US 20050116464 A1
This invention relates to improvements in substrates and in particular to new substrates having magnetic and visual security features, which provide security against imitation. A security substrate comprising a transparent carrier layer bearing indicia formed from a plurality of opaque and non-opaque regions and a transparent magnetic layer supported by the carrier layer containing a distribution of particles of a hard magnetic material of a size and distributed in a concentration at which the magnetic layer remains transparent.
1. A security substrate comprising a transparent polymer carrier layer bearing indicia formed from a plurality of opaque and non opaque regions and a clear transparent magnetic layer supported by the carrier layer containing a distribution of particles of a hard magnetic material of a size and distributed in a concentration at which the magnetic layer remains transparent, characterized in that the magnetic layer contains between 1 and 50% by weight of magnetic material.
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22. A security document comprising a paper or polymer substrate incorporating a security thread as claimed in
The invention relates to improvements in substrates and in particular to new substrates having magnetic and visual security features, which provide security against imitation.
It is widely known to use in banknotes and other security documents security elements, such as security threads or strips. These threads are partially or wholly embedded in a paper or plastic substrate, and generally provide different viewing conditions depending on whether the security document is viewed in transmitted or reflected light.
EP-A-319157, for example, describes a security element made from a transparent plastic film provided with a continuous reflective metal layer, such as aluminium, which has been vacuumed deposited on the film. The metal layer is partially demetallised to provide clear demetallised regions which form indicia. When wholly embedded within a paper substrate the security element is barely visible in reflected light. However, when viewed in transmitted light the indicia can be clearly seen highlighted against the dark background of the metallised area of the thread and adjacent areas of the paper. Such threads can also be used in a security document provided with repeating windows in at least one surface of the paper substrate at which the security thread is exposed. A security document of this type, when viewed in transmitted light, will be seen as a dark line with the indicia highlighted. When viewed in reflected light on the windowed side, the bright shiny aluminium portions are readily visible in the windows. This thread has been highly successful within the market place and is supplied under the trade mark Cleartext®.
For a number of years banknote issuing authorities have had an interest in combining both the public recognition properties of Cleartext® with the covert properties of a machine readable feature. To this end it is preferable to utilise machine readable features that can be read using detectors already available to the banknote issuing authorities. Examples of such machine readable devices are described in WO-A-92/11142 and EP-A-773872.
The security device of WO-A-92/11142 is an attempt to provide this combination. A security device conforming to this specification has been used commercially with some success. A central region of the security device has a metallic appearance with clear regions forming characters; on either side of this central strip in the width direction, there are layers of magnetic material with obscuring coatings to provide the necessary magnetic component. This is, however, a generally unsatisfactory means of achieving the combination of the appearance of Cleartext® with the required magnetic properties. The magnetic properties are satisfactory, but the requirement to place the magnetic layers on either side of a central region means that the latter must be relatively narrow with respect to the overall thread width and results in characters which are small, typically 0.7 mm high, and therefore not easily legible. Additionally, the structures of the devices described in WO-A-92/11142 are very complex and present substantial lateral registration problems in depositing the various layers; a misregistration of even 0.1 mm or so can allow the presence of the dark magnetic oxide to be apparent to the naked eye, thus revealing its presence and seriously detracting from the aesthetic appearance of the security thread.
A more satisfactory solution, from the processibility, ease of character recognition and aesthetics points of view, would be to manufacture a device of the kind described in EP-A-0319157 from a metal which is itself magnetic such that the size of the characters and ratio of character height:thread width of the Cleartext® product is maintained, whilst providing direct compatibility with existing magnetic thread detectors. One means of achieving this is disclosed in Research Disclosure No. 323 of March 1991. In this Research Disclosure, a magnetic material is deposited onto a flexible substrate by vacuum sputtering or other known techniques; the non-metallised regions are created by selective printing of a resist layer and subsequent chemical etching. The disclosed magnetic materials may be nickel, cobalt, iron or alloys thereof with a preferred combination of cobalt:nickel in the ratio 85:15%. The disadvantage of this method is that vacuum deposition of cobalt:nickel to the necessary thickness is a relatively slow process and somewhat wasteful of cobalt, an expensive material. Furthermore, subsequent to this vacuum deposition process, further significant processing is required to etch the characters. The resultant product is therefore relatively expensive.
A further alternative approach is described in EP-A-773872 wherein a magnetic metal is deposited on a film of polymeric substrate as the substrate passes through a solution containing the magnetic metal, and a preparatory operation is carried out on a surface of the substrate prior to immersion of the substrate in the solution. The preparatory operation ensures that magnetic metal is deposited on the substrate in a chosen pattern such that when the security product is produced from the film by cutting the film, the magnetic metal on the security thread has a specific pattern and provides both a visual discernable security feature and a magnetically detectable security feature. This method produces a security thread with satisfactory visual and machine readable characteristics but the manufacture is not straight forward and is costly.
One further approach is detailed in WO-A-9928852. Here the security device includes a carrier substrate, a metallic layer disposed on the carrier substrate, and a magnetic layer disposed on the metallic layer in substantial registration with at least a portion of the metallic layer, thereby providing both metallic security features and magnetic security features. The metallic layer and the magnetic layer also form graphic or visually identifiable indicia on the carrier substrate to provide a visual security feature. According to one method, the metallic layer is applied to the carrier substrate, the magnetic layer is applied to the metallic layer, and the layers are etched to form the graphic indicia. The magnetic layer can, in one embodiment, include a magnetic chemical resist that is printed on the metallic layer in the form of the graphic indicia. This method again produces a security device with acceptable visual and magnetic characteristics but again has a high cost with regard to processing and production.
The present invention therefore seeks to provide a security substrate that may be slit into security threads for partially or wholly embedding into paper or JO polymer which has acceptable magnetic and visual characteristics as described above and also greatly simplifies the manufacturing process. Such a simplification produces costs savings for both manufacture and materials as levels of spoil are greatly reduced.
A security substrate comprising a transparent polymer carrier layer bearing indicia formed from a plurality of opaque and non-opaque regions and a transparent magnetic layer supported by the carrier layer containing a distribution of particles of a hard magnetic material of a size and distributed in a concentration at which the magnetic layer remains transparent.
A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which:—
FIGS. 28 to 35 are cross-sectional side elevations of further alternative substrates incorporating optically variable devices;
The present invention makes use of transparent magnetic materials that are now available from a number of suppliers. Examples of such materials are described in U.S. Pat. No. 6,996,996, EP-A-660311, U.S. Pat. No. 5,590,954, EP-A-994386 and U.S. Pat. No. 6,258,519 and references therein. Such materials were originally developed for use within the photographic industry to allow information relating to a visual image to be stored magnetically on the photographic film. In the most basic form such transparent magnetic media comprises a polymeric film in which have been suspended magnetic particles of a hard magnetic material. The particles themselves are not colourless, but the degree of concentration is such as to allow the polymeric film to remain transparent. The film has a colour tint, which strengthens if the concentration of particles is increased. Various other forms of transparent magnetic media are described in the cited prior art any of which would be suitable for the present application. It has been found that low concentrations of these hard magnetic materials within such films is able to allow detection using existing banknote detection equipment. In particular, the wider the thread, the lower the concentration of magnetic particles is required for accurate machine detection, due to the fact that the signal recovery is considerably differentiated from the normal cash processing system noise.
The invention requires the use of hard magnetic materials, namely those which have a magnetic remenence in the absence of an applied magnetic field, and preferably a coercivity of greater than 100 oersteds.
The hard magnetic particles may be black iron oxide, gamma iron oxide, cobalt treated gamma iron oxide, barium or strontium ferrites, metallic iron, metallic nickel, metallic cobalt, samarium cobalt, neodymium iron boron or aluminum nickel cobalt. Suitable magnetic materials are commercially available from Magnox Inc., Pfizer Pigments Inc or Toda Kogyo Corp., and suitable varnishes include 1462 from Luminescence, VHL 31534 from Sun Chemicals or 31833XSN, 20784XSN and 90838XSN, all from Coates Lorilleux. The carrier layer (1) may be PET, BOPP or another suitable polymer.
A surprising benefit lies in the provision of a distinctive colour or reflection by varying the coat weights of the magnetic material, whilst maintaining the transparency of the magnetic layer (2). This surprising effect can be enhanced or reduced dependent upon material type and coating thickness to suit the application.
Alternatively, as shown in
The substrate is provided with indicia formed from a plurality of opaque and non-opaque regions, which may be metallised, demetallised, printed or provided in another manner. The magnetic layer (2) may be located below the indicia, over the indicia, or in a full or partial layer which may or may not be in register with the indicia.
The transparent magnetic layer (2, 6) is preferably vacuum metallised and then selectively demetallised in a known manner to provide the indicia, which are formed by metallised regions (3) and demetallised regions (4).
The resulting substrate can therefore have both public (overt) and machine readable (covert) features.
A further polymer layer (5) (12 μm polyester for example) may optionally be laminated to the aforementioned substrate to cover the metallised and demetallised regions (3, 4) to improve its durability. The additional polymer layer (5) may or may not contain magnetic particles depending upon requirements.
The thus formed substrate may then be slit in register to form thin strips suitable for inclusion as security threads into banknotes or other security documents. Typical widths for security threads lie in the range 0.5 mm to 50 mm, and more preferably 1 mm to 10 mm. The use of the substrate of the present invention is not merely limited to use as security threads, but may also be used to provide other security media such as secure tear tapes for brand protection, or a secure substrate for the manufacture of holograms, labels, transfers, hang tags, certificates, bonds, cheques, banknotes and other documents of value. In particular the substrate is particularly suitable for manufacturing plastic banknotes. When utilised as a substrate for such applications it is envisaged that an opaque ink receptive coating be applied over at least part of the substrate.
The secure substrate described above can be further enhanced as will be understood by those skilled in the art. Such enhancements include, but are not limited to, the application of luminescent, thermochromic and, photochromic materials and embossed optically variable devices. Examples of how this might be achieved are described in EP-A-319157, GB-A-2274428, WO-A-00/54985, and WO-A-00/39391.
It would also be possible to use the invention to provide a coded security thread. Such a thread may use interspersed magnetic and text regions, or it could incorporate a coded format, such as that described in EP 407550A or a fixed length or code or use special thickness or coercivity variants to achieve a code. Fixed length coding is a spatially variant of magnetic print with a repeat length equal for, say, all denominations of a particular currency or security document set. The advantage to this type of coding is that the clocking of the code during read is easily established without the need for clocking bits in the code format. Additionally, a magnetic layer could be coated onto at least a part of the substrate to provide a magnetic code. Said additional magnetic layer could contain a magnetic material of different coercivity to that of the substrate film.
Additionally, the use of hard magnetic enables the substrate to be used not only to store predetermined information, but information can be written thereto during use using suitable equipment.
The invention will now be described in more detail by reference to the following examples.
In a first example, as shown in
Potential alternative constructions are shown in
In a second example, as shown in
As a further alternative a layer of pressure sensitive or hot melt adhesive (7) may be applied to the partially metallised surface (3, 4) as shown in
In this example the magnetic particles have been included as part of the polymer carrier layer (6), as shown in
As an alternative a high refractive index (HRI) layer (8) such as ZnS or a polymer liquid crystal layer can be applied in preference to or in addition to the partial metal layer (3, 4) as shown in
If no metal layer is present, opaque inks may be printed in selected regions (9) onto the transparent magnetic media containing layer (2, 6) to form the indicia, as shown in FIGS. 13 to 15, using any of the traditional print processes such as gravure, flexo, intaglio, litho, thermal transfer, dye diffusion and so forth. Additional security can be achieved using iridescent, luminescent (visible or invisible in daylight), optically variable, liquid crystal, thermochromic or photochromic inks in conjunction with, or as an alternative to, the opaque ink. It is preferable that such inks be applied in selected regions of the substrate so as to overlie or highlight the indicia, or even provide additional indicia. Optionally an HR1 or polymer liquid crystal layer (8) may be provided.
The inks described above may also be applied in selected regions (9) in addition to demetallised indicia to further enhance security as shown in FIGS. 16 to 19 with the HRI or polymer liquid crystal layer (8) applied thereover, or with a second polymer layer (5) as shown in FIGS. 20 to 23.
In this example, as shown in FIGS. 24 to 27 the printed regions (9) are located within the demetallised regions 4, but not wholly filling them.
It is also possible to produce a variant of the invention incorporating an optically variable device such as a hologram, Kinegram or Exelgram. Here an additional embossing lacquer (10) is applied on to the substrate and embossed to provide an embossed surface (11). The reflection enhancing layer may be metal, as shown in FIGS. 28 to 31, or an HRI layer, as shown in FIGS. 32 to 34.
FIGS. 28 to 31 show alternative constructions for the optically variable device utilising a metallic reflection enhancing layer. FIGS. 32 to 34 show alternative constructions for utilising the HRI reflection enhancing layer.
In this example, as illustrated in
This is an example of a coded thread as mentioned previously and as illustrated in
This is a further example of a coded substrate, as illustrated in
In all the aforementioned examples it should be noted that, as mentioned in conjunction with Example 34, the demetallised construction consisting of the carrier layer (1) and partially metallised surface (3, 4) can be formed separately from the transparent magnetic construction comprising the protective layer (5) with the magnetic material containing varnish (2) and then laminated together using a suitable adhesive.