EP4049852B1 - Security element, data carrier and manufacturing method - Google Patents

Description

The invention relates to a security element for securing valuables, a data carrier with such a security element, and a method for producing such a security element.

Data carriers, such as valuables or identification documents, but also other valuables, such as branded items, are often provided with security elements for security purposes, which allow the authenticity of the data carrier to be checked and which also serve as protection against unauthorized reproduction. In this context, it is known to use luminescent substances to secure valuables or identification documents. The presence of the luminescent substances can then be checked, for example, using a UV lamp.

In recent years, due to their low price, inkjet printers have become readily available, with which would-be counterfeiters can create impression counterfeits of banknotes that, at first glance, bear a close resemblance to the original. The printing can take place without observation by third parties and without the possibility of tracing back to a specific person. Inkjet fluorescent colors are now relatively easily available, especially through online retail, so that luminescence features can also be recreated using inkjet printers.

The document GB 2562262 A discloses a security element according to the preamble of claim 1.

Proceeding from this, the invention is based on the object of providing security elements and valuable documents which, in addition to an attractive appearance, have a high level of security against forgery and are protected in particular against counterfeiting using office printers, such as multi-color inkjet printers.

This task is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

The invention contains a security element according to claim 1.

As explained in more detail below, the shape of the first color area can show a visually visible motif within a different colored environment. When viewed under UV or IR excitation light, the feature area shows at least two different luminescence colors.

The term luminescence includes phosphorescence and fluorescence, with the excitation of luminescence using invisible UV radiation or IR radiation can occur. The luminescent substances are preferably transparent in the visible spectral range.

A homogeneous appearance when viewed with the naked eye means in particular that the viewer cannot see any structures from a normal viewing distance of 25 cm or more, but that the first color area creates the impression of a uniformly printed area. The color of the first color range of the feature range is uniform at least in some areas; the first color range preferably even shows only a single, uniform visible color.

Advantageously, at least two luminescent substances of the second color range, which produce two different luminescent colors, lie completely within a region of the first color range with a uniform visible color.

The luminescence colors of the feature area generated by excitation preferably differ from the respective uniform visible colors of the feature area, in particular they differ from this in the case of a single uniform visible color.

The second color area advantageously has two or more luminescence areas which are designed in the form of patterns, characters or codes and which each show one of the different luminescence colors under UV or IR excitation light. The second color area may be located entirely within the feature area and cover only a portion of the feature area. However, it is also possible for the second color range to completely cover the feature range and/or for the second color range to also lie partially outside the feature range. In In an advantageous embodiment, the second color range lies completely within the first color range.

The microstructure elements have two or more different colors, which produce the perceived color impression for the viewer from the normal viewing distance through color mixing, in particular subtractive color mixing. In addition to the colors of the microstructure elements, a background color, for example the color of the carrier on which the microstructure elements are applied, can also contribute to the mixed color. In the case of paper substrates in particular, this background color is often white, but it can also be provided by a colored underprint layer. The background color can be present in particular in spaces between the microstructure elements and/or in recesses in the microstructure elements and contribute to the mixed color.

gegeben.It is advantageously provided that the different colors of the microstructure elements in the CIELab system have a color difference ΔE of at least 4.0, preferably at least 6.0. The color difference ΔE is a measure of the perceived color difference and is constructed in such a way that it is essentially the same distance for all colors that occur. Two colors F ₁ and F ₂ are specified by their coordinates F ₁ = (L ₁ *, a ₁ *, b ₁ *) and F ₂ = (L ₂ *, a ₂ *, b ₂ *) in the CIELab color space , then the color difference mentioned is through $$\Delta \mathrm{E}=\surd \left({\left({\mathrm{L}}_1*-{\mathrm{L}}_2*\right)}^2+{\left({\mathrm{a}}_1*-{\mathrm{a}}_2*\right)}^2+{\left({\mathrm{b}}_1*-{\mathrm{b}}_2*\right)}^2\right)$$

given.

The microstructure elements of the first color range can be arranged adjacent to one another or at a distance from one another. The microstructure elements can be shown in positive form in the form of geometric symbols, Letters and/or numbers and/or in negative representation as a surface with recesses in the form of geometric symbols, letters and/or numbers. In particular, line fragments, squares, triangles or other polygons, each with or without filling, come into consideration as geometric symbols. Advantageously, the microstructure elements at least partially accommodate geometric elements that are visible to the naked eye elsewhere in the security element in order to establish a connection between the various elements of the security element. Such a connection also makes it easier to recognize or identify the content of information encoded by the microstructure.

The characteristic dimensions of the microstructure elements are given, for example, by the diameter of the geometric symbols or the line thickness of letters or numbers. In negative representations, the distance between adjacent recesses forms a characteristic dimension of the microstructure elements. Regardless of the specific design of the microstructure arrangement, the only important thing in the present case is that the microstructure elements cannot be recognized as such with the naked eye due to their small dimensions from the normal viewing distance of 25 cm or more, but that the microstructure arrangement is due to the color mixing of the element colors like a fine print grid is perceived as a homogeneous surface.

In an advantageous embodiment, the microstructure elements contain a first group of microstructure elements of a first color in a negative representation and a second group of microstructure elements of a second, different color in a positive representation, the microstructure elements of the second group are arranged in the recesses of the first group of microstructure elements.

The luminescent substances of the second color range are present at least in some areas in a luminescent layer arranged above and/or below the visually visible printing inks.

In a further advantageous embodiment, the luminescent substances of the second color range are present in a luminescence layer arranged below the visually visible printing inks and the visually visible printing inks of the first color range contain a UV blocker in some areas, which prevents UV excitation at least in a partial range of the UV spectrum 200 nm and 400 nm reduced or prevented.

In a further development of the invention it is provided that the first and second color ranges are overprinted with a line structure with a non-luminescent, visually visible color, the color of which differs from the uniform color or colors of the first color range. The line structure preferably accommodates geometric shapes that can be seen with the naked eye elsewhere in the security element, in particular the outline shape of a luminescent or non-luminescent partial area of the feature area. With the additional line structure you can Any visible color differences, gloss differences and/or registration fluctuations of the visually visible printing inks are masked.

In a visually very attractive design, the at least two different macroscopic luminescence areas have a different colored luminescent outer contour, which corresponds in color to the other luminescence color or a mixed color of the two luminescence colors.

The microstructure arrangement is advantageously arranged on a transparent or opaque carrier, in particular on a transfer film element. The microstructure arrangement can in particular be arranged directly on the carrier, in particular printed onto the carrier.

The security element is advantageously a security thread, in particular a window security thread or a pendulum security thread, a tear thread, a security tape, a security strip, a patch or a label for application to a security paper, document of value or the like. The security element can contain a carrier film or be present without a carrier film.

The invention also contains a method for producing a security element of the type described according to claim 14.

In the process, the microstructure arrangement and/or the luminescent substances are advantageously applied in offset printing, letterpress printing, indirect letterpress printing, gravure printing or in a digital printing process such as ink-jet printing or laser printing process.

• einem Merkmalsbereich, der einen ersten Farbbereich enthält, der aus visuell sichtbaren Druckfarben gebildet ist,
• einem zweiten Farbbereich, der aus ohne Anregung nicht sichtbaren Lumineszenzstoffen gebildet ist und der den Merkmalsbereich zumindest teilweise überlappt,
• der Merkmalsbereich bei Betrachtung im sichtbaren Licht zumindest zwei verschiedene sichtbare Farben zeigt,
• der zweite Farbbereich des Merkmalsbereichs bei Betrachtung mit bloßem Auge unter UV- oder IR-Anregungslicht ein homogenes Erscheinungsbild mit einer zumindest bereichsweise jeweils einheitlichen Lumineszenzfarbe zeigt und
• wobei der zweite Farbbereich eine Mikrostrukturanordnung aus verschiedenfarbig lumineszierenden Mikrostrukturelementen enthält, die eine charakteristische Abmessung unterhalb der Auflösungsgrenze des menschliche Auges aufweisen und die jeweils eine von zumindest zwei unterschiedlichen Lumineszenzfarben aufweisen und durch Farbmischung die zumindest bereichsweise jeweils mit bloßem Auge sichtbare, einheitlichen Lumineszenzfarbe erzeugen.

In another, unclaimed aspect, the description includes a security element for securing valuables

• a feature area that contains a first color area that is formed from visually visible printing inks,
• a second color area which is formed from luminescent substances that are not visible without excitation and which at least partially overlaps the feature area,
• the feature area shows at least two different visible colors when viewed in visible light,
• the second color range of the feature area has a homogeneous appearance when viewed with the naked eye under UV or IR excitation light with a luminescence color that is uniform at least in some areas and
• wherein the second color range contains a microstructure arrangement of differently colored luminescent microstructure elements, which have a characteristic dimension below the resolution limit of the human eye and which each have one of at least two different luminescence colors and, by color mixing, produce the uniform luminescence color that is visible to the naked eye at least in some areas.

Preferably, the second color range even shows only a single uniform luminescence color. The uniform luminescence colors of the feature area generated upon excitation, or the only uniform luminescence color, advantageously differ from the colors of the feature area that are visible in visible light.

The first color range advantageously has two or more color ranges, which are designed in the form of patterns, characters or a coding and which each show one of the different visible colors in visible light.

The microstructure elements have two or more different luminescent colors, which produce the perceived color impression for the viewer from the normal viewing distance through color mixing, in particular additive color mixing and absorption of the emission color by the visually visible colors. In addition to the colors of the microstructure elements, a luminescent background color can also contribute to the mixed color. It is advantageously provided that the different luminescence colors of the microstructure elements in the CIELab system have a color difference ΔE of at least 4.0, preferably of at least 6.0.

Analogous to the first aspect of the invention, the microstructure elements of the second color range can be arranged adjacent to one another or at a distance from one another. The microstructure elements can be designed in the positive representation in the form of geometric symbols, letters and/or numbers and/or in the negative representation as a surface with recesses in the form of geometric symbols, letters and/or numbers. In particular, line fragments, squares, triangles or other polygons, each with or without filling, come into consideration as geometric symbols. Advantageously, the microstructure elements at least partially accommodate geometric elements that are visible to the naked eye elsewhere in the security element in order to establish a connection between the various elements of the security element. Such a connection also makes it easier to recognize or identify the content of information encoded by the microstructure.

The characteristic dimensions of the microstructure elements are given, for example, by the diameter of the geometric symbols or the line thickness of letters or numbers. In negative representations, the distance between adjacent recesses forms a characteristic dimension of the microstructure elements. Regardless of the specific design of the microstructure arrangement, the only important thing in the present case is that the microstructure elements cannot be seen with the naked eye due to their small dimensions from the normal viewing distance of 25 cm or more, but that the microstructure arrangement is created by the additive color mixing of the luminescent colors of the elements like a fine print screen is perceived as a homogeneous surface.

In an advantageous embodiment, the microstructure elements contain a first group of microstructure elements of a first luminescent color in a negative representation and a second group of microstructure elements of a second, different luminescence color in a positive representation, the microstructure elements of the second group being arranged in the recesses of the first group of microstructure elements.

In an advantageous embodiment, the luminescent substances of the second color range are mixed at least in areas with the visually visible printing inks of the first color range and thereby form printing inks that are both visually visible and luminescent.

In another, also advantageous embodiment, the luminescent substances of the second color range can be present at least in some areas in a luminescent layer arranged above and/or below the visually visible printing inks.

The invention also contains a data carrier with a security element of the type described. The data carrier can in particular be a document of value, such as a banknote, in particular a paper banknote, a polymer banknote or a film composite banknote, a share, a bond, a certificate, a voucher , a check, a seal, a tax stamp, a high-quality admission ticket, but also an identification card, such as a credit card, a bank card, a cash payment card, an authorization card, an ID card or a passport personalization page.

The security element can represent a separate security element, for example a film element, which is located at a desired location on a Disk is arranged. With particular advantage, the security element can also form an integral part of the data carrier itself, for example by means of an imprint that is applied to a substrate of the data carrier.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, which were not reproduced to scale and proportions in order to increase clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem eingebetteten Sicherheitsfaden und zwei drucktechnisch erzeugten Sicherheitselementen, jeweils nach Ausführungsbeispielen der Erfindung,

Fig. 2

eine Aufsicht auf ein Sicherheitselement nach einem ersten Ausführungsbeispiel der Erfindung, wobei (a) das Erscheinungsbild des Sicherheitselements im sichtbaren Licht und (b) das Erscheinungsbild unter UV-Licht zeigt,

Fig. 3

in (a) schematisch den Aufbau eines nicht beanspruchten Sicherheitselements im Querschnitt, in (b) das zugehörige Erscheinungsbild bei Betrachtung im sichtbaren Licht und in (c) das Erscheinungsbild im UV-Licht in Aufsicht,

Fig. 4 bis 6

vorteilhafte Abwandlungen der Gestaltung der Fig. 3, wobei die Gestaltungen der Fig. 4 und 6 anspruchsgemäß sind und die Gestaltung der Fig. 5 nicht beansprucht ist,

Fig. 7

ein Sicherheitselement nach einer weiteren nicht beanspruchten Abwandlung der Gestaltung der Fig. 3, wobei (a) schematisch den Aufbau eines Sicherheitselements im Querschnitt zeigt und (b) und (c) das zugehörige Erscheinungsbild bei Betrachtung im sichtbaren Licht bzw. im UV-Licht in Aufsicht zeigen,

Fig. 8

in (a) bis (e) vorteilhafte Ausgestaltungen der Aufteilung der visuell homogen erscheinenden Fläche erfindungsgemäßer Sicherheitselement in Mikrostrukturelemente,

Fig. 9

eine Weiterbildung des Sicherheitselements der Fig. 2, mit einer den ersten und zweiten Farbbereich überdruckenden Linienstruktur, wobei (a) das Erscheinungsbild des Sicherheitselements im sichtbaren Licht und (b) das Erscheinungsbild unter UV-Licht in Aufsicht zeigt,

Fig. 10

ein Sicherheitselement nach einem anderen Aspekt, wobei (a) das Erscheinungsbild des Sicherheitselements im sichtbaren Licht und (b) das Erscheinungsbild unter UV-Licht in Aufsicht zeigt,

Fig. 11

schematisch den Aufbau des Sicherheitselements der Fig. 10 im Querschnitt, und

Fig. 12

eine nicht beanspruchte Abwandlung der Gestaltung der Fig. 11.

Show it:

Fig. 1

a schematic representation of a banknote with an embedded security thread and two security elements produced by printing, each according to exemplary embodiments of the invention,

Fig. 2

a top view of a security element according to a first embodiment of the invention, wherein (a) shows the appearance of the security element in visible light and (b) shows the appearance under UV light,

Fig. 3

in (a) schematically the structure of an unclaimed security element in cross section, in (b) the associated appearance when viewed in visible light and in (c) the appearance in UV light in top view,

Fig. 4 to 6

advantageous modifications to the design of the Fig. 3 , whereby the designs of the Fig. 4 and 6 are required and the design of the Fig. 5 is not claimed,

Fig. 7

a security element according to a further unclaimed modification of the design Fig. 3 , where (a) shows schematically the structure of a security element in cross section and (b) and (c) show the associated appearance when viewed in visible light or in UV light in top view,

Fig. 8

in (a) to (e) advantageous embodiments of the division of the visually homogeneous surface of the security element according to the invention into microstructure elements,

Fig. 9

a further development of the security element of the Fig. 2 , with a line structure overprinting the first and second color areas, (a) showing the appearance of the security element in visible light and (b) showing the appearance under UV light in top view,

Fig. 10

a security element according to another aspect, wherein (a) shows the appearance of the security element in visible light and (b) shows the appearance under UV light in top view,

Fig. 11

schematically the structure of the security element Fig. 10 in cross section, and

Fig. 12

an unclaimed modification of the design of the Fig. 11 .

The invention will now be explained using the example of security elements for banknotes. Figure 1 shows a schematic representation of a banknote 10, which has a substrate made of paper, plastic or a hybrid substrate a combination of paper and plastic layers. The banknote 10 is provided with three security elements 12, 16 and 18 according to exemplary embodiments of the invention, the first security element representing a security thread 12 which emerges from certain window areas 14 on the surface of the banknote 10, while in the intermediate areas inside the banknote 10 Banknote 10 is embedded.

The second security element 16 is formed by a portion of the banknote 10, in which the banknote paper is provided with an imprint that has the various special color areas described in more detail below. The third security element 18 is formed by a portion of the banknote 10, in which the banknote paper is provided with a motif-shaped imprint, namely an imprint with a recess in the form of the value number "10" of the banknote. This print also has the special color ranges described below.

However, it is understood that the invention does not apply to the in Fig. 1 security elements shown by way of example, but in particular also includes glued-on transfer elements of any shape with or without their own carrier film. The security element can also be designed in the form of a cover film which is arranged over a window area or a continuous opening of the banknote. The invention can be used for all types of security elements, for example labels on goods and packaging or for securing documents, ID cards, passports, credit cards, health cards and the like.

The structure and appearance of security elements according to the invention will now be explained in more detail with reference to the following figures.

Figure 2 shows a top view of a security element 20 according to a first exemplary embodiment of the invention, where Fig. 2(a) the appearance of the security element in visible light and Fig. 2(b) represents the appearance of the security element under UV light.

When viewed in visible light, the security element 20 appears to the naked eye from a usual viewing distance of approximately 30 cm as a homogeneous surface 22 with a uniform color, for example red. As in detail D of the Fig. 2(a) illustrated, the surface that appears monochromatic is actually formed from a large number of small microstructure elements 24, 26, all of which have a dimension below the resolution limit of the human eye and are therefore not visible to the naked eye.

In the exemplary embodiment, the microstructure elements are formed by 80 μm × 80 μm squares 24, 26, each of which has a recess 28 in the form of letters or numbers, as in Fig. 2(a) illustrated by the letters “A” and “B” respectively. The squares 24 are printed directly onto the banknote paper of a banknote 10 with a printing ink with yellow color pigments, the squares 26 with a printing ink with magenta color pigments. The background underneath the microstructures, for example the white banknote paper, appears in the letter-shaped recesses 28. The different colored squares 24, 26 produce the mixed color red of the surface 22 through subtractive color mixing, the color saturation of the red color impression being able to be adjusted by the size of the recesses 28. Figure 2 shows the same size Squares 24, 26, but the microstructures can also have different sizes, for example in order to produce a mixed color of a desired color.

The fact that the surface 22, which appears homogeneously monochrome from a normal viewing distance, actually consists of the different colored squares 24, 26 with their letter-shaped recesses 28 can be determined with a magnifying glass or a microscope and represents an authenticity feature of the security element 20 that is difficult to reproduce.

When viewed under UV light, the security element 20 shows the in Fig. 2(b) Appearance shown with two motif-shaped luminescence areas 30, 32 located within the surface 22, which glow with different luminescence colors, for example orange and green. Both luminescence colors are different from the visible red color of the surface 22, so that the luminescence areas 30, 32 appear in a clearly contrasting manner even with the combination lighting of visible and UV light that is usually present. When viewed without UV light, as in Fig. 2(a) shown, the luminescence areas 30, 32 are not recognizable; the same homogeneous, red appearance is visible in their surface areas as in the rest of the surface 22, so that the position of the luminescence areas in Fig. 2(a) is only indicated by dashed lines.

In the exemplary embodiment Fig. 2 The homogeneous appearing surface 22 forms the above-mentioned first color area and at the same time the feature area that is congruent with the first color area, and the luminescence areas 30, 32 together form the above-mentioned second color area, which overlaps the feature area. In the exemplary embodiment Fig. 2 is the second color area arranged completely within the feature area.

The microscopic microstructure elements 24, 26 and the macroscopic luminescence regions 30, 32 can advantageously be coordinated with one another. For example, the recesses 28 of the microstructure elements 24, 26 can be designed alternately in the form of the numbers "1" and "0" of the value number "10" of the banknote, and the two luminescent areas 30, 32 can also be in the form of the numbers "1" or "0" may be applied to represent the value under UV lighting. By relating the microscopic and macroscopic information to one another, an additional security effect is achieved.

Figure 3 shows in (a) schematically the structure of an unclaimed security element 20 in cross section, which Figures 3(b) and 3(c) illustrate the associated appearance of the security element when viewed in visible light or in UV light in top view.

With reference first to the cross section of the Fig. 3(a) the security element 20 has a substrate 36, which in particular represents the substrate of the document of value onto which the security element 20 is applied, for example printed. However, it is also possible for the substrate 36 to be a substrate film of a separate security element, which is applied, for example glued, to a desired target substrate after its production. The security element 20 can also have been produced on a transfer carrier substrate, transferred to the target substrate and the transfer carrier substrate then peeled off.

The surface 22 is formed by a sequence of microstructure elements 24, 26, which are formed, for example, by printing inks with yellow or magenta color pigments. The microstructure elements can also contain recesses, as in Fig. 2 shown, but for the sake of easier presentation Fig. 3 are not shown. The microstructure elements can be applied adjacent to one another or at a small distance next to one another. Due to the small dimensions of the microstructure elements 24, 26, the surface 22 appears from a normal viewing distance with the uniform subtractive mixed color of the yellow and magenta microstructure elements, i.e. in a uniform red color.

As in Fig. 3(a) shown further, the printing inks of the microstructure elements 24, 26 in the first luminescence regions 30 are mixed with a first luminescent substance 40, which is transparent in the visible spectral range and therefore does not influence the visual colors of the microstructure elements. In second luminescence regions 32, a second, visible transparent luminescent substance 42 is mixed into the printing inks of the microstructure elements 24, 26. The luminescent colors of the first and second luminescent substances 40, 42 differ from one another and also differ from the mixed color of the surface 22. In the non-luminescent areas 34, the printing colors of the microstructure elements 24, 26 are present without the admixture of luminescent substances.

The luminescence areas 30, 32 are formed macroscopically in the form of characters or patterns, such as the coat of arms motif or the star motif Fig. 2(b) . In any case, the luminescence regions have such large dimensions that, in contrast to the microstructure elements 24, 26, they can be seen with the naked eye from a normal viewing distance, and therefore each contain a large number of microstructure elements 24, 26. The Luminescence areas 30, 32 can be continuous or gridded, i.e. formed by small luminescent grid elements that cannot be resolved with the naked eye, which together form the desired luminescence motif from a normal viewing distance.

Six different printing colors are therefore used to print the surface 22, namely the visually visible printing ink with the first color (yellow) without the addition of luminescent substance, the visually visible printing ink of the first color with the addition of the first luminescent substance 40 or the second luminescent substance 42 , the visually visible printing ink of the second color (magenta) without admixture of luminescent substance and the visually visible printing ink of the second color with admixture of the first luminescent substance 40 or the second luminescent substance 42.

The registration of these six printing colors represented a high hurdle for potential counterfeiters and cannot be achieved with conventional office printers. Conventional inkjet printers are optimized to reproduce colored images, such as photos, as well as possible and therefore use a special raster technology to display uniform color gradients and color-correct representations. In this case, the colored print structures are composed of individual dots that are slightly offset from each other and therefore do not show any smooth edges. If visually visible colors are also to show fluorescence, this must be done in a further printing step using a second printer equipped with fluorescent ink-jet inks. Due to the re-application of the sheet printed with the visually visible colors, there is inevitably a certain offset between the first and second print due to the printer's system and transport tolerances.

With regard to the visual appearance of the Fig. 3(b) The transparent luminescent substances do not appear when viewed in the visible spectral range. The sequence of the different colored microstructure elements 24, 26 can be seen with a magnifying glass; with the naked eye, the color effects of the microstructure elements 24, 26 mix to form the uniform mixed color of the surface 22.

When viewed under UV light, the luminescent areas 30, 32 glow in the corresponding luminescent colors, as shown in Fig. 3(c) illustrated. In the case of a combination illumination of visible light and UV light, in addition to the luminescent colors, the colors of the microstructure elements 24, 26 also appear, so that the luminescent areas 30, 32 appear to the naked eye against the background of the mixed color of the surface 22.

Figure 4 shows a modification of the design that falls under the main claim Fig. 3 , in which the luminescent substances 40, 42 are not mixed with the printing inks of the microstructure elements 24, 26, but are printed separately as visually transparent, luminescent printing inks 50, 52 on the printing layer with the microstructure elements 24, 26. In this embodiment, it is not essential that the macroscopic luminescence regions 30, 32 fit to the microstructure elements 24, 26. The luminescence areas can be either continuous (illustrated on the luminescence area 30) or rasterized (illustrated on the luminescence area 32), i.e. formed by small luminescent grid elements 38 that cannot be resolved with the naked eye, which form the desired luminescence motif from the normal viewing distance in the manner of a raster image generate.

The printing inks 50, 52 can be printed onto the microstructure elements 24, 26, as in Fig. 4 illustrated, or below the microstructure elements 24, 26 are available. In the latter case, the light emitted after UV excitation passes through the printing inks of the microstructure elements 24, 26, so that the perceptible luminescence colors result from the emitted luminescence colors and the absorption properties of the printing inks of the microstructure elements. It goes without saying that the luminescent printing inks 50, 52 can also be present partly above and partly below the microstructure elements 24, 26. The technological challenge of this design lies in particular in the fit of the microstructure elements 24, 26 to produce the homogeneously monochromatic surface 22.

Compared to the design of the Fig. 3 are used in the design of the Fig. 4 only four different colors (2 visually visible and 2 visually invisible colors with different luminescence) are needed. Instead of two different colored luminescent substances, only one luminescent substance can be used, whereby different luminescent colors can then be obtained by carrying out a first luminescent print in a flat manner and a second luminescent print in a rasterized manner.

In a process-technically more sophisticated variant, the visually invisible luminescent printing ink is printed more or less well registered in the area of the first visually visible microstructure color, for example yellow, and for the second luminescent area in the area of the second visually visible microstructure, for example magenta. When using a white luminescence color, a yellow and a magenta luminescence image appears due to the interaction with the background color

Figure 5 shows another unclaimed modification of the design of the Fig. 3 , in which one of the printing inks, in the exemplary embodiment the printing ink for the microstructure elements 24 ', is formulated to be opaque and these microstructure elements 24' are printed on previously applied microstructure elements 26'. With this approach, registration fluctuations between the two printing passes for the first and second microstructures can be compensated for more easily than in the case of side-by-side printing. The opaque printing ink of the microstructures 24' partially covers the microstructures 26' arranged underneath, so that essentially only the opaque printing ink appears at the overprinted areas. Since the printing ink provided with a luminescent substance 40 or 42 also has an opaque effect, only the luminescent substance of the opaque printing ink is excited to emit in the overprinted areas in the luminescent areas 30 and 32, respectively. Accordingly, the result is essentially an appearance as in Fig. 3(b) in visible light and an appearance like in Fig. 3(c) in UV light.

Figure 6 shows another modification of the design that falls under the main claim Fig. 3 , in which there is a continuous luminescent layer 60 on the substrate 36, which takes up the entire surface 22 and contains a first luminescent substance 40 in some areas and a second luminescent substance 42 in some areas. The microstructure elements 24, 26 are printed onto the luminescent layer 60, with a UV blocker 62 being mixed into the printing inks of the microstructure elements 24, 26 in the non-luminescent areas 34, which prevents UV excitation of the luminescent substances 40, 42 at these points. In the luminescence regions 30 and 32, however, the luminescent substances 40, 42 can be excited through the visible printing inks and the luminescence emission, filtered through the printing inks of the microstructure elements 24, 26, can be observed.

The overall result is essentially an appearance as in Fig. 3(b) in visible light and an appearance like in Fig. 3(c) in UV light. In areas of the luminescent layer 60 without overprinting by visually visible printing inks or in recesses of the visually visible printing inks, there is no filtering of the emission color.

If IR-stimulable luminescent substances are used, corresponding NIR absorbers must be used instead of UV blockers in order to achieve the desired prevention of IR excitation.

Another variation of the design Fig. 3 is in Fig. 7 shown, which in (a) shows schematically the structure of an unclaimed security element 20 in cross section and in (b) and (c) the associated appearance when viewed in visible light or in UV light in top view.

In this embodiment, surface 22 is referenced Fig. 7(a) formed by a sequence of microstructure elements 24, 26, which are applied to the substrate 36 with small gaps 70. The dimensions of the gaps 70 are of the same order of magnitude as the dimensions of the microstructure elements 24, 26. In the luminescence regions 30, 32, the gaps 70 are filled with visually transparent, luminescent printing inks 50, 52, which are filled with first and second luminescent substances 40, 42 are provided. The luminescent printing inks 50, 52 arranged there represent small printing dots or printing elements of a raster image, and form the desired motifs of the luminescent areas from a normal viewing distance, without the raster itself being resolvable with the naked eye.

With reference to the representation of the Fig. 7(b) The transparent, luminescent printing inks 50, 52 do not appear when viewed in the visible spectral range. With a magnifying glass, the sequence of the different colored, spaced-apart microstructure elements 24, 26 can be seen; when viewed with the naked eye at a normal viewing distance, their color effects mix to form the uniform mixed color of the surface 22.

When viewed under UV light, the luminescent areas 30, 32 light up in the corresponding luminescent colors, as shown in Fig. 7(c) illustrated, whereby the luminescent spaces produce the desired luminescence motifs in the manner of raster images as described.

It goes without saying that combinations of the variants described can also be used Figures 2 to 7 are possible and that more than two different visually visible colors and more than two different luminescent colors can be used to further complicate reenactment. The luminescent substances can differ from one another in particular in the excitation spectrum, the emission spectrum and the afterglow duration.

Figure 8 illustrates some advantageous embodiments for dividing the visually homogeneous surface into microstructure elements in the form of various characters and symbols. An enlarged section of the area of the first color area with the microstructure elements is shown schematically. To the naked eye, the surface appears homogeneous from a normal viewing distance, as already explained above.

In the exemplary embodiment of Fig. 8(a) The seemingly homogeneous surface 80 contains microstructure elements 82 of a first color, and microstructure elements 84 of a second, different color. In the exemplary embodiment, the microstructure elements are each formed by letters of a specific font in the same font size and printed on a white substrate base 86. For example, the line width of the letters is 10 µm to 30 µm and the letter height is 30 µm to 100 µm.

In the exemplary embodiment, the letters of the different colored microstructure elements 82, 84 form the word "TALER" as a hidden coding that is only visible with a magnifying glass. The color of the initial letter "T" changes constantly in order to create the most uniform color impression possible of the surface 80 from the normal viewing distance. The color of the surface 80 results from the two different colors of the microstructure elements 82, 84 and the white color of the substrate background 86. As shown, the color of the first letters of each line also advantageously changes from line to line in order to avoid monochrome edge lines.

The exemplary embodiment of the Fig. 8(b) shows a modification of the design Fig. 8(a) , in which the readability of the microwriting formed by the microstructure elements is increased by adding a star-shaped separation symbol 88. The separator symbol 88 preferably has essentially the same area coverage as the letter symbols so as not to introduce any noticeable disturbances in the character string. The addition of the separation symbol 88 results in a further advantage that the color of the initial letter "T" can now always be the same, thereby increasing the readability of the coded word under a magnifying glass. It is understood that instead of the in Fig. 8(b) Others also used Stern symbols, and that multiple separation symbols can also be used.

While the designs of the Figures 8(a) and (b) Using positive representations of the characters is important when designing the Fig. 8(c) A negative representation of the letters is used for the area 80, with which a higher color coverage is achieved. In this exemplary embodiment, the surface is 80, as in the design of the Fig. 2 , formed by a sequence of square microstructure elements 92, 94 in two different colors, the squares each containing a centered recess 98 in the form of the letters of the coded word "TALER". The mixed color of the surface 80 results from the colors of the microstructure elements 92, 94 and the white color of the substrate background in the recesses 98.

In the variant of Fig. 8(d) the homogeneous appearing surface 80 is formed on the one hand by a negative microstructure 102 of a first color and on the other hand by a positive microstructure 104 of a second color. The negative microstructure 102 contains recesses in the form of the letters of the word "TALER", while the positive microstructure 104 congruently contains the same letters in positive representation, which are each arranged in the recesses of the negative microstructure 102. The unprinted portion of the substrate is further reduced by such a combination of two positive/negative microstructures and high color strength is achieved.

With reference to the exemplary embodiment of Fig. 8(e) The first color area 110 of a security element can also contain several partial areas 112, 114 in which the homogeneously appearing surface 80 each appears with a different mixed color. For example, based on the Design of the Fig. 8(d) in a first subregion 112 there is a negative microstructure 102 of a first color and a positive microstructure 104 of a second color, and in a second subregion 114 a negative microstructure 106 of a third color, combined with the positive microstructure 104 of the second color ( or a fourth color). From a normal viewing distance, the surface 80 then appears homogeneous and with a uniform color in both the partial area 112 and the partial area 114, the uniform color in the first partial area 114 being due to subtractive color mixing of the first and second colors, and the uniform color in the second partial area 116 by subtractive color mixing of the third and second colors (or the third and fourth colors).

It is understood that alternatively or additionally the color of the positive microstructure 104 can also change from the first to the second subregion. The partial areas of different colors can be spaced apart or directly adjacent to one another. More than two partial areas with different mixed colors can also be provided. In an advantageous design, the mixed colors of these several partial areas are coordinated with one another in such a way that, from the normal viewing distance, they appear as a quasi-continuous color gradient between two areas with fixed but different mixed colors.

Figure 9 shows a further development of the security element 20 Figures 2 and 3 , in which the first color area 22 and the second color area 30, 32 are overprinted with a line structure 120, the color of which differs from the uniform red mixed color of the first color area. Alternatively, the structure 120 can also be created by leaving out the visually visible colors. The line structure 120 can be designed in any way but preferably takes up a geometric shape present in the partial areas 30, 32 or 34, in the exemplary embodiment approximately the star shape of the second luminescence area 32.

On the one hand, the additional line structure 120 masks any noticeable color differences, gloss differences and/or registration fluctuations between the partial areas 30, 32 or 34, which can remain in some cases despite the basic color sameness and the visual transparency of the luminescent substances. By recording the geometric shape of one of the partial areas 30, 32, 34, even such residual differences, if they should be noticed by an observer, appear targeted and therefore less disturbing.

The line structure 120 is printed with a visually visible, non-luminescent color so that when viewed in visible light it has the masking effect described, as in Fig. 9(a) illustrated. When viewed under UV light, the line structure 120 appears darker in the luminescence areas 30, 32 because it reduces the emission of the luminescent substances there. In Fig. 9(b) To illustrate this effect, this effect is shown with an exaggerated line thickness of the line structure 120 in the case of complete blocking of the luminescence emission.

Figures 10 and 11 illustrate another design of a security element 200, where Fig. 10(a) the appearance of the security element 200 in visible light and Fig. 10(b) represents the appearance of the security element under UV light. Figure 11 shows schematically the structure of the security element 200 in cross section along the line XI-XI of Fig. 10(a) .

The security element 200 appears in visible light with two or more different colors in an area 202, where in Fig. 10(a) To illustrate, two color areas 204, 206 of different colors are shown, which are separated by an unprinted intermediate area 208.

When viewed under UV light, the appearance of the security element 200 changes, so that when viewed with the naked eye from a usual viewing distance of approximately 30 cm, both color areas 204, 206 now glow in the same luminescent color, as in Fig. 10(b) illustrated. For example, the two motifs 204 (coat of arms and star) can appear red against a blue background 206 in visible light, while under UV light both the two motifs 204 and the background 206 appear with yellow luminescence.

As in detail section D of the Fig. 10(b) illustrated, the monochrome luminescent surface is actually composed of a plurality of small luminescent microstructure elements 224, 226, which have a dimension below the resolution limit of the human eye and are therefore not visible to the naked eye.

In the exemplary embodiment, the single-color luminescent surface 202 is formed by a negative microstructure 224 with a first luminescent color, for example red, and a positive microstructure 226 of a second luminescent color, for example green, which together produce the yellow luminescent color of the surface 202 through additive color mixing. The negative microstructure 224 contains the letters of the encoded word "TALER" as recesses, while the positive microstructure 226, congruent with the recesses of the negative microstructure 224, contains the same letters in positive representation.

Regarding Fig. 11 the security element 200 has a substrate 36, which, as in the previously described designs, can be, for example, a substrate film of the security element itself or the substrate of a document of value on which the security element is applied.

The two different colored color areas 204, 206 are printed on the substrate 36 using visually visible printing inks. A luminescent layer 220, which is formed by the above-mentioned sequence of elements of the negative microstructure 224 and the positive microstructure 226, is applied to both color areas. The negative microstructure 224 contains a first luminescent substance 214, which luminesces red after UV excitation, and the positive microstructure 226 contains a second luminescent substance 216, which luminesces green after UV excitation. Due to the small dimensions of the microstructure elements 224, 226, the surface 202 appears with the uniform additive mixed color yellow from a normal viewing distance in UV light. With a magnifying glass or a microscope, the composite character of the area 202 can be proven as an authenticity feature.

It is understood that the microstructure elements 224, 226 can also be applied in other arrangements, in particular in one of the above with reference to Figures 8(a) to 8(e) described arrangements.

In an unclaimed modification of the design of the Fig. 11 The luminescent substances 214, 216 can also each be mixed with a visually visible printing ink, as shown in FIG Fig. 12 illustrated.

The luminescent substances 214 and 216 are each mixed with a blue printing ink in the color areas 206, and the two printing inks 234, 236 thus obtained are printed alternately in the form of the microstructure elements 224, 226 in order to produce the background area 206. In the color areas 204, the luminescent substances 214 and 216 are each mixed with a red printing ink, and the two printing inks 244, 246 thus obtained are printed alternately in the form of the microstructure elements 224, 226 in order to produce the red motif areas 204. The result of this variant also results in the appearance of the security element 200 described above.

The exemplary embodiments were each described with reference to UV light as excitation radiation, but it is understood that luminescent substances that can be stimulated to luminescence by IR light can also be used in the same way.

Reference symbol list

10

Banknote

12

Security thread

14

Window areas

16

Transfer element

20

Security element

22

homogeneous surface

24, 24'

first microstructure elements

26, 26'

second microstructure elements

28

recesses

30.32

Luminescent areas

34

Non-luminescent areas

36

Substrate

38

luminescent grid elements

40, 42

Luminescent substances

50, 52

luminescent printing inks

60

Luminescent layer

62

UV blockers

70

spaces

80

homogeneous appearing surface

82, 84

Microstructure elements

86

Substrate underlay

88

Separation symbol

92, 94

Microstructure elements

98

recess

102

Negative microstructure

104

Positive microstructure

106

Negative microstructure

112,114

Sub-areas

120

Line structure

200

Security element

202

Area

204,206

Color ranges

208

Intermediate area

214,216

Luminescent substances

220

Luminescent layer

224, 226

luminescent microstructure elements

234, 236

Printing colors for blue motif areas

244, 246

Printing colors for red motif areas

Claims (15)

1. A security element (12) for securing valuable articles (10), the security element comprising

   - a feature region that includes a first color region (20) that is formed from visually visible printing inks, and

   - a second color region (30,32) that is formed from luminescent substances that are not visible without excitation, and that at least partially overlaps the feature region,

   - the first color region of the feature region displaying, when viewed with the naked eye in visible light, a homogeneous appearance having a uniform visible color, and

   - the feature region displaying, when viewed under UV or IR excitation light, at least two different luminescent colors,

   characterized in that

   - the first color region includes a microstructure arrangement composed of different colored microstructure elements that comprise a characteristic dimension below the resolution limit of the human eye and that each comprise one of at least two different colors and, through color mixing, produce the uniform color that is visible with the naked eye, and in that

   - the luminescent substances of the second color region are present at least in some regions in a luminescence layer arranged above and/or below the visually visible printing inks.
2. The security element according to claim 1, characterized in that at least two luminescent substances of the second color region lie completely within a region of the first color region having a uniform visible color.
3. The security element according to claim 1 or 2, characterized in that, when viewed with the naked eye in visible light, the feature region displays a homogeneous appearance having a single uniform visible color.
4. The security element according to at least one of claims 1 to 3, characterized in that the luminescent colors of the feature region differ from the in each case uniform visible colors, especially from the single uniform visible color.
5. The security element according to at least one of claims 1 to 4, characterized in that the second color region comprises two or more luminescence regions that are formed in the form of patterns, characters or codes and that, under UV or IR excitation light, display in each case one of the different luminescent colors, the second color region preferably lying completely within the first color region.
6. The security element according to at least one of claims 1 to 5, characterized in that the different colors of the microstructure elements comprise, in the CIELAB system, a color difference ΔE of at least 4.0, preferably of at least 6.0.
7. The security element according to at least one of claims 1 to 6, characterized in that the microstructure elements are arranged adjoining one another, or in that the microstructure elements are arranged spaced apart.
8. The security element according to at least one of claims 1 to 7, characterized in that the microstructure elements are formed in positive display in the form of geometric symbols, letters and/or numbers, and/or in negative display as an area having gaps in the form of geometric symbols, letters and/ or numbers.
9. The security element according to claim 8, characterized in that the microstructure elements include a first group of microstructure elements of a first color in negative display, and a second group of microstructure elements of a second, different color in positive display, the microstructure elements of the second group being arranged in the gaps of the first group of microstructure elements.
10. The security element according to at least one of claims 1 to 9, characterized in that the luminescent substances of the second color region are present in a luminescence layer arranged below the visually visible printing inks, and the visually visible printing inks of the first color region include, in some regions, a UV blocker that reduces or prevents a UV excitation at least in a sub-range of the UV spectrum between 200 nm and 400 nm.
11. The security element according to at least one of claims 1 to 10, characterized in that the first and second color region are overprinted with a line structure having a non-luminescent, visually visible ink whose color differs from the uniform color or colors of the first color region.
12. The security element according to at least one of claims 1 to 11, characterized in that the microstructure arrangement is arranged on a transparent or opaque carrier, especially on a transfer foil element.
13. A data carrier having a security element according to one of claims 1 to 12, the data carrier especially being a value document or an identity card.
14. A method for manufacturing a security element according to one of claims 1 to 12, in which

    - a feature region having a first color region is produced, which color region is formed from visually visible printing inks,

    - a second color region is formed from luminescent substances that are not visible without excitation, such that the second color region at least partially overlaps the feature region,

    - the first color region of the feature region displaying, when viewed with the naked eye in visible light, a homogeneous appearance having a uniform visible color,

    - the feature region displaying, when viewed under UV or IR excitation light, at least two different luminescent colors,

    - the first color region being formed having a microstructure arrangement composed of different colored microstructure elements that comprise a characteristic dimension below the resolution limit of the human eye and that each comprise one of at least two different colors and, through color mixing, produce the uniform color that is visible with the naked eye, and

    - the second color region is formed from luminescent substances that are present at least in some regions in a luminescence layer arranged above and/or below the visually visible printing inks.
15. The method according to claim 14, characterized in that the microstructure arrangement and/or the luminescent substances are applied in offset printing, relief printing, indirect relief printing, intaglio printing or in a digital printing method such as inkjet printing or laser printing methods.

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