JPH0510732B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium having good magnetic properties, and more specifically to a magnetic recording medium in which an Fe-based thin film formed by oblique evaporation is provided on a non-magnetic base material. Relating to a manufacturing method. Technical background of the invention and its problems In recent years, with the increasing demand for high-density magnetic recording, methods such as vacuum evaporation, sputtering, and ion plating (in this specification, transfer of deposited substances through the gas phase and A so-called evaporation-type magnetic recording medium has been developed in which a ferromagnetic metal thin film is formed on a substrate by a method that involves deposition on a substrate (hereinafter collectively referred to as "evaporation"). These vapor-deposited magnetic recording media have various advantages over magnetic recording media using ordinary binders, such as being capable of high-density recording, and efforts are being made to put them into practical use. Such a metal thin film type magnetic recording medium uses a non-magnetic substrate with an incident angle of about 20° or more, defined as the angle between a perpendicular to the substrate and a vapor flow directed toward the substrate. A ferromagnetic metal is vapor-deposited. These ferromagnetic metals include Co, Ni,
Cr, Fe, or alloys mainly composed of these ferromagnetic metals are mainly used.
Research on metal thin films composed of Co or Co-based alloys is being actively pursued. On the other hand, a metal thin film made of the ferromagnetic metal Fe or an alloy mainly composed of Fe (hereinafter referred to as an Fe-based alloy) has a lower production cost than a metal thin film made of Co or a Co-based alloy, and is S/ Although it has various advantages such as low distortion rate,
On the other hand, the magnetic recording medium has serious defects in that the coercive force Hc is highly dependent on the film thickness and the squareness ratio is small, so that it has not been put to practical use yet. OBJECTIVES AND SUMMARY OF THE INVENTION The present invention aims to solve all at once the technical drawbacks associated with metal thin film magnetic recording media in which a ferromagnetic metal is provided on a non-magnetic base material. It has a purpose like. (a) To provide a method for manufacturing a metal thin film type magnetic recording medium that is cheaper to manufacture and has a lower S/N and distortion rate than Co or Co-based alloys. (b) Coercive force Hc is large and film thickness dependence is small,
Moreover, it is an object of the present invention to provide a method for manufacturing a metal thin film magnetic recording medium having a good squareness ratio. The method for manufacturing a magnetic recording medium according to the present invention includes the steps of: () non-magnetic A step of laminating a metal thin film made of Fe or Fe-based alloy to a thickness of 300 to 1000 Å on a substrate by oblique evaporation. and () further laminating a metal thin film made of Fe or Fe-based alloy to a thickness of 300 to 1000 Å on the metal thin film treated with glow discharge in this way, Further, the present invention is characterized in that the above steps (), (), and () are performed continuously in the same vacuum apparatus. Furthermore, if necessary, the
A glow discharge treatment may be applied to a metal thin film made of Fe or Fe-based alloy, and then a metal thin film made of Fe or Fe-based alloy may be laminated to a thickness of 300 to 1000 Å by oblique evaporation, and the same operation may be repeated. Magnetic recording media are manufactured by laminating multiple layers of metal thin films made of , Fe or Fe-based alloys. BACKGROUND ART Conventionally, a method of manufacturing a magnetic recording medium has been known in which a thin metal film made of Co or a Co-based alloy having an inclined columnar structure is laminated on a nonmagnetic base material by oblique evaporation. However, after laminating a metal thin film made of Fe or Fe-based alloy on a non-magnetic substrate by oblique deposition and applying glow discharge treatment to the surface of this metal thin film, another metal thin film made of Fe or Fe-based alloy is layered. There was no known method of manufacturing a magnetic recording medium in which the magnetic recording media were laminated by oblique evaporation. The magnetic recording medium obtained by the above manufacturing method has an excellent coercive force and a good squareness ratio, and therefore, the present invention makes it possible for the first time to produce an inexpensive magnetic recording medium.
It has become possible to use Fe or Fe-based alloys as ferromagnetic metal thin films. DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. The magnetic recording medium 1 according to the present invention is manufactured as follows. First, a Fe first vapor deposited layer 3 having a tilted columnar structure is deposited on a nonmagnetic base material 2 by oblique vapor deposition.
are laminated with a film thickness of 300 to 1000 Å. If the thickness of this Fe first vapor deposited layer 3 is less than 300 Å,
This is not preferable because the film having the inclined columnar structure is immature, and sufficient magnetic flux cannot be obtained, and the shape anisotropy effect is not sufficiently observed, and good squareness ratio and coercive force cannot be obtained. On the other hand, if the film thickness exceeds 1000 Å, the tilted columnar structure grows too much, and the tilted columns adhere to each other at the tips of laterally adjacent tilted columns, resulting in deterioration of magnetic properties, that is, a decrease in squareness ratio and coercive force. This is not desirable because it is recognized that When this Fe first vapor deposition layer 3 is laminated on the non-magnetic base material 2 by oblique vapor deposition, the perpendicular line erected on the non-magnetic base material 2 and the vapor deposition flow directed to the base material from the vapor deposition source are connected. It is desirable that the angle of incidence, expressed as the angle formed, is maintained at 20° or more, preferably 45° or more. As the non-magnetic base material 2, synthetic resin films such as polyethylene terephthalate film, polyimide film, and polycarbonate film, non-magnetic metal foils such as aluminum foil, non-magnetic nickel foil, copper foil, and stainless steel foil, or glass;
A ceramic plate or the like is used. When manufacturing a magnetic recording medium in the form of a tape, it is preferable to use a base material having heat resistance, tensile strength, and dimensional stability, and in this respect, a polyethylene terephthalate film with a thickness of 4 to 25 μm is preferable. Next, the surface of the Fe first vapor deposited layer 3 laminated as described above is subjected to glow discharge treatment in a reactive gas. As the reactive gas, oxygen, nitrogen, ammonia gas, fluorine gas, silane gas, etc. are used, and these reactive gases are preferably present at a pressure of about 10 ^-2 to ^{10 -4} Torr. Further, at this time, the glow discharge voltage is preferably set in a range of 100 to 500W. Next, on the glow discharge treated Fe first vapor deposited layer 3, an inclined columnar structure is formed by oblique vapor deposition.
A Fe second vapor deposited layer 4 is laminated to a thickness of 300 to 1000 Å. The reason why the thickness of the second Fe deposited layer 4 is controlled to be 300 to 1000 Å is the same as the reason for controlling the thickness of the first Fe deposited layer. When stacking the Fe first vapor deposited layer 3 and the Fe second vapor deposited layer 4, as shown in FIG.
An inclined line 5 along the longitudinal direction of the inclined columnar structure in , and an inclined line 6 along the longitudinal direction of the inclined columnar structure in the Fe second vapor deposited layer 4 are bordered by an imaginary perpendicular line 7 erected on the base material 2 . so that they are in the same direction.
Both vapor deposited layers may be laminated. Further, as shown in FIG. 2, the inclined line 5 of the Fe first vapor deposited layer 3 and the inclined line 6 of the Fe second vapor deposited layer 4 are aligned left and right with an imaginary perpendicular line 7 erected on the base material 2 as a boundary. It is preferable to stack both vapor deposited layers so that they are separated from each other in order to improve the magnetic properties of the resulting magnetic recording medium. In the present invention, the surface of the Fe vapor deposition layer is treated with oxygen,
It is presumed that oxidation or nitriding reactions occur on a part of the surface of the Fe deposited layer by glow discharge treatment in an atmosphere of a reactive gas such as nitrogen, resulting in a magnetic material with excellent magnetic properties. It is thought that the recording medium will be obtained. On the other hand, when both vapor deposited layers are laminated so that both inclined lines 5 and 6 are in the same direction with the imaginary perpendicular line 7 as a boundary as shown in FIG. 1, no glow discharge treatment is applied to the surface of the Fe vapor deposited layer. The surface of the Fe vapor deposited layer may be treated with glow discharge without argon or argon.
If glow discharge treatment is performed in an inert gas atmosphere such as helium, a magnetic recording medium with excellent magnetic properties cannot be obtained. This is because, in the above case, the inclined columnar structure of the Fe second vapor deposited layer is stacked on top of the inclined columnar structure of the Fe first vapor deposited layer 3, which is the lower layer, in such a way that the columnar structure is extended. 1
This is thought to be due to the fact that both deposited layers were formed in the same evaporation process, and the film thickness exceeded the range that would provide good magnetic properties. In the above specific example, the vapor deposition source metal is
Although Fe was used, in the present invention, Fe
An alloy of Fe and other ferromagnetic metals such as Co, Ni, Cu, Cr, etc. can also be used as the deposition source metal, and in this case, it is desirable that Fe is contained in an amount of 50% by weight or more. Also. In the above example, two Fe vapor deposited layers were laminated on the non-magnetic base material, but three or more Fe vapor deposit layers can be obliquely deposited on the non-magnetic base material by repeating the above operations. It can also be laminated by. Specifically, the magnetic recording medium according to the present invention is formed using an apparatus as shown in FIG. 3, for example. This magnetic recording medium manufacturing apparatus 8 consists of a vacuum device that is divided into a first vacuum chamber 9 and a second vacuum chamber 10 by a partition plate 11, and is arranged so as to straddle the first vacuum chamber 9 and the second vacuum chamber 10. A first cooling can 12 and a second cooling can 13 are provided. The first vacuum chamber 9 includes an unwinding roll 14 for delivering the non-magnetic base material 2, a first guide roll 15,
A glow discharge device 16, a second guide roll 17, and a take-up roll 18 are provided. and the second
Inside the vacuum chamber 10, a first evaporation source 20 equipped with a heating means 19 at the lower side of the first cooling can, and a second evaporation source 22 equipped with the heating means 21 at the lower side of the second cooling can are provided. and the first cooling can 12
and the second cooling can 13 are separated by a partition plate 23. Further, a first shielding plate 24 is provided at the lower part of the first cooling can 12, and perpendicular lines 25a, 25b, etc. erected on the base material 2 and the first vapor deposition source 20
a vapor stream 26a, 2 directed from
The incident angles θ ₁ , θ ₂ ... shown by the angles with 6b... are
The angle is kept at 20° or more. Similarly, a second shielding plate 2 is provided at the bottom of the second cooling can 13.
7 is provided. In the apparatus having such a configuration, the non-magnetic base material 2 is transported from the unwinding roll 14 to the first cooling can 1.
2 and reaches the second vacuum tank 10, where it is in contact with the vapor flows 26a, 26b directed from the first vapor deposition source 20,
are stacked. And the base material 2 is the first guide roll 1
5 to the glow discharge device 16, where the
A glow discharge treatment is performed on the surface of the Fe first vapor deposited layer 3. The base material 2 subjected to glow discharge treatment is
The vapor stream 2 directed from the second vapor deposition source 22 is transported by winding along the second cooling can 13 via the second guide roll 17 to the second vacuum chamber 10 .
After the Fe second vapor deposition layer 4 is laminated in contact with 6c and 26d, it is wound up on a winding roll 18 as a magnetic recording medium. In addition, in the first vacuum chamber 9, there is a gas introduction system 28 for introducing a reactive gas into the chamber during glow discharge.
is provided. When laminating the Fe vapor deposition layer on the base material 2, it is desirable that the minimum incident angle θmin is 45° to 80°,
The substrate 2 also has first and second cooling cans 12 oriented in a direction such that the vapor flow is directed onto the substrate 2 at a high angle of incidence at an early stage and at a low angle of incidence at a later stage. It is desirable to transfer the winding over 13. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. Example 1 A first deposited layer of Fe was deposited to a thickness of 850 Å on a 6 μm polyethylene terephthalate film substrate by oblique deposition at a minimum incident angle of 65° using the apparatus shown in FIG. At this time, the degree of vacuum in the second vacuum chamber was adjusted to 5×10 ⁻⁵ Torr. Next, the surface of the first Fe deposited layer was subjected to glow discharge treatment at a discharge voltage of 200 W in a first vacuum chamber into which O ₂ gas was introduced at 1×10 ⁻³ Torr. Next, a second Fe deposited layer with a thickness of 850 Å was laminated by oblique deposition at a minimum incident angle of 65° on the first Fe deposited layer that had been subjected to glow discharge treatment to produce a magnetic recording medium. . Coercive force Hc [Oe], saturation magnetic flux density Bm [Gauss], residual magnetic flux density Br [Gauss] of the obtained magnetic recording medium
was measured and shown in the table along with the squareness (Br/Bm). Example 2 A magnetic recording medium was produced in the same manner as in Example 1, except that an Fe-Ni (8:2 weight ratio) Fe-based alloy was used as the deposition source. The coercive force, saturation magnetic flux density, and residual magnetic flux density of the obtained magnetic recording medium were measured and are shown in the table together with the squareness ratio. Comparative Example 1 A magnetic recording medium was manufactured in the same manner as in Example 1, except that the surface of the first Fe deposited layer was subjected to glow discharge treatment in an Algol atmosphere at 1×10 ⁻³ Torr. The coercive force, saturation magnetic flux density, and residual magnetic flux density of the obtained magnetic recording medium were measured and are shown in the table together with the squareness ratio. Comparative Example 2 A magnetic recording medium was produced in the same manner as in Example 1, except that the surface of the first Fe deposited layer was not subjected to glow discharge treatment. The coercive force, saturation magnetic flux density, and residual magnetic flux density of the obtained magnetic recording medium were measured and are shown in the table together with the squareness ratio.

[Table] From this table, it can be seen that the magnetic recording medium according to the present invention has high coercive force and squareness ratio, and therefore has good magnetic properties.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a magnetic recording medium manufactured according to the present invention, and FIG. 3 is a schematic cross-sectional view of an apparatus used to manufacture the magnetic recording medium. 1...Magnetic recording medium, 2...Nonmagnetic base material, 3...
...Fe first vapor deposited layer, 4...Fe second vapor deposited layer, 12...
...First cooling can, 13...Second cooling can, 1
6...Glow discharge device.

Claims (1)

[Claims] 1. When producing a magnetic recording medium by laminating multiple layers of metal thin films made of Fe or Fe-based alloys on a non-magnetic substrate by oblique deposition, () A step of laminating a metal thin film made of Fe or Fe-based alloy to a thickness of 300 to 1000 Å by direct evaporation, () The surface of the metal thin film obtained in the above step () is treated with glow discharge in a reactive gas. and () further laminating a metal thin film made of Fe or Fe-based alloy to a thickness of 300 to 1000 Å on the metal thin film treated with glow discharge in this way, and the above step ( ), (), and () are continuously performed in the same vacuum apparatus.