A planchette for a security paper

Background of the Invention The present invention concerns a planchette for a security paper, a security paper containing a plurality of the planchettes, a method for making the planchette and a method for making the security paper.

It is known to provide a number of security paper products, such as bank notes, cheques, passports, identity papers and fiduciary papers, with some form of counterfeit protection. A number of counterfeit protection measures are known in the art. They include watermarks, holograms, the provision of threads through the paper, the use of

fluorescent particles and the use of optically variable inks and coatings .

Problems with known counterfeit protection measures include the expense of some options and the ease with which some options can be overcome, for example by utilizing methods including digital or laser printing, scanning, photography and xerography. Another problem is the

difficulty in raising public awareness of some of the measures, especially in relation to counterfeit protection for bank notes.

One further known approach is to include in the security paper very small strips of paper (e.g. 0.2 mm x 1 mm) , known as "fibres", that have been printed with

fluorescent inks. The fibres are incorporated in the pulp from which the security paper is made, and so they are randomly distributed in the security paper. The fibres are typically invisible under normal lighting conditions, but fluoresce in bright visible colours when the security paper is illuminated with UV light. It is known to provide a plurality of regions on the fibre, each region producing light of a different colour under the UV illumination.

"Dual colour" and "Multi-Colour" fibres offer a significant advantage over mono-colour fibres, as counterfeiters have found the latter easy to reproduce either by hand, using a simple highlighter pen to make fine pen strokes on the paper to simulate a fibre or by printers simply using one printing unit with an easily obtainable fluorescent ink.

Another known approach is to incorporate a number of small discs of coloured paper, known as planchettes, into a security paper and to use the visual effect generated by the planchettes as an anti-counterfeiting measure. Such an arrangement offers many advantages. The planchettes are embedded in the paper meaning that it is very difficult, if not impossible, for a counterfeiter to find someone with a paper-making machine who would be willing to make

counterfeit paper. It is much more difficult to trace a printed counterfeit note back to a particular printing machine, desk-top printer or foiling machine from the millions used throughout the world, whereas the number of paper machines is far smaller, and the possibility for casual counterfeiting on this type of machine practically zero. For this reason many issuers of currency and high value documents put high importance on the paper substrate and the various inclusions that can be added. The principle of using planchettes in paper making is a very well established and robust technique and has been very

successful in deterring counterfeiting of the substrate.

W02007 /l 44657 describes a planchette for inclusion in a paper product, the planchette having a complex shape and comprising one or more coloured regions, the colours being visible only under ultra-violet light.

The present invention seeks to provide an improved planchette for a security paper. Summary of the Invention

The present invention provides, in a first aspect, a planchette for a security paper, the planchette being a sheet having a first face and a second face, the first face having a first colour and the second face having a second, different, colour.

The first face may have a colorant of a first colour and the second face may have a colorant of a second colour. It may be that the sheet is at least partially transparent, in which case the colorants may both be on the same face of the sheet, with at least one of the colorants being visible through the sheet.

The first colorant may optionally produce the first colour only as fluorescence, when illuminated by ultraviolet light.

The second colorant may optionally produce the second colour only as fluorescence, when illuminated by ultraviolet light.

As discussed above, counterfeiters rarely if ever attempt to make security paper from scratch, for example by manufacturing paper including planchettes ; rather, they typically attempt to simulate security features such as planchettes on the surface of the counterfeit security paper. Because planchettes according to the first aspect of the invention have different colours on each side,

counterfeiters will find it hard to counterfeit a security paper containing them, as to do so convincingly would require them to print two different colours on each side of the counterfeit paper, with the first colours on the first side being in perfect registration with the second colour on the second side.

The sheet may comprise cellulose. The sheet may comprise a synthetic polymer material, e.g. a plastics film.

Optionally, the sheet forming the planchette is such that, when light reflected from the first surface or the second surface is viewed directly, the sheet has the first colour or the second colour, respectively, but when light that has been transmitted through the sheet is viewed, the sheet has a third colour. The third colour may result from a combination of the first colour and the second colour.

Of course the third colour may be the first colour or the second colour. The sheet may comprise a first

fluorescent layer on the first face of the sheet; a layer of UV absorbent material on the first fluorescent layer; and a second fluorescent layer on the layer of UV absorbent material. Therefore, when the first face of the sheet is illuminated in reflected UV light, the fluorescence from the second fluorescent layer is substantially brighter than the fluorescence from the first fluorescent layer and, when the second face of the sheet is illuminated in reflected UV light, the fluorescence from the first fluorescent layer is substantially brighter than the fluorescence from the second fluorescent layer.

When reference is made to a face being illuminated in reflected UV light, it should be understood that means that UV light is incident on the planchette from the side of the planchette on which the face is situated. Thus it may be that the UV light is incident on the face of the sheet, or it may be that the UV light is incident on the outermost layer that is on that face of the sheet.

When reference is made to a face being illuminated in transmitted UV light, it should be understood that means that UV light is incident on the planchette from the opposite side of the planchette to that on which the face is situated. Thus it may be that the UV light is incident on the opposite face of the sheet, or it may be that the UV light is incident on the outermost layer that is on that opposite face of the sheet.

The first fluorescent layer may fluoresce in a

different colour to the second fluorescent layer.

When the first face of the sheet is viewed in reflected UV light, the second fluorescent layer fluoresces strongly. In contrast, the first fluorescent layer fluoresces only weakly, if at all, because the UV absorbent material prevents the UV light from passing through to the first fluorescent layer.

On the other hand, when the second face of the sheet is viewed in reflected UV light, the second fluorescent layer fluoresces only weakly, if at all, because the UV absorbent material prevents the UV light from passing through to the second fluorescent layer. The first fluorescent layer, however, now fluoresces strongly because the UV light falling on the second face excites the first fluorescent layer. The fluorescence passes through the sheet, which may be at least partially transparent, and is visible to the viewer. Thus the first face has a first colour and the second face has a second colour.

It may be that the first and second fluorescent layers are continuous and cover substantially all of the face of the planchette . Such a planchette may be simple and cost- effective to make, whilst still producing a striking visual effect .

It may be that the first and second fluorescent layers each cover only part of the sheet and are non-coextensive, for example non-overlapping (when viewed from the first face of the sheet) . Therefore, when the planchette is turned over, while maintaining the lighting conditions (i.e.

reflected or transmitted UV light) , the effect perceived by the viewer is that the visible fluorescence ^Λ jumps' from the second fluorescent layer to the first fluorescent layer. Such an effect may be even more striking, and easier to detect in an automated fashion, than a colour change. In particular, such an effect is apparent regardless of the ability to detect colour.

The colour switch or the jumping' effect will also be observed if the lighting is switched from transmitted UV light to reflected UV light whilst viewing the same face of the sheet. The sheet may be substantially transparent to UV and visible light. In some embodiments the substrate may be partially transparent to UV and visible light.

The fluorescent regions and the UV absorbent material may be one of printed layers or coatings .

Because both fluorescent layers and the UV absorbent layer are on the same face of the sheet, the planchette has a face of the sheet that may be free from such layers, and may optionally instead comprise one or more indicia, markings, or other security features. That may be

particularly advantageous in that planchettes with multiple security features may be significantly harder to counterfeit and a counterfeiter may successfully reproduce one feature, without appreciating the need to reproduce the other feature on the same planchette. In some embodiments, having a side of the sheet free may also enhance the bonding of the planchette into the security documents.

When the fluorescence from the second fluorescent layer is said to be substantially brighter than the fluorescence from the first fluorescent layer, it may be that the fluorescence from the first fluorescent layer has an intensity that is not more than 10%, preferably not more than 1%, or even more preferably not more than 0.1% of the intensity of the second fluorescent layer. For example, it may be that, when the first face of the sheet is illuminated in reflected UV light, the intensity of the fluorescence from the first fluorescent layer is not more than 10% of the intensity of the fluorescence from the second fluorescent layer and, when the second face of the sheet is illuminated in reflected UV light, the intensity of the fluorescence from the second fluorescent layer is not more than 10% of the intensity of the fluorescence from the first fluorescent layer .

The absorbance of the UV absorbent material may be such that substantially no UV light can pass through the

material, in which case there will be substantially no fluorescence from the fluorescent layer on the side of the UV absorbent material away from the source of UV

illumination. Thus it may be that, when the first face of the sheet is illuminated in reflected UV light, there is substantially no fluorescence from the first fluorescent layer and, when the second face of the sheet is illuminated in reflected UV light, there is substantially no

fluorescence from the second fluorescent layer.

The UV absorbent material may be substantially

transparent to visible light. In some embodiments the UV absorbent material may be at least partially transparent to visible light. In that case, when the first face of the sheet is illuminated in transmitted UV light, the

fluorescence from the first fluorescent layer will be at least partially visible through the UV absorbent layer and, when the second face of the sheet is illuminated in

transmitted UV light, the fluorescence from the second fluorescent layer will be at least partially visible through the UV absorbent layer and the sheet. Thus the first face has a first colour and the second face has a second colour also in transmitted light.

When the planchette is turned over, while remaining viewed in reflected light or transmitted UV light, the effect perceived by the viewer is that the visible fluorescence changes colour, which may be a striking and readily recognisable effect. In each case, when the

planchette is turned over, the fluorescent layer that was illuminated by the UV light becomes masked from the UV light by the UV absorbent layer and the fluorescent layer that was masked by the UV absorbent layer becomes illuminated by the UV light. Thus turning the planchette over, while

maintaining the lighting conditions (i.e. reflected or transmitted UV light) , results in the colour of the

planchette changing and thus the first face of the sheet has a first colour and the second face of the sheet has a second colour .

The planchette may comprise further layers, for example transparent layers, which may be, for example, between the substrate and the first fluorescent layer, between the first fluorescent layer and the UV absorbent layer, or between the UV absorbent layer and the second fluorescent layer.

Alternatively, the sheet of the planchette may comprise an intermediate layer including a colorant of the third colour. It may be that the third colour is visible only when the sheet is illuminated (optionally, directly

illuminated) from behind by sunlight or an artificial light source (which may be a UV light source) . By providing a sheet having an intermediate opacity (i.e. neither fully transparent nor fully opaque), the counterfeiters task is made still more difficult, as he or she must simulate a paper that has regions each having different colours under different viewing conditions, with the colours all being coincident for each region (i.e. when the sheet is viewed in transmitted light, the third colour would be visible, and any residual areas of the first or second colour would indicate that the counterfeit "planchettes" had been printed onto the paper (in imperfect registration)) .

Alternatively, the first and second colours may be deliberately misaligned in the planchette; again, for a successful counterfeit to be produced, the resultant distinctive pattern in transmitted light must be

convincingly reproduced by a counterfeiter, which will be very difficult.

Optionally, a plurality of colours, which may be fluorescent colours, is provided on both the first face and the second face, forming a plurality of distinct coloured regions. The colours may be arranged in a pattern that is the same on the first face and on the second face. The colours may be arranged in a pattern that is reversed on the second face compared with the first face, for example so that colours on the first face are coincident with like colours on the second face.

Optionally, the planchette further includes a machine- readable element, for example a machine-readable colorant. Optionally, the machine-readable colorant is readable only by a machine and not by a human eye. For example, the planchette may include a colorant (e.g. a pigment or dye, which may be comprised for example in an ink) that emits light of a first wavelength that is invisible to the human eye (e.g. RF or infra-red light) when illuminated with light of a second wavelength. The invisible emission is readily detected by a machine, providing a covert security feature.

The planchette may have a regular shape. For example, the planchette may be a circle or a square or a triangle. The colours may be provided in a complex or non-regular shape or pattern on the planchette. The shape or pattern of the colours may be surrounded by a border region. It may be that the border region does not contain any colours. Thus, complex shapes or patterns of colour may be provided on a planchette that has a simple or regular shape, and that is hence easy to cut reliably from a larger sheet.

The planchette may have a complex shape. The

planchette may have a non-regular shape (i.e. not a circle or a square or triangle or another regular figure) . The planchette may for example have a shape that is the shape of a well-known national symbol, for example the Canadian maple leaf, or the Indian Rupee symbol.

It may be that the sheet has a maximum width of between 2 mm and 6 mm, optionally between 3 mm and 5 mm. It may be that the sheet has a minimum width of more than 1.5 mm, optionally more than 2 mm.

According to a second aspect of the invention there is also provided a security paper including a plurality of planchettes according to the first aspect of the invention.

Typically, the planchettes will be randomly distributed in the security paper.

According to a third aspect of the invention there is also provided a method of manufacturing a security paper comprising incorporating planchettes according to the first aspect of the invention into a paper pulp and then making the security paper from the pulp.

According to a fourth aspect of the invention there is provided a method of manufacturing a planchette for use in a security paper, the method comprising applying a first colorant having a first colour to a sheet of material, applying a second colorant having a second, different, colour to the sheet of material and cutting a plurality of planchettes from the sheet. The first colorant may be applied to a first face of the sheet of material. The second colorant may be applied to a second face of the sheet of material. The second colorant may be applied to the first face of the sheet of material, that is to say the second colorant may be applied on top of the first colorant, in which case an additional layer, for example a UV absorbent layer, may be applied on top of the first colorant before application of the second colorant. The planchette made by the fourth aspect of the invention may, for example, be a planchette according to the first aspect of the invention.

It may be that the first colour is applied to a first plurality of regions on the first face and the second colour is applied to a second plurality of regions on the second face, the second plurality of regions being in register with the first plurality of regions. It may be that each planchette is cut to include at least one of the plurality of regions. It may be that the regions of the first plurality and the regions of the second plurality are identical in size and shape.

It will of course be appreciated that features

described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the planchette of the invention and vice versa. Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

Figure 1 is a schematic perspective view of a planchette according to an embodiment of the invention; and

Figure 2 is a schematic view of a security document

according to an embodiment of the invention.

Detailed Description In an example embodiment of the invention, a planchette is film-based and contains two fluorescent colorants, of colours visible only under UV light. The planchette is precision cut into the shape of the New Rupee symbol, having a size of between 3mm-5mm. The symbol is visible in fluorescent light and it also appears in the ^Λ 1οο1; through' of the paper; that is, in transmitted daylight, thus appearing as a ^A miniature watermark' . This provides a readily visible public feature, which on closer inspection under UV light reveals multi-colour fluorescence.

The planchette is of one fluorescent colour on one side and of the other fluorescent colour on the other side.

Also, the planchette comprises a ^A Colour Switch' layer so that the fluorescent colour of the symbol is one colour in transmitted UV light and another colour in reflected UV light. This further complicates the challenge facing any would-be counterfeiter, for they must try and replicate the planchette by printing at least three invisible fluorescent inks onto the paper in exact register to a very small scale and then printing the same on the reverse of the paper.

An additional enhancement to the planchette, in this example embodiment, is a machine-readable taggant, which is coated onto the planchette. The taggant is in register with one the colours of the planchette. This special coating is colourless under UV and visible (or daylight) illumination, so the planchette remains invisible in the sheet of paper and the UV fluorescence is unaffected. In this manner, covert signatures are provided on the example planchette that have a precision of at least 1 part in 104 and are combined to form codes.

An organised counterfeiter might conceivably be tempted to print a simulation of the planchettes onto a paper, using conventional litho techniques; however, the inventors are not aware of any attempt to recreate planchettes in this way. (The Canadian Mounted Police amongst others have well- documented cases showing how counterfeiters first attempt to copy the front-line public-features and are usually

unwilling to increase their costs and difficulty in

simulating second level features such as planchettes.) The technical difficulties faced by a counterfeiter involve printing a simulated planchette onto the sheet of paper where the colours are exactly in register on a very small scale. Additionally, register-cut planchettes with colours in the exact same order require that the counterfeiter would have to ^A back up' or print in exactly the same position on the reverse of the planchette he has printed. Since the genuine planchettes fluoresce on both sides so that they are visible on the obverse and reverse of the bank note, it would be immediately obvious if a counterfeit of the planchette was attempted without this feature.

The cost and difficulty of making a planchette that has even only some of these components is not insignificant and a passable counterfeit might only be achievable by using a Sumultan or Orloff printing process, neither of which is available to a commercial or non-secure printing operation.

Using these example planchettes, the paper maker can add a semi-covert, semi-public feature to the paper without significant difficulty and without significant additional costs of machinery or processing.

The enhancement of planchettes with a machine-readable feature is extremely difficult for the lay-man, commercial or even State-owned printer to replicate. The very high development costs and manufacturing complexity is beyond even most State-owned/sponsored banknote printers or paper mills .

The example planchettes in the shape of the new Rupee symbol offer an attractive, easily distinguishable and easily described feature. The Rupee symbol can be seen without the aid of any equipment and for further examination it is necessary only to have simple inexpensive UV lights which are commonly found at many shop counters, bank tellers and other establishments such as restaurants.

The example planchettes fluoresce brightly and are dispersed evenly over a bank note so that they are readily visible. A description of the Rupee symbol is easy for the layman to understand and so he knows what to look for. He does not need to tilt the note (c.f. colour-shift inks), try to observe some latent effect (c.f. holograms or moving image) ; such features can sometimes be hard to determine or difficult to see in poor lighting conditions.

The machine-readable feature is a feature intended to be detected only in central banks or the like, and is therefore designed so that it is difficult or impossible to detect without specialised equipment and sensing heads.

In addition to inexpensive UV lamps, which paper mills already employ to check that security paper is optically dull, additional hardware to authenticate banknotes

containing the example planchette includes sensors with authentication algorithms interfaced with the sorting platform (G&D: BPS 1000, BPS2000, DLR Cobra, DLR CPS);

quality control equipment on the paper machine

incorporating the RF materials into the banknote paper (provided to paper suppliers and off-line printed banknote equipment for printers); and equipment for determination of the presence and readability of the covert feature.

The example planchettes provide an aesthetic effect that is striking and the relative cost per note is very small .

Figure 1 is a schematic perspective view of a

planchette 1 having a sheet 2, a first fluorescent layer 3, for example a red fluorescent layer, on the sheet 2, a UV absorbent layer 4 on the first fluorescent layer 3 and a second fluorescent layer 5, for example a blue fluorescent layer, on the UV absorbent layer 4.

When the planchette 1 is viewed from the first face in transmitted UV light, the UV light will pass through the sheet 2 and illuminate the first fluorescent layer 3, which will therefore fluoresce. The UV light does not penetrate the UV absorbent layer 4, so the second fluorescent layer 5 does not fluoresce.

The UV absorbent layer 4 is transparent to the visible fluorescence from the first fluorescent layer 3, so the first fluorescent layer 3 of the planchette 1 is seen to fluoresce when the first face is viewed in transmitted UV light.

When the planchette 1 is viewed from the second face in transmitted UV light, the UV light will illuminate the second fluorescent layer 5, which will fluoresce, but will not illuminate the first fluorescent layer 3, because the UV light is blocked by the UV absorbent layer 4. Thus the second fluorescent layer 5 of the planchette 1 is seen to fluoresce .

When the planchette 1 is viewed from first the first face and then the second face in transmitted UV light, the fluorescence will appear to switch from the colour of the first fluorescent layer 3 to the colour of the second fluorescent layer 5. Thus the first face has a first colour and the second face has a second colour. A similar effect will be seen in reflected light, but the first colour will now be the colour of the second fluorescent layer 5 and the second colour will be the colour of the first fluorescent layer 3.

Referring to Figure 2, a security document 200

comprises a plurality of planchettes 100. The planchettes 100 have been incorporated into the security document 200 by mixing the planchettes 100 into the pulp during manufacture of the security document 200. The planchettes 100 are therefore distributed at random throughout the security document 200 and appear in random orientations. Thus, for some of the planchettes 100, the first face will be

uppermost and for some of the planchettes 100 the second face will be uppermost.

When the security document 200 is viewed under

reflected UV light, the planchettes 100 will show a striking pattern of visible fluorescence. When the security document 200 or the source of UV light is moved so that the security document 200 is now viewed in transmitted UV light, the fluorescent pattern will change as the fluorescence switches between the fluorescent layers, as described above. Because the planchettes 100 are in random orientations, some fluorescent regions will switch from the colour of the first fluorescent layer to the colour of the second fluorescent layer and some will switch from the colour of the second fluorescent layer to the colour of the first fluorescent layer, creating a striking and memorable effect. A similar effect will be seen if the security document 200 is viewed from first one side and then the other while maintaining the UV lighting conditions (i.e. reflected or transmitted light) .

Whilst the present invention has been described and illustrated with reference to a particular embodiment, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other

embodiments .