JPS62200520A - Thin metallic film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a thin metallic film type magnetic recording medium having excellent durability and corrosion resistance by providing a magnetic layer consisting of an alloy contg. Co as an essential component on a nonmagnetic substrate and protective layer consisting of an oxide of a Co-Y alloy thereon. CONSTITUTION:The magnetic layer 2 consisting of Co, Co-Cr, Co-V, Co-Mo, Co-W or other alloys contg. Co as the essential component is provided on the nonmagnetic substrate 1. The protective layer 3 consisting of the oxide of the Co-Y alloy is provided thereon. The ratio of the Y atoms incorporated into the layer 3 to the total number of the Co atoms and Y atoms is adequately 0.5-5%, more preferably 1-5%. The thickness of the layer 3 is 30-500Angstrom , more preferably 30-200Angstrom . The durability is improved by executing vapor deposition in such a manner that the C-axis of the magnetic layer 2 is oriented perpendicularly to the medium plane.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a metal corneal magnetic recording medium having excellent durability and corrosion resistance.

[Prior Art] In recent years, there has been a strong demand for higher density magnetic recording, and various research and development efforts are underway. One of these methods is a method using a magnetic layer of a metal-y film, and among these methods, the method using perpendicular magnetization is particularly suitable for high density applications because self-demagnetization approaches zero as the density increases. It is considered to be a method.

Materials for the magnetic layer used in this metal thin film magnetic recording medium include Co, Go-Xi, and Go-P as L.

Co-old-P, Co-Cr, Go-V, Go-H
a, Co-PL, Co-JCo-Or-Pd, G
Alloys whose main components are o-Or-No and Go-Or-RhiCo are being studied. One of the major disadvantages of magnetic recording media with such metal magnetic layers is that they have a significant lack of wear resistance, such as when the magnetic layer and magnetic head come into direct contact with each other, causing scratches on both. there were.

, this notification is an important notification related to the reliability of magnetic recording media, but how to resolve this notification υ: Conventionally, fatty acids, higher fatty acids, oxyfatty acids, fatty acid amides, fatty acid esters , aliphatic alcohol, metal soap, etc. have been applied to the surface. However, in the method described in L, it is difficult to make the thickness of the top coat layer uniform, and the effect decreases with use.

It was not satisfactory because it lacked durability.

As a method to improve this point, forming a protective layer of 001g compound has been carried out. As a means of film formation, a vapor deposition method (for example, JP-A-58-137528-1, JP-A-80
-191425 etc.), reactive sputtering method (for example, JP-A-59-193536, JP-A-80-508)
22) has been proposed.

However, the protective layer of No. 2L has a problem in terms of corrosion resistance, and for example, when recording or reproducing is performed after being left in a hot and humid condition, low F and omissions of the fl'j raw signal occur. This corrosion resistance itself can be significantly improved by increasing the degree of oxidation, but in this case the durability deteriorates and it is not possible to combine both performances, which is a major problem in practical use. ing.

[Problem to be Solved by the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and provide a gold IJi thin film magnetic recording medium that has excellent durability and corrosion resistance. .

[F stage and action 1 for solving the open problem The present invention is
Non-magnetic), (on at least one side of the body, it has a magnetic layer made of an alloy mainly composed of Co, and secondly a protective layer made of an oxide of a Go-Y alloy. This is a metal thin film type magnetic 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. 1 is a non-magnetic substrate, 2 is a magnetic layer made of a 00 alloy film, and 3 is a partially oxidized Go-Y alloy. It is a protective layer. The non-magnetic substrate 1 is polyethylene terephthalate or polyimide.

A plastic film made of polycarbonate, polyamide, etc., or a stainless steel, aluminum, or glass sub-layer can be used. The material for the second magnetic layer is:
Go, Go-Car, Go-V, Go-No.

Go-W, Co-P, Go-Ni, Co-Pt,
Go-Xi-P, Go-Cr-Ru.

Alloys such as Go-Gr-Rh and Go-Cr-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 controlling the direction of adhesion and surface roughness; A magnetic permeability layer etc. may be provided, and a coating of fatty acid, higher fatty acid, oxyfatty acid, fatty acid amide, fatty acid ester, fatty alcohol, or metal soap may be provided as a lubricating layer on the oxide protective layer t. Furthermore, it is also possible to provide a layer for lubrication or antistatic purposes on the back surface of the substrate.

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 does not easily adhere to the head material, and therefore has good lubricity, and at the same time, the CO of the F layer.
It must adhere strongly to the alloy magnetic layer and be difficult to peel off.

Why is Go-based oxide excellent as a protective layer?

This is because when it is in the form of GO30A C spinel structure), it has solid lubricity and the reduction in surface adhesion, J/tj, is large. However, in the case of a completely oxidized protective layer, at the interface with the magnetic layer, the metal phase with c, ρ structure and the oxide phase (Ca30s on top: spinel structure) are in contact, and the crystal lattice of both is in contact. Because it is difficult to align, the bond between the layers is weak, and the protective layer easily peels off due to sliding with the head.
Therefore, in order to obtain a durable protective layer, it is preferable that a small amount of metal phase remain in the protective layer, and this remaining metal phase is responsible for improving the adhesion with the magnetic layer. Presumed.

Corrosion is caused by oxidation of this metallic phase. On the other hand, in the present invention, the metal phase is a Co-Y alloy, and the G
o Since the corrosion resistance is higher than that of a single substance, the corrosion resistance effect can be obtained even if the metal phase remains.

Note that if the content of Y is excessive, the corrosion resistance is rather reduced. There is an optimal range of composition ratio of Y for corrosion resistance effect,
Anything beyond that is actually harmful.

As a result of the following F study, as a star of Y atoms included in the protective layer, YJ<Cr with respect to the total number of Go atoms and Y atoms.
- A suitable number ratio is 0.5 to 5%, more preferably 1 to 5%.

Further, as a result of various studies, the thickness of the protective layer is preferably 30 to 500, and the preferable range is 30 to 200. If the current is 30A or higher, the protective effect is not sufficient, and if the current is 500A or higher,
If it exceeds 8, the recording IIT raw characteristics will deteriorate due to spacing loss.

The present invention is a technology that can be applied to CO-based alloy magnetism 1 model in general, but it is better to use non-oriented or oblique magnetic layers when the C-axis of the magnetic layer (hexagonal system) is oriented in a direction perpendicular to the medium surface. Even when the protective layer was somewhat thinner than in the case of orientation, the durability tended to be relatively good. This is probably due to the difference in the ease of achieving crystallographic consistency between the magnetic layer and the metal phase in the protective layer. The C axis is perpendicular to the medium surface, and the present invention is particularly effective for Go-based alloy recording media. In particular, it has been reported that when using a superimposed magnetic recording medium 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. (9th 11th Annual Meeting of the Japan Society of Applied Magnetics, Abstracts of Academic Lectures P, 100), and the present invention, combined with its high-density recording properties, exhibits remarkable effectiveness in direct magnetic recording media that require a thin protective film. .

Also, according to the technological trends of research and development in recent years.

The co alloy metal magnetic layer is generally formed by a physical vapor deposition process in a vacuum such as vacuum evaporation or sputtering. In this case, in order to increase the coercive force, a technique of oxygen introduction vapor deposition is often used at the same time as oblique vapor deposition, and a surface oxidation layer is also formed at this time (for example, JP-A-58-41439).

At this time, 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 longitudinal recording media with a relatively low recording density, which results in a decrease in Og and poor recording/reproducing characteristics (for example, JP-A-80-191425). Therefore, the present invention can be realized, for example, in a form in which a fully curved vapor flow containing Y is merged with a vapor flow participating in the formation of a surface portion by the film force method disclosed in the Japanese Patent Publication No. 1 & L. On the other hand, due to the high Q density used in the Co-based nail direct magnetization film, it is necessary to reduce the spacing loss as much as possible. It is advantageous if the forming steps are separated.

The present invention provides a thin oxidation protective film that is highly durable and wear-resistant, does not impair the magnetic properties of the magnetic layer, and has good corrosion resistance. It can be suitably used in perpendicular recording media used in the short wavelength region.

[Example 1] Hereinafter, description will be given based on an example. Note that the results here are obtained when the thickness of the protective layer was approximately 10 OA in both Examples and Comparative Examples.

Example 1 A polyimide resin film with a thickness of 10 p- is used as a non-magnetic substrate, and a Co-C film with a thickness of 0.4 JLta is applied thereon.
The alloy film was continuously vaporized to obtain a long sample.

A protective layer of a co-Y oxide film was formed on this sample 1- 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 Ca-Y alloy target, which is connected to an external high-frequency power source. A sample film 7, in which a Go-Cr alloy layer was previously formed on a polyimide film by a vacuum steaming method, was passed from an unwinding roll 8 to an intermediate free roller 9 to a driving can 10. It passes through the intermediate free roller 9 again and reaches the winding roll 11. +2 is an adhesion prevention plate, 13 is an oxygen introduction pipe, and 14 is an argon introduction pipe.

The ultimate pressure during J & film removal is 3 x 10'Pa, the Ar gas pressure is 0.30 Pa, m is not introduced, jjH is 8cc/min, and the input power for medium area attack is 4 W/cm2. The deposition rate is approximately 20 A/sec and the sample film drive rate is 15 c/min.

Example 2 Polyethylene terephthalate fill L1 with a thickness of 12p
After forming a 0.4-thick Ca-old-P alloy layer on the body by plating, Go was applied in the same manner as in Example 1.
-The oxide layer of the Y alloy was formed.

Example 3 Go-P with a thickness of 0.4 was applied to the same substrate as in Example 1.
After forming the L alloy layer by vacuum evaporation, a protective layer of Co--Y oxide film was formed in the same manner as in Example 1.

Example 4 The same Co-C as in Example 1 was applied to the same substrate as in Example 1.
An R alloy layer was provided, a Go-Y oxide film was formed using the apparatus shown in FIG. 3, and a C layer 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 device 16. An electric f-gun 17 is installed in this small room, and the electric f-beam emitted from it fires the Go-Y alloy beret 2 in the crucible 18.
Heat the plate 19. The first reason is to maintain the interior at a high vacuum to prevent damage to the gun due to oxygen inflow.

The ultimate pressure is 5 x 105 Pa or more, and the oxygen introduction hY is 1
2 cc/min, the deposition rate is about 500 A/sec, and the sample film feed rate is 3.5 m/min.

Example 5 After forming a similar Go-Cr alloy layer on the same substrate as in Example 1, a Go-Y 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 Iv elementary plasma generated between 2 degrees of electrodes to perform plasma oxidation.

Conditions are vacuum degree 0.30 Pa, 1% J elementary partial pressure 0.08 P
a. The input power was 300 W, and the feeding speed of the sample film was 40 c/min.

Comparative Examples 1 to 5 Examples 1 to 5 except that the protective layer did not contain Y and was made of Co oxide
Samples prepared in the same manner as above were designated as Comparative Examples 1 to 5, respectively.

Comparative Examples 6 and 7 Samples prepared in the same manner as in Example 1 and Example 4 were used as Comparative Examples 6 and 7, respectively, except that Go-Y1% i-ide containing 77% was used as the protective layer.

Table 1 shows Y of the protective layer for L examples and comparative examples.
The results of content, durability and corrosion resistance tests are shown. However, the Y content is determined by the amount of gold contained in the protective layer.
It shows the ratio of the number of Y atoms to the number of E (ie Go+Y) atoms.

Durability test was carried out using 81 samples of Examples and Comparative Examples in Section E.
After cutting it into width and making it into a tape shape, it was made using a commercially available 8-tear VTR deck. In this method, after recording a test pattern, repeated fIp recordings were performed to examine changes in head output and number of dropouts depending on the number of passes. The criteria for determining durability are as follows. Repeated playback 100 passes
, 3dB or more is B.

In addition, those in which the number of dropouts exceeded 200 per minute after reaching 100 passes were classified as C. Incidentally, a dropout was counted as one dropout when an output paper signal of 113 dB or more than the 11 average output continued for 15 g 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 playback 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 in the outermost 30cm portion of the tape while the tape was left unused, but no other problems occurred.B indicates that normal output was obtained over the entire tape. C1 is the part that appears repeatedly.
A tape in which the portion where 11 f of normal recording could be made was 20% or more of the total length of the tape was designated as D.

Tables 1 and 2 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 and approximately 50 pm thick film as the body in the above Examples and Comparative Examples.
A 50 kBPI signal was recorded and generated.

The criteria for determining durability is A if the output decreases after + million passes is within 3 dB compared to the initial output, B if it is more than 3 dB,
The case where stable main output could no longer be obtained was designated as C.

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 [9, Effect of light] As explained above, Go-Y on the Co-based alloy magnetic layer
By providing a protective layer formed by oxidizing the alloy, it was possible to significantly improve corrosion resistance while maintaining the same durability as in the case of providing a conventional protective layer.

[Brief explanation of drawings]

Figure 1 shows the metal thin film 11 of the present invention)! Figure 2 is a schematic diagram of the high-frequency sputtering device used to form the 1/1 layer.
Figure 3 shows the vacuum steaming equipment used to form the Δ layer.
FIG. 4 shows a plasma oxidation apparatus used for oxidizing the protective layer. 1: Non-magnetic substrate, 2: Ca-based alloy magnetic outer layer, 3: Co-
Y oxide protective layer, 4: Vacuum chamber, 5: Exhaust device, 6: Co
-Y alloy target, 7: sample tenip, 8: unwinding roll. 9: Intermediate free roller, IO = drive can. 11: Winding roll, 12: Anti-adhesion plate. 13: Oxygen introduction pipe, l4: Argon introduction pipe, 15: Separation +5=, 16: I
1 air device, 17 electric f-gun, 18 nil pressure point, 19:C
o-Y alloy pellet, 20: 'mandrel, 21: capacitor, 22: high frequency power supply, 23: ground.

Claims (2)

[Claims] (1) A thin metal film characterized by having a magnetic layer made of an alloy containing Co as a main component on at least one surface of a nonmagnetic substrate, and a protective layer made of an oxide of a Co-Y 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.