EP3687826B1 - Method for producing an optically variable element, and corresponding element - Google Patents

Description

The invention relates to a method for producing an optically variable element and a corresponding element.

Data carriers, such as value or identity documents, but also other objects of value such as branded items, are often provided with elements for security that allow the authenticity of the data carrier to be checked and at the same time serve as protection against unauthorized reproduction. Optically variable elements show a viewer different representations depending on the viewing angle.

In particular with the help of an embossed structure and a contrasting coating, such optically variable elements can be produced. The embossed structure and the coating are matched to one another in such a way that different motifs become visible (or not visible) to the observer at different viewing angles, or a motif moves. For example WO 02/20280 A1 , DE 10 2005 011612 A1 , WO 2006/018232 A1 or DE 10 2014 012207 A1 show coated embossed structures with a change of motif.

The reflective facets of the embossed structure in DE 10 2010 049831 A1 can be provided with a sub-wavelength structure. In EP 2 042 343 A1 a relief structure is provided with metallic nanoparticles. EP 3184318 A1 shows the preamble of claim 1.

The invention is based on the object of specifying a flexible but cost-effective production method for optically variable elements which, in particular, also allows optically variable elements to be produced on the target substrate.

This object is achieved by the features of independent claims 1 and 14. Developments of the invention are the subject of the dependent claims.

A basic idea of the present solution is to additively generate the relief elements of a relief structure - conventionally created by embossing - by means of printing in several partial steps. In particular in special cases, for example when only small numbers of optically variable elements are created on the basis of the same relief structure or for new types of relief structures, for example with negative relief flanks, the approach turns out to be advantageous.

In the method according to the invention for producing an optically variable element, a relief structure is created and the relief structure created is selectively modified, for example colored. The relief structure comprises a multiplicity of relief elements lying next to one another in a plane, which have a relief shape that is not parallel to the plane. The created relief structure is selectively modified. The modification and the relief shape of the relief elements are matched to one another in such a way that the modified relief structure shows different representations for a viewer depending on the viewing angle. In the present case, the relief structure is at least partially created by means of an additive method, several partial steps of the additive method being carried out for relief elements and the relief shape of the relief element being determined by the partial steps.
In their relief shape, the relief elements can be, for example, knobs, cones, pyramids (with a square or n-cornered plan), truncated pyramids (with a square or n-angled plan), truncated cones, round knobs or spherical sections be trained. Furthermore, the relief elements can have a directed surface as a relief shape. The relief element with a directed surface (surface element) can be, for example, a round or n-cornered, preferably square or hexagonal, surface. In the relief structure, the surface elements are preferably arranged adjacent to one another and / or completely filling the area. The surface can be described by its orientation and its inclination (to the plane of the relief structure) and optionally by its height in the relief. The relief element can be designed as a relief line, for example roof-shaped with two flanks or with a round cross-section. The relief elements are preferably arranged next to one another in a (one- or) two-dimensional relief grid. The relief elements can be arranged in the relief grid with a spacing or without a spacing. The relief elements with the relief shape (which is not parallel to the plane of the relief elements) have locally different heights. The relief element with locally different heights is generated by the additive substeps. To this extent, the height profile of the relief elements is the relief shape generated.

In the relief structure, the relief shape of the relief elements is uniform in the first embodiments. In particular, it is only through the modification that the relief elements are formed differently. Previously, relief elements with an identical relief shape lie next to one another in the relief structure. In the second refinements, the relief shapes of the relief elements in the relief structure already differ from one another. The relief elements preferably differ, but the different relief elements do not yet form an optically variable structure. It is only through the selective modification of the relief elements that the visual variability that can be recognized by the observer is created. The relief elements of a relief structure can differ in their relief shape or size (or base area). The relief elements in a relief structure can be different in areas or different in a repeating pattern, each different in terms of relief shape and / or size.

The sub-steps for generating the relief shape are preferably carried out by means of additive printing. In particular, it is possible to print using an inkjet method, with (UV) curable ink preferably being printed and (UV) cured. The relief elements can also be created using (laser) stereolithography. As an alternative to printing, the relief shape could be generated additively by means of selective laser sintering when creating the relief elements.

The sub-steps of creation can also be carried out using screen printing or gravure printing. Relief elements are preferably created with a height of 20-80 µm by means of screen printing or gravure printing. Several round-round or flat-flat screen printing steps can be combined. For example, a relief sub-element or a screen printing layer with a thickness of 30 μm is produced in a first partial step. In a second sub-step, 20 µm of material are applied, and in a final screen printing sub-step, 10 µm of material are applied. Finally, the modification is again printed as a color layer on the structures (using e.g. inkjet, offset, gravure printing).

Usually the same material is added in the sub-steps. The sub-steps within the relief element can be carried out in different ways. In particular, the partial steps can be carried out differently with regard to the amount of the added material and / or with regard to a method parameter for the added material. In particular, a temperature and / or a hardening of a hardenable material can be varied as process parameters. The material preferably has higher temperature an increased viscosity. Thus, different relief sub-elements can be added by selecting the temperature (temperature 1 => round relief sub-element, temperature 2 => oval relief sub-element and temperature 3 => flat sub-element). Likewise, the added material can be cured differently in the sub-steps, for example immediately fully cured, pre-cured or uncured. For example, complete curing over a large area can take place in a later step, in particular only after an overlapping substep.

The material applied in the sub-steps is preferably a radiation-curing material (UV / IR curing). As a rule, the material is opaque, but transparent material can also be used in refinements. The material is preferably glossy or reflective, in particular metallically reflective, at least on its surface. The relief element can thus be configured to be reflective or by means of a reflective coating. It is also conceivable to first apply the first material and only use reflective material in subsequent partial steps (for the visible surface of the relief element).

If, for example, the relief elements are created with a first relief material in shaping sub-steps and the relief structure is coated in an additional step, the coating can be a smoothing coating and / or a coloring coating and / or a reflective coating. The partial relief elements of at least one relief element, preferably several relief elements in one area, particularly preferably all relief elements of the relief structure, are coated together.

As an alternative or in addition, the relief elements are created in several preforming partial steps with a first relief material and in one final smoothing substep created with a second smoothing relief material. The preforming and smoothing substeps thus form the shaping substeps for the relief element. The smoothing relief material (or the coating) can comprise color / effect pigments and / or reflective pigments. The pigments are particularly preferably floating in the material (its solvent and / or binder). Floating pigments are also known as leafing pigments. The pigments collect on top of the binder after the material has been applied.

• durch Färben der Reliefstruktur, insbesondere mittels Drucken, oder
• durch weitere, modifizierende Teilschritte des additiven Verfahrens.

Ein selektives Färben der Reliefstruktur kann insbesondere durch Drucken oder Lasern erfolgen. Das addierte Material kann in (einigen oder allen) Teilschritten insofern ein lasersensitives Material sein. Alternativ erfolgt eine Beschichtung mit lasersensitivem Material. Das selektive Modifizieren erfolgt insbesondere in einem Modifikationsraster, welche an das Raster der Reliefelemente angepasst ist. Nur bevorzugt sind die Raster identisch. Das selektive Modifizieren kann auch mittels weiteren additiven Teilschritten erfolgen. Es wird beispielsweise auf DE 102011114647 A1 verwiesen.The relief structure is selectively modified

• by coloring the relief structure, in particular by means of printing, or
• through further, modifying sub-steps of the additive process.

A selective coloring of the relief structure can be done in particular by printing or lasing. The added material can be a laser-sensitive material in (some or all) sub-steps. Alternatively, it is coated with laser-sensitive material. The selective modification takes place in particular in a modification grid which is adapted to the grid of the relief elements. The grids are only preferably identical. The selective modification can also take place by means of further additive sub-steps. For example, it is on DE 102011114647 A1 referenced.

The selective modification is preferably carried out by printing at least one color, particularly preferably alternately different one color, lines on the relief structure. The lines cover between 40-90% of the surface of the additively generated relief element or the relief structure. It is particularly preferable for the different colored lines to differ in their hue in the CIE-LAB color space. The difference is particularly preferred between the hues of adjacent lines by at least 40 units for the values | a | and / or | b | of the CIE-LAB color space apart.

The step of selective modification makes the relief structure optically variable. In particular, a change of motif and / or motif movement can thereby be generated for the viewer. Depending on the viewing angle, the displayed motif can disappear (or become visible) for the viewer or switch to another motif or move. In particular, pumping movements, rotating movements or linear movements are known as movements.

In advantageous refinements, the entire relief structure is not created additively in its full height - as previously assumed. The relief structure can comprise an embossing part and a shaping part created additively thereon. The embossed portion of the relief elements is preferably formed from identical embossed elements. Starting from a uniform embossed structure, a relief structure with different relief elements can thus be formed. The uniform embossed structure is preferably added to the relief structure in only one area. Alternatively, the embossed portion of the relief elements can also be formed from different embossed elements. In particular, an embossed structure with differently oriented flat relief elements can be provided with the relief portion in an area.

The height of the relief elements is between 5 and 500 µm. A height of the relief element of 100 μm to 300 μm is preferably produced. More preferably, the relief element has a flank with gradients of 5 to 85 degrees, particularly preferably 40 to 85 degrees.

With the present method, relief elements with novel relief shapes can also be produced. The locally different heights of the relief elements are generated by the partial steps. In contrast to the embossing, an undercut can now also be created. Embossed elements can be created with relief shapes or partial areas in an angle range of +/- 90 degrees to the plane of the elements. In particular, a side wall of the embossed relief element can run at a maximum perpendicular (90 degrees). In the present case, relief elements can now be produced with a relief shape which in sections has an angle of more than 90 degrees to the plane, in particular more than +90 degrees in a first section and more than -90 degrees in a second section. The relief structure preferably comprises at least two relief elements with a relief shape which in one section have an angle of more than 90 degrees to the plane, the two sections having different, preferably opposite, orientations.

In preferred embodiments, a primer is first applied, for example sprayed on, before the relief material is applied additively. The primer causes smoothing and / or better adhesion.

In further preferred refinements, the optically variable element comprises additional information which can be recognized by means of UV or IR light. The relief material, the material of the modification or the imprint are IR and / or UV active (in particular absorbent or luminescent).

In addition to the additively created relief elements, the relief structure can comprise further relief elements which were produced in particular by means of (blind) embossing or intaglio printing.

The optically variable element according to the invention comprised a relief structure formed from a multiplicity of relief elements lying next to one another in a plane, the relief elements not having a plane-parallel relief shape; and a modification (for example coloring) coloring of the relief structure, the modification and the relief shape of the relief elements being coordinated with one another in such a way that the modified relief structure shows different representations for a viewer depending on the viewing angle. The relief elements include additively created relief sub-elements which determine the relief shape of the relief element.
The optically variable element can be produced as described above. It can be generated on an intermediate carrier in order to be transferred from the intermediate carrier to a target substrate, or it can be generated directly on a target substrate. The optically variable element can in particular be used as a security element for documents of value, such as bank notes or passports, or as a design element for packaging. Further exemplary embodiments as well as advantages of the invention are explained below with reference to the figures, in the representation of which a reproduction true to scale and proportion was dispensed with in order to increase the clarity.

Fig. 1

ein Wertdokument mit mehreren optisch variablen Elementen;

Fig. 2a, b, c

drei Reliefelemente unterschiedlicher Reliefform mit Aufdruck jeweils im Querschnitt und in Draufsicht;

Fig. 3a, b, c

drei additiv erzeugte Reliefelemente mit entsprechender Relief-form im Querschnitt;

Fig. 4

ein additiv erzeugte Reliefelement mit glättender, reflektierender Beschichtung im Querschnitt;

Fig. 5a, b

zwei wabenförmige, rein additiv erzeugte Reliefelemente im Querschnitt und in Draufsicht;

Fig. 6a, b

zwei unterschiedliche wabenförmige, Reliefelemente mit additiv erzeugtem Anteil auf einheitlichem Prägeanteil im Querschnitt und in Draufsicht;

Fig. 7a, b

zwei unterschiedliche wabenförmige, Reliefelemente mit teilweise additiv erzeugtem Anteil auf uneinheitlichem Prägeanteil im Querschnitt und in Draufsicht; und

Fig. 8

schematische Darstellung einer Vorrichtung zur Herstellung eines optisch variablen Elements mit additiven Teilschritten.

Show it:

Fig. 1

a value document with several optically variable elements;

Figures 2a, b, c

three relief elements of different relief shape with imprint each in cross section and in plan view;

Figures 3a, b, c

three additively generated relief elements with a corresponding relief shape in cross section;

Fig. 4

an additively produced relief element with a smooth, reflective coating in cross section;

Fig. 5a, b

two honeycomb-shaped, purely additively produced relief elements in cross section and in plan view;

Fig. 6a, b

two different honeycomb relief elements with an additively generated portion on a uniform embossed portion in cross section and in plan view;

Figures 7a, b

two different honeycomb relief elements with partially additively generated portion on non-uniform embossed portion in cross section and in plan view; and

Fig. 8

schematic representation of a device for producing an optically variable element with additive sub-steps.

Fig. 1 shows a value document 1, such as a bank note, which is provided with several different types of optically variable security elements 6, 7, 8, 9. A substrate 2 of the document of value 1 has an imprint 3 which in particular covers all surfaces outside the security elements 6, 7, 8, 9. The optically variable security element 6 is a patch that has been transferred to the substrate. Such a patch can be designed with or without its own carrier layer, such as a film. The security element 6 is regularly by means of pressure and / or heat, for example by means of a heat seal lacquer, attached to the substrate. The optically variable security element 7 was created directly on the substrate 2 (or its imprint 3). The optically variable security element 8 is a security thread which lies on the substrate 2, is completely embedded therein (and is only visible through openings / windows in the substrate) or is partially embedded in the substrate and partially lies thereon. The optically variable security element 9 is arranged so as to overlap with, here completely in, the security element 8. It can be a locally created or broadcast item.

Each of the optically variable elements 6, 7, 8, 9 can have been produced according to the present method.

In Figures 2a to 2c For optically variable security elements with a relief structure, three examples of relief elements 10 with imprint 20 are shown. The relief elements 10 are each shown in cross section (upper half of the illustration) and in plan view (lower half of the illustration). The relief elements 10 differ from one another in their relief shape. In addition, the imprint 20 is designed differently in each case.

Fig. 2a shows a relief element 10 with a triangular cross-section, which is linear. In the relief structure, a large number of the linear relief elements lie parallel to one another. The imprint 20 is applied in punctiform fashion, for example as part of a screened imprint, on a flank of the relief element 10. A large number of points, which are applied to the same flank in each case, form an optically variable motif which the viewer only sees under certain viewing angles (from the right or from above) or remains hidden from him at certain viewing angles (from the left).

Figure 2b shows a relief element 10 with an oval cross-section. The relief elements 10 and 11 are formed like knobs and are arranged lying next to one another in the relief structure. The imprint 20 is in Figure 2b designed as an example linear and extends - preferably not parallel over the relief structure of knob-shaped relief elements 10, 11. Among other things, the non-parallel arrangement leads to a movement effect (moving motif) when the relief structure and imprint are appropriately adapted. When the viewing angle changes, a moving motif arises for the viewer, which in particular moves in a rotating, pumping or linear manner. Such an effect is shown, for example, in WO 2016/020066 A2 described in more detail.

For example WO 2006/018232 A1 shows to Figure 2b a multitude of alternative relief shapes for the relief elements, in particular also pyramidal with different base areas, cones, cylindrical or oval (if necessary, each as a stump) and considers non-linear imprints, which are similar to in Fig. 2a enable a change of motif.

DE 102011114647 A1 on the other hand, is an example of another possible form of modification of the relief structure that is not formed by printing (or alternatively by lasering). In a regular relief structure, individual relief elements are modified in their relief shape.

Figure 2c shows a relief element 10, which is designed with a flat, directed surface. In Figure 2c the surface is inclined to the right at a certain angle and provided with a full-surface imprint 20. The alignment is symbolized by an arrow in the illustration below.

The imprint could also be configured over part of the area, for example in the form of a point. An adjacent relief element 11 can - as shown - have a different (or the same) orientation and (also have an imprint of the same type or a different color) or - as shown - be free of an imprint.
The relief elements can differ from one another in particular with regard to alignment and angle of inclination. For example in WO 2013/045054 A1 such a relief structure is described in more detail.

The directed surface of the relief element 10 is in particular a reflective surface.

The relief element 10 is in Figure 2c honeycomb-shaped, but can also have a rectangular, square or similar area-filling shape when viewed from above. The relief structure comprises a multiplicity of the relief elements correspondingly directly adjacent to one another, the orientation of which can be selected individually in each case.

In Figures 3a to 3c is shown how the in Figures 2a to c illustrated relief elements 10, can be created additively from different relief sub-elements.

Fig. 3a shows a triangular relief element 10, which is produced by additive printing of three relief sub-elements 31, 32 and 33. The same relief material is preferably printed one on top of the other in each of the three sub-steps. In Fig. 3a If the relief sub-elements 31, 32, 33 have been produced differently, they are in particular not identical in shape. By suitable selection of the printing parameters, material quantity and / or material temperature, different relief sub-elements can be produced one on top of the other. The relief part element 31 was at higher Temperature (and thus greater viscosity of the material) and optionally generated with a larger amount of material. Due to the increased viscosity, a flat and wide relief sub-element 31 is formed. The relief sub-element 32 was produced at a second (eg normal) temperature and possibly with a second quantity. A rather round relief sub-element 32 is formed. The relief sub-element 33, on the other hand, was produced with a reduced material temperature. The result is an elevated, narrow relief sub-element 33. The relief element 10 comprises at least the three overlapping relief sub-elements which can be seen in cross section. It can be seen that the relief shape of the relief element 10 is determined by the partial steps of the additive method. The relief element can comprise a multiplicity of relief sub-elements lying next to one another (linearly) or can be designed linearly.

The relief sub-elements 31, 32, 33 can be cured in two stages, by means of (UV) irradiation. In particular, each relief sub-element 31, 32, 33 can be hardened individually after it has been applied. The partially hardened relief elements 31, 32, 33 can then be completely hardened together. The relief sub-elements 31, 32, 33 can, for example, have been produced one after the other with one (the same) print head or also one after the other with different print heads.

Figure 3b shows a semicircular (or knob-shaped) relief element 10, which comprises three relief sub-elements 34, 35 and 36. The relief shape of the relief element 10 is in turn produced by means of correspondingly adapted partial printing steps. The relief material and / or the selected temperature lead to an adaptation of the relief sub-elements 35, 36 to the shape of the first relief sub-element. An adaptation of the parameter application width of the added material could also have been varied in the present case. It the same material is additively applied in at least three sub-steps in order to produce the relief element with the relief shape.

Figure 3c shows the directed surface of the relief element 10 from Figure 2c which was generated additively. The relief element 10 comprises a plurality of relief sub-elements 37, 38 and 39. In the illustration shown, the relief sub-elements are again designed or produced differently. For example, the relief sub-elements 37 are produced with more material and increased temperature. The relief sub-elements 38 are created with an average amount of material and an average application temperature. The relief sub-elements 39 are produced as flat relief sub-elements, for example by a small amount and further increased temperature. Alternatively, in particular the relief sub-elements 39 delimiting the relief element, are produced with a different relief material. The other relief material can preferably have reflective properties if the actual relief material is, for example (transparent or opaque and) non-reflective.

Each of the relief elements 10 from Figures 3a to 3c (and the other figures) is one of the plurality of relief elements of a relief structure which - as described above - serves as an optically variable element together with a modification of the relief structure, for example by means of an imprint.

Fig. 4 shows a further preferred variant for producing a relief element 10. A multiplicity of relief sub-elements 41, 42 are created additively in order to determine the relief shape. In a final step, the relief element is provided (individually or together with several relief elements) with a smoothing, preferably reflective, coating 45. The relief elements 10 should primarily reflect according to their orientation. The surface which is formed by the relief sub-elements 42, could not reflect in a sufficiently directional manner, even if reflective material is already used. In order to achieve a sufficiently directed reflection, the smoothing coating 45 takes place. In the present case, the coating comprises floating, reflective pigments 46. The pigments therefore collect on the binder 47 on the upper side of the coating 45. A particularly well-directed reflective surface is formed.

In the Figures 5 to 7 Variants are shown in which relief elements 11, 12 are created completely additively ( Fig. 5 ) or from a coined part and an additively created part ( Figures 6 and 7 ).

Figure 5a shows in cross section - along line A of FIG Figure 5b - Two relief elements 11 and 12. Both relief elements are additively formed in partial steps from the relief sub-elements 51, 52 and 53. The partial steps are adapted so that the relief element 11 has a first angle of inclination (35 degrees) and the relief element 12 has a second angle of inclination (25 degrees). The alignment of the adjoining relief elements 11, 12 is as in FIG Figure 5b indicated by the arrows, identical. Both relief elements are created entirely through additive substeps. It would also be conceivable to provide a first partial area, not shown, as an embossed relief and to create the relief elements completely (and / or partially) additively in a - partly shown - second partial area.

Figure 6a shows again in cross section - along the line A of FIG Figure 6b - Two relief elements 11 and 12. The relief elements 11, 12 comprise an embossed portion 160 and a pressure portion 60. Embossed elements 161 of the same type form the embossed portion of the relief structure. Different relief elements 11, 12 are created by different pressure portions 60, which are additively generated by relief sub-elements 61, 62. The relief element 12 has how in Figure 6b indicated, a different orientation (downward) and a different angle of inclination (25 degrees) than the relief element 11 (35 degrees and to the right). A uniform relief structure, with relief elements 161 of the same type, can thus be configured individually for each relief element.

Figure 7a shows, however, in cross section - along the line A of Figure 6b - Two relief elements 11 and 12, which comprise a non-uniform embossing part 170 and a printing part 70. The embossed elements 171 and 172 are already aligned differently and have different heights. The additively added partial relief elements 71, 72 produce the relief shape of the relief element 11. In the example shown, the relief element 172 remains unchanged.

In Fig. 8 a device for producing the optically variable element is shown schematically. Documents of value 1 are successively fed to printing units 81, 82, 83 and 86 on a conveyor belt 88. The printing units 81, 82, 83 preferably each include a printing unit and a curing unit. The relief printing units 81, 82 and 83 additively print the relief material on the document of value. Each relief printing unit generates at least one relief sub-element. As already indicated above, a parameter of the printing process can be varied during printing. In particular, the temperature and the amount of material are such parameters. The relief material is preferably hardenable, that is to say is added and then hardened by the relief printing unit. The degree of hardening is another parameter that can be used flexibly.

An optional curing unit, which can be used with two-stage curing, is not shown, but can be used to completely cure the relief elements individually pre-cured in the relief printing units 81, 82 and 83 together, in particular before the selective modification takes place. After the relief printing unit 83, the relief structure with relief elements is present on the substrate. A motif printing unit 86 selectively prints a motif at specific positions which is optically variable for the viewer due to the relief structure.

The ink of the relief printing unit comprises a liquid, low-viscosity and possibly pigmented substance that is applied using a nozzle application technique, e.g. the ink-jet technique. It is changed in its aggregate state, preferably hardened. This is done, for example, physically by removing solvent and / or chemically by polymerizing or UV curing to form a solid material.

In the printing units, different materials can optionally be used, which differ primarily in terms of their viscosity. A uniform base material is preferably used, which is of different viscosity due to different admixtures. For example, the first printing unit 81 can apply a viscous material with a pressure nozzle with a large diameter and a highly viscous material can be applied to the printing unit 83 with a smaller pressure nozzle. Optionally, the applied material comprises a solvent which evaporates after application.

To apply different relief materials, it is beneficial to apply them in separate systems to avoid mixing of the process media, whereby one or more nozzles, print heads or spray heads can be used, which are mounted one behind the other parallel to the substrate running direction (e.g. along a paper web or along a cylinder ).

If different or the same materials are added one after the other next to and on top of one another, the individual layers have to harden or harden. The application of the following relief sub-elements takes place at different time intervals depending on the material. For this purpose, they can be applied alternately in different running directions or, if there is sufficient spatial distance between the printing or spray heads carrying the different media, in the same running direction. This spatial distance is preferably adjustable in a targeted manner in accordance with the required time interval in the y and / or x direction by means of variably placeable pressure or spray heads and / or cross members. However, it is also possible to apply only one partial element with each roller revolution and to pass the substrate on to the next production step only after completion.

Other additive manufacturing processes such as selective laser melting and electron beam melting for metals or selective laser sintering for polymers, ceramics and metals can also be used to create functional relief structures that display different appearance colors or "tilted image information" from a given perspective. In the following, selective laser sintering is described in more detail as an example.

In such a process, individual layers of material are cured by means of a laser and the workpiece is built up layer by layer. The powder is applied over the entire surface of a building platform with the aid of a doctor blade or roller in a thickness of 1 to 200 μm. The layers are gradually sintered or melted into the powder bed by controlling a laser beam in accordance with the layer contour of the component. The construction platform is now lowered slightly and a new layer is raised. The powder is made available by lifting a powder platform or as a supply in the doctor blade. The processing is carried out layer by layer in the vertical direction, which makes it possible to create undercut contours. The energy supplied by the laser is absorbed by the powder and leads to a locally limited sintering of particles with a reduction in the total surface area. Any three-dimensional geometries are created that also allow flank angles with undercuts.

With the help of this technology, laser-sintered prototypes or individual parts could be provided directly with a functional "safety feature", which, for example, shows a manufacturer's label as a tilted image that is dependent on the viewing angle.

In addition to securities and product packaging that can be functionalized with tactile inkjet printing, there are other alternative raw materials such as injection-molded parts or deep-drawn parts that are functionalized with (tactile) inkjet printing.

An alternative to the complete generation of the relief elements by means of inkjet is that the relief elements are partially (analogous to Figures 6 and 7 ) are produced in a thermoplastic using a vacuum deep-drawing process, also known as vacuum forming or thermoforming. In contrast to injection molding, in which heated plastic is injected into a cavity (mold), the starting material is a plastic plate. This is heated to a thermoelastic state and then sucked onto the tool. After cooling, the deformed plate retains its given shape. Plates with a thickness of 0.3 to 10 mm are usually used. So everything is possible from light packaging to stable objects. After the nub structure has been formed, spatially resolved colored information can be applied to the material by means of an inkjet, which in turn generates optical variability that is dependent on the tilt angle.

List of reference symbols

1

Value document

2

Substrate

3

imprint

6, 7, 8, 9

Security element

10,11,12

Relief element

20th

Modifying print

31, 32, ... 39

Relief elements

41, 42, 51-53

Relief elements

45

Leveling layer

46

Metal pigments

47

binder

60, 70

Pressure share

61, 62, 71, 72

Relief elements

160.170

Coinage

161,171,172

Embossing element

81, 82, 83

Relief printing unit

86

Motif printing unit

88

Transport track

Claims (15)

1. A method for manufacturing an optically variable element (6, 7, 8, 9), having the steps of:

   - creating a relief structure formed from a plurality of relief elements (10, 11, 12) mutually adjoining in a plane, wherein the relief elements have a relief form not parallel to the plane;

   - selectively modifying the relief structure, wherein the modification and the relief form of the relief elements are matched to one another such that the modified relief structure (10, 20) shows different representations for a viewer depending on the viewing angle;

   wherein the relief structure is created at least partially by means of an additive method;
   characterized in that

   several substeps of the additive method are carried out respectively for relief elements (10, 11, 12), and

   the substeps determine the relief form of the relief element (10, 11, 12).
2. The method according to claim 1, characterized in that

   - the relief form of the relief elements is uniform in the relief structure, or

   - the relief forms of the relief elements differ in the relief structure, in particular with regard to one of the parameters of alignment and/or inclination of a reflecting relief element surface.
3. The method according to claim 1 or 2, characterized in that the substeps are effected by means of additive printing.
4. The method according to any of claims 1 to 3, characterized in that in the substeps at least three relief partial elements are produced in superimposed arrangement.
5. The method according to any of claims 1 to 4, characterized in that the substeps within the relief element are executed differently, in particular differently with regard to the quantity of the added material and/or a method parameter for the added material.
6. The method according to any of claims 1 to 5, characterized in that in the substeps, material is applied which is UV-curing and/or reflecting and/or opaque and/or colored.
7. The method according to any of claims 1 to 6, characterized in that the selectively modifying of the relief structure is effected

   - by dyeing the relief structure, in particular by means of printing, or

   - by further, modifying substeps of the additive method.
8. The method according to any of claims 1 to 7, characterized in that the relief elements are produced in the shaping substeps with a first relief material, and in an additional step the relief structure is coated, wherein the coating (45) is

   - a smoothing coating and/or

   - a regional or full-area color-giving coating and/or

   - a reflective coating.
9. The method according to any of claims 1 to 8, characterized in that the relief elements are produced in a plurality of first, preforming substeps with a first relief material and are produced in a final, smoothing substep with a second smoothing relief material.
10. The method according to any of claims 1 to 9, characterized in that the smoothing relief material comprises color pigments and/or reflective pigments (46) which are in particular floating in the material.
11. The method according to any of claims 1 to 10, characterized in that the relief elements (11, 12) are formed from an embossing portion (160, 170) and a shaping portion (60, 70) additively produced thereon.
12. The method according to claim 11, characterized in that the embossing portion (160) of the relief elements is formed by identical embossing elements (161).
13. The method according to claim 11, characterized in that the embossing portion (160) of the relief elements is formed by different embossing elements (171, 172).
14. The optically variable element (6, 7, 8, 9), having:

    - a relief structure formed from a plurality of relief elements (10, 11, 12) mutually adjoining in a plane, wherein the relief elements have a not plane-parallel relief form;

    - a modification of the relief structure, wherein the modification and the relief form of the relief elements are matched to one another such that the modified relief structure shows different representations for a viewer depending on the viewing angle;

    characterized in that
    the relief elements (10, 11, 12) comprise additively produced relief partial elements (31, 32, 33) which determine the relief form of the relief element.
15. The optically variable element (6, 7, 8, 9) according to claim 14, produced by a method according to any of claims 1 to 13.

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