GB2372232A - Security card with luminescent material - Google Patents

Abstract

A security card comprises a substrate having one or more polymer layers 1,5,6 with one or more luminescent materials therein. The substrate (Fig 1) may comprise a single plastics layer 1 moulded with a first luminescent ink of one colour 2. A second luminescent ink of a second colour may be printed as a general tint and/or in the form of security indicia 3 or biometric indicia 4. Alternatively a substrate (Fig 2) comprising two layers 5,6 has first and second luminescent dyes 7,8 diffused thereinto. The luminescent materials may exhibit fluorescence, phosphorescence or anti-stokes properties.

Description

SECURITY DOCUMENT AND METHOD FOR ITS MANUFACTURE

The invention relates to a security document and a method for its manufacture.

Security documents such as cards are used in a wide variety of applications, and it is important to construct such cards so that they are difficult to tamper with. Many different features have been incorporated into these security cards, including holograms, complex print and the like, but there is a continuing need to improve their security.

Recently, in WO-A-99/46133 we described a co-extruded card which can be printed with special subliming dyes leading to a highly secure product.

Other methods for making security cards are also known, including injection moulding as described in US-A5567362, while the use of dye diffusion as a technique for achieving secure print is described in EP-A-0574618, US-A5706297, US-A-4465728 and EP-A-0444087.

In accordance with one aspect of the present invention, a security document comprises a substrate having one or more polymer layers; and at least one luminescent material in the substrate.

In accordance with a second aspect of the present invention, a method of manufacturing a security document comprises providing a substrate having at least one polymer layer; and providing at least one luminescent material in the substrate.

Typically, where there is only one luminescent material, it is a dye introduced by an extended dwell dye sublimation or diffusion process into the substrate and can thus be in the form of a discrete image.

We have developed an improved security document, in which one but normally two or more luminescent materials are provided in the substrate of a document composed of one or more polymer layers. The first luminescent material may be introduced into the substrate by dye sublimation or a

dye thermal diffusion technique and is preferably introduced in such a way as to form an image. Unlike many dye diffusion processes, the amount of energy used to effect the transfer is relatively large, with the result that the dyes penetrate the plastic to a depth of at least 50 microns.

Where a second luminescent material is used, it is normally introduced as part of the formulation of the plastic, though it may also be introduced in the same way as the first. The two luminescent materials are preferably of contrasting colours or react to simulation by externally applied radiation in different ways, for example phosphorescent decay time. It is known that the differing reaction of the two luminescent materials to external stimulation may be used firstly as one of usually several features to protect against counterfeit. However, in a preferred example of the present invention, an image is formed by a thermally diffused luminescent dye and is so located as to coincide with visually observable personalisation information entered on the card also by dye diffusion, so that deletion of that information will also result in the deletion of the luminescent dye and its absence can be used to identify fraudulent alteration of the personalisation information.

In a first example, a security document comprises a single plastic layer produced by extrusion, injection moulding or other casting technique. The single layer forms the full thickness of the finished card. The formulation of this layer contains no luminescent material.

One or more luminescent materials, in the form of subliming or diffusable dyes are incorporated into inks for printing by offset lithography, gravure, flexography, letterpress, ink jet, digital offset or laser printing. The ink (s) containing the further luminescent dyes may be printed to form an image directly onto the plastic substrate, or, in the case of subliming dye inks, onto a temporary paper carrier. Where the paper and subliming dyes are used, the

printed side is placed in contact with the plastic substrate. In either case, heat is used to drive the dye (s) into the plastic. The temporary paper carrier will typically contain other normally visible images printed in subliming dye based inks. These visible images will typically include security indicia and personalisation data relating to the holder of the card. The thermal diffusion properties of the visible subliming dyes are matched to those of the luminescent dyes so that the depth of penetration into the plastic layer is approximately equal, or preferably the luminescent dye penetrates to a slightly lesser extent. If a fraudulent attempt is made to remove the visible data by abrasion, the thermally diffused luminescent dye (s) will also be removed. Data subsequently replaced fraudulently will then be detectable by the absence of the luminescent property of the thermally diffused luminescent dye.

To be fully effective, the image formed by the printing of the luminescent dye (s) will be located so as to coincide at least in part with the entered personal data.

In a second, and preferred example, the substrate has at least two polymer layers and additionally contains within its outer layer a second luminescent material, which may be either a dye or pigment, incorporated into the formulation of the plastic. Security and personalisation indicia as visible subliming dye images are accompanied by one or more subliming or diffusable luminescent dyes as described in the first example above, the subliming or diffusable dyes being of contrasting luminescent colours or other properties such as phosphorescent decay time.

Where the subliming luminescent dye is printed using a digital process, such as ink jet, digital printing or laser printing, it becomes practical for the resulting luminescent image on the card to contain personalisation information. This can provide extra security as its presence may not be known to those making the alteration.

In a third example of the invention, two or more different thermally diffusible or sublimable dyes may be used which diffuse at different rates. This may be used with or without a further luminescent material in the plastic. For example, two dyes may be used of contrasting luminescent colours, say red and blue, with the red subliming faster. The visual luminescent effect will be a cyan colour. If abrasion is used to grind away the face of the card, the proportion of red will fall and the colour will change towards blue.

Multilayer documents can be made in a number of ways.

One approach is to pre-extrude a single layer of plastic about 30 microns thick and punch from this card size shapes. These shapes are then inserted into each face of an injection moulding tool and core plastic injected between them.

Another approach is to have two injection moulding machines filling a single mould. The flow path would be such that one provided the centre layer, with the other providing two (30 micron) outer layers.

In most cases, at least one of the luminescent inks will define indicia, such as security indicia including line patterns and the like, or personalised indicia such as biometric information, etc.

The or each luminescent material is typically a pigment or dye and/or an ink or contained in an ink. The luminescence may be exhibited by virtue of fluorescence, phosphorescence or anti-stokes properties.

The invention is applicable to a wide variety of security documents, but is particularly suitable for use as security cards including ID cards, passports both books and covers, banknotes, tax discs, bond certificates, cheques, security and tamper evident labels. In addition to the above in any of the name applications or embodiments described above the product could be made"smart"using appropriate chip technology. Many methods have been

disclosed for introduction of chips into injection moulded cards and all these may be used herein.

Some examples of security documents and methods according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic, perspective view of a first example; and, Figure 2 is a schematic cross-section through a second example.

The example shown in Figure 1 comprises a single layer card, comprising an injection moulded polymer layer 1.

Examples of materials for use as this layer 1 include plastics such as PBT, PVC and Polycarbonate. The polymer layer 1 has been injection moulded with a first luminescent ink of one colour as shown schematically at 2.

On to this layer 1 is printed by dye diffusion, a second luminescent ink or material of a second colour.

This may be printed as a general tint and/or in the form of security indicia 3 and biometric indicia 4. Alternatively, the security indica and biometric or personalised indicia 3,4 can be printed in a further printing step in a conventional manner, not using dye diffusion. The card now has tamper evident and security properties. Tamper evidence is achieved because attempts at altering the security and/or personalised indicia will cause similar alterations to the second luminescent material to be revealed.

In a modification of the Figure 1 example, the layer 1 is injection moulded without a luminescent material. Following production of the layer 1, a first subliming ink containing a luminescent material is transferred to the substrate 1, either continuously or as a security imprint, such as a line structure microprint. Then a second, different, luminescent material is transferred onto this masking all or the majority of the first luminescent print.

On to this layer is transferred the general card information, and subsequently the personalisation data.

This final layer may also contain another luminescent layer.

The two different luminescent materials will sublime and leach into the injection moulded substrate to different extents to achieve tamper evidence. This can be controlled by careful knowledge of materials and binders used.

In a further modification of the Figure 1 example, a two layer injection moulded card substrate is produced.

Both layers may contain either the same or different luminescent materials. Typically, the injection moulded layers will be produced in the same mould, but in some circumstances could be produced separately, and then joined by any suitable joining method that provides an irreversible bond while permitting penetration of the dyes into the lower level without image distortion.

If both layers contain the same luminescent material then a further luminescent material will be dye diffused into at least one of the layers.

Security indicia and personalised indicia will be provided in the same manner as the previous examples.

Figure 2 illustrates an example in which two layers 5,6 which have been injection moulded in the same mould are produced. A first luminescent material is then dye diffused as shown at 7 through the first layer 5 and into the second layer 6. This may be in the form of a general tint or define indicia such as security indicia. A second, differently coloured luminescent material 8 is then dye diffused into the first layer 5, so as to mask all or the majority of the first luminescent material. A further one or more printing steps are then carried out to lay down indicia 9 on the surface of the layer 5.

In Figure 2 and some of the other examples mentioned above, two layers have been used. However, three or more layers could be used, some or all of which are injection moulded with luminescent materials either as replacements or in addition to those printed on the surface of the card.

In the examples described above, dye diffusion is described in methods for providing some of the inks or materials in the polymer layers. Dye diffusion may also be accompanied by sublimation as part of the process of transferring inks from the donor substrate onto the card. It is possible, however, that no sublimation step will be necessary.

Claims (23)

1. A security document comprising a substrate having one or more polymer layers; and at least one luminescent material provided in the substrate.

2. A document according to claim 1, wherein the at least one luminescent material has been provided in the substrate during production of the substrate.

3. A document according to claim 2, wherein the or each layer of the substrate has been injection moulded.

4. A document according to any of the preceding claims, the substrate comprising at least two polymer layers, each polymer layer being provided with a respective luminescent material during its production.

5. A document according to any of the preceding claims, wherein at least one of the luminescent materials is diffused into the substrate.

6. A document according to claim 5, wherein the two luminescent materials have been diffused into the substrate to different depths.

7. A document according to any of the preceding claims, wherein at least one of the luminescent materials defines security indicia.

8. A document according to any of the preceding claims, wherein at least one of the luminescent materials defines personalised indicia.

9. A document according to any of the preceding claims, wherein the luminescent materials exhibit one or more of fluorescence, phosphorescence and anti-stokes properties.

10. A document according to any of the preceding claims, wherein the at least one luminescent material is substantially invisible to the naked eye.

11. A document according to any of the preceding claims, wherein the at least one luminescent material is a dye or pigment.

12. A document according to any of the preceding claims, wherein the at least one luminescent material is, or is contained in, an ink.

13. A security document as hereinbefore described with reference to any of the examples shown in the accompanying drawings.

14. A security document according to any of the preceding claims, the document defining one of an ID card or a passport, banknote, tax disc, bond certificate, cheque, security label and tamper evident label.

15. A method of producing a security card, comprising providing a substrate having at least one polymer layer; and providing at least one luminescent material in the substrate.

16. A method according to claim 15, comprising injection moulding the or each polymer layer.

17. A method according to claim 15 or claim 16, further comprising providing at least one of the luminescent materials in a layer of the substrate during the production process.

18. A method according to any of claims 15 to 17, further comprising diffusing at least one of the luminescent materials into the substrate.

19. A method according to any of claims 15 to 18, wherein at least one of the luminescent materials defines security or personalised indicia.

20. A method according to any of claims 15 to 19, further comprising diffusing both luminescent materials into the substrate.

21. A method according to claim 20, wherein the luminescent materials are diffused to different depths.

22. A method of producing security documents as hereinbefore described with defence to any of the examples shown in the accompanying drawings.

23. A method according to any of claims 15 to 22 for producing a security document according to any of claims 1 to 14.