JPS6194220A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To improve the adhesive force between a high molecular film substrate and ferromagnetic body film and to obtain the titled magnetic recording medium having a long service life by oxidizing the high molecular film substrate with plasma, and then forming a magnetic body film on the high molecular film substrate. CONSTITUTION:A Co-Cr film 2, an abrasion-resistant film 3, and a lubricating layer 4 are formed on both surfaces of a substrate 1 consisting of a high molecular film, and a continuous thin film forming device is used for manufacturing the vertical magnetic recording medium. The high molecular thin film substrate is oxidized with plasma as the pretreatment, and the Co-Cr ferromagnetic body film and the abrasion- resistant film are formed by sputtering in an argon atmosphere with a magnetron sputtering system. Namely, a PET film is firstly degasified, and the a high-frequency voltage is impressed on high-frequency electrodes 17a and 17b to oxidize both surfaces of the PET film with plasma. An oxygen atmosphere is used, the pressure of oxygen is regulated, for example, to 8X10<-1>Torr, and the RF electric power is regulated, for example, to 300W. Then the atmosphere is changed into argon, and the temp. of main rollers 14a and 14b is lowered, for example, to 90 deg.C to form a ferromagnetic body film of a Co-Ni film 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a magnetic recording medium, particularly a magnetic recording medium suitable for use in perpendicular magnetization recording, and a method for manufacturing the same.

(Technical background of the invention and its problems) In recent years, Co-Cr based sputtered thin films with a perpendicular magnetization easy axis for high-density recording using magnetization in a direction perpendicular to the medium surface of a magnetic recording medium have been developed. A typical example is a recording film. Such perpendicular magnetic recording media are based on a polymer film such as polyimide or polyethylene terephthalate, and a Co-Cr sputtered film is formed on one or both sides of the film, and a wear-resistant film is formed on the Co-Cr sputtered film. A film (protective film) is formed. When such a perpendicular magnetic recording medium is applied to a magnetic tape or a floppy disk, information is recorded, reproduced, and erased via a magnetic head.

The Co--Cr film is formed by a normal sputtering method or a magnetron sputtering method in an argon atmosphere. The formed Co-Cr film has a columnar structure oriented along the C axis, and in addition to the saturation magnetization M3, which is mainly determined by the film composition as a magnetic property, there is a magnetic anisotropy energy Ku perpendicular to the film surface 1; It has the conditions for 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 trunk with a lubricating oil such as fluorocarbon (fluorocarbon oil) interposed therebetween, the shortcoming was that its lifespan was extremely short. In-plane magnetic recording media typically require a lifetime of 10 million passes, whereas conventional perpendicular magnetic recording media often have a lifespan of less than 1 million passes. Even at the highest lifespan, it rarely exceeds 30 moe passes. Analysis of defects in running tests reveals that the reason for the peeling of the Co-Cr film from the polymer film substrate is that in order to extend the life of the magnetic recording medium, it is necessary to improve the adhesion of the ferromagnetic layer to the polymer film substrate. It is important to increase

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

(Summary of the Invention) The present invention particularly provides a magnetic recording medium characterized in that a ferromagnetic film formed on a polymer film substrate has an oxygen enriched region formed near the interface with the polymer film substrate. and a method for manufacturing a magnetic recording medium, characterized in that a magnetic film is formed on the polymer film substrate after the polymer film substrate is subjected to plasma oxidation treatment.

(Example of the invention) The present invention will be described below with reference to Examples.

FIG. 1 shows a perpendicular magnetic recording medium according to an embodiment of the present invention, in which a Co-Cr film ( 2), a wear-resistant film (3) and a lubricating layer (4) are formed. A continuous thin film forming apparatus shown in FIG. 2 was used to manufacture this perpendicular magnetic recording medium.

For film formation, a Co--Cr ferromagnetic film and an abrasion-resistant film were sputtered in an argon atmosphere using a magnetron sputtering method after plasma oxidation treatment as a pretreatment of the polymer film substrate. A specific method for forming the perpendicular magnetic recording medium is as follows.

First, the PliT film is degassed. The conditions are, for example, 120°C, I x 1 (1'Torr, 30 minutes).The degassing method in the apparatus shown in Fig. 2 is as follows.The heating of the PET film (1) is as follows. This is done by main rollers Ia and α4b. Main rollers α4)a and (
14) Silicone oil (not shown) is loaded in b, and by heating the silicone oil, the main rollers (I4) a and ub are heated, and the PET film base (I4) is heated.
1) Perform degassing. The degassing method is, for example,
As shown in the figure, the PET film substrate (1
), supply roller αυ → auxiliary roller tt31a → main roller CL4) a → auxiliary roller (1■b → main roller (14)
This is done by running in the order b → auxiliary roller (L3C → take-up roller (1e). PET film base (1)
is heated and degassed when it passes in contact with the main rollers (14) and (14) b.

Next, by applying high frequency to the high frequency electrodes (17) and (17)b, plasma oxidation is performed over both sides of the PET film. The atmosphere is oxygen, the oxygen pressure is, for example, 8 x 10-'Torr, and the RF power is, for example, 300W. In general, plasma oxidation is effectively carried out by inputting power in the range of 0.1 to 1.5 W/''cII. The processing time of the polymer film substrate can be controlled by the running speed, but for example, The plasma oxidation treatment is carried out in the opposite direction to the traveling direction in the case of degassing described above.

Next, change the atmosphere to argon and return to the main roller 114).
a and <141 b, for example 90'c! = lower to form a ferromagnetic film Co--Cr film. A PETPE outer membrane substrate (1
), the PET film base (1) is rolled up.
The main roller (I4
) When the substrate (1) runs on the main roller α4) a, the sputter target roller placed opposite the main roller Forms a thin film.

Furthermore, when making a floppy disk with recording films on both sides, after forming a Co-Cr thin film on one side of the PET film substrate (1) from the sputter target (15a), the main roller α4) a→auxiliary roller a31b→ The main roller (14) b and the PET film substrate (1) are sent out, and when the substrate (1) runs on the main roller (14) b, a sputter target placed opposite the main roller (14) b (From 1!1ilb, C on the other side of the base (1)
Form o-Cr film.

Next, it travels from the auxiliary roller 1131c to the winding roller 161 and winds it up.

As mentioned above, the PET film substrate discharged from the supply roller αυ is degassed and then wound onto the take-up roller σQ, and the film substrate undergoes a plasma oxidation process, and a Co-Cr film is further formed on both sides. After that, it is wound up on a winding roller. As a target for Co-Cr film, 1
20-X250X8, Co-21 (at%)
A film having a Cr composition was used, and a film thickness of 5000^ was formed on both sides by the method described above.

Next, the target for forming an aluminum oxide film is Co
- A sintered body of aluminum oxide with the same dimensions as for the Cr film is used. Driving method similar to above! - from C.

-Approximately 200% on both sides of the Cr film in an argon atmosphere
Further, red tron sputtering is performed to form an aluminum oxide film as a wear-resistant film. In addition to aluminum oxide, the wear-resistant film may be a metal oxide such as silicon oxide or zirconium oxide, or a nitride such as electrified silicon or titanium nitride.

A perpendicular magnetic recording medium in which a ferromagnetic film was formed after plasma oxidizing a polymer film substrate according to the present invention and a conventional perpendicular magnetic recording medium without plasma oxidizing treatment were tested on the same track. A lifespan test was conducted. The results of the life test are shown in Figure 3. Fluorocarbon is used as the lubricating oil, and each number is 1.
There are 0 pieces. The circles in the figure indicate the average values. As is clear from the figure, the life of a device in which a ferromagnetic film is formed on a polymer film substrate that has been subjected to plasma oxidation treatment is dramatically improved.

In the magnetic recording medium according to the present invention in which Co--Cr is used as the ferromagnetic film, the vicinity of the interface between the ferromagnetic film and the polymer film is analyzed by Auger electron spectroscopy.

Figure 4 shows the results of analyzing the concentration distribution of Cr, O, C, and N in the depth direction. It can be seen from FIG. 4 that an oxygen-enriched region is formed at the interface between the Co--Cr strong material film and the polymer film substrate. This oxygen enriched region (oxidized layer) increases the adhesion between the ferromagnetic film and the polymer film substrate, contributing to longer life.

Although polyethylene terebutarate was used as the polymer film substrate in the above-mentioned examples, similar effects were obtained with other polymer films such as polyimide films, and the results of Auger electron spectroscopy were also consistent.

In addition, in the above-mentioned example, the oxygen partial pressure was 8
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"" Torr).
Furthermore, in the sputtering method, it is possible to lower the oxygen pressure (for example, on the order of 10-5 Torr). The magnetic properties of the Co-Cr film formed on the polymer film substrate subjected to plasma oxidation treatment are almost the same as those of the untreated one, with a coercive force of 1000θ.

The later one was obtained.

Furthermore, in the above-mentioned examples, the formation of an oxygen-enriched region at the interface between the ferromagnetic film and the polymer film substrate was carried out by pretreatment of plasma oxidation of the polymer film.
It can also be formed by changing the amount of plasma flowing into the film substrate or the substrate temperature during formation of the ferromagnetic film.

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 lined with a soft magnetic layer such as permalloy based on Fe-Ni alloy as the base of the Co--Cr film. The manufacturing method of the present invention, which involves plasma oxidation of a polymer film substrate, can also be applied to the following. Also, Co -C
The present invention is applicable not only to r-alloys but also to other ferromagnetic alloys based on Co.

(Effects of the Invention) According to the present invention, the adhesion between the polymer film substrate and the ferromagnetic film is improved, and a long-life magnetic recording medium can be obtained.

[Brief explanation of drawings]

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. FIG. 3 is a diagram showing the concentration distribution of N and C in the depth direction. (1)...polymer film base, (2)...Co
-Cr film (3)...wear-resistant film v (14a
*(t41b...Main roller P9at(2)b...Spatter target. Agent: Patent attorney Noriyuki Chika (and one other person) Fig. 1 4. Fig. 2

Claims (2)

[Claims] (1) In a magnetic recording medium having a polymer film substrate and a ferromagnetic film formed on the polymer film substrate, oxygen concentration occurs in a region near the interface of the ferromagnetic film in contact with the polymer film substrate. A magnetic recording medium characterized in that a region is formed. (2) A method for producing a magnetic recording medium, comprising the steps of plasma oxidizing a polymer film substrate in an oxidizing atmosphere and forming a magnetic film on the polymer film substrate.