WO1994014161A9

WO1994014161A9 - Protective covers for optical discs

Info

Publication number: WO1994014161A9
Application number: PCT/AU1993/000635
Authority: WO
Filing date: 1993-12-08
Publication date: 1994-09-15

Abstract

The invention relates to a cover (8) for an optical disc (1) havi ng a surface through which information is readable, the cover comprising: (i) a planar member of dimensions sufficient to cover the surface; and (ii) attachment means (9) to attach the planar member to the surface, the planar member being composed of plastic s material which does not interfere with the reading of the information by an optical disc reading apparatus.

Description

PROTECTIVE COVERS FOR OPTICAL DISCS

Field of the invention

The invention relates to a protective cover for an optical storage means (such as, for example, a compact disc) to reduce the possibility of damage to its optical surface.

Background

The invention is described with reference to optical storage means which are discs, although it will be apparent that it is applicable to other optical storage means. In this specification, the term "optical disc" includes, but is not limited to, any optical storage disc, for example text, audio, video, graphics discs or any combination of them.

Compact discs are currently one of the most important means of storing recorded music and are commonly found in both commercial and domestic situations. Further, it is envisaged that greater use of optical discs, including compact discs, will be made as a means for storing computer software and data as a result of the very high density at which information can be stored on an optical disc. Thus, the already substantial use of optical discs is likely to increase quite significantly.

Information is read from an optical disc by the interaction of a laser beam with the optical surface of the optical disc. The accuracy of the reading of the information stored on the optical disc is partly dependent upon the optical surface of the disc being maintained in as good a condition as it was in at the time of manufacture. This is not always possible because, at the very least, the optical surface is exposed when an optical disc is inserted or removed from a playing apparatus. At these times, it may easily be scratched or otherwise damaged due to the build up of airborne dust particles or by being accidentally bumped against the apparatus, its case or a fingernail or ring of the operator. Although in many cases each occurrence of such damage may not of itself cause a substantial deterioration in the accuracy of reading information from the optical disc, the damage is largely irreversible and eventually there is a noticeable deterioration in the reading of information from the optical disc.

Depending on the means used to write information to an optical disc, the factors which result in a deterioration of the accuracy of reading information from an optical disc will also inhibit the accurate writing of information to the optical disc. Although the invention is described with reference to the reading of information from an optical disc, it will be appreciated that the invention can also be used to protect an optical surface for the accurate writing of information. Accordingly, investigations have been carried out with the view of devising a protective cover for the optical surface which can be semi -permanently attached to the optical disc. It was felt that the attachment should be semi-permanent so that the cover would be attached to the optical disc permanently until the protective cover is damaged. At that stage, the protective cover would be removed in a manner which did not damage the optical disc and replaced with a new one, the damaged protective cover then being disposed of. In this way, the protective covers are sacrificed to preserve the optical surface of the optical disc.

Clearly, such protective covers could only be used if they permitted the reading of information from an optical disc and, where applicable, the writing of information to an optical disc.

The use of a sacrificial protective cover for optical equipment is known in the prior art. Australian Patent Application No. 85902/91 in the name of Albert Peter Hawkins describes a system in which a clean film of the sacrificial membrane is continually moved past the optical sensing device in order to protect it from dust or dirt. The system described is adapted to be applied in industrial situations.

Further, there are various examples in the prior art where a transparent protective cover is applied to the "top" surface of an optical disc. In this context, the "top" surface is the surface to which the label identifying the optical disc is usually affixed. In contrast, the "bottom" surface is the surface through which the laser beam passes in order to read information stored underneath the "top" surface.

Accordingly, investigations have been carried out in an attempt to provide a protective cover for an optical disc to protect the optical disc's optical surface from scratches or other damage.

Description of the Embodiments of the Invention

In a first embodiment of the invention a cover for an optical disc is provided having a surface through which information is readable, the cover comprising;

(i) a planar member of dimensions sufficient to cover the surface; and

(ii) attachment means to attach the planar member to the surface, the planar member being composed of plastics material which does not interfere with the reading of the information by an optical disc reading apparatus. In a preferred embodiment of the invention the planar member is in the shape of a disc.

In another preferred embodiment the cover is removable from the optical disc.

In another preferred embodiment the attachment means is an adhesive. In another preferred embodiment the adhesive is attached to the surface in areas devoid of information which is readable.

In another preferred embodiment the attachment means includes at least one peripheral clip adapted to attach to the periphery of the optical disc. In another preferred embodiment the attachment means includes an upstanding rim projecting from the planar member, which rim includes an annular recess to receive the periphery of the optical disc.

In another preferred embodiment the attachment means is the application of a static field to a surface of the cover. The protective cover may be manufactured from any material which:

(i) permits the location of the optical disc into an optical disc reading apparatus; and

(ii) permits the optical disc reading apparatus to read the information on the optical disc.

Typically such material may be a polycarbonate. Further, the cover could be made from any other material from which the optical surface of the disc itself is manufactured.

Description of the Drawings

The invention is now further illustrated with reference to the accompanying drawings in which:

Figure 1 is a plan view of a typical compact disc; Figure 2 is a plan view of an optical disc cover according to one embodiment of the invention;

Figure 3 is a cross-sectional view of an optical disc cover according to another embodiment of the invention; and

Figure 4 is a perspective view of an optical disc cover according to the same embodiment of the invention represented in figure 3.

In the drawings illustrating various embodiments of the invention, for convenience only, like components are given the same numerical reference.

Figure 1 is a representation of a typical compact disc (1) which is commercially available. Such compact discs typically have an inner annular raised portion (2) which is thicker than the body of the compact disc and extends a fixed distance from the central hole (3). In a typical compact disc, the diameter of the overall disc (1) is about 120 mm, the diameter of the raised portion (2) is about 38 mm and the diameter of the central hole (3) is about 15 mm. Figure 2 is a representation of an optical disc cover (4) according to one embodiment of the invention. The cover (4) has a hole (5) which is adapted to receive the raised portion (2). Typically, the diameter of the cover (4) will be about 122 mm and the diameter of the hole (5) will be about 39 mm. A material suitable for the manufacture of an optical disc cover (4) is a non-UV treated polycarbonate sheet of about 0.17mm thickness supplied by Cadillac Plastics Australia of 10 Whitely Parade, Footscray, Victoria, Australia which permits transmission of the laser beam of an optical disc reading apparatus.

Figure 3 is a cross-sectional representation of another embodiment of the invention. It consists of a compact disc (1) shown in position with an optical disc cover (8). The optical disc cover (8) has an upstanding rim (9) from which protrudes an annular ridge (10) to define an annular recess (11) to assist in attaching the optical disc (1) to the optical disc cover (8). The raised portion (2) is not shown.

Figure 4 shows a perspective representation of the protective cover (8) shown in figure 3 together with the compact disc (1) and the raised rim (9). For clarity, the annular ridge (10) is not shown in figure 4.

Although the material from which the optical disc cover (8) is made is resilient and substantially non-flexible, it is possible to bend the main body of the protective cover (8) sufficiently to enable the optical disc (1) to fit within the annular ridge (10) and then be held in position by the annular ridge (10) and the upstanding rim (9). Typically, an optical disc reading apparatus does not depend for its function upon an optical disc being exactly 120 mm in diameter (or any other particular diameter). The part of the apparatus which receives the optical disc usually holds die optical disc only loosely. Thus, an optical disc which is attached to a protective cover (8) according to the present invention can be played by the optical disc reading apparatus without removal of the protective cover. In this manner, the protective cover does not need to be removed at all from the optical disc until it is damaged whereupon it can be replaced by a new protective cover. Accordingly, the optical surface of the optical disc (7) is protected from exposure to any object which may damage it for other than a very short time when the protective optical disc cover is replaced.

In summary, a protective cover is provided for an optical disc which can be permanently attached to the optical disc while it is being played or stored and need only be removed from the optical disc when it is damaged so that it can be replaced.

Claims

ClaimsThe invention is defined by the following claims:

1. A cover for an optical disc having a surface through which information is readable, the cover comprising: (i) a planar member of dimensions sufficient to cover the surface; and

(ii) attachment means to attach the planar member to the surface, the planar member being composed of plastics material which does not interfere with the reading of the information by an optical disc reading apparatus.

2. A cover according to claim 1 wherein the planar member is in the shape of.a disc.

3. A cover according to either claim 1 or 2 wherein the cover is removable from the optical disc.

4. A cover according to any one of claims 1 to 3 wherein the attachment means is an adhesive.

5. A cover according to claim 4 wherein the adhesive is attached to die surface in areas devoid of information which is readable.

6. A cover according to any one of claims 1 to 3 wherein the attachment means includes at least one peripheral clip adapted to attach to the periphery of die optical disc.

7. A cover according to claim 6 wherein the attachment means includes an upstanding rim projecting from me planar member, which rim includes an annular recess to receive the periphery of the optical disc.

8. A cover according to any one of claims 1 to 3 wherein the attachment means is the application of a static field to a surface of the cover.