EP1588332A2

EP1588332A2 - Security element for valuable documents

Info

Publication number: EP1588332A2
Application number: EP03789301A
Authority: EP
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: 2005-10-26
Anticipated expiration: 2023-12-16
Also published as: EP1588332B1; DE10260124A1; ATE545920T1; WO2004056582A2; AU2003293901B2; 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

The invention relates to a security element for documents of value, which comprises a translucent carrier material with two patterns, which only complement one another when viewed in transmitted light to form a visually recognizable, complete image. The invention further relates to a security document with such a security element.

Such security elements, also referred to as “see-through elements”, are known, for example, from EP 0 388090 A and are used in particular for banknotes, checks, shares, tickets, admission cards, identification papers and other paper documents of value, but also credit cards, check cards, identification cards and the like The security documents described there have printed images on the north and back sides that complement one another in transmitted light to form a complete image. Such security elements are difficult to imitate, since they can only be created in register with simultaneous printing, ie with simultaneous printing on both document surfaces. The printed images can be formed as a line pattern with identically spaced lines of identical width, which complement one another in transmitted light to form a full image. For additional security, the printed images can be printed with invisible ink, which absorbs, for example, X-rays is so that the security element is visually inconspicuous and can be checked mechanically.

DE 3208 204 AI also suggests printing a line pattern on the north and back of a document, but the line patterns are arranged in register so that they overlap each other exactly. An identical line pattern can then be seen in reflected light and transmitted light. In the case of counterfeits not made in simultaneous printing, in which the line patterns on the north and back of the Moire structures can be recognized in transmitted light due to the fineness of the lines. Alternatively, moiré structures can be intended and form a visually recognizable translucency feature by deliberate mutual displacement in partial areas.

EP 0 755 799 AI also proposes a printed image, e.g. a number, to be kept in register on both sides of the document, so that counterfeited falsifications can be identified when viewed through transmitted light. The printed image is usually printed on the back of the document with an invisible ink, which prevents copying. This invisible ink is preferably visible in the UN light in order to enable machine inspection.

In addition, it is known in another context to provide security documents with imprints which have special properties in the invisible spectral range in order to produce machine-readable, visually not necessarily recognizable security features. For example, patent CH 287332 describes a security document with a visually perceptible color print that is transparent to IR radiation, which appears colored in incident light, but is white in the transmission test in the IR wavelength range. A color copy of the document would also be visually colored, but would appear black in the IR transmission test and would therefore be identifiable as a forgery.

This idea is further developed in DE 26 54 208 B2, where an IR-transparent color print that appears black in the visual spectral range is covered with a black, IR-absorbing color print or vice versa. The IR-absorbing color print can for example be a barcode, which, however, is only recognizable due to the black environment when viewed in the IR wavelength range. Depending on which color print is on the outside, an incident light and / or transmitted light test is possible.

JP-A-2167771 also suggests the use of IR-transparent and ^' IR-absorbing printing inks which appear in the same spectral range in the visual spectral range. The bars of a barcode are created with the different colors, which then appear to the naked eye as a uniformly colored barcode. The different materials can then only be detected by machine.

The patent specification UK 1 534 403 also discloses printed images, barcodes and the like which are printed with printing inks which appear to be of the same color in the visual spectral range and which have differently pronounced absorption properties in the IR spectral range. These printing inks can be spaced apart or adjoining one another and in particular in one again same color environment, which is printed with conventional color, so that the image is not visually perceptible, but only machine-readable.

The object of the present invention is to create a see-through security element which has increased security compared to conventional see-through elements and which can be checked visually and preferably also by machine. Another object of the present invention is to propose a security document with a correspondingly increased level of security. This object is achieved by a security element with the features of independent claim 1 and by a security document equipped with such a security element. Advantageous developments and refinements of the invention are specified in claims dependent thereon.

In contrast to the prior art, in which the printed images on opposite sides of the document either completely overlap in register (DE 32 08 204 AI, EP 0 755 799 AI) or complement one another to form a complete image (EP 0 388 090 AI) , the solution according to the invention provides that the two images complement one another to form a complete transparent image conveying specific information or a code, but at least partially overlap. The result of this is that the information is largely obscured even with a slight offset of the two patterns, since in this case also those subregions of one pattern that would be covered by the other pattern in the correct position contribute to the appearance of the see-through image. This makes it much easier to identify counterfeits, since if the pattern is not placed in the register, the information normally to be expected cannot be recognized when viewed through transmitted light. In other words, the one pattern acts as a filter for information conveyed by the other pattern, provided that the two patterns are positioned in register.

In that the pattern serving as a filter and the pattern above it, which, when arranged in register together with the filter pattern, conveys information, for example a code, can preferably consist of a material which is absorbing for radiation in a defined, invisible wavelength range in addition to the visual inspection a mechanical transmission test of the see-through security element can also be carried out. It is sufficient if those subregions of the information-conveying pattern in which the information-conveying pattern does not overlap with the filter pattern consist of the absorbent material, or that at least some of these subregions consist of absorbent material. Depending on which sub-areas of the information-conveying pattern are absorbing in the defined, invisible wavelength range, different information can be generated when viewed through transmitted light with visible light on the one hand and with radiation in the invisible wavelength range on the other.

A pattern or both patterns can be made from a color which, when viewed in reflected light, is not or at least hardly visually recognizable compared to the surrounding color.

The effect described above is particularly pronounced if the two patterns are line patterns, the filter pattern preferably being a uniform line pattern and the information-imparting pattern preferably being a pattern made up of staggered lines. Of course, the filter pattern can also be a grid of lines offset from one another. Placement of the two line grids that are not in register is very easy to see visually in transmitted light. If the distance between the lines and the line width of the two patterns are identical, placements that are not in register are all the more conspicuous.

The two patterns are preferably printed in simultaneous printing on opposite sides of a translucent carrier material, ie on a translucent carrier material, so that the two patterns are Complement the view in transmitted light to a complete picture. The translucent daily material can, for example, be the base material of the value document itself, in the case of banknotes and other value documents, for example paper. However, the security element can also be designed as a transfer element, which is only applied to a security document in a further step. The security element can also be a security thread for storage in a value document.

It is not essential that the two samples are produced using the simultaneous printing process. If a precise placement of the two patterns is guaranteed, the patterns can be produced in any desired manner and, if necessary, can also be present together on one side of the carrier material.

A preferred embodiment of the invention provides, for example, that the filter pattern is formed by a partially demetallized metal layer, wherein an information-imparting pattern is applied to the back of the transfer carrier material, for example in background printing. The metallic filter pattern is completely absorbent for almost all wavelengths, so that the choice of material for the information-conveying pattern can be freely selected in a wide range. At least partial areas of the information-imparting pattern are preferably absorbing for radiation in the IR wavelength range. Sensors for the detection of IR-absorbing security elements in reflected light and transmitted light are widespread, comparatively inexpensive and already available in numerous value document checking devices.

The invention is explained below by way of example with reference to the accompanying drawings. Show it: 1 shows a banknote with a see-through security element;

2a shows an information-conveying pattern;

2b shows a filter pattern;

2c shows a see-through element, consisting of the patterns according to FIGS. 2a and 2b when viewed visually by transmitted light;

3a shows an IR-absorbing partial pattern of the information-transmitting

Pattern from Figure 2a;

3b shows an IR-transparent partial pattern of the information-mediating

Pattern according to Figure 2a;

3c shows a see-through element, consisting of the patterns according to FIGS. 2a and 2b when viewed by IR transmitted light, the information-conveying pattern from FIG. 2a being composed of IR-absorbing and IR-transparent partial patterns according to FIGS. 3a, 3b.

4a shows an IR-absorbing partial pattern of the information-transmitting

Pattern from Fig. 2a;

4b shows an IR-transparent partial pattern of the information-mediating

Pattern according to Fig. 2a;

4c is a see-through element consisting of the patterns according to FIG.

2a and 2b in the case of IR transmitted light observation, the information 2a-composed of IR-absorbing and IR-transparent partial patterns according to FIGS. 4a, 4b.

1 shows an example of a banknote 1 with a see-through element 2 and a security thread 3 for all other documents of value mentioned at the beginning, which periodically appears on the surface of the banknote 1 in the manner of a window security thread. The security thread 3 can in turn be designed in the same way as is described below with reference to the viewing element 2. That is, the security thread can also form a see-through security element according to the invention.

The see-through element 2 is formed by overlapping patterns, of which a first pattern is placed on the front of the banknote and a second pattern on the back of the banknote. The samples can be applied to the document using printing technology or a transfer process.

2a shows, for example, a first pattern 4, which is referred to below as the "information-imparting pattern", and FIG. 2b shows an associated second pattern 5, which is referred to below as the "filter pattern". Both patterns can be seen in reflected light. However, one of the patterns or both patterns can also be designed to be indistinguishable from the surrounding material in the visual spectral range or be in the form of a background print, so that they are not recognizable in incident light. It is only essential for the visual inspection that the materials of the two patterns according to FIGS. 2a and 2b are sufficiently opaque so that they appear as dark areas in a bright environment when viewed in transmitted light. 2c shows the appearance of the see-through element 2 formed from the two patterns 4 and 5 when viewed through transmitted light with normal light. This appearance is also referred to below as a visual see-through image 6. It can be seen how the comparatively irregular information-conveying pattern 4 results in a regular visual transparency 6 conveying clear information and superimposed on the filter pattern 5. The information can form, for example, a machine-readable code. This information cannot be derived individually from patterns 4 and 5. It would also not be reconstructable if the two patterns 4 and 5 were only slightly shifted from one another. This would result in a very irregular pattern as a visual transparency.

The filter effect is explained below using an example area X. The example area X of the information-imparting pattern 4 has four upper lines and four lower lines, which are partially offset from one another. The corresponding example area X5 of the filter pattern 5 has corresponding lines which, however, are not offset from one another, but are continuous. The lines of the two patterns 4 and 5 are identical in width and the distances between the lines correspond to the width of the lines. This means that insofar as the lines in the example area X _{4 of} the information-conveying pattern 4 are offset from the lines of the filter pattern 5, they fill in the intermediate areas or gaps between the lines of the filter pattern 5. Otherwise, the lines of the information-conveying pattern 4 and the filter pattern 5 overlap exactly. Correspondingly, when viewed in transmitted light, the example region in transparent image 6, identified by X ₆ in FIG. 2c, has a shape that is visually clearly recognizable. Would the example area X of the information-conveying pattern 4 be only slight or also by a line width shifted relative to the sample area X5 of the filter pattern 5, the sample area X _{6 of} the visual see-through image ₆ would have a completely different shape. By superimposing the other areas of the information-conveying pattern 4 with corresponding areas of the filter pattern 5 according to a similar scheme, the overall appearance of the visual transparent image 6 according to FIG. 2c is easy to grasp.

In order to enable an additional mechanical inspection of the see-through element 2, the patterns 4 and 5 are made of materials which are absorbing for radiation in the IR wavelength range. The appearance when viewed through transmitted light in the IR wavelength range then corresponds to the visual see-through image 6 and is referred to below as "IR see-through image 7". The IR see-through image 7 when using IR-absorbing materials for the patterns 4 and 5 is again shown in Fig. 3c.

It is obvious that in order to obtain the IR see-through image 7 according to FIG. 3c, all subregions of the information-conveying pattern 4 do not necessarily have to consist of an IR-absorbing material if the filter pattern 5 itself also consists of IR-absorbing material. It is sufficient if only the partial areas of the information-conveying pattern 4 consist of an IR-absorbing material, which fill the intermediate areas or gaps of the filter pattern 5. Accordingly, an IR-absorbing partial pattern 4a of the information-averse pattern 4 from FIG. 2a is shown in FIG. 3a. 3b shows the corresponding IR-transparent partial pattern 4b of the information-conveying pattern 4 from FIG. 2a. Both partial patterns 4a, 4b together form the information-conveying pattern 4. However, the actual information is only conveyed by the IR-absorbing partial pattern 4a, which divides the intermediate areas of the if IR-absorbing filter pattern 5 fills, so that when looking at the IR transmission, the IR see-through image 7 according to FIG. 3c results. In contrast, the IR-transparent partial pattern 4b completely overlaps the filter pattern 5.

The variant described with reference to FIGS. 3a and 3b has the advantage that in addition to the IR transmitted light examination, which leads to the IR transparent image 7 according to FIG. 3c, an IR reflected light examination also leads to a meaningful measurement result, since IR reflected light observation only the part pattern 4a which conveys the actual information is measured according to FIG. 3a. This results in an identical image when viewed through transmitted light in the visual and in the IR spectral range, whereas no information is identifiable when viewed in reflected light in the visual spectral range, but the information according to partial pattern 4a (FIG. 3a) can be seen in the IR spectral range.

Another preferred embodiment of the invention is shown in FIGS. 4a to 4c. In this case, the IR see-through image 7 'differs from the visual see-through image 6. The information-conveying pattern 4 thus has a different information content, depending on whether it is viewed in transmitted light in normal light or in the case of IR illumination. This is achieved in that intermediate regions of the filter pattern 5 are partially covered by IR-absorbing material and partially by IR-transparent material of the information-transmitting pattern 4. 4a shows an IR-absorbing partial pattern 4a 'and FIG. 4b shows an IR-transparent partial pattern 4b ¹ , which in turn form the information-transmitting pattern 4 according to FIG. 2a. A comparison with FIGS. 3a and 3b immediately shows that the sub-pattern 4a ¹ from FIG. 4a carrying the actual IR information is compared to the IR-absorbing sub-pattern. ster 4a from Fig. 3a is reduced. The IR-transparent sub-pattern 4b 'from FIG. 4b is correspondingly more extensive than the IR-transparent sub-pattern 4b from FIG. 3b. In superimposition with the filter pattern 5 according to FIG. 2b, an IR transparency image 7 ′ is thus obtained when viewed with IR transmitted light, as shown in FIG. 4c. However, the visual transparency 6 does not change as a result and corresponds to that according to FIG. 2c.

In this embodiment variant, different transparency images 7 ', 6 are thus obtained on the one hand when viewed in the IR spectral range and on the other hand when viewed in normal light. In addition, the information according to the partial pattern 4a 'is also perceptible in this embodiment variant when viewed under IR reflected light, whereas when viewed under reflected light under normal conditions only the undefined pattern 4 according to FIG. 2a is visible.

The variant described with reference to FIGS. 4a to 4c is particularly suitable for different, batch-related IR coding of documents, without the visual appearance being influenced thereby.

Claims

Patent claims

1. Security element (2) for documents of value (1), comprising a translucent carrier material with a first and a second pattern (4, 5), which only add up to a visually recognizable, complete see-through image (6) when viewed in transmitted light, characterized in that the two patterns partially overlap.

2. Security element according to claim 1, wherein the see-through image (6) forms a machine-readable code.

3. Security element according to claim 1 or 2, wherein the first pattern (4), at least in individual partial areas in which it does not overlap with the second pattern (5), does not consist of a material which is defined for radiation in a defined manner visible wavelength range is absorbing, and wherein the second pattern (5) is also absorbing for this radiation.

4. Security element according to claim 3, wherein the defined, non-visible spectral range lies in the IR spectral range.

5. The security element according to claim 4, wherein the first pattern (4) is composed of at least a first and a second partial pattern (4a, 4b; 4a ¹ , 4b ') consisting of different materials, the material of the first partial pattern (4a; 4a ') is transparent in the defined, non-visible spectral range and the material of the second partial pattern (4b; 4b ¹ ) is absorbent in the defined, non-visible spectral range.

6. Security element according to claim 5, wherein all subregions of the first pattern (4) in which the first pattern (4) does not overlap with the second pattern (5) consist of the absorbent material.

7. Security element according to claim 5, wherein only individual partial areas of the first pattern (4), in which the first pattern (4) does not overlap with the second pattern (5), consist of the absorbent material.

8. Security element according to one of claims 3 to 7, wherein the partial areas of absorbent material of the first pattern (4) form a machine-readable code.

9. Security element according to one of claims 1 to 8, wherein at least the first pattern (4) is not or at least hardly visually recognizable in incident light.

10. Security element according to one of claims 1 to 9, wherein the first pattern (4) consists of a grid of mutually offset lines.

11. Security element according to one of claims 1 to 10, wherein the second pattern (5) consists of a line grid.

12. The security element according to claims 10 and 11, wherein the lines of the first and second patterns (4, 5) have an identical line width and the distances between the lines correspond to the line width or an integer multiple of the line width.

13. Security element according to one of claims 1 to 12, wherein the first and the second pattern (4, 5) are present on opposite sides of the carrier material.

14. Security element according to one of claims 1 to 13, wherein it is a transfer element.

15. Security element according to one of claims 1 to 13, wherein the security element (2) forms an integral part of a security document (1) and the carrier material is formed by the base material of the security document.

16. Security element according to one of claims 1 to 13, wherein it is a security thread.

17. Security element according to one of claims 1 to 16, wherein at least one of the two patterns (4, 5) is a printed pattern.

18. Security element according to one of claims 1 to 17, wherein at least one of the two patterns (4, 5) is a partially demetallized metal layer.

19. Security document (1) comprising a security element according to one of claims 1 to 18.