JPH031726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a perpendicular magnetic recording medium for recording information using residual magnetization perpendicular to the magnetic surface of the recording medium in magnetic recording.

[Prior art and its problems]

Recently, perpendicular magnetic recording, which records information at high density using residual magnetization perpendicular to the magnetic surface of a magnetic recording medium, has been developed and researched. The magnetic recording medium used for this type of recording is a flexible substrate made of plastic film, and has an axis of easy magnetization on one or both sides of the substrate in a direction perpendicular to these surfaces.
A disk-shaped recording medium formed with a perpendicularly anisotropic magnetic film such as Co--Cr has been devised. FIG. 1 shows a partial cross-sectional view of a conventional perpendicular magnetic recording medium, in which 1 is a flexible substrate, and 2a and 2b are hard ferromagnetic films with perpendicular anisotropy deposited on the flexible substrate. be. FIG. 2 shows a partial cross-sectional view similar to that in FIG. A hard ferromagnetic film with perpendicular anisotropy is deposited. These ferromagnetic films are generally formed by heating and holding the substrate at a certain temperature and using thin film fabrication techniques such as sputtering to obtain desired magnetic properties. However, when the flexible substrate made of the plastic film or the like is heated to form the ferromagnetic film, when the ferromagnetic layer is formed, the flexible substrate may be directed upward (positive) or downward depending on the heating temperature. (Negative) curvature, a so-called curl phenomenon. As a result, problems such as deterioration of the magnetic head touch, increase in dropout, and increase in output fluctuation occur, which are obstacles to high-density recording.

For example, in the case of a Co--Cr sputtered film that has been developed as a perpendicular magnetic recording medium, the dependence of its most important characteristic, the perpendicular coercive force, on the substrate temperature during sputtering is as shown in FIG. On the other hand, in FIG. 4, the curl of the Co--Cr sputtered film changes from positive to negative as shown by curve B depending on the substrate temperature, and a flat magnetic film without curl is formed at a certain point _T0 .
That is, in general, the substrate temperature T to obtain the desired perpendicular coercive force is different from the substrate temperature T ₀ at which the curl is zero, and it is necessary to match them to obtain a flat substrate with no curl and the desired perpendicular coercive force. It is extremely difficult to obtain magnetic recording media.

It is also possible to cancel the curl by simultaneously depositing a ferromagnetic film on both sides of a flexible substrate made of plastic film, etc. Setting various conditions such as speed balance is extremely strict, and there are many problems in manufacturing large-sized magnetic recording media such as those used as disk media, or in mass producing them.

[Purpose of the invention]

The present invention has been made to solve the problems of the prior art described above, and its purpose is to:
By forming non-magnetic layers on both sides of a flexible substrate, it is possible to form a soft ferromagnetic layer and a hard ferromagnetic layer thereon at a substrate temperature that optimizes their magnetic properties. An object of the present invention is to efficiently provide a flexible perpendicular magnetic recording medium for high-density recording that is flat without curling, highly reliable, and of high quality.

[Summary of the invention]

In the present invention, a flexible substrate such as a plastic film is heated at a temperature at which the curl as shown in FIG. 4 becomes zero.
Heating and holding at T ₀ , non-magnetic metal such as Ti, Cr, etc.
At least one type of Al, Cu, or at least one type of these oxides is deposited on both sides of the above substrate by a sputtering method or the like to create a substrate with no curl and an improved Young's modulus, and then The temperature to obtain the desired perpendicular coercive force H _Cp , for example, as shown in Figure 3.
The above substrate is heated and held in a T _S , and a perpendicularly anisotropic hard ferromagnetic layer such as Co-Cr having an axis of easy magnetization in a direction perpendicular to the above substrate is deposited on both sides of the above substrate by a sputtering method or the like. There is. In other words, conventionally, in order to obtain a magnetic recording medium that does not cause curling, it was necessary to heat and maintain the substrate at a temperature different from that required to achieve the desired magnetic properties, thereby sacrificing the magnetic properties. In the present invention, first, the substrate is heated and held at a temperature that does not cause curling, and a nonmagnetic layer is applied to prevent curling, and then the substrate is heated and held at an optimal temperature to achieve the desired magnetic properties. The greatest feature of the present invention is that a magnetic recording medium can be formed by using the same method.

〔Effect of the invention〕

Furthermore, as the non-magnetic layer, Ti, Cr, Al,
Choosing a metal with high thermal conductivity such as Cu minimizes local temperature non-uniformity within the substrate when depositing the ferromagnetic layer on top of these nonmagnetic layers and prevents curling. It is extremely effective for making the magnetic properties of the ferromagnetic layer uniform. Furthermore, Ti, Cr, etc. also have the effect of increasing the adhesive strength between the substrate and the ferromagnetic layer.

Furthermore, forming the non-magnetic layer on both sides of the flexible substrate has the effect of offsetting curling of the substrate, and is even more effective in preventing curling.

[Embodiments of the invention]

FIG. 5 shows an embodiment of the present invention, in which non-magnetic layers 7a and 7b for preventing curling are formed on both sides of a flexible substrate 6 such as a plastic film, and then both sides of the non-magnetic layers are formed. Perpendicularly anisotropic hard ferromagnetic material layer 8a, such as Co-Cr, at the optimum substrate temperature for
8b, a flat flexible perpendicular magnetic recording medium without curling is effectively realized.

FIG. 6 shows another embodiment of the present invention, in which non-magnetic layers 10a and 10b for preventing curling are formed on both sides of a flexible substrate 9 such as a plastic film. Soft ferromagnetic layers 11a, 1 such as Fe-Ni are formed on both sides at the optimum substrate temperature.
1b and further coated with Co on both sides.
- perpendicular anisotropic hard ferromagnetic layer 12a such as Cr;
12b is deposited to effectively realize a flexible perpendicular magnetic recording medium that is flat without curling and suitable for recording and reproducing using a perpendicular magnetic head.

As described above, the present invention can efficiently provide a flexible perpendicular magnetic recording medium for high-density recording that is curl-free, highly reliable, and of high quality.

Note that the present invention is not limited to the above embodiments. For example, the non-magnetic layer may be deposited on both sides of the substrate at the same time, or may be deposited one after the other and the non-magnetic layers deposited on the top and bottom surfaces of the substrate may have different thicknesses. It is also possible to create a magnetic recording medium that is free from curl. In short, the present invention can be implemented in various forms without departing from the spirit thereof.

[Brief explanation of the drawing]

Figures 1 and 2 are partial cross-sectional views of conventional perpendicular magnetic recording media, Figure 3 is a diagram showing the dependence of perpendicular coercive force on substrate temperature, Figure 4 is a diagram showing the dependence of curl on substrate temperature, and Figure 4 is a diagram showing the dependence of curl on substrate temperature. 5 and 6 are diagrams showing an embodiment of the present invention. 1, 3, 6, 9: flexible substrate, 2a, 2b, 5
a, 5b, 8a, 8b, 12a, 12b: perpendicular anisotropic hard ferromagnetic layer, 4a, 4b, 11a, 11
b: Soft ferromagnetic layer, 7a, 7b, 10a, 10
b: Nonmagnetic layer.

Claims (1)

[Claims] 1. In a magnetic recording medium that performs perpendicular magnetic recording using residual magnetization perpendicular to the magnetic plane, a flexible substrate with nonmagnetic layers deposited on both sides is used, and on both sides of this substrate, A perpendicular magnetic recording medium characterized by forming a hard ferromagnetic layer having an axis of easy magnetization in a direction perpendicular to these planes. 2. Claim 1, wherein the flexible substrate on which the nonmagnetic layer is adhered is flat.
The perpendicular magnetic recording medium described in . 3. The perpendicular magnetic recording medium according to claim 1, wherein the nonmagnetic layer is made of Ti, Cr, Al, or Cu. 4. Claim 1, wherein the hard ferromagnetic layer is formed directly on the nonmagnetic layer.
The perpendicular magnetic recording medium described in . 5. The perpendicular magnetic recording medium according to claim 1, wherein the hard ferromagnetic layer is formed via a soft ferromagnetic layer.