JPH0638287B2 - Magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a metal thin film magnetic recording medium, and more particularly to a metal thin film magnetic recording medium having improved running durability.

[Conventional technology]

In recent years, with the increasing density of recording media, so-called metal thin film type magnetic recording media have been attracting attention in place of conventional coating type magnetic recording media.

However, in the metal thin film magnetic recording medium, it is difficult to mix a lubricant or an abrasive into the magnetic layer like a conventional coating type magnetic recording medium, so that the running durability is generally extremely poor,
For example, in the case of a perpendicular magnetic recording disk provided with a Co—Cr alloy film, adhesion often occurs between the alloy layer on the surface and the head after about 100 travel passes, which makes traveling impossible.

Therefore, in order to solve such a problem, it has been proposed to apply a liquid lubricant to the magnetic layer surface or to provide a solid protective layer on the magnetic layer surface. Among them, it is known that providing a protective layer containing carbon as a solid lubricant as a main component on the surface of the magnetic layer is particularly effective for improving running durability (Japanese Patent Publication No. 54-33521).

[Problems to be solved by the invention]

However, even if such a protective layer containing carbon as a main component is provided on the surface of the magnetic metal thin film, the running durability is still insufficient. This is mainly because the deposits on the head increase the coefficient of friction with the protective layer.

An object of the present invention is to provide a metal thin film type magnetic recording medium in which deposits are not formed on the head and which is excellent in lubricity and therefore has significantly improved running durability.

[Means for solving problems]

The problem is that Cr, Mn, Mo,
By providing a protective layer containing graphite-like carbon as a main component and containing at least one selected from Nb, Ta, Ti, V, and W, and further providing a lubricating layer containing a fluorine lubricant thereon, The protective layer containing graphite-like carbon as a main component has excellent lubricity, but easily deposits on the head. Once the deposits occur, the coefficient of friction increases at once and the vehicle stops running. Therefore, in the graphite-like carbon protective layer, Cr, Mn, Mo, Nb, Ta, Ti,
By providing a lubricating layer containing at least one selected from V and W and further containing a fluorine-based lubricant thereon, the deposits produced on the head can be scraped off without impairing the lubricity, and as a result, The head is less likely to have deposits, and therefore the running durability is significantly improved.

According to the present invention, a metal thin film type magnetic layer is provided on a non-magnetic substrate, and Cr, Mn, Mo, Nb, Ta, Ti, and
The present invention relates to a magnetic recording medium in which a protective layer containing graphite-like carbon as a main component containing at least one selected from V and W is provided, and a lubricating layer containing a fluorine-based lubricant is further provided thereon.

The fluorine-based lubricant used in the present invention includes a compound having a perfluoroalkyl group or a perfluoroalkenyl group, a perfluoroalkylene oxide polymer and its derivative, and a polymer or copolymer of a fluorine-substituted ethylene compound. preferable.

Specific examples of the compound having a perfluoroalkyl group or a perfluoroalkenyl group include a carboxylic acid having a perfluoroalkyl group or a perfluoroalkenyl group, an alcohol having a perfluoroalkyl group or a perfluoroalkenyl group, a perfluoroalkyl group or An ester compound having a perfluoroalkenyl group, a mercaptan having a perfluoroalkyl group or a perfluoroalkenyl group, a nonionic surfactant having a perfluoroalkyl group or a perfluoroalkenyl group,
Cationic surfactants having a perfluoroalkyl group or perfluoroalkenyl group, anionic surfactants having a perfluoroalkyl group or perfluoroalkenyl group, amphoteric surfactants having a perfluoroalkyl group or perfluoroalkenyl group, etc. Is mentioned.

Specific examples of perfluoroalkylene oxide polymers and derivatives thereof include perfluoropropylene polymers, perfluoroethylene / perfluoromethylene copolymers, perfluoropropylene / perfluoromethylene copolymers, and the ends of these molecules. And the like in which a polar group is bonded.

In addition, specific examples of the polymer or copolymer of a fluorine-substituted product of ethylene include polytetrafluoroethylene, polytrifluoroethylene, poly1,1-difluoroethylene (polyvinylidene fluoride), trifluoroethylene-
1,1-difluoroethylene copolymer etc. are mentioned.

In the lubricating layer in the present invention, a lubricant other than one or two or more of the above-exemplified fluorine-based lubricants is used.
0 wt%, preferably 0 to 50 wt% may be mixed.

Lubricants that can be mixed in addition to fluorine-based lubricants include fatty acids, metal soaps, fatty acid amides, fatty acid esters, higher aliphatic alcohols, monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates,
Examples thereof include paraffins, silicone oils, animal and vegetable oils, mineral oils, higher aliphatic amines, and fine resin powders of polyethylene, polypropylene, polyvinyl chloride, ethylene-vinyl chloride copolymers and the like.

As a method of forming a lubricating layer, a method of dissolving the above lubricant in an organic solvent and coating or spraying on the substrate and then drying, a method of melting and coating on the substrate, and a method of immersing the substrate in a solution dissolved in the organic solvent And a method of adsorbing it on the surface of the substrate, a method of forming a monomolecular film on the surface of the substrate by the Langmuir-Projet method, and the like.

The protective layer containing graphite-like carbon as a main component used in the present invention is a graphite-based amorphous film formed by vacuum vapor deposition, sputtering or the like. Analytically, it is a film that shows no clear peak in X-ray diffraction and is amorphous, and that the plasmon loss energy of carbon in X-ray photoelectron spectroscopy (XPS) is graphite.

The content of at least one selected from Cr, Mn, Mo, Nb, Ta, i, V and W is appropriately 10% or less. It is preferable if it is 0.5% or more and 5% or less.

As the metal thin film type magnetic layer, ferromagnetic metals such as Fe, Co and Ni, or Fe-Co, Fe-Ni, Co-Ni,
Fe-Si, Co-Cr, Co-V, Co-Sm, Co
-Pt, Co-P, Co-Ni-P, Fe-Cr-Co
Ferromagnetic alloys such as the above, those added with additives, those laminated in layers, and the like.

As the non-magnetic substrate, a film-shaped polymer material such as polyethylene terephthalate, polyimide or polyamide, a disk-shaped polymer material such as polycarbonate or polymethylmethacrylate, a ceramic such as glass or a metal such as aluminum can be used. The shape of the substrate may be any of sheet, card, disk, drum, tape and the like.

To prepare the magnetic recording medium of the present invention, first, a magnetic metal layer is deposited on a non-magnetic substrate by a method such as vacuum deposition, sputtering, ion plating, plating, etc. to form a magnetic layer, and further on that. Cr, Mn, Mo, Nb, Ta,
By forming a protective layer containing, as a main component, at least one type of graphite-like carbon selected from Ti, V and W by vacuum vapor deposition, sputtering or the like, and further providing a lubricating layer containing a fluorine-based lubricant thereon. good.

In this case, the magnetic layer may be a laminated type using two different kinds of magnetic materials, a single layer type provided with an underlayer, or a laminated type provided with an intermediate layer. In any case, the thickness of the magnetic layer is preferably about 0.1 to 2 μm.

If the thickness of the protective layer and the lubricating layer is too thick, the electromagnetic conversion characteristics deteriorate due to spacing loss between the head and the medium, while if it is too thin, the running durability cannot be improved. It is 10-1000Å, preferably 50-
About 200Å is good, and the thickness of the lubrication layer (abundance is referred to as thickness here) is 0.5 mg / m ² -1.
00 mg / m ² is preferable, and more preferably 2 mg / m ^{2 to} 20.
It is mg / m ² .

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto. A 50 μm thick polyimide film was used as the non-magnetic substrate.

First, on this substrate, CoCr having a thickness of 2500 Å was sputtered in Ar gas with CoCr as a target.
A thin film was formed.

Next, on the graphite target, Cr, Mn, Mo,
A pellet made of Nb, Ta, i, V, and W is placed and sputtered in Ar gas to contain at least one of Cr, Mn, Mo, Nb, Ta, Ti, V, and W on the CoCr thin film. A 200 Å-thick protective layer containing graphite-like carbon as a main component was formed.

Next, the following various lubricants (a) to (e) were dissolved in methyl ether ketone and applied and dried to form a lubricating layer having a thickness of 15 mg / m ² .

Lubricant (a) Octadecyl perfluorooctanoate (b) Perfluorononyl alcohol (c) Perfluorooctyl ethylene oxide adduct (Number of chains of ethylene oxide = 7 on average) (d) Perfluoroethylene / perfluoromethylene copolymer Montefluos Fomblin Z4000 (e) trifluoroethylene-1,1-difluoroethylene copolymer produced by the above was processed into a disc shape having a diameter of 3.5 inches and incorporated into a commercially available disc jacket to prepare a sample.

After recording with a commercially available floppy disk drive, 600 r.
p. m. A running durability test (environmental conditions: 25 ± 2 ° C., 30 ± 5% PH) was performed by rotating the test piece at a temperature of 10 ° C. and measuring the number of passes until the friction coefficient suddenly increased. At the same time, the state of peeling of the protective film and the extent of head deposits were examined with an optical microscope.

The contents of Cr, Mn, Mo, Nb, Ta, Ti, V, and W were obtained from the peak ratio of the differential spectrum of each element and carbon measured by Auger electron spectroscopy. In addition, it was similarly confirmed that there was no change in the composition of the constituent elements of the protective layer in the film thickness direction.

For comparison, Cr, Mn, Mo, Nb, Ta, Ti, V,
A comparative example 1 was also prepared, in which a protective layer having a thickness of 200Å containing graphite-like carbon containing no W and W was provided and a lubricating layer was not provided. Further, as another comparative example, a medium provided with only a lubricating layer without providing a protective layer containing graphite-like carbon as a main component is referred to as Comparative Example 2,
A 200 Å protective layer containing only a 200 Å protective layer containing graphite-like carbon as a main component containing at least one metal and no lubricating layer was used as Comparative Example 3, and a graphite-like carbon containing no metal as a main component. Was also provided, and a sample having a lubricating layer as an upper layer was also prepared, which was referred to as Comparative Example 4.

The protective layer additive species, amount, lubricant species, and the obtained results are shown in Tables 1 to 8. As is clear from the table, C
Sample in which a protective layer containing graphite-like carbon as a main component containing a proper amount of r, Mn, Mo, Nb, Ta, Ti, V, and W was provided, and a lubricating layer containing a fluorine-based lubricant was further provided thereon. Is superior in running durability as compared with one provided with a protective layer containing graphite-like carbon as a main component containing no such metal, or one provided with no lubricating layer. As a result of observing the head and the film surface with a microscope, it was confirmed that the sample having excellent running durability had neither an attached matter nor a scratch.

The head deposit was observed with an optical microscope (× 20).

◯ indicates that there is almost no deposit, Δ indicates that there is some, and x indicates that there are many.

The scratches on the film surface were observed with an optical microscope (× 160).

○ means almost nothing, △ means a little, and × means a lot.

〔The invention's effect〕

As described above, by using the magnetic recording medium according to the present invention,
The coefficient of friction with the magnetic head can be made extremely small, and no deposits are produced on the head, no scratches are generated on the medium, and running durability can be greatly improved.

Claims (1)

[Claims] 1. A magnetic metal conductive film is provided on a non-magnetic substrate, and a graphite-like carbon containing at least one selected from Cr, Mn, Mo, Nb, Ta, Ti, V, and W as a main component is formed on the magnetic metal conductive film. The magnetic recording medium is characterized in that a protective layer is provided, and a lubricating layer containing a fluorine-based lubricant is further provided thereon.