JPH10249972A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having stable output by improving a shape of a surface protrusion, providing satisfactory handleability, feeding properties, preventing dropout, clogging of a magnetic recording head and improving still durability. SOLUTION: The magnetic recording medium comprises a metal magnetic thin film provided on a non-magnetic support 1. In this case, the support 1 has a laminated film of a base film 4 having a thickness of 0.1 to 10μm and a second film 3 containing particles having a mean particle size of 0.2 to 1.0μm, and the support 1 has large protrusions 7 at a ratio of 1.0 to 100,000 pieces/mm<2> on both surfaces of the support 1, and the film is formed at the first film 4 side of the support 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium of the metal magnetic thin film type.

[0002]

2. Description of the Related Art Iron, cobalt, nickel or alloys or oxides containing these as main components are deposited on a base film such as a polyester film by a vacuum deposition method, a sputtering method, an ion plating method or the like. The metal magnetic thin film type magnetic recording medium can greatly improve the recording density as compared with the conventional coating type magnetic recording medium. In order to increase the recording density, it is necessary to reduce the gap of the magnetic recording head and smooth the surface of the magnetic recording medium to reduce so-called spacing loss as much as possible.

However, it has been found that if the surface of the magnetic recording medium is too smooth, a sufficient effect cannot be obtained in terms of running performance and head clogging in repeated running, and Japanese Patent Publication No. 6-79844. As described above, there is known a technique in which the surface of a base film on which a metal magnetic thin film is formed is roughened with fine particles.

On the other hand, the surface of the non-magnetic support is preferably rough from the viewpoint of improving the handleability in the step of forming a base film or in the step of forming a tape using the film. For example, for the purpose of improving the handleability, measures have been taken to make the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed coarse with particles, as in JP-B-7-110533.

In view of the above, it is desired that the surface of the non-magnetic support on which the magnetic layer is formed is smooth and the surface on the opposite side is rough, and a plurality of base films to which particles having different particle sizes are added. It has been proposed to change the surface roughness of both surfaces by using a laminated film obtained by laminating as a nonmagnetic support.

However, when particles are contained in the polyester film on the side on which the magnetic layer is formed as in Japanese Patent Publication No. Hei 6-79844, the magnetic recording head due to the chipping of the particles after a long period of repeated running. There is a problem that the effect of preventing clogging of the metal is reduced, and the dropout of particles causes dropout.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances of the surface of a base film constituting a non-magnetic support, and has been made in view of the step of forming a base film or a tape using the film. In addition, it improves the handling characteristics in the process of forming a tape, and is excellent in the runnability with tape and the effect of clogging of the magnetic recording head due to chipping of particles during repeated running, and also prevents dropout due to falling off of particles. It is another object of the present invention to provide a magnetic recording medium exhibiting excellent electromagnetic conversion characteristics and running properties.

[0008]

The present inventors have conducted intensive studies on the above-mentioned problems, and as a result, in a magnetic recording medium having a metal magnetic thin film provided on a non-magnetic support, the non-magnetic support has a laminated structure. By adding relatively large particles to the base film on the surface on which the metal magnetic thin film is to be provided, and by specifying the particle size, distribution density, and even the thickness of the base film, these correlations are used. Improves handling in the base film forming process or in the process of forming a tape using the film, and furthermore, the clogging of the magnetic recording head due to the running performance on the tape and the chipping of particles during repeated running. The present invention was found to be able to achieve both excellent electromagnetic conversion characteristics and running performance by preventing the performance of the prevention effect from dropping and preventing dropout due to falling off of particles. It was.

That is, according to the present invention, for example, the thickness is 6 μm
On a very thin non-magnetic support, for example:
A magnetic recording medium provided with an extremely thin metal magnetic thin film having a thickness of from 0.1 to 0.5 μm, wherein the nonmagnetic support comprises: a first base film having a thickness of 0.1 to 1.0 μm; A laminated film comprising a second base film containing particles having a diameter of 0.2 to 1.0 μm, wherein both surfaces of the nonmagnetic support have large projections at a rate of 1.0 to 100,000 / mm ^2. Further, a magnetic recording medium is provided, wherein a metal magnetic thin film is formed on the first base film side of the nonmagnetic support.

According to the above construction, the handling property and the running property with a tape can be improved, the dropout due to the falling off of the particles can be prevented, and the effect of preventing the clogging of the magnetic recording head is excellent. Can exhibit excellent electromagnetic conversion characteristics.

In the present invention, a polymer coating containing particles having an average particle size of 0.01 to 0.05 μm is provided on a first base film of a nonmagnetic support, and the thickness of the polymer coating is Is not more than the average particle diameter of the particles, and the polymer coating preferably has small projections at a rate of 500 to 15,000,000 particles / mm ² . By providing the above-mentioned polymer film, a magnetic tape having excellent running properties can be obtained.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing a main part of a non-magnetic support of the magnetic recording medium of the present invention. The non-magnetic support 1 includes a second base film 3 including large particles 2 having an average particle diameter of 0.2 to 1.0 μm, and a thickness of 0.1 to 1. It comprises a first base film 4 of 0 μm and a polymer coating 6 provided on the first base film 4 and containing fine particles 5 having an average particle size of 0.01 to 0.05 μm. A magnetic recording medium is formed by forming a thin film made of a ferromagnetic metal as a magnetic layer on the surface of the nonmagnetic support 1 on the side of the polymer film 6.

On the surface of the nonmagnetic support 1, the large magnetic particles 2 in the second base film 3 form the metal magnetic thin film forming surface (the polymer coating 6 side) and the opposite side (the second base film side). 1.0 to 100,000 pieces / mm ²
Large projections 7 are formed. In particular, on the polymer film 6 side, the first base film 4 and the polymer film 6 follow the large protrusions of the second base film 3 so that the large protrusions 7 are formed.
Is formed. On the surface of the polymer coating 6, 5 to 15 million particles /
The fine projections 8 are formed at a rate of mm ² .

In the present invention, the second base film 3
The particle size of the large particles 2 added therein is set to 0.2 to 1.0 μm. This is because if the particle size is less than 0.2 μm, the handleability in the process is inferior, and the head clogging cannot be sufficiently effected. If the particle size exceeds 1.0 μm, the spacing is increased. This causes a decrease in electromagnetic conversion characteristics and a drop-out due to an increase in the number. Large particle 2
A more preferred range for the particle size is 0.2 to 0.1.
6 μm.

The particle size of the fine particles 5 added to the polymer film 6 is set to 0.01 to 0.05 μm. This is because if the particle size is less than 0.01 μm, the running property (still life) becomes insufficient, and if the particle size exceeds 0.05 μm, the electromagnetic conversion characteristics are deteriorated due to an increase in spacing. is there. A more preferable range of the particle size of the fine particles 5 is 0.01 to 0.04 μm.

Examples of the material of the large particles 2 and the fine particles 5 include polystyrene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, and benzoguanamine resin. And inorganic fine particles such as silica, alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black and barium sulfate.

In the present invention, the first base film 4
As a material of the second base film, a material mainly composed of polyester, particularly linear polyester is preferable. For example, polyethylene terephthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylene methylene terephthalate, polyethylene-2,6-
And naphthalene dicarboxylate.

When a polyester film is used as the base film, the polyester film is formed by melting a polyester film formed by a known method, that is, extruding the polyester into a sheet or a cylinder and stretching it in at least one direction. The mechanical axis direction of the film is desirably one of a normal balance type, a type enhanced in a uniaxial orientation in a machine axis direction or a direction perpendicular thereto, and a type enhanced in a biaxial direction. In the present invention, a laminated film laminated by co-extrusion is used as the first base film 4 and the second base film 3.

The thickness of the first base film 4 is 0.1 to
Set to 1.0 μm. This is because if the thickness of the first base film 4 is less than 0.1 μm, the height of the projections due to the large particles 2 added to the second base film 3 is too high to cause dropout, and If the thickness of the base film 4 exceeds 1.0 μm, the height of the projections becomes insufficient, and the effect of preventing clogging of the head cannot be sufficiently exhibited. A more preferable range of the thickness of the first base film 4 is 0.5 to 1.0 μm. Considering that the large particles 2 do not fall off, the thickness of the second base film 3 is preferably 3.0 μm or more, preferably 3.0 μm.
It is more preferable that the thickness be 6.0 to 6.0 μm. Polymer coating 6
Considering that the fine particles 5 do not fall off,
It is preferably from 0.01 to 0.02 μm.

The polymer film 6 may be continuous or discontinuous. Examples of the material of the polymer film 6 include polar polymer materials having a polar group such as a hydroxyl group, an ether group, an ester group, an amide group, a methoxy group, and a hydroxypropyl group, for example, polyvinyl alcohol, tragacanth rubber, gum arabic, Examples include casein, gelatin, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and a water-soluble polyester ether copolymer, and a mixture thereof can also be used. In addition, as a method of forming this on a base film such as a polyester film, a method of applying a resin coating solution containing fine particles 5, preferably an aqueous paint, to the film surface during a polyester film production process and drying and solidifying the same. Alternatively, a method of applying a resin coating liquid containing the particles to a biaxially oriented polyester film, followed by drying and solidification can be employed.

The non-magnetic support of the magnetic recording medium of the present invention has large projections 7 formed on both sides thereof at a rate of 1.0 to 100,000 / mm ² . If the rate of forming the large projections 7 is less than 10,000,000 pieces / mm ² , the running property (still life) is insufficient, and if the rate of forming the large projections 7 exceeds 100,000 pieces / mm ^2. Spacing increases, electromagnetic conversion characteristics are reduced, or dropout is caused. A more preferable range of the formation ratio of the large projections 7 is 1.0 to 500000 / mm ² .

Further, 500 to 15
Fine projections 8 are formed at a rate of one million / mm ² . When the rate of forming the fine projections 8 is less than 5 million pieces / mm ² , the running property (still life) is insufficient, and when the rate of forming the fine projections 8 exceeds 15 million pieces / mm ² , the fineness becomes small. Rushing increases and causes a decrease in electromagnetic conversion characteristics. A more preferable range of the ratio of forming the fine projections 8 is:
It is 900 to 15 million pieces / mm ² .

The height and the number of the large projections 7 and the fine projections 8 can be adjusted by adjusting the particle size of the large particles 2 and the fine particles 5 and the amount of addition to the base film or the polymer film. it can. The height of the large projection 7 can be adjusted by the thickness of the first base film 4.

In the magnetic recording medium of the present invention, the metal magnetic thin film formed on the nonmagnetic support 1 is formed by, for example, an oblique evaporation method or a vertical evaporation method. As a material of the metal magnetic thin film, Co, Ni, Fe, an alloy thereof, or the like can be used. Improvement of adhesion strength to the base film constituting the non-magnetic support 1, corrosion resistance of the ferromagnetic thin film itself,
In order to improve abrasion resistance, it is desirable that the atmosphere at the time of vapor deposition be an atmosphere in which oxygen gas is dominant, and the ferromagnetic thin film formed on the nonmagnetic support 1 be a ferromagnetic thin film containing oxygen.

As a method for forming a metal magnetic thin film, a vacuum evaporation method in which a ferromagnetic material is heated and evaporated under a vacuum and deposited on a non-magnetic support is preferable. A so-called PVD technique may be used, which is an ion plating method performed, a sputtering method in which glow discharge is caused in an atmosphere containing argon as a main component, and atoms of the target surface are beaten by the generated argon ions.

In the magnetic recording medium of the present invention, between the non-magnetic support and the metal magnetic thin film, or when the magnetic recording medium has a multi-layer structure, to improve the adhesion between the layers and to control the coercive force, May be provided with a base layer or an intermediate layer. Further, a back coat layer may be formed as necessary. As the back coat layer, non-magnetic pigments such as carbon and calcium carbonate are used for polyurethane, vinyl chloride, and vinyl chloride.
It is formed using a material dispersed in a binder such as a vinyl acetate copolymer.

For the purpose of enhancing the durability and weather resistance of the magnetic recording medium, a hard carbon film may be provided on the surface of the metal magnetic thin film by a sputtering method or a CVD method as required. Thus, it is also possible to further enhance the running property based on the shape of the particulate projections.

The magnetic recording medium of the present invention has a rust preventive on the front surface, the back surface or in the vicinity thereof, a gap in the ferromagnetic metal thin film, an interface between the ferromagnetic metal thin film and the nonmagnetic support, a nonmagnetic support, or the like. Various additives such as an agent and an antistatic agent may be present as necessary.

Hereinafter, examples performed to clarify the effects of the present invention will be described. Substantially non-oriented, containing as little as possible internal particles formed based on polymerization residues,
A first base film composed of a raw material A using an amorphous polyethylene terephthalate raw material (A) and a raw material A obtained by adding 0.2 wt% of SiO ₂ particles having a particle size of 0.2 μm to the raw material A (B). Is melt co-extruded so that the thickness of the second base film composed of the raw material B is 5.0 μm, and is quenched to form a long film (base layer). did.

After the base layer thus formed is sequentially stretched in one direction by a biaxial stretching method, 0.01 μm SiO ₂ particles having a particle size of 0.01 μm are coated on the surface on which the metal magnetic thin film is to be formed.
A polymer film (surface-treated layer) is formed by applying and drying an aqueous solution containing a weight% of the aqueous solution, and thereafter, the long film is stretched in the width direction thereof and subjected to a heat treatment to form a base layer and a polymer. A non-magnetic support comprising a coating was obtained. Here, the total thickness of the nonmagnetic support is 6 μm.

On the surface of the non-magnetic support thus produced, a continuous winding evaporation apparatus shown in FIG. 2 was used.
In an atmosphere containing trace amounts of oxygen, continuous oblique vapor deposition
A metal magnetic thin film made of (cobalt) was formed. Specifically, the procedure was performed as follows.

In this continuous winding type vapor deposition apparatus,
For example, in a vacuum chamber 10 having an internal pressure of 10 ⁻³ Pa, a cooling can 11 cooled to, for example, −20 ° C., and a metal magnetic thin film material, for example, a Co vapor deposition source 31 are arranged. Then, the non-magnetic support 1 having the above-described configuration is arranged so as to be unwound from the supply roll 50 and moved along the periphery of the cooling can 11 to be taken up by the take-up roll 51.

In the evaporation source 31, Co, which is the above-described magnetic metal material, is contained in a container 30, and the Co is accelerated and irradiated with an electron beam 21 from an electron beam generating source 20 so that C is emitted.
o is made to fly and is attached to the non-magnetic support 1 running along the periphery of the cooling can 11 to form a metal magnetic thin film. In this case, a shutter 32 is provided between the vapor deposition source 31 and the cooling can 11 to allow only vapor deposition particles incident on the non-magnetic support 1 at a predetermined incident angle to pass therethrough. Is formed.

Further, when depositing such a metal magnetic thin film, oxygen gas is supplied to the surface of the non-magnetic support 1 via an oxygen gas inlet (not shown), whereby oxygen is contained in the metal magnetic thin film, The magnetic properties, durability and weather resistance of the recording medium are improved. In addition, in order to heat the evaporation source, for example, a resistance heating unit, a high-frequency heating unit, a laser heating unit, or the like can be used in addition to the above-described heating unit using an electron beam.

The vapor deposition conditions at this time are as follows. Degree of vacuum: 10 ^-3 (Pa) Oxygen flow rate: 2 (1 / min) Feed rate of nonmagnetic support: 55 (m / min) Thickness of metal magnetic thin film: 180 (nm)

After depositing the magnetic metallic material on the non-magnetic support, 83.5 parts of a 1.5% by weight solution of acryl-polyester resin (Takamatsu Oil & Fat Co., Ltd.) was formed on the first base film.
1. Resin SH551A), a 1.5% by weight solution of polymethyl methacrylate fine particles (particle size: 0.03 μm)
5 parts (Nippon Shokubai Chemical Industry Co., Ltd., Eposter MA),
And a 1.5% by weight solution of polyoxyethylene nonyl phenyl ether (NS240, manufactured by NOF Corporation) 15
Parts were applied at a wet weight of 2.7 g / m ² .

Next, this nonmagnetic support was cut into a width of 8 mm to prepare a sample tape. The height and the number of the large projections 7 were changed by respectively changing the thickness of the first base film and the amount and type (particle size) of the large particles added to the polyethylene terephthalate raw material B. The height and number of the fine projections were changed by changing the amount and type (particle size) of the fine particles added to the polymer film. Thus, magnetic recording media (Examples 1-4 and Comparative Examples 1-6) in which the thickness of the first base film, the particle size of the large particles, the particle size of the fine particles, and the like are variously changed with the same configuration as described above. Produced. However, in Comparative Example 5, a non-magnetic support consisting of a single layer without using the first base film in Example 1 was used, and in Comparative Example 6, a polymer film was formed on the second base film side, and a polymer film was formed. Non-magnetic support with metal magnetic thin film formed on it
79844). Table 1 below shows the particle diameters of the large particles and the fine particles, the thickness of the first base film, and the numbers of the large protrusions and the fine protrusions in each of Examples and Comparative Examples.

[0038]

[Table 1]

Here, the number of protrusions on the surface of the non-magnetic support was measured using a scanning electron microscope (SEM: ultra-high resolution cold FE-SEM “S-900” manufactured by JEOL Ltd.) and an accelerating voltage of 20 kV. At a magnification of 30,000 (5 fields of view) and converted to the number per 1 mm ² .

The characteristics of the sample tapes of Examples 1 to 4 and Comparative Examples 1 to 6 were evaluated under the following conditions. Handling properties: Judgment was made based on the shape (vertical wrinkles) of the roll after forming the metal magnetic thin film on the non-magnetic support. If there are some wrinkles, it is acceptable, but if it occurs over the entire surface, it is impossible to collect it as a tape. Running durability: The vehicle was repeatedly run 100 times, and the state of the output value drop after running compared to the initial output value and the state of output fluctuation due to clogging of the magnetic recording head during running were measured. The reduction in output is acceptable up to approximately -2.0 dB. Still life: Time (minutes) required for the output value (dB) to become half of the first reproduction time was measured. The higher the value, the better the durability, but the measurement was performed for a maximum of 120 minutes. Dropout: Using a dropout counter, a reproduction output having an attenuation of −16 dB or more and a length of 10 μsec or more was determined. An allowable range of 50 pieces / min or less was set. Electromagnetic conversion characteristics (S / N ratio): 8m high band manufactured by Sony Corporation
The measurement was made with a modified m-video deck “EV-900”. However, the values in the table were measured at a relative speed of 3.8 m / sec and a recording frequency of 7 MHz, and the S / N ratio of the sample tape was 0 dB (0 dB) for a commercially available Hi-8ME tape (so-called metal tape) manufactured by Sony Corporation. Is a comparative measurement. The results are shown in Table 2 below.

[0041]

[Table 2]

As is clear from Tables 1 and 2, the thickness of the first base film is 0.1 to 1.0 μm.
m, and the second base film has an average particle size of 2
Large particles of 100 to 1000 μm are added, and the large particles add 1.0 to 100,000 particles / mm ^{2 on} both surfaces of the nonmagnetic support.
Large projections are formed on the first base film, and fine projections having an average particle diameter of 10 to 50 μm are formed on the first base film.
In each of Examples 1 to 6 provided with a polymer coating on which fine projections were formed at a rate of 00 to 15 million / mm ² , still life, running durability (output fluctuation), electromagnetic conversion characteristics, dropout, Almost all requirements could be met with regard to handling properties.

On the other hand, Comparative Example 1 has a short still life because the number of small projections in the polymer film is insufficient. In Comparative Example 2, since the particle size of the large particles in the first base film was too large, the handleability was excellent and the effect of preventing clogging of the magnetic recording head was sufficiently obtained, but the electromagnetic conversion characteristics were low.

In Comparative Example 3, the number (frequency) of large projections and the particle size are sufficient, and the handling properties are satisfied. However, since the first base film is thick, the large size in the second base film is small. The effect of the protrusion on the metal magnetic thin film side is reduced, and the effect of preventing clogging of the magnetic recording head is not obtained. In Comparative Example 4, the effect of preventing clogging of the magnetic recording head was not obtained because the number (frequency) of large projections was insufficient, and the handling property did not satisfy the requirements.

Comparative Example 5 is a sample tape using a non-magnetic support consisting of a single layer without forming the first base film in Example 1, but large particles in the second base film are directly Since large projections are formed on the thin film side, the handleability satisfies the requirements, but the dropout is large and the electromagnetic conversion characteristics are low. Comparative Example 6 is a sample tape using a nonmagnetic support in which particles are contained in the first base film on the side on which the metal magnetic thin film is formed and particles are not contained in the second base film. It does not meet requirements for handling, dropout and magnetic recording head clogging prevention effects.

[0046]

As described above, the magnetic recording medium of the present invention is intended to prevent scraping and falling off during the tape forming step,
The handleability is excellent, the dropout can be prevented, and the durability of the still can be improved. The effect of preventing the clogging of the magnetic recording head even during repeated running is high, and the output is stable.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a main part of a non-magnetic support of a magnetic recording medium of the present invention.

FIG. 2 is a schematic configuration diagram showing a continuous winding type vapor deposition apparatus used for manufacturing the magnetic recording medium of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic support, 2 ... Large particle, 3 ... Second base film, 4 ... First base film, 5 ... Fine particle, 6 ...
Polymer coating, 7 large projection, 8 fine projection, 10 vacuum chamber, 11 cooling can, 20 electron beam source, 21
... Electron beam, 30 ... Container, 31 ... Evaporation source, 32 ... Shutter, 50 ... Supply roll, 51 ... Winding roll

Claims (2)

[Claims] 1. A magnetic recording medium comprising a metal magnetic thin film provided on a nonmagnetic support, wherein the nonmagnetic support comprises:
A laminated film comprising a first base film having a thickness of 0.1 to 1.0 μm and a second base film containing particles having an average particle size of 0.2 to 1.0 μm, wherein the nonmagnetic support A magnetic recording medium, wherein both surfaces have large projections at a rate of 1.0 to 100,000 / mm ² , and a metal magnetic thin film is formed on the first base film side of the nonmagnetic support. 2. A polymer film containing particles having an average particle size of 0.01 to 0.05 μm is provided on a first base film of the non-magnetic support, and a film thickness of the polymer film is provided. ^2. The magnetic recording medium according to claim 1, wherein is smaller than the average particle size of the particles, and the polymer coating has small projections at a rate of 5 to 15 million particles / mm ² .