Security element with identification marks

ES 2 582 010 T3

DESCRIPTION

Security element with individual marking

The invention relates to a security element having an individualized marking for the protection of valuables. The invention also relates to a data carrier with said security element and to a method of manufacturing said security element.

Data carriers, such as valuable documents or identification documents, as well as other valuable objects, such as, for example, branded items, are normally provided with security elements for their protection, allowing said elements to verify the authenticity of the data carrier and, at the same time, serve as protection against its unauthorized reproduction.

Security features with viewing angle-dependent effects play an important role in protecting authenticity, as they cannot be reproduced, not even with the most modern photocopiers. For this, the security elements are provided with, for example, optically variable elements, which provide the observer with a different printed image when observing said elements under different viewing angles, showing, depending on the viewing angle, for example, another color. or glitter and / or other graphic element.

Document WO 01/59745 A1 discloses a security element, according to the preamble of claim 1.

Starting from the foregoing, the present invention aims to provide a security element of the type mentioned above that provides highly effective protection against counterfeiting and an attractive visual appearance, the authenticity of which can be easily and ideally checked even by inexperienced persons.

This object is solved by the features of the independent claims. The dependent claims are intended to further embodiments of the invention. The term "fixed color printed image" designates a color printed image that does not change with the angle of view. Conventional color printed images generally comprise a fixed color printed image. In contrast to these, color printed images change with angle of view, for example by changing color in an optically variable layer. Such a color printed image that changes with angle of view is called, for the purposes of this description, a "variable color printed image". The term "variable color printed image" includes, for the purposes of the present invention, each of the printed images that are perceptible by an observer and that change with the angle of view. In addition to the effect of color change referred to above, said "variable color printed image" can also be, for example, by a change in brightness or contrast as a function of the angle of view perceptible by an observer.

In accordance with the present invention, the first section of the individualized marking is observed by an observer under a first viewing angle with the same printed image as the effect layer, the printed image disappearing when said angle changes. Under the first viewing angle, however, the second section of the individualized marking is recognizable, showing a different fixed color printed image and thus contrasting the effect layer. Under other viewing angles, the first section of the individualized marking can also be recognized, since then its fixed color printed image no longer corresponds to the printed image, due to the change of the variable printed image of the effect layer. . The first determined viewing angle may, for example, correspond to a vertical view of the security element. It should be understood that the principle of the invention continues to exist when the effect layer and a section, under a certain viewing angle, do not have exactly the same color printed image but, for the observer, the color printed image of the layer effect and section are apparently the same, although the color printed image of section and effect layer are only substantially the same. Therefore, according to the concept of the invention, it is ultimately decisive that the observer perceives the color printed image of a certain section and the color printed image of an effect layer as the same image, there being no exact match requirement. in terms of a definition of a particular color space. As far as the present application is concerned, the concepts of "the same" or "identical" color printed image of two sections of the security element therefore include also color printed images of two sections that are substantially the same.

Furthermore, it is to be understood that the security element, according to the invention has a plurality of zones in which are present an optically variable effect layer according to the invention and an optically non-variable color layer, according to the invention, with at least two sections, having a first and second fixed color printed image. For example, a security element may be provided having, in a first zone, a first optically variable effect layer and an optically non-variable color layer, having a first and a second section, in which the first section provides a first fixed color printed image and the second section

ES 2 582 010 T3 provides a second fixed color printed image. A second optically variable effect layer is arranged in a second section of this security element, which is combined with an additional optically variable color layer with two sections and two fixed color printed images, the color printed image of which may be different. the first and second optically variable effect layers, as well as said respective sections. Furthermore, the first and second optically variable effect layers and said sections may have different structures, according to the invention.

The sections of the color layer and the effect layer are associated with each other in such a way that the variable color printed image of the effect layer under a determined second viewing angle corresponds to the second fixed color printed image. The second determined viewing angle may correspond, for example, to an oblique view of the security element. In this case, the second section of the individualized marking is only recognizable when viewed vertically, while when viewed obliquely only the first section of the individualized marking is recognizable. The respective other section remains hidden from the viewer due to the color match with the effect layer.

The effect layer is essentially transparent. In a variant, an opaque laser-sensitive intermediate layer is arranged between the effect layer and the color layer, and the individual marking is formed by voids or transparent local transformations of the intermediate layer, which are generated respectively by the action of laser radiation. In the areas where the laser radiation does not act, the effect layer is present, then, in front of the opaque background of the intermediate layer, while in the areas where it acts, through the voids or the transparent transformation zones they release locally, respectively, the color layer disposed below the effect layer and the intermediate layer being visible.

In the variant described above it is to be understood that a substantially transparent effect layer and an opaque laser-sensitive intermediate layer, between said effect layer and a colored layer, is basically also an effect layer that does not absorb laser radiation and is semi-transparent or even opaque. As described above, the intermediate layer is made by means of local transparent recesses or transformations, so that the application of laser radiation provides, at the same time, according to the invention, a color-changing effect to the interesting observer.

The optically variable appearance of the effect layer is especially attractive when the opaque interlayer is dark, especially black. The interlayer may contain, for example, an infrared (IR) absorber in a transparent binder, such as CIPB1.7 carbon black or graphite, to be ablated with infrared laser laser application. Other types of materials suitable for the laser-sensitive opaque interlayer, in particular selectable materials for the absorbent components in compositions, can be taken from the publications WO 2005/108110 A1, DE 10 2008 049 512 A1 and DE 10 2006 008 247 , the descriptions of which are incorporated with respect to the present description.

The effect layer is configured substantially transparent and, in a variant, the color layer itself includes at least one laser-sensitive color composition, as described, for example, in the aforementioned documents DE 10 2008 049 512 A1, DE 10 2006 008 247 and WO 2005/108110. The individualized marking is, in this configuration, formed by local color changes in the laser-sensitive color composition, which are generated by the action of laser radiation. For example, the color composition may contain first and second colored pigments, in which the second colored pigments are present in a plurality of core-shell particles, the shells of which are surrounded by an ablation-promoting functional layer, as described above. described in DE 10 2008 049 512 A1. Then, through laser application, the second colored pigments can be removed from the color composition, so that the color printed image in the marked areas is only effected by the first pigments. To produce different fixed color printed images, different first colored pigments can be provided in different sections of the color layer, or the color composition can contain multiple colored pigments, removable at different laser intensities.

In a preferred embodiment of the invention, the color layer exhibits a gradation between the first and second fixed color printed image. Such a gradation can be produced, for example, by a plurality of color elements having different colors. In a particularly suitable configuration, gradation occurs, however, by a plurality of first and second color elements arranged next to each other, where each plurality of first or second color elements shows, respectively, the first or second fixed color printed image, and they vary spatially in their respective area ratios to produce a nearly continuous gradation from the first to the second color printed image. The first and second color elements can be, in particular, color stripes or hatch dots, arranged next to each other.

ES 2 582 010 T3

Of course, in principle it can also be envisaged that, for an optically non-variable color layer, for example, a color gradation is obtained with three color printed images, between the first and the second color printed image, as well as between the second and third color printed image, generating a color gradation between each of the fixed color printed images, being obtained by means of the procedure described above. At present, however, the above-described embodiments with color grading between the first and second fixed color printed image of a color layer with two sections are particularly preferable, due to their ease of manufacture and for the better visual impression. which causes the resulting color change effect on the observer.

Additionally, an embodiment can be envisaged in which the optically non-variable color layer has an additional security feature, such as, for example, a microtext, which can be used, for example, in the area of ​​individualized marking as a authenticity feature.

Additionally, an effect layer can be envisioned to have an optically variable diffraction structure, showing the printed image in variable color, according to the present invention, due to its specific diffraction structures.

In all configurations, the color layer and / or effect layer may contain a characteristic substance, in particular a magnetic, electrically conductive, luminescent or infrared radiation absorbing substance. In case an intermediate layer is provided, it may contain such a characteristic substance.

The optically variable effect layer preferably contains one or more layers of interference pigments or cholesteric liquid crystal pigments.

Such interference pigments have, like the two-dimensional layer structures usable in the context of this invention, optically effective interference layers. Such interference layers typically have a thin-layer structure and include, for example, in the case of a thin-layer multilayer structure, a reflection layer, an absorbent layer, and one or more separating intervening dielectric layers, based, for example, on in mica, SO2 or Al2Ü3. Said interference layers correspond to the number of dielectric layers, being designated as single or multiple layers. Printing inks with interference layer pigments, eg under the brand name Iriodin® (single layer) or Colorcrypt® (multi-layer) are sold by Merck KGaA. Printing inks with multilayer interference pigments are also marketed, for example, under the trademark OVI®, from the company SICPA.

Effect layers with holographic pigments, or pigments with a constant diffraction structure, are also contemplated. Holographic pigments can be prepared, in particular, by grinding holographic foils. It can be done both in transparent and opaque form.

In a further development, individualized marking continues outside the coating zone, in particular by local transformation to a standard color or local transformation, such as, for example, by foaming or blackening of a substrate. The marking or the security element can be integrated into the design of the data carrier where the security element is applied. Such an extension of the marking in the contour region of the data carrier is particularly suitable if, according to the invention, the security element is subsequently individualized. In general, the individual marking can extend outside the coating area in such a way that a part of the individual marking is already arranged outside the coating area. Typically, however, the continuation of such an extension of the individualized marking entails problems of manufacturing tolerances, so that the embodiment described above with the extension of the individualized marking in the contour area by subsequent individualization is especially preferred.

Advantageously, according to the invention, the individualized marking can be carried out in the form of a raster, and preferably represents a grayscale image in a raster form or a color halftone image in a raster form.

The color layer and the effect layer can be, at least in the coating area, covered with a lacquer layer, which compensates for a different matte or gloss effect in the area of ​​the individual marking. In this way, it is possible to achieve that parts of the individualized marking can be recognizable due to the differentiated effect of matte, or gloss, and that, otherwise, due to its color coincidence with the effect layer under a certain viewing angle , they could be practically unseen.

It can even be achieved that, by means of certain additives in the optically non-variable color layer, parts of the individualized marking can nevertheless be recognizable by the observer under certain lighting and observation conditions, and that, otherwise, due to their coincidence of color with the effect layer under a certain angle of view,

ES 2 582 010 T3 could be practically unseen. These additives can be, for example, silver pigments, which give the optically non-variable color layer a bright color printed image, which closely approximates the printed image of the optically variable effect layer arranged thereon, for example, with also optically variable bright pigments. In other words, the visual perception by the observer of the observed areas, due to the brightness, or to the luminous flash, is deviated from the possible presence of minor deviations existing in the images printed in color, so that the images printed in color of these areas, as they are subjectively perceived, by the observer are the same.

The individualized marking sections of the first and second color image preferably represent information that is complementary to each other or relative to each other. For example, the information in the first section may reproduce that in the second section or serve as a supplement to general information.

Advantageously, the security element comprises a substrate on which the color layer, an optionally provided intermediate layer, and the effect layer are arranged, in this order. Any suitable type of paper can be used as the substrate material, in particular cotton paper or paper containing a polymeric material in a proportion x in the range of 0 <x <100% by weight. Additionally, the substrate material can also be a plastic sheet, such as a polyester sheet. Said sheet can be unidirectionally or bidirectionally stretched. The stretching of the sheet, among other properties, allows obtaining polarization properties, which can be used as an additional security feature. The substrate is preferably opaque, since the security element, according to the invention, is arranged for monitoring when viewed. Of course, a transparent or translucent substrate can also be used, for example, when the non-variable color layer is made opaque, or the security element is placed on a reflective background, in particular on a white background. Said transparent or translucent substrate can also be a plastic film, which is arranged in the region of a window-like perforation on a data carrier. At present, however, opaque or substantially opaque substrate materials are preferred for the security element, since thus the security element according to the invention, due, for example, to its higher color saturation, is generally more attractive to the observer.

The invention also includes a data carrier with a security element of the type described. The data carrier can be, in particular, a document of value, such as a banknote, in particular a paper banknote, a polymer banknote or a banknote formed by a foil, or even also a card identification card, such as a credit card, bank card, cash card, authorization card or pass, identity card or card, or personalized passport page.

The individualization of the marking can advantageously be carried out by continuing its extension on the data carrier. This can be done, for example, by foaming or blackening of the substrate of the data carrier, or by transformation of one of the layers present on the data carrier, such as, for example, by local transformation of a layer of color or the removal of metal from a metal layer. By subsequent individualization by means of laser application, this continuation can be carried out with a narrow tolerance margin.

The invention further relates to a method of manufacturing a security element, according to any one of claims 1 to 7.

The individualized marking is preferably formed by application of laser radiation, in particular with an infrared laser, such as a CO2 laser, Nd: YAG laser or Nd: YVO4 laser. The individualization advantageously occurs in a separate manufacturing step after the sequencing of the substrate layers, the color layer and the effect layer.

Laser individualization allows a subsequent obtaining of the security element, so that the individualized information does not necessarily have to be known at the time of manufacture. On the contrary, said realization can be carried out on a certain document of value later, for example, during the use of the security element. For this, by way of example, the serial number of a banknote can be detected by a reader and subsequently the detected serial number written as individual marking on the security element. Even with subsequent individualisation, the individualized marking of the security element can also be carried out with a narrow tolerance margin in a contour area of ​​the security element, and thus further improve the protection against counterfeiting of the security element system / data carrier.

Preferably, the color layer and / or the effect layer is applied by a printing process. Most preferably, both layers are printed. The effect layer can be printed, in principle, by any conventional printing process, such as screen printing, flexography, intaglio and intaglio. Without

However, at present a screen printing or flexo printing is preferable. Furthermore, the intaglio printed image process is particularly advantageous, in particular, for substrates based on plastic foil with and without a print preparation layer.

The various sections of the optically non-variable color layer can also be applied, in principle, with almost all the most common printing procedures. However, preferably the offset printing method is used, in which the application of the color layer is done in wet offset or dry offset, more preferably relief printing can be done indirectly. Advantageously, the indirect relief printing process for the color layer and the flexographic printing process for the effect layer are applied in a printing process that includes, for example, three successive printing steps (two printing steps of the color layer, a printing step of the effect layer).

If an opaque laser-sensitive intermediate layer is provided, printing also brings advantages, the aforementioned printing methods can be used for this. It is therefore particularly advantageous if all the layers of the set of layers are printed, while the individual marking is carried out by laser application.

In addition, it can be envisaged, in principle when the color layer and / or the effect layer have an inadequate opacity on a substrate, that an opaque white layer is applied in certain areas and, subsequently, the color layer is arranged , where appropriate, the intermediate layer and, over them, the effect layer. Such an opaque white layer can be applied by known printing methods, with relatively narrow tolerances, on the substrate, resulting in a security element prepared with high saturation in the opaque white area.

In a preferred embodiment, the security element is produced, according to the invention, with the layers and individualized marking on a foil, in particular a plastic foil, and said security element thus produced is applied in the form of foil strip or foil patch on the substrate of the invention by hot or cold stamping (hot or cold foil transfer processes). Naturally, it can also be envisaged that, by a suitable process, the layers, according to the invention, are produced on an intermediate support and only the sheets, according to the invention, are transferred to the substrate of the invention.

In a further alternative embodiment, it is further envisaged that the optically non-variable color layer is arranged on a substrate of the invention and that, by means of a suitable transfer method to form the security element, according to the invention, the optically variable effect layer is transferred to the color layer. Hot or cold foil transfer processes, as well as similar techniques, can be used as the transfer method.

It should be understood that, in the transfer procedure described above, if necessary, an intermediate layer arranged between the color layer layer and the effect layer can be incorporated, whether it is transferred together with the entire security element to the substrate of the invention as if arranged together with the effect layer on top of the color layer.

Furthermore, it should be mentioned that the optically non-variable color layer can include an additive that promotes the generation of individualized marking by ablation, in particular by laser ablation, in which, by means of electromagnetic radiation, in particular, the laser radiation, a separation layer of the effect layer is formed. Said additive can be constituted, for example, by low melting point waxes, especially carnauba waxes.

In a corresponding manner, the effect ink may contain an additive which, advantageously, by producing the individualized marking by ablation, in particular by laser ablation, makes it possible to reduce the bonding forces to the optically non-variable color layer. Low-melting waxes, especially carnauba waxes, can also be used with the effect ink additive.

Of course, it can also be envisaged that the optically non-variable color layer and the effect layer all contain an ablation-promoting additive, as described above.

Other embodiments and advantages of the invention are explained below, by way of example, with reference to the figures, in which a representation to scale and proportion has been omitted to improve clarity.

It shows:

ES 2 582 010 T3

Figure 1, a schematic representation of a banknote with a security element, according to the invention, Figure 2, the visual appearance of the security element of Figure 1, at (a) when viewed vertically and at ( b) when viewed obliquely, figure 3, in (a) and (b), respectively, a schematic cross section of the security element of figure 2, illustrating the layer structure and how the change of digit information is effected, Figures 4 to 7, various advantageous modifications of the security element of figure 3, figure 8, a schematic top view of a security element, according to another embodiment of the invention, figure 9, a color gradation for use in the security element of Figure 8, and Figure 10, a cross section of the security element of Figure 8 through the line XX.

The invention is described below through the example of security elements for banknotes. Figure 1 shows a schematic representation of a banknote -10- with a security element -12-, according to the invention. The security element -12- shows an optically variable appearance and, moreover, is provided with an individualized marking -14- corresponding to the banknote, the individualized marking of which is only recognizable in a section depending on a respective viewing angle.

The individualized marking -14- can be, for example, the serial number or a repetition of the denomination -15- of the banknote. In the exemplary embodiment, for the sake of simplicity, the individualized dial -14- is made up of the digits 3456.

As an illustration that the individualized marking -14- is only recognizable in sections under different viewing angles, figure 2 shows, in (a), the visual appearance of the security element -12- when viewed vertically and, in ( b), when viewed obliquely at an angle of, for example, about 45 °.

The individualized marking -14- contains two sections -16-, -18-, each having a different fixed color printed image. As explained above, the expression fixed color printed image designates a color printed image that does not change with the angle of view, whereas if a printed image changes with the angle of view, it is called a color printed image. variable. The term "variable color printed image" also includes, for example, changes in brightness or contrast.

The individualized marking -14- has, in its first section -16-, a printed image in green fixed color, which is formed by the digits 34, and, in its second section -18-, a printed image in magenta color, which is formed with the digits 56.

The contour area -20- of the individualized marking -14- does not show a fixed color printed image, but has a color change effect with a variable color printed image, which, in the exemplary embodiment, changes magenta, when viewed vertically, to green, when viewed obliquely.

In Figure 2 (a), according to a vertical viewing angle, the magenta color printed image of section -18- and the magenta variable color printed image of contour area -20- coincide, while section - 16- presents a defined contrast with the contour area -20- due to its green fixed color printed image. Therefore, an observer looking vertically at the security element, sees only the digits 34 of section -16- in green on a uniform magenta background -18-, -20 In figure 2 (b), according to a viewing angle of 45 °, the green color printed image of section -16- and the green variable color printed image of the contour area -20- coincide, while in this case section -18- presents a defined contrast with the area contour -20- by its image printed in fixed color magenta. Therefore, an observer viewing the security feature obliquely sees only the digits 56 of section -18- in magenta on a uniform green background -16-, -20 When the security feature -12 is tilted back and forth -, the observer sees a change of information of the digits 34 and 56 of the sections, thus allowing an easy verification of the authenticity, even by inexperienced persons. The observer, by tilting the security element -12- rapidly backwards and forwards

ES 2 582 010 T3 in front, visually perceives the complete individualized marking 3456, due to the effect of persistence of human vision and gradual color change by color change.

The layer structure of the security element -12- and the visual perception of the change of digit information is explained in more detail below, with reference to figure 3.

Figure 3 (a) schematically shows a cross section of the security element -12- in the area of ​​the individualized marking -14-. The security element -12- comprises a substrate -30-, which can be formed, for example, by a sheet, as well as by banknote paper from the banknote itself -10-. First, on the substrate -30- an optically non-variable color layer -32- is printed, which contains a first section -34- with the first image printed in a fixed color magenta, and a second section -36- with the first image printed in solid green color.

On the color layer -32- a laser-sensitive black intermediate layer -38- is printed and, on the intermediate layer -38-, a transparent optically variable effect layer -40, which provides the desired color change effect , from magenta, when viewed vertically, to green, when viewed obliquely, on the background of the black interlayer -38-.

After the preparation of said sequence of layers, the sections -16-, -18- of the individualized marking -14-, the intermediate layer -38- black and the effect layer -40- are treated locally by ablation with laser application , thus providing the security element -12- with its individualized character.

Figure 3 (a) shows a laser ablation of the layers -38-, -40-, however, it is also possible by laser application to volatilize parts of the layer or apply in the same transformations, making them transparent or colored different.

Once individualized by laser application, the color printed image is seen perpendicularly -42- in the exposed sections -16-, -18-, through the corresponding color printed image of the sections -34-, -36 - of the color layer -32-, thus resulting in the green color printed image (G), in section -16-, and the magenta color printed image (M), in section -18-. In the contour area -20-, the optically variable effect layer -40- is shown on the background of the black intermediate layer -38- when the magenta (M) printed image is viewed vertically, thus resulting in When the entire assembly is viewed perpendicularly, the printed image shown in Figure 2 (a) is visible.

Figure 3 (b) illustrates the generation of the color printed image when viewed obliquely -44-. The color printed image does not change in the exposed sections -16-, -18-, as seen through the corresponding fixed color printed image of the sections -34-, -36- of the color layer -32 -, thereby resulting in the printed image in green (G) in section -16- and the printed image in magenta (M) in section -18-. In the contour area -20-, the optically variable effect layer is shown on the background of the black intermediate layer -38- when the green (G) printed image is viewed obliquely, thus resulting in that, when viewed obliquely as a whole, the printed image shown in Figure 2 (b) appears.

A particular advantage of the security element, according to the invention, is that the colored layer -32-, the intermediate layer -38- and the effect layer -40-, on the one hand, can all be applied by means of a printing, thus being able to be manufactured easily and at low cost, and, on the other hand, it is possible to individualize the security element through the subsequent application of laser. In this way, the information present with the individualized marking may not be known yet at the time of its manufacture, and may not be produced until the security element is to be used.

Figures 4 to 7 show various advantageous modifications of the security element of Figure 3.

The security element -12- of the embodiment of figure 4 corresponds substantially to the security element of figure 3, except that the black intermediate layer -38- is not removed in the individualized marking sections -16 -, -18- by laser application, but simply a transparent transformation -46- is carried out. The effect layer 40 can be treated in this variant by ablation with the application of laser radiation, as shown in FIG. 3, or it can also be left untreated, as shown in FIG. 4. The latter is particularly appropriate when the color printed images of the sections -34-, -36- of the color layer are relatively luminous, since the optically variable effect layer -40- allows the background light to be perceptible in individual marking sections -16-, -18- before it fades. It is also conceived that the effect layer -40- has a modified shape in an area above the individualized marking sections -16-, -18-.

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Figure 5 shows another embodiment of the invention, in which the security element -12- comprises an optically variable opaque effect layer -48-. Such opaque effect layers can be produced, for example, by color printing inks with multilayer interference pigments, such as, for example, those sold under the trademark OVI®, ex SICPA. The individualized marking -14- is formed in this case by the recesses -16-, -18- or, alternatively, by transparent local transformations, produced by applying laser radiation on the effect layer -48-.

In the exemplary embodiment of FIG. 6, the color layer -50- is formed by a laser-sensitive color composition, by means of which, by the action of laser radiation, a part of color can be removed. Such color compositions may contain, for example, first colored pigments and laser sensitive core-shell particles, which contain a second colored pigment, and where the core-shell particles are provided with an ablation-promoting functional layer. Then, in the zone not exposed to the laser -20-, both colored pigments are present and together they constitute a dark background of an optically variable transparent effect layer -40-. In the zone exposed to the laser -16-, the core-cortex particles sensitive to the laser are removed with the second colored pigments of the color layer -50-, so that the color printed image is determined, in said exposed zone , just because of the first colored pigment.

In the second zone exposed to the laser -18- there may be, for example, another first colored pigment in the color layer -50-, and thus another individualized marking color can be generated by applying the laser.

Alternatively, the color composition of the color layer 50 may contain a greater number of laser sensitive core-shell particles with a second, or a third, colored pigment, which are removed from the composition with different amounts of High laser intensity of different functional layers favoring ablation. Then, in the zone not exposed to the laser -20-, all three colored pigments are present and together they constitute a dark background of an optically variable transparent effect layer -40-. In the area exposed to the laser -16-, with a low laser intensity, only laser-sensitive core-cortex particles with the third pigment are removed, for example, so that the color printed image is determined, in said exposed area, by an overlap of the first and second colored pigments (first image printed in fixed color). In the zone exposed to the laser -18-, with a high laser intensity, core-cortex particles sensitive to the laser with the second pigment are additionally removed, so that the color printed image is determined, in said exposed zone , only by the first colored pigment (second fixed color printed image). In this way, with a suitable choice of the colored pigments, the desired color printed images can be generated in the first and second sections -16-, -18- of the individualized marking.

A further variant of the invention is shown in figure 7. In this exemplary embodiment, the color layer -52 is made up of a layer -54- of a fixed color not sensitive to the laser and a layer -56- applied thereon, which contains, in addition to first pigments, also core particles. -cortex with a second colored pigment, where the core-cortex particles are provided with a functional layer that favors ablation. In the area exposed to the laser -16-, laser-sensitive core-cortex particles are removed with the second colored pigment, so that the color printed image is determined, in said exposed area, by the first colored pigment (first image printed in fixed color). In the area exposed to the laser 18, the entire layer -56- is ablated with a high intensity laser, so that the color printed image is determined, in said exposed area, by the lower layer of fixed color -54- (second still color printed image).

Figure 8 shows a security element -60- according to another embodiment of the invention, in which the individualized marking -62- of 50 Euro, in the form of letters, has a color gradation with a smooth transition. For example, the color printed image of the individualized marking -62- can slowly change from top to bottom from green to magenta. It should be emphasized that this color gradation is not a variable color printed image, since the security element -60- remains unchanged at any time during the tilting thereof. In contrast, the fixed color printed image itself changes almost continuously from the upper edge to the lower edge of the individualized marking -62-.

In the exemplary embodiment, this almost continuous color gradation is produced with the aid of only two colors (green and magenta) by gradually changing the proportion of the color area in adjacent stripes. Figure 9 shows in this regard a gradation -70- having a plurality of green stripes -72- and magenta stripes -74-, which are arranged in unidirectionally spaced cells with a cell width -d-. Within the width of each cell -d-, the proportion of the green area -g- of the green stripe -72- decreases, from top to bottom, from 100% to 0%. Accordingly, the magenta color area ratio -m = 100% - g- of the magenta color stripe -74- increases from top to bottom, from 0% to 100%. If the cell width -d- is chosen small enough, a continuous gradation -70- from green to magenta is directly visible to the eye. In practice, in general,

ES 2 582 010 T3 to generate a smooth gradation perceptible with the eye, only a small number of cell periods is necessary, for example 6, 8 or 10 cells.

Figure 10 below shows a cross section in the security element -60- through the line XX of figure 8. As shown in figure 10, a colored layer -82- is printed on the substrate -80 -, which contains the graduation -70- of figure 9 in the area of ​​the individualized marking -62-. The color printed image varies from the first section 84 to the second section 86 almost continuously from the first fixed color printed image of magenta to the first fixed color printed image of green.

On the color layer -82- a laser-sensitive black intermediate layer -38- is printed and, on the intermediate layer -38-, a transparent optically variable effect layer -40-, which provides the color change effect desired from magenta, when viewed vertically, to green, when viewed obliquely, against the background of the black interlayer. After the preparation of said sequence of layers, the black intermediate layer -38- and the effect layer -40- are treated locally by ablation with laser application, thus providing the security element -60- with individualized marking -62, in the form of letters, from “50 Euro.

When viewed perpendicularly, the effect layer -40- is visible in the contour area -20- of the individualized marking on the background of the intermediate layer -38- in black with the image printed in magenta and, therefore, with the same color printed image as the lower part -62-U- of the individualized marking -62-. Therefore, only the middle and upper parts of the individualized marking -62- can be seen when viewed vertically.

By tilting the security element -60- in the direction of the arrow -64-, the color printed image of the effect layer -40- in the contour area -20- initially changes to a color mixed between magenta and green , thus indicating the same color printed image of the middle part -62-M- of the individualized marking. If it is tilted further, the color printed image of the effect layer -40- changes to green, indicating the individualized marking, therefore, the same color printed image of the upper part -62-O-.

Therefore, by tilting in the direction of the arrow -64-, first the middle part disappears and then the upper part of the individualized marking, due to the lack of contrast in the contour area -20- for the observer, while the lower magenta -62-U- is visible. When moving rapidly back and forth, all parts of the individualized marking -62- are recognizable again, due to the inertia of the human eye.

The security element -60-, shown in Figures 8 to 10 and described above, can also be considered as a security element comprising a plurality of sections, each with a fixed color printed image in a certain section, of according to the invention.

List of references

16, 18

34, 36

62-O, 62-M, 62-U banknote security element marking denomination sections contour area substrate optically non-variable color layer sections intermediate layer optically variable effect layer perpendicular view oblique view transparent transformation optically variable effect opaque layer color layer color layer fixed color layer non-laser sensitive layer security element marking part of the marking direction of the arrow

ES 2 582 010 T3

82

84, 86 color gradation green stripes magenta stripes substrate color layer sections