EP3275686B1 - Method for producing a safety element - Google Patents

Description

The invention relates to a method for producing a security element, wherein a substrate is provided which has a front and a back, at least for certain radiation is translucent and has a watermark, which modulates the opacity of the substrate and which has a certain range on the front side a printing element is applied, which covers the particular area of the watermark and is modifiable by the particular radiation, and the substrate is irradiated from the back with the particular radiation, wherein the particular area of the watermark is used with respect to the modification of the printing element as a mask and the printing element in the register is modified to the watermark.

To increase the security against forgery of protected objects, for example banknotes, watermarks are known. They are usually introduced in the production of the substrate from which the security element is made, usually a paper. Watermarks are easily recognizable when the security element is viewed through transmitted light, since they modify the opacity of the substrate. As a rule, in the production of the paper, the thickness of the substrate is varied, so that a reduction in thickness leads to an opacity reduction. However, other approaches to generating a watermark are also known, for example using so-called watermark colors, which also locally modify the opacity of the substrate.

Watermarks are formed in the substrate in the production of the security material starting material, for example in the manufacture of banknote paper. Due to tolerances in tool production the round screen required for watermark generation, tolerances in watermark production in the paper machine, and variations in the cutting process of a paper substrate, paper sheets usually have variations in the position of the watermark, which are in the millimeter range. Therefore, it is difficult to arrange security features, eg printed elements in exact position to the watermark, so to pass. This problem arises regardless of the specific design of the security feature, not only when printing with different inks, but also during coating or application with printing elements, when applying transfer films or laminating films, when applying a window filament or laser-assisted processing, eg laser beam cutting , In the process of applying the security feature, additional registration variations are added due to variations in investment locations, transfer variations in presses, paper moisture swings, and a paper swaging effect on stitching.

To apply a security feature in the register to a watermark, it describes the WO 2013/124059 A1 as conceivable, by means of a transmission sensor to detect the position of the watermark in the substrate, and to set a subsequent printing process to the current position of the watermark, z. B. by a mechanical adjustment of a printing cylinder or correction of the printing data of a digital printing system. However, it has been shown that watermarks are usually difficult to detect accurately with an image recognition. In particular, the edge structures of a watermark are usually provided with a contrast profile, which makes accurate measurement of the position of the watermark difficult.

The WO 2013/0124059 A1 as well as the EP 2199095 A2 describe that a watermark can be used as a mask for laser radiation to pattern a layer printed on the watermark. For example, a laserablatierbare printing layer can be arranged above the watermark, and the opacity variation, which has the watermark, serves to ablate the print layer structured in the exact register to the watermark. However, this approach has the disadvantage that the contrast curve of the watermark is converted into an identical contrast profile for the security feature. In the case of ablation, the print layer is ablated where the watermark is lighter, and not ablated where the watermark is darker.

The invention is therefore based on the object of specifying a method with which a security element is generated, in which a security feature in the register is a watermark, without any definition of the contrast course of the watermark.

This object is achieved according to the invention with a method for producing a security element, wherein a substrate is provided which has a front and a back, at least for certain radiation is translucent and has a watermark, which modulates the opacity of the substrate and which has a certain range has applied to the front of a printing element, which covers the particular region of the watermark and is modifiable by means of the particular radiation, and the substrate is irradiated from the back with the particular radiation, wherein the particular region of the watermark with respect to the modification of the printing element as Mask is used and the printing element is modified in the register to the watermark, wherein the particular area of the watermark formed structured is that the modified printing element forms an alignment structure, in a subsequent process, a security feature is applied to the substrate, wherein the position of the Justierstruktur detected and taken into account and the security feature is adapted to the position of the Justierstruktur and thus arranged to the watermark.

The invention is based on the concept of WO 2013/0124059 A1 on, which can generate a printing element in the register to a watermark. The watermark is now designed in a certain range so that the pressure element forms an alignment structure after the modification. This is then used as the basis for a subsequent process for applying a security feature to the substrate. In this way, the security feature can be adapted to the position of the adjustment structure and thus ultimately to the watermark, without any limitation with respect to the security feature. In particular, it is no longer limited to the effect that the security feature must be designed as a printing element and imperative to emulate the contrast of the watermark. At the same time, the modified printing element forms an adjustment structure that is significantly more contrast-rich than an evenly high-contrast, ideal watermark. The problem that the location of a watermark is very difficult to determine avoids the invention so.

In one embodiment, a motif is printed as a security feature. Here, in the printing process, registration is made for the alignment structure so that the motif in the perfect register is part of the watermark without any binding to the contrast of the watermark with respect to the printed motif. Since the position of the Justierstruktur is detected before printing the subject, it is possible in a development to make the motif so that the Justierstruktur overprinted when imprinted or supplemented. In both cases, it is then no longer recognizable to a viewer in the original form which they had as an adjustment structure.

In the case of a printing motif, it is particularly advantageous if the subsequent process comprises application of a laser-modifiable coating and a motif is produced by irradiation of laser radiation, which modifies the coating in the form of the motif. Again, it is possible to overprint or supplement the Justierstruktur.

The security feature, which is generated by evaluating the position of the alignment structure in the perfect register to the watermark is, as already mentioned, not limited to that printing techniques are used. It is also possible to apply a film element or, more preferably, to use a laser beam cutting process. In the latter case, the adjustment structure can be cut out and thus removed with particular preference. This is possible since the position of the alignment structure is determined before the start of the laser beam cutting process. The adjustment structure itself is therefore no longer needed in the process and after the process.

Of course, various processes for applying a security feature can be combined, in particular printing, and / or laser beam cutting and / or the application of diffractive structures and / or the application of holographic structures. If the security feature covers, supplements or removes the adjustment structure, this is preferably done in the last process step in the case of several processes for generating the security feature. However, this is not mandatory since, upon removal of the alignment structure within the several processes, the further referencing for the following processes is, of course, also due to the results the previous processes can be aligned. For example, when combining a printing process and a laser beam process, it is possible to overprint the alignment structure with the printing process and to align the positional orientation for the following laser beam process on the printed motif. The same applies if first a laser beam cutting is performed, which cuts out and removes the Justierstruktur. Subsequent processes can then be aligned with the results of the laser beam process, ensuring perfect registration within the security feature and the watermark.

The particular shape of the watermark ultimately dictates the shape of the alignment structure. The shape of a Justierkreuzes is preferred.

The alignment structure may be in the form of a negative structure, i. be formed as a light structure against a dark background. In such an adjustment structure, the ablation of the pressure element can preferably be carried out. Similarly, it is possible to design the adjustment structure as a positive element, i. dark against light background. For this purpose, indirect ablation methods, as described below, can be used. Finally, it can be determined by design of the particular area or ablation method whether the alignment structure is negative or positive.

To generate the alignment structure, the invention utilizes the fact that the energy of radiation is attenuated by the substrate. The more opaque (eg thicker) the substrate, the stronger the attenuation. Therefore, the property of the watermark to modulate the opacity (eg, thickness) of the substrate is used to advantage. The watermark is used in the specific area as a mask by a pressure element is used, which is modifiable by certain radiation for which the substrate is translucent, and that certain radiation is irradiated from the back of the substrate to the front side, on which the printing element is applied overlying the watermark. As a result, masked by the watermark, the modification of the printing element to the Justierstruktur, which automatically lies in the perfect register to the watermark.

As a modification of the pressure element is in particular an ablation in question when a pressure element is used, which is ablatierbar. In principle, however, any suitable modification of a printing element can be used.

This modification can be done directly, ie by direct action of the particular radiation on the printing element, or indirectly. In the latter case, the particular radiation modifies an element, which in turn is used to modify the pressure element, which is perceivable on the front side. For example, by means of the specific radiation, a layer can be modified which influences the adhesion of the pressure element on the front side. After the modification of this adhesion-influencing layer, in a further step the printing element is then removed in the areas in which the layer has been modified (or not modified in the inverse case). The procedure is similar to the principle of the so-called wash color. A further possibility for indirect modification is the modification of a developer layer which, in interaction with a developer or fixing medium, modifies the printing element at those points at which the developer layer has been suitably exposed. Indirect influence of the pressure element is also possible in a two-stage process if the pressure element has an adhesive layer, which is applied to the front and exposed from the back with the participation of the watermark as a mask. In a second step, a color layer of the printing element can then be applied, which adheres only to those places where the exposure took place. Optionally, the exposed adhesive layer can also be acted upon here in an intermediate step so that it remains only in those areas in which a suitable exposure took place (positive effect) or remains in those areas in which no suitable exposure took place (negative effect).

In the context of this description, the term "pressure element" is understood to mean an element applied to a substrate, which optionally, after further processing, realizes a visually or mechanically evaluable element. Of course, most widely used are printing elements based on printing inks. As far as this description speaks of a printing ink, this is to be understood by way of example for a printing element.

As far as is spoken in this specification and in particular in the claims thus of "printing element" or "printing ink" and the application of this printing element is mentioned on the front over the watermark, it is also included that applied by a printing element layer system, only a part of the layer system and is exposed to the specific radiation; the other part is then applied after these steps and interacts with the exposed portion of the layer system to create a printed image in the watermark to the watermark.

The term "printing element" thus also means a multilayer system, wherein a part of the layer system is applied to the front surface before the exposure and then illuminated with the specific irradiation becomes. Another part of the layer system is then applied only after the exposure.

Especially for the use of banknotes watermarks are common, which modulates the opacity of the substrate by varying a thickness of the substrate at a constant density of the substrate, since such watermarks are usually very difficult to emulate. These watermarks are well suited for the process of the invention.

A watermark that modulates the opacity of a substrate can also be generated by a so-called watermark color, rather than by varying the thickness of the substrate. The watermark color causes a reduction of the scattering of light in the substrate core. Basically, scattering is due to a large number of interfaces of fibers, fillers, glue, etc. to the surrounding air. These ambient airborne interfaces are significantly reduced by suitable binder components in the watermark ink, thus decreasing opacity in these areas. Such a binder component is, for example, glycerol, which penetrates into the substrate and remains in the pores of the substrate. The same applies analogously if the watermark is caused by a coloration which modulates the opacity of the substrate.

Of course, instead of ablation, which usually leads to brightening when using dark colors, it is also possible to design the modification such that it leads to a color change, for example by thermal activation of a color. This is especially true when using effect inks based on inks that show a viewing angle-dependent color impression (so-called optical variable ink) and colors that are structurable before drying by a magnetic field.

It is therefore preferred for the printing ink to comprise one or more of the following substances: an optically variable color, a magnetically orientable color, a metallic color, a color which is effective in the non-visible spectral range.

The term "certain radiation" used in this description therefore expresses that a pressure element is used which is modifiable by means of this radiation. The modification, for example in the form of an ablation, is achieved when the particular radiation at the front has a suitable intensity. The opacity modulation caused by the watermark reduces the intensity of the radiation on the front surface on which the printing element is located. The radiation intensity on the back side is therefore adjusted so that the opacity modulation, which is caused by the watermark, leads to a radiation modulation on the front side, which modulates the modification effect on the printing element. In other words, the radiation intensity at the backside is chosen so that at the places where the watermark causes the lowest opacity in the substrate, a modification of the printing element occurs at the places where the watermark causes the highest opacity of the substrate, however, no or only a very slight modification is achieved. Then, the watermark serves as a mask in the irradiation of the substrate with the specific radiation. Since the modification of the printing element usually requires a relatively high radiation intensity, the use of a beam is advantageous, which is rastered over the back of the substrate.

The term ink used here stands out for the printing effect achieved by the watermark-masked and radiation-based modification. Of course, the printing ink itself can also comprise structures, which go beyond conventional color systems, such as a foil coating or metallization.

Items to be protected within the scope of this description may include, for example, security papers, identity and value documents (such as banknotes, chip cards, passports, cards, identification cards, identity cards, stocks, bonds, certificates, vouchers, checks, tickets, credit cards, health cards,. ..) as well as product security elements, such as Labels, seals, packaging, be.

The term security paper is understood here to mean, in particular, the precursor that can not yet be processed to a document of value (eg a card) which, in addition to the printing produced according to the invention, can also have other authenticity features (such as luminescent substances provided in the volume, for example). Under value documents here on the one hand from security papers produced documents, eg. B. banknotes understood. On the other hand, value documents can also be other documents and articles which are processed with the printing method according to the invention, so that the value documents have non-copyable authenticity features, whereby an authenticity check is possible and at the same time unwanted copies are prevented.

The substrate is particularly preferably made of paper made of cotton fibers, as used for example for banknotes. Preferably, the substrate may also be made of paper of other natural fibers, also preferably of synthetic fibers, ie a mixture of natural and synthetic fibers. Further preferably, the substrate consists of a combination of at least two superimposed and interconnected different substrates, a so-called hybrid. It may be, for example, a combination of plastic film paper or even a three-layer composite, such as plastic film paper plastic film, ie a paper substrate is covered on either side by a plastic film or paper plastic film paper, ie a substrate a plastic film is covered on both sides by a paper substrate.

Preferably, the substrate consists of an at least partially transparent plastic film. The watermark is generated in this case by a color which is applied to one side of the substrate and whose hue is at least similar to the hue of the substrate. Such a watermark is for example off DE 10 2009 056 462 A1 known.

Under translucency or translucent in this description, the partial translucency of a body understood, so the property of transmitting light scattering. Translucency is among others in contrast to the transparency (= image or view permeability) to see. The reciprocal property of translucency is opacity. As far as there is talk here that a watermark modulates the opacity, it can equally be said that it inversely modulates the translucency.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the specified combinations but also in other combinations or alone, without departing from the scope of the present invention, as far as this is covered by the scope of the claims is.

Fig. 1a und 1b

eine Schemadarstellung eines Substrates in Schnittdarstellung (Fig. 1a) bzw. in Draufsicht (Fig. 1b) zur Veranschaulichung der Opazitätsmodulation durch ein Wasserzeichen,

Fig. 2

eine Schemadarstellung des Substrates der Fig. 1 zur Erzeugung eines zum Wasserzeichen gepasserten Justierelements,

Fig. 3a und 3b

eine Schemadarstellung ähnlich der Fig. 1a und 1b, betreffend eine Ausführungsform, bei der das Wasserzeichen durch eine Wasserzeichenfarbe erzeugt ist,

Fig. 4

eine Darstellung ähnlich der Fig. 2 für das Substrat der Fig. 3a und 3b,

Fig. 5 - 7

Draufsichten auf ein Sicherheitselement 1 in unterschiedlichen Phasen der Herstellung, wobei Fig. 7 das fertiggestellte Sicherheitselement zeigt, und

Fig. 8

eine Darstellung ähnlich der Fig. 7 für eine weitere Ausführungsform des Herstellverfahrens.

The invention will be explained in more detail by way of example with reference to the accompanying drawings, which also disclose features essential to the invention. Show it:

Fig. 1a and 1b

a schematic representation of a substrate in a sectional view ( Fig. 1a ) or in plan view ( Fig. 1b ) to illustrate the opacity modulation by a watermark,

Fig. 2

a schematic representation of the substrate of Fig. 1 for generating a watermarked adjustment element,

Fig. 3a and 3b

a schema representation similar to the Fig. 1a and 1b relating to an embodiment in which the watermark is generated by a watermark color,

Fig. 4

a representation similar to the Fig. 2 for the substrate of Fig. 3a and 3b .

Fig. 5-7

Top views of a security element 1 in different stages of production, wherein Fig. 7 shows the completed security element, and

Fig. 8

a representation similar to the Fig. 7 for a further embodiment of the production method.

Fig. 1a shows in a sectional view of a security element 1, wherein for simplicity, only a substrate 2 is drawn. The substrate 2 has a front side 3 (which is arranged below in the figures without further restriction) and a back side 4. In the substrate 2, a watermark 5 is incorporated, which modulates the thickness of the substrate 2 and thus its opacity. This opacity modulation is in Fig. 1b which shows a plan view of the front side 3 of the substrate 2 schematically. There are areas 6 with high opacity at locations where the substrate. 2 has the normal (not diminished) thickness. In regions 7 where the thickness is reduced by an average amount, the substrate 2 has a medium opacity. In a region 8 in which the thickness is greatly reduced, the substrate 2 has a low opacity or a high translucency.

With watermarking, the paper thickness can also be increased by embossing. This can be used for branding. The brand is then pronounced as a thin spot, the environment of the brand as a thick spot. The mask effect for the laser is enhanced in such an embodiment.

In the method for producing the security element, a security feature, for example a printed image and / or a laser beam cutting area and / or a film element and / or a diffractive structure and / or a hologram is to be generated in registration with the watermark, which is in perfect registration with the watermark , To accomplish this, first an alignment structure is created which is fitted to the watermark.

To produce the alignment structure, which is matched to the watermark 5, an ink is applied to the front side 3, which is ablatierbar by means of laser radiation. Fig. 2 shows the substrate 2 with applied on the front side 3 ink 9. The ink 9 is not structured (yet), but at least partially covers a certain area 13 in which the watermark 5 is present in the substrate 2.

From the rear side, a laser beam 10 is now guided over the substrate. It passes through the substrate 2. The wavelength of the laser beam is such that the ink 9 absorbs the radiation. The laser beam 10 becomes dependent of the opacity of the substrate 2, which is modulated by the watermark 5 attenuated. At a position 10a where the substrate has high opacity by the watermark, the laser beam 10 is greatly attenuated. At a position 10b where the substrate has the least opacity, the laser beam is least attenuated. In Fig. 2 This is schematically illustrated by the thickness of the laser beam 10. In fact, of course, only the intensity of the laser beam 10, but not its radiation cross section when passing through the substrate 2 is attenuated.

The intensity of the laser beam 10 is adjusted so as to give a modulation of the ablation effect that the laser beam 10 has on the printing ink 9 applied to the front side 3: in the area 8 with low opacity, the printing ink 9 is ablated a maximum, in areas 7 with medium Opacity, the ink is ablated to a lesser degree, and in areas 6 with maximum opacity, the least or possibly even no ablation occurs. Of course, this applies only insofar as the printing ink 9 on the front side 3 covers the specific area 13 in which the watermark 5 is formed in the substrate 2.

Instead of ablating a printing ink, a laser-sensitive ink can also be discolored. The laser-sensitive ink only discolors in areas of low opacity.

The watermark is formed in the specific region 13 so that after the ablation of the printing ink 9, an alignment structure is produced, which is embodied purely by way of example in the form of at least one adjustment cross 14 in subsequent figures. This adjustment structure forms the local referencing for subsequent processes for applying a security feature, which then lies in the perfect register for the watermark 5.

The described embodiment can be modified such that instead of the watermark 5, which modulates the opacity by a thickness variation of the substrate, a so-called "false" or printed watermark 11 occurs, ie a watermark which generates on the substrate 2 by a so-called watermark color has been. The Fig. 3a and 3b schematically show the provision of such a printed watermark 11. On the back 4 of the substrate 2, a watermark color is printed. The watermark color penetrates accordingly Fig. 3b into the substrate 2 and causes after drying or other suitable processing, a translucency 12 in the substrate 2 at the points where the watermark ink 11 was printed. Press now, as in Fig. 4 Once again, the substrate 2 with the printed watermark 12 with the laser beam 10 results in the effect that the laser beam 10 is attenuated less in intensity at positions 10a at which the watermark increases the translucency of the substrate 2 at positions 10b where the watermark does not have this effect. In turn, an ablation of the printing ink 9 in the exact register to the watermark 11 is obtained, without this register having been set during the application of the printing ink 9. In this way, an adjusting structure, for example, in the form of a Justierkreuzes 14 are equally generated.

It should be noted that in the embodiments of the Fig. 1 to 4 the printing ink 9 is arranged on the underside 3 of the substrate 2, ie opposite the front side 4, on which the watermark 5 embossed or the watermark 11 is printed. Of course this is not mandatory. Similarly, the ink 9 can also be arranged on the front side 4. The laser radiation is then radiated from the bottom 3.

Fig. 5 shows the security element 1 with the watermark 5, which in this embodiment, the shape of a triangle and in addition to the specific area 13, here in the form of a Justierkreuzes comprises. The watermark 5 is printed in the specific area 13 with the ink 9 (where it does not depend on registration accuracy), which then, as based on the Fig. 1 to 4 is explained, is structured so that a Justierkreuz 14 is formed, which is formed here as a negative mold in a circular spot of the ink 9. Of course, in other ablation techniques, a positive form is possible. Similarly, the positive shape can also be achieved by appropriate design of the particular area 13 by providing it with the shape that in Fig. 6 for the adjustment cross 14 is shown.

It is essential that the Justierkreuz 14 by this procedure always in a fixed and very precise position to the remaining part of the watermark 5, in this case the triangle.

The Justierkreuz 14 is now used in terms of its location to apply a further security feature. In the embodiment of the Fig. 7 this is a printed image 15, which includes, for example, a five-pointed star and a six-pointed star. The six-pointed star is arranged so that the Justierkreuz 14 is overprinted, which is thus no longer visible. The security feature 15 in the form of the printed image is, since it was applied in exact registration to Justierkreuz 14, even in exact registration to the rest of the watermark 5, without replicating its contrast profile. The same applies to the in Fig. 8 shown embodiment, in which the security feature is performed in the form of a laser cut 16, which also exemplarily cuts out the area with the Justierkreuz 14, so that this is no longer visible afterwards.

LIST OF REFERENCE NUMBERS

1

security element

2

substratum

3

front

4

back

5

watermark

6, 7, 8

Area

9

printing ink

10

laser beam

10a, 10b

position

11

watermark

12

Transluzenzerhöhung

13

certain area

14

Justierkreuz

15

print motif

16

cut out area

Claims (6)

1. Method for producing a security element (1), wherein

   - a substrate (2) is provided, which has a front side and a rear side (3, 4), is translucent at least for specific radiation (10), and comprises a watermark (5, 11) modulating the opacity of the substrate (2) and comprising a specific region (13),

   - a print element (9), which covers the specific region of the watermark (5, 11) and is modifiable by way of the specific radiation (10), is applied onto the front side (3), and

   - the specific radiation (10) is radiated through the substrate (2) from the rear side (4), wherein the specific region (13) of the watermark (5, 11) is used as a mask with respect to the modification of the print element (9), and the print element (9) is modified in register with the watermark (5, 11),

   characterized in that

   - the specific region (13) of the watermark (5, 11) has been structured such that the modified print element forms an alignment structure (14),

   - a security feature (15, 16) is applied onto the substrate (2) in a subsequent process, wherein the location of the alignment structure (14) is captured and taken into account and the security feature (15, 16) is arranged in register with respect to the location of the alignment structure (14) and consequently the watermark (5, 11).
2. Method according to Claim 1, characterized in that the subsequent process comprises printing on a motif (15) as a security feature.
3. Method according to one of the preceding claims, characterized in that the subsequent process comprises applying a laser-modifiable coating and producing a motif by way of irradiation with laser radiation.
4. Method according to Claim 2 or 3, characterized in that the alignment structure (14) is overprinted or supplemented during the printing or application.
5. Method according to one of the preceding claims, characterized in that the subsequent process comprises producing a motif (16) by way of laser cutting, wherein the alignment structure (14) is also cut out and removed.
6. Method according to one of the preceding claims, characterized in that the specific region (13) has the form of an alignment cross (14).

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