JPS6220126A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a flat disk having no warpage by constructing the disk in such a manner that the outside circumferential part is bent in the circumferential direction. CONSTITUTION:A thin CoCr alloy film is formed on a polyimide film. Two sheets of annular holders 12 made of stainless steel respectively provided with recesses and projecting parts in the circumferential part are used as a film holder 12 in this stage. A film blanked to a disk shape is held in place between the recesses and the projecting parts and uniform tension is exerted to the film to flatly hold the surface thereof. The peripheral part of the disk sample prepd. by such a method is plastically deformed as said part is held by the holder and is heated. A square groove is thus formed in said part. The disk having no curling is thereby obtd.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magnetic recording medium such as a floppy disk that has a thin film of a ferromagnetic metal or oxide as a magnetic recording layer, and particularly relates to a magnetic recording medium with a flat surface and no curl. Regarding the recording medium 7.

[Background of the invention]

As a method to prevent curling, for example, Japanese Patent Application Laid-Open No. 56-169
There is a technique shown in Publication No. 214. This method attempts to balance stress and cancel curl by providing magnetic metal thin films on both sides of the film. However, even if a magnetic film is formed on both sides under the same conditions (film thickness, substrate temperature at the time of film deposition), when a magnetic layer is formed on one side and then a film is formed on the other side a second time, There is already a magnetic layer on the base film, so the thermal dimensional change or temperature change over time during thin film deposition is different from the first time, and simply forming magnetic layers on both sides will not eliminate the curl. There is a problem that it is difficult.

[Purpose of the invention]

An object of the present invention is to correct curls and flatten even if curls exist in a magnetic recording medium that has an organic polymer film as a base and a ferromagnetic metal or ferromagnetic oxide thin film as a magnetic recording layer on its surface. The goal is to provide a structure that allows for

[Summary of the invention]

With the increase in the density of magnetic recording, the recording medium is γ-Fe2O3.
Fe, Fe,
Sputtering of ferromagnetic metals mainly composed of Go, Ni, etc.
It was formed on the substrate by vacuum evaporation method or the like. There is a transition to magnetic thin film media.

In particular, the perpendicular magnetic recording method proposed by Iwasaki et al.
In principle, the higher the recording density, the smaller the demagnetizing field, so it is believed that a dramatic increase in recording density is possible. This perpendicular magnetic recording medium requires a magnetic film with excellent perpendicular magnetic anisotropy, and C
o Cr film is a typical example.

To make a floppy disk using this CoCr film, a long piece of polyester terephthalate (commonly known as PET) is used.
This is carried out by using a film or polyimide film as a base material, and forming a thin film of Co 2 Cr on one or both sides thereof by vacuum evaporation or sputtering to obtain a raw material, which is then punched into a predetermined shape. However, in many cases, the film on which the CoCr film is formed is curled, and if this is severe, it cannot be used as a floppy disk. Especially when the CoCr fpJ is formed on only one side of the film, the curvature Large curls with a radius of several tens of I are likely to occur. On the other hand, although curling is reduced when CoCr films are formed on both sides of the film, curling often occurs even if the CoCr films on both sides are of the same thickness and are deposited at the same substrate temperature. . Therefore, C on one side
o When depositing a Cr film, methods are used such as making the film thickness different from that on the other side, and changing the temperature during deposition on the front and back sides to balance stress and eliminate curling. However, with this method, it is not possible to create a double-density floppy disk that uses both sides because the front and back sides have different characteristics.

The present invention attempts to dynamically correct and flatten the curls even if they are curled when the CoCr film is formed, by forming the outer peripheral part of the magnetic recording medium into a structure that is bent along the circumferential direction. It is something. The present invention will be explained in detail below with reference to examples.

[Embodiments of the invention]

[Example 1] A Co Cr alloy thin film was formed on a polyimide film using an electron beam heating type vacuum evaporation apparatus as shown in FIG. At this time, as shown in FIG. 2, two ring-shaped stainless steel holders 12 each having a concave portion and a convex portion on one circumference were used as the film holders 12.

A disc-shaped film was cut out between the uneven parts, and a uniform tension was applied to the film to keep the surface flat. CoCr was deposited as follows. The film and holder 12 are heated to 170° C. by the heater 11 to form a CoCr film with a film thickness Q of 3 μm and a Cr concentration of 22 wt%.
A thin film was deposited on the first side. Thereafter, the substrate holder 12 was cooled, the vacuum was broken, and the substrate holder was turned over, and a CoCr thin film was formed on the back side of the first surface and the second surface under the same conditions to form a sample A. Note that the thickness of the film used was 50 μm.

Further, a Co Cr thin film was formed on the first and second surfaces of the polyimide film under the same conditions as described above, except that the substrate temperature was 200° C., and Sample B was obtained.

The periphery of the disk-shaped sample produced by this method undergoes plastic deformation because it is sandwiched between the holders and heated, and a rectangular groove as shown in FIG. 2 is formed.

When sample A was curled, the radius of curvature was 100 holes or more, and a disk without curls could be obtained. Furthermore, when the deformed outer circumferential portion of this sample was cut off to form a disk, a curl was formed in which the first surface side was convex, and the radius of curvature was 17 square centimeters.

Also, the radius of curvature of sample B was more than 100 cm, similar to sample A, and there was almost no curl, but the radius of curvature of the disk whose outer periphery was cut off after undergoing heat-induced deformation was 10 cm! It was found that a large curl was generated.

As can be seen from the above embodiments, by providing a rectangular deformed portion on the outer periphery of the disk, it is possible to correct the warp that originally exists in the disk and produce a flat disk.

[Example 2] A Co 2 Cr film was formed on a long polyimide film using a continuous winding type vapor deposition apparatus in which the main controller 32 can heat as shown in FIG. 3 .

The deposition conditions were as follows: the main roller surface temperature was 200°C, the film thickness was 0.3 μm, and the Cr'a degree of the film was 21 wt%.
o A Cr thin film was formed on the first surface of the film, and then the film was turned over, and a CoCr film was formed on the back side of the first surface to the second surface under the same conditions as the first surface.

A disk-shaped disk is punched out from the long tape thus produced, and the outer periphery of the disk is cut using a stainless steel ring-shaped jig with a built-in heater as shown in Figure 4. The ends were bent at right angles and hot pressed at 250°C for 2 minutes. In this way, a disk with its outer periphery bent at right angles was produced, and when its curl was measured, it was found that the radius of curvature was 100 square meters or more, and a substantially flat disk could be obtained.

On the other hand, the radius of curvature of a disk punched out from a long tape with CoCrN on both sides is 23an.
The first surface showed a curl with a convex shape.

As is clear from this example, the step of bending and hot pressing the outer periphery may be carried out after the metal film has been deposited on both sides of the film, and the curl can be corrected.

〔Effect of the invention〕

As explained above in the embodiments, according to the present invention, when producing a floppy disk in which a magnetic metal film such as a CoCr film is formed on the front and back surfaces of a polymer film as a substrate, the outermost peripheral edge portion of the floppy disk is By thermally deforming and bending the film in the process, a flat disk without warpage can be produced. In this example, an example of a CoCr film produced by a vapor deposition method as a magnetic metal film was shown, but the effects of the present invention do not depend on the film formation method or the type of magnetic film deposited. Alternatively, a sputtering method, an ion blating method, etc. may be selected. Also, as a magnetic film, C
o Ni alloy film, γ-Fe20. Needless to say, the method can also be applied to membranes, etc.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the electron beam heating type vapor deposition apparatus used in Example 1, Figure 2 is a holder for holding the base film, and Figure 3 is a schematic diagram of the continuous winding type vapor deposition apparatus used in Example 2. , FIG. 4 is a diagram showing a hot press jig for film. 1]...Film heating heater, 12...Base film holder, 13...Shutter, 14...Electron beam heating type vapor deposition source, 15...Film thickness monitor, 21...Ring-shaped film holder , 22... base film, 31...
...Film supply roller, 32...Main roller, 33.
...Base film, 34...Shutter, 35...
・Film take-up roller, 36... Pierce-type electron gun, 3
7... Evaporation source crucible, 41... Ring-shaped film holder, L・' Z 1 Figure DA Z Figure

Claims (1)

[Claims] Magnetic recording having an organic polymer film as a base and having a magnetic thin film made of metal or metal oxide as a magnetic recording layer on both or one side of the film, the outermost part of which is bent along the circumferential direction. Medium.