EP2190676A1

EP2190676A1 - Security element

Info

Publication number: EP2190676A1
Application number: EP08806229A
Authority: EP
Inventors: David Allen Stone
Original assignee: De la Rue International Ltd
Current assignee: De la Rue International Ltd
Priority date: 2007-09-19
Filing date: 2008-09-10
Publication date: 2010-06-02
Anticipated expiration: 2028-09-10
Also published as: BRPI0816833B1; CA2699848C; CN101827712A; WO2009037423A1; MY158211A; EA018158B1; CA2699848A1; BRPI0816833A2; GB0718278D0; EG25978A; CN101827712B; MX2010002964A; CO6260116A2; EP2190676B1; EA201070373A1

Abstract

A security element formed by at least two printed portions (1,2). The first portion (1) is a printed, raised line structure defining a background region (6) in which the lines extend substantially parallel in a firs direction, and an image region (5) defining a boundary (8) with the background region. The printed lines in the image region (5) extend substantially parallel in second direction orthogonal to the first direction to define a first, non-diffractiv latent pattern intended to be non-visible to the naked eye when viewe perpendicularly but intended to be visible when viewed at other viewing angles. In locations where the boundary (8) extends at an acute angle to the line defining that part of the boundary, the image and background regions abut. The second portion (2) defines a second, non-diffractive pattern (3) intended to be visible when viewed perpendicularly and at said other viewin angles, and wherein the second, non-diffractive pattern is located relative to th first, non-diffractive latent pattern to enable the security element to be verified.

Description

SECURITY ELEMENT

The invention relates to a security element, a method of manufacturing a security element and an article such as a security document carrying such a security element.

In the field of document and other article security, and particularly in the field of documents of value such as banknotes, counterfeiters are becoming increasingly expert and there is a need to generate new security elements which are difficult to counterfeit. As a result, very complex elements have been produced. A typical example is described in US-A-5722693. In this example, a latent image is provided by printing a pattern onto a substrate and then embossing the pattern while providing a background pattern. The effect is that the embossed pattern is not visible when the element is viewed perpendicularly but becomes visible at certain viewing angles (a "latent" effect). A similar type of device is described in US-A-4033059.

More complex devices are described in US-B-6918616 in which an intaglio printed latent image is provided over a non-intaglio printed image so as to enhance the latent effect.

Other examples of latent images are described in US-A-4588212, GB-A- 2283456, and WO-A-99/48697.

In WO-A-90/02658 a security device is described in which a transitory image such as a latent image is embossed into a metal and a separate linear area visible from substantially all viewing angles is also embossed. In some cases, difficulties can arise with this embossed form of element. For example, the embossing is not particularly durable while the images are hard to visualise. Furthermore, there are difficulties in controlling embossing through a printing process so as to achieve consistency between embossing plates.

Several years ago, the Benelux authorities issued a visa printed by Enschede in which parts of some letters were formed as latent images with a strongly visible outline while the other parts of the letters were permanently visible. The problem with this was that the existence of the latent image was not covert. As will be apparent, therefore, despite the problems mentioned above, latent images are particularly advantageous as security elements. It is particularly difficult to counterfeit such elements using a photocopier for example. However, one of the problems with latent images is that they are often so well hidden that it is difficult for someone wishing to inspect a document to check that it is not a counterfeit, to locate the latent image or even detect its presence. At the same time, the presence of the latent image should not be so overt as to render it insecure as in the Benelux visa. Furthermore, often latent images are difficult to view since they are not particularly strong in tone. In accordance with a first aspect of the present invention, we provide a security element formed by at least two printed portions, a first portion being a printed, raised line structure defining a background region in which the lines extend substantially parallel in a first direction, and an image region defining a boundary with the background region, and in which the printed lines extend substantially parallel in a second direction orthogonal to the first direction to define a first, non-diffractive latent pattern intended to be non- visible to the naked eye when viewed perpendicularly but intended to be visible when viewed at other viewing angles, and wherein, in locations where the boundary extends at an acute angle to the lines defining that part of the boundary, the image and background regions abut; and a second printed portion defining a second, non-diffractive pattern intended to be visible when viewed perpendicularly and at said other viewing angles, and wherein the second, non-diffractive pattern is located relative to the first, non-diffractive latent pattern to enable the security element to be verified. In this invention, we distinguish between holographic and diffractive structures (with which the invention is not concerned) on the one hand and printed relief structures on the other hand in which the latent effect is obtained as a result of varying one or more of the heights and directions of the relief and is not due to diffractive effects. With this invention, we link a latent pattern with a non-latent pattern which is visible both perpendicularly and at the other viewing angles. The advantage of this is that it enables a user to locate the latent (first) pattern by first locating the second pattern but since the image region abuts the background region in locations where the boundary extends at an acute angle to the lines defining that part of the boundary, it is not obvious to the naked eye that the latent pattern is present. This should be contrasted with the Benelux visa mentioned above in which the boundary between the latent pattern and the background region is formed by a distinct gap extending alongside the latent pattern.

Typically, the first and second patterns are registered with one another and this can be most easily achieved by printing them in the same printing pass, for example using the same printing plate.

It is particularly advantageous if the first and second patterns form different parts of a recognisable symbol or character. Thus, on initial viewing perpendicularly the recognisable symbol or character will appear incomplete to the viewer thus hinting at least at the presence of the latent pattern. Examples of symbols or characters include pictorial images for example portraits, symbols for example stars, geometric shapes and alphanumeric characters and combinations thereof. Possible characters include those from non-Roman scripts of which examples include but are not limited to, Chinese, Japanese, Sanskrit and Arabic.

Of course, in other cases, the first and second patterns can be discreet and unrelated or define discreet symbols or characters which are in fact related. For example, the patterns may define a serial number or date with some of the characters being present in the first pattern and the other(s) in the second pattern. It is preferred if the first and second patterns are at least complementary. Alternatively the patterns may define alternate individual letters in a word such that when both patterns are viewed together the word is revealed to the authenticator. In further examples the patterns form individual parts of a composite image, for example the composite image may be a corporate logo comprising a recognizable geometric pattern and alphanumeric characters. The first pattern may form the alphanumeric character and the second pattern may form the geometric pattern such that the corporate logo is visible when both patterns are visible.

In further examples patterns may not form a recognizable image but the combination of the patterns forms a recognizable image which can be a piece of identifiable information for example an alphanumeric character or the national flag of a country. The formation of a recognizable image on combination of the patterns facilitates the authenticator in identifying counterfeits that do not exhibit perfect registration.

In yet other examples, the second pattern could comprise an arrow pointing towards the first pattern.

The first and second portions will typically abut one another but in more sophisticated examples, the portions could overlap or be interlaced. For example, a number of first portions could be located in spaces between second portions, In the case of abutting portions, the portions do not need to fully abut, but have to be close enough together that precise registration is required. For example if one portion contained the numeral 1 and the second portion contained the numeral 0 the two portions could have a 1-2mm horizontal gap but the feature would still require good registration.

Preferably, the portions are printed such that when viewed at at least one non-perpendicular angle the tone of the first latent pattern changes so that both patterns can be seen with substantially the same tonality. This is important as the composite image formed from the two patterns will have a uniform appearance and thus appear as one image, making it easier for the authenticator to identify and authenticate the combined image. Typically, both portions will be printed in the same colour, for example black, but there are other possibilities. For example, the two portions could be printed in different colours or one or both portions may exhibit a varying colour.

Conveniently, the portions are intaglio printed although other forms of relief printing such as screen printing could be used. Intaglio printing is preferred because it is conventionally used in the security printing industry and it provides a very convenient way of achieving precise registration between the patterns since they can both be printed from the same intaglio plate.

The latent portion will typically be provided with suitably imprinted line structures as known in the art and described in US-A-4033059. The lines can be straight or curved.

The non-latent portion may be printed as a non-relief pattern such as by wet or dry lithographic printing, letterpress printing, flexographic printing, screen- printing, and/or gravure printing. In a preferred example it may also be provided with relief printed raised line structures, for example printed by intaglio. In a further preferred example the non-latent portion is relief printed, for example by intaglio, with a continuous uniform tone. One method for printing a uniform continuous tone image is described in WO-A-2006/087129. An alternative method for printing a uniform continuous tone region is to intaglio print an array of dot structures similar to dot structures used in conventional inkjet printed half tone images. The advantage of using such dot structures is that the tonal appearance remains constant as the angle of view is changed. This is particularly advantageous for the non-latent second portion as it enables this region to be easily identified by the authenticator. The dot structure can comprise an array of dots of the same size but of varying density or alternatively of varying size but of the same density.

Although the security element has been described so far as comprising just two portions, the element may comprise more than two portions and each of the additional portions can comprise either a latent pattern or a non-latent pattern. It will be appreciated that complex combinations of portions can be created in this way.

The security element can be provided directly on an article or could be provided on a transferable label which can then be transferred in a conventional manner onto an article.

The security elements of the invention can be used in a wide variety of fields in order to secure articles and documents such as a document of value, for example a banknote, a fiscal stamp, a cheque, a postal stamp, a certificate of authenticity, brand protection article, bond or payment voucher. In the case of documents of value, additional security can be achieved if the patterns defined by the security element are related to other pattern(s) on the document. For example, the denomination of a banknote could be printed in the normal way in one location on the banknote and then repeated within the security element. Of course, other logos, symbols and characters could be duplicated in this way. In accordance with a second aspect of the present invention, we provide a method of manufacturing a security element comprising printing on a substrate at least two printed portions, a first portion being a printed, raised line structure defining a background region in which the lines extend substantially parallel in a first direction, and an image region defining a boundary with the background region, and in which the printed lines extend substantially parallel in a second direction orthogonal to the first direction to define a first, non-diffractive latent pattern intended to be non-visible to the naked eye when viewed perpendicularly but intended to be visible when viewed at other viewing angles, and wherein, in locations where the boundary extends at an acute angle to the lines defining that part of the boundary, the image and background regions abut; and a second printed portion defining a second, non-diffractive pattern intended to be visible when viewed perpendicularly and at said other viewing angles, and wherein the second, non-diffractive pattern is located relative to the first, non-diffractive latent pattern to enable the security element to be verified.

Typically intaglio printing is preferred using the same intaglio plate so as to print both portions simultaneously. This ensures perfect register. Alternatively screen printing could be used to print the first portion in relief. Alternatively the non-latent portion can be printed using any conventional printing technique such as wet or dry lithographic printing, letterpress printing, flexographic printing, screen-printing, and/or gravure printing.

Some examples of security elements according to the invention will now be described with reference to the accompanying drawings, in which:- Figures 1A and 1 B illustrate a first example of a security element when viewed perpendicularly and at an acute viewing angle respectively;

Figures 2A and 2B are views similar to Figures 1A and 1 B but of a second example;

Figures 3A and 3B are views similar to Figures 1A and 1B but of a third example; and,

Figures 4 and 5 are enlarged, schematic views of fourth and fifth examples respectively.

The security element shown in Figure 1A is made up of two portions 1 , 2.

The first portion 1 is defined by a line structure clearly visible in Figure 1A, a first array of lines 5 defining a latent pattern or region against a background region 6.

The line structure arrangement of the portion 1 defining a latent image or pattern is constructed in a similar way to the method described in US-A-4033059. The second portion 2 is printed using an intaglio printed dot structure in which dots in a region 3 are spaced to define a "second" non-diffractive pattern with a uniform continuous tone while dots in a region 4 are less densely spaced but still provide a region of continuous uniform tone to define a background. Examples of dot densities are 80% for the region 3 and 30% in the region 4. However, lower densities in the region 4 are possible down to zero.

The dot structures 3,4 are similar to those used to create halftone images in commercial printing. In one method of generating such a dot structure a design is first generated or captured digitally. Onto this design a dot screen is applied directly utilising a standard software package such as Corel Draw. One type of screen structure is an error diffusion screen. The artwork generated is then converted directly into a suitable output file for driving intaglio platemaking equipment such as laser engraving apparatus described in WO03103962 or mechanical engraving apparatus described in EP906193. The two portions 1,2 are preferably printed using intaglio printing.

When viewed normally or perpendicularly, as seen in Figure 1A, the viewer will see a flat tone presented by the portion 1 , and the pattern 3 in the portion 2.

When the security element is turned with respect to the observer's naked eye and the light so that it is viewed at an acute angle, the latent image defined by the array of lines 5 will become visible against the background 6, the pattern

3 remaining visible throughout. As a result, as can be seen in Figure 1 B, a letter

"X" becomes visible enabling the security element to be verified. It can be seen therefore that the pattern 3 in the portion 2 provides a hint, when the security element is viewed normally or perpendicularly, that there may be some form of covert, matching latent image in the adjacent portion 1.

A very preferred feature is that the pattern in the region 3 and the array of lines 5 defining the latent image are in perfect register. This makes the element very difficult to counterfeit and is achieved by intaglio printing the entire security element using a single intaglio printing plate.

Typical line widths in the latent image region 5 range from 100 μm to 250 μm, preferably 175 μm, with line repeats of 200 μm to 440 μm, preferably 250 μm, and line to space ratios of 30-80%, preferably 50-70%. The lines in the background region 6 typically have similar dimensions to the lines in the region 5 but extend orthogonally thereto. In the non-latent portion 2 the dot size is typically in the range 20-100 μm and the dot coverage is preferably in the range 20-90% and even more preferably in the range 40-90%. The background area 4 in the non-latent portion 2 may be printed in a tone or colour to provide contrast with the "first" non-diffractive pattern. Alternatively the background area in the non-latent portion may be left blank, i.e. non-printed.

A more complex security element is shown in Figures 2A and 2B. In this case, the final pattern when viewed at the acute angle (Figure 2B) is again a letter "X". As can be seen in Figure 2A, however, a number of latent, "first" portions 10 are provided in a regular array interspersed or interlaced with a number of "second" non-latent portions 12. The method of printing each of these portions is similar to the method of printing the portions 1 ,2 respectively. However, as can be seen in Figure 2A₁ each first portion 10 defines a latent pattern corresponding to the relevant part of the letter "X" with which it coincides. The respective "second" portions 12 define respective parts of the letter "X" with which they coincide and are visible at all viewing angles.

It will be appreciated that many different arrangements of portions are feasible. In the examples described, it is preferable that as the security element is tilted so that the pattern 5 becomes visible, the tone of the two patterns 3, 5 becomes the same so that the final symbol or letter has the same, uniform tone throughout. It will be appreciated, however, that other variations are possible with the two patterns having different tones or indeed varying colours. In the examples, the area coverage of the first and second portions

1 ,2;10,12 is substantially the same. However, this is not essential. In other examples, the total area coverage of the non-latent portion(s) may be at least 25%, preferably 40% and even more preferably at least 50% of the area of the security element. Thus, in a preferred embodiment, the area of the final pattern that is non-latent is preferably in the range 25-70% and even more preferably in the range 40-60%.

A third example is illustrated in Figures 3A and 3B. This is similar to the first example in which the line structure of the first portion 1 is the same as in Figure 1A. However, in this case, the second portion 20 is formed by two line structures, a first set of parallel lines extending horizontally in Figure 3A at 21 defining a pattern visible at all angles set against a background of vertically arranged horizontal lines 22 defining a background region. In this case, the horizontal lines defining the pattern 21 are thicker than those defining the pattern 5 thus rendering them visible at all angles. For example, if the lines defining the pattern 5 have a thickness or width of 175 μm then the thickness or width of the lines defining the pattern 21 could be 215 μm. The lines defining the background 22 will have the same dimensions and repeat as the lines defining the background 6.

When this device is viewed normally or perpendicularly only the image defined by the lines 21 will be seen, the portion 1 presenting a uniform appearance. However, when the device is tilted so it is viewed at an acute angle by the naked eye, the full letter "X" will be seen as shown in Figure 3B. As explained above, the latent portion 1 needs to be hidden and we have found that an important aspect of this is the way in which the raised, printed lines defining the latent portion are formed at the boundary between the image region and the background region. This means that care needs to be taken on how the image region and background region meet, the aim being to maintain substantially constant density for the local ink coverage, avoiding dark or light edges.

Figure 4 illustrates this in more detail. This is a schematic, enlarged view to illustrate the principle of the invention. In Figure 4, a background region 30 of vertical, intaglio printed lines 30A-30M is provided. This forms with an image region 32 a first portion of the security element while a second portion is provided at 34. The image region 32 abuts the background region 30 so as to define a boundary 36 and is defined by horizontal, intaglio printed lines 32A-32H. This boundary 36 has a first section 36A extending along a straight line at an acute angle to both the vertical printed lines of the background region 30 and the horizontal printed lines of the image region 32. A vertical section 36B of the boundary is defined by a small gap 37 between one of the vertical lines 3OM of the background region 30 and the image region 32 while a further section 36C of the boundary is defined by a small gap 39 between the lowermost, horizontal printed line 32A of the image region 32 and adjacent, vertical lines 30B-30L of the background region 30.

It will be seen in Figure 4 that along the boundary section 36A, where the vertical printed lines of the background region 30 and the horizontal printed lines of the image region 32 abut or meet, they are allowed to do so naturally line to line, line to space or space to space. We have found that this makes it very difficult to see the outline of the latent image when viewed with the naked eye. For example, horizontal line 32G meets, and is continuous with, vertical line 30I. Horizontal line 32F meets vertical line 3OJ and the gap between vertical lines30J and 3OK. The gap between horizontal lines 32F.32G meets the gap between vertical lines 30I, 3OJ.

Where the boundary extends parallel to one of the sets of the lines as shown as 36B and 36C, it is possible to reduce the visual effect by ensuring that the corresponding gap 37,39 is smaller than the gap between the lines themselves. Typically, a reduction by 50% is suitable or even more. However, if the vertical and horizontal lines touch in these regions, we have found that there is a significant change in density of ink with the result that the edge can be seen with the naked eye.

The pattern defined by the second portion 34 which is visible at all angles is formed by a combination of continuations of the horizontal, printed lines 32A- 32H of the image region 32 and further, thinner, intaglio printed raised lines 38A- 38G interleaved between pairs of the lines 32A-32H. For example, the horizontal lines 32A-32G running from the image region 32 into the second portion 34 may have a width or thickness of 150 μm while the thinner, interleaved printed lines 38A-38G may have a thickness or width of 40 μm. Further, in this case, the lines 32A-32G defining the image region 32 have a repeat of 250 μm while the background region 30 is defined by vertical, intaglio printed raised ink lines 30A-30M having a width of 150 μm and a repeat of 250 μm. As an alternative to the thin lines 38A-38G, the spaces between the lines

32A-32F in the second portion 34 may be filled with printed dots, for example at 600 dots per inch. The pattern defined by the second portion 34 has a symmetrical form to the pattern defined by the image region 32 thus providing a hint to the viewer of the location of the latent image region pattern 32 and also making it easy to verify when viewed with the second pattern 34 at an acute angle. Figure 5 illustrates a further example. In this case, a background region

40 is defined by intaglio printed, raised ink, vertical lines having dimensions similar to those of Figure 4. This forms a first portion of the security element with an image region 42 while a second portion is provided at 44. When viewed at an acute angle, the region 42 and second portion 44 define a circle located within the background region 40. The image region 42 defines a semicircular image region formed by horizontal, raised ink intaglio printed lines while the second portion 44 defining an image visible at all angles is formed by the same horizontal lines as the image region 42 but with additional interleaved intaglio printed lines 46. The structure is therefore similar in principle to that shown in Figure 4 with the second portion 44 hinting at the presence of the latent portion 42. Similar line dimensions would be used. In this case, when viewed perpendicularly, the naked eye will see the semicircle defined by the second portion 44 but will not detect the semicircle defined by the image region 42. This is because the horizontal lines and gaps of the image region 42 abut and blend into the vertical lines and gaps of the background 40 along the inner and outer boundaries 48,50 which are curved and hence define tangents that extend at acute angles relative to the lines of the image and background regions. As in previous examples, at the boundary of the image region 42 and the background 40, printed lines of one meet printed lines or gaps of the other, or gaps in the two meet one another.

Referring back to Figure 1 , it will be seen that the boundary 8 between the image and background regions 5,6 extends at an acute angle to the lines defining the regions and the lines and gaps meeting in the same way as in Figures 4 and 5. The same applies to the Figure 2 example.

Claims

1. A security element formed by at least two printed portions, a first portion being a printed, raised line structure defining a background region in which the lines extend substantially parallel in a first direction, and an image region defining a boundary with the background region, and in which the printed lines extend substantially parallel in a second direction orthogonal to the first direction to define a first, non-diffractive latent pattern intended to be non- visible to the naked eye when viewed perpendicularly but intended to be visible when viewed at other viewing angles, and wherein, in locations where the boundary extends at an acute angle to the lines defining that part of the boundary, the image and background regions abut; and a second printed portion defining a second, non-diffractive pattern intended to be visible when viewed perpendicularly and at said other viewing angles, and wherein the second, non-diffractive pattern is located relative to the first, non-diffractive latent pattern to enable the security element to be verified.

2. A security element according to claim 1 , wherein the second portion is defined by a raised, printed line or dot structure.

3. A security element according to claim 2, wherein the second portion is defined by a raised, printed line structure in which the printed lines extend substantially parallel in said second direction.

4. A security element according to claim 3, wherein the lines of the image region of the first portion extend continuously into the lines of the second portion.

5. A security element according to any of the preceding claims, wherein at least one part of the boundary extends parallel with lines of the image region or lines of the background region, a gap being defined between the lines of the respective parts of the image and background regions defining that part of the boundary.

6. A security element according to claim 5, wherein the gap has a thickness less than, preferably about 50% of, the gap between lines of the background region.

7. A security element according to any of the preceding claims, wherein the lines of the first portion have substantially the same width in both the background and image regions.

8. A security element according to any of the preceding claims, wherein the lines of the first portion have substantially the same pitch in both the background and image regions.

9. A security element according to any of the preceding claims, wherein where the image and background regions abut, lines of the image region extend continuously into lines of the background region, and/or lines of the image region meet gaps between the lines of the background region, and/or lines of the background region meet gaps between lines of the image region.

10. A security element according to any of the preceding claims, wherein the first and second patterns form different parts of a recognisable symbol or character.

11. A security element according to claim 10, wherein the second non-diffractive pattern forms at least 25%, preferably 40%, and more preferably 50% of the recognisable symbol or character.

12. A security element according to claim 10 or claim 11 , wherein the recognisable symbol or character comprises one or more of an alphanumeric character, geometric pattern, pictorial images and symbols.

13. A security element according to any of the preceding claims, wherein the area defined by each pattern is substantially the same.

14. A security element according to any of the preceding claims, having a plurality of first portions and a plurality of second portions, wherein the first and second portions are interlaced.

15. A security element according to any of the preceding claims, wherein the portions are printed such that when viewed at at least one non-perpendicular angle the tone of the first latent pattern changes so that both patterns can be seen with substantially the same tonality.

16. A security element according to any of the preceding claims, wherein both portions are printed in the same colour.

17. A security element according to any of claims 1 to 15, wherein one portion is printed in a different colour from the other portion.

18. A security element according to any of claims 1 to 15, wherein one or both portions exhibit a varying colour.

19. A security element according to any of the preceding claims, wherein the raised printed structure(s) is intaglio printed.

20. An article provided with a security element according to any of the preceding claims.

21. An article according to claim 20, wherein the first and second patterns relate to one or more other patterns provided on the article.

22. An article according to claim 20 or claim 21 , the article comprising a security document such as a document of value for example a banknote, a fiscal stamp, a cheque, a postal stamp, a certificate of authenticity, brand protection article, bond or payment voucher.

23. A method of manufacturing a security element, the method comprising printing on a substrate at least two printed portions, a first portion being a printed, raised line structure defining a background region in which the lines extend substantially parallel in a first direction, and an image region defining a boundary with the background region, and in which the printed lines extend substantially parallel in a second direction orthogonal to the first direction to define a first, non-diffractive latent pattern intended to be non-visible to the naked eye when viewed perpendicularly but intended to be visible when viewed at other viewing angles, and wherein, in locations where the boundary extends at an acute angle to the lines defining that part of the boundary, the image and background regions abut; and a second printed portion defining a second, non-diffractive pattern intended to be visible when viewed perpendicularly and at said other viewing angles, and wherein the second, non-diffractive pattern is located relative to the first, non-diffractive latent pattern to enable the security element to be verified.

24. A method according to claim 23, wherein the raised line structure is intaglio printed.

25. A method according to claim 23 or claim 24, wherein the second portion is defined by a raised, printed line or dot structure.

26. A method according to claim 24, wherein the first and second portions are printed using the same intaglio plate.

27. A method according to any of claims 23 to 26, the method being adapted to print a security element according to any of claims 1 to 18.

28. A method according to any of claims 23 to 27, wherein the security element is printed directly on an article such as a document of value.

29. A method according to any of claims 23 to 27, wherein the security element is printed on a transferable label.