Stock material or miscellaneous articles – Circular sheet or circular blank – Recording medium or carrier
Reexamination Certificate
2001-11-30
2004-03-09
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Circular sheet or circular blank
Recording medium or carrier
C428S066600, C369S282000, C360S082000, C264S001310, C264S001330, C264S001700, C264S002100, C264S002200, C264S106000, C264S107000
Reexamination Certificate
active
06703100
ABSTRACT:
TECHNICAL FIELD
This invention relates to a disc-shaped recording medium used for recording a variety of information signals, such as speech or video signals, and a method for producing the same.
BACKGROUND ART
Up to now, a disc-shaped recording medium having a signal recording layer formed on a substrate molded from synthetic resin has been in use. As this type of the disc-shaped recording mediums, there are presently known a magnetic disc for magnetically recording and/or reproducing information signals, a magneto-optical disc for recording and/or reproducing information signals by exploiting changes in the direction of magnetization caused by illuminated light, and an optical disc for recording and/or reproducing the information mainly by optical means.
Such a disc-shaped recording medium, that can be mounted exchangeably on a recording and/or reproducing apparatus, is being used. The exchangeable type disc-shaped recording medium is detachably loaded on a turntable of a disc rotating driving mechanism provided in the recording and/or reproducing apparatus. This disc-shaped recording medium is loaded so as to be unified to the turntable to permit synchronous rotation of the disc-shaped recording medium in unison with the turntable.
There are several systems for uniting the exchange type disc-shaped recording medium on a turntable.
One of such systems is the so-called mechanical securing system in which the disc-shaped recording medium is chucked between the turntable and a chuck member to permit the disc-shaped recording medium to be rotated in unison with the turntable. In this mechanical securing system, a center hole provided in the disc-shaped recording medium is engaged by a centering pin formed on a disc setting surface of the turntable to align the center of rotation of the disc-shaped recording medium with that of the turntable. By coincidence of the center of rotation positions, the disc-shaped recording medium is able to be rotated without producing eccentricities with respect to the turntable. Among the disc-shaped recording mediums loaded on the turntable by the mechanical securing system, there are a compact disc (CD), an optical video disc and a DVD (digital versatile disc).
In the mechanical securing system, in which the turntable and the chuck member need to be arranged on both sides of the disc-shaped recording medium, the recording and/or reproducing apparatus is bulky in size. Moreover, there is required a mechanism for causing the chuck member to be moved into contact with and away from the disc-shaped recording medium on the turntable, thus complicating the mechanism for clamping the disc-shaped recording medium.
Another system is a magnetic clamping system which clamps the disc-shaped recording medium for rotation of the disc-shaped recording medium in unison with the turntable by exploiting the magnetic suction. The disc-shaped recording medium used in this system includes a center opening in which to mount a magnetically attracted metallic clamp member. The metallic clamp member has a center positioning hole in which is engaged the distal end of a spindle shaft carrying the turntable. This disc-shaped recording medium is clamped to the turntable by having the clamp member attracted by a magnetic provided on the turn table and by having the distal end of a spindle shaft engaged in a positioning hole provide in the clamp member. At this time, the center of rotation of the disc-shaped recording medium is caused to coincide with that of the turntable by the distal end of the spindle shaft engaged in the positioning hole provided in the clamp member. Typical of the disc-shaped recording mediums loaded on the disc table by magnetic clamp system is a MO (magneto-optical disc).
In the magnetic clamp system, the clamp member provided on the disc-shaped recording medium is attracted by a magnet provided on the turntable to clamp the disc-shaped recording medium and the turntable so that these will be rotated in unison. Since there is no necessity of providing a chuck member for pressure-supporting the disc-shaped recording medium on the turntable, it is possible to realize a simplified clamp mechanism and a thin type recording and/or reproducing apparatus.
Meanwhile, the disc-shaped recording medium, used in the magnetic clamp system, is clamped by the spindle shaft engaging in a positioning hole formed in the clamp member, with the center of rotation of the disc-shaped recording medium then coinciding with that of the turntable. That is, for correctly recording and/or reproducing information signals, the recording tracks of the disc-shaped recording medium need to be scanned correctly by e.g., an optical head. So, the clamp member needs to be loaded correctly in position at the center of the disc-shaped recording medium. For mounting the clamp member, there is such a method in which the clamp member is secured to the disc-shaped recording medium after the center of the recording track formed in the disc-shaped recording medium is brought on e.g., an X-Y table into coincidence with the center opening formed in the clamp member.
In the case of a disc-shaped recording medium used in the magnetic clamp system in which a clamp member is used both for clamping and for positioning the disc-shaped recording medium on the turntable, it is necessary not only to work the clamp member to high accuracy but also to load the clamp member highly accurately at the center of the disc-shaped recording medium thereby rendering the manufacture extremely difficult. In order to eliminate this deficiency, there is also used a magnet clamp system in which the clamp member is afforded with a function of clamping the disc-shaped recording medium to the turntable and with a function of positioning the disc-shaped recording medium with respect to the turntable. In this magnetic clamp system, a centering member provided centrally for the disc table is engaged in a center opening provided centrally on the disc-shaped recording medium to realize coincidence of the center of rotation of the disc-shaped recording medium and that of the turntable, whilst a metallic clamp member mounted on one surface of the disc-shaped recording medium for closing the center opening is magnetically attracted by a magnet provided on the turntable to clamp the disc-shaped recording medium for rotation in unison with the turntable. Typical of the disc-shaped recording medium loaded on the turntable in accordance with this system is a magneto-optical disc with a diameter of 64 mm.
By designing the disc-shaped recording medium in this manner to realize coincidence of the center of rotation with that of the turntable, it becomes possible to facilitate the working of the clamp member and the mounting thereof on the disc-shaped recording medium. By the centering member on the turntable engaging in the center hole formed in the disc-shaped recording medium, the center of rotation formed in the disc-shaped recording medium can be brought more accurately into coincidence with that of the turntable. That is, since the center opening is formed so that its center is coincident with the center of recording tracks formed on the disc-shaped recording medium, the center of the recording tracks can be directly brought into coincidence with the center of the turntable by the centering member engaging in the center opening.
Meanwhile, in recording and/or reproducing an image file or a computer memory with a larger data volume on or from a disc-shaped recording medium, the data transfer speed needs to be increased, so that the rpm of the disc-shaped recording medium needs to be increased, in contradistinction from the case of recording and/or reproducing the speech or still image as conventionally. For high-speed data processing, the rpm of the disc-shaped recording medium of approximately 4000 to 4500 rpm is required.
If a disc-shaped recording-medium is to be rotated at a constant linear velocity (CLV) to record and/or reproduce information signals, it is rotationally controlled so that the linear velocity of the recording track
Akiyama Yuji
Arakawa Nobuyuki
Kashiwagi Toshiyuki
Minemura Ken
Kiliman Leszek
Sony Corporation
LandOfFree
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