Optical recording medium for use with a laser recording beam

Details Optical recording medium for use with a laser recording beam Optical recording medium for use with a laser recording beam

1994-05-13

1995-12-12

Wolff, John H.

Dynamic information storage or retrieval

Storage medium structure

Layered

369283, G11B 370, G11B 584, G11B 726

Patent

active

054756731

DESCRIPTION:

BRIEF SUMMARY
RECORDING MEDIA

This invention relates to recording media in particular to recording media of the type produced in the form of a tape which can be wound onto a spool and from which it can subsequently be unwound.
Such media in general comprise a polymeric substrate having on one side a layer of recording material, for example a magnetic, magneto-optical or optical recording material and, typically, on the other side, a back coat to import desirable characteristics for example good handling and frictional properties.
In magnetic media applications, it is known to apply a super coat to the back coat and/or recording layer to provide for improved wear resistance and other desirable characteristics. For example, magnetic recording media comprising a back coat may have a lubricating layer topically provided on the back coat which is not bound to the back coat and which may readily transfer to the recording layer for example when the media is in tape form and wound onto a spool.
Hitherto, optical recording media, especially in tape form having a super coat one the back coat of the media have not been disclosed.
The Invention provides an optical recording medium for use with a laser recording beam of a given wavelength comprising a substrate having on its obverse side a recording layer which is capable of absorbing radiation of said given wavelength, a back coat on its reverse side and a super coat on the back coat.
When recording media in tape form tape is wound onto a spool the obverse and reverse sides of the media come into contact. In such winding operations it is usually necessary to wind the tape tightly to reduce the possibility of undesirable lateral slippage between winds of the tape this effect may be referred to as "stepping". "Stepping" may occur for several reasons including shock loads and/or temperature variation during transport or tape relaxation during storage. As a result of such winding, high compressive forces may exist and cause undesirable adhesion between the adjacent obverse (recording layer side) and reverse side (back coat side) of the recording media.
Where such adhesion occurs, areas of one of the adjacent layers may remain adhered to the other layer upon unwinding the tape and thereby transfer to the other layer.
Furthermore problems due to unwanted transfer of material, during winding, to hardware components, for example transport rollers may also occur. Such unwanted transfer may also occur in media in a form other than tape where the obverse and reverse sides of the media are in contact, for example when media are stacked.
We have found that by providing on at least one of the back coat or the recording layer of the recording media, a super coat which is adsorbed onto the underlying layer, problems associated with non-bonded coatings, for example lubricant layers in magnetic media, including unwanted transfer and migration of one layer to another may be reduced.
According to the present invention there is provided a recording medium comprising a substrate having on its obverse side a recording layer and on its reverse side, a back coat at least one of which layers is an underlying layer to a super coat, and a super coat on at least one side of the medium wherein the super coat is adsorbed onto the underlying layer.
The underlying layer may be the recording layer, the back coat layer or, in cases where the recording layer and back coat layer have a super coat, both.
By adsorbed we mean chemi-sorbed and/or physi-sorbed wherein the super coat is bonded, desirably chemically, to the underlying layer to increase the strength of the bond between the super coat and the underlying layer as compared with a super coat which is deposited on an underlying layer without any significant adsorption. Suitably, adsorption of the super coat provides a heat of adsorption which is greater in magnitude than any heat evolved by deposition of a super coat in which no significant adsorption to the underlying layer occurs.
The adsorbed super coat reduces the possibility of unwanted transfer of part of t

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