JPH08287458A - Production of magnetic recording medium and producing device therefor - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium having a ferromagnetic metal thin film as a recording layer which enables high-density magnetic recording and to obtain a producing method of a magnetic recording medium having extremely high reliability for practical use and excellent durability even after stored for a long period, especially stored for a long period in a high temp. and high humidity environment. CONSTITUTION: A subchamber 14 equipped with an electrode 15 on one face and having an opening opposite to the electrode is disposed in a vacuum chamber 6. A magnetic tape web 8 having a ferromagnetic metal thin film 2 on its surface is arranged on the opening of the subchamber 14 so that a hard carbon film is formed as a protective film layer 3 on the ferromagnetic metal thin film 2 by plasma CVD method using the electrode 15 and the ferromagnetic metal thin film 2 as the counter electrode. In this method, by evacuating the subchamber 14 is such a manner that evacuation in the longitudinal direction of the film is performed more than evacuation in the width direction of the film, a hard carbon film having uniform characteristics in the width direction can be formed at a high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a ferromagnetic metal thin film type magnetic recording medium used in a VTR, a magnetic disk device or the like, and particularly, it has high electromagnetic conversion characteristics and practical reliability. The present invention relates to a manufacturing method and a manufacturing apparatus of a magnetic recording medium in which a protective film made of a hard carbon film is provided on a magnetic layer in order to achieve both dimensions.

[0002]

2. Description of the Related Art In the field of magnetic recording, high performance such as digitalization, miniaturization and long time has been advanced in recent years, and the demand for high density magnetic recording medium has been increased accordingly, and magnetic recording A metal thin film magnetic recording medium having a layer made 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. 2 is an enlarged cross-sectional view of a conventional magnetic recording medium. In FIG. 2, reference numeral 1 is a polymer film such as a polyester film or a polyimide film, or a non-magnetic substrate such as an aluminum thin film. Reference numeral 2 is a magnetic recording layer made of a ferromagnetic metal thin film, and cobalt, nickel, iron or an alloy containing them as a main component is deposited on the substrate 1 by a vacuum vapor deposition method such as an electron beam vapor deposition method, a sputtering method or an ion plating method. Has been formed.
Reference numeral 4 denotes a lubricant layer, which is formed on the magnetic recording layer of the ferromagnetic metal thin film 2 by a conventional coating method or vacuum deposition method of an organic compound.

In the magnetic recording medium having the above-mentioned structure, for example, in the case of a magnetic tape, the surface of the magnetic layer has a very good surface property in order to achieve high density magnetic recording. Therefore, the running durability is greatly affected by friction and wear under high speed sliding with the magnetic head during the recording / reproducing process of the magnetic signal, and its improvement is a major issue.

Therefore, a fluorine-based lubricant having excellent lubricating properties has been developed and studied. For example, a polar group such as a carboxyl group, an amino group, a phosphoric acid group, a hydroxyl group, a mercapto group, or a fluoro group is attached to the terminal of the molecule in order to improve the adhesion to the ferromagnetic metal thin film 2 and to exhibit excellent lubricity. Fluorine-based lubricant having at least one alkyl group and at least one aliphatic alkyl group (JP-A-61-10)
7529, JP-A-62-92225, JP-A-62-92226, JP-A-62-92227, JP-A-61-107527, JP-A-61-
Japanese Patent Laid-Open No. 107528 and Japanese Patent Laid-Open No. 60-229221).

However, in the above example, the durability,
Since the running property and the corrosion resistance are not sufficiently satisfied, there is an increasing number of ideas that the respective roles are shared by stacking them. That is, as shown in FIG. 1, a lubricant layer is formed on a protective film, for example, a lubricant layer 4 is formed on a Si—N—O type thin film (Japanese Patent Laid-Open No. 61-131231). One in which a fluorine-based lubricant is disposed on the carbon layer (Japanese Patent Laid-Open No. 61-126627, Japanese Patent Laid-Open No. 62-2).
(Japanese Patent No. 19314) and the like have been proposed and are being actively studied.

[0007]

However, in the above conventional structure, it cannot be said that it is sufficient to form a uniform hard carbon film on a wide film raw material, and a high performance hard carbon film can be obtained. It is desired to be able to manufacture uniformly and with high yield.

The present invention has been made in view of the above circumstances, and provides a magnetic recording medium which is excellent in durability after being stored for a long time, particularly after being stored in a hot and humid environment for a long time, and which has extremely high practical reliability. An object of the present invention is to provide a method and an apparatus for manufacturing a magnetic recording medium that can be manufactured uniformly and with a high yield.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an electrode on one surface of a vacuum chamber,
By a plasma CVD method in which a sub-chamber in which a raw film of a film having a ferromagnetic metal thin film on the surface is arranged is provided on the facing opening surface and the electrode and the ferromagnetic metal thin film are used as the counter electrodes
In the method of producing a hard carbon film on the surface of a ferromagnetic metal thin film, the exhaust from the sub-chamber is performed more in the film longitudinal direction than in the film width direction, and the gap between the ferromagnetic metal thin film surface and the sub-chamber is used. Has a total area in the longitudinal direction of the film larger than that in the width direction of the film, and has a plurality of rollers at the opening on the side surface in the width direction of the sub chamber. A hard carbon film using a sub-chamber having nozzles for supplying the inert gas and the reaction gas at different ratios in the width direction, and respectively supplying the inert gas and the reaction gas into the sub-chamber. Is formed.

[0010]

The present invention improves the plasma uniformity of the reactive gas and the inert gas in the width direction of the original film in the sub-chamber in plasma CVD, that is, the exhaust from the sub-chamber is performed. By performing more in the film longitudinal direction than in the film width direction, the change in the reactive gas plasma in the width direction is improved, thereby effectively improving the plasma uniformity. This is achieved by using a sub chamber in which the area of the gap between the thin film surface and the sub chamber is larger in the film longitudinal direction than in the film width direction. By having a plurality of rollers in the opening on the side surface in the width direction, the exhaust from the sub-chamber is likewise fitted. In which are realized by performing many by the film lengthwise direction than the beam width.

Further, by supplying the inert gas and the reactive gas at different ratios in the width direction into the sub-chamber, the variation of the reactive gas in the width direction of the plasma is improved, and the plasma in the width direction of the original film is improved. Is effectively improved, and this is achieved by using a sub-chamber having a nozzle that supplies the inert gas and the reaction gas individually into the sub-chamber. is there.

[0012] By effectively improving the uniformity of plasma in the width direction of the film, a hard carbon film having high uniformity in the width direction is formed, and even after being stored at high temperature and high humidity for a long time, It is possible to provide a magnetic recording medium having durability with a high yield.

[0013]

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,
3 is a protective film layer made of a hard carbon film, 4 is a lubricant layer, and 5 is a back coat layer.

Polyethylene terephthalate is often used as the non-magnetic substrate 1, but other polyester films such as polyethylene naphthalate, cellulose derivatives such as cellulose acetate, plastic films such as polyamide and polyimide, and aluminum thin films. Can be used.

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

The protective film layer 3 made of a hard carbon film can be formed by a plasma CVD method using a mixed gas of hydrocarbon and an inert gas such as argon.

The method for forming the hard carbon film will be described in more detail with reference to FIG. 3 which is a schematic view of a film forming apparatus for the hard carbon film.

In FIG. 3, reference numeral 6 denotes a vacuum chamber, which is a vacuum port.
The pressure inside the tank is 10 ^-Fourtorr-10^-Five
Evacuation is performed so that a high vacuum state of torr is achieved.
8 is a ferromagnetic metal thin film 2 and a back coat on the non-magnetic substrate 1.
Is a magnetic tape original sheet on which the winding layer 5 is formed, and
2 rolls 11, 12 and
It is taken up by the take-up roll 10 via the can 13.
It The can 13 conveys the original magnetic tape 8 at a constant speed.
It controls the rotation so that it can be done.

Reference numeral 14 is a sub-chamber (plasma generating portion) for forming a hard carbon film on the surface of the ferromagnetic metal thin film 2 of the magnetic tape raw material 8. Inside the sub-chamber 14, a discharge electrode 15 is installed. Has been done. The discharge electrode 15 is connected to a plasma generating power supply 16.

Further, the pass rolls 11 and 12 not only serve to stabilize the running of the magnetic tape stock 8,
It also serves as an energizing roll for grounding the current flowing through the ferromagnetic metal thin film 2 of the magnetic tape raw material 8 in the sub-chamber 14 via a resistor. At this time, the local contact between the pass rolls 11 and 12 and the original magnetic tape 8 prevents the problem that the current concentrates on the contact portion and the non-magnetic substrate 1 loses heat. It is preferable to use a semiconductor material for 12, for example, SiC.

The raw material gas composed of a hydrocarbon gas and an inert gas passes through the mixers 18 from the gas introduction ports 19 and 20, respectively, becomes a uniform mixed gas, and is supplied from the raw material gas introduction port 17 into the sub-chamber 14. .

In order to form a hard carbon film, a mixed gas of a hydrocarbon gas and an inert gas is introduced into the sub-chamber 14 and discharge is carried out inside the sub-chamber 14 while maintaining a pressure of 0.001 to 1 Torr. Then, plasma of hydrocarbon gas is generated to form a hard carbon film on the surface of the ferromagnetic metal thin film. The discharge type may be DC discharge, AC discharge, or discharge in which AC is superimposed on DC, and the discharge frequency can be experimentally determined. Further, the hardness of the film can be improved by applying a voltage of 0 to -2 KV to the electrode on the ferromagnetic metal thin film side and by increasing the ratio of the inert gas in the mixed gas.

As a mixed gas ratio of hydrocarbon gas and inert gas, 10: 1 to 1: 3 can be used, but the film quality,
It can be determined by design in consideration of the film forming speed and the like.

As the hydrocarbon gas, methane, ethane,
Aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane and octane, aromatic hydrocarbons such as benzene, toluene and xylene can be used, and argon gas is suitable as the inert gas.

Further, in order to form a hard film, it is desirable to maximize the discharge energy. Further, it is desirable that the temperature of the substrate is as high as possible within a range where the original magnetic tape 8 is not damaged.

The thickness of the hard carbon film is 100 to 3
The range of 00 angstroms is appropriate, and if it is thinner than this range, a sufficient protective film effect cannot be obtained, and if it is larger than this range, the output due to spacing is greatly reduced and the practicality is reduced.

The lubricant used in the present invention is not particularly limited, but a polar group such as a carboxyl group, an amino group, a phosphoric acid group, a hydroxyl group and an ester group,
A fluorinated lubricant having at least one fluoroalkyl group or at least one perfluoropolyether group is effective. For forming the lubricant layer 4 in the present invention, a conventional coating method such as a bar coating method, a reverse roll coating method or a die coating method can be applied.

A more specific embodiment will be described below. (Example 1) Introduction of oxygen onto a polyethylene terephthalate film having a thickness of 8 μm and a width of 520 mm, which has granular projections composed of a modified silicone in which silica fine particles having a particle diameter of 180 Å are dispersed on a smooth surface and a thickener. While performing continuous oblique vapor deposition by the electron beam method, a film thickness of 18
A Co-O film of 00 angstrom was formed.

Then, a coating solution prepared by dispersing a mixture of carbon black and calcium carbonate in a ratio of 3: 2 by weight in a resin component in a ratio of 3: 2 by weight of polyurethane and nitrocellulose on the side opposite to the vapor-deposited layer is applied in a reverse roll system. It was applied by a coating machine and dried at a temperature of 110 ° C. to form a back coat layer 5 with a film thickness of 0.6 μm, and a magnetic tape raw fabric 8 was produced.

Then, using the film forming apparatus shown in FIG. 3, a mixed gas of hexane and argon (3: 1) was introduced into the sub-chamber 14 under the condition of 400 sccm, and high frequency (10 KH
z) A direct current voltage of -1.0 KV is applied to the ferromagnetic metal thin film 2 of the magnetic tape raw material 8 by plasma, using the electrode and the magnetic tape raw material 8 itself as a counter electrode, and discharge is performed 180
A hard carbon film (protective film layer 3) having an angstrom thickness was formed.

In FIG. 3, the raw magnetic tape 8 is arranged along a can 13, and an opening (side surface:
The sub-chamber 14 having a length of 500 mm and a longitudinal portion of 500 mm is arranged so as to be adjusted to have a gap with the magnetic tape original fabric 8, the side surface portion 21 is 150 μm and the longitudinal portion 22 is 800 μm.

Further, a lubricant containing a fluorine-containing carboxylic acid is applied to the surface of the hard carbon film by a reverse roll coater,
The lubricant layer 4 was formed by drying at a temperature of 75 ° C. next,
8m width by cutting the raw tape 8 of magnetic tape with a slitter
A magnetic tape A for mVTR was prepared.

Further, as a comparative example 1, a sub chamber 1
4 the gap between the opening and the magnetic tape original 8
A magnetic tape D was prepared in the same manner as in Example 1 except that the magnetic tape D was arranged to be 800 μm in No. 1 and 800 μm in the longitudinal portion 22.

(Embodiment 2) 45 rollers 23 made of Teflon having a diameter of 10 mm are arranged on both sides of the side opening as shown in FIG. The gap is 800
The sub-chamber 14 is arranged under the condition of μm and the longitudinal portion 22 is 800 μm, and other conditions are the same as in the first embodiment.
A hard carbon film (protective film layer 3) having a film thickness of 180 Å was formed. After forming the lubricant layer 4 in the same manner as in Example 1, the magnetic tape B was produced by cutting into a width of 8 mm.

(Embodiment 3) As shown in FIG. 5, an octane gas of 200 sccm was used by using a film-forming apparatus provided with gas introduction nozzles 24 and 25 for supplying hexane gas and argon gas individually. Argon gas 100
It is supplied under the condition of sccm, and the gap between the opening of the sub-chamber 14 and the original magnetic tape 8 is set to 800 μm in the side surface portion 21 and 800 μm in the longitudinal portion 22, and the sub-chamber 14 is arranged under other conditions. A hard carbon film having a thickness of 180 Å was formed in the same manner as in 1.
After forming the lubricant layer 4 in the same manner as in Example 1, 8 m
Magnetic tape C was produced by cutting into m width.

These magnetic tapes A to D were prepared at 45 ° C. and 83%.
Of a commercially available 8mm VTR (EV-S90
0, manufactured by Sony) was used for the measurement. The measurement is
In each of the magnetic tapes A to D, the central portion and the end portion 5 slits in the magnetic tape raw material 8 were used. The results are shown in (Table 1).

[0038]

[Table 1]

The still durability was measured 5 times with 2 samples in an environment of 5 ° C. and 80% RH, and the time from the initial output to a decrease of 6 dB was measured. The average value was taken as the still life of the tape.

The durability during repeated running was measured at 5 ° C. 8
After repeatedly running 200 passes in an environment of 0% RH, the decrease in output with respect to the initial stage was measured.

As is clear from (Table 1), the magnetic tapes A to C of the present invention show a still life of 120 minutes or more at each slit in both the central portion and the end portion, and the output decreases after repeated running. Also shows a low value within 2 dB. However, in the magnetic tape D manufactured in the comparative example, a decrease in the still life and output reduction after repeated running was observed in the slits at the eight ends of the original magnetic tape.
In particular, in the 2 slits at the end, the still life was greatly reduced, and when the tape surface was stored under an environment of 45 ° C. and 83% for 2 months and the surface of the tape was observed with an optical microscope, the color of corrosion products was partially generated. Was observed.

[0042]

Industrial Applicability As described above, according to the present invention, a uniform hard carbon film can be formed on a wide film raw material, and it can be stored for a long time, especially in a hot and humid environment for a long time. After that, a magnetic recording medium having excellent durability can be manufactured with a high yield, and a magnetic recording medium having extremely high practical reliability can be provided on an industrial scale.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing the structure of a ferromagnetic metal thin film type magnetic tape according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the structure of a conventional ferromagnetic metal thin film magnetic tape.

FIG. 3 is a schematic diagram of a magnetic recording medium manufacturing apparatus according to a first embodiment of the present invention.

FIG. 4 is a schematic view of a sub-chamber in which a roller is arranged on a side surface of an opening of a magnetic recording medium manufacturing apparatus of Example 2 of the present invention.

FIG. 5 is a schematic view showing a raw material gas introduction port of a magnetic recording medium manufacturing apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

1 Non-Magnetic Substrate 2 Ferromagnetic Metal Thin Film 3 Protective Film Layer 4 Lubricant Layer 5 Backcoat Layer 6 Vacuum Tank 7 Vacuum Pump 8 Magnetic Tape Roll 9 Unwinding Roll 10 Winding Roll 11, 12 Pass Roll 13 Can 14 Subchamber 15 Discharge electrode 16 Plasma generation power source 17 Raw material gas inlet 18 Raw material gas mixer 19 Gas inlet (hydrocarbon gas supply pipe) 20 Gas inlet (inert gas supply pipe) 21 Side portion between the original film and the sub chamber Gap 22 Longitudinal gap between original film and sub chamber 23 Teflon roller 24 Hydrocarbon gas introduction nozzle 25 Inert gas introduction nozzle

Claims (5)

[Claims] 1. A sub-chamber provided with an electrode on one surface and a film material having a ferromagnetic metal thin film on the surface on the opposite opening surface is provided in a vacuum chamber, and the electrode and the ferromagnetic metal thin film are opposed electrodes. In the method for producing a hard carbon film on the surface of the ferromagnetic metal thin film by the plasma CVD method, the exhaust from the sub-chamber is performed more in the film longitudinal direction than in the film width direction. Production method. 2. A sub-chamber provided with an electrode on one surface and a film raw material having a ferromagnetic metal thin film on the surface on the opposite opening surface is provided in a vacuum chamber, and the electrode and the ferromagnetic metal thin film are opposed electrodes. In the apparatus for producing a hard carbon film on the surface of the ferromagnetic metal thin film by the plasma CVD method, the area of the gap between the ferromagnetic metal thin film surface and the sub-chamber is larger than the film width direction in the film longitudinal direction. An apparatus for manufacturing a magnetic recording medium, characterized in that a sub-chamber having a large total area is used. 3. A vacuum chamber is provided with a sub-chamber having an electrode on one surface and an original film having a ferromagnetic metal thin film on the opposite opening surface, and the electrode and the ferromagnetic metal thin film are opposed electrodes. In the apparatus for producing a hard carbon film on the surface of the ferromagnetic metal thin film by the plasma CVD method, a plurality of rollers are provided in the opening on the side surface in the sub-chamber width direction, the method for producing a magnetic recording medium. 4. A sub-chamber provided with an electrode on one surface and a raw film of a film having a ferromagnetic metal thin film on its surface on the opposite opening face in a vacuum chamber, and the electrode and the ferromagnetic metal thin film are opposed electrodes. In the method for producing a hard carbon film on the surface of the ferromagnetic metal thin film by the plasma CVD method, the magnetic recording is characterized in that the inert gas and the reaction gas are supplied into the sub-chamber at different ratios in the width direction. Medium manufacturing method. 5. A sub-chamber provided with an electrode on one surface and an original film having a ferromagnetic metal thin film on the surface on the opposite opening surface is provided in a vacuum chamber, and the electrode and the ferromagnetic metal thin film are opposed electrodes. In the apparatus for producing a hard carbon film on the surface of the ferromagnetic metal thin film by the plasma CVD method, a magnetic recording medium having a nozzle for individually supplying an inert gas and a reactive gas into the sub-chamber. Manufacturing equipment.