JPH0121535B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a magnetic recording medium.

As a magnetic recording method with excellent short wavelength recording characteristics,
There is a perpendicular recording method. This method requires a perpendicular recording medium whose axis of easy magnetization is perpendicular to the film surface of the magnetic recording medium. When a signal is recorded on such a magnetic recording medium, the residual magnetization is oriented perpendicular to the film surface of the medium, and therefore, the shorter the wavelength of the signal, the smaller the demagnetizing field within the medium, and excellent reproduction output can be obtained.

Currently used perpendicular recording media are made by sputtering a magnetic layer containing Co and Cr as main components and having an axis of easy magnetization in the perpendicular direction, either directly on a non-magnetic substrate or through a soft magnetic thin film such as permalloy. It was formed by A sputtered film mainly composed of Co and Cr has a close-packed hexagonal crystal structure when the amount of Cr is approximately 30% by weight or less, and its c-axis can be oriented perpendicularly to the film surface. ,
In addition, since it is possible to reduce the saturation magnetization until the perpendicular anisotropic magnetic field becomes larger than the demagnetizing field, a perpendicularly magnetized film can be realized.

However, since the sputtering method slows down the formation speed of the magnetic thin film, it is difficult to produce a perpendicularly magnetized film at low cost.

In contrast to this sputtering method, the vacuum evaporation method (including methods that ionize some of the evaporated atoms, such as the ion plating method) has a thickness of several thousand Å/
The inventors have discovered that a Co--Cr perpendicularly magnetized film can be obtained at a formation speed as fast as seconds. In the vacuum evaporation method, a tape-shaped perpendicular recording medium can be obtained with high productivity by forming a thin film while moving the substrate along the circumferential side of a cylindrical can. FIG. 1 schematically shows the internal structure of such a vacuum evaporation apparatus. A substrate 1 made of a polymeric material runs along a cylindrical can 2 in the direction of arrow A. A mask 4 is placed between the evaporation source 3 and the cylindrical can 2, and the evaporated atoms pass through the slit S and adhere to the substrate 1. 5 and 6 are a supply roll and a take-up roll for the substrate 1, respectively.

In order for the Co-Cr vapor deposited film to become a perpendicular magnetization film,
The c-axis of the dense hexagonal structure is oriented perpendicular to the film surface,
It is necessary that the anisotropic magnetic field in the perpendicular direction be larger than the demagnetizing field. That is, it is necessary that the vertical anisotropy energy Ku becomes positive. As a result of experiments, we found that Ku depends on the substrate temperature Ts during deposition, and also on the coercive force in the direction perpendicular to the film surface (hereinafter simply expressed as Hc).
It was also revealed that the temperature depended on the substrate temperature during deposition.

Figure 2 shows the relationship between the substrate temperature Ts and Ku and Hc during vapor deposition. Curve A in the figure shows the relationship between Ku and Ts,
Further, curve B shows the relationship between Hc and Ts.
It can be seen from this that both Ku and Hc increase as Ts increases.

When a Co--Cr perpendicularly magnetized film was produced using the apparatus shown in FIG. 1, the properties varied in the width direction and the length direction, and a stable film could not be obtained. An investigation into the cause of this revealed that the adhesion of the substrate to the can is not uniform, with some parts adhering closely to the can and others not, resulting in variations in characteristics. That is, as shown in FIG. 3, a portion 7 of the substrate 1 that is in close contact with the can 2 and a portion 8 that is floating from the can 2 are formed. During vapor deposition, the temperature of the substrate 2 does not rise much because the heat diffuses into the can 2 in the contact area 7;
Because heat cannot diffuse in the floating part 8,
The temperature of the substrate 2 increases. As a result, the contact area 7
Ku and Hc have larger values than the floating part 8.

An object of the present invention is to provide a method for forming a Co-Cr perpendicularly magnetized film with less variation in properties in the longitudinal and width directions by uniformly adhering a substrate made of a polymeric material to a can. It is something to do.

FIG. 4 shows the basic configuration of an apparatus for carrying out the method of the present invention. In the figure, 21 is the can 2
This is a substrate made of a polymeric material and has a conductive film formed on the opposite surface in contact with 2. A DC voltage is applied between the metal roller 23 and the can 22 by a power source 24. Note that the polarity of the applied voltage may be opposite to that shown in the figure, or may be alternating current instead of direct current. Since the substrate 21 runs with the conductive film in contact with the metal roller 23, an attractive force due to static electricity is generated between the conductive film and the can 22, so that the substrate 21 is evenly adhered to the can 22. If a Co--Cr film is formed in this state, a Co--Cr perpendicularly magnetized film with less variation in properties in the longitudinal and width directions can be obtained.

In the figure, 25 is an evaporation source, 26 is a mask, and 27 and 28 are a supply roll and a take-up roll, respectively.

FIG. 5 shows an example of the relationship between the voltage applied between the metal roller 23 and the can 22 and the longitudinal variation of Hc. However, the maximum value of Hc in the longitudinal direction of a 1 m long area is defined as Hcmax, and the minimum value is
When Hcmin is set, Hcmax−Hcmin/Hcmax is defined as the longitudinal variation of Hc. From this figure,
It can be seen that when the applied voltage exceeds 30V, the fluctuation in Hc decreases rapidly. Furthermore, when the applied voltage exceeds 200 V, electric discharge occurs between the metal roller 22 and the substrate 21 on which the conductive film is formed, and between the can 22 and the substrate 21, so that the resulting magnetic recording medium has no pins. Many holes occur. Therefore, it is preferable to set the applied voltage within the range of 30 to 200V.

Examples of the method of the present invention will be described below.

Example 1 Thickness made of polyamide heat-resistant polymer material
A Cu film with a thickness of 700 Å was formed on a 10 μm substrate by vapor deposition, and a voltage of 60 V was applied to the metal roller with respect to the can using the apparatus shown in Figure 4 to form a Cu film with a thickness of 1500 Å.
As a result of depositing a Co--Cr film with a thickness of .ANG., a Co--Cr perpendicularly magnetized film with uniform properties in the longitudinal and width directions was obtained. FIG. 6 shows the structure of the magnetic recording medium obtained as described above. In the figure, 31 is a substrate;
32 and 33 are a Cu film and a Co-Cr perpendicular magnetization film, respectively.

Example 2 Thickness made of polyamide heat-resistant polymer material
A permalloy film with a thickness of 1500 Å was formed on a 10 μm substrate by vapor deposition, and a 1500 Å thick Co-Cr film was deposited using the apparatus shown in Figure 4 by applying a voltage of 60 V to the metal roller relative to the can. A Co-Cr perpendicular magnetization film with uniform properties in the longitudinal and width directions was obtained on the permalloy film.

As described above, according to the method of the present invention, one side of the substrate made of a polymeric material having a conductive film formed on both sides is moved while the other side is brought into contact with the conductor. When forming a magnetic layer mainly composed of Co and Cr whose axis of easy magnetization is perpendicular to the film surface on the side of the substrate by vacuum evaporation, a voltage is applied between the conductive film on the substrate and the conductor. To apply the voltage, the substrate uniformly contacts the conductor. This ensures uniform properties in the longitudinal and width directions.
A Co-Cr perpendicular magnetization film can be obtained.

[Brief explanation of drawings]

Figure 1 shows the basic configuration of an apparatus for manufacturing perpendicular recording media using the vacuum evaporation method, and Figure 2 shows the perpendicular anisotropy energy Ku and the perpendicular FIG. 3 is a diagram showing the relationship between the coercive force Hc in the direction and the substrate temperature Ts during vapor deposition, and FIG. 3 is an enlarged sectional view of the main part for explaining the state of contact of the substrate to the can in this apparatus. Fig. 4 shows an example of the configuration of an apparatus for carrying out the method of the present invention, and Fig. 5 shows the voltage applied between the can of this apparatus and the conductor on the substrate and the variation of the coercive force Hc in the perpendicular direction. FIG. 6 is a cross-sectional view of a magnetic recording medium obtained by an example of the method of the present invention. 21...A substrate made of a polymeric material on which a conductive film is formed on the surface opposite to that in contact with the can, 22
...Can, 23...metal roller, 24...power supply, 25...evaporation source.

Claims (1)

[Scope of Claims] 1. While moving a substrate made of a polymeric material on which a conductor film is formed on one side with the other side in contact with a conductor, one side of the substrate is moved. Co and Co whose axis of easy magnetization is perpendicular to the film surface.
A method for manufacturing a magnetic recording medium, comprising applying a voltage between the conductive film on the substrate and the conductor when forming a magnetic layer containing Cr as a main component by vacuum evaporation. 2. The method for manufacturing a magnetic recording medium according to claim 1, wherein the conductor is a cylindrical can.