JPH07105036B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium having a ferromagnetic metal thin film suitable for high density magnetic recording as a magnetic recording layer.

2. Description of the Related Art A so-called vapor-deposited tape in which a Co-Ni alloy is vapor-deposited on a polymer film by an electron beam vapor deposition method directly or through an underlayer, electromagnetic conversion characteristics, durability, We are trying to improve corrosion resistance [for example, foreign journals. I EEE TRANSACTIONS ON MAGNETIC
S) vol-MA G-20, NO-5, pp824-826 (1984)].

Further, an effective means for improving the durability is to make the magnetic recording layer finely roughened (see the above-mentioned journal.vol-MA G-21,
pp1524 to 1526 (1985)], and many combinations of a protective film and a lubricant have been proposed, and attention is particularly paid to the protective property of a diamond-like hard carbon thin film (hereinafter referred to as a DLC film). See IE 85, Magnetic Recording Study Group. MR85-56 (1986)].

Problems to be Solved by the Invention However, when the DLC film is formed by a conventionally known method, the film thickness is large enough to reach the required level of protection performance, so if the wavelength of the recorded signal is further shortened, Since pacing loss is large and C / N is deteriorated to affect the error rate in digital recording, improvement is desired.

In view of the above-mentioned circumstances, the present invention has an object to provide a manufacturing method capable of obtaining sufficient durability even when the DLC film is thin, and also capable of achieving high speed.

Means for Solving the Problems In order to achieve the above object, a method of manufacturing a magnetic recording medium according to the present invention comprises applying a DC voltage containing ripples to an electrode for accelerating a hydrocarbon gas plasma to form a ferromagnetic metal thin film. A hard carbon film is formed on top.

By the above manufacturing method, the hard carbon film is formed on the moving ferromagnetic metal thin film in a state where a dense film with few pinholes can be obtained, so that the film thickness can be reduced.
The speed can be improved while ensuring the durability.

Embodiment Hereinafter, one embodiment according to the present invention will be described with reference to the drawings. The figure is a schematic view of the essential parts of a hard carbon thin film (DLC film) forming apparatus used for carrying out the production method of the present invention. In the figure, 1 is a polymer film such as polyethylene phthalate or polycarbonate, Co--Cr, Co -Cr-Nb, Co-Ni
An object to be processed on which a ferromagnetic metal thin film such as -O is formed, 2 is an object to be processed on which a DLC film is formed, 3 is a rotary support, 4 is an unwinding shaft, 5 is a winding shaft, 6 is a reaction tube made of Pyrex glass, quartz, etc., 7 is an external high frequency coil,
8 is a mesh-shaped accelerating electrode, 9 is an accelerating power source, 10 is a hydrocarbon-based gas, 11 is a vacuum tank, and 12 is a vacuum exhaust system. The diameter of the rotary support 3 is 50 cm, the distance between the tip of the reaction tube 6 and the rotary support is 7 mm, and the external high-frequency coil 7 is a water-cooled coil capable of applying a high frequency of 13.56 MHz and a diameter of 4 turns of 25 cm. The accelerating electrode 8 is made of mesh Mo, the accelerating power source 9 is positive with respect to the ground potential, and outputs the superimposed alternating electric field.

Using the equipment shown in the figure, 1.4 × 10 SiO ₂ particles with a diameter of 100 Å were formed on a polyethylene terephthalate film with a thickness of 12 μm.
⁹ / cm ² coating and Co-C on it by high frequency sputtering
r-Ti (Co: Cr: Ti = 78.5: 14.5: 7wt%) Perpendicular magnetic film 0.15
A film having a thickness of μm is prepared as the object to be processed 1, and the temperature is set.
While moving the object 1 to be processed along the rotary support 3 at 25 ° C., a DLC film was formed, and 50Å perfluoroarachidic acid was vacuum-deposited on it to form an 8 mm wide magnetic tape. Comparative evaluation was performed using Millivideo [AV-300, manufactured by Sony].

Tape A forms plasma by introducing 13.56 (MHz) and 1.96 (KW) while introducing methane gas to the DLC film at 0.8 / min, and applies alternating voltage of 260V and 70KHz to the accelerating electrode 8 at a DC voltage of 1.2KV. By applying the superimposed voltage, a film having a film thickness of 70 A was formed. At that time, the winding speed of the film was 16 m / min.

Tape B forms a plasma by introducing 13.56 (MHz) and 1.96 (KV) into the DLC film while introducing methane gas at 0.8 / min, and a DC voltage of 1.4 KV is applied to the accelerating electrode 8 to give a film thickness of 70 Å. The film was formed and the film winding speed was 11 m / min.

PC with both of them with a ferrite head with a gap length of 0.14 μm
We recorded M and compared the error rates in LP mode. Initial values are 1.2 x 10 ^{-4 to} 1.3 x 10 ^-4 for tape A and 1.3 x 10 for tape B.
^Although it was ^{-4 to} 3.2 x 10 ^-4 , the value after 190 passes in the environment of 23 ° C and 16% RH was 1.1 x 10 ^{-4 to} 1.3 x 10 ^-4, which was the same as that of Tape A. variation due tape B is 1.9 × 10 ^-4 ~8.9 × 10 ^-4 and the recording position is large.

As described above, according to this embodiment, the error rate during PLM recording is significantly improved.

In the above embodiment, the Co-Cr-Ti film was specifically described, but other Co-Cr, Co-Ti, Co-Ta, Co-Mo, Co-W, Co-Sm, Co-Ni,
The same effect can be obtained on ferromagnetic metal thin films such as Co-O, Co-P, Co-Ni-O, and Co-Cr-Nb. Hydrocarbon-based gas can be used alone or mixed with propane, acetylene, butane, etc. A gas and further another gas may be mixed if necessary. When the accelerating voltage is DC voltage E _D [KV], the superimposed alternating voltage is 0.1 ~
0.3E _D is preferred, the frequency is preferably 10 (KHz) ~1 (MHz) .

EFFECTS OF THE INVENTION According to the present invention, a hard carbon film can be obtained at a high speed because a method of applying a DC voltage containing ripples to an electrode for accelerating plasma of hydrocarbon gas is obtained, and sufficient durability is obtained even with a thin thickness. There is an excellent effect that the error rate can be secured.

[Brief description of drawings]

FIG. 1 is a schematic view of the essential parts of a hard thin film forming apparatus used to carry out the method of manufacturing a magnetic recording medium of the present invention. 1 ... Object to be treated, 3 ... Rotating support, 6 ... Reaction tube, 7
...... External high-frequency coil, 8 ...... accelerating electrode, 9 ...... accelerating power supply.

Claims (1)

[Claims] 1. When forming a hard carbon film on a ferromagnetic metal thin film on a moving polymer film, a DC voltage containing ripples is applied to an electrode for accelerating plasma of a hydrocarbon gas. Method for manufacturing magnetic recording medium.