JPH0572017B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a metal thin film type magnetic recording medium and a method for manufacturing the same. Conventional structure and its problems In recent years, with the demand for higher density magnetic recording,
In place of the conventional coated type magnetic recording media, development of metal thin film type magnetic recording media in which a ferromagnetic metal thin film is provided as a magnetic recording layer on a plastic substrate is actively underway. Metal thin film type magnetic recording media can be obtained by forming a ferromagnetic metal thin film of Co, Fe, Ni, or an alloy thereof on a plastic substrate by oblique incidence evaporation or oblique incidence ion plating. It was found that there were problems as described below. (i) In order to improve magnetic properties, especially coercive force, the angle of incidence must be increased, which reduces mass productivity. (ii) In general, many of these ferromagnetic metals have poor corrosion resistance and require some kind of countermeasure. OBJECTS OF THE INVENTION It is an object of the present invention to improve coercive force and corrosion resistance without reducing mass productivity. Structure of the Invention The present invention involves depositing a metal with a negative standard electrode potential in an oxygen atmosphere to form an underlayer containing the metal and oxygen on a nonmagnetic substrate, and further forming a ferromagnetic metal thin film layer on the underlayer. It forms the DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows an example of an apparatus for manufacturing the magnetic recording medium of the present invention. As shown in the figure, vacuum chamber 1
consists of a first vacuum chamber 2 for forming an underlayer and a second vacuum chamber 3 for forming a magnetic layer, each of which is evacuated to 10 ^-4 to 10 ^-6 torr by independent evacuation systems 4 and 5. A substrate transport system consisting of an unwinding roll 6, a guide roll 8, a vapor deposition roll 10, and a winding roll 7 is installed in the vacuum chamber 1. The non-magnetic substrate 9 is mainly made of plastic, which is first wound around an unwinding roll, and is conveyed along the guide roll 8 and the vapor deposition roll 10 in the direction of the arrow.
Finally, it is wound up on a winding roll 7. While the non-magnetic substrate 9 is being transported, the base metal 11 is vapor-deposited on the non-magnetic substrate 9 by the heating source 12 in the first vacuum chamber 2 . At this time, oxygen gas is introduced from the gas introduction system 15 and the film is formed in an oxygen atmosphere. Subsequently, the second vacuum chamber 3 is entered, where a ferromagnetic metal 13 is vapor-deposited using a heating source 14 . At this time, the main magnetic properties are determined by the incident angle of the vapor defined by the oblique vapor deposition mask 17 and the amount of oxygen introduced from the oxygen introduction system 16. The magnetic recording medium manufactured in this way is
As shown in the figure. The nonmagnetic substrate 9 is made of a plastic film with a thickness of 10 to 20 .mu.m, and films of polyester, polyimide, polyamide, polycarbonate, etc. are generally used, but the present invention is not affected by the material of the substrate. The magnetic layer 19 is generally made of an alloy based on Co, and has a magnetic flux of 1000 Å/sec.
The film formation rate is 30~50℃, the minimum vapor incidence angle is 30~50℃, and the film thickness is 1000~2000Å. Next, conditions for forming the base layer 18 will be described. (i) Underlayer formation method; Physical vapor deposition methods such as sputtering, ion plating, and vacuum evaporation were investigated as methods for forming the underlayer. In all methods, the effect of introducing oxygen gas during film formation was confirmed. We focused on the vacuum evaporation method in terms of film formation speed and simplicity. (ii) Base film formation atmosphere; first vacuum chamber 2 at 10 ^-5 to 10 ^-6
Evacuate to torr, then from gas introduction system 15
Introducing various gases such as Ar, H ₂ , N ₂ , CH ₄ and O ₂ ,
The dependence on the atmosphere or the amount introduced was investigated. As a result, it was confirmed that only O ₂ gas had an effect on the atmosphere, and the amount introduced needed to be adjusted experimentally to obtain the maximum effect, taking into account the underlying material and film thickness. (iii) Base layer metal: Au, Ag,
We investigated Pt, Pd, and Cu, which have a positive standard electrode potential, and Fe, Ni, Co, Al, Sn, and Si, which have a negative standard electrode potential. the result,
There was clearly a difference between the two, with the negative standard electrode potential having a marked effect (details will be described later). Furthermore, in the case of magnetic materials such as Co and Ni, it is desirable to increase the amount of oxygen introduced to make them non-magnetic, considering the influence on magnetic properties. (iv) Base layer: The effect is seen from a base layer thickness of about 20 to 30 Å, and it tends to improve as the film thickness increases up to about 300 Å.
Above that, it tends to be saturated. Next, the magnetic properties and corrosion resistance of the magnetic recording medium obtained by the present invention will be described. First, the manufacturing conditions of the tested samples A to E are shown in the table. In addition, sample A
1 is a case where there is no underlayer, and D and E are cases where the underlayer does not contain oxygen, and both are for comparison.

[Table] All metals with a negative standard electrode potential have a strong affinity for oxygen and have the property of incorporating a large amount of oxygen into the underlying layer. This oxygen diffuses into the ferromagnetic metal thin film layer, improving magnetic properties and corrosion resistance. This is thought to lead to. In addition, the symbol "←" in the table on the previous page means "same as left."
This is the meaning of Figure 3 shows the magnetic properties of these samples. Measurements were performed using a sample vibrating type magnetometer. The horizontal axis shows the amount of oxygen introduced during magnetic layer formation.
The vertical axis shows coercive force. This figure shows that the coercive force can be significantly improved by providing an underlayer containing oxygen. This means that if you try to obtain the same coercive force as before,
The angle of incidence at the time of forming the magnetic layer can be lowered, and therefore, mass productivity can be improved by allowing effective use of steam. Figure 4 shows the corrosion resistance of each sample (in this case, magnetic layers with an oxygen introduction rate of 0.2/mm were used), and the saturation magnetic flux density versus the number of days left at 60°C and 90% humidity. This shows the changes in This figure shows that a decrease in corrosion resistance appears as a decrease in saturation magnetic flux density, but it can be seen that materials with an oxygen-containing underlayer are superior in terms of corrosion resistance as well. These phenomena are also thought to be caused by oxygen taken in during the formation of the underlayer diffusing into the grain boundaries of the magnetic layer. Effects of the Invention According to the present invention, a magnetic recording medium having high coercive force and excellent corrosion resistance can be easily obtained without reducing mass productivity.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an apparatus for manufacturing a magnetic recording medium according to the present invention, FIG. 2 is a cross-sectional view of a magnetic recording medium according to the present invention, and FIGS. 3 and 4 each illustrate the effects of the present invention. FIG. 3 shows the relationship between the amount of oxygen introduced during the formation of the magnetic layer and the coercive force, and FIG. 4 shows the change over time in the saturation magnetic flux density in a humid atmosphere. 1... Vacuum chamber, 4, 5... Vacuum exhaust system, 9...
Nonmagnetic substrate, 10... Vapor deposition roll, 18... Base layer, 19... Magnetic layer.

Claims (1)

[Claims] 1 Fe with a negative standard electrode potential on a nonmagnetic substrate,
At least one metal among Ni, Co, Al, Sn, and Si is deposited in an oxygen atmosphere to form a base layer, and then a ferromagnetic metal is deposited to form a ferromagnetic metal thin film layer on the base layer. A method for manufacturing a magnetic recording medium, characterized by forming a magnetic recording medium.