GB2578621A

GB2578621A - Security device

Info

Publication number: GB2578621A
Application number: GB1817858.2A
Authority: GB
Inventors: Donald Spinks Gary
Original assignee: Security Fibres Uk Ltd
Current assignee: Security Fibres Uk Ltd
Priority date: 2018-11-01
Filing date: 2018-11-01
Publication date: 2020-05-20
Also published as: GB201817858D0

Abstract

A security device 1 comprising a substrate 2 with a first surface 2' and an opposing second surface. Provided on the first surface are printed regions 3, 4, 5. The printed regions comprise fluorescent inks which glow, emitting a coloured light when they are excited by ultra violet radiation. The printed regions are provided on the substrate 2 such that each one of the printed regions partially overlaps with each of the other two printed regions. The printed regions overlap so that there is a region 9 where all three printed regions overlap. Where all three printed regions overlap in the centre white light is produced as a result additive mixing of the emitted colours. The substrate may be in the form of a fibre or planchette.

Description

Security Device

Field of the Invention

The present invention concerns improvements in and relating to security documents.

More particularly, this invention concerns a security device for a security document arid a method of manufacturing a security device for a security document.

Background of the Invention

Security documents, for example banknotes, passports, lottery tickets, some certificates and other items of potentially high value, are targets for counterfeiters, who seek to produce counterfeit copies of the security documents and thus illegally benefit from the high value of the genuine items. Security documents typically include various security devices or features that are difficult for a counterfeiter to simulate; such devices include holograms, security planchettes, and security fibres. In order to increase the burden for the counterfeiter, security documents have traditionally included fine detailing in their design.

In order to be effective, a security device must exhibit characteristics that are easily identified by a user seeking to verify the authenticity of the security document concerned whilst increasing the burden for a potential counterfeiter. To that end, many security devices exhibit a fluorescent response.

An example of a security feature that is incorporated into a security paper is a security fibre.

Paper is made from paper pulp, which contains cellulose fibres, for example wood, hemp, straw and cotton linters (note that, whilst those cellulose fibres are used to make paper, they are not themselves made from paper). A known security technique is to replace, with artificial fibres made from materials such as polyester, nylon and rayon, some of the cellulose fibres used to make a security paper. A relatively small -2 -number of the artificial fibres can be included in the paper pulp, along with a majority of cellulose fibres, which results in the security paper that is manufactured from the pulp having the artificial fibres embedded within it and randomly distributed. The artificial fibres can be dyed or coated, resulting in the paper including a random pattern of small printed regions. The dye can be a dye that is responsive to ultraviolet (UV) light, so that the coloured random pattern is visible only under UV light.

Such artificial fibres are generally fibrous in shape (i.e. predominantly one-dimensional, rather than two-dimensional or sheet-like), like the cellulose fibres they replace. W02004/025028A1 (D W Spinks (Embossing) Ltd) describes security features that are referred to as "fibres" because they substitute for and bond with the cellulose fibres used in the manufacture of security paper, and because, in the manufactured paper, they give a visual impression that suggests that they are similar to such fibres. In fact, however, the paper fibres described in that document are small strips of paper, and are not fibrous in shape.

Thus, security fibres in the form of small strips of paper, (for example approximately 4mm x 0.3mm) can be added to the paper pulp during manufacture and become embedded in the sheets of paper that are produced. The security fibres are often invisible in daylight and remain unseen by the naked eye. However, when irradiated by ultra-violet light they become fluorescent and visible in the sheet of paper. Mono-colour fibres are relatively easy and inexpensive to produce. However, counterfeiters have been able to use highlighter-type fluorescent marker pens to simulate mono-colour fibres in a sheet of paper. Invisible fluorescent inks are becoming widely available, and the ease of the counterfeiting process, making a few pen strokes on a sheet of paper, are reducing the effectiveness of mono-colour fibres as a security device.

One solution is to make security fibres comprising different colour regions, which raises the difficulty and cost of producing counterfeit fibres. Such security fibres are described in detail in W02004/025028 Al. The "fibres" are intended for incorporation into paper products as a form of counterfeit protection. Each fibre has -3 -a plurality of printed regions visible on front and rear sides of said fibre, wherein the colours are visible only under UV light. The regions may be in the form of stripes, or may be arranged in a pseudo-random pattern. The regions may be differently printed. The security fibres become much more difficult to simulate if the different colour regions are printed with a particular colour sequence, for example, the colours of a national flag.

Summary of the Invention

The present invention provides, in a first aspect, a security device, for inclusion in a security document, the security device comprising one or more of: a substrate having a first surface and a second surface, a plurality of printed regions provided on at least one of the first or second surfaces, wherein said printed regions fluoresce under ultra violet light emitting coloured light.

The printed regions may be arranged on the at least first or second surface such that the coloured light emitted by the fluorescing printed regions mixes to produce white light.

Security devices that produce white light under ultra-violet light are challenging to counterfeit. The particular arrangement of fluorescent printed regions enable emitted colour produced under ultraviolet light to mix additively to provide white light.

According to another aspect of the invention, there is provided method of manufacturing a security device, the method comprising one or more of: providing a substrate having a first surface and a second surface; providing a printed region on at least the first surface or second surface of the substrate, by printing at least three different inks that fluoresce under ultra violet light emitting coloured light of three different colours; and cutting the substrate to create a security device including at least one of the printed regions that produces white light under ultra violet light. -4 -

The inks may be arranged on the at least first or second surface of the substrate such that the coloured light emitted by the fluorescing printed regions mixes to produce white light; and 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 apparatus 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 shows a first embodiment of the invention where the security device is a planchette; Figure 2 is a side view of a second embodiment of the invention where the security device is a planchette; Figure 3 is a plan view of the second embodiment of the invention; Figure 4 is a plan view of a third embodiment of the invention where the security device is a fibre; Figure 5 is a plan view of a fourth embodiment of the invention as viewed under ultra-violet light, where the security device is a fibre; Figure 6 is a schematic showing how fluorescent inks can be provided in an overlapping manner on the substrate surface to produce pattern of colours shown in the fourth embodiment; Figure 7 is a schematic showing the pattern of colours produced when the overlapping fluorescent inks of Figure 6 are irradiated with ultra violet light; Figure 8 shows a fifth embodiment of the invention where the security device is a star shaped planchette; -5 -Figure 9 shows a sixth embodiment of the invention where the security device is a triangle shaped planchette; Figure 10 shows a security document comprising the security device of the third embodiment of the invention, (a) is the security document as viewed under visible light and (b) is the security document as viewed under ultraviolet light; Figure 11 is a flowchart showing steps in the manufacture of the example security device of Figure 4 or Figure 5; and Figure 12 is a flowchart showing the steps of manufacture of the example security document of Fig. 10.

Detailed Description

According to a first aspect of the invention, there is provided a security device for inclusion in a security document. The security device comprises a substrate having a first surface and a second surface. The device may further comprise a plurality of printed regions provided on at least one of the first or second surfaces, wherein said printed regions fluoresce under ultra violet light emitting coloured light. The printed regions may be arranged on the at least first or second surface such that the coloured light emitted by the fluorescing printed regions mixes to produce white light.

The first and second surface of the substrate may be opposing surfaces.

The security device may be a particulate. The security device may be a fibre. The security device may be a planchette. The security device may a starlight.

The security device may be at least 1 mm in length. The security device may be not more than 10 mm in length.

The printed regions may be arranged on the at least first or second surface such that the colour light emitted by the flouorescing printed regions mixes to produce other, different, colours at different regions of the first and/or second surface. -6 -

A printed region may fluoresce under ultraviolet light to produce one of red light, a blue light or green light. Thus, a printed region may be printed using an ink comprising pigments that produce one of red, blue or green light when exposed to ultra violet light. A printed region may fluoresce under ultraviolet light to produce light formed of a mixture of red, blue and/or green light. Thus, a printed region may be printed using an ink comprising a mix of pigments of different colours, for example pigments that produce red, blue and/or green light.

The plurality of printed regions may include at least two printed regions, for example at least three printed regions. The printed regions may be provided on both the first and second surface of the substrate. The printed regions may be arranged on the first and/or second surface such that they at least partially overlap. The printed regions may be arranged on the first and/or second surface such that they completely overlap. Each printed region may comprise a discrete block of a single colour (for example, red, blue, green or a mixture thereof). Thus, the present invention may comprise providing printing blocks of different colours, some of which overlap, in order to produce a coloured pattern. It may be that the blocks of colour overlap such that the light produced by said blocks mixes to produce white light. That may be achieved by using three blocks, one each of red, green and blue. Thus, additive mixing of the light may provide white light. Alternatively, that may be achieved by using two blocks of colour (one block being a mix of two of red, green and blue, the other block being the remaining one of red, green and blue). The blocks of colour may have any shape, for example circular, square, rectangular or other.

The plurality of printed regions maybe provided on the first and/or second surface whereby the distance between the printed regions is less than 0.02 mm. The distance between the centre of two adjacent printed regions may be less than 0.02 mm.

The regions where a red, blue and green ink region overlap may be provided with a ratio of red: blue: green fluorescent ink of 33%:25%:41%. The regions where a red, blue and green ink region overlap may be provided with a ratio of red: blue: green fluorescent ink of 33%:33%:33%. -7 -

The printed regions may be provided using inks that have an excitation wavelength of 365 nm. The printed regions may be provided using inks that comprise microencapsulated fluorescent organic or organometallic dyes. Said dies may have a lightfastness of at least 3 on the blue wool scale.

The substrate may be transparent. The substrate may be paper. The substrate may be tissue paper. The substrate may be without optical brighteners. The substrate may be is paper of a high porosity, high wet strength tissue paper with a nominal basis weight of between 23 and 28 g/m2. The substrate may be paper of a high porosity, high wet strength tissue paper with a nominal basis weight of 25 g/m2.

The security device may further comprise a layer of varnish on at least the printed regions.

According to a second aspect of the invention, there is provided a method of manufacturing a security device. The method may comprise the step of providing a substrate having a first surface and a second surface. The method may further comprise the step of providing a printed region on at least the first surface and/or second surface of the substrate, by printing at least two, for example three, inks that fluoresce under ultra violet light emitting coloured light. The inks may be arranged on the at least first or second surface of the substrate such that the coloured light emitted by the fluorescing printed regions mixes to produce white light. The method may comprise the step of cutting the substrate to create a security device including at least one of the regions that produce white light under ultra violet light.

The first and second surface of the substrate may be opposing surfaces.

The printed region may be provided using inks that emit a single one of red, blue and green light under ultra violet light. The printed region may be provided using inks that emit a mixture of two or more of red, blue and green light. The printed regions may be provided on the first and second surface of the substrate. -8 -

The step of providing printed regions on both the first and second surface of the substrate may comprise printing on one of the front or the rear sides of the substrate and allowing the ink to soak through to the other side of the substrate. The step of providing printed regions on both the first and second surface of the substrate may comprise individually printing on the front side of the substrate and printing on the rear side of the substrate.

The printed regions maybe provided on the first and/or second surface of the substrate such that there are regions where all three inks overlap. The printed regions may be provided on the first and/or second surface of the substrate such that for every one region that all three inks overlap, there are three printed regions in which the inks do not overlap. The printed regions may be provided on the first and/or second surface of the substrate such that for every region that all three inks overlap, there are three regions where each one of the three inks overlaps with one of each of the other two inks. The printed regions may be arranged on the first and/or second surface of the substrate such that they are no more the 0.02 mm apart. The printed regions may be arranged on the first and/or second surface of the substrate such that they at least partially overlap. The printed regions may be arranged on the first and/or second surface of the substrate such that they completely overlap.

The regions where a red, blue and green ink region overlap may be provided with a ratio of red: blue: green fluorescent ink of 33%:25%:41%. The regions where a red, blue and green ink region overlap may be provided with a ratio of red: blue: green fluorescent ink of 33%:33%:33%.

According to a third aspect of the invention, there is provided a security document comprising the security device according to the first aspect of the invention. The security document may be a bank note, a cheque, a passport, identity papers, or fiduciary papers.

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 -9 -invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

In a first example embodiment of the invention (Figure 1), there is provided a security device 1, namely a planchette, for a security document. The security device 1 comprises a substrate 2 (Figure 1). The substrate 2 having a first surface 2' and an opposing second surface (run shown). Provided on Lhe firsL surface 2' of Lhe substrate 2 are printed regions (3, 4, 5). The printed regions 3, 4,5 are only visible when viewed under ultra-violet light. Printed region 3 comprises an ink that fluoresces to produce red light. Printed region 4 comprises an ink that fluoresces to produce blue light, and a region 5 comprises an ink that fluoresces to produce green light, when viewed under ultraviolet light. The printed regions 3, 4, 5 are provided on the substrate 2 such that each one of the printed regions 3, 4, 5 partially overlaps with each of the other two printed regions. The printed regions 3, 4, 5 overlap so that there is a region 9 where all three printed regions overlap, there are also three other regions (6, 7, 8) where only two of the three printed regions (3, 4, 5) overlap such that each of the three colours overlaps with the other two in isolation. There are also printed regions 2, 3 and 4 where there is no overlap at all.

When the overlapping printed regions 6, 7, 8 are viewed under ultra-violet light, the inks fluoresce and the light produced mixes resulting in colours different to those produced by the non-overlapping printed regions 3, 4, 5. For example, the area where the printed regions overlap 6, 7, 8 will reflect fluorescent light of a colour that results from the additive mixing of the reflected red and blue light (magenta 6), blue and green light (cyan 7), red and green light (yellow 8). Where all three printed regions overlap in the centre 9, white light is produced as a result of the mixing of the red, blue and green wavelengths. At region 9, the ratio of red: blue: green fluorescent inks is 33.3% red to 41.6% blue to 25% green.

In another embodiment of the invention (Figure 2 and Figure 3), there is provided a security device 10, namely a planchette, for a security document. The security device 10 comprises a substrate 12 having a first surface 17 and a second surface 18 that -10 -opposes the first surface 17. Provided on the first surface 17 is a printed region 16, such that the printed region does not cover the entire first surface 17. The printed region 16 is visible only under ultra-violet light, and comprises three layers of fluorescent inks (13, 14, 15). The first fluorescent ink layer 13 is printed directly onto the first surface 17 of the substrate 12 and comprises a fluorescent ink that that produces red light under ultra-violet radiation. Printed directly on top of the first fluorescent ink layer 13, is a second fluorescent ink layer 14, which produces blue light under ultra-violet radiation. Printed directly on top of the second fluorescent ink layer 14, is a third fluorescent ink layer 15, which produces green light under ultra-violet radiation. The first, second and the third fluorescent ink layers (13, 14 and 15) are disposed on the first surface 17 of the substrate 2 such that they superimpose each other to provide printed region 16. In this way, when printed region 16 is irradiated with ultra-violet light, it produces white light as a result the of the mixing of the red, blue and green light wavelengths produced by the three printed fluorescent ink layers 13, 14 and 15 (Figure 3).

In another embodiment of the invention (Figure 4), there is provided a security device 20, namely a fibre, for a security document. The security device 20 comprises a substrate 22, a first surface 27 and a second surface (not shown) that opposes the first surface 27. Provided on the first surface 27 is a plurality of printed regions 29 those regions include individual stripes or blocks of fluorescent ink that produce red 23, blue 24 and green 25 light under ultraviolet irradiation. The printed regions 23, 24, 25 are visible only under ultra-violet light. The plurality of printed striped regions 23, 24, 25 are printed in close proximity to one another such that they are unresolvable by the naked eye. When the substrate 22 is irradiated with ultra-violet light, the reflected light wavelengths additively mix to produce white light. In an alternative embodiment, the inks are printed on the substrate 22 such that they overlap with one another (not shown), and irradiation with ultra-violet light produces white light.

In another embodiment of the invention (Figure 5), there is provided a security device 30, namely a fibre, for a security document. The security device 30 comprises a substrate 32, a first surface 37 and a second surface (not shown) that opposes the first surface 37. Provided on the first surface 37 is a plurality of printed striped regions 39. Those regions are printed with fluorescent inks that produce red 33 blue 34 and green 35 light. Each of the fluorescent inks are printed in an interrupted manner along striped regions 39 so that there are regions along stripe 39 where all three printed regions overlap 36. For every region where the three inks overlap, there are also three other regions where only two of the three printed regions overlap 40, 38, 41 (Figures 6 and 7) such that each of the three printed regions overlaps with each of the other two printed regions in isolation. There are also printed regions where there is no overlap at all (33, 34 and 36).

Figure 6 shows an embodiment of the invention where the fluorescent red, blue and green inks 33, 34 and 35 are printed in repeating pattern along striped region 39 of fibre 30. The pattern of inks is provided according to Table 1 below, where letters A to G represent successive units of surface area on stripe 39 that are the same size, and / indicates that the unit has been printed with the corresponding fluorescent ink.

A B C D E F G

Red / / / / Green / / / / Blue / / / / Observed colour under UV light Blue Magenta Red Yellow Green Cyan white In this way, striped regions 39 can produce a number of further colours (38, 40 and 41), as shown in Table 1 beyond those emitted by the fluorescent inks as well as white (Figure 7).

According to one embodiment of the invention, the inks are microencapsulated organic or organometallic dyes that have a wool scale lightfastness of at least 3.

-12 -In another embodiment, both the first surface and a second opposing surface of the substrate are provided with the printed regions. In this embodiment, the printed regions are provided on both the first surface and second surface of the substrate such that they are unresolvable by naked eye, or the inks are printed on the first or second surface of the substrate such that they overlap with one another at certain points.

Figure 8 shows a further embodiment of the invention where the security device is a planchette 72. The planchette 72 is in the form of a star. The planchette 72 includes printed striped regions 79, produced by the overlapping in fluorescent red, blue and green inks in a pattern as shown in Figure 6, and producing a colour pattern under ultra violet as shown in Figure 7. Each stripe 79 extends diagonally across planchette 72 and are only visible under ultra-violet light. The planchette 72 is small, typically having a maximum dimension of between 2mm and 5mm.

In one embodiment, the colours are visible when ultraviolet light having a wavelength between 245 nm and 365 nm is shone at the planchette.

A large number of planchettes, such as the planchette 72, can be cut from a single sheet of paper. The printed stripes 79 are printed onto the paper prior to the planchettes 72 being cut. The printed stripes 79 may be printed on both sides of the planchette 72 and overlap at certain points.

The planchettes in accordance with the present invention are intended to be incorporated into a paper product, such as a bank note, as a counterfeit protection device.

In one form of the invention, the planchettes are made from a material with a different density and structure to the base paper with which it is to be used. This allows the planchette to be seen in the so-called "look through" of the paper. The effect is similar to viewing a watermark.

-13 -The star 70 shown in Figure 8 is, of course, only one of many possible shapes for a planchette in accordance with the present invention. For example, the planchette may take any shape such as a triangle 80 (figure 9) or the shapes of national symbols, such as a fern for New Zealand or a maple leaf for Canada.

The substrate (2, 12, 22, 32, 72) is a thin and porous paper and printing on a single side of the substrate (2, 12, 22, 32, 72) with an appropriate amount of ink means that the ink soaks through the substrate (2, 12, 22, 32, 72) and so both sides of the substrate have been printed on. In an alternative embodiment, each side of the substrate (2, 12, 22, 32, 72) is printed individually, such that the printed regions on each side of the paper overlap with each other, or are printed in close proximity such that they are indistinguishable from one another when viewed by the naked eye.

The printed regions may also be coated with a varnish. The varnish protects the printed regions against abrasion and improves the affinity of security device in the finished paper. In one embodiment, the varnish is a 4% solution of Solvitose NX in acrylic water based binder.

The substrates (2, 12, 22, 32, 72) from which the security devices are produced, in the embodiments of the invention as described above, are a tissue or thin paper without optical brighteners. The optimum paper is a high porosity, high wet strength tissue paper with a nominal basis weight of 25 grams per square metre. The substance of the paper is significant since the ability to print and cut a thin substrate provides a technical barrier to duplicating the fibres.

Paper products in accordance with the present invention are made by mixing slurry paper pulp with the security devices of the present invention. The security devices of the present invention form a hydrogen bond with the cellulose fibres in the paper pulp and when the pulp is formed into a continuous web of paper, the security devices in the pulp become an integral part of the web or sheet of paper. The printed regions of the fibres can only be seen under ultra-violet light, thereby providing a security feature that cannot be seen in normal light conditions (Figure 10, (a)).

-14 -The security devices, for example a plurality of fibre 30, are incorporated into paper pulp used to manufacture a security paper, in this example banknote 50 (Fig. 10). Under visible light (Fig. 10(a)), the fibres 30 are unremarkable, blending in with other cellulose fibres that make up the paper of the banknote 50. However, under ultra-violet light, the fibres 30 fluoresce, forming a random pattern of coloured and white markings in Lhe banknote 50 (shown schematically for ease of illusLraLion by Lhe dotted pattern in Fig. 10(b)). Thus a UV light is used for a check of the validity of the security paper, e.g. in a shop, or by a bank teller.

Fibres 20 or 30 are manufactured by the process shown in Figure 11. Paper is drawn from a roll in a paper store 60 and passed to a printing machine 70. Printing machine 70 includes ink reservoirs 80 (a) to (c), which contain three inks containing pigments that fluorescent in red, blue or green when illuminated under UV light. The printing machine prints regions 23, 24 and 25 to form multiple copies across the paper substrate 22. The printed paper substrate passes to cutting machine 90, where it is cut into fibres 20. The cut fibres 20 are deposited into a bin 100 for transport to a paper mill.

At the paper mill, the banknote of Fig. 10 is manufactured by the method shown in Figure 12. Security fibres 20, produced by the method of Figure 11, are drawn from store 110 and mixed with water and conventional cellulose fibres (from a second store 120) to form a pulp 130. A paper making machine 140 manufactures paper from pulp 130 using conventional methods. At step 150, further processing of the paper takes place, including printing of standard images and the like. The manufactured and printed paper is then cut (step 160) to form the paper product 170, in this case, banknotes.

Thus, paper products in accordance with the present invention are made by mixing slurry paper pulp with the security fibres of the present invention. The security fibres of the present invention form a hydrogen bond with the cellulose fibres in the paper pulp and when the pulp is formed into a continuous web of paper, the security fibres in the pulp become an integral part of the web or sheet of paper. The printed regions -15 -of the fibres can only be seen under ultra-violet light, thereby providing a security feature that cannot be seen in normal light conditions.

Whilst the present invention has been described and illustrated with reference to particular embodiments, 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. By way of example only, cer Lain possible variations will now be described.

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.

Claims

-16 -Claims 1. A security device for inclusion in a security document, the security device comprising: a substrate having a first surface and a second surface, a plurality of printed regions provided on at least one of the first or second surfaces, wherein said printed regions fluoresce under ultra violet light erniaing coloured lighL; arid the printed regions are arranged on the at least first or second surface such that the coloured light emitted by the fluorescing printed regions mixes to produce white light.
2. The security device according to claim 1, wherein the first and second surface of the substrate are opposing surfaces.
3. The security device according to claim 1 or claim 2, wherein the security device is a particulate, for example a fibre, a planchette or a starlight.
4. The security device according to any preceding claim, wherein the plurality of printed regions includes at least three printed regions.
5. The security device according any preceding claim, wherein the printed regions are provided on both the first and second surface of the substrate.
6. The security device according to any preceding claim, wherein the printed regions are arranged such that they at least partially overlap.
7. The security device according to any preceding claim, wherein the printed regions are arranged such that they completely overlap.
8. The security device according to any preceding claim, wherein the printed regions include a region that fluoresces under ultraviolet light to produce red light, another region that that fluoresces under ultraviolet light to produce -17 -blue light and yet another region that fluoresces under ultraviolet light to produce green light.
9. The security device according to any preceding claim wherein the printed regions are provided using inks that have an excitation wavelength of 365 nm.
10. The security device according to any of the preceding claims wherein the printed regions are provided using inks that comprise microencapsulated fluorescent organic or organometallic dyes, having a lightfastness of at least 3 on the blue wool scale.
11. A method of manufacturing a security device, the method comprising: providing a substrate having a first surface and a second surface; providing a printed region on at least the first surface and/or second surface of the substrate, by printing inks that fluoresce under ultra violet light emitting coloured light; the inks being arranged on the at least first or second surface of the substrate such that the coloured light emitted by the fluorescing printed regions mixes to produce white light; and cutting the substrate to create a security device including at least one of the printed regions that produce white light under ultra violet light.
12. The method according to claim 11, wherein the first and second surface of the substrate are opposing surfaces.
13. The method according to claim 11 or 12, wherein three printed regions are provided, the ink of each region fluorescing to emit one of red, blue or green light under ultra violet light.
14. The method according to any one of claims 11 to 13, wherein the printed region is provided on the first and second surface of the substrate.
-18 - 15. The method according to claim 14, wherein the step of providing printed regions on both the first and second surface of the substrate comprises printing on one of the front or the rear sides of the substrate and allowing the ink to soak through to the other side of the substrate.
16. The method according to claim 14, wherein the step of providing printed regions on both Lhe first arid second surface of Lhe substrate comprises individually printing on the front side of the substrate and printing on the rear side of the substrate.
17. The method according to any one of claims 13 to 16, wherein the three inks are printed the substrate such that there are regions where all three inks overlap.
18. The method according to claim 17, wherein for every one region that all three inks overlap, there are three printed regions in which the inks do not overlap.
19. The method according to claim 17 or 18, wherein for every region that all three inks overlap, there are three regions where each one of the three inks overlaps with one of each of the other two inks.
20. The method according to any of claims 11 to 19, wherein the inks are arranged on the at least first or second surface of the substrate, such that they at least partially overlap.
21. The method according to any of claims 11 to 20, wherein the inks are arranged on the at least first or second surface of the substrate, such that they completely overlap.
22. A security document comprising the security device of claims 1 to 10.
23. The security document of claim 22, wherein the document is a bank note, a cheque, a passport, identity papers, or fiduciary papers.