JP3232948B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic metal thin film type magnetic recording medium used for a VTR, a magnetic disk drive, etc., and more particularly, to achieve a high level of compatibility between electromagnetic conversion characteristics and practical reliability. Therefore, the present invention relates to a method for manufacturing a magnetic recording medium in which a functional thin film such as a hard carbon film is provided on a magnetic layer.

[0002]

2. Description of the Related Art In the field of magnetic recording, digitalization, miniaturization, long time, and other high performances have been advanced in recent years. A metal thin film type magnetic recording medium having a layer formed of a ferromagnetic metal thin film has been actively studied because it is extremely advantageous for short wavelength recording.

A conventional ferromagnetic metal thin film type magnetic recording medium will be described below. FIG. 4 is an enlarged sectional view of a conventional magnetic recording medium. In FIG. 4, reference numeral 1 denotes a non-magnetic substrate such as a polymer film such as a polyester film or a polyimide film or an aluminum thin film. Numeral 2 denotes a magnetic recording layer made of a ferromagnetic metal thin film, which is made of a non-magnetic substrate 1 made of cobalt, nickel, iron or an alloy containing these as a main component by vacuum evaporation such as electron beam evaporation, sputtering, or ion plating. Is formed on. Reference numeral 4 denotes a lubricant layer formed on the ferromagnetic metal thin film 2 by an ordinary coating method or a vacuum evaporation method of an organic compound.

In the magnetic recording medium constructed as described above, for example, in a magnetic tape, the surface of the magnetic layer has extremely good surface properties in order to achieve high-density magnetic recording. For this reason, running durability is greatly affected by friction and abrasion under high-speed sliding with the magnetic head in the process of recording and reproducing the magnetic signal, and the improvement thereof is a major issue. In addition, the magnetic metal thin film is easily corroded, and improvement of storage characteristics is also a major problem.

For this reason, the development of lubricants having excellent running durability, corrosion resistance, etc., and the idea of forming a two-layer structure and sharing the respective roles for running durability, corrosion resistance, etc., have been increasing. That is, as shown in FIG. 5, a lubricant layer 4 is formed on a protective film 3, for example, a lubricant layer is formed on a Si-NO-based thin film (Japanese Patent Laid-Open No. 61-131231). With a fluorine-based lubricant disposed on a hard carbon layer (JP-A-61-126627, JP-A-62-162627)
219314) and the like.

[0006] Further, efforts have been made to further increase the performance of the overall protective film by making the protective layer multi-layered and sharing the function of each layer (for example, JP-A-6-195696).
No.).

[0007]

However, the demands for improving the performance of magnetic recording media are severe, and the above-mentioned conventional configuration cannot be said to have sufficient characteristics. Therefore, electromagnetic conversion characteristics at higher dimensions and practical reliability cannot be achieved. It is necessary to achieve both.

The present invention solves the above-mentioned conventional problems, and has excellent durability after storage for a long period of time, particularly after storage for a long period of time in a high-temperature and high-humidity environment, and has extremely high practical reliability. It is an object of the present invention to provide a method for producing the same.

[0009]

In order to achieve the above-mentioned object, a method of manufacturing a magnetic recording medium according to the present invention comprises the steps of: using a film raw material having a metal magnetic thin film moving in a vacuum on its surface as a counter electrode; A plasma apparatus having a plurality of discharge chambers for forming a thin film by a CVD method and having different thicknesses and components.
When a plurality of thin films are collectively formed, each layer is formed within 2 seconds immediately after forming each lower layer.

[0010]

The method of manufacturing a magnetic recording medium according to the present invention improves the adhesion strength of a thin film by plasma CVD.
The mechanism is not well understood, but probably plasma C
It is considered that the formation of the next layer in a state where the surface of the thin film formed by VD keeps the activity forms a chemical bond and improves the adhesion strength. By improving the adhesion strength, the repeated running durability, especially after repeated storage at high temperature and high humidity for a long period of time, can be improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a magnetic tape used in an embodiment of the present invention. In FIG. 1, 1 is a non-magnetic substrate made of a polymer film, 2 is a ferromagnetic metal thin film,
Reference numeral 3 denotes a protective film composed of multiple layers, 4 denotes a lubricant layer, and 5 denotes a back coat layer.

As the nonmagnetic substrate 1, polyethylene terephthalate is often used. Other polyester films such as polyethylene naphthalate, cellulose derivatives such as cellulose acetate, plastic films such as polyamide and polyimide, and aluminum thin films are used. Can be used.

As the ferromagnetic metal thin film 2, a vacuum evaporation method,
It is possible to use iron, cobalt, nickel, an alloy containing these as a main component, or a partial oxide or a partial nitride thereof formed by a sputtering method or an ion plating method.

The protective film 3 composed of multiple layers is composed of a hydrocarbon gas,
A hydrocarbon gas containing nitrogen, fluorine or other elements or a mixed gas of these gases and an inert gas such as helium, neon, argon or the like is formed by a plasma CVD method. A thin film can be formed by appropriately selecting a material gas and film forming conditions in order to have functions such as strong adhesive force, good gas shielding effect, and good orientation of a lubricant. In addition, from the viewpoint of securing productivity and film performance, it is possible to form a multilayer film while maintaining a vacuum with a single vacuum exhaust without repeating vacuum evacuation and air leak from the viewpoint of securing productivity and film performance. Desirably, more desirably, a plurality of layers are formed simultaneously by one film transport.

The method for forming the protective film 3 (hard carbon film) will be described in more detail with reference to FIG. 2 which is a schematic diagram of the apparatus for forming a hard carbon film of the first embodiment.

In FIG. 2, reference numeral 6 denotes a vacuum chamber,
When the pressure inside the tank is 10 ^-Fourtorr-10^-Five
Evacuation is performed so as to be in a high vacuum state of torr.
Reference numeral 8 denotes a ferromagnetic metal thin film 2 and a back coat
The raw material of the magnetic tape on which the
6 roll rolls 11-a, b,
via c, d, e, f and can 12-a, b, c
It is taken up by a take-up roll 10. Can 12-a,
b and c can transport the raw magnetic tape 8 at a constant speed.
It works to control rotation.

13-a, b and c are protective films 3-a, b and c
Sub-chamber (plasma generator) for forming a film on the surface of the ferromagnetic metal thin film 2 of the magnetic tape raw material 8,
The discharge electrode 1 is provided inside the sub-chambers 13-a, 13b, 13c.
4-a, b, and c are provided. Discharge electrodes 14-a,
b and c are connected to power sources 15-a, b and c for plasma generation.

16-a, b and c represent hydrocarbon-based gas or Ar
A source gas inlet for introducing a source gas such as a gas or a nitrogen gas into the sub-chamber 13.

Also, pass rolls 11-a, b, c, d,
e and f represent not only a function for stabilizing the running of the magnetic tape raw material 8 but also a current flowing to the ferromagnetic metal thin film 2 of the magnetic tape raw material 8 in the sub-chambers 13-a, b, and c. Also serves as an energizing roll for grounding (grounding) via a resistor. At this time, pass roll 11-
Due to local contact between a, b, c, d, e, and f and the raw magnetic tape 8, the problem that the current concentrates on the contact portion and the non-magnetic substrate 3 loses heat does not occur. , Pass rolls 11-a, b, c, d, e, and f are semiconductor materials;
For example, it is preferable to use SiC.

In order to form a hard carbon film, a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas is introduced into the sub-chamber 13 and the pressure is 0.001 to 1 Torr.
Is discharged inside the sub-chamber 13 to generate a plasma of a hydrocarbon gas to form a hard carbon film on the surface of the ferromagnetic metal thin film 2. As a discharge type, any of a DC discharge, an AC discharge, and a discharge in which an AC is superimposed on a DC may be used.
It can be determined experimentally. The ferromagnetic metal thin film 2
By applying a voltage of 0 to -2 KV to the electrode on the side, the hardness of the film can be increased and the adhesion can be improved.

As the hydrocarbon gas, methane, ethane,
Propane, butane, pentane, hexane, heptane, octane, benzene and the like can be used.

In order to form a hard film, it is desirable to increase discharge energy as much as possible. Further, it is desirable that the temperature of the substrate is as high as possible within a range where the raw film is not damaged.

The thickness of the hard carbon film is 50 to 30.
The range of 0A is appropriate. If the thickness is thinner than this, a sufficient protective film effect cannot be obtained.
The output is greatly reduced due to the spacing, and the practicality is reduced.

Further, a film having good adhesion to the ferromagnetic metal film 2 and a thin film having good adhesion between the hard carbon film and the lubricant are simultaneously formed by the same plasma CVD method as the above-described method of forming the hard carbon film. For the thin film for improving the adhesiveness, various conditions of the plasma discharge and the type of the reaction gas were examined, and a film suitable for the above-mentioned purpose was selected.

The lubricant used in the present invention is not particularly limited, but includes polar groups such as a carboxyl group, an amino group, a phosphate group, a hydroxyl group and an ester group.
A fluorine-based lubricant having at least one fluoroalkyl group or at least one perfluoropolyether group is effective. The lubricant layer in the present invention can be formed by a conventional coating method such as a bar coating method, a reverse roll coating method, and a die coating method.

Hereinafter, a second embodiment will be described. On a 7 micron-thick polyethylene terephthalate film having wavy projections and granular projections composed of a modified silicone in which silica fine particles having a particle size of 100 A are dispersed on a smooth surface and a thickener, by an electron beam method while introducing oxygen. Continuous oblique deposition was performed to form a 1800 A-thick Co—O film (ferromagnetic metal thin film 2).

Then, a coating liquid obtained by dispersing a mixture of carbon black and calcium carbonate at a weight ratio of 3: 2 in a resin component of polyurethane and nitrocellulose at a weight ratio of 3: 2 was applied to the side opposite to the vapor deposition layer by a reverse roll method. It was applied with a coating machine and dried at a temperature of 110 ° C. to form a backcoat layer 5 having a thickness of 0.7 μm, thereby producing a raw magnetic tape 8.

Next, using the film forming apparatus shown in FIG. 5 as a protective film, cyclohexane is introduced as a raw material gas into the first sub-chamber 13-a, and a plasma polymerization film is formed at a degree of vacuum of 0.1 Torr, a frequency of 15 kHz, and a voltage of 500 V at a voltage of 500 V. 10A
Form.

Next, in the second sub-chamber 13-b,
A mixed gas of methane and argon (ratio: 4: 1) is introduced, the frequency is 15 KHz, the voltage is 1100 and the degree of vacuum is 0.2 Torr.
A hard carbon film having a thickness of 150 A was formed by plasma polymerization at V.

Further, a mixed gas of methane, argon, nitrogen and ammonia (the ratio is 8: 2: 1: 1) is introduced into the third sub-chamber 13-c, and the degree of vacuum is 0.2 Torr.
A nitrogen-containing hard carbon film having a thickness of 20 A was formed by plasma polymerization at a frequency of 15 KHz and a voltage of 800 V at r.

The thin films formed in the first, second and third sub-chambers may be formed simultaneously by a single film transport or may be separately formed by reciprocating the film. Further, the number of the sub-chambers 13 is not limited to one around one can 12, and a plurality of sub-chambers 13 can be provided.

Further, a lubricant containing a fluorinated carboxylic acid is applied to the surface of the protective film 3 by a reverse roll coater,
Drying was performed at a temperature of 5 ° C. to form a lubricant layer 4. Next, the raw magnetic tape 8 was cut into a width of 8 mm with a slitter and cut to 8 mm.
A magnetic tape for VTR was prepared.

When forming the protective film 3, the sub-chamber 1
The magnetic tape was prepared by changing the time from the formation of each film to the formation of the next layer by changing the position 3 and the film transport speed. At that time, when changing the transport speed,
In order to make the thickness of the protective film 3 constant, the amount of gas introduced into the sub-chamber was adjusted to make the thickness uniform. This magnetic tape was left for one week in a high-temperature and high-humidity environment (50 ° C., 80% RH), and then 8 mm VTR (SONY) in an environment of 23 ° C., 60%.
The vehicle was repeatedly run using EVS-900 (manufactured by Corporation) to check the stability of the output, and the point in time when the output decreased by 3 dB from the initial output was determined as the life.

[0035]

[Table 1]

As is clear from Table 1, all of the magnetic tapes of Sample Examples 1 to 4 according to the present invention were 200 tapes.
Shows the repetition running life of more than pass. However, the running life of the magnetic tapes of Sample Examples 5 to 9 is short, and the life is remarkably reduced particularly when the time from the formation of the first layer to the formation of the second layer is long.

[0037]

As described above, according to the present invention, a hard carbon film having good adhesion can be formed on a ferromagnetic metal thin film, and it can be stored for a long period of time, especially in a high temperature and high humidity environment. It is possible to improve the durability after storage for a period, to provide a magnetic recording medium having extremely high practical reliability, and to provide an excellent effect of improving the practical characteristics of the metal thin film type magnetic recording medium.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a configuration of a magnetic recording medium (ferromagnetic metal thin film type magnetic tape) according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a protective film forming apparatus according to a first embodiment of the present invention.

FIG. 3 is a schematic diagram showing a protective film forming apparatus according to a second embodiment of the present invention.

FIG. 4 is an enlarged sectional view showing the structure of a conventional magnetic recording medium (ferromagnetic metal thin film type magnetic tape).

FIG. 5 is an enlarged sectional view showing the configuration of a conventional magnetic recording medium (ferromagnetic metal thin film type magnetic tape with a protective film).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic substrate 2 Ferromagnetic metal thin film 3 Protective film 4 Lubricant layer 5 Back coat layer 6 Vacuum tank 7 Vacuum pump 8 Magnetic tape raw material 9 Unwind roll 10 Take-up roll 11 Pass roll 12 Can 13 Sub-chamber 14 Discharge electrode 15 Power source for plasma generation 16 Source gas inlet

Claims (1)

(57) [Claims] 1. A metal magnetic thin film moving in a vacuum on a surface thereof.
Plasma CVD using the raw material film as a counter electrode
The thickness and components of the multilayer on the film
A method for manufacturing a magnetic recording medium for forming a composed thin film of the multilayer by a plasma apparatus having a plurality of discharge chambers
When forming the layers, make sure that each layer is
Of magnetic recording media characterized in that a film is formed within 2 seconds
Construction method.