JPH08221752A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE: To easily produce a magnetic recording medium having many layers of magnetic layers varying in film quality. CONSTITUTION: A base is transported by plural can rolls disposed in a vacuum atmosphere and the plural magnetic layers are formed by vapor deposition on this base. The min. incident angles at the respective can rolls are adjusted by shielding plates 5, etc., in such a manner that the min. incident angle (θ1 ) of the can roll 1 disposed upstream of the transporting route for the base attains the angle larger than the min. incident angle (θ2 ) of the can roll 2 disposed downstream of this can roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal thin film type magnetic recording medium, and more particularly to a method for manufacturing a magnetic recording medium having multiple magnetic layers having different column structures.

[0002]

2. Description of the Related Art A so-called metal thin film type magnetic recording medium in which a metal is deposited on a support by vacuum evaporation or the like can increase the density of the magnetic material because the magnetic layer contains no binder. It is said to be promising for high density recording.

Today, the recording wavelength tends to become shorter as the recording density becomes higher, and a thick magnetic layer causes a problem of thickness loss at the time of recording / reproducing such as reduction in output. This problem cannot be sufficiently solved only by adjusting the thickness of the single magnetic layer, and attempts have been made to deal with it by using two magnetic layers. In this method, usually, can rolls having the same diameter as shown in FIG. 2 arranged in the same or different vacuum chambers are used to continuously form two magnetic layers having the same column structure and the same film thickness. are doing.

[0004]

It is considered that the electromagnetic conversion characteristics required for magnetic recording media will be further diversified and sophisticated in the future, but the two magnetic layers obtained by the above-mentioned method will be described. Since all have the same film quality, it is expected that they cannot sufficiently meet such requirements.

[0005]

As a result of intensive studies to solve the above problems, the present inventors have found that a magnetic recording medium in which a plurality of can rolls are used to continuously form a multilayer magnetic layer on a support by vapor deposition. In the manufacturing method of (1), the minimum incident angle of the can roll on the upstream side of the transport path of the support is made larger than the minimum incident angle of the can roll on the downstream side, whereby a magnetic recording medium having multiple magnetic layers having different column structures can be obtained. This has led to the completion of the present invention.

That is, the present invention is a method of transporting a support by a plurality of can rolls arranged in a vacuum atmosphere and forming a plurality of magnetic layers on the support by vapor deposition, in the transport path of the support. The minimum incident angle of each can roll is adjusted such that the minimum incident angle of the can roll arranged upstream of the can roll is larger than the minimum incident angle of the can roll arranged downstream of the can roll. The present invention provides a method for manufacturing a magnetic recording medium. Here, the "minimum incident angle" means the smallest incident angle.

The manufacturing method of the present invention is a method in which a plurality of (n) can rolls are used to continuously form a multi-layered magnetic layer on a support by vapor deposition. The minimum incident angle (θ ₁ ) of the first can roll arranged upstream, the minimum incident angle (θ ₂ ) of the _second can roll, and the minimum incident angle (θ _n ) of the nth can roll are θ It is carried out by adjusting the minimum incident angle in each can roll so that ₁ > θ ₂ ...> θ _n . The minimum incident angle is adjusted by a shield plate or the like.

The column structure of the magnetic layer of the magnetic recording medium manufactured according to the present invention is schematically shown in FIG. The magnetic recording medium is formed with three magnetic layers, but all the magnetic layers have the same thickness, and the inclination angle (α ₁ , of the column structure with respect to the normal (P ₁ , P ₂ , P ₃ ) is α ₂ , α ₃ ) is
The smaller the magnetic layer is from the base material, the smaller. On the other hand, the minimum incident angle in each can roll is θ ₁ > θ ₂ ...
When >&thgr; _n , the column structure of the magnetic layer is as shown in Fig. 4 that the angle of inclination of the column structure with respect to the normal becomes larger as the magnetic layer is farther from the base material. In some cases, excellent output characteristics may not be obtained. Note that, in FIGS. 3 and 4, the column structure is schematically shown by diagonal lines, and the normal line is expressed as a perpendicular line in the cross section for convenience. The arrows in FIGS. 3 and 4 indicate the traveling direction of the medium.

In the present invention, vapor deposition is carried out at the same rotation speed of the plurality of can rolls, but as described above for the minimum incident angle, the second can roll is more preferable than the first can roll. In order to make it smaller, the vapor deposition region in the second can roll becomes larger than the vapor deposition region in the first can roll, so that the thickness of the magnetic layer that is formed as it is toward the upper layer (as the distance from the base material increases ) It becomes thick. When forming multiple magnetic layers, it may be advantageous to reduce the thickness of the upper magnetic layer. Therefore, in the present invention, the thickness of the magnetic layer is adjusted to adjust the thickness of a plurality of magnetic layers. You may. As one of the methods, there is a method of adjusting the output of the ion beam so that the thickness of the plurality of magnetic layers is constant or becomes thinner toward the upper layer. Further, each can roll may be installed in the same chamber or may be installed in different chambers.

Further, in the present invention, the minimum incident angle (θ ₁ ) in the first can roll, which is the most upstream of the conveying path, is
It is preferably 50 ° or more. If θ ₁ is less than 50 °, it is impossible to obtain a magnetic recording medium that can sufficiently support a wide range of recording wavelengths.

As an example of the embodiment of the present invention, two can rolls are used, and in this case, the relationship between the minimum incident angles in the first and second can rolls is θ ₁ > θ ₂ and the two layers of magnetic properties are set. A method of manufacturing a magnetic recording medium having a layer may be mentioned. In this method, θ ₁ and θ ₂ are such that θ ₂ / θ ₁ <2
It is desirable to satisfy the relationship of / 3, whereby a magnetic recording medium excellent in short wavelength recording can be obtained.

In the present invention, examples of the magnetic material for forming the magnetic layer include ferromagnetic metal materials used in the production of ordinary metal thin film type magnetic recording media, such as Co, Ni,
Ferromagnetic metals such as Fe, Fe-Co, Fe-Ni, Co-Ni, Fe
-Co-Ni, Fe-Fh, Fe-Cu, Co-Cu, Co-Au, Co-Y,
Co-La, Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-Cu, Mn
-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-
Examples include ferromagnetic alloys such as Co-Cr and Ni-Co-Cr. As the magnetic layer, a thin film of iron or a thin film of a ferromagnetic alloy containing iron as a main component is preferable, and at least one selected from a ferromagnetic alloy containing iron, cobalt, nickel as a main component and nitrides or carbides thereof is preferable. .

By forming an oxide on the surface of the magnetic layer by introducing an oxidizing gas when forming the magnetic layer by vapor deposition, the durability can be improved. The degree of vacuum during vapor deposition is about 10 ⁻⁴ to 10 ⁻⁷ Torr.

The number of magnetic layers corresponds to high frequency recording,
The larger the number, the better, but it is considered that two to five layers are suitable as a practical range. In the case of two layers, the thickness of the magnetic layer is 100 to 2000Å for the lower magnetic layer and 50 to 50 for the upper magnetic layer.
1000Å is preferable, and in the case of three layers, the thickness of the lower magnetic layer is
It is preferable that the thickness of the intermediate magnetic layer is 100 to 2000Å, the thickness of the intermediate magnetic layer is 100 to 1000Å, and the thickness of the upper magnetic layer is 50 to 1000Å.

In the method for producing a magnetic recording medium of the present invention, as the support, polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; Polyvinyl chloride; polyimide; plastics such as aromatic polyamide are used. The thickness of these supports is about 3 to 50 μm.

In the method of manufacturing a magnetic recording medium of the present invention, a back coat layer can be formed on the surface of the support opposite to the surface on which the magnetic layer is formed. The back coat layer may be formed before or after the formation of the magnetic layer. The back coat layer may be formed by applying a back coat paint by a conventional method, or the back coat layer can be formed by depositing a metal or a semimetal in vacuum. There are various possible metals for the back coat layer, but Al, Cu, Z
n, Sn, Ni, Ag, etc. and their alloys are used. However, in terms of price, adhesion rate, and stability after oxidation, Al, Cu
Is the best. Moreover, Si, Ge, As, Sc, Sb, etc. are used as a semi-metal which forms a back coat layer. In particular, Si is most suitable in terms of price, adhesion speed, and the like. The thickness of the back coat layer is not limited, but is 0.1 when coated.
It is about 1.0 to 1.0 μm, and about 0.05 to 1.0 μm in the case of metal deposition.

In the method for producing a magnetic recording medium of the present invention, a top coat layer made of a suitable lubricant may be further formed on the magnetic layer. The top coat layer may be applied in the atmosphere, or the lubricant may be sprayed in vacuum onto the magnetic layer formed on the support by an atomizer equipped with an ultrasonic oscillator (hereinafter referred to as an ultrasonic atomizer). You may. The thickness of the top coat layer is not limited, but in the case of coating 5-100 Å,
When spraying, it is about 10 to 200 Å.

When the back coat layer is provided, the top coat layer may be formed on the back coat layer. By forming the top coat layer on the back coat layer, the running property and durability can be further improved.

[0019]

Embodiments of the present invention will be described below. However, the invention is not limited to these examples.

Examples 1 to 3 and Comparative Example 1 (i) Production of magnetic recording medium A magnetic recording medium having two magnetic layers was prepared by using the apparatus shown in FIG. FIG. 1 shows an essential part of an apparatus for manufacturing a magnetic recording medium. The minimum incident angle (θ) of a vapor deposition region 3 in a first can roll 1 arranged in the same chamber is shown in FIG.
₁ ) and the minimum incident angle (θ ₂ ) of the vapor deposition region 3 ′ in the second can roll 2 are shown. In this apparatus, the first can roll 1 and the second can roll 2 are defined by means (not shown), respectively, and are connected to vacuum means (not shown) so that an appropriate degree of vacuum is maintained.

First, a PET film 4 having a thickness of 6.5 μm is run on the first can roll 1 to deposit cobalt as a magnetic metal to form a first magnetic layer having a thickness of 1000 Å. The PET film 4 on which the layer is formed runs on the second can roll 2 and is further deposited with cobalt to have a thickness.
A 1000 Å second magnetic layer was formed.

At this time, the evaporation regions 3 and 3'in each can roll are adjusted by the shield plate 5, and the relationship between the minimum incident angle θ ₁ in the _first can roll and the minimum incident angle θ ₂ in the second can roll is shown. As shown in Table 1, various changes were made to form two magnetic layers having different film qualities.

Then, the PET film was taken out into the atmosphere,
A video cassette for Hi-8 was produced by slitting (cutting) to a width of 8 mm and inserting into a cassette of 8 mm.

(Ii) Performance Evaluation The outputs of the video cassettes obtained above at 5, 20, and 30 MHz were measured. Table 1 shows the results.

[0025]

[Table 1]

[0026]

As described above, according to the present invention, it is possible to easily manufacture a magnetic recording medium having a plurality of magnetic layers having different film qualities.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a main part of a magnetic recording medium manufacturing apparatus of the present invention.

FIG. 2 is a schematic view showing an example of a main part of a conventional magnetic recording medium manufacturing apparatus.

FIG. 3 is a schematic view showing a structure of a magnetic layer of a magnetic recording medium manufactured according to the present invention.

FIG. 4 is a schematic view showing the structure of a magnetic layer of a magnetic recording medium manufactured by a method other than the present invention.

[Explanation of symbols]

 1 first can roll 2 second can roll 3 vapor deposition region 4 support 5 shielding plate 21 support 22,23,24 magnetic layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirohide Mizunoya, 2606 Akabane, Kaiga-cho, Haga-gun, Tochigi Prefecture Kao Corporation Information Science Laboratory (72) Inventor Katsumi Sasaki 2606, Akabane, Kaiga-cho, Haga-gun, Tochigi Prefecture Oo Co., Ltd.Institute of Information Science (72) Inventor Shigemi Wakabayashi 2606, Akabane, Kai, Cho, Haga-gun, Tochigi Prefecture Information Science Laboratory, Wang Co., Ltd.

Claims (4)

[Claims] 1. A method of transporting a support by a plurality of can rolls arranged in a vacuum atmosphere and forming a plurality of magnetic layers on the support by vapor deposition, in the upstream of a transport path of the support. The magnetism characterized by adjusting the minimum incident angle of each can roll so that the minimum incident angle of the can roll arranged is larger than the minimum incident angle of the can roll arranged downstream of the can roll. Recording medium manufacturing method. 2. A method of transporting a support by a plurality of can rolls arranged in a vacuum atmosphere and forming a plurality of magnetic layers on the support by vapor deposition, in the upstream of a transport path of the support. The minimum incident angle of each can roll is adjusted so that the minimum incident angle of the can roll arranged is larger than the minimum incident angle of the can roll arranged downstream of the can roll. A method of manufacturing a magnetic recording medium, characterized in that the evaporation amount of a magnetic metal is adjusted so that the thicknesses of the magnetic recording media are the same. 3. The minimum incident angle in the first can roll upstream of the support conveyance path using two can rolls.
The magnetic recording according to claim 1 or 2, wherein (θ ₁ ) and the minimum incident angle (θ ₂ ) in the second can roll downstream of the conveying path of the support satisfy the relationship of θ ₂ / θ ₁ <2/3. Medium manufacturing method. 4. The method for manufacturing a magnetic recording medium according to claim 1, wherein the minimum incident angle of the first can roll is 50 ° or more.