JPH04134624A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To exceedingly improve durability and corrosion resistance by forming a resin layer contg. an arom. hydrocarbon group and polar group on a ferromagnetic thin film, then forming a hard carbon film on the ferromagnetic thin film 2 formed with the hard carbon film and lubricating agent layer. CONSTITUTION:The ferromagnetic thin film 2 is formed on the nonmagnetic base 1 and the resin layer 3 contg. the arom. hydrocarbon group and polar group is formed thereon. Further, the hard carbon film 4 and the lubricating agent layer 5 are successively formed on the resin layer 3. The damage to the surface of the ferromagnetic thin film 2 at the time of forming the hard carbon film 4 is prevented by forming the resin layer 3. The arom. hydrocarbon group of the resin layer 3 improves the effect of preventing the damage and the polar group improves the effect of forming the uniform resin layer 3. The deterioration in the property and decrease of the surface oxide layer on the surface of the ferromagnetic thin film 2 are prevented by the effects of both. The traveling durability and the corrosion resistance are extremely improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a ferromagnetic metal thin film type magnetic recording medium suitable for high-density magnetic recording media. The present invention relates to a magnetic recording medium having a magnetic recording layer.

Conventional technology In the field of magnetic recording, high performance such as digitization, miniaturization, and longer recording times has progressed in recent years.
With the increasing demand for high-density magnetic recording media, magnetic recording media in which the magnetic recording layer is made of a ferromagnetic metal thin film are being actively studied because they are extremely advantageous for short wavelength recording.

However, in ferromagnetic metal thin film magnetic recording media,
Because the surface of the magnetic layer has extremely good surface properties, durability, runnability, and corrosion resistance are greatly affected by friction and wear caused by high-speed sliding with the magnetic head during the recording and reproducing process of magnetic signals. Improvement is a major challenge.

Therefore, attempts have been made to provide a top coat layer on the surface of the magnetic layer to improve the durability, runnability, and corrosion resistance.

For example, formation of vapor-deposited film of fatty acid metal salt (JP-A-54-1
13303), formation of sputtered films of polymers having imide groups (JP-A-57-116771), sputtered films targeting polymers, carbon, BN, M
Formation of thin films of O82, Sio2, etc. by sputtering or vapor deposition, formation of diamond-like hard carbon films (Japan Society of Applied Magnetics, 46th research meeting materials), formation of lubricant layers of fatty acids, fatty acid amides, etc. (for example, Many attempts have been made, including Publication No. 56-30609).

However, in the above-mentioned example, durability, runnability, corrosion resistance, etc. cannot be fully satisfied, so the idea of laminating layers and sharing the roles of each layer is increasing.

Formation of a fluorocarbon-based lubricating layer on an adsorption layer of fatty acid metal salts (Japanese Patent Application Laid-open No. 6-120331), and formation of a fluorine-containing lubricating oil on a hard carbon layer (Japanese Patent Application Laid-Open No. 61-1989)
126627 (Japanese Patent Application Laid-open No. 126627), and Chinoku JP-A-61-131231 (Japanese Unexamined Patent Publication No. 131231/1981) in which a lubricating layer is formed on a 5i-N-○ thin film.

Problems to be Solved by the Invention However, there are strict requirements regarding the durability of magnetic recording media, and the above-described configuration cannot be said to have sufficient characteristics, and improvements in the -layer are desired.

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

Means for Solving the Problems In order to solve the above-mentioned problems, the magnetic recording medium of the present invention is provided by forming a ferromagnetic metal thin film on a non-magnetic support, and forming an aromatic hydrocarbon group on the ferromagnetic metal thin film. A resin layer containing a polar group is formed, and a hard carbon film and a lubricant layer are sequentially formed on the resin layer.

Effect The magnetic recording medium of the present invention has the above-described structure, and prevents damage to the surface of a ferromagnetic metal thin film during the formation of a hard carbon film by forming a resin layer, and the aromatic hydrocarbon group of the resin layer is It has the function of improving the damage prevention effect, and the polar group improves the effect of forming a uniform resin layer. Both effects prevent deterioration and reduction of the surface oxidation layer on the surface of the ferromagnetic metal thin film. The surface oxidation layer and hard carbon film act as a double protective film.
It can significantly improve running durability and corrosion resistance.

Embodiment FIG. 1 is a sectional view showing the basic configuration of an embodiment of the present invention in a magnetic tape.

In the figure, 1 is a substrate, 2 is a ferromagnetic metal thin film, 3 is a resin layer containing an aromatic hydrocarbon group and a polar group, 4 is a hard carbon film,
5 is a lubricant layer.

The substrate used in the present invention is preferably a polyethylene terephthalate film (although other polyesters,
Polyolefins such as polypropylene, cellulose,
It may be a cellulose derivative such as acetate, a plastic film such as polyamide, polyimide, etc.
A non-magnetic metal substrate may also be used.

In addition, the ferromagnetic metal thin film is made of iron or cobalt formed by electron beam evaporation, sputtering, ion blating, or electroless plating.

Nickel or an alloy containing nickel as a main component, or a partially oxidized film or partially nitride film of these may be used.

As the resin containing an aromatic hydrocarbon group and a polar group of the present invention, (1) an aromatic polyester resin containing an ester group, a carboxylic acid group, or a hydroxyl group as a polar group, such as Toyobo (8)
) Vylon series, (2) styrene-acrylic copolymer resin containing an ester group or carboxylic acid group as a polar group, (3) epoxy resin, (4) phenol resin, etc.

To form a resin layer with the above composition on a ferromagnetic metal thin film,
Conventional methods such as a bar coating method and a gravure coating method can be used to prepare a solution containing the resin.

The appropriate thickness of the resin layer is the minimum thickness that provides sufficient protection, and can be determined experimentally. If it is larger than that, it will provide sufficient protection, but due to the spacing loss due to its thickness, the high output characteristics in short wavelength recording, which is a feature of thin film recording media, will be impaired, making it less practical. .

The hard carbon film of the present invention can be formed by plasma of a hydrocarbon gas or by sputtering carbon or graphite in an atmosphere of an inert gas or an inert gas and a hydrocarbon gas.

In the case of plasma formation using hydrocarbon gas, a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas is introduced into a vacuum container, and the pressure is maintained at 0.001 to 1 Torr. A discharge is caused inside to generate hydrocarbon plasma and form a carbon film on the surface of the substrate. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be determined experimentally. Also, the electrode on the substrate side should be O~-3K.
By applying a voltage of V, the hardness and adhesion of the film can be increased.

As the hydrocarbon, methane, ethane, propane, butane, etc. can be used.

Further, in order to form a hard film, it is preferable to increase the discharge energy as much as possible. Furthermore, it is desirable to make the temperature of the substrate as high as possible.

On the other hand, sputtering methods include direct current sputtering, alternating current sputtering, high frequency sputtering, magnetron sputtering, ion beam sputtering, etc., and any of them may be used. In order to form a hard film, the pressure is preferably 0 or less, and the energy density is preferably high, for example,
In high frequency magnetron sputtering, I per target area
W/c! The above is preferable, and by sputtering while applying a voltage of O to -3K V to the electrode on the side that holds the substrate, the hardness of the film can be increased like plasma.
And adhesion can be improved.

The appropriate thickness of the hard carbon film is 50 to 300A; if it is smaller than 50A, a uniform film cannot be formed, a hard carbon film with low strength is formed, and the durability is low. Become. If the number of recording media exceeds 300, the spacing loss due to the thickness will impair the high output characteristics in short wavelength recording, which is a feature of thin-film recording media, and the recording medium will be less practical.

As the lubricant used in the present invention, fluorine-containing carboxylic acids or esters thereof and perfluoropolyethers can be used alone or in combination.

The method for forming these lubricants on a hard carbon film is as follows:
The lubricant can be obtained by a conventional coating method, by spraying, or by dipping into the solution and drying.

Moreover, the coating amount is preferably 0.1 to 20.7·'i. If the coating amount is too small, the friction coefficient will decrease,
If the amount is too large, a sticking phenomenon will occur between the sliding member and the magnetic recording medium, and the running performance will deteriorate.

The present invention will be described in more detail below while comparing Examples and Comparative Examples.

Example 1 Oxygen partial pressure 5 x 10-5 Tor was applied on a 10 μm thick polyethylene terephthalate film with a smooth surface.
C was obliquely evaporated using an electron beam method while introducing oxygen under the conditions of r to a film thickness of 1500A.

A Ni-0 film was formed. Next, Toyobo Byron 20
0 methyl ethyl ketone solution was applied by a bar coating method to form a resin layer. Further, a hard carbon film was formed thereon by a plasma method. That is, by applying a CH4/Ar mixed gas of 0.03 Torr and a DC voltage of 750 V, plasma polymerization was performed with the electrode set as positive and the side of the ferromagnetic metal thin film as negative, and the processing speed was adjusted to form a hard carbon film. The thickness was controlled.

Next, a fluorine-containing carboxylic acid partial ester represented by C7FI5CH2O0C(CH2)2COOH was coated on the hard carbon film by a bar coating method to a coating amount of 6/-, and the film was cut into a width of 81 m and magnetically coated. Tapes 1 and 2 were created.

Example 2 Magnetic tape 3.4 was produced in the same manner as in Example 1, except that a styrene-acrylic acid copolymer was used as the resin. The resin was produced using a radical polymerization method with a monomer ratio of 3;
1 (styrene:acrylic acid) to synthesize a polymer with a molecular weight of 130,000.

Example 3 Magnetic tapes 5 and 6 were prepared in the same manner as in Example 1 except that bisphenol A type epoxy resin was applied as the resin.
It was created.

Example 4 Magnetic tape 7.8 was produced in the same manner as in Example 1 except that phenol resin was applied as the resin.

Comparative Example 1 A magnetic tape 9 was produced in the same manner as in Example 1 except that the resin layer was not formed.

Comparative Example 2 A magnetic tape 10 was produced in the same manner as in Example 1 except that the resin layer and hard carbon film were not provided.

The magnetic tape obtained above was used as a commercially available 8 wm VT.
5℃, 80% R in a testing machine with the same function as R.
A still durability test was conducted under the H environment, and the playback output was
The time required for the temperature to drop by 6 dB from the initial level was measured. Also,
Corrosion resistance was evaluated by storing in an environment of 40° C. and 90% RH, observing with an optical microscope at a magnification of 100 times, and determining the number of days until rust appeared.

The results are shown in Table 1.

(Margins below) As can be seen from Table 1, in the magnetic tapes 1 to 8 of each example of the present invention, the output drop was within 6 dB even after 60 minutes in the still durability test, and Even after 8 weeks of storage under high temperature and high humidity, no rust was observed, and the still durability and corrosion resistance were extremely good.

On the other hand, in the still durability test, the magnetic tape 9 of Comparative Example 1, in which a hard carbon film was formed without forming a resin layer, showed a decrease in output of 6 dB or more after 30 minutes, and was Even in storage, rust was observed after 5 weeks, the still durability and corrosion resistance were low, and the practical reliability was low. In addition, in the still durability test, the magnetic tape 10 of Comparative Example 2, which did not have a resin layer or hard carbon film, showed a decrease in output of 6 dB or more after 10 minutes, and a decrease in output of 6 dB or more after 2 weeks when stored under high temperature and humidity. , rust was observed, the still durability and corrosion resistance were low, and the practical reliability was extremely low.

Effects of the Invention As can be seen from the above explanation, according to the present invention, a resin layer containing an aromatic hydrocarbon group and a polar group is formed on a ferromagnetic metal thin film, and a hard carbon film and a lubricating layer are further formed on the resin layer. By forming a hard carbon film on a ferromagnetic metal thin film on which a ferromagnetic metal layer is sequentially formed, durability and corrosion resistance can be dramatically improved, and the practical reliability of ferromagnetic metal thin film magnetic recording media can be dramatically improved. I was able to improve my performance.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a magnetic tape as an embodiment of the present invention. 1...Substrate, 2...Ferromagnetic metal thin film,
3...Resin layer containing an aromatic hydrocarbon group and a polar group, 4...Hard carbon film, 5...Lubricant layer.

Claims (1)

[Claims] A ferromagnetic metal thin film is formed on a non-magnetic support, a resin layer containing an aromatic hydrocarbon group and a polar group is formed on the ferromagnetic metal thin film, and a hard carbon film and a lubricant are further formed on the resin layer. A magnetic recording medium characterized by sequentially forming layers.