JPH0386916A - Metal coating type magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent traveling property and output characteristics by using thermoplastic resin containing inert particles and specifying the relation between the particle size and film thickness and the amt. of the particles to certain ranges. CONSTITUTION:The medium is a biaxially oriented film consisting of a layer comprising thermoplastic resin A (layer A) as the substrate film and a layer comprising thermoplastic resin B containing inert particles (layer B) laminated on the one side of the layer A. The inert particles have the average particle size dB of 10 - 600nm and are incorporated into the layer B by the amt. of 1.5 - 40wt.%. The ratio tB/dB of thickness of layer B to the average particle size tB is specified to the range 0.1 - 3. Thereby, the obtd. medium has excellent output characteristics and traveling property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 in which a metal-coated magnetic layer is provided on a support film is regarded as important as a magnetic recording medium for high-density recording because of its output characteristics and frequency characteristics. However, the conventional metal-coated magnetic recording media mentioned above generally use a smooth base film, which has a large coefficient of friction and insufficient running performance without slippage. There was a problem in that increasing the size resulted in poor output characteristics.

The present invention improves these problems and maintains the excellent output characteristics originally possessed by metal-coated magnetic recording media (hereinafter referred to as "excellent output characteristics"), while providing excellent running performance (hereinafter referred to as "excellent running performance"). The purpose is to provide a metal coated magnetic recording medium.

[Means for Solving the Problems] The present invention provides (1) a metal-coated magnetic recording medium in which a metal-coated magnetic layer is provided on at least one side of a base film, the base film being made of thermoplastic resin; It is a biaxially oriented film formed by laminating a layer made of thermoplastic resin B (layer B) containing inert particles on at least one side of a layer made of A (layer A), and the inert particles contained in layer B. The average particle size ds of the particles is 10 to eonm, the content of the particles in the B layer is 1.5 to 40% by weight, the thickness ta of the B layer and the average particle size d
A metal-coated magnetic recording medium characterized in that the B ratio ta/dB is in the range of 0.1 to 3, (2) a metal-coated magnetic layer is provided on at least one B layer side of the base film; The metal coated magnetic recording medium according to (1) above, wherein the inert particles contained in the B layer on the magnetic layer side have an average particle size dB of 10 to 450 nm;
) The base film is a biaxially oriented film in which the B layer is laminated only on one side of the A layer, and a metal coated magnetic layer is provided only on the A layer side, and the inert contained in the B layer is The metal-coated magnetic recording medium according to (1) above, characterized in that the average particle diameter d[l of the particles is 50 to 600 nm;
4) The base film has a layer made of thermoplastic resin A (layer A) containing inert particles on one side and a layer made of thermoplastic resin B (layer B) containing inert particles on the other side. A biaxially oriented film formed by laminating a layer (C layer) made of thermoplastic resin C, in which a metal-coated magnetic layer is provided only on the B layer side of the base film, and the B layer has a metal-coated magnetic layer. The average particle diameter dB of the inert particles contained is 10 to 45 Q n m-
s the content of the particles in the B layer is 1.5 to 40% by weight,
B layer thickness tB and average grain size dB (7) ratio to/dB is 0
．． 1 to 3, the average particle size d of the inert particles contained in the 0 layer
c is 50 to 600 nm, the content of the particles in the zero layer is 1.5 to 40% by weight, and the ratio tC/ac of the thickness of the zero layer to the average particle diameter dc is 0.1 to 3. This invention relates to a metal coated magnetic recording medium.

Thermoplastic resins A and B constituting the base film of the present invention,
C may be the same or different types, and is not particularly limited to polyester, polyolefin, polyamide, polyphenylene sulfide, etc., but in particular polyester, especially ethylene terephthalate, ethylene α
, β-bis(2-chlorophenoxy)ethane-4,4'
It is desirable to use at least one type of structural unit selected from -dicarboxylate and ethylene 2,6-naphthalate units as the main constituent, since the runnability becomes even better.

In addition, thermoplastic resin B and/or C constituting the present invention
If it is crystalline, the runnability will be even better, which is extremely desirable. Crystallinity 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, it is extremely desirable that the heat of fusion (change in enthalpy of fusion) measured by a differential scanning calorimeter exhibits crystallinity of 7.5 cal/g or more, since this will further improve runnability. Furthermore, polyester containing ethylene terephthalate as a main component is particularly desirable because it provides even better running properties.

In addition, within the range that does not impede the present invention, thermoplastic resin A,
At least one selected from B and C may be mixed with another type of thermoplastic resin, or a copolymer may be used. In addition, at least one selected from thermoplastic resins A, B, and C may contain an antioxidant, within a range that does not impede 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 normally added.

The average particle diameter dB of the inert particles in the 8 layers of the base film constituting the present invention is 10 to 600 dB from the viewpoint of runnability and output characteristics.
If a magnetic layer is provided on the B layer side, the thickness is preferably 10 to 450 nm, and if no magnetic layer is provided, the thickness is preferably 50 to 60 nm. Further, the content of inert particles in the 8 layers of the base film of the present invention is 1.5 to 4.
It is necessary that the amount is 0% by weight, preferably 2 to 30% by weight, and more preferably 3 to 20% by weight. If the content is more than the above range, the output characteristics will not be satisfactory, and if it is less, the running performance will be poor, which is not preferable. Furthermore, the ratio of the thickness ta of the eight layers of the base film of the present invention to the average particle diameter dB of the inert particles contained in the eight layers, 1°/ds, is 0.1 to 3, preferably 0. 2 to 2,01, more preferably 0. 3-1
．． It is necessary to be in the range of 5. If TB/dB is smaller than the above range, running performance will be poor, whereas if it is larger than the above range, output characteristics will be poor, which is not preferable.

Further, the average particle diameter dc of the inert particles in the C layer of the base film constituting the present invention needs to be 50 to 600 nm in order to obtain good running properties and output characteristics. Furthermore, the content of inert particles contained in the base film C layer is set to 1.
It is necessary that the amount is 5 to 40% by weight, preferably 2 to 15% by weight. Moreover, the ratio tc/dc of the thickness jc of this zero layer and the average particle diameter dc of the inert particles contained is 0. 1-3
It is desirable that the ratio is within this range because the running performance and output characteristics will be even better.

Furthermore, although it is not particularly necessary to contain inert particles in the base film A layer, inert particles with an average particle size of 5 to 600 nm, particularly 10 to 450 nm, are 0.001 to 0.15 nm.
If it is contained in an amount of 0.005 to 0.05% by weight, the running performance and output characteristics will be even better, so it is desirable.

The inert particles used in the present invention have a particle size ratio (longer diameter of particle/
Particles having a minor axis of 1.0 to 1.3, particularly spherical particles, are preferable because they provide even better running properties and output characteristics. The inert particles used in the present invention have a single particle index in the base film of 0.7 or more, preferably 0.7 or more. A value of 9 or more is particularly desirable because running performance and output characteristics become even better. The inert particles used in the present invention have a relative standard deviation of particle size of 0. A value of 6 or less, preferably 0.5 or less is desirable because running performance and output characteristics become even better.

The type of inert particles used in the present invention is not particularly limited, but includes substantially spherical silica particles caused by colloidal silica, particles made of crosslinked polymers (for example, crosslinked polystyrene), etc., but especially when reduced by 10% by weight. Running properties and output characteristics of crosslinked polymer particles with a high degree of crosslinking until the temperature (measured in nitrogen using a thermogravimetric analyzer Shimadzu TG-30M, heating rate 20°C/min) is 380°C or higher. This is particularly desirable because it provides even better results. Note that in the case of spherical silica derived from colloidal silica, substantially spherical silica with a low sodium content produced by an alkoxide method is particularly preferable because the runnability and output characteristics are even better. However, other particles, such as particles of calcium carbonate, titanium dioxide, alumina, etc., can also be used satisfactorily by appropriately controlling the ratio of the thickness tB of the thermoplastic resin B layer to the average particle diameter dB.

The base film constituting the present invention is a biaxially oriented laminated film made of the above-mentioned composition, and negative-axis or non-oriented films are not preferred because they result in poor running properties. 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 a polymer, is 350 kg/mm2 or more in both the longitudinal direction and the width direction, the output characteristics and runnability are even better. This is extremely desirable. Although the upper limit of Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, the manufacturing limit is usually about 1500 kg/mm 2 .

When the total reflection Raman crystallization index of the surface of the B layer of the base film constituting the present invention is 20 cm-" or less, the runnability
This is particularly desirable since the output characteristics will be even better.

Further, it is particularly desirable that the total reflection Raman crystallization index of the surface of the C layer of the base film constituting the present invention be 20 cm'' or less, since the runnability and output characteristics will be even better.

The present invention is a magnetic recording medium comprising a metal coating type magnetic layer provided on at least one side of the biaxially oriented film described above. The magnetic powder used is not particularly limited, but includes ferromagnetic powder, especially Fe, Co, Fe-Co, Fe-Co-Ni,
Metals or alloys such as Co-Ni, these and AI, Cr,
An alloy with Si or the like is preferably used.

Magnetic powder can be made into a magnetic paint using various binders, but thermosetting resin binders and radiation curing binders are generally preferred, and other additives such as dispersants, lubricants, and antistatic agents can be added according to conventional methods. May be used. For example, binders made of vinyl chloride/vinyl acetate/vinyl alcohol copolymers, polyurethane prepolymers, and polyisocyanates can be used.

The thickness tM of the metal-coated magnetic layer is not particularly limited, but
Thickness tB of layer B on the magnetic layer side (-layer) ratio, tB
/tM is 0.002 to 10. Especially 0.01~10.
More preferably, it is in the range of 0.01 to 5 because output characteristics and running properties become even better. Also, the value of tM is 0. It is preferable to keep the thickness in the range of 5 to 5 μm because output characteristics and runnability become even better.

It is particularly desirable that the thickness unevenness in the width direction of the B layer of the base film constituting the present invention be 25% or less, more preferably 20% or less, since the output characteristics and runnability will be even better.

The thickness of the B layer of the base film constituting the present invention is 0.0
A thickness of 1 to 2 .mu.m, preferably 0.02 to 1 .mu.m, is particularly desirable because running properties and output characteristics are even better.

When the ratio of the center line average roughness Ra to the maximum height Rt of the surface of the B layer of the base film constituting the present invention, Rt/Ra, is 9.0 or less, particularly 8.5 or less, the output characteristics and runnability This is particularly desirable because it provides even better results.

The surface layer particle concentration ratio measured by the secondary ion mass spectrum of the surface of the B layer of the base film constituting the present invention is not particularly limited, but the surface layer particle concentration ratio is 1/10 or less,
In particular, when it is 1150 or less, running performance and output characteristics become even better, so it is particularly desirable.

Next, a method for manufacturing a magnetic recording medium according to the present invention will be explained.

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

A method for adjusting the particle content is to prepare a high-concentration master using the above method, and then dilute it with a thermoplastic resin that does not substantially contain inert particles during film formation to adjust the particle content. The method is valid.

Next, after drying the pellets of thermoplastic resin B containing a predetermined amount of inert particles of thermoplastic resin A1 as necessary,
It is supplied to a known extrusion device for melt lamination, extruded into a sheet through a slit-shaped die, and cooled and solidified on a casting roll to produce an unstretched film. That is, thermoplastic resins A and B are laminated using two or three extruders, a two or three-layer manifold or a merging block,
Two or three layers of sheet are extruded from the die and cooled with casting rolls to form an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer flow path of thermoplastic resin B will prevent stretching and tearing, and the film will have a relationship between thickness and average particle size, content, and a surface layer particle concentration ratio within the desired range of the present invention. It is effective to obtain Further, it is extremely effective to use a rectangular feed block as the merging block in order to obtain the relationship between the thickness and the average particle size within the range of the present invention. In addition, setting the melting temperature of the extruder on the thermoplastic resin B side 10 to 40°C higher than that on the thermoplastic resin A side will prevent stretching breakage, and the relationship between the thickness and average particle size, the content, and the content within the range of the present invention. This is effective in obtaining a film with desired ranges of lamination thickness unevenness, surface layer particle concentration ratio, and total reflection Raman crystallization index. The above explanation is based on the configurations A/B, B
/A/B has been described, but in the case of B/A/C configuration, thermoplastic resins B1A and C are laminated using three extruders and a three-layer manifold or merging block. The three-layer sheet is extruded from a die and cooled with a casting roll to form an unstretched film.

Next, this unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, by using a sequential biaxial stretching method in which stretching is first performed in the longitudinal direction and then in the width direction, the stretching in the longitudinal direction is divided into three or more stages, and the total drawing ratio is 3.
．． The method carried out at a magnification of 0 to 6.5 times is effective for obtaining a film having a relationship between thickness and average particle size and content within the range of the present invention.

Although the longitudinal stretching temperature varies depending on the type of thermoplastic resin and cannot be generalized, it is usually 50 to 130 ℃ in the first stage.
It is effective to set the temperature at a temperature of 0.degree. The longitudinal stretching speed is preferably in the range of 5,000 to 50,000%/min.

A common method for stretching in the width direction is to use a stenter. The stretching ratio is 3.0 to 5.0 times, the stretching speed is 1000 to 20000%/min, and the temperature is 80 to 160°C.
A range of is suitable. Next, this stretched film is heat treated. The heat treatment temperature in this case is 170-200℃, especially 1
Preferably, the temperature is 70 to 190°C and the time is 0.5 to 60 seconds.

Next, a predetermined magnetic layer is applied to this film.

The magnetic layer can be applied by any known method, but the method of applying with a gravure roll provides a film with a relationship between thickness and average particle size within the range of the present invention and a surface layer particle concentration ratio within the desired range of the present invention. It is effective for In the drying step after coating, the temperature is preferably 90 to 120°C.

In addition, the calendering process uses polyamide or polyester as an elastic roll, and
C. is effective for obtaining a film having a relationship between thickness and average particle size within the range of the present invention and a surface layer particle concentration ratio within the desired range of the present invention. Furthermore, after the magnetic layer of this film is cured, the original fabric (wide width) is slit to obtain the metal-coated magnetic recording medium of the present invention.

[Method of Measuring Physical Properties and Method of Evaluating Effects] The method of measuring characteristic values and the method of evaluating effects of the present invention are as follows.

(1) Average particle size of particles The thermoplastic resin is removed from the film by plasma low-temperature ashing treatment to expose the particles. The processing conditions are selected so 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 performed with different observation points and the number of particles is 5.000 or more, and the number average diameter obtained thereby is taken as the average particle diameter.

D=ΣD, /N Here, DI is the equivalent circular diameter of the particles, and N is the number of particles.

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

Long axis = ΣD 1 + / N Short axis = ΣD2. /N Di,,D2. is the long axis (maximum diameter) of each individual particle
, the shortest axis (shortest axis), and N are the number of particles.

(3) Relative standard deviation of particle size Standard deviation σ(=(Σ(D,
−D) 2/N) ”' ) divided by the average diameter (σ
/D).

(4) A cross section of the single particle index film is photographed and observed using a transmission electron microscope (TEM) to detect particles. If the observation magnification is set to about 100,000 times, a single particle that cannot be separated any further can be observed. When the total area occupied by particles is A1, and the area occupied by aggregates in which two or more particles are aggregated is B, (
A-B)/A is the single particle index. The TEM conditions are as follows: one field of view area: 2 μm2 is measured at different locations, and 500 fields of view are measured.

・Observation magnification: 100,000 times ・Acceleration voltage: 100kV ・Section thickness: Approximately 1,0OOA (5) Particle content Select a solvent that dissolves the thermoplastic resin but does not dissolve the particles, and centrifuge the particles from the thermoplastic resin. The particles are separated and the ratio (weight %) to the total weight of the particles is defined as the particle content.

(6) Crystallization parameter ΔTcg, heat of fusion measured using a differential scanning calorimeter (DSC).

The DSC measurement conditions are as follows. That is, sample 1
0 mg was set in a DSC device, melted at a temperature of 300° C. for 5 minutes, and then rapidly cooled in liquid nitrogen.

This rapidly cooled sample was heated at a rate of 10°C/min, and the glass transition point Tg
Detect. The temperature was further increased, and the exothermic peak temperature of crystallization from the glass state was defined as the cold crystallization temperature Tcc.

The temperature was further increased, and the heat of fusion was determined from the melting peak. Here, the difference between Tcc and Tg (Tcc-Tg) is defined as a crystallization parameter ΔTcg.

(7) Young's modulus 2 using an Instron type tensile tester according to the method specified in J I 5-Z-1702.
Measurement was performed at 5° C. and 65% RH.

(8) Total reflection Raman crystallization index The total reflection Raman spectrum was measured, and the half-value width of 1 730 er', which is the stretching vibration of the carbonyl group, was taken as the total reflection Raman crystallization index of the surface. The measurement conditions are as follows. However, the measurement depth was approximately 500 to 100 OA from the surface.

■Light source Argon ion laser (5,145 people) ■Setting the sample Press the film surface onto a total reflection prism so that the laser polarization direction (S polarization) and the film longitudinal direction are parallel, and the laser is incident on the prism. The angle (angle with the film thickness direction) was 60'.

■Detector PM: RCA31034/Pboton Coun
ting S7stBmS75tB+tsu C12
30) (supp171.600Y) ■Measurement conditions 5LIT 1,000 μm LASER
100mW GATE TIME 1.0secSCAN
5PEED 12cm-”/minSAMPL
ING INTERVAL O, 2cm “REPEA”
T TIME 6 (9) Intrinsic viscosity [η] (unit: di/g) A value calculated by the following formula from the solution viscosity measured at 25° C. in orthochlorophenol is used. That is, ηsp/c=[η]+K[η]2・Nikode η8. = (solution viscosity/solvent viscosity) -1, C is the weight of dissolved polymer per 100 ml of solvent (g/l 00 m
L is usually 1.2), K is Huggins constant (C, 343). In addition, solution viscosity and solvent viscosity were measured using an Ostwald viscometer.

(10) Surface layer particle concentration ratio Using secondary ion mass spectroscopy (SIMS), the concentration ratio of the element with the highest concentration among the elements originating from particles in the film and the carbon element of the thermoplastic resin is defined as the particle concentration, and Perform an analysis in the horizontal direction. The ratio of the particle concentration A at the outermost layer particle concentration (point at depth O) measured by SIMS to the maximum concentration B obtained by further 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: 02 Primary ion acceleration voltage: 12KV Primary ion current: 200nA Raster area: 400μm mouth analysis area: Gate 30% Measurement vacuum degree: 6. OX 10-9 TorrE −
GU Neo, 5kV-3,0A (11) Surface roughness parameters Ra (center line average roughness), Rt (maximum height) Measured using a surface roughness meter. The conditions were 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) As standard running conditions, at 20°C and 60% relative humidity,
A 1/2 inch wide tape is brought into contact with a fixed shaft having an outer diameter of 6 mmφ at an angle θ=πr@d, and is run at a speed of 3.3 cm/s. Measure the outlet tension T2 when the artificial tension T1 is 25 g, and calculate the dynamic friction coefficient (μ
, ) is calculated.

tth = (1/θ)! n (T'2/TI)"
'(1/π) In (T2/25) this μ,
is 0.27 or less.Drivability: Excellent, exceeds 0.27 and is 0.30.
The following were judged as good running properties, and those exceeding 0.30 were judged as poor running properties.

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

Compare this chroma S/N with a commercially available standard videotape.If the one is equivalent (with a difference of 10 dB or less), the output characteristics are poor.If the difference is +2 dB or less, the output characteristics are good.If the difference is less than +2 dB, the output characteristics are good. Output characteristics exceeding +2 dB were considered excellent.

[Example] The present invention will be explained based on examples.

Example 1.2.5 and Comparative Example 2.3 Ethylene glycol slurry containing crosslinked polystyrene particles and silica particles derived from colloidal silica having different average particle sizes was prepared, and the ethylene glycol slurry was heated at 190°C for 1. After heat treatment for 5 hours, a transesterification reaction with dimethyl terephthalate was performed, polycondensation was performed, and the particles were reduced to 0. Pellets of polyethylene terephthalate (hereinafter abbreviated as PET) containing 5 to 10% by weight were made. At this time, the polycondensation time was adjusted to give an intrinsic viscosity of 0.70 (thermoplastic resin B). In addition, by the usual method, the intrinsic viscosity was 0.62.
PET was manufactured and designated as thermoplastic resin A.

These polymers were each dried under reduced pressure at 180°C for 6 hours (
3 Torr), thermoplastic resin B is supplied to extruder 1 and melted at 290°C, thermoplastic resin A is further supplied to extruder 2 and melted at 280°C, and these polymers are merged in a merging block. The layers were laminated and wound around a casting drum with a surface temperature of 30° C. using an electrostatic casting method, and cooled and solidified to produce a laminated unstretched film. At this time, adjust the discharge rate of each extruder to determine the total thickness and thermoplastic resin B.
The layer thickness was adjusted.

This unstretched film was heated to 4.5 mm in the longitudinal direction at a temperature of 80°C.
Stretched twice. This stretching is done by the difference in circumferential speed between the two sets of rolls.
It was done in 4 stages. This -axially stretched film was stretched 4.0 times in the width direction at 100°C at a stretching rate of 2.000%/min using a stenter, and then heat-treated at 190°C for 5 seconds under constant length to give a total thickness of 15 μm. A biaxially oriented laminated film was obtained.

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: 033 μm Acicular ratio: 10/1 Coercive force: 20000e ・Polyurethane resin 15 parts ・Vinyl chloride/vinyl acetate copolymer 5 parts ・Nitrocellulose resin
5 parts aluminum oxide powder 3 parts (
Average particle size: 0.3μm) ・Carbon black 1 part・Lecithin 2 parts・Methyl ethyl ketone 100 parts・Methyl isobutyl ketone
100 parts, toluene 100 parts, stearic acid 2 parts After mixing and dispersing the above composition in a ball mill for 48 hours, adding 6 parts of a hardening agent and filtering the resulting kneaded product with a filter to prepare a magnetic coating liquid, Coated on the above film and oriented in a magnetic field,
■Dry at 10℃, and then use a small test calendar device (
Steel roll/nylon roll, 5 stages), temperature 70
After calendering at ℃ and linear pressure of 200 kg/cm,
Curing was performed at 70° C. for 48 hours to obtain a metal coated magnetic recording medium.

Example 3.4 and Comparative Example 1.4 In Example 3, a three-layer laminated unstretched film was produced using three extruders, and in Example 4, an A-layer was further produced. A three-layer laminated unstretched film with different polymers laminated on both sides, a normal single-layer film in Comparative Example 1, and a three-layer laminated unstretched film using three extruders in Comparative Example 4. Obtained.

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

Magnetic paint is applied to this film using a gravure roll. The same magnetic paint as in the above example was prepared.

After mixing and dispersing the magnetic paint in a ball mill for 48 hours,
The kneaded product obtained by adding 6 parts of a curing agent was filtered to prepare a magnetic coating solution, which was coated and oriented in a magnetic field.
Dry at 0°C, then dry at 70°C using a small test calender (steel roll/nylon roll, 5 stages).
After calendering with a linear pressure of 200 kg/cm, 70
Cure for 48 hours to obtain a metal coated magnetic recording medium.

These characteristics are shown in Table 1, and the metal-coated magnetic recording medium of the present invention had excellent or good running properties and output characteristics, but in other cases, the running properties and output properties were satisfied. A metal coated magnetic recording medium could not be obtained.

[Effects of the Invention] The present invention uses a thermoplastic resin containing inert particles by devising a manufacturing method, and sets the relationship between particle size and film thickness and content within a specific range, thereby improving runnability and output. A magnetic recording medium with excellent properties has been obtained, and can respond to increases in film processing speed in various applications.

Claims (7)

[Claims] (1) A metal-coated magnetic recording medium comprising a metal-coated magnetic layer on at least one side of a base film,
Thermoplastic resin B containing inert particles on at least one side of a layer (A layer) in which the base film is made of thermoplastic resin A
It is a biaxially oriented film formed by laminating layers (B layer) consisting of layers, in which the average particle diameter d_B of the inert particles contained in the B layer is 10 to 600 nm, and the content of the particles in the B layer is 1.
5 to 40% by weight, and the ratio T_B/d_B of the thickness t_B of the B layer to the average grain size d_B is in the range of 0.1 to 3. (2) A metal-coated magnetic layer is provided on at least one B layer side of the base film, and the average particle diameter d_B of the inert particles contained in the B layer on the magnetic layer side is 10 to 450 nm.
The metal coated magnetic recording medium according to claim 1, wherein the metal coating type magnetic recording medium is m. (3) The base film is a biaxially oriented film in which the B layer is laminated only on one side of the A layer, and a metal-coated magnetic layer is provided only on the A layer side, and the B layer contains 2. The metal-coated magnetic recording medium according to claim 1, wherein the inert particles have an average particle diameter d_B of 50 to 600 nm. (4) The base film is a layer made of thermoplastic resin A (A
thermoplastic resin B containing inert particles on one side of the layer)
A biaxially oriented film formed by laminating a layer (B layer) consisting of a thermoplastic resin C containing inert particles on the other side (C layer) on the B layer side of the base film. A metal-coated magnetic layer is provided only in the B layer, the average particle diameter d_B of the inert particles contained in the B layer is 10 to 450 nm, and the content of the particles in the B layer is 1.5 to 40% by weight. The ratio T_B/d_B of the thickness t_B of the B layer and the average grain size d_B is 0
．． 1 to 3, average particle diameter d of the inert particles contained in the C layer
__c is 50 to 600 nm, the content of the particles in the C layer is 1.5 to 40% by weight, the thickness t_c of the C layer and the average particle diameter d
A metal coated magnetic recording medium characterized in that the ratio t_c/d_c of _c is 0.1 to 3. (5) Thermoplastic resin C is crystalline polyester, and the total reflection Raman crystallization index of the C layer surface is 20 cm^-
5. The metal-coated magnetic recording medium according to claim 4, wherein the magnetic recording medium is ^1 or less. (6) Thermoplastic resin B is crystalline polyester, and the total reflection Raman crystallization index of the B layer surface is 20 cm^-
Claims (1) to (5) characterized in that ^1 or less
The metal coated magnetic recording medium according to any one of the above. (7) Thickness t_B of layer B on the magnetic layer side and thickness t of the magnetic layer
7. The metal coating type magnetic recording medium according to claim 1, wherein the ratio of _M, t_B/t_M, is in the range of 0.002 to 10.