EP3403844A1 - Method for producing a security element having a metallized relief area and associated security element - Google Patents

Abstract

The invention relates to a method for producing a security element having a metallized relief region (22, 24) and a narrow, demetallised flat region (28) which has been adapted for this purpose, in which
R) a carrier (40, 42) is provided with a relief structure (14) with elevations and depressions (30) such that a relief region (32, 34) and a narrow flat region (38) adapted for this purpose are formed without elevations and depressions, wherein the flat region (38) separates at least two partial regions (32, 34) of the relief region from one another,
W) for the carrier (40, 42) in the relief region (32, 34) and in the flat region (38) a wash ink layer (46, 48) of small layer thickness is provided and applied to the carrier,
M) the carrier (40, 42) provided with wash ink (44, 46, 48) is metallized at least in the relief region (32, 34) and flat region (38), and
A) the metallized carrier (40, 42, 50) is subjected to a solvent washing step, wherein in the flat region (38) the wash ink (48) is removed together with the overlying metallization (50) and the flat region (38) is thereby demetallised while the metallization (50) remains in the relief region (32, 34) on the carrier (40, 42) and forms the metallized relief region (22, 24).

Description

The invention relates to a method for producing a security element with a metallized relief region. The invention also relates to a security element which can be produced by means of such a method for securing valuables.

Data carriers, such as valuables or identity documents, but also other valuables, such as branded articles, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data medium and / or serve as protection against unauthorized reproduction. The security elements can for example be embedded in a banknote in the form of metallized films or arranged over an opaque area, a window area or a continuous opening of the data carrier.

In addition to metallized subregions, the metallized foils also contain demetallized subregions which serve to depict a desired motif and / or additional authenticity protection of the data carrier. These metal-free areas are usually produced by means of a washing process, as described for example in the publication WO 99/13157 is described. In this case, a translucent carrier film is printed using a printing ink with a high pigment content with a desired pattern. Due to the high pigment content, the ink forms a porous, sublime color after drying. On the printed carrier film, a thin metallic cover layer is then formed, which only partially covers the color body in the region of the paint application because of its large surface area and the porous structure. The paint application and the Overlying metallic cover layer can then be removed by washing with a suitable solvent, so that in the cover layer in the originally printed areas of the carrier film recesses are generated.

However, the achievable with such a washing process resolution is only at a line thickness of about 100 to 200 microns. For the production of finer structures, other methods, such as laser demetallization, have to be resorted to, but this involves considerable additional time and expense.

Based on this, the object of the invention is to avoid the disadvantages of the prior art and, in particular, to provide a method for producing a security element with which filigree demetallization areas in a metallized relief area can be produced in a simple manner.

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

• R) ein Träger so mit einer Reliefstruktur mit Erhebungen und Vertiefungen versehen wird, dass ein Reliefbereich und ein dazu gepasserter schmaler Flachbereich ohne Erhebungen und Vertiefungen gebildet werden, wobei der Flachbereich zumindest zwei Teilbereiche des Reliefbereichs voneinander trennt,
• W) für den Träger im Reliefbereich und im Flachbereich eine Waschfarbenschicht geringer Schichtdicke bereitgestellt und auf den Träger aufgebracht wird,
• M) der mit Waschfarbe versehene Träger zumindest im Reliefbereich und Flachbereich metallisiert wird, und
• A) der metallisierte Träger einem Auswaschschritt mit einem Lösungsmittel unterworfen wird, bei dem in dem Flachbereich die Waschfarbe zusammen mit der darüberliegenden Metallisierung entfernt und der Flachbereich dadurch demetallisiert wird, während die Metallisierung im Reliefbereich auf dem Träger verbleibt und den metallisierten Reliefbereich bildet.

According to the invention, it is provided in a method for producing a security element with a metallized relief area and a narrow, demetallized flat area which is matched thereto

• R) a carrier is provided with a relief structure with elevations and depressions, that a relief area and a narrow flat area adapted to be formed without elevations and depressions wherein the flat region separates at least two subregions of the relief region from one another,
• W) for the carrier in the relief area and in the flat area, a washing ink layer of small layer thickness is provided and applied to the carrier,
• M) the carrier provided with wash color is metallized at least in the relief area and flat area, and
• A) the metallized support is subjected to a washing-out step with a solvent, wherein in the flat area the wash color is removed together with the overlying metallization and the flat area is demetallized thereby, while the metallization in the relief area remains on the support and forms the metallized relief area.

The invention is based on the surprising finding that the thin wash ink layer applied in step W) in the flat area and in the relief area has different effects on the subsequent demetallization in step A). While the thin washcoat layer in the narrow flat area leads to removal of the metallization, no demetallization takes place in the relief area. An explanation of this phenomenon, which corresponds to the current understanding, is presented below.

Since relief and flat structures can be produced with great accuracy and the metallization or demetallization produced by the present process adapted to these structures, metallized and non-metallized portions are aligned with high precision on each other and on the underlying relief structure. The distance between the edge of the relief structure and the demetallization can be kept smaller than 10 .mu.m, in particular smaller than 3 .mu.m or even 2 .mu.m. With conventional methods, such registration accuracy is generally unattainable, especially for fine demetallization structures. Since the conventional, partial printing of wash ink takes place in an independent printing step, a positional tolerance of about 300 μm was created.

Within the scope of this description, the relief region is often also referred to as a height-structured region, since it has elevations and depressions as structural elements. It is understood that the relief region of the carrier may have, in addition to the two subregions mentioned, further subregions which are separated from one another by narrow flat regions. The following remarks on the flat area and the partial areas of the relief area preferably apply to all flat areas and relief partial areas present on the carrier.

In particular, for the carrier in the relief area and in the flat area, the wash-dye layer with a small layer thickness is provided on a printing form. The printing plate is brought into contact with the carrier. The wash ink layer is applied by the contact with the different areas, relief area and flat area, different. In the flat region of the support, the wash-dye layer with a small layer thickness is applied by contact with the printing forme (full area). In the relief region of the carrier, the wash ink layer of small layer thickness is only selectively transferred by the contact with the printing plate. The wash ink layer is provided on the printing plate without structure (unstructured). conventional Restrictions on structure widths are therefore not relevant. In particular, the washcoat layer with a low layer thickness is provided for the support in the relief area and in the flat area unstructured (and on an unstructured area of the printing form).

In an advantageous embodiment, in step W), the washcoat layer of low layer thickness in the relief area is selectively applied only to the elevations of the relief structure, preferably to the upper 20%, in particular to the upper 10% of the elevations. In an alternative embodiment, the washcoat layer of small layer thickness in the relief region is selectively introduced only into the depressions of the relief structure, preferably into the lower 20%, in particular into the lower 10% of the depressions.

In both variants, the properties of the wash color can be selected specifically so that a selective application or introduction is supported. A high viscosity of the wash ink promotes a selective application only to the elevations, while a low viscosity assists a selective introduction only in the depressions of the relief structure.

Advantageously, a narrow flat area having a width of less than 1000 μm is formed in step R), preferably a flat area with a width of between 10 μm and 1000 μm, particularly preferably between 10 μm and 500 μm, and very particularly preferably between 10 μm and 250 μm.

The elevations and depressions of the relief structure advantageously form structural elements with a height of more than 0.5 μm, preferably more than 1 μm or more than 2 μm, in particular about 4 μm. The height of the structures is - in each case - preferably less than 8 microns, ie in particular between 0.5 to 8 microns, 2 to 8 microns and 3 to 5 microns. The lateral extent the structural elements is preferably less than 100 microns and is for example 10 microns to 30 microns.

By peaking a particularly small contact surface of the relief area can be obtained with a printing plate, such as a gravure cylinder. The relief structure therefore advantageously has a non-sinusoidal cross-section. In particular, the relief structure is advantageously formed with pointed elevations, in particular in the form of prisms or three, four or more sided pyramids. Prism-shaped structural elements are in particular arranged so that one of its edges roof-like forms a line-shaped tip. The small layer thickness of the wash ink layer is preferably below 20%, in particular in the range of 1 to 20%, preferably between 1 and 10%, of the relief structure height.

Preferably, the relief structure is formed by an embossed structure, as can be produced by embossing the desired structures easily and with high accuracy. The relief structure may in particular be a micromirror arrangement, a blazed grating with a sawtooth-type furrow profile, a Fresnel lens arrangement, or else a diffractive structure, such as a hologram, a holographic grating image or a hologram-like diffraction structure. Advantageously, the metallized relief structure acts as a diffuse or metallic reflector, but it is also within the scope of the invention that the relief structure merely serves as a spacer for the printing plate during the printing process and does not or hardly influences the visual reflection properties of the security element.

For washing colors, suitable solvents are available in each case. In a simple embodiment, water can be used as a solvent.

In a presently particularly advantageous embodiment, it is provided that the wash ink layer with a small layer thickness is applied to the relief area and the flat area in step W) as toning in a gravure printing step. Furthermore, it is advantageously provided that in the deep-pressure step, a washcoat of normal thickness is simultaneously applied in a demetallization area, that in step M) the demetallization area is also metallized, and that in step A) in the demetallization area the washcoat of normal thickness together with the overlying metallization removed and demetallisiert the Demetallisierungsbereich thereby.

A "normal layer thickness" refers to a layer thickness of the washing ink which ensures a safer demetallization in the large-area demetallization areas. The "small layer thickness" is preferably at least (5 times or) 10 times smaller than the normal layer thickness.

The conventionally undesirable Tonung the wash color can be used selectively in the context of the invention and increased to a value at which the Demetallisierung is promoted in the flat area, an undesirable Demetallisierung in the relief area but not yet occurs. The toning of the wash ink can be adjusted by at least one of the following parameters (or combinations thereof): the pigmentation of the wash color, the choice of binder, by the electrostatics during the printing process (switching on or off of the electrostatic pressure assist ESA), the setting of Squeegee (such as angle), type and pressure of the impression, the circumference of the impression cylinder and / or the atmosphere of the impression cylinder are affected.

The demetallization in the flat area does not necessarily have to be complete, since small metal remnants in the narrow flat areas between the reflective relief partial areas are hardly noticeable. In practice, degrees of demetallization have proven to be above 70%, preferably above 80% and in particular above 90%.

The binder of the washing ink is advantageously water-soluble and the washing ink used advantageously has a particularly high color transfer. Further, the gravure cylinder is expediently provided with a certain roughness in its flat areas, in particular in order to optimize the running of the doctor blade.

In another embodiment, which is likewise advantageous, it is provided that the wash ink layer with a small layer thickness is applied to the relief area and the flat area in step W) as an ultrathin color layer in a flexographic printing step. In this case, it is further provided with advantage that wash ink of normal layer thickness is simultaneously applied in a demetallization region in step, the demetallization region is metallized in step M), and that in step A) in the demetallization region the wash color of normal layer thickness together with the overlying Metallization removed and the Demetallisierungsbereich is thereby demetallisiert. The above statements on the normal or low layer thickness of the wash color and their properties apply accordingly in this embodiment.

In addition to the above-mentioned areas, the security element on the support can also contain a conventional, large-area metallized subarea in which there are no relief structures.

In order to prevent the washing ink from drying out on the roll, the washing ink is advantageously applied in a solvent atmosphere.

The metallization in step M) is advantageously formed by a single metal layer, preferably with a thickness between 5 nm and 100 nm, or by one or more individual metal layers in a multi-layer structure. As a single metal layer, for example, an aluminum, chromium or copper layer can be applied. The metal layer and possible further layers of the multilayer structure are preferably vapor-deposited (by means of CVD or PVD methods). Multilayer structures can be produced, for example, in the form of a color-shifting thin-film element with a metallic absorber layer, a dielectric spacer layer and a metallic reflector layer. With the metal layer of the metallization optionally also non-metallic layers can be removed at the same time.

The invention also includes a security element for securing valuables, which can be produced by a method of the type mentioned. The security element contains a carrier with a metallized relief structure with elevations and depressions and a narrow demetallised flat area without elevations and depressions which has been adapted to the relief structure. The flat region separates at least two partial regions of the relief region from one another and has a width of less than 1000 μm, preferably a width of between 10 μm and 500 μm, in particular between 10 μm and 250 μm.

The relief structure advantageously consists of structural elements with pointed elevations, in particular in the form of prisms or of pyramids of three, four or more sides. The elevations and depressions of the relief structure form advantageous structural elements with a height of more than 0.5 microns, preferably more than 1 micron or more than 2 microns, in particular of about 4 microns. , The height of the structures is-in each case-preferably less than 8 μm, that is to say in particular between 0.5 and 8 μm, preferably between 2 and 8 μm or particularly preferably between 3 and 5 μm. The lateral extent of the structural elements is preferably less than 100 μm and, for example, 10 μm to 30 μm. Incidentally, the other statements made in the description of the production method also apply to the security element produced by this method.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen Sicherheitselement in Form eines Folienpatches mit einem Reliefmotiv,

Fig. 2

einen Detailausschnitt des Reliefmotivs der Fig. 1 in Aufsicht,

Fig. 3

einen Querschnitt des Detailausschnitts der Fig. 2 entlang der Linie III-III, und

Fig. 4

in (a) bis (d) jeweils den Detailausschnitt der Figuren 2 und 3 bei Zwischenschritten des Herstellungsprozesses.

Show it:

Fig. 1

a schematic representation of a banknote with a security element according to the invention in the form of a foil patch with a relief motif,

Fig. 2

a detail of the relief motif of Fig. 1 in supervision,

Fig. 3

a cross section of the detail of the Fig. 2 along the line III-III, and

Fig. 4

in (a) to (d) each detail of the FIGS. 2 and 3 at intermediate steps of the manufacturing process.

The invention will now be explained using the example of security elements for banknotes and other value documents. FIG. 1 shows a schematic representation of a banknote 10, which is provided with a security element according to the invention in the form of a film patch 12. However, the invention is not limited to the transfer element shown in the illustration for banknotes, but can also be used, for example, in security threads, wide security strips or cover foils which are arranged above an opaque area, a window area or a through opening of any desired data carrier.

The foil patch 12 shows a metallized, for the viewer out of the x-y plane of the security element herauswölbendes, three-dimensional relief motif 14, which may be formed for example in the form of a portrait, an architectural or technical motif or a nature motif. The relief motif 14 contains not only metallized subregions but also demetallized subregions which, on the one hand, have a creative function within the image motif, but on the other hand can also assume the information-carrying function and can, for example, represent a negative typeface.

If the demetallized subregions are conventionally produced by the imprint of wash ink and a washout step after the metallization, only relatively large-area subregions with the smallest dimension of 1 mm or a line thickness of 100 μm or more can be introduced.

For a more detailed explanation of the inventive feature show FIGS. 2 and 3 a detail 16 of the relief motif 14, wherein Fig. 2 a supervision and Fig. 3 a cross section along the line III-III of Fig. 2 represents. The detail could be a button, an epaulette or, for example, an eye (elsewhere in the subject). The detail 16 of the relief motif 14 contains a metallized relief region 20 with partial regions 22, 24, a large demetallized region 26 and a narrow, demetallized strip 28, which separates the two metallized partial regions 22, 24 of the relief region 20 from one another.

How best in the cross section of Fig. 3 To recognize, the relief structure of the partial regions 22, 24 on a plurality of inclined, small micromirror 30, which reflect due to their metallization incident light efficiently in a predetermined direction. Due to their orientation, the micromirrors 30 give the viewer the impression of a predetermined three-dimensional relief motif 14, for example the portrait of the person Fig. 1 ,

The demetallized strip 28 separating the two subregions 22, 24 is very delicate and, in the exemplary embodiment, has a width of only 50 μm. The strip 28, in contrast to the subregions 22, 24, in which the inclined micromirrors 30 form elevations and depressions, is formed as a flat region 38 without elevations and depressions.

Despite its small width, the demetallized flat area 38 is arranged in perfect register with the metallized relief areas 22, 24. As explained above, conventional printing of wash paint does not produce such narrow demetallized structures. The method according to the invention is based on the surprising finding of the inventors that the toning film, which is unavoidable in terms of process technology, can be used and utilized in a simple and reliable manner to produce filigree, precisely matched demetallised structures 28 within metallized relief structures 22, 24.

The principle of the invention will now be described with reference to Fig. 4 based on the production of the security element 12 of Fig. 1 described in detail, wherein (a) to (d) each detail section 16 of FIGS. 2 and 3 at intermediate steps of the manufacturing process show.

With reference first to Fig. 4 (a) An embossing lacquer layer 42 is applied to a carrier film 40 and the desired relief structure with the arrangement of micromirrors 30 is embossed into the embossing lacquer layer 42. In detail detail 16, the relief structure is provided in a relief area with two partial areas 32, 34 whose shape and size are precisely the shape and size of the areas to be metallized 22, 24 (FIG. Fig. 2 ) corresponds.

The micromirrors 30 thereby form elevations and depressions in the embossing lacquer layer 42, which in the exemplary embodiment have a structure width of approximately 10 μm and, depending on the angle of inclination of the micromirrors 30, a structure height of up to approximately 8 μm.

The two partial areas 32, 34 are separated from each other by a narrow flat area 38, in which there are no micromirrors or other elevations or depressions. Outside the subregions 32, 34, a large-area demetallization region 36 is provided in which likewise no metallization should be present in the finished security element 12.

While the large-area demetallization area 36 has a smallest dimension of more than 1 mm and can therefore be demetallized by the imprint of wash ink and a subsequent wash step in a conventional manner, this is not possible for the narrow flat area 38 because wash color is not so low line width still with the required accuracy relative to the height-structured portions 32, 34 can be applied.

In order nevertheless to achieve the desired high-precision demetallization in the flat region 38, wash ink is printed by gravure printing only on the demetalization regions 36 and other large-area demetallization regions of the carrier 40, 42 and thereby deliberately exploited the normally unwanted toning. The inventors have surprisingly found that the in the nominally unprinted surface areas 32, 34, 38 unavoidable Tonungsfilm in the flat areas 38 and in the height-structured areas 32, 34 has different effects on the subsequent demetallization: During the thin Tonungsfilm the wash color in the narrow Flat areas 38 leads to a substantial or even complete Demetallisierung finds in the height-structured areas 32, 34 despite the Tonung no demetallization instead.

Without wishing to be bound by any particular explanation, this phenomenon is currently understood as follows: With reference to Fig. 4 (b) For example, the wash ink 44 is printed in the large-area demetallization regions 36 in a layer thickness d sufficient for a safer demetallization. In the regions 32, 34, 38, which represent nominally unprinted surface areas, a thin toning film 46, 48 is produced by the toning which is unavoidable in gravure printing.

This thin toning film 48 now forms a substantially continuous thin wash-ink layer in the flat areas 38. In contrast, in the height-structured regions 32, 34, the elevations and depressions of the micromirrors 30 act as small spacers for the color-guiding gravure cylinder, so that the latter only comes into contact with the tips of the micromirrors 30 comes and transfers only to this wash 46. In the height-structured regions 32, 34, this results in a non-contiguous toning film with a significantly lower surface density, as in FIG Fig. 4 (b) schematically illustrated. The surface density of the transferred Tonungsfilms 46 can be influenced on the one hand by the shape of the surveys, on the other hand, but also by the properties of the wash and the process conditions during the printing process. For example, the contact surface of the height-structured regions can be kept very small with the gravure cylinder by pointed elevations. The toning of the wash color can be influenced by the pigmentation of the wash color, the choice of the binder or by the electrostatics during the printing process.

Subsequently, the carrier 40, 42 provided with wash ink 44, 46, 48 is provided in the usual manner over its entire area with a metal layer 50 which covers both the demetallization areas 36 and the flat areas 38 and the height-structured micromirror areas 32, 34, as in FIG Fig. 4 (c) shown. Simple metallizations made of Al, Cr, Cu and the like, as well as multi-layer structures with one or more metal layers may be considered as the metal layer 50.

Regarding Fig. 4 (d) Finally, the metallized support is subjected to a washing-out step with a solvent, for example water, in which the washing color 44 with the metallization 50 in the demetallization regions 36 is completely or completely removed in the flat regions 38. By contrast, the metallization in the height-structured regions 32, 34 is retained and forms the desired metallized regions 22, 24, since the surface density and the cohesion of the wash-dye layer 46 are not there for demetallization suffice. In this way, in addition to the large-area demetallization in the areas 36, the desired register-accurate filigree demetallization of the flat area 38 is also created.

Since the normally unwanted toning of the wash ink is advantageous in the procedure according to the invention, the toning can be deliberately increased to the extent that the demetallization in the flat area 38 is promoted, but without producing undesired demetallization in the height-structured regions 32, 34. Although demetallization in the flat area 38 is preferably complete, this is not absolutely necessary for many applications, since small metal residues hardly appear in the narrow flat areas 38 between the reflective areas 22, 24. The separating effect of the strips 28 already occurs when the metallization of the flat areas is largely, ie, for example, 70% or more removed.

LIST OF REFERENCE NUMBERS

10

bill

12

foil patch

14

in relief

16

callout

20

metallized relief area

22, 24

subregions

26

large area demetallised area

28

narrow demetallised strip

30

micromirror

32, 34

Subareas of the relief area

36

large-area demetalization area

38

flat area

40

support film

42

Embossing lacquer layer

44

washable ink

46, 48

Tonungsfilm

50

metal layer

Claims (15)

Method for producing a security element having a metallized relief area and a narrow, demetallised flat area, which has been adapted therefor, in which R) a support is provided with elevations and depressions in such a way that a relief area and a narrow flat area which has been adapted for this purpose are formed without elevations and depressions, wherein the flat area separates at least two partial areas of the relief area from one another, W) for the carrier in the relief area and in the flat area, a washing ink layer of small layer thickness is provided and applied to the carrier, M) the carrier provided with wash color is metallized at least in the relief area and flat area, and A) the metallized support is subjected to a washing-out step with a solvent, wherein in the flat area the wash color is removed together with the overlying metallization and the flat area is demetallized thereby, while the metallization in the relief area remains on the support and forms the metallized relief area. A method according to claim 1, characterized in that in step W) the wash ink layer of low layer thickness in the relief region selectively is applied only to the elevations of the relief structure, preferably on the upper 20%, in particular on the upper 10% of the surveys. A method according to claim 1 or 2, characterized in that in step R), a narrow flat area is formed with a width below 1000 microns, preferably a flat area with a width between 10 microns and 1000 microns. Method according to at least one of Claims 1 to 3, characterized in that the elevations and depressions of the relief structure form structural elements with a height of more than 0.5 μm, preferably of more than 1 μm. Method according to at least one of claims 1 to 4, characterized in that the relief structure is formed with pointed elevations, in particular in the form of prisms or three, four or more sided pyramids. Method according to at least one of claims 1 to 5, characterized in that the relief structure is an embossed structure. Method according to at least one of claims 1 to 6, characterized in that the relief structure is a micromirror arrangement, a blazed grating with a sawtooth groove profile, a Fresnel lens arrangement, or a diffractive structure, such as a hologram, a holographic grating image or a hologram-like diffraction structure. Method according to at least one of claims 1 to 7, characterized in that the wash ink layer of small layer thickness in step W) is applied as toning in a gravure printing step on the relief area and the flat area. A method according to claim 8, characterized in that in the deep-pressure step in a Demetallisierungsbereich wash with normal thickness is applied, that in step M) and the Demetallisierungsbereich is metallized, and that in step A) in the Demetallisierungsbereich the wash color of normal thickness together with the removed overlying metallization and the Demetallisierungsbereich is thereby demetallisiert. Method according to at least one of claims 1 to 7, characterized in that the wash ink layer of small layer thickness in step W) is applied as an ultrathin ink layer in a flexographic printing step on the relief area and the flat area. A method according to claim 10, characterized in that in the flexographic printing step at the same time in a demetalization washcoat is applied with normal thickness, that in step M) also the demetallization is metallized, and that in step A) in the demetalization the wash color normal thickness together with the removed overlying metallization and the Demetallisierungsbereich is thereby demetallisiert. Method according to at least one of claims 1 to 11, characterized in that the wash color is applied in a solvent atmosphere. A method according to at least one of claims 1 to 12, characterized in that the metallization is formed by a single metal layer, preferably with a thickness between 5 nm and 100 nm, or by one or more metal layers in a multi-layer structure, in particular also non-metallic layers may include. Security element for securing valuables, with a support having a metallized relief structure with elevations and depressions and a narrow, demetallized flat area without elevations and depressions, which separates at least two partial areas of the relief area and which has a width of less than 1000 μm, preferably has a width between 10 .mu.m and 500 .mu.m, in particular between 10 .mu.m and 250 .mu.m. A security element according to claim 14, characterized in that the relief structure consists of structural elements with pointed elevations, in particular in the form of prisms or three, four or more sided pyramids.

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