JPH04134625A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To exceedingly improve durability and corrosion resistance by forming a resin layer contg. a fluorine group and polar group on a ferromagnetic thin film, and further, successively forming a hard carbon film and lubricating layer thereon. CONSTITUTION:The ferromagnetic thin film 2 is formed on the nonmagnetic base 1 and the resin layer 3 contg. the fluorine group and polar group is formed thereon. Further, the hard carbon film 4 and the lubricating layer 5 are formed on the resin layer 3. The damage to the surface of the ferromagnetic thin film at the time of forming the hard carbon film is prevented by forming the resin layer 3. The fluorine group of the resin layer 3 improves the effect of preventing the damage and improves the corrosion resistance. The polar group forms 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 surface oxide layer, the fluorine-contg. resin layer 3 and the hard carbon film 4 constitute triple protective films. The durability and the corrosion resistance are thus exceedingly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film suitable for high-density magnetic recording such as perpendicular magnetic recording.

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 composed 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, various methods have been used to improve durability, runnability, and corrosion resistance. For example, firstly, a lubricating layer of carboxylic acid, phosphorus, perfluoropolyether, etc. is provided on a ferromagnetic metal thin film, and secondly, a non-magnetic metal layer, plasma polymerized film, 5i02 film, etc. is similarly protected. The third method is to uniformly provide fine protrusions [JP-A-61-224128, JP-A-61-13].
9919, JP-A-61-5426, etc.]
.

Furthermore, recently, consideration has been given to using a hard carbon film as a protective film.

Problems to be Solved by the Invention However, at present, the above-mentioned method cannot fully satisfy durability, contact resistance, etc.
Digital recording or high-density recording has stricter requirements than ever before, and further improvements are desired.

The present invention was devised in view of the above-mentioned circumstances, and provides a magnetic recording medium with excellent durability, corrosion resistance, and 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 substrate, and including a fluorine group and a polar group on the ferromagnetic metal thin film. Form a resin layer,
Furthermore, a hard carbon film is 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 fluorine groups in the resin layer prevent damage. It works to improve the effect and corrosion resistance, and the polar group forms a uniform resin layer. The synergistic effect of the two can prevent the surface oxidation layer on the surface of the ferromagnetic metal thin film from deteriorating, and the surface oxidation layer, fluorine-containing resin layer, and hard carbon film form a triple protective film, resulting in durability and corrosion resistance. This dramatically improves the

Embodiment FIG. 1 is an enlarged sectional view showing the basic structure 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 layer, 3 is a resin layer containing a fluorine group and a polar group, 4 is a hard carbon film, and 5 is a lubricating layer.

The substrate used in the present invention is polyethylene terephthalate, polyamide, or polyetherketone.

polyether sulfone, polyethylene naphthalate,
It may be a polymer film such as polyimide or polyphenylene sulfide, or it may be a nonmagnetic metal substrate.

Further, as the ferromagnetic metal thin film, Co-0, C is used.

Os, Co-Ti, Co-Cr, Co-Mo.

Co-Ru, Co-Ni, Co-N1-P, C.

Ni-0, Co-Cr-Nb, Co-Cr-Nd, etc. are formed by electron beam evaporation, high frequency sputtering, ion blating, or the like.

Examples of resins containing fluorine groups and polar groups include Lumiflon (manufactured by Asahi Glass Co., Ltd.), pentafluorostyrene acrylic acid copolymer, and perfluoroacrylic acid polymer.

In order to form the resin layer, a well-known method such as a gravure coating method or a bar coating method can be used for a solution containing the resin.

The appropriate thickness of the resin layer is 5 to 100A. If the film thickness is smaller than 5A, a uniform film cannot be formed, sufficient protection cannot be obtained during the formation of the hard carbon film, and the oxide layer on the surface of the ferromagnetic metal thin film is altered, resulting in poor durability. deteriorates. Furthermore, if the film thickness is greater than 100 A, a sufficient protective effect can be obtained, but the spacing loss due to the thickness becomes large, and the high output characteristics in high-density magnetic recording are impaired, making it impractical.

The hard carbon film of the present invention can be formed by generating plasma of a hydrocarbon gas such as methane, ethane, propane, butane, pentane, isooctane, or Hensen, or a mixed gas of a hydrocarbon gas and an inert gas, or It can be formed by sputtering or the like using carbon or graphite as a target in an atmosphere of an inert gas or a hydrocarbon gas and an inert gas.

Further, in order to form a hard carbon film, it is preferable to increase the discharge energy as much as possible. It is also desirable to make the temperature of the substrate as high as possible, which can increase the hardness of the film and improve its adhesion.

The appropriate film thickness is 50 to 300A, and the film thickness is 50A to 300A.
When it is smaller than 0A, a uniform film cannot be formed and the durability becomes low. If the film thickness is greater than 300A, due to spacing loss due to the thickness,
The high output characteristics in high-density magnetic recording are impaired, making it less practical.

The lubricant used in the present invention includes perfluoropolyether,
Fluorine-containing esters, fluorine-containing carboxylic acids, and the like can be used alone or in combination.

The lubricant layer can be formed using these lubricants by coating and drying a solution containing the lubricant, or by a well-known coating method such as vacuum deposition.

Hereinafter, the present invention will be explained in more detail while comparing Examples and Comparative Examples.

Example 1 A vacuum level of 6 x 1 O-5 Torr was applied on a polyethylene terephthalate film with a thickness of 10 μm and a smooth surface.
C was obliquely deposited using the electron beam method while introducing oxygen under the following conditions, and the film thickness was 1800A.

-N i-0 film was formed. On the Co-Ni-0 film, apply Lumiflon from Asahi Glass ■ for 5 to 50 minutes using a solution coating method.
A resin layer of 100A was formed. Furthermore, 50 to 30
0 hard carbon film with CH4/Ar mixed gas of 0.04
It was formed by a plasma method using Torr and a DC voltage of 1000V. The film thickness was controlled by the processing speed.

Next, a 40A perfluoropolyether was formed as a lubricating layer by a solution coating method, and the film was cut into a width of 8 ml to prepare a magnetic tape.

Example 2 A magnetic tape was produced in the same manner as in Example 1, except that a perfluoroacrylic acid polymer was formed as the resin layer by a solution coating method.

Example 3 As a resin layer, pentafluorostyrene, acrylic acid,
A magnetic tape was produced in the same manner as in Example 1, except that the copolymer was formed by a solution coating method.

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

Comparative Example 2 On the Co-Ni-0 film, using a sputtering method, 5
A 120A i02 film was formed, and then a 40A perfluoropolyether was formed as a lubricant layer by solution coating.
The tape was cut into a width of m to create a magnetic tape.

Comparative Example 3 Example 1 except that the resin layer and hard carbon film were not formed.
A magnetic tape was made in the same way.

The magnetic tapes of Example 1 and Comparative Example 1.2.3 thus prepared were placed on a commercially available 8 mm video deck (AV-300
, manufactured by Sony ■).

Durability was determined by performing still playback in an environment with a temperature of 35° C. and a humidity of 3%, and measuring the time until the playback output decreased by 6 dB from the initial level. In addition, regarding corrosion resistance,
It was stored in an environment with a temperature of 50°C and a humidity of 90%, and was observed using an optical microscope at a magnification of 100 times, and was expressed as the number of days until rust appeared.

The results are shown in Table 1.

(Margin below) As can be seen from the table, in each example of the present invention, the durability was such that even after 120 minutes, the output drop was within 6 dB, and
Corrosion resistance was also extremely good. On the other hand, the tape of Comparative Example 1 had low corrosion resistance (the tapes of Comparative Examples 2 and 3 had short durability, low corrosion resistance, and low practical reliability.

Effects of the Invention As described above, by forming a resin layer containing a fluorine group and a polar group on the ferromagnetic metal thin film of the present invention, and then sequentially forming a hard carbon film and a lubricating layer, durability and corrosion resistance can be improved. This resulted in a dramatic improvement in the practical reliability of high-density magnetic recording media.

[Brief explanation of drawings]

FIG. 1 is a schematic enlarged sectional view of a magnetic recording medium according to the present invention. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Ferromagnetic metal thin film layer, 3...Resin layer containing a fluorine group and a polar group, 4...
...Hard carbon film, 5...Lubricating layer.

Claims (1)

[Claims] A ferromagnetic metal thin film disposed on a non-magnetic substrate, a resin layer containing a fluorine group and a polar group formed on the ferromagnetic metal thin film, and a hard carbon film disposed on the resin layer. A magnetic recording medium characterized by: