JPH02220224A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium with excellent magnetic characteristics and durability by introducing O2 gas cooled below 0 deg.C in the process of forming a magnetic metal thin film on a nonmagnetic supporting body by vapor deposition. CONSTITUTION:A long-length nonmagnetic supporting body 2 is released from an unwinding roll 3, run on a cooling can 5 and wound up by a winding roll 4. The cooling can 5 contains a cooling device inside (not shown in the figure) to eliminate deformation of the supporting body 2 due to elevation of temperature. The O2 gas is cooled by a cooling device to below 0 deg.C and introduced into the chamber 1 through a O2 gas feeder 9, the nozzle of which is disposed near the cooling can 5 to blow the O2 gas over the width of the supporting body 2. By introducing the O2 gas below 0 deg.C, the oxygen concentration in the center region of the magnetic layer can be decreased, which results in a magnetic recording medium with excellent magnetic characteristics and durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a so-called vapor deposition type magnetic recording medium in which a magnetic layer is a metal magnetic thin film.

[Summary of the invention]

The present invention aims to improve magnetic properties and durability by introducing cooled oxygen gas when forming a metal magnetic thin film on a nonmagnetic support by vapor deposition.

[Conventional technology]

Conventionally, magnetic recording media have been made by using a powder magnetic material such as oxide magnetic powder or alloy magnetic powder on a non-magnetic support and a vinyl chloride-vinyl acetate polymer.

BACKGROUND ART Coating-type magnetic recording media, which are manufactured by coating and drying a magnetic paint dispersed in an organic binder such as polyester resin or polyurethane resin, are widely used.

On the other hand, with the increasing demand for high-density magnetic recording, metal magnetic materials such as Co-Ni alloys and co-O alloys have been developed using vacuum thin film forming means such as vacuum evaporation, sputtering, or ion blating. A so-called metal magnetic thin film type magnetic recording medium, which is directly deposited on a non-magnetic support such as a polyester film or a polyimide film, has been proposed and is attracting attention. This magnetic recording medium is
It not only has excellent coercive force and squareness ratio, and excellent electromagnetic conversion characteristics at short wavelengths, but also has extremely small thickness loss during recording demagnetization and reproduction because the thickness of the magnetic layer can be made extremely thin. It has many advantages, such as being able to increase the packing density of nonmagnetic material in the magnetic layer.

In order to manufacture this metal magnetic thin film type magnetic recording medium, as disclosed in, for example, Japanese Unexamined Patent Publication No. 63-121126, a metal magnetic thin film is used to further increase the coercive force of the resulting magnetic recording medium. A method has been proposed in which oxygen gas is simultaneously introduced during vapor deposition. According to this method, not only the magnetic properties such as coercive force are improved in both vertical and oblique evaporation, but also the durability is improved because an oxide film is formed on the surface of the magnetic layer, and the electromagnetic conversion It is said that it will also be easier to control the characteristics.

[Problem to be solved by the invention]

By the way, oxygen gas introduced during vapor deposition of a metal magnetic thin film is usually introduced at room temperature (for example, about 20° C.).

However, when oxygen gas is introduced at room temperature, the thickness of the oxide film formed on the surface of the magnetic layer becomes very thin, or the oxygen concentration at the surface is low and the oxide film is not dense. Furthermore, the oxygen concentration tends to be higher in the central portion of the magnetic layer in the thickness direction. In this way, if the surface oxide film is thin or the oxygen concentration on the surface is low, durability will deteriorate, and if the oxygen concentration in the center of the magnetic layer is too high, the magnetic properties will deteriorate. arise.

In order to deal with this problem, conventionally the distribution of the oxygen gas has been controlled by various combinations of the oxygen gas blowing position, direction, oxygen gas flow rate, etc., but this method does not solve these problems. I couldn't do it.

Therefore, the present invention was proposed in view of the conventional situation, and an object of the present invention is to provide a method for manufacturing a magnetic recording medium that can control the distribution of oxygen gas and improve magnetic properties and durability. It is something to do.

[Means to solve the problem]

The method for manufacturing a magnetic recording medium of the present invention has been proposed to achieve the above object, and includes cooling to below 0°C when forming a metal magnetic thin film on a non-magnetic support by vapor deposition. This method is characterized by introducing oxygen gas.

The magnetic recording medium manufactured according to the present invention is a so-called vapor deposition type magnetic recording medium in which a magnetic layer is a metal magnetic thin film.

Here, as the metal magnetic material constituting the metal magnetic thin film, any material normally used in this type of medium can be used. Examples include magnetic metals such as Fe, Co, and Ni, Fe-Co, Co-Ni, Fe-Co-Ni, and C.

Cr, Fe-Co-Cr, Co-Ni-Cr.

These include alloys such as Fe-Co-Ni-Cr, or metal oxides such as Co-○.

Furthermore, as the non-magnetic support, those commonly used in this type of media can be used, such as polyethylene terephthalate (PET) film.

Polyester resin films such as polyethylene-2,6-naphthalate and aromatic polyamide films.

Examples include polyimide resin films.

The temperature of the oxygen gas introduced when depositing the metal magnetic thin film is set to below O'C. More preferably, the temperature is -20°C or lower. Here, the reason why the temperature of the introduced oxygen gas is set to be 0°C or lower is that if the oxygen gas temperature is 0°C or higher, the surface oxide film of the magnetic layer becomes thin, the durability deteriorates, and at the same time, the temperature at the center of the magnetic layer increases. This is because the oxygen concentration increases and the magnetic properties also deteriorate. Note that the temperature of the oxygen gas needs to be at least 0°C or less at the time of introduction into the chamber, and of course this condition must be met when it is blown out from the tip of the oxygen gas introduction pipe arranged in the chamber. Good too.

As a method for reducing oxygen gas to below O'C, for example, a cooling pipe or the like through which a refrigerant (e.g., liquid nitrogen) is passed is placed around or inside the oxygen gas introduction pipe led into the chamber. Examples include a method of cooling itself. Note that the means is not limited to this, and liquefied oxygen may also be used.

Regarding the oxygen gas flow rate, for example, when the non-magnetic support is tape-shaped and its width is about 150Ilff1, it is desirable to be about 150 to 400 d/min. Also, regarding the direction in which oxygen gas is introduced, It may be on the upstream side or downstream side in the running direction of the non-magnetic support.

Note that the vapor deposition method employed in the present invention is to evaporate magnetic materials such as pure metal 8 alloys or metal oxides under vacuum using resistance heating, high frequency heating, electron beam heating, etc., onto the non-magnetic support. This is the so-called vacuum evaporation method. Here, in order to manufacture magnetic recording media such as tape,
In order to increase the coercive force, a so-called oblique evaporation method is used in which the magnetic material is deposited on the non-magnetic support from an oblique direction, but the present invention is not limited to this oblique evaporation method. may be used.

[Function] According to the method for manufacturing a magnetic recording medium of the present invention, 1. Since oxygen gas cooled to below O'C is introduced when depositing a metal magnetic thin film, its kinetic energy becomes small and most of the oxygen is absorbed into the film near the oxygen gas introduction tube (i.e. near the end of the vapor deposition). It is estimated that this will be incorporated into the Therefore, the surface oxide film becomes thicker and the oxygen concentration at the center of the magnetic layer becomes lower.

〔Example〕

Hereinafter, specific examples to which the present invention is applied will be described.

First, the vapor deposition apparatus used in this example will be explained with reference to FIG.

As mainly shown in the first part, the above vapor deposition apparatus has an unwinding roll (3), a winding roll (4),
), a traveling system consisting of a cooling can (5), a container (6) containing a metal magnetic material (7) which is an evaporation source, and an oxygen gas introduction pipe (9) that introduces oxygen gas during vapor deposition. It is constructed by accommodating.

A long non-magnetic support (2) is sequentially passed over the unwinding roll (3), cooling can (5), 9 winding rolls (4), and is cooled by the unwinding roll (3). Can (5
) side and is finally wound up on the winding roll (4). Further, a cooling device (not shown) is provided inside the cooling can (5),
It is designed to control deformation of the non-magnetic support (2) due to temperature rise.

The storage container (6) is arranged below the cooling can (5). The metal magnetic material (7) accommodated in the container (6) is heated and evaporated by an electron gun (not shown), and the non-magnetic support (2) runs around the outer periphery of the cooling can (5). A magnetic layer is deposited thereon.

Further, a curved shutter (8) is disposed near the outer periphery of the cooling can (5) to block metal storage airflow caused by heating and evaporation of the metal magnetic material (7). The shutter (8) covers a predetermined area of the non-magnetic support (2) so that the metal vapor flow is obliquely deposited at a predetermined angle range with respect to the non-magnetic support (2).

Further, on the downstream side in the running direction of the non-magnetic support 2), that is, on the low incidence angle side of the metal vapor flow, an oxygen gas introduction pipe (9) guided from the outside into the chamber (1) is arranged. ing. This oxygen gas introduction pipe (9) is provided with, for example, a cooling mechanism through which a refrigerant passes, and the oxygen gas introduction pipe (9)
The temperature of the oxygen gas flowing through the tube is kept below O'C. In addition, the said cooling mechanism may be provided in any of the tubes inside and outside the chamber (1). Of course, it is only necessary that the temperature of the oxygen gas be below O'C at the time it is introduced into the chamber (1), so it is not necessary to provide it in the tube inside the chamber (1), but in order to eliminate temperature distribution, (1) It is desirable to provide a cooling mechanism for the inner tube as well. Further, the tip of the oxygen gas introduction pipe (9) is
A non-magnetic support (2) is provided close to the cooling can (5) and runs along the outer periphery of the cooling can (5).
) Oxygen gas is blown out over the entire width direction.

In this example, the oxygen gas introduction pipe (9) was arranged on the low incidence angle side of the non-magnetic support (2) in the running direction, but of course it was arranged on the high incidence angle side of the non-magnetic support (2) in the running direction. It may also be arranged on the upstream side.

A non-magnetic support (
2) To form a metal magnetic thin film thereon, first, the inside of the chamber (1) is evacuated, and then the non-magnetic support ( 2)
run. Then, the metal magnetic material (7) is heated and evaporated using an electron gun or the like, and the metal vapor flow is directed to the non-magnetic support (2) which travels along the outer periphery of the cooling can (5) by operating the shutter (8). ) is supplied to a predetermined angle range. At this time, at the same time, oxygen gas cooled with a refrigerant or the like at a temperature of 0° C. or lower is introduced from the oxygen gas introduction pipe (9). Then, the metal magnetic material (7) is deposited on the non-magnetic support (2) running along the outer periphery of the cooling can (5), forming a metal magnetic thin film having a thick oxide film. be done. Then, a non-magnetic support (2
) is wound up on the take-up reroll (4).

Here, a magnetic recording medium was produced using the above vapor deposition apparatus under the following conditions.

A long polyethylene terephthalate film (PET film) with a width of 150 cm was used as the nonmagnetic support, and Co was used as the metal magnetic material. An alloy material having a composition expressed as Ni1O (numbers represent atomic %) was used, the running speed of the nonmagnetic support was 20 m/min, the minimum incident angle for oblique deposition was 451, and oxygen gas was After cooling to -25°C with a refrigerant, the above PE was introduced at a gas flow rate of 200 m/min.
A metal magnetic thin film was formed on the T film to a thickness of 2000 mm.

Note that the outlet of the oxygen gas introduction pipe is 1 point from the cooling can.
It was placed on the low incidence side 5cm away. In addition, the introduced oxygen gas is 125 cm at the time it exits from the outlet of the oxygen gas introduction pipe.
The tube inside the chamber was also cooled with a refrigerant so that the temperature was ℃.

Comparison Team In this comparative example, a metal magnetic thin film was formed on a PET film while introducing oxygen gas at 20° C. from an oxygen gas introduction tube. The oxygen gas introduction pipe used here was one that was not equipped with a cooling mechanism, etc., which is normally used in this type of pipe.
A magnetic recording medium was otherwise manufactured in the same manner as in the experimental example.

The magnetic properties, durability, and presence or absence of rust on the surface of the magnetic layer were measured for each magnetic recording medium manufactured in the above experimental examples and comparative examples, and the distribution state of oxygen contained in the magnetic layer of these magnetic recording media was also measured. was measured by depth profiling using Auger electron spectroscopy.

The results are shown in the table below and Figure 2. In FIG. 2, the vertical axis shows the oxygen content, and the horizontal axis shows the thickness of the magnetic layer, and the line a shows the experimental example, and the line b shows the comparative example.

The magnetic properties measured here were coercive force Hc and residual magnetic flux ψr, and durability was defined as still property and shuttle property. The still characteristics were determined by recording a 4.2 MHz video signal on a magnetic recording medium and measuring the time until the reproduction output attenuated to 50%. On the other hand, the shuttle characteristics were determined as a decrease in output when the magnetic recording medium was run 200 times. Regarding the presence or absence of rust on the surface of the magnetic layer, the temperature was 60°C and the relative humidity was 95%.
After leaving it under the conditions of 14 days, the surface of the magnetic layer was optically exposed! J
The occurrence of rust was visually observed using an i@mirror. In addition, those with no rust were evaluated as Δ, and those with slight O1 rust were evaluated as Δ.

(The following is a blank space) As can be seen from the above results, it can be seen that the experimental examples exhibit higher still characteristics than the comparative examples. This is because, as can be seen from FIG. 2, the concentration of oxygen present on the surface of the magnetic layer is higher in the experimental example than in the comparative example. In other words, when considering the thickness of the oxide film on the surface, in Comparative Example E, the oxygen concentration near the surface gradually decreases and the effective thickness of the oxide film becomes thinner. It is thought that durability is improved because the oxygen concentration is reliably increased and the effective thickness of the oxide film becomes thicker up to the depth of .

On the other hand, regarding the magnetic properties, especially the residual magnetic flux ψr, it can be seen that the experimental example shows a better value than the comparative example. This is because, as can be seen from FIG. 2, the oxygen concentration at the center of the magnetic layer was lower in the experimental example than in the comparative example.

It can also be seen that the experimental example has better reliability against mackerel.

[Effects of the Invention] As is clear from the above explanation, according to the method of the present invention, oxygen gas cooled to below 0°C is introduced when depositing a metal magnetic thin film, so that the surface of the magnetic layer is The oxide film can be made thicker, and the oxygen concentration at the center of the magnetic layer can also be lowered.

Therefore, the obtained magnetic recording medium has excellent magnetic properties and durability, and is free from rust and has excellent reliability, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the configuration of a vapor deposition apparatus used in Examples. FIG. 2 is a characteristic diagram showing the distribution state of oxygen in the magnetic layer. 2...Nonmagnetic support 5...Cooling can 7...Gold m1tt material 9...Oxygen gas introduction tube Patent applicant Sony Corporation representative Patent attorney Akira Koike (and two others) Figure 1 Figure 2

Claims (1)

[Claims] 1. A method for producing a magnetic recording medium, which comprises introducing oxygen gas cooled to 0° C. or lower when forming a metal magnetic thin film on a non-magnetic support by vapor deposition.