JP3310165B2 - 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 excellent in electromagnetic conversion characteristics, dropout, running property of the magnetic layer, excellent durability, especially for high density magnetic recording medium. It relates to a suitable 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.

In the above-described high-density magnetic recording medium, the surface condition of the non-magnetic support greatly affects the surface properties of the magnetic recording layer. The surface condition of the magnetic recording layer 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 an increase 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 it has excellent dispersibility in the film when viewed in a fine visual field, the presence of coarse aggregated particles when viewed in a macro visual field causes problems such as increased dropout when used as a magnetic tape. is there.

In general, inorganic particles have high 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. 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 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]

According to the present invention, first, inert particles A having an average particle diameter of 40 to 400 nm and a volume shape factor of 0.1 to π / 6 are firstly prepared. on at least one surface of the thermoplastic resin layer a projection frequency contains an amount containing from 05,000 to 50,000 pieces / mm ^2, flexibility outside than inside acrylic resin and average particle diameter d _B of the aqueous is 5~100nm A laminated film having laminated thereon a coating layer B containing particles B having a fine core-shell structure, wherein the average particle diameter d of the particles B is
_B (nm), the particle size dc _B (nm) of the core portion of the particle B, and the layer thickness t _B (nm) of the coating layer B simultaneously satisfy the following expressions (1) and (2), and the particles of the coating layer B The frequency of surface protrusions due to B is 1 × 10 ⁶ to 1 × 10 ⁸ / mm ² , and the surface roughness ARa of the coating layer B measured by an atomic force microscope (AFM)
_B (nm) and 10-point average roughness ARz _B (nm) simultaneously satisfy the following expressions (3) and (4), and the frequency of protrusions whose height due to the macroaggregate of particles B is 0.5 μm or more is 25 Pieces/
It is achieved by laminating a film which is characterized in that cm ² or less.

[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.

Further, the above-mentioned polyester is an alkali metal salt derivative of sulfonic acid which is non-reactive with the polyester,
At least one of a polyalkylene glycol or the like substantially insoluble in the polyester may be mixed so as not to exceed 5% by weight.

The thermoplastic resin layer A in the present invention has an average particle size of 40 to 400 nm, preferably 50 to 200 n.
m, more preferably 60 to 120 nm, and a particle A having a volume shape factor of 0.1 to π / 6 having a surface projection frequency of 0.5 to 5 (10,000 particles / mm ² ), preferably 0.75 ~ 4
(10,000 pieces / mm ² ), more preferably 1-3 (10,000 pieces / mm ² )
² ) It is contained. The average particle size of the particles A is 40 n
If it is less than m, the friction of the magnetic layer against the VTR head is high, the repetitive running durability of the magnetic layer is poor, and the winding property in the film forming process is also poor. On the other hand, when the average particle size is larger than 400 nm, the electromagnetic conversion characteristics as a high-density magnetic recording medium are hindered. If the frequency of surface protrusions caused by the particles A is less than 0.5 (10,000 / mm ² ), the friction of the magnetic layer against the VTR head is still high, the durability of the magnetic layer for repeated running is poor, and the film is wound in the film forming process. Bad nature. On the other hand, if the frequency is 5
If it is larger than (10,000 pieces / mm ² ), the electromagnetic conversion characteristics as a high-density magnetic recording medium will be affected. Furthermore, the shape of the particles A is

[0023]

F = V / d _A ³ (where V represents the volume (μm ³ ) of the fine particles and d _A represents the maximum diameter (μm) of the projection surface of the fine particles). Must satisfy 0.1 to π / 6. Further, those having a volume shape factor f of 0.3 to π / 6 are preferable, and those having a volume shape factor f of 0.4 to π / 6 which are substantially spherical or rugby ball-shaped elliptical spheres are particularly preferable. 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 types of the particles A include cross-linked silicone resin, cross-linked polystyrene, cross-linked styrene-divinylbenzene copolymer, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene Fluoride, polyacrylonitrile, fine particles made of a heat-resistant organic polymer such as benzoguanamine resin, silica,
Any fine particles made of an inorganic compound such as alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, barium sulfate and the like may be used.

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 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. Acrylic resins of this aqueous may be either a copolymer of a single polymer, 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 with a functional group in the molecule, or can be crosslinked with a crosslinking agent such as a melamine resin or an epoxy compound.

[0028]

[0029]

The particles B (hereinafter referred to as shell core particles) which are softer on the outside than on the inside in the present invention 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 part (hereinafter referred to as a shell part) of the particles 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 performing heat treatment to adhere to the film base. The core portion) 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 portion. From the viewpoint of the division of functions between the shell and the core, the shell must have excellent affinity with the film base and have appropriate physical, chemical, and thermal properties at the film formation and heat treatment temperatures. 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 portion of the shell core particles B include polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride,
Organic materials such as polyacrylonitrile and benzoguanamine resin, silica, alumina, titanium dioxide, kaolin,
Any of inorganic materials such as talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, 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 may have an arbitrary ratio in the molecule. It is preferable to introduce a functional group having reactivity or affinity with the base, 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 addition, the glass transition temperature of the shell (hereinafter referred to as Tg)
) Is preferably 80 ° C or lower, more preferably 2 ° C or less.
0 ° C or less is good. If the Tg exceeds 80 ° C., the shell core particles fall off from the film. By using such a polymer having the above composition in the shell portion, excellent abrasion resistance can be exhibited.

The ratio (d _B / dc _B ) of the particle diameter d _B (nm) of the shell core particles B to the particle diameter dc _B (nm) of the core portion 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 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 diameter is reduced below 5 nm, the slip 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 aggregation rate 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 frequency of protrusions having a height of 0.5 μm or more due to macro aggregates of the shell core particles B is 25 / cm.
² or less. The projection frequency due to this macro aggregate is 25
When the number of pieces / cm ² is exceeded, dropout becomes remarkable,
This is a practical problem.

The shell core particles B are contained in the coating layer B in such an amount that the frequency of surface projections 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. More preferably, the frequency of surface projections is 2 × 10 ^{6 to} 5 × 10 ⁷ / mm ² , and further preferably, 3.0 × 10 ^{6 to} 3.0 × 10 ⁷ / mm ^2.
It is.

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 by, for example, 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.

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 the 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. And this coating liquid, preferably an aqueous 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 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 agglomeration rate and the frequency of macroaggregates 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) has a surface roughness ARa _B of 0 . A 7～2.5Nm, and 10-point average roughness ARz _B is 10 to 100 nm,
More preferably 15 to 70 nm, particularly preferably 20 to
~40nm Ru Der. If this AR a _B is excessively 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, if AR a _B is too small, or A
When Rz _B (nm) is less than 10 nm, the slipperiness is extremely deteriorated and the running durability is insufficient, or the tape sticks to the magnetic head to cause squealing, so that the tape cannot 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. On the other hand, when the average particle size exceeds 1000 nm, or when the content exceeds 5.0% 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 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 26 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 layers A and C are melted in or before the extrusion die (generally, the former is called a multi-manifold system, and the latter is called a feed block system). It is performed in the same manner as the above-mentioned coating method except that a two-layer laminated unstretched film is formed by co-extrusion to obtain a suitable thickness ratio to form a two-layer unstretched film, and after uniaxially stretching, a coating solution for forming a film layer B. And good. By this method, a biaxially oriented laminated polyester film having good interlayer adhesion can be obtained.

In the production of the laminated film, if necessary, additives other than the above-mentioned inert particles may be added to the thermoplastic resin.
For example, a stabilizer, a coloring agent, a specific resistance modifier for the molten polymer, and the like can be added and 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 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] f = V / d ³ wherein, f is the volume spherical coefficient, V is the particle volume ([mu] m ^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 .5KV-3.0A

In the case where 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 the co-extruded layer. In the case of the coated layer, a small piece of the film is fixedly formed with an epoxy resin, and an ultra-thin section (thickness of the film) having a 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 and Aggregation Rate Using a SEM (scanning electron microscope, JEOL T-300), the surface of the laminated film was magnified 5,000 times or 3 times.
Twenty photographs were taken at an angle of 0 °, and the number of granular projections was counted, and the average value was calculated as the number of projections per piece / mm ² by area conversion. In addition, the aggregation rate is the same SE
It calculates by the following formula using M 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 coating 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 ° and a tilt angle of 45 °. 1 at 400x magnification with transmission microscope
cm ² is scanned and observed, and the number of transmitted lights whose maximum length (corresponding to the protrusion height) of the non-evaporated portion due to the shadow of the protrusion is 0.2 mm or more is counted. (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 at a length of 25 to 30 cm and a width of 1/2 inch, and a leather blade was applied under the conditions of an angle of 90 ° with respect to the surface of the coating layer B 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). The width of the shavings in the depth direction was 3 μm or less (◎), 3 μm to 5 μm was (○), and 5 μm or more was (×). 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 vacuum evaporation.
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, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and inert particles shown in Table 1 as a lubricant were used. It was added and polymerized by a conventional method to obtain polyethylene terephthalate (PET).

The polyethylene terephthalate was heated at 70 ° C.
After drying for 3 hours, the mixture was fed to an extruder and melted at a temperature of 280 to 280.
Melted at 300 ° C, extruded from a die into a sheet,
After quenching, an unstretched film having a thickness of 84 μm was obtained.

The obtained unstretched film 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 surface of the vertically-stretched film. The aqueous coating solution containing the aqueous resin and the particles B of the coating layer B of Table 1 was coated on the other side with the aqueous coating liquid containing the resin and the particles C of the coating layer C of Table 2 at 0.005 μm each.
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 6.4 μm.

[Example 2, Comparative Examples 4, 7, 9] Film Layer B
A laminated biaxially oriented polyester film was obtained in the same manner as in Example 1, except that the thickness of the resin and particles of the coating layer C and the thickness of the thermoplastic resin layer A were changed as shown in Tables 1 and 2.

[0079] [ratio Comparative Examples 2,6] supplies Tables 1 and 2 of the thermoplastic resin layer A, a polyethylene terephthalate for coating layer C to the respective two extruders, using a multi-manifold type co-extrusion die The laminated biaxially oriented polyester film was laminated in the same manner as in Example 1 except that the aqueous coating solution containing the aqueous resin and the particles B of the coating layer B in Table 1 was applied to the surface opposite to the surface on the coating layer C side. I got

[Example 3 , Comparative Examples 1, 3 , 5 , 10] Except that the particles shown in Table 1 were used and that the same molar amount of dimethyl 2,6-naphthalenedicarboxylate was used instead of dimethyl terephthalate. Polyethylene-2,6-naphthalate (PEN) was obtained in the same manner as in 1.

After drying the 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.

[0083] [ratio Comparative Examples 8] Tables 1 and 2 of the thermoplastic resin layer A, polyethylene for film layer C
Feeding terephthalate to each of two extruders
Using a multi-manifold type coextrusion die
And an aqueous coating containing the aqueous resin and particles B of the coating layer B in Table 1.
The solution was applied to the surface opposite to the surface on the side of the coating layer C, and instead of polyethylene terephthalate, polyethylene-2,6-naphthalate was used in place of polyethylene terephthalate as shown in Table 1, except that a laminated biaxial film was formed in the same manner as in Example 1. An oriented polyester film was obtained.

[0084]

[Table 1]

[0085]

[Table 2]

[0086] Example 1 the surface characteristics of the multilayer biaxially oriented film was obtained in 3 and Comparative Examples 1 to 10, 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, coating layer Ratio t between the layer thickness t _{B of B} and the particle size dc _B of the core portion of the shell core particles
Table 3 shows _B / dc _B , abrasion resistance, winding property, and characteristics of a ferromagnetic thin film-deposited magnetic tape using this film.

[0087]

[Table 3]

As is evident 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, 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 simultaneously satisfy these characteristics.

[0089]

According to the present invention, the shaving property in the film forming process,
It is possible to provide a laminated film which is excellent as a base film of a magnetic recording medium having excellent winding properties and excellent electromagnetic conversion characteristics, dropout characteristics and running durability.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-241962 (JP, A) JP-A-7-232420 (JP, A) JP-A 7-249217 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (9)

(57) [Claims] 1. A heat containing inert particles A having an average particle diameter of 40 to 400 nm and a volume shape coefficient of 0.1 to π / 6 in such an amount that the frequency of projections on the surface becomes 50,000 to 50,000 / mm ^2. A laminated film comprising, on at least one side of the plastic resin layer A, a coating layer B containing an aqueous acrylic resin and particles _B having an average particle size dB of 5 to 100 nm and having a core-shell type structure whose outside is softer than the inside. And the average particle diameter d _B (n
m), the particle diameter dc _B (nm) of the core portion of the particle _B , and the layer thickness t _B (nm) of the coating layer B simultaneously satisfy the following expressions (1) and (2). Is 1 × 10 ⁶ to 1 × 10 ⁸ / mm ² , and the surface roughness ARa _B of the coating layer B measured by an atomic force microscope (AFM).
(Nm) and 10-point average roughness ARz _B (nm) satisfy the following expressions (3) and (4) 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 25. /
laminated film which is characterized in that cm ² or less. 1.01 ≦ d _B / dc _B ≦ 2.0 (1) 0.02 ≦ t _B / dc _B ≦ 0.6 (1) 2) [Expression 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 inert particles C The laminated film according to claim 1, wherein the content is 1 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 types of particles having different sizes, the average particle size of the single particle or the average particle size of the largest particle of the two or more types of particles is 0.1 to 1 μm, and inert Particle 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.