JPH05274665A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce a magnetic recording medium excellent in corrosion resistance and durability. CONSTITUTION:A thin ferromagnetic metal film is formed on a long-sized nonmagnetic substrate and a lubricative layer and/or a protective layer is further formed on the thin ferromagnetic metal film. At this time, the thin ferromagnetic metal film is formed by vapor-depositing a ferromagnetic metal while applying 0.8-3kg/mm<2> tension to the substrate. The resulting wound body is unwound in a soln. of a lubricant and/or a soln. of a protective agent and the thin ferromagnetic metal film is coated with the soln. or it is heated to 80-150 deg.C and coated with the soln. The objective magnetic recording medium excellent in corrosion resistance and durability is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic recording medium. More specifically, the present invention relates to a method of manufacturing a thin film magnetic recording medium having improved durability and corrosion resistance.

[0002]

2. Description of the Related Art A magnetic recording medium that has been widely used in the past is a coating type in which a magnetic coating mainly containing acicular magnetic powder and a polymer binder is applied on a non-magnetic substrate to form a magnetic layer. Magnetic recording medium. At present, magnetic recording / reproducing devices tend to have higher densities, and there is a demand for magnetic recording media having excellent short wavelength recording characteristics.

However, there is a limit to the improvement of short wavelength recording characteristics in the coating type magnetic recording medium. On the other hand, C
A metal thin film type magnetic recording medium in which a ferromagnetic material containing Co as a main component such as o, CoNi, CoNiP, and CoCr is formed on a non-magnetic substrate composed of a long tape by a vacuum deposition method is used. Since no magnetic binder is mixed in, a remarkably high residual magnetic flux density can be obtained, and
Since the magnetic layer can be formed extremely thin, it has the advantages of high output and excellent short wavelength response. Due to this feature, the metal thin film type magnetic recording medium has recently become the mainstream of the magnetic medium.

[0004]

However, when the surface of the magnetic film of the raw material of the long tape reaches the dew point or higher due to moisture in the atmosphere, the ferromagnetic metal (for example, cobalt, iron, etc.) easily becomes water. It forms a Japanese product and causes so-called corrosion. For example, in the case of cobalt or iron, the surface is covered with a corrosive substance having a mechanically weak sliding strength, and as a result, the output is deteriorated due to head clogging caused by dirt on the head.

In order to prevent such problems in the thin-film magnetic recording medium, it has been conventionally proposed to form an organic and / or inorganic protective film having excellent adsorption and corrosion resistance on the surface of the magnetic film. In particular, the organic protective / lubricating layer is excellent in mass productivity.

The durability of the metal thin film medium depends on the durability of the boundary lubricating layer formed by chemisorption. However, there is a drawback that the lubricant layer formed on the surface of the magnetic film simply by chemical adsorption is easily peeled off by sliding the head. As a result, durability and corrosion resistance tended to be lost in a short time.

Therefore, an object of the present invention is to provide a method for manufacturing a metal thin film type magnetic recording medium in which corrosion resistance and durability are drastically improved while using a conventional organic protective / lubricating layer.

[0008]

To achieve the above object, in the present invention, a ferromagnetic metal thin film layer is provided on a long non-magnetic substrate, and a lubricating layer and / or a protective layer is provided on the ferromagnetic metal thin film layer. In a method for producing a metal thin film magnetic recording medium, which comprises forming a layer, a vapor-deposited raw roll body provided with the ferromagnetic metal thin film layer is unrolled in a solution of the lubricant and / or protective agent and applied. A method for manufacturing a metal thin film magnetic recording medium is provided. In the above method, when the ferromagnetic metal is vapor-deposited on the non-magnetic substrate while applying tension in the range of 0.8 to 3 kg / mm ² to the non-magnetic substrate, the subsequent lubricating layer and / or protective layer may be formed. Better results are obtained in formation. Alternatively, if the surface of the ferromagnetic metal thin film is heated to a temperature in the range of 80 ° C. to 150 ° C. immediately before applying the lubricant and / or protective agent solution, the magnetic material having better corrosion resistance and durability can be obtained. A recording medium is obtained.

[0009]

[Operation] On the surface of the magnetic film of the metal thin film medium by the vapor deposition method,
There are microscopic voids due to the unevenness of the substrate surface. Since this void is almost in a vacuum state immediately after vapor deposition, if a long winding body is "dipped" in a solution of a lubricant or a protective agent and unwound, a part of the solution becomes a microscopic void. Can easily get into. As a result, even if the lubricant film or the protective film on the surface of the magnetic film is peeled off due to the head sliding, the solution taken in the voids gradually exudes to the surface of the magnetic film, and a new protective film or lubricant film is again removed. As it is formed, durability and corrosion resistance are maintained for a long period of time.

If tension is applied to the non-magnetic substrate during vapor deposition, or if the surface of the vapor deposited film is heated during application of a lubricant or the like, the volume of the voids shrinks during cooling, and the lubricant component together with the solvent reaches the interior. As it enters, it retains the same effect as steam. In addition, the surface of the magnetic film immediately after vapor deposition is not exposed to the outside air, so it is very active. On this surface, the formation of the lubricating film or the protective film occurs completely over the entire surface.

The tension applied to the non-magnetic substrate during vapor deposition is 0.8.
It is preferably in the range of 3 kg / mm ² . When the tension is less than 0.8 kg / mm ² , the permeation and storage effect of the lubricant and the protective agent is insufficient, and the durability and corrosion resistance of the medium are hardly improved. On the other hand, if the tension is more than 3 kg / mm ² , an unrecoverable permanent strain may occur in the non-magnetic substrate, or an inconvenient situation such as breakage may occur.

When the surface of the ferromagnetic metal thin film is heated during the coating of the lubricating layer, the heating temperature is preferably in the range of 80 to 150 ° C. When the heating temperature is lower than 80 ° C., the effect of permeation and storage of the lubricant and the protective agent becomes insufficient, and the durability and corrosion resistance of the medium are hardly improved. On the other hand, if the heating temperature exceeds 150 ° C., the base film may be thermally deformed by a long-time treatment, which is not preferable.

The material forming the lubricating layer and / or the protective layer must be capable of being liquefied.
Such materials are well known to those of ordinary skill in the art. The protective layer is used not only by its name but also by including a rust preventive agent layer and the like. When a rust preventive is also used together with the lubricant, it is preferable to apply the rust preventive first.

[0014]

The present invention will be described in more detail with reference to the following examples. Example 1 Polyethylene terephthalate (PE
T) film and Co-20wt as a ferromagnetic metal
% Ni, an CoNi film having a film thickness of 2000 Å was obliquely vapor-deposited on the PET traveling along the cooled drum by electron beam vapor deposition. At this time, the tension applied to the film substrate is 1.2 to 2.4 kg / mm ^2, and oxygen gas is introduced into the vacuum chamber at a rate of 200 ml / min, and the magnetic film surface is mainly composed of cobalt oxide. This vapor-deposited raw roll is taken out from the vacuum chamber, immediately put into a 0.03 wt% solution of nitrobenzotriazole in isopropyl alcohol, and the magnetic surface and the back surface thereof are immersed in the solution while the roll is unrolled. Then, it was introduced into the atmosphere, and a blade was used to uniformly spread the adhered matter, and then dried and wound. A measurement sample was cut out from this product.

Example 2 A measurement sample was prepared in the same manner as in Example 1 except that a 0.04 wt% solution of perfluoropolyether was used as a lubricant.

Example 3 A sample for measurement was prepared in the same manner as in Example 2 except that a 0.04 wt% solution of a benzotriazole fatty acid salt was used in place of the perfluoropolyether of Example 2.

Comparative Example 1 In Example 1, a measurement sample was prepared by a conventionally used gravure coating method while changing the solution concentration so that the amount of adhesion to the magnetic film was the same.

Comparative Example 2 In Example 2, a measurement sample was prepared by a conventionally used gravure coating method while changing the solution concentration so that the amount of adhesion to the magnetic film was the same.

Comparative Example 3 In Example 3, a conventionally used gravure coating method was used to prepare a measurement sample by changing the solution concentration so that the amount of adhesion to the magnetic film was the same.

With respect to the samples obtained in Examples 1 and 3 and Comparative Examples 1 and 3, the reduction ratio of saturation magnetization after 1 week was measured in an atmosphere of 60 ° C. and 90% RH. Three
And 8 mm VT for the samples obtained in Comparative Examples 2 and 3.
The life of the still mode by R was measured. The results are shown in Table 1 below. In the table below, the saturation magnetization deterioration rate was calculated by (Ms ₀ −Ms) / Ms ₀ (%). here,
Ms ₀ is the initial value before exposure. The still life is the time until the output level drops by -6 dB from the initial output level.

[0021]

[Table 1] Table 1 Saturation magnetization deterioration rate Still life (%) (min) Example 1 2.2 --- Example 2 ---> 120 Example 3 3.3> 120 Comparative Example 1 5.6- --- Comparative Example 2 --- 35 Comparative Example 3 7.0 26

Example 4 Polyethylene terephthalate (PE
T) film and Co-20wt as a ferromagnetic metal
% Ni, an CoNi film having a film thickness of 2000 Å was obliquely vapor-deposited on the PET traveling along the cooled drum by electron beam vapor deposition. At this time, oxygen gas is added to the vacuum chamber at 20
It is introduced at a rate of 0 ml / min and the surface of the magnetic film is mainly composed of cobalt oxide. The vapor-deposited original roll was taken out from the vacuum chamber and a 0.03 wt% solution of nitrobenzotriazole in isopropyl alcohol was applied by a gravure coater. The surface of the magnetic film immediately before coating was heated with an infrared lamp to adjust the temperature of the film surface to 80 to 150 ° C.

Example 5 0.1 wt% of perfluoroalkyl polyether as a lubricant
% Solution was used, and prepared in the same manner as in Example 4.

Example 6 Instead of the perfluoroalkyl polyether of Example 5,
It was prepared in the same manner as in Example 5 except that a 0.1 wt% solution of benzotriazole fatty acid salt was used.

Comparative Example 4 A device was manufactured in the same manner as in Example 4 except that the heating by the infrared lamp was omitted.

Comparative Example 5 A sample was prepared in the same manner as in Example 5 except that the heating by the infrared lamp was omitted.

Comparative Example 6 The same procedure as in Example 6 was carried out except that the heating by the infrared lamp was omitted.

Samples for measurement were cut out from the coated original fabrics produced by each of the above-mentioned methods, and the samples obtained in Examples 1 and 3 and Comparative Examples 1 and 3 were stored in an atmosphere of 60 ° C. and 90% RH for 1 week. The subsequent deterioration rate of saturation magnetization was measured, and 8 was obtained for the samples obtained in Examples 2 and 3 and Comparative Examples 2 and 3.
The life of the still mode at 5 ° C. and 20% RH was measured by mmVTR. The results are shown in Table 2 below. In the table below, the saturation magnetization deterioration rate is (Ms ₀ −Ms) / Ms
_{It was calculated as 0} (%). Here, Ms ₀ is an initial value before exposure. The still life is -6dB from the initial output level.
It is time to decrease.

[0029]

Table 2 Table 2 Saturation magnetization deterioration rate Still life (%) (minutes) Example 1 2.2 --- Example 2 ---> 120 Example 3 3.3> 120 Comparative Example 1 5.6- --- Comparative Example 2 --- 35 Comparative Example 3 7.0 26

As is clear from the results shown in Tables 1 and 2, the magnetic recording medium obtained by the method of the present invention exhibits extremely excellent corrosion resistance and durability.

[0031]

As described above, according to the method of the present invention, a magnetic recording medium having excellent corrosion resistance and durability can be obtained.

Claims (2)

[Claims] 1. A method for producing a magnetic recording medium, comprising a ferromagnetic metal thin film layer provided on a long non-magnetic substrate, and a lubricating layer and / or a protective layer formed on the ferromagnetic metal thin film layer. To form a ferromagnetic metal thin film layer by evaporating a ferromagnetic metal while applying a tension of 0.8 to 3 kg / mm ^{2 to} the film, and forming the lubricating layer and / or the protective layer.
A method for producing a magnetic recording medium, comprising: applying a vapor-deposited original roll body provided with the ferromagnetic metal thin film layer while unrolling it in the lubricant solution and / or the protective agent solution. 2. A method for producing a magnetic recording medium, comprising a ferromagnetic metal thin film layer provided on a long non-magnetic substrate, and a lubricating layer and / or a protective layer formed on the ferromagnetic metal thin film layer. And / or when the protective agent solution is applied onto the ferromagnetic metal thin film layer, the ferromagnetic metal thin film layer is applied at 80 ° C to 150 ° C.
A method for producing a magnetic recording medium, which comprises applying the solution after heating to a temperature in the range of ° C.