JPS61236017A - Metallic thin film magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the lubricity and resistance to wear and corrosion of the title medium by placing a protective layer consisting of the thin film of a group IV element in the periodic table on a metallic thin film magnetic layer provided on a nonmagnetic substrate and further furnishing a lubricating protective layer of laminated lubricating layers. CONSTITUTION:A protective layer consisting of the thin film of a group IV element in the periodic table or a nonmetallic element is placed on a metallic thin film magnetic layer provided on a nonmagnetic substrate and a lubricating protective layer of laminated lubricating layers consisting of a fluorine lubricant having a polar group is further furnished thereon. For example, a substrate of polyethylene terephthalate film is prepared and then a magnetic layer consisting of a metallic thin film is formed on the base film by sputtering. The magnetic layer, for example, is formed with a Co-Cr alloy and an Si protective layer is formed on the surface of the magnetic layer by sputtering Si in a gaseous Ar atmosphere. Subsequently, soln. contg. perfluoroethylene is coated on the surface of the Si protective layer to form a lubricating layer. Consequently, a metallic thin film magnetic recording medium having a lubricating protective layer having excellent corrosion resistance, lubricity and wear resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the structure of a magnetic recording medium comprising a magnetic metal thin film as a magnetic recording layer.

(Prior art and its problems) In recent years, there has been a demand for higher recording densities in recording media in the information processing field. As a high recording density medium, a metal thin film type magnetic recording medium having a magnetic layer made of a metal thin film is considered to be promising. Particularly recently, perpendicular magnetic recording systems using metal thin films have been attracting attention because of their high-density recording properties.

However, this metal thin film magnetic recording medium.

For example, in order to improve the abrasion resistance and $4fi resistance of the magnetic layer surface, a thin protective layer made of plastic, ceramic, etc. is conventionally formed on the surface of the magnetic layer, but these protective layers have poor lubricity. None of them could be said to be satisfactory due to lack of strength and poor adhesion to the magnetic layer.

Therefore, attempts have been made to form a lubricating and protective layer using lubricants such as fatty acids and fluorinated hydrocarbons. and,
Fluorinated lubricants, especially perfluoropolyethers (trade name: Krytx, manufactured by DuPont, etc., Honprin (trade name, manufactured by Montecani Edison), etc.) have excellent corrosion resistance and lubricity when used as a lubricating protective layer. It is known to exhibit excellent properties such as However, when perfluoropolyether is applied onto a thin metal film, that is, the surface of a magnetic layer, it is repelled by the metal surface. It has the disadvantage that it is difficult to apply it uniformly to the surface of the magnetic layer. Recently, hydroxyl groups (-〇H) and carboxyl groups (-COOH) are added to the terminals of perfluoropolyether molecules.
Types equipped with polar groups, such as, have come to be used as lubricating protective layers, and their conformity to metal surfaces has improved considerably, but protective layers with sufficient uniformity have not yet been obtained. In general, lubricants cannot fully exhibit the above-mentioned excellent properties unless they are applied uniformly, which is a problem.

In addition, the protective layer made of liquid lubricant as described above is too weak to prevent wear and damage to the surface of the magnetic layer of the medium under severe boundary friction conditions when the head and medium contact and slide during recording and reproduction. There is. Therefore, a thin protective layer made of plastic, ceramic, etc. is first formed on the surface of the magnetic layer.
Furthermore, a method of applying a lubricant thereon is also being considered, but it is still difficult to apply the lubricant uniformly and with good adhesion.

(Object of the Invention) The present invention was made in view of the above points, and its object is to provide a metal thin film type magnetic recording medium having a lubricant and slip protection layer with excellent lubricity, abrasion resistance, and corrosion resistance. It's about doing.

(Structure of the Invention) The above-mentioned object of the present invention is to provide a thin film protective layer made of a thin film of a metal or non-metallic element belonging to Group Ⅰ of the periodic table on a metal thin film magnetic layer provided on a non-magnetic substrate. This is accomplished by providing a lubricating protective layer with a structure in which a lubricating layer made of a fluorine-based lubricant having a polar group is further laminated on top of the lubricating layer.

(Example) Next, an outline of the present invention will be shown. First, a base film of, for example, a polyethylene terephthalate film is prepared. Next, a magnetic layer made of a thin metal film is formed on the base film by, for example, sputtering. This magnetic layer is made of, for example, a Co-Cr alloy. Then, by sputtering Si in an Ar gas atmosphere, a Si protective layer having a thickness of, for example, 500 nm is formed on the surface of this magnetic layer.

Next, a solution containing perfluoropolyether is applied to the surface of this Si protective layer to form a lubricating layer. The composition of the above solution is, for example, as follows.

Perfluoropolyether (having a carboxyl group at the end) 1 mΩ Trichlorotrifluoroethane A metal thin film type magnetic recording medium provided with a lubricating protective layer as an embodiment of the present invention is produced through the steps of 1+nfi or more.

Next, I will describe the evaluation.

(A) Magnetic layer surface on which no Si protective layer is formed.

(B) The surface of the lubricating layer formed by applying the above solution to the surface of the magnetic layer on which no Si protective layer is formed, (C) The surface of the magnetic layer on which the Si protective layer is formed, (D) The surface of the magnetic layer on which the Si protective layer is formed. The surface of the lubricating layer formed by applying the above solution on the formed magnetic layer, the surface of the protective layer formed by forming a thin film of (E) SiO□ on the magnetic layer, and (F) Si○ The results of experiments conducted on six types of surfaces (A) to (F), which are the surfaces of the lubricating layer formed by applying the above solution to the surface on which the second protective layer was formed, are shown below. The above embodiment corresponds to (D).

Table 1 shows the contact angles of the above surfaces and water, and Table 2 shows the friction coefficients of each surface.

From the above experimental results (D), that is, the surface of the magnetic recording medium of the present invention, which has a lubricating protective layer formed by further applying the above solution on the magnetic layer surface on which the Si protective layer is formed, has a water contact angle. It can be seen that the coefficient of friction is the smallest.

A large water contact angle means that the wettability of the 5 surface is poor and water can be prevented from entering.

This shows that it is resistant to corrosion. Furthermore, a small coefficient of friction indicates excellent lubricity and wear resistance. From the above, it can be seen that in the magnetic recording medium of the present invention, the above solution is applied extremely uniformly to the surface of the magnetic layer, and thereby the excellent properties of perfluoropolyether are fully exhibited.

Next, the present invention will be explained in more detail with reference to more specific examples.

(Specific Example) A 0.5 μm thick Go-Cr thin film was formed on a 50 μm thick polyethylene terephthalate base film using a high frequency magnetron sputtering device. The composition is 17wt% Cr and the remaining 83νt
% was made up of Go. Then the above Co-
A Si thin film having a thickness of 300 Å was formed on the Cr thin film using a high frequency magnetron sputtering device in the same manner as described above, and then this was punched out into a disk shape to obtain a magnetic recording disk. Next, this was immersed in a lubricant solution consisting of 1 part of Krytux 157FSL (trade name of perfluoropolyether with a carboxyl group at the end of the molecule, manufactured by DuPont) and 1000 parts of trichlorotrifluoroethane, and after being pulled out, it was left to stand for a while. It dried to form a lubricating layer.

(Comparative Example 1) G prepared in the same manner as in the example.

A -Cr thin film was punched out into a disk shape to form a magnetic recording disk, and a lubricating layer was directly formed on the Go-Cr thin film in the same manner as in (Specific Example).

(Comparative Example 2) Go-
A Si protective layer with a thickness of 300 nm was formed on the Cr thin film, and then a disk was punched out to form a magnetic recording disk.

(Comparative Example 3) Instead of the Si thin film in (Specific Example), a 300-layer Sio2 thin film was formed, and then a lubricating layer was formed in the same manner as in (Specific Example).

The magnetic disks of the above (specific examples) and (comparative examples 1 to 3) were both inserted into a commercially available magnetic recording disk stain prevention jacket, loaded into a recording and reproducing device,
The recording/reproducing head was brought into contact with the recording/reproducing head at 0 revolutions, and the total number of revolutions and the critical recording density were measured until the output became 80% or less of the initial value. Also, wear when rotating the medium 1 million times,
Table 3 shows the results obtained by evaluating the state of damage.

From Table 3, it can be seen that according to the specific examples, the durability of the metal thin film magnetic recording medium can be dramatically improved without substantially impairing the high density properties of the medium. This indicates that the lubricating protective layer of the magnetic recording medium of the invention has sufficient uniformity and is particularly excellent in adhesion of the lubricating layer.

Note that the above-mentioned embodiments are for explaining the present invention, and the present invention is not limited to the above-mentioned embodiments. For example, instead of the Si protective layer, another element belonging to Group 1 of the periodic table, such as a Ge thin film, may be used as the protective layer. Also, for example, the composition of the solution.

The concentration is also not limited to the examples and can be changed as necessary. Furthermore, although the above embodiments have shown a metal thin film magnetic recording medium having a magnetic layer formed of a Go-Cr alloy metal thin film and a base film made of polyethylene terephthalate, the present invention provides other combinations, For example, this can also be applied to a metal thin film type magnetic recording medium having a magnetic layer made of a Go--P alloy thin film and a base film made of polyester. Furthermore, the method of forming the thin protective layer and the lubricating layer can be changed as necessary. The method for forming the metal thin film of the magnetic layer used in the present invention also includes:
Not limited to sputtering method, vacuum evaporation method.

It is also possible to use a plating method, an ion blating method, or the like.

(Effects of the Invention) According to the configuration of the present invention as detailed above, a fluorine-based lubricant solution having a polar group is uniformly applied onto the magnetic layer with good adhesion, thereby improving corrosion resistance, lubricity, and resistance. A metal thin film magnetic recording medium having a lubricating protective layer with excellent abrasion resistance can be obtained.

Claims (3)

[Claims] (1) On the metal thin film magnetic layer provided on the nonmagnetic substrate,
It has a lubricating protective layer with a structure in which a thin film protective layer made of a thin film of a metal or non-metallic element belonging to Group IV of the periodic table is placed, and a lubricating layer made of a fluorine-based lubricant having a polar group is further laminated thereon. A metal thin film type magnetic recording medium characterized by the following. (2) The thin film protective layer is a thin film created by sputtering in an inert gas atmosphere targeting a metal or nonmetal element belonging to Group IV of the periodic table, and the thickness thereof is 50 Å or more and 500 Å or less. 2. The metal thin film magnetic recording medium according to claim 1, wherein the content of oxides and nitrides as impurities in the thin film is 1% by weight or less. (3) The above fluorine-based lubricant having a polar group is a perfluoropolyether having a polar group at the end, and the polar group is a hydroxyl group (-OH) or a carboxyl group (-CO
3. The metal thin film magnetic recording medium according to claims 1 and 2, characterized in that the metal thin film magnetic recording medium is one or a combination of both.