JPS5963027A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To improve magnetic stength and corrosion resistance without reducing mass-production capability by vapor-depositing a metal whose standard electrode potential is negative, in an oxygen atmosphere, forming a foundation layer containing metal and oxygen, on a nonmagnetic substrate, and also forming a ferromagnetic metal thin film layer on this foundation layer. CONSTITUTION:A substrate carrying system consisting of an uncoiling roll 6, a guide roll 8, a vapor-depositing roll 10 and a winding roll 7 is installed in a vacuum tank 1. A nonmagnetic substrate 9 consists essentially of plastic, is wound around the uncoiling roll, is carried along the guide roll 8 and the vapor-depositing roll 10 in the direction as indicated with an arrow, and is wound by the winding roll 7 in the end. While the nonmagnetic substrate 9 is carried, a foundation metal 11 is vapor-deposited onto the nonmagnetic substrate 9 by a heating source 12, in the first vacuum chamber 2. In this case, oxygen gas is led in from a gas leading-in system 15 and a film is formed in an oxygen atmosphere. Subsequently, the substrate goes into the second vacuum chamber 3, in which a ferromagnetic matal 13 is vapor-deposited by a heating source. In this case, a main magnetic characteristic is determined by an incident angle of vapor prescribed by a diagonal vapor-depositing mask 17, and the leading-in quantity of oxygen from an oxygen leading-in system 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a metal thin film type magnetic recording medium and a method for manufacturing the same.

Structures of conventional examples and their problems In recent years, along with the demand for higher density magnetic recording, metal thin films, in which a ferromagnetic metal thin film is provided as a magnetic recording layer on a plastic substrate, have replaced the conventional coated type. Development of magnetic recording media of this type is actively underway.

Metal thin film type magnetic recording media include Co, Fe, Ni,
Alternatively, a ferromagnetic metal thin film of these alloys can be formed on a plastic substrate by an oblique incidence evaporation method or an oblique incidence ion blating method, but it has been found that there are problems as described below.

(1) In order to improve magnetic properties, especially coercive force, the angle of incidence must be increased, which reduces mass productivity.

(11) 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 depositing a ferromagnetic metal thin film layer on this 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, the vacuum chamber 1 consists of a first vacuum chamber 2 for forming a base layer and a second vacuum chamber 3 for forming a magnetic layer, each of which is operated by an independent evacuation system 4, 6.
10. ．． It is exhausted to torr. In this vacuum chamber 1, an unwinding roll 6° guide roll 8. Vapor deposition roll 10.
A substrate transport system consisting of rolls 7 is installed. The non-magnetic substrate 9 is mainly made of plastic, and is first wound on an unwinding roll ((( 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, from the gas introduction system 15, Oxygen gas is introduced and a 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 1 and the amount of oxygen introduced from the oxygen introduction system 16.

A magnetic recording medium manufactured in this manner is shown in FIG. The nonmagnetic substrate 9 is made of a plastic film with a thickness of 10 to 20 μm, 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 mainly composed of Co,
0008/5 deposition rate, minimum vapor incidence angle 30-50
The film is formed at a temperature of 1,000 to 2,000 degrees Celsius.

Next, conditions for forming the base layer 18 will be described.

(1) Underlayer formation method: Physical vapor deposition methods such as sputtering, ion blating, and vacuum evaporation were examined 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.

(11) Underlying film forming atmosphere; first vacuum chamber 2 at 10 to 10
' Evacuate to torr, and then inject Ar, H2, N2, etc. from the gas introduction system 15. Introducing various gases such as CH4,02,
The dependence on the atmosphere or the amount introduced was investigated. As a result, it was confirmed that only the 02 gas was effective in terms of the atmosphere, and the amount introduced needed to be adjusted experimentally to obtain the maximum effect, taking into account the thickness of the two base materials.

41::) Base layer metal; As base layer metal, A u +
Ag + Pt, Pd, Cu having a positive standard electrode potential and Fe, Ni, Co, Al, Sn, Si having a negative standard electrode potential were investigated. As a result, there was clearly a difference between the two, with the negative standard electrode potential being more effective (details will be described later). Further, in the case of a magnetic material such as CO or N1, it is desirable to increase the amount of oxygen introduced and make it non-magnetic, considering the influence on magnetic properties.

Results were seen, and up to about 300 people showed improvement in film thickness.
Above that, it tends to be saturated.

Next, the magnetic properties of the magnetic recording medium obtained by the present invention,
Let's talk about corrosion resistance. First, the manufacturing conditions of the tested samples A to C are shown in a table. Note that Sample A is for comparison without a base layer.

[ Figure 3 shows the magnetic properties of these samples. Measurements were performed using a sample vibrating magnetometer. The horizontal axis shows the amount of oxygen introduced during the formation of the magnetic layer. The vertical axis shows the coercive force.From this figure, it can be seen that by providing an underlayer containing oxygen, the coercive force can be significantly improved. In order to achieve this, the incident angle at the time of forming the magnetic layer can be lowered, and therefore mass production can be improved by making effective use of steam.

Figure 4 shows the corrosion resistance of each sample (in this case, the magnetic layer had an oxygen introduction rate of 0.2 l/min), and shows the corrosion resistance against the number of days left at 60°C and 90% humidity. It shows the change in saturation magnetic flux density. From this figure, a decrease in corrosion resistance appears as a decrease in saturation magnetic flux density.
It can be seen that those with an oxygen-containing underlayer are also superior in terms of corrosion resistance.

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 sectional view of a magnetic recording medium according to the present invention, and FIGS. 3 and 4 are detailed diagrams of the present invention. These diagrams are for illustration purposes only; 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... Non-magnetic substrate, 1o... Evaporation roll, 18... - Base layer, 19...magnetic layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3

Claims (2)

[Claims] (1) A magnetic recording medium, characterized in that an underlayer and a ferromagnetic metal thin film layer are provided in this order on a nonmagnetic substrate, and the underlayer contains a metal with a negative standard electrode potential and oxygen. (2) A metal with a negative standard electrode potential is deposited in an oxygen atmosphere to form an underlayer on a nonmagnetic substrate, and then a ferromagnetic metal is deposited to form a ferromagnetic metal thin film layer on the underlayer. A method for manufacturing a magnetic recording medium, characterized by: