JPH0798832A - Magnetic recording medium, its production and producing device - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium improved in both of low frequency output and high frequency output by forming a magnetic layer on a nonmagnetic supporting body in such a manner that the width of the columnar structure in the layer is gradually decreased with the distance from a nonmagnetic supporting body in the perpendicular direction to the longitudinal plane of the nonmagnetic supporting body. CONSTITUTION:This magnetic recording medium is produced by allowing a nonmagnetic supporting body 4 to travel in a vapor deposition zone of specified length in a vacuum chamber 1 so that an enough amt. of metal particles to form a magnetic layer can be deposited on the nonmagnetic supporting body 4. The position of a crucible 6 as the vapor deposition source and a deposition- preventing plate 7 to the nonmagnetic supporting body 4 is controlled so that the amt. of metal particles to be deposited on the nonmagnetic supporting body 4 is gradually decreased in the vapor deposition zone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film type magnetic recording medium having a magnetic layer having a specific column structure, a manufacturing apparatus and a manufacturing method thereof.

[0002]

2. Description of the Related Art A magnetic recording medium is a so-called coating type magnetic recording medium obtained by coating a film which is a non-magnetic support with a magnetic paint in which magnetic powder is dispersed in a binder, and a film in a vacuum. There is a so-called metal thin film type magnetic recording medium which does not include a binder formed by depositing a metal by vapor deposition, sputtering or the like. The metal thin film type magnetic recording medium is considered to be promising for high-density recording because the density of the magnetic material can be increased because the magnetic layer does not contain a binder.

A metal thin film type magnetic recording medium commercially available today is manufactured by an apparatus as shown in FIG.
The magnetic layer is formed by depositing a magnetic metal on the film by a vacuum vapor deposition method or the like so as to have a thickness of about 1000 to 2000Å.

Generally, when a metal is vaporized by vapor deposition, the distribution of vaporized particles forms a Gaussian distribution centered on the portion on which the electron beam hits (maximum value). Therefore,
In the apparatus shown in FIG. 3, the column starts to grow from the region where the amount of evaporated particles is small. Therefore, as shown in FIG. 4, the column structure of the magnetic layer becomes thin near the film and becomes thick as the distance from the film increases.

[0005]

In the conventional metal thin film type magnetic recording medium having such a column structure, the output in the low range becomes low, and in particular, the color may not be sufficiently clear on a video tape. Further improvement in low frequency output is desired. It is also desired to further improve the high frequency output together with the low frequency output.

[0006]

As a result of intensive studies to solve the above problems, the present inventors have found that the thickness of the column structure of the magnetic layer gradually becomes smaller as it goes away from the non-magnetic support. However, they have found that both low-frequency output and high-frequency output can be improved, and that such a magnetic recording medium can be manufactured by a specific manufacturing apparatus, thus completing the present invention.

[Magnetic Recording Medium of the Present Invention] That is, the present invention has a non-magnetic support and a magnetic layer formed on the non-magnetic support, and the column structure of the magnetic layer has the thickness of the non-magnetic support. The present invention provides a magnetic recording medium characterized in that it gradually becomes thinner with increasing distance from the non-magnetic support in a direction perpendicular to the longitudinal plane of the support.

A model of the column structure of the magnetic recording medium of the present invention is shown in FIG. The amount of metal particles attached to the non-magnetic support gradually decreases from the surface of the non-magnetic support, and as a result, as shown in FIG. 2, in the direction perpendicular to the longitudinal plane of the non-magnetic support, the non-magnetic support is non-magnetic. It becomes thinner gradually as it gets away from the support.

Although the change in the thickness of the column structure is not particularly limited, for example, the ratio of the thickness (B) of the thinnest portion to the thickness (A) of the thickest portion is A: B = 10: 1 to 10 :. A range of 3 is sufficient.

In the method of manufacturing a magnetic recording medium of the present invention, examples of the magnetic material for forming the magnetic layer include ferromagnetic metal materials used for manufacturing ordinary metal thin film type magnetic recording media, such as Co and Ni. , A ferromagnetic metal such as Fe,
Fe-Co, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe-Fh, Fe-C
u, Co-Cu, Co-Au, Co-Y, Co-La, Co-Pr, Co-G
d, Co-Sm, Co-Pt, Ni-Cu, Mn-Bi, Mn-Sb, Mn-A
l, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr, Ni-Co-Cr
And other ferromagnetic alloys. The magnetic layer is preferably an iron thin film or a thin film of a ferromagnetic alloy mainly containing iron, and particularly preferably at least one selected from iron, a ferromagnetic alloy mainly containing iron, and nitrides or carbides thereof.

For high density recording, the magnetic layer of the magnetic recording medium is preferably formed on the substrate by oblique vapor deposition. The method of oblique vapor deposition is not particularly limited and is based on a conventionally known method. The degree of vacuum during vapor deposition is about 10 ⁻⁴ to 10 ⁻⁷ Torr. The magnetic layer formed by vapor deposition may have either a single-layer structure or a multi-layer structure, and in particular, the durability can be improved by introducing an oxidizing gas to form an oxide on the surface of the magnetic layer. Further, by oxidizing the surface of the magnetic layer, it is magnetically dispersed, the coercive force is improved, and the high frequency characteristics are improved.

In the present invention, the magnetic layer may be a single layer or multiple layers, but at least one layer needs to be a magnetic layer having a specific column structure as described above. It is preferable that the magnetic layer has a magnetic layer farthest from the non-magnetic support. Of course, all the magnetic layers having a multilayer structure may be magnetic layers having a specific column structure.

In the case of forming a multilayer magnetic layer by vapor deposition, the thickness of the magnetic layer is two, and in the case of two layers, the thickness of the lower magnetic layer is 100 to 100.
2000Å, the thickness of the upper magnetic layer is preferably 50 ~ 1000Å,
In the case of three layers, the thickness of the lower magnetic layer is 100 to 2000Å, the thickness of the middle magnetic layer is 100 to 1000Å, and the thickness of the upper magnetic layer is
50 to 1000Å is preferable. Further, the number of magnetic layers is preferably as large as possible for high frequency recording, but it is considered that two to five layers are suitable as a practical range.

In the magnetic recording medium of the present invention, a top coat layer and a back coat layer are formed if necessary. The top coat layer is not limited, but is preferably formed of a fluorine-based lubricant such as perfluoropolyether. The thickness of the top coat layer is about 50 to 200Å. Further, the back coat layer can be formed by applying a coating material in which carbon black or the like is dispersed in a binder, or by depositing a metal or a metalloid. As the metal to be deposited,
Al, Cu, Zn, Sn, Ni, Ag, etc. and their alloys are used. However, Al and Cu are most suitable from the viewpoints of price, deposition rate, and stability after oxidation, and Al is particularly preferable. Further, as the semi-metal forming the back coat layer, Si, Ge, As,
Sc, Sb, etc. are used. In particular, Si is most suitable in terms of price, adhesion speed, and the like. The thickness of the back coat layer formed by coating after drying is about 0.4 to 1.0 μm, and the thickness of the back coat layer formed of metal or metalloid is about 0.05 to
It is about 1.0 μm.

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

[Manufacturing Apparatus of the Present Invention] The present invention also includes a chamber and a vacuum means for maintaining the chamber in a vacuum, the chamber carrying a non-magnetic support, and a lower portion of the cylindrical can. Deposition means for depositing metal particles on the non-magnetic support, which is conveyed on the cylindrical can, a deposition preventive plate for regulating the deposition area, and an oxidation gas for introducing an oxidizing gas during or after the deposition. In the apparatus for manufacturing a magnetic recording medium having a reactive gas introducing means, the distribution of metal particles evaporated from the vapor deposition means has a Gaussian distribution, and a perpendicular line extending from the center of the maximum distribution area of the Gaussian distribution is the can. The vapor deposition means is arranged at a position not intersecting or contacting,
The deposition preventive plate is arranged at a position that regulates a vapor deposition region so that a minimum incident angle (θ _min ) of the metal particles vaporized from the vapor deposition means with respect to the can is 20 to 50 °. An apparatus for manufacturing a magnetic recording medium is provided.

An example of the manufacturing apparatus of the present invention is shown in FIG.
The feature of the manufacturing apparatus of the present invention is that in the vapor deposition region, the amount of metal particles attached to the non-magnetic support gradually decreases.
The position of the vapor deposition means is controlled and arranged, and the deposition preventive plate is arranged so as to control the minimum incident angle (θ _min ) with respect to the can of the metal particles.

As described above, in the conventional apparatus, in the Gaussian distribution of the metal particles evaporated from the vapor deposition means, the column starts to grow from the region where the metal particles are few, so that the column structure of the magnetic layer becomes narrower as it approaches the film. However, in the device of the present invention, the non-magnetic support gradually moves from a region with many metal particles to a region with few metal particles and column growth starts.
Therefore, a magnetic layer is formed in which the column structure as described above is gradually thinned away from the non-magnetic support.

In the present invention, the center of the maximum distribution region of metal particles generated from the vapor deposition means means the maximum value in the Gaussian distribution curve.

Further, the deposition preventive plate has a minimum incident angle (θ _min ) with respect to the can of the metal particles evaporated from the vapor deposition means.
Is arranged at a position that regulates the vapor deposition region so as to be 20 to 50 ° in order to improve the vapor deposition efficiency while maintaining the magnetic characteristics.

Further, the manufacturing apparatus of the present invention has an oxidizing gas introducing means for introducing an oxidizing gas such as oxygen, air or ozone during or after vapor deposition. Each of the oxidizing gas introducing means is composed of an oxidizing gas introducing pipe or an appropriate opening.

Further, the manufacturing apparatus of the present invention has a transport roller and the like as necessary, but the vapor deposition means and the deposition preventive plate need to be arranged at the positions defined above.

Usually, the vapor deposition means includes a container for the metallic material, which is open to the cylindrical can, and an electron beam generator for irradiating the metallic material in the container with an electron beam.

In the manufacturing apparatus of the present invention, the cylindrical can is usually a cooling can having a cooling function.

[Production Method of the Present Invention] Furthermore, the present invention is a magnetic method in which a non-magnetic support is run in vacuum and metal particles are deposited on the non-magnetic support by vapor deposition to form at least one magnetic layer. In the method of manufacturing a recording medium, a non-magnetic support is run in a vapor deposition region of a certain length to which a sufficient amount of metal particles for forming a magnetic layer can be attached, and the non-magnetic support in the vapor deposition region. The position of the vapor deposition source relative to the non-magnetic support and the minimum incident angle of the metal particles relative to the non-magnetic support (θ
_The magnetic recording medium is characterized in that in the direction perpendicular to the longitudinal plane of the non-magnetic support, the thickness of the column structure of the magnetic layer gradually becomes smaller as the distance from the non-magnetic support is controlled. A method of manufacturing is provided.

According to the manufacturing method of the present invention, it is possible to manufacture the magnetic recording medium of the present invention in which the above-mentioned magnetic layer has a specific column structure. The degree of vacuum when forming the magnetic layer, the thickness of the magnetic layer, and the like are in accordance with the above-described magnetic recording medium of the present invention. Further, the steps other than the step of forming the magnetic layer conform to the usual method for manufacturing a metal thin film type magnetic recording medium.

[0027]

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

Example 1 The vacuum vapor deposition apparatus shown in FIG. 1 will be described. The vacuum container 1 is
A vacuum state is set by a vacuum means (not shown). An unwinding roll 2 and a winding roll 3 are provided in the vacuum container 1. While the unwinding roll 2 unwinds and the winding roll 4 winds up the non-magnetic support 4, It is designed so that it can be wrapped around the lower side and run. A crucible 6 made of MgO is placed below the can 5, and a Co—Ni (80% -20%) alloy is put therein as a magnetic metal. Here, the deposition preventive plate 7 for restricting the vapor deposition range on the non-magnetic support 4 is disposed between the crucible 6 and the can 5 at the minimum incident angle θ _min.
Is installed at a position of 25 °. Further, the Co—Ni alloy in the crucible 6 is irradiated with the electron beam curved from the electron beam gun 8 to heat the Co—Ni alloy to evaporate the Co—Ni alloy. Here, the crucible 6 is at a position where the perpendicular P extending from the center of the maximum distribution area of the evaporated metal (generally the center where the electron beam is irradiated) does not contact the can 5 (the right side of the drawing in FIG. 1). It is located in. The tip of the oxygen introducing tube 9 guided from the outside to the inside of the vacuum container 1 is arranged above the shielding plate 7 so as to face the vapor deposition surface. The amount of oxygen introduced can be adjusted by a flow rate control valve (not shown).

The non-magnetic support is set on the unwinding roll 2 and is run on the can 5, and while introducing oxygen through the oxygen introducing tube 9, Co-Ni which is heated and evaporated by the electron beam gun 8 is evaporated. It was deposited on a non-magnetic support. The amount of oxygen introduced is not limited, but for example, 99.98% pure oxygen may be introduced at about 25 cc / min. Then, the non-magnetic support 4 on which the magnetic layer has been vapor-deposited is wound around the winding roll 2. The column structure of the magnetic layer of the magnetic recording medium manufactured as described above gradually becomes smaller as it is separated from the surface of the non-magnetic support as shown in FIG. Note that FIG. 2 schematically shows an image of a column structure in the magnetic recording medium of the present invention, in which an oxidized portion (23 in the figure) is clearly depicted. This film was cut to produce an 8 mm video tape (invention product).

As a comparative product, a magnetic metal similar to the above was vapor-deposited using the apparatus shown in FIG. 3 to obtain an 8 mm video tape (comparative product).

Comparing the outputs of both, 4 dB at an output of 7 MHz and 3 dB at an output of 1 MHz were superior to the product of the present invention.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram showing a column structure of a magnetic layer of the magnetic recording medium of the present invention.

FIG. 3 is a schematic view showing an example of a conventional magnetic recording medium manufacturing apparatus.

FIG. 4 is a schematic diagram showing a column structure of a magnetic layer of a conventional magnetic recording medium.

[Explanation of symbols]

 1: Vacuum container 2: Unwinding roll 3: Winding roll 4: Non-magnetic support 5: Cylindrical can 6: Crucible 7: Protective plate 8: Electron beam 9: Oxygen introduction tube 21,41: Base film 22,42 : Column structure of magnetic layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Shiga 2606 Akabane, Kaigai-cho, Haga-gun, Tochigi Prefecture Kao Corporation Information Science Laboratory

Claims (4)

[Claims] 1. A non-magnetic support and a magnetic layer formed on the non-magnetic support, wherein the column structure of the magnetic layer has a thickness of
A magnetic recording medium, wherein the magnetic recording medium is gradually thinned away from the non-magnetic support in a direction perpendicular to a longitudinal plane of the non-magnetic support. 2. The ratio of the thickness (B) of the thinnest portion to the thickness (A) of the thickest portion of the column structure is A:
The magnetic recording medium according to claim 1, wherein B is in the range of 10: 1 to 10: 3. 3. A chamber including a chamber and a vacuum means for keeping the chamber in a vacuum, the chamber carrying a non-magnetic support, the chamber being disposed below the cylindrical can, and carrying on the cylindrical can. Of a magnetic recording medium having a vapor deposition means for adhering metal particles on a non-magnetic support, a deposition preventive plate for regulating a vapor deposition region, and an oxidizing gas introducing means for introducing an oxidizing gas during or after vapor deposition In the apparatus, the distribution of the metal particles evaporated from the vapor deposition means has a Gaussian distribution, and the vapor deposition means is arranged at a position where a perpendicular line extending from the center of the maximum distribution area of the Gaussian distribution does not intersect or contact the can. The deposition-preventing plate is disposed at a position that regulates the vapor deposition region so that the minimum incident angle (θ _min ) of the metal particles vaporized from the vapor deposition means with respect to the can is 20 to 50 °. Characterizing Manufacturing equipment for magnetic recording media. 4. A method for producing a magnetic recording medium, which comprises running a non-magnetic support in vacuum and depositing metal particles on the non-magnetic support by vapor deposition to form at least one magnetic layer. Is run in a deposition region of a certain length to which a sufficient amount of metal particles to form a magnetic layer can adhere,
In addition, the position of the vapor deposition source relative to the non-magnetic support and the minimum incident angle (θ _min ) of the metal particles relative to the non-magnetic support are set so that the amount of the metal particles attached to the non-magnetic support in the vapor deposition region gradually decreases. A method of manufacturing a magnetic recording medium, wherein the thickness of a column structure of a magnetic layer gradually decreases in a direction perpendicular to a longitudinal plane of a non-magnetic support as the distance from the non-magnetic support increases. .