AU2003293901B2

AU2003293901B2 - Security element for valuable documents

Info

Publication number: AU2003293901B2
Application number: AU2003293901A
Authority: AU
Inventors: Eckhard Braun
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2002-12-19
Filing date: 2003-12-16
Publication date: 2008-06-26
Anticipated expiration: 2023-12-16
Also published as: EP1588332B1; DE10260124A1; ATE545920T1; EP1588332A2; WO2004056582A2; WO2004056582A3; AU2003293901A1

Abstract

The invention relates to a transparent security element for valuable documents, comprising superimposed patterns on two opposing sides of a translucent carrier material. In a precise arrangement according to register, the two patterns complete each other to form a full image forming a code. If the positioning is not precise according to register, the code is illegible. The patterns consist of IR-absorbent material and can thus be read by a machine. A pattern can consist of IR-absorbent and IR-transparent partial patterns such that when observing transmitted light with normal light, a different transparent image can be recognised to that recognised when observing transmitted light with IR illumination.

Description

Security element for documents of value This invention relates to a security element for documents of value that comprises a translucent carrier material with two patterns that complement each other to form a visually recognizable, complete image only on viewing in transmitted light. The invention relates further to a security document having such a security element.

Such security elements also referred to as "see-through elements" are known for example from EP 0 388 090 Al and used in particular for bank notes, checks, shares, travel tickets, admission tickets, identification papers and other documents of value made of paper, as well as credit cards, check cards, ID cards and the like. The security documents described therein have printed images on the front and back that complement each other to form a complete image in transmitted light. Such security elements are difficult to imitate since they can be produced in exact register only by simultaneous printing of both document surfaces. The printed images can be formed as line patterns with identically spaced lines of identical width that complement each other to form the full image in transmitted light. To increase security additionally, the images can be printed with invisible ink that is absorbent to x-rays for example so that the security element is visually inconspicuous and machine testable.

DE 32 08 204 Al likewise proposes printing line patterns on the front and back of a document, the line patterns being disposed in register so that they exactly overlap. In both reflected light and transmitted light an identical line pattern is then recognized. In the case of forgeries not produced by simultaneous printing, by which the line patterns are not applied in exact register on the front and back of the document, moir6 structures can be seen in transmitted light due to the fineness of the lines. Alternatively, moir6 structures can be intended and form a visually recognizable see-through authenticity feature through desired mutual offset in partial areas.

EP 0 755 799 Al also proposes applying a printed image, e.g. a number, to both sides of the document in register so that inexactly registered forgeries are identifiable on transmissive viewing. Preferably, the image is printed on the back of the document with invisible ink, thereby preventing forgery by copying. Said invisible ink is preferably visible in UV light to permit machine testing.

In addition, it is known in a different context to provide security documents with prints having special features in the invisible spectral region to produce security features that are machine-readable but not necessarily recognizable visually. For example, the patent CH 287332 describes a security document having a visually perceptible color print transparent to IR radiation that appears colored in reflected light but is white in transmission testing in the IR wavelength range. A color copy of the document would likewise appear colored visually but black in IR transmission testing and thus be identifiable as a forgery.

This idea is developed in DE 26 54 208 B2 where an IR-transparent color print appearing black in the visible spectral region is covered with a black, IR-absorbent color print, or vice versa. The IR-absorbent color print can be for example a bar code that is recognizable only on viewing in the IR wavelength range due to the black surroundings. Depending on which color print is on the outside, reflected-light and/or transmitted-light testing is possible.

JP-A-2167771 also proposes the use of IR-transparent and IR-absorbent printing inks that appear the same color in the visible spectral region. The different inks produce the bars of a bar code which then appears as a uniformly colored bar code to the naked eye. The different materials are then only detectable by machine.

The patent UK 1 534 403 also discloses printed images, bar codes and the like that are printed with inks appearing similarly colored in the visible spectral region and having absorption properties of different strength in the IR spectral region. Said inks can be spaced apart or contiguous and in particular again present in similarly colored surroundings printed with conventional ink, so that the image is not perceptible visually but only machine-readable.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

According to a first aspect of the invention, there is provided a security element for documents of value comprising a translucent carrier material with first and second patterns that complement each other to form a visually recognizable, complete seethrough image only on transmissive viewing, characterized in that the two patterns partly overlap, and the complemented see-through image is formed by the overlapping and the non-overlapping areas of the two patterns.

According to a second aspect of the invention, there is provided a security element for documents of value, comprising a translucent carrier material with first and second patterns that complement each other to form a visually recognizable, complete see-through image only on transmissive viewing, characterized in that the two patterns partly overlap so that the areas of the other pattern covered by one of the patterns do not contribute to an appearance of the see-through image when positioned in exact register.

According to a third aspect of the invention, there is provided a security document comprising a security element in accordance with either the first aspect of the invention or the second aspect of the invention.

It is an advantage of at least a preferred embodiment of the present invention to provide a see-through security element that has elevated security compared to conventional see-through elements and is testable visually and preferably also by machine. It is a further advantage of a preferred embodiment of the present invention to provide a security document having elevated security.

In contrast to the prior art, where the printed images located on opposite sides of the document either completely overlap in register (DE 32 08 204 Al, EP 0 755 799 Al) or complement each other to form a complete image (EP 0 388 090 Al), preferred embodiments of the invention provide that the two images complement each other to form a complete see-through image conveying specific information or a code, on the one hand, but are at least partly superimposed, on the other hand. This has the consequence that the information is largely concealed upon even a small offset of the two patterns, since in such a case those partial areas of one pattern that would be covered by the other pattern if the position was exactly registered also contribute to the appearance of the see-through image. This substantially facilitates the recognition of forgeries since the normally expected information is not recognizable on transmissive viewing if the patterns are not positioned in register. In other words, one pattern acts as a filter for information conveyed by the other pattern, provided the two patterns are positioned in exact register.

Since the pattern serving as a filter and the pattern thereabove that conveys information, e.g. a code, together with the filter pattern when disposed in register preferably consist of a material that is absorbent to radiation in a defined, invisible wavelength range, transmission testing of the see-through security element can be done by machine in addition to visual testing. It is sufficient if those partial areas of the information-conveying pattern where the information-conveying pattern does not overlap the filter pattern consist of the absorbent material, or at least individual said partial areas consist of absorbent material. Depending on which partial areas of the informationconveying pattern are absorbent in the defined, invisible wavelength range, different information can be produced on transmissive viewing with visible light, on the one hand, and with radiation in the invisible wavelength range, on the other hand.

One or both patterns can be produced from a color that is not, or at least hardly, visually recognizable with respect to the surrounding color when viewed in reflected light.

The above-described effect is especially pronounced if the two patterns are line patterns, the filter pattern preferably being a uniform line screen and the informationconveying pattern preferably being a screen of mutually offset lines. The filter pattern can of course also be a screen of mutually offset lines. Inexactly registered positioning of the two line screens is very easily recognizable visually in transmitted light. If the spacing between the lines and the line width of the two patterns is identical, misregistered positionings are all the more striking.

The two patterns are preferably printed on opposite sides of a translucent carrier material by simultaneous printing, so that the two patterns complement each other to form a complete image on viewing in transmitted light. The translucent carrier material can be for example the basic material of the document of value itself, for example pa per in the case of bank notes and other documents of value. However, the security element can also be formed as a transfer element, which is applied to a security document only in a further step. The security element can also be a security thread to be embedded into a document of value.

It is not necessary for the two patterns to be produced by simultaneous printing.

If exactly registered positioning of the two patterns is guaranteed, the patterns can be produced in any desired way and optionally also both be present on one side of the carrier material.

A preferred embodiment of the invention provides for example that the filter pattern is formed by a partly demetalized metal layer, an information-conveying pattern being applied to the back of the transfer carrier material for example in the background print. The metallic filter pattern is completely absorbent to virtually all wavelengths so that the choice of material for the information-conveying pattern is freely selectable within wide limits. Preferably, at least partial areas of the information-conveying pattern are absorbent to radiation in the IR wavelength range. Sensors for detecting IRabsorbent security elements in reflected light and transmitted light are widespread, comparatively inexpensive and already present in numerous apparatuses for testing documents of value.

In the following, preferred embodiments of the invention will be explained by way of example with reference to the accompanying drawings, in which: the description continues on page Fig. 1 shows a bank note with a see-through security element; Fig. 2a shows an information-conveying pattern; Fig. 2b shows a filter pattern; Fig. 2c shows a see-through element consisting of the patterns according to Figures 2a and 2b on visual transmissive viewing; Fig. 3a shows an IR-absorbent partial pattern of the information-conveying pattern from Figure 2a; Fig. 3b shows an IR-transparent partial pattern of the information-conveying pattern according to Figure 2a; Fig. 3c shows a see-through element consisting of the patterns according to Figures 2a and 2b on IR transmissive viewing, the information-conveying pattern from Figure 2a being composed of IR-absorbent and IR-transparent partial patterns according to Figs.

3a, 3b; Fig. 4a shows an IR-absorbent partial pattern of the information-conveying pattern from Fig. 2a; Fig. 4b shows an IR-transparent partial pattern of the information-conveying pattern according to Fig. 2a; Fig. 4c shows a see-through element consisting of the patterns according to Figs. 2a and 2b on IR transmissive viewing, the information-conveying pattern from Fig. 2a being composed of IR-absorbent and IR-transparent partial patterns according to Figs. 4a, 4b.

Fig. 1 shows, as an example of all the other abovementioned documents of value, bank note 1 with see-through element 2 and security thread 3 that appears periodically on the surface of bank note 1 in the manner of a windowed security thread. Security thread 3 can itself be formed in the same way as described in the following with respect to seethrough element 2. That is, the security thread can likewise form an inventive seethrough security element.

-6- See-through element 2 is formed by overlapping patterns, a first pattern being positioned on the front of the bank note and a second pattern on the back of the bank note. The patterns can be applied to the document by printing technology or the transfer method.

Fig. 2a shows by way of example first pattern 4, referred to in the following as "information-conveying pattern," and Fig. 2b shows associated second pattern 5, referred to in the following as "filter pattern." Both patterns can be recognizable in reflected light.

One of the patterns or both patterns can also be formed so as to be indistinguishable from the surrounding material in the visible spectral region or be present as a background print, so that they are not recognizable in reflected light. What is essential for visual testing is only that the materials of the two patterns according to Figs. 2a and 2b are sufficiently opaque so that they appear as dark areas in light surroundings on transmissive viewing.

Fig. 2c shows the appearance of see-through element 2 formed from patterns 4 and on transmissive viewing with normal light. This appearance will also be referred to in the following as visual see-through image 6. One can see how superimposition of comparatively irregular information-conveying pattern 4 with filter pattern 5 yields regular visual see-through image 6 conveying clear information. The information can form a machine-readable code for example. Said information is not deducible from patterns 4 and 5 taken alone. It would also not be reconstructable if patterns 4 and 5 were mutually offset only slightly, because this would result in a very irregular pattern as a visual see-through image.

The filter effect will be explained in the following by example area X. Example area

X

4 of information-conveying pattern 4 has four upper lines and four lower lines that are partly mutually offset. Corresponding example area X 5 of filter pattern 5 has corresponding lines that not mutually offset but continuous. The lines of patterns 4 and have identical width and the spacing between the lines corresponds to the width of the lines. This means that insofar as the lines in example area X 4 of information-conveying pattern 4 are offset from the lines of filter pattern 5, they fill the intermediate areas or gaps between the lines of filter pattern 5. Otherwise the lines of information-conveying pattern 4 and filter pattern 5 exactly overlap. Accordingly, transmissive viewing results in the example area in see-through image 6 marked X 6 in Figure 2c, which has a visually -7clearly recognizable shape. If example area X 4 of information-conveying pattern 4 were offset only slightly or even one line width from example area Xs of filter pattern example area X 6 of visual see-through image 6 would have a totally different shape.

Since the other areas of information-conveying pattern 4 are superimposed on corresponding areas of filter pattern 5 in a similar way, the result is an altogether easily detectable appearance of visual see-through image 6 according to Fig. 2c.

To permit additional machine testing of see-through element 2, patterns 4 and 5 are produced of materials that are absorbent to radiation in the IR wavelength range. The appearance on transmissive viewing in the IR wavelength range then corresponds to visual see-through image 6 and will be referred to in the following as "IR see-through image IR see-through image 7 using IR-absorbent materials for patterns 4 and 5 is shown again in Fig. 3c.

Obviously, IR see-through image 7 according to Fig. 3c can be obtained without all partial areas of information-conveying pattern 4 necessarily having to consist of an IRabsorbent material, if filter pattern 5 itself also consists of IR-absorbent material. It suffices if only those partial areas of information-conveying pattern 4 consist of an IRabsorbent material that fill intermediate areas or gaps of filter pattern 5. Fig. 3a accordingly shows IR-absorbent partial pattern 4a of information-conveying pattern 4 from Fig. 2a. Fig. 3b shows corresponding IR-transparent partial pattern 4b of information-conveying pattern 4 from Fig. 2a. Both partial patterns 4a, 4b together form information-conveying pattern 4. The actual information is only conveyed, however, by IR-absorbent partial pattern 4a filling the intermediate areas of likewise IR-absorbent filter pattern 5, so that IR transmissive viewing results in IR see-through image 7 according to Fig. 3c. IR-transparent partial pattern 4b completely overlaps filter pattern on the other hand.

The variant described with respect to Fig. 3a and Fig. 3b has the advantage that in addition to IR transmissive viewing leading to IR see-through image 7 according to Fig.

3c, IR reflective viewing leads to a useful measuring result since on IR reflective viewing only partial pattern 4a conveying the actual information according to Fig. 3a is measured.

An identical image thus results on transmissive viewing in both the visual and the IR spectral regions, whereas on reflective viewing in the visible spectral region no r -8information is identifiable but in the IR spectral region the information according to partial pattern 4a (Fig. 3a) becomes recognizable.

A further preferred embodiment of the invention is shown in Figs. 4a to 4c. In this case, IR see-through image 7' differs from visual see-through image 6. Informationconveying pattern 4 thus has different information content depending on whether it is viewed transmissively by normal light or by IR illumination. This is obtained by intermediate areas of filter pattern 5 being covered partly by IR-absorbent material and partly by IR-transparent material of information-conveying pattern 4. Fig. 4a shows IRabsorbent partial pattern 4a' and Fig. 4b IR-transparent partial pattern 4b' which together form information-conveying pattern 4 according to Fig. 2a. Comparison with Figs. 3a and 3b makes it immediately apparent that partial pattern 4a' carrying the actual IR information from Fig. 4a is reduced with respect to IR-absorbent partial pattern 4a from Fig. 3a. IR-transparent partial pattern 4b' from Fig. 4b is accordingly more extensive in comparison with IR-transparent partial pattern 4b from Fig. 3b. Superimposition with filter pattern 5 according to Fig. 2b thus results in IR see-through image 7' as shown in Figure 4c on IR transmissive viewing. Visual see-through image 6 is not altered thereby, however, and corresponds to that according to Fig. 2c.

Thus, different see-through images 6 are obtained in this embodiment on viewing in the IR spectral region, on the one hand, and on viewing in normal light, on the other hand. In addition, the information according to partial pattern 4a' is also perceptible on IR reflective viewing in this embodiment, whereas only undefined pattern 4 according to Fig. 2a is visible under normal conditions on reflective viewing.

The variant described with respect to Figs. 4a to 4c is especially suitable for different, batch-related IR codings of documents without this influencing the visual appearance.

Claims

1. A security element for documents of value comprising a translucent carrier ma- terial with first and second patterns that complement each other to form a visually rec- ognizable, complete see-through image only on transmissive viewing, characterized in that the two patterns partly overlap, and the complemented see-through image is formed by the overlapping and the non-overlapping areas of the two patterns.

2. A security element according to claim 1, wherein the see-through image forms a machine-readable code.

3. A security element according to claim 1 or 2, wherein the first pattern consists, at least in individual partial areas where it does not overlap the second pattern, of a ma- terial that is absorbent to radiation in a defined, invisible wavelength range, and wherein the second pattern is also absorbent to said radiation.

4. A security element according to claim 3, wherein the defined, invisible wave- length range is in the IR spectral region.

5. A security element according to claim 3 or claim 4, wherein the first pattern is composed of at least first and second partial patterns consisting of different materials, the material of the first partial pattern being transparent in the defined, invisible wave- length range and the material of the second partial pattern being absorbent in the de- fined, invisible wavelength range.

6. A security element according to claim 5, wherein all partial areas of the first pattern where the first pattern does not overlap the second pattern consist of the absor- bent material.

7. A security element according to claim 5, wherein only individual partial areas of the first pattern where the first pattern does not overlap the second pattern consist of the absorbent material.

8. A security element according to any of claims 3 to 7, wherein the partial areas of absorbent material of the first pattern form a machine-readable code. 00

9. A security element according to any of claims 1 to 8, wherein at least the first ;pattern is not, or at least hardly, visually recognizable in reflected light. O 10. A security element according to any of claims 1 to 9, wherein the first pattern consists of a screen of mutually offset lines.

11. A security element according to any of claims 1 to 10, wherein the second pattern consists of a line screen. t",

12. A security element according to claims 10 and 11, wherein the lines of the first N and second patterns have an identical line width and a spacing between the lines corresponds to a line width or to an integral multiple of the line width.

13. A security element according to any of claims 1 to 12, wherein the first and second patterns are present on opposite sides of the carrier material.

14. A security element according to any of claims 1 to 13, wherein said element is a transfer element.

15. A security element according to any of claims 1 to 13, wherein the security element forms an integral part of a security document and the carrier material is formed by the basic material of the security document.

16. A security element according to any of claims 1 to 13, wherein said element is a security thread.

17. A security element according to any of claims 1 to 16, wherein at least one of the two patterns is a printed pattern.

18. A security element according to any of claims 1 to 17, wherein at least one of the two patterns is a partly demetalized metal layer.

19. A security document comprising a security element according to any of claims 1 to 18. 00 11 A security element as claimed in any one of claims 1 to 18 and substantially as hereinbefore described with reference to the accompanying drawings.

21. A security document as claimed in claim 19 and substantially as hereinbefore described with reference to the accompanying drawings.