JPH07111777B2 - Metal coated magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal-coated magnetic recording medium.

[Prior Art] As a metal-coated magnetic recording medium, a magnetic recording medium in which a metal-coated magnetic layer is provided on a polyester film is known (for example, JP-A-60-66319).

[Problems to be Solved by the Invention] A magnetic recording medium provided with a metal coating type magnetic layer on a support film is regarded as an important magnetic recording medium for high density recording because of its output characteristics and frequency characteristics. However, in the above-mentioned conventional metal-coated magnetic recording medium, since a smooth base film is generally used, the friction coefficient is large, the running property is not slippery, and the running property is insufficient. When the size is increased, there is a problem that the output characteristic becomes defective.

The present invention solves the above problems and, while maintaining the excellent output characteristics originally possessed by the metal-coated magnetic recording medium (hereinafter referred to as excellent output characteristics), has excellent running characteristics (hereinafter referred to as excellent running characteristics). An object is to provide a metal coated magnetic recording medium.

[Means for Solving the Problems] The present invention is (1) a metal-coated magnetic recording medium comprising a base film and a metal-coated magnetic layer provided on at least one surface thereof, wherein the base film is a thermoplastic resin. A biaxially oriented film obtained by laminating a layer (B layer) made of a thermoplastic resin B containing inert particles on at least one surface of a layer made of A (A layer), wherein the inert particles contained in the B layer. Has an average particle diameter d _B of 10 to 600 nm, and the content of the particles in the B layer is 1.5 to
40 wt%, 0.1 ratio t _B / d _B of the B layer and the thickness t _B average particle diameter d _B
(3) A metal-coated magnetic recording medium, wherein (2) a metal-coated magnetic layer is provided on at least one B layer side of the base film, and the B layer on the magnetic layer side is provided.
Metal coating type magnetic recording medium of (1), wherein the average particle diameter d _B of the inert particles contained in the layer is 10～450Nm, on one side of (3) the base film layer A Only B
A biaxially oriented film obtained by laminating layers, and metal coating type magnetic layer is provided only on the A layer side, the average particle diameter d _B of the inert particles contained in the B layer is in 50~600nm The metal-coated magnetic recording medium according to the above (1), (4) the base film is a thermoplastic resin containing inert particles on one surface of a layer (A) made of a thermoplastic resin A. A biaxially oriented film obtained by laminating a layer made of a resin B (B layer) on the other surface and a layer made of a thermoplastic resin C containing inert particles (C layer) on the other surface of the base film B. only the layer side and the metal coating type magnetic layer is provided, the average particle diameter d _B of the inert particles contained in the B layer is 10～450Nm, said particles B
1.5 to 40% by weight content in the layer, the average particle diameter of the inert particles the ratio t _B / d _B having an average particle diameter d _B and the thickness t _B of the B layer is 0.1 to 3, it is contained in the C layer d _C is 50 to 600 nm, the amount contained in the particles of the C layer is 1.5 to 40 wt%, average particle diameter d _C the thickness t _C of the C layer
The present invention relates to a metal-coated magnetic recording medium having a ratio t _C / d _C of 0.1 to 3.

Thermoplastic resin A, B, which constitutes the base film of the present invention,
C's may be the same or different, and are not particularly limited to polyester, polyolefin, polyamide, polyphenylene sulfide, etc., but especially polyester, especially ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ) Ethane-4,4 '
When at least one structural unit selected from the group consisting of dicarboxylate and ethylene 2,6-naphthalate units is used as a main constituent, the running property is further improved, which is desirable.

Further, the thermoplastic resin B and / or C constituting the present invention
Is more desirable when it is crystalline, because the running property is further improved. The crystallinity referred to here indicates that it is not so-called amorphous, and quantitatively the cold crystallization temperature Tcc in the crystallization parameter is detected, and the crystallization parameter ΔTcg is 150 ° C. or less. . Further, when the heat of fusion (change in enthalpy of fusion) measured by a differential scanning calorimeter shows a crystallinity of 7.5 cal / g or more, the running property is further improved, which is highly desirable. Further, in the case of a polyester containing ethylene terephthalate as a main constituent, the running property is further improved, which is particularly desirable.

In addition, as long as the thermoplastic resin A,
At least one selected from B and C may be mixed with another type of thermoplastic resin, or a copolymerized polymer may be used. Further, at least one antioxidant selected from thermoplastic resins A, B, and C, within a range that does not impair the object of the present invention,
Organic additives such as heat stabilizers, lubricants, and ultraviolet absorbers may be added to the extent that they are usually added.

The average particle diameter d _B of the inert particles in the B layer of the base film constituting the present invention must be 10 to 600 nm from the viewpoints of running properties and output characteristics, and a magnetic layer is provided on the B layer side. 10 to 450 nm in the case, 50 to 600 if no magnetic layer is provided.
nm is preferred. The content of the inert particles in the base film B layer of the present invention must be 1.5 to 40% by weight, preferably 2 to 30% by weight, more preferably 3 to 20% by weight. If the content is more than the above range, the output characteristics cannot be satisfied, and if the content is less than the above range, the running property becomes poor, which is not preferable. Further the average particle diameter d _B ratio of the inert particles contained in the thickness t _B and the B layer of the base film layer B of the present invention, t _B / d _B is from 0.1 to 3,
It is necessary that the range is preferably 0.2 to 2.0, more preferably 0.3 to 1.5. If t _B / d _B is smaller than the above range, running performance becomes poor, and conversely if t _B / d _B is large, output characteristics become poor, which is not preferable.

Further, the average particle diameter d _C of the inert particles in the C layer of the base film constituting the present invention is required to be 50 to 600 nm in order to obtain good running properties and output characteristics. Further, the content of the inert particles contained in the base film C layer is 1.5 to 40% by weight, preferably 2 to 15% by weight in order to obtain a magnetic recording medium having good running properties and output characteristics. It is necessary.
Further, when the ratio t _C / d _C of the thickness t _{C of the} C layer and the average particle diameter d _C of the inert particles contained is in the range of 0.1 to 3, the running property and the output characteristic are further improved. So desirable.

Further, it is not particularly necessary for the base film A layer to contain inert particles, but the average particle size is 5 to 600 nm, especially 10 to 4 nm.
0.001 to 0.15% by weight of 50 nm inert particles, especially 0.005 to 0.
The content of 05% by weight is desirable because the running property and output characteristics are further improved.

The inert particles used in the present invention have a particle size ratio (particle length / major axis).
Particles having a (minor diameter) of 1.0 to 1.3, particularly spherical particles, are preferable because the runnability and output characteristics are further improved.
The inert particles used in the present invention are particularly desirable when the single particle index in the substrate film is 0.7 or more, preferably 0.9 or more, because the running properties and output characteristics are further improved. The inert particles used in the present invention have a relative standard deviation of the particle size of 0.6 or less, preferably 0.5 or less, because the running properties and output characteristics are further improved, which is desirable.

The type of the inert particles used in the present invention is not particularly limited, but there are substantially spherical silica particles caused by colloidal silica, particles by a crosslinked polymer (for example, crosslinked polystyrene), etc. Temperature (measured using a thermogravimetric analyzer Shimadzu TG-30M in nitrogen.
(/ Min) is 380 ° C. or higher, the cross-linked polymer particles having a high degree of cross-linking are particularly desirable because the running properties and output characteristics are further improved. In the case of spherical silica due to colloidal silica, it was manufactured by the alkoxide method,
In the case of substantially spherical silica having a low sodium content, runnability and output characteristics are further improved, which is particularly desirable. However, other particles, such as calcium carbonate, titanium dioxide, and alumina when cooled, can be sufficiently used by appropriately controlling the ratio of the thickness t _B of the thermoplastic resin B layer to the average particle diameter d _B.

The substrate film constituting the present invention is a film obtained by biaxially orienting a laminated film made of the above composition, and a uniaxial or non-distributed film is not preferable because the running property becomes poor. The degree of this orientation is not particularly limited, but when the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 350 kg / mm ² or more in both the longitudinal direction and the width direction, the output characteristics and runnability are further improved. So highly desirable. The upper limit of the Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, but the production limit is usually about 1500 kg / mm ² .

When the total reflection Raman crystallization index of the surface of the B layer of the substrate film constituting the present invention is 20 cm ^-1 or less, the running property and the output property are further improved, which is particularly desirable.

Further, the total reflection Raman crystallization index of the surface of the C layer of the substrate film constituting the present invention is 20 cm ^-1 or less, the running property,
It is particularly desirable because the output characteristics are further improved.

The present invention is a magnetic recording medium comprising a metal-coated magnetic layer provided on at least one surface of the above biaxially oriented film. The magnetic powder used is not particularly limited, but it is a ferromagnetic powder, among them, Fe, Co, Fe-Co, Fe-Co-Ni, Co-Ni and other metals or alloys, and alloys of these with Al, Cr, Si and the like. Etc. are preferably used.

The magnetic powder can be made into a magnetic coating using various binders, but in general, thermosetting resin-based binders and radiation-curable binders are preferable, and other additives such as dispersants, lubricants, and antistatic agents are used according to a conventional method. You may use. For example, a binder made of vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate can be used.

The thickness t _M of the metal-coated magnetic layer is not particularly limited, but the ratio t _B / t _M to the thickness t _B (one layer) of the B layer on the magnetic layer side is 0.002 to.
A range of 10, particularly 0.01 to 10, and more preferably 0.01 to 5, is desirable because the output characteristics and running performance are further improved. Further, it is desirable that the value of t _{M be} in the range of 0.5 to 5 μm because the output characteristics and the running property are further improved.

It is particularly desirable that the widthwise unevenness of the layer B of the base material film constituting the present invention is 25% or less, more preferably 20% or less, because the output characteristics and the running property are further improved.

The thickness of the B layer of the base film constituting the present invention is 0.01 to
When the thickness is 2 μm, preferably 0.02 to 1 μm, the running property and the output characteristics are further improved, which is particularly desirable.

The ratio of the center line average roughness Ra to the maximum height Rt of the B layer surface of the substrate film constituting the present invention, Rt / Ra is 9.0 or less, particularly 8.5.
In the following cases, the output characteristics and the running property are further improved, which is particularly desirable.

The surface layer particle concentration ratio measured by the secondary ion mass spectrum of the B layer surface of the substrate film constituting the present invention is not particularly limited, but the surface layer particle concentration ratio is 1/10 or less, particularly
When it is 1/50 or less, the running property and the output property are further improved, which is particularly desirable.

Next, a method of manufacturing the magnetic recording medium of the present invention will be described.

First, as a method of incorporating the inert particles into the thermoplastic resin B, a method in which the inert particles are made into a slurry of ethylene glycol and kneaded into the thermoplastic resin using a vent-type twin-screw kneading extruder The relationship between the thickness and the average particle diameter within the range of the present invention and the content of the base material film are extremely effective.

As a method for adjusting the content of particles, a high-concentration master is prepared by the above method, and the content of particles is adjusted by diluting it with a thermoplastic resin that does not substantially contain inert particles during film formation. The method is effective.

Next, after drying the pellets of the thermoplastic resin A and the thermoplastic resin B containing a predetermined amount of inert particles, if necessary,
The film is supplied to a known extruder for melt lamination, extruded into a sheet form from a slit die, and cooled and solidified on a casting roll to produce an unstretched film. That is, using two or three extruders, a two- or three-layer manifold or a merging block, the thermoplastic resins A and B are laminated,
A two- or three-layer sheet is extruded from the die and cooled with a casting roll to produce an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer flow path of the thermoplastic resin B is a film having a relationship of thickness and average particle diameter within the range of the present invention, content, and a surface layer particle concentration ratio within a desirable range without stretching breakage. Is effective in obtaining. Further, it is extremely effective to use a rectangular feed block as the merging block to obtain the relationship between the thickness and the average particle diameter within the range of the present invention. Further, increasing the melting temperature of the extruder on the side of the thermoplastic resin B by 10 to 40 ° C. higher than that on the side of the thermoplastic resin A does not cause stretching breakage, and the relationship between the thickness and the average particle size in the range of the present invention, the content, It is effective in obtaining a film having a lamination thickness unevenness, a surface layer particle concentration ratio, and a total reflection Raman crystallization index in a desired range. In the above description, A / B and B / A / B were described as the configuration, but in the case of the configuration of B / A / C, three extruders are used and a three-layer manifold or a merge block is similarly used. Using the thermoplastic resins B, A, and C, a three-layer sheet is extruded from the die and cooled with a casting roll to produce an unstretched film.

Next, this unstretched film is biaxially stretched and biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction first and then in the width direction is performed first,
Stretching in the longitudinal direction is divided into 3 or more steps to obtain a total longitudinal stretching ratio.
The method of 3.0 to 6.5 times is effective for obtaining a film having the content and the content of the thickness and the average particle diameter in the range of the present invention. The stretching temperature in the longitudinal direction varies depending on the type of thermoplastic resin and cannot be generally stated, but usually, the first step should be set at 50 to 130 ° C. and the second step and thereafter should be higher than that. It is effective for obtaining a film having a particle size ratio and a surface layer particle concentration ratio within the desirable range of the present invention. The longitudinal stretching speed is preferably in the range of 5,000 to 50,000% / min. As a stretching method in the width direction, a method using a stenter is generally used. Stretching ratio is 3.0 to 5.0 times, stretching speed is 1000 to 20
The range of 000% / min and the temperature of 80 to 160 ° C are suitable. Next, this stretched film is heat-treated. In this case, the heat treatment temperature is preferably 170 to 200 ° C., particularly 170 to 190 ° C., and the time is preferably 0.5 to 60 seconds.

Next, a predetermined magnetic layer is applied to this film. The method of applying the magnetic layer can be performed by a known method,
The method of coating with a gravure roll is effective in obtaining a film having a relationship between the thickness and the average particle diameter within the range of the present invention and a surface layer particle concentration ratio within the desirable range of the present invention. The temperature of the drying step after coating is preferably 90 to 120 ° C.

Further, the calendering step, using polyamide or polyester for the elastic roll, is carried out in the temperature range of 25 to 90 ° C., particularly 40 to 70 ° C., and the relationship between the thickness and the average particle size of the present invention range,
It is effective for obtaining a film having a surface layer particle concentration ratio within the desirable range of the present invention. Further, after curing the magnetic layer of this film, the original fabric (wide width) is slit to obtain the metal-coated magnetic recording medium of the present invention.

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows.

(1) Average particle size of particles The thermoplastic resin is removed from the film by a plasma low temperature ashing method to expose the particles. The treatment conditions are selected such that the thermoplastic resin is incinerated but the particles are not damaged.
This is observed with a scanning electron microscope (SEM), and the image of the particles is processed with an image analyzer. The following numerical processing is carried out when the number of particles is changed to 5,000 or more by changing observation points, and the number average system D thus obtained is taken as the average particle diameter.

D = ΣD _i / N where D _i is the equivalent circle diameter of the particles and N is the number of particles.

(2) Particle size ratio This is the ratio of (average value of major axis) / (average value of minor axis) of individual particles in the measurement of (1) above. That is, it is calculated by the following formula.

Major axis = ΣD1 _i / N long diameter short diameter _{= ΣD2 i / N Di i,} D2 i each individual particle (maximum diameter), short diameter (the shortest diameter), N is the number of particles.

(3) the individual particle size D _i measured by the method of particle size of the relative standard deviation above (1), the average diameter D, the standard deviation calculated from the particle number N σ (= {Σ (D i -
D) ² / N} ^1/2 ) was divided by the average diameter D to express (σ / D).

(4) Single particle index The cross section of the film is photographed with a transmission electron microscope (TEM) to detect particles. If the observation magnification is about 100,000 times,
One particle can be observed that cannot be further divided. When the total area occupied by particles is A and the area occupied by aggregates in which two or more particles are aggregated is B, (A
-B) / A is a single particle index. The TEM conditions are as follows. 1 field of view area: 2 μm ² measurement is carried out at different locations to measure 500 fields of view.

・ Observation magnification: 100,000 times ・ Acceleration voltage: 100kV ・ Section thickness: Approximately 1,000Å (5) Particle content Select a solvent that dissolves the thermoplastic resin but not the particles, and centrifuge the particles from the thermoplastic resin. Then, the particle content is defined as a ratio (% by weight) to the total weight of the particles.

(6) Crystallization parameter ΔTcg, heat of fusion It was measured using a differential scanning calorimeter (DSC). The DSC measurement conditions are as follows. That is, 10 mg of a sample is set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The temperature of this quenched sample is raised at 10 ° C./min, and the glass transition point Tg is detected. When the temperature rises further, the crystallization exothermic peak temperature from the glass state is reached and the cold crystallization temperature Tcc
And The temperature was further raised and the heat of fusion was determined from the melting peak. Here, the difference between Tcc and Tg (Tcc-Tg) is defined as the crystallization parameter ΔTcg.

(7) Young's modulus 25 ° C, 65% RH using an Instron type tensile tester according to the method specified in JIS-Z-1702
It was measured at.

(8) Total reflection Raman crystallization index The total reflection Raman spectrum was measured and the half-value width of 1730 cm ^-1 , which is the stretching vibration of the carbonyl group, was used as the total reflection Raman crystallization index of the surface. The measurement conditions are as follows. However, the measurement depth was about 500 to 1000Å from the surface.

Light source Argon ion laser (5,145Å) Setting the sample Press the film surface to the total reflection prism so that the laser polarization direction (S polarization) and the film longitudinal direction are parallel, and the incident angle of the laser to the prism (the film thickness direction) The angle with was 60 °.

Detector PM: RCA31034 / Photon Counting System (Hamamatsu C123
0) (supply 1,600V) Measurement condition SLIT 1,000 μm LASER 100 mW GATE TIME 1.0sec SCAN SPEED 12 cm ^-1 / min SAMPLING INTERVAL 0.2cm ^-1 REPEAT TIME 6 (9) Intrinsic viscosity [η] (Unit: dl / g ) Use the value calculated from the following formula from the solution viscosity measured at 25 ° C in orthochlorophenol. That is, η _SP / C = [η] + K [η] ² · C where η _SP = (solution viscosity / solvent viscosity) -1, C is the solvent
Dissolved polymer weight per 100 ml (g / 100 ml, usually 1.2),
K is the Huggins constant (0.343). Also, the solution viscosity,
The solvent viscosity was measured using an Ostwald viscometer.

(10) Surface layer particle concentration ratio Using the secondary ion mass spectrum (SIMS), the concentration ratio of the highest concentration element of the particles in the film to the carbon element of the thermoplastic resin is defined as the particle concentration, Perform a vertical analysis. The ratio of the particle concentration A at the outermost surface particle concentration (point at the depth of 0) measured by SIMS and the maximum concentration B obtained by continuing the analysis in the depth direction, A / B was defined as the surface layer particle concentration ratio. The measuring device and conditions are as follows.

Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12KV Primary ion current: 200nA Raster area: 400μm □ Analysis area: Gate 30% Measuring vacuum degree: 6.0 × 10 ^-9 Torr E-GUN: 0.5kV-3.0 A (11) Surface roughness parameter Ra (centerline average roughness), Rt
(Maximum height) Measured using a surface roughness meter. The conditions are as follows, and the average value of 20 measurements was taken as the value.

・ Stylus tip radius: 0.5μm ・ Stylus load: 5mg ・ Measurement length: 1mm ・ Cutoff value: 0.08mm (12) Travelability As standard conditions, the outside diameter is 20 ° C and 60% relative humidity.
1/2 inch tape on 6mmφ fixed shaft with angle θ = πrad
And make it run at a speed of 3.3 cm / s. The outlet tension T ₂ is measured when the inlet tension T _{1 is set} to 25 g, and the dynamic friction coefficient (μ _K ) is calculated from the following equation.

_{μ K = (1 / θ)} 1n (T 2 / T 1) = (1 / π) 1n (T 2/25) This mu _K is runnability 0.27 or less: Yu, runnability 0.30 or less than 0.27: Good, and those exceeding 0.30 were determined as runnability: poor.

(13) Output characteristics The original tape was incorporated into a VTR cassette to make a VTR tape.
A 100% chroma signal was recorded on this tape by a TV test waveform generator using a home VTR, and the chroma S / N was measured from the reproduced signal by a color video noise measuring instrument.

This Chroma S / N is equivalent to a standard video tape on the market (with a difference of +0 dB or less). Output characteristics: Poor, with a difference of +2 dB or less Output characteristics:
Good, output characteristics with a difference exceeding +2 dB: excellent.

[Examples] The present invention will be described based on Examples.

Examples 1, 2, 5 and Comparative Examples 2, 3 An ethylene glycol slurry containing crosslinked polystyrene particles having different average particle diameters and silica particles derived from colloidal silica was prepared, and the ethylene glycol slurry was heated at 190 ° C. for 1.5 hours. After heat treatment, it is transesterified with dimethyl terephthalate and polycondensed to give 0.5 to 10 particles.
Polyethylene terephthalate (wt. PET)
Abbreviated) was made. At this time, the polycondensation time was adjusted so that the intrinsic viscosity was 0.70 (thermoplastic resin B). Also,
By a conventional method, PET having an intrinsic viscosity of 0.62 was produced and designated as a thermoplastic resin A.

Each of these polymers was dried under reduced pressure at 180 ° C for 6 hours (3To
rr), and then the thermoplastic resin B is fed to the extruder 1 at 290 ° C.
Melt, and then the thermoplastic resin A is supplied to the extruder 2 and melted at 280 ° C., these polymers are combined and laminated in a confluent block, and a surface temperature of 30 ° C. is obtained by using an electrostatically applied casting method.
It was wound around a casting drum of No. 1 and cooled and solidified to make a laminated unstretched film. At this time, the total amount and the thickness of the thermoplastic resin B layer were adjusted by adjusting the discharge amount of each extruder.

This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80 ° C. This stretching was carried out in four stages with the difference in peripheral speed between each pair of rolls. This uniaxially stretched film was stretched 4.0 times in the width direction at 100 ° C at a stretching speed of 2,000% / min using a stenter and heat-treated at 190 ° C for 5 seconds under a constant length to give a total thickness of 15μ.
A biaxially oriented laminated film of m was obtained.

A magnetic paint is applied to this film using a gravure roll. The magnetic paint was prepared as follows.

Fe 100 parts Average particle size Length: 0.3 μm Needle ratio: 10/1 Coercive force: 2000 Oe ・ Polyurethane resin 15 parts ・ Vinyl chloride / vinyl acetate copolymer 5 parts ・ Nitrocellulose resin 5 parts ・ Aluminum oxide powder 3 parts (Average particle size: 0.3 μm) ・ Carbon black 1 part ・ Lecithin 2 parts ・ Methyl ethyl ketone 100 parts ・ Methyl isobutyl ketone 100 parts ・ Toluene 100 parts ・ Stearic acid 2 parts Mix and disperse the above composition in a ball mill for 48 hours and then cure The kneaded material obtained by adding 6 parts of the agent was filtered with a filter to prepare a magnetic coating liquid, which was coated on the film, magnetically oriented, dried at 110 ° C., and further a small test calendar device (steel roll / Nylon roll, 5 layers), calendered at 70 ℃, linear pressure 200kg / cm, then 70 ℃,
Curing was carried out for 48 hours to obtain a metal-coated magnetic recording medium.

Examples 3, 4 and Comparative Examples 1, 4 Similar to the above examples, in Example 3, three extruders were used to form a three-layer laminated unstretched film, and in Example 4, a layer A was further added. A three-layer laminated unstretched film in which different polymers were laminated on both sides, a comparative single-layer film was used in Comparative Example 1, and a three-layer laminated unstretched film was used in Comparative Example 4 using three extruders. Obtained.

These unstretched films were heated in the longitudinal direction at a temperature of 80 ° C to 4.2%.
It was stretched twice. This uniaxially stretched film was stretched 4.5 times in the width direction at 105 ° C. at a stretching speed of 2,000% / min using a stenter,
It was heat-treated at 190 ° C. for 5 seconds under a constant length to obtain a biaxially oriented film.

A magnetic paint is applied to this film using a gravure roll. The same magnetic coating material as that used in the above-described example was prepared.
After mixing and dispersing the magnetic paint for 48 hours in a ball mill, the kneaded product obtained by adding 6 parts of a curing agent is filtered through a filter to prepare a magnetic coating solution, which is applied, magnetic field oriented, and 100 ° C.
Dry with a small test calender (steel roll / nylon roll, 5 steps), temperature 70 ℃, linear pressure 20
After calendering at 0 kg / cm, it was cured at 70 ° C. for 48 hours to obtain a metal-coated magnetic recording medium.

Comparative Example 5 On one surface of the single film used in Comparative Example 1, 5% by weight of spherical silica (0.3 μm) was added to the polyurethane resin binder.
The coating liquid contained was applied by a known method and dried to obtain a film having a coating thickness of 1 μm.

These characteristics are as shown in Table 1. The metal-coated magnetic recording medium of the present invention had excellent or good running characteristics and output characteristics, but otherwise, the running characteristics and output characteristics are satisfied. No metal coated magnetic recording medium was obtained.

[Effects of the Invention] In the present invention, since the thermoplastic resin containing the inert particles is used to make the relationship between the particle size and the film thickness and the content within a specific range, the running property and the output are improved by devising the manufacturing method. The magnetic recording medium having excellent characteristics is obtained, and it is possible to cope with the increase in the film processing speed in each application.

Claims (7)

[Claims] 1. A metal-coated magnetic recording medium comprising a base film and a metal-coated magnetic layer provided on at least one surface of the base film, wherein the base film comprises a thermoplastic resin layer (A).
Layer B) is a biaxially oriented film obtained by laminating a layer (B layer) made of a thermoplastic resin B containing inert particles on at least one side thereof, and the average particle diameter d _{B of the} inert particles contained in the B layer.
But 10 to 600 nm, 1.5 to 40% by weight content in the particles of the layer B, a ratio t _B / d _B of the B layer and the thickness t _B average particle diameter d _B is in the range of 0.1 to 3 Characteristic metal coating type magnetic recording medium. 2. A metal coating type magnetic layer is provided on at least one B layer side of a base film, and B on the magnetic layer side is provided.
Claim (1) Metal coating type magnetic recording medium according to the average particle diameter d _B of the inert particles contained in the layer is characterized in that it is a 10～450Nm. 3. A biaxially oriented film in which a base film is formed by laminating a B layer only on one side of an A layer, and a metal coating type magnetic layer is provided only on the A layer side, and the B layer contains it. claim (1) metal coating type magnetic recording medium according to the average particle diameter d _B of the inert particles is characterized in that it is a 50~600nm being. 4. A base film comprising a layer (B layer) made of a thermoplastic resin B containing inert particles on one side of a layer (A layer) made of a thermoplastic resin A, and an inert layer on the other side. A biaxially oriented film obtained by laminating a layer (C layer) comprising a thermoplastic resin C containing particles, wherein a metal coating type magnetic layer is provided only on the B layer side of the base film, the average particle diameter d _B is 10~450nm inert particles contained in the B layer, the ratio of the average particle diameter d _B content 1.5 to 40 wt%, the B layer and the thickness t _B in the particle layer B t _B / d _B is 0.1 to 3, the average particle diameter d _C of the inert particles contained in the C layer is 50 to 600 nm, the content of the particles in the C layer is 1.5 to 40% by weight, and the thickness of the C layer is t _C and average particle size d
Metal coating type magnetic recording medium having a ratio t _C / d _C of _C is equal to or from 0.1 to 3. 5. The thermoplastic resin C is a crystalline polyester, and the total reflection Raman crystallization index of the surface of the C layer is 20 cm ^-1.
The metal coated magnetic recording medium according to claim 4, wherein: 6. The thermoplastic resin B is a crystalline polyester, and the total reflection Raman crystallization index of the surface of the B layer is 20 c ^-1.
It is the following, The metal coating type magnetic recording medium in any one of Claims (1)-(5) characterized by the following. 7. The thickness t _B of the B layer on the magnetic layer side and the thickness of the magnetic layer
The metal coated magnetic recording medium according to any one of claims (1) to (6), wherein the ratio of t _M , t _B / t _M is in the range of 0.002 to 10.