JP2626051B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium using a ferromagnetic metal thin film suitable for high-density magnetic recording as a magnetic recording layer.

2. Description of the Related Art While the tendency of high-density recording in magnetic recording is increasing year by year, increasing the surface recording density is, as is well known, the realization of a high C / N medium that can withstand narrower tracks and shorter wavelengths.

Ferromagnetic metal thin films, which are promising for realizing high-density recording in which the amount of magnetic flux per signal is reduced, have been developed and are approaching the practical range. FIG. 4 shows a typical configuration of a magnetic recording medium which is under development and uses a ferromagnetic metal thin film, which is not known, as a magnetic recording layer. In FIG. 4, 1 indicates a center line average roughness of 0.001 to 0.01 μm.
And a smooth polymer film such as polyethylene terephthalate, polyamide imide, or polyimide.
Those in which a polymer is arranged and arranged in an earthworm shape, or in which fine particles are arranged may be used. 2 is Co-Ni in oxygen atmosphere
Evaporated by electron beam heating, so-called Co-Ni-O thin film with high coercive force obtained by oblique deposition and Co-Cr etc., which are excellent proposals for improving short wavelength output to eliminate self-demagnetization A magnetic recording layer 3 composed of a perpendicular magnetization film and the like is a back coat layer 3 which is disposed as necessary on the surface of the polymer film opposite to the magnetic recording layer, and is made of a binder resin such as a polyurethane resin or a polyvinyl chloride resin. And a filler of carbon, Al ₂ O ₃ , CaCO _3, etc. dispersed therein. Reference numeral 4 denotes a protective lubricating layer in which an amorphous carbon film and a fluorocarbon-based lubricating layer are laminated (JP-A-61-142525). Lamination of plasma polymerized film and organic vapor-deposited film (JP-A-61-151837) Vacuum-deposited film of perfluoroalkylcarboxylic acid (JP-A-61-220116)
Many combinations have been proposed.

Problems to be Solved by the Invention However, although the above-described configuration has sufficient practicality within a limited range of conditions, the camera-integrated type
There has been a problem that sufficient practicality cannot be secured when used in a VTR or a commercial VTR, and a solution has been desired. The present invention has been made in view of the above circumstances, and provides a magnetic recording medium having excellent durability.

Means for Solving the Problems In order to solve the above-mentioned problems, the magnetic recording medium of the present invention is such that a part of a lubricant disposed on a ferromagnetic metal thin film having a surface oxide layer reacts and adheres to a metal part. It was made.

Effect The magnetic recording medium of the present invention has the above-described configuration, and even under high-speed sliding with the magnetic head, the reaction-adhered surface of the lubricant is not directly attacked. Since it can be continued, the durability will see a significant improvement.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 1 is an enlarged schematic sectional view of a magnetic recording medium according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a polymer film, and reference numeral 3 denotes a back coat layer. Reference numeral 5 denotes a ferromagnetic metal thin film having a surface oxide layer 7, which is schematically shown as being composed of a metal layer 6;
Included here are those in which the surfaces of the columnar fine particles are oxidized so that they can be obtained by obliquely depositing Co-Ni or the like in an oxygen atmosphere, and those in which a ferromagnetic metal thin film is formed and then post-oxidized. The surface oxide layer contains elements constituting the ferromagnetic metal material, and the thickness is preferably thinner in terms of spacing loss, and thicker in terms of durability. Preferred, 50 mm compromise
In the range of 150 to 150 mm. Reference numeral 8 denotes a lubricant selected from known lubricants such as fatty acids, fatty acid esters, fatty acid amides, perfluoroalkyl carboxylic acids, perfluoropolyethers, and various kinds of newly synthesized lubricants. The lubricant 9 penetrates through the surface oxide layer of the ferromagnetic metal thin film and reacts and adheres to the metal part to be lubricated by the remaining lubricant 10 disposed on the surface of the surface oxide layer. Things.

A method of obtaining a lubricant layer having such a configuration is to select some of the lubricants with optimal energy (by penetrating the oxide layer) and implant the remaining lubricant by a solution coating method, a vacuum deposition method, or the like. The method is suitable.

Hereinafter, more specific examples will be described in comparison with comparative examples.

On a polyethylene terephthalate film with a thickness of 10 μm and an average roughness of 0.0025 μm, 30 pieces of SiO ₂ fine particles with a diameter of 200 mm
(Μm) ² x 8 x 1 along a cylindrical can with a diameter of 1m
0 ^-5 (Torr) at the minimum incident angle of 45 degrees in an oxygen Co-Ni of (Co: 80 w
t%) was 0.2 μm electron beam evaporated. This membrane is
It has a surface oxide layer composed of CoO and NiO films. Put the above film along the heating roll (diameter 25cm)
Ionizes stearic acid at 100 ° C and accelerates voltage from 1500V to 90V
Irradiation was carried out by changing the temperature in the range of
Salt and Ni salt.

Thereafter, the surface was washed with isopropyl alcohol to remove the non-reacted material, and a lubricant was applied. The coating amount was constant at 0.5 [mg / m ² ]. As a comparative example, stearic acid is also adsorbed on Co-O and Ni-O, so stearic acid was applied, washed with isopropyl alcohol, and the portion other than the adsorbed portion was removed, and then a lubricant was applied. Example and Comparative Example
An 8 mm tape was formed by disposing a 0.4 μm back coat layer.
The results of comparative evaluation of each tape with a commercially available 8 mm video (CCD-F300, manufactured by Sony Corporation) are shown in Table 1 in comparison with the tape conditions.

For evaluation, set the mode (mode A) to repeat 10 passes at 5 ° C 80% RH and 40 ° C 15% RH, respectively, and the mode (mode B) at 20 ° C 10% RH and 40 ° C 80% RH. We looked at how many cycles image abnormalities (mass, clogging, jitter) occurred.

As is clear from Table 1, according to the present invention, a magnetic recording medium having good durability can be obtained.

[Example 2] Another means for solving the problem is that a part of a lubricant having a protective film disposed on a ferromagnetic metal thin film reacts and adheres to a surface oxide layer.

According to the magnetic recording medium of the present invention, the surface to which the reaction of the lubricant is applied is not directly slid by the above configuration, so that the lubricant does not run out and the protective effect of the protective film can be maintained. Significant improvements can be provided in the characteristics and CSS characteristics of the magnetic disk.

FIG. 2 is an enlarged sectional view of a magnetic disk according to an embodiment of the present invention, 11 is a ferromagnetic metal thin film such as Co-Ni, Co-Ni-P, Co-Cr-Nb, 12 is a SiO ₂ film, TiC 9 is a protective film such as a film, a WC film, a Si ₃ N ₄ film, and a plasma polymerized film. 9 is a part of a lubricant, and is formed by reacting with 11 surface oxide films slightly penetrating the protective film. FIG. Reference numeral 13 denotes a nonmagnetic substrate such as an Al-Mg alloy for a hard disk, and a polymer film such as polyethylene terephthalate or polyphenylene sulfide for a floppy disk.

Hereinafter, more specific examples will be described in detail in comparison with comparative examples.

Polish a 3mm thick Al-Mg alloy disc and apply a Ni-P plating
μm, polished again, and Ar + O ₂ = 0.04 (Tor
r), Ar: O ₂ = 6: 1, 13.56 (MHz), 1.1 (KW) and Co-Ni (Co: 8
0wt%) and 0.1μm
A Co-Ni film was formed. This film has 40 ° CoO and NiO as the surface oxide layer. A TiC film (Knoop hardness of 2600 kg / mm ² ) is disposed as a protective film over a thickness of 150 mm, and a film obtained by plasma polymerization of CF ₄ as a monomer at a high frequency of 13.56 (MHz) is disposed over a distance of 100 mm. Prepared, ionized arachiic acid, changed the accelerating voltage in the range of 1300 V to 8000 V, and irradiated it, so that a part of the arachidic acid reacted with CoO and NiO. Thereafter, the surface was washed with isopropyl alcohol to remove the non-reacted material, and a lubricant was applied. The application amount is 0.
4 (mg / m ² ) was fixed. The comparative example was obtained by applying a mixed lubricant. The contact start / stop (CSS) was repeated for each disk using a ferrite head, and the change in friction coefficient was examined. Table 2 summarizes the conditions of the magnetic disk and the obtained characteristics.

From Table 2, it is understood that stable lubrication is maintained according to the present invention.

Next, on a polyimide film having a thickness of 10 μm,
SiO 13 SiO ₂ fine particles / (μm) ^{2 are} arranged along a cylindrical can with a diameter of 50 cm (can temperature 220 ° C.), and Co-Cr (Co: 80 wt%) is 8 × 10 within an incident angle of 13 degrees. ^{-7 to} 1.2 × 10 ^-6 (Tor
r) Electron beam evaporation to form a 0.19 μm Co-Cr perpendicular magnetization film, and further, using graphite as a target, Ar + H ₂ = 0.03 (Torr), Ar: H ₂ = 4: 1, 13.56 ( MHz),
At 1.3 (KW), a diamond-like hard carbon film is formed 80Å,
Ionize tridecanoic acid from above, irradiate it in the range of 1900 V to 3200 V, make the reaction-deposited interface a Co-Cr surface, wash the unreacted one with isopropyl alcohol, and then lubricate again 0.5 (mg / m ² ), 0.45μm
Was provided to obtain a magnetic tape having a width of 8 mm. In the comparative example, the one simply coated with a lubricant was used. Table 3 shows the results of comparison between the conditions of each tape and the still characteristics after repeated running with the CCD-V300.

The still characteristic showed the minimum value when measured at arbitrary 15 places on the tape. Since the measurement was stopped for 60 minutes or more,> 60 indicates that the output did not decrease by 3 dB in the still state up to 60 minutes.

As described above, according to the present invention, even if the amount is small, the durability is remarkably improved by including the lubricant which is not removed by sliding with the head.

[Example 3] Another means for solving the problem is that a part of a lubricant disposed on a ferromagnetic metal thin film via a hard film and a carbon film having a graphite structure is adhered by reaction with the hard film. It is.

In the magnetic recording medium of the present invention, the above-described configuration ensures the graphite even if the lubricity is thin, so that even if the spacing loss is improved, sufficient durability can be obtained even under sliding with a large load. Become.

FIG. 3 is an enlarged sectional view of the magnetic recording medium of the present invention. In FIG. 3, reference numeral 11 denotes Co, Co-Ni, Co-Cr, Co-O, Co-Ti, Co-Ta, Co-W, Co. -
Ferromagnetic metal thin film such as Ni-O, Co-Cr-Nb, etc.
Hard carbon film, plasma polymerized film, SiO ₂ film,
A protective film, such as a Si ₃ N ₄ film, which has a high hardness but does not have sufficient lubricity, is a carbon film having a graphite structure, which is formed by an electron beam evaporation method, a sputtering method, etc., and has a graphite structure of 70%. % To 50Å to 100 含 ん
Within the range, sufficient lubricity can be maintained with the lubricant composition of the present invention. A portion 9 of the lubricant 8 must be configured to react with the protective film 12. The present invention may be either a magnetic disk or a magnetic tape. Hereinafter, examples of the present invention will be described more specifically.

On a polyethylene terephthalate film having a thickness of 12 μm, 16 particles of ZrO ₂ having a diameter of 150 ° / (μm) ^{2 are} arranged, and along a cylindrical can having a diameter of 1 m, a minimum of 3 × 10 ^-5 (Torr) oxygen 0.2 μm of Co-Ni (Co: 80wt%) at an incident angle of 50 degrees
Electron beam evaporation, a protective film is formed thereon by a reactive sputtering method, a carbon film is further formed by an electron beam evaporation method, and perfluorostearic acid is ionized.
Accelerate to 600V, irradiate, apply reactive coating on the protective film, wash the surface with isopropyl alcohol, and apply 0.45 (mg
/ m ²⁾ was applied to obtain a magnetic tape _^1/2 inch width arranged backcoat layer of 0.45 [mu] m. In Comparative Examples, those without perfluorostearic acid ion irradiation were used.

Table 4 summarizes the results of a comparison of the durability of the respective tapes and the VTR for broadcasting [Matsushita Electric AU-660] based on the still characteristics. The still characteristic was the time required for the output to drop by 3 dB from the initial value. Note that (> 60) indicates that measurement was centered in 60 minutes.

It can be seen that a sufficient durability can be obtained even under severe interface condition _^1/2 inch series as described above.

Advantageous Effects of the Invention As described above, according to the present invention, the lubricant reacts and adheres to the stress under high-speed sliding with the head, so that the lubricity is maintained and sufficient durability is secured. There is an excellent effect of being done.

[Brief description of the drawings]

1, 2 and 3 are enlarged sectional views of a magnetic recording medium according to an embodiment of the present invention, and FIG. 4 is an enlarged sectional view of a magnetic recording medium under development. 1 ... polymer film, 5,11 ... ferromagnetic metal thin film, 7 ...
... Surface oxide layer, 9 ... Reactive lubricant, 12 ... Protective film, 14 ...
... Graphite-like carbon film.

Claims (3)

(57) [Claims] 1. A magnetic recording medium characterized in that a part of a lubricant disposed on a ferromagnetic metal thin film having a surface oxide layer reacts and adheres to a metal part. 2. A magnetic recording medium characterized in that a part of a lubricant disposed on a ferromagnetic metal thin film via a protective film is deposited by reacting with a surface of the ferromagnetic metal thin film. 3. A magnetic recording medium characterized in that part of a lubricant disposed on a ferromagnetic metal thin film via a hard film and a graphite-like carbon film is reactively deposited on the hard film.