Layer structure comprising at least two layers having different engravings

Abstract

The invention relates to a layer structure comprising: A. a first, preferably transparent or white, radiation-engravable layer A., ​​with a first surface al., and a second surface a2., which is substantially parallel to the surface a1.; at least one transparent plastic layer B. with a first surface b1., which faces in the direction of layer A., ​​and a second surface b2., wherein layer B. contains an IR absorber in an amount in the range of ≥ 0.7 wt.% to ≤ 4.5 wt.%, calculated as the solid content of inorganic IR absorber, wherein the layer structure has both a milky-white and a black engraving, which were produced by means of non-ionizing electromagnetic radiation E. and are visible from at least one side of the layer structure, wherein the black engraving has an optical density of at least 0.5, preferably in the range of 0.5 to 2, measured according to ISO 5-3:2009.

Description

[0001] The invention relates to a layer structure, in particular a security document, for example an ID card, a data page in a passport or a banknote, comprising a first radiation-engravable layer A., ​​with a partial black engraving and at least one transparent plastic layer B., which contains an IR absorber and has a milky white engraving, wherein the black engraving has an optical density of at least 0.2.

[0002] Layered structures, especially security documents, are constantly being enhanced with new security features. For example, the marking of layered structures or security documents by laser engraving is already known, used to incorporate names and other user data into the structure, as described in US20210170441A1.

[0003] WO 2017 / 167651 also describes a method for the partial coloring, in particular laser engraving, of plastic parts, especially thermoplastic plastic parts, and especially plastic films.

[0004] However, what all these coloring techniques cannot achieve is the superimposed engraving of a white and a black inscription. In particular, the prior art does not describe how it is possible to create an inner and an outer inscription on and within the surface of a layered structure in such a way that the underlying inscription is still perceived with sufficient precision to, for example, represent a security feature.

[0005] Therefore, it was an object of the present invention to provide a layer structure that at least partially minimizes at least one disadvantage of the prior art. It was also an object to provide a layer structure with at least two engravings that overlap at least partially, in particular engravings that have a high optical density. Furthermore, it was an object to provide a layer structure with two different engravings that does not distort the overall appearance of the engravings despite partial overlap. In addition, it was an object to provide the fastest possible, material-saving, and / or energy-efficient method for producing a layer structure with at least two engravings. Finally, it was an object to provide an energy-saving method for producing layer structures with overlapping engravings that have a high optical density.

[0006] A first object of the invention relates to a layer structure, in particular a security document, comprising: A. a first radiation-gravitable layer A. with a first surface a1., and a second surface a2. which is substantially parallel to the surface a1.; B. at least one transparent plastic layer B. with a first surface b1. which points towards layer A., ​​and a second surface b2., wherein layer B. contains an IR absorber in an amount in the range of ≥ 0.7 wt.% to ≤ 4.5 wt.%, calculated as the solid content of inorganic IR absorber. wherein the layer structure has both a milky-white and a black engraving, which was produced by means of non-ionizing electromagnetic radiation E. and is visible from at least one side of the layer structure, wherein the black engraving has an optical density of at least 0.3, preferably in a range of 0.3 to 2, particularly preferably from 0.4 to 1.8, most preferably from 0.5 to 1.5 measured according to ISO 5-3:2009.

[0007] Preferably, the first layer A. is transparent. Alternatively, layer A. can also be translucent or opaque and can be any color on which the black engraving is visible. Preferably, layer A. is a light color that provides the greatest possible contrast with the black engraving; in particular, layer A. is white. If layer A. is white, it preferably comprises titanium dioxide as a filler. This is preferably the case when the optional layer C. is not present. If layer C. is present, it contains the filler, preferably in the form of titanium dioxide.

[0008] The first layer A, and optionally also layer B and / or layer C, can be made of any radiation-engravable material that can be blackened by laser. Preferably, layer A is a plastic layer. According to the application, "blackenable by laser" means that, with a minimum energy input of 1 watt in continuous radiation or 5 watts in pulsed radiation, a blackening can be achieved in the material of layer A such that this engraving is visible to the naked eye. For the pulsed radiation, a pulse frequency in the range of 2 kHz to 1000 kHz, preferably from 3 kHz to 100 kHz, and particularly preferably from 5 kHz to 50 kHz is used.

[0009] The first layer A. is preferably transparent and clear. According to the invention, "transparent" means that layer A. transmits light in a wavelength range of 400 to 700 nm to more than 80%, preferably more than 85%, particularly preferably more than 90%, and most preferably more than 95%, as measured according to ISO 13468-2:2006-07.

[0010] The first layer A preferably comprises a thermoplastic polymer. Preferably, the first layer A comprises a thermoplastic polymer in an amount in the range of 10 to 100 wt.%, more preferably 20 to 95 wt.%, more preferably 30 to 90 wt.%, particularly preferably 50 to 85 wt.%, and most particularly preferably 60 to 80 wt.%, based on the total weight of layer A.

[0011] The plastic layer B preferably comprises a thermoplastic polymer. Preferably, layer B comprises a thermoplastic polymer in an amount in the range of 10 to 100 wt.%, more preferably 20 to 95 wt.%, more preferably 30 to 90 wt.%, particularly preferably 50 to 85 wt.%, and most preferably 60 to 80 wt.%, based on the total weight of layer B.

[0012] Preferably, layers A and B are arranged directly adjacent to each other. Preferably, at least layer A and layer B are bonded so tightly together that an adhesive force of ≥ 1 N / cm, preferably ≥ 5 N / cm, particularly preferably ≥ 10 N / cm, and most preferably ≥ 50 N / cm exists to separate the layers. Particularly preferably, the adhesive force between layer A and layer B is so strong that layer A cannot be separated from layer B without destroying the layer structure. Destruction is understood to mean, in particular, that at least a portion of layer B remains on layer A during separation, or vice versa. Preferably, layer C is bonded so tightly to one of layers A or B that an adhesive force of ≥ 1 N / cm, preferably ≥ 5 N / cm, particularly preferably ≥ 10 N / cm, and most preferably ≥ 50 N / cm exists to separate the layers. Should there be a difference between layer A and layer B.If at least one further layer C or D is present, the adhesive forces between all layers A, B, C and D, regardless of their order, are preferably in the range of ≥ 1 N / cm to 100 N / cm. Adhesive force measurements were carried out according to ISO 10373-1:2020 Section 5.3.

[0013] Preferably, layers A and B, and optionally also layers C to Z, are joined together to form a layered structure by lamination. Alternatively, at least layers A and B can be produced by co-extrusion of the layers of the layered structure.

[0014] Preferred thermoplastic polymers are one or more polycarbonates or copolycarbonates based on diphenols, poly- or copolyacrylates and poly- or copolymethacrylates such as, for example, and preferably, polymethyl methacrylate or poly(meth)acrylate (PMMA), poly- or copolymers with styrene such as, for example, and preferably, polystyrene (PS), acrylonitrile butadiene styrene (ABS), or polystyrene acrylonitrile (SAN), thermoplastic polyurethanes, and polyolefins such as, for example, and preferably, polypropylene types 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 copolybutylene terephthalate (PBT or CoPBT)), polyamide (PA), poly- or copolycondensate(s) of naphthalenedicarboxylic acid, such as, for example and preferably, polyethylene glycol naphthalate (PEN), poly- or copolycondensate(s) of at least one cycloalkyldicarboxylic acid, such as, for example and preferably, polycyclohexanedimethanolcyclohexanedicarboxylic acid (PCCD), polysulfones (PSU), mixtures of at least two of the aforementioned or their blends.

[0015] Particularly preferred thermoplastic polymers are one or more polycarbonates or copolycarbonates based on diphenols or blends containing at least one polycarbonate or copolycarbonate. Blends containing at least one polycarbonate or copolycarbonate and at least one poly- or copolycondensate of terephthalic acid, naphthalenedicarboxylic acid, or a cycloalkyldicarboxylic acid, preferably cyclohexanedicarboxylic acid, are especially preferred. Particularly preferred are polycarbonates or copolycarbonates, especially those with average molecular weights (Mw) of 500 to 100,000, preferably 10,000 to 80,000, and particularly preferably 15,000 to 40,000, or blends thereof with at least one poly- or copolycondensate of terephthalic acid with average molecular weights (Mw) of 10,000 to 200,000, and preferably 21,000 to 120,000.

[0016] In preferred embodiments of the invention, polyalkylene terephthalates are suitable as poly- or copolycondensates of terephthalic acid. Suitable polyalkylene terephthalates are, for example, reaction products of aromatic dicarboxylic acids or their reactive derivatives (e.g., dimethyl esters or anhydrides) and aliphatic, cycloaliphatic, or araliphatic diols and mixtures of these reaction products.

[0017] Preferred polyalkylene terephthalates can be prepared from terephthalic acid (or its reactive derivatives) and aliphatic or cycloaliphatic diols with 2 to 10 carbon atoms using known methods (Plastics Handbook, Vol. VIII, p. 695 ff, Karl-Hanser-Verlag, Munich 1973).

[0018] Preferred polyalkylene terephthalates contain at least 80 mol%, preferably 90 mol% terephthalic acid residues, based on the dicarboxylic acid component, and at least 80 mol%, preferably at least 90 mol% ethylene glycol and / or butanediol-1,4- and / or 1,4-cyclohexanedimethanol residues, based on the diol component.

[0019] The preferred polyalkylene terephthalates may contain, in addition to terephthalic acid residues, up to 20 mol% of residues of other aromatic dicarboxylic acids with 8 to 14 C atoms or aliphatic dicarboxylic acids with 4 to 12 C atoms, such as residues of phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, succinic, adipic, sebacic acid, azelaic acid, cyclohexanedioacetic acid.

[0020] The preferred polyalkylene terephthalates may contain, in addition to ethylene or butanediol-1,4-glycol residues, up to 80 mol% of other aliphatic diols with 3 to 12 carbon atoms or cycloaliphatic diols with 6 to 21 carbon atoms, e.g. B. residues of propanediol-1,3, 2-ethylpropanediol-1,3, neopentyl glycol, pentane-diol-1,5, hexanediol-1,6, cyclohexane-dimethanol-1,4, 3-methylpentanediol-2,4, 2-methylpentanediol-2,4, 2,2,4-trimethylpentanediol-1,3 and 2-Ethylhexanediol-1,6, 2,2-Diethylpropanediol-1,3, Hexanediol-2,5, 1,4-Di-([beta]-hydroxyethoxy)-benzene, 2,2-Bis-(4-hydroxycyclohexyl)-propane, 2,4-Dihydroxy-1, 1,3,3-tetramethylcyclobutane, 2,2-Bis-(3-[beta]-hydroxyethoxyphenyl)-propane and 2,2-Bis-(4-hydroxypropoxyphenyl)-propane (see DE-OS 24 07 674, 24 07 776, 27 15 932).

[0021] The polyalkylene terephthalates can be branched by incorporating relatively small amounts of trihydric or tetrahydric alcohols or tribasic or tetrabasic carboxylic acids, as described, for example, in DE-OS 19 00 270 and US-PS 3,692,744. Examples of preferred branching agents are trimesic acid, trimellitic acid, trimethyl olethane and propane, and pentaerythritol.

[0022] Preferably, no more than 1 mol% of the branching agent is used, based on the acid component.

[0023] Particularly preferred are polyalkylene terephthalates produced solely from terephthalic acid and its reactive derivatives (e.g. its dialkyl esters) and ethylene glycol and / or butanediol-1,4 and / or 1,4-cyclohexanedimethanol residues, and mixtures of these polyalkylene terephthalates.

[0024] Preferred polyalkylene terephthalates also include copolyesters made from at least two of the above-mentioned acid components and / or from at least two of the above-mentioned alcohol components; particularly preferred copolyesters are poly(ethylene glycol / butanediol-1,4) terephthalates.

[0025] The polyalkylene terephthalates preferably used as components preferably have an intrinsic viscosity of approximately 0.4 to 1.5 dl / g, preferably 0.5 to 1.3 dl / g, each measured in phenol / o-dichlorobenzene (1:1 parts by weight) at 25°C.

[0026] Preferably, the blend of at least one polycarbonate or copolycarbonate with at least one poly- or copolycondensate of terephthalic acid is a blend of at least one polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate. In such a blend of polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, it may preferably be one with 1 to 90 wt.% polycarbonate or copolycarbonate and 99 to 10 wt.% poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, preferably with 1 to 90 wt.% polycarbonate and 99 to 10 wt.% polybutylene terephthalate or glycol-modified polycyclohexanedimethylene terephthalate, wherein the proportions add up to 100 wt.%.Particularly preferably, such a blend of polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate may be one comprising 20 to 85 wt.% polycarbonate or copolycarbonate and 80 to 15 wt.% poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, preferably comprising 20 to 85 wt.% polycarbonate and 80 to 15 wt.% polybutylene terephthalate or glycol-modified polycyclohexanedimethylene terephthalate, wherein the proportions add up to 100 wt.%. Particularly preferred is such a blend of polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, containing 35 to 80 wt.% polycarbonate or copolycarbonate and 65 to 20 wt.-% poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, preferably comprising 35 to 80 wt.% polycarbonate and 65 to 20 wt.% polybutylene terephthalate or glycol-modified polycyclohexanedimethylene terephthalate, wherein the proportions add up to 100 wt.%. In particularly preferred embodiments, the composition may consist of blends of polycarbonate and glycol-modified polycyclohexanedimethylene terephthalate in the aforementioned compositions.

[0027] In preferred embodiments, particularly aromatic polycarbonates or copolycarbonates are suitable as polycarbonates or copolycarbonates.

[0028] The polycarbonates or copolycarbonates can be linear or branched in a known manner.

[0029] These polycarbonates can be produced in a known manner from diphenols, carbonic acid derivatives, optionally chain terminators and optionally branching agents. Details of the production of polycarbonates have been documented in numerous patents for approximately 40 years. For example, reference may be made to Schnell, "Chemistry and Physics of Polycarbonates", Polymer Reviews, Volume 9, Interscience Publishers, New York, London, Sydney 1964; to D. Freitag, U. Grigo, PR Müller, H. Nouvertne', BAYER AG, "Polycarbonates" in Encyclopedia of Polymer Science and Engineering, Volume 11, Second Edition, 1988, pages 648-718; and finally to Drs. U. Grigo, K. Kirchner and PR Müller "Polycarbonate" in Becker / Braun, Kunststoff-Handbuch, Volume 3 / 1, Polycarbonate, Polyacetale, Polyester, Celluloseester, Carl Hanser Verlag Munich, Vienna 1992, pages 117-299.

[0030] Suitable diphenols can be, for example, dihydroxyaryl compounds of the general formula (I), HO-Z-OH (I) wherein Z is an aromatic residue with 6 to 34 C atoms, which may contain one or more optionally substituted aromatic nuclei and aliphatic or cycloaliphatic residues or alkylaryls or heteroatoms as bridging elements.

[0031] Examples of suitable dihydroxyaryl compounds are: dihydroxybenzenes, dihydroxydiphenyls, bis-(hydroxyphenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes, bis-(hydroxyphenyl)-aryls, bis-(hydroxyphenyl)-ethers, bis-(hydroxyphenyl)-ketones, bis-(hydroxyphenyl)-sulfides, bis-(hydroxyphenyl)-sulfones, bis-(hydroxyphenyl)-sulfoxides, 1,1'-bis-(hydroxyphenyl)-diisopropylbenzenes, and their kemalkylated and core-halogenated compounds.

[0032] These and other suitable dihydroxyaryl compounds are described, for example, in DE-A 3 832 396, FR-A 1 561 518, in H. Schnell, Chemistry and Physics of Polycarbonates, Interscience Publishers, New York 1964, pp. 28 ff.; pp. 102 ff. and in DG Legrand, JT Bendler, Handbook of Polycarbonate Science and Technology, Marcel Dekker New York 2000, pp. 72 ff.

[0033] Bevorzugte Dihydroxyarylverbindungen sind beispielsweise Resorcin, 4,4'-Dihydroxydiphenyl, Bis-(4-hydroxyphenyl)-methan, Bis-(3,5-dimethyl-4-hydroxyphenyl)-methan, Bis-(4-hydroxyphenyl)-diphenyl-methan, 1,1 -Bis-(4-hydroxyphenyl)-1 -phenyl-ethan, 1,1 -Bis-(4-hydroxyphenyl)-1-(1-naphthyl)-ethan, 1,1-Bis-(4-hydroxyphenyl)-1-(2-naphthyl)-ethan, 2,2-Bis-(4-hydroxyphenyl)-propan, 2,2-Bis-(3-methyl-4-hydroxyphenyl)-propan, 2,2-Bis-(3,5-dimethyl-4-hydroxyphenyl)-propan, 2,2-Bis-(4-hydroxyphenyl)-1-phenyl-propan, 2,2-Bis-(4-hydroxyphenyl)-hexafluor-propan, 2,4-Bis-(4-hydroxyphenyl)-2-methyl-butan, 2,4-Bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutan, 1,1-Bis-(4-hydroxyphenyl)-cyclohexan, 1,1-Bis-(3,5-dimethyl-4-hydroxyphenyl)-cylohexan, 1,1-Bis-(4-hydroxyphenyl)-4-methyl-cylohexan, 1,3-Bis-[2-(4-hydroxyphenyl)-2-propyl]-benzol, 1,1'- Bis-(4-hydroxyphenyl)-3-diisopropyl-benzol, 1,1'-Bis-(4-hydroxyphenyl)-4-diisopropyl-benzol, 1,3-Bis-[2-(3,5-dimethyl-4-hydroxyphenyl)-2-propyl]-benzol,Bis-(4-hydroxyphenyl) ether, bis-(4-hydroxyphenyl) sulfide, bis-(4-hydroxyphenyl) sulfone, bis-(3,5-dimethyl-4-hydroxyphenyl) sulfone and 2,2',3,3'-tetrahydro-3,3,3',3'-tetramethyl-1,1'-spirobi-[1H-indene]-5,5'-diol or dihydroxydiphenylcycloalkanes of formula (1a) , wherein R1< and R2< independently denote hydrogen, halogen, preferably chlorine or bromine, Ci-Cs-alkyl, C5-C6-cycloalkyl, C6-C10-aryl, preferably phenyl, and C7-C12-aralkyl, preferably phenyl-C1-C4-alkyl, in particular benzyl, m being an integer from 4 to 7, preferably 4 or 5, R3< and R4< being individually selectable for each X, independently denoting hydrogen or C1-C6-alkyl and X being carbon, with the proviso that at least one atom X, R3< and R4< simultaneously denote alkyl. Preferably, in formula (1a), one or two atoms X, in particular only one atom XR3< and R4< simultaneously denote alkyl.

[0034] The preferred alkyl group for R3< and R4< in formula (Ia) is methyl. The X atoms in the alpha position to the diphenyl-substituted carbon atom (C-1) are preferably not dialkyl-substituted, whereas alkyl disubstitution in the beta position to C-1 is preferred.

[0035] Particularly preferred dihydroxydiphenylcycloalkanes of formulas Ia are those with 5 and 6 ring carbon atoms X in the cycloaliphatic residue (m = 4 or 5 in formula Ia)), for example the diphenols of formulas Ia-1 to Ia-3,

[0036] A particularly favored dihydroxydiphenylcycloalkane of formula (Ia) is 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethyl-cyclohexane (formula (Ia-1) with R 1< and R 2< equal to H).

[0037] Such polycarbonates can be produced from dihydroxydiphenylcycloalkanes of formula (Ia) according to EP-A 359 953.

[0038] Particularly preferred dihydroxyaryl compounds are resorcinol, 4,4'-dihydroxydiphenyl, bis-(4-hydroxyphenyl)-diphenyl-methane, 1,1-bis-(4-hydroxyphenyl)-1-phenyl-ethane, bis-(4-hydroxyphenyl)-1-(1-naphthyl)-ethane, bis-(4-hydroxyphenyl)-1-(2-naphthyl)-ethane, 2,2-bis-(4-hydroxyphenyl)-propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)-propane, 1,1-bis-(4-hydroxyphenyl)-cyclohexane, 1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane, 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1'-Bis-(4-hydroxyphenyl)-3-diisopropyl-benzene and 1,1'-Bis(4-hydroxyphenyl)-4-diisopropylbenzene.

[0039] Particularly favored dihydroxyaryl compounds are 4,4'-dihydroxydiphenyl and 2,2-bis-(4-hydroxyphenyl)-propane.

[0040] Either a single dihydroxyaryl compound forming homopolycarbonates or several dihydroxyaryl compounds forming copolycarbonates can be used. Either a single dihydroxyaryl compound of formula (I) or (Ia) forming homopolycarbonates or several dihydroxyaryl compounds of formula (I) and / or (Ia) forming copolycarbonates can be used. The different dihydroxyaryl compounds can be linked together either statistically or in blocks.In the case of copolycarbonates made from dihydroxyaryl compounds of formula (I) and (Ia), the molar ratio of dihydroxyaryl compounds of formula (Ia) to the other dihydroxyaryl compounds of formula (I) that may optionally be used is preferably between 99 mol% (Ia) to 1 mol% (I) and 2 mol% (Ia) to 98 mol% (I), preferably between 99 mol% (Ia) to 1 mol% (I) and 10 mol% (Ia) to 90 mol% (I), and in particular between 99 mol% (Ia) to 1 mol% (I) and 30 mol% (Ia) to 70 mol% (I).

[0041] A particularly preferred copolycarbonate can be prepared using 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethyl-cyclohexane and 2,2-bis-(4-hydroxyphenyl)-propane dihydroxyaryl compounds of formula (Ia) and (I).

[0042] Suitable carbonic acid derivatives can be, for example, diaryl carbonates of general formula (II), wherein R, R' and R" independently represent hydrogen, linear or branched C 1 -C 34 -alkyl, C 7 -C 34 -alkylaryl or C 6 -C 34 -aryl, and R may also represent -COO-R‴, where R‴ represents hydrogen, linear or branched C 1 -C 34 -alkyl, C 7 -C 34 -alkylaryl or C 6 -C 34 -aryl.

[0043] Bevorzugte Diarylcarbonate sind beispielsweise Diphenylcarbonat, Methylphenyl-phenyl-carbonate und Di-(methylphenyl)-carbonate, 4-Ethylphenyl-phenyl-carbonat, Di-(4-ethylphenyl)-carbonat, 4-n-Propylphenyl-phenyl-carbonat, Di-(4-n-propylphenyl)-carbonat, 4-iso-Propylphenyl-phenyl-carbonat, Di-(4-iso-propylphenyl)-carbonat, 4-n-Butylphenyl-phenyl-carbonat, Di-(4-n-butylphenyl)-carbonat, 4-iso-Butylphenyl-phenyl-carbonat, Di-(4-iso-butylphenyl)-carbonat, 4-tert-Butylphenyl-phenyl-carbonat, Di-(4-tert-butylphenyl)-carbonat, 4-n-Pentylphenyl-phenyl-carbonat, Di-(4-n-pentylphenyl)-carbonat, 4-n-Hexylphenyl-phenyl-carbonat, Di-(4-n-hexylphenyl)-carbonat, 4-iso-Octylphenylphenyl-carbonat, Di-(4-iso-octylphenyl)-carbonat, 4-n-Nonylphenyl-phenyl-carbonat, Di-(4-n-nonylphenyl)-carbonat, 4-Cyclohexylphenyl-phenyl-carbonat, Di-(4-cyclohexylphenyl)-carbonat, 4-(1-Methyl-1-phenylethyl)-phenyl-phenyl-carbonat, Di-[4-(1-methyl-1-phenylethyl)-phenyl]-carbonat, Biphenyl-4-yl-phenyl-carbonat,Di-(biphenyl-4-yl)-carbonat, 4-(1-Naphthyl)-phenyl-phenyl-carbonat, 4-(2-Naphthyl)-phenyl-phenyl-carbonat, Di-[4-(1-naphthyl)-phenyl]-carbonat, Di-[4-(2-naphthyl)phenyl]-carbonat, 4-Phenoxyphenyl-phenyl-carbonat, Di-(4-phenoxyphenyl)-carbonat, 3-Pentadecylphenyl-phenyl-carbonat, Di-(3-pentadecylphenyl)-carbonat, 4-Tritylphenyl-phenyl-carbonat, Di-(4-tritylphenyl)-carbonat, Methylsalicylat-phenyl-carbonat, Di-(methylsalicylat)-carbonat, Ethylsalicylat-phenyl-carbonat, Di-(ethylsalicylat)-carbonat, n-Propylsalicylat-phenyl-carbonat, Di-(n-propylsalicylat)-carbonat, iso-Propylsalicylat-phenyl-carbonat, Di-(iso-propylsalicylat)-carbonat, n-Butylsalicylat-phenyl-carbonat, Di-(n-butylsalicylat)-carbonat, iso-Butylsalicylat-phenyl-carbonat, Di-(iso-butylsalicylat)-carbonat, tert-Butylsalicylat-phenyl-carbonat, Di-(tert-butylsalicylat)-carbonat, Di-(phenylsalicylat)-carbonat und Di-(benzylsalicylat)-carbonat.,

[0044] Particularly preferred diaryl compounds are diphenyl carbonate, 4-tert-butylphenyl phenyl carbonate, di-(4-tert-butylphenyl) carbonate, biphenyl-4-yl phenyl carbonate, di-(biphenyl-4-yl) carbonate, 4-(1-methyl-1-phenylethyl) phenyl phenyl carbonate, di-[4-(1-methyl-1-phenylethyl)-phenyl] carbonate, and di-(methyl salicylate) carbonate. Diphenyl carbonate is especially preferred.

[0045] Both one diaryl carbonate and several diaryl carbonates can be used.

[0046] To control or modify the end groups, one or more monohydroxyaryl compounds can be used as chain terminations, provided they were not used in the preparation of the diaryl carbonate(s). These can be compounds of general formula (III). where RA< stands for linear or branched C1-C34 alkyl, C7-C34 alkylaryl, C6-C34 aryl or for -COO-R D<, where RD< stands for hydrogen, linear or branched C1-C34 alkyl, C7-C34 alkylaryl or C6-C34 aryl, and RB< , RC< independently of each other, the same or different, stand for hydrogen, linear or branched C1-C34 alkyl, C7-C34 alkylaryl or C6-C34 aryl.

[0047] Such monohydroxyaryl compounds are, for example, 1-, 2- or 3-methylphenol, 2,4-dimethylphenol, 4-ethylphenol, 4-n-propylphenol, 4-iso-propylphenol, 4-n-butylphenol, 4-isobutylphenol, 4-tert-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol, 4-iso-octylphenol, 4-n-nonylphenol, 3-pentadecylphenol, 4-cyclohexylphenol, 4-(1-methyl-1-phenylethyl)phenol, 4-phenylphenol, 4-phenoxyphenol, 4-(1-naphthyl)phenol, 4-(2-naphthyl)phenol, 4-tritylphenol, methyl salicylate, Ethyl salicylate, n-propyl salicylate, iso-propyl salicylate, n-butyl salicylate, iso-butyl salicylate, tert-butyl salicylate, phenyl salicylate and benzyl salicylate.

[0048] 4-tert-Butylphenol, 4-iso-Octylphenol and 3-Pentadecylphenol are preferred.

[0049] Suitable branchers can be compounds with three or more functional groups, preferably those with three or more hydroxyl groups.

[0050] Suitable compounds with three or more phenolic hydroxyl groups include, for example, phloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene-2, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane, 1,3,5-tri-(4-hydroxyphenyl)-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane, tri-(4-hydroxyphenyl)-phenylmethane, 2,2-bis-(4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-propane, 2,4-bis-(4-hydroxyphenyl-isopropyl)-phenol and tetra-(4-hydroxyphenyl)-methane.

[0051] Other suitable compounds with three or more functional groups include, for example, 2,4-dihydroxybenzoic acid, trimesic acid (trichloride), cyanuric acid trichloride and 3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

[0052] Preferred branchers are 3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole and 1,1,1-tri-(4-hydroxyphenyl)-ethane.

[0053] Preferably, layer B comprises the IR absorber in an amount in the range of ≥ 0.6 wt.% to ≤ 2 wt.% and particularly preferably ≥ 0.7 wt.% to ≤ 1.5 wt.%, calculated as the solid fraction of inorganic IR absorber.

[0054] Preferably, the layers of the layer structure according to the invention are arranged such that layer B forms an outer layer.

[0055] The IR absorber in the plastic layer B is a laser-sensitive additive. The laser-sensitive absorbers typically include an absorber in the wavelength range of the radiation E to be used. Preferably, the IR absorber comprises at least one or more organic and / or inorganic IR absorbers, preferably inorganic IR absorbers. Such additives, in particular IR absorbers, and their use in molding compounds are described, for example, in WO-A 2004 / 50766 and WO-A 2004 / 50767 and are commercially offered by DSM under the brand name Micabs™.

[0056] Suitable organic IR absorbers are, for example, compounds that exhibit the highest possible absorption between 700 and 2500 nm (near-infrared = NIR). Suitable examples include infrared absorbers known from the literature, such as those described by class in M. Matsuoka, *Infrared Absorbing Dyes*, Plenum Press, New York, 1990. Particularly suitable are infrared absorbers from the classes of azo, azomethine, methine, anthraquinone, indanthrone, pyranthrone, flavanthrone, benzanthrone, phthalocyanine, perylene, dioxazine, thioindigo, isoindoline, isoindolinone, quinacridone, pyrrolopyrrole, or quinophthalone pigments, as well as metal complexes of azo, azomethine, or methine dyes or metal salts of azo compounds. Of these, phthalocyanines and naphthalocyanines are particularly suitable. Due to their improved solubility in thermoplastic materials, phthalocyanines and naphthalocyanines with bulky side groups are preferable.

[0057] Suitable inorganic IR absorbers are, for example, mixed oxides of metals such as phosphorus-containing tin-copper mixed oxides, as described in WO-A 2006 / 042714, those from the group of borides and / or tungstates and their mixtures, preferably at least one or more IR absorbers from the group of borides and / or tungstates, and their mixtures, particularly preferably at least one or more IR absorbers from the group of tungstates.

[0058] Examples of inorganic IR absorbers from the boride group include compounds of the type M x B y (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 an integer from 1 to 6) where lanthanum hexaboride (LaB 6 ), praseodymium boride (PrB 6 ), neodymium boride (NdB 6 ), cerium boride (CeB 6 ), terbium boride (TbB 6 ), dysprosium boride (DyB 6 ), holmium boride (HoB 6 ), yttrium boride (YB 6 ), samarium boride (SmB 6 ), europium boride (EuB 6 ), erbium boride (ErB 6 ), Thulium boride (TmB 6 ), Ytterbium boride (YbB 6 ), Lutetium boride (LuB 6 ), Strontium boride (SrB 6 ), Calcium boride (CaB 6 ), Titanium boride (TiB 2 ), Zirconium boride (ZrB 2 ), Hafnium boride (HfB 2 ), Vanadium boride (VB 2 ), Tantalum boride (TaB 2 ), Chromium boride (CrB and CrB 2 ), Molybdenum boride (MoB 2 , Mo 2 B 5 and MoB ), Tungsten boride (W 2 B 5 ), or combinations of these borides are suitable.

[0059] Examples of inorganic IR absorbers from the tungstate group include those from the group of tungsten compounds of the type WyOz (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, Tl, 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 represents the elements H, Cs, Rb, K, Tl, In, Ba, Li, Ca, Sr, Fe, and Sn are preferred, with Cs being particularly preferred. Ba 0.33 WO 3, Tl 0.33 WO 3, K 0.33 WO 3, Rb 0.33 WO 3, Cs 0.33 WO 3, Na 0.33 WO 3, Na 0.75 WO 3, and mixtures thereof are especially preferred. In a particular embodiment of the present invention, the sole use of Cs 0.33 WO 3 as the inorganic IR absorber is particularly preferred.Cs / W ratios of 0.20 and 0.25 are also preferred.

[0060] Among the inorganic IR absorbers, wolframates are preferable to borides due to their low inherent coloration, provided that the inventive method is to be carried out on layer structures that have a radiation transmittance of ≥ 10% to ≤ 99%, preferably ≥ 30% to ≤ 95%, particularly preferably ≥ 40% to ≤ 93% for the selected radiation, determined according to the UV-VIS-NIR-MIR method according to DIN EN ISO / IEC 17025.

[0061] To produce such tungstates, for example, tungsten trioxide, tungsten dioxide, a hydrate of tungsten oxide, tungsten hexachloride, ammonium tungstate, or tungstic acid, and optionally other salts containing the element M, such as cesium carbonate, are mixed in specific stoichiometric ratios, such that the molar ratios of the individual components are represented by the formula M x W y O z. This mixture is then treated at temperatures between 100 °C and 850 °C in a reducing atmosphere, e.g., an argon hydrogen atmosphere, and finally the resulting powder is annealed at temperatures between 550 °C 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 milled in suitable mills, such as...The nanoparticles are milled in ball mills with the addition of zirconium oxide (e.g., with a diameter of 0.3 mm) to produce the desired particle size distribution. The nanoparticles are obtained in the form of a dispersion. After milling, further dispersants can optionally be added. The solvent is removed at elevated temperatures and reduced pressure. Nanoparticles with a mean size of less than 200 nm, and particularly less than 100 nm, are preferred. The particle size 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. Soc. 2008, 91, 2897-2902.

[0062] The production of tungstates is described in more detail in EP-A 1 801 815, for example, and they are commercially available from companies such as Sumitomo Metal Mining Co., Ltd. (Japan) under the designation YMDS 874.

[0063] Preferably for use in layered structures with at least one layer A and one layer B, comprising preferably transparent thermoplastics with a radiation transmittance for the selected radiation of ≥ 10% to ≤ 99%, preferably of ≥ 30% to ≤ 95%, particularly preferably ≥ 40% to ≤ 93%, determined according to the UV-VIS-NIR-MIR method according to DIN EN ISO / IEC 17025, the particles thus obtained are dispersed in an organic matrix, e.g. in an acrylate, and optionally milled as described above using suitable additives such as zirconium dioxide and optionally using organic solvents such as toluene, benzene or similar hydrocarbons.

[0064] Preferably, all layers except layer B, and in particular layer A, layer C, and layer D, do not contain an IR absorber. However, should an IR absorber be present in minimal quantities, layer A, layer C, and layer D preferably contain an IR absorber in an amount of < 0.1 wt.%, more preferably ≤ 0.05 wt.%, and particularly preferably ≤ 0.01 wt.%, calculated as the solid fraction of inorganic IR absorber in the respective layer.

[0065] Suitable polymer-based dispersants are primarily dispersants that exhibit high transmission, such as polyacrylates, polyurethanes, polyethers, polyesters or polyester urethanes, as well as polymers derived from them.

[0066] Preferred dispersants include polyacrylates, polyethers, and polyester-based polymers, with polyacrylates such as polymethyl methacrylate and polyester being particularly preferred as high-temperature-stable dispersants. Mixtures of these polymers or acrylate-based copolymers can also be used. Such dispersants and methods for the preparation of tungstate dispersions are described, for example, in JP 2008214596 and in Adachi et al. J. Am. Ceram. Soc. 2007, 90 4059-4061. Suitable dispersants are commercially available.

[0067] Polyacrylate-based dispersants are particularly suitable. Such suitable dispersants are available, for example, from Ciba Specialty Chemicals under the trade names EFKA™<, e.g., EFKA™< 4500 and EFKA™< 4530. Polyester-containing dispersants are also suitable. They are available, for example, from Avecia under the trade names Solsperse™<, e.g., Solsperse™< 22000, 24000SC, 26000, and 27000. Furthermore, polyether-containing dispersants are known, for example, from Kusumoto Chemicals under the trade names Disparlon™< DA234 and DA325. Polyurethane-based systems are also suitable. Polyurethane-based systems are available from Ciba Specialty Chemicals under the trade names EFKA™< 4046 and EFKA™< 4047. Texaphor™< P60 and P63 are corresponding trade names of Cognis.

[0068] The amount of IR absorber in the dispersant can be 0.2 wt.% to 50.0 wt.%, preferably 1.0 wt.% to 40.0 wt.%, more preferably 5.0 wt.% to 35.0 wt.%, and most preferably 10.0 wt.% to 30.0 wt.%, based on the dispersion of the inorganic IR absorber used according to the invention. In addition to the pure IR absorber and the dispersant, the overall composition of the ready-to-use IR absorber formulation may contain further excipients such as zirconium dioxide and residual solvents such as toluene, benzene, or similar aromatic hydrocarbons.

[0069] There are no restrictions regarding the amount of inorganic IR absorbers, particularly preferably those from the tungstate group, in the polymer compositions of the layered structures. Typically, the inorganic IR absorbers, especially the tungstates, can be used in an amount of ≥ 0.7% wt.% to ≤ 4.5% wt.%, preferably ≥ 0.6% wt.% to ≤ 2% wt.%, and particularly preferably ≥ 0.7% wt.% to ≤ 1.5% wt.%, calculated as the solid fraction of inorganic IR absorber, in the overall polymer composition.

[0070] In this context, the term "solid fraction of inorganic IR absorber, in particular tungstate" refers to the inorganic IR absorber, in particular the tungstate, as a pure substance and not to a dispersion, suspension or other preparation containing the pure substance. Furthermore, the following information regarding the content of IR absorber, in particular the tungstate content, always refers to this solid fraction unless explicitly stated otherwise.

[0071] Preferably, in addition to the tungstates, other IR absorbers can optionally be used, provided that their proportion in such a mixture is always lower than that of the tungstates described above. For mixtures, compositions containing two to five, and particularly preferably two or three different IR absorbers, are preferred. The additional IR absorber is preferably selected from the group consisting of borides and tin oxides, and particularly preferably contains LaB6, antimony-doped tin oxide, or indium tin oxide.

[0072] Furthermore, the layer structure preferably comprises at least one additional layer C. The additional layer C is preferably composed of the same thermoplastic materials as described for layers A or B. Preferably, layer C comprises a thermoplastic material selected from the group consisting of one or more polycarbonates or copolycarbonates based on diphenols or blends containing at least one polycarbonate or copolycarbonate.Particularly preferred are blends containing at least one polycarbonate or copolycarbonate and at least one poly- or copolycondensate of terephthalic acid, naphthalenedicarboxylic acid, or a cycloalkyldicarboxylic acid, preferably cyclohexanedicarboxylic acid. Particularly preferred are polycarbonates or copolycarbonates, especially with mean molecular weights Mw of 500 to 100,000, preferably of 10,000 to 80,000, particularly preferably of 15,000 to 40,000, or blends thereof with at least one poly- or copolycondensate of terephthalic acid with mean molecular weights Mw of 10,000 to 200,000, preferably of 21,000 to 120,000.

[0073] Layer C preferably comprises a thermoplastic polymer. Preferably, layer C comprises the thermoplastic polymer in an amount in the range of 10 to 100 wt.%, more preferably 20 to 95 wt.%, more preferably 30 to 90 wt.%, particularly preferably 50 to 85 wt.%, and most preferably 60 to 80 wt.%, based on the total weight of layer C.

[0074] Preferably, layer C comprises at least one filler. The filler is preferably at least one color pigment and / or at least one other filler for generating translucency in the filled layers, particularly preferably a white pigment, most preferably titanium dioxide, zirconium dioxide and / or barium sulfate, and in a particularly preferred embodiment, titanium dioxide.

[0075] The fillers mentioned are preferably added in amounts of 2 to 50 wt.%, particularly preferably 5 to 40 wt.%, based on the total weight of the layer containing the filler. If layer C is present, preferably only this layer contains the filler, preferably in the form of titanium dioxide, in the aforementioned amounts.

[0076] Preferably, layer C comprises the thermoplastic material, in particular polycarbonate or co-polycarbonate, in an amount of 70 to 95 wt.%, particularly preferably 80 to 90 wt.%, and the filler in an amount of 5 to 30 wt.%, preferably 10 to 20 wt.%, based on the total weight of layer C.

[0077] Layer C preferably has a light transmission in the range of ≥ 0.1% to ≤ 25% as determined according to ISO 13468-2:2006-07, and a layer thickness in the range of ≥ 20 µm to ≤ 70 µm, preferably ≥ 20 µm to ≤ 60 µm, and particularly preferably ≥ 25 µm to ≤ 55 µm.

[0078] Preferably, the layer structure comprises at least one further layer D. The further layer D is preferably composed of the same thermoplastic materials as described for layers A or B. Preferably, layer D comprises a thermoplastic material selected from the group consisting of one or more polycarbonates or copolycarbonates based on diphenols or blends containing at least one polycarbonate or copolycarbonate.Particularly preferred are blends containing at least one polycarbonate or copolycarbonate and at least one poly- or copolycondensate of terephthalic acid, naphthalenedicarboxylic acid, or a cycloalkyldicarboxylic acid, preferably cyclohexanedicarboxylic acid. Particularly preferred are polycarbonates or copolycarbonates, especially with mean molecular weights Mw of 500 to 100,000 g / mol, preferably of 10,000 to 80,000 g / mol, particularly preferably of 15,000 to 40,000 g / mol, or blends thereof with at least one poly- or copolycondensate of terephthalic acid with mean molecular weights Mw of 10,000 to 200,000 g / mol, preferably of 21,000 to 120,000 g / mol.

[0079] Layer D preferably comprises a thermoplastic polymer. Preferably, layer D comprises the thermoplastic polymer in an amount in the range of 10 to 100 wt.%, more preferably 20 to 95 wt.%, more preferably 30 to 90 wt.%, particularly preferably 50 to 85 wt.%, and most preferably 60 to 80 wt.%, based on the total weight of layer D.

[0080] Preferably, layer D comprises at least one filler. The filler is preferably at least one color pigment and / or at least one other filler for generating translucency in the filled layers, particularly preferably a white pigment, most preferably titanium dioxide, zirconium dioxide and / or barium sulfate, and in a particularly preferred embodiment, titanium dioxide.

[0081] The fillers mentioned are preferably added in amounts of 2 to 50 wt.%, particularly preferably 5 to 40 wt.%, based on the total weight of the layer containing the filler.

[0082] Preferably, layer D comprises the thermoplastic material, in particular polycarbonate or co-polycarbonate, in an amount of 70 to 95 wt.%, particularly preferably 80 to 90 wt.%, and the filler in an amount of 5 to 30 wt.%, preferably 10 to 20 wt.%, based on the total weight of layer D. Layer D preferably has a light transmission in the range of ≥ 0.1% to ≤ 25% as determined according to ISO 13468-2:2006-07, and a layer thickness in the range of ≥ 20 µm to ≤ 70 µm, preferably ≥ 20 µm to ≤ 60 µm, particularly preferably ≥ 25 µm to ≤ 55 µm.

[0083] Preferably, layer D comprises a different material than layer C. Preferably, layer A comprises a different material than layer C.

[0084] The layer structure preferably comprises one or more additional layers Z. The at least one additional layer Z. is preferably at least one protective layer that is applied to one or both sides of the layer structure and can be peeled off, preferably by hand, before use of the layer structure. The at least one additional layer Z. preferably comprises polyethylene or polypropylene as its main component.

[0085] One or more security features can be incorporated at any location within the layer structure according to the invention. Security features can be implemented as electronic components, such as antennas and IC chips, holograms, and / or security prints within the layered structure. Ideally, one or more security features are positioned within the layer structure according to the invention in such a way that they are at least partially covered by layer B. For example, one or more security features could be placed between layers A and B, or between layers A and C, or B and C, depending on the arrangement of the layers. However, additional security features can also be included at other locations within the layer structure according to the invention. Ideally, a security feature is positioned so that it does not cover any engravings.

[0086] The individual layers of the layered structure can be pressed together using a laminating press under heat and pressure for a specific period of time, creating a monolithic composite of the individual layers, a so-called laminate. The pressure and temperature during the lamination process must be selected so that the individual layers and any security features they may contain are not damaged, but the individual layers form a strong bond that does not subsequently separate back into their individual layers. The engravings are preferably applied after the laminate has been created. The at least one additional layer Z. is preferably removed before the lamination process.

[0087] It is preferred that layer B forms an outer surface of the layer structure. Furthermore, the layer structure preferably comprises an arrangement of layers selected from the group consisting of layer B - layer A, layer B - layer C - layer A, layer B - layer A - layer B, layer B - layer C - layer A - layer C - layer B, wherein additional layers Z may be arranged on each outer surface, which preferably can be removed from the layer structure at any time without leaving any residue.

[0088] In a preferred embodiment of the layer structure, the black engraving is located within layer A to a minimum of 20%, preferably at least 40%, more preferably at least 50%, particularly preferably at least 60%, and most preferably at least 70%, based on the optical density. According to the invention, "within layer A" means that less than 20%, preferably less than 10%, particularly preferably less than 5%, and most preferably less than 1% of the engraving is arranged on one of the surfaces a1 or a2, or is located in layer B or one of the further layers C to Z.

[0089] In a preferred embodiment of the layer structure, the material of layer A comprises a polymer selected from the group consisting of a polycarbonate, a copolycarbonate, a blend of different polycarbonates, copolycarbonates, or mixtures of polycarbonates and copolycarbonates, or mixtures of at least two thereof. Preferably, the polycarbonate, copolycarbonate, or blend of different polycarbonates or copolycarbonates is at least partially one of those described above.

[0090] In a preferred embodiment of the layer structure, the milky white engraving within layer B is formed as a foam. Preferably, during the application of the engraving, preferably by means of a laser, layer B changes its initially clear structure at the engraved areas to the foamed structure that forms the milky white engraving. The milky white engraving preferably results in a raised area of ​​the foamed material. If layer B forms an outer layer of the layer structure, the material expands during engraving on the second surface b2 of the transparent plastic layer B. Preferably, the milky white engraving exhibits a thickness expansion of layer B by 1.5 to 5 times, more preferably by 2 to 4 times, and particularly preferably by 2.5 to 3.5 times, compared to the thickness at the non-engraved areas of layer B.Preferably, the milky white structure has a thickness 2 to 400 µm, more preferably 5 to 300 µm, further preferably 10 to 200 µm, and particularly preferably 40 to 100 µm greater than the areas of layer B that do not have the milky white structure. It is also possible to generate very fine lines of this foamed structure, which can be produced at relatively low laser powers. These structures can be perceived by the eye, but protrude only very slightly from the plane of the layer structure and are almost as transparent as layer B otherwise.

[0091] In a preferred embodiment of the layer structure, the milky white engraving has a turbidity of ≥ 20%, preferably ≥ 50%, more preferably ≥ 80%, measured with an instrument from BYK-Gardner, model haze gard plus, according to the standard ASTM D1003:2013.

[0092] In a preferred embodiment of the layer structure, the milky white engraving or the black engraving forms a structure selected from the group consisting of a photograph, in particular a passport photo, a fingerprint, a Braille inscription and a combination of at least two thereof.

[0093] Preferably, the depicted structure is formed from the superposition of at least a part of the milky white engraving and the black engraving.

[0094] Alternatively, the formed structure, in particular the photograph, can be formed partly from the milky white and partly from the black engraving, which preferably overlap in a range of 0 to 20%, more preferably from 0.1 to 10%, and most preferably from 0.2 to 1% of the total area of ​​the structure.

[0095] Especially for the development of Braille, the engraving consists predominantly, preferably exclusively, of milky white engraving.

[0096] The resolution of the milky white engraving is preferably in the range of 50 to 2000 DPI, more preferably from 100 to 1000 DPI, and most preferably from 150 to 600 DPI.

[0097] The resolution of the black engraving is preferably in the range of 50 to 2000 DPI, more preferably from 100 to 1000 DPI, and most preferably from 150 to 600 DPI.

[0098] In a preferred embodiment of the layer structure, parts of the white engraving cover parts of the black engraving. Preferably, up to 50% of the white engraving covers up to 50% of the black engraving. "Covering" is understood to mean that the covering engraving is the one perceived by the viewer looking at surface b2. It is also possible that only parts of the white engraving cover up to 100% of the black engraving, and the black engraving can still be perceived.

[0099] In a preferred embodiment of the layer structure, layer B has a thickness at the areas with the milky white engraving that is at least 0.001 mm, preferably 0.001 to 1 mm, and particularly preferably 0.01 to 0.1 mm thicker than at the areas without milky white engraving. In particular, if the milky white engraving is designed as Braille, it has a raised area relative to the rest of the layer structure of at least 0.01 to 0.5 mm.

[0100] In a preferred embodiment of the layer structure, the layer structure, comprising at least layers A, B, and optionally C, preferably has a layer thickness in the range of 100 µm to 10,000 µm, preferably 200 µm to 1,000 µm, and most preferably 50 µm to 500 µm.

[0101] Preferably, layer A has a thickness in the range of 10 to 1000 µm, preferably 20 µm to 500 µm, most preferably 50 µm to 200 µm.

[0102] Preferably, layer B has a thickness in the range of 10 to 1000 µm, preferably 20 µm to 500 µm, most preferably 50 µm to 200 µm.

[0103] Preferably, layer C or layer D, or layer C and layer D, has a layer thickness in the range of 10 µm to 1 000 µm, preferably 20 µm to 500 µm, most preferably 50 µm to 200 µm.

[0104] Layers A, B, and optionally C and D, can each be of the same thickness or of different thicknesses. Preferably, the thickness of layers A, B, and optionally C and D differs from each other by no more than 50%, more preferably by no more than 25%, and most preferably by no more than 10%, relative to the thickness of layer A.

[0105] Preferably, at least layer A." and preferably also layer B, comprises a thermoplastic polymer selected from the group consisting of polymers of ethylene unsaturated monomers, polycondensates of bifunctional reactive compounds and polyaddition products of bifunctional reactive compounds or combinations of at least two thereof, preferably a polycarbonate or a copolycarbonate.

[0106] Examples of preferred thermoplastic materials, in particular preferred polycarbonates or copolycarbonates, have already been mentioned above for layers A and B. The polycarbonates and copolycarbonates already mentioned are also preferred for layers C and D.

[0107] Another aspect of the invention relates to a method for producing a colored layer structure, in particular a security document, comprising the steps: i) Provision of a layered structure comprising at least i)1. a preferably transparent, radiation-engravable polymer layer B, comprising an IR absorber in a range of ≥ 0.7 wt.% to ≤ 4.5 wt.%, calculated as the solid content of inorganic IR absorber in layer B; i)2. a preferably transparent, radiation-engravable polymer layer A, with a first surface a1. facing in the direction of polymer layer B and a further surface a2. facing in the opposite direction and therefore away from the first layer B; i)3. optionally at least one preferably white layer C, preferably combined with layer A.is in contact, ii) providing a rasterized photo file with a raster resolution of 7 DPI to 800 DPI, more preferably of 10 DPI to 600 DPI, particularly preferably of 50 DPI to 400 DPI; iii) Irradiating the layer structure from step i) using the rasterized photographic file from step ii) with focused non-ionizing electromagnetic radiation from a laser with a peak pulse power of 5 to 100 kW and a pulse duration in the range of 10 ns to 500 ns, from the side of polymer layer B, to produce the black engraving, iv) Irradiating the layer structure from step i) using the rasterized photographic file from step ii) with focused non-ionizing electromagnetic radiation from a laser with a peak pulse power of 5 to 100 kW and a pulse duration in the range of 0.01 ns to < 10 ns, from the side of polymer layer B, to produce the milky white engraving, . wherein the focus of the laser during step iii) or step iv) or step iii) and iv), i.e. the point with the highest energy density, 0.5 to 7 mm, preferably 1 to 6 mm, particularly preferably 2 to 5 mm above or below the surface of the layer structure, which points in the direction of the laser.

[0108] The presentation of the layer structure in step i) can take any form that a person skilled in the art would choose for this purpose. Preferably, the presentation of the layer structure takes the form of a layer structure with at least one layer A, here step i) 1, and one layer B, here step i) 2, and optionally one layer C, here step i) 3, which is preferably in a form such as is customary for identification documents. Preferably, the provision of layer C in step i) 3 takes place such that layer A is located between layer B and layer C.

[0109] The composition and properties of layer A, layer B, and the optional layer C correspond to those of the compositions and properties of the respective layers previously specified for the layer structure according to the invention. If the layer structure does not include the optional layer C, layer A contains a filler, preferably in the form of titanium dioxide, in an amount ranging from 2 to 50 wt.%, particularly preferably from 5 to 40 wt.%, and most preferably from 10 to 30 wt.%, based on the total weight of layer A. If the layer structure includes the optional layer C, layer C contains a filler, preferably in the form of titanium dioxide, in an amount ranging from 2 to 50 wt.%, particularly preferably from 5 to 40 wt.%, and most preferably from 10 to 30 wt.%, based on the total weight of layer C.

[0110] The provision of the rasterized photo file in step ii) can be carried out in any form and by any means known and suitable to a person skilled in the art. Preferably, the provision of the rasterized photo file is carried out using software programs such as Adobe Photoshop® (USA). The rasterized photo file preferably has a resolution in the range of 100 to 2000 DPI, more preferably 150 to 1500 DPI, further preferably 200 to 1000 DPI, and most preferably 500 to 1500 DPI.

[0111] In the inventive process, in step iii), the focused non-ionizing electromagnetic beam E of the laser beam is directed onto the surface b2 of layer B to be colored, provided that this surface is the outer surface of the layer structure. The peak pulse power of the laser is in the range of 5 to 100 kW. The laser is preferably directed and illuminated at an angle of 90° onto the surface b2 of layer B. The laser preferably emits radiation in a wavelength range of 1064 nm ± 100 nm, with a pulse duration of 2 nm to 350 nm, a repetition rate of 1 kHz to 300 kHz, and a peak pulse power of 1 kW to 500 kW.

[0112] In step iv), the focused non-ionizing electromagnetic beam E. of the laser beam is directed onto the surface b2. of layer B. of the layer structure to be colored or structured. The peak pulse power of the laser is in the range of 5 to 100 kW. The laser is preferably directed at an angle of 45 to 90°, more preferably 60 to 90°, particularly preferably 80 to 90°, and most preferably 90° onto the surface b2. of layer B., and the radiation E. is emitted directly onto it.

[0113] The laser focus in step iii) or iv), or in steps iii) and iv), i.e., the point with the highest energy density, lies in a range of 0.5 to 7 mm, preferably 1 to 6 mm, and particularly preferably 2 to 5 mm above or below the surface of the layer structure facing the laser. Furthermore, steps iii) and iv) differ in that different pulse frequencies are used for the laser. For example, to generate the black engraving in layer A or layer C, if present, a pulse duration in the range of 5 ns to < 300 ns is used, while in step iv) to generate the milky white engraving in layer B, a pulse duration in the range of < 5 ns is used.

[0114] In a preferred embodiment of the method for producing the layer structure, the irradiation of the layer structure in step iv) takes place before, during, or after the irradiation in step iii). Preferably, the irradiation of the layer structure in step iv) takes place after the irradiation of the layer structure in step iii). Preferably, the irradiation of the layer structure in step iii) is carried out using the same photo file as the irradiation of the layer structure in step iv). Due to the use of the same photo file for both the black and the white engraving, a completely black image of the photo can be generated, which is partially overlapped above the black engraving by the milky white engraving. Furthermore, other photo files can also be used for the two engravings. In addition to the overlapping areas, areas engraved purely in black or purely in milky white can also be produced.

[0115] In a preferred embodiment of the method for producing the layer structure, at least layer A." and preferably also layer B. comprises a thermoplastic polymer selected from the group consisting of polymers of ethylene unsaturated monomers, polycondensates of bifunctional reactive compounds and polyaddition products of bifunctional reactive compounds or combinations of at least two thereof.

[0116] Preferably, the materials, compositions, properties and dimensions of layers A, B and optionally C are selected as previously described for the layer structure according to the invention.

[0117] Another object of the invention relates to a security document containing a layer structure according to the invention or a layer structure produced according to the inventive method, wherein the security document is preferably selected from the group consisting of a data page in a passport, an identity card, for example in the form of an ID card, a driver's license, a banknote and a combination of at least two thereof. Examples Example 1) Production of the transparent layer B. with a thickness of 100 µm.

[0118] Masterbatch: A highly concentrated IR masterbatch made of polycarbonate was produced. The masterbatch for the production of layer B of the layer structure according to the invention was produced using a conventional twin-screw compound extruder (ZSK 32) at processing temperatures of 250 to 330°C, typical for polycarbonate.

[0119] A master batch with the following composition was compounded and then granulated: 94.744 wt% polycarbonate Makrolon™ < 3108 granules from Covestro Deutschland AG; 0.75 wt% YMDS 874 IR absorber from Sumitomo; 4.5 wt% Makrolon™ < 3108 powder from Covestro Deutschland AG; 0.006 wt% (6 ppm) carbon black 101 (carbon black from Evonik-Degussa GmbH) with a mean particle size of 95 nm Production of layer B as an extruded film

[0120] The equipment used to produce the extruded layer B included: An extruder for extruding layer B, comprising at least one polycarbonate, with a screw of 60 mm diameter (D) and a length of 33 D (i.e., 33 times the diameter). The screw has a degassing zone; a melt pump; a deflector head; a slot die with a width of 450 mm; a three-roll calender with a horizontal roll arrangement, wherein the third roll is pivotable by + / - 45° from the horizontal; a roller conveyor; thickness measurement; a device for applying optional protective films to both sides; a take-up device for the optional protective films; and a winding station.

[0121] The granules of the master batch were conveyed from a dryer into a feed hopper of the extruder. Within the extruder's cylinder / screw plasticizing system, the material was melted and conveyed. From the wide-slot die, the melt passed onto the smoothing calender. On the smoothing calender, which consisted of three rollers, the final shaping and cooling of layer B into an extruded film took place. A textured steel roller (6-sided) and a textured silicone rubber roller (2-sided) were used to emboss the surface. The rubber roller used for structuring the film surface is disclosed in US Patent 4,368,240, published by Nauta Roll Corporation. The film was then transported by a take-up unit and subsequently wound onto a reel. Example 2) Production of the laminates a), b) and c).

[0122] The following types of film were used for the production of laminates a), b) and c): Transparent film Makrofol® < ID6-2 000000; 100 µm from Covestro Deutschland AG. Transparent laser-reactive film Makrofol® < ID6-2 750061; 100 µm from Covestro Deutschland AG. White film Makrofol® < ID4-4 010207; 300 µm from Covestro Deutschland AG. Transparent IR film made of polycarbonate, from example 1)

[0123] For the production of the laminates, the above types of film were stacked as follows and then laminated: Laminate a) 100 µm IR film from Example 1) as layer B. 300 µm Makrofol® < ID4-4 010207 white film as layer A. 100 µm IR film from Example 1) as layer B. Laminate b) 100 µm IR film from Example 1) as layer B. as layer B. 100 µm Makrofol® < ID6-2 000000 transparent film as layer A. 300 µm Makrofol® < ID4-4 010207 white film as layer C. 100 µm Makrofol® < ID6-2 000000 transparent film as layer A. 100 µm IR film from Example 1) as layer B. as layer B. Laminate c) 100 µm IR film from Example 1) as layer B. 100 µm Makrofol® < ID6-2 750061 transparent laser-engravable film as layer A. 300 µm Makrofol® < ID4-4 010207 white film as layer C. 100 µm Makrofol® < ID6-2 750061 transparent laser-engravable film as layer A. 100 µm IR film from example 1) as layer B.

[0124] The foil stacks a), b), and c) were subsequently laminated as follows: The lamination was carried out on a Bürckle laminating press, model 50 / 100. The foil stacks a), b), and c) were laminated with the following press settings: Heating zone: Temperature 190°C, duration 8 minutes, pressure 60 N / cm²< Cooling zone: Temperature 38°C, duration 10 minutes, pressure 100 N / cm²< Example 3) Laser marking, in the form of engraving into the laminates a) b) and c)

[0125] Laminates a), b), and c) were engraved using a Trumpf laser. The laser model used is the TruMark 3130 type with the following specifications: Laser parameters: Max. peak pulse power 40 kW at 20 kHz; Beam quality (M 2< ) 1.2; Wavelength 1064 nm; Laser medium Nd:YVO4; Pulse duration 8 ns at 20 kHz; Pulse repetition frequency 1 kHz - 100 kHz; Min. focus diameter 28 µm at focal length 100 mm; Max. internal focus position control ± 60 mm at focal length 420 mm; Scanner calibration accuracy ± 50 µm; Max. text field size 290 mm x 290 mm at focal length 420 mm

[0126] The laminates were laser-marked using two settings: one for a light laser mark and one for a black laser mark. The design was a photograph. The following settings were used for the light laser marking: frequency of 2 kHz; power 95%. The following settings were used for the black laser marking: frequency of 12.5 kHz; power 30%.

[0127] The frequencies of 2 and 12.5 kHz result in the pulse durations as described in Figure 1shown, namely for 2 kHz a pulse duration of between 5 and 7 nanoseconds [ns] results and for 12.5 kHz a pulse duration of approximately 8 ns results.

[0128] Each of the laminates a), b), and c) was laser-marked with five focus settings. Focus 0 mm: The focus of the laser beam is precisely set on the top surface of the film laminate, in this case the outer surface of layer B.

[0129] Focus shift from +1 mm to +4 mm in 1 mm increments: The distance between the laser lens and the top of the film laminate was increased by 1 mm each time, resulting in an increasing defocusing of the laser beam. Example 4) Measurement of the optical density at the darkest areas of the milky white engraving in or on layer B and the black laser engraving in layer A.

[0130] After the laser marking, as previously described, the optical density (OD) was measured at various points in the photographs. This was done at the darkest areas of the milky white and black markings, represented by the milky white engraving in layer B and the black engraving in layer A. To achieve the highest possible contrast in an image, it is desirable to achieve the lowest possible OD value in the darkest areas of the milky white engraving and the highest possible OD value in as many points as possible of the black engraving. A densitometer from Techkon was used for the OD measurement, which was carried out in accordance with the standards DIN 16 527 Part 3, ISO 5-3:2009, and as described in the handbook for standardization of the BVD (German Printing and Media Industries Federation) and FOGRA (Research Association for Printing Industries).

[0131] In the two following tables 1 and 2, the measured OD values ​​for the darkest areas of the milky white engravings and the darkest areas of the black engraving are shown. Figure 2a for laminate a), Figure 2b for laminate b) and Figure 2c Listed for 2c. Table 1: OD values ​​for black engraving Defocusing Laminate a) laminate b) Laminate c) 0 mm 0,74 0,63 0,84 +1 mm 0,93 0,63 1,22 +2 mm 0,77 0,56 1,3 +3 mm 0,6 0,44 1,34 +4 mm 0,44 0,32 1,27 Table 2: OD values ​​for the milky white engraving Defocusing Laminate a) laminate b) Laminate c) 0 mm 0,07 0,08 0,12 +1 mm 0,07 0,08 0,12 +2 mm 0,05 0,08 0,08 +3 mm 0,02 0,05 0,04 +4 mm 0,02 0,02 0,01

[0132] As can be seen from the OD values ​​in Tables 1 and 2, the optical density values ​​for the black engraving range from 0.44 for laminate a) with 4 mm defocus and laminate b) with 3 mm defocus to 1.34 for laminate c), while the optical density values ​​for the milky white engraving range from 0.01 for laminate c) with 4 mm defocus to 0.12 for laminate c) without defocus. The optical density values ​​for the black engraving therefore differ by at least 0.3 points from those for the milky white engraving. Figures 3a and 3bThis is particularly evident for laminate c), where maximum defocus of 4 mm achieves optimal conditions for distinguishing between the milky white and black engravings. Here, the difference in optical density values ​​is at its maximum. The optical density for the milky white engraving at a defocus of 4 mm is 0.01 for laminate c), while the optical density for the black engraving at a defocus of 4 mm is 1.27.

[0133] In the description of the Figure 1 Figures 8 to 8 show exemplary layer structures according to the invention, which are not to be read as restrictive: Figure 1: Dependence of the frequency of the laser used on the pulse length; Figures 2a to 2c: Photograph of laminates produced according to the inventive method a) to c), which were produced with different laser defocusing distances; Figures 3a and 3b: Diagram of the optical densities in the black ( Fig. 3a ) and milky white engravings ( Fig. 3b ) of the laminates a) to c); Figures 4a and 4b: Photographs of a laminate produced according to the inventive method c), once at an oblique angle ( Fig. 4a ) and at a 90° angle to the surface of the laminate; Figures 5a and 5b: Photograph ( Fig. 5a ) and schematic representation ( Fig. 5b ) of a layer structure according to the invention after the application of the milky white engraving; Figures 6a and 6b: Photograph ( Fig. 6a ) and schematic representation ( Fig. 6b) of a layer structure according to the invention after the introduction of the black engraving; Figure 7: Photograph of an overlap area of ​​black and milky white engraving on a layer structure according to the invention, produced according to the method according to the invention.

[0134] In Figure 1 The diagram illustrates the relationship between the frequency of the laser used and the pulse length. It can be seen that the frequency increases almost linearly with increasing pulse duration.

[0135] In Figure 2aTwo staggered rows each show a photograph of an engraved layer structure 100 in the form of a laminate a) from Example 2, each with a milky white engraving labeled with the odd numbers 1, 3, 5, 7, and 9, and with a black engraving labeled with the even numbers 2, 4, 6, 8, and 10. Different defocus distances of the laser used were selected for each pair of milky white and black engravings. Figures 1 and 2 of the Figure 2aThe images were engraved using a laser defocused by 0 mm relative to the surface of the layer structure. The laser settings were configured as described for Example 4. Images 3 and 4 were engraved with a laser defocus of 1 mm. Images 5 and 6 were engraved with a laser defocus of 2 mm. Images 7 and 8 were engraved with a laser defocus of 3 mm. Images 9 and 10 were engraved with a laser defocus of 4 mm. The optical densities measured in the milky white and black engravings, respectively, are listed in Tables 1 and 2.

[0136] In Figure 2b Photos of laminate b) from example 2 are shown, taken with the same laser defocusing settings as laminate a). Figure 2a were generated. Consequently, images 1 to 10 were generated in Figure 2bThe same defocusing distances of the laser used were employed as for images 1 to 10 from Figure 2a for the laminate a) described. The values ​​for their optical densities at the darkest areas are also listed in Tables 1 and 2.

[0137] In Figure 2c The same laser defocusing settings were applied to a laminate c) as in Example 2, whereby the same defocusing distances of the laser used were employed for generating images 1 to 10 as in Figure 2a for the laminate a) described and listed in Tables 1 and 2 with the darkest areas in the form of optical density.

[0138] In Figure 3aThe optical densities from Table 1 for the black engravings of the three laminates, laminate a) 20, laminate b) 30, and laminate c) 40, are shown graphically against the defocus distances. A laser defocus distance of at least 2 mm is particularly recommended for laminate c) 40 to produce the best possible black engravings.

[0139] In Figure 3b The optical densities from Table 1 for the three laminates, laminate a) 20, laminate b) 30, and laminate c) 40, for the milky white engravings are also shown graphically in relation to the defocus distances. It is clearly evident that a defocus distance of 4 mm yields the lowest optical density and thus the optimal white color for the white engraving for all three laminates a) 20, b) 30, and c) 40. Here, too, the best value is achieved for laminate c) 40.

[0140] In Figures 4a and 4bare a photograph of a layer structure 100 with engravings according to the invention, in the form of at least one milky white engraving 160 and at least one black engraving 170, wherein Figure 4a was photographed at an angle of approximately 45° relative to the surface of the layer structure 100, while Figure 4b The photograph was taken at 90° relative to the surface of the layer structure 100. It can be seen that, in particular, the milky white engraving 160 appears raised at a viewing angle of 45° and allows the photograph to show its full contour, while at a viewing angle of 90° to the layer structure 100, the milky white engraving 170 is only vaguely visible.

[0141] In Figure 5aA photograph of a sectioned layer 100 is shown at the location of a milky white inscription 160. It can be seen that at the location of the milky white inscription 160, the material of layer B. 110 has foamed up significantly, namely by twice its original thickness of 79 µm, namely by 82 µm, to a total thickness of 161 µm. The layer 100 consists of Figure 5a is that of the laminate c) from Example 1, which is why adjacent to layer B. 110 with 100 µm, there is a layer A. 120 with 100 µm followed by a layer C. 130 with a thickness of 300 µm, which on the other side of layer C. 130 again has a mirrored layer A. 140 and a layer B. 150.

[0142] Figure 5b The photo shows Figure 5aThis schematic drawing illustrates layer structure 100 with its layers and the white, milky engraving. Here too, layer C. 130 is a white layer in the center of the structure, with layers A. 120 and 140 arranged symmetrically outwards, each followed by a layer B. 110 and 150, respectively, as specified for laminate c) from Example 1. The white, milky engraving 160, created by the laser, is visible in layer B. 110.

[0143] In Figure 6a Figure 1 shows another photograph of the layer structure 100, in the form of laminate c) after engraving, but in an area where parts of the black engraving 170 are found. The layer sequence, layer B. 110, layer A. 120, layer C. 130, layer A. 140, layer B. 150, is the same as in Figure 5a Unlike the photo in Figure 5aIt can be seen here that the parts of the black engraving through which the cut was made are predominantly located in layer A. 120. Less than 10% of the black engraving is found in the marginal area bordering layer C. 130 or layer B. 110. Figure 6b The photo shows Figure 6a This schematic drawing illustrates layer structure 100 with its layers and the black engraving. Here too, layer C. 130 is a white layer in the center of the structure, with layers A. 120 and 140 arranged symmetrically outwards, each followed by a layer B. 110 and 150, respectively, as specified for laminate c) from Example 1. The black engraving 170, created by the laser, is visible in layer A. 130.

[0144] In Figure 7A photograph of a layer structure 100 according to the invention is shown, corresponding to a structure of the laminate c), on whose surface both a milky white engraving 160 in the form of a fingerprint and a black engraving 170 in the form of number and letter combinations are visible. As can be clearly seen, the writing of the black engraving 170 can be read completely through the milky white engraving 160. It can also be seen that the milky white engraving 160 is raised and protrudes from the surface of the layer structure 100 and is therefore also perceptible or tactile and can thus represent Braille.

Claims

1. A layered structure comprising: A. a first, preferably transparent or white, radiation-engravable layer A., ​​with a first surface a1., and a second surface a2., which is substantially parallel to the surface a1., B. at least one transparent plastic layer B., with a first surface b1., which faces in the direction of layer A., ​​and a second surface b2., wherein layer B. comprises an IR absorber in an amount in the range of ≥ 0.7 wt.% to ≤ 4.5 wt.%, calculated as the solid content of inorganic IR absorber, wherein the layered structure has both a milky-white and a black engraving, which were produced by means of non-ionizing electromagnetic radiation E. and are visible from at least one side of the layered structure, wherein the black engraving has an optical density of at least 0.5, preferably in the range of 0.5 to 2, as measured according to ISO 5-3:2009.

2. The layer structure according to claim 1, wherein the black engraving is located within layer A to at least 20%, preferably to at least 40%.

3. The layer structure according to one of the preceding claims, wherein the material of layer A comprises a polymer selected from the group consisting of a polycarbonate, a copolycarbonate, a blend of different polycarbonates, copolycarbonates or mixtures of polycarbonates and copolycarbonates or mixtures of at least two thereof.

4. The layer structure according to one of the preceding claims, wherein the milky white engraving within layer B is formed as a foam.

5. The layer structure according to one of the preceding claims, wherein the milky white engraving has a turbidity of ≥ 20%, preferably ≥ 50%, measured according to the standard ASTM D1003:2013.

6. The layer structure according to one of the preceding claims, wherein the milky white engraving or the black engraving depicts a structure selected from the group consisting of a photograph, in particular a passport photo, a fingerprint, a Braille inscription and a combination of at least two thereof.

7. The layer structure according to one of the preceding claims, wherein parts of the white engraving cover parts of the black engraving, preferably up to 50% of the white engraving and up to 50% of the black engraving.

8. The layer structure according to one of the preceding claims, wherein layer B has a layer thickness at the locations with the milky white engraving that is at least 0.001 mm thicker than at the locations without milky white engraving.

9. The layer structure according to one of the preceding claims, wherein the layer structure comprises at least layers A, B and optionally C and has a total layer thickness in a range of 100 to 10,000 µm.

10. The layer structure according to one of the preceding claims, wherein at least layer C, preferably also layer B, comprises a thermoplastic polymer selected from the group consisting of polymers of ethylene unsaturated monomers, polycondensates of bifunctional reactive compounds and polyaddition products of bifunctional reactive compounds or combinations of at least two thereof, preferably a polycarbonate or a copolycarbonate.

11. A method for producing a colored layer structure comprising the steps of: i) Preparing a layer structure comprising at least i)1. A preferably transparent radiation-engravable polymer layer B, comprising an IR absorber in a region of ; i)2. A preferably transparent radiation-engravable polymer layer A, with a first surface a1. facing in the direction of the first layer B, and a further surface a2. facing in the opposite direction and therefore away from the first layer B; i)3. optionally at least one preferably white layer C, preferably bonded to layer A.in contact, ii) providing a rasterized photographic file with a raster resolution of 7 DPI to 800 DPI; iii) irradiating the layer structure from step i) using the rasterized photographic file from step ii) with focused non-ionizing electromagnetic radiation from a laser with a peak pulse power of 5 to 100 kW and a pulse duration in the range of 10 ns to 500 ns, from the side of polymer layer B, to generate the black engraving, iv) irradiating the layer structure from step i) using the rasterized photographic file from step ii) with focused non-ionizing electromagnetic radiation from a laser with a peak pulse power of 5 to 100 kW and a pulse duration in the range of 0.01 ns to < 10 ns, from the side of polymer layer B.from, to produce the milky white engraving, wherein the focus of the laser during step iii) or step iv) or step iii) and iv), i.e. the point with the highest energy density 0.5 to 7 mm, preferably 1 to 6 mm, particularly preferably 2 to 5 mm above or below the surface of the layer structure, which points in the direction of the laser.

12. The method according to claim 11, wherein the irradiation of the layer structure in step iii) takes place before, during or after the irradiation in step ii), preferably after step ii).

13. A security document comprising a layer structure according to any one of claims 1 to 10 or obtainable according to the method according to any one of claims 11 and 12, wherein the security document is preferably selected from the group consisting of a data page in a passport, an identity card, for example in the form of an ID card, a driver's license, a banknote and a combination of at least two thereof.

Images