JPS62150520A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve magnetic characteristics and corrosion resistance by consisting a magnetic layer of a Co-Ni alloy contg. 4-14at% Pt and consisting of a nonmagnetic metallic underlying layer of W. CONSTITUTION:A nonmagnetic substrate 2 is formed by a disk-shaped aluminum plate finished to <=20mum surface in both circumferential and radial directions, forming an electroless plating film of the Ni-P alloy thereon to about 30mum thickness and finishing the plating film to a specular surface up to 0.02mum average surface roughness and 15mum thickness. The nonmagnetic metallic underlying layer 3 is then formed on the substrate 2 by the sputtering W. The magnetic layer 4 is formed by sputtering onto the W underlying layer 3 to about 500Angstrom thickness within the same sputtering vessel immediately after the formation of the layer 3. The Co-30at%Ni alloy contg. 10at% Pt is used as the magnetic layer 4 to determine the thickness of the W film. A long life is thus stably maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a magnetic recording medium such as a magnetic disk used in a magnetic recording device.

[Prior art and its problems]

In recent years, magnetic recording media such as magnetic disks used in magnetic recording devices have tended to have higher and higher recording densities, and with this trend, the thickness of the magnetic layer of magnetic recording media has been reduced from the conventional process of about 1 μm to 0.1 μm or less. Thinly cut.

It is also necessary to increase the coercive force (Hc). For this reason, sputtering and plating methods, which can easily form a uniform thin film, are attracting attention as a manufacturing method for magnetic recording media, as they can easily form a uniform thin film, instead of the spin code method, which results in non-uniform magnetic layer thickness on the submicron order. Along with.

Conventional magnetic layers of iron oxides, such as γ-Fe2O3, have low magnetic properties, especially residual magnetic flux density, and low output. Cobalt-nickel (Ni) alloy magnetic thin films have come into use. It is known that the Ni content range of this alloy is preferably 20 to 30 at%.

FIG. 5 shows a sectional view of a main part of a disk-shaped magnetic recording medium having a magnetic layer made of a Co--Ni alloy magnetic thin film, for example.

The magnetic recording medium shown in FIG. 5 has a non-magnetic base layer 2 on an alloy substrate 1.
A Co--Ni alloy simulated magnetic layer 4a is further coated on the non-magnetic base layer 2 via a non-magnetic metal underlayer 3a, and a protective layer 1@53 is formed on the magnetic layer 4X1 and A lubricating layer 5b is formed thereon.

Aluminum alloy is often used for the alloy substrate 1 of the magnetic recording medium constructed in this way, but plastic may also be used in some cases, and the substrate is finished to a predetermined surface roughness, parallelism, and flatness.

The nonmagnetic base layer 2 is preferably obtained by electroless plating of a nickel-phosphorus (Ni-P) alloy, or by alumite treatment of the substrate 1 itself. Both require a certain hardness, and the surface is mechanically coated. Polish to a mirror finish. The nonmagnetic metal underlayer 3a is usually made of chromium (Cr) or the like, and is formed to a thickness of about 3000 mm by sputtering or the like.

As the magnetic layer 4a, a magnetic recording medium in which a Co-20 to 3Qat%Ni alloy thin film is formed by sputtering is effective in that it exhibits good magnetic properties.
As further research progresses on alloy thin films.

Although the initial magnetic properties were excellent, it was found that the corrosion resistance of the thin film magnetic layer itself was insufficient, and depending on the environment in which the magnetic recording medium was used, the magnetic properties would eventually deteriorate.Therefore, the present inventors As a result of extensive research, we have overcome the problem of magnetic properties and corrosion resistance, which were conventionally considered to be in conflict with each other, and found that CO20~3Qat%Ni alloy containing platinum (αt) has both magnetic properties and corrosion resistance as the magnetic layer 4a. The same applicant has proposed this magnetic recording medium.

Cr or Cr oxide (cr; o
A protective layer 5a such as s) and a lubricating layer 5b such as carpo/silicon dioxide (Sin2) are both successively provided by sputtering. Depending on the medium, the protective layer 5a
In some cases, a thin film of carbon or SiO□ is formed as a protective lubricant layer without forming two layers, ie, the magnetic layer and the lubricating layer 5b, but the provision of a Cr or Cr oxide layer takes into consideration the corrosion resistance of the magnetic layer 4. This is because they are doing so.

Here, the nonmagnetic metal underlayer 33 will be described again.

The non-magnetic metal underlayer 3a is a Co-Ni alloy thin film magnetic layer 4a.
The coercive force of the magnetic layer 4a changes depending on the thickness of the underlayer 3a. The underlayer 3a tends to saturate the coercive force of the magnetic layer 4a as its thickness increases, and the thickness of the underlayer 3a that saturates the coercive force varies greatly depending on the material. Further, as shown in FIG. 5, after forming a Co--Ni alloy thin film containing PT as described above as the magnetic layer 4a on the underlayer 3a by sputtering, a retaining layer 5a of Cr or Cr2O3 and further a carbon or SiO A magnetic recording medium constructed by continuously coating a lubricating layer 5b such as □ with a magnetic layer 4a
In addition to having good magnetic properties and corrosion resistance, since the protective layer 5a is provided, the corrosion resistance is further enhanced.

From the above, this magnetic recording medium expects the effect of the protective layer 5a, and the underlying layer 5a is
It has the possibility of reducing the sputtering time by making a as thin as possible <17. Therefore, conventional 3
Instead of Cr, which forms the underlayer 3a with a thickness of about 0.000A, it is necessary to select a material for forming an underlayer with an even thinner thickness, and to exhibit optimal magnetic properties in combination with this underlayer. By determining the range of the pt content added to the magnetic layer Co--Ni alloy, it is possible to obtain a magnetic recording medium with high manufacturing efficiency and good magnetic properties and corrosion resistance.

[Object of the Invention] The present invention has been made in view of the above points, and its object is to provide a nonmagnetic metal underlayer and a Pt-containing Co--Ni alloy thin film magnetic layer on a non-magnetic base coated on a substrate.

A protective layer and a lubricant layer are sputtered and laminated in this order, and the combination of a particularly thin non-magnetic metal underlayer and a thin Co-Ni alloy magnetic layer containing an appropriate amount of PT provides good magnetic properties and corrosion resistance. The object of the present invention is to provide a magnetic recording medium that has the following characteristics.

[Key points of the invention]

The present invention deals with N on an aluminum substrate in an inert gas atmosphere.
1-A base layer formed by continuous sputtering on the P layer,
The base layer of the laminated thin film consisting of a magnetic layer, a protective layer and a lubricating layer, a W film with a film thickness t1 of about 500^, and a Pt4-14a magnetic layer.
This can be achieved by forming a Co--Ni alloy film containing t%.

[Embodiments of the invention]

The present invention will be described below based on examples. FIG. 1 shows a cross section of the main part of a magnetic recording medium obtained according to the present invention, and parts common to those in FIG. 5 are denoted by the same reference numerals. The basic structure of FIG. 1 is the same as that of FIG. 5, but the difference between FIG. 1 and FIG.
The point is that the Co--Ni alloy has a high pt content that provides good magnetic properties for the W underlayer.

First, as the non-magnetic alloy substrate 1, a disk-shaped aluminum plate is used which has been lathe-processed and pressure-sintered to have a surface with a sufficiently small radius, that is, 20 μm or less in both the circumferential and radial directions. Approximately 30% electroless plating of P alloy
The plating film is coated to a thickness of μm and has an average surface roughness of 0.0.
The non-magnetic substrate 2 is formed by performing a mirror finish to a thickness of 2 μm and a thickness of 15 μm. Next, a nonmagnetic metal underlayer 3 is formed on the nonmagnetic substrate 2 by sputtering W in the present invention, but the thickness of the underlayer 3 affects the magnetic properties of the magnetic layer 4 as described above. In order to investigate how thin it can be made, K O was varied from 05 μm to 0.3 μm at 0.1 μm intervals. After forming the W base layer 3,
Immediately thereafter, in the same sputtering tank, a magnetic layer 4 was formed on the W underlayer 3 to a thickness of about 50A (by sputtering). W
For the magnetic layer 4 that determines the thickness of the film, 10% of Pi is used.
A Co-3Q at% Ni alloy containing at% was used.

FIG. 2 is a diagram showing the change in Hc of the magnetic layer 4 with respect to the thickness of the W film provided as the underlayer 3. In Figure 2, the horizontal axis is the thickness of the W film, scaled at 0.05 μm intervals.

Although the vertical axis indicates Hc of the magnetic layer, FIG. 2 also shows two comparative examples to clearly demonstrate the effectiveness of the present invention by comparing the present invention and a conventional example.

The manufacturing method of the magnetic recording medium of Comparative Example 1 is the same as that of this example, except that the magnetic layer is a thin film made of CO alone, and in Comparative Example 2, the magnetic layer is similarly made of C0-3Qat%N.
It is a thin film of i and no pi is added.

From FIG. 2, when W is used as the base layer 3 of the present invention,
The Co-Ni alloy of the magnetic layer 4 may contain Pi.

It can be seen that the effect of increasing the Hc of the magnetic layer 4 is remarkable, and that when the W film thickness becomes approximately 0.05 μm or more, the HC reaches saturation at a large value. This means that Co-30at%
When a Ni-10at%Pt alloy magnetic film is used as the magnetic layer 4 in combination with the W underlayer 3, the thickness of the W film is approximately 0.
This means that it is possible to reduce the thickness to 0.5 μm.

On the other hand, in Comparative Examples 1 and 2, the Hc of the magnetic layer did not increase much even if the W film thickness was increased, and the W underlayer 3 and P
The effect of the combination with the Co-Ni alloy magnetic layer 4 containing t is clear from FIG.
If it is left in the sputtering tank for too long or exposed to the atmosphere, the effect of Shimoike Layer 3 will not be exhibited.
The large coercive force required by the magnetic layer 4 cannot be obtained.

For example, when the underlayer 3 is formed and then the magnetic layer 4 is formed thereon by exposing it to the atmosphere, the coercive force of the magnetic layer 4 is only 200.
0e L or not obtained. The same result occurs even when the material is left in a sputtering tank for a long time, so the magnetic layer 4 must be sputtered immediately after the underlayer 3 is formed.

Next, when the film thickness of the W underlayer 3 is set to be constant at 5ooA.

In order to determine the amount of pt added to the Co-Ni alloy magnetic layer provided thereon, the Co-30at% of the magnetic layer 4 is
The Pt content of the N1-pt alloy was varied in the range of O to 15 at%, and the magnetic properties were investigated. The results are shown in Figure 3 (a
) to (d). FIG. 3 is a diagram in which the horizontal axis is the pt content and the vertical axis is the magnetic property, and the average value of three points is plotted. In other words, all other conditions are the same, such as coercive force in Figure 3 (a), coercive force square ratio tooth in Figure 3 (b), and residual magnetic flux density in Figure 3 (C), and all other conditions are set as ■゛Using a sputtering device, output 500W, total gas pressure 40X10
Torr, the substrate temperature was set to room temperature, and the W film thickness of the underlayer 3 was all set to 500 A as described above.

As can be seen from FIGS. 3(a) to 3(d), p of the magnetic layer 4
The magnetic property that changes the most with respect to the t content is (a) HC in the figure, and the range of Pt content that can be obtained is 9000e or more, which is effective as a magnetic recording medium, is from 4 to 14a pass, and option 10.
The most preferred range above 000e is 6 to 12 at%.

Looking at the pt content in this range, S in figure (b).

Br・δ in the figure (C) and Bs・δ in the figure (d) are both p
Although it tends to decrease as the t content increases, this degree of decrease does not pose a particular problem in terms of magnetic properties.

Thus, even if the magnetic recording medium of the present invention uses a 3KW underlayer film and the film thickness is reduced to 5oot, the magnetic layer 4 provided thereon contains Co-30at%Ni-4 to 14at%P.
1 alloy thin film can maintain better magnetic properties than K, but in addition, a protective layer 5a of Cr or Cr2O3 and a lubricant layer 5 of carbon or Si02 are added at the end.
It is formed by sputtering b to a film thickness of 500λ to provide excellent corrosion resistance.

FIG. 4 shows a first magnetic recording medium of the present invention exposed to an atmosphere at a temperature of 40° C. and a relative humidity of 80° C., in which the underlayer 3 is a W film and the magnetic layer 4 is Co-30 at% Ni-10 at% Pt. FIG. 3 is a diagram showing the change in the number of errors with respect to the neglect period when a recording device having the configuration shown in the figure is used.

In the case of Fig. 4, Comparative Example 1 and Comparative Example 2 are the same as in Fig. 2.
Also listed. As shown in FIG. 4, the number of errors in the magnetic recording medium of the present invention is only slightly counted after being left for 12 hours, whereas the number of errors in the magnetic recording medium of the comparative example 1. Comparative example 2
The number of errors increases rapidly within a short period of time, making it unusable. This means that although the magnetic properties of the entire magnetic layer do not change significantly over a relatively long period of time depending on environmental conditions, when exposed to moisture etc., conventional magnetic layers are Whereas corrosion progresses sequentially and alteration progresses.

It can be seen from FIG. 4 that the magnetic recording medium of the present invention having a magnetic layer containing an appropriate amount of Pt also has excellent corrosion resistance. Although not shown in FIG. 4, similar results can be obtained for any Co--Ni alloy magnetic layer containing Pl in the range of 4 to 14 at%.

Furthermore, as a result of conducting a C8S test by incorporating the magnetic recording medium of the present invention into a magnetic recording device, no scratches occurred on the surface of the recording medium even after 20,000 contacts, starts, and stops, and the reproduction output hardly decreased. It has been demonstrated that it has sufficient durability without any damage.

As explained above, the magnetic recording medium of the present invention shortens the sputtering time by using a thin W film as a non-magnetic metal underlayer, and also uses a magnetic layer having a composition that exhibits good magnetic properties corresponding to the W film. It can be said that it has excellent corrosion resistance.

〔Effect of the invention〕

In order to increase the recording density of magnetic recording media such as magnetic disks, the thickness of the magnetic layer is reduced to improve magnetic properties.
Sputtered Co-Ni alloy thin films have come to be used, but on the other hand, Co-Ni alloy magnetic layers have the disadvantage that their corrosion resistance in the usage environment is inferior to, for example, iron oxide films. 't that retains magnetic properties
The determination of the third element and the range of its addition to the Co-Ni alloy that imparts corrosion resistance, combined with the effect of the Cr pupil retention layer provided on the magnetic layer, makes it possible to make the base layer even thinner. As a result of repeated research on materials, the present invention uses Co-N containing 4 to 14 at% of Pt, as explained in the examples.
The i-alloy thin film is used as the magnetic layer, and the underlying layer has a film thickness of approximately 500 mm.
By using a W film thinned to ^^, the W underlayer acts effectively to increase the Hc of the magnetic layer, and at the same time improves the corrosion resistance of the magnetic layer itself.
The combination of a magnetic layer with a composition of t%Pt and a W underlayer solves the conventionally contradictory problems of magnetic properties and corrosion resistance at once, making it possible to combine these two properties into a single recording medium. It was made.

Moreover, since a W film whose thickness can be reduced to approximately 500 Å is used as the underlayer, manufacturing efficiency is improved by shortening sputtering time. Therefore, the magnetic recording medium of the present invention has many advantages, such as being able to provide a sufficient output when used in a recording device and stably maintain a long life.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part of the magnetic recording medium of the present invention, and FIG.
The figure is a diagram showing the change in Hc of the magnetic layer with respect to the thickness of the underlayer, Figure 3 is a diagram showing the relationship between the amount of PT and magnetic properties of the magnetic layer, and Figure 4 is a diagram at a temperature of 40°C. A diagram showing the relationship between the storage period and the number of errors of a magnetic recording medium exposed to an atmosphere with a relative humidity of 80%, and FIG. 5 is a sectional view of the main part of a conventional magnetic recording medium. 1... Alloy substrate, 2... Nonmagnetic base layer, 3, 3a
...Nonmagnetic metal underlayer, 4,4a...Magnetic layer, 5
a...Protective layer, 5b...W&1 Figure 2 Pt content (at'/,) Pt content! (
at'/, ) (a) (b
)(υ (d) Figure 3 Za period (weekS) Figure 4 Figure 5

Claims (1)

[Claims] 1) A magnetic recording medium in which a nonmagnetic metal underlayer, a magnetic layer, a protective layer, and a lubricant layer are laminated in this order by successive sputtering on a nonmagnetic substrate that covers the main surface of a substrate. . A magnetic recording medium, wherein the magnetic layer is made of a Co-Ni alloy containing 4 to 14 at% of Pt, and the nonmagnetic metal underlayer is made of W. 2) A magnetic recording medium according to claim 1, wherein the magnetic layer has a Pt content of 6 to 12 at%. 3) A magnetic recording medium according to claim 1 or 2, characterized in that the W film thickness is approximately 500 Å.