EP2860041B1 - Multi-layer body and method for producing a multi-layer body - Google Patents

Description

The invention relates to a method for producing a multilayer body having at least one partially formed layer of a material with a high refractive index, and a multi-layer body obtainable thereafter. The invention further relates, in particular, to a security element for security and value documents with such a multilayer body.

Optical security elements are often used to complicate and prevent the copying and misuse of documents or products. Thus, optical security elements are often used for securing documents, banknotes, credit cards, cash cards, ID cards, packaging and the like. It is known to use optically variable elements which can not be duplicated by conventional copying methods. It is also known, security elements with layers of high refractive index materials (HRI = High Refractive Index = high Refractive index), such as ZnS, to provide special optical structures. While full-surface reflection layers of HRI materials can be produced relatively easily by common application methods, such as, for example, sputtering, vapor deposition or the like, structured, partial HRI layers are considerably more complicated to produce.

HRI layers can serve as reflective layers, as they coexist with adjacent resist layers, which typically have average indices of refraction, e.g. B. 1.5, form an optical boundary layer. This optical boundary layer makes structures visible at this boundary layer, although the structures are embedded between both layers.

The more manufacturing steps are provided for the production of the security element, the greater importance receives the registration accuracy of the individual process steps or the accuracy of the positioning of the individual tools in the formation of the security element with respect to the security element already existing features or structures.

The term "registration accuracy" or "register accuracy" comes from the printing technology. There register marks or register marks are applied, which are applied to different layers or layers. On the basis of these registration marks or register marks, it is very easy to adjust the exact relative positional accuracy of the layers or layers to each other and thus to achieve a so-called register accuracy or register accuracy. "In the register" thus means that the respective layers or layers are aligned with the registration marks or registration marks with sufficient accuracy to one another. In the following, these terms are used in this sense. Ie. it works Therefore, to align superimposed layers as accurately as possible relative to each other and to arrange them "in the register".

From the WO 95/27925 a method is known in which a metal or titanium dioxide layer is partially provided with a protective lacquer and patterned by etching.

The DE 103 33 255 B3 describes another method in which a metal or HRI layer is chemically structured by the action of acids or alkalis.

From the US 2012/0064303 A1 It is also known to chemically etch reflective layers of metal or HRI materials by acid or alkali.

From the DE 10 2006 037 431 A1 For example, a method for producing a multilayer body is known in which a functional layer is structured in register with a replication layer by chemical etching or by the use of a washcoat.

It is an object of the present invention to provide a method for producing a multilayer body, which is particularly simple and process reliable to perform. Furthermore, it is an object of the present invention to provide a multilayer body which is obtainable by means of such a method.

This object is achieved by a method for producing a multilayer body, in which a layer of a material having a high refractive index is applied at least partially to a substrate and then at least a portion of the layer is physically removed from the substrate by treatment with an alkali.

The layer of the material with a high refractive index is also referred to below as the HRI layer (high refractive index = high refractive index).

It has been found that such a lye treatment triggers a detachment of the layer in the partial area to be removed as a whole. In other words, the layer of high refractive index material does not chemically dissolve in the liquor, but physically breaks away from the substrate. It is therefore not an etching process. In contrast to, for example, the dissolution of zinc sulfide by hydrochloric acid, this produces no toxic by-products, such as in the above example hydrogen sulfide. Also, no toxic heavy metal solutions remain. The process can therefore be carried out particularly safely, does not require special protective measures and is also environmentally friendly. Compared with known physical methods for partial removal of layers, such as laser ablation, is also the expenditure on equipment significantly lower and the achievable process speed significantly higher.

This object is further achieved by a method for producing a multilayered body in which at least a first relief structure is molded into a first surface of the substrate in at least a first region of the substrate, followed by at least one layer or layer of high refractive index material such that the layer at least partially covers the at least one first region and at least one second region of the substrate, in which the first relief structure is not molded into the first surface of the substrate, and then a Part of the layer is physically removed again by treatment with a liquid from the substrate in such a way that the first layer is removed in the partial area covering the at least one second area and in the subregion covering the at least one first area on the S substrate remains.

It has been found that in the area of relief structures, the adhesion of the HRI layer to the substrate is significantly greater than on smooth surfaces. This can be used for a partial removal of the HRI layer. For this, conditions are created under which the interlayer adhesion of the HRI layer and the surface in the smooth second region is just not sufficient to hold the HRI layer to the surface, while the larger interlayer adhesion in the first region continues to adhere to the HRI layer the surface binds. This variant of the method can be carried out under particularly mild conditions, in particular low alkali concentrations, so that it is also suitable for sensitive material combinations. Optionally, the use of water as a liquid may be sufficient.

Another advantage of this process variant is that the remaining HRI layer remains in register with the relief structures formed in the surface. It is therefore also possible to create very filigree structures and patterns whose optical effect arises from the interaction of the HRI layer with the appropriately precisely arranged relief structure.

This object is further achieved by a multilayer body having a substrate and a layer of a material having a high refractive index, wherein at least a first relief structure is molded into a first surface of the substrate in at least a first region of one or the substrate, the layer partially over the first Surface of the substrate is applied, such that the first layer is removed in the at least a second region overlapping portion and in which the at least one first region overlapping portion is provided on the substrate.

Such a multi-layer body can be obtained by means of the methods explained above and is distinguished by particularly good registration between the first relief structure and the HRI layer.

This object is further solved by a multi-layer body having at least one partially formed layer of a material with a high refractive index in register with at least one further partially formed functional layer. Such a multi-layer body is also obtainable by means of the method variants described above and is particularly tamper-proof due to the registration between the HRI layer and the partially formed functional layer.

It is advantageous if the high refractive index material is selected from the group of zinc sulfide, titanium dioxide, niobium pentoxide.

It is also advantageous if the liquor is selected from the group of sodium hydroxide, potassium hydroxide, sodium bicarbonate, tetramethylammonium hydroxide, sodium ethylenediaminetetraacetate.

Preferably, a pH of the liquor is at least 10, since at lower pH values no reliable detachment of the HRI layer from the substrate can be guaranteed. Preferably, the pH of the liquor is in the range of 10.5 to 14, more preferably 11 to 13.

The pH value and information on the conductivity are temperature-dependent. The above values and all subsequent pH values and information on the conductivity refer to room temperature of approx. 18 ° C to 22 ° C.

Preferably, the treatment is carried out with the liquor at a temperature of 10 ° C to 80 ° C.

Typically, the reaction rate increases with the concentration of the liquor and the temperature. The choice of process parameters depends on the reproducibility of the process and the durability of the multilayer body. Factors influencing the treatment with lye are typically the composition of the lye bath, in particular the concentration of lye, the temperature of the lye bath and the inflow conditions of the HRI layer to be treated in the lye bath.

The treatment with the liquor may further have a temporal temperature profile to optimize the result. So can be treated at the beginning of cold and warmer with increasing exposure time. In the alkaline bath, this is preferably realized by a spatial temperature gradient, wherein the multi-layer body is pulled through an elongated alkaline bath with different temperature zones.

Preferably, during and / or after the treatment with the liquor, a mechanical treatment of the layer to aid in the release of the layer takes place.

The physical detachment of the HRI layer from the substrate is based on the penetration of the liquor into fine pores of the HRI layer, where optionally also hydroxo complexes of the HRI material can form. As a result, mechanical stresses in the HRI layer are built up, which eventually leads to the popping of the layer in the form of fine flakes. By an additional mechanical treatment, therefore, the spalling is promoted and carried out in a controlled manner.

Preferably, the mechanical treatment comprises brushing and / or wiping with a sponge and / or wiping roller and / or ultrasonic treatment and / or streaming or spraying the layer with a liquid.

In a further preferred embodiment, a mask layer is applied to the layer before the treatment with the alkali to protect at least one portion of the layer which is not to be removed. The mask layer is preferably made of a material which is not reactive with the alkali. By the mask layer so the contact between the liquor and the HRI layer prevented, so that in the covered by the mask layer portion of the HRI layer can not detach from the substrate during the lye treatment. This allows the desired patterns and structures to be created in the HRI layer. Depending on the application method used, structure resolutions of 0.05 to 0.2 mm can be achieved. This size denotes, for example, the minimum width of a line or a grid point, which can still be realized cleanly. The patterning of a pressure roller used to apply the mask layer can be significantly finer. If necessary, the mask layer can also be printed finer. The structure resolution takes into account the entire process up to and including the structuring of the HRI layer, whereby, depending on the process control and the materials used, such as printing varnishes, for example, significant differences may result.

The mask layer is preferably applied to the layer by printing, in particular by intaglio printing, flexographic printing, screen printing or inkjet printing of a protective lacquer. In particular, in the case of ink-jet printing, it is possible to provide each individual multilayer body produced with an individual identification, for example a serial number, which improves the security against forgery or the authenticity of the multilayer body.

It is advisable if the protective lacquer is a physically drying or chemically crosslinking or radiation-curing lacquer.

In particular, it is also possible to use a protective lacquer comprising pigments and / or dyes and / or UV-activatable pigments and / or nanoparticles and / or upconverters and / or thermochromic dyes and / or photochromic dyes. Such a protective lacquer may remain on the multilayer body even after the lye treatment and the appearance of the optical system Contribute multi-layer body. Since the HRI layer is protected from detachment by the protective lacquer during the lye treatment, the remaining HRI layer is also arranged in register with the protective lacquer layer.

However, it is also possible to remove the protective coating at least in some areas after treatment with the alkali. Just a partial removal of the resist can also contribute to the overall optical effect of the multi-layer body, especially since here the remaining portions of the resist are also arranged in register with the HRI layer.

It is also advantageous if the mask layer is formed by applying a positive photoresist over the entire surface, exposing the portion of the layer to be removed and removing the exposed photoresist. For a positive photoresist, exposed portions of the photoresist will dissolve upon treatment with a corresponding developer, which may also be the caustic. In the unexposed areas of the photoresist remains on the HRI layer and protects it during the lye treatment from the influence of the alkali.

Alternatively, the mask layer may be formed by applying a negative photoresist over its entire area, exposing the non-removable portion of the layer, and removing the unexposed photoresist. A negative photoresist dissolves in the unexposed areas during development of the layer. Here, therefore, the photoresist remains in the exposed subregions on the HRI layer, where it protects the layer from the influence of the alkali. In a further variant, the photoresist can be applied only in partial areas, for example by a printing process, and then patterned by exposure.

Combinations of negative and positive photoresists can also be used to create complex patterns. Regardless of the type of photoresist used, exposures of up to 0.01 mm can be achieved by exposure. As already mentioned in printed mask layers, must be between the achievable by exposure in a photoresist resolution (which may be up to the sub-micrometer range) and the further process-related resolution, resp. minimum feature size, the structuring of the HRI layer are differentiated.

It is further advantageous if a photoresist is used which contains dyes and / or pigments and / or UV-activatable pigments and / or nanoparticles and / or upconverters and / or thermochromic dyes and / or photochromic dyes. Such a photoresist can remain on the multilayer body and also contribute there to the desired optical effect. As with the use of printed protective lacquers, the photoresist is then placed in register with the remaining HRI layer.

However, the photoresist can also be removed at least in some areas after the treatment with the alkali. Again, a particular partial removal of the photoresist contribute to the visual appearance.

Preferably, the exposure is performed over the entire surface and / or part of the surface by means of a laser. In the case of partial exposure, it is possible to provide each individual multilayer body produced with an individual identification, for example a serial number, which improves the security against forgery or the authenticity of the multilayer body. This effect can also be achieved with adjustable or changeable masks.

It is also advantageous if the liquor is printed on the portion of the layer to be removed. Due to the direct pressure of the liquor, the HRI layer is attacked only where it comes in contact with the liquor, so that in this way particularly easily structured HRI layers can be created without the need for a mask or the like. Such a method is therefore particularly simple and fast to perform. After detachment of the HRI layer in the printed area then the lye must only be rinsed off. Since the liquor in this variant of the process only comes into contact with the regions of the HRI layer to be detached, the process can also be used if the multilayer body has constituents which do not have good alkali resistance and which could possibly be attacked in a caustic bath.

Preferably, the liquor is printed by flexographic or gravure printing. Depending on the printing process used, structures with a resolution of 0.1 to 0.2 mm can be incorporated into the HRI layer.

Preferably, an alkali is used which contains at least one additive for increasing the viscosity and / or at least one wetting agent. This ensures that the printed liquor does not flow, so that the desired structure in the HRI layer is reliably obtained. At the same time, the addition of wetting agents ensures good contact of the liquor with the surface of the HRI layer, as well as easier penetration of the liquor into the pores of the layer.

Calcium carbonate is preferably used as the additive. In addition to calcium carbonate, for example kaolin, titanium dioxide, Aerosil, or silicon dioxide can be used. The criterion here is a material which is largely inert to the liquor and which is available in a fine grain size and thus can be sufficiently well dispersed in the liquor. As a result, the so-treated liquor can be printed better.

It is also advantageous if at least one relief structure is molded at least in a partial region of the substrate before the layer of the high-refractive index material is applied. By means of such a relief structure, further optical effects can be achieved which, in particular in cooperation with the reflective HRI layer, contribute to the overall visual impression and to the security against forgery of the multilayer body.

As already explained, it has been found that relief structures in the surface of the substrate influence the adhesion of the HRI layer on this surface of the substrate. This can be used for a partial removal of the HRI layer. For this purpose, conditions are created under which the interlayer adhesion of the HRI layer and the surface in a second region is just insufficient to hold the HRI layer to the surface, while the larger interlayer adhesion in the first region continues to adhere to the HRI layer Surface binds. This variant of the method can be carried out under particularly mild conditions, in particular low alkali concentrations, so that it is also suitable for sensitive material combinations. Optionally, the use of water as a liquid may be sufficient.

Another advantage of this process variant is that the remaining HRI layer remains in the perfect register with the relief structures formed in the surface. It is therefore also possible to create very filigree structures and patterns, the visual effect of which results from the interaction of the HRI layer with the relief structure arises. The achievable structure resolution in the partial HRI layer is about 0.015 mm.

The relief structure is typically formed in a so-called replication layer. A replication layer is generally understood as meaning a layer which can be produced superficially with a relief structure. These include, for example, organic layers such as plastic or lacquer layers or inorganic layers such as inorganic plastics (eg silicones), semiconductor layers, metal layers, etc., but also combinations thereof. Most of these layers have average refractive indices of about 1.5.

A replication layer formed as a plastic or lacquer layer, in particular made of thermoplastics or of a lacquer curing under UV irradiation, is superficially imprinted with a relief structure, in particular by means of a tool, in particular a stamp or a roller. A formation of a superficial relief structure by means of injection molding or the use of a photolithographic process is also possible. Depending on the production method used and the later intended use of the multilayer body formed, it is possible to use transmissive or non-transmissive replication layers, in particular transparent or opaque replication layers for the human eye.

It is particularly advantageous if the first relief structure is formed with a depth-to-width ratio of the individual structural elements of more than 0.1, in particular more than 0.15, preferably more than 0.2. Relief structures having such a depth-to-width ratio have been found to be particularly effective in increasing the interlayer adhesion of substrate and HRI layer. This is probably in particular in the enlarged surface and gearing in Established area of the relief structure. The relief structure also prevents the propagation of cracks in the HRI layer that cause the layer to flake off.

It is furthermore particularly advantageous if the structure has one of the following relief shapes: rectangular, triangular, step-like, sinusoidal or even with irregular, in particular random elevations and depressions, as occur, for example, in matt structures.

The dimensionless depth-to-width ratio is a characteristic feature for the enlargement of the surface, preferably of a periodic structure, for example with a sine-squared profile. Depth is the distance between the highest and the lowest consecutive point of such a structure, ie the distance between "mountain" and "valley". Width is the distance between two adjacent highest points, ie between two "mountains". The higher the depth-to-width ratio is, the steeper the "mountain flanks" are formed and the thinner the HRI layer deposited on the "mountain flanks", which leads to a different microcrystalline structure of the HRI layer than when deposited on a smooth surface, which also improves layer adhesion, but it can also be structures to which this model is not applicable, for example, discretely distributed line-shaped areas formed only as a "valley" , where the distance between two "valleys" is many times higher than the depth of the "valleys." In formal application of the above definition, the thus calculated depth-to-width ratio would be close to zero and would not reflect the characteristic physical behavior Therefore, in discretely arranged structures, which are essentially formed only by a "valley", the depth of the "valley to relate it to the width of the valley.

In a further preferred embodiment, no relief structure is molded into the substrate in the at least one second region or at least one second relief structure is molded into the substrate, which differs from the first relief structure. In this way it can be precisely controlled where the HRI layer should be preserved. In addition, by using different relief structures, the visual appearance of the multilayer body can be made even more complex, which contributes to the protection against counterfeiting.

It is particularly advantageous if the first relief structure and the second relief structure are formed such that due to the relief structures in the at least one first region the adhesion of the layer on the substrate is higher than in the at least one second region, wherein in particular the spatial frequency of first relief structure is higher than the Spatialfrequenz the second relief structure, the depth-to-width ratio of the structural elements of the first relief structure is greater than the depth-to-width ratio of the structural elements of the second relief structure and / or the product of spatial frequency and the depths -to-width ratio of the structural elements of the first relief structure is greater than that of the second relief structure. In this way, in the region of the first relief structure, a higher adhesion of the HRI layer to the substrate is achieved than in the region of the second relief structure and, furthermore, a different optical variable appearance in the first and second regions.

It is particularly advantageous if the at least one first relief structure and / or second relief structure is formed as a particular one- or two-dimensional diffractive grating structure, in particular with a spatial frequency of more than 500 lines / mm, preferably of more than 1000 lines / mm.

The diffractive grating structure of the second relief structure is preferably formed with a period of less than 3 μm or with a low aspect ratio <0.1.

The at least one first and / or second relief structure is preferred as a light-diffractive and / or refractive and / or light-scattering and / or light-focusing microstructure or nanostructure, as an isotropic or anisotropic matt structure, as a binary or continuous Fresnel lens, as a microprism structure, as a blazed grating, as a macrostructure or formed as a combination structure of these. As a result, a variety of optical effects can be realized.

It is also advantageous if at least one further functional layer is applied in particular partially before and / or after the application of the high-index layer. A functional layer is understood here to be one which either displays a visually discernible color or brightness impression or whose presence can be detected electrically, magnetically or chemically. For example, it may be a layer containing colorants such as colored pigments or dyes and in normal daylight colored, especially colorful. But it may also be a layer that includes special colorants, such as photochromic or thermochromic substances, luminescent substances, an optically variable effect-generating substances such as interference pigments, liquid crystals, metameric pigments, etc., reactive dyes, indicator dyes, which react reversible or irreversible color change with other substances, light-emitting pigments which show different color emissions when excited by radiation of different wavelengths, magnetic substances, electrically conductive substances in the electric or magnetic field color change showing substances, so-called E-ink ^® and the like.

Preferably, the at least one further functional layer is formed as a lacquer layer or a polymer layer.

The at least one further functional layer can also be formed with the addition of one or more colored, in particular colorful functional layer materials. It is also possible, additionally or alternatively, to form at least one partially formed functional layer as a hydrophobic or hydrophilic layer.

It is possible for the at least one further functional layer to be formed as an optically variable layer with a different optical effect depending on the viewing angle and / or as a metallic reflection layer and / or as a dielectric reflection layer.

In this case, it is particularly preferred if the optically variable layer is formed in such a way that it contains at least one material with different optical effect depending on the viewing angle and / or formed by at least one liquid crystal layer with different optical effect depending on the viewing angle and / or by a thin film layer stack with an interference color effect depending on the viewing angle becomes.

In a further preferred embodiment, after removal of the subregion of the high-index layer, a further layer of a material with a high refractive index is applied. Subsequently, at least a portion of the layer can be physically removed from the substrate by treatment with an alkali, in particular one or more of the methods described above being applied twice or more than once. In this way So subregions are created with different layer thickness of the HRI layer. Since the layer thickness influences the optical properties of the HRI layer, in particular its reflection behavior with respect to different wavelengths, this too can be used to produce various optical effects. Optionally, after the application of the further layer, it is also possible to dispense with removal of the layer in a partial region, so that a full-surface coating with locally different layer thicknesses results.

It is particularly advantageous if the removed portion of the high refractive index layer and the distant portion of the further high refractive index layer not or only partially overlap. In the case of a partial overlapping of the subregions, stepwise layer thickness gradients can also be generated.

It is advantageous if the at least one or a partially formed functional layer of the multilayer body and / or the at least one partially formed layer of a material with a high refractive index is deposited with a diffractive relief structure and exhibits a holographic or kinegraphic optically variable effect.

It is also advantageous if the at least one or a partially shaped functional layer of the multilayer body and the at least one partially formed HRI layer complement each other to a decorative and / or informative geometric, alphanumeric, pictorial, graphic or figurative representation. This contributes particularly to the security against forgery of the multilayer body, since it is necessary in this case for the functional layer to be arranged in register with the HRI layer. If this is not the case, the desired Presentation not realized. However, the necessary registration is difficult or impossible to achieve in counterfeit trials.

Preferably, the at least one or a partially formed functional layer of the multilayer body and / or at least the at least one partially formed HRI layer is formed as at least one line with a line width in the range of less than 100 μm, in particular in the range of 5 to 50 μm, and / or formed as at least one pixel with a pixel diameter in the range of less than 100 .mu.m, in particular in the range of 5 to 50 microns.

It is also advantageous if the at least one or partially formed functional layer of the multilayer body comprises one or more of the following layers: a, in particular opaque, metal layer, a layer containing liquid crystals, a thin-film reflection layer stack with viewing-angle-dependent interference color effect, a colored lacquer layer, a dielectric reflection layer , a layer containing fluorescent or radiation-stimulable pigment or dye. This also makes attractive optical effects and the integration of additional security features in the multi-layer body, which are perceptible or excitable, for example, only in certain spectral ranges.

In a further preferred embodiment, the at least one or a partially formed functional layer of the multilayer body and the HRI layer, seen at least from a certain angle or under a certain type of irradiation, are formed in complementary colors.

In a further preferred embodiment, the at least one or a partially shaped functional layer of the multilayer body and the HRI layer each formed in such a linear shape that the lines merge into each other without lateral offset. This also contributes to the security against counterfeiting, since a particularly good registration must also be achieved here in the production of the multilayer body.

The lines are preferably merged with one another with a continuous color gradient.

In a further preferred embodiment, the at least one or a partially formed functional layer of the multilayer body and / or the layer of a material having a high refractive index at least partially form a raster image constructed from pixels, pixels or lines that are not individually resolvable for the human eye. This can be used for attractive visual effects.

A screening of the first layer is also possible to the effect that in addition to raster elements, which are lined with a reflective layer and - optionally different - diffractive diffraction structures are provided in addition to raster elements that represent transparent areas without reflection layer. As screening, an amplitude or area modulated screening can be selected. A combination of such reflective / diffractive regions and non-reflective, transparent - possibly also diffractive - regions can be achieved interesting optical effects. If such a raster image is arranged, for example, in a window of a value document, a transparent raster image can be recognized in transmitted light. In incident light, this raster image is visible only at a certain angle range in which no light is diffracted / reflected by the reflecting surfaces. Furthermore, it is also possible to use such elements not only in a transparent window, but also to apply a colored imprint. Furthermore is It is also possible that a number of reflecting reflection areas decreasing in their reflection effect are formed by a correspondingly selected screening.

Preferably, the multi-layer body has at least one further partially formed layer of a high refractive index material.

In a further preferred embodiment, a first transparent spacer layer is formed between the at least one or a partially formed functional layer of the multilayer body and the one or more partially formed layer.

It is further preferred if the at least one or a partially formed functional layer of the multilayer body and the HRI layer are formed in such a way that shows at least one, optionally viewing angle-dependent, optical overlay effect.

The multilayer body is preferably designed as a film element, in particular as a transfer film, a hot stamping film or a laminating film. It may also be a security thread for insertion or application to a security paper or a card. In this case, the film element preferably has an adhesive layer on at least one side.

However, the multilayer body may not only be a foil element but also a rigid body.

Furthermore, the multilayer body preferably forms a decorative element or security element, in particular for securing security documents, such as banknotes or ID documents. Advantageously, rigid bodies, such as a badge, a base plate for a sensor element, semiconductor chips or surfaces of electronic devices, such as a housing shell for a mobile phone, can be provided with a multi-layer body of the type described.

The invention will be explained by way of example with reference to the drawings.

Fig. 1

schematische Schnittdarstellungen von drei unterschiedlichen Vorprodukten zur Herstellung eines Mehrschichtkörpers;

Fig. 2

eine schematische Schnittdarstellung eines Ausführungsbeispiels eines Mehrschichtkörpers;

Fig. 3

eine schematische graphische Darstellung der Einflüsse auf die Haftung einer HRI-Schicht bei der physikalischen Ablösung mit einer Lauge;

Fig. 4

eine schematische Schnittdarstellung durch einen Mehrschichtkörper während verschiedener Stadien der Durchführung eines ersten Ausführungsbeispiels eines Verfahrens zum Erzeugen des Mehrschichtkörpers;

Fig. 5

eine schematische Schnittdarstellung durch einen Mehrschichtkörper während verschiedener Stadien der Durchführung eines zweiten Ausführungsbeispiels eines Verfahrens zum Erzeugen des Mehrschichtkörpers;

Fig. 6

eine schematische Schnittdarstellung durch einen Mehrschichtkörper während verschiedener Stadien der Durchführung eines dritten Ausführungsbeispiels eines Verfahrens zum Erzeugen des Mehrschichtkörpers;

Fig. 7-13

unterschiedliche Design- und Sicherheitselemente, die mittels verschiedener Ausführungsbeispiele eines Verfahrens zum Erzeugen von Mehrschichtkörpern erzeugbar sind;

Fig. 14

eine schematische grafische Darstellung der Abhängigkeit der optischen Eigenschaften einer HRI-Schicht von der Schichtdicke;

Fig. 15

ein weiteres, mittels eines Ausführungsbeispiels des Verfahrens zum Erzeugen von Mehrschichtkörpem erzeugbares Design- und Sicherheitselement.

Show it

Fig. 1

schematic sectional views of three different precursors for producing a multilayer body;

Fig. 2

a schematic sectional view of an embodiment of a multi-layer body;

Fig. 3

a schematic graphical representation of the influences on the adhesion of an HRI layer in the physical separation with a liquor;

Fig. 4

a schematic sectional view through a multi-layer body during various stages of performing a first embodiment of a method for producing the multi-layer body;

Fig. 5

a schematic sectional view through a multi-layer body during various stages of carrying out a second embodiment of a method for producing the multi-layer body;

Fig. 6

a schematic sectional view through a multi-layer body during various stages of carrying out a third embodiment of a method for producing the multi-layer body;

Fig. 7-13

different design and security elements that can be generated by means of various embodiments of a method for producing multilayer bodies;

Fig. 14

a schematic graphical representation of the dependence of the optical properties of an HRI layer of the layer thickness;

Fig. 15

a further, by means of an embodiment of the method for producing Mehrschichtkörpem producible design and security element.

Fig. 2 shows a multi-layer body 100. The multi-layer body 100 comprises a carrier film 1. On this, a first functional layer 2 and a second functional layer 3 are applied. The functional layers 2, 3 can be, for example, release layers and / or protective layers. On the functional layer 3, a replication layer 4 is arranged. This has on its surface a first relief structure 5 and a second relief structure 6. In the register with the first relief structure 5 and in the partial register with the relief structure 6, a layer 7 of a high refractive index material (HRI layer) 7 is applied. The replication layer 4 and the HRI layer 7 are covered by a transparent protective lacquer 8.

Such multilayer bodies 100 can be produced in various ways. The starting material can be the in Fig. 1 precursors 100a, 100b, 100c are used. The precursor 100a comprises the carrier film 1, which can be made of PET or PEN, for example, functional layers 2 and 3 and the replication layer 4. The functional layers 2 and 3 determine the detachment behavior of the transfer layer from the carrier film 1, the resistance to environmental influences and optical properties of the multilayer body 100. The functional layers 2, 3 can also be chosen such that the carrier film 1 remains on the finished multilayer body 100, cf. that a laminating film is obtained.

The precursor 100b is a variant in which the carrier film 1 itself serves to receive the relief structures 5, 6. This may be, for example, a film made of PET, BoPP, PVC or PC.

The precursor 100c shows a carrier sheet 1 coextruded together with a second layer 4 serving as a replication layer, or laminated with a second sheet 4 serving as a replication layer.

In all variants, the thickness of the carrier film is 6 μm to 250 μm, preferably 10 μm to 75 μm. The thickness of the functional layers and the replication layer together is in the range of 0.5 μm to 20 μm, preferably 1 μm to 5 μm.

The replication layer 4 is superficially structured by known methods. For this purpose, for example, as a replication layer 4, a thermoplastic replication varnish is applied by printing, spraying or laking, and a relief structure is molded into the replication varnish by means of a heated stamp or a heated replicating roller.

The replication layer 4 can also be a UV-curable replication lacquer, which is structured, for example, by a replication roller. However, the structuring can also be produced by UV irradiation through an exposure mask. In this way, the relief structures 5 and 6 can be molded into the replication layer 4. In the relief structures 5 and 6 may be, for example, the optically active structures of a hologram or a Kinegram ^® -Sicherheitsmerkmals.

In order to produce the partial HRI layers 7, a layer of a high refractive index material is first applied to the replication layer 4 over the whole area. The material may be zinc sulfide, niobium pentoxide or titanium dioxide. This can be done, for example, by vapor deposition of the surface of the replication layer with the material.

The layer thickness of the HRI layer is preferably between 25 nm and 500 nm. The layer thickness depends on the properties to be achieved, such as a specific coloring. Thinner layers in the range of 45 nm to 65 nm appear more neutral in color, while thicker layers may show pronounced color effects, depending on the thickness.

As a result, the HRI layer 7 has to be removed, so that it remains only in a first subregion 9 and is removed from the replication layer 4 in a second subregion 10. It has been found that treatment with a lye can lead to the physical detachment of the HRI layer 7. This effect is particularly pronounced when using ZnS for the HRI layer. The HRI layer 7 is not chemically dissolved by the alkali, but bursts and can by mechanical action easily removed in the form of fine flakes. Even a thin cover layer of a lacquer of a few 100 nm, which keeps the liquor from the HRI layer 7, prevents this effect.

The cause of the physical detachment of the HRI layer 7 is due to the structure of the HRI layer 7. Typically, the HRI layer 7 is evaporated at relatively high deposition rates (greater than 1000 nm / min). The forming HRI layer 7 is not perfectly closed, but has fine pores. Furthermore, there is no monocrystalline phase, but at least one polycrystalline or partially amorphous layer. For example, ZnS is essentially not soluble in water or caustic, which also applies to the vapor deposited HRI layer 7. However, if an alkali is allowed to act on the HRI layer 7, it will at least partially penetrate the layer and form zinc hydroxo complexes. As a result, a mechanical stress is generated in the HRI layer 7, which can lead to the spalling of the HRI layer 7. Furthermore, by the penetration of moisture into the HRI layer 7, the interlayer adhesion to the replication layer 4 can be reduced, which further promotes the chipping.

Fig. 3 schematically shows the dependence of the chipping phenomenon of the layer thickness of the HRI layer 7. It is assumed a certain process condition (alkali concentration, composition of the liquor, temperature, exposure time, etc.). With very small thicknesses of the HRI layer 7, on the one hand, the microcrystalline structure of the vapor-deposited layer is different from the structure of a thicker HRI layer 7, and on the other hand, only a limited amount of mechanical stress can build up. Thus, there is a lower limit to the thickness of the HRI layer 7 for the process of spalling. On the other hand, for thick layers of many 100 nm, both the microcrystalline structure of the HRI layer 7 as well as the intrinsic stability of the HRI layer 7 to the fact that the HRI layer 7 can not be easily removed.

Fig. 3 illustrates the adhesion of the HRI layer 7 on a substrate (typically the replication layer 4) as a function of the layer thickness under alkaline conditions (process characteristic 11). Depending on the design of the influencing factors, this curve varies. The dynamics of the spalling is essentially determined by mechanical action on the HRI layer 7 during or after the alkali. If forming scales are removed mechanically, uncontrolled spalling and undesired infiltration of the HRI layer 7 through the liquor is prevented. It also prevents already detached scales from remaining on the replication layer. The process characteristic 12 illustrates that layers with an adhesion below a certain threshold can be mechanically removed. This results in a layer thickness range 13, in which a removal of the HRI layer 7 with the described method is possible.

The actual course of the characteristic 11 depends on a large number of influencing factors. Of importance initially mechanical properties and thickness of the carrier film. 1

The replication layer 4 also has an influence on the characteristic curve 11. Of particular importance here are the chemical composition, a possible pretreatment of the surface of the replication layer (SiO x, Cr nucleation, corona, plasma, flame treatment etc.) and the design of the relief structures 5 and 6 (spatial frequency, relief depth, depth-to-width ratio, profile shape of the relief structure, etc.).

The type of application of the HRI layer 7, in particular by vapor deposition, also influences the adhesion of the HRI layer under the influence of alkali. Important influencing factors here are the vapor deposition rate, as well as the material used for the HRI layer 7, the layer thickness, the temperature and vacuum conditions during the vapor deposition, and the conditions of the aforementioned pretreatment (for example plasma).

Finally, the intercoat adhesion is still influenced by the chemical composition, concentration, temperature and exposure time of the liquor to the multi-layer body 100. Also mechanical effects during and / or after the lye treatment, the structure of the surface, stresses in carrier film 1, and various pre-treatment techniques before the lye treatment affect the course of the process.

An important parameter in the setting of the process parameters is the characteristic of the chipping (size and shape of the flakes formed, stability of possibly coated with a resist areas against infiltration by the liquor, ease of removal of flaked flakes, etc.), as well as the selectivity of Influence of the relief structures 5 and 6 on the adhesion of the HRI layer 7.

Lye concentrations in the range of 0.01% to 15% are preferably used. However, the more preferred ranges are dependent on the type of liquor used, as well as on the method variant used. It is important that a pH of more than 10 is set. As lye is z. As metal hydroxides, such as NaOH or KOH, but also sodium bicarbonate, TMAH (tetramethylammonium hydroxide) or EDTA (Na ₂ EDTA) (ethylenediaminetetraacetate). The temperatures are preferably in the range of 10 ° C to 80 ° C. exposure times may preferably be in the range of a few seconds but also be up to several minutes.

The release of the HRI layer 7 can be assisted by mechanical action, such as brushing or wiping with sponges or a wiping roller. A strong influx in a bath or spraying can have the same effect. In addition, the removal of the HRI layer 7 can be supported by ultrasound.

In order to ensure only partial detachment of the HRI layer 7 in the regions 10, various possibilities exist, which can be used either individually or in combination.

A first variant of the method is in Fig. 4 shown. Shown are fragmentary sectional views through a multi-layer body 100 during different process steps. In each case only the replication layer 4 is shown. Here, too, of course, the carrier foil 1 and the functional layers 2 and 3 may be present. Fig. 4A shows the replication layer 4, in which the relief structures have already been introduced with the techniques described above. The replication layer 4 is now over the entire surface with the HRI layer 7 steamed or sputtered to the in Fig. 4B to obtain shown intermediate. As Fig. 4C shows, a lye layer 14 is now printed in the areas 10 on the HRI layer 7. The lye can therefore act only locally where the lye layer 14 is in direct contact with the HRI layer 7, so that it is detached from the surface of the replication layer 4 only in the regions 10 and remains in the regions 9. After the action of the lye, this is washed off and the detachment of the HRI layer 7 in the areas 10 by wiping, brushing, Ultrasound treatment or influx assisted with the washing medium, so that finally the in Fig. 4D structure shown is obtained.

For printing the liquor, the flexographic printing or intaglio printing is preferably used. With these printing methods, a resolution (cleanly printed lines, positive as well as negative) of the printed base layers 14 can be from 0.1 nm to 0.2 mm. The achievable register tolerance of the remaining HRI layers 7 in the areas 9 to the relief structures 5 and 6 is about 0.5 mm. The register tolerance depends essentially on the printing technique used, as well as on the dimensional stability of the substrate (that is, the resistance to distortion caused by thermal and / or mechanical influences during the processes) and the system technology used. Thus, significantly lower register tolerances can be achieved.

To make the liquor printable, additives such as CaCO ₃ and / or wetting agents may be added thereto. For this process variant, for example, sodium hydroxide solution in a concentration of 15% can be used.

A second embodiment of the method is in Fig. 5 shown.

Shown are fragmentary sectional views through a multi-layer body 100 during different process steps. In each case only the replication layer 4 is shown. Here, too, of course, the carrier foil 1 and the functional layers 2 and 3 may be present. Fig. 5A shows the replication layer 4, in which the relief structures have already been introduced with the techniques described above. The replication layer 4 is now over the entire surface with the HRI layer 7 steamed or sputtered to the in Fig. 5B to obtain shown intermediate. Subsequently, a protective varnish 15 is printed on the areas 9 to there the Protect HRI layer 7 from alkali ( Fig. 5C ). In the subsequent lye treatment, for example in a bath, the HRI layer 7 dissolves from the replication layer 4 only in the unprotected regions 10, so that after washing and mechanical treatment in the manner described in FIG Fig. 5D product shown is obtained.

For application of the protective lacquer, flexo, offset or gravure printing is preferably used. With this printing method, a resolution of the printed protective lacquer of 0.1 mm to 0.2 mm can be achieved. The achievable register tolerance of the remaining HRI layers 7 in the areas 9 to the relief structures 5 and 6 is about 0.1 mm to 0.2 mm, while a register tolerance can be achieved to possibly existing structures in the functional layers of 0.025 mm. The register tolerance depends essentially on the printing technique used. Furthermore, remaining flakes of the HRI material at the pressure edge, as well as a possible infiltration of the protective lacquer layer 15 affect the resolution and registration of the remaining HRI layers.

For this process variant is preferably caustic soda with a conductivity of about 30 mS / cm, ie with a pH of about 13 at a temperature of 40 ° C, or sodium hydroxide with a conductivity of 80 mS / cm, ie a pH Value of about 13.5 at a temperature of 22 ° C.

The protective lacquer 15 can be left on the remaining HRI layer after the partial removal of the HRI layer 7, or can be removed again, for example by solvent treatment. If the protective varnish remain on the multilayer body 100, the protective varnish can take on additional functions, for example, act as an adhesive or at least one UV-excitable or visually recognizable color or serve as a protective layer for further processing steps.

A third embodiment of the method is in Fig. 6 shown. Shown are fragmentary sectional views through a multi-layer body 100 during various process steps. In each case only the replication layer 4 is shown. Here, too, of course, the carrier foil 1 and the functional layers 2 and 3 may be present. Fig. 6A again shows the replication layer 4 into which the relief structures have already been introduced by the techniques described above. The replication layer 4 is now over the entire surface with the HRI layer 7 steamed or sputtered to the in Fig. 6B to obtain shown intermediate.

It has been found that the adhesion of the HRI layer 7 on the replication layer 4 and in particular its chip-off behavior under alkaline conditions is largely influenced by the type of relief structures 5, 6 of the replication layer 4. Thus, the type of relief structures 5, 6 can be used to influence the chipping behavior targeted.

Thus, it can be seen that in particular diffraction-optical structures 5, 6 with a high depth-to-width ratio and / or a high spatial frequency lead to a significantly increased adhesion of the HRI layer 7. The depth-to-width ratio is preferably selected in the range of 0.1 to 1.0. The spatial frequency is preferably between 1000 and 4000 l / mm.

If the HRI layer 7 is treated with caustic, the HRI layer 7 begins to break up outside the regions 9 with a high depth-to-width ratio and can be removed mechanically. It is particularly advantageous to choose the pH of the liquor in the following range: 11 to 13.

After this process step, the HRI layer is present only in the regions 9 in the perfect register relative to the relief structures 5, 6, such as Fig. 6C shows. At the same time very filigree patterns are possible.

This behavior is likely to be due to a combination of different effects. First, the enlarged surface in the area of the relief structures 5, 6 leads to increased interlayer adhesion between HRI layer 7 and replication layer 4. The propagation of the chipping off of the HRI layer 7 is furthermore prevented by the relief structures 5, 6 in that they function as predetermined breaking points. In addition, the design of the caustic-induced stress in the HRI layer 7 is changed, so that the forces that promote the chipping of the HRI layer 7 are distributed differently. Also, the microcrystalline structure of the HRI layer 7, which is formed during vapor deposition, is different due to the different wall inclinations of relief structures 5, 6 and smooth surfaces.

For this process step, relatively low alkali concentrations have been proven. Concentrations of about 0.02-0.06%, ie a pH of about 12.1 to 12.8, and a temperature of about 35-55 ° C. were found to be advantageous for NaOH as the lye. At high concentrations (> 0.5%), the spalling of the HRI layer 7 is less controlled and it can also breakouts in the areas to be obtained 9 occur.

Important for a precise breaking out of the HRI layer 7 is a suitable mechanical action. By removing even small flakes, the propagation of the flaking is controlled. Proved are spray nozzles (continuous or pulsed), ultrasound, but also in different directions rotary scrubbing rollers (brushes, cloths, sponges) or devices in the nature of an orbital sander.

Relief structures 5, 6 in the form of lattice structures (1-dimensional or 2-dimensional) with periods in the range of <3 μm have proved particularly suitable for increasing the adhesion of the HRI layer 7 to the replication layer 4. The profile shapes of the grid structures can be sinusoidal, rectangular or triangular but also have more complex profile shapes. Furthermore, the aspect ratio is preferably greater than 0.1 and in particular greater than 0.15.

In addition to ordered lattice structures, stochastic microstructures, for example matt structures, in the relief structures 5, 6 also increase the intercoat adhesion particularly well.

Fig. 7 shows a plurality of motifs 16a-16e, which were generated by means of the above-described second embodiment of the method. On a replicated and fully coated with ZnS replicate layer 4, a protective coating 15 was applied by gravure. The black-colored areas of the motifs 16a-e show the protective varnish 15. The removal of the HRI layer 7 outside the overprinted areas takes place by an action in a lye bath and subsequent rinsing by means of spray nozzles and wiping by means of brushes.

Depending on the printing varnish 15 used, printing process and process control for removing the HRI layer 7, certain restrictions may have to be taken into account. Thus, it has been found that a negative (not printed) surface area must be at least 0.8 mm and a positive (printed) area extent at least 0.4 mm. Depending on the process control, however, these values can also be significantly undercut. Small subjects in the Motives 16a-e must be connected with each other and must not be free, otherwise there is a risk of breaking out of HRI layer 7. The described embodiment is therefore not suitable for feinziselierte subjects. In the case of the illustrated motifs 16a-e, this applies in particular to the motifs 16a and 16b. For these, the other methods described here are better suited.

The printing varnish 15 can fulfill other functions in addition to the protection of the HRI layer 7 before the alkaline solution. For example, the protective lacquer 15 can serve as a bonding agent between HRI layer 7 and an adhesive layer. It is also possible to avoid an additional function as a mechanically stabilizing layer in order to avoid a degradation of the visual impression of the optical effects when applied to a substrate or laminating in a layer composite (for example in the case of plastic cards made of polycarbonate, PET or PVC). The protective lacquer 15 can also serve as an adhesive for the subsequent application of the multilayer body 100 to a substrate or introduction into a layer composite.

The printing ink 15 may be a physically drying, chemically crosslinking or by means of radiation, in particular ultraviolet or electron radiation, hardened system.

Furthermore, the printing ink 15 can be colored by means of dyes or pigments in order to improve the contrast and the recognizability of the optical effects of the HRI layer 7. However, the printing varnish 15 can also be removed here as described.

Fig. 8 shows a multilayer body 100, which was manufactured according to a fourth embodiment of the method and which as KINEGRAM ^® TKO serves to protect the data pages of a passport. A KINEGRAM ^® TKO is a transparent protective layer with security features, which is applied to a substrate as a foil laminate or as a transfer element.

In this exemplary embodiment, as already described, the replication layer 4 is also provided with the relief structures 5, 6 and over the entire area with ZnS vapor deposition in order to form the HRI layer 7. Subsequently, the HRI layer 7 is coated over its entire surface with a photoresist. However, the job can also be done only partially, for example by means of a printing process. This is particularly useful in those cases when larger areas without HRI layer 7 are to be generated.

The photoresist may be, for example, a positive photoresist, such as AZ 1512 or AZ P4620 from Clariant or S1822 from Shipley, which has an areal density of 0.1 g / m ² to 50 g / m ² on the first layer 3m is applied. The layer thickness depends on the desired resolution and the process. Preferred basis weights are in the range of 0.2 g / m ² to 10 g / m ² .

After application, the photoresist is exposed by means of a mask, wherein one of the functional layers 2 and 3 can serve as a mask, for example if these layers 2, 3 have a corresponding modification, coloring or pigmentation which can serve as a masking of an exposure wavelength, and removed exposed areas of the photoresist by developing. Subsequently, the HRI layer 7 is treated with alkali in those areas where the photoresist has been removed, the remaining photoresist serving as a protective layer against the liquor. The HRI layer 7 is therefore removed only in the areas in which the photoresist was exposed and / or was not applied in the case of a partial pressure.

The photoresist can analogously to the protective coating 15 take over the other functions described there, but optionally also be removed in a further process step.

The Fig. 8 shows a schematic representation of the multi-layer body 100 for pass applications in supervision. The black areas 9 show a full-coverage with the HRI layer 7, while in the white areas 10, the HRI layer 7 is completely removed. Gray areas (world map 17, portrait 18) show a partial area occupation with the HRI layer 7 below the resolving power of the human eye. In the stylized world map in the form of a 2-dimensional fine grid and in portrait 18 in the form of a microprint with locally varying line width.

In this exemplary method, the high resolution which can be achieved in the case of photostructuring by means of a photoresist is utilized in particular. For example, photoresists of up to sub-micron resolution can be patterned, the realizable resolution being largely determined by the thickness of the photoresist, the resolution of the exposure mask, and the process control. Due to the binary configuration of the photoresist as a protective lacquer, a high resolution of the partial HRI layer 7 can also be ensured by suitable process control. In particular, with the described method, a resolution of the HRI layer 7 of 0.03 mm or better can be achieved. The achievable register tolerance to relief structures 5, 6 is about 0.1-0.3 mm, while the register tolerance of the HRI layer 7 to further functional layers, if the photoresist itself remains as a functional layer or the functional layers 2, 3 are used as a mask, from 0 , 01 mm or better can be achieved.

Furthermore, it is possible to introduce an individual identification, for example a consecutive number. For this purpose, the photoresist is exposed by a laser or a controllable mask.

Furthermore, the photoresist can also be colored in one or more colors (for example by means of dissolved dyes or pigments) in order to improve the contrast and the detectability or also to serve as a further security element.

For the partial removal of the HRI layer, sodium hydroxide solution having a conductivity of about 12 mS / cm, ie a pH of about 12.6, at a temperature of 45 ° C. is used in this exemplary embodiment. Under these conditions, the sodium hydroxide solution can simultaneously serve for the development or for the removal of the exposed photoresist, resulting in a particularly simple process procedure.

Fig. 9 shows a further embodiment of a multi-layer body 100, which can be produced by means of the above-described second embodiment of the method. The multilayer body 100 again has a Kinegram ^® and serves to protect the data pages of a passport.

Again, the black colored areas 9 indicate a full-surface covering with the HRI layer 7, while in the white areas 10 the HRI layer 7 is completely removed. In the upper right corner there is a rectangle in which the HRI layer 7 has been removed over a large area. In this area, the HRI layer 7 was removed to ensure high transparency to UV radiation at a wavelength of 254 nm. On the protected data page of the Passes are in this region UV-active pigments that are to be stimulated for verification at this wavelength.

In addition, four letterings "VALID", which each have an HRI layer 7, can be found in this rectangular area. Each of the logos is deposited in the register with another, under UV irradiation (eg 365 nm) fluorescent color, z. B. red, green, yellow & blue. The respective protective lacquer 15, which was used to protect the HRI layer 7 from the alkali to remove the HRI layer 7, thus each has a further function and is present in the register to the HRI layer 7. Only in these regions with HRI layer 7 are the optical diffraction structures molded in the replication layer 4 also optically active.

The additional functions of the resist 15 may be different. For example, the protective coating 15 may be provided with UV-active pigments, nanoparticles or upconverters. But it may also be a protective varnish 15 with OVI pigments, with thermo or photochromic dyes. Furthermore, the protective lacquer 15 may also be colored in the visual area.

The protective lacquer can be applied by a variety of printing processes, for. B. by gravure, offset, flexo or screen printing. Furthermore, a pressure by means of digital printing, for example, inkjet, possible, in which case in particular an individual marking can be applied, which also shows in the partial design of the HRI layer 7.

Particularly advantageous are combinations of different printing techniques and colors.

Fig. 10 shows a multi-layer body 100 having a Kinegram ^® for a map application. Shown are the line-shaped design elements with typical line widths around 50 μm. The background has no structures and is essentially a mirror. For the production of this embodiment of the multi-layer body 100, the above-described third variant of the method is particularly suitable, ie the HRI layer 7 is structured without the use of a protective lacquer 15 or photoresists on the basis of the structures introduced into the replication layer 4 - in this case the linear design elements. For the embodiment shown here, the above-mentioned process parameters are suitable. Advantages of this example include the very high register retention of the HRI layer for diffractive design, while providing an unobstructed view of the substrate in the regions removed from the HRI layer.

Fig. 11 shows another embodiment of a multi-layer body 100 which includes a Kinegram ^® for a map application. The gray-backed surface 9 has been protected by a pressure varnish 15 according to the second exemplary embodiment of the method described above and has a full-surface HRI layer 7. The black curved lines 19 have diffractive optical structures. In the central rectangle 10, the HRI layer 7 is completely absent in the background without diffraction-optical structures, but the diffractive structures of the curved lines 19 are deposited in the perfect register with an HRI layer 7. The lye treatment was carried out in this embodiment with NaOH at a conductivity of 2 mS / cm, ie a pH of about 11.9, and a temperature of 45 ° C.

For a viewer, the KINEGRAM ^® opens up completely without interruptions over the entire surface. In the background of the central rectangle However, no HRI layer 7 is present and allows an unobstructed view of the substrate.

This combination can also be applied to not due to the present Denden in these areas, structures of a liquor exposure resist portions of a KINEGRAM ^®, the HRI layer 7 to protect specifically, whereas the remaining areas have the HRI layer 7 in the register to the diffraction-optical structures ,

Fig. 12 shows another embodiment of a multilayer body 100 having a KINEGRAM ^® TKO for a map application. The entire surface has diffractive optical structures, with only a portion 20 (circle with letter K) is shown. High-frequency linear grating structures, which form a zero-order diffraction structure, can be found in this area.

In order to produce an optimum optical effect, the layer thickness of the HRI layer 7 in the region 20 of the zero order diffraction structure should be relatively large, so that a full-surface applied HRI layer 7 of this thickness in the surrounding regions due to the interference in the HRI layer would lead to a disturbing coloring. The diffraction efficiency of other structures for producing effects in the first or higher order of diffraction (rainbow effects, but also, for example, diffractive structures for producing macroscopic relief effects) may decrease. An optimally configured feature for the card should thus have an increased layer thickness in the area 20 of the circle compared with the further area 21, but only there. The layer thickness in the region 20 is preferably 70 nm to 200 nm.

In order to produce such an HRI layer 7 with varying layer thickness, an HRI layer 7 having a layer thickness which corresponds to the target difference of the two thicknesses in the two regions 20, 21 is applied to the replication layer 4 in a first step. Taking advantage of the higher adhesive property of the high-frequency lattice structure, that is to say according to the third embodiment of the method described above, this first HRI layer 7 is removed in register in the surrounding region 21. In a second step, a second evaporation with HRI material is then carried out over the entire area, so that the optimum layer thickness is achieved both in the background 21 and in the circle 20.

Optionally, a repeated repeated application and removal of HRI layers 7 can take place in order to create a plurality of regions, each with different layer thicknesses of the HRI layer 7.

Fig. 13 shows a further embodiment of a multilayer body 100 with an HRI layer 7 with locally different layer thickness. The multilayer body 100 again comprises a KINEGRAM ^® TKO for a mapping application. Only by locally different configuration of the layer thickness of the HRI layer appears in reflection the lettering "VALID" 22 in a predetermined interference color, while the background 23 continues to be color neutral.

The layer thickness of the HRI layer 7 determines the color impression which a viewer recognizes in reflection. The relationship between layer thickness and color impression is in Fig. 14 shown graphically. The three graphs show simulated Lab values in reflection under D65 illumination and a normalized viewer (10 °, CIE1964).

At very low layer thicknesses of 10 nm to 40 nm, the HRI layer 7 appears bluish. Standard thicknesses of around 55 nm are typically chosen so that the appearance is color-neutral. If the layer thickness increases further, different color impressions (yellow, orange, green, blue, etc.) can be produced in the thickness range from 65 nm to several 100 nm. The methods described above now allow areas with specifically different color impressions to be generated.

In a first step, an HRI layer 7 is applied over the entire surface with a first layer thickness and removed again in the background 23 of the VALID lettering 22. Through the full-surface vapor deposition of a second HRI layer 7 is achieved that in the lettering 22, the addition of both layer thicknesses is present and in the background 23, the desired color-neutral layer thickness.

The color impression in reflection serves as an additional security feature for verification of authenticity. In contrast to a printed-only color, the color impression due to the thickness of the HRI layer 7 can be seen mainly in reflection. The coloring can be further by applying a metal layer, such. B. a chrome layer can be changed. In the case of very thin configurations of the metal layers of a few nanometers, no closed layer is formed so that such metal layers do not provide any protection against the action of alkali. Such layers can thus be removed together with an underlying HRI layer 7. For thicker metal layers, in a first step, the metal layer can be removed and then the metal layer can be used as a mask for removing the underlying HRI layer 7.

Fig. 15 schematically shows another motif 24 for a multi-layer body 100, which can be produced by the methods described above. The motif 24 comprises a combination of metallic areas and areas with one HRI layer 7, which are partially structured in register with each other. First, to make the subject 24, as on the left side of Fig. 15 shown an arrangement 25 of an HRI layer 7 and a metal layer 26 created by vapor deposition on a substrate. This arrangement can be carried out, for example, by partial vapor deposition or by full vapor deposition and partial structuring of the two layers. Subsequently, as in the middle of Fig. 15 shown, the protective varnish 15 applied in the illustrated printed image. After lye treatment results in the motif 24 shown on the right in the figure.

Since only a single printing step takes place and the regions of the metal layer 26 and HRI layer 7 not protected by the protective varnish 15 are removed simultaneously by the alkali treatment, the transitions between the metallic reflection layer 26 and HRI layer 7 are perfectly matched to one another. If the metal layer can not be structured by means of a lye, two separate treatments with different media can also be carried out. The layers 7, 26 can be arranged side by side or overlap.

The lye treatment is carried out in this embodiment with sodium hydroxide solution with a conductivity of 12 mS / cm, ie a pH of about 12.7, at a temperature of 45 ° C. Alternatively, sodium hydroxide solution with a conductivity of 5 mS / cm, ie a pH of about 12.3, at 55 ° C, or potassium hydroxide solution with a conductivity of 20 mS / cm, ie a pH of about 13, be used at a temperature of 30 ° C.

LIST OF REFERENCE NUMBERS

1

support film

2

functional layer

3

functional layer

4

replication

5

relief structure

6

relief structure

7

HRI layer

8th

transparent protective varnish

9

Area

10

Area

11

Process characteristic

12

curve

13

thickness range

14

lye layer

15

protective lacquer

16

motive

17

map of the world

18

portrait

19

line

20

Area

21

background

22

lettering

23

background

24

motive

25

arrangement

26

metal layer

100

Multi-layer body

Claims (15)

1. Method for producing a multilayer body (100), in which an HRI layer (7), which consists of a material with a high refractive index, in particular from the group zinc sulphide, niobium pentoxide, titanium dioxide, is applied to a substrate (4) at least over part of the surface, and, subsequently, at least one partial region (10) of the layer (7) is again physically removed from the substrate (4) by treatment with a lye, wherein the layer does not chemically dissolve in the lye during such a lye treatment and wherein a pH value of the lye amounts to at least 10, preferably from 10.5 to 14, and the treatment with the lye takes place at a temperature of 10°C to 80°C, and wherein at least one further partial region of the layer (7) remains on the substrate.
2. Method according to claim 1,
   characterised in that
   the lye is selected from the group sodium hydroxide, potassium hydroxide, sodium bicarbonate, tetramethylammonium hydroxide, sodium-ethylenediaminetetraacetate.
3. Method according to one of claims 1 or 2,
   characterised in that
   during and/or after the treatment with the lye, a mechanical treatment of the HRI layer (7) takes place to support the dissolution of the HRI layer (7), wherein the mechanical treatment in particular comprises brushing and/or wiping with a sponge and/or a wiping roller and/or an ultrasonic treatment and/or blasting and/or spraying the HRI layer (7) with a liquid.
4. Method according to one of claims 1 to 3,
   characterised in that
   before the treatment with the lye, a mask layer (15) for protecting at least one partial region (9) of the HRI layer (7) that is not to be removed, is applied to the HRI layer (7), in particular by printing, in particular by gravure printing, offset printing, flexographic printing, silk-screen printing or inkjet printing of a protective varnish (15), wherein the protective varnish (15) is a physically drying or chemically crosslinking or beam-hardening varnish and/or comprises pigments and/or dyes and/or UV-activatable pigments and/or nanoparticles and/or upconverters and/or thermochromic dyes and/or photochromic dyes.
5. Method according to claim 4,
   characterised in that
   the mask layer is formed by completely or partially applying a positive photoresist, exposing the partial region (10) of the HRI layer (7) to be removed and removing the exposed photoresist, or by completely or partially applying a negative photoresist, exposing the partial region (9) of the HRI layer (7) that is not to be removed and removing the unexposed photoresist, wherein a photoresist is respectively used which contains dyes and/or pigments and/or UV-activatable pigments and/or nanoparticles and/or upconverters and/or thermochromic dyes and/or photochromic dyes.
6. Method according to one of claims 1 to 5,
   characterised in that
   the lye is imprinted on the partial region (10) of the HRI layer (7) to be removed, in particular by flexographic printing or gravure printing, wherein, in particular, a lye is used that contains at least one additive for increasing the viscosity and/or at least one wetting agent, wherein in particular calcium carbonate, kaolin, titanium dioxide, Aerosil or silicon dioxide is used as an additive.
7. Method for producing a multilayer body (100), in particular according to one of the preceding claims, in which, in at least one first region of one or the substrate (4), at least one first relief structure (5) is moulded into a first surface of the substrate (4), then one HRI layer (7) or the HRI layer (7), which consists of a material with a high refractive index, is applied to the first surface of the substrate (4) at least over part of the surface in such a way that the HRI layer (7) at least regionally covers the at least one first region and at least one second region of the substrate (4), in which the first relief structure (5) is not moulded into the first surface of the substrate (4), and then a partial region (10) of the HRI layer (7) is again physically removed from the substrate (4) by treatment with a liquid in the form of water or a lye in such a way that the HRI layer (7) is removed in the partial region (10) covering the at least one second region and remains on the substrate (4) in the partial region (9) covering the at least one first region, wherein the layer does not chemically dissolve in the lye by a lye treatment and wherein the first relief structure (5) is formed in particular with a depth-to-width ratio of the individual structural elements of more than 0.1, in particular more than 0.15, preferably of more than 0.2, wherein the interlayer adhesion of the HRI layer (7) and the surface in the flat second region is no longer quite sufficient to hold the HRI layer (7) on the surface, while the greater interlayer adhesion in the first region binds the HRI layer (7) to the surface.
8. Method according to claim 7,
   characterised in that
   a relief structure is not moulded into the substrate (4) in the at least one second region or at least one second relief structure (6) is moulded into the substrate (4), said second relief structure differing from the first relief structure (5), wherein the first relief structure (5) and the second relief structure (6) are formed in such a way in particular that, as a result of the relief structures (5, 6), the adhesion of the layer (7) on the substrate (4) in the at least one first region is greater than in the at least one second region, wherein, in particular, the spatial frequency of the first relief structure (5) is greater than the spatial frequency of the second relief structure (6), the depth-to-width ratio of the structural elements of the first relief structure (5) is greater than the depth-to-width ratio of the structural elements of the second relief structure (6) and/or the product of the spatial frequency and the depth-to-width ratio of the structural elements of the first relief structure (5) is greater than that of the second relief structure (6).
9. Method according to one of claims 7 or 8,
   characterised in that
   the at least one first relief structure (5) and/or second relief structure (6) is formed in particular as a one- or two-dimensional diffractive lattice structure, in particular with a spatial frequency of more than 1000 lines/mm, preferably of more than 1500 lines/mm, and/or the diffractive lattice structure of the second relief structure (6) is formed having periods of less than 3µm, and/or the at least one first (5) and/or second relief structure (6) is formed as a light-diffracting and/or light-refracting and/or light-scattering and/or light-focusing micro or nanostructure, as an isotropic or anisotropic matt structure, as a binary or continuous Fresnel lens, as a micro-prism structure, as a blazed grating, as a macrostructure or a combination structure of these.
10. Method according to one of claims 1 to 9,
    characterised in that
    before and/or after applying the HRI layer (7), at least one further functional layer (2, 3) is applied, which is formed in particular as a varnish layer or a polymer layer and/or by adding one or more coloured, in particular multi-coloured functional layer materials, and/or at least one partially formed functional layer (2, 3) is formed as a hydrophobic or hydrophilic layer and/or as an optically variable layer with a different optical effect depending on perspective and/or as a metallic reflection layer and/or as a dielectric reflection layer, wherein the optically variable layer is formed in such a way in particular that it contains at least one substance with a different optical effect depending on the perspective and/or is formed by at least one liquid crystal layer with a different optical effect depending on the perspective and/or by a thin film layer stack with an interference colour effect depending on the perspective.
11. Method according to one of claims 1 to 9,
    characterised in that,
    after removing the partial region (10) of the HRI layer (7), a further HRI layer (7) is applied and then in particular at least one partial region (10) of the HRI layer (7) is again physically removed from the substrate (4) by treatment with a lye, wherein in particular the method according to one of claims 1 to 10 is repeated one or more times, wherein the removed partial region (10) of the HRI layer (7) and the removed partial region (10) of the further HRI layer (7) are in particular not or only partially covered.
12. Multilayer body (100), produced or able to be produced according to one of claims 1 to 11,
    having a substrate (4) and at least one partially formed HRI layer (7) which consists of a material with a high refractive index, in register with at least one further partially formed functional layer (2, 3, 15).
13. Multilayer body (100), able to be produced according to one of claims 7 to 9, having a substrate (4) and an HRI layer (7) which consists of a material with a high refractive index, wherein, in at least a first region of a or the substrate (4), at least one first relief structure (5) is moulded into a first surface of the substrate (4), the HRI layer (7) is applied to the first surface of the substrate (4) over part of the surface in such a way that the HRI layer (7) is removed in the partial region (10) covering the at least one second region and is provided on the substrate (4) in the partial region (9) covering the at least one first region.
14. Multilayer body (100) according to one of claims 12 and 13,
    characterised in that
    the at least one or one partially formed functional layer (2, 3, 15) of the multilayer body (100) and/or the at least one partially formed HRI layer (7) is deposited with a diffractive relief structure (5, 6) and shows a holographic or kinegraphic optically variable effect, and/or the at least one or one partially formed functional layer (2, 3, 15) of the multilayer body (100) and the at least one partially formed HRI layer (7) are mutually added to a decorative and/or informative geometric, alphanumerical, visual, graphical or figurative coloured depiction, and/or the at least one or one partially formed functional layer (2, 3, 15) of the multilayer body (100) and/or at least the at least one partially formed HRI layer (7) is formed as at least one line having a line width ranging from < 200µm, in particular ranging from 5 to 100µm, and/or the at least one or one partially formed functional layer (2, 3, 15) of the multilayer body (100) comprises one or more of the following layers: a particularly opaque metal layer, a layer containing liquid crystals, a thin film reflection layer stack with an interference colour effect, a dyed varnish layer, a dielectric reflection layer, a layer containing fluorescent or a radiation excitable pigment or dye, and/or the at least one or one partially formed functional layer (2, 3, 15) of the multilayer body (100) and the HRI layer (7), at least seen from certain perspective or under a certain type of radiation, are formed in complementary colours.
15. Multilayer body (100) according to one of claims 12 to 14,
    characterised in that
    the at least one or one partially formed functional layer (2, 3, 15) of the multilayer body (100) and the HRI layer (7) are respectively formed to be linear in such a way that the lines without lateral offset cross over one another in particular with a continual colour gradient, and/or the at least one or one partially formed functional layer (2, 3) of the multilayer body (100) and/or the HRI layer (7) at least regionally forms/form a raster display constructed from pixels, image points or lines that are not able to be individually resolved by a human eye.

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