JPS6226623A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the film crack by the stress of a film and to obtain excellent magnetic characteristics by roughening the surface of a glass substrate to increase the adhesive power to an underlying layer. CONSTITUTION:The glass substrate 1 is made of soda lime glass and the main surface thereof is finished to a specular surface by prescribed sand blasting, polishing and washing; thereafter the substrate is immersed into an aq. soln. having 0.2 hydrofluoric acid concn. to roughen the surface. A Cr film 2 as the underlying layer is then laminating by a sputtering method on the surface of the glass substrate 1 and in succession of, a Co-Ni alloy film 3 contg. 25wt% Ni is laminated by the sputtering method on the Cr film 2; further a thin carbon film 4 is laminated as a protective film by the sputtering method on the Co-Ni alloy film. Since the glass substrate has the rough surface, the contact area with the Cr film 2 as the underlying layer is increased and adhesive power is increased. The film crack by the stress of the film 2 is thus prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium used in a magnetic storage device.

[Conventional technology]

In recent years, due to the demand for higher density recording in magnetic recording media, continuous thin film magnetic recording media having a magnetic layer made of a metal magnetic thin film have been attracting attention. As such a metal magnetic thin film, CO or Co-Ni formed by sputtering method etc.
, Co-Ni, -P, Co-P and other alloy-based gold 12Lm [films] are known, and in order to improve their magnetic properties, Cr [9] is interposed as an underlayer between the substrate and the above magnetic layer. It is known that
AG, Volume 15, 3 @ Page 1135 (■E E E Tra
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9) ). Conventionally, aluminum alloy substrates have been mainly used as substrates for these magnetic recording media, but with the demand for higher density recording, it is desired to improve the processing accuracy of aluminum alloy substrates, and Glass substrates are attracting attention as an alternative to aluminum alloy substrates, as surface defects caused by interlayer compounds have become a problem. The surface of the glass substrate is extremely smooth with an average surface roughness of about 30 scratches by ordinary polishing, and there are almost no protrusions that would be a fatal defect in a magnetic disk. In addition, in the case of glass substrates, the material itself is cheaper than 8i or 5i alloy substrates, and in order to prevent corrosion of the magnetic layer, a Ni-P plating layer or anodized A20
It is possible to eliminate the step of forming three layers (which results in a mirror finish with an average surface roughness of about 200 by the polishing method), which has the advantage of greatly contributing to cost reduction.

[Problem that the invention seeks to solve]

On the other hand, with the increase in density, magnetic films are becoming thinner and
There is a growing demand for magnetic recording media with higher coercivity.

One way to improve the magnetic properties of a magnetic recording medium using a glass substrate is to increase the thickness of the Cri underlayer (for example, 4000 Å or more).
In this case, the adhesive force cannot resist the increase in membrane stress,
Microscopic film cracking phenomenon is less likely to occur. Such cracks in the underlayer occur when the distance between the magnetic head and the magnetic head is 0.2 to 0.3μ.
This is a fatal flaw for magnetic recording media that are rotated while maintaining a small value of m.

[Means for solving problems]

In order to solve these problems, a magnetic recording medium according to the present invention is a magnetic recording medium in which an underlayer and a magnetic layer are sequentially laminated on the surface of a glass substrate, in which the surface of the glass substrate is rough. It is characterized by Further, the magnetic recording medium according to embodiment J of the present invention is characterized in that the surface roughness of the glass substrate is within a range of 50 Å to 200 Å in terms of maximum height (Rmax). In addition, the surface roughness is
Conforms to JIS surface roughness JBO601.

〔Example〕

The drawing is a sectional view showing a magnetic recording medium according to an embodiment of the present invention.

The glass substrate 1 of this embodiment is made of soda lime glass, and its main surface is polished to a mirror finish (the surface roughness is about 30 mm at the maximum height) through a prescribed sanding, polishing, and cleaning process. 1 in an aqueous solution with a hydrofluoric acid concentration of 0.2%.
By soaking for 0 minutes, the surface roughness can be reduced to about 8 in maximum height.
It was processed and cleaned by 0 people.

Next, on the surface of this glass substrate 1, a Cr film 2 (thickness: 2,000 yen) was laminated as an underlayer by sputtering, and then 25 wt% N was added as a magnetic layer on this Cr film 2.
A Co--Ni alloy film 3 (thickness: 600) containing i was laminated by sputtering, and a carbon thin film 4 was further laminated as a protective film on this Co--Ni alloy film by sputtering. A magnetic recording medium was manufactured. In addition, in the drawing, the surface roughness of the glass substrate 1 and the uneven shapes of the <cr film 2) Co--Ni alloy film 3 and carbon thin film 4 are omitted.

Next, as a comparative example, a magnetic recording medium was manufactured in which a Cr film 2) a Co-Ni alloy film 3 and a carbon thin film 4 were laminated on the surface of the mirror-like glass substrate described above without hydrofluoric acid treatment. The magnetic properties of the magnetic recording media of Examples and Comparative Examples were measured, and the results are shown in the following table.

As is clear from the above table, the magnetic recording medium according to the present example has a larger coercive force Hc than that according to the comparative example, so that the recording density can be further increased, and the residual magnetic flux density B
Since r is large, the output j voltage can be increased by -.000 m, and the squareness ratio (residual magnetic flux density Br/saturation magnetic flux density Bs) is large, so it is excellent in magnetic properties such as recording and erasing.

In addition, since the magnetic recording medium according to this embodiment has a rough glass substrate surface, the contact area with the Cr film 2 as the underlayer is increased, and the adhesion force is increased. Film cracking can be prevented.

Regarding the practical range of the surface roughness of the glass substrate 1, a maximum height (Rmax) of 50 Å to 200 is effective in order to achieve the effects of the present invention, particularly the magnetic properties. If it is made smaller than 50 people, the magnetic properties approach those shown in the comparative example, and its significance is lost; if it is made smaller than 200 people, the effect of further improving the coercive force 11c can be obtained. However, the unevenness of the surface of the magnetic recording medium (carbon thin film surface) is too large, causing defects such as missing pits and deterioration of override characteristics during high-density recording.

The surface roughness may be adjusted by taking into consideration the concentration of hydrofluoric acid and the treatment time.

Next, the material for the glass substrate is not only soda lime glass but also multi-component glass such as aluminosilicate glass,
It may be made of quartz glass, etc., and the means for roughening the surface of the glass substrate include a chemical corrosion method by immersing it in a hydrofluoric acid aqueous solution, or a so-called chemical polishing method that uses a combination of this and a mechanical polishing method. method may be used. For the underlayer, a non-magnetic material such as No may be used in addition to Cr, and for the magnetic layer, a Co-Ni alloy with a different mixing ratio, CO alone, or Fe with Co-old as the main component may be used. Or other C such as alloys mixed with PT and Co-pt.

Other alloys may also be used. In addition to the carbon thin film, protective films include Cr film, C composite layer, Si02 layer, C
r/5i02 composite layer, Cr/C/Si 02 composite layer, S
It may also be an iO2/C composite layer. As for the film forming method, in addition to the sputtering method, a vacuum evaporation method, an ion blating method, etc. may be used.

〔Effect of the invention〕

As explained above, according to the present invention, since the surface of the glass substrate is roughened, the adhesion force with the Cr film as the underlying layer is increased, and film cracking due to stress in the Cr film is prevented. In addition, it is possible to provide a magnetic recording medium substrate that has excellent magnetic properties and is free from surface defects like an aluminum alloy substrate.

[Brief explanation of the drawing]

The drawing is a sectional view showing a magnetic recording medium according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Glass substrate, 2...Cr film, 3...C.

Claims (2)

[Claims] (1) A magnetic recording medium comprising an underlayer and a magnetic layer sequentially laminated on the surface of a glass substrate, characterized in that the surface of the glass substrate is rough. (2) In claim (1), the surface roughness of the glass substrate is 50 Å to 20 Å in maximum height (Rmax).
A magnetic recording medium characterized in that the magnetic recording medium is within a range of 0 Å.