JPH097153A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium having improved durability and increased saturation magnetic flux density by forming 1st and 2nd magnetic layers each having a columnar structure grown in a required direction by vapor deposition on a base film. CONSTITUTION: A 1st magnetic layer 2 having a columnar structure grown at a right angle to the surface of a base film 1 is formed by vapor deposition on the base film 1. A 2nd magnetic layer 3 having a columnar structure grown in an oblique direction to the growth direction of the columnar structure of the layer 2 is then formed by vapor deposition on the layer 2. The packing property of the columns is improved, the bonding property of the magnetic layers to the base film is also improved and the objective magnetic recording medium having high durability and high saturation magnetic flux density is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor-deposited magnetic recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a magnetic recording medium, an evaporation type in which a magnetic layer made of a metal thin film containing no binder is attached on a non-magnetic base film by a vacuum evaporation method in which a magnetic metal is evaporated on a base film in a vacuum. Magnetic recording media are known. In recent years, magnetic recording is in the direction of high-density recording, and a vapor-deposited magnetic recording medium is promising for high-density recording because the magnetic layer does not contain a binder and therefore the density of the magnetic material can be increased. Has been done.

The manufacture of magnetic recording media by the vacuum deposition method is
Fe, a base film that continuously runs in a vacuum atmosphere,
A magnetic layer is formed by depositing a magnetic metal such as Co or Ni or a magnetic alloy of Co-Ni system or Co-Cr system by vapor deposition, and as a vapor deposition method, Japanese Patent Publication No. 41-19389.
The so-called oblique vapor deposition, which is disclosed in Japanese Laid-Open Publications and the like, occupies the mainstream today. The oblique vapor deposition method is to attach vapors of magnetic metal to the surface of the base film from an oblique direction, and the resulting magnetic recording medium is a column grown obliquely on the base film 21 as shown in FIG. Has 22.

[0004]

A magnetic recording medium having a magnetic layer formed by oblique vapor deposition generally has a coercive force (H
Although it is excellent in c), in the usual oblique vapor deposition method, since the interface between the base film and the magnetic layer is formed in a region where the amount of metal vapor is small (the initial stage of vapor deposition), the amount of metal deposited is small, and The binding strength and crystallinity of the column are inferior to those of the column upper layer. Therefore, the durability and running stability tended to be insufficient. In addition, since the packing property between columns is not sufficient, the saturation magnetic flux density (Bs)
Was not enough.

[0005]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors formed a first magnetic layer in which columns grow vertically on a base film,
By forming a second magnetic layer in which columns grow obliquely on the first magnetic layer, the binding property between the magnetic layer and the film is improved and the durability is excellent, and the packing property between columns is improved. Therefore, it was found that a magnetic recording medium excellent in Bs can be obtained, and the present invention has been completed.

That is, the present invention comprises a base film, a first magnetic layer formed on the base film by vapor deposition, and a second magnetic layer formed on the first magnetic layer by vapor deposition. The column structure of one magnetic layer grows perpendicularly to the surface of the base film, and the second column structure grows obliquely to the growth direction of the column structure of the first magnetic layer. The present invention provides a magnetic recording medium characterized by:

In the magnetic recording medium of the present invention, magnetic metal is vapor-deposited in a direction perpendicular to the surface of the base film in vacuum to form a first magnetic layer on the base film.
Then, a magnetic metal is vapor-deposited obliquely to the surface of the base film to form a second magnetic layer on the first magnetic layer.

In the magnetic recording medium of the present invention, as shown in FIG. 1, a first magnetic layer 2 having a column structure grown vertically to the surface of the base film 1 is formed on the base film 1, On the first magnetic layer 2, the second magnetic layer 3 having a column structure grown obliquely with respect to the growth direction of the column structure of the first magnetic layer is formed.

Such a magnetic recording medium is manufactured by the method as shown in FIG. FIG. 3 is a schematic view showing a main part of an apparatus for manufacturing the magnetic recording medium of the present invention. In FIG. 3, the cooling can rolls 31, 31 'and the crucibles 32, 32' are housed in a vacuum container (not shown) kept at a desired degree of vacuum.
The film 33 first runs on the cooling can roll 31.
Below the cooling can roll 31 is a crucible (for example, MgO).
32) is placed, and the magnetic metal 34 is housed in this. Electron beam gun for magnetic metal 34 in this crucible 32
Irradiate an electron beam from 35. This allows the magnetic metal 34
Is heated and vaporized.

Film 33 running on cooling can roll 31
A first magnetic layer is formed on the upper surface of the magnetic metal layer 34.
It is necessary to evaporate in a region with a large amount of vapor and in the direction perpendicular to the surface of the base film.
The vapor deposition is performed by appropriately adjusting the positional relationship between the base film 33 running on the substrate 31 and the vapor deposition region.

Next, the base film 33 runs on the cooling can roll 31 ', and the magnetic metal 34' in the crucible 32 'is irradiated with an electron beam from the electron beam gun 35' in the same manner as described above, so that the first magnetic layer is formed. A second magnetic layer is formed on top. On this occasion,
In order to form the column structure of the second magnetic layer as described above, it is necessary to evaporate the magnetic metal obliquely to the surface of the base film (so-called oblique evaporation). Oblique vapor deposition is performed by appropriately adjusting the positional relationship between the film 33 and the vapor deposition region. In this way, the magnetic recording medium of the present invention in which the first magnetic layer and the second magnetic layer are formed on the base film 33 is obtained.

As described above, the magnetic recording medium of the present invention has the structure shown in FIG. 1, but the first magnetic layer is formed on the base film by the vapor deposition region having high energy, high crystallinity, and high binding property. Is formed vertically (in the figure), a thin film having high binding property to the film is formed first, and then the second magnetic layer is obliquely vapor-deposited on the film, so that the magnetic layer becomes a base film. The binding property of the entire magnetic layer is improved as compared with the case where it is directly formed on the magnetic layer. The second magnetic layer is affected by the orientation of the metal crystals of the first magnetic layer at the vapor deposition start (initial vapor deposition) portion where the vapor concentration is low, and the metal particles in the initial vapor deposition are likely to crystallize. That is, since the first magnetic layer is crystallized, the lower portion (initial vapor deposition particles) of the second magnetic layer is easily crystallized, and the packing property of the metal crystals of the second magnetic layer is improved. Therefore, durability and Bs are improved. Since the first magnetic layer is vapor-deposited in a portion having a high vapor density as described above, the first magnetic layer is formed quickly even when the traveling speed of the film is constant.

In the present invention, examples of the magnetic material 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-
Ferromagnetic alloys such as Co-Cr and Ni-Co-Cr are exemplified. The magnetic layer is preferably a thin film of iron or a thin film of a ferromagnetic alloy mainly composed of iron, and particularly preferably a ferromagnetic alloy mainly composed of iron, cobalt and nickel, and at least one selected from nitrides and carbides thereof. . The thickness of the magnetic layer is preferably such that the thickness of the second magnetic layer is larger than the thickness of the first magnetic layer. Specifically, the thickness of the first magnetic layer is
The thickness of 100 to 1500Å and the thickness of the second magnetic layer are preferably about 500 to 2500Å, but it is particularly preferable that the first magnetic layer is 300 to 1000Å and the second magnetic layer is 800 to 2000Å. If the second magnetic layer is too thin, there is no effect of improving the crystallinity and packing property, while if it is too thick, the warp to the magnetic layer side becomes large and the head touch deteriorates.

In the present invention, both the vapor deposition method for forming the first magnetic layer and the oblique vapor deposition method for forming the second magnetic layer may be performed according to conventionally known methods. The degree of vacuum during vapor deposition is about 10 ⁻⁴ to 10 ⁻⁷ Torr. Further, by introducing an oxidizing gas when forming the second magnetic layer to form an oxide on the surface of the second magnetic layer, it is possible to improve durability.

In the present invention, a protective layer may be provided on the second magnetic layer. The protective layer is carbon or carbide,
Nitride, oxide, particularly diamond-like carbon, diamond, boron carbide, silicon carbide, boron nitride, silicon nitride, silicon oxide, it is preferably formed by depositing a film such as silicon oxide and aluminum oxide on the magnetic layer. Above all, it is most desirable to form a protective layer made of diamond-like carbon. These protective layers are preferably formed in vacuum by an ECR method using microwave or a method using high frequency (RF). The thickness of the protective layer is not particularly limited, but is appropriately 10 to 300 Å, preferably 30 to 150 Å.

Further, in the present invention, a lubricant layer may be formed on the second magnetic layer or the protective layer. The lubricant layer may be formed by dissolving a suitable lubricant in a solvent and coating it in the air by a conventional method, or by spraying the lubricant in a vacuum. Also,
A back coat layer may be formed on the surface of the base film opposite to the surface on which the magnetic layer is formed. The back coat layer may be formed by applying a liquid in which carbon black or the like is dispersed in a suitable solvent, or by vapor-depositing a metal or a metalloid by a physical vapor deposition method (PVD), particularly a thermal evaporation method or a sputtering method. You may let me. The thicknesses of these lubricant layer and back coat layer are not limited.

The base film constituting the magnetic recording medium of the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; polychlorination. Vinyl; polyimide; plastics such as aromatic polyamide are used. The thickness of these base films is about 3 to 50 μm.

[0018]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Using the apparatus shown in FIG. 3, a magnetic recording medium having a first magnetic layer and a second magnetic layer was manufactured. That is, thickness 10μm, width 15c
m PET film 33 was set and run on the cooling can roll 31 at a running speed of 10 m / min. The cobalt 34 contained in the crucible 32 is irradiated with an electron beam from the electron gun 35 to vapor deposit the cobalt 34 toward the surface of the film 33 to obtain a thickness of 200.
The first magnetic layer of Å was formed. The vacuum degree of the apparatus is kept at 2 × 10 ⁻⁵ Torr by a vacuum means (not shown).

Next, the base film 33 on which the first magnetic layer is formed is run on the cooling can roll 31 'to form the crucible.
Cobalt 34 'contained in 32' was vapor-deposited to form a 1000 Å thick second magnetic layer on the first magnetic layer.

After forming the first and second magnetic layers, a backcoat layer made of carbon black having a thickness of 5000Å and a binder resin made of a vinyl chloride resin and a urethane prepolymer is used as a magnetic layer of the base film by an ordinary method. A lubricant layer made of perfluoropolyether having a thickness of 20 liters was formed on the magnetic layer and the back coat layer by a conventional method on the opposite surface.

The obtained film was cut to a width of 8 mm and loaded into a cassette case to obtain an 8 mm cassette tape. About this 8mm cassette tape, static magnetic characteristics,
The still durability characteristics were measured. Table 1 shows the results. In addition, each evaluation was performed as follows.

(1) Magnetostatic characteristics Coercive force (Hc) Measured with a VSM (vibrating sample magnetometer). Saturation magnetic flux density (Bs) It measured with VSM (vibration sample type magnetometer). (2) Still durability characteristics 8mm cassette tape is set on a commercially available 8mm VTR, and output is 3dB under the conditions of 20 ° C / 50% (temperature / humidity).
The still mode time until it decreased was measured.

Example 2 An 8 mm cassette tape was manufactured by the same method as in Example 1. However, the thickness of the first magnetic layer was 400 Å, and the thickness of the second magnetic layer was 800 Å. Others are the same as in Example 1,
The same evaluation as in Example 1 was performed. Table 1 shows the results.

Comparative Example 1 An 8 mm cassette tape was manufactured by the same method as in Example 1. However, only a magnetic layer consisting of a single layer having a thickness of 1200 Å was formed by ordinary oblique vapor deposition. Others were the same as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

[0026]

[Table 1]

[0027]

According to the present invention, a vapor deposition type magnetic recording medium having improved durability and saturation magnetic flux density (Bs) can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a magnetic recording medium of the present invention.

FIG. 2 is a schematic diagram showing the structure of a conventional vapor deposition type magnetic recording medium.

FIG. 3 is a schematic view of a main part of an apparatus for manufacturing a magnetic recording medium of the present invention.

[Explanation of symbols]

 1 Base Film 2 First Magnetic Layer 3 Second Magnetic Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohide Mizutani 2606 Akabane Kai, Haga-gun, Tochigi Prefecture Kao Stock Company Research Institute (72) Inventor Katsumi Sasaki 2606 Akabane Kai-cho, Haga-gun, Tochigi Research Institute Kao Stock Company (( 72) Inventor Yuzo Matsuo, 2606, Akao, Kabane, Haga-gun, Tochigi Prefecture, Kao Institute of Stock Companies (72) Inventor, Akira 2606, Akabane, Kai-cho, Haga-gun, Tochigi, Institute of Kao Corporation

Claims (2)

[Claims] 1. A first magnetic layer comprising a base film, a first magnetic layer formed on the base film by vapor deposition, and a second magnetic layer formed on the first magnetic layer by vapor deposition. Column structure is grown perpendicularly to the surface of the base film, and the second column structure is grown obliquely to the growth direction of the column structure of the first magnetic layer. Magnetic recording medium. 2. A first magnetic layer is formed on a base film by evaporating a magnetic metal from a direction perpendicular to the surface of the base film in a vacuum, and then a magnetic metal is obliquely directed to the surface of the base film. And a step of forming a second magnetic layer on the first magnetic layer by vapor-depositing.