Mold for making disc substrate, process for producing mold and d

Details Mold for making disc substrate, process for producing mold and d Mold for making disc substrate, process for producing mold and d

1998-04-30

2000-05-30

Kiliman, Leszek

Stock material or miscellaneous articles

Circular sheet or circular blank

Recording medium or carrier

428 644, 428 653, 428141, 428694ST, 428694SL, 428694SG, 428900, 264 133, 264 27, 264106, 264107, 264 22, 264 25, 264 136, 264 138, G11B 566

Patent

active

060689064

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a metal mold apparatus used for molding disc substrate constituting disc-shaped recording medium such as magnetic disc, etc. and a method of manufacturing such a metal mold apparatus, and relates to a disc substrate manufactured by metal mold apparatus as described above.


BACKGROUND ART

Hitherto, as a data memory unit for computer, there is used a disc drive unit using magnetic disc as a recording medium.
As a magnetic disc used as a recording medium of the disc drive unit, there is used a magnetic disc in which magnetic film serving as a recording layer for information signals is formed on the surface of a disc substrate obtained by molding synthetic resin.
In disc drive units using magnetic disc of this kind as recording medium, the magnetic head is caused to scan, along inner and outer circumferential directions, the signal recording area of the magnetic disc rotated so that recording/reproduction of information signals is carried out. The magnetic discs used in this disc drive units are adapted so that high density has been realized along with increase in the recording capacity. In order to efficiently carry out recording and/or reproduction of information signals with respect to the magnetic discs in which high density has been realized and recording capacity has been increased as described above, it is necessary to improve transfer rate of information signals. In order to improve the transfer rate of information signals, it is necessary to increase the rotational speed of the magnetic disc, and to shorten the time required when the magnetic head seeks recording tracks of the magnetic disc.
In order to improve the seek speed of the magnetic head, there is used a disc drive unit such that dynamic pressure produced as the result of the fact that the magnetic disc rotates is utilized to produce air flow between the magnetic disc and the magnetic head to thereby carry out recording and/or reproduction of information signals in the state where the magnetic head is caused to float from the magnetic disc.
By using such flowing type magnetic head in this way, improvement in the transmission rate of information signals can be realized and the recording density of the magnetic disc can be improved. In addition, long life time of the magnetic disc and the magnetic head can be realized.
Meanwhile, in the magnetic head floating from the magnetic disc, in order to carry out stable recording and/or reproduction of information signals, the magnetic head is required to maintain stable attitude during recording and/or reproduction thus to scan on the magnetic disc with a fixed spacing being held from the magnetic disc. Namely, it is necessary to prevent that the spacing between the magnetic head and the magnetic disc is changed so that magnetic field strength across the magnetic head and the magnetic disc is fluctuated.
In view of the above, in the disc drive unit using the floating type magnetic head, the magnetic head is caused to float with a spacing of 1 .mu.m or less from the surface of the magnetic disc.
In the magnetic disc used in the disc drive unit adapted for allowing the magnetic head to float to carry out recording and/or reproduction of information signals as stated above, it is necessary to smooth, with high accuracy, the surface that the magnetic head scans. Since the magnetic head is permitted to float only by about 1 .mu.m or less from the surface of the magnetic disc, when very small uneven portion is waviness takes place at the surface of the magnetic disc, the magnetic head may collide with the rotating magnetic disc. As a result, there is also possibility that the magnetic head and/or the magnetic disc may be damaged.
In magnetic discs and/or optical discs using disc substrate obtained by molding synthetic resin, which are used as a recording medium of the disc drive unit, there have been proposed discs on which there are formed track pattern indicating recording tracks where information signals are recorded, and information signals and/or control sign

REFERENCES:
patent: 4892692 (1990-01-01), Takada

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