JPH05128503A - Method of manufacturing magnetic recording medium - Google Patents

Abstract

(57) [Abstract] [Purpose] In a magnetic recording medium using a ferromagnetic metal thin film as a magnetic recording layer capable of high-density magnetic recording, the problem of damage to a protective film occurring in the manufacturing process is solved, and durability is improved. An object of the present invention is to provide a manufacturing method for obtaining a magnetic recording medium with improved corrosion resistance and high practical reliability. In a magnetic recording medium having a magnetic recording layer 2 made of a ferromagnetic metal thin film on a polymer film 1 and a protective film layer 3 made of a hard carbon film thereon, after the protective film is formed, until the magnetic recording medium is completed. By treating with a tension of F0.5 or less in the manufacturing process, a magnetic recording medium having a protective film which is not damaged can be obtained.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

However, in the magnetic recording medium of the ferromagnetic metal thin film type, the surface of the magnetic layer has a very good surface property, and therefore friction and wear under high speed sliding with the magnetic head during the recording / reproducing process of the magnetic signal. As a result, durability, running property, corrosion resistance, etc. are greatly affected, and their improvement is a major issue.

Therefore, attempts have been made to improve the durability, running property and corrosion resistance by providing a top coat layer on the surface of the magnetic layer.

For example, formation of a fatty acid metal salt (Japanese Patent Application Laid-Open No. 54-54
No. 113303), formation of a sputtered film of a polymer compound having an imide group (JP-A-57-116771), a sputtered film targeting a polymer compound, carbon, BN, MoS ₂ , SiO _2, etc. Thinning by sputtering or vapor deposition, formation of diamond-like hard carbon film (materials of the 46th meeting of the Japan Society for Applied Magnetics), formation of lubricants such as fatty acids and fatty acid amides (for example, JP-A-56-
No. 30609), many attempts have been made.

However, in the above example, the durability,
Since the running property and the corrosion resistance are not sufficiently satisfied, the concept that the respective roles are divided and laminated is increasing.

A fluorocarbon lubricant layer is formed on the fatty acid metal salt adsorption layer (Japanese Patent Laid-Open No. 61-120331), and a fluorine-based lubricant is arranged on the hard carbon layer (Japanese Patent Laid-Open No. 61-120331). -126627), Si-N-
A lubricant layer formed on an O-based thin film (JP-A-61-1)
No. 31231).

[0008]

However, the demands for improving the performance of the magnetic recording medium are strict, and it cannot be said that the above constitution has sufficient characteristics, and further improvement in durability and corrosion resistance is desired.

The present invention has been made in view of the above circumstances, and provides a method of manufacturing a magnetic recording medium having excellent durability and corrosion resistance and extremely high practical reliability.

[0010]

In order to solve the above problems, the present invention provides a magnetic recording layer made of a ferromagnetic metal thin film on a polymer film, and a protective film layer made of a hard carbon film thereon. In the magnetic recording medium having the above, the tension applied to the magnetic recording medium is 0.5% or less (hereinafter, F0.
The treatment is performed with a tension of 5 or less).

[0011]

In the present invention, F0.5 is used in the manufacturing process after forming the protective film.
By treating with the following tension, the protective film is prevented from being damaged, and generation of microcracks and peeling of the film are eliminated.

That is, durability and corrosion resistance are improved by preventing damage to the protective film layer.

[0013]

【Example】

(Embodiment 1) An embodiment 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 polymer film, 2 is a magnetic recording layer made of 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 polymer film used in the magnetic recording medium of the present invention, but other polyester films such as polyethylene naphthalate, cellulose derivatives such as cellulose acetate, and plastic films such as polyamide and polyimide can be used. Good.

As the ferromagnetic metal thin film, iron, cobalt, nickel formed by vacuum deposition, sputtering, or ion plating, or an alloy containing them as a main component, or their partial oxides, partial nitrides, etc. Can be used.

The protective film made of a hard carbon film can be formed by plasma polymerization of a hydrocarbon gas, a mixed gas of hydrocarbon and argon, or sputtering of carbon or graphite.

When the hydrocarbon gas is formed by plasma polymerization, the hydrocarbon gas or a mixed gas of the hydrocarbon gas and the inert gas is introduced into a vacuum vessel, and 0.00
While maintaining a pressure of 1 to 1 Torr, discharge is performed inside the vacuum container to generate plasma of hydrocarbon gas, and a hard carbon film is formed on the surface of the substrate. The discharge method may be either an external electrode method or an internal electrode method, and the discharge frequency can be experimentally determined. Also, by applying a voltage of 0 to -3 kV to the electrode on the substrate 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.

Further, in order to form a hard film, it is desirable to maximize the discharge energy. Also, it is desirable to raise the temperature of the substrate as high as possible.

On the other hand, the sputtering method includes DC sputtering, AC sputtering, high frequency sputtering, magnetron sputtering,
There are ion beam sputtering and the like, but any method may be used. In order to form a hard film, the pressure is preferably 0.01 Torr or less and the energy density is preferably high. For example, in high frequency magnetron sputtering, 1 W / cm ² or more per target area is preferable, and the substrate is retained. By applying sputtering while applying a voltage of 0 to -3 kV to the electrode on the charging side, the hardness of the film can be increased and the adhesion can be improved as in the case of plasma polymerization.

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

Fluorine-based lubricants are effective as the lubricant, and there are perfluorocarboxylic acid and its ester, and perfluoropolyether and its derivative, which can be used alone or in combination.

The manufacturing process from the formation of the protective film to the completion of the magnetic recording medium includes a protective film forming process from formation of the protective film to winding, and formation of a back coat layer on the polymer film opposite to the magnetic layer. There are a process, a process of forming a lubricant layer on the protective film layer, a slit process of cutting into an arbitrary width, a process of winding a slit magnetic tape on a reel, a process of heat treatment with a heating roller, and the like.

In the above steps, each tension is adjusted to F0.5 or less. The F0.5 value can be obtained by sampling the magnetic recording medium to be processed, measuring the elongation while applying a load at the temperature of the processing environment, and calculating from the weight at 0.5% elongation.

A more specific embodiment will be described below. On a polyethylene terephthalate film having a thickness of 10 μm and having wavy projections and granular projections, which are composed of a modified silicone in which fine silica particles having a particle diameter of 180A are dispersed on a smooth surface, and a thickener, an electron beam method is used while introducing oxygen. Continuous oblique vapor deposition was performed to form a Co-Ni-O film having a film thickness of 1800A. Then, on the side opposite to the vapor-deposited layer, a coating solution of carbon black and calcium carbonate in a ratio of 1: 1 by weight was dispersed in a resin component of polyurethane and nitrocellulose in a ratio of 3: 2 by weight, and a reverse roll type coating machine was used. And then dried at a temperature of 100 ° C. to form a back coat layer with a film thickness of 0.6 μm. Further, a high-frequency (10 kHz) plasma of a mixed gas of methane and argon was applied to the vapor-deposited layer, and a DC voltage of -1.5 kV was applied to the magnetic tape raw material by using the electrode and the magnetic tape raw material as the counter electrodes.
Discharging was performed to form a hard carbon film having a film thickness of 250A. Furthermore, on top of that, perfluoropolyether type KRT
OX-157 and FS-M (manufactured by DuPont) were coated with a reverse roll coater as shown in FIG. 2 under the condition of 9 mg / m ² and dried at a temperature of 70 ° C. to form a lubricant layer. That is, in FIG. 2, the magnetic tape raw material 10 that has come out from the unwinding portion 6 passes through the infeed portion 11 and then the coater head portion 7
After being applied in (1), it is dried in a drying furnace 8 to form a lubricant layer, and is wound on a winding section 9 via an outfeed section 12. Next, the raw magnetic tape was cut into a width of 8 mm with a slitter to obtain a magnetic tape for 8 mm VTR.

In the above steps, the magnetic tape is prepared by changing the tension between the outfeed section and the winding section of the coating machine in the coating step for forming the lubricant layer within the range of 2.1 kg to 5.9 kg. (Magnetic tapes 1 to 9). The tension of other manufacturing processes was adjusted to be F0.25 or less. Commercially available 8mm VTR (EV-
S900, manufactured by Sony Corporation) was used to measure the still durability and storage characteristics.

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

The storage characteristics were as follows: the sample was left in an environment of 40 ° C. and 80% RH for 1 month, the surface was observed with an optical microscope at a magnification of 100, and the dropout was measured.

Dropout was recorded and played back for 10 minutes with two samples, the number of signal defects in which the output decreased by 3 μsec, 10 dB or more was measured, the average value for 1 minute was calculated, and the value before storage was set to 1.0. , The rate of increase was calculated.

The F0.5 value of the raw magnetic tape was sampled from the magnetic recording medium before the treatment in each step, and was loaded with the universal tensile tester Tensilon (manufactured by Toyo Baldwin Co., Ltd.) at the treatment environmental temperature. -Elongation property was measured and calculated.

Table 1 shows the process conditions and evaluation results.

[0033]

[Table 1]

As is clear from (Table 1), the magnetic tapes 1 to 5 of the present invention wound with a tension of F0.5 or less have a small increase in dropout after long-term storage and a decrease in corrosion resistance. However, the magnetic tapes 6 to 9 wound with a tension higher than F0.5 showed a decrease in the still durability and a dropout after storage. Also shows a large decrease in corrosion resistance.

Further, when the magnetic tape after storage was observed with an optical microscope at a magnification of 100 times, almost no corrosion products were observed in the magnetic tapes 1 to 5, but in the magnetic tapes 6 to 9, cracking was observed. Corrosion products were found, indicating that corrosion started from the damaged part of the hard carbon film.

[0036]

As described above, according to the present invention, it is possible to prevent damage in the manufacturing process of the protective film, improve still durability and corrosion resistance. It has an excellent effect of improving the practical characteristics of the thin film magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a schematic enlarged cross-sectional view showing the structure of a magnetic tape used in an embodiment of the present invention.

FIG. 2 is a schematic view of a coater used for forming a lubricant layer in one embodiment of the present invention.

[Explanation of symbols]

 1 Polymer film 2 Magnetic recording layer 3 Protective film layer 4 Lubricant layer 5 Back coat layer 6 Unwinding part 7 Coater head part 8 Drying furnace 9 Winding part 10 Magnetic tape roll 11 Infeed part 12 Outfeed part

Claims (1)

[Claims] 1. A magnetic recording layer made of a ferromagnetic metal thin film on a polymer film, and a protective film layer made of a hard carbon film on the magnetic recording layer, and having a F0.5 or less in a manufacturing process after forming the protective film. A method for manufacturing a magnetic recording medium, which comprises treating with tension.