JPH0766543B2 - Magnetic alloy material for producing magnetic recording medium and method for producing magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic alloy material for producing a magnetic recording medium and a method for producing a magnetic recording medium using the alloy material.

2. Description of the Related Art Prior Art and Problems There are active developments of magnetic recording media for video, audio, etc., which have a metal thin film type magnetic thin film because of their compactness when formed into a tape and wound.

Among these magnetic recording media, the perpendicular magnetic recording media capable of high-density recording have attracted particular attention.

This perpendicular magnetic recording medium has an easy axis of perpendicular magnetization on the film surface.
It has a Co-Cr magnetic thin film. Various methods such as a sputtering method, a vacuum deposition method, an ion plating method, and a plating method have been proposed as a method for manufacturing the magnetic thin film.

Although each of these manufacturing methods has advantages and disadvantages, the vacuum deposition method and the ion plating method, which have a high film formation rate, are excellent in terms of productivity and the like. However, on the other hand, there is a drawback that a magnetic thin film having a uniform composition cannot be stably obtained for a long time during the production of the medium.

For example, if an ingot-shaped or pellet-shaped Co—Cr alloy material is used as the evaporation source in accordance with the usual circumstances, the Cr content of the evaporation source decreases with time, and the amount of Cr in the magnetic thin film changes significantly.

On the other hand, for example, so-called binary vapor deposition in which Co and Cr are separately provided as evaporation sources has been proposed, but even in this case, special composition control is required and the film composition becomes extremely unstable.

II Object of the Invention An object of the present invention is to provide a magnetic alloy material for an evaporation source, which can easily obtain a magnetic thin film having a uniform composition by a vacuum deposition method or an ion plating method, and a method for producing a magnetic recording medium using the same. To do.

III DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, the first invention contains cobalt and chromium,
A magnetic alloy material for producing a magnetic recording medium, having a particle diameter of 3 mm or less.

A second invention is a method of manufacturing a magnetic recording medium in which a magnetic thin film containing cobalt and chromium is formed on a non-magnetic substrate, wherein a magnetic alloy material containing cobalt and chromium and having a particle diameter of 3 mm or less is used. This is a method for producing a magnetic recording medium, characterized in that a magnetic thin film is formed by a vapor deposition method in which an evaporation source is used and heated by an electron beam to be vaporized.

IV Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

The present invention relates to an evaporation source material for manufacturing a so-called perpendicular magnetic recording medium having a magnetic thin film containing cobalt and chromium, and a manufacturing method using the same.

That is, when a magnetic thin film containing cobalt and glom is formed on a non-magnetic substrate, a magnetic alloy material for producing a recording medium containing cobalt and chromium (hereinafter referred to as an alloy material) is used as an evaporation source, The magnetic thin film is manipulated by a vapor deposition method in which this is heated by an electron beam to be vaporized.

The alloy material used as the evaporation source contains cobalt and chromium, the composition ratio of which is substantially equal to the composition ratio of the target magnetic thin film, and the composition of chromium is usually about 18 to 23% by weight.

The magnetic material is usually particles such as granules and powder. Further, it may be a sintered body of an aggregate of these particles. The particle size is 3 mm or less.

If this particle size exceeds 3 mm, it becomes difficult to control the composition during film formation.

The alloy material used in the present invention has such a particle diameter, and may be a so-called crystal grain or a granule produced by sieving a lump of a uniform mixture regardless of crystallinity.

Further, it may be a powder obtained by pulverizing a powder of a certain size into a powder.

In this case, these particles may have various shapes such as spherical shape, crushed piece shape, flake shape, and short fiber.

Further, such powder or the like may be heated to a temperature equal to or lower than the melting point or partially melted and partially sintered or bound. As a result, the handleability can be improved. However, at this time, it is necessary that the particles having the above-mentioned particle diameter remain.

If such an alloy material is used as the evaporation source, each particle evaporates sublimably during the production by the vapor deposition method or the ion plating method, so that the composition ratio of the evaporation source becomes constant, and therefore the composition is constant. A magnetic thin film can be stably obtained over a long period of time.

When used as a sintered body, its porosity is 10-50%.
It is preferable to use a graded one.

Further, such an alloy material may contain iron, nickel, titanium, carbon, oxygen or the like as the third component in addition to cobalt and chromium as described above.

Using such an alloy material as an evaporation source, a magnetic thin film is formed by a vapor deposition method such as a vacuum evaporation method or an ion plating method. In this case, the above alloy material is used as an evaporation source, and a predetermined amount thereof is put into a hearth and heated by an electron beam.

A known electron gun may be used, and various conditions such as a beam used for heating are not particularly limited. By using an electron beam as a means for heating the evaporation source, sublimation from the alloy material is stably performed.

The vacuum vapor deposition method and the ion plating method may use various known devices, and the conditions such as the distance between the hearth and the substrate and the volume velocity of the film may be appropriately determined, and are not particularly limited.

Here, the vacuum vapor deposition method is an evaporation source in a high vacuum of 10 ⁻⁵ Torr or less, and in the present invention, the evaporation source is heated and melted and evaporated by an electron beam method or the like, and the vapor is thinned on a substrate surface, for example. It is a method to adhere as. The kinetic energy obtained by the vaporized particles during this vaporization is about 0.1 eV to 1 eV.

The ion plating method is an atomistic film forming method in which a vapor deposition material is bombarded onto a substrate surface with sufficient kinetic energy before and during film formation.

Its basic function is to sputter the substrate by projecting ions,
It has the effects of heating, ion implantation, etc.
Affects nucleation and film growth of deposited films.

This ion plating method can be further divided into the plasma method and the ion beam method from the working area. In the plasma method, after the substrate (negative potential) is cleaned by Ar ⁺ impact by DC glow discharge. When the evaporation source is heated to vaporize the vapor deposition material, it is ionized in the plasma and accelerated by the strong electric field in the cathode dark part of the glow discharge surrounding the substrate, and is bombarded onto the substrate with high energy for vapor deposition.

Many types such as a direct current application type, a high frequency excitation type and a combination type thereof and a combination of various heating types of an evaporation source can be used, and a plasma electron beam method using a hollow cathode plasma electron gun may be used.

In the ion beam method, the vapor deposition material ions generated by an ion source such as a sputter type, an electron impact type, or an improved duoplasmatron type are drawn into a high vacuum region, and the acceleration voltage is adjusted to continue cleaning and vapor deposition of the substrate surface. Do it. In cluster ion beam technology (vapor deposition and crystal growth), the vapor deposition material is ejected from a crucible injection nozzle into a high vacuum, and 10 ² to 10 ³ atoms are loosely bonded to each other by utilizing the supercooling phenomenon due to adiabatic expansion. Create a cluster of clustered atoms,
Ionize and use.

Further, a so-called arc discharge method may be used.

In the arc discharge ion plating method, the thermoelectrons emitted from the thermoelectron emission source are made to collide with the vapor flow obtained by heating the vaporization source and evaporating, when the vapor flow density near the vaporization source is relatively high. The vaporized gas is ionized, and the ionized vaporized stream is converged in the direction perpendicular to the carrier by an electric field or a magnetic field to form a film.

The kinetic energy of ions in ion plating is several tens of eV to 5 KeV.

The thickness of the magnetic thin film formed by such a vapor deposition method is usually about 0.05 to 1.5 μm, and more preferably 0.1 to 1.0 μm.

Although the film forming conditions are not particularly limited as described above, the film deposition rate is usually about 100 to 2000Å / sec, more preferably 200 to 1000Å / sec. If this speed is less than 100Å / sec, the effect of residual gas during film formation cannot be ignored, and reproducibility and uniformity deteriorate. Also,
If it exceeds 2000Å / sec, a splash (momentary abnormal evaporation) may occur due to heat concentration.

As the non-magnetic substrate on which the magnetic thin film is formed, polyester (PET), polyamide, polyimide, polyphenylene sulfide, polysulfone, wholly aromatic polyester, polyetheretherketone, polyethersulfone, polyetherimide, or other resin, or A metal such as Al or glass may be used. Further, the shape of the substrate used is not limited.

Note that various known layers may be formed on the magnetic thin film, between the substrate and the magnetic thin film, or on the back surface of the substrate using various known layering methods.

V Specific Effect of the Invention According to the present invention, the particle size containing cobalt and chromium
The magnetic thin film of 3 mm or less is used as the evaporation source, and the magnetic thin film is manipulated by the vapor deposition method in which this is heated by the electron beam to be vaporized, so that the magnetic thin film is stable for a long time with a constant composition. You can get it.

Therefore, the obtained magnetic recording medium has extremely good and stable electromagnetic conversion characteristics. It also has excellent productivity.

VI Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown to explain the present invention in more detail.

(Example 1) Cobalt-chromium alloy pellets (chromium 20 wt%) made by the induction heating method were crushed under pressure to have a particle diameter of 3 mm.
Granule particles distributed below were obtained.

100 g of this was stored in a water-cooled copper hearth having an internal volume of 30 cm ³ to obtain an evaporation source material.

Film-shaped polyester (PET) as non-magnetic substrate
After disposing the base, the vacuum chamber was set to 2 × 10 ⁻⁶ Torr, and the evaporation source material was heated and evaporated by an electron gun.

The pressure during vapor deposition was 2 × 10 ⁻⁵ Torr, and the can was water-cooled (can temperature T <30 ° C.).

With the distance between the base and the evaporation source being 30 cm and the power of the electron beam being constant, a 0.4 μm thick cobalt-chromium thin film was obtained over 20 m.

The composition of the obtained sample was analyzed every 1 m in the length direction, and the results shown in FIG. 1 were obtained. As shown in the figure, the fluctuation of Cr content {Cr / {Co + Cr)} is ± 0.4
It was wt% (variation range about 0.8 wt%).

The composition analysis was performed by using the intensities of Co and Cr of fluorescent X-ray.

Comparative Example 1 The evaporation source material was 25 ^mmφ × 25 ^mmh cobalt and chromium alloy pellets (chromium 20 wt%). A sample was obtained in the same manner as in Example 1 except for the above.

The composition of the obtained sample was similarly analyzed, and the results as shown in FIG. 2 were obtained.

Comparative Example 2 Cobalt and chromium used as evaporation source materials were put in separate hearths. Cobalt has a block shape, and chromium has a particle size of 3 m.
The granules were distributed below m.

Using an electron gun with a 3-point jumping mechanism,
The input power of each was controlled.

Others were the same as in the case of Example 1.

FIG. 3 shows the result of the obtained composition analysis.

(Example 2) In Example 1, except that the arc discharge ion plating method was used instead of the vapor deposition method used as the vapor deposition method,
A sample was prepared according to Example 1.

The composition of the obtained sample was analyzed every 1 m in the lengthwise direction in the same manner as in Example 1, and the fluctuation range of Cr / Co + Cr amount was calculated as the composition fluctuation rate (%). ± 0.4 wt% (variation range: 0.8 wt%).

From these results, the effect of the present invention is clear.

[Brief description of drawings]

1 to 3 are graphs showing the relationship between the sample position and the Cr composition amount in Examples of the present invention and Comparative Examples.

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Claims (4)

[Claims] 1. A particle diameter of 3 m containing cobalt and chromium.
A magnetic alloy material for producing a magnetic recording medium, which is characterized by being m or less. 2. A magnetic alloy material for producing a magnetic recording medium according to claim 1, wherein the chromium content is 18 to 23% by weight. 3. A method of manufacturing a magnetic recording medium comprising a magnetic thin film containing Gobart and chromium on a non-magnetic substrate, wherein a magnetic alloy material containing cobalt and chromium and having a particle diameter of 3 mm or less is vaporized. A method of manufacturing a magnetic recording medium, characterized in that a magnetic thin film is formed by a vapor deposition method in which a magnetic layer is used as a source and heated by an electron beam to be vaporized. 4. The method of manufacturing a magnetic recording medium according to claim 3, wherein the vapor deposition method is a vacuum vapor deposition method or an ion plating method.