Security features

Abstract: The invention relates to improvements in security features in paper and other substrates and in particular to an activatable feature to warn of tampering. The invention further relates to a security feature (11) for a security document comprising at least one activatable layer and at least one visually apparent masking layer, said at least one activatable layer comprising a composition which is generally non-mobile but which becomes mobile when wetted with a liquid, said composition further including at least one detectable component, in which under dry conditions said at least one masking layer wholly covers the activatable layer and renders it non-detectable.

Description: The invention relates to improvements in security features in paper and other substrates and in particular to an activatable feature to warn of tampering. Documents of value and means of identification, such as banknotes, passports, identification cards and the like, are vulnerable to copying or counterfeiting. The increasing popularity of colour photocopiers and other imaging systems, and the improving technical quality of colour photocopiers, has led to an increase in the counterfeiting of such documentation. There is, therefore, a need to improve the security features of such documentation, or paper, to add additional security features or to enhance the perceptions and resistance to simulation of existing features. Steps have already been taken to introduce optically variable features into such documentation which cannot be reproduced by a photocopier. Furthermore, features are now available which are discernible by the naked eye, but invisible to, or viewed differently by, a photocopier. Known examples of such security features include watermarks, embedded and windowed security threads, fluorescent pigments and the like. However, in addition to attempting to reproduce security features, counterfeiters also endeavour to tamper with or remove information or print or other security indicators associated with documents by immersing the document in water or a solvent. It is therefore an object of the present invention to provide an improved security feature for a security document which services as an indicator of tampering of the document. According to the invention there is provided a security feature for a security document comprising at least one activatable layer and at least one visually apparent masking layer, said at least one activatable layer comprising a composition which is generally non-mobile but which becomes mobile when wetted with a liquid, said composition further including at least one detectable component, in which under dry conditions said at least one masking layer wholly covers the activatable layer and renders in non-detectable. Furthermore, according to the invention there is provided a substrate comprising such a security feature. Further embodiments of the invention are disclosed in the dependent claims. A preferred embodiment of the present invention will now be described in detail, by way of example only, with references to the accompanying drawing in which:- Fig. 1 is a plan view of a security document including the security feature of the present invention; Figs. 2 and 3 are cross sectional side elevations of a security element or thread comprising the security feature of Fig. 1; Fig. 4 is a schematic view of a holographic label including the security feature of the present invention; and Fig. 5 is a plan view of security document including the security feature of the present invention having a UV element. Referring to Fig. 1 there is illustrated a typical security document, such as a banknote, identification card, cheque, certificate etc. which includes the security feature of the present invention in the form of a windowed security thread or element 11. The security element 11 is preferably made from a transparent colourless polyester film which is flexible and water-impermeable and which is provided with a layer of metal on one side thereof. Commonly used films for security elements 11 are vacuum deposited with aluminium or another suitable metal. The film is slit to form a number of individual security elements 11 having a width typically of at least 0.5mm and preferably at least 2mm. However, the size is not relevant to the present invention. The security element 11 is inserted into a sheet of paper by one of a number of known methods. One of the most commonly used methods is using a cylinder mould paper machine, for example by the method disclosed in EP-A-0,059,056. In the resulting security paper the security element 11 is exposed on one side of the sheet at intervals along the length of the element 11, the region of exposure being referred to as a window 12. Bridges 13 are formed from paper fibres between the windows 12 to wholly embed the element 11 in those regions. In the present invention, the security element 11, as illustrated in Fig. 2, comprises the polyester film substrate 16, on an upper side of which is located a metal layer 17. ("Upper" being defined as being nearer to the surface 15 which is exposed in the window 12). A further "activatable" layer 18, which comprises a composition containing an activatable component is provided on an opposite "lower" side to the metal layer 17. The activatable component is one generally non-mobile, under normal conditions, but which is soluble in a liquid such as a solvent to become mobile. The composition also includes a colourant. In a security document 10 made from security paper containing the security feature according to the present invention, under normal conditions the security element 11 will be seen in reflected light in the windows 12 as bright shiny metallic blocks. The metal layer 17, however, wholly masks the activatable layer 18 so that it cannot be seen in the windows 12, so that the document 10 looks like a typical window thread document in both reflection and transmission. However, if a counterfeiter were to attempt to tamper with the document 10 by immersing it in a liquid with the aim of removing the thread, printed information or any other security features on the document 10, the activatable component which holds the colourant in place will become mobile in the solvent allowing it to leach out into the surrounding paper to provide a highly visible frame or halo 19 stained with the colourant surrounding the windows 12. The activatable layer 18 is therefore no longer masked and is now clearly visible to the naked eye. In an alternative embodiment of the feature described above, the security element 11 may have the construction shown in Fig. 3. In this security element 11, the transparent polyester film 16 has the activatable component layer 18 applied to its upper surface. A metal layer 17 is applied over the top of the activatable component layer 18. Since the polyester film 16 and the metal layer 17 are water impermeable, the solvent to activate layer 18 enters through the sides of the thread 20. The metal layer 17 thus acts as a visible or dominant component the function of which is to mask an activatable component. The metal layer 17 may, therefore, in other embodiments of the present invention, be replaced by other layer, patches all of which serve these functions. The masking layer may be optically variable , such as irridescent or pearlescent coating, a UV dull or inhibiting substance such as a coating containing titanium dioxide or hindered phenol or an opaque coloured strip or layer. In other embodiments of the present invention, the nature of the security feature may be something other than a security element 11. For example, it may be a hologram applied to the security paper overlying a patch of an activatable component to thereby mask the activatable component in normal conditions. In another example the masking, or dominant, component may consist of a coating strip of opaque ink applied over a similar strip of the activatable component, or alternatively an OVI. In yet another embodiment of the invention the dominant masking component is provided by a label applied to a paper or other substrate, and the activatable component is incorporated into the adhesive. When the security document bearing this embodiment of the invention is immersed in a solvent designed to dissolve adhesive, the activatable component becomes mobile and the colourant leaches out into and/or around the label. Where the masking component itself is made from paper or another permeable substrate, the security document itself can be made of an impermeable substrate such as plastic. In this situation the water or solvent is able to permeate the masking layer to reach the activatable component. A further embodiment of the invention may comprise a combination print, such as flexographic or screen printing. In the first mentioned example the activatable component is described as including a colourant which on leaching out into the area around the thread 11 becomes visible to the naked eye. What is important, however, is that an element of the activatable component is clearly detectable whether by eye, under normal light, under UV light or IR light or with another type of machine or detector. The composition may therefore alternatively contain a fluorescent substance which is invisible to the naked eye and is initially masked by an ultraviolet dull coating, instead of a layer of metal. After activation the frames 19 of the fluorescence will be clearly discernible from the windowed side of the document 10 when examined under ultraviolet light, although to the naked eye it will not be visible. On the reverse side of the document 10, a long strip of fluorescence can be clearly detected. Other detectable components may alternatively include a non-bleachable dye, polar/non-polar or a pH sensitive component. The security feature may include a plurality of activatable component features which may include different components which are activated by different liquids, e.g. one water soluble component, one solvent soluble component etc. The security feature may also include a plurality of masking features being the same or different. Some specific examples of the present invention will be described below. Example 1 In this example a stripe is applied to a paper substrate using a gravure coater. The stripe is formed from a composition which includes an optically variable ink that has been doped with a mixture of UV fluorescent water soluble component plus an ultraviolet inhibitor, such as a hindered phenol. Under normal conditions, this stripe is visible as an optically variable image in normal light and is UV dull in UV fluorescent light. Immersing a document made from such paper in water or an aqueous eradicator causes the water mobile component to move. After activation, under normal light the strip remains optically variable. However under UV fluorescent light the strip is UV dull with a fluorescent halo appearing around the strip. When the document is turned over the back of the strip is distinctively UV fluorescent. Example 2 In this example, the document is readable using fluorescent bar code sorter. This involves detecting a preprinted fluorescent bar code which sorts the documents into denominations. Following activation, an additional fluorescent strip is produced which would cause the document to be rejected, thus providing machine detection of potentially tampered documents. Example 3 As shown in Figure 4, holographic label (21) is manufactured by a conventional embossing process. When the adhesive is applied to the back of the foil it is applied over a printed mesh of mobile component (22) such as a solvent soluble dye stuff. Thus the adhesion to the foil to the receptive substrate is not effected. On the immersion of the document in a solvent or water, the mobile component bleeds into the surrounding fibres creating a halo around the holographic label. Example 4 An ink is prepared containing a mixture of a UV dull chemical, such as a hindered phenolic or titanium dioxide and a UV fluorescent product such as Uvitex (trade mark). This ink is printed by a variety of techniques such as flexography, gravure or litho onto a UV dull paper, as shown in Figure 5. The print will be a message, such as "void". Before immersion the document is viewed under UV light and found to be dull with no message showing, as shown on the left hand side of Figure 5. On immersion in water or a solvent the fluorescent components separates from the print producing the word "void" in hollow letters, as shown on the right hand side of Figure 5.

Claims: A security feature (11) for a security document (10) comprising at least one activatable layer (18) and at least one visually apparent masking layer (17), said at least one activatable layer comprising a composition which is generally non-mobile but which becomes mobile when wetted with a liquid, said composition further including at least one detectable component, in which under dry conditions said at least one masking layer wholly covers the activatable layer and renders it non-detectable. A security feature (11) as claimed in claim 1 in which the composition becomes mobile when wetted with an aqueous liquid. A security feature (11) as claimed in claim 1 in which the composition becomes mobile when wetted with a liquid which is a solvent. A security feature (11) as claimed in any one of the preceding claims further comprising a plurality of activatable layers (18) each containing a different composition which becomes mobile when wetted with different types of liquid. A security feature (11) as claimed in any one of the preceding claims in which the masking layer (17) comprises a UV dull layer. A security feature (11) as claimed in any one of claims 1 to 4 in which the masking layer (17) comprises an optically variable layer. A security feature (11) as claimed in any one of claims 1 to 4 in which the masking layer (17) comprises a layer of coloured ink. A security feature (11) as claimed in any one of claims 1 to 4 in which the activatable layer (18) comprises a layer of coloured ink. A security feature (11) as claimed in any one of claims 1 to 4 in which the masking layer (17) comprises a hologram or holographic image. A security feature (11) as claimed in any one of claims 1 to 8 in which the masking and activatable layers (17, 18) are supported on a flexible strip, which comprises an elongated security element. A security feature (11) as claimed in any one of claims 1 to 8 in which the masking and activatable layers are supported on a planchette. A security feature (11) as claimed in any one of claims 1 to 8 in which the masking and activatable layers are supported on a fibre. A security feature (11) as claimed in any one of the preceding claims further comprising a plurality of masking layers (17). A security feature (11) as claimed in any one of the preceding claims in which the detectable component comprises a fluorescent dye. A security feature (11) as claimed in any one of claims 1 to 13 in which the detectable component comprises a coloured ink. A security feature (11) as claimed in any one of claims 1 to 13 in which the detectable component comprises a non-bleachable dye. A security feature (11) as claimed in any one of claims 1 to 13 in which the detectable component comprises a pH sensitive component. A security feature (11) as claimed in any one of claims 1 to 13 in which the detectable component comprises a polar component. A security feature (11) as claimed in any one of claims 1 to 13 in which the detectable component comprises a non-polar component. A security feature (11) as claimed in any one of the preceding claims further comprising a plurality of detectable components. A substrate for a security document (10) having two opposing surfaces for receiving identifying indicia and further comprising a security feature (11), as claimed in any one of the preceding claims. A substrate as claimed in claim 21 in which the security feature is at least partially exposed in one or more windows (12) in one or both of the surfaces of the substrate. A substrate as claimed in claim 21 in which the security feature (11) is wholly embedded within the substrate. A substrate as claimed in claim 21 in which the security feature (11) is applied to the surface of the substrate. A substrate as claimed in claim 21 in which the activatable layer (18) is contained within the substrate and the masking layer (17) applied to one of the surfaces of the substrate. A substrate as claimed in any one of claims 21 to 25 comprising a plurality of security features (11) as claimed in any one of claims 1 to 20.

Inventors: JOTCHAM RICHARD BRYAN, PAYNE GERALD SIDNEY, JOTCHAM, RICHARD BRYAN, PAYNE, GERALD SIDNEY
Applicants: RUE DE INT LTD, DE LA RUE INTERNATIONAL LIMITED
Application year: 1999
Main classification: B42D15
IPC codes: B41M3