JPH0133924B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a longitudinal metal thin film type magnetic recording medium and a method for manufacturing the same, and an object of the present invention is to improve magnetic properties by adding Cr to a Co-Ni magnetic layer. , and improve corrosion resistance.

In recent years, in the field of video or digital recording, research on metal thin film type magnetic recording media has been progressing in order to achieve higher recording densities.
This is a method of depositing a magnetic layer mainly made of ferromagnetic metals such as Fe, Co, and Ni, or their alloys, or intermetallic compounds on a nonmagnetic substrate using vacuum evaporation, electroplating, chemical plating, sputtering, or ion plating. It is directly formed by a method such as plating. In particular, vacuum evaporation methods, ion plating methods, etc. are attracting attention from the viewpoint of mass production and pollution-free properties.

On the other hand, the conditions required for this type of magnetic recording medium are first of all excellent magnetic properties, especially high coercive force (Hc) (approximately 1000 O¨e). For this purpose, a method called oblique evaporation has traditionally been used, but this method alone requires an incident angle of approximately 65 degrees or more (the angle of incidence relative to the normal to the evaporation surface), and the evaporation source It is difficult to mass-produce the steam as it cannot be used effectively. The next required condition is excellent corrosion resistance. It is generally considered that surface treatments, overcoats, and corrosion-resistant alloys can be used to solve this problem. For industrialization, at least both of these issues must be solved at the same time at a mass production pace, but so far they have not been achieved to a satisfactory level.

The present invention was obtained through examination and testing of various magnetic materials and film-forming conditions to solve the above-mentioned problems, and will be described below with reference to examples and drawings.

FIG. 1 is a perspective view of a longitudinal metal thin film magnetic recording medium as a sample. The magnetic layer 2 of the present invention is formed on a nonmagnetic substrate 1 made of nonmagnetic glass, plastic, metal, etc. by vacuum evaporation, ion plating, or the like.

FIG. 2 shows a schematic diagram of an experimental apparatus in which the present invention was studied. In the figure, 3 indicates a vacuum deposition chamber, and the inside of the chamber 3 is evacuated by a vacuum pump system 4 and maintained at an appropriate degree of vacuum. An evaporation source 6 is installed below the chamber 3 to house a ferromagnetic metal 5 and heat it to melt and evaporate it. Above that, a nonmagnetic substrate 1 made of a nonmagnetic material such as glass, plastic, metal, etc. is set on a substrate support 7 obliquely with respect to the direction of the vapor. This oblique angle θ (generally called the angle of incidence) can be changed arbitrarily.

The present inventors conducted experiments by variously changing this angle of incidence. A shutter 8 is provided between the evaporation source 6 and the substrate 1 so that the evaporation is performed on the substrate 1 only for the necessary time. Reference numeral 9 denotes a gas introduction port that determines the atmosphere during vapor deposition, and this is connected to an external introduction gas cylinder 10. Experiments were conducted by introducing various gases into the vacuum deposition chamber 3.

Next, a study of magnetic materials to solve the above problems will be described. Co-Ni, which is relatively easy to generate coercive force among various ferromagnetic metals, was used as the base material. However, in the case of Co-Ni, the coercive force decreases rapidly when the Ni content is 55% by weight or less, so it was excluded from the scope of study. Typical film formation conditions are a film formation rate of 10 Å/sec to 1000 Å/sec, and a film thickness of
The thickness was about 500 Å to 1000 Å, the substrate temperature was 0° C. to 200° C., and the substrate was glass and polyimide film. These base materials are then coated with various elemental metals (e.g. Be,
B, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Cu,
Zn, Ge, Ga, Zr, Nb, Mo, Rh, Pd, Ag,
In, Sn, Pt, Au, Bi, Gd, Sm, etc.) is 0
It was sequentially added up to 30% by weight and deposited, and the resulting samples were examined for magnetic properties and corrosion resistance. Magnetic properties are measured mainly by measuring coercive force and squareness ratio using a sample vibrating magnetization measuring device (usually called a VSM).
Corrosion resistance tests are performed in high humidity environments at two levels: 40°C, 90% and 60°C, 90%, and the occurrence of corrosion over time is determined by observing the presence or absence of discoloration in the form of spots using an optical microscope. It is. From this series of experiments, it was concluded that only the material to which Cr was added was superior in both magnetic properties and corrosion resistance.

This will be discussed in detail below. FIG. 3 shows the state of improvement in the magnetic properties, and shows the relationship between the vapor incidence angle and the coercive force. According to this, it can be seen that a lower incident angle is sufficient than when trying to obtain a certain desired coercive force. For example, 1000O¨e is
Obtained at an angle of incidence of 45 degrees to 50 degrees. Next, Co−Cr
-Narrowing down the material to Ni and further improving film formation speed and substrate temperature.
Cr composition. Substrate material. Film thickness. Degree of vacuum. The relationship between atmospheric gas and film formation conditions was investigated in detail.

As a result, it was found that Cr composition and vacuum degree, especially oxygen partial pressure in residual gas, are important. These are shown in FIGS. 4 and 5. At this time, Cr
The composition was determined by atomic absorption spectrometry. From these figures, (i) there is a limit to the amount of Cr added in order to significantly increase the coercive force Hc, that is, it must be in the range of 2 to 15% by weight. (ii) It was found that when the degree of vacuum during vapor deposition, especially when the partial pressure of oxygen in the residual gas exceeds 10 ^-4 torr, Hc begins to decrease rapidly and the effect of Cr addition disappears. These Cr
The effects of the amount added or the partial pressure of oxygen in the residual gas are as follows:
This is thought to be due to the effect on crystal growth during the deposition of the Co--Ni magnetic layer, but the exact cause has not yet been determined.

Although the present invention limits the amount of Cr added to Co-Ni, even when other elemental metals are included, as long as this relationship is satisfied, the scope of the present invention falls within the scope of the present invention.

Next, other embodiments of the present invention will be described.

FIG. 6 shows an example of an apparatus for producing the magnetic recording medium according to the present invention on an industrial scale, in which a film transport system is installed in a vacuum chamber and a long magnetic recording medium is obtained by continuous vapor deposition. It is something that can be done. In the figure, the same parts as the device in Figure 2 are given the same numbers, and the different parts are explained as follows:
11 is an unwinding roll, and plastic film 1
2 is wound, and the film 12 is conveyed along with the cylindrical can 13. At this time, the cylindrical can 13 is also rotating in the same direction to assist the traveling.
Subsequently, it is wound up with a winding roll 14. During this time,
Vapor deposition takes place below the cylindrical can 13. 15
is a mask that controls the oblique components of vapor. At this time, a wide range of incident angle components is included, but the minimum incident angle θmin is representative of the incident angle. When the characteristics of the magnetic film produced using this apparatus were compared with those of the magnetic film produced under the static film forming conditions shown in FIG. 2, both magnetic properties and corrosion resistance were basically the same. Next, we will summarize their effects.

(i) Magnetic properties: O ₂ partial pressure in residual gas during evaporation
10 ^-4 torr or less and reduce the Cr content.
The magnetic layer with 2 to 15% of Co-Ni-Cr is
A coercive force of nearly 1000O¨e was obtained at an incident angle of nearly 45 degrees, and a squareness ratio of over 0.9 was obtained.
It has ideal magnetic properties. In the conventional method using a continuous evaporator shown in Fig. 6 without adding Cr, the film thickness is 500 Å at a film speed of 4 to 5 m/min.
A sample with a coercive force of 1000 O¨e was prepared, but with the present invention, in which Cr is added, the speed can be increased to about 30 m/min with the same input power.

(ii) Corrosion resistance: Cr is generally known as a corrosion-resistant metal and is widely used for plating, etc.; however, in the accelerated corrosion resistance test mentioned above, Cr
Corrosion resistance of the samples with the addition of chlorine was improved compared to the samples without the addition of . An example of this is shown in FIG. This figure shows that in both tests, no change was observed in the products to which Cr was added even after more than 100 days. Corrosion, which is a fatal problem for magnetic recording media as it causes speckled discoloration and peeling, has been considerably improved.

As described above, the addition of Cr according to the present invention not only improves the magnetic properties but also improves the corrosion resistance, making a great contribution to the industrialization of metal thin film magnetic recording media.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a magnetic recording medium according to the present invention;
Figure 2 is a schematic cross-sectional front view of the experimental equipment used to carry out the manufacturing method of the present invention, Figures 3 and 4.
5 shows the magnetic characteristics of the magnetic recording medium, FIG. 6 shows a schematic cross-sectional front view of the manufacturing equipment used to carry out the manufacturing method of the present invention, and FIG. 7 shows the corrosion resistance of the magnetic recording medium. It is a diagram. DESCRIPTION OF SYMBOLS 1... Nonmagnetic substrate, 2... Magnetic layer, 3... Vacuum deposition chamber, 5... Magnetic metal, 6... Evaporation source, 12...
...Nonmagnetic substrate (plastic film), 13...
...Cylindrical can.

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer is formed on a non-magnetic substrate, wherein the magnetic layer mainly consists of Co, Ni, and Cr, and the content of Cr is greater than that of Co, Ni, and Cr. An in-plane metal thin film type magnetic recording medium characterized in that the magnetic flux is 2 to 15%. 2 Mainly composed of Co, Ni, and Cr on a non-magnetic substrate, and the content of Cr is 2 to 2 with respect to Co, Ni, and Cr.
15%, the magnetic layer is formed by vacuum evaporation in a residual gas having an oxygen partial pressure of 10 ^-4 Torr or less. Production method.