In modern society, thin films are widely used in our daily life. Particularly, thin films used for wrapping paper, magnetic tapes, capacitors, etc. are manufactured by a continuous winding vacuum deposition method which allows for high speed mass production. Research and development of thin film magnetic recording media is widely practiced so as to increase recording density. Among highly dense magnetic recording thin film media, Co oxide-based thin films are popular, being commercialized for video tapes.
As a method of manufacturing tape-type Co oxide-based thin film magnetic recording media, the continuous winding vacuum deposition method (Journal of the Magnetic Society of Japan. Vol. 18, Supplement, No. S1 (1994), Proceedings of the Third Perpendicular Magnetic Recording Conference '94, page 439-442) is generally applied. The method is excellent in its productivity. A conventional continuous winding vacuum deposition method is explained by FIG. 2. Referring to the figure, an electron beam 6 is irradiated so as to deposit magnetic layer on a film on a long macromolecular substrate 4 while the substrate is running along the surface of a cylinder can 5. As a result, magnetic recording media are mass produced. In other words, long macromolecular substrate 4 is unwound from a unwinding roller 3 in a rotating direction 12 in a vacuum container 2, which is vacuum exhausted by an exhaust system 1. The substrate is irradiated by means of electron beam 6 while the substrate is running along the surface of cylinder can 5. After the substrate is deposited by an electron beam deposition source 7 at the aperture of a shielding plate 9, it is wound by a winding roller 10. Reaction gas is introduced from a gas-introducing nozzle 8 so as to carry out reactive deposition. In the figure, 10 is the winding roller, 11 is a guide roller, 12 indicates the rotating direction, and 21 is an electron gun. Co or Co--Ni is used as a magnetic material. Since the reactive deposition are carried out in an oxygen atmosphere by introducing oxygen from gas-introducing nozzle 8, a long Co--O or Co--Ni--O magnetic tape is manufactured. Due to the reactive deposition in an oxygen atmosphere, crystal particles constituting the thin film separate magnetically, thus increasing coercive force. In addition, oxidized sections formed on the surface of the film and between crystal grain boundaries prevent rust, thereby improving the hardness of the film and its mechanical durability.
As mentioned above, the continuous winding deposition method is suitable for mass-producing thin films and can improve the properties of a thin film by the above-mentioned reactive deposition. However, gas introduced to the deposition atmosphere scatters vaporized atoms even though it improves the properties of the film. The properties depend on the incidence angle of vaporized atoms into the substrate and the scattering conditions of the atoms, so that the properties decline when the flow of vaporized atoms is disturbed by introduced gas. Thus, gas should be introduced so as not to disturb the flow of vaporized atoms. In addition, the recording density of magnetic recording media should be improved since the amount of information for recording is further increasing with the development of the information age. Besides high recording density, mass productivity as well as the excellent recording and reproducing properties of the media are required in manufacturing the media. In order to reduce media noise and provide high C/N, conventional magnetic recording media should have a two-layered magnetic layer, so that the deposition of a magnetic layer has to be carried out twice. In order to make the orientation of magnetic particles the same, the second magnetic layer has to be formed after forming the first magnetic layer and then winding the first layer, so that the productivity of the media declines. Therefore, an improvement in recording density of the media is expected by introducing gas without disturbing the flow of vaporized atoms, while the mass productivity and the recording and reproducing properties of media are maintained.
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