the coating layer, the same resin as the water-soluble resin used for forming the coating layer B can be exemplified. Further, these may further contain a cellulosic resin.

When the coating layer C is formed by a co-extrusion method, the inert particles C consist of a single particle or two or more particles having different sizes. The single particles and the largest particle of the two or more particles have an average particle size of 100 to 1000 nm, preferably 100 to 500 nm. The content of the inert particles C in the coating layer C is 0.001 to 5.0% by weight, preferably 0.005 to 1.0% by weight. This average particle size is 10
If the content is less than 0 nm or the content is less than 0.001% by weight, the winding property of the film, the transportability in the film-forming step, etc. cannot be satisfied, and blocking tends to occur. On the other hand, when the average particle size exceeds 1000 nm, or when the content exceeds 5% by weight, the effect of pushing up the surface on the coating layer B side becomes remarkable, and the electromagnetic conversion characteristics deteriorate.

Examples of the type of the inert particles C include the same particles as those used when the coating layer C is used as the coating layer.

The laminated film of the present invention can be manufactured by a conventionally known method.

For example, in the case of the coating method, first, the polyethylene-2,6-naphthalenedicarboxylate A is extruded from a die into a film at a melting point of Tm ° C. to (Tm + 70) ° C., and then at 40 to 90 ° C. Rapidly solidifies to obtain an unstretched film. Thereafter, the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) according to a conventional method.
(Tg: glass transition temperature of polyester) at a temperature of (Tg + 70) ° C. (2.5 to 8.0 times magnification)
Preferably, the film is stretched at a magnification of 3.0 to 7.5 times, and then a coating solution for forming the coating layers B and C is applied to both sides of the film, and then Tg to (Tg) in a direction perpendicular to the above direction.
At a temperature of +70) ° C, the film is stretched at a magnification of 2.5 to 8.0 times, preferably at a magnification of 3.0 to 7.5 times. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. That is, stretching in two, three, four, or multiple stages may be performed. The total stretching ratio is usually 9 times or more, preferably 12 to 35 times, more preferably 15 to 3 times, as the area stretching ratio.
It is twice. Subsequently, the biaxially oriented film is placed in the (T
g + 70) to (Tm-10) ° C., for example, 180 to
Heat set crystallization at 250 ° C. provides excellent dimensional stability. The heat setting time is preferably 1 to 60 seconds.

In the case of the co-extrusion method, two kinds of polyethylene-2,6-naphthalenedicarboxylate for the layer A and the layer C are put in or before the extrusion die (generally, the former is a multi-manifold system, the latter is a feed block system). ) In the molten state in a molten state, co-extrusion at a suitable thickness ratio to form a two-layer unstretched film, and further applying a coating liquid for forming a film layer B after uniaxial stretching. This is performed in the same manner as the above-mentioned coating method. By this method, a biaxially oriented laminated polyester film having excellent interlayer adhesion can be obtained.

In the production of the laminated film, additives such as a stabilizer, a colorant, and an agent for controlling the resistivity of the molten polymer (antistatic agent) are added to polyethylene-2,6-naphthalenedicarboxylate as required. It can be contained.

The laminated film of the present invention has a ferromagnetic film composed of iron, cobalt, chromium, or an alloy or oxide containing these as a main component, on the surface of the coating layer B by a method such as vacuum deposition, sputtering, or ion plating. A metal thin film layer is formed, and on its surface, a protective layer such as diamond-like carbon (DLC),
By sequentially providing a fluorine-containing carboxylic acid-based lubricating layer and further providing a known back coat layer on the surface of the layer A or the coating layer C, the electromagnetic conversion characteristics such as output in the short wavelength region, S / N, C / N, etc. It is possible to provide a vapor-deposited magnetic recording medium for high-density recording which has excellent dropout and low error rate. This evaporation type electromagnetic recording medium is an analog signal recording H
i8, a digital video cassette recorder (DVC) for recording digital signals, 8 mm data, and extremely useful as a tape medium for DDSIV.

The laminated film of the present invention further comprises a coating layer B
On the surface of, iron or iron-like fine magnetic powder containing iron as a main component is uniformly dispersed in a binder such as polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, and the magnetic layer thickness is 1 μm or less, preferably 0.1 μm or less. １1 μm, and further by providing a back coat layer on the surface of the layer A or the coating layer C by a known method, especially in a short wavelength region,
Excellent electromagnetic conversion characteristics such as N, C / N, dropout,
A metal-coated magnetic recording medium for high-density recording with a low error rate can be obtained. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like may be dispersed and coated on the coating layer B in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. Can also. This metal-coated magnetic recording medium includes 8 mm video for recording analog signals, Hi8, β cam SP, W-VHS, and digital video cassette coder (DV) for recording digital signals.
C), data 8mm, DDSIV, digital β cam,
It is extremely useful as a tape medium for D2, D3, SX and the like.

The laminated film of the present invention further comprises a coating layer B
On the surface of, needle-shaped fine magnetic powder such as iron oxide or chromium oxide,
Alternatively, plate-like fine magnetic powder such as barium ferrite is uniformly dispersed in a binder such as polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, and coated so that the magnetic layer thickness is 1 μm or less, preferably 0.1 to 1 μm. Further, by providing a back coat layer on the layer A or the coating layer C by a known method, the output in a short wavelength region, S / N, C / N
It is possible to obtain a coating type magnetic recording medium for high-density recording having excellent electromagnetic conversion characteristics such as low dropout and error rate. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like is dispersed and coated on the coating layer B in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. You can do it. This oxide-coated magnetic recording medium is useful as a high-density oxide-coated magnetic recording medium such as a data streamer QIC for digital signal recording.

[0054]

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.

(1) Average particle size of particles (average particle size: 0.06 μm or more) CP-50 type centrifugal particle size analyzer manufactured by Shimadzu Corporation (Centrifuga)
l Particle Size Analyzer)
Measure using 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. (Book "Particle Size Measurement Technology", published by Nikkan Kogyo Shimbun, 1975, pp. 242 to 24)
See page 7).

(2) Average Particle Size of Ultrafine Particles (Average Particle Size: 0.06 μm)
The 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) Volume Shape Factor f A photograph of each particle is taken with a scanning electron microscope at a magnification corresponding to the size used, and the maximum diameter of the projected surface is measured using an image analysis processing device Luzex 500 (manufactured by Nippon Regulator). And the volume of the particles are calculated by the following equation.

[0058]

[6] f = in V / d ³ formula, f is the volume shape factor, V is the particle volume (μm ^3),
d represents the maximum diameter (μm) of the particle projection surface.

(4) Layer Thickness The total thickness of the film is randomly determined by a micrometer.
Measure the points and use the average value. The layer thickness is obtained by measuring the layer thickness on the thinner side by the method described below, and subtracting the layer thickness on the thicker side from the layer thickness on the thinner side than the total thickness. That is, using a secondary ion mass spectrometer (SIMS), a concentration ratio (M ⁺ /) of an element originating from the highest concentration particle among the particles in the film having a depth of 5000 nm from the surface layer to the carbon element of the polyester. C ⁺ ) as the particle concentration and a depth of 5000 from the surface
Analyze in the thickness direction to nm. In the surface layer, the particle concentration is naturally low, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, there are cases where the particle concentration once reaches a stable value 1 and then increases or decreases to a stable value 2 and cases where the particle concentration monotonously decreases. Based on this distribution curve, the former has a depth giving a particle concentration of (stable value 1 + stable value 2) / 2, and the latter has a depth at which the particle concentration becomes 1/2 of the stable value 1. (This depth is deeper than the depth that gives a stable value of 1), which is the layer thickness of the layer.

Secondary ion mass spectrometer (SIMS): P
The measurement conditions of 6300 manufactured by ERKIN ELMER are as follows. Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 mA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6.0 × 10 ⁻⁹ Torr E-GUNN: 0.5 KV-3 .0A

When the particles most contained in the range of 5000 nm from the surface layer are organic polymer particles other than silicone resin, it is difficult to measure by SIMS. Therefore, FT-IR (Fourier transform infrared spectroscopy) is performed while etching from the surface. Method), and depending on the particles, a concentration distribution curve similar to the above is measured by XPS (X-ray high electron spectroscopy) or the like, and the layer thickness is determined.

The above is an effective measuring method for a co-extruded layer. In the case of a coated layer, a small piece of a film is fixedly formed with an epoxy resin, and an ultra-thin section having a thickness of about 60 nm is formed with a microtome. The sample is cut parallel to the flow direction), and this sample is taken with a transmission electron microscope (H-8, manufactured by Hitachi, Ltd.).
(Type 00), and the layer thickness is determined from the boundary surface of the layers.

(5) AFM Surface Roughness ARa and ARz Using a J scanner of an atomic force microscope Nano Scope III AFM manufactured by Digital Instruments, ARa (root mean square roughness) and ARz (ARz) calculated under the following conditions: 10 point average roughness) is measured under the following conditions. Probe; single bond silicon sensor Scanning mode: tapping mode Scanning range: 2 μm × 2 μm Pixels: 256 × 256 data points Scanning speed: 2.0 Hz Measurement environment: room temperature, in air

(6) Number and Aggregation Rate of Particle Protrusions Using a SEM (scanning electron microscope, JEOL T-300), 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. The aggregation rate is calculated by the following equation using the same SEM photograph.

[0065]

## EQU00007 ## Aggregation ratio (%) = [(total number of aggregates in which two or more particles aggregate) / (total number of one or more particles)]. Times.100

(7) Difference in Dimensional Displacement in Longitudinal and Width Directions of Film Dimensional displacement in the longitudinal direction of film L _T (%) Using a thermomechanical tester TA-1500 manufactured by Vacuum Riko Co., Ltd., a 15 cm long film. Apply a load of 200 g / mm ² and raise the film environmental temperature from 20 ° C. to 80 at a rate of 2 ° C./min.
The temperature is changed in the order of ° C → 20 ° C, and the dimensional displacement L _T (%) at the time of 80 ° C → 20 ° C is measured. Except that the dimensions displacement L _M (%) load of the film width direction and 60 g / mm ² measures the dimensional displacements L _M (%) in the same manner as described above. The dimensional displacement difference (%) is calculated from the following equation.

[0067]

│L _T −L _M │

(8) Abrasion resistance The film was sampled to a length of 25 to 30 cm and a width of 1/2 inch, and a leather blade was applied to the surface of the coating layer B at an angle of 90 ° and a depth of 0.5 mm. , Load 500g /
The width in the depth direction of the shaving powder adhering to the razor blade when running at a speed of 6.7 cm / sec at a speed of 0.5 inch is determined by taking a microphotograph (× 160). When the width of the shavings in the depth direction is 3 μm or less (◎), 3 to 5 μm (○), 5
μm or more is defined as (×). The smaller the width of the shaving powder in the depth direction, the better the shaving properties.

(9) Winding property After optimizing the winding conditions at the time of slitting, slitting 10 rolls with a size of 560 mm in width and 9000 m in length, and leaving one week after leaving the film free of film wrinkles. Using the book as a good product, the winding property is evaluated based on the following criteria. Number of good rolls Judgment criteria 8 or more ◎ 5 to 7 ○ 3 to 4 × 2 or less ××

(10) Production and Characteristic Evaluation of Magnetic Tape On the surface of the film layer B of the laminated film, a vacuum evaporation method was used.
A ferromagnetic thin film of 100% cobalt is formed in two layers (each layer thickness is about 0.1 μm) so as to have a thickness of 0.02 μm, and a diamond-like carbon (DLC) film and a fluorine-containing carboxylic acid-based lubricating layer are formed on the surface. A back coat layer is formed on the surface of the thermoplastic resin A or the coating layer C by a known method. Then, slit into 8mm width, commercially available 8mm
Load on 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. ◎: +2 dB or more: -1 to +2 dB ×: -4 to -2 dB XX: -4 dB or less

Dropout (D / O) Measurement Using a dropout counter, 15 μs / 18 d
The number per minute is measured in B. ◎: 0 to 10 pieces / min: 10 to 20 pieces / min ×: 20 to 50 pieces / min XX: 50 pieces / min or more

Running Durability C / N was measured after repeating recording and reproduction 500 times at 40 ° C., 80% RH and a tape at a running speed of 85 cm / min.
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 to +0.0 dB with respect to the initial value ×: less than -1.0 dB with respect to the initial value

[Examples 1 and 2, Comparative Examples 1 to 4] Dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, and zinc oxide as a stabilizer were used. Phosphoric acid was added and polymerized by a conventional method to obtain polyethylene-2,6-naphthalenedicarboxylate (PEN) containing substantially no inert particles.

The polyethylene-2,6-naphthalenedicarboxylate was dried at 170 ° C. for 6 hours, supplied to an extruder, melted at a melting temperature of 280 to 300 ° C., extruded from a die into a sheet, and rapidly cooled. Thus, an unstretched film was obtained.

The obtained unstretched film is preheated, further stretched in a longitudinal direction at a film temperature of 135 ° C. at a predetermined ratio between low-speed and high-speed rolls, quenched, and then coated on one surface of the longitudinally stretched film. The aqueous coating liquid containing the water-soluble resin and the inert particles B of the coating layers B of the first and second coatings, and the aqueous coating liquid containing the resin of the coating layer C and the inert particles C on the other surface were each 0.005 μm.
m and a thickness of 0.015 μm (after stretching and drying), and then supplied to a stenter and stretched at 155 ° C. in the horizontal direction at a predetermined magnification. The obtained biaxially stretched film was heat-set with hot air at 200 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having the thickness shown in Table 1.

Tables 1 and 2 show the properties of the obtained laminated film. The stretching ratio in the vertical and horizontal directions in each example was 4 in Example 1.
5 × 4.6, Example 2 was 4.0 × 5.1, Comparative Examples 1 and 2.
Is 3.5 × 5.6, Comparative Example 3 is 4.5 × 4.6, and Comparative Example 4 is 5.5 × 3.0.

[Example 3, Comparative Examples 5 to 7] Polyethylene-2 for layer A and coating layer C shown in Tables 1 and 2
6-Naphthalenedicarboxylate (PEN) is supplied to each of two extruders and laminated using a multi-manifold type coextrusion die, and an aqueous coating solution containing the resin and particles of the coating layer B in Table 1 is coated. A laminated biaxially oriented polyester film was obtained in the same manner as in Example 1, except that the coating was applied to the surface opposite to the surface on the layer C side.

Tables 1 and 2 show the properties of the obtained laminated film. Note that the stretching ratio in the vertical and horizontal directions in each example was 4 in Example 3.
0 × 5.1, Example 4 is 3.5 × 5.6, Comparative Example 5 is 3.0 × 6.5, Comparative Example 6 is 3.5 × 5.6, Comparative Example 7.
Is 4.0 × 5.1.

[0080]

[Table 1]

[0081]

[Table 2]

As is evident from Table 2, the laminated film according to the present invention is excellent in shaving property and winding property in a film forming process, and when used as a magnetic recording medium, electromagnetic conversion characteristics, dropout characteristics, running durability. Extremely excellent. On the other hand, those which do not satisfy the requirements of the present invention cannot satisfy these characteristics at the same time.

[Usability of the Invention] The laminated film of the present invention has a total thickness of about 2.5 to 20 μm and is suitably used as a base for a magnetic recording medium.
The magnetic recording medium is useful for a metal thin film type. In addition, the laminated film substrate of the present invention can be used for a coating type magnetic recording medium having a magnetic layer thickness of 1 μm or less,
It can also be used for digital signal recording type magnetic recording media.

[0084]

According to the present invention, it is useful as a base film of a magnetic recording medium which is excellent in abrasion resistance and winding property in a film forming process and excellent in electromagnetic conversion characteristics, dropout characteristics and running durability. A laminated film can be provided.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-241962 (JP, A) JP-A-7-232420 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (4)

(57) [Claims] On at least one surface of 1. A substantially non polyethylene-2,6-naphthalene dicarboxylate layer A contains inert particles, the average particle diameter d _B is 5 to 100 nm, a volume shape factor of 0.1~π / 6, soluble a containing inert particles B inside from outside flexible core-shell structure of the particles
A laminated film provided with a coating layer B made of a cryl resin, wherein a dimensional displacement L _M (%) in the longitudinal direction of the film and a dimensional displacement L _{T in the} width direction when the environmental temperature is changed from 80 ° C. to 20 ° C. (%) satisfies the following formula (1), the average particle diameter d _B of the inert particles B (nm) coating layer thickness t _B of the B (n
m) satisfies the following formula (2), and the frequency of surface protrusions of the coating layer B due to the inert particles is 1 × 10 ⁶ to 1 × 1.
0 Ri ⁸ / mm ² der, measured by an atomic force microscope (AFM)
Surface roughness ARa _B (nm) of the coating layer B and 10 points
The average roughness ARz _B (nm) is given by the following equations (3) and (4).
A laminated film for a magnetic recording medium, wherein the laminated film is simultaneously filled . [Number 1] _{│L T -L M │ ≦ 8.0 ×} 10 -4 ...... (1) 0.05 ≦ t B / d B ≦ 0.8 ...... (2) Equation 2] 0.7 ≦ ARa _B ≦ 2.5 (3) 10 ≦ ARz _B ≦ 100 (4) 2. A polyethylene-2,6-naphthalenedicarboxylate layer A having a coating layer B on one surface and a coating layer C comprising an application layer containing inert particles C on the other surface. The inert particles C in the coating layer are composed of single particles or two or more types of particles having different sizes, and the average particle size of the single particles or the average particle size of the largest particle among the two or more types of particles is 20. 2. The laminated film for a magnetic recording medium according to claim 1, wherein the content of the inert particles C is 3 to 50% by weight. 3. 3. A polyethylene-2,6-naphthalenedicarboxylate layer A having a coating layer B on one surface and a coating layer C comprising a co-extruded layer containing inert particles C on the other surface, The inert particles C in the co-extruded layer consist of single particles or two or more types of particles having different sizes, and the average particle size of the single particles or the average particle size of the largest particle of the two or more types of particles is 0. 2. The laminated film for a magnetic recording medium according to claim 1, wherein the thickness is 1 to 1 μm, and the content of the inert particles is 0.001 to 5.0% by weight. 3. 4. A magnetic recording medium laminated film according to any one of claims 1 to 3 is used as a base film for high density magnetic recording medium.