JPH0551969B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a metal film type magnetic recording medium. More specifically, the present invention relates to a method that satisfies improvement in performance and productivity when forming a ferromagnetic layer by electron beam evaporation and ion blating. In recent years, there has been remarkable progress in high-density recording in the field of magnetic recording, and some vapor-deposited metal film-type magnetic recording media have been put into practical use in audio applications, while there are also indications that the technology may be applicable to video applications. ,
Development is active in all areas. Especially in short wavelength recording, a medium that exhibits excellent properties requires a coercive force close to 1000 Oe, so it has become important to find a method that can be expected to significantly improve productivity. ing. Generally, recording media, except for hard disks, use flexible polymer molded substrates. When polyester, which is the most versatile material, is used as a substrate, the main problem during vapor deposition is thermal degradation. The solution of increasing the evaporation rate by forcibly increasing the input power in order to improve productivity has an upper limit due to the thermal deterioration mentioned above. Therefore, it is important to effectively dissipate heat to the rotating support. The present invention was developed in view of the above, and is an improvement on the method of heating ferromagnetic materials by heating them with an electron beam. The point of the incident angle component where deposition occurs at the deposition rate is called the principal incidence, and it is important that the value is 40° or more, and that the irradiation angle of the heating electron beam to the evaporation material is within 45°. The gist of this is that Here, the irradiation angle of the electron beam to the evaporation material is
The vapor deposition material is assumed to be horizontal and defined geometrically and optically. Even the slight spread of an electron beam is quantified as defined by the central axis of the electron beam. FIG. 1A shows the main incident angle and the electron beam irradiation angle to the evaporation material. In FIG. 1A, θ is the angle at which the vapor from the evaporation source from which the molten metal 6 has evaporated is incident on the polymer molded substrate. Further, FIG. 2 shows the main structure of the apparatus used to carry out the present invention, and the embodiment will be described in detail below. As shown in FIG. 2, the polymer molded substrate 1 is
It moves from the delivery shaft 2 along the rotating support 3,
It is wound up on a winding shaft 4. When moving along the rotating support 3, a ferromagnetic layer is formed on the substrate 1, and the vapor flow radiated from the molten ferromagnetic material 6 in the evaporation source container 5 is
In relation to the degree of narrowing of the electron beam and the irradiation angle,
It is used for vapor deposition in a changed state, such as a tilted angular distribution of radiation. FIGS. 1B and 1C show the relationship between the incident angle of vapor and the vapor deposition rate. Figure 1C
10 indicates the distribution of steam. As shown in these figures, in the case of vapor deposition in which the incident angle of vapor and the vapor deposition rate change, for example, the formation of a film starts from the side where the incident angle of vapor is 90°, and as the incident angle of vapor gradually decreases, The vapor deposition rate increases, and eventually reaches a maximum at a certain angle (this angle of incidence of vapor is called the main incident angle: θmax), then decreases again, taking into consideration the magnitude of the coercive force that you want to obtain, If necessary, block out the steam with mask 7.
Vapor deposition ends at that cut-off incident angle θc. Note that max may match both θc and θc depending on the setting conditions. Now, the irradiation angle of the electron beam 8 to the evaporation material used for heating the evaporation source is β (see Figure 1C and Figure 2).
shall be. Note that the broken line 9 in FIG. 1C indicates the virtual evaporation surface of the ferromagnetic material. The reason why θmax is set to 40° or more is that the larger the incident angle of the vapor, the greater the self-shading effect that occurs during the formation process due to oblique vapor deposition, thereby increasing the coercive force. In other words, vapor deposition starts from the side where the incident angle of the vapor, which has a large self-shading effect, is 90°.
It can be assumed that as the incident angle gradually decreases, the film thickness increases, which makes it easier to obtain a high coercive force. The oblique evaporation disclosed in Japanese Patent Publication No. 19389/1989 is a technique for obtaining a high coercive force by setting a fixed incident angle to 45° or more. In addition to always including a portion (in terms of thinking, evaporation can be considered to start from a point close to the tangent), especially by using oxygen during evaporation, the cutoff angle θc can be made small (for example, 30°).
In addition, due to the relationship between the directivity of the vapor distribution (the distribution is more directional for cos ² α than for cos α) and the cylindrical surface of the rotating support, θmax is set to 40° or more to enhance the oblique evaporation effect. It is possible to obtain high coercive force under conditions of good productivity. Further, the evaporation source changes by changing the irradiation angle β of the electron beam. In particular, when the electron beam is well focused, the molten metal surface created by the evaporation material melted by the pressure of the electron beam becomes sloppy, the radiation direction of the vapor flow is tilted, and the spatial distribution of the evaporation flow changes.
In addition, part of the incident electrons is reflected, and the distribution of reflected electrons emitted outside the evaporation source changes. At this time, since the molten metal surface is concave, it is difficult to strictly discuss the spatial distribution of the reflected electrons in the radiation direction, but it can be seen that as the electron beam irradiation angle β becomes smaller, the proportion of the electrons emitted directly upward increases. It is estimated that some of this energy is high, so it easily enters the polymer molded substrate, forms an electrostatic field, and generates an electrostatic attraction between the rotating support at ground potential and the polymer molding. By pressing the object substrate against the rotating support, contact is improved and the substrate is effectively cooled during production to prevent thermal damage to the polymer molded article. The spatial distribution of the radiated vapor flow also increases as the proportion of it moves toward the rotating support.
Productivity can also be improved. In the example of the present invention, a cylindrical can with a diameter of 100 cm was prepared as a rotating support. The source of the electron beam was a piercing type electron gun, which was a straight type and had an accelerating voltage of 30 KV. A polyethylene terephthalate film (height: 11.5 μm, width: 50 cm) was used as the substrate. The surface roughness of the vapor deposition surface and the reflective side of the substrate was 450 Å. The surface of the rotating support was 0.1S. The tension of the substrate when entering the rotating support was constant at 5 kg. The oxygen introduction conditions were also constant at 10.5 Torr/sec.
The thickness of the resulting magnetic layer was also constant at 0.1 μm. Under these common conditions, the main effects of the main incident angle θmax and electron beam irradiation angle β were investigated from the aspects of characteristics and productivity. It is effective in ensuring performance, improving productivity, and preventing thermal deterioration of the substrate, and these effects are a combined effect of the main incident angle θmax and the electron beam irradiation angle β, but the magnetic properties are mainly related to the main incident angle θmax. , the irradiation angle β of the electron beam is mainly related to the temperature rise of the substrate when the main incident angle θmax is set large. (Although the table does not distinguish between states with no thermal deterioration of the board, there is a difference in temperature rise.)

[Table] In the conventional examples *1 to *3 in the table, under the conditions where thermal deterioration can be prevented, the moving speed of the board is 30, 27.5, 27.5,
21m/min, and its superiority in terms of both productivity and characteristics is clear. Here, an example of how to select conditions for making θmax 40° or more will be described below. As shown in Figure 1 D and E, the rotating support (diameter
By shifting the position of the evaporation source container 5 from directly below the 100 cm can (100 cm) to the opposite side to the moving direction of the substrate film (Y _OD is Y _OE ), the irradiation angle β of the electron beam to the evaporation surface is changed, (Let β _D be β _E ),
Make sure that θmax is 40° or more. Also, at this time, the angle between the irradiated electron beam 8 and the vapor 11 having the maximum deposition rate is α _D
decreases from to α _E. Specifically, as shown in the table, when the evaporation source container 5 is moved in a direction that reduces the irradiation angle β of the electron beam, the angle θmax increases. On the other hand, by reducing the irradiation angle β to the evaporation surface, the proportion of reflected electrons emitted directly above increases. Therefore, an electrostatic field is efficiently formed near the 90° side of the incident angle of the vapor, and the polymer molded substrate is sufficiently cooled while rotating on the rotating support. The simplest method to determine experimentally is to perform deposition with the rotating support stopped and measure the film thickness distribution. In this method, by measuring the film in the direction of movement of the substrate on the substrate and converting the position at which the maximum film thickness occurs to the circumferential side position on the rotating support, the incident angle θmax at which the maximum film thickness is obtained can be determined geometrically. Therefore, it is sufficient to conduct such an experiment two or three times.
θmax can be easily set to 40° or more. In order to confirm that the limiting values of the main incident angle and the electron beam irradiation angle are values specific to the above-mentioned system and are not simply experimentally found favorable conditions, the can diameters are set to 30 cm, 50 cm, and 120 cm. about,
Also, the circumference of the rotating support is 120cm, 180cm, 215cm,
290cm stainless steel endless belt (0.2t)
For the case where the acceleration voltage of the electron beam is
The usefulness of the present invention was confirmed for 20KV, 40KV, and 60KV. It was also confirmed that the same effect was obtained even when the material, thickness, surface roughness, and type of magnetic material of the substrate were changed, and even when applied to ion brating. As described above, according to the present invention, magnetic recording media with excellent performance can be manufactured with high productivity.
Its industrial value is great.

[Brief explanation of the drawing]

Figure 1 A, B, and C are diagrams for explaining the definition of the main incident angle and the electron beam irradiation angle on the evaporation material, and Figure 1 D and E are diagrams for explaining the conditions for making the main incidence angle 40° or more. FIG. 2 is a diagram for explaining the relationship between the electron beam irradiation angle and the main incident angle on the evaporation material when selecting an evaporation material, and FIG. 2 is a diagram for explaining an embodiment of the present invention. 1... Substrate, 3... Rotating support, 5... Evaporation source container, 6... Molten metal, 7... Mask, 8... Electron beam, 10... Vapor distribution of evaporation source, 11... Maximum evaporation Direction of steam with velocity.

Claims (1)

[Claims] 1. When electron beam evaporating a Co-based alloy in an oxygen atmosphere onto a polymer molded substrate moving along a rotating support, the irradiation angle of the electron beam is 45° or less,
A method for manufacturing a magnetic recording medium, characterized in that the incident angle at which the vapor flow of the Co-based alloy reaches a maximum deposition rate on the substrate is 40° or more.