JPS62202312A - Thin metallic film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability and corrosion resistance by providing a magnetic layer consisting of an alloy contg. Co as an essential component and a protective layer consisting of oxide of a Co-Cu alloy thereon on a nonmagnetic substrate surface. CONSTITUTION:The magnetic layer 2 consisting of the Co alloy film and the protective layer 3 formed by partially oxidizing the Co-Cu alloy are provided on the nonmagnetic substrate 1. Co and alloys such as Co-Cr, Co-V, Co-Mo, Co-Cr-Rh and Co-Cr-Mo are used for the material of the magnetic layer 2. Some metallic phase remains preferably in the protective layer in order to obtain the protective layer 3 having good durability. Corrosion arises when the metallic phase is oxidized but the metallic phase is the Co-Cu alloy and has the corrosion resistance higher than the corrosion resistance of the simple substance of Co and therefore, the corrosion resistant effect is obtd. even if the metallic phase remains.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a metal thin film type magnet with excellent durability and corrosion resistance,
This relates to recording media.

[Prior Art] In recent years, there has been a strong demand for higher density magnetic recording, and various research and development efforts are underway. Gold FigJ
One example of this is a method using a vague magnetic layer. Among these, the method using a perpendicularly magnetized film is considered to be a method suitable for increasing the density because self-demagnetization approaches zero as the density increases.

The materials for the magnetic layer used in this metal thin film magnetic recording medium are mainly Co, Co-Ni, and Co-P.

Co-Xi-P, Co-Cr, Co-V, Co-
Ha, Co-Pt, Co-W.

Co-Cr-Pd, Co-Or-No, Co-Cr
Co-based alloys such as -Rh are being studied. One of the major problems with magnetic recording media with such metal magnetic layers is that they lack a significant amount of wear resistance, with direct contact between the magnetic layer and the magnetic head causing scratches on both. .

This problem is an important problem related to the reliability of magnetic recording media, but conventional methods for solving this problem include using fatty acids, higher fatty acids, oxyfatty acids, fatty acid amides, fatty acid esters, fatty alcohols, and metal soaps. etc. have been applied to the surface. However, the above method was not satisfactory because it was difficult to make the thickness of the top coat layer uniform, its effectiveness decreased with use, and it lacked durability.

As a method to improve this point, forming a protective layer of CO oxide has been carried out. As a means of film formation, a vapor deposition method (for example, JP-A No. 5 [(-137528), JP-A No. 10-11]
-191425 etc.), reactive sputtering method (for example, JP-A-59-1935313, JP-A-6O-50)
i322) has been proposed.

However, the protective layer described above has a problem in terms of corrosion resistance; for example, when recording and reproducing are performed after being left under high temperature and high humidity conditions, the reproduced signal deteriorates or is lost. This corrosion resistance itself can be considerably improved by increasing the degree of oxidation, but in this case the durability deteriorates and it is not possible to achieve both properties at the same time, which is a major problem in practical use. There is.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the above-mentioned problems of the prior art and provide a metal thin film magnetic recording medium that is excellent in both durability and tactility.

[First step and action for solving the problem] The present invention has the following features:
A metal thin film type magnet, characterized in that at least one of the non-magnetic substrates has a magnetic layer made of an alloy containing 0 as a main component, and a protective layer made of an oxide of a Co-Cu alloy thereon. It is a recording medium that achieves the above object.

FIG. 1 shows the basic structure of the metal thin film magnetic recording medium of the present invention, where l is a nonmagnetic substrate and ? 3 is a magnetic layer made of a Co alloy film, and 3 is a protective layer made of a partially oxidized C-low-Cu alloy. As the non-magnetic substrate 1, a plastic film made of polyethylene terephthalate, polyimide, polycarbonate, polyamide, etc., stainless steel, aluminum, glass, etc. can be used. 2
Materials for the magnetic layer include Co, co-Or, C
o-V, Co-No.

Co-W, Co-P, Co-old, Co-Pt,
Co-Ni-P, Co-Cr-Ru.

Alloys such as Co-Cr-Rh and Co-Or-No can be used.

In addition, the metal thin film magnetic recording medium of the present invention includes, for example, an intermediate layer between the substrate and the magnetic layer for the purpose of improving adhesion and controlling surface roughness, and a high permeability layer that is effective when using a perpendicular head. A magnetic layer or the like may be provided, or a coating of fatty acid, higher fatty acid, oxyfatty acid, fatty acid amide, fatty acid ester, fatty alcohol, metal soap, etc. may be provided as a lubricating layer on the oxide protective layer. Further lubrication or band on the back side of the base? It is also possible to provide a layer for If prevention. In addition, a structure in which magnetic layers, protective layers, etc. are provided on both sides of the substrate is also possible.

The properties that the protective layer should have are that it is unlikely to cause aggregation with the head material, and therefore has good lubricity, and at the same time, it should reduce CO2 in the underlying layer.
It must adhere strongly to the alloy magnetic layer and be difficult to peel off.

Co-based oxide is excellent as a protective layer because CO3O
4 (spinel structure) has solid lubricity, which largely contributes to the reduction in surface visibility. However,
In the case of a completely oxidized protective layer, at the interface with the magnetic layer,
c, p, metal phase and oxide phase (mainly Co:+04:
Since the crystal lattices of the two are in contact with each other, the bond between the layers is weak, and the protective layer is likely to peel off due to sliding with the head. Therefore, in order to obtain a highly durable layer, It is preferable that some metal phase remains in the protective layer, and it is presumed that this remaining metal phase is responsible for improving the adhesive force with the magnetic layer.

Corrosion is caused by oxidation of this metallic phase. On the other hand, in the present invention, the metal phase is a Ca-Cu alloy,
Since the corrosion resistance is higher than that of the cobalt material, the corrosion resistance effect can be obtained even if the metal phase remains.

Note that if the content of Cu becomes excessive, the durability will decrease.

This is thought to be caused by an increase in the amount of Cu phase precipitated within the metal phase.

As a result of the above studies, the ratio of the number of Cu atoms to the total number of GO atoms and Cu atoms is preferably 5 to 50%, and more preferably 10 to 50%. be.

Further, as a result of various studies, the thickness of the protective layer is preferably 30 to 500 mm, more preferably 30 to 200 mm. If it is less than 30A, the protective effect is not sufficient, and if it is less than 500A,
If it exceeds this, the recording and reproducing characteristics will deteriorate due to spacing loss.

Although the present invention is a technology that can be applied to Co-based alloy magnetic films in general, when the C axis of the magnetic layer (hexagonal system) is oriented in a direction perpendicular to the medium surface, it is better to use non-oriented or peel-oriented magnetic films. Even when the protective layer was somewhat thinner, the durability tended to be relatively good. This is probably due to the difference in ease of achieving crystallographic consistency between the magnetic layer and the metal phase in the protective layer. In Co-perpendicularly magnetized films such as Co--Cr, which have been extensively studied in recent years, the C-axis is perpendicular to the medium surface, and the present invention is particularly effective for CO-based alloy perpendicular magnetic recording media. In particular, it has been reported that when a perpendicular magnetic recording medium is used in combination with a ring head, the spacing loss is greater than in the longitudinal magnetic recording method, and better adhesion between the magnetic layer and the magnetic head is required. (The 9th Japan Society of Applied Magnetics Academic Conference Abstracts P, 100), and the present invention, combined with its high-density recording properties, exhibits remarkable effectiveness in perpendicular magnetic recording media that require a thin protective film.

Furthermore, according to recent technical trends in research and development, it is generally easier to obtain a high-quality magnetic film by forming a Co alloy bottom-tropic magnetic layer by a physical vapor deposition process in a vacuum, such as a vacuum evaporation method or a sputtering method. For example, in the case of an in-plane magnetized film such as a Co-Ni alloy film, in order to increase its coercive force, an oxygen-introducing evaporation technique is often used at the same time as oblique evaporation, and a surface oxide layer is also created at that time (for example, Showa 58-4
No. 1439).

At this time, some oxidation occurs to the inside of the magnetic material, so if you try to strongly oxidize the outermost surface, the inside of the magnetic layer will actually be oxidized.
This method has sufficient practicality for target in-plane recording media with relatively low recording densities, where recording and reproducing characteristics deteriorate due to a decrease in Bs (for example, Japanese Patent Laid-Open No. 112425). Yes, the present invention can be realized, for example, by the film forming method disclosed in the above-mentioned publication, in which a vapor flow of a metal containing Cu is merged with a vapor flow participating in the formation of a surface portion. On the other hand, the description Q used in the CO-based perpendicular magnetization film is
Due to the high density, it is necessary to reduce the spacing loss as much as possible, and it is advantageous to separate the steps of forming the magnetic film and the oxide film, as disclosed in the forming method of the embodiment of the present invention.

The present invention provides an oxidation protective film that is thin, durable, highly abrasive, does not impair the magnetic properties of the magnetic layer, and has good corrosion resistance.

From this point of view, it can be suitably used in perpendicular recording media used in high recording density and short wavelength regions.

[Example] The following is a description based on an example. Note that here, the results are obtained when the thickness of the protective layer was approximately 100A in both Examples and Comparative Examples.

Example 1 A polyimide resin film with a thickness of 10 gtm was used as a non-magnetic substrate, and a Co-Ca film with a thickness of 0.4 pm was applied thereon.
A long sample was obtained by continuously depositing an r-alloy film.

A protective layer of a Co--Cu oxide film was formed on this sample by a reactive sputtering method using the apparatus shown in FIG. 4
5 is a vacuum chamber, 5 is an exhaust device, and 6 is a Co-Cu alloy target, which is connected to an external high-frequency power source. A sample film 7, in which a Co-Cr alloy layer was previously formed on a polyimide film by a vacuum evaporation method, was transferred from an unwinding roll 8 to a medium rlf free roller 9 to a driving can l.
O1: Winding roll 11 via intermediate free roller 9 again
reach. 12 is an anti-adhesion plate, 13 is an oxygen introduction pipe, 14
is the argon introduction pipe.

The ultimate pressure during film formation was 3 x 10-'Pa or less, the Ar gas pressure was 0.30 Pa, the amount of oxygen introduced was 8 cc/min, and the input power per unit surface was 4 W/c+a2. At this time, the deposition rate was about 20 A/sec, and the sample film drive rate was 15 c+a/min.

Example 2 After forming a Co-Ni-P alloy layer with a thickness of 0.4 gn+ on a polyethylene terephthalate film substrate with a thickness of 12 g rs by plating, a Co-Cu alloy layer was formed in the same manner as in Example 1. An oxide protective layer was formed.

Example 3 A 0.4 gm thick Co-
After forming a Pt alloy layer by vacuum evaporation.

A protective layer of Co--Cu oxide film was formed in the same manner as in Example 1.

Example 4 The same Co-C as in Example 1 was deposited on the same substrate as in Example 1.
A Co-Cu alloy layer is provided, and the Co-Cu
A protective layer of oxide film was formed by vacuum evaporation.

The overall structure is almost the same as the apparatus shown in FIG. 2, and oxygen is introduced into the vacuum chamber through an introduction pipe (not shown). A part of the vacuum chamber is partitioned by a partition wall 15, and the inside thereof is evacuated by another exhaust system a16. An electron gun 17 is installed in this small room, and the electron beam emitted from the electron gun 17 causes the Co-Gu alloy pellet 1 in the crucible 18 to
Heat 9. The purpose of providing the partition wall is to maintain the interior at a high vacuum to prevent damage to the electron gun due to oxygen inflow.

The ultimate pressure is 5 x 101 Pa or less, and the amount of oxygen introduced is 12
cc/min, the deposition rate is about 50 OA/sec, and the sample film feed rate is 3.5 m/min.

Example 5 After forming a similar Co-Cr alloy layer on the same substrate as in Example 1, a Co-Cu alloy layer was formed using the same equipment, and this surface was subjected to plasma oxidation using the equipment shown in Figure 4. A protective layer was formed by doing this. The sample is passed through oxygen plasma generated between the electrodes 20 to perform plasma oxidation.

The conditions are vacuum degree 0.30 Pa, oxygen partial pressure Q 08 Pa, input power 300 W, and sample film feeding speed 40 c.
m/min.

Comparative Examples 1 to 5 Examples 1 to 5 except that the protective layer did not contain Cu and was made of GO oxide
Samples prepared in the same manner as in Comparative Examples 1 to 5
And so.

Comparative Examples 6 and 7 Comparative Examples 6 and 7 were samples prepared in the same manner as in Example 1 and Example 4, except that Cut (Co-Cu oxide containing 0%) was used as the protective layer.

Table 1 shows the C of the protective layer for the above Examples and Comparative Examples.
The results of u content, durability and corrosion resistance tests are shown. However, the Cu content is the metal (
That is, the ratio of the number of Cu atoms to the number of Co+Cu atoms is shown.

Durability tests were conducted on the samples of the above examples and comparative examples.
After cutting to width and making into tape form, reprint 8a+mVT
This was done using an R deck. The method involved recording a test pattern and repeatedly playing it back to examine changes in head output and number of dropouts depending on the number of passes. The criteria for determining durability are as follows. If the output of the 100th bus repeatedly played is within 3 dB of the initial output, A, 3
B for more than dB.

Also, the number of dropouts is 2 before reaching 100 passes.
Those exceeding 00 pieces/min were rated C. Note that a dropout was counted as one dropout when the output decreased by 16 dB or more from the average output for 15 p seconds or more.

Corrosion resistance test was performed using sample tape prepared in the same manner as above.
After leaving it in a constant temperature and humidity chamber at 0° C. and 70% humidity for 50 hours, recording and reproduction were attempted using the same deck as above. A indicates that there was no problem at all, and B indicates that there was an increase in dropouts at the outermost part of the tape (about 30C), which was the outermost part while the tape was left unattended, but no problems were found elsewhere. C indicates a part where a certain output cannot be obtained repeatedly.
2 A tape in which the portion that can be recorded and reproduced normally was 20% or more of the total length of the tape was designated as D.

Tables 1 and 2 also show the test results for durability and corrosion resistance. However, the sample in this case was formed into a disk shape using the same material as in the above Examples and Comparative Examples and having a thickness of 50 p-m as a substrate.
This is a recording and reproduction of BPI signals.

The criteria for determining durability are A when the output decreases within 3 dB compared to the initial output after 1 million passes, B when the output exceeds 3 dB, and C when stable playback output cannot be obtained.

The criteria for determining corrosion resistance were as follows: After being left under the same conditions as described above, recording and reproducing were attempted, and those with no problems were rated A, those with output loss were rated B, and those with no stable output were rated C.

Table 2 [Effects of the Invention] As explained above, Co-Cu alloy is formed on the Co-based alloy magnetic layer.
By providing a protective layer formed by oxidizing an alloy, it was possible to significantly improve corrosion resistance while maintaining durability equivalent to or higher than that obtained when a conventional protective layer is provided.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram showing the basic structure of the metal thin film magnetic recording medium of the present invention, Fig. 2 is a schematic diagram of the high frequency sputtering apparatus used for forming the protective layer, and Fig. 3 is also a schematic diagram for forming the protective layer. Figure 4 shows the plasma oxidation equipment used to oxidize the protective layer. 1: non-magnetic substrate, 2: Co-based alloy magnetic layer. 3: Co-Cu oxide protective layer, 4: Vacuum chamber, 5: Exhaust device, 6: Co-Cu alloy target. 7: Sample tape, 8: 3 output roll, 9: Intermediate free roller, 10: Drive can. ll: Winding roll, 12: Anti-adhesive plate, 13: Oxygen introduction pipe, 14: Argon introduction pipe, 15: Partition wall, 16: Exhaust device, 17: Electron gun, 18 Nil pot, 19: Co-Cu alloy pellet, 20 : Electrode, 21: Capacitor, 22:
High frequency power supply, 23: Earth.

Claims (2)

[Claims] (1) A metal thin film characterized by having, on at least one surface of a non-magnetic substrate, a magnetic layer made of an alloy containing Co as a main component, and a protective layer made of an oxide of a Co-Cu alloy thereon. type magnetic recording media. (2) The metal thin film type magnetic recording medium according to claim 1, wherein the magnetic layer is provided with anisotropy so that the magnetization is aligned in a direction perpendicular to the plane of the medium.