Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
1999-06-16
2001-11-20
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064400, C428S064700, C428S913000, C430S270110
Reexamination Certificate
active
06319580
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a recording disk in which an information is recorded by electrical, magnetic and/or optical characteristic change therein caused by thermal, electrical, magnetic and/or optical energy applied to the recording disk, and a producing method therefor.
JP-A-5-212755 discloses a method for producing a substrate of a recording disk from a thermoplastic resin while controlling a temperature distribution in a molding die to obtain an evenness in thickness of the substrate in a radial direction of the recording disk.
JP-A-62-231733 discloses a method for obtaining a flat surface of a ring-shaped recording disk substrate made of a plastic material by removing simultaneously outer and inner peripheral portions of the substrate whose surfaces have relatively lower flatness.
JP-A-8-77602 discloses an optical recording medium substrate whose outer peripheral area in which an optical characteristic is deteriorated is removed to expand a recordable area radially outward on the substrate.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a recording disk comprising a substrate including a plastic material and an overlay including a recording substance for recording therein an information, in which recording disk the overlay is restrained from being injured.
In a recording disk comprising a substrate including a plastic material, and an overlay arranged over the substrate and including a recording substance for recording therein an information, since a radially-outer periphery of the overlay is substantially within a radially-outer periphery of the substrate as seen in an axial direction of the recording disk, that is, the radially-outer periphery of the overlay extends substantially along the radially-outer periphery of the substrate and/or at a radially inner side with respect to the radially-outer periphery of the substrate, or is substantially prevented from extending radially outward beyond the radially-outer periphery of the substrate (while a slight burr or a significantly small and thin projection of the overlay inevitably formed by a treatment of the radially outer periphery of the overlay and/or the substrate may extend radially outward beyond the radially-outer periphery of the substrate) as seen in the axial direction, the overlay is securely supported on the substrate, or is prevented from bearing a most of a supporting or holding force of the recording disk applied to a radially-outer periphery of the recording disk, so that the overlay is restrained from being injured.
It is preferable that the substrate includes a main surface which extends substantially perpendicular to the axial direction and on which the overlay is arranged, and a side surface which extends radially outward from the main surface and is prevented from extending parallel to the main surface, the overlay includes a front surface extending substantially parallel to the main surface and exposed to the environment of the recording disk and an edge surface extending radially outward from the front surface, prevented from extending parallel to the front surface and exposed to the environment of the recording disk, and a radially-outer periphery of the front surface is substantially within a boundary between the main surface and the side surface, that is, the radially-outer periphery of the front surface extends substantially along the boundary between the main surface and the side surface and/or at a radially inner side with respect to the boundary between the main surface and the side surface (while the slight burr or the significantly small and thin projection of the overlay inevitably formed by the treatment of the radially outer periphery of the overlay and/or the substrate may extend radially outward beyond the boundary between the main surface and the side surface)as seen in the axial direction, so that an outer peripheral edge of the front surface on which a slider head run is more securely protected by the substrate and bears none of the supporting or holding force of the recording disk applied to the radially-outer periphery of the recording disk, so that the front surface is more securely prevented from being injured by the supporting or holding force. It is preferable that the radially-outer periphery of the front surface is radially inward distant from the boundary between the main surface and the side surface as seen in the axial direction, so that the outer peripheral edge of the front surface on which a slider head run is further securely protected by the substrate and bears none of the supporting or holding force of the recording disk applied to the radially-outer periphery of the recording disk, so that the front surface is further securely prevented from being injured by the supporting or holding force while a recording area formed on the front surface is kept large. It is preferable that a radial distance between the radially-outer periphery of the front surface and the boundary between the main surface and the side surface as seen in the axial direction is not more than 50 &mgr;m.
If the substrate includes a main surface (extending perpendicular to a rotational axis of the recording disk) on which the overlay is arranged and a side surface which extends radially outward from the main surface and is prevented from extending parallel to the main surface, and the overlay is prevented from extending on at least a part of the side surface, a moisture can be discharged radially outward from the substrate to an environment thereof through the at least a part of the side surface so that a chemical reaction of the overlay and/or the substrate and/or a separation of the overlay from the substrate caused by the moisture is restrained. The moisture discharge from the at least a part of the side surface is accelerated by a rotation of the recording disk on the axial axis thereof.
When the substrate includes a main surface on which the overlay is arranged and a side surface which extends radially outward from the main surface and is prevented from extending parallel to the main surface, and the overlay extends to a boundary between the main surface and the side surface, a continuity in surface shape of the recording disk is improved to reinforce a resistance against a corrosion and an exfoliation of the overlay.
When the substrate includes a main surface on which the overlay is arranged and a side surface which extends radially outward from the main surface, is prevented from extending parallel to the main surface and exposed to an environment of the recording disk, the overlay includes a front surface extending substantially parallel to the main surface and exposed to the environment of the recording disk and an edge surface extending radially outward from the front surface, prevented from extending parallel to the front surface and exposed to the environment of the recording disk, and an angle formed in the substrate between the main surface and a tangential line of the edge surface is more than 90 degrees (preferably not less than 120 degrees), an exfoliation and/or chip-off of the overlay at a joint point between the main surface and the edge surface is restrained, the continuity in surface shape of the recording disk is improved to reinforce the resistance against the corrosion and the exfoliation of the overlay.
When the substrate includes a main surface on which the overlay is arranged and a side surface which extends radially outward from the main surface and is prevented from extending parallel to the main surface, and an angle formed in the substrate between the main surface and a tangential line of the side surface is more than 90 degrees (preferably not less than 120 degrees), a chip-off of the substrate at a boundary between the main surface and the side surface is restrained.
When the substrate includes a main surface on which the overlay is arranged and an radially-outer-peripheral edge surface arranged at a relatively radially outer side with respect to the main surface, an i
Araki Tatsuo
Hirata Hiroyuki
Ishizaki Osamu
Maro Tsuyoshi
Ohta Hiroyuki
Birch & Stewart Kolasch & Birch, LLP
Evans Elizabeth
Hitachi Maxell Ltd.
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