JPH0198123A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent a high-polymer film from wrinkling by disposing an electrode for discharge near a bobbin so as to face the surface of the high-polymer film, on which face a magnetic layer is not formed, and generating a glow discharge. CONSTITUTION:The electrode 10 for discharge is disposed near the bobbin 4 so as to face the surface of the high-polymer film 1, on which surface the magnetic layer is not formed. The electrode 10 is connected to a high-frequency power supply 11. A gas introducing port 12 is disposed near the electrode 10 and gas is introduced from said port into a vacuum vessel in order to generate the glow discharge. The film 1 on which a vapor deposited film is not formed is first wound on the bobbin 3 and is run toward the bobbin 4 so that a Ti film is deposited by evaporation on the film. The glow discharge is generated near the bobbin 4 by the electrode 10 at this time. The film 1 on which the Ti film is formed is then run from the bobbin 4 toward the bobbin 3 and a Co-Cr film is deposited by evaporation on the film. The wrinkles are not generated at this time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium in which a magnetic layer made of a thin metal film is formed on a polymer film.

Conventional technology Conventionally, coated magnetic recording media have been used, in which magnetic powder is coated on a non-magnetic substrate such as a polymer film, but in order to achieve high recording density, A thin film type, in which a metal thin film is formed on a nonmagnetic substrate by sputtering or vacuum evaporation, is being put into practical use. Among thin-film magnetic recording media, perpendicular magnetic recording media in which a Co-based alloy magnetic thin film with perpendicular magnetic anisotropy is formed as a magnetic layer are attracting attention because of their excellent short wavelength recording characteristics. Co-based alloy perpendicular magnetic anisotropy films include Co-Cr, Co-Ni-
0r, Co-V, Co-0r-W, C
o -Cr-Mo, Co-Cr-Nb, Co-
Alloy thin films such as Cr-Ta are mainly being studied. These Co-based alloy perpendicular magnetic anisotropy films are produced by sputtering or vacuum deposition (including methods such as ion blating, in which a part of evaporated atoms is ionized to deposit the film), but in particular According to the latter method, a high deposition rate of several thousand people/second or more can be achieved and is suitable for mass production.

A method of manufacturing a metal thin film magnetic recording medium by vacuum evaporation using a polymer film as a non-magnetic substrate involves depositing a magnetic layer while running the polymer film along the circumferential surface of a cylindrical can. method is the best. Second
The figure schematically shows the internal structure of a vacuum evaporation apparatus using this method.

The polymer film 1 runs along the circumferential surface of the cylindrical can 2. A magnetic layer is formed on this polymer film 1 by an evaporation source 6. 3 and 4 are bobbins around which the polymer film 1 is wound. As the evaporation source 5, a resistance heating evaporation source, an induction heating evaporation source, an electron beam evaporation source, etc. can be considered, but in order to evaporate the Co-based alloy, which is a high melting point metal, at high speed, an electron beam evaporation source is adopted. There is a need. A shielding plate 6 is arranged between the evaporation source 6 and the cylindrical can 2 in order to prevent the vapor 7 evaporated from the evaporation source 6 from adhering to unnecessary parts. The shielding plate 8 is opened as shown in FIG.

When forming a perpendicular magnetic anisotropic film made of a Co-based alloy on a polymer film, it is necessary to
Ti with a film thickness of about 100 to 300A.

It is known that when a perpendicular magnetic anisotropy film is deposited via an underlayer made of a thin film of Ge, Si, etc., the perpendicular magnetic anisotropy energy increases and short wavelength recording characteristics are improved. The formation of such an underlayer is also performed in exactly the same manner as the formation of the magnetic layer explained using FIG. .

Problems to be Solved by the Invention When a CO-based alloy thin film perpendicular magnetic recording medium is put to practical use as a magnetic tape for a VTR or the like, it is necessary to reduce the thickness of the polymer film to about 16 μm or less. Especially household V
Considering TR, a very thin polymer film of around 10 μm must be used. On such a thin polymer film, using the vacuum evaporation apparatus shown in Fig. 2,
When a CO-based alloy thin film was formed through an underlayer, the following problems occurred.

A polyimide film with a thickness of 8 μm was used as the polymer film, and a Ti base layer was formed on the polymer film.
A Go-Cx perpendicular magnetic anisotropy film was further formed on the Ti film. In addition, in both films, the evaporation material was evaporated using an electron beam evaporation source. Further, when depositing any film, a potential difference was provided between the film and the circumferential surface of the cylindrical can 2. In order to provide this potential difference, a power source 9 may be installed between the free roller 8 and the cylindrical can 2 which are in contact with the vapor deposited film, as shown in FIG. Although the figure shows a DC power supply, an AC power supply may also be used.

Alternatively, the polymer film may be charged by injecting electrons into it without using a power source.

In this way, the polymer film 1 comes into strong contact with the cylindrical can 2 due to electrostatic attraction. As a result, the heat received by the polymer film during vapor deposition due to radiant heat from the evaporation source, condensation heat of vapor-deposited atoms, etc. does not easily transfer to the cylindrical can, and thermal damage to the polymer film can be reduced. As for this potential difference, the film thickness of the polymer film is 10 μm.
When the voltage is around m, approximately 60 to 300V is suitable.

However, when a magnetic recording medium is manufactured using the above method, C
Wrinkles occurred during the formation of the o-Cr film. If wrinkles occur, it is impossible to use the tape as a magnetic tape, and some solution is required.

Means for Solving the Problems The present invention has a structure in which a magnetic layer made of a thin metal film is formed on a polymer film running along the circumferential surface of a cylindrical can with an underlying layer interposed therebetween. In a method for producing a magnetic recording medium by vacuum evaporation, when the polymer film on which the underlayer is evaporated is wound around a bobbin,
Alternatively, when the polymer film is unwound from the bobbin during the magnetic layer deposition, a glow discharge is generated by a discharge electrode placed near the bobbin facing the surface of the polymer film on which the magnetic layer is not formed. I'll keep it.

Effect: According to the manufacturing method of the present invention, the charge on the polymer film can be removed without changing the surface condition of the underlayer after the underlayer is deposited, and as a result, a perpendicular magnetic recording medium with no wrinkles and excellent magnetic properties can be obtained. is obtained.

Embodiment An embodiment of the present invention will be described with reference to FIG. A Ti film as a base layer is deposited on a polyimide film with a film thickness of 8 μm using the vacuum deposition apparatus shown in FIG. 1, and C! An o-Or perpendicular magnetic anisotropy film was formed. In addition, when depositing either film, a potential difference of 200 V was provided between the deposited film and the cylindrical can 2 by a power source 9. The film thicknesses of the Ti film and the Go-Cτ perpendicular magnetic anisotropy film were 2000 and 2000, respectively.

An example in which a medium is manufactured using a conventional method, that is, a method that does not generate glow discharge will be described. First, a polyimide film on which no vapor deposited film is formed is wound around the bobbin 3.
It was run toward the bobbin 4 to deposit a Ti film. Ti
No wrinkles were observed in the polyimide film on which the membrane was formed.

Next, the polyimide film on which the Ti film was formed was run from the bobbin 4 toward the bobbin 3, and the Co-Cr
A film was deposited. In this step, wrinkles occurred in the polyimide film on the cylindrical can 2.

By implementing the present invention, it is possible to prevent the above wrinkles. This will be explained below. In order to carry out the present invention, as shown in FIG. 1, a discharge electrode 1o is placed near the bobbin 4, facing the surface of the polymer film on which the magnetic layer is not formed. The discharge electrode 10 is connected to a high frequency power source 11. Note that this power source is not limited to a high frequency power source, and may be an alternating current power source or a direct current power source. A gas inlet 12 is arranged near the discharge electrode 1o, and Ar, N2, . N2. A gas such as He is introduced into the vacuum chamber. By adopting such a configuration, the diagonal line 1 in FIG.
Glow discharge occurs in the area indicated by 3.

Embodiments of the present invention will be specifically described below while comparing them with the above-mentioned conventional examples.

First, a polyimide film on which no vapor-deposited film was formed was wound around a bobbin 3 and moved toward a bobbin 4 to vapor-deposit a Ti film. At this time, the discharge electrode 1 is placed near the bobbin 4.
Glow discharge was generated by o. Note that the power supplied to the discharge electrode was 300W. In addition, Ar is used as the gas for generating glow discharge, and the bobbin 4
The nearby gas pressure was 4×10 Torr. At this time, the gas pressure near the evaporation source was 6×10 Torr.

No wrinkles were observed in the polyimide film on which the T1 film was formed.

Next, the polyimide film on which the Ti film was formed was run from the bobbin 4 toward the bobbin 3, and the Co-Cr
A film was deposited. At this time, unlike the conventional example described above, no wrinkles were generated.

As mentioned above, the reason why the method of the present invention has a remarkable improvement effect on wrinkles compared to the conventional method is that the glow discharge treatment removes the charge on the surface (base surface) on which the magnetic layer is not formed in the polymer film. It is thought that there is. This will be explained in detail. Since the polyimide film and the cylindrical can are in strong contact during T1 deposition, the base surface of the polyimide film is charged by contact charging.

In particular, when the Ti film and the cylindrical can are deposited with a potential difference between them, the electrification is strong. In the conventional method, the wire is wound onto the bobbin 4 while being electrically charged. After this, the Co-Cr film is deposited by traveling in the opposite direction, but because the base surface of the polyimide film is electrically charged, it adheres unevenly to the circumferential surface of the cylindrical can 2. Wrinkles occur.

In contrast, in the method of the present invention, when the polyimide film on which the Ti film is deposited is wound onto the bobbin 4, the charge on the base surface is removed by glow discharge. the result,
It is thought that the polyimide film is uniformly attached to the circumferential surface of the cylindrical can 2 during deposition of the Co--Cr mock film, thereby preventing the occurrence of wrinkles.

Note that the glow discharge treatment during Ti vapor deposition was performed not near the bobbin 4 as shown in FIG. 1, but as shown in FIG.
Even if it is done in a part away from the bobbin 4, it is possible to remove the charge on the base surface.C.

-Cr No wrinkles occur during vapor deposition. However, with this configuration, a problem arose in that the magnetic properties of the Co-0r film deteriorated. The magnetic properties of a Co--Cr film strongly depend on the dispersion angle Δθ of the C axis in the direction perpendicular to the film surface in the dense hexagonal structure. Δθ. The smaller the value, the sharper the orientation of the C-axis in the direction perpendicular to the film surface, resulting in a film with higher perpendicular magnetic anisotropy. When the discharge electrode is arranged at the position shown in FIG. 1, the Δθ of the produced Go-Cr film. is 4 to 7, but in the case of the position shown in FIG. 4, Δθ. was 10 or more, and the perpendicular magnetic anisotropy was insufficient for use in perpendicular magnetic recording media.

Δθ of the Co-0r film depends on the position of the discharge electrode.

The reason for the change in is considered to be that the glow discharge affects the surface condition of the Ti film as the underlayer. In other words, when the discharge electrode is placed at the position shown in Figure 1, most of the ions and excited atoms of nitrogen and oxygen in Ar and residual gas do not reach the surface of the deposited film. remains in the state immediately after evaporation. C on such a Ti film.

-Or When a film is formed, Δθ. A small film is obtained. On the other hand, when the discharge electrode is located at the position shown in FIG. 4, the surface state of the Ti film changes because it is exposed to Ar and ions and excited atoms such as nitrogen and oxygen in the residual gas. When a Co--Cr film is formed on such a Ti film, Δθ6° becomes 10 or more. Therefore, the discharge electrode needs to be positioned near the bobbin 4 as shown in FIG. 1, that is, to face the base surface of the polymer film wound around the bobbin.

In the above embodiments, the effect of glow discharge treatment was explained when the polymer film on which the Ti film was formed was wound up on the bobbin 4 during the deposition of the Ti simulated film. C after vapor deposition.

- When the polymer film is unwound from the bobbin 4 during vapor deposition of the Cr mock film, even if glow discharge treatment is performed using the discharge electrodes arranged at the positions shown in FIG. Effects can be obtained.

In addition, the underlayer is not a Ti film (Ge film or St film), and the magnetic layer is a Co-Cr film.
Even with the O-based alloy thin film, the same results as in the above example were obtained. Further, the same applies when a polyamide film, a polyethylene terephthalate film, or the like is used instead of a polyimide film as the polymer film.

Effects of the Invention According to the present invention, a perpendicular magnetic recording medium using a thin polymer film with a film thickness of about 1011 m as a substrate can be stably manufactured without wrinkles, so it can be used for ultra-high recording densities such as those for digital VTRs. It is possible to realize perpendicular magnetic tape.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the inside of a vacuum evaporation apparatus for carrying out the present invention, FIG. 2 is a diagram showing an outline of the inside of a conventional vacuum evaporation apparatus, and FIG. FIG. 4 is a diagram for explaining the method of creating a potential difference between the two electrodes, and FIG. 4 is a diagram for explaining the influence of the position of the discharge electrode. 1... Polymer film, 2... Cylindrical can, 3.4... Bobbin, 6... Evaporation source, 6... Shielding plate, 7... Steam, 8
...Free roller, 9...Power supply, 10
...Discharge electrode, 11...High frequency power source, 12...Gas inlet, 13...Glow discharge generation area, S... Aperture. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 4

Claims (4)

[Claims] (1) A method for producing a magnetic recording medium using a vacuum evaporation method, which has a structure in which a magnetic layer made of a thin metal film is formed on a polymer film running along the circumferential surface of a cylindrical can with an underlying layer interposed therebetween. When the polymer film on which the underlayer is deposited is wound onto a bobbin, or when the polymer film is unwound from the bobbin during the deposition of the magnetic layer, the surface of the polymer film on which the magnetic layer is not formed is A method of manufacturing a magnetic recording medium, characterized in that a glow discharge is generated by discharge electrodes arranged near the bobbin so as to face each other. (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein a potential difference is provided between the underlayer and the cylindrical can when depositing the underlayer. (3) The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the magnetic layer is a Co-based alloy thin film having perpendicular magnetic anisotropy. (4) The base layer is a Ti film, a Ge film, or a Si film.
2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the magnetic recording medium is a film.