JPS62200521A - 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-Cd mixture 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-Cd mixture is provided thereon. The ratio of the Cd atoms incorporated into the layer 3 to the total number of the Co atoms and Cd atoms is adequately 0.3-35%, more preferably 5-35%. 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] The present invention relates to a metal thin film magnetic recording medium that has 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 made of a thin metal film. 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 magnetic layer materials used in this metal thin film magnetic recording medium mainly include Co, Co-Ni, Co-P,
'Co-Ni-P, Co-Or, Co-V, Co-Mo
, Co-PL, Co-Ill.

Co-Or-Pd, Co-Or-No, Co-Cr
-Alloys containing Rh9Co as a main component 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 the way to solve this problem is as follows:
Conventionally, fatty acids, higher fatty acids, oxyfatty acids, fatty acid amides, fatty acid esters, fatty alcohols, and metal soap caps have been applied to surfaces. However, the method described in L is not satisfactory because it is difficult to make the thickness of the top coat layer uniform, its effectiveness decreases as it is used, and it lacks durability.

As a method to improve this point, forming a protective layer of CO oxide has been carried out. One step of film formation is the vapor deposition method (for example, JP-A-5B-137528, JP-A-80-1).
91425 P'g-), reactive sputtering method (see
For example, JP-A-59-193538, JP-A-80-50
822) has been proposed.

However, the protective layer described in E has a problem in terms of corrosion resistance, for example, after being left in hot and humid conditions.
When playback is performed, low r and dropouts of the ILF raw signal occur. 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 performance characteristics, which is a major problem in practical use. There is.

[9. Problems to be Solved by Ming] The present invention has 11 objectives: to eliminate the problems of the prior art mentioned above and to provide a metal thin film type magnetic recording medium that is excellent in both durability and corrosion resistance. shall be.

[Step B and operation 1 for solving the problems The present invention has the following features:
A metal thin film type magnet, characterized in that at least one of the nonmagnetic substrates has a magnetic layer made of an alloy containing Co as an L component, and the L is a protective layer made of an oxide of a Co-Cd mixture. It is a recording medium, and thereby achieves the objective r) i.

Figure 1 shows the basic structure of the metal thin film magnetic recording medium of undeveloped IJ1. 1 is a non-magnetic substrate, 2 is a magnetic layer made of 00 alloy film, and 3 is a partially oxidized Co-Cd mixture. It is a protective layer. As the non-magnetic substrate (2), a plastic film made of polyethylene terephthalate, polyimide, polycarbonate, polyamide, etc., stainless steel, aluminum, glass, etc. can be used. Materials for the magnetic layer 2 include Co, Co-Cr,
Co-V, Co-No.

Co-J Co-P, Co-Ni, Co-Pt,
Co-Ni-P, Co-Cr-Ru.

An alloy of Co-Cr-Rh or Co-Cr-No3 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, and a highly transparent layer that is effective when using a Kawamuki head. A magnetic layer or the like may be provided, and a lubricating layer may be added to the protective layer of oxides, such as fatty acids, higher fatty acids, oxyfatty acids, and fatty acids.

A coating of fatty acid ester, aliphatic alcohol, metal soap, etc. may be provided, and it is also possible to provide a layer for lubrication or antistatic on the back surface of the body. 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 layer should have are that it is unlikely to cause adhesion with the head material, and therefore has good lubricity, and at the same time, the lower C
It must adhere strongly to the O-based alloy magnetic layer and must not be difficult to peel.

The reason why Co-based oxides are excellent as a protective layer is that Co
This is because when it is in the form of 304 (spinel horizontal), it has solid lubricity and the surface adhesion decreases greatly. However, in the case of a completely oxidized IC layer, at the interface with the magnetic layer, a metal phase with a c,p structure and an oxide phase (mainly Ga) are formed.
zes: spinel structure) are in contact with each other, and since the crystal lattices of the two are difficult to match, 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 durable protective layer, It is preferable that a young metal phase remains in the protective layer, and it is presumed that this remaining metal phase impairs the direction of the bias 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 Co--Cd mixture, and the Co core material X also has high corrosion resistance, so even if the metal phase remains, a corrosion-resistant effect can be obtained.

Note that if the Cd content is excessive, the durability will be low. The reason for this is considered to be that more Cd phase was precipitated within the metal phase. Moreover, when the Cd content is 0.2% or more F, fiIJ11Il! Almost no effect on sexual improvement was observed. It is presumed that this is because Cd is completely dissolved in the CO phase and does not precipitate.

As a result of the above study, we found that the image of Co atoms and Cd atoms contained in the layer 1;
Cd1J: (The ratio of f-number is preferably 0.3 to 35%, more preferably 5 to 35%.

In addition, the thickness of the protective layer is 30 to 50 as a result of various tests.
0A is suitable; ・The preferred range of layers is 30 to 200
It is A. If the current exceeds 30 A, the protective effect will not be sufficient, and if the current exceeds 500 A, the recording and reproducing characteristics will deteriorate due to spacing loss.

The present invention is a technology that can be applied to CO-based alloy magnetic films in general, but 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 Moreover, compared to the case of straight orientation, the durability tended to be relatively good even when the customer base was somewhat thin. 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. Co-based materials such as Co-Cr, which have been actively researched in recent years! (1) Direct magnetization is such that the C axis is superimposed on the medium surface, and the present invention is particularly effective for Co-based alloy perpendicular magnetic recording media. In particular, when a perpendicular magnetic recording medium is used in combination with a ring head, the spacing loss is smaller than that of the longitudinal magnetic recording method, and the distance between the magnetic layer and the magnetic head is better.
It has been reported that the 9th 11th Annual Meeting of the Applied Magnetics Society: A Collection of Abstracts, P, 100), and the present invention, combined with its high-density recording properties, provides a thin layer of protection.6 Demonstrates remarkable effectiveness in direct magnetic recording media.

In addition, according to recent technological trends in research and development, Co alloy metal magnetic layers can be formed by physical vapor deposition processes in vacuum, such as vacuum evaporation or sputtering, which generally makes it easier to obtain high-quality magnetic films. 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-
No. 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 may have sufficient practicality for in-plane recording media with relatively low recording densities, which result in low F of Bs and poor recording/reproducing characteristics (for example, Japanese Patent Application Laid-Open No. 191425/1983). The ungenerated IJ can be realized, for example, in a form 71 in which a metal vapor flow containing Cd is merged with a vapor flow participating in the formation of a surface cloth using the film forming method disclosed in the above-mentioned publication. - On the other hand, due to the high recording density used in the Co-based orientally magnetized film, it is necessary to reduce the spacing loss as much as possible, and as disclosed in the forming blade υ: of the embodiment of the present invention, the magnetic film and It is advantageous to separate the process of forming the oxide film.

The present invention provides an oxidation protective film that is thin, durable, has good corrosion resistance, does not impair the magnetic properties of the magnetic layer, and has good corrosion resistance. , which can be suitably used for eastward recording media used in the short wavelength region.

[Example] 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 100.8 cm in both Examples and Comparative Examples.

Example 1 -11 - Using a 10 μm thick polyimide resin film as the magnetic substrate, a 0.4 gs thick Co-
One model of Cr alloy was continuously deposited to obtain a long sample.

A protective layer of a Co--Cd oxide film was formed on this sample L 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-Cd composite 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 vacuum evaporation, was rolled from an unwinding roll 8 to an intermediate free roller 9 to a drive can 10. It passes through the intermediate free roller 9 again and reaches the winding roll 11. 12 is an adhesion prevention plate, 13 is an oxygen introduction pipe, and 14 is an argon introduction pipe.

The ultimate pressure during film formation was 3 x 104 Pa, the Ar gas pressure was 0.30 Pa, the oxygen introduction was 8 cc/min, and the input power per medium area was 4 W/ca+'. At this time, the deposition rate was The driving speed of the sample film is 15 cm/min at approximately 2 OA/sec.

Example 2 J'/Sil After forming a Co-Ni-P alloy layer with a thickness of 0.4 μm on a 2 μm polyethylene terephthalate film substrate by plating, Co-Cd was coated in the same manner as in Example 1. An oxide protective layer of the mixture was formed.

Example 3 Co-P with a thickness of 0.4μ was deposited on the same substrate F as in Example 1.
After forming the t-alloy layer by vacuum evaporation.

A protective layer of Co--Cd 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.
Co-Cd was formed using the apparatus shown in Figure 3.
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 device 18. Inside this small room, an electric gun 17 is installed, and the electron beam that will be emitted from it will cause a crucible! Co-Cd pellet 1 in 8
Heat 9. The purpose of providing the partition wall is to maintain the interior at a high vacuum to prevent damage to the rifle due to oxygen flow.

Ultimate pressure is 5 x 105 Pa, oxygen introduction jt+L
is 12 cc/min, the deposition rate is approximately 50 OA/sec, and the sample film feed rate is 3.5 layers/min.

Example 5 After forming a similar Co-Cr alloy layer on the same substrate as in Example 1, a Co-Cd layer was formed using the same device, and this surface was subjected to plasma oxidation using the apparatus shown in FIG. A protective layer was formed by doing this. The sample is passed through an oxygen plasma generated between the electrodes 2o.

Perform plasma oxidation.

The conditions are vacuum degree 0.30 Pa, oxygen partial pressure 0.08 Pa, input power 300 W, and sample film feeding speed 40 c.
+s/min.

Comparative Examples 1-5 Samples prepared in the same manner as Examples 1-5 were used as Comparative Examples 1-5, respectively, except that a 1% Ca oxide containing Cd was used in the layer.

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 a Co-CdIv compound containing 40% Cd was used as the protective layer.

: IS1 table shows the Cd content of the protective layer, durability, and corrosion resistance test results for Examples and Comparative Examples listed in L. However, Cd-containing 11+L indicates the ratio of the number of Cd atoms to the number of metal (i.e., Co+Cd) J';(E-) contained in the layer.

The durability test was carried out using 8 samples of Examples and Comparative Examples.
■ After cutting to width and making into tape shape, 8-layer VT of City IM
This was done using an R deck. The method was to record a test pattern and then perform il+raw repeatedly to examine changes in head output and number of dropouts depending on the number of passes. IfI
Judgment of J durability), ':, quasi are as follows. <Repeat 1q raw 100 passes [A decrease in output of 1 is within 3 dB of the initial output, B is 3 dB or more.

In addition, those in which the number of droplets I/min exceeded 200 before reaching 100 passes were rated C. In addition, the way to count dropouts is as follows: 15. It was counted as one when it followed the second mark.

For the corrosion resistance test, sample tape prepared in the same manner as in 1.
After leaving it in a constant temperature and humidity chamber at 0° C. and 70% humidity for 50 hours, recording was performed using the same deck as described in L. 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. If the part that cannot be reproduced appears repeatedly, C1 is normally recorded at 11 + the part that can be recorded is 20 of the total length of the tape.
% or more 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 and approximately 50 pm thick film as the substrate in the above-mentioned Examples and Comparative Examples.
This is a recording of the BPI signal.

Judgment of durability), (Quasi is A if the low F of the output after running IQQ 10,000 passes is within 3 dB compared to the initial output, B if it is 3 dB or more)
, The one in which stable 1rg raw output could no longer be obtained was designated as C.

1. The criteria for judging corrosion resistance is to record and play after leaving it under the same conditions as described in L. If there is no problem, it is A, if there is a drop in output, it is B, and if stable output cannot be obtained, it is C. did.

Table 2 [Effects of the Invention] As explained above, Co-Cd in the CO-based alloy magnetic layer
By providing a protective layer formed by oxidizing the mixture, it was possible to significantly improve the corrosion resistance while maintaining the same or higher durability than in the case of providing a conventional protective layer.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram showing the basic structure of a metal thin film magnetic recording medium with undeveloped IJJ, Figure 2 is a schematic diagram of the high frequency sputtering equipment used to form the protective layer, and Figure 3 is a schematic diagram of the high frequency sputtering equipment used to form the protective layer. The vacuum evaporation equipment used for the formation is shown in Figure 4, and the plasma oxidation equipment used to oxidize the Hoichiki layer is shown in Figure 4. 1: Non-magnetic substrate, 22 CO alloy magnetic layer, 3: Co
-Cd oxide protective layer, 4: Vacuum chamber, 5: Exhaust device, 6
:Co-Cd mixture target. 7: Sample tape, 8: Unwinding roll. 9: Intermediate free roller, 10: Drive can, 11: Winding roll, 12: Anti-adhesion plate, 13 Dioxygen introduction pipe, l4: Argon introduction pipe, 15: Distance r<*. 16: Exhaust device, 17: Electric f-gun, 18 Nil pressure point. 19: Co-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-Cd mixture 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.