WO2018184715A1

WO2018184715A1 - Security element having relief structure and production method therefor

Info

Publication number: WO2018184715A1
Application number: PCT/EP2018/000100
Authority: WO
Inventors: Hans Lochbihler; Christian Fuhse; Thomas Gerhardt; Maik Rudolf Johann Scherer; Falk Amthor; Michael Rahm; Matthias Pfeiffer
Original assignee: Giesecke+Devrient Currency Technology Gmbh
Priority date: 2017-04-04
Filing date: 2018-03-19
Publication date: 2018-10-11
Also published as: CN110520304A; JP2020517486A; EP3606765B1; CN110520304B; DE102017003281A1; EP3606765A1; JP7104062B2

Abstract

The invention relates to a security element (S) for producing security documents, such as bank notes, checks, or the like, which shows a theme in front of a background, which has a relief structure (7, 10, 12-14, 16, 17), which covers a theme region (1, 4) of the security element (S) and provides the theme there and covers a background region (2) of the security element (S) and provides the background there, wherein there is an outline (3), which delimits the theme from the background, which is also formed by the relief structure, wherein the relief structure (12, 14 and 17) of the outline differs from the relief structure (10, 13, 16a) of the theme region and the relief structure (7, 16b) of the background region (2) such that there is a brightness and/or color contrast between the outline (3), on the one hand, and the theme region (1, 4) and background region (2), on the other.

Description

S u c h e r i o n c e m e n t i o n t i o n c o n t i o n c e m e n t i o n s h e rs a n d i o n s h o f s

The invention relates to a security element for producing value documents, such as banknotes, checks or the like, which shows a motif in front of a background, wherein the security element has a relief structure which covers a motif area of the security element and provides the motif there and a background area of security - Selements covered and there provides the background.

The invention further relates to a value document with a security element. Finally, the invention also relates to a production method for a security element for producing value documents, such as banknotes, checks or the like, which shows a motif against a background, wherein a relief structure is produced, which covers a motif area of the security element and provides the motif there and covers a background area of the security element and provides the background there.

Banknote security features include motifs, such as symbols, images or true color images, which are supposed to achieve particularly good recognizability and security against counterfeiting. Such motifs are known, for example, from the following publications: H. Lochbihler, "Collored images generated by metallic sub-wavelength gratings", Opt. Express, Vol. 17, pages 12189-12196, 2009, WO 2012/156049 A1, EP 1434695 Bl; EP 2453269 A1; WO 2013/091858 A9; US 9188716 B2 and DE 102014011425 A1. Motifs with such security elements, however, are in need of improvement in terms of visibility in low light conditions.

The invention is therefore based on the object to improve a security element, a value document and a manufacturing method of the type mentioned so that the recognizability is increased. At the same time a simple production should be possible.

The invention is defined in claims 1, 10 and 11.

The security element for producing value documents, such as banknotes, checks or the like, which shows a motif against a background, has a relief structure which covers a motif area of the security element and provides the motif there and covers a background area of the security element and provides the background there; In addition, an outline region is provided which delimits the motif region from the background region and which is likewise formed by the relief structure, wherein the relief structure of the contour line region differs from the relief structure of the motif region and that of the background region, such that a brightness and / or color contrast between the outline area on the one hand and the subject area and the background area on the other hand.

In the manufacturing process for a security element for producing value documents, such as banknotes, checks or the like, which shows a motif against a background, a relief structure is created, which covers a motif area of the security element and provides the motif there and covers a background area of the security element and there Background provides, and an outline area, which the The relief structure of the contour area differs from the relief structure of the motif area and that of the background area, so that a brightness and / or color contrast between contour line area on the one hand and the subject area and background area on the other consists.

The invention is based on the recognition that the motif is easier to recognize when it is delimited from the background by a high-contrast outline. In order to achieve a particularly good contrast and ease of manufacture, the outline is also defined by the relief structure, which, however, differs in the contour area from the subject area and the background area, so that a brightness and / or color contrast between the contour area on the one hand and the subject area and the On the other hand. This approach circumvents registration requirements that would arise, for example, in the conventional printing of a contour line with high-contrast color. At the same time, the outline can be designed to achieve the maximum contrast to the subject as well as the background, i. For example, a bright outline is easily possible. The invention thus significantly increases the perceptibility of the subject for a viewer.

The contrast between contour line area and motif area as well as background area can be achieved, for example, by appropriate selection of the profile geometry of the relief structure. The relief structures are usually coated, for example metallic, high-index, or with a color effect-producing layer composite, as known, for example, from WO 2008/080499 A1. For creating motifs, state-of-the-art different relief structures known, ie with these relief structures, a contrast between the subject area on the one hand and the background area on the other hand can be achieved. For example, relief structures with micromirrors are known from the prior art (see DE 102010049617 A1). These micromirrors can be arranged in pixels, each of which has identically oriented micromirrors. Furthermore, Fresnel structures (cf.

EP 1562758 Bl) or combined with micromirrors. Relief heights of 1 μιτι to a maximum of 100 μιη are known for micromirrors and lateral dimensions of less than 10 μπι to less than 100 μπι. Another known relief structure for generating a motif are hologram gratings in the form of relief holograms. They consist of metallized relief structures with grating periods of 500 nm to 2 μπι and are arranged so that a viewer perceives a motif or a true color image in the first diffraction order. US Pat. No. 9,187,716 B1 uses relief structures in the form of retroreflective structures for producing colored motifs. For generating a motif or the background, further one- or two-dimensional subwavelength gratings are known, for example from the publication H. Lochbihler, "Colored images generated by metallic sub-wavelength gratings", Opt. Express, Vol. 17, pages 12189-12196, 2009 , or WO 2012/156049.Pixel-wise arrangement of relief structures with different profile parameters can be generated true color images in the zeroth order of diffraction, which can also be used to create a motif against a background.Furthermore, it is possible with the juxtaposition of certain Relief structures, for example microstructures, for causing motion effects in an image (see DE 102010047250 A1) All of these different relief structures can be used in the context of the present invention for generating the motif and the background, ie in the motif area and the background area and for generating the outline and be combined Of course, A different relief structure can be used for the background area and the motif area and the outline. The decisive factor is that there is a visually perceptible contrast between the outline area and the motif area as well as between the outline area and the background area with the unaided eye. Another example of subwavelength structures are so-called moth eye structures (compare WO 2006/026975 A2 and EP 2453269 A1). The creation of colored motifs can be done by staining a relief structure. In a development, the contour area can be provided with a structuring by the relief structure is designed accordingly. The structuring may mean an interruption of the contour area and / or micro-text or information that is invisible to the naked eye.

The outline area may also be a contour line within a complex subject. A complex motif consists of several motif components, whereby one of the motif components in the optical perception is to be understood as a background, so that the contour area delimits the background area, ie a motif area of the complex motif, against another area of the complex subject. The contour area may also be unstructured in specific embodiments. The invention will be explained in more detail with reference to the figures by way of example, which also show features essential to the invention. In the drawings shows: 2 is a schematic sectional view of the security element S with three areas I to III corresponding to the motif area, the contour area and the background area of the security element of FIG 1, FIG. 3 shows a representation similar to FIG. 2, wherein other relief structures are used for the motif area, the background area and the outline area, and FIG

, 4 shows a representation similar to FIGS. 2 and 3, again using other relief structures for motif area, background area and contour line area.

Fig. 1 shows a security element S, which represents as a motive a hummingbird with a year in front of a textured background. A motif area 1 and a background area 2 are formed by different relief structures, which form an optical contrast in reflection, so that the subject can be perceived with the unaided eye. The motif is delimited by a narrow outline from the background. The year is also separated from the background by an outline. The contour lines in contour regions 3 are likewise produced by relief structures which are designed such that they form a contrast both to the motif area 1, 4 and to the background area 2. For a viewer, this significantly increases the perceptibility of the motifs. The motif area 1, 4 and the background area 2 are by relief structures formed, for example, which are metallized and embedded in a dielectric. The same applies to the outline 3. The contrast between the different areas is created by appropriate selection of the profile geometry of the relief structure.

Fig. 2 shows schematically a sectional view for examples of such relief structures. In this case, the region I corresponds to the motif region 1 or 4, the region II to the background region 2 and the region III to the contour line region 3. The security element S is formed on a substrate film 5 on which an embossing lacquer layer 6 has been applied, into which the relief structure has been introduced, which was then metallized. A topcoat layer 8 and a cover film 9 complete the security element S, which can span, for example, a window area of a banknote. Both the region I and the region II are formed in the embodiment of the hologram gratings 7, 10 with a sinusoidal profile. The hologram gratings 7 and 10 differ in their design with respect to the image generated by them. The contrasting contour line region 3 is realized by a sub-wavelength grating 12 in the region III. The subwavelength grating 12 can be periodic on one or two-dimensionally. It produces a contrast both with respect to the hologram grating 7 and with respect to the hologram grating 10 and thus highlights as an outline the motif formed by the motif area 1, 4, against the background formed by the background area 2.

Fig. 3 shows a further embodiment to illustrate that the relief structures in the areas I, II and III are freely selectable in large areas as long as there is a contrast between the areas I and II and a contrast between the area III and the areas I and II given is. In the embodiment of FIG. 3, the background area 2 is designed differently. It is on the one hand, ie in some sections, formed by the hologram grid 7 and on the other, ie in other sections, by a smooth surface 15. The motif area is realized by a Mikrospiegelan- order 13. The contour regions are filled with light-absorbing moth-eye structures 14 in regions III.

Fig. 4 shows an embodiment in which the contour line area realizes a bright border. The regions I and II are here designed with transmogrammogramme lattices, as they are known for example from DE 102014011425 AI. They also have an additional effect in transmission, ie incident radiation E is not only reflected as reflected radiation R, as in the embodiments of FIGS. 2 and 3 of FIG Case was, but also partially transmitted as transmitted radiation T. In this way, a transmitted light motif is possible. In area III, this is combined with a conventional hologram grid, which is opaque after metallization. In this way, a delineation of the motif area 1, 4 against the background area 2 is achieved in plan view, which causes a clear outline. The structure of FIG. 4 also shows a motif in transmission. In this perspective, the outline, ie the area III appears dark and enhances the recognizability of this motif. These contrast changes in transmission can generally be realized by opaque outlines. Relief structures which are metallized and have a profile which have an aspect ratio, ie a depth to period ratio of less than 0.4, are suitable for this purpose. Particular examples are smooth metallized surfaces, micromirror arrangements, matt structures or conventional holographic structures, etc. Transmissive structures can be, in particular, those described in the publication cited in the introduction. Publication of Lochbihler, Opt. Express, or WO 2012/156049 are known. Such transmissive structures generally appear darker in reflection than opaque metallic structures with a low aspect ratio because the transmitted light decreases reflection. Therefore, these flat structures as bright outlines clearly enhance the perception of the subject in reflection.

Of course, the embodiments of FIGS. 2 to 4 show, by way of example only, the lateral arrangement of different relief structures in the regions I to III. Equally, other combinations of micromirror arrangements, fresnel-like structures, μ-lenses, hologram gratings, retroreflection structures, one- or two-dimensional subwavelength gratings or moth-eye structures and microcavities are possible, which for a viewer results in a brightness and / or color contrast between the respective areas provide.

It is also possible to provide dark structures in the outline areas. Such appear dark from different, preferably all viewing directions. Particularly suitable for this purpose are the moth-eye structures 14 used in FIG. 3. Various possibilities are known from the literature for producing such moth-eye structures 14. Reference is made by way of example to the already mentioned WO 2006/026975 A2 or EP 1434695 Bl. These publications describe metallically vapor-deposited random surfaces which form a refractive index gradient layer and have a good absorption effect. In this case, the structure depth is preferably more than 50 nm and the mean distance between adjacent elevations is less than 500 nm, hence the name sub-wavelength structures. Such random surfaces can be produced from plastic substrates, eg PMMA, with a plasma etching process. Alternatively, be arranged mischievous moth eye structures. Furthermore, it is known that moth-eye structures which are coated with a multilayer, for example a so-called color-shift coating, provide high-contrast dark colors (cf EP 2453269 A1). Even structures which have a mean distance greater than 500 nm can show a high absorption effect after metallization. Such so-called microcavities preferably have a semispherical recess with a ratio of depth to aperture width greater than 0.5 and are arranged, for example, hexagonal or orthogonal next to one another. From EP 1434695 Bl a moth eye structure is known, which is formed by a metallized cross lattice with a period of less than 420 nm. It is also possible to use a two-dimensionally periodic sub-wavelength grating for light absorption, as described, for example, in WO 2012/156049 A1. This grid is also suitable for color filtering. The geometry parameters of the grating can be chosen so that maximum light absorption occurs and the average reflection is less than 20%, preferably less than 10%.

The delimitation between the background area, the motif area and the outline area can be achieved by such structures acting as color filters. These do not necessarily have to be black, but can also appear in a different color, eg red or blue. Dark colors, however, are advantageous for the recognizability of the subject. These mentioned metallic subwavelength structures show an increased light absorption in the visible spectral range, partly due to a resonant light absorption, which leads to a colourfulness of the reflection. A high contrast between the contour area and the subject area or background area is ensured, since the average absorption in the visible wavelength range is always higher than that of mirror-smooth surfaces, such as micromirrors. Alternatively, these structures can also be made from some Directions do not be dark. For example, the outline area can also be filled by micromirrors, which are all the same orientation and then light up brightly only at one angle. Although this has the disadvantage that the areas III then light up (undesirably) brightly under a certain angle, the contour line area does not cause the demarcation between motif and background at this angle under certain circumstances, however, one obtains a particularly technical disadvantage for this disadvantage easy realizability, since no further structures have to be produced in addition to micromirrors, in particular no nanostructures. It is then possible to carry out the relief structures for the background area, outline area and motif area exclusively by means of micromirrors, wherein only the orientation of the micromirrors between the individual areas changes. It is advantageous to choose the angle of the unwanted illumination of these areas so that it is as unimportant as possible, for example, in this area all mirrors can be oriented maximally downwards, so that the luminous effect only occurs with a very oblique view. Alternatively, a tilt in east / west direction can be selected with extremely far oriented, for example, east-oriented alignment of the micromirrors.

To form bright outlines, relief structures with a low aspect ratio are suitable. After metallization, such structures are largely opaque in transmission and appear bright to a viewer in reflection. Particularly suitable for this purpose are micromirrors, hologram gratings, retractive reflection structures and planar surfaces.

When using color shift coating, the relief structure can change the color shift color in the outline area to effect the demarcation. For good visibility, the average brightness of the outline area is less than 50% of the average brightness of the subject area as well as the background area in reflection and optionally also in transmission. Alternatively, the average brightness of the contour line area is more than 20% higher than that of the motif area and the background area in reflection and optionally also in transmission.

Micromirrors, hologram gratings and / or sawtooth gratings are preferably used in the motif region and the background region, in the contour region sub-wavelength structures (in particular color-filtering or moth-like eyes), hologram gratings and / or matt structures.

The relief structure is preferably produced by lithographic methods, for example an e-beam system or a laser writing system which operates, for example, with a two-photon absorption process. Alternatively, it can be produced in a two-step lithographic process. In a first step, a nanostructuring is carried out. This is done, for example, by an electron beam lithographic process. Alternatively, laser beam interference method come into question. Aperiodic moth eye structures can also be generated by plasma etching or by structuring with ultrashort laser pulses. In a subsequent step, such an original or a copy thereof is leveled with photoresist. Particularly suitable for this purpose are spin coating or dip coating. Then the relief structure is written into the photoresist in a photolithographic step and the desired areas of the structures are free-scanned. This process can be carried out with the help of a laserwriter using the direct exposure method. The resulting original can then be copied by electroplating or using photopolymers (eg Ormocere). The surface structure of a piece produced in this way The stamp can now be replicated side by side using a step-and-repeat procedure on a larger area. By galvanic molding of this replicated on the surface of the original of an embossing cylinder can be made. Finally, the structure can be imprinted in a continuous roll-to-roll process on film. In this case, nanoimprint processes such as hot stamping or embossing in UV-curable materials come into question. Finally, the embossed film is metallized metallically. The usual vapor deposition methods are electron beam vapor deposition, thermal evaporation or sputtering. The metallic material used may be metals such as aluminum, silver, copper, palladium, gold, chromium, nickel, iron, cobalt and / or tungsten and their alloys. After vapor deposition, the structure is optionally laminated and protected with the cover film 9. Instead of a simple metal coating, the relief structure can also be coated with a multiple layer. For this purpose, in particular so-called color-shift coatings come into question, which consist of a semi-transparent metal layer, a dielectric spacer layer and an underlying metallic mirror layer. Suitable dielectrics are, in particular, SiO ₂ , MgF ₂ , Ta ₂ Os, ZnS and polymers. Another alternative is a dielectric coating with a high refractive index material. In addition, if demetallized areas on the film element are required, wash ink is printed on the desired areas before steaming and then removed after evaporation. Alternatively, these regions can also be produced by laser demetallization or wet-chemical etching processes.

In a further embodiment, a motif (eg in the form of a cord) is provided with a movement effect. The motif area 1, 4 is produced by a juxtaposition of micro-mirrors and has a "rolling Bar effect, as they are known, for example, from DE 102010047250 AI, in which light bars move up and down when tilted The movements of several bars can be the same or even in opposite directions Such motifs are much better with contour lines otherwise a viewer might otherwise only see a "clutter" of bright light reflections. The outline area makes the actual shape clearly visible to a viewer. He can z. B. color-filtering sub-wavelength structures or - if a dark contour is desired - be realized by moth eye structures. In particularly advantageous variants, the micromirrors can be provided with a color-shifting coating (eg triple-layer structure with the sequence absorber, dielectric, reflector). Particularly advantageous change the relief structures in the outline area the color impression of this coating, z. By suitable subwavelength structures. Thus, not only light or dark outlines, but also outlines with a different color than the color within the motion effects can be generated.

Another effect, which can be generated in particular with subwavelength structures in the contour line region, is a higher transmission. Metallic sub-wavelength gratings, which have a pronounced transmission, show a clear contrast to flat surfaces, hologram gratings or micromirror structures. Particularly in the use of moth eye structures in the outline area this appears in supervision dark and in review (eg when used in a banknote window) bright. In color-tilting coatings (especially for example with two thin absorber layers, so the structure absorber, dielectric, absorber) and / or Using color-filtering subwavelength structures in the outline area, the color of the contour area may be different from the color of the area of the subject with the effect of moving upwards and forwards. divorce. Even the outline area itself can show different colors in reflected and transmitted light.

S e c tio ns

1, 4 motif area

2 background area

3 outline area

5 substrate film

6 embossing lacquer layer

7 hologram structure

8 topcoat

9 cover sheet

10 hologram structure

12 subwavelength gratings

13 micromirror structure

14 moth eye structure

15 smooth area

16 transmissive hologram grid

17 opaque hologram grids

S security element

E incident radiation

R reflected radiation

T transmitted radiation

0. O. Zero order

L.O. First order

I-III area

Claims

Patent claims

1. security element for producing value documents, such as bank notes, checks or the like, which shows a motif against a background, wherein the security element (S) has a relief structure (7, 10, 12, 13, 14, 16, 17), which covers a motif area (1, 4) of the security element (S) and provides the motif there and covers a background area (2) of the security element (S) and provides the background there, characterized in that an outline area (3) is provided delimits the motif area (1, 4) against the background area (2) and which is likewise formed by the relief structure, the relief structure (12, 14, 17) of the contour line area extending from the relief structure (12, 13, 16a) of the motif area (FIG. 1, 4) and the relief structure (7, 16) of the background area (2) differs, so that a brightness and / or color contrast between contour line area (3) on the one hand and Motivbereich (1, 4) and Hintergrundbereich (2) anderse its exists.

2. Security element according to claim 1, characterized in that the relief structure (12, 14) of the contour line region (3) has a sub-wavelength grating.

3. Security element according to claim 2, characterized in that the motif area (1, 4) and the background area (2) are otherwise free of sub-wave gratings.

4. Security element according to claim 2 or 3, characterized in that the relief structure of the contour line region (3) has a moth eye structure (14). - 2 -

5. Security element according to claim 4, characterized in that the motif area (1, 4) and background area (2) are otherwise free of moth eye structures.

6. Security element according to one of claims 1 to 5, characterized in that the relief structure (12, 14) of the contour line region (3) has micro cavities.

7. Security element according to one of claims 1 to 6, character- ized in that the relief structure of the contour line region (3) has a micromirror structure.

8. Security element according to one of claims 1 to 7, characterized in that the relief structure of the contour line region (3) has a Hogrogrammstruktur.

9. Security element according to one of claims 1 to 8, characterized in that the relief structure of the contour line region (3) has retroreflection structures.

10. Security element according to one of claims 1 to 9, characterized in that the relief structure of the contour line region (3) is coated metallic, high-refractive index or with a color effect-generating layer composite.

11. Security element according to one of claims 1 to 10, characterized in that the relief structure forms the contour line region (3) with a structuring of the contour line region (3).

12. The security element as claimed in claim 11, characterized in that the structuring of the contour line region (3) comprises interruptions of the contour line region (3) and / or microtext or information that is not detectable or resolvable by the naked eye.

13. document of value with a security element according to one of claims 1 to 12.

14. A manufacturing method for a security element (S) for the production of value documents, such as banknotes, checks or the like, the

Scene against a background shows, wherein a relief structure (7, 10, 12, 13, 14, 16, 17) is created, which covers a motif area (1, 4) of the security element (S) and there provides the subject and a background area ( 2) of the security element (S) and provides the background there, characterized in that an outline area (3) is provided which delimits the motif area (1, 4) against the background area (2) and which is likewise formed by the relief structure, wherein the relief structure (12, 14, 17) of the contour line region (3) differs from the relief structure (10, 13, 16a) of the motif region (1, 4) and the relief structure (7, 16b) of the background region (2) , so that there is a brightness and / or color contrast between contour line area (3) on the one hand and the motif area and background area (2) on the other hand.

15. A manufacturing method according to claim 14, characterized in that the security element according to one of claims 1 to 12 is produced.