Dual-surface flexible magnetic tape

Abstract

A flexible magnetic-tape substrate is coated on both sides with an underlayer of relatively-low coercivity magnetic medium, which in turn is coated with a submicron layer of chromium dioxide in ultra small particles having a high coercivity. For longitudinal magnetic recording systems, magnetic layers with a coercivity of at least 1,500 Oe with underlayers having a coercivity between 25 and 500 Oe are used. For helical magnetic recording systems, magnetic layers with a coercivity of at least 2,000 Oe with underlayers having a coercivity between 25 and 800 Oe are used. These properties greatly reduce the effects of neighboring magnetic fields, thereby improving signal retention and virtually eliminating print-through and contact recording.

Description

[0001] This application is a continuation application of U.S. application Ser. No. 10 / 167,155, filed on Jun. 10, 2002.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to magnetic media for recording and, in particular, to a flexible tape with dual magnetic surfaces. [0004] 2. Description of the Related Art [0005] With the ever increasing demand for miniaturization, greater recording speed, and larger storage capacity, it has been a long-term objective of the magnetic recording industry to be able to record magnetic information on both surfaces of the magnetic medium of interest. That goal has been accomplished satisfactorily with disks, but is has been difficult to implement it with flexible-tape magnetic media. A problem for wound spools of tape, as compared to disks, arises from the very thin substrate used to separate the magnetic layers, which allows what in the art is referred to as a “print-through” or “ghost” imaging of the data patte...

AI Technical Summary

Benefits of technology

[0015] A final objective is an approach that can be implemented easily and economically according to the above stated criteria.

[0017] Although not critical, particle orientation has also been found to be a useful parameter for implementing the objectives of the invention when combined with the coercivity specifications disclosed above. For example, in linear systems the particle orientation should always be greater in the recording layers than in the underlayers, with values preferably greater than about 1.5:1 OR (orientation ratio) in the recording layers and less than about 2.0:1 OR in the underlayers. In helical systems, the particle orientation should be as low as possible in both types of layers, preferably lower than about 1.5:1 OR. These combinations of particle orientation and coercivity parameters enabled the successful implementation of dual-surface flexible magnetic tapes having recording layers less than 0.25 μm thick over underlayers about twice as thick.

Problems solved by technology

That goal has been accomplished satisfactorily with disks, but is has been difficult to implement it with flexible-tape magnetic media.

A problem for wound spools of tape, as compared to disks, arises from the very thin substrate used to separate the magnetic layers, which allows what in the art is referred to as a “print-through” or “ghost” imaging of the data pattern from one surface onto the opposite surface of the tape.

The use of a thicker tape substrate reduces print-through, but it also reduces the volumetric storage capacity of the tape.

None of these patents, though, addressed the use of weak magnetic underlayers to enable dual-surface recording.

Another problem for spools of dual-surface tape lies in the fact that the two magnetized layers are placed in close proximity to one another when the two surfaces of the tape are spooled into a wound pack of tape.

Moreover, when two recording surfaces are placed in direct contact with one another, errant magnetization on either side of the tape may also result.

Since both sides of the tape are utilized for a single recording operation, though, this invention does not improve the storage capacity of the medium.

Because of the mentioned special requirements and shortcomings, none of the solutions heretofore described in the prior art has gained commercial acceptance.

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