EP3279006A1 - Method for producing a safety element - Google Patents

Abstract

The invention relates to a method for producing a security element (1), wherein a substrate (2) is provided that is translucent at least for certain radiation (10) and has a watermark (3) which modulates the opacity of the substrate (2). wherein on one side (6) of the substrate (2) an embossing layer (7) is applied, which covers the watermark (3), a hologram structure (9) is embossed in the embossing layer (7) and on the hologram structure (9) a reflector layer (8) is applied, and the substrate (2) from the opposite side (6) with the particular radiation (10) is irradiated, wherein an intensity of the radiation (10) is adjusted so that the watermark (3) by means of it caused opacity modulation acts as a mask and the reflector layer (8) by the radiation (10) in the register to the watermark (5,11) is removed structured.

Description

The invention relates to a method for producing a security element, wherein a substrate is provided which is translucent at least for certain radiation and has a watermark which modulates the opacity of the substrate.

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 local reduction in thickness leads to a local reduction in opacity. 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 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 other security features in an exact location to the watermark, so to pass.

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, e.g. 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 laser-ablatable print layer can be arranged above the watermark, and the opacity variation, which has the watermark, serves to remove the print layer in a structured manner in the exact register to the watermark. However, this procedure is limited to print layers which, in addition, have a contrast characteristic identical to the watermark after removal.

Holograms are known for securing items or documents from counterfeiting. They are particularly hard to fake.

The invention has for its object to provide a method by which a security element is generated in which a hologram image in the register is a watermark.

This object is achieved according to the invention with a method for producing a security element, wherein a substrate is provided which is translucent at least for certain radiation and a watermark which modulates the opacity of the substrate, wherein on one side of the substrate an embossing layer is applied, which at least partially covers the watermark, a holgram structure is embossed into the embossing layer and a reflector layer is applied to the hologram structure, and the substrate from the opposite side is irradiated with the particular radiation, wherein an intensity of the radiation is adjusted so that the watermark acts by means of the opacity modulation effected by him as a mask and the reflector layer is removed by the radiation in the register to the watermark structured.

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. Based on this concept, the reflector layer, which is located on a stamped embossed layer with a hologram, is now structured. As a result, the reflector layer remains only in dark areas of the watermark, and the remaining hologram stands in perfect register with the watermark, since a reflective hologram is only visible in the non-ablated areas of the reflector layer. The hologram is effective only in the areas as a reflective hologram in which the reflector layer has not been removed. Optionally, in areas where the reflector layer has been removed, holographic structures which are still slightly visible can be suppressed by the optional application of a protective lacquer to the regions of the hologram structure exposed by the removal of the reflector layer. This is because the hologram structures after the ablation in these areas are open and when covered with a protective lacquer no holographically effective structure more, especially when the refractive index of the protective lacquer is adjusted within +/- 0.2 to that of the embossing layer.

The watermark may be a so-called "true watermark" if the substrate is a paper substrate. The watermark is then formed by depressions on a screen side of the substrate and modulates the thickness of the substrate. It is then preferred to apply the embossing layer and the reflector layer on the opposite felt side of the substrate, since this is flat. 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, organic and inorganic 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.

Another possibility to modulate the opacity of the substrate are substrate erosions and / or substrate recesses by, for example, laser technology, grinding and / or punching, optionally in combination with a paper-made watermark and / or a watermark color.

In addition, the hologram can be combined with a Stahldruckverprägung. A steel print embossment passes through the entire substrate and leads to a tactile perceptible structure that is comparatively coarser than the hologram structure.

The reflector layer can be provided with further pigments or dyes to produce additional register-containing effects.

The embossing layer can be a UV-curable embossing lacquer or a thermoplastic lacquer.

The embossing layer or the reflector layer can be provided with laser-sensitive dyes, so that the hologram, which is produced by the hologram structure, complement an additional color motif by the laser-sensitive dyes which were modified during the ablation and the watermark in register.

After removal with the laser radiation, it is possible to apply a different colored mirror layer, so that the reflective hologram in the color of the reflector layer, the reflective hologram in color of the differently colored mirror layer and the watermark complement each other in register.

The term hologram structure is generally understood to mean a diffractive structure, in particular a diffractive structure, which makes a hologram recognizable. But there are also other diffractive effects possible.

The term "certain radiation" as used in this description therefore expresses that it can remove the reflector layer. The ablation is achieved when the particular radiation has an intensity suitable for ablation at the exit on the side of the reflector layer. The opacity modulation caused by the watermark reduces the intensity of the radiation on the side on which the reflector layer is located. The irradiated radiation intensity is therefore adjusted so that the opacity modulation, which is caused by the watermark, results in a radiation modulation which modulates the ablation effect. Thus, the watermark serves as a mask in the irradiation of the substrate with the specific radiation.

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 in particular as the precursor that can not yet be processed to form a value document (eg a card) which, in addition to the pressure produced according to the invention, can also have further 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, or substantially of the natural polymer-cellulose, as it is 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 consist. More 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 Substrate made of a plastic film is covered on each side by a paper substrate.

Optionally, 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.

Plastic films may include, for example, polypropylene, polyethylene, polyethylene terephthalate, and polyamide.

Under translucency or translucent in this description, the partial translucency of a body understood, so the property of transmitting light scattering. Translucency is to be seen, among other things, in contrast to the transparency (= image or eye transmittance). 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 not only in the combinations indicated, but also in other combinations or alone, without departing from the scope of the present invention.

Fig. 1

eine Schnittdarstellung durch ein Sicherheitselement in einer ersten Ausführungsform und

Fig. 2

eine Schnittdarstellung ähnlich der Fig. 1 durch ein Sicherheits-element einer zweiten Ausführungsform.

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. 1

a sectional view through a security element in a first embodiment and

Fig. 2

a sectional view similar to the Fig. 1 by a security element of a second embodiment.

Fig. 1 shows a sectional view through a security element 1, which is constructed on a substrate 2 produced in the paper-based embodiment. The security element 1 has a watermark 3, which modulates the thickness of the substrate 2 and thus its opacity. In the embodiment of the Fig. 1 the watermark is formed by the fact that 2 recesses 4 were incorporated in the top 5 of the substrate 2 in the manufacture of the substrate. Wells are examples of forming regions of reduced pulp (and reduced opacity). They can also be formed on the bottom. Due to the production of the watermark 3, the top 5 is also referred to as the screen side; the opposite bottom 6 as a felt side.

On the bottom 6 a stamping layer 7 is applied, on which a reflector layer 8, z. As a metallization is located. In the embossing layer 7, a hologram structure 9 is embossed before the application of the reflector layer 8, which, together with the reflector layer 8, produces an effective reflection Hologram when viewed on the top 5 makes recognizable. The reflector layer 8 is first applied flat, ie without initial structuring. Structuring takes place by irradiating laser radiation 10 from the upper side 5, the intensity of which is adjusted such that it removes the reflector layer 8 from the embossing layer 7 after passing through the substrate 2 in the regions of the depressions 4. In areas without recesses 4, the intensity of the laser radiation 10 is so far attenuated that no ablation of the reflector layer 8 takes place more. In other words, the intensity of the laser radiation 10 is set exactly so that when passing through the substrate 2 in a non-reduced thickness just no removal of the reflector layer 8 more, with a reduced thickness due to the wells 4, however, a removal is achieved. In this way, the watermark 3 modulates the removal of the reflector layer 8.

From the upper side 5, the laser beam 10 is guided over the substrate 2. It passes through the substrate 2. The wavelength of the laser beam is such that the reflector layer 8 absorbs the radiation. The laser beam 10 is attenuated depending on the opacity of the substrate 2, which is modulated by the watermark 3. At a point where the substrate has high opacity by the watermark, the laser beam 10 is greatly attenuated. At a location where the substrate 2 has reduced opacity, the laser beam is less attenuated. The intensity of the laser beam 10 is adjusted so as to result in a modulation of the ablation effect which the laser beam 10 has on the reflector layer 8 applied to the embossing layer 7.

Due to the structuring ablation on the underside 6, exposed portions of the embossing layer 7 are produced in individual areas in the register for the watermark 3. These sections no longer act as a reflective hologram. Only the areas in which the metallization 8 remained and acts as a reflector layer do so. In order to prevent regions with an exposed hologram structure 9 from being able to be visually perceived under certain viewing conditions, a protective lacquer 13 is additionally applied which covers the entire embossing layer 7 at least in the uncovered regions. A precise structuring is not required because it is completely harmless when the resist 13 also covers the reflector layer 8. Since the protective lacquer 13 has a refractive index which deviates at most 0.2 from that of the embossing layer 7, the protective lacquer equalizes the hologram structure 9 in the uncovered regions in which no reflector layer 8 is present, leaving a remaining, slightly perceptible holographic effect optically disappear completely.

Basically, top 5 (wire side) and bottom 6 (felt side) are interchangeable, i. Stamping layer 7 and reflector layer 8 (eg metallization) could also be applied to the screen side.

Fig. 1 shows the manufacturing method for a substrate 2, which has a watermark 3 in the form of depressions 4. Fig. 2 refers to an embodiment in which the watermark 3 is generated by a watermark color 11. The structuring of the reflector layer 8 takes place in the same way - with the difference that the not printed with watermark ink 11 areas of the substrate correspond to the wells 4, so are areas with lower opacity of the substrate 2.

Fig. 2 shows yet another, optional embodiment to the effect that after the structured removal of the reflector layer 8 additionally a further mirror layer 12 is applied, which is not further structured. It thus covers both the reflector layer 8 and the reflector layer 8 exposed areas of the hologram structure 9 from. The mirror layer 12 differs from the reflector layer 8 in terms of their color effect. In this way, two hologram structures are created, which complement one another register-specifically, the hologram structure with the reflector layer 8 and mirror layer 12 lying over it (eg also metallization), which produce a first color effect for the reflective hologram, the hologram structure only with the mirror layer 12, which causes a second color effect for the hologram structure, and the watermark 3. Of course, this embodiment with the further mirror layer 12 also with a real watermark according to Fig. 1 and is not limited to being implemented with a watermark color 11. The same applies to the protective coating 13, which is also in Fig. 2 can be used.

If the substrate 2 contains printable windows or if it is fully transparent, there is additionally a different holographic effect of top side 5 and bottom side 6. A two-sided different coloration of the hologram in perfect register is then obtained.

Further, it is possible to provide the embossing layer and / or the reflector layer with a laser-modifiable substance, which is modified during removal with the laser radiation, so that in addition a colored motif is obtained, which is in register with the watermark 3 and the hologram.

LIST OF REFERENCE NUMBERS

1

security element

2

substratum

3

watermark

4

deepening

5

top

6

bottom

7

embossing layer

8th

reflector layer

9

hologram structure

10

laser beam

11

Watermark Color

12

mirror layer

13

protective lacquer

Claims (7)

Method for producing a security element (1), wherein a substrate (2) is provided which is translucent at least for certain radiation (10) and has a watermark (3) which modulates the opacity of the substrate (2), characterized in that on one side (6) of the substrate (2) a stamping layer (7) is applied which at least partially covers the watermark (3), - A holgram structure (9) is embossed in the embossing layer (7) and on the Holgrammstruktur (9) a reflector layer (8) is applied, and - The substrate (2) from the opposite side (5) with the particular radiation (10) is irradiated, wherein an intensity of the radiation (10) is adjusted so that the watermark (3) acts by means of the opacity modulation caused by it as a mask and the reflector layer (8) is removed in a structured manner by the radiation (10) in the register to the watermark (3). A method according to claim 1, characterized in that the substrate (2) is a paper-based substrate and the watermark (3) through regions of reduced mass of the substrate (2) modulates a thickness of the substrate (2) and the embossing layer (7) and the reflector layer (8) on the laser beam (10) opposite side (6) of the substrate (2) are applied. A method according to claim 1, characterized in that the substrate (2) is a film or composite substrate and a watermark ink (11) on at least one of the substrate sides (5,6) is the opacity of the substrate (2) modulated and the embossing layer (7) and the reflector layer (8) on the laser beam (10) opposite side (6) of the substrate (2) are applied. Method according to claim one of the above claims, characterized in that the embossing layer (7) and / or the reflector layer (8) contains / contains a laser-modifiable substance and an additional motif is produced during ablation. Method according to one of the above claims, characterized in that on that a different colored reflective layer (12) is applied after the removal of the reflector layer (8). Method according to one of the above claims, characterized in that the embossing layer (7) is provided with laser-sensitive, chromatic, fluorescent, metallic or effect pigments. Method according to one of the above claims, characterized in that on the reflector layer (7) after their removal structurable and the resulting exposed regions of the hologram structure (9) a protective lacquer (13) is applied.

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