JPS60242513A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a vertical magnetic recording medium having a long life and hig reliability by forming ferromagnetic alloy layers consisting essentially of Co of which the surfaces are Co oxide on a base body and forming a wear resistance film on the surfaces. CONSTITUTION:The base body 1 which is, for example, a polyethylene terephthalate film (PET), etc. is traveled along main rollers 14a and 14b and is thoroughly subjected to degassing and thereafter the temp. of the rollers 14a, 14b is decreased to 90 deg.C and a take-up roller 16 and a feed roller 11 are rotated reverse from the direction in the stage of the degassing. A film such as thin Co-Cr film consisting essentially of Co is formed from a sputtering target 15b onto the body 1. The thin Co-Cr film or the like 2 is also formed on another surface of the body 1 from the next target 15a. The films 2, 2 on both surfaces are then plasma-oxidized by high-frequency electrodes 17a, 17b. The targets 15a, 15b are replaced to an Al2O3 target and wear-resistant Al2O3 films 3, 3 are formed on the surface oxide layers of the films 2, 2. Lubricating oil is coated on the films 3, 3. The runnability, wear resistance and durability are thus improved.

Description

TECHNICAL FIELD The present invention relates to a perpendicular magnetic recording medium, and particularly to a perpendicular magnetic recording medium having a ferromagnetic alloy mainly based on Co, such as Co--Cr.

(Technical background of the invention and its problems) Perform playback and deletion.

The Co--Cr film is formed by a normal sputtering method or a magnetron sputtering method in an argon atmosphere. Formed Co-Or [% is C
It has a columnar structure with two orientations, and in addition to the saturation magnetization Ms, which is mainly determined by the film composition as a magnetic property, the magnetic anisotropy energy Ku perpendicular to the film surface is large, and the coercive force in the direction perpendicular to the film surface is large. It has conditions for high Hcl and high recording density.

By the way, when the above-mentioned perpendicular magnetic recording medium was subjected to a running test in which a magnetic head was run on the same track with a lubricating oil such as fluorocarbon (fluorocarbon oil) interposed therebetween, the service life of the medium was extremely short. When a magnetic recording medium that rotates at high speed and a magnetic head come into contact, the wear-resistant film often peels off at the interface between the wear-resistant film and the ferromagnetic layer, and the reason for this is thought to be that the interface is formed with different amounts of substances. , therefore, the wear-resistant film itself is an oxide of Co, Coos Co1.
04 is proposed in Japanese Unexamined Patent Publication No. 58-41439 ζ2.

However, according to detailed experiments conducted by the present inventors, even when an oxide of Co was used as the wear-resistant film, the life was short in running tests, similar to the conventional wear-resistant film.

That is, a magnetic recording medium with in-plane magnetization is normally required to have a life of 10 million passes, but a perpendicular magnetic recording medium using a wear-resistant film often has a life of less than 1 million passes. Even at the highest lifespan, it almost never exceeds 3 million passes. Analysis of defects in running tests shows that most of the lifespan is maintained by lubricating oil, and when the lubricating oil dries up, the wear-resistant film maintains a certain lifespan in any case, and eventually the wear-resistant film becomes Co - Part of it peels off from the interface with the Cr film. The Co--Cr film wears out and its life ends. Note that the thickness of the wear-resistant film is usually several tens of tens of meters in consideration of space loss.
It is from X to several 10OA.

(Objective of the Invention) The present invention provides a long-life, highly reliable perpendicular magnetic recording medium.

(Summary of the Invention) The present invention provides a perpendicular magnetic recording medium comprising a Co-based ferromagnetic alloy layer whose surface is mainly an oxide of Co on a substrate, and an abrasion-resistant film formed thereon. be.

(Example of the invention) Hereinafter, the present invention will be explained with reference to Examples.

FIG. 1 shows a perpendicular magnetic recording medium according to an embodiment of the present invention.
A Co--Cr film (2) and an abrasion-resistant film (3) are formed on both sides of a substrate (1) made of a polymer film (abbreviated as ET). In manufacturing this perpendicular magnetic recording medium, a second
The continuous thin film forming apparatus shown in the figure was used.

As the film formation method, a magnetron sputtering method was used, and sputtering was performed in an argon atmosphere.

A specific method for forming the perpendicular magnetic recording medium is as follows.

First, the PET film is degassed. The conditions are, for example, 120°C, I x 10-Torr, and 30 minutes. The degassing method is as follows in the apparatus shown in Figure 2.Heating of the PET film (1) is performed by the main roller (
14) a and (14) b. Main roller (1
4) and 04)b are loaded with silicone oil (not shown), and by heating the silicone oil, the main rollers (1a and 14b) are heated, and the PET
The film substrate (1) is degassed. The degassing method is
For example, as shown in FIG. 2, before forming the Co-Cr film, the PET film substrate (1) is moved at a constant speed of 1 from the supply roller αυ to the auxiliary roller (1 wrinkle a to the main roller (14), to the auxiliary roller (13) b→Main roller α4) b→Auxiliary roller (131C→Take-up roller e) (by running the PET film substrate (1) in the order of the main rollers (14) a and (14) When passing in contact with b, it is heated and degassed.

Next, by lowering the temperature of the silicone oil, main roller a4. and (14) lowering the temperature of b to, for example, 90° C. to form a Co—Cr film. The PET film substrate (1) is wound up on a take-up roll Oe to perform degassing treatment.
ie→auxiliary roller (13C→main roller 01111b→・
...--Spatter is sent out in the opposite direction to the supply roller a1) and placed opposite the main roller 04)b when the substrate (1) runs on the main roller α4)b. A continuous thin film is formed by depositing a Co--Cr film on the substrate (1) from the target eye 15)v.

Furthermore, when making a floppy disk with recording films on both sides, a sputter target (Lsb to PET
After forming a Co-Cr thin film on one side of the film substrate (1), main roller α4)b → auxiliary roller α3)b → main roller α4)a and the PET film base (1) are sent out.
When the substrate (1) runs on the main roller (14), Co-Cr is applied to the other surface of the substrate (1) from a sputter target α placed opposite to the main roller C14) a.
After forming the film, the auxiliary roller C13, → the supply roller (
It runs with the winding reroller (11) and winds up.

As mentioned above, the PET film substrate discharged from the supply roller α°C is degassed and then wound up by the winding rollers a and e, a Co-Cr film is formed on both sides, and the PET film substrate is taken up by the supply roller (
11). As a target for Co-Cr film, 120 im x 250 mvt x 8 m
A film having a composition of tg, Co-21 (at %) and Cr was used, and a film thickness of 500X was formed on both sides by the method described above.

Next, by applying high frequency to high frequency electrodes α7)a and (17)b, plasma oxidation is performed over both surfaces of the Co--Cr film. First, the atmosphere is switched from argon to oxygen. The oxygen pressure is, for example, 8 X IQ -7To
rr, and the RF power is, for example, 170W. The discharge time is, for example, 10 minutes. The plasma oxidation treatment is performed on both sides of the Co--Cr film using the above-described traveling method.

Next, targets α51a and α5b are used to form a wear-resistant film, for example, an aluminum oxide film. The target for forming the aluminum oxide film is Co −
A sintered body of aluminum oxide with the same dimensions as for the Cr film is used. Using the same running method as described above, about 2000X magnetron sputtering is performed in an argon atmosphere on both sides of the plasma oxidized Co--Cr film to form an aluminum oxide film as a wear-resistant film.

A perpendicular magnetic recording medium in which a Co-Cr film according to the present invention is subjected to plasma oxidation treatment and then an aluminum oxide wear-resistant film is formed thereon, an aluminum oxide wear-resistant film is formed without plasma oxidation treatment, and plasma We created a perpendicular magnetic recording medium that does not form a wear-resistant film through oxidation treatment, and conducted a lifespan test by running it on the same track. Figure 3 shows the test results when fluorocarbon was used as the lubricant and when no lubricant was used. The number of samples subjected to the life test was 10 each, and the circles in the figure indicate the average values. As is clear from the figure, the lifetime of the perpendicular magnetic recording medium is improved when a wear-resistant film of aluminum oxide is formed by plasma oxidation treatment.

FIG. 4 shows the results of analyzing the concentration distribution of Co, Cr, O, and C in the depth direction of the plasma-oxidized Co--Cr film by scanning Auger electron spectroscopy.

This reveals that a high oxygen concentration region is formed in the surface region of the Co-, Cr film. This surface layer.

When analyzed by reflection line diffraction, it was found that Co504 was the main component, and there was also a complex oxidation layer of Co2O3 and Coo.

Note that the high oxygen concentration region is located 30X from the surface of the Co-Cr film.
A sufficient effect could be obtained with the above thickness.

In the above example, the oxygen partial pressure was set to 8 Xl0-' To
Although plasma oxidation treatment was performed as rr, the oxygen partial pressure may vary depending on the discharge method such as conventional method or sputter method. That is, in the conventional method, it is possible to increase the introduced oxygen pressure (for example, 10-' Tor
Furthermore, in the sputtering method, it is possible to lower the introduced oxygen pressure (for example, on the order of 10-6 Torr). The magnetic properties of the CoCr film subjected to the plasma oxidation treatment were almost the same as those of the untreated one, and a coercive force of 1000θ8 was obtained. The surface oxide layer can be formed not only by plasma oxidation but also by changing the atmosphere during Co-Cr magnetron sputtering from argon to oxygen, or by using a target of copal oxide (CO3O4). Alternatively, it may be prepared and formed by magnetron sputtering.

Further, the oxidation treatment according to the present invention is particularly effective when the wear-resistant film is a metal oxide; for example, even when zirconium was used, the same results as with aluminum oxide were obtained.

Furthermore, in the above embodiments, the case where the ferromagnetic alloy layer is a single layer of Co--Cr film was explained, but in the case where the ferromagnetic alloy layer is backed with a soft magnetic layer such as permalloy based on re-Ni alloy as the base of the Co--Cr film. The present invention is also applicable to Also, Co =
Not only Cr alloys but also other ferromagnetic alloys based on Co can be applied.

(Effect of the invention) The perpendicular magnetic recording medium according to the present invention mainly has c.

Since the ferromagnetic alloy layer based on ferromagnetic alloy has an oxide layer at the interface with the wear-resistant film, it has a long life and a long life in the life test by running test.
High reliability.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a perpendicular magnetic recording medium, FIG. 2 is a diagram showing an outline of a continuous thin film forming apparatus, and FIG. 3 is a diagram showing a comparison of the life characteristics of perpendicular magnetic recording media of the present invention and the prior art. Fourth
The figure shows Co in a perpendicular magnetic recording medium according to an embodiment of the present invention.
, Cr, 0, and C in the depth direction. (1) ...substrate, (2) -Co-Cr film (3
) -... Wear-resistant film t 04) a, (L4b"/Main roller 0.5) a, α5) b... Sputter target. Representative Patent attorney Noriyuki Chika (and 1 other person) 1st Figure 3 Lifespan: First opening Figure 4; YOY Saku A> Procedural amendment (spontaneous) Showa period, October 9th, Commissioner of the Japan Patent Office, 1, Case indication patent application No. 1983-96571 2 , Name of the invention Perpendicular magnetic recording medium 3 Relationship with the case by the person making the amendment Patent applicant (307) Toshiba Corporation 4, Agent 1-1-6 Shibaura-chome, Minato-ku, Tokyo 105 Contents of the amendment ( 1) "Polyethylene ticrate" on page 2, line 7 to line 8 C of Specification 4IF is corrected to "polyethylene terephthalate." 12) Specification, page 4, line 1 to page 5, line 1, 1: Correct "polyethylene ticrate" to "polyethylene terephthalate." (3) Approximately 2000'k on page 8, line 7 of the specification
"of. Corrected to "approximately 200'A."that's all

Claims (3)

[Claims] (1) Perpendicular magnetic recording comprising a substrate, a CO-based ferromagnetic alloy layer formed on the substrate and whose surface is mainly made of Co oxide, and a wear-resistant film formed on the ferromagnetic alloy layer. Medium. (2) The perpendicular magnetic recording medium according to claim 1, wherein the wear-resistant film is a metal oxide. (3) The perpendicular magnetic recording medium according to claim 1, further comprising lubricating oil on the wear-resistant film.