Embossed substrate for use as dovid and method of its manufacture

Abstract

The present invention relates to a thermoplastic polymeric substrate bearing on part of at least one of its surfaces at least one embossed diffractive structure, to a use of said substrate as diffractive optical variable image device (DOVID), a method for manufacturing said thermoplastic polymeric substrate, target products obtainable from the thermoplastic polymeric substrate, an embossing die or matrix suitable for use of manufacturing the thermoplastic polymeric substrate, wherein said die or matrix bears a structure on part of at least one of its surfaces, which is the negative image of the embossed structure of the aforementioned thermoplastic polymeric substrate, as well as to a use of said die or matrix for transferring a negative image of its structure onto at least one surface of a thermoplastic polymeric material.

Description

[0001] Embossed substrate for use as DOVID and method of its manufacture

[0002] The present invention inter alia relates to a thermoplastic polymeric substrate bearing on part of at least one of its surfaces at least one embossed diffractive structure, to a use of said substrate as diffractive optical variable image device (DOVID), a method for manufacturing said thermoplastic polymeric substrate, target products obtainable from the thermoplastic polymeric substrate, an embossing die or matrix suitable for use of manufacturing the thermoplastic polymeric substrate, wherein said die or matrix bears a structure on part of at least one of its surfaces, which is the negative image of the embossed structure of the aforementioned thermoplastic polymeric substrate, as well as to a use of said die or matrix for transferring a negative image of its structure onto at least one surface of a thermoplastic polymeric material.

[0003] Background of the invention

[0004] Optical security elements such as diffractive optical variable image devices (DOVID) are frequently used to prevent copying and misuse of documents including in particular plastic documents, e.g., for securing documents such credit cards, money cards, identity cards, passports, etc. The optical security elements ideally should be in a form, which cannot be copied using any conventional copying methods. DOVID structures can for instance be incorporated into a foil, which is then stamped onto a suitable document such as a paper document, e.g., a banknote, or onto a plastic document such as a credit card, incorporated into the structure of a product being composed of a multilayer system, e.g., a passport or driver license before personalization, or can be integrated in a laminate that is heat sealed to the surface of a card after personalization, e.g., in case of identity cards. Usually, the security elements used are equipped with at least one layer made of at least one reflective material, for example a material having a high refractive index in order to create special optical structures on the surfaces of the elements, in particular based on visual optical effects created by diffraction phenomena. The reflective layer present can, e.g., be able to form an optical boundary layer, which renders structures such as reliefs at this boundary layer visible, although the structures as such are embedded. The reflective layer of the DOVID structures has a higher refractive index than both the substrate such as a polymer substrate used for preparation of the DOVID and other materials being also optionally present, which surround the structure such as the relief in the final product. If part of the reflective layer was removed, the relief would not be visible when, e.g., surrounded by polymer materials with similar refractive indices, and, hence, the relief would “disappear” in areas without reflection layers. An image thus only exists in the areas being covered with a reflective layer made of at least one reflective material. The resolution of said image corresponds to the image resolution of the reflective layer. An excellent image resolution is, of course, desired.

[0005] US 9,969,203 B2 describes a method of manufacturing a DOVID, which includes embossing a diffractive relief on a substrate, applying a reflective layer of a material having a high refractive index over the entire surface of the substrate, treating the reflective layer with the alkaline solution, which selectively flakes off pieces of that material from the substrate in at least one partial region, followed by a mechanically removing the pieces of the material having a high refractive index. A disadvantage of the method of US 9,969,203 B2 is that the pieces of the material having a high refractive index that flake off in any smooth areas often break partially in the relief areas as well, which leads to a curled border of the reflective layer and decreases the image resolution of the reflective layer, which undesired. A further disadvantage of the method of US 9,969,203 B2 is that any depressions, which take part in forming the embossed reliefs, are located in the same plane as the smooth areas not comprising any relief structures, which leads to a decrease in the differences in adhesion of the reflective layer to the substrate in the relief structure areas on the one hand and the non-relief smooth areas on the other hand, making the process of flaking off pieces of the of the material having a high refractive index, which forms the reflective layer, and subsequent washing out of these pieces more difficult due to an insufficient selectivity with regard to flaking off pieces of the reflective layer only in the non-relief smooth areas.

[0006] Thus, there is a need to be able to provide a substrate suitable to be used as a DOVID and bearing an embossed diffractive structure on its surface in a cost-efficient and productive manner, wherein the embossed structure has an improved image resolution of the reflective layer, in particular compared to conventional DOVIDs such as the ones disclosed in US 9,969,203 B2, and wherein a higher selectivity regarding the presence of the reflective layer only in the embossed structure regions and not in any non- embossed regions of the surface of the DOVIDs can be achieved, again in particular compared to conventional DOVIDs such as the ones disclosed in US 9,969,203 B2.

[0007] Problem

[0008] It has been therefore an objective underlying the present invention to be able to provide a substrate suitable to be used as a DOVID and bearing an embossed diffractive structure on its surface in a cost-efficient and productive manner, wherein the embossed structure has an improved image resolution, in particular compared to conventional DOVIDs, and wherein a higher selectivity regarding the presence of a reflective layer only in the embossed structure regions of the surface of the DOVIDs and not in any non-embossed regions can be achieved, again in particular compared to conventional DOVIDs.

[0009] Solution

[0010] This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. , by the subject matter described herein.

[0011] A first subject-matter of the present invention is a thermoplastic polymeric substrate (1 ) bearing on part of at least one of its surfaces at least one embossed diffractive structure, wherein said at least one surface of the substrate (1 ) comprises at least two kinds of surface regions (2) and (3), namely at least one non-embossed region (2) not bearing any embossed structure and at least one embossed region (3) bearing said at least one embossed diffractive structure, wherein the surface of the non-embossed regions (2) is formed by a plane (5), wherein each embossed structure of each embossed region (3) contains at least two kinds of depressions (4) and (4’), both relative to the plane (5), wherein the depressions (4) are located in a plane (7) and the depressions (4’) are located in a plane (7’), wherein plane (7’) is located below plane (7), relative to plane (5), and wherein each embossed structure of each embossed region (3) further contains at least one kind of elevations (8), relative to plane (7), characterized in that each embossed region (3) is entirely contoured by non-embossed regions (2), wherein the depressions (4’) of each embossed region (3) are located adjacent to said contouring non-embossed regions (2), all structural elements, which form the embossed structure of each embossed region (3), including the at least two kinds of depressions (4) and (4’) and the at least one kind of elevations (8), are located below the plane (5), which forms the surface of the non- embossed regions (2), and each embossed region (3) comprises at least one reflective layer (6), which is present at least within the depressions (4) and (4’) and the elevations (8) of each embossed region (3), whereas the non-embossed regions (2), which entirely contour each embossed region (3), do not bear any reflective layer.

[0012] Preferably, plane (5) represents the first plane (5), plane (7) represents the second plane (7), and plane (7’) represents the third plane (7’). Preferably, depressions (4) represent the first depressions and depressions (4’) represent the second depressions (4’).

[0013] A further subject-matter of the present invention is a use of the inventive thermoplastic polymeric substrate (1 ) as diffractive optical variable image device (DOVID), and / or for the manufacture of documents, preferably made at least partially of at least one kind of plastic and / or paper, preferably for the manufacture of passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates, and / or for preventing copying and misuse of documents, preferably made at least partially of at least one kind of plastic and / or paper, preferably of passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates.

[0014] A further subject-matter of the present invention is a method for manufacturing an inventive thermoplastic polymeric substrate (1 ), which comprises at least steps 1 ) to 4) and optionally 1 a), namely

[0015] 1 ) contacting an embossing die or matrix bearing on part of at least one of its surfaces at least one structure, said structure being the negative image of the embossed structure of the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter, with at least one surface of at least one thermoplastic polymeric substrate to obtain a thermoplastic polymeric substrate bearing on part of at least one of its surfaces at least one embossed structure, wherein said at least one surface of the substrate after performance of step 1 ) comprises at least two kinds of surface regions (2) and (3), namely at least one non-embossed region (2) not bearing any embossed structure and at least one embossed region (3) bearing said at least one embossed diffractive structure,

[0016] 1 a) optionally subjecting the surface of the thermoplastic polymeric substrate obtained after step 1 ), which surface contains the at least one embossed structure, to an activation treatment,

[0017] 2) applying a reflective material onto the entire surface of the thermoplastic polymeric substrate obtained after step 1 ) or optional step 1 a), which surface contains the at least one embossed structure, to form a reflective layer thereon,

[0018] 3) contacting the reflective layer formed on the surface of the thermoplastic polymeric substrate with an aqueous alkaline solution or composition, and 4) washing said surface that has been contacted according to step 3) with water and / or mechanically treating the surface that has been contacted according to step 3) to obtain the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter.

[0019] A further subject-matter of the present invention is a target product comprising the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter, which is preferably selected from documents, preferably plastic and / or paper documents such as passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates, wherein said target product preferably is present in form of a multilayer substrate selected from the group consisting of multilayer foils, multilayer labels and multilayer laminates.

[0020] A further subject-matter of the present invention is an embossing die or matrix as defined in connection with step 1 ) of the inventive method bearing on part of at least one of its surfaces at least one structure, said structure being the negative image of the surface of the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter.

[0021] A further subject-matter of the present invention is a use of the inventive embossing die or matrix according for transferring a negative image of its structure onto at least one surface of a thermoplastic polymeric material, preferably by embossing, more preferably according step 1 ) of the inventive method as defined hereinbefore and hereinafter.

[0022] It has been found that the presence of the depressions (4’) of each embossed region (3), which are located adjacent to the contouring non-embossed regions (2), which in turn entirely contour each embossed region (3), has the advantage that said depressions (4’) being located in this position can act as edges for breaking the reflective material used for providing the embossed regions (3) with the reflective layer (6) during preparation of the inventive thermoplastic polymeric substrate (1 ) and to make sure that only the embossed regions (3) stay covered with said reflective layer (6). Breaking can take place along the width of the depressions (4’), which, hence, function as sort of border (boundary) in this respect. It has been further found in this regard, that it is particularly advantageous that all structural elements being present within the embossed structure of each embossed region (3) including the depressions (4) and (4’) and elevations (8), wherein said structural elements form the embossed structure of each embossed region (3), are located below the plane (5), which forms the surface of the non-embossed regions (2), i.e. , that the height of the plane (5), which forms the surface of the non-embossed regions (2) exceeds the maximum height of any structural elements being present within the embossed structure of each embossed region (3) (including, of course, depressions (4) and (4’) and elevations (8)).

[0023] It has been further found that the adhesion of the reflective material used for providing the reflective layer (6) to the depressions (4) and (4’) and elevations (8) of each embossed region (3) of the surface of the inventive thermoplastic polymeric substrate

[0024] (1 ) during its preparation depends on the height of the structural elements present in the embossed regions (3). In each non-embossed region (2) it has been found that adhesion is the lowest. In each embossed region (3), however, the adhesion is better / increased, compared to the adhesion observed in non-embossed regions (2), particularly since the presence of depressions (4) and (4’) and further structural elements forming each embossed region (3) such as elevations (8), relative to a plane (7’), in which the depressions (4’) are located within each embossed region (3), allows the reflective material used for providing the reflective layer (6) to better adhere in this region, i.e., in embossed region (3). For preparing the inventive thermoplastic polymeric substrate (1 ) it has been found that this has the advantage that, after having applied over its whole surface a reflective material used for providing the reflective layer (6), said material can be effectively removed from any non-embossed regions

[0025] (2), e.g., by alkaline treatment followed by washing and / or mechanical treatment, whereas the reflective layer (6) is not removed under these conditions from the embossed regions (3) due to the better adhesion of the reflective layer (6) to the substrate in these regions. Hence, due to a resulting different adhesion of the reflective layer (6) within the different regions (2) and (3), it is possible to achieve a selectivity in this respect and to be able to provide a thermoplastic polymeric substrate (1 ) selectively bearing a reflective layer (6) only in its embossed regions (3), i.e., at least in the depressions (4) and (4’) as well as in the elevations (8) of each embossed region

[0026] (3), but not in its non-embossed regions (2). The depressions (4’) as part of the embossed regions (3) during preparation of the thermoplastic polymeric substrate (1 ) form kind of a border between “low adhesion areas”, i.e. , non-embossed regions (2)) as such, from which the reflective layer (6) can be removed, and “higher adhesion areas”, i.e., embossed regions (3), where the reflective layer (6) is retained.

[0027] Moreover, it has been found that the presence of the depressions (4’) does not negatively affect any of the optical features, e.g., optical effects and / or brightness, of the inventive thermoplastic polymeric substrate (1 ), in particular when used as DOVID, since the depressions (4’) do not take significant part in preparation of the diffractive image as they are too small. It has been in particular found that an increased image resolution of the embossed regions (3) being covered with the reflective layer (6) of up to 5 pm could be achieved, in particular compared to the respective resolutions achieved according to the method disclosed in US 9,969,203 B2, wherein image resolutions of about 15 pm can be achieved.

[0028] As far as the inventive method for preparing the thermoplastic polymeric substrate (1 ) is concerned, it has been found that due to the specific embossed structure present, optimal and balanced conditions could be provided regarding the alkaline treatment and the subsequent mechanical treatment and / or washing step, which allowed to maintain the reflective layer (6) applied in the in its embossed regions (3) but to break and wash off the reflective layer (6) applied in its non-embossed regions (2), however, in a comparably gentle manner under mild conditions, in particular compared to the method disclosed in US 9,969,203 B2.

[0029] The technical effects of being able to selectively form flakes of the reflective layer (6) during the preparation of the thermoplastic polymeric substrate (1 ) in the non- embossed regions (2), and the effect that, in particular due to the specific geometry of the embossed region (3), no flakes break into the embossed regions (3), during the preparation of the thermoplastic polymeric substrate (1 ), in particular when performing step 4), which would lead to an undesired decrease in image resolution of the reflective layer in the embossed regions (3), are advantages compared to the method disclosed in US 9,969,203 B2. It has also been found that the inventive method allows mass production of thermoplastic polymeric substrates (1 ) being suitable as DOVIDs in a very costefficient manner and with a high process productivity.

[0030] Detailed description of the invention

[0031] The invention is exemplarily described in a number of figures.

[0032] Fig. 1 illustrates an exemplary embodiment of the thermoplastic polymeric substrate with the aid of reference signs (1 ) to (8) including (4’) and (7’). In Fig. 1 a thermoplastic polymeric substrate (1 ) is illustrated. One surface of the substrate (1 ) comprises both non-embossed regions (2) and embossed regions (3) comprising an embossed structure, wherein each embossed region (3) is contoured by non-embossed regions (2). The surface of the non-embossed regions (2) is formed by a plane (5). Each embossed structure of each embossed region (3) contains at least two kinds of depressions (4) and (4’), both relative to the plane (5). The depressions (4) are located in a plane (7) and the depressions (4’) are located in a plane (7’). The difference in depths between plane (5) and plane (7’) is referred to as hi in Fig. 1. All structural elements being present within the embossed structure of each embossed region (3) including the at least two kinds of depressions (4) and (4’) and including elevations (8), relative to the plane (7), in which the depressions (4) are located within each embossed region (3), are located below the plane (5). The difference in depths between elevations (8) and plane (7’) is referred to as h2 in Fig. 1. Each embossed region (3) comprises at least one reflective layer (6), which is present at least within the depressions (4) and (4’) and also on the elevations (8) of each embossed region (3), whereas the non- embossed regions (2), which contour each embossed region (3), do not bear any reflective layer.

[0033] Fig. 2 illustrates the exemplary embodiment of the thermoplastic polymeric substrate of Fig. 1 with the exception that the reflective layer (6) has been omitted for the sake of readability and that only reference signs (1 ) to (4), (4’) and (8) have been indicated.

[0034] Fig. 3 illustrates an exemplary embodiment of the surface (11 ) of an embossing die or matrix, which can be used for an embossing step 1 ) according to the present invention and which comprises the negative image of the structure embossed in at least one surface of the thermoplastic polymeric substrate. The surface (11 ) comprises nonstructured regions (12) and structured regions (13). Each structured region (13) comprises one or more depressions (15) and one or more elevations (14), both relative to a plane (16), in which the depressions (15) are located within each structured region (13). The depth of the depressions (15) (or the height of the elevations (14)) is referred to as hi 1 in Fig. 3 The surface of the non-structured regions (12) is formed by a plane (17), which is positioned below plane (16). The difference in depth between planes (16) and (17) is referred to as hi2 in Fig. 3. Each structured region (13) further comprises a contouring elevation (18), which entirely contours each structured region (13). The height of the contouring elevations (18) exceeds hn by the height indicated as h in Fig. 3 The contouring elevations (18) in Fig. 3 are protrusions having a rectangular profile. Fig. 3 further comprises a birds-eye view of the structured regions (13) of the surface (11 ) of the embossing die or matrix, illustrated therein as “DH”. The elevations (14), depressions (15) and the contouring elevation (18) are indicated.

[0035] The term “comprising” in the sense of the present invention, in connection for example with the inventive method and / or the inventive thermoplastic polymeric material, preferably has the meaning of “consisting of”.

[0036] Thermoplastic polymeric substrate (1 )

[0037] A first subject-matter of the present invention is a thermoplastic polymeric substrate (1 ) bearing on part of at least one of its surfaces at least one embossed diffractive structure, wherein said at least one surface of the substrate (1 ) comprises at least two kinds of surface regions (2) and (3), namely at least one non-embossed region (2) not bearing any embossed structure and at least one embossed region (3) bearing said at least one embossed diffractive structure, wherein the surface of the non-embossed regions (2) is formed by a plane (5), wherein each embossed structure of each embossed region (3) contains at least two kinds of depressions (4) and (4’), both relative to the plane (5), wherein the depressions (4) are located in a plane (7) and the depressions (4’) are located in a plane (7’), wherein plane (7’) is located below plane (7), relative to plane (5), and wherein each embossed structure of each embossed region (3) further contains at least one kind of elevations (8), relative to plane (7), characterized in that each embossed region (3) is entirely contoured by non-embossed regions (2), wherein the depressions (4’) of each embossed region (3) are located adjacent to said contouring non-embossed regions (2), all structural elements, which form the embossed structure of each embossed region (3), including the at least two kinds of depressions (4) and (4’) and the at least one kind of elevations (8) are located below the plane (5), which forms the surface of the non-embossed regions (2), each embossed region (3) comprises at least one reflective layer (6), which is present at least within the depressions (4) and (4’) and the elevations (8) of each embossed region (3), whereas the non-embossed regions (2), which entirely contour each embossed region (3) (also referred to in the sense of the present invention as contouring non-embossed regions (2)), do not bear any reflective layer.

[0038] Preferably, the thermoplastic polymeric substrate (1 ) bears on part of precisely one of its surfaces the at least one embossed diffractive structure.

[0039] Preferably, thermoplastic polymeric substrate (1 ) has a uniform thickness, more preferably over its entire size. Preferably, the thermoplastic polymeric substrate (1 ) has a flat geometry such as in case of a foil or sheet, and, particularly, is not of any curved shape. Preferably, the thermoplastic polymeric substrate (1 ) has a thickness, which is in a range of from 5 pm to 250 pm, more preferably of from 10 to 150 pm.

[0040] Preferably, the thermoplastic polymeric substrate (1 ) is suitable to be used as diffractive optical variable image device (DOVID) due to the presence of the at least one embossed diffractive structure, which preferably is a holographic structure, on part of at least one of its surfaces.

[0041] The term “diffractive optical variable image device (DOVID)” is a term known to a person skilled in the art, e.g., from PRADO (Public Register of Authentic Travel and Identity Documents Online), Glossary, “Technical elements related to security features and to security documents in general”, which has been issued by the Council of the Ell, General Secretariat, v. 12344 / 2022.

[0042] A DOVID contains structural elements such as gratings, which are present in the surface of a suitable substrate, e.g., in the form of surface reliefs, which are able to modify light by diffraction, which leads to generation of different optical effects such as two- or three-dimensional (2D or 3D) images and / or kinematic and / or color changing effects and / or brightness effects. A hologram is an example of a DOVID. A number of effects are possible, e.g., 2D holograms with structural and / or color changes, 3D holograms with images, holograms with kinematic effects, etc.

[0043] Preferably, the at least one embossed diffractive structure is an embossed diffractive relief structure, in particular a microrelief structure. “Relief structure” in the sense of the present invention preferably means that at least both depressions such as depressions (4) and (4’) and at least elevations such as elevations (8) are present as structural elements forming the relief structure, which preferably lead to the formation of gratings in the embossed regions (3). Microrelief structure” in the sense of the present invention preferably means that the depth of the depressions and the heights of any elevations present in the relief structure does not exceed 1000 nm, preferably does not exceed 900 nm, 800 nm, 750 nm or 500 nm.

[0044] The contouring non-embossed regions (2), preferably all present non-embossed regions (2), of the at least one surface of the thermoplastic polymeric substrate (1 ) do not bear or essentially do not bear any reflective layer.

[0045] It is evident that the non-embossed regions (2) do not comprise any embossed structures at all. Preferably, the non-embossed regions (2) do not comprise any structures incorporated onto their surfaces by any other techniques besides embossing, more preferably do not comprise any artificially induced structures at all. The non-embossed regions (2) may, however, of course, e.g., exhibit a natural surface roughness.

[0046] Preferably, each of the depressions (4’) of each embossed region (3) has a width of at least 100 nm, more preferably of at least 200 nm, still more preferably in a range of from 200 to 500 nm.

[0047] Preferably, each of the depressions (4’) of has a rectangular profile.

[0048] Preferably, the height hi of the plane (5), which forms the surface of the non-embossed regions (2), exceeds the maximum height h2 of any structural elements that are present in each embossed region (3) including the elevations (8) relative to a plane (7’), in which the depressions (4’) are located within each embossed region (3), more preferably by at least 25 nm, still more preferably by at least 35 nm, even more preferably by at least 50 nm, wherein both heights hi and h2 are in each case calculated from the plane (7’), in which the depressions (4’) are located within each embossed region (3).

[0049] Preferably, the maximum height h2 of any structural elements that are present in each embossed region (3) including the elevations (8) relative to a plane (7’), in which the depressions (4’) are located within each embossed region (3), is in a range of from 50 nm to <1 000 nm, preferably of from 75 nm to 750 nm, more preferably of from 100 nm to 500 nm, wherein height h2 is calculated from a plane (7’), in which the depressions (4’) are located within each embossed region (3).

[0050] Preferably, the boundaries of each embossed region (3), which are formed by the contouring non-embossed regions (2), coincide, preferably exactly coincide, with the boundaries of the reflective layer (6) being present at least within the depressions (4) and (4’) and elevations (8) of each embossed region (3), more preferably being present within or on the structural elements of each embossed region (3). Preferably, the tolerance is defined by the width of each of the depressions (4’), more preferably in his regard is not more than 0.5 pm

[0051] Each embossed region (3) comprises at least one reflective layer (6), which is present at least within the depressions (4) and (4’) of each embossed region (3) and also on any further structural elements present including the elevations (8) being present in the embossed region (3). The reflective layer (6) preferably is obtainable from application of at least one preferably inorganic reflective material, more preferably being selected from the group consisting of zinc sulfide and titanium dioxide, has a layer thickness in a range of from 20 to 200 nm, more preferably of from 25 to 150 nm, even more preferably of from 30 to 100 nm. Layer thickness is determined by spectral interferometry. The term “reflective” in the sense of the present invention in connection with the reflective layer (6) is understood by a person skilled in the art. It preferably means that layer (6) is able to reflect the light of the visual spectral band from 380 nm to 750 nm.

[0052] The reflective layer (6) preferably is a layer having a high refractive index (HRI) and is preferably obtainable from application of at least one material having a high refractive index (HRI material). The term “high” in this context preferably means that the refractive index of the reflective layer (6) is higher than the refractive index of the thermoplastic material of substrate (1 ), more preferably is >1.50, even more preferably is >1.80. For example, reflective layers formed from ZnS or TiCh have refractive indices of about 2.40 to 2.50.

[0053] Preferably, an image resolution of the reflective layer (6) of up to 5 pm is achieved.

[0054] The non-embossed regions (2), which entirely contour each embossed region (3), preferably all non-embossed regions (2) present, do not bear any reflective layer.

[0055] Preferably, the thermoplastic polymeric material of the thermoplastic polymeric substrate (1 ) is selected from the group consisting of polyesters, polycarbonates, polyamides, polyurethanes, polyureas, polyvinyl chlorides, poly(meth)acrylates, (meth)acrylic copolymers, cellulose polymers and / or derivatives, rosin polymers and / or derivatives, and mixtures thereof. Polyesters are polyesters, which are not polycarbonates.

[0056] Preferably, the thermoplastic polymeric substrate (1 ) is present in the form of a foil, sheet, label, or is part of a multilayer substrate, wherein the multilayer substrate preferably is selected from the group consisting of multilayer foils including hot- stamping and cold-stamping foils, preferably hot-stamping foils, multilayer labels and multilayer laminates, the multilayer substrates preferably comprising a base substrate, optionally a release layer, in particular in case of hot-stamping foils and labels, the thermoplastic polymeric substrate (1 ), and an adhesion layer including a temperature activated adhesion layer, in particular in case of hot-stamping foils, and a pressure activated adhesion layer, in particular in case of labels. Method of manufacturing the thermoplastic polymeric substrate (1 )

[0057] A further subject-matter of the present invention is a method for manufacturing an inventive thermoplastic polymeric substrate (1 ), which comprises at least steps 1 ) to 4) and optionally 1 a). The method may comprise further steps that are performed prior to, after, or between any of the aforementioned steps.

[0058] All preferred embodiments described hereinbefore in connection with the inventive thermoplastic polymeric material (1 ) are also preferred embodiments in relation to the aforementioned inventive method of the invention.

[0059] Step 1) - embossing step

[0060] In step 1 ) an embossing die or matrix bearing on part of at least one of its surfaces at least one structure, said structure being the negative image of the embossed structure of the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter, is contacted with at least one surface of at least one thermoplastic polymeric substrate to obtain a thermoplastic polymeric substrate bearing on part of at least one of its surfaces at least one embossed structure, wherein said at least one surface of the substrate after performance of step 1 ) comprises at least two kinds of surface regions (2) and (3), namely at least one non-embossed region (2) not bearing any embossed structure and at least one embossed region (3) bearing said at least one embossed diffractive structure.

[0061] Preferably, the contacting in step 1 ) comprises pressing the preferably heated die or matrix into at least one surface of the thermoplastic polymeric material to incorporate a negative image of the structure of the die or matrix into the at least one surface of the thermoplastic polymeric material. The die or matrix, preferably die, is preferably part of an embossing tool. The die or matrix can, e.g., be made of at least one kind of metal and / or metal alloy. An exemplary die is a shim made of at least one metal and / or alloy thereof. Preferred is nickel, but other metals can be used as well such as Cu, Cr, steel, etc. The embossing step 1 ) can be performed by conventional techniques and standard devices known to a person skilled in the art.

[0062] The temperature and pressure used for embossing step 1 ) depend on the kind of thermoplastic polymeric material used for replication of structure of the die or matrix. The temperature range for heating the die or matrix can, e.g., be in a range of from 100 °C to 180 °C.

[0063] Step 1 ) of the method of the invention is preferably performed in a continuous manner.

[0064] Optional step 1a) - activation

[0065] In optional step 1 a) the surface of the thermoplastic polymeric substrate obtained after step 1 ), which surface contains the at least one embossed structure, is optionally subjected to an activation treatment, in particular to clean and activate the surface.

[0066] The activation treatment preferably includes at least one of a corona (discharge) treatment and a treatment by means of UV radiation. Most preferred is a corona treatment. In case of a corona treatment preferably a current in a range of 5 to 20 A is applied. The speed of movement of the substrate, in particular when it is a foil, preferably is in a range of from 5 to 20 m / min during optional step 1 a).

[0067] Optional step 1 a) preferably and advantageously leads to predominant formation of the crystalline form of the reflective layer in subsequent step 2), in particular under vacuum evaporation. Crystalline forms contain greater mechanical stresses than amorphous forms, which in turn facilitates detachment of flakes of the reflective layer in the non-embossed regions (2) in subsequent steps 3) and 4). This further allows to decrease the pH level of the aqueous alkaline solution or composition used and applied in step 3) and its temperature.

[0068] Step 2) - reflective layer formation

[0069] In step 2) a reflective material is applied onto the entire surface of the thermoplastic polymeric substrate obtained after step 1 ) or after optional step 1 a), namely onto the surface, which contains the at least one embossed structure, to form a reflective layer thereon.

[0070] Step 2) can be performed by conventional techniques and standard devices known to a person skilled in the art. Preferred are vapor deposition techniques and sputtering techniques.

[0071] Step 3) - alkaline treatment step

[0072] In step 3) the reflective layer formed on the surface of the thermoplastic polymeric substrate is contacted with an aqueous alkaline solution or composition. Step 3) (in combination with subsequent step 4)) is particularly performed in order to remove the reflective layer formed in step 2) on the entire surface of the substrate from the nonembossed regions (2) including the contouring non-embossed regions (2).

[0073] Preferably, the aqueous alkaline solution or composition used in step 3) has a pH value in a range of from >7.0 to 13.0, more preferably of from >7.0 to 12.5, still more preferably of from 8.0 to 12.0, even more preferably of from 9.0 to 11 .5.

[0074] Preferably, the aqueous alkaline solution or composition used in step 3) has a temperature in a range of from >30 to <100 °C, more preferably of from 35 to 90 °C, even more preferably of from 40 to 80 °C.

[0075] Preferably, the duration of step 3) is in a range of from 1 second to 2 minutes, more preferably of from 1 second to 1 minute, still more preferably of from 1 second to 30 seconds or to 25 seconds, even more preferably of from 2 seconds to 20 seconds.

[0076] Preferably, contacting in step 3) comprises dipping of the substrate into the alkaline solution or composition. Other techniques such as brushing or spraying are, however, also possible.

[0077] Preferably, the aqueous alkaline solution or composition comprises at least one suitable alkali and / or earth alkali salt, more preferably at least one hydroxide and / or carbonate as alkaline agent. Examples are NaOH, KOH, Na2CO3, and / or K22CO3. Other suitable and preferably organic alkali and / or earth alkali salts can be used as well such as Na2EDTA and / or K2EDTA.

[0078] Preferably, by performing step 3) at least a partial formation of flakes of the reflective layer selectively in the non-embossed regions (2) and / or formation of cracks in the reflective layer selectively in the non-embossed regions (2) takes place. The alkaline solution or composition can penetrate through any cracks formed in the reflective layer and can reach the reflective layer / thermoplastic polymer boundary. The presence of the alkali agent at this position can lead to an increase in volume, which can result in lifting the reflective layer near the crack. Due to mechanical stress flakes can be formed. In the embossed regions (3), said mechanical stress is significantly lower and flake formation takes significantly more time compared to the non-embossed regions

[0079] (2), since the surface in regions (3) is much rougher due to the presence of the embossed structure, and the stress be distributed over a larger surface area more evenly. In addition, the layer thickness of the reflective layer in the embossed regions

[0080] (3) preferably is lower than in the non-embossed regions.

[0081] Step 4) - washing and / or mechanical rubbing step

[0082] In step 4) washing of the surface that has been contacted according to step 3) with water and / or mechanically treating the surface that has been contacted according to step 3) to obtain the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter is performed.

[0083] Preferably, washing with water and mechanical treatment are both performed in step 4), either simultaneously or one after another, preferably simultaneously.

[0084] The temperature of the water used for washing preferably is lower than the temperature of the aqueous alkaline solution or composition used in step 3), more preferably is in a range of from 18 to 30 °C, still more preferably is in a range of from 20 to 25 °C. A change in the temperature, comparison between the composition or solution used in step 3) and the water used in step 4), advantageously creates (additional) mechanical stress in the reflective layer and promotes the separation and flake formation of the reflective layer in the non-embossed regions (2). The duration of step 4) preferably is in a range of from 5 seconds to 2 minutes, more preferably of from 10 seconds to 1 minute, even more preferably of from 15 seconds to 30 seconds or to 25 seconds.

[0085] Preferably, the mechanical treatment comprises a mechanical rubbing, preferably with a roll such as a textile covered roll.

[0086] Preferably, by performing step 4) detaches flakes originating from the reflective layer in the non-embossed regions (2) are removed, in particular since all structural elements being present within the embossed structure of each embossed region (3) are located below the plane (5), which forms the surface of the non-embossed regions (2). Hence, the non-embossed regions (2) are the regions, which represent the most outwardly protruding regions of the surface of the substrate and, therefore, experience more of the mechanical impact during washing than the embossed regions (3). Since the adhesion of the reflective layer in the embossed regions (3) is higher than the adhesion in the non-embossed regions, it is possible to (i) selectively dissolve / form flakes of the reflective layer in the non-embossed regions (2). Further, (ii) due to the specific geometry of the surface, it can be advantageously achieved that no flakes break into the embossed regions (3), which would lead to decrease in resolution of the reflective layer.

[0087] Optional step 0) - preparation of an embossing die or matrix used in step 1)

[0088] Prior to step 1 ) the method optionally comprises at least one step 0) for preparation of the embossing die or matrix used in step 1 ).

[0089] Step 0) can be performed by conventional techniques and standard devices known to a person skilled in the art, and preferably includes several sub-steps.

[0090] The die or matrix is preferably part of an embossing tool. The die or matrix can, e.g., be made of at least one kind of metal and / or metal alloy. An exemplary die is a shim made of at least one metal and / or alloy thereof. Preferred is nickel, but other metals can be used as well such as Cu, Cr, steel, etc. Preferably, after a structure such as relief structure, in particular hologram, has been originated in a first sub-step, it is formed onto the surface of a suitable polymer resist material in a second sub-step by suitable techniques, preferably by lithography techniques such as e-beam lithography. In a third sub-step, this structure is then copied to the die or matrix by a suitable technique, preferably by an electroforming method.

[0091] The resulting die or matrix can be used as embossing die in step 1 ) and contains the negative image of the embossed structure of the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter.

[0092] Use of the thermoplastic polymeric substrate (1 )

[0093] A further subject-matter of the present invention is a use of the inventive thermoplastic polymeric substrate (1 ) as diffractive optical variable image device (DOVID), and / or for the manufacture of documents, preferably made at least partially of at least one kind of plastic and / or paper, preferably for the manufacture of passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates, and / or for preventing copying and misuse of documents, preferably made at least partially of at least one kind of plastic and / or paper, preferably of passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates.

[0094] All preferred embodiments described hereinbefore in connection with the inventive thermoplastic polymeric material (1 ) and the inventive method are also preferred embodiments in relation to the aforementioned inventive use.

[0095] Target products obtainable from the thermoplastic polymeric substrate (1 )

[0096] A further subject-matter of the present invention is a target product obtainable from or comprising the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter, which is preferably selected from documents, preferably plastic and / or paper documents such as passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates, wherein said target product preferably is present in form of a multilayer substrate selected from the group consisting of multilayer foils, multilayer labels and multilayer laminates.

[0097] All preferred embodiments described hereinbefore in connection with the inventive thermoplastic polymeric material (1 ), the inventive method and the inventive use are also preferred embodiments in relation to the aforementioned inventive target products.

[0098] Embossing die or matrix

[0099] A further subject-matter of the present invention is an embossing die or matrix as defined in connection with step 1 ) of the inventive method bearing on part of at least one of its surfaces at least one structure, said structure being the negative image of the surface including the embossed structure of the inventive thermoplastic polymeric substrate (1 ) as defined hereinbefore and hereinafter.

[0100] All preferred embodiments described hereinbefore in connection with the inventive thermoplastic polymeric material (1 ), the inventive method, the inventive use and the inventive target products are also preferred embodiments in relation to the aforementioned inventive embossing die or matrix.

[0101] An inventive die has already been described hereinbefore in connection with step 1 ) of the inventive method. An inventive matrix preferably is a resist material such as a polymer resist material described hereinbefore in connection with optional step 0) of the inventive method.

[0102] An embodiment of the surface (11 ) of the embossing die or matrix has been illustrated in Fig. 3.

[0103] Preferably, the surface (11 ) of the embossing die or matrix comprises non-structured regions (12) and structured regions (13). Each structured region (13) preferably comprises one or more depressions (15) and one or more elevations (14), both relative to a plane (16), in which the depressions (15) are located within each structured region (13). The depth of the depressions (15) (or the height of the elevations (14)) is referred to as hi 1 in Fig. 3 The surface of the non-structured regions (12) is preferably formed by a plane (17), which is positioned below plane (16). The difference in depth between planes (16) and (17) is referred to as hi2 in Fig. 3. Each structured region (13) preferably further comprises a contouring elevation (18), which preferably entirely contours each structured region (13). The height of the contouring elevations (18) preferably exceeds hi 1 by the height indicated as hi3 in Fig. 3. The contouring elevations (18) preferably are protrusions having a rectangular profile.

[0104] Use of the embossing die or matrix

[0105] A further subject-matter of the present invention is a use of the inventive embossing die or matrix according for transferring a negative image of its structure onto at least one surface of a thermoplastic polymeric material, preferably by embossing, more preferably according step 1 ) of the inventive method as defined hereinbefore and hereinafter.

[0106] All preferred embodiments described hereinbefore in connection with the inventive thermoplastic polymeric material (1 ), the inventive method, the inventive use, the inventive target products and the inventive embossing die or matrix are also preferred embodiments in relation to the aforementioned use of the embossing die or matrix.

[0107] EXAMPLES

[0108] The following examples further illustrate the invention but are not to be construed as limiting its scope.

[0109] 1. Manufacture of a diffractive optical variable image device (DOVID) and use thereof

[0110] 1.1 Preparation of a holographic structure and transfer thereof to an embossing die

[0111] A holographic structure was prepared on a polymer resist material. The structure comprised guilloches and microtexts as well as singular lines. The guilloches were consisting of about 5 pm thick repeated lines having a space of about 5 pm between each line. The microtexts had a minimal line thickness of 5 pm. The singular lines were placed more than about 100 pm apart from the guilloches and microtexts. The relief structure was formed onto the polymer resist material by e-beam lithography technique. Exposure took place on a plate, which was covered with the resist material (positive e-beam resist). The lines of the guilloches and microtexts were hatched with diffractive gratings with periods in a range from 0.8 to 1.2 pm and different directions of the grooves to obtain optical effects in the DOVID to be prepared. Each grating section was contoured with a line having a thickness of about 0.5 pm. Two kinds of grooves of the gratings were prepared with depressions having depths of 0.25 pm and 0.20 pm, respectively. The depth of the contouring line was about 0.3 pm.

[0112] After development of the plate the holographic structure present on the resist material was obtained. This relief structure was then copied by an electroforming method to a shim made of nickel to be used as an embossing die.

[0113] 1.2 Embossing a thermoplastic material by making use of the die to prepare a DOVID The nickel shim obtained by the method steps outlined in item 1.1 was then used for embossing a thermoplastic polycarbonate material in order to obtain a material having a negative image of the structure of the embossing die on its surface. For this, the nickel shim was heated and then pressed onto a surface of the thermoplastic polycarbonate material. Afterwards, the surface of the polycarbonate material bearing the negative image of the structure of the embossing die on its surface was subjected to a corona treatment and then covered with a layer of zinc sulfide (ZnS) having a layer thickness of 50 nm by vacuum evaporation in order to form a reflective layer on its surface.

[0114] Then, the polycarbonate material including its surface bearing the embossed structure was dipped into an aqueous alkaline solution (KOH) having a pH of about 11 and a temperature of 60 °C for about 10 seconds (s) followed by mechanically rubbing its surface with a textile roll in flowing water having a temperature of about 20 °C for 20 s. By this treatment the ZnS layer was removed from any of the non-embossed regions of the surface of the polycarbonate material, but retained in the embossed regions of the material with perfect registration and minimal image resolution of the reflective layer of 5 pm. An inventive DOVID was obtained this manner.

[0115] 1.3 Use of the DOVID for preparing and securing of plastic documents such identity (ID) cards and passports

[0116] The DOVID obtained by the method steps outlined in item 1.2 was then laminated with further polycarbonate layers to form the body of an ID card or a passport.

Claims

CLAIMS1. A thermoplastic polymeric substrate (1 ) bearing on part of at least one of its surfaces at least one embossed diffractive structure, wherein said at least one surface of the substrate (1 ) comprises at least two kinds of surface regions (2) and (3), namely at least one non-embossed region (2) not bearing any embossed structure and at least one embossed region (3) bearing said at least one embossed diffractive structure, wherein the surface of the non-embossed regions (2) is formed by a first plane (5), wherein each embossed structure of each embossed region (3) contains at least two kinds of depressions, the first depressions (4) and the second depressions (4’), both relative to the first plane (5), wherein the first depressions (4) are located in a second plane (7) and the second depressions (4’) are located in a third plane (7’), wherein the third plane (7’) is located below the second plane (7), relative to the first plane (5), and wherein each embossed structure of each embossed region (3) further contains at least one kind of elevations (8), relative to the second plane (7), characterized in that each embossed region (3) is entirely contoured by non-embossed regions (2), wherein the second depressions (4’) of each embossed region (3) are located adjacent to said contouring non-embossed regions (2), all structural elements, which form the embossed structure of each embossed region (3), including the at least two kinds of depressions, the first depressions (4) and the second depressions (4’), and the at least one kind of elevations (8) are located below the first plane (5), which forms the surface of the non- embossed regions (2), andeach embossed region (3) comprises at least one reflective layer (6), which is present at least within the first depressions (4) and the second depressions (4’) and the elevations (8) of each embossed region (3), whereas the non-embossed regions (2), which entirely contour each embossed region (3), do not bear any reflective layer.

2. The thermoplastic polymeric substrate (1 ) according to claim 1 , characterized in that the height hi of the first plane (5), which forms the surface of the nonembossed regions (2), exceeds the maximum height h2 of any structural elements that are present in each embossed region (3) including the elevations (8) relative to the third plane (7’), in which the second depressions (4’) are located within each embossed region (3), preferably by at least 25 nm, more preferably by at least 35 nm, even more preferably by at least 50 nm, wherein both heights hi and h2 are in each case calculated from the third plane (7’), in which the second depressions (4’) are located within each embossed region (3).

3. The thermoplastic polymeric substrate (1 ) according to claim 1 or 2, characterized in that the maximum height h2 of any structural elements that are present in each embossed region (3) including the elevations (8) relative to the third plane (7’), in which the second depressions (4’) are located within each embossed region (3), is in a range of from 50 nm to <1 000 nm, preferably of from 75 nm to 750 nm, more preferably of from 100 nm to 500 nm, wherein height h2 is calculated from the third plane (7’), in which the second depressions (4’) are located within each embossed region (3).

4. The thermoplastic polymeric substrate (1 ) according to one or more of the preceding claims, characterized in that each of the second depressions (4’) of each embossed region (3) has a width of at least 100 nm, preferably of at least 200 nm, more preferably in a range of from 200 to 500 nm, wherein each of said second depressions (4’) preferably has a rectangular profile.

5. The thermoplastic polymeric substrate (1 ) according to one or more of the preceding claims, characterized in that it is suitable to be used as diffractiveoptical variable image device (DOVID) due to the presence of the at least one embossed diffractive structure, which preferably is a holographic structure, on part of at least one of its surfaces.

6. The thermoplastic polymeric substrate (1 ) according to one or more of the preceding claims, characterized in that the reflective layer (6) is obtainable from application of at least one preferably inorganic reflective material being preferably selected from the group consisting of zinc sulfide and titanium dioxide, has a layer thickness in a range of from 20 to 200 nm, preferably of from 25 to 150 nm, more preferably of from 30 to 100 nm.

7. The thermoplastic polymeric substrate (1 ) according to one or more of the preceding claims, characterized in that the thermoplastic polymeric material of the thermoplastic polymeric substrate (1 ) is selected from the group consisting of polyesters, polycarbonates, polyamides, polyurethanes, polyureas, polyvinyl chlorides, poly(meth)acrylates, (meth)acrylic copolymers, cellulose polymers and / or derivatives, rosin polymers and / or derivatives, and mixtures thereof.

8. The thermoplastic polymeric substrate (1 ) according to one or more of the preceding claims, characterized in that it is present in the form of a foil, sheet, label, or is part of a multilayer substrate, wherein the multilayer substrate preferably is selected from the group consisting of multilayer foils including hot- stamping and cold-stamping foils, preferably hot-stamping foils, multilayer labels and multilayer laminates, the multilayer substrates preferably comprising a base substrate, optionally a release layer, in particular in case of hot-stamping foils and labels, the thermoplastic polymeric substrate (1 ), and an adhesion layer including a temperature activated adhesion layer, in particular in case of hot-stamping foils, and a pressure activated adhesion layer, in particular in case of labels.

9. A use of the thermoplastic polymeric substrate (1 ) according to one or more of the preceding claims as diffractive optical variable image device (DOVID), and / orfor the manufacture of documents, preferably made at least partially of at least one kind of plastic and / or paper, preferably for the manufacture of passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates, and / or for preventing copying and misuse of documents, preferably made at least partially of at least one kind of plastic and / or paper, preferably of passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates.

10. A method for manufacturing a thermoplastic polymeric substrate (1 ) according to one or more of claims 1 to 8, which comprises at least steps 1 ) to 4) and optionally 1 a), namely1 ) contacting an embossing die or matrix bearing on part of at least one of its surfaces at least one structure, said structure being the negative image of the embossed structure of the thermoplastic polymeric substrate (1 ) as defined in one or more of claims 1 to 4, with at least one surface of at least one thermoplastic polymeric substrate to obtain a thermoplastic polymeric substrate bearing on part of at least one of its surfaces at least one embossed structure, wherein said at least one surface of the substrate after performance of step 1 ) comprises the at least two kinds of surface regions (2) and (3), namely at least one non-embossed region (2) not bearing any embossed structure and at least one embossed region (3) bearing said at least one embossed diffractive structure,1 a) optionally subjecting the surface of the thermoplastic polymeric substrate obtained after step 1 ), which surface contains the at least one embossed structure, to an activation treatment,2) applying a reflective material onto the entire surface of the thermoplastic polymeric substrate obtained after step 1 ) or optional step 1a), which surface contains the at least one embossed structure, to form a reflective layer thereon,3) contacting the reflective layer formed on the surface of the thermoplastic polymeric substrate with an aqueous alkaline solution or composition, and4) washing said surface that has been contacted according to step 3) with water and / or mechanically treating the surface that has been contacted according to step 3) to obtain the thermoplastic polymeric substrate (1 ) according to one or more of claims 1 to 8.11 . The method according to claim 10, characterized in that the aqueous alkaline solution or composition used in step 3) has a pH value in a range of from >7.0 to 13.0, preferably of from >7.0 to 12.5, more preferably of from 8.0 to 12.0, even more preferably of from 9.0 to 11 .5, and / or in that the aqueous alkaline solution or composition used in step 3) has a temperature in a range of from >30 to <100 °C, preferably of from 35 to 90 °C, more preferably of from 40 to 80 °C, and / or in that duration of step 3) is in a range of from 1 second to 2 minutes, preferably of from 1 second to 1 minute, more preferably of from 1 second to 30 seconds or to 25 seconds, even more preferably of from 2 seconds to 20 seconds.

12. The method according to claim 10 or 11 , characterized in that washing with water and mechanical treatment are both performed in step 4), either simultaneously or one after another, preferably simultaneously, wherein the temperature of the water used for washing preferably is lower than the temperature of the aqueous alkaline solution or composition used in step 3), more preferably is in a range of from 18 to 30 °C, still more preferably is in a range of from 20 to 25 °C, wherein the duration of step 4) preferably is in a range of from 5 seconds to 2 minutes, more preferably of from 10 seconds to 1 minute, even more preferably of from 15 seconds to 30 seconds or to 25 seconds, andwherein the mechanical treatment preferably comprises a mechanical rubbing, preferably with a textile covered roll.

13. A target product comprising the thermoplastic polymeric substrate (1 ) according to one or more of claims 1 to 8, which is preferably selected from documents, preferably plastic and / or paper documents such as passports, identity cards, money cards including credit cards, tax stamps, bank cheques, vignettes, tickets and certificates, wherein said target product preferably is present in form of a multilayer substrate selected from the group consisting of multilayer foils, multilayer labels and multilayer laminates.

14. An embossing die or matrix as defined in connection with step 1 ) of claim 10 bearing on part of at least one of its surfaces at least one structure, said structure being the negative image of the surface of the thermoplastic polymeric substrate (1 ) as defined in one or more of claims 1 to 4.

15. A use of the embossing die or matrix according to claim 14 for transferring a negative image of its structure onto at least one surface of a thermoplastic polymeric material, preferably by embossing, more preferably according step 1 ) of the method as defined in one or more of claims 10 to 12.

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