Magneto-optical recording medium having lubrication on both...

Dynamic information storage or retrieval – Storage medium structure – Optical track structure

Reexamination Certificate

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C428S064100, C369S283000, C369S013350

Reexamination Certificate

active

06625107

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a magneto-optical recording medium which can carry out magneto-optical recording and/or reproducing, and to an optical head device in which an objective lens is installed in a slider.
Optical disks, such as phase-change-type optical disks and magneto-optical disks, that are rewritable recording media with a large capacity have received much attention as a recording media for computers. The phase-change-type optical disks, typically including DVD-RAMs, and the magneto-optical disks, typically including AS-MOs, have been under development in order to achieve higher density recording with a larger capacity.
With respect to recording systems for magneto-optical disks, there have been known a light-intensity-modulation recording system in which the intensity of a laser light beam released from a laser light source such as a laser diode is changed and a magnetic-field-modulation recording system in which the intensity of a magnetic field generated by a magnetic head is changed; and either of these is used to carry out information recording. In the magnetic-field-modulation recording system, a floating-slider-type magnetic head or a sliding-slider-type magnetic head, which is used for recording and reproducing a magnetic disk, is also used for a magneto-optical disk. The magneto-optical disk has a layer construction including at least a substrate and a recording layer, and, for example, the floating-slider-type magnetic head is placed on a side closer to the recording layer. Upon recording and reproducing that requires a reproducing magnetic field, the slider is allowed to float above a disk face in the proximity thereof by an air flow that is generated in response to rotation of the magneto-optical disk, and after the slider has been shifted to a desired position above the magneto-optical disk, a magnetic field is applied thereto.
In the case of the above-mentioned magnetic head of a floating-slider type, the slider is maintained in a floating state while the magneto-optical disk is in rotation. However, even in such a floating state, when dusts, stains, etc. adhere to the disk surface, or when the disk has a warp, the stable floating state of the slider tends to deteriorate, with the result that the slider collides with the disk surface, causing damages to the disk surface. Moreover, the collision or crash of the magnetic head onto the disk surface might further damage a supporting mechanism for the magnetic head. Also in the case of the magnetic head of a sliding-slider type, when a sliding frictional force between the slider and the disk is not sufficient, the slider tends to jump, causing the possibility of scratches on the disk surface. Moreover, there is a possibility that a stable sliding operation with a constant speed is not available.
In order to avoid these problems, Japanese Patent Applications Laid-Open Nos. 6-176353 (1994), 7-254180 (1995) and 7-334865 (1995) have proposed magneto-optical recording media that are provided with a lubricating protective layer on the surface of a recording layer, that is, on the surface opposite to the substrate. The application of the lubricating protective layer minimizes a frictional force between the slider and the disk surface, thereby making it possible to prevent scratching even in the event of contact and collision and consequently to achieve a stable operation.
In recent years, a technique has been reported in which light-intensity-modulation recording or magnetic-field-modulation recording is carried out on a magneto-optical disk by using an optical head of a floating-slider type or a sliding-slider type. With respect to such an optical head of the slider type, various constructions have been proposed; and for example, some of them have a construction in which: an optical lens is installed on a slider, and a laser light beam, which is released toward a prism that operates in a manner so as to follow the slider, is allowed to pass through the optical lens and applied onto the disk surface.
In the same manner as the aforementioned magnetic head, the optical head of the slider type having the above-mentioned construction is susceptible to scratches on the disk surface due to degradation of the floating stability caused by dusts, stains, a warp in the disk, etc., when it is allowed to float above the disk surface by an air flow. Moreover, it is also susceptible to scratches on the disk surface due to degradation of the travelling stability caused by dusts, stains, a warp in the disk, etc., when it is allowed to slide on the disk surface. Furthermore, the supporting mechanism of the optical head might be damaged due to contact, collisions, etc. of the head onto the disk surface.
Generally, upon recording and/or reproducing of a magneto-optical disk, a laser light beam is made incident on a side closer to the substrate of the disk. Therefore, the optical head of the slider type is placed on the substrate. In the magneto-optical disks disclosed by the aforementioned Japanese Patent Applications Laid-Open Nos. 6-176353 (1994), 7-254180 (1995) and 7-334865 (1995), since the lubricating protective layer is formed on the surface of the recording layer opposite to the substrate, the resulting problem is that it is not possible to prevent scratches on the disk surface caused by the optical head of the slider type. Moreover, since the optical head requires a positional controlling operation with higher precision and has quicker movements as compared with the magnetic head, the resulting problem is that scratches on the disk surface and damages to the optical head tend to occur.
BRIEF SUMMARY OF THE INVENTION
The present invention has been devised to solve the above-mentioned problems, and its objective is to provide a magneto-optical recording medium which can prevent scratches on the disk surface caused by a slider-type optical head, and improve the floating stability and travelling stability of the optical head.
The magneto-optical medium of the present invention is characterized by comprising: a substrate; a recording layer, formed on the substrate, for recording information; a first lubricating protective layer formed on the recording layer; and a second lubricating protective layer having a transparent/translucent property, being formed on a face of the substrate opposite to the recording layer. In the present invention, the transparent/translucent lubricating protective layer is placed on the same side that the optical head is located on in a magneto-optical recording medium of a type in which a light beam is projected from a side closer to the substrate. Therefore, upon carrying out recording/reproducing of information on the magneto-optical recording medium by using an optical head of a slider type such as a floating-type slider or a sliding-type slider, when the slider of the optical head is allowed to float above the lubricating protective layer in the proximity thereof, superior floating stability is achieved, and when it is allowed to slide on the lubricating protective layer, the sliding frictional force is minimized so that higher travelling stability is achieved. Moreover, since the lubricating protective layer minimizes the impact at the time when the slider contacts or collides with it, it is possible to prevent scratches on the disk surface.
The magneto-optical recording medium of the present invention is characterized by comprising: a substrate; a recording layer, formed on the substrate, for recording information; and a lubricating protective layer having a transparent/translucent property, being formed on the recording layer.
In the present invention, the transparent/translucent lubricating protective layer is placed on the same side that the optical head is located on in a magneto-optical recording medium of a type in which a light beam is made incident on a side closer to the recording layer. Therefore, when the slider of the optical head is allowed to float above the lubricating protective layer in the proximity thereof, superior floating stability is achiev

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