JPH04291022A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the process for producing the magnetic recording medium which is improved in noise characteristics and has excellent electromagnetic conversion characteristics. CONSTITUTION:A mask 6 having a part 6a where the vapor flow of a ferromagnetic metallic material evaporated from an evaporating source 4 is shut off and a part 6b along the direction where the above-mentioned vapor flows is disposed in the intermediate part of a region where a nonmagnetic base 2 is subjected to vapor deposition at the time of making the above-mentioned vapor flow incident on the above-mentioned nonmagnetic base. The ferromagnetic metallic material is deposited on the nonmagnetic base 2 exposed from this mask 6 to form a magnetic layer having pseudo multilayered structures with one time of vapor deposition stage. The magnetic layer having magnetically discontinuous parts are formed in the thickness direction with one time of the vapor deposition stage, by which the good noise characteristics are obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium using a ferromagnetic metal thin film as a magnetic layer.

0002

[Prior Art] Conventionally, in the field of magnetic recording, magnetic oxides such as γ-Fe2 O3, chromium oxide, Fe, Co, Ni, etc. So-called coating-type magnetic recording media are widely used, in which a magnetic layer is formed by applying a magnetic coating in which powder of a magnetic alloy, etc., whose main components are dispersed in a binder made of an organic polymer material. . In response, with the increasing demand for high-density magnetic recording, magnetic materials made of metals or alloys such as Co-Ni are being developed by plating and vacuum thin film forming techniques (vacuum evaporation, sputtering, ion plating, etc.). A so-called vapor deposition type magnetic recording medium is known in which a metal magnetic thin film is formed by directly depositing on a non-magnetic support such as a polyester film. This vapor-deposited magnetic recording medium has excellent coercive force, squareness ratio, and electromagnetic conversion characteristics in the short wavelength range, and because the magnetic layer can be made thinner, there is no need for recording demagnetization or thickness loss during playback. It has a number of advantages, such as being extremely small, and because the magnetic layer does not contain a non-magnetic material such as a binder, the packing density of the magnetic material can be increased.

[0003] In particular, the vacuum evaporation method described above does not require drainage treatment unlike the plating method, and the manufacturing process is simple, and the film formation rate can be increased. It is considered very practical. When forming a magnetic layer by such a vacuum evaporation method, for example, as shown in FIG.
is wound around the crucible 13 while moving the non-magnetic support 12 in a predetermined direction according to the rotation of the drum 11.
A vapor flow from an evaporation source 14 filled in the evaporation source 14 is made incident on the surface of the non-magnetic support 12, thereby depositing the ferromagnetic material on the non-magnetic support 12. At this time, the drum 1
A mask 15 is arranged near the mask 1 . This results in
The vapor flow is incident only on the non-magnetic support 12 exposed from the mask 15, and the vapor deposition on the moving non-magnetic support 12 is stopped when the non-magnetic support 12 is blocked by the mask 15. Therefore, the non-magnetic support 1 of the vapor flow
The angle of incidence with respect to the normal direction of 2 is regulated. Further, for the purpose of improving the magnetic properties of the resulting magnetic layer, O2 gas is introduced into the vapor flow through an O2 gas inlet 16 provided at the end of the mask 15.

0004

[Problems to be Solved by the Invention] In the method of forming a magnetic layer by such a vacuum evaporation method, in order to improve the electromagnetic conversion characteristics, it is necessary to form the magnetic layer with a single layer structure as in the conventional method. It is considered advantageous to have a multilayer structure that is magnetically discontinuous with respect to one another. For this reason, a technique has been proposed in which two or more vapor-deposited magnetic thin films having an inclined columnar structure are laminated on a substrate to form a multilayer structure, as described in, for example, Japanese Patent Application Laid-open No. 57-133519. . Furthermore, in this technique, a nonmagnetic layer made of an oxide, a nitride, or the like is interposed between the deposited magnetic thin films, thereby further improving the electromagnetic conversion characteristics.

However, this method of laminating vapor-deposited magnetic thin films to form a multilayer structure has the disadvantage that the vapor deposition process for forming the magnetic layer becomes complicated. Therefore, it is difficult to satisfactorily improve magnetic properties and electromagnetic conversion properties using conventional methods of manufacturing magnetic recording media. Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and it forms a magnetic layer having magnetically discontinuous portions in the thickness direction in a single vapor deposition process, and has excellent electromagnetic conversion characteristics. An object of the present invention is to provide a method for manufacturing a magnetic recording medium.

[0006]

[Means for Solving the Problems] As a result of repeated studies in order to achieve the above-mentioned object, the inventors of the present invention have devised a magnetic layer using a mask having a specific shape during vapor deposition to form a magnetic layer. The inventors discovered that noise characteristics can be improved by forming a magnetic layer having discontinuous portions, leading to the present invention. That is, the method for manufacturing a magnetic recording medium of the present invention is a method for manufacturing a magnetic recording medium in which a ferromagnetic metal thin film is formed on a non-magnetic support by a vacuum thin film forming technique. , having a portion blocking the vapor flow of the ferromagnetic metal material evaporated from the evaporation source and a portion along the flow direction of the vapor flow in an intermediate portion of the region where vapor deposition is performed on the non-magnetic support. It is characterized by the provision of a mask.

In the present invention, the ferromagnetic metal thin film serving as the magnetic layer is formed by a vacuum thin film forming technique. Vacuum thin film forming techniques include vacuum evaporation, sputtering, ion plating, etc., and vacuum evaporation is particularly effective. In addition to the usual vacuum evaporation method, this vacuum evaporation method involves ionizing and accelerating the vapor flow using electric fields, magnetic fields, electron beam irradiation, etc., and supports non-magnetic support in an atmosphere with a large mean free path of the evaporated species. A method such as forming a thin film on the body may also be used. In the present invention, such a vacuum thin film forming technique is introduced to typically perform oblique deposition.

[0008] The above-mentioned oblique evaporation means that the vapor flow of the ferromagnetic metal material evaporated from the evaporation source is made incident from a direction forming a predetermined incident angle with respect to the normal direction of the surface of the moving non-magnetic support. This is a method in which a ferromagnetic metal material is deposited on the non-magnetic support. During such vapor deposition, a mask is provided in the middle of the area where the non-magnetic support is subjected to vapor deposition. This mask has a portion that blocks the vapor flow and a portion that extends in the direction in which the vapor flow flows. By providing a portion of this mask that blocks the vapor flow, there is a region where the vapor flow is partially blocked, and in this region, the oxygen
2 Gas concentration increases. Therefore, oxidation progresses partially in this region, and the proportion of oxygen in the composition of the resulting film increases. Further, by providing a portion along the flow direction of the vapor flow, the incident angle of the vapor flow with respect to the surface of the non-magnetic support is regulated, so that the orientation of the film formed in this region is improved. Here, when vapor deposition is performed on the non-magnetic support exposed through this mask, magnetically discontinuous portions are formed in the thickness direction of the resulting ferromagnetic metal thin film, and a pseudo-magnetic layer having an intermediate oxide layer is formed. It has a multi-layered structure. Therefore, by forming the magnetic layer into such a pseudo multilayer structure, the noise characteristics can be improved.

In the present invention, the metal material constituting the ferromagnetic metal thin film is not particularly limited, and includes, for example, Co, Co-Cr, Co-Ni, Co-Fe-
Any conventionally known ferromagnetic metal material such as Ni or Co-Ni-Cr can be used. Furthermore, as the non-magnetic support, any of those normally used in this type of magnetic recording medium can be used. Furthermore, in the present invention,
If necessary, a step of forming an undercoat film, a back coat layer, a top coat layer, etc. on the non-magnetic support may be added. In this case, the conditions for forming the undercoat film, backcoat layer, topcoat layer, etc. are not particularly limited, as long as they are generally applied to the manufacturing method of this type of magnetic recording medium.

0010

[Function] During vapor deposition to form a magnetic layer, there is a part in the middle of the area where vapor deposition is performed on the non-magnetic support that blocks the vapor flow incident on the non-magnetic support. When a mask having a part along the flow direction is arranged,
A ferromagnetic metal thin film having magnetically discontinuous portions in the thickness direction is obtained. That is, by providing the portion of the mask that blocks the vapor flow, the vapor flow is partially blocked, and the O2 gas concentration relative to the evaporation element supplied to the surface of the non-magnetic support becomes relatively high. A region arises. Therefore, oxidation progresses partially in this region, making it appear as if an intermediate oxide layer had been formed.

Furthermore, by providing a portion of the mask along the flow direction of the vapor flow, the incident angle of the vapor flow with respect to the surface of the non-magnetic support is regulated, so that the film formed in this region is Orientation is improved. Here, when vapor deposition is performed on the non-magnetic support exposed through this mask, a magnetically discontinuous portion is formed in the thickness direction of the resulting ferromagnetic metal thin film, and a pseudo-magnetic layer having an intermediate oxide layer is formed. It has a multi-layered structure. In this way, when the magnetic layer has a pseudo multilayer structure, noise characteristics are improved.

0012

EXAMPLES Preferred examples of the present invention will be described below based on experimental results. In this example, vapor deposition is performed by disposing a mask having a part blocking the vapor flow and a part along the vapor flow in the middle part of the vapor deposition area, and using a mask that has a magnetically discontinuous part in the thickness direction. This is an example of forming layers.

First, as shown in FIG. 1, the non-magnetic support 2 is wound around the outer peripheral surface 1a of the drum 1, and as the drum 1 rotates, the non-magnetic support 2 is moved in the direction a in the figure. While moving, the vapor flow Y from the evaporation source (pure Co) 4 filled in the crucible 3 is directed in the normal direction X to the surface of the non-magnetic support 2.
The ferromagnetic metal thin film 8 is formed on the non-magnetic support 2 by making it incident at a certain angle of incidence θ with respect to the non-magnetic support 2. It is preferable that the range of change of the incident angle θ is set to 45 to 90°. In this way, by controlling the incident angle θ of the vapor flow, it is possible to ensure good vapor deposition efficiency, and at the same time, it is possible to improve the magnetic properties. At this time, the drum 1
A mask 5 and a mask 6 are arranged near the.

The mask 5 is disposed at the final portion of the region where vapor deposition is performed on the nonmagnetic support 2 (vapor deposition region). As a result, the vapor deposition on the non-magnetic support 2 ends when the surface of the moving non-magnetic support 2 is shielded by the mask 5. That is, when the incident angle θ is continuously changed from a high angle to a low angle as the non-magnetic support 2 moves, vapor deposition is performed on the non-magnetic support 2 exposed from the masks 5 and 6. The vapor deposition is performed on the non-magnetic support 2 until the surface of the non-magnetic support 2 is shielded by the mask 5, that is, the vapor flow is incident at an incident angle θmin. Ru. Further, an O2 gas inlet 7 is provided on the end side of the mask 5, and the O2 gas inlet 7 is connected to the non-magnetic support 2.
O2 gas is supplied to the surface. In this way, O2
By introducing a gas into the vapor flow from the evaporation source 4, the magnetic properties of the resulting ferromagnetic metal thin film are improved.

On the other hand, the mask 6 is placed in the middle of the vapor deposition region. The mask 6 has a portion 6a that blocks the vapor flow and a portion 6b that extends in the direction of the vapor flow, and the portion 6b that extends in the vapor flow direction is above the vapor flow blocking portion 6a. The configuration is such that it is attached to the end closer to the mask 5. Here, the above mask 6
Since the vapor flow is partially blocked by the vapor flow blocking portion 6a, there is a region where the O2 gas concentration in the deposition gas supplied to the surface of the non-magnetic support 2 is temporarily high. The ferromagnetic metal thin film 8 formed in this region has a composition with a high oxygen content. Further, since the incident angle of the vapor flow with respect to the surface of the non-magnetic support 2 is regulated by the portion 6b along the direction in which the vapor flow flows, the orientation of the film formed in this region is improved. By disposing the mask 6 in the middle of the vapor deposition region, the resulting ferromagnetic metal thin film 8 has magnetically discontinuous portions in the thickness direction, as if an intermediate oxide layer were formed. As shown in the figure, it becomes a pseudo multilayer structure. As a result, noise characteristics are improved.

The composition of each magnetic layer was confirmed using the magnetic tape thus obtained and a magnetic tape (comparative example) on which a magnetic layer was formed by conventional oblique deposition without using the above-mentioned mask. In order to do this, we investigated the depth profile using an Auger electron spectrometer. As a result, Figure 3
As shown in Fig. 2, the magnetic layer formed by conventional oblique evaporation had a single layer structure, but as shown in Fig. 2,
In the magnetic tape of this example, a peak of oxygen atoms appeared near a depth of about 600 Å from the surface of the magnetic tape, and it was confirmed that Co was relatively reduced. From this, by performing oblique deposition using the above-mentioned mask, a magnetic layer having regions with different compositions in the thickness direction can be obtained, and this magnetic layer has a pseudo-multilayer structure with an intermediate oxide layer. became clear.

Next, the output characteristics and noise characteristics were examined using the magnetic tape of this example and the magnetic tape of the above-mentioned comparative example. The results are shown in Table 1 below. Note that the output characteristics are based on the wavelength of the signal recorded by the fixed magnetic head.
The value is the measured reproduction output at 54 μm (frequency f = 7 MHz), the noise characteristic is the value measured by the noise at the reproduction frequency f = 6 MHz, and each measured value is expressed as a relative value when the value of the comparative example is set to 0 dB. Ta.

[Table 1]

From Table 1, it is clear that in this example, good output characteristics and noise characteristics can be ensured. Furthermore, since noise is proportional to the square root of the playback output, when calculating the ratio of the output characteristic to the noise characteristic, in this example, the value of the output characteristic/noise characteristic is as low as 1.13, indicating that the noise characteristic has been improved. It turns out that there is.

[0019]

[Effects of the Invention] As is clear from the above explanation, the method for manufacturing a magnetic recording medium of the present invention uses a mask having a specific shape when performing vapor deposition on a non-magnetic support. , it is possible to partially block the vapor flow incident on the surface of the non-magnetic support, and to control the incident angle of the vapor flow with respect to the non-magnetic support. Therefore, a magnetic layer having magnetically discontinuous portions in the thickness direction can be formed in a single vapor deposition process. In this way, by forming the magnetic layer into a pseudo multilayer structure, noise characteristics are improved and good electromagnetic conversion characteristics can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a step of depositing a ferromagnetic metal thin film in the method of manufacturing a magnetic recording medium of the present invention.

FIG. 2: Depth and depth measurements obtained by Auger spectroscopy of a magnetic tape manufactured by applying the method for manufacturing a magnetic recording medium of the present invention.
It is a profile.

FIG. 3 is a depth profile obtained by Augur spectroscopy of a conventional magnetic tape having a magnetic layer having a single-layer structure.

FIG. 4 is a cross-sectional view showing a step of depositing a ferromagnetic metal thin film in a conventional method for manufacturing a magnetic recording medium.

Claims (1)

[Claims] 1. A method for manufacturing a magnetic recording medium in which a ferromagnetic metal thin film is formed on a non-magnetic support by a vacuum thin film formation technique, in which when forming the ferromagnetic metal thin film, the non-magnetic support is A mask having a part that blocks the vapor flow of the ferromagnetic metal material evaporated from the evaporation source and a part along the flow direction of the vapor flow is disposed in the middle of the region where vapor deposition is performed. A method for manufacturing a magnetic recording medium.