EP2439074B1 - Security paper with watermark - Google Patents

Description

The invention relates to a security paper with a watermark and a method for producing such a security paper.

Data carriers, such as security, value or identity documents, but also other valuables are often equipped with security features for security, which allow verification of the authenticity of the data carrier and at the same time serve as protection against unauthorized reproduction.

In particular, security papers for banknotes, identity documents and the like are often provided with watermarks for protection, distinguishing between two-level watermarks with a strong light-dark effect and multi-level watermarks with smooth transitions between light and dark. To produce two-stage watermarks, for example, metal wires or metal moldings, so-called electrotypes, are soldered or welded onto the paper screen structure in order to completely close the paper screen at these locations. As a result, the paper accumulation is obstructed in these sections of the papermaking screen and thin spots form in the paper, which appear very bright in transmitted light. For the production of multi-level watermarks, a three-dimensional relief is embossed in the dewatering screen, so that the paper thickness of the finished paper varies according to the relief and, in transmitted light, reveals soft, gradual transitions between lighter and darker areas.

Traditional watermarks show motifs such as portraits of people, animals or buildings. However, such watermarks only allow a simple security of a security paper equipped therewith.

The document EP 1 607 235 A discloses a security paper having the features of the preamble of claim 1.

Proceeding from this, the object of the invention is to provide a security paper with watermarks, which combines a high degree of anti-counterfeiting security with a high visual attractiveness.

This object is achieved by the security paper having the features of the independent claim. A method for producing such a security paper is specified in the independent claim. Further developments of the invention are the subject of the dependent claims.

According to the invention, a security paper of the type mentioned in the beginning contains a watermark which forms a first motif, and the watermark is superimposed by a recessed area which forms a second motif. The recess region is formed from at least one line-shaped cutout produced in the security paper by the action of laser radiation, so that the superposition of the watermark and recess region forms a combination motif of the first and second motif, which has a visual impression changed in transmitted light compared to reflected light.

Such a combination motif combines the advantageous properties of proven watermarks with those of modern, laser-cut security features. As a result of the laser radiation, either a continuous cut line or a non-continuous dilution line in the paper is produced in the paper, depending on the local paper thickness. When viewed in incident light, the watermark and thinning lines are virtually indistinguishable from the surrounding vellum area of the security paper. On the other hand, when viewed in a transparent manner, both the watermark and the dilution lines are clearly visible. The relative brightness of watermark areas and dilution lines can be be adjusted by the depth of cut and by the paper thickness in the watermark in a wide range.

Due to the dependence of the cutting result on the local paper thickness results in a complex interaction of watermarks and laser pattern, so that a variety of possible visual appearances in supervision or review is available for the combination motif. On the one hand, this opens up a great deal of creative freedom for the designer and, on the other hand, enhances the two individual security features. For the user results in a visually appealing and easily checked for authenticity combination feature.

The term "recess" is used in the context of this description as a generic term for through openings or cuts and for non-continuous dilutions of the security paper. A line-shaped recess or recess line can therefore be either a cutting line passing completely through the paper or a non-continuous dilution line with a certain remaining residual thickness of the paper.

The mentioned overlay of recess area and watermark also includes the case that the recess area and the watermark overlap one another only in a partial area, so that the overall motif area is significantly increased by the combination of the two features.

According to an advantageous variant of the invention, the watermark comprises a thin spot with a paper thickness reduced in relation to the surroundings. Alternatively or additionally, it may also be provided that the watermark a thick spot with a paper thickness increased from the environment. The watermark can be formed in two stages or in multiple stages. In this case, watermarks with a very large number of stages and thus a virtually continuous thickness variation in the description are referred to as multi-level watermark.

The first motif of the watermark advantageously represents a portrait, an architectural, technical or natural motif, or an alphanumeric string, in particular a value number. Strings and, in particular, denominations which indicate, for example, the denomination of a banknote, are expediently produced with electrotypes as two-level watermarks.

In an advantageous embodiment, the first and second motif represent information that is related or complementary to one another. For example, the information of the watermark motif (first motif) can repeat the information of the recapture area motif (second motif) or supplement it into overall information.

In the vote of the first and second motif is appropriately taken into account that a watermark within a benefit has a comparatively large position tolerance. The second motif is therefore preferably designed so that a positional tolerance of the first motif of a few millimeters does not affect or destroy the desired combination effect.

The recessed area can be formed by a single line-shaped recess in the security paper, for example by a lettering or a simple graphic motif. However, the recess region preferably comprises a plurality of line-shaped recesses and is formed in particular by a plurality of line-shaped recesses in the security paper. In the following, for the sake of simplicity, we will always speak of linear recesses in the plural, it being understood that this formulation should always include the case of only a linear recess.

The line-shaped recesses may comprise both continuous cut lines and dilution lines not passing through the security paper. If both cutting lines and dilution lines are present in a recess area, they can be present in separate areas next to one another, or the cutting and dilution lines can also adjoin one another and merge into one another. Due to the production by laser cutting in one operation, the cutting lines and dilution lines in this case adjoin one another without offset.

In an advantageous embodiment, it is provided that the recessed area is arranged completely within the watermark.

The recessed area can be designed in various ways. For example, the recess area may be formed by a plurality of straight, parallel line-shaped recesses, or by a plurality of straight, diverging line-shaped recesses. The recess lines may also be curved, so that the recess area is formed by a plurality of curved, equidistant or by a plurality of curved, diverging line-shaped recesses.

The line-shaped recesses preferably have a width between 0.05 mm and 1 mm, in particular between 0.1 mm and 0.4 mm.

According to one development of the invention, the security paper is provided with a laser-modifiable marking substance at least in a sub-area and the line-shaped recesses have in this sub-area a boundary area modified by the action of laser radiation. The security paper is preferably provided in the subregion with a marking substance whose visible color can be changed by the action of the laser radiation, so that the line-shaped recesses in this subregion have a colored edge region.

Even with the embodiments provided with a laser-modifiable marking substance, the line-shaped recesses may comprise both continuous cutting lines and dilution lines not passing through the security paper. If both cut lines and dilution lines are present, then the cut lines can be used in particular in edge-modified, for example, colored dilution lines.

As markers, laser-modifiable effect pigments or pigment-free laser-modifiable marking substances can advantageously be used. Examples of suitable markers, as well as the manner of their inclusion or incorporation in the security paper can the document WO 2010 / 072329A1 are removed, the disclosure of which is included in the present application in this respect.

The security paper may in particular be a single- or multi-ply paper, preferably with a high percentage of cotton. Also coated Papers or composite materials in which at least one layer is based on paper can be advantageously used according to the invention.

In the case of multilayer composites, such as those arising from a subsequent combination of several layers of different substrates, of which at least two layers are paper-based, a recessed area produced by laser radiation can be combined with a watermark per individual layer. However, the combination can also take place in different positions. For example, a first paper-based layer of a composite can include a watermark with a laser-generated recessed area, a watermark in conjunction with a laser-generated recessed area in a second paper-based layer, or a laser-generated recessed area in conjunction with a watermark in a second paper-based layer , A second paper-based sheet may then include a watermark having a recessed area created by laser radiation, a watermark in combination with a recessed area created by laser radiation in the first paper-based layer, or a recessed area created by laser radiation in conjunction with a watermark in the first paper-based layer. If the first layer already contains a combination feature, the second paper-based layer can of course also be feature-free.

The invention also includes a method for producing a security paper of the above type. In this case, a security paper is provided with a first motif forming watermark and the watermark is superimposed by a recess portion which forms a second motif and of a plurality of linear, through Action of laser radiation generated recesses formed in the security paper becomes, so that the superposition of watermark and recessed area forms a combination motif of the first and second motif, which has a changed in transmitted light compared to reflected light visual impression.

The line-shaped recesses are advantageously produced by laser application with an infrared laser, preferably with a CO ₂ laser.

In an advantageous development, the security paper is provided with a laser-modifiable marking material, at least in a subarea, so that the line-shaped recesses in this subarea are modified by the action of the laser radiation in its edge region. Preferably, the security paper is provided in the subregion with a marking substance, the visible color of which can be changed by the action of the laser radiation, so that the line-shaped recesses in this subarea receive a colored edge region due to the action of the laser radiation.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

Fig.1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen Kombinationsmotiv,

Fig. 2

für ein Kombinationsmotiv in (a) und (b) die beiden zu kombinierenden Sicherheitsmerkmale Wasserzeichen und Ausnehmungsbereich jeweils einzeln, in (c) einen Querschnitt des Sicherheitspapiers im Bereich des Kombinationsmotivs, in (d) das Erscheinungsbild des erzeugten Kombinationsmotivs bei Betrachtung im Auflicht und in (e) das Erscheinungsbild des Kombinationsmotivs bei Betrachtung im Durchlicht,

Fig. 3

in (a) bis (e) eine Darstellung wie in Fig. 2 für ein Kombinationsmotiv nach einem anderen Ausführungsbeispiel der Erfindung,

Fig. 4

für ein weiteres erfindungsgemäßes Kombinationsmotiv in (a) und (b) die beiden zu kombinierenden Sicherheitsmerkmale Wasserzeichen und Ausnehmungsbereich einzeln, in (c) das Erscheinungsbild des erzeugten Kombinationsmotivs bei Betrachtung im Auflicht und in (e) das Erscheinungsbild des Kombinationsmotivs bei Betrachtung im Durchlicht,

Fig. 5

in (a) bis (e) eine Darstellung wie in Fig. 2 für ein Kombinationsmotiv nach einem weiteren Ausführungsbeispiel der Erfindung,

Fig. 6

schematisch die räumliche Energieverteilung eines Schneidlaserstrahls und die resultierenden Schnittbreiten bei verschiedenen Papierdicken,

Fig. 7

die Einzelheit VII der Fig. 5(d) im Detail, wobei das Laserschneiden mit einem Laserstrahl mit der in Fig. 6 gezeigten gaußförmigen Energieverteilung durchgeführt ist, und

Fig. 8

in (a) bis (d) verschiedene Varianten zur Ausgestaltung des Ausnehmungsbereichs.

Show it:

Fig.1

a schematic representation of a banknote with a combination motif according to the invention,

Fig. 2

for a combination motif in (a) and (b) the two security features watermarks and recess areas to be combined individually, (c) a cross section of the security paper in the area of the combination motif, (d) the appearance of the generated combination motif when viewed in reflected light and in (e) the appearance of the combination motif when viewed in transmitted light,

Fig. 3

in (a) to (e) a representation as in Fig. 2 for a combination motif according to another embodiment of the invention,

Fig. 4

for a further inventive combination motif in (a) and (b) the two security features to be combined watermark and recessed area individually, in (c) the appearance of the generated combination motif when viewed in reflected light and in (e) the appearance of the combination motif when viewed in transmitted light,

Fig. 5

in (a) to (e) a representation as in Fig. 2 for a combination motif according to a further embodiment of the invention,

Fig. 6

schematically the spatial energy distribution of a cutting laser beam and the resulting cutting widths at different paper thicknesses,

Fig. 7

the detail VII of Fig. 5 (d) in detail, wherein the laser cutting with a laser beam with the in Fig. 6 shown Gaussian energy distribution is performed, and

Fig. 8

in (a) to (d) different variants for the design of the recessed area.

The invention will now be explained using the example of a banknote. Fig. 1 shows a schematic representation of a banknote 10 with a combination motif 12 according to the invention, which is formed from a superimposition of a watermark 14 and a rastered recessed area 16. The watermark 14 represents as motif the value number "10", which is surrounded by the cloud-shaped or flower-shaped recessed area 16. The visual impression of the combination motif 12 changes markedly when changing between reflected-light and transmitted-light viewing, as explained in more detail below.

The combination motives according to the invention combine the advantageous properties of the long-known and proven watermarks with modern laser-cut laser-cut holes produced by laser cutting. Depending on the local paper thickness within the watermark, the laser radiation generates either continuous cut lines or only non-continuous dilution lines in the paper. As stated above, the term "recess" is an umbrella term for through-openings or cuts and for non-continuous dilutions of the paper, so that a cut-off line can be a cut line or a dilution line.

Due to the dependency of the cutting result on the paper thickness, the two security features watermark and laser cut interact and produce a complex combination motif, which offers the viewer a different visual impression in transmitted light than when viewed in reflected light. The visual effect of the combination motif 12 goes far beyond the effect of an ordinary watermark. The gridded recess area is also visually enhanced by the combination with the watermark motif. Overall, the security paper according to the invention is therefore visually attractive and easy to test for laymen for authenticity. In addition, the security paper is difficult to imitate for potential counterfeiters due to the need to reconcile two security features generated at different stages of papermaking.

As explained in more detail below, the mutual influence of the two security features allows a large variety of appearances of the combination motif in reflected light and transmitted light.

Regarding Fig. 2 show the FIGS. 2 (a) and (b) First, the two to be combined security features watermark 22 and recessed area 30 each individually. Fig. 2 (a) shows a view of the security paper 20, in which the value of value "10" of the banknote is introduced as a watermark 22 with an electrootype. How best in the cross section of Fig. 2 (c) To recognize, the range of the value number forms a thin spot 24 in the paper 20, in which the layer thickness dw compared to the layer thickness do of lying outside the thin spot 24 Velin region 26 is reduced.

Fig. 2 (b) schematically shows a plan view of the recess pattern of the recessed portion 30, which consists of a plurality of line-shaped parallel Recesses 32 is formed with the outline of a cloud. The recess lines 32 are shown in black in the figure, while the remaining unchanged at the subsequent laser cut areas 34 are shown in white. For ease of illustration, the embodiments will first be described in terms of parallel, straight recesses, even if, as discussed below with reference to FIG Fig. 8 explains that the Ausnehmungslinien can also be curved and / or diverging.

The line grid of the Ausnehmungslinien 32 has in the embodiment shown a period length of 0.75 mm at a cutting width of the cutting lines of 0.25 mm, but there are, depending on the desired design, other cutting widths and distances in question.

gilt.The depth of cut d _{A of} the recesses 32 is in the embodiment of Fig. 2 chosen so that 24 continuous cut lines 36 are generated during laser cutting in the region of the thin spot, but that in the thicker Velinbereich 26 no continuous cut lines, but only non-continuous dilution lines 38 are generated. Expressed mathematically, the depth of cut d _A is thus chosen such that $${\mathrm{<figure-callout\; id="0"\; label="d"\; filenames="imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{0}}>{\mathrm{d}}_{\mathrm{A}}\ge {\mathrm{d}}_{\mathrm{W}}$$

applies.

Then, the security paper 20 in the region of the watermark 22 in a laser cutting system according to the specification of the recess pattern of Fig. 2 (b) cut and thereby the recessed area 30 is superimposed on the watermark 22. As in Fig. 2 (c) 24, continuous cut lines 36 are produced in the region of the thin spot 24, non-continuous dilution lines 38 in the vellum region 26.

As a result of the superposition of the two security features, four different thickness ranges are created in the security paper 20. In the vellum region 26, the security paper 20 has thinning lines 38 with a remaining paper thickness dv = do-d _A. Outside the thinning lines 38, the paper thickness of the velin area is unchanged. The thin spot 24 has a paper thickness dw outside the cut lines 36; in the continuous cut lines 36, the remaining paper thickness is equal to zero.

The relative paper thicknesses and thus the brightnesses in the transmitted light can be set as desired by the depth of cut d _A and the thin layer thickness dw in many areas. In this case, depending on the design of the combination motif, the remaining paper thickness dv of the dilution lines 38 may be larger, equal to or smaller than the thin layer thickness dw.

For example, by dw = 0.2 do and d _A = 0.3 do a reliable cut of the cutting lines 36 in the thin section 24 can be ensured and at the same time the paper thickness dv of the dilution lines dv = 0.7 do is made significantly larger than the thin layer thickness dw become. The thinning lines 38 therefore appear darker in transmitted light than the thin spot 24, but lighter than the Velinbereich 26th

On the other hand, by choosing dw = 0.7 do and d _A = 0.8 do both a reliable cut of the cut lines 36 in the thin spot 24 can be ensured, and the paper thickness dv of the dilution lines dv = 0.2 do significantly smaller be made as the thin-layer thickness dw. The thinning lines 38 therefore appear brighter in transmitted light than the thin spot 24, which in turn appears lighter than the vellum region 26.

Finally, for example, by choosing dw = 0.4 do and d _A = 0.6 do again a reliable section of the cutting lines 36 in the thin section 24 can be ensured and at the same time the paper thickness dv of the dilution lines dv = 0.4 do equal to the thin layer thickness dw to get voted. The thinning lines 38 therefore appear in transmitted light with the same brightness as the thin spot 24 and both appear brighter than the vellum region 26.

When viewed in incident light, that is, in reflected light, the different paper thickness dv, dw or do, on the other hand, has practically no influence on the visual impression of the paper area. In incident light, the observer can thus only distinguish between the continuous cut lines 36, in which the background becomes visible, and the areas of paper not provided with continuous cut lines.

For illustration shows Fig. 2 (d) the appearance of the generated combination motif 12 when viewed in incident light, Fig. 2 (e) the appearance when viewed in transmitted light.

When viewed in incident light, only the continuous cut lines 36 are distinguished from their surroundings, as explained above and in FIG Fig. 2 (d) shown. As a result of the interaction of watermarks 22 and recess area 30, the sectional lines 36 with their outline reproduce the value "10", since continuous cut lines 36 were generated by the laser cut only in the region of the thin spot 24 and thus in the form of the value "10".

When viewed in transmitted light, the combination motif 12 shows a more complex appearance, in which not only the cutting lines 36 but also the thinned paper spots 24 and 38 stand out against the background of the vellum region 26, as in FIG Fig. 2 (e) shown. As explained above, the relative Brightness of the thin spot 24 and the dilution lines 38 can be set largely as desired, in the embodiment shown, the two brightnesses are selected to be about the same size.

The watermark can be formed within the scope of the invention not only by a thin point, but also by a thick spot 44 in the security paper, as described in the in Fig. 3 illustrated security paper 40 illustrated.

As with the representation of Fig. 2 show the FIGS. 3 (a) and (b) First, the two to be combined security features watermark 42 and recessed area 50 each individually. Fig. 3 (a) shows a plan view of a security paper 40 containing the value "10" in the form of a thick place 44. In the region of the thick point 44, the layer thickness dw of the paper is increased in relation to the layer thickness do of the velin region 46 lying outside the thick point 44, as is also the case in the cross-section of FIG Fig. 3 (c) shown.

gilt.This in Fig. 3 (b) shown recess pattern of the recessed area 50 is as in Fig. 2 (b) formed in the form of a cloud of a plurality of linear parallel recesses 52. The depth of cut d _{A of} the recess lines 52 is selected such that continuous cutting lines 56 are produced during laser cutting in the velin area, but that in the area of the thick area 44 no continuous cutting lines but only non-continuous dilution lines 58 are produced. Expressed mathematically in the embodiment of the Fig. 3 Thus, the depth of cut d _A chosen so that $${\mathrm{d}}_{\mathrm{W}}>{\mathrm{d}}_{\mathrm{A}}\ge {\mathrm{<figure-callout\; id="0"\; label="d"\; filenames="imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{0}}$$

applies.

Is the security paper 40 in the area of the watermark 42 now in a laser cutting system according to the specification of the recess pattern of Fig. 3 (b) cut, the recessed area 50 is superimposed on the watermark 42. In the vellum region 46, continuous cutting lines 56 are produced by the laser cutting, and non-continuous dilution lines 58 in the area of the thick section 44, as in FIG Fig. 3 (c) shown.

Overall, the overlapping of the two security features results in four different thickness ranges in the security paper 40. In the vellum region 46, the security paper 40 has cut lines 56 with a remaining paper thickness of zero, outside the cut lines 56 the paper thickness of the vellum region is unchanged. Thickness 44 contains thinning lines 58 of a remaining paper thickness dv = dw-d _A , outside of thinning lines 58 the paper thickness is dw. Again, the relative paper thicknesses and thus the brightness of thick spot and dilution lines in the transmitted light through the depth of cut d _A and the thick layer thickness dw can be specified as desired.

For illustration shows Fig. 3 (d) the appearance of the generated combination motif when viewed in reflected light, Fig. 3 (e) the appearance when viewed in transmitted light.

When viewed in incident light, here too only the continuous cut lines 56 cancel out from their surroundings, as in FIG Fig. 3 (d) shown. As a result of the interaction of the thick area 44 with the recess area 50, the sectional lines 56 with their outer contour reproduce the cloud shape of the recess area 50 and contain in their interior a region 44 in the form of the value "10" in which dilution lines 58 but no continuous cut lines are present , Since the dilution lines 58 and the thick point 44 in incident light are practically indistinguishable from the vellum area, this results in Fig. 3 (d) illustrated appearance.

When viewed in transmitted light, the combination motif 12 shows a more complex appearance, in which, against the background of the velin area 46, the thinning lines 58 as brightening and the thickened area 44 additionally become visible as darkening, as in FIG Fig. 3 (e) illustrated.

Another embodiment of the invention is in Fig. 4 shown, wherein the FIGS. 4 (a) and (b) again show the two to be combined security features watermark 62 and recess 70 individually. Fig. 4 (a) shows a plan view of the security paper 60, the watermarks 62 a dark font, here the letter sequence "PL" in the form of thickened paper areas 64 contains. As in the embodiment of Fig. 3 the layer thickness in the area of the thick places 64 is increased compared to the layer thickness of the vellum area 66 lying outside the thick places 64.

This in Fig. 4 (b) The recess pattern 70 of the recessed area shown is again formed by a plurality of line-shaped parallel recesses 72 having the outer contour of a cloud. In its interior, the recessed area 70 also contains the value "10" as a recessed area-free areas. As in the embodiment of Fig. 3 the depth of cut of the recess lines 72 is selected such that continuous cutting lines 76 are produced during laser cutting in the velin area 66, but that in the region of the thick places 64 no continuous cutting lines but only thinning lines 78 are produced. The resulting appearance of the combination motif when viewed in reflected light is in Fig. 4 (c) , the appearance when viewed in transmitted light in Fig. 4 (d) shown.

The emergence of the two appearances results from the interaction of the different paper thicknesses as already at Fig. 3 explained.

Fig. 5 shows a further embodiment of the invention, in which the in Fig. 3 (b) shown recess area 50 is not combined with a two-stage, but with a multi-level watermark 82.

Fig. 5 (a) shows a top view of a security paper 80 with the multi-level watermark 82, wherein the watermark 82 in the exemplary embodiment has a virtually continuous thickness variation and the layer thickness between a minimum layer thickness d _{W, min} and a maximum layer thickness d _{W, max} varies. In practice, the watermark 82 is usually a portrait, an architectural, technical or nature motif.

Instead of having a virtually continuous variation in thickness, the watermark may also be designed to be visibly stepped and have only a few discrete paper thicknesses. The watermark 82 may include only thinned areas, thickened areas only, or, as in the illustrated embodiment, both areas 84 thinned with respect to the surrounding vellum area 86 and thickened areas 88.

so dass in den dünneren Teilbereichen des Wasserzeichens 82 beim Laserschneiden Schnittlinien 96 erzeugt werden, während in den dickeren Teilbereichen Verdünnungslinien 98 erzeugt werden, wie in Fig. 5(c) gezeigt.The in Fig. 5 (b) shown recess area 90 corresponds in shape to the recessed area 50 of Fig. 3 (b) , However, the depth of cut d _{A of} the recess lines 92 is chosen between d _{W, min} and d _{W, max} . $$\mathrm{dw}.\mathrm{Max}>{\mathrm{d}}_{\mathrm{A}}>{\mathrm{d}}_{\mathrm{W}.\min }.$$

so that in the thinner portions of the watermark 82 during laser cutting cut lines 96 are generated, while in the thicker portions dilution lines 98 are generated, as in Fig. 5 (c) shown.

Fig. 5 (d) shows the appearance of the generated combination motif when viewed in reflected light, Fig. 5 (e) the appearance when viewed in transmitted light. When viewed in incident light, a relatively simple visual appearance is shown, since only the continuous cut lines 96 stand out from their surroundings and neither the watermark 82 itself nor the dilution lines 98 are visible. However, the paper thickness distribution in the watermark 82 determines in which parts of the watermark intersection lines 96 are generated at all so that the interaction of the two security features is already evident in reflected light.

When viewed in transmitted light, the full complexity of the combination motif becomes visible. Both the multilevel watermark 82 with its different brightness levels appears as well as the dilution lines 98 with their different sized paper thicknesses (FIG. Fig. 5 (c) ) and their thus also different brightnesses.

$$\mathrm{E}(\mathrm{x},\mathrm{y}=\mathrm{0}\mathrm{sonst}$$

eingesetzt wird. Mit einer solchen Energieverteilung ist die Breite der Ausnehmungslinien praktisch unabhängig von der lokalen Papierdicke. Allerdings ist bei Ausnehmungslinien, die nicht parallel zu einer der Achsen der Energieverteilung sind, die Zeitdauer, die der Laserstrahl auf das Papier einwirken kann, und damit auch das Schnitt- bzw. das Abtragungsergebnis abhängig vom Ort des Papiers innerhalb der Energieverteilung.The embodiments described so far assume that during laser cutting a laser beam with a cuboidal energy distribution $$\mathrm{e}\left(\mathrm{x}\mathrm{y}\right)={\mathrm{<figure-callout\; id="0"\; label="e"\; filenames="imgf0004.png"\; state="\{\{state\}\}">e</figure-callout>}}_{\mathrm{0}}.\mathrm{f}\ddot{\mathrm{u}}\mathrm{r}-{\mathrm{x}}_{\mathrm{0}}\le \mathrm{x}\le {\mathrm{x}}_{\mathrm{0}}\mathrm{and}-{\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="imgf0004.png"\; state="\{\{state\}\}">y</figure-callout>}}_{\mathrm{0}}\le \mathrm{y}\le {\mathrm{y}}_{\mathrm{0}}$$

$$\mathrm{e}(\mathrm{x}.\mathrm{y}=\mathrm{0}\mathrm{otherwise}$$

is used. With such an energy distribution, the width of the recess lines is practically independent of the local paper thickness. However, with recess lines that are not parallel to one of the axes of energy distribution, the length of time that the laser beam strikes the paper can affect, and thus the cutting or Abtragungsergebnis depending on the location of the paper within the energy distribution.

It may therefore be advisable in some variants of the invention to use a cutting laser with a torus or donut-shaped energy distribution, in which the cut or the removal result in any direction of the Ausnehmungslinien has only a small dependence on the location within the energy distribution.

Cuboid or donut-shaped energy distributions of the cutting laser beam can be generated by suitable optical elements, for example by means of diffractive optical elements.

Conversely, it may also be advisable to use energy distributions with a particularly strong dependence of the cut or ablation result on the location of the paper within the energy distribution, such as in Fig. 6 The use of a cutting laser with a Gaussian energy distribution results in a dependence of the width of the generated cut-off lines on the local paper thickness such that the width of the cut or thinning lines is smaller the larger the local paper thickness. For example, with a large paper thickness, the laser energy W is sufficient only in a narrow cutting area 102 in order to completely cut through the paper, while at a location with a smaller paper thickness the laser energy in a wider cutting area 104 exceeds the cutting threshold.

This effect can be specifically exploited to provide a watermark with locally different paper thicknesses with recess lines of varying width. For illustration shows Fig. 7 the detail VII of FIG. 5 (d) in detail, wherein the laser cutting in contrast to the embodiment of Fig. 5 at Fig. 7 with a laser beam with Gaussian energy distribution 100 takes place. This results in cutting lines 96 which have a larger cutting width 104 in the thinner paper areas and a smaller cutting width 102 in the thicker paper areas. With a continuous change in the paper thickness, the width of the cutting lines 96 changes continuously, as in Fig. 7 shown.

The recess lines 112 of the recess portion 110 need not be straight and parallel, as in the previous embodiments and in Fig. 8 (a) shown. Rather, the recess area 110 may, for example, also contain straight and diverging recess lines 114, as in FIG Fig. 8 (b) shown, or curved, equidistant Ausnehmungslinien 116, as in Fig. 8 (c) represented or curved, diverging Ausnehmungslinien 118, as in Fig. 8 (d) shown.

It is understood that the embodiments shown can be combined with each other as desired. For example, the diverging and / or curved cut-off lines of the FIGS. 8 (b) to (d) can be combined with any of the described types of watermarks with thinned or thick spots, or they can be produced with a paper thickness dependent cut width. Also, the recess lines of all embodiments can be provided with a laser-modified edge region, as generally described above.

Claims (18)

1. A security paper for manufacturing security and value documents, having a watermark that forms a first motif, characterized in that the watermark is superimposed by a recess region that forms a second motif and that is formed from at least one line-shaped recess that is produced in the security paper by the action of laser radiation, such that the superimposition of the watermark and the recess region forms, from the first and second motif, a combination motif that has a visual impression that is modified in transmitted light compared with reflected light.
2. The security paper according to claim 1, characterized in that the watermark comprises a thin site having a paper thickness that is reduced compared with the surroundings.
3. The security paper according to claim 1 or 2, characterized in that the watermark comprises a thick site having a paper thickness that is increased compared with the surroundings.
4. The security paper according to at least one of claims 1 to 3, characterized in that the watermark is formed to be bi- or multi-level.
5. The security paper according to at least one of claims 1 to 4, characterized in that the first motif of the watermark constitutes a portrait, an architectural, technical or nature motif, or an alphanumeric character string, especially a value numeral.
6. The security paper according to at least one of claims 1 to 5, characterized in that the first and second motif constitute pieces of information that are related to or that complement each other.
7. The security paper according to at least one of claims 1 to 6, characterized in that the recess region is formed from a plurality of line-shaped recesses in the security paper.
8. The security paper according to at least one of claims 1 to 7, characterized in that the line-shaped recesses comprise through cutting lines.
9. The security paper according to at least one of claims 1 to 8, characterized in that the line-shaped recesses comprise non-through thinning lines in the security paper.
10. The security paper according to at least one of claims 1 to 9, characterized in that the line-shaped recesses comprise cutting lines and thinning lines that connect to each other without offset.
11. The security paper according to at least one of claims 1 to 10, characterized in that the recess region is arranged completely within the watermark.
12. The security paper according to at least one of claims 1 to 11, characterized in that the recess region is formed by a plurality of straight, parallel or divergent line-shaped recesses.
13. The security paper according to at least one of claims 1 to 11, characterized in that the recess region is formed by a plurality of curved, equidistant or divergent line-shaped recesses.
14. The security paper according to at least one of claims 1 to 13, characterized in that the line-shaped recesses have a width between 0.05 mm and 1 mm, especially between 0.1 mm and 0.4 mm.
15. The security paper according to at least one of claims 1 to 14, characterized in that the security paper is provided at least in a sub-region with a laser-modifiable marking substance, and in that the line-shaped recesses in said sub-region comprise an edge region that is modified by the action of laser radiation, preferably in that the security paper is provided in the sub-region with a marking substance whose visible color is modifiable by the action of the laser radiation, and in that the line-shaped recesses in said sub-region comprise a colored edge region.
16. A method for manufacturing a security paper according to one of claims 1 to 15, in which a security paper having a watermark that forms a first motif is provided, and the watermark is superimposed by a recess region that forms a second motif and that is formed from in the security paper, plurality of line-shaped recesses that are produced in the security paper by the action of laser radiation, such that the superimposition of the watermark and the recess region forms, from the first and second motif, a combination motif that has a visual impression that is modified in transmitted light compared with reflected light.
17. The method according to claim 16, characterized in that the line-shaped recesses are produced by laser impingement with an infrared laser, preferably with a CO₂ laser.
18. The method according to claim 16 or 17, characterized in that the security paper is provided at least in a sub-region with a laser-modifiable marking substance such that, in said sub-region, the line-shaped recesses are modified in their edge region by the action of the laser radiation, preferably in that the security paper is provided in the sub-region with a marking substance whose visible color is modifiable by the action of the laser radiation, and in that, in said sub-region, the line-shaped recesses are provided with a colored edge region by the action of the laser radiation.

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