Nowadays counterfeiting is rampant in a very wide variety of fields and more and more measures need to be taken to endeavour to offset this problem.

One field which has long needed to address this type of problem is that of security documents, and in particular banknotes. To help reduce counterfeiting security devices, such as security threads or strips which are made from a transparent polyester film provided with a wholly or partially reflective layers or other such security features, have long been used.

The threads or strips are wholly or partially embedded within the paper substrate and as they require skills or materials not commonly available to counterfeiters, they do provide a high degree of security against counterfeiting. However, as the paper itself is still subject to wear and tear, this has led to proposals for plastic banknotes made from polymer films such as described in W083/00659 and GB 2338678. As most counterfeiters do not have access to equipment for making such material and plastic banknotes are wear resistant, this can provide an even more significant increase in counterfeit resistance.

However, there are numerous other fields where there is a need for a substrate which is less durable than for typical security documents but which provides an anti-counterfeitability or anti-tamper feature, but where the cost of the materials described above might be prohibitive. Examples of such uses fields are teartapes for packaging, labels, hang tags, tickets, vouchers and the like.

It is therefore an object of the present

invention to provide a substrate made from a polymeric material which is cost-effective to manufacture to address the problems of counterfeitability in a wide variety of applications.

According to the invention there is therefore provided a two ply synthetic substrate comprising a first layer of biaxially oriented polymeric film laminated together with a second layer of biaxially oriented polymeric film with a discontinuous metal layer therebetween, and a continuous metal layer provided on an exposed surface of the first polymeric film layer.

The provision of a two-ply substrate according to the present invention provides a significant number of advantages over the known three-ply material. They are cheaper and simpler to manufacture. Furthermore, the consequential reduction in thickness provides greater number of applications for use of the substrate. This substrate can be made having a thickness comparable to existing security thread materials, shrink wrap materials and thus can be used as existing machinery. It is easier to handle than the known three-ply material with regard to slitting and cutting both before and after incorporation into or onto another substrate. The two-ply structure lends itself well to use as a tamper evident device.

Furthermore, the provision of an exposed metal layer provides a better surface for additional coatings such as adhesives to bond to as some such coatings bond better with metal than they do with polymeric film.

The metal in the continuous and discontinuous metal layers may be the same or visually similar.

Preferably a coloured lacquer is applied to an exposed surface of the second biaxially oriented polymeric film layer.

A layer of pressure sensitive adhesive is

preferably applied to the exposed surface of the metallic layer.

A carrier layer is preferably applied to the adhesive layer.

A layer of hot melt adhesive may be applied to an exposed surface of the metallic layer.

Preferably a release layer applied to an exposed surface of the second polymeric film layer and a support layer applied to the release layer.

A carrier layer of paper or card may be laminated to the metal layer.

A tamper evident feature comprising a preferential release layer is preferably provided.

In a preferred embodiment a coating of photochromic or thermochromic ink is provided on one side of the partially demetallised layer which is located between the partially demetallised layer and the metallic layer.

A photochromic or thermochromic ink is preferably coated to an exposed surface of the second polymeric film layer.

Preferably a partial magnetic layer is applied to an exposed surface of the metallic layer.

The metal layer may be any one of aluminium, copper and sputtered cobalt.

Preferably the biaxially oriented polymeric material is polypropylene, tensile polyester or polyethylene.

In a preferred embodiment machine-readable taggants are located in one or more of the biaxially oriented polymeric layers, adhesive layers, metallic layers or in a coating on top of the substrate.

The invention also provides a tear tape for use with filmic packaging comprising an elongate strip of the afore-mentioned substrate laminated to the packaging film.

Alternatively a self-adhesive label comprises the

afore-mentioned substrate cut to form discrete labels.

As a further alternative a hot stamping foil comprises the afore-mentioned substrate.

Alternatively a shrink sleeve material is made from the afore-mentioned substrate.

The invention also provides a seal for bottles or packaging or a hang tag printed to provide information, or a lottery ticket.

The invention will now be described by the following examples with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional side elevation of the substrate according to the present invention ; Figures 2 to 9 are alternative embodiments of the substrate of Figure 1.

The basic substrate according to the present invention is shown in Figure 1 and comprises two layers la, lb of a biaxially oriented polymeric, film, laminated together with a discontinuous metal layer 2 sandwiched therebetween.

The preferred thickness for the layers la, lb lies in the range 10 to 40 microns, and is more preferably 20 microns.

Although biaxially oriented polypropylene is one of the preferred materials for layers la and lb, it can in fact be any biaxially oriented polymer. Other suggested options include tensiled polyester, and polyethylene.

The discontinuous metal layer 2 essentially comprises a transparent polymeric film, bearing regions of opaque metal 3 and clear regions 4 forming indicia. The indicia may be of a positive nature, in which the indicia are formed by the metallic regions 3, or negative, in which the indicia are formed by the clear regions 4. The indicia may be in the form of

images, alphanumeric text, a pattern or any other appropriate form.

The discontinuous metal layer 2 is provided by partially metallising or demetallising the biaxially oriented polymeric film layer lb.

In the case of the layer 2 being provided by selective demetallisation, the metal of the metallised film (la, 2) which is subjected to the demetallisation process is preferably vacuum deposited aluminium in the range of 1 to 2 microns, although another metal such as cobalt or sputtered nickel/iron may be used.

The metallised film (la, 2) may be an SHM (TM) polypropylene film from Hoechst Trespafan, or any other similar such film, which is available in various thicknesses. The metallised film (la, 2) can be selectively demetallised by an appropriate known process such as direct etching or indirect etching using a resist.

Alternatively the polymeric layer lb can be formed from a transparent film, which is not metallised, such as GND (TM) film also from Hoechst Trespafan, or any other such material, which is also available in various thicknesses. This film can then be selectively metallised by an appropriate known process to provide the partial metal layer 2 or the metal regions 3 may be created by printing with a high reflectivity metallic ink. If printed, any of the known offset, gravure, flexo, intaglio and screen printing methods would be suitable.

In addition to the metallised regions 3 of layer 2, a continuous metallic layer 5 is provided on the exposed surface of the polymeric layer la as shown in Figure 1. This layer is preferable aluminium, in the range of 1 to 2 microns. A metallised film (la, 5) such as SHM (M) polypropylene as mentioned above is preferably used to provide layers (la, 5), although an unmetallised film could be used to which a metal layer

5 is subsequently applied.

The continuous metallised layer (la, 2) and the discontinuous metallised layer (lb, 5) are laminated together, preferably with a cross-linking or thermally activated adhesive. The density of the adhesive is preferably in the range of 1 to 4 gsm, and more preferably 2 gsm. A suitable adhesive would be Holden adhesive NC2525/3 and NC3164 mixed in a 9: 1 ratio. As an alternative to lamination using an adhesive, the polymeric film selected for layers la, lb may be co- extruded multilayer thermoplastic films, of the type used in heat salable packaging films, which may be laminated together when thermally activated.

The metals or metallic substances used in the layers 2 and 5 may be the same or visually similar, so that in ordinary light there is no visual distinction between the metallic regions 3 of the partially demetallised layer 2 and the full metallic layer 5.

This is so that a single metallic colour is seen under ordinary viewing conditions from either side of the substrate, causing the indicia to be hidden.

However, the biaxially oriented polymeric films of layers la, lb exhibit interesting birefringent characteristics, with birefringence colours being dependent on the refractive index, orientation, degree of orientation and thickness of film. When viewed between a pair of polarising filters, either crossed or parallel, some such biaxially orientated polymeric films will provide birefringent colours. Where such a film is placed over a reflective metallic layer, the oriented film provides birefringent colours when viewed through one polarising filter.

Thus, in this embodiment of the present invention, when the substrate is viewed with a single suitable polarising filter such birefringent characteristics are exhibited which reveals the hitherto hidden indicia, which provides a useful

anticounterfeit device.

The birefringence colours change according to the thickness of the film, so the colours can be varied by laminating different numbers and/or thicknesses of polymeric layers together. Thus, say, in the example illustrated in Figure 1, the layers la, lb have respective thicknesses of 20 microns each, a different birefringent colour will be seen when the substrate is viewed at arrow A, through a polarising filter, in the metallic regions 3 covered by one biaxially oriented polymeric layer lb from that seen when viewed at arrow B in the near regions 4, through which the continuous metallic layer 5 can be seen covered by the two biaxially oriented layers la, lb. In other words, the previously hidden indicia are revealed in the form of different colours.

Furthermore, when the angle of view is varied, a colour shift is observed due to the change in light path length through the film. This. colour shift has the advantage that the observed colours in the direction of the major orientation are different to those in the perpendicular direction. For example a structure having 40 microns of biaxially oriented polypropylene over metal exhibits a purple colour when overlaid with a polarising filter and viewed close to normal. At increased angles of view (i. e. angle measured from normal) the colour changes through blue- green to a greyish colour when the observer moves in the long direction and from purple through yellow/green to blue, when the observer moves in the cross direction. This colour shift is especially effective when both of the two colours of the metallic regions 3 and the continuous metallic layer 5 exhibit different colour shifts.

Obviously, as an alternative the metals used in layers 2 and 5 may be visually different to provide a permanently visible feature.

An alternative method for making the substrate would be to laminate the layers la, lb together with one fully and one pre-imaged metal foil layer therebetween. A further alternative would be to image the discontinuous metallised layer 2 by laser cutting or ablation of the metal either as an intermediate step in the construction of the substrate, or subsequent to its assembly. This would be particularly useful for a metal other than aluminium, e. g. stainless steel.

This basic substrate can then be used in a number of different applications where the requirements for durability are not as stringent as for banknotes and other such typical security documents, as described in the following examples.

Example 1 The substrate can be laminated to the inside of packaging films to provide teartapes for packaging film used for cigarettes, perfumery and food products.

The metallisation can be optionally disguised by applying a layer 6 of coloured lacquer to the exposed surface of the layer lb, as shown in Figure 2. This may be advantageous in circumstances where the teartape is to match the packaging without emphasising the presence of the teartape. A suitable lacquer would be gold lacquer PPT 1046 or PPT 1052, the lacquer layer 6 have a density between 6,5 and 3 gsm and made preferably 1.5 gsm.

Example 2 By applying a layer 7 of pressure sensitive adhesive to the exposed surface of the continuous metal layer 5, the substrate can be used as a self- adhesive labels. A suitable adhesive would be

Indatex SE 5219 having a density in the region of 2 to 20 gsm and more preferably 1.5 gsm. A glassine or other suitable carrier layer 8 can be applied on top of the adhesive layer 7, as shown in Figure 3. The carrier layer could be PET, having a thickness of 5 to 100 microns and more preferably 20 microns.

Example 3 The substrate can easily be used as part of a hot stamping foil. In this example a waxed or other release layer 10 and glassine or other support layer 11 are applied to the remaining exposed surface of the layer lb, which may or may not have a coloured lacquer layer 6 thereon. This constructions is shown in Figure 4 and further requires a layer 9 of hot melt adhesive coated onto the continuous metal layer 5. A suitable adhesive would by RK14 supplied by De la Rue Holographics.

Example 4 The substrate shown in Figure 1 can be employed, without further modification of the substrate, for manufacturing shrink sleeves for application to bottle tops and other fastenings.

Example 5 The substrate illustrated in Figure 1 could also be used, without further modification, in the manufacture of seals for bottles and packaging.

Example 6 The substrate illustrated in Figure 1 may be laminated to a suitable carrier layer e. g. of paper or

card, and used as a hang tag such as are commonly applied to clothing in order to provide point of sale information such as price and garment size. The polarising filter viewer could be attached as a separate hang tag or part of the same hang tag.

Example 7 The substrate may also be used in the manufacture of lottery tickets or scratch cards. Rather than scratching off a layer of metallic ink to reveal a preprinted message or other indicia, a polarising filter viewer can be used to reveal whether the player has won. This could be used in conjunction with a scratch off coating or as a replacement.

Example 8 The substrate of the present invention can also be provided with tamper evident features by applying a preferential release layer of selective coating of adhesives. If an attempt was made to remove a label, or other item made from the substrate, the substrate would fall apart to reveal the hidden indicia.

Example 9 In another embodiment of the invention, suitable photochromic or thermochromic inks could be coated, as shown in Figure 5, in a layer 12 on one side of the discontinuous metal layer 2 so that it is located between the discontinuous metal layer 2 and the continuous metal layer 5. Shining light or applying heat would then bring about a colour change making the hidden text visible. Alternatively the photochromic or thermochromic layer 12 could be applied in place of the coloured lacquer layer 6 of Example 1 to the

exposed surface of the layer lb. This would be of benefit to the consumer should they lose the polarising viewer and still wish to authenticate the product. It would also be possible to use liquid crystal materials to achieve a similar effect. A suitable photochromic ink would be 0.05% Reversacol Oxford Blue (from James Robinson) in 4: 1 Seristar SX Varnish/ZC50 Thinner (from Sericol). A suitable thermochromic ink would be ZA50020 (from SICPA).

Example 10 In further embodiments of the present invention, magnetic readability may be introduced, as shown in Figures 6 to 9. Figure 6 shows the simplest form whereby a continuous or discontinuous magnetic layer 13 is printed or otherwise applied on the exposed surface of the continuous metal layer 5. Suitable magnetic materials would be gamma ferric oxide (375 Oersted) or a modified ferric oxide of different coercivity, chromium dioxide or barium ferrite amongst others.

Example 11 In Figure 7 a soft magnetic layer 13 is printed in register on the side of the discontinuous metal layer 2 which faces the continuous metal layer 5.

Example 12 In Figure 8 the magnetic layers of Figures 6 and 7 are both incorporated. The soft and hard magnetic materials can be interchanged and such construction would allow the substrate to be read as described in W097/48990.

Example 13 In figure 9 the continuous metallic layer 5 is replaced by a sputtered cobalt layer 14. The preferred means of this layer is 1 to 2 microns sputtered cobalt has the benefit of being reflective, thereby providing the same effect as the metal layer, with the added benefit of being magnetic.

Example 14 In yet another embodiment of the present invention, a range of taggants may be incorporated into the structure to give further machine readability. The taggants could be in the biaxially oriented polymeric layers, in the adhesives, in the metallic regions 3 or 5 layer or coated on top of the substrate. Suitable taggants include phosphors, fluophors, UV converters or any material which is detectable within the electromagnetic spectrum.

Example 15 Indicia provided by the potentially metallised layer 2 may take the form of a barcode or other optically readable marking. As it would be invisible under normal viewing conditions it would therefore not detract from the packaging design, and would only be apparent when viewed with a polarising filter. The barcode would be readable using a barcode reader fitted with such a filter and could contain information such as batch codes or other such information.

Some of the features of the foregoing examples may, where appropriate, be combined.