JPS62282858A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability in a medium as well as to make its variations smaller, by polishing the surface of a recording magnetic layer consisting of the metallic thin film formed on a substrate, or the surface of a nonmagnetic protective layer to be formed on this recording magnetic layer, and removing a projection on this surface. CONSTITUTION:If there is a projection 21 on the surface of a recording magnetic layer 11 or a nonmagnetic protective layer 12, a magnetic head 25 is made contact with a magnetic recording medium and, at the time of its running, the recording magnetic layer 11 or the nonmagnetic protective layer 12 of this projection part is shaved away so that dust is produced there. If this dust is rolled in between the medium and the head, it causes breakdown of the medium, incurring a main cause of damage to its durability. Therefore, a surface of the recording magnetic layer 11 or the nonmagnetic protective layer 12 is polished by an abrasive tape 4, removing the projection 12 on the surface, thus any dust out of the medium itself is brought to nothing so that damage to the medium due to infoldment of the dust between the medium and the head is checked, and improvement in durability is well promoted.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to a method of manufacturing a magnetic recording medium having a recording magnetic layer made of a metal thin film.

(Prior Art) Perpendicular magnetic recording has many excellent features as a high-density recording technology, and intensive research is being conducted in various places to put it into practical use. Recording medium used for perpendicular magnetic recording (hereinafter referred to as
Perpendicular magnetic recording media) include those whose recording magnetic layer is an oxide thin film having a magnetoplumb I-type crystal structure such as Ba-ferrite, and Go-Cr, Co-
V.C.

In recent years, research has mainly been carried out on recording magnetic layers made of metal thin films such as -Cr-Rh. In particular, the latter metal thin film type, which can be formed at a lower temperature than the Ba ferrite film, is possible because it can be formed at a temperature that allows use of flexible resin film substrates used in floppy disks, etc. The medium is seen as promising as a perpendicular magnetic recording medium.

The metal thin film type perpendicular magnetic recording medium is a conventionally used coating type medium, that is, γ-Fe203.

Because the structure is completely different from that of a magnetic recording medium in which fine ferromagnetic particles such as co-γ-Fe2O3 are dispersed in a binder and coated on a substrate, it is a new technology that did not pose any problems with coated media in practical use. Challenges arise. A typical example of this is the ability to withstand contact running of a magnetic head, that is, ensuring durability.

In order to improve the durability of metal thin film media, methods such as forming a non-magnetic protective layer on the recording magnetic layer and further providing a lubricating layer using liquid or solid lubricant thereon have been considered. However, the improvement in durability achieved by these methods is still insufficient from a practical standpoint. Specifically, this can be seen as a phenomenon in which the durability evaluation results vary widely. In other words, even if a non-magnetic protective layer or lubricant layer is formed with a thin film thickness (approximately 100 to 300 layers) that does not impair high-density recording, according to one sample, the
While it exhibits excellent durability of 1,000,000 passes,
Another sample with the same media configuration may exhibit much lower durability with a probability of several percent to several tens of percent.

Therefore, the future goal of improving durability is not only to improve the highest level of durability, but also to raise the overall level, that is, to reduce the number of cases where media damage occurs relatively quickly. There is a way to suppress it.

(Problems to be Solved by the Invention) As described above, in the conventional technology, even if methods such as forming a protective layer or providing a lubricating layer are used in manufacturing metal thin film magnetic recording media, variations in durability occur. Because of the large size, it has been difficult to obtain a magnetic recording medium that can be put to practical use.

Therefore, an object of the present invention is to provide a method for manufacturing a magnetic recording medium that has a recording magnetic layer made of a thin metal film, has high durability, and can suppress variations in durability to a small level.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method for improving the surface of a recording magnetic layer made of a metal thin film formed on a substrate or the surface of a nonmagnetic protective layer formed on the recording magnetic layer. , the above object is achieved by polishing to remove protrusions on the surface.

(Function) If there are protrusions on the surface of the recording magnetic layer or the non-magnetic protective layer, when the magnetic head runs in contact with the medium, the recording magnetic layer or non-magnetic protective layer at the protruding parts is scraped away, causing dust to form. occurs. When this dust is caught between the medium and the head, it causes destruction of the medium and impairs its durability.

When protrusions on the surface of the recording magnetic layer or the surface of the non-magnetic protective layer are removed by polishing based on the present invention, the dust supply from the medium itself disappears, resulting in dust being caught between the medium and the head. Damage to the medium is suppressed and durability is improved.

(Example) FIG. 1 is a diagram showing the configuration of a polishing apparatus for explaining a polishing process in an example of the present invention.

Magnetic recording medium 1 manufactured in the form of a diskette
A center hub 2 is attached to the center of the motor 3, and the center hub 2 is connected to a motor 3.

When the magnetic recording medium 1 is rotated by the motor 3, the medium 1 is pressed against the surface of the polishing tape 4 with a force. Further, the polishing tape 4 is fed at a constant speed as shown by an arrow 5. As a result, the surface of the magnetic recording medium 1 is polished and protrusions on the surface are removed. The abrasive tape 4 may be, for example, a tape-shaped base material with A as an abrasive material.Q203
The one coated with #10,000 particles is used.

On the other hand, in order to remove the fragments removed by this polishing, the cleaning tape 6 is sent in the direction indicated by the arrow 7 while being in contact with the surface of the magnetic recording medium 1 in the same manner as the polishing tape 4. -- Rumors about the heart ----゛=---U Figures 2 and 3 are enlarged views of polishing the surface of the magnetic recording medium 1 with the polishing tape 4.
FIG. 2 shows a case in which the surface of a medium is polished in which only a recording magnetic layer 11 made of a metal thin film is formed on a flexible resin film substrate 10, and FIG. This is a case where the surface of a medium on which the protective layer 12 is laminated is polished. In the case of a magnetic recording medium having a nonmagnetic protective layer 12 as shown in FIG. 3, polishing may be performed after forming the recording magnetic layer 11 and before forming the protective layer 12.

The recording magnetic layer 11F3 and the nonmagnetic protective layer 12 can be formed using a continuous thin film forming apparatus as shown in FIG. A supply roll 41 and a heating roller 43 that supply the flexible resin film substrate 42 to the inside of the vacuum chamber 40
a, 43b1 and a winding roll 44 that winds up the base body 42
is provided. Note that guide rollers and the like are omitted in the figure.

Also, facing the circumferential surfaces of the heating rollers 43a and 43b, for example, a co-Cr alloy target 45a.

45b are provided, and these targets 45a,
45b is supplied with power from external power sources 46a and 46b.

Using the above-described device, the flexible resin film base 42 sent out from the supply roll 41 is transferred to the first heating roller 4.
3a, a recording magnetic layer made of a Co-Cr alloy thin film is first formed on one surface of the base 42 by sputtering, and then the base 42 passes through the peripheral surface of the second heating roller 43b. At the same time, the Co-Cr alloy 1! A recording magnetic layer consisting of 1 was formed. After recording magnetic layers are formed on both sides in this way,
The base body 42 is wound onto a take-up roll 44 .

Next, the target is replaced with an oxide target such as S i 02, and a nonmagnetic protective layer made of oxide is deposited on the recording magnetic layer to a thickness of 0.02 μm by sputtering.
It was formed to a film thickness of . Then, the substrate on which the recording El layer and the nonmagnetic protective layer were formed was punched into a disk shape with a diameter of 3.5 inches, and then a liquid lubricant was applied thinly to the surface.

Table 1 shows the main specifications of the 3.5-inch floppy disk thus produced.

Forty similar floppy disks were prepared, 20 of which were washed as they were, and then a liquid lubricant was applied thinly to lubricate them. The remaining 20 discs were polished using the apparatus shown in Figure 1 with a polishing tape containing AQ203 #10000 particles to remove protrusions on the disc surface, and then subjected to similar lubrication treatment. .

A durability test was conducted on each of these 20 unpolished disks and polished disks using the same magnetic head (Mn--Zn ferrite head, radius of curvature 50R) under the same pressure conditions. The disk life was defined as the point in time when the reproduction output decreased to 70% of the initial output, and the number of times the disk was run (buses) until reaching that state was defined as the durability. The results of the durability test are shown in Figure 6. The horizontal axis in Figure 6 is durability,
The vertical axis is the percentage of media showing each durability, (a
) and (b) are the results for unpolished discs and polished discs, respectively.

As is clear from FIG. 6, the discs subjected to the polishing treatment according to the present invention have less variation in durability. In other words, in the polished discs, there is no disc with a durability of less than 4 million busses, which was present in a considerable proportion in the unpolished discs, and moreover, the proportion of discs with a high durability of 10 million busses or more has increased dramatically to Co%. ing.

In addition, 3.5-inch floppy disks having the specifications shown in Table 2 with different thicknesses of the co-crIitl layer were fabricated using the same process as described above.

Below in Table 2, prepare 40 same floppy disks as above, 20 of them are unpolished disks, and the remaining 20 disks are unpolished disks.
A durability test was conducted using the polished disc, and the results are shown in FIG. 7(a) (1)).

It is clear from these results that the polished disks according to the present invention have smaller variations in durability and are more durable overall.

The reason why the durability is improved by performing the polishing treatment according to the present invention is that the protrusions on the disk surface are removed by polishing. That is, the eighth
If there is a projection 21 on the disk surface as shown in FIG.

The dust generated in this way will not be caught between the disk head and the disk when the head is running stably, but when the head moves in the radial direction of the disk, due to thermal expansion of the disk, or when the device It is easy to get caught between the disk head in an unbalanced state such as shooting. Dust caught between disk heads has a non-negligible probability of destroying the disk.

FIG. 9 shows a case where a non-magnetic protective layer 12 is formed on the recording magnetic layer 111. In this case as well, if there is a protrusion 21 on the surface of the disk, dust 22 is generated and the same problem occurs.

On the other hand, if polishing is performed as in the present invention, the tenth factor, the protrusions on the disk surface, as shown in FIG. Can be done.

Incidentally, FIGS. 8 to 11 are examples in which a protrusion is formed on the surface of the base 10 and the shape of the protrusion appears even on the surface of the recording magnetic layer 11 or the nonmagnetic protective layer 12.
The surface of the base body 10 is smooth, and protrusions may be formed on the recording magnetic layer 11 or the nonmagnetic protective layer 12 itself during the film formation process. It goes without saying that the polishing process according to the present invention is also effective for such protrusions.

The present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the scope of the invention.

For example, in the embodiment, a magnetic recording medium in which a recording magnetic layer and a nonmagnetic protective layer are formed on both sides of a substrate has been described, but it goes without saying that the present invention can also be applied to a medium in which a recording magnetic layer and a nonmagnetic protective layer are formed on only one side. As a continuous thin film device for forming a recording magnetic layer and a nonmagnetic protective layer on one side of a substrate, the fifth
As shown in the figure, a supply roll 51 for feeding a flexible resin film substrate 52 into a vacuum chamber 50, and one set of a heating roller 53, a winding roll 54, and a target 55 may be used.

Further, in the embodiment, cleaning was performed after the polishing process, but the cleaning process may be omitted if the effect of the cleaning tape 6 described in FIG. 1 is sufficient.

Furthermore, in the durability test mentioned above, the recording magnetic layer was G.

- This is the case of a Qr alloy thin film, and this is an example of a medium in which a nonmagnetic protective layer is formed on the recording magnetic layer.
The polishing treatment for removing surface protrusions according to the present invention is effective when the recording magnetic layer is other metal thin film or when the nonmagnetic protective layer is 5iO
Other than z, such as Aff203, Zr0z, etc. (7) II
1ml film, oxynitride thin film such as 5i-0-N, or nitride ii1! such as 5isN+! I! , carbide thin film,
This method is effective in the case of a carbon thin film or the like, and even in the case of a medium without a non-magnetic coercive layer.

[Effects of the Invention] According to the present invention, the supply of dust from the medium itself can be eliminated by removing the protrusions on the surface of the recording magnetic layer made of a metal thin film or the surface of the non-magnetic retainer II by polishing. , it is possible to prevent damage to the medium due to dust being caught between the medium and the head, and to improve durability, particularly to reduce variations in durability.

[Brief explanation of drawings]

Figures 1 (a) and (b) are front and side views showing the configuration of a polishing device to explain the polishing process in one embodiment of the present invention, and Figures 2 and 3 are enlarged views showing the polishing process. Figures 4 and 5 are diagrams showing an example of a continuous thin film forming apparatus used for forming the recording magnetic layer and the non-magnetic protective layer.
Figures (a) and (b) are diagrams showing examples of durability test results for conventional unpolished media and polished media based on the present invention, and Figure 7 (
a)(1)) is a diagram similarly showing other examples of durability test results for unpolished media and polished media, and FIGS. 8(a)(b) and 9(a)(b). Figures 10 and 1 are diagrams for explaining the mechanism of durability deterioration caused by surface protrusions of a magnetic recording medium having a recording magnetic layer made of a thin metal film.
FIG. 1 is a diagram for explaining the protrusion removal effect by the polishing process in the present invention. 1...Magnetic recording medium (floppy disk), 4...
・Abrasive tape, 6...Cleaning tape, 1o...
- Flexible resin film substrate, 11... Recording magnetic layer, 1
2...Nonmagnetic recording layer, 21...Protrusion, 22...Dust, 23...Magnetic head. Applicant's representative Patent attorney Takehiko Suzue (a) (b) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 (a) (b) Figure 8 (a) (b) Figure 9 1st floor

Claims (4)

[Claims] (1) In a method for manufacturing a magnetic recording medium in which a magnetic recording layer made of a thin metal film is formed on a substrate, the surface of the magnetic recording layer or the surface of a nonmagnetic protective layer formed on the magnetic recording layer is A method for manufacturing a magnetic recording medium, comprising the step of polishing to remove protrusions on the surface. (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the surface of the magnetic recording layer or the surface of the nonmagnetic protective layer is polished using a polishing tape. (3) The method for manufacturing a magnetic recording medium according to claim 1, wherein the recording magnetic layer is made of a thin film of an alloy containing Co and Cr as main components. (4) The method for manufacturing a magnetic recording medium according to claim 1, further comprising the step of cleaning after polishing the surface of the magnetic recording layer or the surface of the nonmagnetic protective layer.