JPS63300429A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent wrinkling by contact electrification by using a substrate formed with a metallic layer having a specific thickness or below to the face of a side where a magnetic layer is not formed and forming the magnetic layer by a vacuum deposition method on the other face. CONSTITUTION:An electrode 10 facing the magnetic surface of an electrode 9 for electric discharge used to make a discharge treatment of a film prior to formation of a perpendicularly magnetically anisotropic Co-Cr film with a vacuum deposition device is made of Ti and an electrode 11 facing the base face is made of Cu. The sputtering rate of the electrode 10 is thereby decreased to the rate lower than the sputtering rate of the electrode 11 and since the electrode material adheres extremely thinly to the base material, the contact electrification of the base face is suppressed and the wrinkling is obviated in an ensuing process for vapor deposition of the magnetic layer. The film is subjected to a thermal damage at the time of vapor deposition if the thickness of the metallic layer on this base face exceeds 50Angstrom . The wrinkling is, therefore, prevented by forming the metallic layer on the base face to <=50Angstrom .

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 higher recording density, non-magnetic substrate Thin film types, in which a thin metal film is formed on top by sputtering or vacuum evaporation, are being put into practical use. Among thin-film magnetic recording media, perpendicular magnetic anisotropic films, 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 properties. . Examples of perpendicular magnetic anisotropic films of CO-based alloys include Co-Cr and C.

-Ni-Cr, Co-V, Co-Cr-W, Co-Cr
-Mo.

Go-Cr-Nb, Co-Cr-Ta alloy films, etc. are mainly being studied. These Co-based alloy perpendicular magnetic anisotropy films are produced by sputtering or vacuum deposition (including methods such as ion grating, in which a part of evaporated atoms is ionized to deposit a film), but the latter method is particularly suitable. According to the method of
A very high film deposition rate of 0.0 OA/sec or more can be achieved, making it suitable for mass production.

A method for producing a metal thin film magnetic recording medium by vacuum evaporation using a polymer film as a non-magnetic substrate is to run the polymer film along the circumferential surface of a cylindrical can while depositing the magnetic layer. The best method is vapor deposition. Second
The figure schematically shows the internal structure of a vacuum evaporation apparatus using such a method. The polymer film 1 runs along the circumferential surface of the cylindrical can 2. 3 and 4 are bobbins for winding the polymer film, and 7a, 7b, and 7c are free rollers. A magnetic layer is formed on the polymer film 1 by the evaporation source 5 . Possible evaporation sources include resistance heating evaporation sources, induction heating evaporation sources, and electron beam evaporation sources, but in order to evaporate Go-based alloys, which are high-melting point metals, at high speed, it is necessary to employ electron beam evaporation sources. There is. A shielding plate e is arranged between the evaporation source 6 and the cylindrical can 2 in order to prevent the vapor evaporated from the evaporation source 6 from adhering to unnecessary parts. The shielding plate 6 has an opening as shown in FIG. 2 S, and the vapor passing through the opening S adheres to the polymer film.

Note that in order to improve the adhesion between the polymer film and the magnetic layer, the surface of the polymer film is usually subjected to a discharge treatment before vapor deposition. This will be specifically explained using FIG. 2.

First, the polymer film wound around the bobbin 4 is run in the direction of arrow B. At this time, a direct current, an alternating current, or a high frequency voltage is applied to the discharge electrode 8 disposed opposite to the side on which the vapor deposited film is formed to generate a discharge. In addition,
SUS is generally used as a material for the discharge electrode.

Additionally, Ar was placed in the vacuum chamber to generate electric discharge.

A gas such as N2, 02, etc. is introduced, and the gas pressure near the discharge electrode is kept at about 1 to 100 mTorr. The polymer film subjected to the discharge treatment in this manner is wound onto the bobbin 3. Next, the polymer film is run in the direction of arrow A, and a magnetic layer is formed by the vapor deposition source 6.

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 for home use
Considering TR, it is required to use a very thin polymer film of around 10 μm. When a Co-based alloy thin film was formed on such a thin polymer film using the vacuum evaporation apparatus shown in FIG. 2, the following problems occurred.

As the polymer film, a polyimide film with a thickness of 8 μm was used. First, this film was run in the direction of arrow B, and the surface on which the deposited film was formed (hereinafter this surface will be referred to as the magnetic surface) was subjected to a discharge treatment. The film running speed at this time was 20 m/min, the discharge electrode was connected to a high frequency power source, and 500 W of power was supplied. In addition, Ar gas was introduced into the vacuum chamber to generate electric discharge, and the gas pressure was increased to 20
mTorr.

Next, the discharge-treated film was run in the direction of arrow A, and a Co--Cr perpendicular magnetic anisotropy film having a thickness of 0.2 μm was deposited. In addition, during vapor deposition, the vapor deposited film and the cylindrical can 2
A potential difference was established between the two. In order to provide a potential difference, for example, the 7 Lee roller 7C in FIG. 2 is made of metal,
This free roller and the cylindrical can 2 may be connected to a DC power source or an AC power source. In this manner, by providing a potential difference between the film and the circumferential surface of the cylindrical can 2, the film is brought into strong contact with the cylindrical can due to electrostatic attraction.

As a result, heat received by the film during vapor deposition due to radiant heat from the evaporation source, condensation heat of vaporized atoms, etc., is easily transferred to the cylindrical can, and thermal damage to the film can be reduced. As this potential difference, when the thickness of the polymer film is about 10 μm, approximately 50 to 300 V is suitable.

However, in the above process, the film actually has a film thickness of 0.
When a 2 μm Co-Cr film was deposited, wrinkles were generated in the deposited film when it passed through the 7-ree roller 7C and when it was wound around the pobbin 4. Once wrinkles occur, it is impossible to use it as a magnetic tape,
Some kind of solution is needed.

Means for Solving the Problems The present invention provides a method for forming a magnetic layer made of a thin metal film by vacuum evaporation on one side of a substrate made of a polymer film running along the circumferential surface of a cylindrical can. , a method of manufacturing a magnetic recording medium, characterized in that the substrate is a substrate on which a metal layer with a thickness of 50 Å or less is formed on the surface on which the magnetic layer is not formed.

Function: According to the manufacturing method of the present invention, the amount of charge on the polymer film can be reduced, and as a result, a perpendicular magnetic recording medium can be manufactured without wrinkles.

Embodiment An embodiment of the present invention will be described using FIGS. 1 to 3. A Co--Cr perpendicular magnetic anisotropy film was formed on a polyimide film having a film thickness of 8 μm using a vacuum evaporation apparatus shown in FIG. However, as an electrode for discharging the film before vapor deposition, instead of the conventional one shown in Fig. 2,
An electrode shown in FIG. 1, which is an example of the present invention, was used.

The discharge electrodes 9 of the present invention are arranged facing both sides of the film 1. Moreover, the sputtering rate of the discharge electrode 10 facing the magnetic surface (the surface indicated by arrow C in FIG. 1) is lower than the sputtering rate of the discharge electrode 10 facing the other surface (hereinafter referred to as the pace surface). That's what I do. Specifically, the materials of the discharge electrodes 10 and 11 were Ti and Cu, respectively. The sputtering rates of Ti and Cu are as shown in Table 1 when Aτ is used as the discharge gas.

Table 1 20 mTotr of Ar gas for discharge treatment was introduced into the vacuum chamber. Both discharge electrodes have an oscillation frequency of 13, eMHz R.
The discharge treatment was performed by connecting to the F power source 12 and applying 1 KW of power. During processing, the film was run in the direction of arrow B in Figure 2, and the running speed was 20 m1.
5+ closed. Next, the film subjected to such treatment was run at a speed of 10 m15+ in the direction of arrow A in FIG. 2 to form a Co--Cr film with a thickness of 0.2 μm. Note that during vapor deposition, 2
A potential difference of 00V was provided.

The film on which the Co-Cr film was formed and exited the cylindrical can did not have any wrinkles at all after passing through the free roller 7C and when it was wound up on the hehihohin 4, which was a significant improvement compared to the conventional method. Ta.

As described above, the reason why the present invention has a remarkable improvement effect on wrinkles compared to the conventional method is due to the reduction in the amount of charge on the surface (base surface) of the polymer film that comes into contact with the cylindrical can peripheral surface. . That is, in the conventional method, the base surface of the film is charged due to contact charging due to strong contact between the film and the circumferential surface of the cylindrical can, and this charging causes
Due to uneven adhesion to the free roller or the winding bobbin, wrinkles occur when the winding passes through the free roller and when winding up. On the other hand, in the method of the present invention, the electrode with a high sputtering rate is sputtered during the discharge treatment, and the electrode material adheres to the base surface extremely thinly (several to several tens of layers). Contact charging on the base surface is suppressed and wrinkles are improved. Here, the metal layer of several to several dozen layers attached to the base surface may not be a continuous film but may be in the form of islands. The film thickness in this case is the average film thickness, that is, the film thickness assuming that the film is averaged and the film is uniform and continuous. In addition, 50 on the base surface
When a metal layer that is thicker than a human being is formed, even if a potential difference is created between the cylindrical can and the deposited film, the adhesion of the film to the circumferential surface of the cylindrical can becomes weak, causing thermal damage to the film during deposition. As a result of experiments, it became clear that

Furthermore, if the discharge electrode on the magnetic surface side of the film is made of Cu IIC, which has a high sputtering rate like the base surface side, a thin layer of Cu, which is the electrode material, is also formed on the magnetic surface side during the discharge treatment. If a Co-0r film is formed on top of this, the magnetic properties will deteriorate.

The above phenomena are summarized in Table 2. In Table 2,
One example of the present invention as a discharge electrode (electrode material: Ti on the magnetic surface side, Cu on the base surface side), and a conventional example (S on the magnetic surface side only)
It has the same structure as the present invention except for the US-made electrode).
The electrode material is on the magnetic side.

The results are also shown for the case where both the base side is made of Ti and the case where both the both sides are made of Cu. The discharge treatment was carried out in the same manner as described above, by introducing Ar gas at 2 0 mTorr into the vacuum chamber and varying the input power from the RF power source. The film running speed during the discharge treatment was 20 m/7%.

After this discharge treatment is completed, the film thickness is 0.1 μm at a film deposition rate of 1 μm.
A 2 μm Go-Cr perpendicular magnetic anisotropy film was deposited. There is a 200V voltage between the can and the Go-Cr film.
A table potential difference was provided.

As for film physical properties, the smaller the dispersion angle Δθ6° of the C-axis to the direction perpendicular to the film surface in the dense hexagonal structure, which most accurately expresses the magnetic properties of the Co-Cr film, the more the C-axis is oriented in the direction perpendicular to the film surface. This means that the film has good properties and excellent magnetic properties.

Table 2 shows that when the discharge treatment is performed using the method of the present invention with the input power from the RF power source being 0, sKW or more, no wrinkles occur and Δθゎ is 50, which shows extremely excellent crystal orientation. It can be seen that a medium is obtained. On the other hand, in the conventional method and the method in which discharge electrodes made of Ti were arranged on both sides, the wrinkles did not disappear even if the power applied from the RF power source was changed. In addition, in the method in which discharge electrodes made of KCu were arranged on both sides, the wrinkles disappeared when the input power from the RF power source was increased to O.sKW or more, but C
The Δθ6° of the o-Cr film exceeded 10°, and an extreme deterioration in magnetic properties was observed. A Go-Cr film in which Δθ6° exceeds 100 has a decreased perpendicular magnetic anisotropy and a significant decrease in short wavelength reproduction output.

As explained above, only by the method of the present invention can a medium with no wrinkles and high short wavelength reproduction output be obtained.

In the above, an example was explained in which the discharge electrode on the base surface side was made of Cu and the discharge electrode on the magnetic surface side was made of Ti.
The present invention is not limited to these materials, and the discharge treatment may be performed by arranging a discharge electrode with a high sputtering rate on the base surface side and a discharge electrode with a low sputtering rate on the magnetic surface side. Materials for the radiation 1 electrode with a high sputtering rate include:
In addition to Cu, there are Ni, Cr, Co, Fe, or alloys thereof. In addition to Ti, materials for the discharge electrode with a low sputtering rate include Si, Mo, Nb, Ta,
Examples include W and alloys thereof.

Examples of the structure of the discharge electrode used in the method of the present invention include:
In addition to the configuration shown in FIG. 1, the configuration shown in FIG. 3 may be used.

Furthermore, in the above embodiments, the case where a Co--Cr film was used as the magnetic layer was explained, but as a matter of course, Go
The same holds true for the Co-based alloy thin film outside the -Cτ film.

The case where a Co-based alloy thin film is directly deposited on a polymer film has been described above. Generally, when depositing a perpendicular magnetic anisotropic film made of a CO-based alloy on a polymer film, if the perpendicular magnetic anisotropic film made of a Co-based alloy is formed via an underlayer such as Ti or Go, It is known that Δθ5o becomes smaller and short wavelength reproduction output is improved. The method of the present invention is also effective in the case of a medium having such a configuration.

That is, by first depositing a base layer on a polymer film subjected to discharge treatment using the method of the present invention described above, and then depositing a Co-based alloy perpendicular magnetic anisotropic film on top of the base layer, a wrinkle-free film can be obtained. , and a perpendicular magnetic recording medium with excellent crystal orientation can be manufactured. 1 Furthermore, since the method of the present invention can be carried out during the conventional discharge treatment, no new steps are required and productivity is not reduced. In addition,
The discharge treatment may be performed in a vacuum device different from the device for depositing the magnetic layer.

The above example describes an example in which an extremely thin metal layer is formed on the base surface of a polymer film during discharge treatment, but even if a metal layer of 50 Å or less is formed on the base surface by a method such as sputtering, the same effect as described above is obtained. A wrinkle-free medium is obtained.

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 10 μm as a substrate can be stably produced 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]

Figure 1 is a diagram showing an example of a discharge electrode for performing the discharge treatment of the present invention, Figure 2 is a diagram showing an outline of the inside of a vacuum evaporation apparatus, and Figure 3 is a diagram showing an example of a discharge electrode for performing the discharge treatment of the present invention. It is a figure which shows the other example of the electrode. 1...Polymer film, 2...Cylindrical can, 3.4...Bobbin for winding polymer film, 6...Evaporation source, 6... ...Luck board,
7a, 7b, 7c...Free roller, 8...
...Conventional discharge electrode, 9...Discharge electrode of the present invention, 1o...Discharge electrode facing the magnetic surface, 11...Counter to the base surface discharge electrode, 1
2...RF power supply. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
--Film/2-ff

Claims (7)

[Claims] (1) When forming a magnetic layer made of a thin metal film by vacuum evaporation on one surface of a substrate made of a polymer film running along the circumferential surface of a cylindrical can, the magnetic layer is used as the substrate. A method of manufacturing a magnetic recording medium, comprising using a substrate on which a metal layer with a thickness of 50 Å or less is formed on a non-forming surface. (2) When forming a magnetic layer made of a thin metal film by vacuum evaporation on one surface of a substrate made of a polymer film running along the circumferential surface of a cylindrical can, as a pretreatment of the substrate, Discharging electrodes are disposed opposite both surfaces of the substrate, and the sputtering rate of the discharging electrode facing the surface on which the magnetic layer is formed is lower than the sputtering rate of the discharging electrode facing the other surface. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the magnetic layer is formed after the treatment. (3) A method for manufacturing a magnetic recording medium according to claim 1, characterized in that a magnetic layer made of a metal thin film is formed on the substrate with an underlayer interposed therebetween. (4) A method for manufacturing a magnetic recording medium according to claim 2, characterized in that a magnetic layer made of a thin metal film is formed on a pretreated substrate with an underlayer interposed therebetween. (5) The method for manufacturing a magnetic recording medium according to claim 1, wherein a potential difference is provided between the cylindrical can and the magnetic layer when forming the magnetic layer. (6) The method for manufacturing a magnetic recording medium according to claim 3 or 4, wherein a potential difference is provided between the cylindrical can and the underlayer when forming the underlayer. (7) The method for manufacturing a magnetic recording medium according to any one of claims 1 to 6, wherein the magnetic layer is a Co-based alloy magnetic thin film having perpendicular magnetic anisotropy.