EP4067104A1 - Method of manufacturing an optically variable security element - Google Patents

Abstract

The invention relates to a method for producing a security element which contains a feature layer (24) with first and second feature regions (30, 40) in which different first and second embossing lacquer layers are present. In the method, a layer of a first embossing lacquer (42) is applied to a carrier (22) in the first feature areas (40). A layer of a second, different embossing varnish (32) is then applied over the entire surface, so that the second embossing varnish is present in the second feature regions (30) on the carrier (22). The feature layer (24) formed by the two embossing lacquer layers is then partially removed from its free upper side and the first embossing lacquer areas (42) are thus uncovered, so that the first embossing lacquer layer in the first feature areas (40) and the second feature areas (30) the second layer of embossing varnish are next to each other with an exact register. The removal can be done mechanically using a milling cutter (120) or by etching (FIG. 14).

Description

The invention relates to a manufacturing method for an optically variable security element for protecting valuables, which contains a carrier and a feature layer with first and second feature areas in which different first and second embossing lacquer layers are present.

Data carriers, such as value or ID documents, but also other valuables, such as branded items, are often provided with security elements for protection, which allow the authenticity of the data carrier to be checked and which at the same time serve as protection against unauthorized reproduction. The security elements can be designed, for example, in the form of a security thread embedded in a bank note, a cover film for a bank note with a hole, an applied security strip, a self-supporting transfer element or also in the form of a feature area applied directly to a document of value.

Some time ago, optically variable security elements were proposed which have two relief structures which are arranged at different height levels and are each provided with a color coating and which are embossed in suitably colored embossed lacquer layers, see FIG WO 2020/011390 A1 , WO 2020/011391 A1 and WO 2020/011392 A1 . However, in order to view the deeper-lying relief structure, the viewer usually has to look through the embossing lacquer layer of the higher-lying relief structure, so that depending on the desired visual impression for the coloring of the embossing lacquers, in particular the embossing lacquer of the higher-lying embossing lacquer layer, there can be considerable restrictions.

If several printing inks or embossing lacquer layers are applied to a substrate during the production of such security elements, unavoidable register fluctuations in the printing machines prevent an exact registration of the layers in the plane to less than about 50 μm. Such register fluctuations can occur both longitudinally and transversely to a printed web.

Proceeding from this, the invention is based on the object of specifying a method with which generic optically variable security elements can be produced with high register accuracy of the different first and second embossing lacquer layers.

This object is solved by the features of the independent claims. Developments of the invention are the subject matter of the dependent claims.

In order to achieve the stated object, the invention provides a method for producing a security element which can be used in particular to protect valuables. The security element to be produced contains a feature layer with first and second feature areas in which different first and second embossing lacquer layers are present.

In the method, a layer of a first embossing lacquer is applied to a carrier in the first feature areas.

A layer of a second, different embossing lacquer is then applied over the entire surface, so that the second embossing lacquer is present in the second feature regions on the carrier. The one through the two layers of embossing lacquer The feature layer formed is then partially removed from its free upper side. As a result, the first embossing lacquer areas are uncovered, so that in the first feature areas the first embossing lacquer layer and in the second feature areas the second embossing lacquer layer lie next to one another with an exact register.

In the context of the present description, a precisely registered arrangement of feature regions refers in particular to an arrangement in which the feature regions abut one another or are arranged at a predetermined, defined small distance from one another. A close distance is in particular a distance of a few microns or a few tens of microns up to 100 µm and in some applications up to 200 µm.

The carrier can remain permanently in the security element or it can represent a production carrier which is removed from the security element again after the security element has been transferred to a target substrate.

If a system has to dry physically, it usually has to be dried before embossing. Crosslinking reactions, for example by radiation, or slower reactions (e.g. in 2K systems) should generally take place after embossing, as they can make embossing difficult or even impossible.

The second embossing varnish is preferably applied in such a way that it is also present, at least partially or over the entire surface, in the first feature areas (40) on the areas with, in particular dried or pre-cured, first embossing varnish (42).

The first embossing varnish is preferably dried or pre-cured before the removal, in particular before the application of the second embossing varnish. An actual crosslinking reaction can thus take place during or after embossing or can only be triggered during or after embossing, in particular by irradiation.

In an advantageous method, the first embossing lacquer is applied in a first layer thickness d ₁ , and preferably dried or pre-cured, which is greater than the desired target layer thickness d ₀ . The second embossing varnish is applied over the entire surface in a second layer thickness d ₂ which is greater than the desired target layer thickness d ₀ and preferably greater than the first layer thickness d ₁ . At least in the second feature area, the second embossing lacquer layer is then present on the carrier with the second layer thickness d ₂ . In the first feature area, the second embossing lacquer is at least partially present, preferably over the entire surface and/or with a layer thickness of at least or exactly d ₂ -d ₁ , only alternatively only partially. The second embossing varnish is preferably dried or pre-cured. The feature layer formed by the two embossing lacquer layers is removed mechanically down to the desired target layer thickness d ₀ .

The second embossing varnish is preferably applied in several steps and after each application step a wiping or doctoring step takes place in order to keep the layer thickness of the second embossing varnish small on the areas with dried or cured first embossing varnish.

In an advantageous variant, the feature layer formed by the two embossing lacquer layers is removed with a milling machine down to the desired target layer thickness d ₀ .

The two embossing varnishes advantageously have different optical properties, in particular different colors. Then, mechanical ablation can incrementally remove material from the exposed top of the feature layer at increasing depths, and the end point of the mechanical ablation can be determined by analysis of the optical properties, particularly the color, of the ablation material. The end point is preferably determined by checking whether the color of the first embossing varnish also appears in the ablation material in addition to the color of the second embossing varnish.

In another, likewise advantageous method, the first and second embossing varnish are matched to one another, so that the second embossing varnish is soluble in a removal medium, while the first embossing varnish is insoluble in the removal medium, at least in the dried or hardened state. After being applied once or several times, the second embossing varnish is dried and the second embossing varnish is removed with the removal medium until the areas with dried or hardened first embossing varnish are exposed. The removal process is then stopped.

In this method variant, the second embossing varnish is preferably applied in several steps and after each application step there is a wiping or squeegee step in order to keep the layer thickness of the second embossing varnish small on the areas with dried or cured first embossing varnish. The second embossing lacquer can in particular contain a colorant or color pigments, with the concentration of the colorant or color pigments preferably being reduced as the number of application steps increases. It is also possible to reduce the amount or the layer thickness of the applied embossing varnish with an increasing number of application steps.

The second embossing varnish is advantageously applied once or several times until the second embossing varnish in the second feature areas fills the depressions between the areas with dried or hardened first embossing varnish.

In both process variants, an embossed structure is advantageously embossed into the first embossed lacquer layer, which produces a first optical effect, and an embossed structure is embossed into the second embossed lacquer layer, which produces a second, different optical effect. The embossed structures of the first and second embossed lacquer layers are advantageously essentially at the same height, which means in particular that the mean heights of the two embossed structures differ by no more than the difference in height within each embossed structure.

It can expediently be provided that the embossing lacquer layers are each provided with an embossing structure one after the other in an earlier and a later embossing step. In the earlier embossing step, only one of the two embossing lacquer layers is embossed, and in the later embossing step only the other of the two embossing lacquer layers is embossed, preferably by using a flexible embossing tool, a soft embossing press or a flexible compensating layer in the layer structure of the security element in order to correct the subsequent embossing structure only to be transferred to the embossed lacquer layer that has not already been embossed.

In both variants, it is preferred that the two embossing varnishes have different solidification properties, and the embossing varnishes particularly preferably also have different optical properties.

Lacquers that harden by physical drying, in particular thermoplastic embossing lacquers, can be applied as embossing lacquers. If both the first and the second embossing varnish are each formed by a thermoplastic embossing varnish, they advantageously have different softening temperatures, which preferably differ by more than 10 °C, particularly preferably by more than 25 °C, in particular by more than 50 °C differentiate.

Two “thermoplastics” can also be used side by side as embossing lacquers, with a first “thermoplastic” being able to be post-crosslinked, for example by radiation. For example, a removal process is used until both thermoplastics are next to each other and have the same height. Neither have comparable melting points and can be embossed at the same time. After the embossing step, the first thermoplastic is crosslinked. As a result, it has a higher melting point, which means that its structure is not destroyed in the second embossing step, and the second thermoplastic can be embossed.

In likewise advantageous configurations of both aspects, it is provided that a radiation-curing, in particular UV-curing, embossing varnish is applied as an embossing varnish and a thermoplastic embossing varnish is applied as another embossing varnish. Designs in which both embossing varnishes are formed by UV embossing varnishes are also possible.

The embossing lacquers can in particular be applied in different colors, different transparency and/or different luminescence. The embossing varnishes are preferably colored with a translucent color and are therefore both colored and partially translucent.

The embossing lacquer layers of the first and second feature areas are advantageously arranged next to one another without gaps or overlaps.

In an advantageous development of the invention, the first and second embossing lacquer layers are provided with a common reflection-increasing coating, in particular a high-index or metallic coating. This coating preferably takes place after an embossing of the first and second embossing varnish with a respective embossing structure that produces different first and second optical effects.

Advantageously, the embossed structures of the first and second embossing lacquer layers each contain structural elements with structural dimensions in the plane that are between 30 μm and 200 μm, in particular between 50 μm and 150 μm. One or both embossed structures advantageously contain micromirror arrangements with directed reflecting micromirrors, in particular with non-diffractive mirrors, and preferably with planar mirrors, concave mirrors and/or Fresnel-like mirrors as structural elements.

It goes without saying that the optically variable security element can contain further layers, such as protective, cover or additional functional layers, machine-readable elements, primer layers or heat-sealing lacquer layers, which, however, do not represent the essential elements of the present invention and are therefore not described in detail. The security element to be produced is advantageously a security thread, in particular a window security thread or a pendulum security thread, a tear-open thread, a security band, a security strip, a patch or a label for application to security paper, a document of value or the like.

The UV embossing lacquers and thermoplastic lacquers used (also known as thermoplastics) typically have the properties described below, although lacquers with different properties can also be used for special applications.

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 foil. This reaches the embossing tool without roller contact. The film with the embossing lacquer is brought into contact with the embossing tool using an impression roller, whereby the lacquer surface adopts the structure of the embossing tool. In a theoretical arbitrarily slow process, no pressure would be required, the paint would simply flow into the structures, displacing the air. In practice, however, the embossing process on the machine is not arbitrarily slow, so that when embossing with too little impression pressure, the varnish can no longer completely displace the air in the specified time. In practice, therefore, a certain embossing pressure is used when certain requirements are placed on the speed and freedom from bubbles. If UV curing were not to take place, the lacquer would flow again immediately after coming into contact with the embossing tool after the film was pulled off the embossing tool. In practice, however, the film wraps around the embossing tool to a certain extent. If the film with the paint comes into contact with the embossing tool through the impression roller, the film normally no longer spontaneously removes itself from the embossing tool. After the impression roller, in the actually non-pressurized area, UV emitters are arranged, which cross-link the UV coating while it is still in contact with the embossing tool. Only after this reaction is the film removed from the embossing tool. The entire process usually runs continuously. The paint cured in this way is usually a duroplastic.

A thermoplastic embossing usually runs differently than the UV embossing described. A thermoplastic is solid at room temperature and therefore not flowable, at elevated temperature it becomes embossable at a certain temperature. If the temperature is further increased, the lacquer becomes sticky, which limits the meaningful embossing with a standard embossing tool. If necessary, however, non-stick coated tools can be used. In the case of thermoplastic embossing, for example, the embossing die can be heated, embossed at an elevated temperature, and the embossing die can, if necessary, be cooled down again somewhat before demoulding. In a roll-to-roll process, there is usually no cooling before demoulding. In the case of thermoplastic embossing, for example, the film can be heated with contact to the embossing tool, embossed at the highest temperature and immediately removed from the mold without getting into the sticky area of the thermoplastic. Such high heating that the thermoplastic actually becomes liquid is advantageously avoided.

In order to avoid adhesion of a lower-melting thermoplastic, the embossing tool is advantageously provided with a non-stick coating. Alternatively, a metallization of the unembossed embossing lacquer to prevent adhesions can be provided, or care is taken to ensure that the higher-melting thermoplastic only becomes higher-melting at a later point in time. This can be ensured, for example, with the aid of the crosslinkers mentioned elsewhere (for example isocyanates) or also by radiation crosslinking. For example, two thermoplastically embossable UV raw materials can be located next to one another, with one of these two formulations containing a photoinitiator. After the first embossing, exposure can be carried out - in this case, demoulding follows possible because the solid lacquer maintains the embossed structure even without contact with the embossing tool. As a result, the formulation containing the photoinitiator increases in melting point and can no longer be deformed under the previous embossing conditions. Then the second embossing can be done. Either the second "thermoplastic" is left uncrosslinked or it is post-crosslinked by electron beam curing, since the latter process can be carried out without photoinitiators. Alternatively, the second thermoplastic may also contain a photoinitiator that is not addressed at the wavelength(s) of the first emitter.

In addition to the already mentioned and advantageous configurations of the embossing lacquers, it is basically also possible to use embossing lacquers which harden or crosslink thermally instead of photochemically. For example, some embossing lacquers have a softening point T ₁ and a hardening point T ₂ >T ₁ . Such embossing varnishes can, for example, be based on acrylates with isocyanates.

A further procedure consists of selectively heating one of the embossing varnishes. An area with a selectively excitable substance (in the UV/visible/IR or electrically/capacitive/magnetic with an alternating field) selectively only leads to heating of the area containing this substance. In this way, for example, two areas with UV embossing varnish can also be provided and processed one after the other, in particular embossed.

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

Fig. 1

eine schematische Darstellung einer Banknote mit einem optisch variablen Sicherheitselement,

Fig. 2

in schematischer Darstellung ein Sicherheitselement mit einem Trägersubstrat mit einer geprägten Merkmalsschicht,

Fig. 3

in (a) bis (d) vier Zwischenschritte bei der Herstellung eines Sicherheitselements mit einer Merkmalschicht mit zwei thermoplastischen Prägelacken unterschiedlicher Erweichungstemperatur,

Fig. 4

in (a) bis (d) vier Zwischenschritte bei der Herstellung eines Sicherheitselements mit einer Merkmalschicht aus einem thermoplastischer Prägelacke und einem UV-Prägelack,

Fig. 5

in (a) bis (c) Zwischenschritte bei der Herstellung eines Sicherheitselements unter Verwendung eines flexiblen Prägewerkzeugs,

Fig. 6

in (a) bis (c) Zwischenschritte bei der Herstellung eines Sicherheitselements unter Verwendung eines harten Prägewerkzeugs in Verbindung mit einem weichen Prägepresseur,

Fig. 7

in (a) bis (c) Zwischenschritte bei der Herstellung eines Sicherheitselements, in dessen Schichtaufbau eine flexible Ausgleichsschicht vorgesehen ist,

Fig. 8

in (a) bis (d) Zwischenschritte bei der Aufbringung zweier unterschiedlicher Prägelacke in einer Merkmalsschicht ohne Registerschwankungen nebeneinander,

Fig. 9

in (a) bis (c) Zwischenschritte bei einer anderen Variante zur Aufbringung zweier unterschiedlicher Prägelacke in einer Merkmalsschicht ohne Registerschwankungen nebeneinander,

Fig. 10

in (a) bis (c) Zwischenschritte bei einer weiteren Variante zur Aufbringung zweier unterschiedlicher Prägelacke in einer Merkmalsschicht ohne Registerschwankungen nebeneinander,

Fig. 11

in (a) und (b) Zwischenschritte bei der Aufbringung und hochaufgelösten Strukturierung einer UV-Prägelackschicht,

Fig. 12

in (a) und (b) Zwischenschritte bei einer weiteren Möglichkeit, zwei unterschiedliche Prägelacke in einer Merkmalsschicht ohne Registerschwankungen nebeneinander aufzubringen,

Fig. 13

in (a) bis (c) Zwischenschritte bei einem Verfahren zur registrierten Aufbringung zwei unterschiedliche Prägelacke mit Hilfe eines mechanischen Schichtabtrags, und

Fig. 14

in (a) bis (d) Zwischenschritte bei einem Verfahren zur registrierten Aufbringung zwei unterschiedliche Prägelacke mittels Hilfe eines selektiven Abtragsmediums.

Show it:

1

a schematic representation of a banknote with an optically variable security element,

2

a schematic representation of a security element with a carrier substrate with an embossed feature layer,

3

in (a) to (d) four intermediate steps in the production of a security element with a feature layer with two thermoplastic embossing lacquers with different softening temperatures,

4

in (a) to (d) four intermediate steps in the production of a security element with a feature layer made of a thermoplastic embossing lacquer and a UV embossing lacquer,

figure 5

in (a) to (c) intermediate steps in the production of a security element using a flexible embossing tool,

6

in (a) to (c) intermediate steps in the production of a security element using a hard embossing tool in connection with a soft embossing press,

7

in (a) to (c) intermediate steps in the production of a security element in whose layer structure a flexible compensation layer is provided,

8

in (a) to (d) intermediate steps in the application of two different embossing varnishes in a feature layer next to each other without register fluctuations,

9

in (a) to (c) intermediate steps in another variant for applying two different embossing varnishes next to one another in a feature layer without register fluctuations,

10

in (a) to (c) intermediate steps in a further variant for the application of two different embossing varnishes next to one another in a feature layer without register fluctuations,

11

in (a) and (b) intermediate steps in the application and high-resolution structuring of a UV embossing varnish layer,

12

in (a) and (b) intermediate steps in a further possibility of applying two different embossing varnishes next to one another in a feature layer without register fluctuations,

13

in (a) to (c) intermediate steps in a method for the registered application of two different embossing lacquers with the aid of mechanical layer removal, and

14

in (a) to (d) intermediate steps in a method for the registered application of two different embossing lacquers using a selective removal medium.

The invention will now be explained using the example of security elements for banknotes. figure 1 shows a schematic representation of a bank note 10 with an optically variable security element 12 in the form of a glued-on transfer element. It goes without saying, however, that the invention is not limited to transfer elements and banknotes, but can be used with all types of security elements, for example labels on goods and packaging or to protect documents, ID cards, passports, credit cards, health cards and the like. In the case of banknotes and similar documents, in addition to transfer elements (such as patches with or without their own backing layer), security threads or security strips, for example, can also be considered.

Despite its flat design, the security element 12 gives the viewer a three-dimensional impression and shows, for example, at the same time a binary color and effect change when the banknote 10 is tilted, in which a first three-dimensional motif in a first color is visible from a first viewing direction and a second three-dimensional motif is seen from a second viewing direction motif appears in a second colour.

Such and numerous other visual effects can advantageously be produced with security elements in which two or more embossing lacquer layers are arranged next to one another in a registered manner in one plane of the security element and are specifically provided with different, mutually independent embossing structures. In addition to the different embossing, the embossing lacquer layers expediently also have other different properties, namely in particular different visual properties, such as different color, transparency and/or luminescence. In this way, the optically variable effects produced by the embossing on the one hand and the visual effects produced by the additional properties of the embossing lacquer layers on the other hand can be perfectly matched to one another.

For illustration shows 2 a schematic representation of 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 desired shape and size (only one of the feature areas is provided with reference numerals), which differ from each other both by the different glazing coloring of the applied embossing lacquer layers 32, 42, as well as by the different Formation of the respective embossed structures 34, 44 differ.

The embossed structures 34, 44 of the two feature regions 30, 40 lie in a common plane essentially at the same level and are provided with a common reflection-increasing metal coating 26, for example a vapor-deposited aluminum layer. In the exemplary embodiment, the metallized embossed structures are leveled with a lacquer layer 28 and the security element can be glued to the desired target substrate, such as the bank note 10 , via an adhesive layer 29 . After sticking on, the carrier substrate 22 can be pulled off or remain in the security element as a protective film.

The security element 20 is designed to be viewed through the translucent embossing lacquer layers 32, 42. The observer 14 looks in the feature areas 30 through the embossing lacquer layer areas 32 at the metalized embossed structures 34 , while in the feature areas 40 he looks through the embossed lacquer layer areas 42 at the metalized embossed structures 44 . For example, the embossing varnish 32 can be colored red and the embossing structures 34 can produce a curved representation of the value number “10” as a motif, while the embossing varnish 42 is colored green and the embossed structures 44 produce a curved representation of a coat of arms as a motif. The two motifs can also be recognizable from different viewing directions. How out 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 embossing 34, 44 are arranged in register directly next to one another without gaps or overlaps.

The basic principle of an advantageous production of feature layer 24, for example of security element 20, will now be explained in more detail with reference to FIGS. 3 and 4, which each show four intermediate steps in the production of security element 20 in (a) to (d).

First, with reference to 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 lacquer 32 or 42 of the desired color effect. The thermoplastic embossing varnishes 32, 42 are matched to one another in such a way that, in addition to the different colors, they also have different softening temperatures and can therefore be embossed at different temperatures. For example, the thermoplastic embossing lacquer 42 can already be embossed at a lower temperature T ₂ , while the thermoplastic embossing lacquer 32 can only be embossed at a higher temperature T ₁ >T ₂ .

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 in FIG 3(b) illustrated.

The carrier film with the embossed feature layer is then cooled to the lower temperature T ₂ and removed from the mold, thereby solidifying the embossing lacquer 32 in the feature areas 30 with the embossed embossing structure 34 while the embossing lacquer 42 remains deformable. The embossing varnish 42 will therefore flow partially or completely after demoulding and will at best accept the first embossing incompletely, as in 3(c) indicated by reference numeral 34'.

In 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 regions 40 at the lower temperature T ₂ . The embossing structure 34 of the feature regions 30 is already solidified, it is no longer significantly influenced by the second embossing step, in particular due to the measures described in more detail below.

After the second embossing step, the carrier film with the feature layer embossed twice is cooled to a temperature T<T ₂ , for example to room temperature, and the embossing lacquer 42 in the feature areas 40 is thereby also solidified.

In this way, a feature layer 24 with the desired double embossing 34, 44 registered on the feature regions 30, 40 is obtained, as shown in FIG 3(d) shown. Subsequently, the feature layer 24 can be metallized, as in 2 illustrated, or the intermediate of 3(d) can be further processed in a different way to a desired security element.

When designing the 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 configurations described below, in the design of the 4 first the thermoplastic embossing varnish and only then the UV embossing varnish. Even if a UV embossing varnish is typically easier to emboss than a thermoplastic embossing varnish, when using suitable embossing varnishes and/or under suitable conditions, an embossing sequence as in 4 come into use.

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

Then, in a first embossing step, the first embossing structure 34 is embossed with a first embossing tool 50 under embossing conditions in which the thermoplastic embossing lacquer 32 can be embossed, as in FIG Fig.4(b) illustrated. The embossing conditions can include, for example, a temperature T ₁ of 120° C. and high embossing pressure.

The carrier film with the embossed feature layer is then cooled to a lower temperature T ₂ <T ₁ and removed from the mold, and the embossing lacquer 32 in the feature regions 30 is thereby solidified. The lower temperature T ₂ can be T ₂ =30° C., for example. The UV embossing lacquer 42 is not embossed under the embossing conditions of the first embossing step, so that after the first embossing step in the feature areas 30 the embossing lacquer 32 provided with the embossing structure 34 and in the feature areas 40 the unembossed UV embossing varnish 42 is present, as in Fig.4(c) shown.

also in Fig.4(c) The second embossing tool 52 is shown, with which the second embossing structure 44 is embossed into the UV-curable embossing lacquer layer 42 of the feature regions 40 at the lower temperature T ₂ and under UV radiation 54 . The heat input into the thermoplastic layer 32 can be minimized by the hardening of the embossing lacquer layer 42 by means of the radiation of a UV LED. Because of the low temperature during the second embossing step and because of the measures described in more detail below, the already solidified embossing structure 34 of the feature regions 30 is not significantly influenced by the second embossing step.

After the second embossing step and the UV curing, the embossing varnish 42 is also solidified in the feature areas 40, so that as in FIG 3 a feature layer 24 with a desired double embossing 34, 44 registered on the feature areas 30, 40 is obtained, as in FIG Figure 4(d) shown.

In the context of the Figures 3 and 4 In the configurations described, the two embossing lacquer layers 32, 42 are already present on the carrier film in the first embossing step. However, it is also possible to apply the layer to be embossed later only after the embossing of the layer to be embossed first has taken place. Also in this case it is essential that the embossing of the layer embossed first is preserved under the embossing conditions of the layer embossed later. This usually requires special measures that are related to the Figures 5 to 7 will now be explained in more detail.

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.

This is based on the design of the figure 5 illustrated in which the feature layer 24 similar to the example of FIG 4 on the one hand feature areas 30 with a thermoplastic embossing lacquer 32 and on the other hand feature areas 40 with a UV embossing lacquer 42 . The structures 34 and 44 to be impressed in each case have structure dimensions L ₁ and L ₂ of 50 μm to 150 μm in the plane. The structure height is typically in the order of a few micrometers.

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

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

Since the transition areas 64, in which the shape of the embossing tool 60 changes greatly, have dimensions of the order of magnitude λ «L ₁ , L ₂ , the transition areas 64 are therefore significantly smaller than the structural dimensions of the embossings 34, 44, a possibly lower Inadequate or even missing embossing in the transition areas 64 has no significant influence on the quality of the embossed structures 34 in the feature area 30 overall.

After the thermoplastic embossing varnish 32 has cooled and the flexible embossing tool 60 has been removed from the mold, the feature layer 24 is therefore provided with the desired registered double embossing 34, 44 in the feature areas 30, 40, as shown in FIG Fig.5(c) shown.

Another possibility is related to 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.

With this design, the in 6(a) The initial situation shown largely corresponds to the initial situation of the Fig.5(a) , that is, on a suitable carrier film 74, described in more detail below, there is a feature layer 24, in which a thermoplastic embossing varnish 32 is applied in feature areas 30 and a UV embossing varnish 42 is applied in feature areas 40. The UV embossing varnish 42 has already been provided with a desired embossing 44 in a first embossing step. Here, too, the structures 34, 44 to be embossed have structure dimensions L ₁ and L ₂ in the plane, which are between 50 μm and 150 μm.

For the embossing of the embossing structure 34 in the second embossing step in the method of 6 a hard embossing tool 70 is used, which can consist of nickel, for example. The hard embossing tool 70 is particularly well suited for embossing thermoplastic paint 32, but it is less able to compensate for differences in height than the flexible embossing tool 60 of the design figure 5 .

However, in order to ensure that the already embossed and hardened lacquer areas 42 are not deformed or damaged in the second embossing step, use is made of the fact that embossing always requires counter-pressure, which is generally applied by an embossing press 72 . A special feature of the process is the 6 a relatively soft embossing device 72 is used, which consists of an elastomer with a hardness of less than 90 Shore, in particular less than 85 Shore.

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

After cooling and demoulding of the thermoplastic embossing varnish 32, the feature layer 24 is then provided with the desired registered double embossing 34, 44 in the feature areas 30, 40, as shown in FIG 6(c) shown.

As an alternative or as a supplement to the use of a soft embossing impression 72, the impression can also have a structured surface be equipped, which locally limits a deformation of the impression roller. For example, the surface can be divided into independent honeycombs with a characteristic dimension λ _c ≈ 25 μm, so that, for example, with structure dimensions of the embossed structures 34, 44 of L ₁ , L ₂ = 100 μm, it is to be expected that several, in particular 9, honeycomb segments will have their can exert ideal embossing pressure, while the adjacent segments are severely deformed.

Coming back to the advantageous properties of the carrier film 74, it must be easily deformable enough under the embossing conditions of the second embossing step in order to Fig.6(b) illustrated height adjustment by the embossing pressur 72 to allow.

For this purpose, for example, a very thin carrier film 74 can be used, the thickness of which is preferably less than 23 μm, in particular less than 19 μm and particularly preferably between 6 μm and 15 μm. Alternatively or additionally, the carrier film 74 can also be matched to the embossing conditions in that the glass transition temperature _Tg of the carrier film is exceeded under the embossing conditions of the second embossing step and the film is therefore particularly easily deformable.

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 compensation layer 80 in the layer structure of the security element itself.

For explanation shows 7 the layer structure of the security element to be produced, in which a compensation layer 80 is provided between a carrier film 22 and the feature layer 24, which at least in the Embossing conditions of the second embossing is flexible and preferably has elastic properties. If it is provided 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 compensating layer, the compensating layer is preferably transparent and designed with a low scattering effect. Specifically, the compensation layer 80 can be formed from a silicone rubber, for example.

In the Fig.7(a) The initial situation shown largely corresponds to the initial situation of 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.

A hard embossing tool 70 which is particularly well suited for embossing a thermoplastic lacquer 32 can then be used for embossing the embossing structure 34 in the second embossing step. With reference to the presentation of 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 hardened UV embossing lacquer areas 42 are pressed locally into the leveling layer 80 by the hard embossing tool 70 . This prevents the embossing structure 44 from being deformed or damaged and at the same time allows the embossing lacquer layer 32 to be embossed.

In order to allow the UV embossing lacquer areas 42 to be sufficiently pressed in, the layer thickness of the compensating layer 80 should be somewhat greater than the height difference to be compensated for, which is generally between 2 and 15 μm in the case of typical embossed microstructures 44 . The leveling layer 80 can advantageously also deform in such a way that when the UV embossing lacquer areas 42 are pressed in, the thermoplastic embossing lacquer areas 32 are simultaneously pressed somewhat upwards and thereby support the second embossing. Such a deformation can in particular take place while preserving the volume.

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 recovers, so that the feature layer 24 produced is provided with the desired registered double embossing 34, 44 in the feature regions 30, 40, as shown in FIG Fig.7(c) shown.

In the configurations described so far, a situation was assumed in which in the feature areas 30, 40 there are already matched embossing lacquer areas on a carrier film. A number of advantageous options are now described below for applying two or more different embossing varnishes next to one another in a feature layer without register fluctuations and thus ideally without unintentional gaps or overlaps.

First, variants are described in which the phenomenon of surface energy or surface tension is used. Depending on the material of the carrier film used, it may be necessary to first provide it with a coating that has a suitable surface energy. Additional layers, for example a primer layer or a release layer for later detachment, may be required for this purpose. A corona treatment, a plasma treatment or a flame treatment of the film can also be helpful for sufficient adhesion. The following description assumes that that said carrier 90 is or comprises a suitable carrier film and, if appropriate, has been correspondingly pretreated or provided with further layers in order to provide a surface energy suitable for the respective method.

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

The carrier film provided with the UV embossing varnish is then moistened with a dampening solution 92 in-line or in a separate process. Only the hydrophilically coated feature areas 40 accept the dampening solution 92, while the hydrophobic feature areas 30 remain free of dampening solution, as in Fig.8(b) illustrated.

A second embossing lacquer layer of a thermoplastic embossing lacquer 32 is then applied to the carrier film, for which purpose a printing cylinder 94 is used in the exemplary embodiment, on which the embossing lacquer layer 32 is provided over the entire surface, as in FIG Fig.8(b) shown. The surface of the printing cylinder 94 is equipped with a compressible element 96 in order to ensure that the embossing lacquer 32 is only applied in the gaps 30 between the areas 40 that have already been coated.

The compressible element 96 is deformed when the embossing lacquer layer 32 is printed on by the pressure peaks generated by the already cured UV lacquer layer 42, as shown in FIG Fig.8(c) shown, so that the embossing lacquer 32 comes into contact with the carrier 90 in the non-raised feature regions 30 and is transferred there without the embossing structure 44 already present being damaged. Although the UV embossing varnish 42 of the feature areas 40 is also in 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 .

In this way, the thermoplastic embossing varnish 32 is only deposited in the feature areas 30 in the printing step, as shown in FIG Figure 8(d) shown. The already embossed and hardened UV embossing varnish 42 is present in the feature areas 40 . The intermediate product thus obtained can then, for example in connection with the Figures 5 to 7 described, further processed and the embossing lacquer layer 32 can also be provided with the desired embossing. Instead of a thermoplastic embossing varnish, another UV embossing varnish can also be used which, since the first embossing varnish is already solidified when the further embossing varnish is printed on, can also have the same solidifying properties as the first embossing varnish.

In the process variant of 9 a soft impression roller 98 with a shore hardness of less than 90, in particular less than 85, is used instead of a compressible element in the printing cylinder.

In the 9(a) The initial situation shown essentially corresponds to the initial situation in 8 and shows a carrier 90 placed in feature areas 40 was coated with a UV embossing varnish 42 that is hydrophilic after curing. The UV embossing varnish 42 was embossed with the desired embossing structure 44 and cured by UV crosslinking. The carrier film coated in this way was then moistened with a dampening solution 92 in-line or in a separate process, with only the hydrophilically coated feature regions 40 accepting the dampening solution 92, while the uncoated feature regions 30 remain free of dampening solution.

A second embossing lacquer layer of a thermoplastic embossing lacquer 32 is then provided over the entire surface of a printing cylinder 94 . A soft impression roller 98 provides a counter-pressure for the imprinting step, but due to its low hardness of less than 90 or less than 85 Shore it can be locally deformed by pressure peaks. As in Fig.9(b) schematically illustrated, when the embossing lacquer layer 32 is printed on, the already cured UV embossing lacquer areas 42 are pressed slightly by the printing cylinder 94 together with the carrier film 90 into the soft impression roller 98, so that the thermoplastic embossing lacquer 32 in the marking areas 30 comes into contact with the carrier film 90 and transferred there without damaging the already existing embossing structure 44 .

Although the UV embossing varnish areas 42 are also in contact with the embossing varnish layer 32, they are ink-repellent due to the dampening solution 92 applied and therefore do not accept the embossing varnish 32. The overprinting step therefore creates a design with unembossed thermoplastic embossing varnish 32 in the feature areas 30 and with embossed, hardened UV embossing varnish 42 in the 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 is already solidified when the further embossing varnish is printed on is, can also have the same solidification properties as the first embossing lacquer.

In this variant, the carrier film 90 must be sufficiently easily deformable under the printing conditions of the second embossing varnish 32 in order to Fig.9(b) to allow height compensation illustrated by the impression roller 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, in particular thickness between 6 µm and 15 µm) and/or a carrier film 90 with a low glass transition temperature can be used which meets the printing conditions of the second embossing varnish is exceeded, so that the and the film is particularly easily deformed.

Another possibility is to provide a compensation layer 80 in the layer structure of the security element itself. With reference to FIG 10 a compensating layer 80 is arranged in the layer structure of the security element to be produced on the carrier film 22, which is flexible at least under the printing conditions of the embossing lacquer layer 32 and preferably has elastic properties.

In the 10(a) The initial situation shown corresponds to the initial situation, except for the leveling layer 9(a) and shows a carrier film 22 with an applied leveling layer 80, for example made of silicone rubber, which has been coated in feature areas 40 with a UV embossing varnish 42 that is hydrophilic after curing. The leveling layer can also be provided with a thin covering layer in order to facilitate the subsequent application of the embossing lacquer layers 32, 42 and/or to provide a suitable surface energy. The UV embossing varnish 42 was embossed with the desired embossing structure 44 and cured by UV crosslinking.

The carrier film coated in this way was then moistened with a dampening solution 92 in-line or in a separate process, with only the hydrophilically coated feature regions 40 accepting the dampening solution 92, while the uncoated feature regions 30 remain free of dampening solution.

A second embossing lacquer layer of a thermoplastic embossing lacquer 32 is then provided over the entire surface of a printing cylinder 94 . As in 10(b) illustrated, the leveling layer 80 is elastic under the printing conditions of the thermoplastic lacquer 32, so that the already cured UV embossing varnish areas 42 are pressed locally into the leveling layer 80 by the impression cylinder 94. This prevents the embossing structure 44 from being deformed or damaged and enables the embossing lacquer layer 32 to be applied without any problems precisely in the interstices 30 between the UV embossing lacquer regions 42 .

In order to enable the UV embossing lacquer areas 42 to be pressed in sufficiently far, the layer thickness of the compensating layer 80 should be somewhat greater than the height difference to be compensated for, which is typically between 2 and 15 μm.

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

After completion of the imprinting step, the deformation of the elastic compensation layer 80 returns so that the 10(c) desired design shown with unembossed thermoplastic embossing varnish 32 in the feature areas 30 and embossed, cured UV embossing varnish 42 in the feature regions 40 arises, which can be further processed as described above.

If, in the configurations described, a particularly high-resolution structuring of the UV embossing lacquer layer 42 can be achieved, the embossing lacquer layer 42, instead of as in the exemplary embodiments of FIG Figures 8 to 10 printed structured, also be applied in a process of residue-free embossing, as it is basically in the publication EP 3 230 795 B1 is described.

In order to be able to successfully carry out such a high-resolution, residue-free embossing, the surface energies of the carrier, the embossing tool used and the surface tension of the embossing varnish must be coordinated.

Regarding 11(a) a UV embossing varnish 42 is first applied to the carrier 90 over the entire surface in the method mentioned. A structured embossing tool 100 contains tool areas 102, 104 with different height levels, which correspond in shape and size to the feature areas 30 (protruding tool areas 102) and 40 (recessed tool areas 104). The desired embossing structure 44 of the feature areas 40 is arranged in the recessed tool areas 104, which are further away from the layer 42 to be embossed in the subsequent embossing step.

When the structured embossing tool 100 approaches the full-area and not yet cured embossing lacquer layer 42, the protruding areas 102 reduce the layer thickness of the embossing lacquer 42 present there due to their geometry by displacement. More precisely, this is due to the wetting properties of embossing varnish 42 the splitting coefficient, i.e. the interfacial energy between carrier 90 and embossing varnish 42 and between embossing varnish 42 and structured embossing tool 100 is negative, so that embossing varnish 42 withdraws from feature areas 30 below the protruding tool areas 102 into feature areas 40 below the recessed tool areas 104 .

This tendency of wetting and dewetting is not only dependent on the surface energy, but also on the layer thickness. In the feature areas 30, the raised tool areas 102 of the embossing tool 100 thus lead locally to a residue-free dewetting of the embossing lacquer 42 when they approach.

After the embossing lacquer 42 has hardened, the carrier film 90 thus contains the desired high-resolution structure with embossed, hardened UV lacquer areas 42 and still uncoated feature areas 30 lying in between, as in Fig. 11(b) shown. Further processing can then, for example, as in connection with the Figures 8 to 10 already described.

According to another variant of the method, which also uses the phenomenon of surface energy or surface tension, with reference to 12(a) a layer of a first embossing lacquer 32 is first printed on a carrier 90, which has a particularly low surface energy after it has dried or crosslinked. The printed first embossing varnish 32 is embossed and dried or cured. The first embossing lacquer 32 is applied in a structured manner so that feature areas 30 with this first embossing lacquer and still uncoated feature areas 40 without embossing lacquer. It has turned out to be advantageous if approximately half of the total area to be coated is provided with the first embossing lacquer 32 .

A second embossing lacquer formulation 42, which has a low viscosity and a high surface tension, is then applied over the entire surface. This corresponds to the situation of the in Figure 12(a) illustrated intermediate step. The second embossing lacquer formulation 42 can be a UV embossing lacquer, in particular a water-dilutable formulation, which may also have to be dried physically before embossing.

Due to its low viscosity and high surface tension, the second formulation 42 dewets from the first low surface energy stamping varnish 32, as in FIG 12(a) indicated by the arrows 110, so that after dewetting the in Fig. 12(b) situation shown arises. In the case of complete dewetting as in Fig. 12(b) is illustrated, the application of the second embossing lacquer formulation 42 can also be repeated several times, so that material with high surface tension is successively built up in the feature regions 40 until there is a sufficient quantity of second embossing lacquer 42 for the desired second embossing.

In addition to the described utilization of the phenomenon of surface energy and surface tension, there are also advantageous ways based on a layer removal to apply two or more different embossing lacquer layers side by side without register fluctuations, which are now related to the figures 13 and 14 be described in more detail.

Referring first to 13 a first layer of a first thermoplastic embossing varnish 42 with a desired first coloring is applied to a carrier film 22 in a structured manner and dried. The first embossing lacquer 42 is applied in a structured manner in the pattern of the feature regions 40, but with a greater layer thickness d ₁ than the layer thickness d ₀ actually required at the end, as in FIG 13(a) shown.

A second layer of a second thermoplastic embossing varnish 32 with a desired second coloring is then applied over the entire surface. As in 13(b) shown, the second embossing lacquer 32 is advantageously applied in a layer thickness d ₂ >d ₁ , but in principle it is sufficient if the second embossing lacquer is applied in a layer thickness d ₂ >d ₀ . The second embossing lacquer 32 can also be applied in several steps and in each case in connection with wiping or squeegee steps in order to keep the layer thickness of the second embossing lacquer 32 small on the embossing lacquer areas 42 applied first.

After the second embossing varnish 32 has solidified or dried physically, the resulting structure is removed mechanically down to the desired layer thickness d ₀ , for example by milling off 120 the layer regions 122 that protrude beyond the layer thickness d ₀ . If the milling cutter 120 is set to the desired target layer thickness, in the simplest case, be milled up to this target layer thickness, in which both embossing lacquers 32, 42 are exposed in the feature regions 30, 40 arranged exactly next to each other, as in 13(c) shown.

A fine adjustment and feedback of the milling step 120 can be carried out with the aid of the milling removal, ie the material removed from the layer regions 122 . As in 13(b) illustrated, is initially at Milling only removes material of the second embossing varnish 32 that is higher up when the layer is removed 124 ; material of the first embossing varnish 42 is also removed only if the layer is removed to a greater extent. A desired removal depth can therefore be checked by means of a spectroscopic examination or, if appropriate, simply by checking the color of the milling removal. This can ensure that the excess of the second embossing lacquer 32, which is present on the first embossing lacquer areas 42, is completely removed and the in 13(c) end position shown is reliably reached.

In the further design of 14 For example, two different embossing varnishes are used to produce the feature layer 24, one of which is soluble in an ablation medium and the other is insoluble.

Referring first to 14(a) a UV embossing varnish 42 of a first color is applied to a carrier film 22, initially structured in feature regions 40. The UV embossing varnish 42 is typically embossed with the desired embossing structure 44 and cured. The feature areas 30 lying between the embossing lacquer areas 42 ideally remain completely uncoated.

A thermoplastic embossing varnish 32 of a second color is then provided for which a suitable removal medium exists which can remove the dried embossing varnish 32 with a well-defined removal rate, but which does not dissolve the UV embossing varnish 42 .

A second layer is applied to the entire surface of the carrier film 22 with this embossing varnish 32, as shown in 14(b) shown. The application can take place, for example, in flexographic printing, with the flexo sleeve being subjected to high pressure already presses a considerable part of the embossing varnish 32 into the depressions 130 between the already cured UV embossing varnish areas 42 and only relatively little ink comes to lie on the embossing varnish areas 42 .

Immediately after the embossing lacquer 32 has been applied, it is still liquid, so that the excess can be wiped off or scraped off the printed foil and thus in particular removed from the already hardened embossing lacquer areas 42 . After the embossing varnish 32 has been physically dried, the depressions 130 between the already cured UV embossing varnish regions 42 are partially filled, as shown in FIG 14(b) shown. A thin toning film 132 of embossing lacquer material is also generally present on the embossing lacquer areas 42 .

The application of embossing lacquer 32 and the removal of excess material are repeated until the depressions 130 are sufficiently filled or even overfilled, as in FIG 14(c) shown. The repetition improves the relationship between the degree of filling of the depressions 130 and the unwanted toning 132 of the embossing lacquer areas 42. It may be advisable to vary the color concentration of the embossing lacquer 32 during the gradual filling process, in particular towards an increasingly low color concentration, since the Wiping or squeegeeing also reduces the toning of the penultimate application step in each case and thus the proportion of undesired color on the embossing lacquer areas 42 is reduced.

After the last repetition of the application and wiping or squeegeeing, the thermoplastic embossing varnish 32 is physically dried so that the in 14(c) situation shown arises.

A development step with the associated removal medium is then carried out for the embossing varnish 32 . The removal medium can be aqueous, have a defined pH value or be solvent-based. In this case, it may be necessary to expose the embossing lacquer 32 before the removal.

As soon as the embossing lacquer 32 has been sufficiently removed by the removal medium to expose the embossing lacquer areas 42, the removal process is stopped, for example by rinsing with another medium. The hardened UV embossing lacquer 42 is not removed by the removal medium of the embossing lacquer 32, so that the exposure takes place with a high degree of selectivity.

After the removal step has ended, the desired structure is present on the carrier film 22 with feature regions 40 with the embossed UV embossing lacquer layer 42 of the first color and with feature regions 30 with the still unembossed thermoplastic embossing lacquer layer 32 of the second color lying in between, as in FIG 14(d) shown. Further processing can, for example, follow the procedure already described.

Instead of the UV embossing varnish 42, in the procedure of 14 another thermoplastic embossing varnish can also be used. This can be insoluble in the removal medium of the embossing lacquer 32 from the beginning or it can contain a crosslinking agent that makes it insoluble for the removal medium of the embossing lacquer 32, but whose crosslinking reaction has not progressed so far at the time of the first embossing that embossing would be prevented . Such a crosslinker can be an isocyanate, for example, with the use of aliphatic isocyanates leading to a slower reaction leads if the embossing is to take place with a certain time delay after the application step.

The first embossing lacquer layer 42 can be applied by applying a desired motif in a structured manner to the feature regions 40 . In the case of UV embossing varnishes in particular, however, it is also possible to first apply the embossing varnish layer over the entire surface and then to structure it as desired. Advantageous options for this, in particular for high-resolution structuring of a UV embossing lacquer layer, have already been described above. If a thermoplastic embossing varnish is applied as the first layer of embossing varnish, pressure at elevated temperature or from the melt may be required for successful fine structuring if the layer thickness is sufficient.

Before and/or after the embossing of the first embossing lacquer layer 42, a further method step can be provided, with which the embossing lacquer is converted into a permanent and/or embossable form. This can be, for example, an exposure step or an annealing step. A wet-chemical treatment, in which the embossing lacquer is brought into contact with a liquid medium in order to bring about hardening or crosslinking, can also be provided.

Reference List

10

bank note

12

security element

14

viewer

20

security element

22

carrier film

24

feature layer

30

feature areas

32

embossing layer

34

embossing structures

34'

incompletely adopted embossing structures

40

feature areas

42

embossing layer

44

embossing structures

50, 52

embossing tools

60

flexible embossing tool

62

deformation

64

transition areas

70

hard embossing tool

72

soft embosser

74

carrier film

80

leveling layer

90

carrier

92

dampening solution

94

printing cylinder

96

compressible element

98

soft pressur

100

textured embossing tool

102

protruding tool areas

104

reset tool areas

110

dewetting

120

milling machine

130

indentations

132

toning film

Claims (18)

Method for producing a security element for protecting valuables, which contains a feature layer (24) with first and second feature areas (30, 40) in which different first and second embossing lacquer layers are present, with the method - A layer of a first embossing lacquer (42) is applied to a carrier (22) in the first feature regions (40), - A layer of a second, different embossing varnish (32) is applied over the entire surface, so that the second embossing varnish is present in the second feature regions (30) on the carrier (22), and - the feature layer (24) formed by the two embossing lacquer layers is partially removed from its free upper side and the first embossing lacquer areas (42) are thereby exposed, so that in the first feature areas (40) the first embossing lacquer layer and in the second feature areas (30) the second layer of embossing varnish are next to each other with an exact register. Method according to Claim 1, characterized in that the second embossing lacquer is applied in such a way that it is also present in the first feature areas (40) on the areas with the first embossing lacquer (42). Method according to Claim 1 or 2, characterized in that the first embossing lacquer is dried or pre-cured before it is removed, in particular before the second embossing lacquer is applied. The method according to any one of claims 1 to 3, characterized in that - the first embossing varnish (42) is applied and dried or cured in a first layer thickness (d ₁ ), which is greater than the desired target layer thickness (do), - the second embossing varnish (32) is applied over the entire surface in a second layer thickness (d ₂ ) which is greater than the desired target layer thickness (do) and preferably greater than the first layer thickness (d ₁ ), - the second embossing varnish (32) is dried or hardened, and - The feature layer (24) formed by the two embossing lacquer layers is removed mechanically down to the desired target layer thickness (do). Method according to Claim 4, characterized in that the second embossing varnish (32) is applied in several steps and after each application step there is a wiping or doctoring step to reduce the layer thickness of the second embossing varnish (32) on the areas with dried or cured first embossing varnish (42) to be kept low. Method according to Claim 4 or 5, characterized in that the feature layer (24) formed by the two embossing lacquer layers is removed with a milling machine (120) down to the desired target layer thickness (do). Method according to at least one of Claims 4 to 6, characterized in that the two embossing lacquers (32, 42) have different optical properties, that during the mechanical removal of the free upper side of the feature layer (24) material is removed step by step from increasing depth, and that the end point of the mechanical abrasion is determined by an analysis of the optical properties, in particular the color of the ablation material, preferably by checking whether the color of the first embossing varnish (42) also appears in the ablation material in addition to the color of the second embossing varnish (32). The method according to any one of claims 1 to 3, characterized in that - the first and second embossing lacquer (32, 42) are matched to one another, so that the second embossing lacquer (32) is soluble in a removal medium, while the first embossing lacquer (42) is insoluble in the removal medium, at least in the dried or hardened state, - the second embossing varnish (32) is dried after being applied once or several times, and - The second embossing lacquer (32) is removed with the removal medium until the areas with dried or hardened first embossing lacquer (42) are exposed, and the removal process is then stopped. Method according to Claim 8, characterized in that the second embossing lacquer (32) is applied in several steps and after each application step there is a wiping or squeegee step to reduce the layer thickness of the second embossing lacquer (32) on the areas with dried or cured first embossing lacquer (42) to be kept low. Method according to Claim 9, characterized in that the second embossing varnish (32) contains a colorant or color pigments and the concentration of the colorant or color pigments is reduced as the number of application steps increases. The method according to at least one of claims 8 to 10, characterized in that the second embossing lacquer (32) is applied once or several times until the second embossing lacquer (32) in the second feature areas (30) has the depressions (130) between the areas with dried or hardened first embossing varnish (42) fills. Method according to at least one of Claims 1 to 11, characterized in that an embossed structure (44) is embossed into the first embossed lacquer layer, which generates a first optical effect, and an embossed structure (34) is embossed into the second embossed lacquer layer, which has a second, different visual effect. Method according to Claim 12, characterized in that the embossing lacquer layers are each provided with an embossing structure (34, 44) in succession in an earlier and a later embossing step, only one of the two embossing lacquer layers being embossed in the earlier embossing step and only in the later embossing step the other of the two embossing lacquer layers is embossed, preferably by using a flexible embossing tool (60), a soft embossing press (72) or a flexible compensating layer (80) in the layer structure of the security element, in order to transfer the subsequent embossing structure only to the embossing lacquer layer that has not already been embossed . Method according to one of Claims 1 to 13, characterized in that thermoplastic embossing lacquers with different softening temperatures are applied as embossing lacquers (32, 42). The method according to any one of claims 1 to 14, characterized in that as an embossing varnish a radiation-curing, in particular UV-curing Embossing lacquer (42) and, as another embossing lacquer, a thermoplastic embossing lacquer (32) are applied. Method according to at least one of Claims 1 to 15, characterized in that embossing lacquers (32, 42) of different colors, different transparency and/or different luminescence are applied. Method according to at least one of Claims 1 to 16, characterized in that the embossing lacquer layers of the first and second feature regions (30, 40) are arranged next to one another without gaps or overlaps. Method according to at least one of Claims 1 to 17, characterized in that the first and second embossing lacquer layers are provided with a common reflection-increasing coating (26), in particular a high-index or metallic coating.

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