MAGNETIC RECORDING/REPRODUCING APPARATUS

Abstract: A magnetic recording/reproducing apparatus, which performs at least one of the two functions of recording and reproducing by using a flexible magnetic recording medium (1) with a magnetic recording layer of a thin metal film, and which has a magnetic head (2), a drive unit (4, 5, 7) and a recording/reproducing circuit (6). The drive unit (4, 5, 7) causes a relative movement between the magnetic head (2) and the magnetic recording medium (1) in accordance with recording/reproducing. The recording/reproducing appar­ atus is operated in accordance with the drive unit (4, 5, 7) and inputs/outputs a recording/reproducing signal with respect to the magnetic head (2). The magnetic head is formed such that its surface contacting the magnetic recording medium (1) has a radius of curvature of 40 to 100 mm. The speed of relative movement of the drive unit (4, 5, 7) at least in the access mode is 1.5 to 5.0 m/s.

Description: The present invention relates to a magnetic recording/reproducing apparatus having a magnetic head and a flexible magnetic recording medium. Developments in information processing techniques have recently been rapidly accelerating. Along with this, the amount of information that must be contained in a memory device has increased. In order to cope with this situation, research into increased recording densities in magnetic recording apparatuses such as floppy disk apparatuses has been ongoing. This research includes development of magnetic recording mediums, i.e., so-called magnetic metal recording mediums which utilize as a magnetic recording layer a thin magnetic metal film of Co-Cr or the like. The magnetic metal recording medium appears promising as an efficient medium for high-density recording. A magnetic metal recording medium has a drawback in that scratching and wearing down of the medium tend to occur relatively sooner and relatively more frequently than in conventional particulate media. To prevent this, various countermeasures, including the provision of a protective layer on the surface of the medium, have been researched. However, a satisfactory answer to the problem has not yet been found. IBM Technical Disclosure Bulletin VOL 18, Nr. 11, April 1976, pages 3859 to 3860 discloses a magnetic head for a flexible disc. The magnetic head is spherically shaped and has a radius of curvature of 40 to 100 mm. Due to the specific shape of the magnetic head, a large area air bearing is obtained. In accordance with the pre-characterizing part of claim 1, EP-A 0097975 discloses a magnetic recording/reproducing apparatus in which the magnetic head has also a radius of curvature of 40 to 100 mm. Along the direction of relative movement between the magnetic head and the flexible magnetic recording medium grooves are formed with respect to the head. EP-A 0109481 discloses a magnetic recording medium in the form of a recording disc in which on a silicon substrate a non-magnetic undercoat layer is applied, and a magnetic layer is applied to the free surface of the undercoat layer. Finally, a non-magnetic overcoat layer is applied to the free surface of the magnetic layer. The undercoat layer is of Cr while the overcoat layer is of SiO₂. The problem underlying the present invention is to provide for a magnetic recording/reproducing apparatus of the type defined in the pre-characterizing part of claim 1, wherein various problems such as scratching and wear arising from friction between the magnetic head and the magnetic recording medium are effectively limited to prolong the service life of the medium, thereby improving the reliability of both the medium and the apparatus. This problem is solved by the features included in the characterizing part of claim 1. In regard of the recording medium, a magnetic recording layer is formed on a substrate and a hard protective layer is formed on the magnetic recording layer, the protective layer having a hardness of not less than 1000 kg/mm². In accordance with a specific embodiment of the present invention, the relative speed between the magnetic head and the medium at least in the access mode is 1.5 to 5.0 m/s. As a result the friction coefficient between the magnetic head and the recording medium is greatly decreased. Since the relative speed is sufficiently high, the data transfer rate in the recording/reproducing mode can be increased. This effect was confirmed by experiments conducted by the present inventors. Fig. 1 shows the relationship between the friction coefficient and the relative slide speed between a magnetic head and a recording medium when the magnetic head has a spherical head surface with a radius of curvature of 50 mm contacting the magnetic recording medium. As is apparent from Fig. 1, when the slide speed is 1.5 m/s or more, the friction coefficient can be reduced to 0.1 or less. Fig. 2 shows the relationship between the radius of curvature of the head surface of the magnetic head and the friction coefficient when the slide speed between the magnetic head and the magnetic recording medium is 2 m/s. As is apparent from Fig. 2, the friction coefficient can be maintained at 0.1 or less when the radius of curvature of the magnetic head falls within a range of 40 to 400 mm. Therefore, when the slide speed and the radius of curvature are set as above, the friction coefficient between the magnetic head and the magnetic recording medium can be greatly reduced. As a result, according to the present invention, the service life of a magnetic recording medium can be effectively extended, and the reliability thereof can be increased. This invention can be more fuly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 shows the relationship between the friction coefficient and the relative slide speed between a magnetic head and a magnetic recording medium when the head surface of the magnetic head is a spherical surface with a radius of curvature of 50 mm for explaining the principle of the present invention; Fig. 2 shows the relationship between the radius of curvature of the head surface of the magnetic head and the friction coefficient when the slide speed between the magnetic head and the magnetic recording medium is 2 m/s for explaining the principle of the present invention; Fig. 3 schematically shows an arrangement of a magnetic recording/reproducing apparatus according to an embodiment of the present invention; Fig. 4 is a sectional view of part of a magnetic recording medium used in the apparatus of Fig. 3; and Figs. 5 to 7 are sectional views, respectively, of part of magnetic recording media used in other embodiments of the present invention. [First Embodiment] A magnetic recording/reproducing apparatus according to a first embodiment of the present invention will be described with reference to Fig. 3. In this embodiment, the present invention is applied to a single-sided floppy disk apparatus which uses floppy disk 1 as a flexible disk-like magnetic recording medium. Magnetic head 2 having a spherical head surface with radius of curvature R of 50 mm is provided for recording/reproducing disk 1. Felt pad 3 is arranged to oppose the head surface of head 2 through disk 1. Disk 1 is rotated by disk driving mechanism 4. Head 2 and pad 3 are driven in the radial direction of disk 1 and to approach and separate therefrom. More specifically, head 2 and pad 3 are driven by head drive mechanism 5 to move in two different manners. First, head 2 and pad 3 are moved in the radial direction of disk 1 so as to be correctly positioned on a predetermined recording/reproducing track and to switch the recording/reproducing track. Second, head 2 and pad 3 are brought into contact with disk 1 by a predetermined pressure in the access, i.e., recording/reproducing mode, and are otherwise separated from disk 1, i.e., in a wait or seek mode. Thus, approach and separation movement with respect to disk 1 is performed in the wait or seek mode. Head 2 is connected to recording/reproducing circuit 6. Circuit 6 supplies a recording signal corresponding to an input to head 2 and detects and outputs a reproduction signal from head 2. Mechanisms 4 and 5 and circuit 6 are controlled by control circuit 7. Gaining access to disk 1 is performed by the interlocked operation of mechanisms 4 and 5, and circuit 6 controlled by circuit 7. Mechanism 4 drives disk 1 so as to obtain a relative speed of 1.5 to 5.0 m/s between disk 1 and head 2. Magnetic recording medium 1 is obtained by forming magnetic recording layer 12 of a thin Co-Cr metal film on substrate 11 of a flexible resin film, forming Si₃N₄ protective layer 13 thereon, and forming fluorine-series lubricating oil layer 14 thereon by spin coating. Spin coating is used to drop lubricating oil 14 on a central portion of substrate 11 having layers 12 and 13 thereon while substrate 11 is being rotated at a high speed, so that oil 14 disperses across the surface of layer 13 by a centrifugal force, thereby forming layer 14 on the surface of medium 1. Medium 1 is rotated by mechanism 4 such that relative speed v between medium 1 and head 2 is 1.5 to 5.0 m/s. During access, head 2 and medium 1 are brought into contact with each other at a predetermined pressure by movement of head 2 and pad 3 by mechanism 5. The following experiments were conducted to confirm the effect of the first embodiment of the present invention. [Experiment 1] An experiment was performed with the arrangement of the first embodiment, and the service life of disk 1 was studied. Head 2 (having a head surface with radius of curvature R of 50 mm) was movably supported by an air bearing. Felt pad 3 was arranged to oppose head 2 through medium 1. Medium 1 was rotated such that relative speed v between medium 1 and head 2 was 2.2 m/s, and head 2 and medium 1 were brought into contact with each other at a predetermined surface pressure. A track on medium 1 on which head 2 slides was repeatedly reproduced to determine how many times medium 1 can be rotated before its output is decreased by 20% of the initial output. The result was an index representing the service life of medium 1. A service life of 15 million rotations was confirmed in Experiment 1. [Control Experiment 1] The following experiment was also conducted as a control of Experiment 1. The service life of a medium was examined under the same conditions as in Experiment 1 except that the relative speed of head 2 and medium 1 was set to 1.0 m/s. Then, a service life of 2.8 million rotations was obtained. [Second Embodiment] In the second embodiment of the present invention, Aℓ₂O₃ protective layer 13' was provided in place of Si₃N₄ protective layer 13 in medium 1 of the first embodiment. [Experiment 2] The service life of a medium with a structure according to the second embodiment was examined by setting the relative speed of head 2 and medium 1 at 2.5 m/s. A service life of 8.5 million rotations was obtained. [Control Experiment 2] The service life of a medium was examined using a magnetic head having a radius of curvature of 30 mm in place of head 2 used in the second embodiment and setting the relative speed of the magnetic head and the magnetic recording medium to 1.1 m/s. A service life of 2 million rotations was obtained. [Third Embodiment] In the third embodiment of the present invention, SiO₂ protective layer 13'' was provided in place of Si₃N₄ protective film 13 in medium 1 in the first embodiment. [Experiment 3] The service life of a medium with a structure according to the third embodiment was examined in the same manner as described above by setting the relative speed of head 2 and medium 1 to 2.7 m/s. A service life of 12 million rotations was obtained. As described above, by the Experiments corresponding to the three embodiments of the present invention and the two Control Experiments not corresponding to the present invention, it was confirmed that the service life of the magnetic recording medium of the present invention is considerably longer than that of the Control Experiments. This is attributable to the following reason. Namely, when the slide speed of the magnetic head and the magnetic recording medium exceeds a specific value, a hydrodynamic force acts to separate them and a spacing gap is formed between them, thereby decreasing their friction coefficient. However, when the radius of curvature of the magnetic head exceeds 100 mm or when the slide speed exceeds 5.0 m/s, the spacing gap between the magnetic head and the medium becomes too large, making high-density recording difficult. Other preferable conditions were obtained as follows from various experiments. The hardness of protective layers 13, 13' and 13'' is preferably 1,000 kg/mm² or more. The pressure of the felt pad against the magnetic recording medium is preferably 5 to 20 gf; the contact area between the felt pad and the magnetic recording medium, 3 mm² or more; the Young's modulus of substrate 11, 600 to 800 kg/mm²; the thickness of substrate 11, 50 to 100 µm; and the total thickness of layer 13 and lubricating oil layer 14, 0.005 to 0.05 µm. The present invention is not limited to the above three embodiments. It has been confirmed that the same effect as above can be obtained if the radius of curvature of the magnetic head is 40 to 100 mm and the slide speed of the magnetic head and the magnetic recording medium is 1.5 to 5.0 m/s. The present invention can be applied to an apparatus which uses a recording medium shown in Fig. 7. This magnetic recording medium has a triple-layered structure consisting of substrate 11, magnetic recording layer 12 and protective layer 13. In this case, it is preferable that an unwoven fabric impregnated with a lubricating oil is placed between the magnetic recording medium and the package for housing the same. Also, the present invention can be applied not only to a magnetic recording/reproducing apparatus using a metal magnetic recording medium with Co-Cr as a recording layer, but also to an apparatus using another magnetic metal recording medium or Ba ferrite. The head surface need not be spherical as long as it has a radius of curvature falling within the range mentioned above.

Claims: A magnetic recording/reproducing apparatus having a magnetic head and a flexible magnetic recording medium (1), a drive unit which causes, for recording/reproducing, a relative movement between said magnetic head and the medium, said magnetic head (2) having a spherical contact surface contacting the magnetic recording medium (1) with a radius of curvature of 40 to 100 mm, characterized in that the recording medium (1) has a magnetic recording layer of a thin metal film (12), formed on a substrate (11) and a hard protective layer (13, 13', 13'') with a hardness of not less than 1000 kg/mm² on the magnetic recording layer (12), and in that a recording/reproducing circuit (6) is operated in accordance with said drive unit for inputting/outputting a recording/reproducing signal with respect to said magnetic head (2), and for performing at least one of two functions of recording and reproducing on/from only one side of the magnetic recording medium (1). An apparatus according to claim 1, characterized in that said drive unit (4, 5, 7) drives said magnetic head (2) and the magnetic recording medium (1) such that a relative speed between the magnetic head (2) and the magnetic recording medium (1) at least in an access mode is 1.5 to 5.0 m/s. An apparatus according to claim 1 or 2, characterized in that a lubricating oil layer (14) is formed on the protective layer (13, 13', 13''). An apparatus according to claim 3, characterized in that the magnetic recording layer of the magnetic recording medium (1) is a Co-Cr thin metal film (12). An apparatus according to claim 3, characterized in that the magnetic recording layer of the magnetic recording medium (1) comprises barium ferrite. An apparatus according to claim 3, 4 or 5, characterized in that the protective layer of the magnetic recording medium (1) comprises Si₃N₄ (13). An apparatus according to claim 3, 4 or 5, characterized in that the protective layer of the magnetic recording medium (1) comprises Al₂O₃ (13'). An apparatus according to claim 3, 4 or 5, characterized in that the protective layer of the magnetic recording medium (1) comprises SiO₂ (13''). An apparatus according to claim 3, 4, 5, 6, 7 or 8, characterized in that the lubricating oil layer of the magnetic recording medium (1) comprises a fluorine-series lubricating oil (14). An apparatus according to any of claims 1 to 3 or 5 to 9 when not dependent from claim 4, characterized in that the magnetic recording layer of the magnetic recording medium (1) comprises a Co-Cr thin metal film (12).

Inventors: SAITOH, MITSUYOSHI C/O PATENT DIVISION, SEKINE, KUNIO C/O PATENT DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1986
Main classification: G11B5
IPC codes: G11B5, G11B19