Process of making magnetic recording disk

Details Process of making magnetic recording disk Process of making magnetic recording disk

2000-05-03

2002-08-13

Tentoni, Leo B. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Direct application of electrical or wave energy to work

Producing or treating magnetic product precursor thereof

C264S101000, C264S293000, C264S310000, C264S320000

Reexamination Certificate

active

06432346

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the production of magnetic recording disks and more particularly to a method of smoothing the media to increase the recording capacity of the flexible disk.
BACKGROUND OF THE INVENTION
U.S. Pat. Nos. 4,874,633 Kasaga et al., 5,804,283 Inaba et al., and 5,851,622 Ejiri et al. relate to a method of producing magnetic recording media used by Fuji Photo Film Co. This process is often referred to as a “wet on wet” process. For the typically flexible high density media, the substrate is between 30 and 60 microns thick and has bumps which facilitate the unrolling of the film. The bumps may be one or two microns tall. A planarizing layer is applied to the substrate to cover most of these rough spots. Then the magnetic layer is applied which has particles and binders. One of the last steps in the process is to pass the web of media through rolls in a calendaring process which flattens the web of media. In some instances an attempt is made to burnish the media. However, it is well known that even with calendaring and burnishing the media still has bumps which are quite large in the scale of magnetic recording wherein disparities in the range of 30 nanometers or larger present a problem. If a magnetic recording head hits the disparity this causes the head to ride over the disparity and causes spacing loss preventing effective recording on some areas oft he material.
A continuously running web of media is cut into disks which are referred to as “cookies.” The “cookies” cut from the web material are made into flexible magnetic recording disks used in cartridges for flexible media magnetic recording systems such as the ZIP and Clik! storage systems made by Iomega corporation. These recording systems have increasingly higher data capacities. The higher density recording requires an exceptionally smooth recording system.
One of the critical processes in making the cookies into disks for high capacity recording cartridges is laying down servo tracks on the media. This is typically performed by a very expensive machine that has exceptionally good positional accuracy. The machine writes the servo on the information medium by magnetic recording. This takes as long as six to eight minutes. Steps have been taken to spin the disk faster so that the write operation will take less time, but still it is a very expensive procedure to servo write a flexible disk. It has been suggested to print the servo track or stamp the servo track. This is often referred to as “embossed servo”. Embossed servo techniques are described in the following references: IBM TDB vol. 21, No. 10, “Floppy Disc Embossing for Servo Applications,” Acosta et al., 3/79 pp.4259-4260; “Embossed Servo Techniques for Floppy Discs”, Thompson, et al., 1979, pp. 321-327; U.S. Pat. No. 4,935,835, Goodwin, et al., 4,958,425, Roth, et al.; 5,067,039 Godwin, et al.; 5,535,069, Chiao, et al.
It is an object of the present invention to smooth or flatten recording media for increased capacity flexible disk magnetic recording systems.
SUMMARY OF THE INVENTION
In accordance with the invention a magnetic recording disk is smoothed by positioning the disk between flat plates and increasing the temperature and pressure on the disk. Pressure is increased until the pressure approaches the yield strength of the substrate of the disk. Temperature is increased to above the glass transition temperature of the substrate, thereby allowing local deformation with low residual stress.
Further in accordance with the invention, one of the flat polished plates may be engraved with a servo pattern. When the disk is pressed between the flat plates, servo tracks are embossed on the media. The plates compress the media locally and plastically deform it. The disk is then passed through a magnetic field. The spacing over the embossed holes is so great that there is no magnetic signal in selected areas. This produces a magnetic servo track in an efficient manner.
The foregoing and other objects, features and advantages of the invention will be better understood from the following more detailed description and appended claims.


REFERENCES:
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patent: 63259822 (1988-10-01), None
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Embossed Servo Techniques for Floppy Disks by D.A. Thompson, R.E. Acosta, DW. Gilligan, G.L. Hutchins, S. Krongelb and L.T. Romankiw, Institution of Electronic and Radio Engineers—Proceedings of the Conference on Video and Data Recording, pp. 321-327 ( Jul. 1979).
Floppy Disc Embossing for Servo Applications by R.E. Acosta, G.L. Hutchins, A.T. Pfeiffer, L.T. Romankiw and D.A. Thompson, IBM Technical Disclosure Bulletin, vol. 21, No. 10, Mar. 1979 pp. 4259-4260.

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