Optically variable security element, production process and embossing arrangement

Abstract

The invention relates to an optically variable security element (20) for safeguarding articles of value. The security element has a feature layer (24) containing, in a common plane, first and second feature regions (30, 40) arranged so as to accurately fit together. The first feature regions (30) contain a first embossing lacquer layer of a first embossing lacquer (32) into which an embossed structure (34) that creates a first optical effect has been embossed. The second feature regions (40) contain a second embossing lacquer layer of a second embossing lacquer (42) into which an embossed structure (44) that creates a second, different optical effect has been embossed. The first and second embossing lacquers (32, 42) have different solidification properties and different optical properties. The invention also relates to a production process for such an optically variable security element, and to embossing arrangements comprising a semifinished security element product and means of impressing an embossed structure.

Description

[0001] The invention relates to an optically variable security element for securing valuables and a manufacturing method for such an optically variable security element. The invention also relates to embossing arrangements comprising a security element semi-finished product and means for embossing a structure.

[0002] Data carriers, such as valuables or identification documents, but also other valuables like branded goods, are often equipped with security features to ensure their authenticity and protect against unauthorized reproduction. These security features can take the form of, for example, a security thread embedded in a banknote, a protective film for a banknote with a hole, an applied security strip, a self-supporting transfer element, or even a feature area applied directly to a valuable document.

[0003] Some time ago, optically variable security elements were proposed, featuring two relief structures arranged at different heights and each coated with a color layer, embossed into appropriately colored embossed lacquer layers (see WO 2020 / 011390 A1, WO 2020 / 011391 A1 and WO 2020 / 011392 A1). However, to view the lower relief structure, the observer must generally look through the embossed lacquer layer of the higher relief structure, so that, depending on the desired visual effect, there can be considerable limitations on the coloring of the embossed lacquers, especially the embossed lacquer of the higher embossed lacquer layer.

[0004] In DE 102009031386 A1, an embossed structure is introduced into two embossing lacquer layers arranged on different sides of a substrate. WO 2020 / 244806 A1 shows the preamble of claim 1.

[0005] Based on this, the invention aims to provide a generic optically variable security element with an attractive appearance and high counterfeit protection, as well as advantageous manufacturing processes for such optically variable security elements.

[0006] This problem is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0007] The invention provides an optically variable security element to solve the aforementioned problem, which can be used in particular for securing valuables. The security element is equipped with a feature layer that contains first and second feature areas arranged precisely in relation to each other in a common plane.

[0008] A precise alignment of feature areas refers in particular to an arrangement in which the first and second feature areas abut each other or are arranged at a predetermined, defined small distance from one another. A small distance is, in particular, a distance of a few micrometers or a few tens of micrometers up to 100 µm, and in some applications up to 200 µm.

[0009] The first feature areas contain a first embossing lacquer layer into which an embossed structure is imprinted, creating a first optical effect. The second feature areas contain a second embossing lacquer layer into which an embossed structure is imprinted, creating a second, different optical effect.

[0010] The first and second embossing varnishes exhibit both different hardening properties and different optical properties.

[0011] The aforementioned differing hardening properties of embossing lacquers can result from different hardening processes, each leading to a hardening of the lacquers. These processes include, in particular, physical drying for thermoplastic embossing lacquers or radiation curing for radiation-curing lacquers. The different hardening properties can also arise from different hardening parameters within the same process, such as different softening temperatures for thermoplastic embossing lacquers or different types of radiation, radiation intensities, or irradiation durations for radiation-curing lacquers. Radiation-curing lacquers include, in particular, UV-curing, IR-curing, and electron-beam-curing lacquers.

[0012] In a preferred embodiment, the first and second embossing varnishes are each formed by a thermoplastic embossing varnish with different softening temperatures, so that the embossing varnishes exhibit different hardening properties due to the different hardening parameter 'temperature'. The softening temperatures preferably differ by more than 10 °C, preferably by more than 25 °C, and particularly by more than 50 °C.

[0013] According to another, equally advantageous embodiment, the first embossing lacquer is formed by a radiation-curing, in particular UV-curing, embossing lacquer, and the second embossing lacquer is formed by a thermoplastic embossing lacquer. While the first embossing lacquer can thus be cured by the action of radiation, the second embossing lacquer can be embossed at elevated temperature and solidifies upon cooling, so that different solidification processes lead to the hardening of the lacquers.

[0014] The first and second embossing varnishes can exhibit different optical properties, particularly different colors, transparency, and / or luminescence. The embossing varnishes are advantageously tinted in a translucent manner and are therefore both colored and partially translucent.

[0015] Typically, the UV embossing varnishes and thermoplastic varnishes (also called thermoplastics) used have the properties described below, although varnishes with different properties can also be used for special applications.

[0016] Typical UV embossing varnish is initially much easier to emboss than thermoplastic embossing varnish. For UV embossing, for example, a liquid embossing varnish can first be applied to a film. This reaches the embossing die without roller contact. The film with the embossing varnish is brought into contact with the embossing die using a pressure plate, whereby the varnish surface takes on the structure of the embossing die. In a theoretical, arbitrarily slow process, no pressure would be required; the varnish would simply flow into the structure and displace the air. In practice, however, the embossing process on the machine is not arbitrarily slow, so if the pressure plate is too low, the varnish cannot completely displace the air within the given time. Therefore, when certain speed and bubble-free results are required, a certain embossing pressure is used in practice.Without UV curing, the lacquer would immediately run again after contact with the embossing die and once the film is removed. In practice, however, the film wraps around the embossing die to a certain extent. Once the film with the lacquer makes contact with the embossing die via the presser, the film typically does not detach spontaneously. UV lamps are positioned downstream of the presser, in the area that is normally pressure-free. These lamps crosslink the UV lacquer while it is still in contact with the embossing die. Only after this reaction is the film removed from the embossing die. The entire process is usually continuous. The lacquer cured in this way is generally a thermoset.

[0017] Thermoplastic embossing generally differs from the UV embossing described above. A thermoplastic is solid at room temperature and therefore not flowable; at elevated temperatures, it becomes embossable at a certain point. At further elevated temperatures, the coating becomes sticky, which limits its effectiveness when using a standard embossing tool. However, non-stick coated tools can be used if necessary. For thermoplastic embossing, for example, the die can be heated, the embossing performed at the elevated temperature, and the die then cooled slightly before demolding. In a roll-to-roll process, cooling before demolding is generally not required.In thermoplastic embossing, for example, the film can be heated, if necessary in contact with the embossing tool, and embossed at the highest temperature and immediately demolded without coming into contact with the sticky area of ​​the thermoplastic. Heating to such a high temperature that the thermoplastic actually becomes liquid is advantageously avoided.

[0018] To prevent adhesion of a lower-melting-point thermoplastic, the embossing tool is advantageously coated with a non-stick coating. Alternatively, adhesion-preventing metallization of the unembossed coating can be provided, or measures can be taken to ensure that the higher-melting-point thermoplastic only becomes more highly meltable at a later stage. This can be achieved, for example, using the crosslinking agents mentioned elsewhere (such as isocyanates) or by radiation crosslinking. For instance, two UV-curable thermoplastic raw materials can be placed side by side, with one of these formulations containing a photoinitiator. After the initial embossing, exposure to light is possible – in this case, demolding is then possible, as the solid coating retains the embossed structure even without contact with the embossing tool.The formulation containing the photoinitiator consequently has a higher melting point and is no longer deformable under the previous embossing conditions. The second embossing can then be performed. Either the second thermoplastic is left uncrosslinked, or it is post-crosslinked by electron beam curing, as the latter process can be carried out without photoinitiators. Alternatively, the second thermoplastic can also contain a photoinitiator that is not activated at the wavelength(s) of the first emitter.

[0019] In addition to the aforementioned advantageous formulations of embossing lacquers, it is also possible to use embossing lacquers that cure or crosslink thermally rather than photochemically. For example, some embossing lacquers have a softening temperature T1 and a curing temperature T2 > T1. Such embossing lacquers can, for example, be based on acrylates with isocyanates.

[0020] Another approach involves selectively heating one of the embossing lacquers. In this method, an area containing a selectively excitable substance (in the UV / visible / IR spectrum or electrically / capacitively / magnetically with alternating fields) leads to the selective heating of only the area containing that substance. In this way, for example, two areas with UV embossing lacquer can be provided and processed, in particular embossed, sequentially.

[0021] Advantageously, the embossing structures of the first and second embossing lacquer layers each contain structural elements with in-plane dimensions between 30 µm and 200 µm, particularly between 50 µm and 150 µm. One or both embossing structures advantageously include as structural elements micromirror arrangements with directionally reflecting micromirrors, particularly with non-diffractive mirrors, and preferably with planar mirrors, concave mirrors, and / or Fresnel-type mirrors.

[0022] The embossing structures of the first and second embossing lacquer layers can advantageously adjoin each other directly. However, it is also possible for a narrow transition zone to exist between the embossing structures of the first and second embossing lacquer layers, in which the embossing height and / or embossing quality of one of the embossing structures decreases. The transition zone preferably has a width of less than 10 µm, and particularly less than 5 µm. In the transition zone, for example, the shape of the embossing structures can be maintained, but the height of the embossing structures can decrease from a maximum value in the interior of the feature area to a minimum value at the edge of the feature area adjacent to the subsequent feature area. The minimum value can also be zero.In the transition area, the quality of the embossing structures may also be reduced compared to the interior of the feature area; for example, the structural elements of the embossing may only be incompletely transferred to the embossing varnish there.

[0023] The embossing lacquer layers of the first and second feature areas are advantageously arranged next to each other without gaps or overlaps.

[0024] The embossing structures of the first and second embossing lacquer layers are advantageously located essentially at the same height, which in particular means that the mean heights of the two embossing structures differ by no more than the height difference within each embossing structure.

[0025] In an advantageous further development, the first and second embossing lacquer layers are provided with a common reflection-enhancing coating, in particular a high-refractive-index or metallic coating.

[0026] According to an advantageous embodiment, the security element comprises an easily deformable carrier film, in particular a carrier film with a thickness of less than 23 µm, preferably a thickness of less than 19 µm, and most preferably a thickness between 6 µm and 15 µm. A carrier film with a glass transition temperature Tg that is lower than the softening temperature of at least one thermoplastic embossing lacquer of the feature layer is also advantageously suitable as an easily deformable carrier film.

[0027] According to a further advantageous embodiment, the safety element includes a leveling layer which is flexible, in particular elastic, i.e. reversibly deformable at the softening temperature of at least one thermoplastic embossing lacquer of the feature layer.

[0028] The leveling layer can, for example, be made of silicone rubber. Depending on the properties of the leveling layer, it can be advantageous to use it as the middle layer in a sandwich structure consisting of a carrier film, the leveling layer, and a thin cover layer. This ensures that the final cover layer allows for easy recoating. The thin cover layer advantageously has a thickness of 3 to 6 µm, for example, 4.5 µm. The thickness of the leveling layer is advantageously between approximately 2 and 20 µm.

[0029] The leveling layer can also be formed by or comprise a foam. Such leveling layers made of or containing foams are particularly flexible and compressible, but often exhibit light scattering at bubble boundaries and therefore generally have somewhat lower transparency.

[0030] It is understood that the optically variable security element may contain further layers, such as protective, covering or additional functional layers, machine-readable elements, primer layers or heat-seal lacquer layers, which, however, do not constitute the essential elements of the present invention and are therefore not described in more detail.

[0031] The security element is advantageously a security thread, in particular a window security thread or a pendulum security thread, a tear strip, a security tape, a security strip, a patch or a label for application to a security paper, valuable document or the like.

[0032] The invention also includes a method for producing an optically variable security element in which a feature layer is created on a carrier, which contains first and second feature areas arranged in a common plane in a precise alignment with each other.

[0033] In this process, a first embossing lacquer layer is applied to the first feature areas, and an embossing structure is embossed into the embossing lacquer layer, creating a first optical effect.

[0034] In the second feature areas, a second embossing lacquer layer is applied and a second embossing structure is embossed into the embossing lacquer layer, creating a second, different optical effect.

[0035] In this process, the first and second embossing varnishes are applied, each exhibiting different optical properties as well as different hardening properties. While the use of embossing varnishes with different hardening properties is currently preferred, varnishes with the same hardening properties can also be used if they are hardened at different times. For example, UV embossing varnishes can be used as the first and second varnishes, with the first UV embossing varnish being hardened after UV embossing, and then a second UV embossing varnish being applied and also hardened after UV embossing. In this case, the embossing varnishes are hardened at different times but can otherwise have the same hardening properties.

[0036] In an advantageous variant of the process, it is provided that In the first feature areas, a first embossing varnish layer made of a thermoplastic embossing varnish with a higher softening temperature is applied, and in the second feature areas, a second embossing varnish layer made of a thermoplastic embossing varnish with a lower softening temperature is applied; a first embossing step is carried out at a higher temperature and the first embossing varnish layer is provided with the first embossing structure; and subsequently, a second embossing step is carried out at a lower temperature and the second embossing varnish layer is provided with the second embossing structure.

[0037] In another, equally advantageous variant of the process, it is provided that In the first feature areas, a first embossing lacquer layer made of a thermoplastic embossing lacquer is applied, and in the second feature areas, a second embossing lacquer layer made of a radiation-curing embossing lacquer is applied. A first embossing step is carried out at a higher temperature, and the first embossing lacquer layer is thereby provided with the first embossing structure. Subsequently, a second embossing step is carried out at a lower temperature and under radiation, and the second embossing lacquer layer is thereby provided with the second embossing structure and cured.

[0038] In all process variants, it is advantageous to emboss and solidify the first embossing lacquer layer in a first embossing step, while the second embossing lacquer layer remains deformable and flows partially or completely after the first embossing step.

[0039] In another advantageous method variant, it is provided that In the first feature areas, a first embossing lacquer layer made of a radiation-curing embossing lacquer is applied, and in the second feature areas, a second embossing lacquer layer made of a thermoplastic embossing lacquer is applied, and the radiation-curing embossing lacquer is provided with the first embossing structure and cured in a first embossing step, and subsequently a second embossing step is carried out and the second embossing lacquer layer is provided with the second embossing structure.

[0040] The second embossing structure is only transferred to the second embossing lacquer layer during the second embossing step, but not to the first embossing lacquer layer.

[0041] A particularly advantageous aspect of the second embossing step is the use of a flexible embossing tool, a soft embossing press, or a flexible leveling layer within the layer structure of the security element. This ensures that the embossing in the second feature areas is transferred to the second embossing layer without destroying or damaging the existing first embossing structure. As explained in more detail below, the flexible embossing tool can deform in the area of ​​the hardened first embossing structure, or the areas with the hardened first embossing structure can be pressed sufficiently far into the soft embossing press or the flexible leveling layer.

[0042] The invention further comprises an embossing arrangement A semi-finished security element for further processing into an optically variable security element of the type described above, comprising a feature layer containing first and second feature areas arranged in a common plane with precise alignment, wherein -- the first feature areas comprise an embossing lacquer layer made of a hardened embossing lacquer into which an embossing structure is embossed, producing a first optical effect, and -- the second feature areas comprise a second embossing lacquer layer made of an unhardened embossing lacquer, -- wherein the first and second embossing lacquers have both different hardening properties and different optical properties, and a flexible embossing tool with a second embossing structure, preferably for embossing an embossing structure that produces a second, different optical effect, only into the embossing lacquer layer with the unhardened embossing lacquer of the semi-finished security element.

[0043] The flexible embossing tool can be made of silicone rubber in particular.

[0044] Finally, the invention also includes an embossing arrangement comprising A semi-finished security element for further processing into an optically variable security element of the type described above, comprising a feature layer containing first and second feature areas arranged in a common plane with precise alignment, wherein: -- the first feature areas comprise an embossing lacquer layer made of a hardened embossing lacquer into which an embossing structure is embossed, producing a first optical effect; and -- the second feature areas comprise a second embossing lacquer layer made of an unhardened embossing lacquer; -- wherein the first and second embossing lacquers have both different hardening properties and different optical properties; and a hard embossing tool with a second embossing structure and a soft embossing press with a Shore hardness of less than 90, in particular less than 85, preferably for embossing an embossing structure that produces a second, different optical effect.only into the embossing lacquer layer with the unhardened embossing lacquer, by embossing the security element semi-finished product between the hard embossing tool and the soft embossing press.

[0045] Further embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a scale and proportion-accurate reproduction has been omitted in order to increase clarity.

[0046] They show: Fig. 1 a schematic representation of a banknote with an optically variable security feature, Fig. 2 a schematic representation of a security feature with a carrier substrate with an embossed feature layer, Fig. 3 in (a) to (d) four intermediate steps in the production of a security feature with a feature layer using two thermoplastic embossing varnishes of different softening temperatures, Fig. 4 in (a) to (d) four intermediate steps in the production of a security feature with a feature layer made of a thermoplastic embossing varnish and a UV embossing varnish, Fig. 5 in (a) to (c) intermediate steps in the production of a security feature using a flexible embossing tool, Fig. 6 in (a) to (c) intermediate steps in the production of a security feature using a hard embossing tool in conjunction with a soft embossing press, Fig.Fig. 7 in (a) to (c) Intermediate steps in the manufacture of a security element in whose layer structure a flexible compensating layer is provided, Fig. 8 in (a) to (d) Intermediate steps in the application of two different embossing lacquers in a feature layer without register variations side by side, Fig. 9 in (a) to (c) Intermediate steps in another variant for the application of two different embossing lacquers in a feature layer without register variations side by side, Fig. 10 in (a) to (c) Intermediate steps in a further variant for the application of two different embossing lacquers in a feature layer without register variations side by side, Fig. 11 in (a) and (b) Intermediate steps in the application and high-resolution structuring of a UV embossing lacquer layer, Fig. 12 in (a) and (b) Intermediate steps in another possibility for applying two different embossing lacquers in a feature layer without register variations, Fig.Figures 13(a) to (c) show intermediate steps in a method for the registered application of two different embossing lacquers using mechanical layer removal, and Figures 14(a) to (d) show intermediate steps in a method for the registered application of two different embossing lacquers using a selective removal medium.

[0047] The invention will now be explained using the example of security features for banknotes. Figur 1 Figure 1 shows a schematic representation of a banknote 10 with an optically variable security element 12 in the form of an affixed transfer element. It is understood, however, that the invention is not limited to transfer elements and banknotes, but can be used for all types of security elements, for example, for labels on goods and packaging or for securing documents, identity cards, passports, credit cards, health insurance cards, and the like. In addition to transfer elements (such as patches with or without their own backing layer), security threads or security strips, for example, are also suitable for banknotes and similar documents.

[0048] Despite its flat design, the security element 12 gives the viewer a three-dimensional impression and, for example, simultaneously shows a binary change in color and effect when the banknote 10 is tilted, in which a first three-dimensional motif in a first color appears from a first viewing direction and a second three-dimensional motif in a second color appears from a second viewing direction.

[0049] Such visual effects, and numerous others, can be advantageously created with security elements in which two or more layers of embossed lacquer are arranged side by side in a single plane of the security element, each layer specifically designed with different, independent embossing structures. In addition to the different embossing patterns, the embossed lacquer layers also excel in other different properties, particularly different visual properties such as varying color, transparency, and / or luminescence. In this way, the optically variable effects created by the embossing, on the one hand, and the visual effects produced by the additional properties of the embossed lacquer layers, on the other, can be perfectly coordinated.

[0050] To illustrate, Fig. 2 In schematic representation, a security element 20 with a carrier film 22 in the form of a transparent PET film, which is provided with an embossed feature layer 24. The feature layer 24 consists of an alternating sequence of feature areas 30, 40 of desired shape and size (only one of the feature areas is provided with a reference numeral), which differ from each other both by the different translucent coloring of the applied embossing lacquer layers 32, 42, and by the different formation of the respective embossing structures 34, 44.

[0051] The embossed structures 34, 44 of the two feature areas 30, 40 lie in a common plane, essentially at the same height, and are provided with a common reflectivity-enhancing metal coating 26, for example, a vapor-deposited aluminum layer. In the exemplary embodiment, the metallized embossed structures are flattened with a lacquer layer 28, and the security element can be adhered to the desired target substrate, such as the banknote 10, via an adhesive layer 29. After application, the carrier substrate 22 can be removed or remain in the security element as a protective film.

[0052] The security element 20 is designed to be viewed through the translucent embossed lacquer layers 32, 42. In feature areas 30, the viewer 14 looks through the embossed lacquer layer areas 32 at the metallized embossed structures 34, while in feature areas 40, they look through the embossed lacquer layer areas 42 at the metallized embossed structures 44. For example, the embossed lacquer 32 can be translucent red, and the embossed structures 34 can create a convex representation of the value numeral "10" as a motif, while the embossed lacquer 42 is translucent green, and the embossed structures 44 create a convex representation of a coat of arms as a motif. The two motifs can also be recognizable from different viewing angles. As can be seen from Fig. 2 As can be seen, the feature areas 30, 40 with their different color effects produced by the embossing lacquer layers 32, 42 and their different motifs produced by the embossings 34, 44 are arranged directly next to each other without gaps or overlaps.

[0053] The basic principle of an advantageous manufacturing of the feature layer 24, for example of the safety element 20, is now explained with reference to the Figu-ren 3 und 4 further explained, which in (a) to (d) show four intermediate steps in the manufacture of the safety element 20.

[0054] First, with reference to Fig. 3(a) A carrier film 22, for example a transparent, colorless PET film, is provided and coated in the desired feature areas 30, 40 with a thermoplastic embossing varnish 32 or 42 of the desired color effect. The thermoplastic embossing varnishes 32, 42 are coordinated so that, in addition to their different colors, they also have different softening temperatures and can therefore be embossed at different temperatures. For example, thermoplastic embossing varnish 42 can be embossed at a lower temperature T2, while thermoplastic embossing varnish 32 can only be embossed at a higher temperature T1 > T2.

[0055] Then, in a first embossing step, which is carried out at a higher temperature T 1, both embossing lacquers 32, 42 are provided with the first embossing structure 34 using a first embossing tool 50, as shown in Fig. 3(b) illustrated.

[0056] The carrier film with the embossed feature layer is then cooled to the lower temperature T2 and demolded, thereby hardening the embossing lacquer 32 in the feature areas 30 with the embossed embossing structure 34, while the embossing lacquer 42 remains deformable. Therefore, after demolding, the embossing lacquer 42 will still partially or completely flow and may only incompletely form the initial embossing, as shown in Fig. 3(c) indicated by the reference symbol 34'.

[0057] In Fig. 3(c) Also shown is the second embossing tool 52 for the second embossing step, with which the second embossing structure 44 is embossed into the still deformable embossing lacquer layer 42 of the feature areas 40 at the lower temperature T 2. The embossing structure 34 of the feature areas 30 is already hardened; it is no longer significantly affected by the second embossing step, particularly due to the measures described in more detail below.

[0058] After the second embossing step, the carrier film with the double-embossed feature layer is cooled to a temperature T < T 2 , for example to room temperature, thereby also hardening the embossing varnish 42 in the feature areas 40.

[0059] In this way, a feature layer 24 is obtained with the desired double embossing 34, 44, which is adapted to the feature areas 30, 40, as in Fig. 3(d) The feature layer 24 can then be metallized, as shown in Fig. 2 illustrated, or the intermediate product of Fig. 3(d) can be further processed in another way to create a desired security element.

[0060] In the design of the Fig. 4 Instead of two thermoplastic embossing varnishes with different softening temperatures, a thermoplastic embossing varnish 32 and a UV embossing varnish 42 are used. Unlike the embodiments described below, the design of the Fig. 4 First, the thermoplastic embossing varnish is applied, followed by the UV embossing varnish. Although a UV embossing varnish is typically easier to emboss than a thermoplastic embossing varnish, with the use of suitable embossing varnishes and / or under suitable conditions, an embossing sequence as shown in [reference to relevant example] is also possible. Fig. 4 to be used.

[0061] With reference to Fig. 4(a) A carrier film 22, for example a transparent, colorless PET film, is provided and coated in the feature areas 30 with a thermoplastic embossing varnish 32 and in the feature areas 40 with a UV embossing varnish 42, each with a desired different color effect.

[0062] Then, in a first embossing step, the first embossing structure 34 is embossed using a first embossing tool 50 under embossing conditions in which the thermoplastic embossing varnish 32 is embossable, as shown in Fig. 4(b) illustrated. The embossing conditions can include, for example, a temperature T1 of 120 °C and high embossing pressure.

[0063] The carrier film with the embossed feature layer is then cooled to a lower temperature T₂ < T₁ and demolded, thereby solidifying the embossing varnish 32 in the feature areas 30. The lower temperature T₂ can, for example, be T₂ = 30 °C. The UV embossing varnish 42 is not embossed under the embossing conditions of the first embossing step, so that after the first embossing step, the embossing varnish 32 with the embossed structure 34 is present in feature areas 30, and the unembossed UV embossing varnish 42 is present in feature areas 40, as shown in Fig. 4(c) depicted.

[0064] Also in Fig. 4(c) The second embossing tool 52 is shown, which, at the lower temperature T2 and under UV irradiation 54, imprints the second embossing structure 44 into the UV-curable embossing lacquer layer 42 of the feature areas 40. By curing the embossing lacquer layer 42 using the radiation of a UV LED, the heat input into the thermoplastic layer 32 can be minimized. Due to the low temperature during the second embossing step and the measures described in more detail below, the already hardened embossing structure 34 of the feature areas 30 is not significantly affected by the second embossing step.

[0065] After the second embossing step and UV curing, the embossing varnish 42 is also hardened in the feature areas 40, so that, as with Fig. 3 a feature layer 24 with a desired double embossing 34, 44 adapted to the feature areas 30, 40 is obtained, as in Fig. 4(d) depicted.

[0066] In connection with the Figuren 3 and 4 In the described designs, both embossing lacquer layers 32 and 42 are already present on the carrier film during the first embossing step. However, it is also possible to apply the layer to be embossed later only after the first layer has been embossed. In this case, too, it is essential that the embossing of the first layer is retained under the embossing conditions of the layer to be embossed later. This generally requires special measures, which are described in relation to the Figuren 5 bis 7 This will now be explained in more detail.

[0067] One way to ensure that the embossing of the first embossed layer is not destroyed or damaged by the subsequent embossing step is to use a flexible embossing tool for the second embossing.

[0068] This is based on the design of the Fig. 5 illustrated, in which feature layer 24 is similar to the example of the Fig. 4 The system comprises, on the one hand, feature areas 30 with a thermoplastic embossing varnish 32 and, on the other hand, feature areas 40 with a UV embossing varnish 42. The structures 34 and 44 to be embossed, respectively, have in-plane structural dimensions L1 and L2 of 50 µm to 150 µm. The structure height is typically on the order of a few micrometers.

[0069] In the variant of Fig. 5 First, the UV embossing lacquer 42 is provided with the desired second embossing structure 44 and then cured, as in Fig. 5(a) The thermoplastic embossing lacquer 32 can also be embossed, or it can be, as shown in Fig. 5(a) , having remained without an imprinted structure due to flowing.

[0070] The first embossing structure 34 is now embossed using a flexible embossing tool 60, which has the desired embossing structure 34 on its surface. The flexible embossing tool 60 is made, for example, of silicone rubber and deforms under pressure peaks on a length scale λ of a few micrometers. During embossing, the feature areas 40 with the already cured UV embossing varnish 42 cause a corresponding deformation 62 of the flexible embossing tool 60, so that, on the one hand, the already cured embossing varnish areas 42 are not damaged, but on the other hand, embossing varnish 32 can be embossed in the feature areas 30 with the embossing structure 34, as shown in Fig. 5(b) illustrated.

[0071] Since the transition areas 64, in which the shape of the embossing tool 60 changes significantly, have a dimension of the order of λ « L 1 , L 2, and the transition areas 64 are therefore significantly smaller than the structural dimensions of the embossings 34, 44, any potentially lesser, defective or even missing embossing in the transition areas 64 has no significant influence on the quality of the embossing structures 34 in the feature area 30 overall.

[0072] After the thermoplastic embossing lacquer 32 has cooled and the flexible embossing tool 60 has been demolded, the feature layer 24 is therefore provided in feature areas 30, 40 with the desired matching double embossing 34, 44, as shown in Fig. 5(c) depicted.

[0073] Another possibility relates to Fig. 6 in the use of a hard embossing tool 70 in conjunction with a soft embossing press 72 and a suitable carrier film 74 in the security element.

[0074] In this design, the in Fig. 6(a) The initial situation presented largely reflects the initial situation of Fig. 5(a) That is, a feature layer 24 is present on a suitable carrier film 74, which is described in more detail below. In feature areas 30, a thermoplastic embossing varnish 32 is applied, and in feature areas 40, a UV embossing varnish 42 is applied. The UV embossing varnish 42 was already provided with a desired embossing 44 in a first embossing step. Here, too, the structures 34 and 44 to be embossed have structural dimensions L1 and L2, respectively, in the plane, which lie between 50 µm and 150 µm.

[0075] For the embossing of the embossing structure 34 in the second embossing step, the following procedure is used: Fig. 6 A hard embossing tool 70 is used, which can be made of nickel, for example. The hard embossing tool 70 is particularly well suited for embossing thermoplastic lacquer 32; however, it is less able to compensate for height differences than the flexible embossing tool 60 in the design of the Fig. 5 .

[0076] To ensure that the already embossed and hardened lacquer areas 42 are not deformed or damaged in the second embossing step, the fact that embossing always requires counter-pressure is exploited; this is usually applied by an embossing press 72. A special feature of the process is... Fig. 6 A relatively soft embossing press 72 is used, which consists of an elastomer with a hardness of less than 90 Shore, in particular less than 85 Shore.

[0077] As in Fig. 6(b) As schematically illustrated, in the second embossing step the already hardened UV embossing varnish areas 42 are pressed sufficiently far into the soft embossing press 72 by the hard embossing tool 70 together with the carrier film 74 in order to be able to emboss the thermoplastic embossing varnish 32 without damaging or destroying the UV embossing varnish areas 42.

[0078] After cooling and demolding of the thermoplastic embossing lacquer 32, the feature layer 24 is then provided in feature areas 30, 40 with the desired matching double embossing 34, 44, as shown in Fig. 6(c) depicted.

[0079] As an alternative or supplement to the use of a soft embossing presser 72, the presser can also be equipped with a structured surface that locally limits deformation of the presser. For example, the surface can be divided into independent honeycombs with a characteristic dimension λ c ≈ 25 µm, so that, for example, with structural dimensions of the embossing structures 34, 44 of L 1 , L 2 = 100 µm, it can be expected that several, in particular 9, honeycomb segments can exert their ideal embossing pressure, while the adjacent segments are strongly deformed.

[0080] Returning to the advantageous properties of the carrier film 74, it must be sufficiently easily deformable under the embossing conditions of the second embossing step to accommodate the in Fig. 6(b) To allow illustrated height compensation by the embossing press 72.

[0081] For this purpose, for example, a very thin carrier film 74 can be used, the thickness of which is preferably less than 23 µm, particularly less than 19 µm, and most preferably between 6 µm and 15 µm. Alternatively or additionally, the carrier film 74 can also be adapted to the embossing conditions by ensuring that the glass transition temperature Tg of the carrier film is exceeded under the embossing conditions of the second embossing step, and that the film is therefore particularly easy to deform.

[0082] Another way to ensure that the first embossed layer is not destroyed or damaged under the embossing conditions of the later embossed layer is to provide a leveling layer 80 in the layer structure of the security element itself.

[0083] To illustrate, show Fig. 7 The layer structure of the security element to be manufactured, in which a leveling layer 80 is provided between a carrier film 22 and the feature layer 24, which is flexible at least under the embossing conditions of the second embossing and preferably exhibits elastic properties. If it is intended that the optical effect of the security element is viewed from the side of the embossing lacquer layers 32, 42 and thus also through the leveling layer, the leveling layer is preferably transparent and has a low scattering effect. Specifically, the leveling layer 80 can, for example, be made of silicone rubber.

[0084] The in Fig. 7(a) The initial situation depicted largely corresponds to the initial situation of the Fig. 6(a) , in particular the feature layer 24 contains a thermoplastic embossing varnish 32 in the feature areas 30 and a UV embossing varnish 42 in the feature areas 40, which has already been provided with a desired embossing 44 in a first embossing step.

[0085] For the embossing of the embossing structure 34 in the second embossing step, a hard embossing tool 70 can then be used, which is particularly well suited for embossing a thermoplastic varnish 32. With reference to the representation of the Fig. 7(b) The second embossing step of the thermoplastic lacquer 32 takes place at an elevated temperature, at which the leveling layer 80 is elastic, so that the already cured UV embossing lacquer areas 42 are locally pressed into the leveling layer 80 by the hard embossing tool 70. This prevents deformation or damage to the embossing structure 44 and simultaneously enables embossing of the embossing lacquer layer 32.

[0086] To allow sufficient impression of the UV embossing varnish areas 42, the thickness of the leveling layer 80 should be slightly greater than the height difference to be compensated for, which is typically between 2 and 15 µm for typical embossed microstructures 44. The leveling layer 80 can advantageously deform in such a way that, when the UV embossing varnish areas 42 are pressed in, the thermoplastic embossing varnish areas 32 are simultaneously pushed slightly upwards, thus supporting the second embossing. Such deformation can be achieved in a volume-preserving manner.

[0087] After completion of the second embossing step and the cooling and demolding of the thermoplastic embossing lacquer 32, the deformation of the elastic compensation layer 80 returns, so that the produced feature layer 24 is provided in feature areas 30, 40 with the desired fitted double embossing 34, 44, as shown in Fig. 7(c) depicted.

[0088] The designs described so far assume a situation in which pre-applied embossing varnish areas already exist on a carrier film in feature areas 30 and 40. The following describes some advantageous methods for applying two or more different embossing varnishes side by side in a feature layer without register variations, and thus ideally without unintended gaps or overlaps.

[0089] This section first describes variants that utilize the phenomenon of surface energy or surface tension. Depending on the material of the carrier film used, it may be necessary to first coat it with a layer possessing a suitable surface energy. For this purpose, additional layers, such as a primer layer or a release layer for subsequent removal, may be required. Corona treatment, plasma treatment, or flame treatment of the film can also be helpful for ensuring sufficient adhesion. The following description assumes that the carrier 90 mentioned is a suitable carrier film and, if necessary, has been pretreated accordingly or coated with additional layers to provide a surface energy suitable for the respective process.

[0090] At the in Fig. 8 In the illustrated process variant, a carrier 90 is first printed in the feature areas 40 using any method with an embossable, hydrophilic formulation 42 after drying, which exhibits the desired color or transparency in the feature areas 40. In the described design, the formulation is a UV embossing varnish 42, which, after printing in the feature areas 40, is embossed with the associated embossing structure 44 and finally cured by UV crosslinking, as shown in Fig. 8(a) The feature areas 30 are initially uncoated and represent areas with a hydrophobic surface.

[0091] The carrier film coated with the UV embossing varnish is then moistened with a dampening solution 92, either inline or in a separate process. Only the hydrophilically coated feature areas 40 absorb the dampening solution 92, while the hydrophobic feature areas 30 remain free of dampening solution, as shown in Fig. 8(b) illustrated.

[0092] Subsequently, a second embossing varnish layer of a thermoplastic embossing varnish 32 is applied to the carrier film, for which purpose a printing cylinder 94 is used in the exemplary embodiment, on which the embossing varnish layer 32 is provided over the entire surface, as shown in Fig. 8(b) shown. In order to ensure that the embossing varnish 32 is applied only in the spaces 30 between the already coated areas 40, the surface of the printing cylinder 94 is equipped with a compressible element 96.

[0093] The compressible element 96 deforms during the printing of the embossing varnish layer 32 due to the pressure peaks generated by the already cured UV varnish layer 42, as shown in Fig. 8(c) The embossing varnish 32 is shown so that it comes into contact with the substrate 90 in the non-recessed feature areas 30 and is transferred there without damaging the existing embossing structure 44. Although the UV embossing varnish 42 of the feature areas 40 also comes into contact with the embossing varnish layer 32 during printing, it is ink-repellent due to the previously applied dampening solution 92 and therefore does not accept the embossing varnish 32.

[0094] In this way, the thermoplastic embossing varnish 32 is deposited only in the feature areas 30 during the printing step, as shown in Fig. 8(d) The feature area 40 contains the already embossed and cured UV embossing lacquer 42. The intermediate product thus obtained can then be used, for example, in connection with the Figuren 5 bis 7 The material is described, further processed, and the embossing varnish layer 32 is also given the desired embossing. Instead of a thermoplastic embossing varnish, another UV embossing varnish can also be used, which, since the first embossing varnish has already hardened when the second embossing varnish is printed, can also have the same hardening properties as the first embossing varnish.

[0095] In the procedural variant of Fig. 9 Instead of a compressible element in the printing cylinder, a soft Presseur 98 with a Shore hardness of less than 90, in particular less than 85, is used.

[0096] The in Fig. 9(a) The initial situation shown essentially corresponds to the initial situation of the Fig. 8 Figure 1 shows a carrier 90 coated in feature areas 40 with a hydrophilic UV embossing varnish 42 after curing. The UV embossing varnish 42 was embossed with the desired embossing structure 44 and cured by UV crosslinking. The carrier film thus coated was then moistened inline or in a separate process with a dampening solution 92, whereby only the hydrophilically coated feature areas 40 absorbed the dampening solution 92, while the uncoated feature areas 30 remained free of dampening solution.

[0097] Subsequently, a second embossing varnish layer of a thermoplastic embossing varnish 32 is applied over the entire surface of a printing cylinder 94. A soft presser 98 provides counter-pressure for the printing step; however, due to its low hardness of less than 90 or less than 85 Shore, it is locally deformable by pressure peaks. As in Fig. 9(b) As schematically illustrated, when the embossing varnish layer 32 is printed, the already hardened UV embossing varnish areas 42 are pressed slightly into the soft presser 98 by the printing cylinder 94 together with the carrier film 90, so that the thermoplastic embossing varnish 32 comes into contact with the carrier film 90 in the marking areas 30 and is transferred there, without damaging the already existing embossing structure 44.

[0098] Although the UV embossing varnish areas 42 are also in contact with the embossing varnish layer 32, they are color-repellent due to the applied dampening solution 92 and therefore do not accept the embossing varnish 32. The printing step thus creates a design with unembossed thermoplastic embossing varnish 32 in feature areas 30 and with embossed, cured UV embossing varnish 42 in feature areas 40, which can be further processed as described above. Instead of a thermoplastic embossing varnish, another UV embossing varnish can also be used here, which, since the first embossing varnish has already hardened when the second embossing varnish is printed, can also exhibit the same hardening properties as the first embossing varnish.

[0099] In this variant, the carrier film 90 must be sufficiently deformable under the printing conditions of the second embossing varnish 32 in order to accommodate the in Fig. 9(b) to allow the illustrated height compensation by the presser 98. For this purpose, for example, a very thin carrier film 90 can be used (thickness preferably less than 23 µm, in particular 19 µm, especially thickness between 6 µm and 15 µm) and / or a carrier film 90 with a low glass transition temperature can be used, which is higher than the printing conditions of the second embossing varnish, so that the film becomes particularly easy to deform.

[0100] Another possibility is to provide a leveling layer 80 in the layer structure of the safety element itself. With reference to Fig. 10 In the layer structure of the security element to be produced, a leveling layer 80 is arranged on the carrier film 22, which is flexible at least under the printing conditions of the embossing varnish layer 32 and preferably has elastic properties.

[0101] The in Fig. 10(a) The initial situation shown corresponds, except for the leveling layer, to the initial situation of the Fig. 9(a) Figure 1 shows a carrier film 22 with an applied leveling layer 80, for example made of silicone rubber, which was coated in feature areas 40 with a hydrophilic UV embossing varnish 42 after curing. The leveling layer can also be provided with a thin cover layer to facilitate the subsequent application of the embossing varnish layers 32, 42 and / or to provide suitable surface energy. The UV embossing varnish 42 was embossed with the desired embossing structure 44 and cured by UV crosslinking. The carrier film thus coated was then moistened inline or in a separate process with a dampening solution 92, whereby only the hydrophilically coated feature areas 40 absorbed the dampening solution 92, while the uncoated feature areas 30 remained free of dampening solution.

[0102] Subsequently, a second embossing varnish layer of a thermoplastic embossing varnish 32 is applied over the entire surface of a printing cylinder 94. As in Fig. 10(b) As illustrated, the leveling layer 80 is elastic under the printing conditions of the thermoplastic varnish 32, so that the already cured UV embossing varnish areas 42 are locally pressed into the leveling layer 80 by the printing cylinder 94. This prevents deformation or damage to the embossing structure 44 and enables the embossing varnish layer 32 to be applied easily, especially into the spaces 30 between the UV embossing varnish areas 42.

[0103] In order to allow sufficient indentation of the UV embossing lacquer areas 42, the thickness of the leveling layer 80 should be slightly greater than the height difference to be leveled, which is typically between 2 and 15 µm.

[0104] Although the UV embossing varnish areas 42 are also in contact with the embossing varnish layer 32, they are color-repellent due to the applied dampening agent 92 and therefore do not accept the embossing varnish 32.

[0105] After completion of the printing step, the deformation of the elastic compensation layer 80 returns to its original state, so that the in Fig. 10(c) The desired design shown is created with unembossed thermoplastic embossing varnish 32 in feature areas 30 and embossed, cured UV embossing varnish 42 in feature areas 40, which can be further processed as described above.

[0106] If a particularly high-resolution structuring of the UV embossing varnish layer 42 is to be achieved in the described designs, the embossing varnish layer 42 can be applied instead of as in the embodiments of the Figuren 8 bis 10 to be printed in a structured manner, also in a residue-free embossing process, as is basically described in the printed document EP 3 230 795 B1.

[0107] In order to successfully carry out such high-resolution residue-free embossing, the surface energies of the substrate, the embossing tool used, and the surface tension of the embossing lacquer must be coordinated.

[0108] With reference to Fig. 11(a) In the aforementioned process, a UV embossing lacquer 42 is first applied over the entire surface of the substrate 90. A structured embossing tool 100 contains tool areas 102 and 104 with different height levels, whose shape and size correspond to feature areas 30 (protruding tool areas 102) and 40 (recessed tool areas 104), respectively. The desired embossing structure 44 of the feature areas 40 is located in the recessed tool areas 104, which are situated further away from the layer 42 to be embossed during the subsequent embossing step.

[0109] As the structured embossing tool 100 approaches the full-surface and not yet hardened embossing lacquer layer 42, the protruding areas 102 reduce the layer thickness of the embossing lacquer 42 due to their geometry by displacement. More precisely, due to the wetting properties of the embossing lacquer 42, the cleavage coefficient, i.e., the interfacial energy between the carrier 90 and the embossing lacquer 42 and between the embossing lacquer 42 and the structured embossing tool 100, becomes negative, so that the embossing lacquer 42 is withdrawn from the feature areas 30 below the protruding tool areas 102 into the feature areas 40 below the recessed tool areas 104.

[0110] This tendency towards wetting and dewetting is not only dependent on surface energy but also on layer thickness. In feature areas 30, the raised tool areas 102 of the embossing tool 100 thus lead locally to residue-free dewetting of the embossing lacquer 42 upon approach. The embossing lacquer 42 that collects in feature areas 40 is embossed there by the embossing structure 44 arranged in the recessed tool areas 104.

[0111] After the embossing varnish 42 has cured, the carrier film 90 thus contains the desired high-resolution structure with embossed, cured UV varnish areas 42 and intervening uncoated feature areas 30, as shown in Fig. 11(b) further processing can then be carried out, for example, as in connection with the Figuren 8 bis 10 This will already be described.

[0112] According to another method variant, which also utilizes the phenomenon of surface energy or surface tension, with reference to Fig. 12(a) A layer of a first embossing varnish 32 is printed onto a substrate 90. This varnish, after drying or cross-linking, has a particularly low surface energy. The printed first embossing varnish 32 is then embossed and dried or cured. The application of the first embossing varnish 32 is structured so that feature areas 30 are coated with this first embossing varnish, while feature areas 40 remain uncoated. It has proven advantageous to apply the first embossing varnish 32 to approximately half of the total surface area to be coated.

[0113] Subsequently, a second embossing lacquer formulation 42, which has a low viscosity and high surface tension, is applied over the entire surface. This corresponds to the situation described in Fig. 12 (a) The intermediate step shown. The second embossing varnish formulation 42 can be a UV embossing varnish, in particular a water-dilutable formulation, which may need to be physically dried before embossing.

[0114] Due to its low viscosity and high surface tension, the second formulation 42 dewettes the first embossing varnish 32, which has a lower surface energy, as in Fig. 12(a) as indicated by arrows 110, so that after de-wetting the in Fig. 12(b) The situation described arises. In the case of complete disconnection, as occurs in Fig. 12(b) As illustrated, the application of the second embossing varnish formulation 42 can also be repeated several times, so that material of high surface tension is successively built up in the feature areas 40 until a sufficient quantity of second embossing varnish 42 is present there for the desired second embossing.

[0115] In addition to the described utilization of the phenomena of surface energy and surface tension, there are also advantageous possibilities based on layer removal for applying two or more different embossing lacquer layers side by side without register fluctuations, which are now being discussed in connection with the Figuren 13 and 14 will be described in more detail.

[0116] With reference to, first of all, Fig. 13 A first layer of a first thermoplastic embossing varnish 42 with a desired first color is applied in a structured manner to a carrier film 22 and dried. The application of the first embossing varnish 42 is carried out in a structured pattern according to the feature areas 40, but with a greater layer thickness d1 than the layer thickness d0 actually required at the end, as shown in Fig. 13(a) shown.

[0117] Then a second layer of a second thermoplastic embossing varnish 32 with a desired second color is applied over the entire surface.

[0118] As in Fig. 13(b) As shown, the second embossing varnish 32 is advantageously applied in a layer thickness d₂ > d₁; however, it is generally sufficient if the second embossing varnish is applied in a layer thickness d₂ > d₀. The application of the second embossing varnish 32 can also be carried out in several steps, each combined with wiping or squeegeeing steps, in order to keep the layer thickness of the second embossing varnish 32 low on the first applied embossing varnish areas 42.

[0119] After the second embossing lacquer 32 has solidified or physically dried, the resulting structure is mechanically removed down to the desired layer thickness d 0, for example by milling 120 off the layer areas 122 that protrude beyond the layer thickness d 0. If the milling machine 120 is set to the desired target layer thickness, in the simplest case milling can be carried out down to this target layer thickness, at which both embossing lacquers 32, 42 are exposed in the feature areas 30, 40, arranged exactly next to each other, as in Fig. 13(c) shown.

[0120] Fine adjustment and feedback of the milling step 120 can be carried out using the milling material removal, i.e., the material removed from the layer areas 122. As in Fig. 13(b) As illustrated, initially, during milling, with a small layer removal rate 124, only material from the higher-lying second embossing lacquer 32 is removed; only with a larger layer removal rate is material from the first embossing lacquer 42 also removed. A desired removal depth can therefore be controlled by spectroscopic analysis or, if necessary, simply by checking the color of the milled material. This ensures that the excess of the second embossing lacquer 32 present on the first embossing lacquer areas 42 is completely removed and that the in Fig. 13(c) The indicated end position is reliably reached.

[0121] In the further development of the Fig. 14 Two different embossing lacquers are used to produce the feature layer 24, one of which is soluble in a removal medium and the other is insoluble.

[0122] With reference to, first of all, Fig. 14(a) A UV embossing varnish 42 of a first color is applied to a carrier film 22, initially structured in feature areas 40. The UV embossing varnish 42 is typically embossed with the desired embossing structure 44 and cured. The feature areas 30 located between the embossing varnish areas 42 ideally remain completely uncoated.

[0123] Subsequently, a thermoplastic embossing varnish 32 with a second color is provided, for which a suitable removal medium exists with which the dried embossing varnish 32 can be removed with a well-defined removal rate, but which does not dissolve the UV embossing varnish 42.

[0124] With this embossing varnish 32, a second layer is applied to the carrier film 22 over the entire surface, as shown in Fig. 14(b) The application can be carried out, for example, using flexographic printing, whereby the flexosleeve, under high pressure, already presses a considerable part of the embossing varnish 32 into the recesses 130 between the already cured UV embossing varnish areas 42, and only a relatively small amount of ink lies on the embossing varnish areas 42.

[0125] Immediately after application of the embossing varnish 32, it is still liquid, so that the excess can be wiped or scraped off the printed film and thus removed, in particular, from the already cured embossing varnish areas 42. After physical drying of the embossing varnish 32, the recesses 130 between the already cured UV embossing varnish areas 42 are partially filled, as shown in Fig. 14(b) shown. A thin toning film 132 made of embossing lacquer material is also usually present on the embossed lacquer areas 42.

[0126] The application of embossing varnish 32 and the removal of excess material are repeated until the depressions 130 are sufficiently filled or even overfilled, as shown in Fig. 14(c) The repetition improves the relationship between the fill level of the recesses 130 and the unwanted tint 132 of the embossing varnish areas 42. It may be advisable to vary the color concentration of the embossing varnish 32 during the stepwise filling process, particularly towards a progressively lower color concentration, since wiping or scraping also reduces the tint of the penultimate application step and thus the proportion of unwanted color on the embossing varnish areas 42.

[0127] After the final application and wiping or scraping, the thermoplastic embossing varnish 32 is physically dried so that the in Fig. 14(c) The situation shown arises.

[0128] Subsequently, a development step is carried out for the embossing lacquer 32 using the corresponding removal medium. The removal medium can be aqueous, have a defined pH value, or be solvent-based. It may be necessary to expose the embossing lacquer 32 before removal.

[0129] Once the embossing lacquer 32 has been sufficiently removed by the abrasive medium to expose the embossing lacquer areas 42, the abrasion process is stopped, for example by rinsing with another medium. The cured UV embossing lacquer 42 is not removed by the abrasive medium of the embossing lacquer 32, so that the exposure occurs with high selectivity.

[0130] After completion of the ablation step, the desired structure with feature areas 40 with the embossed UV embossing varnish layer 42 of the first color and with intermediate feature areas 30 with the still unembossed thermoplastic embossing varnish layer 32 of the second color is present on the carrier film 22, as shown in Fig. 14(d) shown. Further processing can, for example, follow the procedure already described.

[0131] Instead of UV embossing lacquer 42, the following procedure can be used: Fig. 14 Another thermoplastic embossing lacquer can also be used. This can be insoluble in the removal medium of the embossing lacquer 32 from the outset, or it can contain a crosslinker that renders it insoluble in the removal medium of the embossing lacquer 32, but whose crosslinking reaction at the time of the first embossing has not yet progressed to the point where embossing would be prevented. Such a crosslinker can be, for example, an isocyanate, whereby the use of aliphatic isocyanates leads to a slower reaction if the embossing is to take place with a certain time delay after the application step.

[0132] The first embossing varnish layer 42 can be applied by applying a desired motif in a structured manner to the feature areas 40. However, particularly with UV embossing varnishes, it is also possible to first apply the embossing varnish layer over the entire surface and then structure it as desired. Advantageous possibilities for this, especially for high-resolution structuring of a UV embossing varnish layer, have already been described above. If a thermoplastic embossing varnish is applied as the first embossing varnish layer, then, for successful fine structuring with sufficient layer thickness, pressure at an elevated temperature or from the melt may be necessary.

[0133] Before and / or after the application of the first embossing lacquer layer 42, a further process step may be provided to transform the embossing lacquer into a stable and / or embossable form. This may, for example, be an exposure step or a tempering step. A wet chemical treatment, in which the embossing lacquer is brought into contact with a liquid medium to effect hardening or cross-linking, may also be provided. Bezugszeichenliste

[0134] 10 Banknote 12 Security element 14 Viewer 20 Security element 22 Carrier foil 24 Feature layer 30 Feature areas 32 Embossing varnish layer 34 Embossing structures 34 'Incompletely assumed embossing structures 40 Feature areas 42 Embossing varnish layer 44 Embossing structures 50, 52 Embossing tools 60 Flexible embossing tool 62 Deformation 64 Transition areas 70 Hard embossing tool 72 Soft embossing die 74 Carrier foil 80 Compensation layer 90 Carrier 92 Humidifier 94 Printing cylinder 96 Compressible element 98 Soft die 100 Textured embossing tool 102 Protruding tool areas 104 Recessed tool areas 110 Dewetting 120 Milling cutter 130 Recesses 132 Toning film

Claims

1. Optically variable security element (20) for safeguarding articles of value, having a feature layer (24) which comprises, arranged in register with one another in a common plane, first and second feature regions (30, 40), wherein - the first feature regions (30) comprise a first embossing varnish layer composed of a first embossing varnish (32) and impressed with an embossed structure (34) which generates a first optical effect, and - the second feature regions (40) comprise a second embossing varnish layer composed of a second embossing varnish (42) and impressed with an embossed structure (44) which generates a second, different optical effect, and - the first and second embossing varnishes (32, 42) have different optical properties, characterized in that the first and second embossing varnishes (32, 42) have different solidification properties.

2. Security element according to Claim 1, characterized in that the first and second embossing varnishes (32, 42) are each formed by a thermoplastic embossing varnish with different softening temperatures; or the first embossing varnish is formed by a radiation-curing, more particularly UV-curing, embossing varnish and the second embossing varnish is formed by a thermoplastic embossing varnish.

3. Security element according to at least one of Claims 1 to 2, characterized in that the first and second embossing varnishes (32, 42) have different colour, different transparency and / or different luminescence.

4. Security element according to at least one of Claims 1 to 3, characterized in that the embossed structures (34, 44) of the first and second embossing varnish layers each have structural dimensions in the plane that lie between 30 µm and 200 µm, more particularly between 50 µm to 150 µm; and / or between the embossed structures of the first and second embossing varnish layers there is a narrow transition region, preferably having a width of less than 10 µm, more particularly of less than 5 µm, in which the embossed height and / or embossed quality of one of the embossed structures decreases.

5. Security element according to at least one of Claims 1 to 4, characterized in that the embossing varnish layers of the first and second feature regions (30, 40) are arranged next to one another without gaps and overlaps; and / or the first and second embossing varnish layers are provided with a common reflection-increasing coating (26), more particularly a high-refractive-index or metallic coating.

6. Security element according to at least one of Claims 1 to 5, characterized in that the security element has a readily deformable carrier foil (74), more particularly a carrier foil having a thickness of less than 23 µm, preferably of less than 19 µm and more preferably of between 6 µm and 15 µm, or a carrier foil having a glass transition temperature Tg which is lower than the softening temperature of at least one thermoplastic embossing varnish (32) of the feature layer (24).

7. Security element according to at least one of Claims 1 to 6, characterized in that the security element comprises a compensating layer (80) which is flexible, more particularly elastic, at the softening temperature of at least one thermoplastic embossing varnish (32) of the feature layer (24).

8. Process for producing an optically variable security element (20) wherein on a carrier (22) a feature layer (24) is generated which comprises, arranged in register with one another in a common plane, first and second feature regions (30, 40), wherein, in the process, - in the first feature regions (30 or 40), a first embossing varnish layer composed of a first embossing varnish (32 or 42) is applied and an embossed structure (34 or 44) is embossed into the embossing varnish layer and generates a first optical effect, and - in the second feature regions (40 or 30), a second embossing varnish layer composed of a second embossing varnish (42 or 32) is applied and a second embossed structure (44 or 34) is embossed into the embossing varnish layer and generates a second, different optical effect, and - where embossing varnishes applied as first and second embossing varnishes (32, 42) each have not only different optical properties but also different solidification properties.

9. Process according to Claim 8, characterized in that - in the first feature regions (30), a first embossing varnish layer composed of a thermoplastic embossing varnish (32) having a relatively high softening temperature and in the second feature regions (40) a second embossing varnish layer composed of a thermoplastic embossing varnish (42) having a lower softening temperature are applied, - a first embossing step is carried out at relatively high temperature and in this case the first embossing varnish layer is provided with the first embossed structure (34), and - subsequently a second embossing step is carried out at lower temperature and in this case the second embossing varnish layer is provided with the second embossed structure (44).

10. Process according to Claim 8, characterized in that - in the first feature regions (30), a first embossing varnish layer composed of a thermoplastic embossing varnish (32) and in the second feature regions (40) a second embossing varnish layer composed of a radiation-curing embossing varnish (42) are applied, - a first embossing step is carried out at relatively high temperature and in this case the first embossing varnish layer is provided with the first embossed structure (34), and - subsequently a second embossing step at lower temperature is carried out with radiation exposure and in this case the second embossing varnish layer is provided with the second embossed structure (44) and cured.

11. Process according to at least one of Claims 8 to 10, characterized in that in a first embossing step, the first embossing varnish layer is embossed and solidified, while the second embossing varnish layer remains deformable and runs partially or completely after the first embossing step.

12. Process according to Claim 8, characterized in that - in the first feature regions (40), a first embossing varnish layer composed of a radiation-curing embossing varnish (42) and in the second feature regions a second embossing varnish layer (30) composed of a thermoplastic embossing varnish (32) are applied, and - the radiation-curing embossing varnish is provided with the first embossed structure (44) in a first embossing step and cured, and - subsequently a second embossing step is carried out and in this case the second embossing varnish layer is provided with the second embossed structure (34), wherein preferably, in the second embossing step, the second embossed structure (34) is transferred only into the second embossing varnish layer.

13. Process according to Claim 12, characterized in that in the second embossing step, a flexible embossing tool (60), a resilient opposed embossing roll (72) or a flexible compensating layer (80) is used in the layer construction of the security element in order to transfer the second embossed structure only into the second embossing varnish layer.

14. Embossing arrangement comprising - a security element preproduct for further processing to an optically variable security element according to any of Claims 1 to 7, having a feature layer (24) which comprises, arranged in register with one another in a common plane, first and second feature regions (30, 40), wherein -- the first feature regions (40) comprise a first embossing varnish layer composed of a first, solidified embossing varnish (42) impressed with an embossed structure (44) which generates a first optical effect, and -- the second feature regions (30) comprise a second embossing varnish layer composed of a second, unsolidified embossing varnish (32), -- wherein the first and second embossing varnishes (32, 42) have not only different solidification properties but also different optical properties, and - a flexible embossing tool (60) having a second embossed structure (34), preferably for impressing an embossed structure which generates a second, different optical effect only into the embossing varnish layer with the unsolidified embossing varnish (32) of the security element preproduct.

15. Embossing arrangement comprising - a security element preproduct for further processing to an optically variable security element according to any of Claims 1 to 7, having a feature layer (24) which comprises, arranged in register with one another in a common plane, first and second feature regions (30, 40), wherein -- the first feature regions (40) comprise a first embossing varnish layer composed of a first, solidified embossing varnish (42) impressed with an embossed structure (44) which generates a first optical effect, and -- the second feature regions (30) comprise a second embossing varnish layer composed of a second, unsolidified embossing varnish (32), -- wherein the first and second embossing varnishes (32, 42) have not only different solidification properties but also different optical properties, and - a hard embossing tool (70) having a second embossed structure (34) and a resilient opposed embossing roll (72) having a Shore hardness of less than 90, more particularly of less than 85, preferably for impressing an embossed structure (34) which generates a second, different optical effect only into the embossing varnish layer with the unsolidified embossing varnish (32), the security element preproduct being embossed between the hard embossing tool (70) and the resilient opposed embossing roll (72).

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