JPS5845624A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enable a nonmagnetic support low in heat resistance to be used and to obtain a magnetic recording medium having magnetic isotropy and high coercive force, by using a thalium Tl undercoat. CONSTITUTION:A >=5nm thick thalium Tl layer is formed as an undercoat 2 by vapor deposition on the surface of a nonmagnetic support 1 made of a polymer film such as polyethylene terephthalate low in heat resistance, and further on this layer a 20-55nm thick metallic magnetic thin film 3 made of cobalt Co or the like is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a magnetic layer made of a metal magnetic thin film.

As described above, magnetic recording media using a metal thin film magnetic layer can improve the packing density because no binder is mixed into the magnetic layer, and are now attracting attention as high-density recording media.

As a magnetic material for this type of magnetic recording medium, cobalt CO has characteristics such as large crystal magnetic anisotropy, high coercive force, and is quite chemically stable, making it an excellent magnetic recording medium. has the potential to become However, even if Cobalt (Co) is simply deposited on a non-magnetic support, its coercive force is less than 1000e, making it unsuitable for use as a magnetic recording medium.

As a way to solve this problem, it is known that a high coercive force can be obtained by diagonally depositing cobalt on the nonmagnetic support, but in this case, the direction of the deposition is 40° to 80° with respect to the surface to be deposited. Since it is necessary to concentrate on the process, the deposition efficiency is low and productivity is problematic. Furthermore, a method using a chromium Cr underlayer in the deposition of cobalt co, that is, a thin film magnetic recording medium having a cobalt Co/chromium Cr two-layer structure, is known, but in the case of this gold layer magnetic thin film two-layer structure, The temperature of the non-magnetic support is an important factor in the deposition of metal magnetic thin films, and for example, to obtain a coercive force He of 4 (1 (loe) or more, the substrate temperature Ts should be set to 3001 λ when the film thickness is 400 λ, which is the thickness of 60 cobalt layers. Therefore, in order to obtain a coercive force Hc of 4000e or more,
It has been difficult to use a polymer film with poor heat resistance, such as polyethylene terephthalate (PET), as a material for a nonmagnetic support.

In view of the above points, the present invention provides a magnetic recording medium that is magnetically isotropic, has high coercive force, and allows the use of a nonmagnetic support that has poor heat resistance.

The magnetic recording medium according to the present invention is characterized in that it has a magnetic thin film based on a two-layer structure film consisting of a thallium TQ underlayer and a metallic magnetic thin film, such as a cobalt CO layer, thereon. That is, as shown in the enlarged cross-sectional view of FIG. 1, the present invention deposits a thallium TR underlayer (2) on the main surface of a nonmagnetic support (1), and deposits a Cobalt (Co) layer (3) thereon. is deposited to form a magnetic recording medium (4).

As the nonmagnetic support (1), a polymer film (polyimide, polyethylene terephthalate, etc.), a glass plate, a ceramic plate, a metal plate with an oxidized surface, etc. can be used.

The temperature of the support (1) during vapor deposition is selected to be 70°C to 150°C, the thickness of the thallium TQ underlayer (2) is set to 50f or more, and the thickness of the Cobalt (Co) layer (3) is set to 200x to 150°C.
It is preferable to set it as 550X. In addition, the top and 800 layers (
The film thickness in 3) was calculated from the amount of magnetization.

FIG. 2 schematically shows a vapor deposition apparatus applied to the present invention. In the same figure, ■) indicates a vacuum container in which the degree of vacuum is approximately 5XIO'Torr using a vacuum pump (12+), and an evaporation source (IJ
and a non-magnetic support (1) for the object to be deposited.

This non-magnetic support (1) is supported by the substrate boulder (05) and is supplied with a heat medium (05) to the substrate holder (05).
16), the substrate temperature is maintained at a predetermined temperature. Evaporation source (
(3) is heated and evaporated by the impact of an electron beam, for example. Note that the evaporation of the evaporation source (13) can also be performed by a resistance heating method or a high frequency induction heating method, and a shutter 07) is arranged between the nonmagnetic support (1,) and the evaporation source (13). .

Note that each film thickness can be controlled by a crystal oscillator monitor.

Next, embodiments according to the present invention will be described.

Example 1 A non-magnetic support (1) made of polyethylene terephthalate film was heated to
Then, a Tg evaporated film (2) of thallium is placed on top of this.
Vapor deposited to a film thickness of 00X, and then coated with cobal) C
A magnetic recording medium was obtained by depositing an o layer (3) to a thickness of 400×.

The magnetic recording medium according to this example has a coercive force TIc of 410
The squareness ratio & was 074 at 0e.

Example 2 As in the case above, using the vapor deposition apparatus shown in FIG.
2) was evaporated to a thickness of 300×, and Cobal) was deposited on top of this.
A magnetic recording medium was obtained by depositing a Co layer (3) to a thickness of 400 Å.

The magnetic recording medium according to this embodiment has a coercive force f (c of 420
At 0e, the squareness ratio Rs is 0.78.

In addition to the above examples, the heating temperature of the nonmagnetic support was kept constant at 120C, the thickness of the thallium TQ underlayer was kept constant at aooX, and the thickness of the Cobal layer was changed. The characteristics of the coercive force Hc are shown in FIG.

Figure 4 shows the coercive force Hc with respect to the heating temperature of the non-magnetic support in an example in which the thickness of the Cobalt layer was constant at 400× and the thickness of the thallium TQ underlayer and the heating temperature of the non-magnetic support were varied. Show characteristics. However, * mark, × mark and ○
The marks indicate the thickness of the thallium T2 underlayer, 200X and 30X, respectively.
This is the case for 0X and 500X.

As is clear from the above results, in the magnetic recording medium according to the present invention, the temperature of the nonmagnetic support is 70C to 150C.

Coercive force Hc = 2800e to 4200e can be obtained when the thickness of the thallium noble underlayer is 50X to 500X and the thickness of the edge and 800 layers is 200X to 550X.

In particular, a high coercive force He can be obtained when the temperature of the non-magnetic support is 12f) C, thallium noble underlayer thickness 300X and cobal)-Co layer thickness 400X. Even polymer films with poor heat resistance can be used as the material for the nonmagnetic support, increasing the degree of freedom in selecting the support material.

In addition, when a polymer film is used as a non-magnetic support, a base layer with a low boiling point (1
457C), the heating power for evaporation during deposition of the thallium TR layer is small;
Thermal radiation of polymer films is small. Next, the top layer and 800 layer have a high boiling point (3185 tl'), so the heating power required for vapor deposition is extremely high, and the thermal radiation is large, but since the thallium TQ layer is attached, no direct heat is applied to the polymer film. Radiation is small and thermal deformation is reduced.

The upper side is constructed by depositing a magnetic thin film with a two-layer structure of a thallium actual underlayer and a cobalt (Cobal) layer on a non-magnetic support, but a thallium TQ underlayer and a thallium TQ underlayer are also used to obtain the necessary magnetic flux. It is also possible to multilayer a magnetic thin film based on a two-layer structure of cobalt 00 layers. Moreover, although cobalt alone was used as the metal magnetic thin film on the upper side, other metal magnetic thin films such as a Co--Ni alloy may also be used.

As described above, according to the present invention, a magnetic recording medium can obtain a magnetic layer with high coercive force without oblique vapor deposition of a metal magnetic material, so that the vapor deposition efficiency can be increased and the thallium TQ layer can be Since the geological layer can be formed by a normal vapor deposition method, it is possible to improve productivity and reduce costs, and since the non-magnetic support only needs to be heated to a temperature of 100-odd degrees, it is suitable for use as a support. 1- It is possible to use a polymer film such as a polyethylene terephthalate film having excellent performance, and it has the advantage that magnetic recording media can be constructed according to various usage modes and purposes.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view showing an example of the magnetic recording medium of the present invention, FIG. 2 is a schematic diagram of a vapor deposition apparatus applied to the present invention, and FIG.
Figures 1 and 4 are characteristic diagrams of the magnetic recording medium of the present invention, respectively. In the figure, ( ) is a nonmagnetic support, (2) is a thallium underlayer, and (3) is a cobalt 00 layer. Figure 1 Figure 2

Claims (1)

[Claims] A magnetic recording medium comprising a nonmagnetic support, an underlayer made of thallium, and a gold-Ra thin film with a thickness of 200X to 550X formed on the underlayer.