JPS6344319A - Production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a perpendicular magnetic recording medium having multi- layered structure in which the perpendicular coercive force increases from the lower layer part toward the surface layer part by forming perpendicularly magnetized layers nearer a nonmagnetic substrate under the higher atmospheric pressures. CONSTITUTION:The lower layer parts nearer the nonmagnetic substrate 20 are formed under the relatively higher atmospheric pressures and the layers are formed under the lower atmospheric pressure on progression toward the surface layer. The atmospheric pressures are changed within a 1X10<-4>-5X10<-7>Torr range. The regulation of the atmospheric pressure at the time of forming the films of the respective magnetized layers is executed by; for example, introducing an inert gas such as N2 into a vacuum vessel. The perpendicular magnetic recording medium having the multi-layered structure in which the perpendicular coercive force increases from the lower layer part toward the surface layer part is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a magnetic recording medium having an improved recording magnetic layer. In particular, the present invention relates to a method for manufacturing a perpendicular magnetic recording medium with excellent recording and reproducing characteristics.

[Prior Art] Perpendicular magnetic recording is a recording method that performs recording by magnetizing a recording medium in a direction perpendicular to its film surface. Therefore, a recording medium using the perpendicular recording method is required to have recorded magnetization stably present in the perpendicular direction.

However, in general, in order for the magnetization of the magnetic layer to exist stably in the perpendicular direction, the coercive force in the perpendicular direction must be high, although it depends on the saturation magnetization value of the film.

On the other hand, the strength of the recording magnetic field generated by the magnetic head decreases as it progresses from the surface of the recording medium in the depth direction of the film thickness. Therefore, in the case of a recording medium that has a uniform perpendicular coercive force distribution in the film thickness direction, such as a conventional perpendicular magnetic recording medium, when the coercive force is small, the reproduction output is low, but as the coercive force increases, Reproduction output increases. This is probably because the recorded magnetization becomes more stable in the perpendicular direction as the eastward coercive force increases.

However, when the perpendicular coercive force of the recording magnetic layer increases further, the reproduction output shows a maximum value at a constant coercive force, and when the coercive force increases beyond that, the reproduction output actually decreases. This phenomenon occurs because, as described above, the recording magnetic field strength of the magnetic head decreases as it increases in the depth direction of the film, so that recording is performed only near the surface layer of the recording magnetic layer, and recording cannot be performed in the upper layer.

Therefore, in the case of a recording medium that has a uniform perpendicular coercive force distribution in the film thickness depth direction, the maximum reproduction output will be achieved at a certain coercive force, but in the region of lower coercive force, the recorded magnetization will decrease. The tlT raw output is tilted from the perpendicular direction due to the influence of the demagnetizing field, and in the high coercive force region, saturation recording cannot be performed because a magnetic field sufficient to cause magnetization reversal to the lower layer of the recording layer is not applied.
Conversely, the output also decreases.

Alleviate these issues and increase the ILT raw power output l)
As a means of
The eastward coercive force of the magnetic layer is high near the magnetic recording surface.
A perpendicular magnetic recording medium is disclosed that has a recording magnetic layer having a structure in which the thickness decreases as the thickness increases in the depth direction.

According to the +FI publication, changes in the perpendicular coercive force can be suppressed by changing the degree of substrate closing during lamination.

Therefore, in order to obtain a recording magnetic layer having the above structure, it was necessary to sequentially lower the substrate temperature by -L for each laminated layer.

However, when the substrate temperature was raised in this way, a problem arose in that the characteristics of the previously formed perpendicular magnetic layer deviated from the originally designed characteristics due to the influence of heat.

[Problems to be Solved by the Invention] This invention provides a new method for manufacturing a multilayer perpendicular magnetic recording medium having different perpendicular coercive forces in order to solve the drawbacks of the prior art as described above. The purpose is to

[Means for solving the problem] The above problem is solved by laminating a perpendicular magnetization layer with a small perpendicular coercive force as the first layer on the non-magnetic substrate -1-, and sequentially layering one layer with a large coercive force. When manufacturing a perpendicular magnetic recording medium with a multilayer structure consisting of laminated layers, this problem can be solved by forming the perpendicular magnetic layer near the nonmagnetic substrate at a high atmospheric pressure.

As a result of extensive research and prototyping carried out over many years, the present inventors discovered the fact that the coercive force of the perpendicularly magnetized layer increases as the atmospheric pressure during the formation of the perpendicularly magnetic layer decreases. Based on this discovery, the upper layer was created at a relatively high atmospheric pressure,
When the magnetic recording medium was produced at a lower atmospheric pressure as it progressed toward the surface layer, we succeeded in obtaining a multilayer perpendicular magnetic recording medium in which the coercive force increases from the lower layer toward the surface layer.

When stacking multiple layers from the bottom layer to the surface layer to form a perpendicular magnetization layer with a multilayer structure, the film forming atmosphere pressure for each layer is 1xlO.
-q-5xlO-7 Torr.

Atmospheric pressure adjustment when forming each magnetized layer is performed, for example, by introducing an inert gas such as N2 into the vacuum chamber.

Although it is possible to laminate two or more magnetized layers having different coercive forces, it is also possible to continuously increase the perpendicular coercive force from the base side.

To change the vertical coercive force continuously from the base side,
The film may be formed while continuously changing the atmospheric pressure.

The perpendicularly magnetized film material to which the manufacturing method of the present invention can be applied is preferably one in which nonmagnetic elements are segregated on the surface of the columns constituting the film when the film is formed, so that a nonmagnetic layer is easily formed.

For example, Co-Cr5 Co-Mo1Co-Re1Co
-Alloys mainly composed of CO such as W, or Fe-Cr
Particularly preferred materials include alloys containing iron and Fe as main components.

The manufacturing method of the present invention can be applied to a thin film forming method called a so-called vapor deposition method.

"U paper debonding method" means a method in which a substance or compound to be deposited is deposited on a gas as vapor or ionized vapor in a gas or vacuum space.This method includes vacuum evaporation method, Ion-brating method, high-frequency ion-brating method, ion-brating method,
Examples include cluster beam method, ion beam deposition method, sputtering method, and CVI method.

Examples of the nonmagnetic substrate used in the magnetic recording medium produced by the method of the present invention include polymer films such as polyimide and polyethylene terephthalate.

Glass, ceramic, aluminum, anodized aluminum.

There are metal plates such as brass, Si'P-crystal plates whose surfaces are subjected to thermal oxidation treatment, and the like.

[Function] As described above, according to the manufacturing method of the present invention, when manufacturing a multilayered perpendicular magnetic medium, the film forming atmosphere pressure of each layer is set to a higher value for the layer closer to the nonmagnetic substrate.

This manufacturing method makes it possible to form perpendicularly magnetized layers with different coercive forces without changing the substrate temperature, and as a result, the magnetic properties of the perpendicularly magnetized layer due to heat can be improved as described above. Changes will be greatly eased.

[Embodiments] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

A multilayer perpendicular magnetic recording medium was manufactured using the vacuum evaporation apparatus shown in FIG.

First, the inside of the vacuum chamber 1 is evacuated from the exhaust duct 3 to a pressure of 3xlO-7 Torr, and then the glass substrate 7 is heated to 150° C. by the heater 5.

Thereafter, N2 gas is introduced through the barrier pull leak valve 10, and the pressure inside the vacuum chamber is increased to 5xlO''-6 Torr.

In this state, the Coy7Cr of the evaporation source 12? Alloy film thickness 0
．． 12 μm steaming? Furthermore, for the convenience of the experiment, 5i02 was laminated from the evaporation source 14 to this alloy layer to a film thickness of 0.01 μm. Note that the Co-
The Cr content of the Cr film is 22 wt%.

The reason for intervening the 5i02 nonmagnetic layer is to magnetically insulate each magnetic layer.

Next, before laminating the second magnetic layer, in order to confirm the magnetic properties of the first magnetic layer, a part was cut out and the rest was set again.

The second magnetic layer was formed under the following conditions, except that N2 gas was not introduced and the pressure in the vacuum chamber was 8X10-7 Torr.
It is exactly the same as the case of the first @ sex tank.

FIG. 2 shows the cross-sectional structure of the multilayer perpendicular magnetic recording medium manufactured in this manner.

As shown in FIG. 2, a first magnetic layer 22 is laminated on a nonmagnetic substrate 20, a 5i02 nonmagnetic layer 24 is laminated thereon, and a second magnetic layer 26 is further laminated. ing.

In order to compare the magnetic properties of the multilayer perpendicular magnetic recording medium produced by the method of the present invention with the magnetic properties of the recording medium disclosed in JP-A-80-95720, A multilayer perpendicular magnetic recording medium with the same structure was manufactured using a method of varying temperature.

A control recording medium is manufactured using the same equipment used to manufacture the recording medium of the present invention.

First, after evacuating the inside of the vacuum chamber to 3XIC)'' Torr, the glass substrate 7 is heated to 90° C. by the heater 5.

In this state, Co-C with a film thickness of 0.12 μm was prepared as in the example.
r layer and film thickness 0. A 5i02 layer of OIIlm was laminated.

Then, the substrate temperature was raised to 270°C and the film thickness was 0.12 μm.
Co--Cr layers were laminated.

The composition ratio of Co and Cr and the Cr content f'T ratio are the same as those of the recording medium of the present invention in the example.

The magnetic properties of the recording medium manufactured by the method of the present invention and the magnetic properties of the recording medium manufactured by the method disclosed in Japanese Patent Application Laid-Open No. 60-95720 are summarized in the table below.

As is clear from the above results, according to the method of the present invention, there is almost no change in the coercive force of the first magnetic layer before and after laminating the second magnetic layer. On the other hand, JP-A-60-9572
In the recording medium manufactured by the method disclosed in Publication No. 0, the coercive force of the first magnetic layer changes significantly before and after laminating the second magnetic layer, and deviates significantly from the set target value. be understood.

The characteristics of the first magnetic layer after laminating the second magnetic layer are as follows:
The second magnetic layer is removed by chemical etching and ii[
l+ was determined.

Hereinafter, the method of the present invention has been described with respect to a magnetic layer made only of a ferromagnetic material, but the magnetic layer can also be a composite film of a ferromagnetic material and an organic material.

Examples of organic materials that can be used for this purpose include polyethylene, polyethylene terephthalate, polypropylene,
Polystyrene, polytetrafluoroethylene, polybutane, polyvinyl chloride.

Low molecular weight (for example, oligomers) derived from polymers such as polyurethane and their constituent monomers and intermediates are preferred. Compounds other than these can also be used.

When an organic material is used in combination, the ferromagnetic material and the organic material are mixed in an appropriate ratio to form a perpendicular magnetic layer. The preferred volume ratio of the ferromagnetic material contained in the perpendicular magnetization layer is approximately 4.
Qvol is within the range of 1% to 95vol''A.

When the ferromagnetic material content exceeds 40 vol%, drop and pull-out increase in high-density recording, and SZN also decreases. -・Volume ratio of force and ferromagnetic material is 95volX
If it exceeds this value, the rigidity will be extremely poor and the magnetic head will be easily damaged by sliding.

When an organic material is used in combination, in order to increase the adhesion of the M-deposited material and increase its mechanical durability, a vapor flow of some material may be passed through the plasma, or an electron beam may be applied during or after the organic material precipitation. , ionizing rays such as α-rays, β-rays, electromagnetic rays such as micro-rays, ultraviolet rays, X-rays, γ-rays, or proton beams,
It is preferable to irradiate with neutron beams to promote polymerization of some substances.

Furthermore, a soft magnetic underlayer may be interposed between the nonmagnetic substrate and the first magnetic layer. By interposing the soft magnetic underlayer, the durability of the obtained medium and the contactability with the magnetic head are improved. The soft magnetic underlayer used for this purpose can be composed of, for example, a composite film of a ferromagnetic material and an organic material.

The soft magnetic underlayer can be formed by simultaneously depositing a ferromagnetic material on the substrate using a paper fist deposition method, or by depositing a ferromagnetic material while blowing an organic monomer gas onto a non-magnetic substrate L. After the film is deposited by the paper Φ deposition method, it can be formed by irradiating the film surface with excitation rays such as electric gamma rays, ionizing rays, and electromagnetic rays.

[Effects of the Invention] As explained above, according to the manufacturing method of the present invention, when manufacturing a multilayer perpendicular magnetic medium, the film forming atmosphere power of each layer is set to a higher value for the layer near the non-magnetic substrate. .

This manufacturing method makes it possible to form perpendicularly magnetized layers with different coercive forces without changing the substrate temperature, and as a result, the change in magnetic properties of the perpendicularly magnetized layer due to heat as described above is avoided. greatly relieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a vacuum evaporation apparatus used to carry out the method of the present invention, and FIG. 2 is a cross-sectional view of a multilayer perpendicular magnetic recording medium manufactured by the method of the present invention.

Claims (4)

[Claims] (1) Manufacturing a perpendicular magnetic recording medium with a multilayer structure in which a perpendicular magnetization layer with a small perpendicular coercive force is laminated as a first layer on a nonmagnetic substrate, and layers with a large coercive force are successively laminated on this layer. A method for manufacturing a perpendicular magnetic recording medium, characterized in that a perpendicular magnetic layer closer to a nonmagnetic substrate is formed under a higher atmospheric pressure. (2) Manufacturing a perpendicular magnetic recording medium according to claim 1, characterized in that the atmospheric pressure is varied within the range of 1 x 10^-^4-5 x 10^-^7 Torr. Method. (3) A method of manufacturing a perpendicular magnetic recording medium as set forth in claim 1 or 2, wherein the perpendicular magnetic layers are laminated by a paper deposition method. (4) A method for manufacturing a perpendicular magnetic recording medium according to any one of claims 1 to 3, characterized in that a soft magnetic underlayer is previously laminated on the nonmagnetic substrate.