JPH02246018A - Magnetic disk - Google Patents

Abstract

PURPOSE:To reduce variation in the attracting force between the disk and a head and to prevent demagnetization by roughening the area to be used for contact-start-stop (CSS) in the substrate surface of the magnetic disk with a uniform pitch and making the rugged pattern of same height. CONSTITUTION:At least the area for contact-start-stop (CSS) in the substrate surface of a magnetic disk is roughened with a uniform pitch and made to have the rugged pattern of same height. This roughening process is performed by use of cutting tools such as that made of diamond or material of similar hardness to make the rough surface of a uniform pitch and the roughness of same height. Thereby, the contact area to a magnetic head slider is made constant at any position of the magnetic disk surface. Thus, variation in the attracting force to a head depending on the position or demagnetization due to local stress concentration can be avoided.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to contact start-stop (cont
The present invention relates to a magnetic disk that is incorporated into an act-start-stop; C35) type magnetic recording medium.

[Conventional technology]

In the field of magnetic recording technology, as recording density increases, it is necessary to reduce the spacing between a magnetic head and a magnetic recording medium. Therefore, it has been desired that the surface of the magnetic disk be made ultra-smooth. For example, a substrate made of an aluminum alloy plate used as a substrate for a magnetic disk and subjected to nickel phosphor plating is finished with a surface roughness of −X<20OA by polishing after NIP plating. Furthermore, the surface roughness of the slider surface of the magnetic head is similarly finished to be ultra-smooth. However, when the media surface and the Herad slider surface are finished so ultra-smoothly, CCS
When a recording medium is installed in a magnetic disk drive using this method, the head and magnetic disk may stick together while the device is stopped.
There was a problem in that the rotation caused serious damage to the head and magnetic disk.

Therefore, in order to make the surface of the magnetic disk rough, texture processing has been carried out on the surface of the substrate. Texturing is generally a method of creating fine scratches by pressing an abrasive tape onto the surface of a rotated substrate.) An example of the roughness curve of a substrate surface roughened in this way is Shown in Figure 2. In the figure, the horizontal axis is the position of the surface, and the vertical axis is the height of the surface. An example of this textured substrate is, for example, a magazine (IEEE TRANSACT
IONS ONMAGNETIC3* Vol, Mag
-2:L No-5e September 1987
P, 3405-3407).

[Problem to be solved by the invention]

In conventional magnetic disks, the surface of the substrate has irregular irregularities as shown in Figure 2, so the actual contact area with the magnetic rad slider is constant depending on the position of the magnetic disk surface. First, the stress from the slider applied to the magnetic recording layer is uneven, sometimes causing recorded information to disappear (demagnetization), and when the rotation of the magnetic disk stops at a position where the real contact area is large, there is a problem that The problem is that the spindle motor cannot rotate due to the suction force.

The present invention was made to solve the above-mentioned problems, and its object is to obtain a magnetic recording medium that can avoid demagnetization and attraction.

[Means to solve the problem]

In the magnetic disk according to the present invention, at least a region of the substrate surface where CSS 1 is applied is roughened at a uniform pitch, and the heights of protrusions appearing at a uniform pitch are made uniform.

[Effect]

In the magnetic disk according to the present invention, the surface of the substrate is roughened using a cutting tool made of diamond or a material having a hardness close to that, with a uniform pitch and the height of the protrusions. Since the contact area can be made constant at any position on the magnetic disk surface, it is possible to avoid variations in the head attraction force depending on the position and the risk of demagnetization due to local stress concentration.

〔Example〕

The present invention will be explained in detail below.

Sample 1 p After applying NIP plating on the Aj-4%Mg alloy disk, polishing 1 *905+
Using a substrate finished to nmt *130 mmψ, CrtCoNl and C were deposited in this order on this substrate by sputtering. Film thickness is 200OA and 500A respectively.
, 500A.

A magnetic disk produced in this way.

Sample 2: A magnetic disk manufactured by forming a film of Cr*CoNi5C in the same manner as Sample 1 on a polished substrate used in Sample 1 which was textured with a polishing tape (wA#2000).

Sample 3 (an embodiment of the present invention): The polished substrate used in Sample I was rotated at 600 revolutions per minute, and a diamond cutting tool (cutting edge curvature radius of 5 m) was placed on its surface.
By moving the substrate in the radial direction at a speed of &mm per minute, scratches close to concentric circles were formed. A magnetic disk was manufactured by forming a film of Cre CoNi +C on the substrate thus manufactured in the same manner as in sample 1.

Incidentally, FIG. 1 is a curve diagram showing the surface roughness of a magnetic disk according to an embodiment of the present invention manufactured in this manner. Compared to the conventional one shown in FIG. 2, the pitch of the unevenness in the one shown in FIG. 1 is uniform, and the heights of the protrusions appearing at the uniform pitch are well aligned.

The surface roughness (Rz) of Sample 1.2.3 above, and 4
After 24 hours of humidity and temperature at 0'C75S RH, head adsorption force (g) was measured at 24 locations per surface, and C
Demagnetization (decrease in output from the recording level before CSS) (%) after 8.82 million cycles t was measured for 6 surfaces each. The results are shown in Table 1.

Table 1 From this, it can be seen that although Sample 2 and Sample 3 have almost the same average value of surface roughness, Sample 3 has much less variation among the 24 locations. In addition, sample 2 has a considerably uneven adsorption force, but sample 3 has a considerably smaller variation. In addition, the adsorption force of sample 1 is the same as that of sample 2. It is much larger than sample 3. Furthermore, looking at the demagnetization, sample 1 has a range of demagnetization from very small to very large, and sample 2 also shows variations in the magnitude of demagnetization.

In sample 3, the variation in demagnetization is about ±1%, which shows that sample 3 is significantly superior to the others in terms of attraction force and demagnetization. In addition to removal machining that discharges chips, a similar effect is produced by roughening the surface by non-removal machining, that is, by press-fitting the cutting edge to create unevenness due to bulges to the left and right of the cutting edge. That is, any processing means may be used as long as the unevenness has a uniform pitch and the heights of the protrusions are the same.

In addition, the substrate surface material is NiP and N1CuP plating.

Alumite, aluminum, ceramics such as ZrO2 and Ajz03, glass, and plastic may also be used.

In addition to CoNi thin film, CoNlC can be used as a magnetic recording layer.
r.

7'-PI! 203* Thin film such as CoCr e r-F
It goes without saying that an organic coating film mixed with fine powder such as e2031 Fm may be used, and it goes without saying that the surface roughening using a cutting tool may be applied to at least the area on which CSS is to be performed on the surface of the magnetic disk.

It is also possible to further align the protrusion heights by polishing the substrate with the roughened surface according to the present invention using free abrasive grains.

〔Effect of the invention〕

As described above, according to the present invention, at least the area where CSS 6 is applied on the substrate surface of the magnetic disk is roughened at a uniform pitch, and the heights of the protrusions appearing at a uniform pitch are made uniform. Therefore, it is possible to suppress variations in the adsorption force depending on the position of the magnetic disk surface, and to prevent demagnetization due to local stress concentration.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the surface roughness of a magnetic disk according to an embodiment of the present invention, and FIG. 2 is a curve diagram showing the surface roughness of a conventional magnetic disk.

Claims (1)

[Claims] In a magnetic disk that has a recording layer made of a film containing a ferromagnetic material on a substrate and is used in a contact start/stop type magnetic recording device, at least the contact start/stop layer is formed on the surface of the substrate. What is claimed is: 1. A magnetic disk characterized in that a surface roughening process is performed at a uniform pitch in the area where the roughening is performed, and the heights of protrusions appearing at a uniform pitch are made uniform.