WO2017190831A1

WO2017190831A1 - Security element having a luminescent print

Info

Publication number: WO2017190831A1
Application number: PCT/EP2017/000539
Authority: WO
Inventors: Peter Schiffmann
Original assignee: Giesecke+Devrient Currency Technology Gmbh
Priority date: 2016-05-03
Filing date: 2017-05-02
Publication date: 2017-11-09
Also published as: EP3452299B1; EP3452299A1; DE102016005415A1

Abstract

The invention relates to a security element (12) for securing security papers, value documents, and other data carriers, comprising a luminescent print (14), which shows a multi-color motif in UV light. According to the invention, the luminescent print (14) is formed by luminescence white (20W) and at least two luminescence basic dyes, in particular from the group consisting of luminescence green (20G), luminescence red (20R), and luminescence blue (20B), and that the multi-color motif also contains achromatic portions (22) in colored areas, which achromatic portions are formed in the print (14) at least partially by means of luminescence white (20W).

Description

Security element with luminescent imprint

The invention relates to a security element for securing security papers, documents of value and other data carriers, with a luminescent imprint which shows a multicolored motif in UV light. The invention also relates to a method for producing such a security element as well as to a data carrier equipped with such a security element.

Data carriers, such as valuables or identity documents, but also other valuables, such as branded goods, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carrier and at the same time serve as protection against unauthorized reproduction. In this context, it is known to print fluorescent inks on a security paper with various printing methods. In this case, for example, a fluorescent color is printed in the form of a motif, which is not visible in normal daylight, but when viewed under UV illumination is visible. The fluorescent color can also be admixed with a visible color in daylight, so that the printed motif is visible even in daylight, but with a different hue.

In the passport area, the printing of true-color luminescence images has also been known for several years. The implementation is usually done in inkjet printing with special colors, which are not visible in visible light and after excitation by UV light a comparable color impression as a classic picture, such as a portrait of the passport owner show. Based on this, the present invention seeks to provide a security element of the type mentioned above with attractive visual appearance and high protection against counterfeiting. This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

According to the invention, it is provided in a generic security element that the luminescent imprint is formed by printed luminescent white on the one hand and at least two printed luminescent basic dyes, for example from the group consisting of luminescent green, luminescent red and luminescent blue, on the other hand, and the multicolor motif also in FIG colored areas contains achromatic parts, which are formed in the imprint at least partially by luminescent white.

In the context of this description, the term luminescent white refers to a white-luminescent luminescent substance. Similarly, the terms luminescent red, luminescent green, and luminescent blue, respectively red, green, and blue luminescent luminescent. At least two, but usually three, basic luminescent dyes are used. Luminescent red, luminescent green, and luminescent blue form the usual primary colors. Other primary colors to choose for the luminescent basic dyes is possible in the present case. Three luminescent Basic dyes may be chosen so that their additive color mixing results in white.

The luminescence is preferably a photoluminescence. The luminescence includes fluorescence and phosphorescence, in particular also anti-Stokes luminescence. As luminescent substances, for example, all fluorescent and phosphorescent substances come into question. In particular, substances which emit white light after appropriate excitation are suitable as luminescent white. Luminescent white can (before printing) also be provided as a mixture of luminescent pigments, in particular red, blue and green luminescent. The energy transfer from excitation to luminescence can also be multistage, so that a first substance absorbs the excitation energy and transfers it directly or via further intermediate steps to the finally emitting luminescent substance. In the present case the most transparent possible luminescent colors are used, which can be achieved for example by the use of small luminescent pigments, in particular of nanopigments, and / or the use of a highly transparent binder. The excitation of the luminescent substance or, in the case of a transmission of the excitation energy, the excitation of the first substance preferably takes place in the ultraviolet (UV) spectral range. An excitation in the infrared range for the luminescence in the visible range is also conceivable. The wavelength range from 315 nm to 380 nm is described as long-wave UV radiation (UV-A), the wavelength range from 280 nm to 315 nm as medium-wave UV radiation (UV-B) and the wavelength range from 100 nm to 280 nm as short-wave UV Radiation (UV-C). The excitation can be carried out with UV-A and / or UV-B and / or UV-C radiation. The multicolored motif contains not only the primary colors, such as red, green, and blue, but also mixed colors of two or all three primary colors. The motif therefore has a realistic appearance and, in the context of this description, is sometimes referred to as a true color image or true color luminescence image.

It goes without saying that the multicolored motif in subregions can also contain pure grayscale without any color component. In addition, however, the multicolor motif also contains achromatic parts in the colored areas, which result in the manner explained in greater detail below with reference to FIG. 2 by a decomposition of the color structure into an achromatic component and a chromatic component. These achromatic parts of the color structure are now formed in the print according to the invention at least partially by luminescence white.

Due to the use of luminescent white according to the invention, the process stability when printing true color luminescence images can be significantly increased. For example, some printing processes, such as offset or high pressure, may have process problems in printing three primary colors one on top of the other. Through the use of luminescent white, the number of primary colors required can generally be reduced to two, as explained in more detail below.

Also, any problems with the drying of the colors on a substrate, in particular the physical drying of mineral oil-based offset inks can be overcome, since the entire color coverage can be reduced by the use of luminescent white. Finally, problems with the controlled regression of color in the inking of a printing plate cylinder, a transfer cylinder, can also be overcome. For example, a blanket cylinder in offset printing, and overcome the substrate, since the color splitting takes place the more undefined, the greater the number of non-intermediate dried different layers of paint. The inventors have also found that the use of luminescent white in addition to the luminescent basic dyes in the print and the representable color space is increased. The use of fluorescent white further allows increased flexibility in the selection of luminescent basic dyes. In particular, the choice of the luminescent basic dyes must then be less compromised in terms of resistances, luminosity and / or price than when a true color luminescence images is printed exclusively with the three luminescent basic dyes. In addition, color variations when using fluorescent white are less conspicuous than in the case where a white color impression must be produced by printing the three primary luminescent colors one upon the other or side by side. In the latter case, not only does the intensity of the whiteness change in general, but it can also give rise to a certain bluish, yellowish or reddish color.

In a preferred embodiment, the luminescent imprint is formed by luminescent white on the one hand and the three luminescent basic dyes luminescent green, luminescent red and luminescent blue on the other hand.

The achromatic parts of the multicolor motif are preferably formed completely by the luminescent white, at least in a partial region of the motif. In this case, for each color pixel or for each same color Color range to be dispensed with at least one of the luminescent basic dyes used.

The luminescent white may consist of a single luminescent substance, but may also be formed from a mixture of two or more luminescent substances, which in combination give a white. The mixture can contain both dyes and pigments. In order to avoid segregation in the color in the case of a luminescent white, the luminescent substances which form the luminescent white advantageously have a similar surface functionalization by means of a surface coating. Alternatively, a separation of the color can also be counteracted by the fact that the luminescent substances forming the luminescent white are present in a common capsule. The fluorescence white may in particular have a high luminous intensity, which exceeds the luminosity of a combination of the three luminescent basic dyes.

In an advantageous development, the luminescent white of the luminescent imprint can be excited in a first UV excitation area together with the luminescent primary dyes present in the imprint. By contrast, in a second UV excitation region, the luminescent white can be excited individually without the luminescent basic dyes present in the imprint. The first UV excitation region can be, for example, the long-wave UV, the second UV excitation region the short-wave UV.

In this way, it can advantageously be achieved that the luminescent imprint shows the multi-color motif when excited in the first UV excitation region, while it excites in the second UV excitation region shows a grayscale reduction of the multicolor motif, ie a grayscale motif that has the same image content as the multicolored motif and is not just colored.

5 The luminescent white of the imprint has a double function in this development, since on the one hand it is part of a first security feature in the form of the colored luminescent motif. On the other hand, the luminescent white is also part of a separately testable second security feature, which is given in the form of a gray-scale image by the spatial distribution of luminescent white in the imprint. The grayscale image may in particular represent a gray scale reduction of the multicolor motif, but it may also contain additional, in particular hidden, information by means of a spatial variation of the luminescence white fraction, as explained in greater detail below.

15

In order to prevent excitation in the second UV excitation region, the luminescent basic dyes may contain, for example, an absorber for the second UV excitation region, so that excitation with UV radiation from the second UV excitation region does not lead to luminescence of the luminescence. Basic dyes leads.

In another embodiment of the invention, it is provided that the achromatic parts of the motif in a camouflage region of the motif are formed only by the luminescent basic dyes. In this way, it can be advantageously achieved that the camouflage area is not recognizable on excitation in the first UV excitation area, while it emerges visibly upon excitation in the second UV excitation area. In an advantageous embodiment of the invention, the luminescent imprint in the UV light in addition to the multicolor motif also shows a gray scale pattern with different brightness values, which is formed by the luminescent white without using the luminescent base dyes. Such a gray scale pattern can not practically be produced with luminescent basic dyes without a residual color, so that an adjustment of the security element without the use of luminescent white is also easily recognizable to the layman. For example, to obtain a large number of brightness levels in the pure grayscale pattern, it may contain or even consist of a gray wedge. In a gray wedge, a possible residual color of an adjustment is particularly easy to notice. The pure grayscale pattern can in particular also obtain stepless gray transitions, since these too are particularly difficult to recreate with the luminescent basic dyes alone.

In a further embodiment, a multicolored motif is divided into a multicolored subregion and a monochromatic subregion. The monochromatic subregion is preferably printed only with luminescence white. The subregions are arranged precisely to one another, in particular since they are produced in one printing operation. The multicolor subregion is preferably arranged within the monochromatic subregion. A multicolored main motif, such as a building, a tree or a person, can therefore be set off particularly clearly from the monochromatic or grayscale background, such as a landscape, a building or a vehicle. In one development of the embodiment, the entire motif can be excited with a first radiation (UV-A) and selectively only the multicolored partial region with a second radiation (UV-B). For example, the basic dyes can only be excited by radiation from one of the UV regions (UV-A, UV-B or UV-C) while the luminescent white can be excited by UV radiation from at least two (or all) of the UV regions (UV -A, UV-B and UV-C).

In a further embodiment, the luminescent white or at least one of the luminescent basic dyes is phosphorescent. An afterglow after the end of the excitation becomes apparent. The afterglow would only be recognizable to an observer when using phosphorescent agents with a longer afterglow time (> 1-2 seconds). By machine, an afterglow, possibly also shorter, for example in the millisecond range, can be recognized or evaluated as an authenticity feature.

In one embodiment, the luminescent white is printed with a different grid than the luminescent basic dyes. The raster can differ in predetermined raster parameters (in particular raster angle, raster point shape or modulation) and / or in the raster type (eg frequency modulated (1st order, 2nd order), amplitude modulated or crossmodulated). The different screens can be used as an authenticity feature. Detection of the difference is possible, for example, by means of a microscope, raster counter (eg GHG mini-lithometer) and / or moiree structure.

In an advantageous embodiment, the luminescent imprint is imprinted onto a substrate which is substantially non-luminescent after UV excitation. In another, likewise advantageous embodiment, on the other hand, it is provided that the luminescent imprint is imprinted onto a substrate which luminesces after UV excitation, and is provided in partial areas with a UV absorber in order to localize the substrate luminescence suppress. The UV absorber may be absorptive of radiation of all UV ranges (UV-A, UV-B and UV-C) or selectively radiation of one or two of the UV ranges. The invention also includes a method for producing a security element for securing security papers, documents of value and other data carriers, with a luminescent printing, which shows a multicolored motif in UV light, wherein in the process - the luminescent printing by printing luminescence white on the one hand and Printing of at least two luminescent basic dyes, in particular from the group consisting of Lumineszenzgrün, Lumineszenzrot and Lumineszenzblau, on the other hand is formed, and the multicolor motif also in colored areas contains achromatic parts, which are formed in the print at least partially by luminescence white. The imprint can be produced by means of different printing processes, in particular gravure printing, inkjet printing, flexographic printing, screen printing, offset printing or transfer printing (including sublimation transfer or thermal transfer). Preferably, the imprint is screened. In particular, to represent gray levels or different brightness values, the imprint is rasterized. Different brightness values are achieved by area variation (in the raster) and / or layer thickness variation. The imprint can be applied to a substrate, in particular in gravure or offset printing. Preferably, transparent luminescent colors are used. Transparent luminescent colors are particularly suitable for overprinting, in particular two, three or four colors. Thus, finer grid structures can be used, as possible deviations (register variations) are less critical. Possible register variations in the printing process from a first to a next printing unit would require a rather rough grid structure for non-transparent colors. As a grid (for a rasterization) in particular point, chain or frequency modulated grids can be used. In dot or chain grids, the screen angles of the individual colors are advantageously chosen differently from each other in order to avoid unsightly moire structures.

The imprint may alternatively or additionally be made variable in its layer thickness to represent different brightness values, in particular by means of ink-jet printing or gravure printing. In ink-jet printing, it is possible to print several droplets on top of each other or to print droplets of different sizes. In gravure printing, it is possible to engrave the printing plate (produced by means of a stylus or laser) which are different deep. In both cases, different brightness values result from the transferred layer thickness.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation in terms of scale and proportions has been dispensed with in order to increase the clarity. 1 is a schematic representation of a banknote with a security element according to the invention,

2 shows schematically the color composition of a color region of the multicolor motif, in (a) without the use of luminescent white and in (b) using luminescent white,

3 shows a plurality of color pixels for explaining different variants of the color composition,

Fig. 4 shows schematically the appearance of an inventive

Safety elements, in (a) when illuminated with long-wave UV radiation and in (b) when illuminated with short-wave UV radiation,

5 shows in (a) an inventive division of an imprint into a camouflage area and a normal area, in (b) schematically the appearance of the imprint when illuminated with long-wave UV radiation and in (c) schematically the appearance of the imprint when illuminated with short-wave UV Radiation, and

6 schematically shows a luminescent printing of another security element according to the invention. The invention will now be explained using the example of security elements for banknotes. 1 shows a schematic representation of a banknote 10, which is provided with a luminescent imprint 14 in a partial area with a security element 12 according to the invention. The print 14 shows when viewed in UV light in additive color mixing a multi-colored motif, here for illustration in the form of a butterfly. In the exemplary embodiment shown, the security element 12 is part of the banknote 10, but it can also be embodied as a separate security element in other configurations, for example as a transfer element that is applied to a banknote or another data carrier.

A peculiarity of the luminescent imprint 14 consists in the fact that the imprint is not only formed by the luminescent basic dyes luminescence green, luminescent red and luminescent blue, but that at least a fraction of the colored motif passes through at least partially

Lumineszenzweiß, ie a white luminescent luminescent substance is generated.

For a more detailed explanation of the occurrence of the color mixture with the luminescent substances mentioned, FIG. 2 (a) schematically shows the color composition of a specific color region of the multicolor motif, for example a color pixel or a monochrome surface region. For example, the color range shows a mixed color (true color), for example, by Lumineszenzrot 20R, ie a red luminescent luminescent, with a coverage of 100%, by Lumineszenzgrün 20G, ie a green luminescent luminescent, with a coverage of 75%, and by Lumineszenzblau 20B , that is to say a blue-luminescent luminescent substance, with a surface coverage of 40%. Since the luminescent colors red, green and blue together give a white or, more generally, an achromatic hue, the color structure of FIG. 2 (a) can be decomposed into an achromatic component 22 and a chromatic component 24. In the imprint 14, this colored portion 22 is now at least partially formed according to the invention not by a combination of luminescent green 20G, luminescent red 20R and luminescent blue 20B, but by the additional luminescent luminescent white 20W, as shown in FIG. 2 (b). By the amount of luminescent white 20W used, the areal coverage of the three luminescent basic dyes can be reduced (reference numerals 26R, 26G, 26B), so that the overall result is a lower areal coverage.

The achromatic component 22 of a color region can also be completely formed by luminescence white 20 W. In this case, it is possible to dispense with at least one of the luminescent basic dyes used. For example, in the exemplary embodiment of FIG. 2, the areal coverage of luminescent blue 20B can be reduced to zero by a sufficiently large proportion of luminescent white 20W and the true color of the color area can only be generated with luminescent green 20G, luminescent red 20R and luminescent white 20W.

The different variants will be explained again with reference to FIG. 3 on the basis of color pixels of a luminescent printing. The color pixels can also be representative of a larger, monochrome area of the imprint. The layer sequence or the arrangement of the color pixels can be generated in any order. First, in the color pixels 30 printed on a substrate 16, there are three luminescence colors 20R, 20G, 20B of luminescent green 20G, luminescent red 20R and luminescent blue 20B printed over one another. The color pixel 30 has a structure corresponding to FIG. 2 (a) without the use of luminescent white 20W. In the present invention, such color pixels or color areas can be used in particular for generating additional effects, such as the introduction of hidden information, described in more detail in connection with FIG. 5, into a true color luminescence image.

The color pixel 32 luminesces in the suitable UV light with the same true color as the color pixel 30 and has a structure according to FIG. 2 (b). In the case of the color pixel 32, part of the colored portion of the illustrated true color is replaced by luminescent white 20W, so that the area coverage of the luminescent primary colors 20R, 20G, 20B is correspondingly reduced.

The color pixel 34 luminesces in the suitable UV light with the same true color as the color pixels 30 and 32. In the color pixel 34, however, the colorant part of the true color is completely replaced by luminescent white 20W and the use of luminescent blue 20B can be dispensed with desired true color alone with luminescent white 20W and the two luminescent basic dyes Lumineszenzgrün 20G and Lumineszenzrot 20R can be generated. The color pixel 36 is a modification of the color pixel 32 with all four luminescent colors 20W, 20R, 20G, 20B, wherein the colors are not printed one above the other but side by side. Not shown separately is, for example, a possible layer sequence in which the luminescent white 20W is printed on the luminescent basic colors. Also not shown is the additional possibility to arrange at least one absorber layer between the luminescent layers of the color pixel 34. The absorber layer should preferably be absorbent for only a partial region, for example UV-A radiation, from the (UV) excitation radiation. The absorber layer can be printed in full color on one of the luminescent layers in the color pixel 34 or only partially cover one of the luminescent layers 20R, 20G, 20B or 20W.

A further peculiarity of the present invention with reference to FIG. 4 is that the luminescent substances 20W, 20R, 20G, 20B are selected such that the luminescent white 20W of the imprint 14 in the long-wave UV, for example at an excitation wavelength of 366 nm, together with the Lumineszenz basic dyes 20R, 20G, 20B is excitable, while excitation in the short-wave UV, for example at an excitation wavelength of 254 nm, only the luminescent white 20W, but not the luminescent basic dyes 20R, 20G, 20B are excitable. By way of illustration, it is assumed in FIG. 4 that the achromatic parts 22 of the butterfly motif are completely formed in all colored areas by luminescent white 20W. If the imprint 14 of the security element 12 is then exposed to long-wave UV radiation 42 of a UV lamp 40, all four luminescent colors 20W, 20R, 20G, 20B are excited and luminesce in the corresponding color white, red, green or blue. The print 14 thus shows the multicolor motif in true color representation 50 under long-wave UV radiation 42, as illustrated schematically in FIG. 4 (a). The luminescent white 20W may be arranged in the layer sequence above the basic dyes 20G, 20B, 20R, in particular if one of the or the base dyes 20G, 20B, 20R include UV absorbing moieties, eg, UVA absorbing. An optional background for the true color representation 50 may be free of luminescent printing, but is preferably designed as a white (or light gray) luminescent background 51, for example printed with luminescent white 20W.

On the other hand, if imprint 14 is acted upon by a UV source 44 with short-wave UV radiation 46, only the luminescent white 20W is excited to luminesce, while the colored luminescent substances 20R, 20G, 20B, which are not stimulable in the short-wavelength, do not shine. Since the luminescent white 20W generates the achromatic portion 22 of the colored areas of the motif, the distribution of the white-luminescent luminescent substance 20W corresponds to the brightness distribution of the respective color areas. If only the luminescent white 20W illuminates in the imprint 14, then the imprint shows an achromatic motif which represents a gray scale reduction 52 of the multicolored butterfly motif. Since no colors can be represented in the illustrative figures, this effect is illustrated in Fig. 4 (b) by a reduction of the halftone image of Fig. 4 (a) to a pure black and white image. If present, optional background 51 will continue to luminesce white (or light gray).

The short-wave UV source 44 and the long-wave UV lamp 40 can be different devices, or can also be integrated in one device and formed, for example, by a switchable lamp or a lamp with selectable (different) filters.

The different excitability of the luminescent substances 20W, 20R, 20G, 20B can be achieved, for example, by the fact that for the luminescence For example, for luminescent green 20G, luminescent red 20R and luminescent blue 20B, luminescent substances which are selectively excitable only in the long-wave UV are selected.

Alternatively, all the luminescent substances used can in principle be stimulated broadband, wherein the luminescent basic dyes 20R, 20G, 20B, an additional UV absorber for the short-wave UV radiation is added so that incident short-wave UV radiation is absorbed and not to a luminescence of Luminescent basic dyes 20R, 20G, 20B leads. Examples of such UV absorbers are Tinuvin 400 or resins or binders which absorb short-wave UV radiation. A typical broad UV-excitable luminescent substance is about CD 350 from Honeywell. In a development of the principle described in FIG. 4, an additional hidden information in a multi-colored motif can be coded by a skillful choice of the luminescent substance combinations. 4, so that in the long-wave UV all four luminescent colors 20W, 20R, 20G, 20B can be excited, while in the short-wave UV only the luminescent white 20W can be excited.

With reference to FIG. 5 (a), a camouflage region 62 is defined in the desired colored motif 60, which in the exemplary embodiment is embodied in the form of the inscription "original". Within the camouflage area 62, the true colors of the subject are generated without the use of luminescent white 20W only with the luminescent primary colors 20R, 20G, 20B as shown in Fig. 2 (a) and the color pixel 30 of Fig. 3. In the normal region 64 lying outside the camouflage region 62, the true colors of the motif are generated using luminescent white 20W, as explained with reference to Fig. 2 (b) and the color pixels 32, 34 of Fig. 3. Advantageously, the non-colored portion 22 of the true colors in the normal region 64 is even completely formed by luminescent white 20W.

As illustrated in FIG. 5 (b), the subject 60 in the present case comprises a true-color luminescent representation 66 in front of an (optional) white-luminescent background 67. The background 67 can, as described later with advantage on FIG. 6, be in gray scale available. The camouflage region 62 should be arranged completely or, as shown, at least partially within the true color representation 66. A camouflage area 62 lying outside the true color representation 66 is conceivable, but much less secure.

If the imprint thus obtained is exposed to long-wave UV radiation 42 of a UV lamp 40, all four luminescent colors 20W, 20R, 20G, 20B are excited and luminesce in the corresponding color white, red, green or blue. The true colors are produced in the camouflage region 62 only by the luminescent primary colors 20R, 20G, 20B. In the normal region 64, the true colors of the representation 66 are generated with additional use (and / or the background 67 under exclusive use) of luminescent white 20W. Since all the luminescent colors are illuminated and the replacement of the colored portion 22 by luminescent white does not change the color hue of the true color, the camouflage area 62 blends seamlessly and without any contrast or color difference into the overall motif in true color representation 66 (and in the white background) , In the long-wave UV light 42 of the camouflage region 62 is thus not visible.

If, on the other hand, the imprint is subjected to short-wave UV radiation 46 of a UV source 44, only the luminescent white 20W is used for luminescence. neszenz excited, while the short-wave non-excitable colored luminescent 20R, 20G, 20B does not shine. As explained in connection with FIG. 4 (b), the imprint thus shows an achromatic motif in the normal region 64, which represents a gray scale reduction 52 of the multicolored butterfly motif. In the camouflage region 62, however, the imprint is formed entirely without the use of luminescent white 20W, so that the camouflage region 62 does not glow with short-wave UV excitation and thus does not take part in the reconstruction of the motif. Thus, as illustrated in Figure 5 (c), the camouflage region 62 appears dark before the normal area 64 luminescent in gray (and / or white). The appearance 68 then shows a total overlay of the gray level reduction in the normal region 64 with the non-luminescent one Tarnbereich 62, the black lettering "Original". The optional background 69 comprises analogous non-luminescent portions of the camouflage region 62, here in the form of portions of the word "original", and the white (or for example uniformly light gray) luminescent, unchanged forming a background, portions of the normal range 64. Figure 6 shows schematically a further imprinting a luminescent imprint 70. The imprint 70 comprises a first partial area 72 with a multicolored motif and a partial area 74 in shades of gray where the imprint 70 shows a colored motif in a first partial area 72 in UV light, in which more detail is given in the above described type achromatic parts of colored areas at least partially formed by luminescence white and partly by the luminescent basic dyes such as luminescence green, luminescent red and luminescent blue.

In addition, the imprint 70 in the second portion 74 is in the same UV light a pure grayscale pattern with different brightness values. Preferably, the greyscale pattern is selected such that the brightness values merge into one another steplessly, cover a large range of the possible brightness values and / or have a high number (at least 5, preferably at least 10) of different brightness values. Schematically represented as subregion 74 in FIG. 6 is a grayscale wedge, as an example of a continuously formed gray scale region. The different brightness values can be achieved by layer thickness variation and / or area variation (as indicated in the figure) of the print.

The pure grayscale pattern can also be formed, for example, by a gray scale reduction of the colored motif of the first subregion 72. It is essential that the imprint 70 in the second subregion 74 without the use of the luminescent basic dyes luminescent green, luminescent red and luminescent blue is printed only by luminescent white. In the UV light, the imprint 70 simultaneously shows a colored motif in the partial region 72 and a pure gray-scale image in the partial region 74.

If the imprint 70 is readjusted by a forger with conventional luminescent substances, that is to say using only the luminescent basic dyes 20R, 20G, 20B, the gray levels of the partial area 74 must each be generated by a combination of the luminescent basic dyes. Due to the specific properties of the luminescent basic dyes, however, it is usually impossible to produce correct hues with several luminescent basic dyes in several brightness levels. Rather, in the sub-area 74, a residual color, which is dependent on the brightness value of the gray levels, for which the human eye is very sensitive, and which therefore also by the untrained observer without another is perceived. An adjustment of the imprint 70 is therefore easy to distinguish from a real imprint 70.

The multicolor subregion 72 may be arranged within the gray scale subregion 74. Thus, the gray scale subregion 74 can thus form a background for the multicolor subregion 72.

LIST OF REFERENCE NUMBERS

10 banknote

12 security element

14 luminescent imprint

16 substrate

20R luminescent red

20G luminescent green

20B luminescent blue

20W luminescent white

22 uncoloured portion

24 colorful part

26R, 26G, 26B reduced color components

30, 32, 34, 36 color pixels

40 long-wave UV lamp

42 long-wave UV radiation

44 'short-wave UV source

46 short-wave UV radiation

50 multicolored motive in true color representation

51, 67 luminescent background

52 Grayscale reduction of the multicolor motif

60 colored motif

62 Camouflage area

64 normal range

66 Overall motif in true color representation

68 Overlay Tarnbereich with appearance

69 Overlay Tarnbereich with background

70 luminescent imprint

72, 74 subareas

Claims

Patent claims

1. security element for securing security papers, value documents and other data carriers, with a luminescent imprint, which shows a multicolored motif in UV light, characterized in that the luminescent imprint formed by printed luminescence white on the one hand and at least two printed luminescent basic dyes on the other is, and the multicolor motif also contains in colored areas achromatic parts, which are formed in the imprint at least partially by luminescence white.

2. The security element according to claim 1, characterized in that the luminescent imprint is formed by luminescent white on the one hand and three luminescent basic dyes, in particular luminescent green, luminescent red and luminescent blue, on the other hand.

3. Security element according to claim 1 or 2, characterized in that the achromatic parts of the multicolor motif are formed completely by the luminescent white at least in a partial region of the motif.

4. Security element according to at least one of claims 1 to 3, characterized in that the luminescent white is formed before printing by a mixture of two or more luminescent substances.

5. The security element according to claim 1, characterized in that the luminescent substances forming the luminescent white have a similar surface functionalization by means of a surface coating or are present in a common capsule.

6. The security element according to claim 1, characterized in that the luminescent white can be excited in a first UV excitation area together with the luminescent basic dyes present in the imprint, and in a second UV excitation area without those present in the imprint Luminescent basic dyes can be excited.

7. A security element according to claim 6, characterized in that the luminescent imprint shows the multicolor motif when excited in the first UV excitation region and shows a gray scale reduction of the multicolor motif when excited in the second UV excitation region.

8. Security element according to claim 6 or 7, characterized in that the luminescent basic dyes contain an absorber for the second UV excitation region.

9. Security element according to at least one of claims 1 to 8, characterized in that the achromatic parts of the motif in a camouflage region of the motif are formed only by the luminescent basic dyes.

10. Security element according to one of claims 6 to 8 and according to claim 9, characterized in that the camouflage region is not visible when excited in the first UV excitation region and emerges visibly upon excitation in the second UV excitation region.

11. A security element according to at least one of claims 1 to 10, characterized in that the luminescent imprint in the UV light next to the multicolor motif shows a grayscale pattern with different brightness values, which is formed by the Lumineszenzwei¬ without using the luminescent basic dyes.

12. The security element according to at least one of claims 1 to 11, characterized in that the luminescent imprint is printed on a substantially non-luminescent after UV excitation substrate.

13. A security element according to at least one of claims 1 to 11, characterized in that the luminescent imprint is printed on a luminescent after UV excitation substrate, and is provided in Teilberei- Chen with a UV absorber to locally suppress the substrate luminescence.

14. A data carrier with a security element according to at least one of claims 1 to 13.

15. A method for producing a security element for securing security papers, documents of value and other data carriers, with a luminescent printing, which shows a multi-colored motif in UV light, wherein in the method the luminescent imprint is formed by printing luminescent white on the one hand and by printing at least two luminescent basic dyes, for example from the group consisting of luminescent green, luminescent red and luminescent blue, on the other hand, and the multicolored motif also contains achromatic parts in colored areas which in the Imprint be formed at least partially by Lumineszenzweiß.