JPH0366731B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) 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 still has some practical problems. For example, in order to improve the abrasion resistance and corrosion resistance of the magnetic layer surface, a thin film protective layer made of plastic, ceramic, etc. is conventionally formed on the magnetic layer surface, but these protective layers lack lubricity. However, the adhesion with the magnetic layer was poor, and none of them could be said to be satisfactory. Therefore, attempts have been made to form a lubricating and protective layer using lubricants such as fatty acids and fluorinated hydrocarbons. Fluorine-based lubricants, especially perfluoropolyethers (Krytx (trade name, manufactured by DuPont), Homblin (trade name, Montecani),
(manufactured by Edison Co., Ltd.) is known to exhibit excellent properties such as corrosion resistance and lubricity when used as a lubricating protective layer. 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 group (-OH),
Types with polar groups such as carboxyl groups (-COOH) have come to be used as lubricating protective layers, and their adhesion to metal surfaces has improved considerably, but it is still not possible to obtain a protective layer with sufficient uniformity. Not yet. Generally, 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 weak and cannot 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. I have it too. For this reason, a method of first forming a thin film protective layer made of plastic, ceramic, etc. on the surface of the magnetic layer and then applying a lubricant on top of that is being considered, but it is still difficult to apply the lubricant uniformly and with good adhesion. Have difficulty. (Object of the invention) This invention was made in view of the above points,
The purpose is to provide a metal thin film type magnetic recording medium having a lubricating protective layer with excellent lubricity, abrasion resistance, and corrosion resistance. (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 Group of the Periodic Table on a metal thin film magnetic layer provided on a non-magnetic substrate. This is achieved by providing a lubricating protective layer having a structure in which a lubricating layer made of a fluorine-based lubricant having a polar group is further laminated thereon. (Example) Next, an outline of the present invention will be shown. First, a base film of, for example, polyethylene terephthalate film is prepared. Next, a magnetic layer made of a thin metal film is formed on the base film by, for example, a sputtering method. This magnetic layer is made of, for example, a Co-Cr alloy. And on the surface of this magnetic layer,
By sputtering Si in an Ar gas atmosphere,
For example, a Si protective layer with a thickness of 500 Å is formed. 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 ml Trichlorotrifluoroethane 1 ml Through the above steps, a metal thin film type magnetic recording medium provided with a lubricating protective layer as an embodiment of the present invention is produced. Next, I will describe the evaluation. (A) Magnetic layer surface without Si protective layer, (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 magnetic layer, the surface of the protective layer formed by forming (E) a SiO ₂ thin film on the magnetic layer, and the surface of the (F) SiO ₂ protective layer. The results of experiments conducted on six types of surfaces (A) to (F), which are the surfaces of lubricant layers formed by applying the above solution to the formed surfaces, are shown below. The above example is
(D) applies.

【table】

[Table] Table 1 shows the contact angle of the above surfaces and water, and Table 2 shows the friction coefficient of each surface. From the above experimental results (D), that is, the surface of the magnetic storage 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 surface has poor wettability 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-mentioned solution is applied extremely uniformly to the surface of the magnetic layer, thereby fully demonstrating the excellent properties of perfluoropolyether. . Next, the present invention will be explained in more detail with reference to more specific examples. (Specific Example) A 50μ thick polyester ethylene terephthalate base film is coated with a 0.5 μm thick base film using a high frequency magnetron sputtering device.
A Co-Cr thin film was created. The composition was 17 wt% Cr and the remaining 83 wt% Co. Next, the above Co-Cr thin film was coated with a thickness of 300 mm using a high-frequency magnetron sputtering device in the same manner as described above.
After forming a Si thin film with a thickness of 1.5 Å, this was punched out into a disk shape to form a magnetic recording disk. Next, this was mixed with 1 part of Krytx 157FSL (trade name of perfluoropolyether with a carboxyl group at the end of the molecule, manufactured by DuPont) and trichlorotrifluoroethane.
It was immersed in a lubricant solution consisting of 1000 parts, pulled up, and left to air dry to form a lubricant layer. Comparative Example 1 A Co-Cr thin film prepared in the same manner as in Example was punched out into a disk shape to form a magnetic recording disk, and then directly
A lubricating layer was formed on the Co--Cr thin film in the same manner as in (Specific Example). Comparative Example 2 In the same manner as in the specific example, a Si protective layer with a thickness of 300 Å was formed on a Co--Cr thin film and then punched out into a disk shape to obtain a magnetic recording disk. Comparative Example 3 After forming a SiO ₂ thin film with a thickness of 300 Å instead of the Si thin film in (Specific Example), a lubricating layer was formed in the same manner as in (Specific Example). Above (specific examples) and (comparative examples 1-
Insert each of the magnetic disks in 3) into a commercially available magnetic recording disk dirt prevention jacket, load it into a recording/playback device, and run it in contact with the recording/playback head at 300 revolutions per minute until the output is 80% or less of the initial level. The total number of rotations and the critical recording density were measured. We also evaluated the state of wear and damage when the media was rotated 1 million times. The results obtained are shown in Table 3.

[Table] According to this Table 3, according to (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. I understand. 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 3 of the periodic table, such as a Ge thin film, may be used as the protective layer. In addition, for example, the composition of the above solution,
The concentration is also not limited to the examples and can be changed as necessary. Furthermore, the above embodiment
A magnetic layer formed of a metal thin film of Co-Cr alloy,
Although a metal thin film type magnetic recording medium having a base film made of polyethylene terephthalate has been shown, the present invention has other combinations, for example, a magnetic layer made of a thin film of Co-P alloy and a base film made of polyester. This can also be applied to metal thin film magnetic recording media. 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 is not limited to the sputtering method, but also methods using a vacuum evaporation method, plating method, ion plating method, etc. are also possible. (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 (1)

[Scope of Claims] 1. A thin film protective layer made of a thin film of a metal or nonmetallic element belonging to group 3 of the periodic table is placed on a metal thin film magnetic layer provided on a nonmagnetic substrate, and a polar 1. A metal thin film type magnetic recording medium characterized by having a lubricating protective layer having a structure in which lubricating layers made of a fluorine-based lubricant having a base are laminated. 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 Group of the Periodic Table, and has a thickness of 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-mentioned fluorine-based lubricant having a polar group is a perfluoropolyether having a polar group at the terminal, and the polar group is either a hydroxyl group (-OH) or a carboxyl group (-COOH), or both. The metal thin film magnetic recording medium according to claims 1 and 2, characterized in that it is a combination.