Reinforced glass substrate

Details Reinforced glass substrate Reinforced glass substrate

1996-08-19

1998-07-14

Group, Karl

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

501 69, 501 70, 65 3013, 65 3014, 428 653, 428694ST, 428694SG, C03C 3093, C03C 1502, C03C 2100

Patent

active

057803714

DESCRIPTION:

BRIEF SUMMARY
The invention relates to glass substrates more particularly used as supports in the production of data storage units. The invention more particularly relates to glass substrates in the form of disks more particularly used as "peripheral" memories in the data processing field. Although the invention is not restricted to this application, it will be described with reference to the production of hard magnetic disks.
A hard magnetic disk is generally constituted by a support element worked in such a way that it is shaped like a centrally perforated disk. On said disk can in particular be deposited a series of thin magnetic films used for the storage of data.
The data are recorded and read with the aid of one or more reading heads, which are placed above the disk, whilst the latter performs a rotary movement. In order to obtain high performance data reading, the reading head must be as close as possible to the disk and the term contact recording is used. Thus, the signal detected by the head decreases exponentially when its altitude increases. Moreover, modern requirements require an ever larger storage density, so that a given information is stored on an ever smaller surface. In order to ensure the reading of data recorded in this way, the distance separating the disk from the reading head must be very small and namely below 300 Angstroms.
Substrates for producing hard magnetic disks are in particular described in U.S. Pat. No. 5,316,844, where the substrates are of aluminium. This document also describes an important aspect of such substrates, namely they must only have a very limited roughness. This document indicates roughness values, whereof the Ra or average roughness is between 100 and 300 Angstroms. Modern requirements, linked for an increasing storage need and therefore an ever smaller distance between the disk and reading head, correspond to a Ra below 30 Angstroms.
Although the requirements concerning the storage capacity of hard magnetic disks become increasingly severe, another requirement, which may appear paradoxical, relates to the dimensions of said disks. Thus, said data storage units must have a minimum overall size and also a reduced weight.
These requirements are linked on the one hand for the increasing need of portable and therefore small and light storage units. The development of portable data processing tools and software requiring large storage capacities form the basis for this requirement. For increasing the data storage capacity, it is also advantageous to be able to combine several hard magnetic disks in a given space and therefore to have substrates with a reduced thickness.
An aluminium substrate cannot have a thickness below 0.6 mm and at the same time the qualities required for forming a hard disk, namely rigidity and resistance to damage when the reading head strikes against the disk.
To obviate these disadvantages and lighten and possibly reduce the thickness of such a substrate, it is proposed in European patent application 579 399 to produce the same from glass. Thus, conventional glass compositions have been used making it possible to obtain a float glass of the building or car type. The float glass is obtained in the form of a ribbon, is then transformed into a sheet and finally cut and worked into disks having the requisite dimensions. The disks are then polished to obtain the desired thickness and roughness.
It has been found during tests that these glass substrates are subject to different disadvantages and consequently are not satisfactory for the production of hard magnetic disks. In particular, the surface of such float glass substrates is subject to a significant loss of alkalis and in particular potassium or sodium and essentially the ion supplied by chemical tampering. These alkalis have prejudicial effects on the magnetic films deposited on the substrates. Thus, it would appear that the salting out of the alkalis into these films causes the destruction of the recorded data over a more or less short term.
The object of the invention is to obviate these disadvant

REFERENCES:
patent: 3772135 (1973-11-01), Hara et al.
patent: 4015045 (1977-03-01), Rinehart
patent: 4119760 (1978-10-01), Rinehart
patent: 4671814 (1987-06-01), Aratani et al.
patent: 4803106 (1989-02-01), Lenhart et al.
patent: 4859636 (1989-08-01), Aratani et al.
patent: 4994415 (1991-02-01), Imai et al.
patent: 5508237 (1996-04-01), Moffatt et al.
patent: 5561089 (1996-10-01), Ishizaki et al.
patent: 5599754 (1997-02-01), Maeda et al.
patent: 5691256 (1997-11-01), Taguchi et al.

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