JPH05258289A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To ensure enhanced still durability and durability at the time of repeated running for a magnetic recording medium using a thin ferromagnetic metal film as a magnetic recording layer and capable of high density magnetic recording and to provide a magnetic recording medium having high practical reliability. CONSTITUTION:When a magnetic recording layer 2 made of a thin ferromagnetic metal film and a protective layer 3 made of a hard carbon film are successively formed on the layer made of a polymer film to produce a magnetic recording medium, a lubricant layer 4b contg. triester having one or more aliphatic hydrocarbon groups and one or more perfluoroalkyl groups at molecular terminals is further formed on the protective layer 3. The triester is synthesized from monobasic fluorine contg. carboxylic acid, monobasic aliphatic carboxylic acid and glycerol The optimum lubricity is imparted to the hard carbonized film and a magnetic recording medium excellent in running durability is obtd.

Description

Detailed Description of the Invention

[0001]

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 increased accordingly, and magnetic recording A metal thin film type 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 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 non-magnetic metal thin film such as an aluminum thin film. Reference numeral 2 is a magnetic recording layer formed 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.
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.

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, 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, fluorine-based lubricants having excellent lubricating properties have been developed and studied. For example, polar groups such as a carboxyl group, an amino group, a phosphoric acid group, a hydroxyl group, and a mercapto group, and a fluoroalkyl group are attached to the terminal of the molecule in order to improve 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 of the magnetic recording medium, and further improvement is desired.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic recording medium having excellent running durability and 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. Lubricating medium, which is composed of a monobasic fluorine-containing carboxylic acid, a monobasic aliphatic carboxylic acid and glycerin, and which contains a triester having at least one aliphatic hydrocarbon group and at least one perfluoroalkyl group at the molecular end The agent layer has a structure 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 can be 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 an 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, 4b is a lubricant layer, and 5 is a back coat layer.

Polyethylene terephthalate is often used as the polymer film for 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 are used. May be.

As the ferromagnetic metal thin film, iron, cobalt, nickel formed by vacuum vapor 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.

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, it is possible to increase the hardness of the film and improve the adhesion.

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. Meanwhile, by performing sputtering, it is possible to increase the hardness of the film and improve the adhesion, as in the case of plasma polymerization.

The hard carbon film has a thickness of 50 to 30
If the range of 0Å 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 is greatly reduced due to spacing and the practicality is reduced.

The lubricant used in this example was synthesized from a monobasic fluorine-containing carboxylic acid, a monobasic aliphatic carboxylic acid and glycerin, and had an aliphatic hydrocarbon group and a perfluoroalkyl group at the molecular ends, respectively. Contains one or more triesters. As the fluoroalkyl group, a linear saturated fluoroalkyl group having 3 to 12 carbon atoms is effective, and as the aliphatic alkyl group, either a linear saturated type or unsaturated type having 3 to 21 carbon atoms is effective. Is.

Hereinafter, more specific examples will be shown. (Example 1) Oxygen was introduced onto a polyethylene terephthalate film having a thickness of 10 microns and having wavy projections and granular projections composed of a modified silicone in which silica particles having a particle diameter of 180Å are dispersed on a smooth surface and a thickener. On the other hand, the continuous oblique vapor deposition is performed by the electron beam method, and the film thickness is 1500Å
An o-Ni-O film was formed. Then, on the side opposite to the vapor-deposited layer, a coating liquid of a reverse roll type was prepared by dispersing a mixture of carbon black and calcium carbonate in a ratio of 1: 1 by weight in a resin component of polyurethane and nitrocellulose in a ratio of 3: 2 by weight. And was dried at a temperature of 100 ° C. to form a back coat layer 5 having a film thickness of 0.5 μm. further,
On the vapor-deposited layer, a high-frequency (10 KHz) plasma of a mixed gas of methane and argon was used to apply a DC voltage of -1.5 KV to the magnetic tape raw material, using the electrode and the magnetic tape raw material as counter electrodes, to discharge. A hard carbon film having a thickness of 250 Å was formed. 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. Also,
As a comparative example, one without a hard carbon film was similarly prepared.

The magnetic tape still durability and the durability against repeated running of these magnetic tapes were evaluated by using a commercially available 8 mm VTR (EV-S90).
0, manufactured by Sony) was used for the measurement. The results are shown in (Table 1) and (Table 2).

[0023]

[Table 1]

[0024]

[Table 2]

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 for 200 passes in an environment of 0% RH, the output reduction from the initial stage was measured.

As is clear from (Table 1) and (Table 2),
Each of the magnetic tapes 1 to 9 of this example has a still life of 60 minutes or more, and has a low output reduction after repeated running. However, in the magnetic tape 10 having no hard carbon film, a significant decrease in still life and output reduction after repeated running are seen, and in the magnetic tapes 11 to 15 using a conventionally known lubricant, still life, after repeated running Shows an inadequate value in the output reduction.

[0028]

As described above, according to the present invention, an optimum lubricant for a hard carbon film can be provided, and still durability and durability during repeated running can be improved. There is 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 (1)

[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. A lubricant layer, which is composed of an acid, a monobasic aliphatic carboxylic acid and glycerin, and which contains a triester having one or more aliphatic hydrocarbon groups and one or more perfluoroalkyl groups at the molecular ends, is formed on the protective film layer. A magnetic recording medium characterized by the above.