JPH05282662A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the still durability, durability at the time of repetitive traveling and environmental durability of the magnetic recording medium with which high-density magnetic recording is possible and a ferromagnetic metallic thin film is formed as a magnetic recording layer and to provide the magnetic recording medium having high practicable reliability. CONSTITUTION:This magnetic recording medium has the magnetic recording layer 2 consisting of the ferromagnetic metallic thin film on a substrate 1 consisting of a high-polymer film and a protective film layer 3 consisting of a hard carbon film thereon. After the above-mentioned protective film is formed, a lubricant layer flows alkyl groups, 4b contg. an org. compd. having respectively >=1 pieces of aliphat. alkyl groups and carboxyl groups at the molecule terminal is formed on the protective film layer 3, by which the lubricant layer 4b optimum for the hard carbon film is provided and the magnetic recording medium having the excellent traveling property is obtd.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a metal thin film type magnetic recording medium suitable for high density magnetic recording, more specifically a magnetic tape,
The present invention relates to a magnetic recording medium such as a magnetic disk.

[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 media has been increased accordingly, and magnetic recording has been increased. A metal thin film type magnetic recording medium whose layer is composed of a ferromagnetic metal thin film has been actively studied because it is extremely advantageous for short wavelength recording.

A conventional magnetic recording medium will be described below. FIG. 2 is an enlarged sectional view of a conventional magnetic recording medium. In FIG. 2, reference numeral 1 is a substrate made of a polymer film such as a polyester film or a polyimide film, or a nonmagnetic metal thin film such as an aluminum thin film. Reference numeral 2 is a magnetic recording layer made of a ferromagnetic metal thin film, which is formed on the substrate 1 by a vacuum deposition method such as an electron beam deposition method, a sputtering method or an ion plating method using cobalt, nickel, iron or an alloy containing them as a main component. Is formed in. A lubricant layer 4a is formed on the magnetic recording layer 2 with an organic compound by a conventional coating method or a vacuum deposition method. Reference numeral 5 denotes a back coat layer, which comprises a coating film in which a filler such as carbon black or calcium carbon is dispersed in a resin such as polyurethane, polyester, nitrocellulose, or vinyl chloride-vinyl acetate copolymer.

In the magnetic recording medium constructed as described above, for example, in the case of a magnetic tape, the surface of the magnetic layer has an extremely good surface property in order to achieve high density magnetic recording. Therefore, friction and wear under high speed sliding with the magnetic head during the recording / reproducing process of the magnetic signal have a great influence on the running durability, and the improvement thereof is a big problem.

Therefore, fluorine-based lubricants having excellent lubricating properties have 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, and a fluoroalkyl group are attached to the molecular end in order to improve the adhesion to a ferromagnetic metal thin film and to exhibit excellent lubricity. Fluorine-based lubricant having at least one 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).

[0006]

However, with the above-mentioned conventional structure, it is not possible to sufficiently satisfy the strict requirements regarding the running durability and environmental durability of the magnetic recording medium.
Further improvement is desired.

The present invention has been made in view of the above problems, and an object thereof is to provide a magnetic recording medium which is excellent in running durability and environmental durability and has extremely high practical reliability.

[0008]

To achieve this object, the present invention provides a magnetic recording having a magnetic recording layer made of a ferromagnetic metal thin film on a non-magnetic substrate and a protective film layer made of a hard carbon film thereon. In the medium, a fluoroalkyl group, an aliphatic alkyl group, and a carboxyl group are added to the end of the molecule, respectively.
A lubricant layer containing at least one organic compound is formed on the protective film layer.

[0009]

With this structure, the hard carbon film has an excellent protective effect, the lubrication property on the hard carbon film is improved, and the running durability can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 one embodiment of the present invention. In FIG. 1, 1 is a substrate made of 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, and 4b.
Is a lubricant layer, and 5 is a back coat layer.

Polyethylene terephthalate is often used as the polymer film used as the substrate 1 of the magnetic recording medium of the present invention, but other polyester films such as polyethylene naphthalate, cellulose derivatives such as cellulose acetate, and plastics such as polyamide and polyimide. It may be a film.

As the ferromagnetic metal thin film used as the magnetic recording layer 2, iron, cobalt, nickel or an alloy containing them as a main component formed by a vacuum deposition method, a sputtering method or an ion plating method, or a partial oxidation thereof is used. A material, a partial nitride, or the like can be used.

The protective film layer 3 made of a hard carbon film can be formed by plasma polymerization of a hydrocarbon gas or a mixed gas of hydrocarbon and argon, or carbon or graphite sputtering.

In the case where 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 container, and 0.00
While maintaining a pressure of 1 to 1 Torr, discharge inside the vacuum container to generate plasma of hydrocarbon gas,
A hard carbon film is formed on the surface of the substrate. As the discharge type,
Either the external electrode method or the internal electrode method may be used, 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 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 increase the discharge energy as much as possible. 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. To form a hard film, the pressure is 0.01 Tor
r or less is desirable, 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 a voltage of 0 to -3 KV is applied to the electrode holding the substrate. On the other hand, by sputtering, the hardness of the film can be increased and the adhesion can be improved, as in the case of plasma polymerization.

The hard carbon film has a thickness of 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.

The lubricant used in this example contains an organic compound having at least one fluoroalkyl group, at least one aliphatic alkyl group and at least one carboxyl group at the end of the molecule. The fluoroalkyl group has 4 to 1 carbon atoms.
The linear saturated fluoroalkyl group of 2 is effective, and as the aliphatic alkyl group, either linear saturated type or unsaturated type having 8 to 22 carbon atoms is effective. When the carbon number is smaller than the above-mentioned carbon number, the friction coefficient increases and a sufficient lubricating effect cannot be obtained, and when it is large, the synthesis becomes very difficult.

Hereinafter, more specific examples will be shown. (Example 1) In FIG. 1, a particle size of 180Å is formed on a smooth surface.
Continuous oblique vapor deposition by an electron beam method while introducing oxygen on a substrate 1 made of a polyethylene terephthalate film having a thickness of 10 μm and having wavy protrusions and granular protrusions composed of a modified silicone having silica fine particles dispersed therein and a thickener. Then, a Co—Ni—O film having a film thickness of 1500 Å was formed.
Then, on the side opposite to the vapor-deposited layer, a coating liquid in which a mixture of carbon black and calcium carbonate in a ratio of 1: 1 by weight is dispersed in a resin component of polyurethane and nitrocellulose in a ratio of 3: 2 by weight is a reverse roll type coating machine. Apply at 100 ℃
The back coat layer 5 was formed by drying at the temperature of 0.5 μm. Furthermore, by high frequency (10 KHz) plasma of a mixed gas of methane and argon on the deposited layer,
A direct current voltage of -1.5 KV was applied to the magnetic tape raw material using the electrode and the magnetic tape raw material itself as a counter electrode, and discharge was performed to form a protective film layer 3 made of a hard carbon film having a thickness of 250 Å. Further, the lubricant of the present invention or a conventionally known lubricant was applied thereon with a reverse roll coater under the condition of 8 mg / m ² and dried at a temperature of 70 ° C. to form a lubricant layer 4b. 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 addition, as a comparative example, one having no hard carbon film was similarly prepared.

The initial temperature of these magnetic tapes and 40 ° C. 90
% RH The still durability after standing for 1 week and the durability during repeated running were measured using a commercially available modified 8 mm VTR (EV-S900, manufactured by Sony Corporation). The results are shown in (Table 1).

[0023]

[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, and 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 output reduction with respect to the initial output was measured.

As is clear from (Table 1), each of the magnetic tapes 1 to 6 of the present invention had an initial temperature of 60 minutes or longer and 40 ° C.
The 90% RH shows a still life of 60 minutes or more after being left for 1 week, and also shows a low output reduction after repeated running. However, the magnetic tapes 7 to 12 using a conventionally known lubricant show insufficient values in the still life and the output reduction after repeated running.

[0027]

As described above, according to the present invention, it is possible to provide an optimum lubricant for a hard carbon film, and to improve the still durability, the durability during repeated running and the environmental durability. And has an excellent effect of improving the practical characteristics of the metal thin film type magnetic recording medium.

[Brief description of drawings]

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

FIG. 2 is an enlarged sectional view of a conventional magnetic recording medium.

[Explanation of symbols]

 1 substrate 2 magnetic recording layer 3 protective film layer 4b lubricant layer 5 back coat layer

Claims (2)

[Claims] 1. A magnetic recording medium having a magnetic recording layer made of a ferromagnetic metal thin film on a non-magnetic substrate, and a protective film layer made of a hard carbon film on the magnetic recording layer, wherein the fluorocarbon is at the molecular end. A magnetic recording medium, wherein a lubricant layer containing an organic compound having at least one alkyl group, at least one aliphatic alkyl group and at least one carboxyl group is formed on the protective film layer. 2. A linear saturated fluoroalkyl group having 4 to 12 carbon atoms, an aliphatic alkyl group having 8 to 22 carbon atoms, and a carboxyl group each having one or more at the terminal of the molecule. The magnetic recording medium described.