EP0516790B1 - Magnetic metallic security thread with negative inscription - Google Patents

Abstract

The invention relates to a security document, in particular a bank note, identity card or the like, having a security element which is provided with characters, patterns, etc., visually readable at least in transmitted light and which is electrically conductive and bears additional substances for machine testing, and to a method for producing such a security element. The security element preferably consists of a transparent film strip that bears negative writing readily capable of visual checking and is additionally provided with electrically conductive and magnetic substances.

Description

The invention relates to a security document, in particular a bank note, identity card or the like, with a security element in the form of a thread or tape made of a transparent carrier material which has a metallic layer with recesses in the form of characters, patterns or the like which can be read in transmission. The invention further relates to such a security element and to methods for producing this element and the document.

Security threads made of plastic, which have a magnetic coating, have long been known (DE 16 96 245, EP 0 310 707 A1) and have become established as a proven machine-readable security feature.

In order to further increase the security against counterfeiting of this proven security feature, it was proposed to combine the magnetic layer with a metallic layer (DE 27 54 267 C3, EP 0 377 160 A1). This has the particular advantage that the features cannot be easily recognized and imitated by a forger. On the other hand, average people who handle such security documents are also unable to recognize these security features.

Therefore, the known threads were often provided with an additional microprint (EP 377 160 A1). But even this microprint turned out not to be a particularly good visual security feature, since the writing on the dark thread is not visible in transmitted light and is very difficult to recognize in incident light.

As an alternative to this, the documents US-A 4,941,617 and EP 279 880 A1 propose a transparent one Thread to provide metallic signs. The metallic layer is hardly recognizable due to its reflective properties after being introduced into the paper when viewed in incident light, when viewed in transmitted light, however, the metal layer stands out in the form of dark characters from the bright surroundings. However, due to the small size of the characters, they are also difficult to find on paper.

A security element is known from documents EP 0 330 733 B1 and EP 0 319 157 A1, which can be checked both visually and by machine. For this purpose, a translucent plastic film is coated with metal and this coating is provided with cutouts in the form of characters or patterns. In addition, the security thread can contain coloring and / or luminescent substances in the areas congruent with the cutouts, as a result of which the characters or patterns differ in color contrasting from the opaque metal coating under suitable lighting conditions. A special process is used to produce the recesses, the so-called negative writing. Before the thread material is metallized, a printed image corresponding to the later cutouts is printed and only then is the metal coating applied. For the application of the printed image, printing inks or lacquers are used, which can then be chemically dissolved again under the metal layer, so that recesses are created in the metal layer at the locations of the printed image, since this is also removed.

This security element already meets a very high security standard. On the one hand, the electrical conductivity can be checked mechanically by means of the continuous metallic coating, and on the other hand, the negative writing serves as visual for the viewer easily recognizable authenticity. In addition, the thread has an additional feature that is not readily recognizable by the viewer, namely the luminescence in the area of the negative writing, which can also be checked by machine. However, it is disadvantageous that, in order to record the two properties that can be checked by machine, a possible test device must also have an optical sensor in addition to a conductivity sensor. Because of the necessary light source, lens systems, filters etc., optical sensors are relatively complex and voluminous. The test device is thus also correspondingly complex and large.

The object of the invention is to create a security element for security documents with at least two machine-checkable security features, which avoids the above-mentioned disadvantages and yet combines the advantages of visual and machine checkability.

The object is solved by the features of the independent claims. Further training is the subject of the subclaims.

The essence of the invention can be seen in the combination of magnetic security feature and negative writing, which offers several advantages. First of all, the security element according to the invention advantageously combines the positive aspects of the security elements which have become known in the prior art, the quick and simple visual verifiability on the one hand and the possibility of machine testing which is not readily recognizable from the outside on the other hand. Because the negative writing, which is embedded in a reflective environment, can be easily recognized by the human eye and can be easily checked for authenticity by the viewer. In addition, it is possible to visual To underpin or, if necessary, to revise the test result of the security document mechanically using a magnetic field measurement. The metallic reflective environment of the negative writing ensures that the security thread in reflected light does not disturb the overall impression of the data carrier or security document, but is clearly recognizable in translucent.

In addition, in contrast to luminescence, there are many coding options available for the detection of the magnetic properties, since the counterfeiter is unable to recognize which of the magnetic properties, such as permeability, magnetization, remanence, etc., is used as the test criterion. Protection against counterfeiting can therefore be increased even further by using a magnetic authenticity feature.

Since the measurement of the electrical conductivity and that of the magnetic properties is possible with a relatively low expenditure on hardware, there is a further economic advantage that the security element according to the invention despite several test options (electrical conductivity and a magnetic property), at least two of which can be detected by machine, can be measured with a relatively simple sensor. In this way, multiple and thus increased counterfeit protection can be achieved without additional changes to the test device and costs.

In a possible embodiment of the safety element according to the invention, a plastic thread is both coated with metal and printed with magnetic ink, the magnetic and metallic areas viewed in the running direction of the thread, for. B. are arranged alternately on the thread. However, the metallic and magnetic areas can optionally also be applied in the longitudinal direction or provided stacked one above the other will. In all cases, the metallization has a negative writing, as is known from EP-OS 0 330 733.

In a preferred embodiment, the machine-testable magnetic paint is present as a full-surface coating underneath the metallization, which is only interrupted in the area of the negative writing which is introduced by the method according to the invention.

In the previously known method for producing a security element with negative writing, such as described in EP-OS 0 330 733, it was not possible to include a full-surface magnetic paint in the structure of the security element. Because of its reflective properties, the metallization must represent the outermost layer of the security element, so that the opaque magnetic ink must inevitably be printed between the soluble printing ink, which will later produce the negative writing, and the metal coating. However, the magnetic paint is relatively difficult to dissolve chemically. It is therefore not possible to produce the negative characters using the known method, since the magnetic layer cannot be removed from the layer structure, or cannot be removed completely, and the contours of the font therefore only appear incomplete.

In contrast to this, the method according to the invention is particularly well suited for a full-surface magnetic layer structure combined with electrically conductive layers. The method according to the invention uses a heat-softenable or vaporizable ink to apply the negative print image instead of the chemically soluble inks.

Because security threads are made in web form and then cut into strips of a given width the method according to the invention offers the advantage that both the magnetic ink and the metallization can be applied over the entire surface without taking into account the negative print image underneath. This makes the process very efficient and therefore also inexpensive.

Process examples and developments of the invention are explained below with reference to the figures. For better clarity of the figures, a representation true to scale and proportion is dispensed with.

Fig. 1

eine Banknote mit eingelagertem Sicherheitsfaden,

Fig. 2

Aufsicht auf den Sicherheitsfaden in einer erfindungsgemäßen Ausführungsform,

Fig. 3

Aufsicht auf eine weitere Ausführungsmöglichkeit des erfindungsgemäßen Sicherheitsfadens,

Fig. 4

Aufsicht auf eine weitere Variante des erfindungsgemäßen Sicherheitsfadens,

Fig. 5

Schnitt A - B der in Fig. 4 dargestellten Variante des erfindungsgemäßen Sicherheitsfadens vor dem Einbringen der Negativschrift,

Fig. 6

Schnitt A - B nach dem Einbringen der Negtivschrift,

Fig. 7

Variante zum Fadenaufbau des in Fig. 4 dargestellten Fadens im Schnitt A - B,

Fig. 8

weitere Variante zum Fadenaufbau des in Fig. 4 dargestellten Fadens im Schnitt A - B.

In it show:

Fig. 1

a banknote with embedded security thread,

Fig. 2

Supervision of the security thread in an embodiment according to the invention,

Fig. 3

Supervision of a further embodiment of the security thread according to the invention,

Fig. 4

Supervision of a further variant of the security thread according to the invention,

Fig. 5

Section A - B of the variant of the security thread according to the invention shown in FIG. 4 before the introduction of the negative writing,

Fig. 6

Section A - B after the introduction of the negative text,

Fig. 7

Variant for thread construction of the thread shown in FIG. 4 in section A - B,

Fig. 8

another variant for thread construction of the thread shown in FIG. 4 in section A - B.

Fig. 1 shows a security 1 with embedded security element 2, which is designed as a so-called window security thread. This embodiment ensures that the element is clearly visible at least in partial areas both in reflected and transmitted light. For this purpose, the security thread is quasi woven into the paper mass, so that it comes directly to the document surface at regular intervals, which is indicated by the hatched boxes.

2, 3 and 4, possible embodiments of the security element 2 according to the invention are shown in supervision.

Fig. 2 shows the security element 2, consisting of a transparent plastic film, which is alternately provided with metallic and magnetic areas 3, 4 seen in the direction of travel. The metallization 3 has cutouts 5, the so-called negative writing, in the form of any characters, numbers or patterns, etc., in which the transparent carrier material underneath is visible. The metallic areas 3 are separated by bars of mostly black, printed magnetic paint 4.

Such a thread can be produced in various ways. For example, a plastic film can be completely coated with metal and then provided with a negative writing using one of the methods known from EP-OS 0 330 733. The text is repeatedly inserted in parallel rows and columns. About this film parallel to the columns bars of magnetic paint are applied at appropriate intervals, so that the negative writing appears completely between these bars at least once. In the last step, the web is cut into threads parallel to the lines, as is known from EP-OS 0 381 112, for example.

As an alternative to this, the text can be introduced in a parallel column arrangement such that it is offset by half the line spacing in adjacent columns, as shown in FIG. 3. Likewise, the bars of magnetic ink 4 can be printed parallel to the lines 3, as can also be seen in FIG. 3. In this case, it must be ensured that the magnetic strips are arranged laterally in register with the negative writing. The plastic film, which is otherwise prepared analogously to the method described above, is cut into threads with a width of approximately 1.2 mm, the approximately 0.8 mm wide metallization 3, which bears the visible negative writing 5, symmetrical of approximately 0. 2 mm wide magnetic strip 4 is framed.

Another embodiment of the security element according to the invention is shown in FIG. 4. Purely externally, this security thread 2 does not differ from the known security threads. Because only the transparent writing 5 can be seen in its metallic surroundings 3. However, the differences become evident when considering the layer structure of the thread 2.

5 and 6 show the section A - B of the preferred embodiment of the security element 2 according to the invention shown in FIG. 4 before and after the introduction of the negative writing 5. As in the previous examples, a transparent plastic film 10 serves as the carrier material. This is first printed with an activatable printing ink 13 in the area of the later negative writing. The film is then metallized over the entire surface, for example with aluminum. About this Layer structure, a magnetic printing ink 4 is also provided over the entire surface. The outermost layer forms a further vacuum-deposited metallization 3.

The drawing does not allow an estimate of the individual layer thicknesses, which is why some typical data are given below for illustration: the carrier film 10 has a thickness of approximately 10 to 30 μm, the activatable printing ink 13 moves between 0.5 and 2 μm, while each of the metallizations is only about 1/100 µm thick, and the magnetic paint has a layer thickness of 1 to 5 µm.

The inner metal coating ensures that the security thread offers the same external appearance regardless of the side due to the transparency of the carrier material. This is necessary in order to be able to check the thread in the same way after being embedded in the document.

By activating the printing ink 13, recesses are created in the three layers 11, 4 and 3 lying above it, congruent with the printing ink, and thus form the negative writing 5. In a last step, a transparent lacquer layer 20 can be used to protect the thin metal layer and the recesses before cutting the web 10 µm thick are sprayed on. On the other hand, it is also possible to provide the finished thread with a protective layer by dipping, as indicated in FIG. 6.

Wax-containing emulsions, for example, are suitable as activatable printing inks, similar to those used in transfer ribbons. When heated, these emulsions soften and thereby reduce the adhesion to the carrier film, so that in these poorly adhering areas, supported by mechanical treatment such as ultrasound, brushing or rubbing, both soften Ink as well as the layers above can be removed.

The printing inks for applying the negative image can, however, also contain foaming additives, as are customary in the production of foams. These blowing agents split off gas under the influence of heat and produce foam structures in a polymer matrix. The decomposition process takes place irreversibly and within a defined temperature interval. In connection with the invention, blowing agents with an activation temperature of around 200 ° C., such as e.g. Azodicarbonamide. As in the case of wax-containing emulsions, the gas development and the associated increase in volume reduce the adhesion to the carrier film. In addition, the overlying layers bulge outwards in accordance with the increase in volume of the printing ink and thus offer the mechanically acting treatment methods a good point of attack, so that the negative writing can be worked out cleanly. Alternatively, the blowing agents can also be added to the printable ink in microencapsulated form.

A simplification in the structure of the layer sequence shown in FIG. 3 results if a solvent for the metal layers is additionally added to the activatable printing inks described above. It is sufficient if the color is slightly acidic or alkaline, because in practice it is only vapor-deposited aluminum. In this way, the first metal coating can be applied directly to the carrier film and only in the following the printed image, as it will later appear as a negative image, is printed, with the result that the layers can be removed even more easily. Because here the detaching printing ink acts practically from the center in two opposite directions, whereby the effectiveness of the stripping of the layers before the mechanical treatment is increased. Acid or alkali residues in the thread are not to be feared, since the negative writing is washed with water after removal.

The activation of the printing ink producing the negative writing can of course also be triggered by other physical influences, such as laser beam, electron beam, pressure, cold, etc.

The method according to the invention can also be used expediently if a printed image is to be carried out with a color layer instead of a metallic layer, which is itself not printable, but e.g. can only be applied by doctor blade or other full-surface coatings. In this case, a negative image is printed under the color according to the invention and this is removed according to the invention.

FIG. 7 shows a variant for the construction of the security element 2 shown in a top view in FIG. 4, in which, in addition to the above-mentioned activatable printing inks, the chemically releasable printing inks known from the prior art can also be used to generate the negative writing. In this case, the carrier material 10 is printed in a multi-color printing machine with metallic strips 40 and congruently with the magnetic ink 4. The activatable printing ink 13 which generates the negative writing is introduced into the gap between the strips in a third printing unit. The carrier material prepared in this way receives a full-surface metallic coating 3, which is then removed again in the area of the negative writing by activating the printing ink 13. As in the previous example, the thread can also be provided with a protective, transparent lacquer layer.

A metal pigment-containing printing ink is used for printing the metallic strips 40, whereas the outer metal coating is preferably made of vacuum-evaporated aluminum.

A similar thread structure is shown in FIG. 8, however, in contrast to the methods described hitherto, it is possible to dispense with the use of an activatable printing ink in the production thereof. Analogous to the thread shown in FIG. 7, the carrier material 10 is first printed with metallic strips 40 and congruently with magnetic ink 4. A metal pigment-containing printing ink 30, such as e.g. Silver bronze, printed in such a way that it has cutouts in the form of the negative sign 5.

In this example, 40, 30 printing pigments containing metal pigment or imitation metal, such as e.g. silver bronze, used. Such printing inks can of course also be used advantageously in the other examples described.

In all the examples of the security element according to the invention shown so far, the electrical conductivity is determined by the properties of the metallic reflecting layers, in particular the visually visible layers 3, 30. However, variants are also possible in which the conductivity is generated or at least supported by corresponding admixture of the magnetic layer with electrically conductive material. The reference number 25 in FIG. 8 indicates such an admixture, which may consist of soot particles, for example.

This has the additional advantage that cracks running across the entire thread width in the metallically conductive Layer, for example in layer 3 of the thread shown in FIG. 4, does not lead to complete loss of electrical conductivity. In this case, the current flows through the adjacent conductive magnetic layer and thus bridges the crack. In this way, the feature of electrical conductivity can also be used as an authenticity feature if the layer to be checked has defects.

With correspondingly limited demands on the signal size of the electrical conductivity and the magnetism, it is also possible to add both the electrically conductive and the magnetic pigments to a single printing ink, which is printed on the carrier material with a recessed negative writing. This offers the advantage that the thread material can be provided with the three security features, electrical conductivity, magnetism and negative writing, in a single printing process.

It is also possible to distribute the characteristics over only two layers. In a first step, the carrier material is provided with a partially permeable, electrically conductive layer, such as a wafer-thin vapor-deposited or sputtered metal or oxide layer. This layer primarily carries the electrical conductivity. Then a metallic pigment layer containing magnetic pigment, i.e. a metal or imitation metal color, printed with recessed negative writing. In this way, a larger electrical signal can be generated and a process step can still be saved.

Claims (27)

1. A security document (1), in particular bank note, identity card or the like, having a security element (2) in the form of a thread or band consisting of a transparent carrier material (10) having a metallic layer (3, 30) with gaps (5) in the form of characters, patterns or the like readable by transmitted light, characterized in that an additional magnetic layer (4) is disposed above or below the metal layer (3, 30) and the geometric arrangement of the areas covered with the magnetic layer (4) is selected so that at least the readable gaps (5) remain free.
2. The security document (1) of claim 1, characterized in that the magnetic layer (4) covers the metallic layer (3) all over in sections regarded in the longitudinal direction of the thread and the visually readable characters (5) are provided in the spaces free from the magnetic layer.
3. The security document (1) of claim 1, characterized in that the magnetic layer (4) is disposed symmetrically on each side of the visually readable characters (5) regarded in the longitudinal direction of the thread (2).
4. The security document (1) of claim 1, characterized in that the metallic layer (3) is disposed above the magnetic layer (4), and both layers (3, 4) have congruently the gaps (5) visually readable by transmitted light.
5. The security document (1) of claim 3 or 4, characterized in that a second metallic layer (11, 40) is disposed congruently below the magnetic layer (4).
6. The security document (1) of at least one of claims 1 to 5, characterized in that the metallic layers (3, 11, 30, 40) are bronze inks, imitation metal inks or vacuum evaporated metal layers.
7. The security document (1) of at least one of claims 1 to 6, characterized in that the magnetic layer (4) has an electroconductive material (25) added thereto.
8. The security document (1) of at least one of claims 1 to 7, characterized in that the magnetic layer (4) consists of a magnetic ink.
9. A security document (1), in particular bank note, identity card or the like, having a security element (2) in the form of a thread or band consisting of a transparent carrier material (10) having a metallic layer (3) with gaps (5) in the form of characters, patterns or the like readable by transmitted light, characterized in that the metallic layer (3) is an ink containing electroconductive pigments, and the ink contains not only electroconductive pigments but also magnetic pigments.
10. A security element (2) in the form of a thread or band to be embedded in a security document (1), in particular a bank note, identity card or the like, which consists of a transparent carrier material (10) having a metallic layer (3, 30) with gaps (5) in the form of characters, patterns or the like readable by transmitted light, characterized in that an additional magnetic layer (4) is disposed above or below the metal layer (3, 30) and the geometric arrangement of the areas covered with the magnetic layer (4) is selected so that at least the readable gaps (5) remain free.
11. A security element (2) in the form of a thread or band to be embedded in a security document (1), in particular a bank note, identity card or the like, which consists of a transparent carrier material (10) having a metallic layer (3) with gaps (5) in the form of characters, patterns or the like readable by transmitted light, characterized in that the metallic layer (3) is an ink containing electroconductive pigments, and the ink contains not only electroconductive pigments but also magnetic pigments.
12. A method for producing a security element (2) in the form of a thread or band which is suitable for incorporation in a security document (1), such as a bank note, identity card or the like, and consists of a transparent carrier material (10) having a metallic layer (3) with gaps (5) in the form of characters, patterns or the like readable by transmitted light, according to claim 10, characterized by the steps of

    a) printing a transparent carrier film (10) with an activatable ink (13) in the form of readable characters, patterns or the like,

    b) providing the side of the carrier film (10) bearing the activatable ink (13) with a metallic layer (3) all over,

    c) activating the ink (13) to produce gaps (5) in the form of the characters, patterns or the like in the metallic coating (3),

    d) applying a magnetic substance (4) in partial areas,

    e) cutting the film (10) into stripes of suitable width.
13. The method of claim 12, characterized in that the characters, patterns or the like (5) applied in step a) are printed on in a parallel line and column arrangement.
14. The method of claim 13, characterized in that the characters, patterns or the like applied in step a) are printed on shifted by half the column space.
15. The method of claim 13 or 14, characterized in that the magnetic substance (4) is applied in step d) in bars parallel to the columns.
16. The method of claim 13 or 14, characterized in that the magnetic substance (4) is applied in step d) in stripes parallel to the lines.
17. A method for producing a security element (2) in the form of a thread or band which is suitable for incorporation in a security document (1), such as a bank note, identity card or the like, and which consists of a transparent carrier material (10) having a metallic layer (3, 11) with gaps (5) in the form of characters, patterns or the like readable by transmitted light, according to claim 10, characterized by the steps of

    a) printing a transparent carrier film (10) with an activatable ink (13) in the form of readable characters, patterns or the like,

    b) providing the side of the carrier film (10) bearing the activatable ink (13) with a metallic layer (11) all over;

    c) providing a machine-testable magnetic substance (4) above the metallic layer (11) all over,

    d) applying a metallic coating (3) above the magnetic substance (4) all over,

    e) then activating the activatable ink (13) to remove all layers above the carrier film (10), thereby giving rise to gaps (5) in the form of the characters, patterns or the like both in the magnetic and in the metallic coatings (3, 4, 11),

    f) cutting the film (10) into stripes of suitable width.
18. A method for producing a security element (2) in the form of a thread or band which is suitable for incorporation in a security document (1), such as a bank note, identity card or the like, and consists of a transparent carrier material (10) having a metallic layer (30, 40) with gaps (5) in the form of characters, patterns or the like readable by transmitted light, according to claim 10, characterized by the steps of

    a) providing a transparent carrier film (10) with a metallic layer (40) in the form of stripes,

    b) providing a machine-testable magnetic substance (4) above the stripes (40) in exact register,

    c) printing the carrier film (10) between the stripes with an activatable ink (13) in the form of the readable characters,

    d) providing the entire layer structure with a metallic layer (30) all over,

    e) then activating the activatable ink (13), thereby giving rise to gaps (5) in the form of the characters, patterns or the like in the metallic layer (30),

    f) cutting the film (10) into threads of suitable width parallel to the magnetic stripes (4).
19. The method of at least one of claims 12 to 18, characterized in that at least one of the metallic layers (3, 11, 30, 40) is a vacuum evaporated metal layer, a bronze ink or an imitation metal ink.
20. The method of at least one of claims 12 to 19, characterized in that the magnetic substance (4) is contained in an ink and printed.
21. The method of at least one of claims 12 to 20, characterized in that the detachment of the layers (3, 4, 11, 30, 40) above the carrier film is supported by mechanical treatment.
22. The method of at least one of claims 12 to 21, characterized in that the activatable ink (13) is a wax-bearing emulsion.
23. The method of at least one of claims 12 to 21, characterized in that the activatable ink (13) contains foamable additives.
24. The method of claim 23, characterized in that the foamable additives are present in the ink (13) in the form of microcapsules.
25. The method of at least one of claims 12 to 24, characterized in that the activatable ink (13) is activated by laser beam, electron beam, temperature treatment or pressure.
26. The method of at least one of claims 12 to 25, characterized in that the finished film (10) is provided with a protective layer of transparent lacquer (20) before the last method step.
27. A method for producing a security document, characterized in that the security element (2) of claim 10 or 11 is incorporated in the document (1) during production of the document.

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