JPS62183021A - Magnetic recording medium having protective layer - Google Patents

Abstract

PURPOSE:To simplify a process for production by providing a thin carbon film by a sputtering method via a thin chromium film layer formed by a wet chromate treatment onto a magnetic layer consisting of a thin metallic film. CONSTITUTION:The magnetic layer consisting of a thin ferromagnetic metallic film is provided on a nonmagnetic base and a protective layer consisting of the thin carbon film is provided via an underlying layer consisting of the thin chromium film layer. The thin chromium film layer is formed to a uniform and defectless thin film of preferably <=50Angstrom by the wet chromate treatment and the thin carbon film is formed by a sputtering method. The sputtering method is used only for the formation of the thin carbon film according to the above-mentioned constitution and therefore, the process for production is simplified. In addition, the spacing loss between the magnetic layer and magnetic head is decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium having a protective layer, and in particular, the magnetic layer is made of a ferromagnetic metal thin film, and the magnetic layer is made of Kumam thin film spread on the magnetic layer. The present invention relates to a magnetic recording medium provided with a retention layer made of a carbon m film with an underlayer interposed therebetween.

[Conventional technology]

As the capacity of magnetic storage devices increases, the magnetic recording media used therein are required to have increasingly high recording density characteristics and high reliability. Conventional magnetic recording media have generally been coated magnetic recording media in which magnetic powder such as y-F.03 is dispersed in a resin binder and coated on a non-magnetic support. However, in response to the recent trend toward higher recording densities, attention has been focused on gold-jiI thin-film magnetic recording media in which a magnetic metal film is formed on a non-magnetic support by vapor deposition, plating, sputtering, etc. .

In this metal thin film type magnetic recording medium, it is possible to make the magnetic layer thinner, and since the magnetic layer does not contain a non-magnetic resin binder, it is possible to increase the magnetic flux density, resulting in a high recording density. becomes possible. however,
In this type of magnetic recording medium, the problem that the magnetic layer is easily destroyed due to sliding contact between the magnetic recording medium and the magnetic head is more likely to occur than in cloth-type magnetic recording media. It is important to treat the surface of the magnetic layer in order to have sufficient wear resistance against contact1lI11
It is 1.

As for this surface treatment, a method of forming a protective layer made of a thin carbon film on the magnetic layer by a vacuum method is well known (Japanese Patent Publication No. 55521/1982) and has been effectively used.

By the way, in a magnetic recording medium using the above method, when a protective layer made of a carbon thin film is formed on a magnetic layer made of a gold B4 thin film, the adhesion between these two layers is poor, so that the protective layer does not serve its original purpose. The problem was that it was not possible to achieve this. As a countermeasure to this problem, an attempt was made to form a base layer made of a thin chromium film between the two layers by sputtering, and it was confirmed that this method was particularly effective in terms of running durability.

[Problem that the invention seeks to solve]

However, in magnetic recording media in which a four-layer thin film is formed as the underlayer by sputtering,
The problem is that different atmospheric conditions are required for the formation of the chromium thin film and the subsequent carbon thin film, which complicates the manufacturing process, and as a result, the structure of the sputtered Mlff must also become complicated. There was a point.

In addition, for magnetic recording media used in a recording method that records while the magnetic head is in contact with the medium, from the 11 problems of spacing between the magnetic layer and the magnetic head,
During manufacturing, the thickness of the chromium thin film must be made as thin as possible, but on the other hand, in magnetic recording media where the chromium thin film is formed by sputtering, If it is not less than 50λ, the weather resistance is insufficient, that is, there is a problem that 1 m Wi as a protective layer of carbon 71 is insufficient.

The present invention has been made in view of the above points, and the chromium thin film layer interposed between the magnetic layer made of a gold thin film and the protective layer made of a carbon thin film can be formed by using a simpler device and process. An object of the present invention is to provide a magnetic recording medium that can be made thinner.

[Detailed description of the invention]

In the magnetic recording medium of the present invention, a magnetic layer made of a ferromagnetic metal thin film is provided on a non-magnetic carrier, and a layer made of a four-layer thin film is formed by wet chromating the metal thin film on the magnetic layer. is formed, and a protective layer made of a carbon thin film is further formed on the four-layer thin film layer by sputtering.

Wet Rita Mate treatment is widely used as a surface treatment for full bending, and its use was also attempted for magnetic recording media (Japanese Patent Application Laid-open No. 47401/1983). When this wet chromate treatment is performed, the treated gold H! , fW is melted and a chromium layer is formed there, resulting in an extremely uniform and defect-free thin film. This film thickness is 5oA or less, and is generally considered to be about 10 people. While I was there,
The wet chromate-treated magnetic recording medium described in this application was only improved mainly in terms of weather resistance, and was insufficient as a recording medium.

In the magnetic recording medium of the present invention, the chromium layer formed by wet chromate treatment has extremely excellent properties as an underlayer for a protective layer made of a carbon thin film.

In the magnetic recording medium of the present invention, the magnetic layer made of a ferromagnetic metal thin film can be formed by a conventional method such as a plating method or a sputtering method. More preferably, it is formed by a method.

The magnetic recording medium of the present invention can be used in many ways, such as a magnetic tape, a 70p disk, and a hard disk.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, and the characteristics of the magnetic recording medium of the present invention will be shown in conjunction with comparative examples.

Example 25 μm thick polyester film base (manufactured by Toshi)
Fireflies were alkali-etched for 30 minutes using a 10% NaOH aqueous solution at 60°C, and Pd nuclei were etched for 30 seconds at room temperature using a Pd/Sn mixture type activator, MS-101B (manufactured by Hitachi Chemical). A pre-plated paste was prepared using a 10% MCI solution for 30 seconds of acceleration.

Cobalt plating was performed on this pace under the following plating conditions.

Plating solution composition; Cobalt sulfate 106 mol/Ni +
/%/ 0.04 mol/Sodium hypophosphite 0.25 mol/I//L Lotuselle salt
too moles/ammonium sulfate
(140 mol/181! I
Add 0.10 mol/l-NaOH p) (9
, 5 for 6 minutes at 70°C.

The magnetic layer thus obtained was subjected to chromate treatment under the following conditions.

・Lifium mate treatment = 2% aqueous chromic acid anhydride solution; treatment time 1 minute; treatment temperature room temperature. Furthermore, on top of this, a protective layer consisting of a thin carbon material with a thickness of 100 mm was formed by sputtering ( Sputtering conditions: Ar gas pressure [1L2P&, DC8kW).

This medium was punched out into a 70-tube disc size having a diameter of 5.25 inches, and was used as a sample for measuring characteristics.

Comparative Example 1 The same process as in Example was carried out, except that a thin PM layer was formed by sputtering (sputtering conditions: Ar gas pressure of 2.OPi, DC 8kWi film thickness of 200 people), and the characteristics were measured. A sample was obtained.

Comparative Example 2 Samples for property measurement were obtained by performing the same operations as in Comparative Example 1 except that the thickness of the chromium thin film layer was increased to 50 mm.Property Measurement The properties of the above three samples were determined as follows. was measured.

(1) Weather resistance: 60°C, RC = 90% in a constant temperature and humidity chamber.
The magnetic properties before and after the sample was left for 0 days were measured using a VSM (manufactured by Toei Kogyo Co., Ltd.). 10K
The rate of change in the maximum magnetic flux Bm (68 m) and the rate of change in coercive force He (ΔHe) when G is applied are expressed as percentages.

(2) Running durability The media were run 10 million times using a 70-tube disc drive, and the scratches that occurred on the media surface were observed, and the running durability was ranked according to the degree of scratches: Rank ◎--- ---No scratches 0--------One less △----------Normal
The output was measured at pms 5 MHz, and the output of Example 1 was expressed as OdB.

The results of the above characteristic tests are shown in Table 1.

Table 1 Results of Characteristic Tests As can be seen from Table 1, the example sample maintained good running durability comparable to that of the sample of Comparative Example 1.2, but was superior to the comparative example in terms of weather resistance and electromagnetic conversion characteristics. was superior to that of the sample.

〔Effect of the invention〕

The magnetic recording medium of the present invention is a magnetic recording medium having a protective layer made of a thin carbon film, in which a chromium thin film layer interposed between a magnetic layer made of a thin metal H. Since it is formed by chromate treatment, the weather resistance of the magnetic recording medium finally manufactured can be improved, and at the same time, the chromium thin film layer can be formed without impairing the running durability of the magnetic recording medium. It has the advantage of being thinner (less than 50 Å, typically about 10 layers), resulting in less spacing loss between the magnetic layer and the magnetic head.

Further, in the magnetic recording medium of the present invention, the chromium thin film layer forming process consists of wet chromate treatment of the magnetic layer as described above, and the sputtering method is only used in the carbon thin layer forming process, so that the fJJI culm is More i? At the same time, a simpler structure can be used for sputtering. Furthermore, this manufacturing process can be further simplified by using a wet plating method in the magnetic layer forming process.

The magnetic recording medium of the present invention is capable of high recording density, and at the same time has very excellent characteristics in terms of running durability, weather resistance, and electromagnetic conversion characteristics.

Claims (3)

[Claims] (1) A magnetic recording medium comprising a magnetic layer made of a ferromagnetic metal thin film on a non-magnetic support, and a protective layer made of a carbon thin film formed by sputtering on the magnetic layer. , and a chromium thin film layer formed by wet chromate treatment as an underlayer of the protective layer. (2) The magnetic recording medium according to claim 1, wherein the thickness of the chromium thin film layer is 50 Å or less. (3) The magnetic recording medium according to claims 1 and 2, wherein the magnetic layer made of the ferromagnetic metal thin film is formed by a wet plating method.