JPH01122032A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Conventional technology]

FIG. 3 shows a schematic cross-sectional view of the main part of a conventionally used magnetic recording medium. The magnetic recording medium shown in FIG. 3 has a non-magnetic metal base layer 2 on an A1-Mg alloy substrate 1.
A magnetic layer 4 of, for example, a Co-Ni-Cr alloy thin film is further coated on the non-magnetic metal base layer 2 via a non-magnetic metal underlayer 3, and a protective lubricant layer 5 is provided on the magnetic layer 4. The structure is such that a nonmagnetic metal base layer 2 to a protective lubricant layer 5 are stacked on a substrate 1 in the order of the numbers.

In the magnetic recording medium configured in this way, the substrate 1 is
The non-magnetic metal substrate layer 2 is preferably formed by electroless plating of N1-P alloy or by alumite treatment of the substrate 1 itself, both of which have a predetermined surface roughness, parallelism and flatness. Hardness is required, and the surface is mechanically polished to a specified surface accuracy. The non-magnetic metal underlayer 3 is generally sputter formed using Cr, followed by a magnetic layer 4 such as a Co--Ni--Cr alloy, and then a protective lubricant layer 5 such as carbon or 5i02 by successive sputtering.

The magnetic recording medium thus obtained also has good mechanical properties such as strength and dimensional accuracy, and magnetic properties, such as Δp-
A non-magnetic metal base layer 3 of Cr is coated on the N1-P base layer 2 coated on the Mg alloy substrate 1, and Co-30at is applied.
%Ni-7,5at%Cr magnetic layer 4 was continuously sputtered by 500 people and carbon protective lubricant layer 5 was formed by 500 people, and the coercive force Ha is 9000 as a typical magnetic property.
It is e.

As magnetic recording media such as those described above have improved in magnetic properties, there has been an increasing demand for lighter weight and lower costs in recent years.

[Problems to be Solved by the Invention] A point to be considered for reducing the weight and cost of a recording medium is the selection of the substrate material. In other words, since AAl-1A alloy is used for the substrate, a hard N+-P layer must be provided on top of it, and it takes a lot of time to polish the surface of the substrate and the N1-P layer. This accounts for a large proportion of costs. Therefore, it would be better to shorten this machining man-hour, but since the surface must be finished to a specified level of surface roughness, parallelism, and flatness, it is impossible to significantly reduce the man-hour, and there is a limit to cost reduction. , much cannot be expected as long as an Al-Mg alloy is used.

On the other hand, regarding the selection of the substrate material, it is promising to use plastic or a composite material of plastic and ceramic, which also reduces the weight of the recording medium.

These materials are lighter than AJ-Mg alloy and can be formed using a mold, so by processing the surface of the mold with high precision, they can be made in good condition without having to polish the surface after molding. This is because it has the advantage of providing good surface roughness and parallelism.

However, other problems arise when plastic or composite materials thereof are used for the substrate. Unlike metal, plastic has high hygroscopicity and absorbs water, which is released during the splatter process and has a negative effect on the magnetic layer, which affects its magnetic properties.

In particular, it lowers the coercive force. Therefore, Al-Mg
Even when plastic or the like is used for the substrate instead of an alloy, it is preferable not to impair the characteristics of the recording medium.

The present invention has been made in view of the above-mentioned points, and its purpose is to make a magnetic recording medium lighter and to reduce costs by using plastic or a composite material of plastic and ceramic, and also by using the conventional sputtering method. An object of the present invention is to provide a magnetic recording medium having a structure that provides excellent magnetic properties.

Means for Solving Problem C] The magnetic recording medium of the present invention consists of a buffer layer made of a ZrO□ thin film, a nonmagnetic metal underlayer, a magnetic layer, and a protective lubricant layer successively formed on a nonmagnetic substrate such as plastic in this order. It is formed by sputtering.

[Effect]

Since plastics absorb moisture, if they are used as a substrate, they will be affected by the gas emitted during the sputtering process, which will particularly reduce the coercive force of the magnetic layer. Since the ZrO thin film is sputter-formed as a buffer layer between the magnetic metal underlayer and the substrate, it is possible to prevent the release of gases such as moisture stored in the substrate, while maintaining good magnetic properties. Therefore, a magnetic recording medium that is lighter and cheaper than the conventional one can be obtained.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 shows a schematic cross-sectional view of the main part of a magnetic recording medium obtained according to the present invention, and parts common to those in FIG. 3 are denoted by the same reference numerals. The basic configuration of Figure 1 is the same as Figure 3, but the difference between Figure 1 and Figure 3 is that the substrate 1
A is made of plastic, and a ZrO2 film is interposed between the substrate 1a and the nonmagnetic metal base layer 3 as a buffer layer 6 instead of the nonmagnetic metal base layer 2.

This recording medium is manufactured by first using polyetherimide resin (trade name Ultem 1000) as a substrate material and molding it with a mold having a predetermined surface precision to produce a substrate 1a.
ZrO2 for the buffer layer 6, Cr for the non-magnetic metal underlayer 3 and Co-3Qat%Ni- for the magnetic layer 4 on a.
7.5 at% Cr alloy was sputtered by 500 people and protective lubricant 15 carbon by 500 people.The thickness of the buffer layer 6 according to the present invention was confirmed by sputtering in a vacuum chamber. Therefore, the number of people was varied from one without the buffer layer 6 to 2,000 people. At the same time, a medium was prepared using a composite material of polyester resin and calcium carbonate as a substrate material, but in this case, the base layer 3.
The magnetic layer 4 and the protective lubricant layer 5 were under exactly the same conditions as those using the plastic substrate.

Next, the magnetic properties of each of the magnetic recording media obtained as described above were compared. In Figure 2, the vertical axis is the coercive force Hc, which is a typical magnetic property of the medium, and the horizontal axis is the ZrO2 film thickness of the buffer layer 6, and the average value of 10 measurements for each medium is plotted. Plastic alone on the board (○).

One using the plastic composite material (△), one without a buffer layer formed thereon, and one using a conventional A2 alloy substrate are also shown for comparison.

As can be seen from FIG. 2, the medium without a buffer layer has a very small Hc of only about 1000e, whereas the 2r02 buffer layer 6 has a very small value of Hc on the substrate 1a.
The medium of the present invention, which is formed between the ZrO2 film and the base layer 3, has a coercive force that increases as the ZrO2 film thickness of the buffer layer 6 increases. A value equivalent to the coercive force of 9000e of the medium coated with the N1-P plating layer 2 can be obtained.

This is an effect brought about by the buffer layer 6 that covers the substrate 1a when plastic or a composite material thereof is used, and gas such as moisture occluded in the substrate is almost removed during the sputtering process of the buffer layer 6. Or, after the medium is formed, it is confined in the buffer layer 6 to prevent it from having a bad influence on the underlayer 3 and magnetic layer 4. Moreover, when plastic or a composite material thereof is used as the substrate 1a, it is approximately 60% lighter than the conventional AJ-Mg alloy substrate 1, and there is no need for a complicated polishing process. can be sputtered sequentially in the same vacuum chamber, and no special means is required to form the buffer layer 6.

Finally, the magnetic recording medium obtained according to the present invention was incorporated into a magnetic recording device and a C8S test was conducted. As a result, no scratches were observed on the surface of this recording medium even after 20,000 contact starts and stops. It was confirmed that the device had sufficient durability, with almost no decrease in playback output.

〔Effect of the invention〕

Magnetic recording media such as magnetic disks are being taken lightly and cost reduction is desired, and instead of the conventional A1 alloy substrate that requires many processing steps, plastic or its composite material that can obtain high surface precision without post-processing is used. However, these plastic materials absorb moisture, and the underlying layer and magnetic layer formed on top of these materials are susceptible to the effects of moisture and other gases released from the substrate during sputtering. In contrast, according to the present invention, as described in the embodiment, a ZrO2 film is formed as a buffer layer between the plastic substrate and the non-magnetic metal underlayer. Since this buffer layer is configured to intervene, the adverse effect of gas released from the substrate on the magnetic properties is eliminated, and the excellent magnetic properties of the original medium can be maintained. It is possible to perform continuous sputtering without reducing manufacturing efficiency.

As described above, the magnetic recording medium of the present invention is lightweight and cost-reduced by using a plastic substrate and omitting the surface polishing process, and by forming a ZrO and buffer layer using a sputtering method. In that it was able to eliminate the drawbacks of magnetic recording media and maintain the original characteristics of the medium, it simultaneously achieved several important goals desired for magnetic recording media.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the main part of the magnetic recording medium of the present invention, and FIG. 2 shows the coercive force and
A diagram showing the relationship between rO and buffer layer thickness in comparison with a medium without a buffer layer and a conventional medium. FIG. 3 is a schematic cross-sectional view of the main part configuration of a conventional magnetic recording medium. . 1, 1a--Substrate, 2--Nonmagnetic metal base layer, 3--Nonmagnetic metal underlayer, 4--Magnetic layer, 5--Protective lubricant layer, 6--Buffer layer. O-1° lath ±・L substrate 1 x 1 lath base/C
-771 layer-"Shiko 12 (101 buff 77t/) ZrO2ALl (A) Ear 2
figure

Claims (1)

Claims: 1) A magnetic recording medium comprising a zirconium oxide buffer layer, a nonmagnetic metal underlayer, a magnetic layer, and a protective lubricant layer successively formed on a substrate by sputtering in this order. 2) A magnetic recording medium according to claim 1, wherein the substrate is a plastic molded body. 3) A magnetic recording medium according to claim 1, wherein the substrate is a molded body of a composite material of plastic and ceramic. 4) A magnetic recording medium according to any one of claims 1 to 3, characterized in that the buffer layer has a zirconium oxide film thickness of at least 500 Å.