EP2817155A1

EP2817155A1 - Method with register between print element and water mark

Info

Publication number: EP2817155A1
Application number: EP13705397.1A
Authority: EP
Inventors: Peter SCHIFFMAN; Harald Reiner; Angelika KECK-ANGERER; Jana Kisselova
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2012-02-21
Filing date: 2013-02-20
Publication date: 2014-12-31
Anticipated expiration: 2033-02-20
Also published as: CA2862057A1; EP2817155B1; ES2585279T3; PL2817155T3; WO2013124059A1; DE102012003601A1

Abstract

The invention relates to a method for producing a security element (1), wherein a substrate (2) is provided which has a front and a rear side (3, 4), is translucent at least for specific radiation (10) and has a water mark (5) which modulates the opacity of the substrate (2), a print element (9) is applied to the front side (3), wherein the print element (9) covers the water mark (5) at least partially on the front side (3), the print element (9) can be modified by means of the specific radiation (10), and the substrate (2) is penetrated by the specific radiation (10) from the rear side (4), wherein the water mark (5) is used as a mask with regard to the modification of the print element (9), and the print element (9) is modified in register with the water mark (5).

Description

Passing with Pa s s he s he s w ith

D u c tio n s a nd s w a s e c tio n s

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 that modulates the opacity of the substrate, and on the front Pressure element is applied. 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 with the aid of so-called watermark colors, which likewise locally modify the opacity of the substrate.

Since watermarks are usually formed in the substrate in the production of the starting material for the security element, for example in the production of a banknote paper, it is fundamentally difficult in later printing to arrange printed elements in exact position relative to the watermark, ie to pass. This problem arises regardless of the specific design of the printing element, not only when printing with different inks, but also during coating or application with printing elements, when applying transfer films or laminating or when applying a window suture. 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. In a printing process, additional register variations are added due to variations in investment positions, transfer variations in printing presses, paper moisture swings, and a swelling effect of the paper in stitching.

To apply a printing element in the register to the watermark, it would be possible to detect the position of the watermark in the substrate by means of a transmission sensor, and to set the 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. This results in effort by the detection of the watermark position, an image analysis to be performed in real time to determine the watermark position and a correction of the printing position to be performed in real time. The effort increases with the printing speed.

The invention is therefore based on the object of specifying a method with which a printing element can be structured in the register to form a watermark, without first having to determine the position of the watermark precisely and adapting the printing system to the position 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 on the front Applied pressure element is solved, in which on the front of the printing element at least partially covers the watermark, the printing element is modifiable by means of the particular radiation, and the substrate is irradiated from the back with the particular radiation, the watermark relative to the modification of the printing element as Mask is used and so the pressure element in the register is modified to the watermark.

The invention is based on the recognition that the energy of radiation is attenuated by the substrate. The more opaque the substrate, the stronger the weakening. Therefore, advantage is taken of the property of the watermark to modulate the opacity of the substrate. The watermark is used as a mask for a modification of the printing element by using a printing element that is modifiable by certain radiation for which the substrate is translucent, and that certain radiation from the back of the substrate to the front side on which the printing element Watermark is applied overlapping, is irradiated. This is done, masked by the watermark jeine modification of the printing element, which automatically lies in the perfect register to the watermark.

As a modification of the pressure element, in particular, an ablation occurs infra-rage when a pressure element is used which can be ablated. 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, that at the front is perceptible. 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 influencing of the printing element is also possible in a two-stage process if the printing element has an adhesive layer which is applied to the front side and exposed from the rear side 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 "printing element" is understood to mean an element which is applied to a substrate and, if appropriate, realizes a visually or mechanically evaluable element after further processing.Of course, printing elements based on printing inks are most widely used , 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 umf asst that applied by a printing element layer system, only a portion of the layer system and exposed to the particular 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. A multilayer system is z. B. to the effect that the pressure element cooperates with an additional layer whose visual effect depends on the prior modification of the printing element. Thus, it is known, for example, for optically variable layers that they are particularly clearly recognizable on a dark or black background in incident light. An embodiment of the invention therefore provides that the printing element is provided by the specific radiation with a contrast structure. The optically modified layer is then applied to the printing element thus modified in the register to the watermark, that is, the visual effect due to the precise fit of the printing element acting as a background is then automatically in the register to the watermark, although the optically variable layer itself was applied without registration requirements. An example of such an optically variable layer is a liquid crystal layer. In this regard, reference is made to EP 0435029 or WO 97/19818, which discloses examples of optically variable layers which use liquid crystals. The disclosure of these publications is fully incorporated herein with respect to the optically variable layers described therein. The term "printing element" thus also refers to a multilayer system, wherein a part of the layer system is applied to the front surface before the exposure and then illuminated with the determined irradiation, a further part of the layer system is then applied only after the exposure.

Especially for the use of banknotes, watermarks are common, modulating the opacity of the substrate by varying a thickness of the substrate while maintaining the density of the substrate, since such watermarks are usually very difficult to emulate. These watermarks are well suited for the printing method according to the invention, which then supplements the appearance of the watermark by further image information, which lies in the register to the watermark. This makes it possible, for example, to add color information provided by the watermark. Also, the image information of the watermark, which appears per se only in transmitted light, by means of the invention produced in Passer print image in incident light observation can be seen.

A watermark that modulates the opacity of a substrate may also be replaced by a so-called "watermark", instead of varying the thickness of the substrate

Watermark color are generated. 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 boundary surfaces to the surrounding air are significantly reduced by suitable binder components in the watermark color, so that in these areas the opacity decreases. Such a binder component is, for example, glycerol, which penetrates into the substrate and remains in the pores of the substrate. Watermarks generated by watermark color are also referred to as "spurious" watermarks, and watermarks produced by varying the thickness of the substrate while maintaining the density of the substrate are also referred to as "true" watermarks.

The same applies analogously if the watermark is caused by a coloration which modulates the opacity of the substrate.

A watermark can binarise the opacity of a substrate, i. H. it produces a structure which can be seen in the transparency in that the substrate is less opaque or more translucent at individual points. However, there are also known watermarks in the sense of gray scale modulation, which modulate the opacity or the translucency between two maximum values. In the transmitted light view you can see a grayscale image. Both types of watermarks are equally suitable for the present printing process. In the case of a watermark which is designed in the manner of a gray-scale image, it is, of course, particularly advantageous to use an ink whose modifiability goes beyond a simple threshold modification, the modification of which thus knows more than two states. The multi-level modulation by the watermark is then converted into a corresponding multi-stage modification of the printing element.

A particularly finely graded opacity modulation can be achieved by combining a paper thickness modulating "true" watermark with a watermark color generated "spurious" watermark. Printing elements usually consist of binders, auxiliaries, driers or drying accelerators and coloring constituents, such as dyes or pigments. By irradiating a radiation having a wavelength which is absorbed to some extent by the coloring constituents, one achieves that the particular radiation ablates the printing element for modification. In the case of ablation, therefore, the pressure element and certain radiation are chosen so that the particular radiation is absorbed by the pressure element in such a way that ablation is possible.

In order to avoid influences of the particular radiation on other components of the substrate or on the substrate applied coatings as possible, it is preferable to irradiate the particular radiation as narrow as possible in the range of an absorption band of the printing element. This is particularly easy to realize with laser radiation.

If a pressure element per se has no component making it suitable for ablation, it is preferable to add a certain amount of additive, for example soot, which absorbs the particular radiation to the pressure element for ablation. The use of an admixture makes it possible, in particular, to select the specific radiation such that it lies in the non-visible spectral range, for example IR radiation, if the admixture increases the absorption coefficient of the pressure element in the corresponding spectral range.

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 in the case of Use of effect inks based on inks, which show a viewing angle-dependent color impression (so-called optical variable ink) and of colors that can be structured 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. As already mentioned, the principle according to the invention provides that the printing element and certain radiation are coordinated so that the specific radiation is able to modify the printing element, wherein the watermark which modulates the opacity of the substrate is used as a mask. The term "certain radiation" used in this description therefore expresses that a pressure element which can be modified by means of this radiation is used The modification, for example in the form of an ablation, is achieved when the specific radiation at the front side The opacity modulation provided by the watermark reduces the intensity of the radiation on the front surface on which the printing element is located. In the other hand, the radiation intensity on the back side is chosen so that at the points where the watermark causes the lowest opacity in the substrate, a modification of the printing element enters, on the places where the watermark causes the highest opacity of the substrate, however, no or only a very small modification is achieved. Then the watermark - lo chen as a mask during 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 beam may be in the form of a laser beam, for example. It is then not only easy to provide the required radiation intensity, also the intensity adjustment can be done easily, since it is less effort to adjust a beam in its intensity, as to effect a homogeneous intensity adjustment of a fanned light beam.

The use of a rasterized beam further has the advantage that the intensity of the particular radiation can be varied in addition to the use of the watermark as a mask to effect additional structuring of the modification of the printing element. Of course, this additional modification is not in the passport to the watermark.

In addition, it is possible to apply additional masking on the backside which attenuates or absorbs the particular radiation. This achieves a further structuring of the printing element modification.

Investigations by the inventors have shown that on the back, as a rule, no visually visible marking is produced when, with the printing method according to the invention on the front side, the printing element is exposed in a masked manner by the watermark and modified, for example ablated.

It is also possible to use the introduction of the modifying radiation, in particular of laser radiation, for the purpose of detecting, on the entrance side of the laser radiation, ie before the masking effect is indicated by the watermark. - li used to cause a visible modification of the substrate, optionally after previous application of a radiation-sensitive layer. Thus, for example, a pulsed laser radiation can be used, which already on the entrance side, the substrate, such as paper, modified, for. B. by a blackening or foaming of the substrate. This effect is then clearly visible in transmission. Thus, a combination of the watermark, the printing element modified to a watermark in the register and a visual modification of the surface of the substrate on the entry side of the modifying radiation advantageously results. Of course, this modification on the entrance side of the radiation depends solely on the application of the radiation. This makes it possible, for example, to create a window in which the watermark and the printing element modified in the register are visible. Basically, the pressure element to be modulated by means of both

Radiation ablatable substances as well as by means of radiation-developable substances (for example, thermochromic substances, which preferably have a non-reversible color or Opazitätswechsel) and in addition also not by means of radiation ablatable or developable substances. Depending on the color formulation, the latter substances remain undetached on the substrate or are only partially removed. Furthermore, the pressure element may contain a substance mixture in which the individual components are modified in stages as a function of the impinging energy. For example, a first component at very low opacity and a second component is already ablated at medium opacity.

According to a preferred embodiment, the printing ink contains a laser-markable feature substance with core-shell particles which is known from EP 1 826 728 A2, one of the materials of the core and shell containing the radiation. The radiation of one marking laser is absorbed and the other of the core and shell materials does not absorb the radiation of the marking laser. According to a further preferred embodiment, the core-shell particle contains a UV-stimulable organic luminescent substance known from EP 1 826 730 A2, wherein the organic luminescent substance forms the core which is coated with a shell which satisfies the chemical and / or physical resistance of the Luminescent increases.

According to a further preferred embodiment, the printing ink contains a modified iron blue pigment known from EP 1 826 246 A2, which is coated with an alkali-resistant and / or acid-resistant shell.

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, for example a film coating or a metallization.

Items to be protected in the context 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, ...) and product securing elements, such as. Labels, seals, packaging, be.

The term "security paper" is understood here in particular as the precursor to a value document (eg a card), which, in addition to the print produced according to the invention, also has other authenticity features (such as, for example, volume Neszenzstoffe) may have. 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 that 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 unwanted copies are prevented at the same time.

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, i. 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, for example, be a combination of plastic film paper or even a three-layer composite such as plastic film-paper plastic film, i. a paper substrate is covered on either side by a plastic film, or paper plastic film paper, i. a substrate made of a plastic film is covered on each of its two 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 color tone is at least similar to the color tone of the substrate. Such a watermark is known for example from DE 10 2009 056462 AI. 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 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.

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

Fig. La and lb is a schematic representation of a substrate in a sectional view

(FIG. 1 a) or in plan view (FIG. 1 b) for illustrating the opacity modulation by the watermark, FIG.

1a and 3b show a schematic view similar to FIGS. 1a and 1b, relating to an embodiment in which the watermark is generated by a watermark color, FIG.

Fig. 4 is a view similar to Fig. 2 for the substrate of Fig. 3a and 3b,

5a is a schematic view similar to FIG. 2 for an embodiment in which a non-modifiable coating is provided on the front side of the substrate;

5b and 5c views of the substrate of Fig. 5a from the back or

6 to 8 are plan views (Figs. 6a, 6b, 7, 8) and sectional views (Figs. 6c, d) of an embodiment having a suture.

Fig. La 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 shown in Fig. Lb, which shows a plan view of the front side 3 of the substrate 2 schematically. There are regions 6 of high opacity at locations where the substrate 2 has the maximum (unreduced) 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.

To produce a printed image which has been adapted to the watermark, an ink is applied to the front side 3 which can be ablated by means of laser radiation. FIG. 2 shows the substrate 2 with printing ink 9 applied on the front side 3. The printing ink 9 is not (yet) structured any further. However, at least in part, it covers the area in which the watermark 5 is present in the substrate 2.

From the front side 3, a laser beam 10 is now passed 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 is attenuated depending on the opacity of the substrate 2, which is modulated by the watermark 5. 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 region in which the watermark 5 is formed in the substrate 2.

The described embodiment can be modified such that instead of a watermark which modulates the opacity by a thickness variation of the substrate, a so-called "fake" printed watermark occurs, so a watermark, which was generated on the substrate 2 by a so-called watermark color.

FIGS. 3a and 3b schematically show the provision of such a printed watermark. On the back 4 of the substrate 2, a watermark ink 11 is printed. The watermark ink 11 penetrates according to Fig. 3b in the substrate 2 and causes after drying or other suitable processing a Transluzenzer elevation 12 in the substrate 2 at the points at which the water was painted sign 11.

If, as shown in FIG. 4, the substrate 2 with the printed watermark 12 is then loaded with the laser beam 10, the effect again results that the laser beam 10 at positions 10a at which the watermark or the watermark color the translucency of the substrate 2, less attenuated in intensity than 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 is obtained, without this register having been set during the application of the printing ink 9. FIGS. 5a to 5c relate to a third embodiment in which a coating 13 that can not be modified by the laser radiation 10 has additionally been applied to the front side 3, which is transparent to the laser radiation 10 and thus does not attenuate it. FIG. 5a shows a sectional view similar to FIG. 2, wherein the coating 13 that is not modifiable by the laser radiation is now applied in some areas. FIG. 5 b shows a plan view of the rear side 4 with the coating 13. 5 c shows a top view of the front side 3 after irradiation with the laser radiation 10. Due to the different opacity of the substrate 2 in the region of the watermark, the printing ink 9 is influenced to a different extent by the laser radiation 10, so that the differentiated areas 14, 15 and 16 result. In the region 16, the ink 9 is almost unaffected, since the energy of the laser beam is greatly attenuated due to the opacity of the substrate 2. In the region 14, the printing ink 9 is modified to an average extent, for example ablated, due to the medium opacity of the substrate 2 due to an average laser energy attenuation. The laser beam had a strong effect on the printing ink 9 in the region 15, because there substrate 2 had a low opacity and weakened the laser beam only slightly.

The embodiment described with reference to FIGS. 5a to 5c can, of course, also be realized with a watermark that was generated by a watermark color and not by a thickness modulation.

Of course, it is basically possible for all embodiments to use a combination of watermark color and thickness modulation. A watermark ink is available, for example, from Sun Chemical under the designation 669440 Vernes UVSP (art.No .: JV 40000009).

Of course, the approaches described here can also be carried out on both sides of a substrate, wherein the ink 9 is then alternately applied to the front and back of the substrate, so that it does not overlap.

In addition, it is also possible to use two different printing inks which are modified by radiation of different spectral ranges. are bar. This makes it possible to work with different intensity profiles for these two radiations or to print on the front and back the same area with radiation-modified inks in the register to the watermark. For this purpose, a first ink is applied to the front and a second ink on the back. Subsequently, these inks are exposed and modified by laser radiation from the back (for the ink on the front) or the back (for the ink on the front). Similarly, the use of possible

• at least two different inks that require different radiation intensities for modification, or

• at least one printing ink containing substances requiring different levels of radiation for modification, or

· At least one printing ink containing a mixture of substances that are modifiable and that are not modifiable.

Three examples are described below for the printing process according to the invention:

Example V.

A black, soot-based offset color was printed over the area of a watermark. The paint was dried for several days and then ablated by an ND vanadate laser from the back of the color on the front. In areas of low paper thickness, ie maximum translucent watermark, 80% to 95% of the color was thereby removed. In areas of maximum paper thickness, ie minimal Translucency of the watermark was ablated only 10% to 30% of the color.

Example 2:

The area of a watermark on the front side was overprinted by means of an OVI screen printing ink WP from the manufacturer SICPA. The paint dried out for several days. Subsequently, the color on the front side was ablated by means of a Nd: Yag laser from the rear side. In areas of low paper thickness, 80% to 95% of the paint was removed. In the areas with maximum paper thickness, 10% to 30% of the paint was ablated.

Example 3:

The area of a watermark on the front side was overprinted by means of a magnetic OVMI screen printing ink of the manufacturer SICPA. The paint dried out for several days. Subsequently, the color on the front side was ablated by means of a Nd: Yag laser from the rear side. In areas of low paper thickness, 80% to 95% of the color except a yellow colorant was removed. In the areas with maximum paper thickness, 10% to 30% of the paint was ablated.

In general, the particular radiation is to be chosen so that no absorption of the radiation occurs in the substrate, which would lead to a change in the substrate. Both continuous wave lasers and pulsed lasers are possible for this purpose. An example of a suitable CW laser is the Innoslab, IS8I-E model manufactured by EdgeWave GmbH, which is a Nd: YV04-based laser at a wavelength of 1064 nm. He poses in the CW operation provides 100 watts of power. At a scan speed of 2.5 m / s to 5 m / s, the ablation of a soot-based color can be performed. If an IR-modifiable color is used as the printing ink, there is the advantage that the printed image and the verification of the register can be machine-based by means of infrared measurement. This color may be visually visible or not visible. The printing method according to the invention is also applicable to a watermark which is provided in connection with a so-called window thread in a substrate of a security element. FIG. 6 a shows a plan view in transmitted light on a front side 3 of a substrate 2, which has a window thread 17. In the substrate 2, a sequence of strip-shaped regions 18 and 19 are provided which form the watermark: in the regions 18 the thickness of the substrate is unchanged, so that the watermark has a high opacity, and in the regions 19 the thickness of the substrate, so that the watermark has a low opacity (in the embodiment of Figures 6 to 8 is in contrast to the embodiments of Figures 1 to 5, the watermark on the front side 3 of the substrate). In reflected light, this has the effect that the window thread 17 has visible portions 20 in which one side of the window thread according to FIG. 6d is not covered by the substrate, and not visible because, according to FIG. 6c, fully embedded portions 21 in the substrate 2 , The effect in reflected light can be seen in Fig. 6b: only the visible portions 20 are exposed at the front 3 and are visible.

Transmitted light is for the purposes of this invention, when an illumination of the substrate takes place from the side opposite to the viewer, ie the Illumination through the substrate takes place. Incident light is in the sense of this invention, when a lighting of the substrate from the side of the viewer is made. In the area of the watermark 5, which is formed from the areas 18 and 19, in turn ink 9 is now applied to the front side 3.

FIGS. 6c and 6d show a section through the substrate 2 of FIG. 6a, wherein FIG. 6c shows a section lying in a region 18, FIG. 6d shows a section in a region 19. In FIG. 6c the thread 17 below the surface of the front side 3, which is why one of the non-visible portions 21 is here. In contrast, in the area 19, according to FIG. 6d, the window thread 17 lies on the surface of the front side 3, so that a visible section 21 is formed.

FIG. 7 shows the plan view of the front side 3 after the irradiation of the laser radiation from the rear side 4. In the regions 18 with high opacity, the printing ink 9 is not ablated, there is an area 16 as in FIG. 5c. In the areas 19, however, the printing ink 9 is ablated, there is an area 14 in the sense of FIG. 2.

Fig. 8 shows a modification in which the laser radiation no ablation, but an inverse modification, for. B. by developing thermochromic effect pigments causes. The areas 14 and 16 are exactly interchanged here.

In principle, it is not essential for the printing process whether the printing ink 9 is applied to the front or back of the substrate. The decisive factor is that the substrate 2 from the side with the radiation is irradiated, which is opposite to the side on which the ink 9 is arranged. Of course, in all embodiments, the ink can be provided on the back and the radiation can be coupled from the front.

B e to g s e c ia

security element

substratum

front

back

watermark

, 7.8 area

printing ink

0 laser beam

0a, 10b position

1 watermark color

2 Translucency increase

3 coating

4, 15, 16 area

7 window thread

8, 19 area

0.21 section

Claims

Patent claims

1. A 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 certain radiation (10) and has a watermark (5) which modulates the opacity of the substrate (2) .

on the front side (3) a pressure element (9) is applied, characterized in that

on the front side (3) the printing element (9) at least partially covers the watermark (5),

the pressure element (9) is modifiable by means of the specific radiation (10), and

the substrate (2) is irradiated from the rear side (4) with the determined radiation (10), the watermark (5) being irradiated with respect to

Modification of the pressure element (9) is used as a mask and the pressure element (9) is modified in the register to the watermark (5).

2. The method according to claim 1, characterized in that the watermark (5) of the provided substrate (2) modulates the opacity of the substrate (2) by modulation of a thickness of the substrate (2).

3. The method according to claim 1 or 2, characterized in that the watermark (5) of the provided substrate (2) has a color which modulates the opacity of the substrate (2).

4. The method according to any one of the above claims, characterized in that the specific radiation (10) ablates the pressure element (9) for modification.

5. The method according to claim 4, characterized in that for Abla- tion the pressure element (9) with a certain radiation (10) absorbing admixture, z. As soot is provided.

6. The method according to any one of the above claims, characterized marked, that the printing element is a printing ink (9) and in particular one or more of the following substances: an optically variable color, a magnetically orientable, optically variable color, a metallic color, a color effective in the non-visible spectral region.

7. The method according to any one of claims 1 to 5, characterized in that the pressure element comprises a coating, transfer film, laminating film and / or a window thread.

8. The method according to any one of the above claims, characterized marked, that the pressure element (9) additionally comprises substances which are not modifiable or ablatable by means of the particular radiation (10) and absorb the radiation in the visual, infrared and / or ultraviolet wavelength range ,

9. The method according to any one of the above claims, characterized in that the specific radiation is applied in the form by a beam, in particular a laser beam (10), over the back (4) is guided.

10. The method according to claim 9, characterized in that in addition to the use of the watermark (5) as a mask during marking and an intensity of the particular radiation (10) is varied to an additional structuring of the modification of the pressure element (9) to be Act.

11. The method according to any one of the above claims, characterized in that on the back (4) an additional masking is applied, which attenuates or absorbs the particular radiation (10).

12. The method according to any one of the above claims, characterized in that the printing element (9) by means of the specific radiation (10) is modified so that it receives a light / dark contrast structure, and that only an additional layer is applied, whose visual Impression of the brightness of the modified printing element (9) depends, which forms the background of the additional layer.

13. The method according to claim 12, characterized in that as an additional layer, an optically variable layer, in particular a liquid crystal, is deposited, which imparts a different color impression against a dark background than against a light background.