EP4232297A1

EP4232297A1 - Layer structure with engraving as visible security element

Info

Publication number: EP4232297A1
Application number: EP21794556.7A
Authority: EP
Inventors: Georgios Tziovaras; Helge Kosthorst; Heinz Pudleiner; Theivanayagam Deivaraj
Original assignee: Covestro Deutschland AG
Current assignee: Covestro Deutschland AG
Priority date: 2020-10-26
Filing date: 2021-10-19
Publication date: 2023-08-30
Also published as: CN116348308A; US20230406025A1; WO2022089986A1; KR20230092915A

Abstract

The invention relates to a layer structure, preferably a security form in a book cover, particularly preferably a security form in a book cover for identification or security documents, comprising at least a) a first radiation-engravable layer a) containing at least one polymeric material; and b) at least one further layer b) containing at least one polymeric material, preferably a thermoplastic elastomer, preferably a thermoplastic polyurethane with a hardness of ≥ 40 Shore A according to DIN ISO 7619-1-2012-2 to ≤ 95 Shore D according to DIN ISO 7619-1-2012-2; wherein the further layer b) overlies the first layer a) at least partly to form an overlapping region, and wherein a contiguous engraving is located partly in the overlapping region, preferably in the further layer b), and partly in the part of the layer a) that extends outside the overlapping region, and also relates to a method for producing this layer structure and to a laminate comprising such a layer structure and to the use of the layer structure in a security document.

Description

Layer structure with engraving as a visible security element

The invention relates to a layer structure with an engraving that extends over an overlapping area of a layer a) and a further layer b).

Plastic-based security and/or valuable documents, in particular identification documents such as ID cards, are nowadays preferably produced without the use of adhesive layers as multi-layer composites by means of lamination at high temperatures and high pressure in order to subsequently separate the layer structures to exchange identification features to prevent. The corresponding security features are introduced into these multi-layer composites before or during the lamination process, which must consequently be designed in such a way that they withstand the lamination process parameters without being destroyed. In addition, the security features must not introduce any weak points into the multi-layer composite that would allow the composite to be subsequently opened again without destroying it. Of particular interest are security features which can be incorporated after the lamination process or in the finished ID document and which can be easily recognized as such if a forgery is present. Ideally, the security feature should also be able to be linked to the data of the document keeper or otherwise be personalized or made tamper-proof.

Security features in security and/or value documents are usually divided into three security levels:

- Level 1 security features are those that can be perceived purely visually with the naked eye without the use of additional aids.

- Level 2 security features are those that require tools (such as a magnifying glass, optical lifter, reader, etc.) to become visible.

- Level 3 security features are those that can only be identified in a laboratory using forensic techniques.

At least partial destruction of the document usually accompanies the analysis. There is therefore an increasing need for security features of level 1, which can be perceived quickly, preferably visually or tactilely, preferably contain personal data of the document keeper and if a forgery is present, it can be recognized as such quickly and without tools or with few tools. Such security features are also referred to below as personalized security features.

For ID documents made of polymeric materials such as plastic, especially polycarbonate, the most important personalized security feature is the photo of the document holder. The reason for this is that once the blank document has been completed, it can be incorporated into the document by means of laser engraving, for example as a black and white photo. In order to improve the protection against counterfeiting of laser-engraved photos, processes have been developed that allow the laser engraving of the photo in color enable, as described in the European patent application with the application number EP 3 613 602 A1. In addition to color laser engraving, this process allows the photo to be partially structured, making it easier to distinguish it from a fake. For example, some areas of the photo can be engraved with more intense laser radiation in order to be able to create additional structures. With increased effort, however, counterfeiters can also create a structure on the photo, for example by partially applying a transparent varnish.

A popular security feature in polycarbonate ID documents are transparent windows. The improved security against counterfeiting consists in the fact that the transparency of the window is disturbed in the event of a counterfeit attempt. The destruction of transparency happens, for example, when a transparent film is stuck over an ID document, or when the document is split by mechanical means. In some cases, the photo or other personal information of the document holder is engraved in transparent windows by means of a laser in order to make an attempt at forgery even more difficult. A variant of this is described in WO 2014/151377 A2.

When producing passport books, in particular passport books with a data sheet in the form of a security form, for example made of polycarbonate, there is a need for a forgery-proof connection of the data sheet with the passport book or the passport book cover, i.e. the remaining part of the passport.

A secure connection, in particular a forgery-proof connection, of the data sheet, also known as the security form, with the passport book via the passport flap is complicated and expensive from a manufacturing point of view.

There is therefore a need to further improve the method for securely connecting the data sheet in the passport, for example in the form of laser engraving or welding, against counterfeiting or to make at least parts of security documents as counterfeit-proof as possible.

It was therefore an object of the invention to provide a layer structure with improved forgery-proof elements, in particular forgery-proof engraving in the layer structure, or to provide a more forgery-proof security document made therefrom. In particular, it was an object of the invention to provide a forgery-proof hinge, ie a forgery-proof connection between a data sheet, for example in the form of a security form, and a passport flap of a passport. Another object was to provide a method for producing a forgery-proof layer structure, or to provide a forgery-proof security document produced by means of the method.

Surprisingly, at least one of the objects could be achieved by a first subject matter of the invention, which relates to a layered structure, preferably a hinge, particularly preferably a hinge formed between a security form and a book cover, for example via a flap, particularly preferably a hinge formed between a Security form and a book cover of an identification or security document, for example a passport, comprising at least a) a first radiation-engravable layer a) containing at least one polymeric material; and b) at least one further layer b) containing at least one polymeric material, preferably a thermoplastic elastomer, preferably a thermoplastic polyurethane with a hardness of >40 Shore A to <95 Shore D, preferably >45 Shore A to <90 Shore D, more preferably >50 Shore A to <85 Shore D, particularly preferably >55 Shore A to <80 Shore D, the Shore hardness being determined in accordance with DIN ISO 7619-1-2012-2; where the further layer b) overlaps the first layer a) in part, forming an overlapping area, and where a coherent engraving is partly in the overlapping area, preferably in the further layer b), very particularly preferably exclusively in the further layer b) , and to a part in the part of layer a) extending outside the overlap area.

The layer structure can be any layer structure that the person skilled in the art would construct as a layer structure in particular as a hinge, particularly preferably as a hinge, e.g. as a flap, between a security form and a book cover, very particularly preferably as a hinge between a security form and a book cover for identification or security documents would select. A hinge is preferably understood to mean a connection, in particular a flexible connection, of two or more parts that make up an identification or security document such as passports or birth certificates. In the case of a hinge between a security form and a book cover, layer b) represents the flap and layer a) represents the security form.

The coherent engraving introduced, for example by means of laser engraving, both in the overlapping area and in the area adjoining the overlapping area on the first layer a), offers the possibility of connecting the data sheet in the form of the first layer a) with the passport book, for example via a flap, in the form of the further layer b) individually and forgery-proof. For example, the engraving can be provided with the personal data of the passport owner.

In a possible interpretation of the passport in which the data page can be connected to other pages of the passport book, as e.g. in EP 2433810, the connection of these pages can be personalized by introducing the coherent engraving, for example by containing the personal data of the passport holder. This is also possible with glued-in visa forms or other passport book entries.

The layer structure is preferably designed as a hinge. The layer structure as a hinge, in the form of a flap, between a security form and a book cover is particularly preferred educated. In particular, it is a cover of an identification or security document, such as a passport or birth certificate. In the following, however, only the layer structure is discussed, even if this can be designed as a hinge or as a hinge between the security form and a book cover. Consequently, all the properties and components of the layer structure mentioned below also apply to a hinge or a hinge between a security form and a book cover.

According to the invention, the part of a security document, such as in a passport or ID card, which contains personal data is referred to as a security form. Such security forms are referred to as data pages and are preferably connected to the cover of the identification or security document via a flap. The flap is preferably sewn and/or glued to the book cover.

The layer structure preferably has a two-dimensional extent. The area of the layer structure is preferably in a range from 1 cm ² to 1 m ² , more preferably in a range from 5 cm ² to 0.8 m ² , particularly preferably in a range from 10 cm ² to 0.5 m ² , very particularly preferably in a range from 50 cm ² to 0.1 m ² . The layer structure preferably has a thickness in a range from 0.1 to 5 cm, particularly preferably in a range from 0.2 to 2 cm, very particularly preferably in a range from 0.5 to 1 cm.

The first layer a) can be any radiation engravable layer that includes a polymeric material. The first layer a) is preferably made of a transparent, radiation-engravable polymeric material. The first layer a) is preferably transparent and clear. According to the invention, transparent means that the layer is at least partially transparent to light in a wavelength range of 400 to 700 nm. The first layer a), more preferably also the further layer b), preferably consists of a polymeric material with a radiation permeability, also referred to as transmission, for the selected radiation in the wavelength range from 400 to 700 nm of >10 to <99.95%, preferably from >30 to <95%, particularly preferably >40 to <93%, determined by means of UV-VIS-NIR-MIR as described in the methods section.

The layer structure, in particular the first layer a), is preferably clear before treatment with a laser. "Clear" within the meaning of the application means that the layer structure or the first layer a) has a haze of <20%, preferably <15%, more preferably <10%, particularly preferably <5%, measured according to the ASTM standard DL 003:2013.

If the layer structure is in the form of a hinge, in particular a hinge, preferably in the form of a flap, between a security form and a book cover, the first layer a) forms the security form and the further layer b) the flap.

The first layer a) and in particular also the further layer b) can consist of a single film or of a composite of at least two films. The polymeric material of the first layer a) can be the same as the material of the further layer b). Alternatively, the polymeric material of the first layer a) is different from the polymeric material of the further layer b). The material of the first layer a) can be harder or softer than the material of the further layer b), it being preferred that the material of the first layer a) is harder than the material of the further layer b). The polymeric material of the first layer a) preferably has an E modulus in a range from 1500 to 2500 MPa, more preferably from 1700 to 2200 MPa. The polymeric material of the further layer b) preferably has a modulus of elasticity in a range from 10 to 150 MPa, more preferably from 20 to 130 MPa.

Preferably, at least one of the at least one film of the first layer a) or the further layer b) has at least one polymeric material selected from the group consisting of a polycarbonate, a copolycarbonate, a polyester, a copolyester or mixtures of at least two of these . The first layer a) and in particular also the further layer b) can have or consist of a thermoplastic material, in particular a thermoplastic elastomer.

The polycarbonate or the co-polycarbonate can be any poly carbonate or co-polycarbonate that the person skilled in the art would select for the production of the first layer a) or the further layer b), but particularly preferably the first layer a) of the layered composite. Particularly suitable polycarbonates, which are preferably contained in layer a) and preferably also in layer b), are preferably high-molecular, thermoplastic, aromatic polycarbonates with _Mw (weight-average molecular weight determined by gel chromatography compared to a polystyrene standard in tetrahydrofuran at 23° C after prior calibration) of at least 10,000 g/mol, preferably from 20,000 to 300,000 g/mol, which contain bifunctional carbonate structural units of the formula (I), wherein

R ¹ and R ² are independently hydrogen, halogen, preferably chlorine or bromine, C i -Cs- alkyl, CS-CÖ -cycloalkyl, Ce-Cio-aryl, preferably phenyl, and Cv-Cn-aralkyl, preferably phenyl-Ci- C4-alkyl, in particular benzyl, m is an integer from 4 to 7, preferably 4 or 5, R ³ and R ⁴ can be selected individually for each X, independently of one another hydrogen or CI-CÖ-alkyl and

X is carbon, with the proviso that on at least one atom X, R ³ and R ⁴ are simultaneously alkyl.

Particularly suitable thermoplastic polymers or thermoplastics are selected from the group consisting of one or more polycarbonates or copolycarbonates based on diphenols, for example as described above, poly- or copolyacrylate(s) and poly- or copolymethacrylate(s), for example and preferably polymethyl methacrylate or poly(meth)acrylate (PMMA), poly- or copolymer(s) with styrene, for example and preferably polystyrene (PS), acrylonitrile butadiene styrene (ABS), or polystyrene acrylonitrile (SAN), thermoplastic polyurethane(s), and polyolefin(s), such as, for example and preferably, types of polypropylene or polyolefins based on cyclic olefins (e.g. TOPAS®, Hoechst), poly- or copolycondensate(s) of terephthalic acid, such as, for example and preferably, poly- or copolyethylene terephthalate (PET or CoPET) , glycol-modified PET (PETG), glycol-modified poly- or copolycyclohexanedimethylene terephthalate (PCTG), or poly- or C opolybutylene terephthalate (PBT or CoPBT)), polyamide (PA), poly- or copolycondensate(s) of naphthalene dicarboxylic acid, such as, for example and preferably, polyethylene glycol naphthalate (PEN), poly or copolycondensate(s) of at least one cycloalkyl dicarboxylic acid, such as, for example and preferably, polycyclohexanedimethanolcyclohexanedicarboxylic acid (PCCD ), polysulfones (PSU), mixtures of at least two of the aforementioned or blends of at least two of the aforementioned.

Thermoplastic elastomers are materials that contain elastomeric phases in polymers that can be processed as thermoplastics, either physically mixed in or chemically bound. A distinction is made between polyblends in which the elastomeric phases are physically mixed and block copolymers in which the elastomeric phases are part of the polymeric structure. Due to the structure of the thermoplastic elastomers, there are hard and soft areas next to each other. The hard areas form a crystalline network structure or a continuous phase whose interstices are filled with elastomeric segments. Due to this structure, these materials have rubber-like properties.

The thermoplastic elastomer is preferably selected from the group consisting of a thermoplastic copolyamide (TPE-A), in particular a polyether block amide, a thermoplastic polyurethane (TPE-U), a thermoplastic polyester elastomer (TPE-E), a styrene block copolymer (TPE-S) , TPE-V - Vulcanized (crosslinked) PP/EPDM compounds or a mixture of at least two of them.

The thermoplastic copolyamide (TPE-A) can be any copolyamide that one skilled in the art would select for a layered construction, particularly polyether block amides (PEBA). Preferred polyether Block amides are, for example, those that consist of polymer chains consisting of recurring

Units corresponding to the formula (II) are constructed. in which

A is the polyamide chain derived from a polyamide having 2 carboxyl end groups by loss of the latter and

B is the polyoxyalkylene glycol chain derived from an OH-terminated polyoxyalkylene glycol by loss of the latter and n is the number of units forming the polymer chain. The end groups are preferably OH groups or residues of compounds which terminate the polymerization.

The dicarboxylic acid polyamides with terminal carboxyl groups are obtained in a known manner, e.g. by polycondensation of one or more lactams and/or one or more amino acids, also by polycondensation of a dicarboxylic acid with a diamine, in each case in the presence of an excess of an organic dicarboxylic acid, preferably with terminal carboxyl groups . These carboxylic acids become part of the polyamide chain during the polycondensation and accumulate in particular at the ends of the same, resulting in a p-dicarboxylic acid polyamide. Furthermore, the dicarboxylic acid acts as a ketene terminating agent, which is why it is also used in excess.

The polyamide can be obtained starting from lactams and/or amino acids with a hydrocarbon chain consisting of 4-14 carbon atoms, such as caprolactam, oenantholactam, dodecalactam, undecanolactam, decanolactam, 11-aminoundecano or 12-aminododecanoic acid.

Examples of polyamides formed by polycondensation of a dicarboxylic acid with a diamine are the condensation products of hexamethylenediamine with adipic, azelaic, sebacic and 1,12-dodecanedioic acid, and the condensation products of nonamethylenediamine and adipic acid.

In the case of the dicarboxylic acid used for the synthesis of the polyamide, i.e. on the one hand for fixing a carboxyl group at each end of the polyamide kete and on the other hand as a ketene terminating agent, those with 4-20 carbon atoms are suitable, in particular alkanedioic acids such as succinic, adipic, cork -, azelaic, sebacic, undecanedioic or dodecanedioic acid, also cycloaliphatic or aromatic dicarboxylic acid, such as terephthalic or isphthalic or cyclohexane-1,4-dicarboxylic acid.

The polyoxyalkylene glycols having terminal OH groups are unbranched or branched and have an alkylene radical having at least 2 carbon atoms. In particular, these are polyoxyethylene, polyoxypropylene and polyoxytetramethylene glycol, and copolymers thereof. The average molecular weight of these OH-group-terminated polyoxyalkylene glycols can vary within a wide range; it is advantageously between 100 and 6000 g/mol, in particular between 200 and 3000 g/mol.

The proportion by weight of the polyoxyalkylene glycol based on the total weight of the polyoxyalkylene glycol and dicarboxylic acid polyamide used to prepare the PEBA polymer is preferably 5-85% by weight, preferably 10-50% by weight.

Processes for the synthesis of such PEBA polymers are known from FR-PS 7 418 913, DE-OS 28 02 989, DEOS 28 37 687, DE-OS 25 23 991, EP-A 095 893, DE-OS 27 12 987 and DEOS 27 16 004 known.

Those PEBA polymers which, in contrast to those previously described, have a statistical structure are particularly suitable. To produce these polymers, a mixture of

1. one or more polyamide-forming compounds from the group of -aminocarboxylic acids or lactams with at least 10 carbon atoms,

2. an a,a>-dihydroxy polyoxyalkylene glycol,

3. at least one organic dicarboxylic acid, in a weight ratio of 1:(2+3) between 30:70 and 98:2, wherein in (2+3) hydroxyl and carbonyl groups are present in equivalent amounts, in the presence of 2 bis 30 wt further treated up to 280°C. Such preferably suitable PEBA polymers are described, for example, in DE-OS 27 12 987.

Preferred PEBA polymers are, for example, under the trade names PEBAX from Atochem, Pebax® 5010, Pebax® 5020, Pebax® 5030, Pebax® 5040, Pebax® 5070 from Arkema (Germany), Vestamid from Hüls AG, Grilamid from EMS-Chemie and Kellaflex from DSM.

The polyether block amides can also contain the additives customary for polymers or plastics. Customary additives are, for example, pigments, stabilizers, plasticizers, lubricants, mold release agents.

Examples of thermoplastic copolyamides are products such as Pebax® 5010, Pebax® 5020, Pebax® 5030, Pebax® 5040, Pebax® 5070 from Arkema (Germany). Examples of thermoplastic polyurethanes will be given later.

The thermoplastic polyester elastomer (TPE-E) can be any polyester elastomer that one skilled in the art would select for a layered construction, preferably the polyester elastomers are copolyesters. Suitable copolyesters (segmented polyester elastomers) are, for example, from a A plurality of recurring short chain ester units and long chain ester units united by ester linkages, the short chain ester units making up 15-65% by weight of the copolyester and having the formula (III-a). in which

R stands for a divalent residue of a dicarboxylic acid with a molecular weight of <350 g/mol,

D stands for a divalent radical of an organic diol with a molecular weight of <250 g/mol; the long chain ester units make up 35-85% by weight of the copolyester according to formula III-b in which

R is a divalent residue of a dicarboxylic acid with a molecular weight of <350 g/mol, G is a divalent residue of a long-chain glycol with an average molecular weight of 350 to 6000 g/mol.

The preferred copolyesters can be prepared by polymerizing together a) one or more dicarboxylic acids, b) one or more linear, long-chain glycols and c) one or more low molecular weight diols.

The dicarboxylic acids for the production of the copolyester are preferably the aromatic acids having 8-16 carbon atoms, in particular phenylenedicarboxylic acids such as phthalic, terephthalic and isophthalic acid.

The low molecular weight diols for the reaction to form the short-chain ester units of the copolyesters preferably belong to the classes of acyclic, alicyclic and aromatic dihydroxy compounds. The preferred diols have 2-15 carbon atoms, such as ethylene, propylene, tetramethylene, isobutylene, pentamethylene, 2,2-dimethyltrimethylene, hexamethylene and decamethylene glycols, dihydroxycyclohexane, cyclohexanedimethanol, resorcinol, hydroquinone and the like. Bisphenols for the present purpose include bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)methane, bis(p-hydroxyphenyl)ethane and bis(p-hydroxyphenyl)propane.

The long-chain glycols used to make the soft segments of the copolyesters preferably have molecular weights of 600 to 3000 g/mol. They include poly(alkylene ether) glycols in which the alkylene groups have 2-9 carbon atoms. Glycol esters of poly(alkylene oxide) dicarboxylic acids or polyester glycols can also be used as the long-chain glycol. The long-chain glycols also include polyformals, which are obtained by reacting formaldehyde with glycols. Polythioether glycols are also suitable. Polybutadiene and polyisoprene glycols, interpolymers thereof and saturated hydrogenation products of these materials make satisfactory long chain polymeric glycols. Methods for synthesizing such copolyesters are known from DE-OS 2,239,271, DE-OS 2,213,128, DE-OS 2,449,343 and US-A 3 023 192 known.

The polymeric material of the first layer a) or the polymeric material, in particular the thermoplastic elastomer of the further layer b), preferably also contains the additives customary for plastics. Typical additives are, for example, lubricants such as fatty acid esters, their metal soaps, fatty acid amides and silicone compounds, antiblocking agents, inhibitors, stabilizers against hydrolysis, light, heat and discoloration, flame retardants, dyes, pigments, inorganic or organic fillers and reinforcing agents. Reinforcing agents are, in particular, fibrous reinforcing materials, such as inorganic fibers, which are produced according to the prior art and can also be coated with a size. Further information on the auxiliaries and additives mentioned can be found in the specialist literature, for example J.H. Saunders, K.C. Fresh: "High Polymers", Volume XVI, polyurethanes, part 1 and 2, Interscience Publishers 1962 and 1964, R. Gachter, H. Müller (ed.): Paperback of plastic additives, 3rd edition, Hanser Verlag, Munich 1989, or DE-A 29 01 774.

The radiation-engravable, polymeric material can preferably be changed in terms of its coloring by means of a laser in the presence of a dye. According to the invention, its coloring can be changed by means of a laser means that in the polymeric material of the first layer a) with an input of energy of >1 watt in continuous radiation or >5 watts in pulsed radiation, coloring with a dye can be realized by means of a laser, so that the resulting coloring can be seen with the naked eye. A pulse frequency in a range from 0.5 to 1000 KHz, preferably from 5 to 100 KHz, particularly preferably from 15 to 50 KHz, is preferably used for the pulsed radiation. In this way, the engraving on the first layer a) can also be colored. The method for introducing a colored engraving is described in EP 3 613 602 A1.

Radiation-engravable first layer a) means in the context of the invention that the layer contains a material with light in a wavelength range of> 0.1 to <1000 pm, preferably from> 1.0 to <50 pm, particularly preferably from > 1.0 to < 2.5 pm interacts in such a way that a color change occurs when irradiated with light of sufficient energy in this wavelength range. This color change can either be changed by radiation-sensitive materials that are located in the first layer a) and their color can be changed by irradiation in the above-mentioned wavelength range, or can be produced by the first layer a) being brought into contact with a colorant, the penetrate into the first layer a) when the first layer a) is irradiated in the abovementioned wavelength range and thereby produce a color change in the first layer a). The layer structure in the first layer a) preferably contains at least one additive which has an absorption maximum in the wavelength range of the focused non-ionizing electromagnetic radiation used. Alternatively, the first layer a) can be coated with at least one additive in the form of a coating agent which has an absorption maximum in the wavelength range of focused non-ionizing electromagnetic radiation. Details on the additives will be given later in connection with other embodiments.

The first layer a) preferably has at least one, particularly preferably all of the following properties:

(El) Has a radiation transmittance of >2 to <99.95%, preferably from >4 to <90%, particularly preferably from >5 to <85%, for the selected radiation, in particular in the wavelength range from 950 to 1200 nm in the wavelength range from 1000 to 1150 nm, determined using UV-VIS-NIR-MIR as described in the methods section;

(E2) a thickness in a range from 0.01 to 20 mm, particularly preferably in a range from 0.02 to 10 mm, very particularly preferably in a range from 0.05 to 5 mm, more preferably in a range from 0 , 1 to 1 mm;

The first layer preferably has a) the combination of properties selected from the group consisting of (E1); (E2); (E1) and (E2) on.

The layer thickness of layer a) can be achieved either by a single film of the appropriate layer thickness or by laminating several thin films to form layer a).

The further layer b) preferably has at least one, more preferably at least two, particularly preferably all of the following properties:

(Bl) has a radiation transmittance of >2 to <99.95%, preferably from >4 to <90%, particularly preferably from >5 to <85%, for the selected radiation, determined by means of UV-VIS-NIR-MIR, as described in the methods section;

(B2) a thickness in a range from 0.05 to 10 mm, particularly preferably in a range from 0.1 to 2 mm, very particularly preferably in a range from 0.15 to 1 mm, more preferably in a range from 0 .2 to 0.8 mm;

(B3) a transmission, also called radiation transmittance, of light in a wavelength range from 950 to 1200 nm in a range from >0 to <50%, preferably from >1 to <40%, particularly preferably from >5 to <30%, very particularly preferably from >7 to <20% for the radiation selected in each case, determined by means of UV-VIS-NIR-MIR as described in the methods section;

(B4) contains an IR absorber with a light transmission of <20% in the wavelength range from 950 to 1200 nm. The further layer b) preferably has the combination of properties selected from the group consisting of (B1); (B2); (B3); (B4); (B1) and (B2); (B1) and (B3); (B1) and (B4); (B2) and (B3); (B2) and (B4); (B3) and (B4); (B1) and (B2) and (B3); (B1) and (B2) and (B4); (B1) and (B3) and (B4); (B2) and (B3) and (B4); (B1) and (B2) and (B3) and (B4) on. Preferred IR absorbers for achieving property (B3) or (B4) are described below.

The layer structure preferably has at least one, preferably at least two, particularly preferably all of the following properties:

(51) Has a radiation transmittance of >2 to <99.95%, preferably from >4 to <90%, particularly preferably from >5 to <85%, for the selected radiation, determined by means of UV-VIS-NIR-MIR such as described in the methods section;

(52) Area in a range from 1 cm ² to 1 m ² , more preferably from 5 cm ² to 0.8 m ² , particularly preferably from 10 cm ² to 0.5 m ² , very particularly preferably from 50 cm ² to ^0.1m2 ;

(53) a thickness in a range from 0.1 mm to 2 cm, more preferably in a range from 0.2 mm to 1.5 cm, most preferably in a range from 0.5 mm to 1 cm, more preferably preferably in a range from 1 mm to 0.5 cm;

(54) exactly one first layer a) and one further layer b).

The layer structure preferably has the combination of properties selected from the group consisting of (SI); (S2); (S3); (S4); (S1) and (S2); (S1) and (S3); (S1) and (S4); (S2) and (S3); (S2) and (S4); (S3) and (S4); (S1) and (S2) and (S3); (S1) and (S2) and (S4); (S1) and (S3) and (S4); (S2) and (S3) and (S4); (Sl) and (S2) and (S3) and (S4).

According to the invention, the further layer b) overlaps the first layer a) in part, forming an overlapping area. In this case, a step can be formed from the further layer b) to the first layer a). A continuous engraving extends partly on layer a) outside the overlapping area. This part of the engraving is referred to below as the first part engraving. The other part of the connected engraving, which is located in the overlapping area, is referred to below as a further partial engraving. This further partial engraving is preferably introduced exclusively into the further layer b). If a step is formed, the step preferably has an extent which corresponds to the thickness of the further layer b) ±10%. The step preferably has an extent in a range from 1 to 1000 μm, more preferably from 2 to 500 μm, particularly preferably from 10 to 100 μm.

The overlapping area is the area of the layer structure in which a part of the surface of the first layer a) is overlapped by a part of the surface of the further layer b). The overlapping area preferably extends over an area of the first layer a) in a range from 1 to 90%, more preferably in a range from 2 to 80%, particularly preferably in a range from 3 to 70%, very particularly preferably in a range from 4 to 60%, more preferably in a range from 5 to 30%, based on the area of one side of the first layer a). The further layer b) overlays the first layer a), preferably over the complete extension area of the further layer b). The further layer b) preferably overlaps the first layer a) in a range from 10 to 90%, more preferably in a range from 20 to 80%, particularly preferably in a range from 30 to 70%, very particularly preferably in a range of 40 to 60%, based on the area of one side of the first layer b). The further layer b) preferably extends outside the overlapping area beyond the first layer a), in particular in a range of 20 to 60%, based on the area of one side of the first layer a).

The overlapping area preferably extends over the entire length of the further layer b) and preferably also over the entire length of the first layer a). The overlapping area preferably has a length in a range from 1 to 1000 mm, more preferably from 2 to 500 mm, particularly preferably from 5 to 200 mm, very particularly preferably from 10 to 100 mm. The overlapping area preferably has a length in a range from 0.1 to 1000 mm, more preferably from 1 to 500 mm, particularly preferably from 5 to 200 mm, very particularly preferably from 10 to 100 mm.

The engraving that is located in the overlapping area at least in a part of the further layer b) and on a part of the first layer a) outside of the overlapping area can be any engraving that the person skilled in the art would select for this purpose. The engraving is preferably a laser engraving.

The engraving preferably has a width in a range of 0.005 to 5 mm, more preferably in a range of 0.01 to 1 mm, particularly preferably in the overlapping area, preferably both for the first partial engraving and for the further partial engraving a range of 0.02 to 0.1 mm. The engraving, which is located in the part of the layer structure that consists exclusively of the first layer a), i.e. the first partial engraving, preferably has a width in a range from 0.005 to 5 mm, more preferably in a range from 0. 01 to 1 mm, particularly preferably in a range from 0.02 to 0.1 mm. The engraving preferably extends over the entire length of the overlapping area. The engraving preferably extends over an area in a range from 0.1 to 100 cm ² , particularly preferably from 1 to 80 cm ² , very particularly preferably from 5 to 50 cm ² of the layer structure.

Depending on the design of the overlapping area, it ends at least at one point, preferably on two sides, or preferably on all sides of the overlapping area in a step that can have at most the thickness of the further layer b). However, the two layers, the first layer a) and the further layer b) can also be joined together in such a way that there is no step in the transition from the overlapping area to the first layer a) outside the overlapping area, but rather a smooth transition from the first layer a). the further layer b) is guaranteed in the overlapping area. Especially without a step, the continuous engraving appears as flowing. The first layer a) extends further at least at one point beyond the overlapping area. The engraving extends from the further layer b) in the overlapping area, optionally across the step, preferably continuously on the first layer a). Coherent or continuous within the meaning of the invention means that at least part of the engraving in the overlapping area at least on the further layer b) merges smoothly into the part of the engraving on the first layer a) that goes beyond the overlapping area. This smooth transition of the engraving from the overlapping area to the first layer a) outside of the overlapping area is preferably formed without an offset between the two areas. This means that no misalignment in the engraving can be seen with the naked eye.

The part of the engraving that is in the overlapping area on the further layer b) covers the further layer b) at least partially in a range from 0.1 mm to 1 cm, more preferably in a range from 0.2 mm to 0, 5 cm, particularly preferably in a range from 0.5 mm to 0.1 cm, based on the extent of the overlapping area following the first layer a) outside the overlapping area. The part of the engraving that is outside of the overlapping area on the first layer a) preferably has an area of 0.1 mm to 1 cm, more preferably an area of 0.2 mm to 0.5 cm, particularly preferably in one area from 0.5 mm to 0.1 cm based on the distance on the first layer a) relative to the overlap area.

The coherent engraving is preferably in the form of lettering or a number with one or more digits or a combination thereof. The continuous engraving is preferably designed in the form of personal data selected from the group consisting of name, date of birth, passport number and other personal data or a combination of at least two of these. In addition to the engraving, which is located beyond the step from the overlapping area to the first layer a), further engravings can also be located either on the further layer b) or on the first layer a).

The area of overlap can take any form or configuration that one skilled in the art would choose. The overlapping area preferably has a shape selected from the group consisting of a circle, an ellipse, a square, a rectangle, an irregular polygon, a regular polygon or a combination of at least two of these. The overlapping area preferably has a rectangular shape.

The overlapping area is preferably arranged on the first layer a) in such a way that it is >20%, more preferably >50%, particularly preferably >80%, very particularly preferably 100%, adjacent to or from the first layer a). the first layer a) is surrounded.

Due to the different structure of the layer structure in the overlapping area and in the part of the layer structure that is formed exclusively from the first layer a), the engraving in the overlapping area can assume a different shape than on the first layer a) outside of the overlapping area. The engraving can be in the overlapping area either only in the further Layer b) can be introduced or it can be introduced both into a part of the first layer a) and into a part of the further layer b). The engraving in the overlapping area is preferably introduced only into a part of the further layer b).

The engraving in the overlapping area preferably has a different shape than the engraving on the first layer a). The different shape is preferably selected from the group consisting of a different color, a different thickness and a different intensity or a combination of at least two of these. The color of the engraving is preferably white or milky in the overlapping area and black in the area on the first layer a) outside the overlapping area.

The engraving in the layer structure in the area of the first layer a) outside the overlapping area preferably has at least one, preferably at least two, particularly preferably all of the following properties:

Ga)l. a depth in a range from 10 to 100%, more preferably from 20 to 95%, particularly preferably from 30 to 90%, very particularly preferably from 50 to 80%, based on the thickness of the first layer a);

Ga)2. a depth in a range from 0.001 to 2 mm, more preferably in a range from 0.002 to 1.5 mm, most preferably in a range from 0.005 to 1 mm, even more preferably in a range from 0.005 to 0.5 mm;

Ga)3. a partial engraving in the first layer a) outside the overlapping area, which differs in color from the partial engraving in the adjoining further layer b).

Preferably, the engraving in the layer structure in the area of the first layer a) outside the overlapping area has the combination of properties selected from the group consisting of Ga)E; Ga)2.; Ga)3.; Ga)l. and Ga)2.; Ga)l. and Ga)3.; Ga)2. and Ga)3.; Ga)l. and Ga)2. and Ga)3. on.

The partial engraving in the first layer a) outside the overlapping area is preferably lighter than the engraving in layer b), specifically by at least 2 units in the L values, measured according to Cielab DIN 5033-3: 1992-07.

The engraving in the layer structure in the area of the overlapping area preferably has at least one, preferably at least two, more preferably at least three in any combination, particularly preferably all of the following properties:

Gb)l. a depth in a range from 10 to 100%, more preferably from 20 to 95%, particularly preferably from 30 to 90%, very particularly preferably from 50 to 80%, based on the thickness of the further layer b);

GB)2. a depth in a range from 5 to 100%, more preferably from 10 to 95%, particularly preferably from 30 to 90%, very particularly preferably from 50 to 80%, based on the thickness of the layer structure; GB)3. a depth in a range from 0 to 80%, more preferably from 10 to 70%, particularly preferably from 20 to 60%, very particularly preferably from 30 to 50%, based on the thickness of the first layer a);

GB)4. a depth in a range from 0.001 to 1 mm, particularly preferably in a range from 0.002 to 0.5 mm, very particularly preferably in a range from 0.005 to 0.01 mm, even more preferably in a range from 1 mm to 0, 5 cm.

The engraving in the layer structure in the area of the overlapping area preferably has the combination of properties selected from the group consisting of Gb)E; Gb)2.; Gb)3.; Gb)4.; Gb)l. and Gb)2.; Gb)l. and Gb)3.; Gb)l. and Gb)4.; GB)2. and Gb)3.; GB)2. and Gb)4.; GB)3. and Gb)4.; Gb)l. and Gb)2. and Gb3); Gb)l. and Gb)2. and Gb)4.; Gb)l. and Gb)3. and Gb)4.; GB)2. and Gb)3. and Gb)4.; Gb)l. and Gb)2. and Gb)3. and Gb)4. on.

In addition to the layers of the first layer a) and the at least one further layer b), the layer structure can comprise at least one further layer c). The first layer a) is preferably directly adjacent to one of the further layers b). Further layers b) and further layers c) are preferably located on both sides symmetrically around the adjacent first layers a) and a further layer b) in the layer structure. The further layer c) differs from the further layers b) at least in one material component.

The at least one further layer b) can consist of a single film or of a composite of at least two films. At least one of the films preferably has at least one thermoplastic elastomer, very particularly preferably at least two or all of the films. The film in layer b), which contains the thermoplastic elastomer, is preferably the outermost film in the layer structure.

The thermoplastic elastomer is preferably selected from the group consisting of a thermoplastic copolyamide (TPE-A), in particular a polyether block amide, a thermoplastic polyurethane (TPE-U), a thermoplastic polyester elastomer (TPE-E), a styrene block copolymer (TPE-S), TPE-V - Vulcanized (crosslinked) PP/EPDM compounds or a mixture of at least two of them. The preferred thermoplastic elastomers have been described above in connection with the first layer a). All statements regarding these thermoplastic elastomers also apply in particular to the additional layer b) and, where applicable, also to the at least one additional layer c). The polymeric materials and other components of layers a) and layer b) are preferably different, but they can also be identical. Thus, in a preferred embodiment, layer a) can be identical to layer b) in the selection of the polymeric materials. However, layers a) and b) preferably have different thicknesses. So it is preferred that the further layer b) is thinner than the layer a). The main reason for this is that the further layer b) should be designed to be particularly flexible, for example in the form of a flap on the one hand with a book cover to be sewn together and, on the other hand, to be able to join at least part of the bending of the book cover together with the book cover without tearing or preventing the book cover from bending as desired or being damaged in any other way. As already mentioned above, the first layer a) can be designed as a security form, which is connected to a book cover of an identification or security document via layer b) in the form of a strap.

The copolyesters can also contain the additives customary for polymers or plastics. Typical additives are, for example, lubricants such as fatty acid esters, their metal soaps, fatty acid amides and silicone compounds, antiblocking agents, inhibitors, stabilizers against hydrolysis, light, heat and discoloration, flame retardants, dyes, pigments, inorganic or organic fillers and reinforcing agents. Reinforcing agents are, in particular, fibrous reinforcing materials, such as inorganic fibers, which are produced according to the prior art and can also be coated with a size. Further information on the auxiliaries and additives mentioned can be found in the specialist literature, for example J.H. Saunders, K.C. Fresh: "High Polymers", Volume XVI, Polyurethane, Part 1 and 2, Interscience Publishers 1962 and 1964, R. Gächter, H. Müller (ed.): Paperback of plastic additives, 3rd edition, Hanser Verlag, Munich 1989, or DE-A 29 01 774.

The thermoplastic styrenic block copolymer (TPE-S) can be any styrenic block copolymer that one skilled in the art would select for a layered construction. The styrene-butylene block copolymers which can be used with preference consist of a polyethylene-butylene rubber mid-block with a polystyrene end-block chemically coupled at both ends. The polystyrene content is less than 30%. The polystyrene end blocks are evenly distributed as spherical polystyrene domains in the ethylene rubber matrix. Processes for synthesizing suitable styrenic block copolymers are known, for example, from U.S. Patents 3,485,787, 4,006,116 and 4,039,629.

The styrene block copolymers can also contain the additives customary for polymers or plastics. Customary additives are, for example, pigments, stabilizers, plasticizers, lubricants, mold release agents.

Examples of styrene block copolymers (TPE-S) are Elastron G, such as Elaston Gl 00 and G101, Elastron D, such as Elaston DL 00 and D101 from Elastron (Turkey) and Kraton™ D SIBS from Kraton Polymers (USA), Septon™, in particular Septon ™ Q1250 or Septon™ V9461 from Kuraray (Japan), Styroflex® 2G66 from Ineos Styrolution Group GmbH (Germany), Thermolast® K from Kraiburg TPE (Germany) and Saxomer® TPE-S from PCW GmbH (Germany). Other suitable styrene-butylene block copolymers are available, for example, under the trade names Kraton G and Elexar from Shell Chemie GmbH.

The thermoplastic, vulcanized (crosslinked) PP/EPDM compound can be any PP/EPDM compound that one skilled in the art would select for a layered construction. Examples of PP/EPDM compounds are Santoprene (from Exxon Mobil) or Sarlink (from DSM). Properties and the low-temperature flexibility contribute to the material properties of the TPU. The TPU-E or TPU for short can have an aliphatic or aromatic character, depending on the organic diisocyanates used. TPU usually have a block or segment structure. A basic distinction is made between hard segments and soft segments. Hard segments are formed from the organic diisocyanates used for the reaction and short-chain compounds having two to three hydroxyl, amino, thiol or carboxyl groups, preferably compounds having two hydroxyl, amino, thiol or carboxyl groups, particularly preferably diols, with a middle Molecular weight from 60 to 500 g/mol. Soft segments are formed from the organic diisocyanates used for the reaction and long-chain compounds having two to three hydroxyl, amino, thiol or carboxyl groups, preferably compounds having two hydroxyl, amino, thiol or carboxyl groups, particularly preferably diols, with a middle Molecular weight of > 500 and < 5000 g/mol.

Hard segments contribute the strength and the upper usage temperatures to the TPU property profiles, soft segments contribute the elastic properties.

Aromatic, aliphatic, araliphatic, heterocyclic and cycloaliphatic diisocyanates or mixtures of these diisocyanates can be used as organic diisocyanates for both the hard segments and the soft segments (cf. HOUBEN-WEYL "Methods of Organic Chemistry", Volume E20 "Macromolecular Substances" , Georg Thieme Verlag, Stuttgart, New York 1987, pp. 1587-1593 or Justus Liebigs Annalen der Chemie, 562, pages 75 to 136).

Specific examples include: aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), cycloaliphatic diisocyanates such as isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate, 1-methyl -2, 4-cyclohexane diisocyanate and 1-methyl -2, 6-cyclohexane diisocyanate and the corresponding isomer mixtures, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate and 2,2'-dicyclohexylmethane diisocyanate and the corresponding isomer mixtures, aromatic diisocyanates such as 2,4-tolylene diisocyanate , mixtures of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, mixtures of 2,4'-diphenylmethane diisocyanate and 4,4'- Diphenylmethane diisocyanate, urethane modified liquid 4,4'-diphenylmethane diisocyanates and 2,4'-diphenylmethane diisocyanates, 4,4'-diisocyanatodiphenyl-ethane-(1,2) and 1,5-naphthylene diisocyanate. Preference is given to using 1,6-hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, diphenylmethane diisocyanate isomer mixtures with a 4,4'-diphenylmethane diisocyanate content of >96% by weight and in particular 4,4'-diphenylmethane diisocyanate and 1 ,5-naphthylene diisocyanate. The diisocyanates mentioned can be used individually or in the form of mixtures with one another. They can also be used together with up to 15% by weight (calculated on the total amount of diisocyanate) of a polyisocyanate, for example triphenylmethane-4,4',4"-triisocyanate or polyphenyl-polymethylene-polyisocyanates preferred organic diisocyanates are, for example, 4,4'-diphenylmethane diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate and hexamethylene diisocyanate.

The preferred short-chain diols with a molecular weight of 60 to 500 g/mol are preferably aliphatic diols having 2 to 14 carbon atoms, for example ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol , 1,5-pentanediol, 1,6-hexanediol, diethylene glycol and dipropylene glycol. Also suitable, however, are diesters of terephthalic acid with glycols having 2 to 4 carbon atoms, e.g. ethoxylated bisphenols, for example 1,4-di(β-hydroxyethyl)bisphenol A, (cyclo)aliphatic diamines such as isophoronediamine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, N-methyl-1,3-propylene - diamine, N,N'-dimethylethylenediamine and aromatic diamines such as 2,4-tolylenediamine, 2,6-tolylenediamine, 3,5-diethyl-2,4-tolylenediamine or 3,5-diethyl-2,6-tolylenediamine or primary mono-, di-, tri- or tetra-alkyl substituted 4,4'-diaminodiphenylmethanes. Ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, 1,4-di(β-hydroxyethyl)hydroquinone or 1,4- Di(ß-hydroxyethyl)bisphenol A used. Mixtures of the abovementioned compounds can also be used. In addition, smaller amounts of trioia can also be added.

The long-chain compounds with two to three hydroxyl, amino, thiol or carboxyl groups, preferably compounds with two hydroxyl, amino, thiol or carboxyl groups, particularly preferably diols, with a number average molecular weight of >500 and <5000 g/mol , can be divided into two main groups: polyether dioie and polyester dioie. The polyether diols are based, for example, on polytetrahydrofuran, polyethylene oxide and polypropylene oxide and mixtures thereof. The polyester diols are typically based on adipates such as 1,4-butanediol adipate and 1,6-hexanediol adipate and caprolactone. Co-condensates are also possible.

Conventional catalysts known from the prior art can be used in the production of the TPU. These can be tertiary amines such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylamino-ethoxy)ethanol, diazabicyclo[2.2.2]octane and the like, and in particular organic metal compounds such as titanic acid esters, Iron compounds or tin compounds such as tin diacetate, tin dioctoate, tin dilaurate or the tin dialkyl salts of aliphatic carboxylic acids such as dibutyltin diacetate or dibutyltin dilaurate or the like. Preferred catalysts are organic metal compounds, especially titanic acid esters, iron and tin compounds. The total amount of catalysts in the TPU is preferably 0 to 5% by weight, more preferably 0.1 to 2% by weight, based on the total amount of TPU.

Furthermore, the TPU can contain auxiliaries and additives up to <20% by weight, based on the total amount of TPU. Typical auxiliaries and additives are pigments, dyes, flame retardants, Stabilizers against the effects of aging and weathering, plasticizers, lubricants and mold release agents, substances with a fungistatic and bacteriostatic effect, as well as fillers and mixtures thereof.

Examples of other additives are lubricants, such as fatty acid esters, their metal soaps, fatty acid amides, fatty acid ester amides and silicone compounds, antiblocking agents, inhibitors, stabilizers against hydrolysis, light, heat and discoloration, flame retardants, dyes, pigments, inorganic and/or organic fillers, for example polycarbonates, and plasticizers and reinforcing agents. Reinforcing agents are, in particular, fibrous reinforcing materials such as, for example, inorganic fibers, which are produced according to the prior art and can also be coated with a size. More detailed information about the auxiliaries and additives mentioned can be found in the specialist literature, for example the monograph by J.H. Saunders and K.C. Frisch "High Polymers", Volume XVI, Polyurethane, Parts 1 and 2, Verlag Interscience Publishers 1962 and 1964, the paperback for plastic additives by R. Gächter and H. Müller (Hanser Verlag Munich 1990) or the DE-A 29 01 774.

Suitable TPUs are available on the market, for example, under the trade names Desmopan™, Elastollan™, Pellethane™, Estane™, Morthane™, Elasthane™ or Texin™.

The TPU of the at least one outer layer a) which can be used with preference or according to the invention can be produced continuously in the so-called extruder process, e.g. in a multi-screw extruder, or in the so-called belt process. The TPUs described above, if appropriate with the auxiliaries and additives described above, can be metered in simultaneously, i.e. in a one-shot process, or in succession, i.e. according to a prepolymer process. The prepolymer method is particularly preferred. The prepolymer can be introduced in batches or continuously in part of the extruder or in a separate upstream prepolymer unit, e.g. a static mixer reactor, e.g. Sulzer mixer.

The at least one further layer b) is preferably in the form of a single-layer or multi-layer TPU film and can be produced by melting the preferred or inventive TPU granules in a melting extruder and forming a film with a thickness of > 20 to <1000 μm, preferably from> 50 to <800 μm, particularly preferably from> 100 to <450 μm.

The at least one further layer b) can be produced by the melt extrusion processes known to those skilled in the art, the blow extrusion process and/or the cast extrusion process. For this purpose, the corresponding TPU granules of the individual layers described above are melted in a melting extruder and extruded through a die to form a film in the appropriate layer thicknesses. The material of the at least one further layer b), in particular when it is the outer layer, is preferably translucent or transparent; the material of the at least one further layer b) is particularly preferably transparent.

The layer structure is preferably characterized in that the color, grain and feel of the outer layer can be individually implemented. In addition, the layer structure after lamination preferably has not only high bond strength but also very good mechanical stability with regard to tear strength and abrasion resistance. The layer structure also exhibits these properties over a period of several years. Furthermore, the layer structure has a self-closing function after lamination and folding.

Furthermore, the layer structure can give off odors, such as the smell of leather, preferably through the addition of aromatic substances in the further layer b). The further layer b) preferably contains flavorings such as LEATHER WOODY from Drom or SUEDERAL IFF from Ventos in an amount in the range from 0.1 to 1% by weight, preferably in the range from 0.2% to 0.8% by weight, particularly preferably in a range from 0.3 to 0.7% by weight, based on the total weight of the further layer b).

In a preferred embodiment of the layer structure, the first layer a), preferably also the further layer b), comprises at least one additive which has an absorption maximum in the wavelength range of the focused non-ionizing electromagnetic radiation used to produce the engraving, or the first layer a), preferably also the further layer b), is coated with at least one additive in the form of a coating agent which has an absorption maximum in the wavelength range of the focused non-ionizing electromagnetic radiation used.

In principle, all laser-sensitive additives are suitable as additives, so-called laser marking additives, i.e. those consisting of an absorber in the wavelength range of the radiation (C) used to create the engraving. The additive preferably comprises at least one or more organic and/or inorganic IR absorbers, preferably inorganic IR absorbers. Such additives and their use in molding compositions are described, for example, in WO-A 2004/50766 and WO-A 2004/50767 and are commercially available from DSM under the brand name Micabs™.

The first layer a) or preferably the further layer b) and optionally also further layers c) preferably have an IR absorber in an amount of >0.5 to <10% by weight, preferably >0.6 to < 7% by weight, particularly preferably >0.7 to <5% by weight, very particularly preferably >0.75 to <2% by weight, based on the total amount of the respective layer a), b) or c) . The further layer b) preferably has an IR absorber in an amount of >0.5 to <8% by weight, particularly preferably >0.6 to <6% by weight, based on the total amount of the further layer b) on. Suitable organic IR absorbers are, for example, compounds which have the highest possible absorption between 700 and 2500 nm (near infrared=NIR). Infrared absorbers known from the literature are suitable, for example, as are described, for. B. in M. Matsuoka, Infrared Absorbing Dyes, Plenum Press, New York, 1990 are described in terms of substance classes. Infrared absorbers from the substance classes of the azo, azomethine, methine, anthraquinone, indanthrene, pyranthrone, flavanthrone, benzanthrone, phthalocyanine, perylene, dioxazine, thioindigo, isoindoline, isoindolinone, Quinacridone, pyrrolopyrrole or quinophthalone pigments and metal complexes of azo, azomethine or methine dyes or metal salts of azo compounds. Of these, phthalocyanines and naphthalocyanines are particularly suitable. Because of the improved solubility in thermoplastics, phthalocyanines and naphthalocyanines with bulky side groups are preferable.

Suitable inorganic IR absorbers are, for example, mixed oxides of metals such as phosphorus-containing tin-copper mixed oxides, such as described in WO-A 2006/042714, those from the group of borides and/or tungstates and mixtures thereof, preferably at least one or more IR absorbers from the group of borides and/or tungstates, and mixtures thereof, particularly preferably at least one or more IR absorbers from the group of tungstates.

Examples of inorganic IR absorbers from the boride group are compounds of the MxBy type (M= La, Ce, Pr, Nd, Tb, Dy, Ho, Y, Sm, Eu, ER, Tm, Yb, Lu, Sr, Ti , Zr, Hf, V, Ta, Cr, Mo, W and Ca; and x and y are an integer from 1 to 6) where lanthanum hexaboride (Lasse), praseodymium boride (PrB ₍ ,), neodymium boride (NdB ₍ ,), cerium boride (CcB ₍ ,). Terbium boride (TbB ₍ ,). Dysprosium boride (DyB ₍ ,). Holmium boride (HoB ₍ ,). Yttrium boride (YB ₍ ,). Samarium boride (SmB ₍ ,). Europium boride (EuB ₍ ,). Erbium boride ( ErB ₍ ,). Thulium boride (TmB ₍ ,). Ytterbium boride (YbB ₍ ,). Lutetium boride (LuB ₍ ,). Strontium boride (SrB ₍ ,). Calcium boride (CaB ₍ ,). Titanium boride (TiB ₂ ). Zirconium boride (ZrB ₂ ), hafhium boride (HfB2), vanadium boride (VB ₂ ), tantalum boride (TaB ₂ ), chromium boride (CrB and CrB ₂ ), molybdenum boride (MoB ₂ , Mo ₂ B5 and MoB), tungsten boride (W ₂ ß5), or combinations of these borides suitable.

Examples of inorganic IR absorbers from the group of tungstates are those from the group of tungsten compounds of the WyOz type (W=tungsten, O=oxygen; z/y=2.20-2.99) and/or MxWyOz (M= H, He, alkali metal, alkaline earth metal, rare earth metal, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, TI, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi; x/y = 0.001-1.000; z/y = 2.2-3.0), where M is the elements H, Cs, Rb, K, TI, In, Ba, Li, Ca, Sr, Fe and Sn are preferred, of which Cs is particularly preferred. Ban WO', are particularly preferred. TI033WO3, K033WO3, Rb _(l 33WO3, CS033WO3, Nao.33WO3, Nao.7sWO3, and mixtures thereof. In a particular embodiment of the present invention, the sole use of CS033WO3 as inorganic IR absorber is very particularly preferred. Also preferred are Cs/W ratios of 0.20 and 0.25.

Among the inorganic IR absorbers, the woframates are preferable to the borides because of their low inherent color, in particular on layers, preferably on layer a), which has a radiation transmittance of >10 to <99%, preferably from >30 to <95%, particularly preferably > 40 to < 93% for the selected radiation, determined using UV-VIS-NIR-MIR as described in the methods section.

To produce such tungstates, e.g. tungsten trioxide, tungsten dioxide, a hydrate of a tungsten oxide, tungsten hexachloride, ammonium tungstate or tungstic acid and optionally other salts containing the element M, such as cesium carbonate, are mixed in certain stoichiometric ratios, so that the molar ratios of the individual components are given by the formula MxWyOz, to be played. This mixture is then treated at temperatures between 100 and 850 °C in a reducing atmosphere, e.g. an argon hydrogen atmosphere, and finally the powder obtained is tempered at temperatures between 550 and 1200 °C under an inert gas atmosphere. To produce the inorganic IR absorber nanoparticles according to the invention, the IR absorber can be mixed with the dispersants described below and other organic solvents, such as toluene, benzene or similar aromatic hydrocarbons, and in suitable mills, such as ball mills, with the addition of zirconium oxide (e.g. with a diameter of 0.3 mm) can be ground to produce the desired particle size distribution. The nanoparticles are obtained in the form of a dispersion. After grinding, further dispersing agents can optionally be added. The solvent is removed at elevated temperatures and reduced pressure. Preference is given to nanoparticles which have an average size of less than 200 nm, particularly preferably less than 100 nm. The size of the particles can be determined using transmission electron spectroscopy (TEM). Such measurements on IR absorber nanoparticles are described, for example, in Adachi et al., J. Am. ceram. society 2008, 91, 2897-2902.

The preparation of the tungstates described is described in more detail, for example, in EP-A 1 801 815 and they are commercially available, for example, from Sumitomo Metal Mining Co., Ltd. (Japan) under the designation YMDS 874.

For example, for their use in layer structures with at least one first layer a) comprising transparent polymers, in particular transparent thermoplastics, with a radiation permeability for the selected radiation of >10 to <99%, preferably >30 to <95%, particularly preferably >40 to < 93%, determined by means of UV-VIS-NIR-MIR as described in the methods section, the particles thus obtained are dispersed in an organic matrix, for example in an acrylate, and optionally as described above in a mill using suitable auxiliaries such as zirconium dioxide and optionally ground using organic solvents such as toluene, benzene or similar hydrocarbons. Suitable polymer-based dispersants are, in particular, dispersants which have high transmission, such as, for example, polyacrylates, polyurethanes, polyethers, polyesters or polyester urethanes and polymers derived therefrom.

Polyacrylates, polyethers and polyester-based polymers are preferred as dispersants, polyacrylates such as polymethyl methacrylate and polyesters being particularly preferred as dispersants which are stable at high temperatures. Mixtures of these polymers or also copolymers based on acrylate can also be used. Such dispersing aids and methods for producing tungstate dispersions are described, for example, in JP 2008214596 and in Adachi et al. J.Am. ceram. society 2007, 90 4059-4061. Suitable dispersants are commercially available.

In particular, polyacrylate-based dispersants are suitable. Such suitable dispersing agents are available, for example, under the trade names EFKA™, e.g., EFKA™ 4500 and EFKA™ 4530 from Ciba Specialty Chemicals. Polyester-containing dispersants are also suitable. They are available, for example, under the trade names Solsperse™, e.g., Solsperse™ 22000, 24000SC, 26000, 27000 from Avecia. Furthermore, polyether-containing dispersing agents are known, for example, under the trade names Disparlon™ DA234 and DA325 from Kusumoto Chemicals. Polyurethane-based systems are also suitable. Polyurethane based systems are available under the trade names EFKA™ 4046, EFKA™ 4047 from Ciba Specialty Chemicals. Texaphor™ P60 and P63 are corresponding trade names of Cognis.

The additive preferably comprises at least one or more organic and/or inorganic IR absorbers. The additive is preferably introduced via a dispersing agent, such as an organic solvent, into the polymeric material in the first layer a) or the further layer b) and further layers c), if present. The amount of IR absorber in the dispersant may be 0.2 to 50% by weight, preferably 1.0 to 40% by weight, more preferably 5.0 to 35% by weight, most preferably 10 to 30% by weight. -%, based on the dispersion used in each case of the inorganic IR absorber. In addition to the pure IR absorber substance and the dispersing agent, the overall composition of the ready-to-use IR absorber formulation can also contain other auxiliaries such as zirconium dioxide and residual solvents such as toluene, benzene or similar aromatic hydrocarbons. The IR absorber is preferably used as a solid.

There are no restrictions whatsoever with regard to the amount of inorganic IR absorbers, particularly preferably those from the group of tungstates, in the polymer compositions of the layer structures. The inorganic IR absorbers, in particular the tungstates, can usually be present in an amount of >0.5 to <10% by weight, preferably >0.6 to <2% by weight and particularly preferably >0.7 to <1 5 wt. The further layer b) preferably has an inorganic IR absorber in an amount of >0.5 to <10% by weight, preferably >0.6 to <7% by weight, particularly preferably >0.7 to <5 % by weight, very particularly preferably >0.75 to <2% by weight, based on the total amount of the further layer b).

Solids content of inorganic IR absorber, in particular tungstate, means in this context the inorganic IR absorber, in particular tungstate, as a pure substance and not a dispersion, suspension or other preparation containing the pure substance, with the following information for IR content -Absorber as an additive, in particular the tungstate content, always relate to this solids content, unless explicitly stated otherwise.

In addition to the tungstates, further IR absorbers can optionally be used as IR absorbers, but their proportion in terms of quantity in such a mixture is in each case below that of the tungstates described above. In the case of mixtures, preference is given here to compositions which contain two up to and including five and particularly preferably two or three different IR absorbers. The further IR absorber is preferably selected from the group of borides and tin oxides, in particular tin oxide doped with lass or antimony or indium tin oxide.

In a preferred embodiment of the layer structure, the part of the engraving on the further layer b) differs in terms of color or structure, in particular in terms of color, from the part of the engraving on the first layer a).

The part of the engraving on the further layer b) preferably differs in color from the part of the engraving on the first layer a). The part of the engraving on the further layer b), ie the further partial engraving, particularly preferably has a color selected from the group consisting of white, black, red, yellow, blue or a mixture of at least two of these colors. The part of the engraving on the first layer a), ie the first partial engraving, preferably has a gray or black color. However, the first partial engraving can also be colored, preferably colored blue, yellow or red. The part of the engraving on the further layer b) preferably has a white or translucent milky color, later also referred to as cloudy. This white or translucent milky color preferably covers all structures located under the engraving, ie also colored or black structures.

The structural difference of the part of the engraving on the further layer b) from the part of the engraving on the first layer a) is preferably selected from the group consisting of the width of the engraving, the depth of the engraving, the sharpness of the engraving or a combination of at least two of these. The engraving on the first layer a) is preferably narrower than the engraving on the further layer b). The difference in width between the engraving on the first layer a) and the engraving on layer b) is preferably in a range from 1 to 100%, more preferably in a range from 2 to 80%, particularly preferably in a range from 5 to 50% , very particularly preferably in a range from 10 to 40%, based on the width of the engraving on the first layer a).

In a preferred embodiment of the layer structure, the part of the coherent engraving that is applied exclusively to the first layer a) has a colored or black finish. embossing, preferably a black expression. The part of the coherent engraving that is introduced exclusively on the first layer a) is very particularly preferably black, with every brightness level of black, ie all shades of gray from light gray to black, also being included.

In a preferred embodiment of the layer structure, the part of the engraving that extends in the overlapping area and is introduced into the further layer b), the further partial engraving, is characterized by a colourless, altered structure of the polymeric material. The altered structure preferably has a cloudy or milky appearance. The areas of the layer structure, in particular the engraving on the further layer b), which contain the changed structure, preferably have a turbidity of >20%, preferably >50%, more preferably >80%, measured with a device from the company BYK-Gardner, model haze gard plus, according to the ASTM D1003:2013 standard. It is assumed that this colorless, altered structure in the further layer b), also referred to below as cloudy engraving, is caused by the fact that the polymeric material stores air at the points heated by the radiation, which breaks the naturally incident light differently than the locations of the further layer b) in the non-engraved area.

In a preferred embodiment of the layer structure, the further layer b) has a layer thickness at the points with the changed structure which is >0.001 mm, more preferably >0.005 mm, particularly preferably >0.01 mm thicker than at the points without changing the structure.

In a preferred embodiment of the layer structure, the first layer a) is joined to the further layer b) via a joining zone at least at the points of the engraving in the overlapping area. The joining zone is understood to mean the part of the layer structure that is created by the merging of the materials of the first layer a) with the further layer b) through the engraving. By engraving, preferably laser engraving, in the overlapping area, the materials of the first layer a) and the further layer b) are joined or welded together in the area of the joining zone in such a way that they cannot be separated from one another without tearing the joining zone be able. As a result of the welding, the materials of the first layer a) are inseparably fused at least in part with the material of the further layer b) in the area where they make contact with one another through the engraving.

In a preferred embodiment of the layer structure, when the further layer b) is removed from the first layer a), the continuous engraving is separated at least in the overlapping area. The first layer a) and the further layer b) are connected to one another in the overlapping area in the joining zone at least at the points where the engraving is located in such a way that they can only be separated with a force of at least 1 N/cm at a peel angle of 90° can be separated according to the DIN 11339:2010-06 standard. Attempting to separate the two layers a) and b) from one another also causes a separation of the continuous engraving in the areas of the overlapping area and the partial engraving located on the overlapping area on the first layer a). When separating layers a) and b) in the overlapping area the partial engravings, i.e. the first partial engraving, are separated from the further partial engraving in such a way that only the first partial engraving remains on the first layer a) and the further partial engraving on the further layer b). A meaningful joining of the separated section of the first layer a) containing the first partial engraving with a further layer b) that contains a different partial engraving than the original further layer b) is not possible while obtaining a meaningful joined engraving. A security form of a passport, which is represented by the first layer a), cannot be separated from the book cover at this predetermined breaking point between the first layer a) and the further layer b) in order to be connected to another book cover over another further layer b ) to be merged. Conversely, the separated further partial engraving on the further layer b) cannot be combined with another first partial engraving of another first layer a) in order to produce a meaningful engraving. This can prevent security documents, such as passports, from being forged, as is usually done by exchanging book covers or parts of the security form in the event of attempts at forgery. During the separation, at least one of the layers, either the first layer a) or the further layer b) or the complete engraving can also be destroyed.

When the two layers a) and b) are separated, in particular by removing the further layer b) from the first layer a), in the overlapping area, in particular in the joining zone, the structure of the engraving is preferably changed in such a way that it does not can be reassembled in such a way that the engraving results in the original structure, i.e. the original appearance, before the further layer b) is removed from the first layer a). This means that after removing the further layer b) from the first layer a), the engraving no longer runs cohesively or continuously. When removing the further layer b) from the first layer a), it is preferred that the engraving on the first layer a) that is not in the overlapping area remains intact. In particular, intact means that the shape, depth, width and sharpness as well as the color are unchanged compared to the state before the further layer b) was removed.

In a preferred embodiment of the layer structure, the part of the engraving that is located in the overlapping area can only be read on the further layer b). Preferably, the engraving in the overlapping area extends only into the further layer b). The engraving in the overlapping area is preferably <99%, more preferably <90%, more preferably <80%, particularly preferably <70%, very particularly preferably <50%, based on the thickness of the further layer b). the further layer b) inside. The engraving, ie the additional partial engraving, preferably does not extend into the first layer a) of the overlapping area. If the engraving does protrude into the first layer a) in the overlapping area, the additional partial engraving preferably has a different color than the first layer a) outside of the overlapping area. In a preferred embodiment of the layer structure, the first layer a) comprises at least one dye and/or at least one pigment. Preferably, the layered structure or the first layer a) additionally comprises a printed layer which is applied over the whole and/or part of the area.

The layer structure or the first layer a) preferably has the pigment in a concentration of from 5 to 1000 ppm, more preferably from 10 to 800 ppm, particularly preferably from 15 to 500 ppm.

The first layer a) preferably contains at least one thermoplastic and/or at least one black pigment, preferably carbon black.

In a preferred embodiment of the layer structure, the further layer b) has a thickness in a range from >20 to <1000 μm, preferably from >50 to <800 μm, particularly preferably from >100 to <450 μm. The first layer a) preferably has a thickness in a range from >20 to <1000 μm, preferably from >50 to <800 μm, particularly preferably from >100 to <450 μm. All layers a), b) and c) preferably have a thickness in a range from >20 to <1000 μm, preferably from >50 to <800 μm, more preferably from >100 to <450 μm.

In a preferred embodiment of the layer structure, the further layer b) contains at least one thermoplastic polyurethane. Examples of preferred polyurethanes have already been mentioned above in connection with TPUs that can be used. The polyurethane is particularly preferably produced from the components of a linear polyol, in particular a diol, such as polyester, polyether or polycarbonate diols, and an organic diisocyanate, in particular an aliphatic diisocyanate, preferably HDI or IPDI, and short-chain, mostly bifunctional alcohols (chain extenders). Examples of bifunctional alcohols have already been described above in connection with the description of TPU and are to be used with particular preference here.

Another subject matter of the invention relates to a method for producing a layer structure with a joining zone, including at least the following steps:

I) providing a first layer a) containing at least one material that can be laser engraved;

II) at least partially overlaying the first layer a) with at least part of a further layer b) containing at least one polymeric material, preferably a thermoplastic polyurethane, with the formation of an overlap region of the further layer b) on the first layer a);

III) Creation of an engraving, preferably a laser engraving, in the layer structure, with part of the engraving, also called the first partial engraving, being located on a part of the first layer a) that is not covered by layer b) and another part the engraving, also further partial engraving, is at least on a part of the further layer b) and optionally on a part of the first layer a), which is overlaid by the further layer b), forming a joining zone, with connect the two layers a) and b) inseparably with each other in the joining zone. The first layer a) can be made of any material that can be engraved by radiation, in particular by laser. In the context of the invention, radiation-engravable first layer a) means that the layer contains a material that can be treated with light in a wavelength range from >0.1 to <1000 μm, preferably from >1.0 to <50 μm. particularly preferably from >1.0 to <2.5 pm interacts in such a way that irradiation with light having sufficient energy in this wavelength range causes a Larbandung. This Lar change can be generated in different ways:

51. either by radiation-sensitive materials which are located in the first layer a) and whose color is changed by irradiation in the above-mentioned wavelength range, or

52. be produced by bringing the first layer a) into contact with a colorant which, when the first layer a) is irradiated in the above-mentioned wavelength range, penetrates into the first layer a) and thereby causes a color change in the first layer a) generated, or

53. by carbonizing the polymeric material of the first layer a) itself.

In the variant Sl. For example, an IR absorber can be used, as has already been described above for the layer structure according to the invention. Carbon black can be used as an alternative or in addition to the IR absorber. Carbon black is preferably used. Carbon black is preferred in an amount in a range from 0.1 to 10% by weight, more preferably in a range from 0.2 to 8% by weight, particularly preferably in a range from 0.5 to 6% by weight. %, very particularly preferably in a range from 1 to 5% by weight, based on the total mass of the first layer a).

The variant S2. is, if a colored engraving is desired on or in the first layer a), preferably in addition to one of steps S1. or S3.

The carbonization represents a structural change in the polymers due to the energy input of the laser radiation. To produce a black or gray laser engraving, the procedure is preferably as follows: By varying the frequency of the laser beam used, the engraving on layer a) can be adjusted to gray levels. At low frequencies, the pulse duration is long enough to allow in-layer carbonization of organic materials, which is variant S3. As a result, the engraving appears in a dark color. This occurs at frequencies less than 30 KHz for a laser with a nominal power of 60 watts. At frequencies above 30 KHz, the pulse duration is particularly short. This means that a structural change in the material can be seen and felt, while carbonization in organic materials only takes place to a limited extent. The engraving appears gray to white. The laser engraving is preferably produced with a laser which emits at a wavelength of 950 to 1500 nm, preferably at a wavelength of 1064 nm. A diode laser is preferably used. Particularly short pulse durations can be achieved with a diode laser in order to generate high energy peaks. This can in the further layer b) a special clear and light partial engraving can be produced, which preferably appears as a dark partial engraving in the part not belonging to the overlapping area in the adjoining first layer a).

The polymeric material of the first layer a) or of the further layer b) is preferably selected from the materials for these layers as have been described in connection with the layer structure according to the invention. To avoid repetition, reference is made below to the above explanations of the polymeric material with regard to preferred embodiments, materials, amounts, composition and additives, as described in connection with the layer structure according to the invention, which also apply here.

The engraving in step III) is preferably produced by irradiating the layer structure with focused non-ionizing electromagnetic radiation. The irradiation in step III) is preferably carried out with laser radiation with a wavelength in the range from >0.1 pm to <1000 pm, preferably from >1.0 pm to <50 pm, particularly preferably from >1.0 pm to <2 .5 p.m.

If the laser is used for irradiation, this can be done in continuous wave mode (CW laser), in particular for engraving pixel files or greyscale files. Pulsed laser radiation is particularly preferably used for irradiating the layered structures or for vector images or rasterized images. A pulse frequency of 0.5 KHz to 1000 KHz is preferably used, pulse frequencies of 5 KHz to 100 KHz are preferably used, particularly preferably pulse frequencies of 15 KHz to 50 KHz.

By varying the power of the laser beam used for the irradiation in step III), the intensity of the coloring at the lasered areas can be influenced, depending on the requirements placed on the desired application. The higher the laser power used, the more intense the black color will be on the lasered areas of the first layer a), as already mentioned.

The radiation used in step III) to produce the engraving produces the engraving or the further partial engraving in the overlapping area at least on the further layer b). The engraving produced in the further layer b) appears as a light engraving. This light engraving is due to structural changes in the polymeric material of the further layer b). In a variant to prevent that part of the first layer a) located under the further layer b) from being engraved in the overlapping area, the further layer b) contains an IR absorber. This IR absorber has already been described above in connection with the layer structure according to the invention, as have the preferred amounts used for this purpose. This selection and amount of IR absorber also apply to the process described here. The use of the IR absorber also allows the energy input from the radiation source to be kept as low as possible in order to change the structure of the polymeric material, which creates the appearance of the engraving. Since the IR absorber absorbs part of the energy of the radiated radiation and converts it into heat, which then leads to the changed structure of the polymeric material taking place, which leads to the colorless, cloudy engraving, almost none gets through Radiation more on the first layer a) lying under the further layer b) in the overlapping area. It is assumed that this cloudy engraving in the further layer b) is caused by the fact that the polymeric material stores air at the points heated by the radiation, which refracts the naturally incident light differently than in the non-engraved area. The areas of the layer structure, in particular the engraving on the further layer b), which contain the changed structure, preferably have a turbidity of >20%, preferably >50%, more preferably >80%, measured with a device from Pirma BYK-Gardner, model haze gard plus, according to the ASTM D1003:2013 standard.

In order to achieve at least one continuous area of engraving between the overlapping area and the area formed only by the first layer a), the laser is continuously applied from the area in which only the first layer a) is located to the overlapping area on the further layer b) out or vice versa. A first partial engraving is thus produced on the first layer a) outside the overlapping area, which preferably has a black coloration. Furthermore, another partial engraving occurs on layer b), which preferably has a cloudy or milky appearance. A joint zone is formed in the overlapping area at the points where the laser is guided. As already described for the layer structure, the two layers a) and b) are inseparably connected to one another in the joining zone. Inseparable is intended to mean that when trying to separate the two layers a) and b) from one another, the continuous engraving in the areas of the overlapping area and the partial engraving in the overlapping area on the first layer a) separate. By separating layers a) and b) in the area of the engraving, it is achieved that each of the two parts that contain part of the engraving cannot be sensibly joined to another part that contains a different engraving. A security form for a passport cannot be separated from the book cover at this predetermined breaking point between the first layer a) and the further layer b) in order to be joined with another security form, as is usually the case with counterfeit attempts. During the separation, at least one of the layers a) or b) or the complete engraving can also be destroyed. One of the two materials of the two layers a) and b) is preferably also at least partially destroyed, so that layers a) and b) can no longer be combined to form a layered structure with an intact engraving.

An NdYAG laser (neodymium-doped yttrium aluminum garnet laser) is preferably used in the method for producing the engraving in step III). Laser types that are suitable for engraving and welding plastic parts, such as layered structures, can also be used for colored laser engraving of layered structures. For example, a CO2 laser can also be used. A laser is preferably used which emits at a wavelength of 950 to 1500 nm, preferably at a wavelength of 1064 nm. A diode laser is preferably used. With a diode laser, particularly short pulse durations can be achieved, with which high energy peaks can be generated. So in the further layer b) a special clear and light partial engraving can be produced, which preferably appears as a dark partial engraving in the part in the adjoining first layer a) that does not belong to the overlapping area.

The two superimposed layers a) and b) in step III) can be irradiated either from the side of the layer structure, with the radiation hitting the first layer a) first, or alternatively from the other side, i.e. from the side, with the radiation first meets the further layer b), take place. In a preferred embodiment of the method, the superimposed layers a) and b) from step II) in step III) are preferably irradiated from the side of the further layer b), the radiation hitting the further layer b) first. When irradiating in step III), the irradiation can be chosen such that the further partial engraving is either only present in the further layer b) or at least partly also in the first layer a) below the further layer b). If, at least in the overlapping area, radiation is alternately irradiated from the first side a) and from the other side b), then alternating black and cloudy areas are obtained in the overlapping area. In this way, patterns can be introduced into the engraving, preferably in the overlapping area, which allow white and black sections to appear alternately.

In a preferred embodiment of the method, at least the first layer a), and preferably also the further layer b), contains a thermoplastic selected from the group consisting of polymers of ethylenically unsaturated monomers, polycondensates of bifunctional reactive compounds and polyaddition products of bifunctional reactive compounds or combinations of at least two of these. Examples and preferred thermoplastics have been described in connection with the layer structure according to the invention and are also valid and transferable for the thermoplastic in the process.

To avoid repetition, reference is made below to the above statements on the thermoplastic with regard to preferred embodiments, materials, amounts, composition and additives, as described in connection with the layer structure according to the invention.

Another object of the invention relates to a laminate comprising a layer structure according to the invention. The laminate preferably has exactly one first layer a) and one further layer b) including the previously described overlapping area of the two layers a) and b) and an engraving, as described in connection with the layer structure according to the invention. In addition to the two layers a) and b) of the layer structure, the laminate can also contain at least one further layer c). The at least one further layer c) preferably has a polymeric material. The polymeric material of the at least one further layer c) is also preferably selected from the group of materials described for the first layer a) and the materials described for the further layer b).

A further object of the invention relates to the use of the layer structure according to the invention or the laminate according to the invention for the production of a security document containing a security form, preferably a security form in a multi-layer book cover, particularly preferably a security form in a book cover for security and identification documents. All embodiments, materials, amounts, composition and additives as described in connection with the layer structure according to the invention can also be used here.

Another subject matter of the invention relates to a method for producing a multi-layer laminate, comprising at least the steps: i) providing a layer structure according to the invention; ii) Lamination of the layer structure from step i) at a temperature of >80°C to <220°C, preferably at a temperature of >100°C to <200°C, particularly preferably at a temperature of >110°C to < 190 ° C, and a pressure of> 2 N / cm ² to <500 N / cm ² , preferably at a pressure of> 10 N / cm ² to <400 N / cm ² , particularly preferably at a pressure of> 20 N /cm ² to <300 N/cm ² , preferably lamination with an engraved laminating sheet, particularly preferably with an engraved laminating sheet comprising an anti-stick coating; iii) optionally folding the layered construction, preferably along a central line of the layered construction, so that the layered construction as well as the laminate is folded symmetrically; iv) Optional pressing of the layered structure after step iii) along the central line, preferably pressing between two rolls, rolls and/or plates, at a temperature of > 0.5 °C to <150 °C, preferably > 1 °C to <50°C, particularly preferably >1°C to <20°C, is above the softening point of the outermost layer for a period of 2 to 20 seconds, preferably 2 to 10 seconds, particularly preferably 2 to 5 seconds. v) Optional removal of the laminate including the layer structure from the press.

The provision in step i) can be any provision of the layer structure that the person skilled in the art would select for this purpose.

High-gloss laminating sheets were used for the lamination in step ii), so the laminate was given high-gloss surfaces on both sides and thus had a crystal-clear appearance

To avoid repetition, reference is made to the above with regard to the embodiments and preferred ranges of the individual layers of the layer structure.

In another embodiment of the method according to the invention, the layer structure can be described before and/or after lamination by means of laser radiation at other points of the layer structure or the laminate with a black, white or colored engraving, as described above.

methods

Transmission/radiation transmittance: To measure the radiation transmittance, also known as transmittance [%], a method was used that works in the spectral ranges UV-VIS-NIR- MIR took place. A UV-VIS-NIR spectrometer from Jasco (V-670) (Japan) was used for the spectral range from -2600 nm to 200 nm. The standard program with the following settings was selected here, unless otherwise specified; UV/VIS bandwidth 1.0nm; NIR bandwidth 4.0nm; scan speed 400nm/min; Light Score 340nm; Grating/detector 850nm.

An FTIR spectrometer from Thermo Fisher Scientific Inc., USA, type Nicolet™ iS™1 0 FT-IR was used for the spectral range from -2500 nm-28000 nm (wave number: 350 to 4000 cm" ¹ ).

The results in the wavelength range from 200 to 2700 nm are shown in FIG. 5, since this is the spectral range in which the engraving at 1064 nm was later introduced into the layer structure by the diode laser. The following settings were made for the spectrometer Jasco (V-670):

SPECTROMETER DESCRIPTION

examples

Example 1)

Production of a highly concentrated IR masterbatch.

The masterbatch for the production of a further layer b) in the form of a TPU film was compounded using a conventional twin-screw compounding extruder, at processing temperatures of 175° C. to 200° C. which are customary for TPU.

A master batch with the following composition was compounded and then granulated:

92.5% by weight of thermoplastic polyurethane, Elastolan™ 1185A from BASF

7.5% by weight of YMDS 874 IR absorber from Sumitomo, (cesium tungsten oxide in toluene).

example 2)

Production of a type a) film type as a further layer b) based on TPU The TPU film was produced by mixing the masterbatch granules from Example 1) with TPU granules in the following concentration:

10% by weight masterbatch

90% by weight thermoplastic polyurethane, Elastolan™ 1185A from BASF

A film was produced on a blown film extrusion line in a thickness of 200 μm. Alternatively, such a film with a thickness of 20 to 800 μm can also be extruded through a die by melting the mixture in a melting extruder and extruding it through a die to form a film. Transmission values of this further layer b) are shown in FIGS. 5 and 6.

example 3)

Production of a type b) film type as a further layer b) based on TPU

The TPU film was produced by mixing the masterbatch granules with TPU granules in the following concentration:

20% by weight masterbatch

80% by weight thermoplastic polyurethane, Elastolan™ 1185A from BASF

Example 4)

Overlaying and joining the films from example 2) or example 3) to passport data pages made of polycarbonate in the form of a first layer a) by vibration welding.

The passport data pages corresponding to a first layer a) of the layer structure according to the invention were produced from polycarbonate films from Covestro. The data pages or the security form were produced in the following structure: 100 μm Makrofol® ID6-2 000000; 100 µm Makrofol® ID6-2 750061; 200 µm Makrofol® ID4-4 010207; 200 µm Makrofol® ID4-4 010207; 100 µm Makrofol® ID6-2 750061; 100 µm Makrofol® ID6-2 000000.

The foils were formed into a monolithic composite with a total thickness of 800 μm under pressure and heat. The lamination was carried out on a Bürkle type 50/100 press. First, the foils were pressed in the heating press at 190° C. for 6 minutes at a pressure of 60 N/cm ² , the pressure was finally increased to 200 N/cm ² and maintained for a further 60 seconds. Subsequently, the laminates were cooled under a pressure of 200 N/cm ² up to a temperature of 35°C, then the laminates were removed from the press. The laminates were then cut to the size of a passport, approx. 92 mm x 125 mm. Next, a further layer b) in the form of a TPU film from example 2 or 3 was placed on one of the 125 mm long sides of the laminate. The overlapping area of the TPU film (further layer b) with the polycarbonate laminate (first layer a) had a width of 6 mm. Joining the materials the first layer a) and the further layer b) to form a layer structure according to the invention was carried out by thermal pulse welding on a WISG device from Heinz Schirmacher GmbH. Welded in 4 seconds at a pressure of 2 bar and a temperature of 140°C. The subsequent cooling time had a duration of 20 seconds.

Example 5)

Overlaying and joining the films from example 2) or example 3) to passport data pages made of polycarbonate in the form of a first layer a) by lamination. The passport data pages were made from polycarbonate films from Covestro.

The data pages or the security form were produced in the following layer structure: 100 μm Makrofol® ID6-2 000000; 100 µm Makrofol® ID6-2 750061; 200 µm Makrofol® ID4-4 010207; 200 µm Makrofol® ID4-4 010207; 100 µm Makrofol® ID6-2 750061; 100 µm Makrofol® ID6-2 000000.

The foils were formed into a monolithic composite with a total thickness of 800 μm under pressure and heat. The lamination was carried out on a Bürkle type 50/100 press. First, the foils were pressed in the heating press at 190° C. for 6 minutes at a pressure of 60 N/cm ² , the pressure was finally increased to 200 N/cm ² and maintained for a further 60 seconds. Subsequently, the laminates were cooled under a pressure of 200 N/cm ² up to a temperature of 35°C, then the laminates were removed from the press. The laminates were then cut to the size of a passport, approx. 92 mm x 125 mm. Next, a further layer b) in the form of a TPU film from example 2 or 3 was placed on one of the 125 mm long sides of the laminate. The overlapping area of the TPU film (further layer b) with the polycarbonate laminate (first layer a) had a width of 6 mm. The materials of the first layer a) and the further layer b) were joined to form a layer structure according to the invention by lamination on a type 50/100 press from Bürkle. First, the materials were pressed in the hot press at 160°C for 60 seconds at a pressure of 30 N/cm ² . Subsequently, the materials were cooled under a pressure of 50N/cm ² up to a temperature of 35°C, then the laminates were removed from the press. Laminating sheets with a non-stick coating were used for the lamination to prevent the TPU film from sticking to the laminating sheet. Laminating sheets from the company 4-Plate with a non-stick coating from the company Plascotec were used.

Example 6)

Sealing of the joint by introducing an engraving while preserving a joint zone.

The joined materials from example 4) and 5) produced with the further layer b) in the form of the TPU film from example 3) were sealed at the joint edge by means of a laser engraving. Thus, when the joined materials of the further layer b) made of TPU and the first layer a) made of PC separate, it is almost impossible to join them again in an exact manner. So counterfeit attempts by Passports are easily identified. To do this, the TPU-PC composites were placed on the workpiece carrier of a laser engraving system. A laser engraving system from Foba, type D84S, was used. It was laser engraved with a current of 30 amps and a frequency of 8 KHz, at a travel speed of 100 mm/s. Both letters and numbers as shown in Figures 1 and 2 were engraved. The engraving was created parallel to and over the joining edge PC to TPU in such a way that the upper half of the letters and numbers in the TPU were engraved in the overlapping area (further partial engraving) and the lower half in the PC outside of the overlapping area (first part -Engraving). The engraving appeared in two colors. In the TPU portion (further partial engraving) this appeared as a white raised engraving. The engraving in the PC portion (first partial engraving) outside the overlap area appeared as a black raised engraving.

In an experiment using tools and heating the further layer b) in the form of the TPU film, this could be removed from the first layer a) in the form of the PC data page. However, the engraved letters and numbers were destroyed. After removing the further layer b) TPU film from the first layer a) in the form of the PC layer, the engraving in the further layer b), in the TPU portion, was no longer recognizable in the underlying PC layer, as can be seen in FIG. Depending on the amount of IR absorber selected, it is possible to introduce the further partial engraving only into the further layer b) or also into the underlying first layer a) while the laser power remains the same in the overlapping area. It is preferred if the further partial engraving is present exclusively on the further layer b).

Example 7)

Sealing of the joint by introducing an engraving while preserving a joint zone.

The joined materials from example 4) and 5) produced with the further layer b) in the form of the TPU film from example 2) were sealed at the joining edge by means of laser engraving to obtain a layer structure according to the invention. Thus, when the joined materials of the further layer b) made of TPU and the first layer a) made of PC separate, it is almost impossible to join them again in an exact manner. This makes it easy to identify attempts to forge passports. To do this, the TPU-PC composites were placed on the workpiece carrier of a laser engraving system.

A laser engraving system from Foba, type D84S, was used, the laser of which operates at a wavelength of 1064 nm. It was laser engraved with a current of 30 amps and a frequency of 8 KHz, at a travel speed of 100 mm/s. Letters as shown in Figures 1 and 2 were engraved. The engraving was created parallel to and over the joining edge PC to TPU in such a way that the upper half of the letters and numbers in the overlapping area were engraved in the TPU (further partial engraving) and the lower half in the PC outside of the overlapping area (first part -Engraving). The engraving appeared as a black raised engraving both in the TPU portion and in the PC portion. In an attempt using tools and heating the TPU film, it could be removed from the PC data page. After removing the TPU film, the engraving in the TPU portion was also visible in the PC layer underneath. A forgery is almost impossible.

Example 8)

Production of a type b) film type as a further layer b) based on TPU with an alternative UV absorber

The TPU film was produced with a thermoplastic polyurethane, Elastolan™ 1185 A from BASF, on a blown film extrusion line, with a thickness of 200 μm. Alternatively, such a film with a thickness of 20 to 800 μm can also be extruded through a die by melting the thermoplastic polyurethane in a melting extruder and extruding it through a die to form a film. The film was then coated with a transparent infrared absorbing liquid by brush application and air dried. An infrared-absorbing liquid from Clearweld, type LD920C, which contains organic IR-absorbing dyes, was used. Alternatively, the infrared-absorbing liquid from Clearweld, type LD920C, can also be incorporated directly into the thermoplastic polyurethane before extrusion.

Example 9)

Superimposing and joining the films from example 8) to passport data pages made of polycarbonate in the form of a first layer a) by vibration welding.

The foils were formed into a monolithic composite with a total thickness of 800 μm under pressure and heat. The lamination was carried out on a Bürkle type 50/100 press. First, the foils were pressed in the heating press at 190° C. for 6 minutes at a pressure of 60 N/cm ² , the pressure was then increased to 200 N/cm ² and maintained for a further 60 seconds. Subsequently, the laminates were cooled under a pressure of 200 N/cm ² up to a temperature of 35°C, then the laminates were removed from the press. The laminates were then cut to the size of a passport, approx. 92 mm x 125 mm. Next, a further layer b) in the form of a TPU film from Example 8 was placed on one of the 125 mm long sides of the laminate. The overlapping area of the TPU film (further layer b) with the polycarbonate laminate (first layer a) had a width of 6 mm. Joining the materials the first layer a) and the further layer b) to form a layer structure according to the invention was carried out by thermal pulse welding on a WISG device from Heinz Schirmacher GmbH. Welded in 4 seconds at a pressure of 2 bar and a temperature of 140°C. The subsequent cooling time had a duration of 20 seconds.

example 10)

Sealing of the joint by introducing an engraving while preserving a joint zone

The joined materials from example 8) and 9) produced with the further layer b) in the form of the TPU film from example 8) were sealed at the joint edge by means of laser engraving to obtain a layer structure according to the invention. Thus, when the joined materials of the further layer b) made of TPU and the first layer a) made of PC separate, it is almost impossible to join them again in an exact manner. This makes it easy to identify attempts to forge passports. To do this, the TPU-PC composites were placed on the workpiece carrier of a laser engraving system. A laser engraving system from Trumpf, type 3130, was used, the laser of which operates at a wavelength of 1064 nm. It was laser engraved with a power of 80% and a frequency of 12 KHz, at a travel speed of 400 mm/s. Both letters and numbers were engraved, as shown in Figurö. The engraving was created parallel to and over the joining edge PC to TPU in such a way that the upper half of the letters and numbers in the TPU were engraved in the overlapping area (further partial engraving) and the lower half in the PC outside of the overlapping area (first part -Engraving). The engraving appeared in two colors. In the TPU portion (further partial engraving) this appeared as a white raised engraving. The engraving in the PC portion (first partial engraving) outside the overlap area appeared as a black raised engraving.

characters

In the figures 1-4 preferred embodiments for the layer structure and the method for its production are described, which are not to be read restrictively. The figures show in

FIG. 1: an illustration of a layer structure in the form of a passport with a personalized engraving on the first layer a) in black and on the further layer b) in the overlapping area in milky to white;

Figure 2: A close-up of the depiction of the security document from Figure 1 in the form of a passport with a personalized engraving on the first layer a) in black (first part engraving) and on the other layer b) in the overlapping area in cloudy or white (further part -Engraving);

FIG. 3: a layer structure according to the invention, in which the personalized engraving cannot be detached without being destroyed;

FIG. 4a: a schematic representation of the method for producing a layer structure according to the invention with a joining zone; FIG. 4b: a schematic representation of the process for producing a multilayer laminate containing the layer structure according to the invention;

FIG. 5: a diagram of the transmission values of two further layers b) from examples 2) and 3) with different proportions of IR absorber in the wavelength range from 200 to 2700 nm;

FIG. 1 shows a layer structure 10 according to the invention in the form of a passport, which represents a security document. The layer structure 10 was produced according to example 7. The layer structure 10 includes at least a first layer a) 14 consisting of a poly carbonate and a further layer b) 12 consisting of a thermoplastic polyurethane. The further layer b) 12 overlaps the first layer a) 14 in the overlapping area 17. There are also several connected engravings 13, each consisting of a white or almost transparent part 16 and a black part 18 in the layer structure 10. The white part of the engraving 16 is in the overlapping area 17 and the black part of the engraving 18 is exclusively on the first layer a) 14. The two parts 16 and 18 of the engraving are connected to one another by a joining zone in which the black part of the engraving , namely the first part-engraving 18, directly to the cloudy or white part of the engraving, the other part-engraving 16 encounters.

FIG. 2 is an enlargement of the middle part of the layered structure 10 from FIG ) 14 are clearly visible.

FIG. 3 shows an attempt to forge a layer structure according to the invention, as shown in FIG. 2, produced according to Example 6. It can be seen that the continuous engraving 13 cannot be separated in such a way that the engraving 13 could be restored or read on one of the layers, layer a) 14 or layer b) 12. It is therefore not possible to detach the further layer b) 12 from the first layer a) 14 without destroying it. From the remaining partial engraving 18, it is difficult or impossible to draw conclusions about the information that was contained in the continuous engraving 13 before the further layer b) 12 was peeled off.

In FIG. 4a, the method for producing a layer structure 10 with a joining zone is shown schematically. In step I) 20 the first layer a) was provided. In step II) 22, the first layer a) was at least partially superimposed by the further layer b) and laminated together by lamination on a Bürkle type 50/100 press. Here, the materials of the first layer a) and the further layer b) were pressed at least in the overlapping area in the stated press at 160° C. for 60 seconds at a pressure of 30 N/cm ² . The materials were then cooled under a pressure of 50N/cm ² to a temperature of 35°C. Then the laminates were removed from the press. Laminating sheets with an anti-stick coating were used for laminating to prevent the TPU film from sticking to the laminating sheet. Laminating sheets from the company 4-Plate were used with a non-stick coating from the company Plascotec of layers a) and b) to form a joining zone and also in the part of the first layer a) which is not covered by the further layer b).

In FIG. 4b, the process for producing a multi-layer laminate is shown schematically. In step i) 30 the layer structure 10 according to the invention was provided. In step ii) 32, the layer structure 10 from step i) 30 was laminated at a temperature of 180° C. and a pressure of 100 N/cm ² in a commercially available press, as described above in connection with FIG. 4a. In step iii) 34, which is optional, the laminated layup 10 from step ii) 32 was folded along a line running through the layup 10 centrally. In step iv) 36, which is optional, the layered structure 10 from step iii) 34 was pressed between two rollers at a temperature of 250° C. for 5 seconds. The laminate was then removed from the press in step v) 38 .

FIG. 5 shows the transmission values of the further layers b) from Examples 2) and 3) in the wavelength range from 200 to 2700 nm, as measured using the measurement method described above. Unexpectedly, the transmission at the wavelength of 1064 nm, at which the engraving 13 is introduced into the layer structure 10, did not decrease linearly but significantly more. Thus, when the IR absorber concentration was doubled, from 0.75% by weight in example 2) to 1.5% by weight in example 3), the transmission did not decrease by half but by 1/3, namely from 45 % to 15%.

FIG. 6 shows a layer structure 10 according to the invention in the form of a passport, which represents a security document. The layer structure 10 was produced according to example 10. The layer structure 10 includes at least a first layer a) 14 consisting of a poly carbonate and a further layer b) 12 consisting of a thermoplastic polyurethane. The first layer a) 14 overlaps the other layer b) 12 in the overlapping area 17. There are also several connected engravings 13, which at least partly consist of a white or almost transparent part 16 and a black part 18, partly on the first Layer a) 14 and partly on the further layer b) 12. The white part of the engraving 16 is on the further layer b) 12 and the black part of the engraving 18 is in the overlapping area 17 on the first layer a) 14. The two parts 16 and 18 of the engraving are connected to one another by a joining zone, in which the black part of the engraving, namely the first partial engraving 18, lies directly on the cloudy or white part of the engraving, the further partial engraving 16 bumps.

Claims

42 A layer structure, preferably a hinge, particularly preferably a hinge formed between a security form and a book cover, for example via a flap, very particularly preferably a hinge formed between a security form and a book cover of an identification or security document, comprising at least a) a first radiation- engravable layer a) containing at least one polymeric material; and b) at least one further layer b) containing at least one polymeric material, preferably a thermoplastic elastomer, preferably a thermoplastic polyurethane with a hardness of >40 Shore A according to DIN ISO 7619-1-2012-2 to <95 Shore D according to DIN ISO 7619-1-2012-2; wherein the further layer b) overlaps the first layer a) in part, forming an overlapping area, and wherein a coherent engraving is partly in the overlapping area, preferably in the further layer b), and partly in the part of layer a ) that extends outside the overlap area. The layer structure according to claim 1, wherein the first layer a), preferably also the further layer b), comprises at least one additive which has an absorption maximum in the wavelength range of the focused non-ionizing electromagnetic radiation used to produce the engraving, or wherein the first Layer a), preferably also the further layer b), is coated with at least one additive in the form of a coating agent which has an absorption maximum in the wavelength range of the focused non-ionizing electromagnetic radiation used. The layer structure according to any one of the preceding claims, wherein the further layer b) an IR absorber with a light transmission of <20% in the wavelength range 950 to 1200 nm, preferably in an amount of >0.5 to <10% by weight, more preferably >0.6 to <7% by weight, particularly preferably >0.7 to <5% by weight, very particularly preferably >0.75 to <2% by weight, based on the total amount of layer b) contains. The layer structure according to one of the preceding claims, wherein the part of the engraving on the further layer b) differs in color or structure, in particular in color, from the part of the engraving on the first layer a). The layer structure according to one of the preceding claims, wherein the part of the coherent engraving which is introduced exclusively on the first layer a) has a colored or black characteristic, preferably a black characteristic. 43 The layer structure according to one of the preceding claims, wherein the part of the engraving that extends in the overlapping area and is introduced into the further layer b) is characterized by a colourless, altered structure of the polymeric material. The layer structure according to one of the preceding claims, wherein when removing the further layer b) from the first layer a), the coherent engraving is separated at least in the overlapping area. The layer structure according to one of the preceding claims, wherein the part of the engraving that is located in the overlapping area can only be read on the further layer b). The layer structure according to one of the preceding claims, wherein the polymeric material of the first layer a) contains a thermoplastic material selected from polymers of ethylenically unsaturated monomers and/or polycondensates of bifunctional reactive compounds and/or polyaddition products of bifunctional reactive compounds. The layer structure according to any one of the preceding claims, wherein the first layer a) comprises at least one dye and/or at least one pigment. The layer structure according to any one of the preceding claims, wherein the further layer b) contains at least one thermoplastic polyurethane. A method for producing a layer structure with a joining zone, including at least the steps:

II) At least partial overlaying of the first layer a) with at least part of a further layer b) containing at least one polymeric material, preferably a thermoplastic polyurethane, with the formation of an overlap region from the further layer b) to the first layer a);

III) Creating an engraving, preferably a laser engraving, in the layer structure, with part of the engraving being on part of the first layer a) that is not covered by layer b) and another part of the engraving being on at least one part of layer b) and optionally on a part of the first layer a), which is overlaid by the further layer b), forming a joining zone, the two layers a) and b) being inseparable with one another in the joining zone have connected. A laminate comprising a layer structure according to any one of claims 1 to 11. 44 The use of the layer structure according to one of claims 1 to 11 or produced by the method according to claim 12 or the laminate according to claim 13 for the production of a security document, preferably a security form in a multi-layer book cover, particularly preferably a security form in a book cover for security and identification documents. Process for producing a multi-layer laminate comprising at least the steps i) providing a layer structure according to any one of claims 1 to 11 or produced by the process according to claim 12; ii) Lamination of the layer structure from step i) at a temperature of> 80 ° C to

<220° C. and a pressure of >2 N/cm ² to <500 N/cm ² , preferably lamination with an engraved laminating sheet, particularly preferably with an engraved laminating sheet comprising a non-stick coating; iii) optionally folding the layered construction, preferably along a central line of the layered construction, so that the layered construction as well as the laminate is folded symmetrically; iv) Optional pressing of the layered structure after step iii) along the central line, preferably pressing between two rolls, rolls and/or plates, at a temperature of > 0.5 °C to <150 °C, preferably > 1 °C to <50°C, more preferably >1°C to

<20°C, above the softening point of the outermost layer, for a period of 2 to 20 seconds, preferably 2 to 10 seconds, particularly preferably 2 to 5 seconds. v) Optional removal of the laminate including the layer structure from the press.