AU2002301508B2 - Security device - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): De La Rue International Limited ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Security device The following statement is a full description of this invention, including the best method of performing it known to me/us:- P OPERUCCSPECIFICATIONS\2S49518240IO7 I s SPAdo-2501207 -1A- The invention relates to a security device, typically for authenticating an article, such as a security document, on which it is provided.

A wide variety of optical security devices have been developed to protect security 00 documents and other articles against unauthorised reproduction, particularly counterfeiting.

5 These often involve the use of holograms or diffraction gratings which make documents Cvery difficult to reproduce by photocopying and the like.

NAs counterfeiters develop more sophisticated techniques for overcoming these problems, there is a continuing need to develop new security devices.

In accordance with the present invention, a security device comprises a security design formed in a material including a light collecting dye, the material and dye cooperating together, in use, to collect incident light and to cause light to be internally reflected in the material and emitted at edges of the material, whereby when the security device is viewed normally the security design is faintly visible but when the security device is viewed at a shallow angle the security design becomes visible.

We have realised that a new type of security device can be constructed using a combination of a light collecting dye and a suitable material in which the dye is provided which concentrates light output along edges of the material. This assists in enabling the device easily to be authenticated. In addition, in some examples, a latent image can be enhanced making the device very difficult to copy while the structure of the device itself is difficult to reproduce.

The device can be fabricated in a variety of ways. For example, the material may comprise an ink printed or otherwise provided on a substrate. This printing may itself define a security design but in the preferred approach, a relief structure is formed in the material, typically by embossing. Thus, in one example, a light collecting dye is added to a resin which is coated onto a substrate and this is then embossed by use of a blind 06-Oct-02 14:29 Fromi-GILL JENNINGS EVERY +4420T37T1310 T-568 P.06/19 F-110 2 embossiflg technique Oni an intaglio press. Alterflatively, the light collecting9 dye could be added t o a scen eX/rvr ink system and printed as a discrete patch or Print, which Is subsequently embossed. Another approach would be to use a coarse screen prinft design Or any print process capable of laying down a thick film of ink and use edges of the print i.e. without any embossing step.- Any embossings carried out does. not need to be restricted to the use of an ;-itag).io press but any suitable technilque could be used- Embossing9 can take place before or after application of the ink or coating containling the light collecti-ng dye- In an alternative approach, the material comprises a is substrate. This is particularly advantageous where it is desired to incorporate the security device as an integral feature of the article or document to be protected. The light collectinlg dye may be diffused into or coated on the substrate and preferably the substrate is transparent or semi-transparent. By semi -transparent we mean with sufficient clarity to still allow internal reflection to occur within the substrate or at least collectioni of light through the substrate to allow the desired edge effect.

In this case, the substrate will typically be provided with a security design in the form of a relief pattern which again may be embossed into it.

As mentioned above, by suitably constructing the security design (with or without embossing) it is possible to view the bright edges of the design from specific view points which leads to the ability to generate a latent type image. Thus, holding the security device normally, either -viewing ini reflection or transmission, the colour will be weak or non-apparelt while holding the device at a shallow angle will enable a bright intense colour to be observed.

The effect is enhanced by holding the device facing a light source viewinlg the edge effect at a shallow angle with a dark background behind it.

06-Oct-02 14:30 From-GILL JENNINGS EVERY +442073771310 T-566 P.07/IS F-110

'A

A further benefit is achieved by Placing the material next to an unprinted area of a document close to its edge.

Any light collected by the material is then transmitted by total internal reflection to the edge of the document.

The cooperation between the material and light collecting dye can be achieved in a variety of ways. In the preferred approach, the light collecting dye comprises a substance which fluoresces in response to incident visible light. By suitably choosing the material., the interface between the material and air together with the fluorescenCe wavelength can be selected so that internal reflection iS caused. However, light collecting9 dyes which emitr light at wavelengths similar to the incident light could also be used.

is Any conventional security design can be implemented with this invention, examples including security indicia such as guilloche patterns, microprint. tine line, latent images and the like.

The security device can be provided as a label which is affixed to an article or may be formed as part of the article. Articles such as packaging are envisaged but the invention is particularly suitable for use with security documents includinlg any document of value such as banknotes, cheques (whether bank or travellers) bonds, share certificates, licences, some types of identity cards.

passports, visas, tickets. passbooks, vouchers, deeds, tamper revealing seals and labels, brand authenticity mnarks or labels and the like. The device may also of course be used on conventional plastic card materials such as relatively rigid

PVC.

Some examples of security documents according to the invention will now be described with reference to the accompanying drawings, in which:- Figure i is a schematic, cros5section through a first example; 06-Oct-02 14:30 From-GILL JENNINGS EVERY +442073771310 T-566 pos/ig F-lID 08-Oct-02 14:30 From-GILL JENNINGS EVERY +442073771310 T-566 P-08/19 F-110 4 figure 2A and Figure 2B illustrate the appearance of the document shown in Figure 2. under different viewing conditions; Figure 3 is a niew similar to Figure I. but of a second example;- and, Figures 4 to 8 are views similar to Figure I but at third to seventh examples respectively.

The example shown in Figure I. comprises an opaque, plastic or paper substrate -I having a thickness in the range 75-120 microns and on which is printed using a conventional printing cechnique such as screnfleo/ravreetc. a security design 2. The substrate may require pre-coating to allow a base f or the dye containing ink to lay on. This prevents loss of edge height due to absorption into the substrate- The design 2 is printed with an inkc comprising a colourless and transparent medium (or vehicle) into which a light collecting dye is incorporated, the inkc having a thickness at 5-50 microns, preferably 10-2.5 microns. Suitable dyes are des~cribed in us-A-44 9 2 6 45 When light from a source 3 is incident on the printed ink 2 it is absorbed by the light collecting dye which then fluoresces. so as to emit light at a different, visible wavelength which is then internally reflected within the ink thickness as shown schematically at 4 until it exits at edges 5,6.

Since little fluorescent light is emitted through the major surface 7, when the document is viewed normally (Figure the security design is only faintly visible but when the document is viewed at a shallow angle as shown at 8 the design becomes visible (Figure 2B). In practice when the ink is coated over a transparent surface the coating9 is ,substantially invisible" but when coated onto an opaque background the coating is lightly coloured. if the embossed design contains areas of solids, these can be made to emit- colour tram the faces of the solids by introducing a fine embossinlg over the surface of the face 08-Oct-02 14:30 From-GILL JENNINGS EVERY +442073771310 T-566 P.09/19 F-liD 08-Oct-02 14:30 From-GILL JENNINGS EVERY +442073771310 T-566 P-09/19 F-110 e.g. using an ink retaining screen as found in intaglio plate rnal reflection is caused by selecting a material for the ink 2 which is optically denser than air, the refractive index of the ink being selected so that the majority of the fluorescent light is internally reflected.

In the Figure 3 example, the opaque substrate i is replaced by a transparent, plastics substrate 10 having a similar thickness. A similar security design 2 is printed on the substrate 10. In this example, light from the source 3 is collected not only by the ink 2 but also from other parts of the transparent substrate and is channelled to the ink 2 where it is absorbed by the light collecting dye. Some internal reflection of the resultant, fluorescent light will thus occur within the substrate as shown at 11 as well as withln the ink layer 2. The result is a much stronger and dramatic effect when the document is viewed at the shallow angle 8.

In the examples described so far, the ink layer 2 has been printed in the form of the security design on the substrate. It would also be possible to print a substantially continuous ink layer 2 on the substrate and then provide it with a relief by, for example, embossing.

In that case, when viewed at the shallow angle 8 a bright image will be viewed as a result of light being emitted through the embossed edges.

In the Figure 4 example, the light collecting dye is absorbed into a transparent substrate 21. When illuminated by the source 3, the light collecting dye will fluoresce as before and internal reflection as shown at 22 will convey light to the edges 23 of the dye and also to the edges of the substrate. This will achieve a limited effect when viewed at the shallow angle. A much more enhanced effect, as shown in Figure 5, can be achieved by embossing the diffused dye 20 as shown at 24. This creates upstanding edges 25 through which light emission is 08-Oct-02 14:31 From-GILL JENNINGS EVERY +442073771310 T-566 P.10/19 F-110 6 concentrated thus leading to a broad image when viewed at the shallow angle.

A variety of security designs can be printed and/or embossed including conventional security features as guilloche patterns but also other known latent images and simple features such as indicia or logos. The presence of the design could be hidden by incorporating it in conjunction with a secondary relief or print working to disguise its presence.

A 0.1% Lumogen F Red 300 (available from BASF) was added to a Sericol Metallic Ink Medium C0382 and coated onto a 80im polypropylene substrare using a kbar no. 6.

The resultant coating thickness is approximately 15 pm.

The uncoated side was then embossed by passing through an intaglio proofing press.

A further example is illustrated in Figure 6. In this case, the light collecting dye 20 is printed onto one surface 30 of a transparent substrate 21. The opposite surface 31 is embossed at 32. Under normal illumination from light source 3, the light collecting dye will fluoresce as before and internal reflection will occur within the dye 20. Some light will leak across the transparent substrate 21 to the embossing 32 where it will become visible when the device is viewed at a shallow angle as seen at 33.

Another example of the invention which may constitute a polymer banhnote is shown in Figure 7. In this example, a transparent substrate of orientated polypropylene 40 is provided having a thickness of about 75 microns and, on its rear surface, being provided with a pair of opacifying coatings 41,42. The front surface of the substrate carries a first opacifying coating 43 having a thickness of about I micron and a second opacifying coating 44 also having a thickness of about 1 microns but defining a window into which a light collecting dye layer 46 is provided.

08-Oct-02 14:31 From-GILL JENNINGS EVERY +442073771310 T-566 P-11/19 F-110 7 A further example is shown in Figure 8 in which a partially metallised layer 50 is provided on a PET or oriented polypropylene layer 51, a light collecting dye layer 52 being provided on the partial metallisation. In one case, this would correspond to the provision of the light collecting dye on a security thread.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Claims (16)

1. A security device comprising a security design formed in a material including a 00 light collecting dye, the material and dye cooperating together, in use, to collect incident 0 5 light and to cause light to be internally reflected in the material and emitted at edges of the material, whereby when the security device is viewed normally the security design is (Ni Sfaintly visible but when the security device is viewed at a shallow angle the security design becomes visible.

2. A device according to claim 1, wherein the material comprises an ink provided on a substrate.

3. A device according to claim 1, wherein the material comprises a substrate, the dye being coated on the substrate.

4. A device according to claim 1, wherein the material comprises a substrate, the light collecting dye being diffused into the substrate.

A device according to any one of claims 2 to 4, wherein the substrate is transparent or semi-transparent.

6. A device according to claim 5, wherein the substrate is a plastics material.

7. A device according to any one of claims 2 to 6, wherein the substrate is coated.

8. A device according to any one of the preceding claims, wherein the security design is in the form of a relief pattern.

9. A device according to claim 8, wherein the security design is a printed pattern.

A device according to any one of claims 1 to 7, wherein the security design is P AOPER'CCSPECIFICATIOSSU54951S240107 In SPAdo252I/2M7 -9- c. embossed into the material.

11. A device according to any one of the preceding claims, wherein the light collecting 00 dye comprises a substance which fluoresces in response to incident visible light. S

12. A security device according to any one of the preceding claims, wherein the security design comprises one or more of security indicia guilloche, fine line, microprint, latent, embossed, or printed structures.

13. A security device substantially as hereinbefore described with reference to any of the examples and/or accompanying drawings.

14. An article provided with a security device according to any one of the preceding claims.

A document provided with a security device according to any one of claims 2 to 7, wherein the substrate of the security device is provided by a substrate of the document.

16. A document according to claim 15, wherein the document comprises one of a banknote, cheque (whether bank or travellers), bond, share certificate, licence, identity card, passport, visa, ticket, passbook, voucher, deed, tamper revealing seal or label, and brand authenticity mark or label.