EP4067104B1 - Method of manufacturing an optically variable security element - Google Patents

Description

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

Data carriers, such as valuables or identification documents, but also other valuables, such as branded items, are often provided with security elements for security purposes, which allow the authenticity of the data carrier to be checked and which 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 banknote, a cover film for a banknote 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 arranged at different heights and each provided with a color coating, which are embossed into suitably colored embossing lacquer layers, see WO 2020/011390 A1 , WO 2020/011391 A1 and WO 2020/011392 A1 . However, in order to view the lower-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 optical impression, there can be considerable restrictions on the coloring of the embossing lacquers, in particular the embossing lacquer of the higher-lying embossing lacquer layer.

If several printing inks or embossing varnish layers are applied to a substrate during the production of such security elements, unavoidable register fluctuations in the printing machines prevent the layers from registering precisely in the plane to less than approximately 50 µm. Such registration fluctuations can occur both along and across a printed web.

WO 2016/173898 A1 describes the preamble of claim 1 or a method in which a first lacquer is applied to a support in first areas and a second lacquer is applied over the entire surface, in the first and second areas. The second lacquer is then removed by etching, exposing the first lacquer in the first areas.

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

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

To solve the stated problem, the invention provides a method for producing a security element, which can be used in particular to secure 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 varnish is applied to a carrier in the first feature areas.

A layer of a second, different embossing varnish is then applied over the entire surface, so that the second embossing varnish is present in the second feature areas on the carrier. The feature layer formed by the two embossing lacquer layers is then partially removed from its free top side. This exposes the first embossing lacquer areas, 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 each other in register. In both process variants, the embossing structure which produces a first optical effect is advantageously embossed into the first embossing lacquer layer, and the embossing structure which produces a second, different optical effect is embossed into the second embossing lacquer layer.

In the context of the present description, a precisely registered arrangement of feature areas refers in particular to an arrangement in which the feature areas abut one another 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.

The carrier can remain permanently in the security element or it can represent a production carrier that 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 through radiation, or slower reactions (e.g. in 2K systems) should generally take place after embossing, as they can make embossing more difficult or even impossible.

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

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

In an advantageous procedure, the first embossing lacquer is applied and preferably dried or pre-cured in a first layer thickness d ₁ which is greater than the desired target layer thickness d ₀ . The second embossing lacquer 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 present at least partially, preferably over the entire surface and/or with a layer thickness of at least or exactly d ₂ - d ₁ , 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 step of application there is a wiping or squeegee step in order to keep the layer thickness of the second embossing varnish on the areas with dried or hardened first embossing varnish low.

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, during mechanical removal, material can be gradually removed from the free top side of the feature layer from increasing depths, and the end point of the mechanical removal can be determined by an analysis of the optical properties, in particular the color of the removal material. The end point is preferably determined by checking whether the color of the first embossing varnish also appears in the removal material in addition to the color of the second embossing varnish.

In another, also advantageous procedure, the first and second embossing varnish are coordinated with 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. The second embossing varnish is dried after being applied once or several times 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 process variant, the second embossing varnish is preferably applied in several steps and after each step of application there is a wiping or squeegee step in order to keep the layer thickness of the second embossing varnish on the areas with dried or hardened first embossing varnish low. The second embossing lacquer can in particular contain a colorant or color pigments, 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 layer thickness of the embossing varnish applied as the number of application steps increases.

The second embossing varnish is advantageously applied one or more 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, the embossing structure which produces a first optical effect is advantageously embossed into the first embossing lacquer layer, and the embossing structure which produces a second, different optical effect is embossed into the second embossing lacquer layer. The embossed structures of the first and second embossed lacquer layers are advantageously essentially at the same height, which means in particular that the average heights of the two embossed structures do not differ by more than the height difference 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 compensation layer in the layer structure of the security element in order to create the later embossing structure only to be transferred into the embossing lacquer layer that has not already been embossed.

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

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

Two "thermoplastics" can also be used side by side as embossing varnishes, with a first "thermoplastic" being able to be post-crosslinked by radiation, for example. For example, a removal process is used until both thermoplastics are next to each other and have the same height. Both still have comparable melting points and can be minted at the same time. After the embossing step, the first thermoplastic is crosslinked. This means that 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 embodiments 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 can also be considered.

The embossing varnishes can in particular be applied in different colors, different transparency and/or different luminescence. The embossing varnishes are preferably colored with a glaze 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-refractive index or metallic coating. This coating is preferably carried out after embossing the first and second embossing varnish with a respective embossing structure that produces different first and second optical effects.

The embossed structures of the first and second embossed lacquer layers each advantageously 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, as structural elements, micromirror arrangements with directionally reflecting micromirrors, in particular with non-diffractive mirrors, and preferably with planar mirrors, concave mirrors and/or Fresnel-like mirrors.

It is understood that the optically variable security element can contain further layers, such as protective, covering 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 more 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 thread, a security tape, a security strip, a patch or a label for application to a security paper, document of value or the like.

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.

Typical UV embossing varnish is initially significantly 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 tool without roller contact. The foil with the embossing varnish is brought into contact with the embossing tool using an presser, whereby the varnish surface takes on 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 and displace the air. In practice, however, the embossing process on the machine is not arbitrarily slow, so that when embossing with too little press pressure, the lacquer can no longer completely displace the air in the specified time. If there are certain requirements for speed and freedom from bubbles, a certain embossing pressure is used in practice. If there was no UV curing, the paint would immediately flow again after contact with the embossing tool after the film was removed from the embossing tool. In practice, however, the film has a certain wrap around the embossing tool. If the film with the lacquer comes into contact with the embossing tool through the presser, the film normally no longer spontaneously moves away from the embossing tool. After the impression roller, in the actually pressure-free area, there are UV lamps that crosslink the UV varnish 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 is usually continuous. The paint hardened in this way is usually a thermoset.

Thermoplastic embossing usually works differently than the UV embossing described. A thermoplastic is solid at room temperature and therefore not flowable; at elevated temperatures it becomes embossable at a certain temperature. If the temperature is further increased, the lacquer becomes sticky, which limits the useful embossability with a standard embossing tool. However, if necessary, non-stick coated tools can be used. When embossing thermoplastics, for example, the embossing die can be heated, embossed at an elevated temperature and the embossing die can, if necessary, be cooled down slightly before demolding. In a roll-to-roll process, there is usually no cooling before demoulding. When embossing thermoplastics, for example, the film can be heated up 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. Heating to such a degree 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 varnish can be provided to avoid adhesion, or it can be ensured that the higher-melting thermoplastic only becomes higher-melting at a later point in time. This can be ensured, for example, using the crosslinkers mentioned elsewhere (e.g. isocyanates) or through radiation crosslinking. For example, two thermoplastically embossable UV raw materials can be placed next to each other, with one of these two formulations containing a photoinitiator. After the first embossing, exposure can take place - in this case there is a demoulding afterwards possible because the solid varnish maintains the embossed structure even without contact with the embossing tool. The formulation containing the photoinitiator thereby rises in melting point and is no longer deformable under the previous embossing conditions. Then the second embossing can be made. Either the second "thermoplastic" is left uncrosslinked or it is crosslinked using electron beam curing, since 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.

In addition to the already mentioned and advantageous embodiments of embossing varnishes, it is also fundamentally possible to use embossing varnishes that harden or crosslink thermally instead of photochemically. For example, some embossing varnishes have a softening temperature T ₁ and a curing temperature T ₂ > T ₁ . Such embossing varnishes can be formed, for example, based on acrylates with isocyanates.

Another procedure involves selective heating of one of the embossing varnishes. An area with a selectively excitable substance (in the UV/visible/IR or electrical/capacitive/magnetic with 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 be provided and processed, in particular embossed, one after the other.

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

Fig. 1

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

Fig. 2

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

Fig. 3

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

Fig. 4

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

Fig. 6

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

Fig. 7

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

Fig. 8

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

Fig. 9

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

Fig. 10

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

Fig. 11

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

Fig. 12

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

Fig. 13

in (a) to (c) intermediate steps in a process for the registered application of two different embossing varnishes using mechanical layer removal, and

Fig. 14

in (a) to (d) intermediate steps in a process for the registered application of two different embossing varnishes 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 banknote 10 with an optically variable security element 12 in the form of a glued-on transfer element. However, it is understood that the invention is not limited to transfer elements and banknotes, but can be used for all types of security elements, for example labels on goods and packaging or for securing documents, ID cards, passports, credit cards, health cards and the like. For banknotes and similar documents, in addition to transfer elements (such as patches with or without their own carrier 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, for example, at the same time shows a binary color and effect change 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 from a second viewing direction Motif appears in a second color.

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

Shows for illustration Fig. 2 in a 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 the desired shape and size (only one of the feature areas is provided with a reference number), which differ from each other both through the different translucent coloring of the applied embossing lacquer layers 32, 42 and through the different The formation of the respective embossed structures 34, 44 differ.

The embossed structures 34, 44 of the two feature areas 30, 40 lie in a common plane at essentially the same height 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 banknote 10, via an adhesive layer 29. After gluing, the carrier substrate 22 can be removed 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 viewer 14 looks at the metallized embossed structures 34 in the feature areas 30 through the embossed lacquer layer areas 32, while in the feature areas 40 he looks through the embossed lacquer layer areas 42 at the metallized embossed structures 44. For example, the embossing varnish 32 can be colored glazing red and the embossing structures 34 can produce a curved representation of the value number "10" as a motif, while the embossing varnish 42 can be colored glazing green is and the embossed structures 44 produce a curved representation of a coat of arms as a motif. The two motifs can also be seen from different viewing directions. How out Fig. 2 As can be seen, the feature areas 30, 40 with their different color effects generated by the embossing lacquer layers 32, 42 and their different motifs generated by the embossings 34, 44 are arranged directly next to one another, registered in register, without gaps or overlaps.

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

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 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 varnish 42 can already be embossed at a lower temperature T ₂ , while the thermoplastic embossing varnish 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 varnishes 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, and thereby the embossing varnish 32 in the feature areas 30 with the embossed embossed structure 34 is solidified, while the embossing varnish 42 still remains deformable. The embossing varnish 42 will therefore partially or completely flow after demoulding and will at best accept the first embossing incompletely, as in Fig. 3(c) indicated by the reference number 34 '.

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 embossed structure 34 of the feature areas 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 double-embossed feature layer is cooled to a temperature T <T ₂ , for example to room temperature, and the embossing lacquer 42 is thereby also solidified in the feature areas 40.

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

When designing 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 configurations described below, the design of the Fig. 4 first embossed with the thermoplastic embossing varnish and only then with 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 Fig. 4 are used.

Regarding 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.

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 varnish 32 can be embossed, as in 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, thereby solidifying the embossing lacquer 32 in the feature areas 30. The lower temperature T ₂ can be, for example, T ₂ = 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 in the feature areas 30 the embossing varnish 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) shown is the second embossing tool 52, with which the second embossing structure 44 is embossed into the UV-curable embossing lacquer layer 42 of the feature areas 40 at the lower temperature T ₂ and under UV radiation 54. 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. Because of the low temperature in the second embossing step and due to the measures described in more detail below, the already solidified embossed structure 34 of the feature areas 30 is not significantly influenced by the second embossing step.

After the second embossing step and UV curing, the embossing varnish 42 has 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. 4(d) shown.

In connection with the Figures 3 and 4 In the designs described, both 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 layer to be embossed first has been embossed. In this case too, it is essential that the embossing of the first embossed layer is retained under the embossing conditions of the later embossed layer. This usually requires special measures 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 Fig. 5 illustrated, in which the feature layer 24 is similar to the example of Fig. 4 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 impressed in each case have structural dimensions L ₁ and L ₂ of 50 μm to 150 μm in the plane. The structure height is typically on the order of a few micrometers.

In the variant of Fig. 5 First, the UV embossing varnish 42 is provided with the desired second embossing structure 44 and then hardened, as in Fig. 5(a) shown. The thermoplastic embossing varnish 32 can also be embossed or it can, as in Fig. 5(a) , remaining without an imprinted structure due to flow.

Now the first embossing structure 34 is 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, for example, of silicone rubber and is deformed by pressure peaks on a length scale λ of a few micrometers. The feature areas 40 with the already hardened 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 hardened embossing varnish areas 42 are not damaged, but on the other hand embossing varnish 32 in the feature areas 30 are 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 significantly, have a dimension of the order of magnitude λ «Li, L ₂ , i.e. the transition areas 64 are significantly smaller than the structural dimensions of the embossings 34, 44, a possibly smaller, defective one or even a lack of embossing in the transition areas 64 has no significant influence on the quality of the embossed structures 34 in the feature area 30 as a whole.

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 in Fig. 5(c) shown.

Another possibility is with reference to Fig. 6 in the use of a hard embossing tool 70 in conjunction with a soft embossing presser 72 and a suitable carrier film 74 in the security element.

With this design, the in Fig. 6(a) The initial situation presented largely corresponds to the initial situation 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 was already provided with a desired embossing 44 in a first embossing step. Here too, the structures 34, 44 to be impressed have structural 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, the method uses the 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 paint 32, but it is less able to compensate for height differences than the flexible embossing tool 60 for the design Fig. 5 .

In order to ensure that the already embossed and hardened lacquer areas 42 are not deformed or damaged in the second embossing step, it is used that counter pressure is always required for embossing, which is usually applied by an embossing presser 72. A special feature of the process is the Fig. 6 a relatively soft embossing presser 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) Illustrated schematically, 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 emboss the thermoplastic embossing varnish 32 without damaging or destroying the UV embossing varnish areas 42 to be able to.

After the thermoplastic embossing varnish 32 has cooled and removed from the mold, the feature layer 24 is then provided with the desired registered double embossing 34, 44 in the feature areas 30, 40, as in Fig. 6(c) shown.

As an alternative or as a supplement to using a soft embossing presser 72, the presser can also have a structured surface be equipped 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 embossed structures 34, 44 of L ₁ , L ₂ = 100 μm, it can be expected that there will be several, in particular 9, honeycomb segments can exert ideal embossing pressure, while the adjacent segments are severely deformed.

Returning to the advantageous properties of the carrier film 74, it must be sufficiently easy to deform under the embossing conditions of the second embossing step in order to achieve the in Fig. 6(b) to allow illustrated height compensation by the embossing presser 72.

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 tailored to the embossing conditions in that the glass transition temperature T _g of the carrier film is exceeded under the embossing conditions of the second embossing step and the film therefore becomes particularly easy to deform.

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

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

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

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 lacquer 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 compensating layer 80 is elastic, so that the already hardened UV embossing lacquer areas 42 are locally pressed into the compensating layer 80 by the hard embossing tool 70. This prevents deformation or damage to the embossed structure 44 and at the same time enables embossing of the embossing lacquer layer 32.

In order to allow sufficient indentation of the UV embossing lacquer areas 42, the layer thickness of the compensating layer 80 should be slightly larger than the height difference to be compensated, which is usually between 2 and 15 μm for typical embossed microstructures 44. The equalizing layer 80 can also advantageously 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 slightly upwards and thereby support the second embossing. Such a deformation can in particular take place while preserving volume.

After completion of the second embossing step and the cooling and demoulding of the thermoplastic embossing varnish 32, the deformation of the elastic compensating layer 80 returns, so that the feature layer 24 produced is provided with the desired registered double embossing 34, 44 in the feature areas 30, 40, as in Fig. 7(c) shown.

The designs described so far were based on a situation in which there are already registered embossing lacquer areas on a carrier film in the feature areas 30, 40. Some advantageous options are now described below for applying two or more different embossing varnishes next to each other in a feature layer without register fluctuations and therefore ideally without unintentional gaps or overlaps.

Variants are first described in which the phenomenon of surface energy or surface tension is exploited. 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. For this purpose, additional layers, for example a primer layer or a release layer, may be required for later detachment. Corona treatment, plasma treatment or 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 has optionally been pretreated accordingly or provided with further layers in order to provide a surface energy suitable for the respective method.

At the in Fig. 8 In the illustrated method variant, a carrier 90 is first printed in the feature areas 40 using any method with an embossable, hydrophilic formulation 42 after drying, which 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 in the feature areas 40 was embossed with the associated embossing structure 44 and finally hardened by UV crosslinking, as in Fig. 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 inline or in a separate process with a dampening solution 92. Only the hydrophilically coated feature areas 40 accept the dampening solution 92, while the hydrophobic feature areas 30 remain dampening agent-free, 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. 8(b) shown. In order to ensure that the embossing varnish 32 is only applied in the spaces 30 between the already coated areas 40, the surface of the printing cylinder 94 is equipped with a compressible element 96.

The compressible element 96 deforms when the embossing lacquer layer 32 is printed on by the pressure peaks generated by the already cured UV lacquer layer 42, as in Fig. 8(c) shown, so that the embossing varnish 32 comes into contact with the carrier 90 in the non-raised feature areas 30 and is transferred there without the already existing embossing structure 44 being damaged. The UV embossing varnish 42 of the feature areas 40 is also in contact with the embossing varnish layer 32 during printing, but it is color-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 in Fig. 8(d) shown. The already embossed and hardened UV embossing varnish 42 is present in the feature areas 40. The intermediate product obtained in this way can then, for example in connection with 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 solidification properties as the first embossing varnish.

In the process variant of Fig. 9 Instead of a compressible element in the printing cylinder, a soft presser 98 with a Shore hardness of less than 90, in particular less than 85, is used.

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

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 presser 98 provides counter pressure for the printing 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) Illustrated schematically, when the embossing lacquer layer 32 is printed, the already hardened UV embossing lacquer areas 42 are pressed slightly into the soft impression roller 98 by the printing cylinder 94 together with the carrier film 90, so that the thermoplastic embossing lacquer 32 comes into contact with the carrier film 90 in the marking areas 30 and is transferred there without damaging the already existing embossed structure 44.

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 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, as the first embossing varnish, already solidifies when the further embossing varnish is printed on is, can also have the same solidification properties as the first embossing varnish.

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 achieve the in Fig. 9(b) to allow 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, 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 corresponds to the printing conditions of the second embossing varnish is exceeded, so that such and such foil becomes particularly easy to deform.

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 Fig. 10(a) The initial situation shown corresponds to the initial situation except for the compensation layer Fig. 9(a) and shows a carrier film 22 with an applied compensation 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 compensation layer can also be provided with a thin cover layer in order to facilitate the subsequent application of the embossing lacquer layers 32, 42 and/or to provide suitable surface energy. The UV embossing varnish 42 was embossed with the desired embossing structure 44 and hardened by UV crosslinking.

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

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 Fig. 10(b) illustrated, the compensation 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 compensation layer 80 by the printing cylinder 94. This prevents deformation or damage to the embossing structure 44 and enables problem-free application of the embossing lacquer layer 32 precisely into the spaces 30 between the UV embossing lacquer areas 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 slightly larger 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 color-repellent due to the applied dampening solution 92 and therefore do not accept the embossing varnish 32.

After completion of the printing step, the deformation of the elastic compensation layer 80 returns, so that the in Fig. 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 areas 40 arises, which can be further processed as described above.

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

In order to be able to successfully carry out such 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 Fig. 11(a) In the method mentioned, a UV embossing varnish 42 is first applied to the entire surface of the carrier 90. 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), respectively. 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-surface and not yet hardened embossing varnish layer 42, the protruding areas 102 reduce the layer thickness of the embossing varnish 42 present there due to their geometry by displacement. It becomes more precise due to the wetting properties of the embossing varnish 42, the splitting coefficient, i.e. the interface energy between carrier 90 and embossing varnish 42 and between embossing varnish 42 and structured embossing tool 100, is negative, so that the embossing varnish 42 retreats from the feature areas 30 below the protruding tool areas 102 into the 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 dependent on the layer thickness. In the feature areas 30, the raised tool areas 102 of the embossing tool 100 lead to a local residue-free dewetting of the embossing varnish 42 when approached. The embossing varnish 42 collecting in the feature areas 40 is embossed there by the embossing structure 44 arranged in the recessed tool areas 104.

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

According to a further method variant, which also uses the phenomenon of surface energy or surface tension, reference is made to Fig. 12(a) a layer of a first embossing varnish 32 is first printed onto 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 hardened. The application of the first embossing varnish 32 is carried out in a structured manner, so that feature areas 30 with this first embossing varnish and still uncoated feature areas 40 are present without embossing varnish. It has proven 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 in Fig. 12 (a) intermediate step shown. The second embossing varnish formulation 42 can be a UV embossing varnish, in particular a water-thinnable formulation, which may have to be physically dried before embossing.

Due to its low viscosity and high surface tension, the second formulation 42 dewets from the first low surface energy embossing lacquer 32, as in Fig. 12(a) indicated by the arrows 110, so that after dewetting the in Fig. 12(b) situation presented arises. In the case of complete dewetting as in Fig. 12(b) is 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 there is a sufficient amount of second embossing varnish 42 for the desired second embossing.

In addition to the described exploitation of the phenomenon of surface energy and surface tension, there are also advantageous options based on layer removal to apply two or more different embossing lacquer layers next to each other without register fluctuations, which are now in connection with Figures 13 and 14 be described in more detail.

With reference first to Fig. 13 A first layer of a first thermoplastic embossing varnish 42 with a desired first color is applied to a carrier film 22 in a structured manner and dried. The application of the first embossing varnish 42 is carried out in a structured manner in the pattern of the feature areas 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 color is then applied over the entire surface. As in Fig. 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 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 on the first applied embossing varnish areas 42 low.

After solidification or physical drying of the second embossing varnish 32, the resulting structure is removed mechanically down to the desired layer thickness d ₀ , for example by milling 120 of 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, can In the simplest case, milled up to this target layer thickness, in which both embossing varnishes 32, 42 are exposed in the feature areas 30, 40 arranged exactly next to each other, as in Fig. 13(c) shown.

A fine adjustment and feedback of the milling step 120 can be carried out with the help of the milling removal, i.e. the material removed from the layer areas 122. As in Fig. 13(b) illustrated, is initially shown at When milling only removes a small amount of layer 124, only material from the higher second embossing varnish 32 is removed; only when larger layers are removed is material from the first embossing varnish 42 also removed. A desired removal depth can therefore be checked by a spectroscopic examination or, if necessary, simply by checking the color of the milling material. This can ensure that the excess of the second embossing varnish 32, which is present on the first embossing varnish areas 42, is completely removed and the in Fig. 13(c) End position shown is reliably reached.

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

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

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

With this embossing varnish 32, a second layer is applied to the entire surface of the carrier film 22, as in Fig. 14(b) shown. The application can be done, for example, using flexographic printing, with the Flexosleeve at high pressure a significant part of the embossing varnish 32 is already pressed into the depressions 130 between the already hardened UV embossing varnish areas 42 and only relatively little ink comes to rest on the embossing varnish areas 42.

Immediately after applying the embossing varnish 32, it is still liquid, so that the excess can be wiped or doctored off from the printed film and can therefore be removed in particular from the already hardened embossing varnish areas 42. After physical drying of the embossing varnish 32, the depressions 130 between the already hardened UV embossing varnish areas 42 are partially filled, as in Fig. 14(b) shown. There is also generally a thin toning film 132 made of embossing lacquer material on the embossing lacquer areas 42.

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

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

A development step is then carried out for the embossing lacquer 32 with the associated 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 varnish 32 before removal.

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

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

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

The application of the first embossing lacquer layer 42 can be carried out in a structured manner by applying a desired motif 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 options for this, in particular for high-resolution structuring of a UV embossing lacquer layer, have already been described above. If a thermoplastic embossing lacquer is applied as the first embossing lacquer layer, printing at elevated temperature or from the melt may be necessary for successful fine structuring with sufficient layer thickness.

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

Reference symbol list

10

Banknote

12

Security element

14

viewer

20

Security element

22

Carrier film

24

Feature layer

30

Feature areas

32

embossed lacquer layer

34

Embossed structures

34'

incompletely assumed embossed structures

40

Feature areas

42

embossed lacquer layer

44

Embossed structures

50, 52

Embossing tools

60

flexible embossing tool

62

deformation

64

Transition areas

70

hard embossing tool

72

soft embossing presser

74

Carrier film

80

Compensating layer

90

carrier

92

Fountain solution

94

printing cylinder

96

compressible element

98

soft pressurizer

100

structured embossing tool

102

above tool areas

104

reset tool areas

110

Dewetting

120

milling machine

130

depressions

132

Toning film

Claims (17)

1. Method for producing a security element for securing valuable objects, which contains a feature layer (24) having first and second feature regions (30, 40) in which different first or second embossing varnish layers are present, in the method

   - a layer of a first embossing varnish (42) being applied to a carrier (22) in the first feature regions (40),

   - a layer of a second, different embossing varnish (32) being applied over the entire surface, such that the second embossing varnish is present on the carrier (22) in the second feature regions (30), and

   - the feature layer (24) formed by the two embossing varnish layers being partially removed from its free upper face and the first embossing varnish regions, that is to say the first embossing varnish (42) in the first feature regions (40), are thus exposed such that the first embossing varnish layer in the first feature regions (40) and the second embossing varnish layer in the second feature regions (30) lie next to one another in perfect register, characterized in that

   - an embossing structure (44) which generates a first optical effect is embossed into the first embossing varnish layer, and an embossing structure (34) which generates a second, different optical effect is embossed into the second embossing varnish layer.
2. Method according to claim 1, characterized in that the second embossing varnish is applied such that it is also present in the first feature regions (40) on the regions having the first embossing varnish (42).
3. Method according to either claim 1 or claim 2, characterized in that the first embossing varnish is dried or pre-hardened before the second embossing varnish is removed, in particular before it is applied.
4. Method according to any of claims 1 to 3, characterized in that

   - the first embossing varnish (42) is applied and dried or hardened in a first layer thickness (d₁) which is greater than the desired target layer thickness (d₀),

   - the second embossing varnish (32) is applied over the entire surface in a second layer thickness (d₂) which is greater than the desired target layer thickness (d₀) and preferably greater than the first layer thickness (d₁),

   - the second embossing varnish (32) is dried or hardened, and

   - the feature layer (24) formed by the two embossing varnish layers is mechanically removed up to the desired target layer thickness (d₀).
5. Method according to claim 4, characterized in that the second embossing varnish (32) is applied in a plurality of steps and, after each application step, a wiping or scraping step is carried out in order to keep the layer thickness of the second embossing varnish (32) small in the regions having the dried or hardened first embossing varnish (42).
6. Method according to either claim 4 or claim 5, characterized in that the feature layer (24) formed by the two embossing varnish layers is removed to the desired target layer thickness (d₀) using a milling machine (120).
7. Method according to at least one of claims 4 to 6, characterized in that the two embossing varnishes (32, 42) have different optical properties, in that, during the mechanical removing of the free upper face of the feature layer (24), material from increasing depths is gradually removed, and in that the end point of the mechanical removing is determined by an analysis of the optical properties, in particular the color of the removed material is preferably determined by checking whether, in addition to the color of the second embossing varnish (32), the color of the first embossing varnish (42) also appears in the removed material.
8. Method according to any of claims 1 to 3, characterized in that

   - the first and second embossing varnishes (32, 42) are matched to one another such that the second embossing varnish (32) is soluble in a removal medium, while the first embossing varnish (42) is insoluble in the removal medium, at least in the dried or hardened state,

   - the second embossing varnish (32) is dried after a single application or multiple applications, and

   - the second embossing varnish (32) is removed using the removal medium until the regions having the dried or hardened first embossing varnish (42) are exposed, and the removal process is then stopped.
9. Method according to claim 8, characterized in that the second embossing varnish (32) is applied in a plurality of steps and, after each application step, a wiping or scraping step is carried out in order to keep the layer thickness of the second embossing varnish (32) small on the regions having the dried or hardened first embossing varnish (42).
10. 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 of the color pigments is reduced with an increasing number of application steps.
11. Method according to at least one of claims 8 to 10, characterized in that the second embossing varnish (32) is applied once or multiple times until the second embossing varnish (32) in the second feature regions (30) fills the recesses (130) between the regions having the dried or hardened first embossing vanish (42).
12. Method according to claim 1, characterized in that the embossing varnish layers are each provided in succession with an embossing structure (34, 44) in an earlier and a later embossing step, only one of the two embossing varnish layers being embossed in the earlier embossing step, and only the other of the two embossing varnish layers being embossed in the later embossing step, preferably by using a flexible embossing tool (60), a soft embossing roller (72) or a flexible leveling layer (80) in the layer structure of the security element in order to transfer the later embossing structure only into the embossing varnish layer that is not already embossed.
13. Method according to any of claims 1 to 12, characterized in that thermoplastic embossing varnishes having different softening temperatures are applied as embossing varnish (32, 42).
14. Method according to any of claims 1 to 13, characterized in that a radiation-curing, in particular UV-curing embossing varnish (42) is applied as an embossing varnish and a thermoplastic embossing varnish (32) is applied as a further embossing varnish.
15. Method according to at least one of claims 1 to 14, characterized in that embossing varnishes (32, 42) of different colors, different transparency and/or different luminescence are applied.
16. Method according to at least one of claims 1 to 15, characterized in that the embossing varnish layers of the first and second feature regions (30, 40) are arranged next to each other without gaps and overlaps.
17. Method according to at least one of claims 1 to 16, characterized in that the first and second embossing varnish layers are provided with a common reflection-increasing coating (26), in particular a high-refractive or metal coating.

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