JP3288926B2 - Laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laminated film. Specifically, it is excellent in winding property, easy sliding property, handling property, etc., and is suitable for use as a magnetic recording medium excellent in electromagnetic conversion characteristics, dropout, running property of the magnetic layer, durability, especially high density magnetic recording medium. 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 magnetic recording media and thin-layer coating type magnetic recording media in which needle-like magnetic powder such as metal powder or iron oxide powder is applied to a thickness of 2 μm or less are progressing.

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 publication) is known. As an example of the latter, for example, high-density magnetic recording using an ultra-thin layer coating type medium (IEICE Technical Report MR94-78 (1995-02)) is known.

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 deposition, sputtering or ion plating is very thin, not more than 0.2 μm, and extremely thin. In the case of a layer coating type medium, the non-magnetic underlayer
It is very thin with a thickness of 3 μm.

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.

On the other hand, from the viewpoint of handling such as film formation of the base film, conveyance / damage, winding and unwinding in the processing step, if the film surface is too smooth, the slipperiness between the film and the film deteriorates. The blocking phenomenon occurs, and the shape when wound on a roll (roll formation) deteriorates, resulting in a decrease in product yield and a rise in product manufacturing cost. Therefore, from the viewpoint of manufacturing cost, it is desirable that the surface of the support is as rough as possible.

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, a serious problem when actually used is running property of the metal thin-film surface. 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. Although it is possible, in the case of a vapor-deposited metal thin film type magnetic recording medium, such measures cannot be taken, and it is very difficult to keep the running property stable, and the running property is particularly poor under high temperature and high humidity conditions. It has problems such as.

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 measure, a specific coating agent is applied to the film surface to form a discontinuous film (Japanese Patent Publication No. 3-80410, JP-A-60-180839).
No., JP-A-60-180838, JP-A-60-180
No. 837, JP-A-56-16937, JP-A-58-6
8223), a method of forming a continuous film having fine projections (JP-A-5-194772, JP-A-5-210)
No. 833), a method of forming a different surface by co-extrusion or the like (JP-A-2-214657, JP-B-7-802).
No. 82), a method using the above + or a combination of + (JP-A-3-73409) and the like have been proposed.

[0011]

However, in the conventional method for forming a discontinuous film or a continuous film having fine projections, problems such as slipping between films and blocking can be solved. It is difficult to uniformly disperse fine inactive particles therein, and coarse protrusions due to aggregated particles are apt to be generated. Therefore, there has been a problem that the quality as a magnetic tape is unstable, such as deterioration of electromagnetic conversion characteristics. Agglomerated particles are more likely to be scraped off by contact with various guide rolls in the film forming process than monodispersed particles, and adhere to and accumulate on the base film to form protrusions, which can cause dropout when used as a magnetic tape. There is also. In addition, even if the dispersibility in the film is excellent when viewed in a fine visual field, the presence of coarse aggregated particles when viewed in a macro visual field causes problems such as an increase in dropout when used as a magnetic tape. .

In general, inorganic particles are high in hardness and are not easily deformed, so that they are excellent in cleaning properties of a magnetic head and easy to produce fine particles of various sizes. It tends 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 particle is deformed by heat or mechanical friction. There is a problem of deterioration.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to be excellent in abrasion and winding properties in a film forming process, and to be used as a vapor-deposited metal thin film type magnetic recording medium or an ultra-thin layer coating type magnetic recording medium. It is an object of the present invention to provide a laminated film having excellent electromagnetic conversion characteristics, dropout characteristics, and running durability.

[0014]

The object of the present invention is to provide, according to the present invention, first, an aqueous acrylic resin layer on at least one surface of a thermoplastic resin layer A substantially containing no inert particles. /> laminate film of fat and an average particle diameter d _B are laminated 5 to 100 nm, the coating layer B having a volume shape factor is outside from inside a 0.1～Pai / 6 containing the particles B of the flexible core-shell structure And the average particle diameter d _B (nm) of the particles B, the particle B
The particle diameter dc _B (nm) of the core portion and the layer thickness t _B (nm) of the coating layer B satisfy the following expressions (1) and (2) at the same time,
The frequency of surface protrusions due to the particles B of the coating layer B is 1 × 10 ⁶ to
1 × 10 ⁸ / mm ² , atomic force microscope (AFM)
Surface roughness ARa _B (nm) of the coating layer B measured in
The 10-point average roughness ARz _B (nm) is given by the following equation (3):
(4) is satisfied at the same time, and the frequency of protrusions having a height of 0.5 μm or more due to the macro aggregate of particles B is 2 to 25 / cm
It is accomplished by lamination film, which is a ^2.

[0015]

[ Expression 5] 1.02 ≦ d _B / dc _B ≦ 2.0 (1)

[0016]

[Formula 6] 0.08 ≦ t _B / dc _B ≦ 0.6 (2)

(Equation 7) 0.7 ≦ ARa _B ≤2.5 ... (3)

(Equation 8) 10 ≦ ARz _B ≦ 100 ... (4)

Examples of the thermoplastic resin in the present invention include polyester resins, polyamide resins, polyimide resins, polyether resins, polycarbonate resins, polyvinyl resins, and polyolefin resins. Of these, polyester-based resins and aromatic polyesters are preferred.

As the aromatic polyester, polyethylene terephthalate, polyethylene isophthalate,
Preferably, polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate and the like can be preferably exemplified. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are preferred.

The polyester may be a homopolyester or a copolyester. In the case of a copolyester, as a copolymerization component of polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate, for example, diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylene glycol, 1,4-cyclohexanedimethanol Diol components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (for polyethylene-2,6-naphthalenedicarboxylate), 2,6-naphthalenedicarboxylic acid (for polyethylene terephthalate), Other dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, and oxycarboxylic acid components such as p-oxyethoxybenzoic acid are exemplified. Incidentally, the amount of the copolymer component is 20 mol% or less,
It is preferably at most 0 mol%. Further, a trifunctional or higher polyfunctional compound such as trimellitic acid or pyromellitic acid can be copolymerized. In this case, the polymer is preferably copolymerized in a substantially linear amount, for example, 2 mol% or less.

In the present invention, it is necessary that the thermoplastic resin layer A does not substantially contain 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,
For example, it means that a very small amount of particles having substantially no lubricating effect, which may be generated by a catalyst necessary for polymerization of polyester, may be contained. For example, other additives such as an antioxidant, a heat stabilizer, and an antistatic agent (excluding particles that form surface protrusions) can be contained as necessary.

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

The aqueous acrylic resin may be, for example, an acrylate ester (alcohol residues include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, and 2-ethylhexyl). Group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); methacrylic acid ester (the alcohol residue is the same as above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate Hydroxy-containing monomers such as 2,2-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.

Such an aqueous 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.

[0024]

[0025]

In the present invention, the particles B which are softer on the outside than on the inside (hereinafter, referred to as shell core particles) B are particles having a multilayer structure in which the inside and the outside are made 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 considered 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 and the core, the shell is required to have excellent affinity with the film base and to have appropriate physical, chemical, and thermal properties 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.

As the material of the core portion of the shell core particles B, 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 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. Further, the glass transition temperature (hereinafter referred to as Tg) of the shell portion is preferably 80 ° C. or less, more preferably 20 ° C.
The following is good. If 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 ratio (d _B / dc _B ) between the particle diameter d _B (nm) of the shell core particles B and the particle diameter dc _B (nm) of the core is 1.
02 to 2.0, preferably 1.04 to 1.5. If the ratio (d _B / dc _B ) exceeds 2.0 , it will strongly take on the properties of organic particles made of only the material of the shell portion having no multilayer structure, and deformation due to heat or mechanical friction will occur. growing. On the other hand, if it is less than 1.02, the properties of inorganic particles become stronger, the adhesion to the film is reduced, the particles fall off and the like tend to increase, and the agglomeration rate also tends to increase. In either case, the workability of the film and the performance of the magnetic tape are liable to be adversely affected, which is not preferable.

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

[0031]

F = V / d ³ Here, V represents the volume (μm ³ ) of the particle, and d represents the maximum diameter (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 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 of the shell core particles B is 5 to 100.
nm, preferably 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 slip property and the abrasion resistance deteriorate, and when the film is wound into a roll, a blocking phenomenon occurs. On the other hand, if the average particle size exceeds 100 nm, the particles will fall off and the abrasion resistance will deteriorate. Further, the spacing with the magnetic head is increased, and it is difficult to provide a high-density magnetic recording medium.

The agglomeration ratio of the shell core particles B in the coating layer B 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 projection frequency of the shell core particles B having a height of 0.5 μm or more due to macro-aggregates is 25 particles / cm ^2.
It is as follows. If the frequency of protrusions due to the macro-aggregates exceeds 25 protrusions / cm ² , dropout becomes remarkable and poses a practical problem. In addition, the lower limit of the projection frequency is 2 / c.
m ² .

The shell core particles B are contained in the coating layer B in such an amount that the frequency of surface protrusions of the coating layer B is 1 × 10 ⁶ to 1 × 10 ⁸ particles / mm ² . This surface protrusion 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 ⁸ / mm ² , the electromagnetic conversion characteristics are adversely affected. The more preferable surface protrusion frequency is 2 × 10 ^{6 to} 5 × 10 ⁷ / mm ² , further preferably 3.0 × 10 ^{6 to} 3.0 × 10 ⁷ / mm ² .

The ratio ( t _B / dc) between the layer thickness t _B (nm) of the coating layer B and the particle size dc _B (nm) of the core portion of the shell core particles B
_B ) is 0.08 to 0.6, preferably 0.1 to 0.5
It is. If the ratio (t _B / dc _B) is more than 0.6, decreases the outgrowth action of shell-core particles B, running durability when formed into a magnetic recording medium is insufficient. On the other hand, when it is smaller than 0.08 , the particles are cut off by contact with various guide rolls in the film forming process, and the running durability becomes insufficient,
The shaved particles adhere to and deposit on the film, causing an increase in dropout.

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

The coating layer B in the present invention is formed by applying and drying a coating liquid containing the above-mentioned shell core particles and an aqueous resin, preferably an aqueous coating liquid, on at least one surface of the thermoplastic resin layer A. The solid content of the liquid is 0.2 ~
10% by weight, more preferably 0.5 to 5% by weight, especially 0.7 to 5% by weight
Preferably it is 3% by weight. The coating liquid, preferably an aqueous coating liquid, may optionally contain other components such as a surfactant, a stabilizer, a dispersant, a UV absorber, a thickener and the like as long as the effects of the present invention are not impaired. Can be added.

The coating is preferably performed on the thermoplastic resin 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 thermoplastic resin film or a longitudinally (uniaxially) stretched thermoplastic resin film. The application method is not particularly limited, but examples include a roll coating method and a die coating method.

By using the shell core particles B in the present invention, the particle aggregation rate and the frequency of macro aggregates in the coating layer B are remarkably improved as compared with the case where conventional inorganic or organic particles are used. However, it is considered that the reasons for this include an increase in repulsion between particles due to a change in potential on the particle surface, a change in a stable pH region, and the like.

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 and the 10-point average roughness ARz _B (nm) is 1
0 to 100 nm, more preferably 15～70Nm, particularly preferably Ru 20~40nm der. Over-the AR a _B
If every large, or if the ARz _B exceeds 100 nm, the electromagnetic conversion characteristics deteriorate particularly when the metal thin film type magnetic recording medium. On the other hand, when the too small <br/> AR a _B, or if ARz _B is less than 10 nm, or insufficient running durability slip properties are significantly deteriorated, the tape squeaking stuck to the magnetic head It is likely to be unable to be put to practical use.

In the present invention, it is preferable to provide a coating layer C containing inert particles C on the surface of the thermoplastic resin layer A which is not in contact with the coating layer B in order to impart the film winding property.

The coating layer C may be formed as a coating layer.
Further, it may be formed by a co-extrusion method described later. When the coating layer C is a coating layer, the contained inert particles C consist of a single particle or two or more types of particles having different sizes, and the single particles and the average of the largest particles in the case of two or more types of particles. The particle size is between 20 and 200 nm, preferably between 30 and 100 nm. The content of the inert particles C in the coating layer C is 3 to 50% by weight, preferably 5 to 30% by weight. When the average particle size of the particles C is less than 20 nm or less than 3% by weight, the film winding property, the transport property in the film forming step, and the like are insufficient, and blocking is easily caused. . On the other hand, when the average particle size exceeds 200 nm, the particles easily fall off the coating film. 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 decreases, and the coating layer C is easily chipped.

The inert particles C contained in the coating 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 dioxide, carbon black, barium sulfate, etc. may be used.
No.

As the resin containing the particles C and forming the coating layer, the same resin as the aqueous resin used for forming the coating layer B can be exemplified. These may further contain a cellulose resin.

When the coating layer C is formed by a co-extrusion method, the contained inert particles C consist of a single particle or two or more types of particles having different sizes. The largest particles have an average particle size of 100 to 100
0 nm, preferably 100-500 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. When the average particle size is less than 100 nm or the content is less than 0.001% by weight, the film is insufficient in winding property, transportability in a film forming process, and the like, and tends to cause blocking. When the average particle size exceeds 1000 nm, or when the content exceeds 5.0% by weight, the coating layer B
The effect of pushing up to the side surface 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 or a method accumulated in the art.

For example, in the case of a biaxially oriented polyester film, in the case of the coating method, first, the thermoplastic resin A is extruded from a die into a film at a melting point of Tm.degree. C. to (Tm + 70) .degree. 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 the polyester) at a temperature of 2.5 to 8.0 times, preferably 3.0 to 7.5 times, and then at a temperature of (Tg + 70) ° C. The coating liquids for forming the layers B and C are applied to both sides of the film, and then at a temperature perpendicular to the above direction at a temperature of Tg to (Tg + 70) ° C. at a magnification of 2.5 to 8.0 times, preferably 3.0 times. ~
Stretch at 7.5 times magnification. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. That is, two stages, three
It is preferable to perform stretching in multiple stages, four stages, or multiple stages. The total stretching ratio is usually 9 times or more, preferably 12 times or more, as the area stretching ratio.
３５35 times, more preferably 15 to 32 times. Subsequently, the biaxially oriented film is moved from (Tg + 70) to (Tm
Heat setting crystallization at a temperature of -10) ° C, for example, 180 to 250 ° C, provides excellent dimensional stability.
The heat fixing time is preferably 1 to 60 seconds.

In the case of the co-extrusion method, two kinds of thermoplastic resins for the layers A and C are melted in the extrusion die or before the die (generally, the former is called a multi-manifold type, and the latter is called a feed block type). Laminated and composite, co-extruded with a suitable thickness ratio to form a two-layer laminated unstretched film,
The coating method is preferably performed in the same manner as the above-mentioned coating method except that a coating liquid for forming the coating layer B is applied after uniaxial stretching. By this method, a biaxially oriented laminated polyester film having good interlayer adhesion can be obtained.

In the production of the laminated film, the thermoplastic resin may optionally contain additives other than the above-mentioned inert particles, such as a stabilizer, a colorant, and a specific resistance modifier for the molten polymer.

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 thermoplastic resin layer A or the coating layer C, the output in the short wavelength region, S / N, C
/ N or the like, and can be a vapor-deposited magnetic recording medium for high-density recording with low dropout and low error rate. 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 DD.
It is extremely useful as a tape medium for SIV.

The laminated film of the present invention further comprises a coating layer B
On the surface of, iron or fine needle-shaped magnetic powder containing iron as a main component is uniformly dispersed in a binder such as vinyl chloride, vinyl chloride / vinyl acetate copolymer, and the magnetic layer thickness is 1 μm or less, preferably 0.1 to 1 μm, and further by providing a back coat layer on the surface of the thermoplastic resin layer A or the coating layer C by a known method, particularly in the short wavelength region, such as S / N and C / N. A metal-coated magnetic recording medium for high-density recording with excellent electromagnetic conversion characteristics and low dropout and error rate can be obtained. 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 also. This metal-coated magnetic recording medium includes 8 mm video for recording analog signals, Hi8, β cam SP, W-VHS,
Digital video cassette coder (DVC) for recording digital signals, 8mm data, DDSIV, digital β
It is extremely useful as a tape medium for cams, 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 vinyl chloride, vinyl chloride / vinyl acetate copolymer, and applied 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 thermoplastic resin layer A or the coating layer C by a known method, output in a short wavelength region, S /
Excellent electromagnetic conversion characteristics such as N, C / N, dropout,
A coating type 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 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.

The above-mentioned W-VHS is a VTR for recording an analog HDTV signal, and DVC is a digital HDTV signal.
The film of the present invention is applicable to recording of a TV signal, and can be said to be a very useful base film for these magnetic recording media for HDTV-compatible VTRs.

[0057]

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 diameter I of particles (average particle diameter: 0.1.
06μm 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. (Book
"Granularity measurement technology", published by Nikkan Kogyo Shimbun, 1975, page 2
42-247).

(2) Average particle size II of particles (average particle size: 0.
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, Nicomp In
instruments Inc. NICOMP M
ODEL 270 SUBMICRON PARTIC
Expressed as the "equivalent spherical diameter" of the particle at the point of 50% by weight of the total particle as determined by LE SIZER.

(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.

[0061]

Equation 10] During f = 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 projection surface.

(4) Layer thickness and core particle size of core-shell particles 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 ⁺ ) is defined as the particle concentration and the depth from the surface is 500
Analysis in the thickness direction is performed up to 0 nm. In the surface layer, the particle concentration is low due to the interface of the surface, 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 stable 1
Is greater than the depth of the layer).

The measurement conditions are as follows. Measuring device Secondary ion mass spectrometer (SIMS): PERKIN
ELMER 6300 Measurement conditions Primary ion species: O2 + Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6.0 × 10 ⁻⁹ Torr E-GUNN: 0 When the particles most contained in the range of 5000 nm from the surface layer are organic polymer particles other than the silicone resin, SI
Since measurement is difficult with MS, the same concentration distribution curve as above is measured by FT-IR (Fourier transform infrared spectroscopy) while etching from the surface, or XPS (X-ray high electron spectroscopy) depending on the particles, and the layer is measured. Find the thickness.

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 (film thickness of about 60 nm) is formed with a microtome. Cut in parallel to the flow direction), and this sample was taken with a transmission electron microscope (H-H
(Type 800), and the layer thickness is determined from the boundary surface between the layers. The particle size of the core portion of the core-shell particles is also determined by observing the cross section of the ultrathin section.

(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 (RMS) are calculated under the following conditions. 10 point average roughness) is measured. 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 of Particle Protrusions, Aggregation Rate The surface of the laminated film was magnified 30,000 times at an angle of 0 ° using an SEM (scanning electron microscope, JEOL T-300 type).
, 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. Aggregation rate (%) = [(total number of aggregates in which two or more particles aggregate) / (total number of one or more particles)] × 100

(7) Height and frequency of protrusions by macro-aggregates An aluminum thin film is formed on the surface of the film layer B of the laminated film by a vacuum evaporation method so as to have a thickness of 0.2 μm from an angle of 45 °. Scan and observe 1 cm ² with a transmission microscope at a magnification of 400 ×, and count the number of transmitted lights whose maximum length (corresponding to the projection height) of the non-evaporated portion due to the shadow of the projection is 0.2 mm or more. (That is, the height is 0.2 mm / 400
= Count the frequency of protrusions due to coarse macro-aggregates of 0.5 μm or more. )

(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 0.5 cm and a speed of 6.7 cm / sec was 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, the width is 560 mm ×
A slit of 10 rolls having a size of 9000 m and slitting after leaving for one week and having no film wrinkles is evaluated as a good product, and 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 of Magnetic Tape and Evaluation of Characteristics The surface of the film layer B of the laminated film was formed by a vacuum evaporation method.
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

Example 1 Dimethyl terephthalate and ethylene glycol were added, manganese acetate was used as a transesterification catalyst, antimony trioxide was used as a polymerization catalyst, and phosphorous acid was used as a stabilizer. Polyethylene terephthalate (P) containing no inert particles
ET).

This polyethylene terephthalate was converted to 170
After drying at 3 ° C. for 3 hours, the mixture was fed to an extruder and melted at a melting temperature of 280.
It was melted at ~ 300 ° C, extruded from a die into a sheet, and quenched to obtain an unstretched film having a thickness of 82 µm.

The unstretched film thus obtained is preheated, stretched 3.2 times in the machine direction at a film temperature of 95 ° C. between low-speed and high-speed rolls, quenched, and then coated on one side of the vertically-stretched film. The aqueous coating liquid containing the aqueous resin and the particles B of the coating layer B in Tables 1 and 2, and the aqueous coating liquid containing the resin and the particles C of the coating layer C on the other opposite surface were each 0.005 μm.
It was applied to a thickness of 0.015 μm (after stretching and drying), was subsequently supplied to a stenter, and was stretched 4.1 times in the horizontal direction at 110 ° C. The obtained biaxially stretched film was
It was heat-set with hot air of 0 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 5.9 μm.

[0077] [ratio Comparative Examples 1, 2, 5, 6] coating layer B and the coating layer C resin and particles, the thermoplastic resin layer A
The laminated biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the thickness of the film was changed as shown in Tables 1 and 2.

Example 3, Comparative Example 9 The polyethylene terephthalate for the thermoplastic resin layer A and the coating layer C shown in Tables 1 and 2 were supplied to two extruders, respectively, to form a multi-manifold type co-extrusion die. And a laminated biaxially oriented polyester film in the same manner as in Example 1 except that the aqueous coating solution containing the resin and the particles of the coating layer B in Table 1 is applied to the surface opposite to the surface on the coating layer C side. I got

[Examples 4 and 5, Comparative Examples 3, 7, 8, 1
1] Polyethylene-2,6-naphthalate (in the same manner as in Example 1) except that the particles shown in Tables 1 and 2 were used, and dimethyl 2,6-naphthalenedicarboxylate was used in the same molar amount instead of dimethyl terephthalate. PEN).

After drying this polyethylene-2,6-naphthalate at 170 ° C. for 6 hours, an unstretched film satisfying each example and comparative example was obtained in the same manner as in Example 1.

The obtained unstretched film was preheated, further stretched 3.6 times in the machine direction at a film temperature of 135 ° C. between low-speed and high-speed rolls, quenched, and then the film layers shown in Tables 1 and 2 The aqueous coating solution of B and the coating layer C was applied in the same manner as in Example 1, then supplied to a stenter, and stretched 6.0 times in the horizontal direction at 155 ° C. The obtained biaxially stretched film was
This was heat-set with hot air of 0 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film.

[0082] [ratio Comparative Examples 4, 10] coating layer B and the coating layer C resin and particles, the thermoplastic resin layer A
Was changed as shown in Tables 1 and 2, and instead of polyethylene terephthalate, polyethylene-2,6-naphthalate was used as shown in Tables 1 and 2, and the laminated biaxial orientation was performed in the same manner as in Example 1. A polyester film was obtained.

[0083]

[Table 1]

[0084]

[Table 2]

[0085] The above examples, surface characteristics of the multilayer biaxially oriented film obtained in Comparative Example, the ratio d _B / dc _B of the particle diameter of the particle diameter d _B and the core portion of the shell core particles, the layer of the coating layer B thickness t _B
Ratio t _B / dc between the diameter of the core portion of the shell core particles and the particle diameter dc _B
Table 3 shows the properties of _B , the abrasion resistance, the winding property, and the properties of the magnetic tape deposited with a ferromagnetic thin film using this film.

[0086]

[Table 3]

As is clear from Table 3, 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, has electromagnetic conversion characteristics, dropout characteristics, and running durability. Extremely excellent. On the other hand, those which do not satisfy the requirements of the present invention cannot simultaneously satisfy these characteristics.

[0088]

According to the present invention, it is useful as a base film of a magnetic recording medium having excellent 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 (9)

(57) [Claims] On at least one surface of 1. A substantially thermoplastic resin layer A containing no inert particles, acrylic resin and average particle diameter d _B of aqueous 5 to 100 nm, a volume shape factor of zero.
A laminated film in which a coating layer B containing particles B having a core-shell type structure whose outside is softer than the inside, which is 1 to π / 6, is laminated, wherein the average particle diameter d _B (nm) of the particles B and the core of the particles B Part particle size dc _B (nm) and layer thickness t of coating layer B
_B (nm) satisfies the following expressions (1) and (2) at the same time, and the frequency of surface protrusions due to the particles B of the coating layer B is 1 × 10 ⁶ to 1
× 10 ⁸ / mm ² , measured by atomic force microscope (AFM)
Roughness ARa _B (nm) and 1
The zero point average roughness ARz _B (nm) is calculated by the following formulas (3) and (4).
, And the frequency of protrusions having a height of 0.5 μm or more due to the macro-aggregates of the particles B is 2 to 25 / cm ² . 1.01 ≦ d _B / dc _B ≦ 2.0 (1) 0.02 ≦ t _B / dc _B ≦ 0.6 (1) 2) Equation 3] _{0.7 ≦ ARa B ≦ 2.5 ······ (} 3) [Expression 4] _{10 ≦ ARz B ≦ 100 ······ (} 4) 2. The laminated film according to claim 1, wherein the aggregation rate of the particles B in the coating layer B is 10% or less. 3. A coating layer C comprising a coating layer containing inert particles C is laminated on a surface of the thermoplastic resin layer A which is not in contact with the coating layer B, and the inert particles C in the coating layer are formed. Is composed of a single particle or two or more particles of different sizes, the average particle size of the single particles or the average particle size of the largest particle of the two or more particles is 20 to 200 nm, and the content of the particles C Is from 3 to 50% by weight. 4. A coating layer C comprising a co-extruded layer containing inert particles C is laminated on a surface of the thermoplastic resin layer A which is not in contact with the coating layer B, and the inert particles in the co-extruded layer are C is a single particle or two or more particles having different sizes, the average particle size of the single particles or the average particle size of the largest particle of the two or more particles is 0.1 to 1 μm, and the particles C The laminated film according to claim 1, wherein the content of the laminated film is 0.001 to 5.0% by weight. 5. The laminated film has a total thickness of 2.5 to 20 μm.
The laminated film according to any one of claims 1 to 4 , wherein m is m. 6. A laminated film according to any one of claims 1 to 5 which is a base film of a magnetic recording medium. 7. The laminated film according to claim 6 , wherein the magnetic recording medium is a metal thin film type magnetic recording medium. 8. The laminated film according to claim 6 , wherein the magnetic recording medium is a coating type magnetic recording medium having a magnetic layer having a thickness of 1 μm or less. 9. The laminated film according to claim 6, wherein the magnetic recording medium is a digital signal recording type magnetic recording medium.