WO2001009886A1

WO2001009886A1 - Disc covers and methods of manufacture thereof

Info

Publication number: WO2001009886A1
Application number: PCT/GB2000/001969
Authority: WO
Inventors: Peter James Culshaw; Douglas Andrew Reynolds
Original assignee: First Elements Limited
Priority date: 1999-08-02
Filing date: 2000-05-22
Publication date: 2001-02-08
Also published as: GB2354627A; GB9918174D0; AU4936600A

Abstract

In combination a data-carrying disc (1) having a data-carrying portion (2) and a data-free inner portion (3), and an axially aligned disc-shaped cover (11) comprising an inner adhesive-carrying portion (13) and an outer adhesive-free portion (12), the cover (11) being so aligned that the inner adhesive-carrying portion adheres to the data-free portion (3) of the disc and the outer adhesive-free portion (12) is in contact with the data-carrying portion (2) of the disc (1), characterised in that the disc (11) is a single, unitary whole and is of a thickness and material such that the adhesive-free portion (12) is maintained in contact with the data-carrying portion (2) of the disc only by the inner adhesive-carrying portion (3), and by the surface contact between the adhesive-free portion (12) and the data-carrying portion (2) of the disc (1).

Description

Disc Covers and Methods of Manufacture Thereof

This invention relates to disc covers and methods of manufacture and application thereof. Particularly, but not exclusively, this invention relates to covers for the data carrying surfaces of optical discs such as compact discs (CD's), and digital versatile disks (DVD) and the like.

Compact Discs have a data carrying surface on which audio or other digital data is recorded. Concentrically within this is an inner land which is free of data, within the centre of which is the hole within which the disc receives the hub of a disc drive. Compact Discs and the like have a sales price of tens of pounds sterling (for audio material) to hundreds of pounds sterling (for computer programs). Attempts are therefore made to keep the discs free from surface damage or dirt, which can prevent data from being read from the discs, rendering them potentially worthless. One method of reducing this problem is to provide a cover for the disc, which remains attached to the disc at all times.

US 4879710 describes such a cover, which is made of a transparent sheet of cellulose triacetate film.

It is desirable to avoid applying adhesive to the data carrying surface of the disc, since the adhesive may degrade the data carrying ("read") surface, or may form an adhesive layer of uneven thickness; either of these could reduce the readability of the disc. Accordingly, US 4879710 provides a ring of adhesive in the centre land of the disc, and a ring of adhesive at the periphery of the disc to stick the cover sheet to the disc.

The applicants are unaware of the existence of a produce corresponding to this patent. It appears that providing two rings of adhesive would make the cover difficult to apply uniformly to the disc (which again would give rise to difficulties in reproduction) and the outer peripheral ring of adhesive would make it difficult to remove the cover when it became dirty or scratched.

EP 0700566 (derived from W095/12881) provides an alternative cover which comprises an inner washer, and an outer transparent disc made of, for example, polycarbonate film. The inner washer is provided with adhesive which adheres to the inner land of the compact disc. It also overlaps with the outer transparent film in a thin annular ring. The two are secured together at the thin annular ring by the adhesive on the washer. In use, the cover comprising the washer and the transparent disc is peeled from a backing sheet of paper and adhered to a compact disc. The adhesive sticks the washer to the centre of the disc. A raised lip runs around the inner land of the CD, and the washer adheres to the lip, allowing the transparent sheet to contact the data carrying surface below the level of the lip, to which it is fairly closely adhered in use due to static electrical attraction and slight "tack". A corresponding product is marketed as Techmoun Protec CD (TM). Lacking the outer ring of adhesive, this cover is more easily attached, removed and replaced than that of the above described US patent. However, it is difficult to manufacture cost effectively since the washer and the transparent sheet need to be closely aligned. Further, since the two are held together only by a thin annulus of adhesive, there is a risk that the transparent sheet might become detached in use from the washer and jam the mechanism of the disc drive.

It is an object of the present invention to provide an improved protective cover for the data carrying surface of a disc such as an optical disc. The present invention provides, in one aspect in combination a data- carrying disc having a data-carrying portion and a data-free inner portion, and an axially aligned disc-shaped cover comprising an inner adhesive-carrying portion and an outer adhesive-free portion, the cover being so aligned that the inner adhesive-carrying portion adheres to the data- free portion of the disc and the outer adhesive-free portion is in contact with the data-carrying portion of the disc, characterised in that the disc is a unitary whole, and is of a thickness and material such that the adhesive-free portion is maintained in contact with the data-carrying portion of the disc only by the inner adhesive-carrying portion and by the surface contact between the adhesive-free portion and the data-carrying portion of the disc.

A cover for such a combination is likewise provided. In another aspect, the present invention provides a method of manufacturing a cover of this type, comprising providing said adhesive regions on a sheet of film; and cutting discs from said sheet around said adhesive regions to provide unitary covers including adhesive and non- adhesive regions.

The present applicants have discovered that a transparent cover of suitable dimensions and material can be made in a unitary piece, and will adhere satisfactorily solely to the centre of the data-carrying disc. The cover can more easily be manufactured and is anticipated to be more reliable in use, than that of EP 0700566.

In a preferred embodiment, a portion of the cover is made responsive to non-visible light (preferably ultra-violet light), for example by printing with a suitable fluorescent ink onto the portion of the cover which overlies the central, non-data carrying land of the disc. A security marking may thus be provided to distinguish genuine covers from those from unauthorised sources

(which may offer less protection to the disc, or may even damage the optical surface thereof).

Other aspects and preferred features of the invention will become apparent from the following description, claims and drawings. The invention will now be illustrated, by way of example only, with reference to the accompanying drawings, in which: Figure la is a plan view of a compact disc; Figure lb is a sectional front elevation of the disc of Figure la;

Figure 2a is a plan view of a cover according to an embodiment of the invention;

Figure 2b is a corresponding view of a backing sheet therefore; Figure 3 is a schematic diagram of a manufacturing line for manufacturing covers according to the embodiment of Figure 1 ;

Figure 4 is an illustrative view of sheet material passing through the manufacturing line of Figure 3;

Figure 5 is flow diagram showing the manufacturing process of the embodiment of Figures 3 and 4;

Figure 6 is a corresponding flow diagram for manufacture of a cover according to a second embodiment of the invention;

Figure 7 is a schematic diagram showing the invention in situ in a CD ROM case; Figure 8 (consisting of Figures 8a and 8b) shows a container for covers according to the invention in an open state; and

Figure 9 shows the container of Figure 8 in the closed state.

Description of CD A compact disc 1 comprises a disc approximately 120mm in diameter.

An inner hole 4 of approximately 15mm in diameter receives a drive hub of a CD drive. Around the inner hole 4 is a land 3 bounded by a raised lip forming a ring 5, the diameter of the ring of the raised lip 5 being approximately 35mm.

Outside the raised lip 5 is the data-carrying region 2 of the disc. First Embodiment The first embodiment of the invention will now be described with reference to Figures 2 and 5.

A protective cover disc 11 comprises a film of POKALON OG (TM) a polycarbonate material available from Lofo High Tech Film GmbH, of Weidstrasse D79576, Weil am Rhein. Germany. The film is 0.08mm (80 microns) in thickness and has an outer diameter of 118mm (i.e. very slightly less than the outer diameter of the compact disc 1) and a central hole 14 of the same diameter as the central hole 4 of the compact disc.

Surrounding the central hole 14 is a concentric ring of adhesive 13, which in this embodiment is a UV curable acrylic adhesive such as 'WM620'. The ring of adhesive is printed on only one side of the cover, and has a diameter of approximately 33mm (i.e. so as to locate within the raised lip 5 on the CD 1).

The cover 11 is provided with a backing sheet shown in Figure 2b, which comprises a sheet of coated paper (e.g. 65 gram per square metre (gsm) Glassine release liner) having a main circular portion 15 of diameter approximately 131mm (i.e. slightly larger than the outer diameter of CD 1) and a central hole 16 of the same diameter as the holes 4 and 14. A semi-circular tab 17 extends radially from the central circular portion 15. Four rectangular corners 18, forming a notional rectangle centred on the hole 16 and of long dimension equal to the diameter of the circular portion 15, also extend from the circular portion 15. Prior to use, the cover 11 and backing 15 are supplied adhered together by the adhesive ring 13, with the centre holes 14, 16 aligned. The accommodation is supplied in a standard CD case or box shown in Figure 7 of conventional design comprising a tray 61 and a lid 62. The backing sheet is uppermost, with the rectangular corners 18 extending into corresponding recesses provided in the CD case to enable finger access to the CD. The hub provided within the CD case 62 (for mounting the CD) extends through the aligned holes 16, 14.

In use, after purchase, a user lifts the lid 62; grips the tab 17; peels the backing sheet 15 from the cover 1 leaving the latter still located centred on the hub 63 with the adhesive ring 13 exposed; and introduces a CD with the data carrying surface 2 downwards, onto the hub 63. The hub 63 thus aligns the holes 4, 14, and the land 3 makes contact with the adhesive ring 13. The CD 1 may then be lifted from the tray 61 bringing with it the cover which remains adhered to the disc both by the effect of the adhesive ring, and by the friction, tack, and static electricity between the transparent film and the data carrying surface of the CD. The CD may then be inserted into a drive. The presence of the cover 11 does not materially affect the optical reading of the CD 1 , and remains in intimate contact with the data carrying surface 2 during read access.

Should the cover 11 become dirty, it can be peeled from the CD 1 and replaced by another in the manner described above.

Method of Manufacture of First Embodiment

Referring to Figures 3 to 5 the method of manufacture of the first embodiment will now briefly be described. Apparatus for the manufacture of adhesive labels or other films on backing sheets, in particular shapes and with particular printing, is well known and will therefore not be described in detail.

The production line comprises an adhesive printing section 30 for printing adhesive onto the support side of an endless web 22 of backing paper, in a succession of rings (step 102). Downstream of the adhesive printing section 30 a laminating roller pair 23 is provided for receiving the web 22 and an endless web 21 of protective film (in this case, POKALON OG) and laminating the two together (step 104). The adhesive rings therefore transfer onto the film web 21.

A first die cutting and punching section 40 comprises an anvil 40b and cutting and punching heads 40a. As the laminated web passes through this section, the aligned holes 14, 16 are centre-punched (step 106) through the rings of adhesive printed by the adhesive printing section 30, and the outer diameters of the cover discs 11 are die cut from the web 21 (step 107). At a second cutting stage in 50, the cutting heads are carried on the lower section 50b, and the periphery of the backing sheet of Figure 2b is die cut (step 108) in the backing web 22. At this point, the laminated film and backing sheet discs are separate of the web and are collected (not shown) for assembly into CD cases as shown in Figure 7.

The whole manufacturing line of Figure 3 is carried out in clean room conditions, with the extraction of all dust and other particles from the atmosphere. It is important that no particles, dirt or other contamination should adhere to the film 22 and discs 1 1 , since this would interfere with the reproduction from the discs 1.

It will be seen that this manufacturing process leads to straightforward production of covers without the need for alignment of several components of the cover, and is thus suitable both for high volume production and for production in clean-room conditions. Second Embodiment

In this embodiment, a pattern is printed onto one of the faces of the cover 11, so as to lie within the adhesive ring 13 thereof. The pattern is transparent to visible light, but when illuminated with ultraviolet or infra-red light or some other non visible wave length it can be detected. As ultraviolet security apparatus (for example, for checking the validity of bank notes) is widely available, it is convenient to use an ultraviolet security or optical brightener which fluoresces when exposed to ultraviolet light. By providing the feature within the adhesive ring 13, it is clear of the data carrying surface 2 of the disc and therefore cannot fluoresce when interrogated by a light source on the disc drive (or otherwise interfere with the optical reading of the disc). Nor can ink attack the data carrying surface of the disc.

Referring to Figure 6, to manufacture the product according to the second embodiment, the positions of the webs 21 and 22 and the printing section 30 are changed in a manner that will be apparent. In a step 202, the fluorescent ink is printed onto an area which will lie within the adhesive ring 13, on the protective film web 21 and, in a step 204, rings of adhesive are printed (covering the fluorescent ink patterns) onto that web 21. In a step 206 the protective film web 21 is laminated to the backing paper web 22.

Subsequently, steps 106 -108 are performed as described above. Thus, in this embodiment, ink and adhesive are both printed to the transparent web prior to punching and cutting the discs.

Third Embodiment

In this embodiment, details are as in the first or second, except as indicated below.

In this embodiment, the cover is made of polymethyl methacrylate (PMMA) such as EUROPLEX™ or PLEXIGLASS™ manufactured by Rohm

GmbH Chemische Fabrik of D-84293, Darmstadt, Germany. The thickness is 0.06 or 0.08mm (i.e. 60 or 80 microns). Surrounding the central hole 14 is a concentric adhesive film ring, of a thickness less than or equal to the height of the raised lip 5 on the CD. The ring consists of a polymer film of any convenient materials, having adhesive on two sides. The adhesive in the interface between the ring and the cover 11 is a permanent fixing such as cured resin adhesive. On the other hand, the adhesive on the side of the ring which is to stick to the CD is a releasable and re-attachable adhesive.

Optically recognisable characters are printed onto the ring before it is attached to the disc. The ring may be attached to the disc by a placing step, instead of the step of printing adhesive described in the previous embodiment.

In this embodiment, the rectangular corners 18 are omitted from the backing sheet.

This embodiment is advantageous, relative to EP 0700566, since it enables adhesives of different strengths to be used to adhere to the cover 11 and to the CD. EP 0700566 using the same adhesive coating over the whole of the "washer", so that if the adhesive is made sufficiently weak to be releasable from the CD (to enabled it to be replaced occasionally), the risk that it may also become detached from the cover arises; particularly since the two are secured together by a thin annulus of adhesive. With the present invention, on the other hand, the risk of detachment of the adhesive ring from the cover 11 can be virtually eliminated whilst still allowing the cover to be detachable from the CD. Fourth Embodiment

A fourth embodiment of the invention (as shown in Figures 8 and 9) provides an alternative container for the covers of the first or third embodiments. Figure 8a shows the lid, which comprises an approximately cylindrical transparent plastics housing 71 with a upper flat top. The housing 71 may be of polycarbonate, for example.

A mounting rose or hub 72, identical to those found within conventional CD cases for receiving a CD, is mounted co-axially on the centre of the top surface, in a recess 73 within which it is secured by adhesive.

The inner diameter of the cover 71 corresponds to the outer diameter of the cover disc 11. A bulge in the periphery of the cylinder runs parallel to the axis of the cylinder, and is dimensioned to accommodate the tab 17.

Referring to Figure 8b, the cover 71 is received with its lower edge in a recess 76 in a plastics base unit 75. Co-axially within the recess 76 is the central portion of the base 75, supporting a co-axial shaft 77 which, in use, extends up into the cover 71 to meet the lower surface of the recess 73.

The container is shown in the closed position, fully assembled, in

Figure 9. In use, at the factory the container is filled with a stack of, for example, 250 or 300 cover discs 11 and backing sheets as described in the third or first embodiments which are stacked onto the base 75, with the shaft 77 passing through the central holes 16 to retain the discs in alignment. The cover 71 is then mounted over the stacked cover discs.

In use, a user wishing to cover a disc removes the lid 71 and places it on a horizontal surface; removes a cover with its backing sheet from the stack; places the cover on the central rose 72; removes the backing sheet; and places the disc, data carrying surface downwards, onto the rose 72 so as to be aligned with the cover. The disc is then urged into contact with the cover, and the two are removed together.

This method of assembly, like that described previously in relation to Figure 7, has the advantage that it is unnecessary to move the cover with its adhesive surface revealed (which would create the possibility of spreading the adhesive onto the data-carrying surface of the disc if handled clumsily by the user). Also, alignment with the optical disc is guaranteed due to the action of the rose 72. Other Embodiments and Variants

It will be apparent that various features of the above described embodiments may be modified by the skilled person. For example, manufacturing is made simpler if the backing paper has an identical circular outer diameter to the disc 11 , in which case both may be simply punched out of sheet at the same time rather than being die cut. However, it is then more difficult for the user to separate the two in use. The sheet 1 1 may be made of other materials than POKALON OG; specifically, a thin, even film of polycarbonate or polymethyl methacrylate (or other optically transparent material) will be suitable, provided that it contains no plasticisers or other chemicals which might attack the surface of the CD and provided that it is of regular thickness and optical surface finish. It is also important that the film should contain no optically active chemicals or other agents, and that it should be free of light scatterers.

In general, for an type of optical recording disc, the cover disc material 11 should be a compound with qualities equivalent in respect of optical clarity and birefringence to the moulding compounds used for the manufacture of the optical discs.

Thicknesses other than 0.08mm may be used. In general, for

POKALON OG, thicknessess of 0.05 to 0.08mm are found satisfactory. In general, however, it is preferred to make the film relatively thick to avoid buckling, but thin enough to be held to the data carrying portion of the disc 2 by surface-acting forces, flexing over the lip 5.

Further, if the thickness is too great then the optical properties of the drive are affected (specifically, the interrogating beam may focus off the data carrying surface, as discussed in EP 0700566). Conveniently, the outer surface of the backing paper (the surface not engaged with the film) may be printed with advertising material). Although the cover has been described in application to a compact disc, it will be clear that it may be used with other optical storage discs, such as digital versatile discs (DVD).

In this connection, an embodiment may comprise a box similar to that shown in Figure 7 but sized for the smaller DVD disc, and containing a pair of covers, one for each of the data carrying sides of the DVD disc. In use, a first side of the disc is covered as described above in relation to Figure 7; and then the disc with the first cover is removed, turned upside down and the process is repeated. For a DVD, a cyclo-olefin polymer such as ZEONEX™ or

ZEONOR™, manufactured by Nippon Zeon Co. Limited of Tokyo, Japan, may be used in a thickness of 0.06mm (60 microns).

The invention may of course be used with other optical storage discs in the various formats in which they are manufactured, such as CD-ROM, CD-R, CD-RW, DVD-5, DVD-9, DVD-R, DVD-RW etc. discs. The invention may therefore be employed with optical discs which will be placed in any read and/or write drives which use the principle of light transmission to read from or write onto the disc.

Many other variations, alterations and modifications of the above embodiment will be apparent to the skilled person. The present invention is intended to extend to all such alternatives which would be apparent to the skilled reader.

Claims

1. In combination a data-carrying disc (1) having a data-carrying portion (2) and a data-free inner portion (3), and an axially aligned disc-shaped cover (11) comprising an inner adhesive-carrying portion (13) and an outer adhesive-free portion (12), the cover (11) being so aligned that the inner adhesive-carrying portion adheres to the data-free portion (3) of the disc and the outer adhesive-free portion (12) is in contact with the data-carrying portion (2) of the disc (1), characterised in that the disc (1 1) is a unitary whole, and is of a thickness and material such that the adhesive-free portion

(12) is maintained in contact with the data-carrying portion (2) of the disc only by the inner adhesive-carrying portion (3) and by the surface contact between the adhesive-free portion (12) and the data-carrying portion (2) of the disc (1).

2. A cover (11) suitable for use in the combination of claim 1.

3. The cover of claim 2, further comprising a security marking.

4. The cover of claim 3, in which the security marking comprises a mark printed onto the cover.

5. The cover of claim 4, in which the marking is printed in ink responsive to non visible wavelengths.

6. The cover of any of claims 3 to 5, in which the security marking is located so as not to obstruct the data-carrying portion (2) of the disc.

7. The cover of claim 6, in which the security marking is provided within the adhesive-carrying portion (3).

8. A disc protection product for use in the combination of claim 1, comprising a disc-shaped cover (11) comprising an inner adhesive-carrying portion (13) and an outer adhesive-free portion (12), in which the cover comprises a unitary body (11) extending over both the data-carrying and data- free portions, and is of a thickness and material such that the adhesive-free portion (12) is maintained in contact with the data-carrying portion (2) of the disc only by the inner adhesive-carrying portion (3) and by the surface contact between the adhesive-free portion (12) and the data-carrying portion (2) of the disc (1); and a sheet of backing material (15) to which the cover (11) is releasably secured by the adhesive-carrying portion (13).

9. The product of claim 8 in which the backing portion (15) comprises at least one tab (17) extending outwardly of the periphery of the cover disc (11) to facilitate release thereof from the backing material (15)

10. The product of claim 8, in which the adhesive-carrying portion (13) comprises a concentrically mounted film having first and second adhesive- coated surfaces, the first adhesive-coated surface being mounted to the disc (11) and the second adhesive covered surfaced being for mounting to the data- carrying disc (1).

11. The product of claim 10, in which the adhesive on the second adhesive-carrying surface is releasable by a user, and the adhesive on the first data-carrying surface is not, whereby the disc-shaped cover (11) may be removed from the data-carrying disc (1) with the film.

12. The product of claim 8 in which the adhesive-carrying portion comprises a layer of releasable adhesive.

13. A method of manufacturing a cover according to any of claims 2 to 7 comprising: providing said adhesive regions on a sheet of film; and cutting discs from said sheet around said adhesive regions to provide unitary covers including adhesive and non-adhesive regions.

14. The method of claim 13, in which said sheet is a continuous web.

15. The method of claim 13 or claim 14 in which said adhesive is printed onto a backing sheet and transferred to said sheet.

16. The method of claim 13 in which a security feature and said adhesive are printed onto said sheet.

17. The method of claim 13 in which the step of providing said adhesive regions comprises depositing an adhesive carrying film onto said sheet of film.

18. A protective product for an optical data-carrying disc substantially as described herein with reference to Figures 2b or 7.

19. A method of manufacturing a protective product for an optical data- carrying disc substantially as described herein with reference to any of the accompanying Figures 3 to 6.

20. A method of attaching a disc-shaped cover (11) to a data-carrying disc (1) comprising providing said cover (11) within a container having a mounting structure (72) with an external diameter closely fitting within the central hole within said data-carrying disc (1); placing said cover (11) on said structure (72) with an adhesive portion thereof outermost, and with said structure (72) fitting closely through a central hole therein; mounting said data carrying disc ( 1 ) onto said structure (72) with the data-carrying surface thereof inwardly, so as to cause said disc to contact said adhesive region; and removing said disc (1) and cover (11) from said structure.

21. A method of attaching a disc-shaped cover (11) to a data-carrying disc (1) comprising providing said cover (11) within a container having a mounting structure (72) with an external diameter closely fitting within the central hole within said data-carrying disc (1); mounting said data carrying disc (1) onto said structure with the data- carrying surface thereof outwardly; placing said cover (11) on said structure (72) with an adhesive portion thereof innermost, and with said structure (72) fitting closely through a central hole therein, so as to cause said disc (1) to contact said adhesive region; and removing said disc (1) and cover (11) from said structure.

22. The method of claim 20 or 21, in which said container is a conventional container dimensioned to carry said data-carrying disc, in which said mounting structure is internal within said container and said covers are provided mounted on said structure.

23. The method according to claim 20 or 21 in which said structure (72) is externally mounted on said container.

24. A container for carrying a plurality of optical disc protective products, the container comprising: a base (75); a shaft (77) extending away from said base and dimensioned to pass through central holes of said products; a removable lid (71) dimensioned to pass over said shaft (77) and engage with or disengage from said base (75) to close or open, respectively, the container; and a data-carrying disc mounting structure (72) mounted on an exterior surface of said container.