JPS63106923A - Manufacture of magnetic recording medium - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for 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 magnetoplumbite crystal structure such as Ba-ferrite, Co-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 media, which can be formed at lower temperatures than Ba-ferrite thin films, is preferred because it allows film formation at temperatures that allow flexible resin film substrates used in floppy disks, etc. It is seen as a promising perpendicular magnetic recording medium.

Metal thin film type perpendicular magnetic recording media are conventionally used coated media, namely γ-Fe2O3゜Co-γ-F.
Since this structure is completely different from a magnetic recording medium such as e2us in which ferromagnetic particles are dispersed in a binder and coated on a substrate, new problems that did not arise with coated media will arise in practical use. Typical examples are maintaining the ability of the medium to withstand environments such as high temperature and high humidity, that is, maintaining corrosion resistance.
The objective is to ensure the properties that can withstand the contact running of the magnetic head, that is, the durability.

In order to improve the durability of metal thin film media, methods such as forming a non-magnetic securing layer on top of the recording magnetic layer and further providing a lubricating layer using a liquid or solid lubricant thereon have been considered. However, the improvements in durability achieved by these methods are still insufficient from a practical standpoint, and the results of durability evaluations vary. In other words, although there are media with high durability, there are also media with low durability. Therefore, in order to improve durability, the surface of the metal thin film medium is polished with a polishing tape or the like in order to remove the protrusions that exist on the surface of the metal thin film medium, which is one of the causes of decreasing durability. This has made it possible to eliminate variations in durability and improve the overall level of durability. However, polishing caused the protective layer on the protruding parts to peel off and the magnetic layer to be exposed, resulting in deterioration in corrosion resistance in some cases. Therefore, in order to improve the reliability of the medium, it is necessary to improve the durability of the medium while maintaining corrosion resistance.

(Problems to be Solved by the Invention) As described above, in the conventional technology, even when methods such as forming a protective layer or providing a lubricating layer are used in manufacturing metal thin film magnetic recording media, there is a large variation in durability. Therefore, it has been difficult to obtain a magnetic recording medium that can be put to practical use. Furthermore, the method of polishing the surface of the medium in order to suppress variations in durability has been insufficient in terms of improving reliability because it may deteriorate corrosion resistance.

Therefore, an object of the present invention is to provide a method for manufacturing a magnetic recording medium having a recording magnetic layer made of a metal thin film, which has high durability, small variations in durability, and high corrosion resistance.

[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 thin metal film formed on a substrate or the surface of a nonmagnetic protective layer formed on the recording magnetic layer. , by polishing to remove the protrusions on the surface, and then forming a non-magnetic protective layer on the polished magnetic recording layer or on the non-magnetic protective layer formed on the magnetic recording layer, thereby achieving the above purpose. The goal is to achieve the following.

(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, there is no longer any dust supplied from the medium itself, so the problem with the medium due to dust entrainment between the medium and the head is eliminated. damage is suppressed and durability is improved.

Furthermore, by forming the nonmagnetic protective layer after polishing, it is possible to suppress deterioration of the recording magnetic layer in the portion where the nonmagnetic protective layer has been peeled off due to polishing, and to prevent deterioration of corrosion resistance.

(Embodiment) FIG. 1 is a diagram illustrating the present invention using a floppy disk as an example. The disk has a recording magnetic layer 11 on a substrate 10.
In addition, a nonmagnetic protective layer 12a is formed. (a)
The protrusions 21 present on the disk surface are removed by polishing. (b) This prevents the protrusions from being destroyed by the head, eliminates the generation of dust, suppresses damage to the medium caused by dust getting caught between the medium and the head, and improves durability, but the non-magnetic protective layer Corrosion may occur from the peeled parts. For this reason, after polishing,
A non-magnetic magnetic layer [1512b] was formed.

(c) As a result, corrosion in high-temperature environments was suppressed, and deterioration of corrosion resistance could be prevented.

Therefore, by performing polishing and forming a nonmagnetic protective layer as in the present invention, durability can be greatly improved while maintaining corrosion resistance.

′! Figure J2 is a diagram for explaining the polishing process in one embodiment of the present invention. A center hub 2 is attached to the center of a magnetic recording medium 1 manufactured in the form of a floppy disk, and this 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 f.

Further, the polishing tape 4 is fed at a constant speed as shown by an arrow 5. This polishes the surface of the magnetic recording medium and removes protrusions on the surface. As the polishing tape 4, for example, Al10361000 is applied as an abrasive on a tape-shaped base.
The one coated with 0 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. The polishing tape 4 and the cleaning tape 6 are also movable in the radial direction of the magnetic recording medium 1 as shown by arrow 8.9 so that at least the entire recording surface of the magnetic recording medium 1 can be polished and cleaned. ing.

3 and 4 show that the magnetic recording medium l is polished by the abrasive tape 4.
FIG. 3 is an enlarged view of the polishing of the surface of the flexible resin film substrate l.

When polishing the surface of a medium on which only the recording magnetic layer 11 made of a metal thin film is formed, FIG. This is the case when polishing the surface of a medium that is

Recording magnetism 1i! ill and the nonmagnetic tI layer 12 can be formed, for example, by a continuous thin film forming apparatus as shown in FIG. A supply roll 41 that supplies the flexible resin film substrate 42, heating rollers 43a and 43b, and a take-up roll 44 that winds up the substrate 42 are provided inside the vacuum chamber 4o.

Note that guide rollers and the like are omitted in the figure. In addition, for example, a Co
-Cr alloy targets 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 this time, a recording magnetic layer made of a Co--Cr alloy thin film was similarly formed on the other surface of the base 42. After recording magnetic layers are thus formed on both sides, the base body 42 is wound up on a winding roll 44.

Next, the target is replaced with an oxide target such as SiO2, and a non-magnetic material U made of oxide is deposited on the recording magnetic layer by sputtering. ! The layer was formed to a thickness of 0,602 μm. Then, the recording magnetic layer and the non-magnetic
The substrate on which one layer was formed was punched into a 3.5 inch diameter disk shape.

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

Forty floppy disks formed in this manner were prepared, and 20 of them were coated with a non-magnetic protective layer on the surface by approximately 0.00 mm using the apparatus shown in FIG. O1μ-
formed to a thickness. The thin film forming apparatus shown in FIG.
A substrate holder 52 and a target (for example, 5i02) 53 facing the substrate holder 52 are provided inside the substrate holder 1, and sputtering is performed on the surface of a floppy disk 55 held by the substrate holder 52 using RF output supplied from a power source 54. Thereafter, the surface of the medium was polished using the apparatus shown in FIG. 2 to remove protrusions.

For the remaining 20 floppy disks, the surface of the media was first polished using the device shown in Figure 2 to remove protrusions, and then a 0.01 μm thick layer was polished on the surface using the device shown in Figure 6. A nonmagnetic protective layer was formed. A total of 40 floppy disks in two different groups were then subjected to the same cleaning and lubrication treatment.

A durability test was conducted on 1620 floppy disks using these two different glues under the same conditions using the same magnetic head (M n -Zn ferrite head, radius of curvature 50R). 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 FIG. In Figure 7, the horizontal axis shows durability, and the vertical axis shows the percentage of media showing each durability. (a) is a disk polished after forming a non-magnetic protective layer, (b) is a disk with non-magnetic protection after polishing. These are the results for a disc with layers formed thereon.

As is clear from FIG. 7, the variation in durability is small for both the disks subjected to polishing after forming the nonmagnetic protective layer and the disks subjected to polishing and then formed with the nonmagnetic protective layer. That is, none of them had durability of 4 million passes or less, and a high proportion of them showed high durability of 10 million passes or more.

Next, a 3.5-inch floppy disk with the specifications shown in Table 2 was created using the same process as above, and 20 of the same floppy disks were prepared in the same manner as above, 10 of which were the same as above. After polishing, a nonmagnetic protective layer was formed, and the remaining 10 sheets were polished after forming nonmagnetic protective layers. First, missing pulses were measured for these 20 floppy disks. The results are shown in FIG. (a) shows a disk that was polished after forming a protective layer, and (b) shows a disk that was polished and then formed with a protective layer.

Next, each 10 discs were heated at a temperature of 80°C and a temperature of 90% Rh.
It was left for 168 hours under these conditions. Thereafter, missing pulses were measured for each of the 10 disks. The results are shown in Figure 9. (a) is a disk that was polished after forming a protective layer, and (b) is a disk that was polished and then formed with a protective layer.

'As is clear from Figures W58 and 9, the disks on which a nonmagnetic protective layer was formed after polishing based on the present invention showed almost no increase in the number of missing pulses even when left in a high temperature and high humidity environment. In other words, the corrosion resistance is good. On the other hand, in the as-polished disk, the number of missing pulses increases, indicating that the recording magnetic layer has deteriorated.

In other words, the corrosion resistance is insufficient.

The reason why durability is improved while maintaining sufficient corrosion resistance by polishing and forming a non-magnetic protective layer based on the present invention is that polishing removes protrusions on the disk surface and removes the protective layer. This is because the formation of the magnetic layer can suppress exposure of the magnetic layer to the outside air.

As shown in FIG. 10(a), a protrusion 21 is formed on the disk surface.
If so, the protrusion 21 breaks and becomes dust 22 while the magnetic head 23 is in contact with it and travels, as shown in FIG. 2(b). 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 vibration.

Dust caught between the disk head has a non-negligible probability of destroying the disk.

On the other hand, by polishing and forming a non-magnetic protective layer as in the present invention, as shown in Figure 11, the protrusions on the disk surface are removed, dust generation is eliminated, and corrosion resistance is maintained while durability is maintained. It can greatly improve your sexuality. In the figure, 10 is a substrate, 11 is a recording magnetic layer, 12a is a nonmagnetic protective layer, and 12b is a nonmagnetic protective layer formed after polishing.

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 examples, polishing and forming the non-magnetic protective layer were performed after punching, but polishing and forming the non-magnetic protective layer can also be performed successively. As shown in FIG. 12, a device for continuously polishing a medium includes a take-up roll 111, a delivery roll 112, and a polishing tape 1.
13. A device provided with a cleaning tape 114 may be used. The nonmagnetic protective layer after polishing may be formed using a thin film forming apparatus shown in FIG.

Of course, it is also possible to use methods other than the sputtering method, such as a vacuum evaporation method, an ion blating method, or a CVD method, if an appropriate device can be easily prepared.

Further, in the embodiment, cleaning was performed after the polishing process, but the cleaning process may be omitted as long as the effect of the cleaning tape 6 explained in FIG. 2 is sufficient.

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

- This is an example of a case of a Cr alloy thin film, and a case of a medium in which a nonmagnetic protective layer is formed on a recording magnetic layer,
The polishing treatment for removing surface protrusions according to the present invention is applicable when the recording magnetic layer is another metal thin film, when the medium does not have a non-magnetic protective layer, and when the non-magnetic protective layer is other than 5to2, for example, Aj2203, ZrO2. etc. oxide thin film, 5i-0-
It is also effective for media that are oxide/nitride thin films such as N, nitride thin films, carbide thin films, and carbon films.

[Effects of the Invention] According to the present invention, corrosion resistance is reduced by removing the surface of the recording magnetic layer made of a metal thin film or the surface of the nonmagnetic protective layer by polishing, and then forming the nonmagnetic protective layer. It is possible to eliminate dust supply from the medium itself, prevent damage to the medium due to dust entrainment between the medium and the head, improve durability, and in particular suppress variations in durability.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the polishing process and nonmagnetic protective layer formation in the present invention, and FIG. 2 is a front view and side view showing the configuration of a polishing apparatus for explaining the polishing process in an embodiment of the present invention. Figures 3 and 4 are enlarged views showing the polishing process, Figure 5 is a diagram showing an example of a continuous thin film forming apparatus used for forming the recording magnetic layer and the non-magnetic protective layer, and Figure 6 is an enlarged view showing the polishing process. FIG. 7 is a diagram showing an example of a thin film forming apparatus used for forming a non-magnetic protective layer on a medium punched into a floppy disk shape; FIG. Figure 8 shows an example of the results of missing pulse measurements on polished media, Figure 9 shows an example of the results of missing pulse measurements on media left in a high temperature and high humidity environment after polishing, and Figure 10. 11 is a diagram 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. diagram for,
FIG. 12 is a diagram showing an example of the configuration of a polishing apparatus that continuously performs polishing processing according to the present invention. 1 ...... Magnetic recording medium (floppy disk) 4 ...... Polishing tape 5 ...... Cleaning tape 10 ...
...Flexible resin film base 11 ... Recording magnetic layer 12 ... Nonmagnetic protective layer 21 ... Protrusion 22 ... Dust 23 ... ...Patent attorney representing Magnetic Head
Noriyuki Ken Yudo Takehana Kikuo (b) Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 (a) (b) Figure 7 (a) (b) Figure 8 Mi/”/-77 ”＼°Russ (s/5ide)
Mitsushin 1 pels (I”/5ide) (a)
(b) Figure 9 (a) (b) Figure 10 Figure 11 Figure 02 Figure 12

Claims (4)

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