JPH0121537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal thin film magnetic recording medium.

The present invention also provides oblique deposition of Co, Co alloy,
In-plane magnetized film by sputtering such as Co-W,
It is useful for forming any ferromagnetic layer of perpendicularly magnetized films by sputtering, vapor deposition, ion plating, etc. such as Co-Cr, and can be used for wide-width media, whether in the form of magnetic tape or magnetic disk. In the process of forming a ferromagnetic layer on a polymer molded substrate, the aim is to make the characteristics uniform in the width direction and to improve mass productivity.

The density of magnetic recording has increased dramatically in recent years, and the shortest recording wavelength has reached the point where it is less than 1 μm.

Improvements are being made with the aim of achieving a further 0.5 μm or less, and the development of metal thin film media is becoming more active as an essential medium to achieve this goal.

Although the thin film forming technology that forms the basis of the production of such media has a wide range of applications and has been refined in various fields, there remain many unresolved problems when it comes to continuously obtaining large quantities of raw material. .

The technique of continuously forming a thin film on a polymer molded substrate is known as a roll-deposition technique, and has been put into practical use in the fields of metallized film capacitors, decorations, and packaging. Compared to Co-based alloys, which are materials for recording media,
The effect of radiant heat on the polymer molded product is small, and the thickness of the medium is required to be about 0.1 μm, whereas with Al, the thickness is only about 0.03 μm, and the effect of condensation heat is small.
Thermal effects on the substrate were hardly a problem.

If the evaporation source in a winding evaporation machine is replaced with an electron beam heating type or a sputter source, a magnetic thin film can be formed.

Regardless of whether it is an in-plane magnetized film or a perpendicularly magnetized film, the basic principle is to make the magnetization characteristics uniform in the width direction and the longitudinal direction.

This problem can be easily solved if the vapor deposition effect is ignored.

That is, it is sufficient to prepare an evaporation source with a width nearly twice the width of the substrate.

However, it is not necessarily easy to address this issue as a mass production technology.

When using an electron beam evaporation source as the evaporation source,
(i) The evaporation material is inserted into a wide container with a long axis in the width direction, and the residence time of the electron beam is changed depending on the position in the width direction of the substrate using deflection magnetic field scanning, and the film thickness is kept constant. Uniform characteristics. (ii) It is conceivable to arrange multiple small-capacity evaporation source containers in the width direction and control the evaporation rate of each individually to make the characteristics uniform, but depending on the relative position of the substrate and the evaporation source, ( Both i) and (ii) need to be readjusted.

When using a sputter source, the film thickness is relatively uniform, but if you try to make it more uniform,
There is no room for improvement.

In addition, the sputtering source has a slow film formation rate because the target is a magnetic material, and when power is applied forcibly, the thermal effect on the substrate becomes large and tends to become non-uniform.

Both require good and uniform characteristics, as well as the ability to process long items on wide substrates (at least 50cm) in a short time. Lack of either is a problem, and no satisfactory manufacturing method has been found at present.

Even with perpendicularly magnetized films, there is a prospect that sufficient practical characteristics can be obtained by electron beam evaporation (or ion plating), and for specific applications, magnetron sputtering with a large input power can also provide sufficient practical speed. Therefore, if the thermal effects can be made uniform when the characteristics are made uniform, it can be evaluated as a technology for mass-producing magnetic recording media that meet strict standards.

The present invention was developed in view of the above points, and it compensates for the unevenness of the thermal effect on the substrate that occurs when trying to make the magnetic properties uniform in the axial direction, and improves the main physical properties other than the magnetic properties in the axial direction. In order to make the deposition uniform, electrons are injected into the substrate, and this purpose is achieved by performing the injection process along the same rotating support as during vapor deposition.

For example, the energy generated by glow discharge treatment is insufficient for electrons, and when a polymer molded substrate is used and its thickness is t [μm], the energy of electrons is 1.5 t [KV] to 5 t [KV]. , more preferably a range of 2t to 3t.

Next, it is important to design the current density, and the heat input from the evaporation source to the substrate must be calculated (it cannot be determined exactly, but it can be approximated).
The current density in the width direction may be changed to compensate for this, and all physical property values may be experimentally determined to be uniform in the width direction.

Broadly speaking, adjustments can be made based on the relationships shown in Figure 2 A and B.

The idea is that when heat input attempts to make the magnetic properties uniform, it will be distributed like A and B (of course, other patterns can be expected as well).
The width direction can be compensated for by cooling during vapor deposition or by heating, but simply compensating by heating is dangerous because the polymer molded substrate has a low melting point, and even if heated, the cooling conditions The basic idea is to keep the fluctuations small in the width and length directions.

The idea of the present invention is to balance heat input and cooling by utilizing the fact that electron injection controls the adhesion between the substrate and the rotating support due to the electrostatic field generated by the trapped charges. .

FIG. 1 shows an example of the main part configuration of a vapor deposition apparatus for carrying out the present invention.

As shown in the figure, the polymer molded substrate 2 fed out from the feeding shaft 1 is guided to the surface of the rotating support 3, and is emitted from the injection electron source 4 along the rotating support. Electrons are injected.

Next, the heat dissipation electron source 5 is operated, and the vapor flow 7 generated from the evaporation source 6 forms a magnetic layer. 8 is a mask that limits the angle of incidence.

The substrate on which the magnetic layer has been formed is wound up on the winding shaft 9.

Pre-processing and post-processing performed as necessary do not limit the present invention in any way.

A winding system, an evaporation source system, and the like are housed inside the vacuum container 10. 11 is a vacuum evacuation system.

Now, using the apparatus shown in Figure 1, a
A magnetic layer consisting of 80% Co and 20% Ni was heated at 2×10 ^-5 Torr.
The film was formed to a thickness of 0.15 μm in oxygen.

The temperature of the cooling medium in the cylindrical can (1 m in diameter) is constant at 5°C. The evaporation source position is 27cm directly below the can.
The minimum angle of incidence is 43°.

The width direction of the vapor deposition was 48 cm, and the coercive force, squareness ratio, and film thickness were all controlled to ±3%.

The result of manufacturing magnetic tape using this (width 8
mm) All but 36 of the 60 strips were not practical due to insufficient flatness of the magnetic tape.

In comparison, the electron injection according to the present invention was applied under the following conditions to examine the flatness distribution.

[Condition 1] Electrons were uniformly irradiated at 25 KV over 50 cm in the width direction. The current density is 1 mA/cm ² .

[Condition 2] Irradiation was performed using 25 KV electrons, maintaining symmetry in the width direction, at 1 mA/cm ² from the center to 12 cm, increasing linearly from 12 cm to 25 cm, and reaching 1.5 mA/cm ² at the 25 cm position.

As a result of the above experiment, under condition 1, 48 pieces were good, but under condition 2, all 60 pieces were good. Next, a polyethylene terephthalate film (thickness 14 μ
m) to a thickness of 0.2 μm.

Both electron beam evaporation and sputtering were used (magnetic properties were controlled within ±3%).

The electron injection conditions are 30KV, symmetrical in the width direction, 0.5mA/cm ² from the center to 10cm, and 18cm from 10cm.
increases linearly up to 0.6mA/cm ² at 18cm position,
From 18 cm to 25 cm, 0.6 mA/cm ² was constant.

Under these conditions, the flatness of the tape could be ensured over the entire width direction.

In sputtering, by injecting electrons under these conditions, we were able to secure a substrate movement speed of 21 m/min. On the other hand, when electrons were not injected, the substrate would melt at this power, and since the power was reduced to 1/5, the substrate movement speed became as slow as 3.8 m/min.

As described above, according to the present invention, a homogeneous metal thin film type recording medium can be easily obtained under conditions of high mass production, and this is extremely useful in technical fields where short wavelength recording is strongly required.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of essential parts of an apparatus used in an embodiment of the present invention, and FIG. 2 is a diagram for explaining electron injection conditions in the same embodiment of the present invention. 2... Substrate, 3... Rotating support, 4... Injection electron source, 6... Evaporation source, 10... Vacuum container.

Claims (1)

[Claims] 1. A ferromagnetic layer is formed by vacuum evaporation on a polymer molded substrate that moves along a support, and prior to forming the ferromagnetic layer, electrons are injected into the substrate and the amount of electron injection is adjusted to the substrate. 1. A method of manufacturing a magnetic recording medium, characterized in that the width of the medium is changed in the width direction.