Layer structure with at least two layers having different engravings

Abstract

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

Description

The present invention relates to a layer construction, especially a security document, for example an ID card, a data page in a passport or a banknote, having a first radiation-engravable layer A. comprising a black engraving over a sub-area thereof and at least one transparent plastic layer B. which contains an IR absorber and comprises a milky white engraving, wherein the black engraving has an optical density of at least 0.2. Layer constructions, especially security documents, are constantly provided with new security features. Thus, the marking of the layer structure or security document by laser engraving, for example to introduce names and other user data into the structure, as described in US20210170441A1, is also already known. WO 2017 / 167651 also discloses a process for partial coloring, especially laser engraving, of plastic parts, especially of thermoplastic plastic parts, very particularly of plastic films. However, what all of these coloring techniques do not accomplish is the superposed engraving of a white and a black engraving. In particular, the prior art does not disclose that it is possible to enable an inner and an outer engraving on and in the surface of a layer construction in such a way that the lower engraving too is perceived sufficiently precisely to represent a security feature for example. It was therefore an object of the present invention to provide a layer construction which at least partially minimizes at least one disadvantage from the prior art. It was a further object to provide a layer construction comprising at least two at least partially overlapping engravings, especially engravings having a high optical density. It was also an object of the invention to provide a layer construction comprising two different engravings which despite partial superposition of the engravings does not destroy the overall appearance of the engravings. It was also an object of the invention to provide a process for producing a layer construction comprising at least two engravings which is as fast, materialsaving and / or energy-efficient as possible. It was a further object of the invention to provide an energyefficient process for producing layer constructions comprising overlapping engravings having a high optical density. The invention firstly provides a layer construction, especially a security document, comprising: A. a first radiation-engravable layer A. having 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. having a first surface b1. facing in the direction of layer A. and a second surface b2., wherein layer B. an IR absorber in an amount in a range from > 0.7% by weight to < 4.5% by weight calculated as the solids content of inorganic IR absorber, wherein the layer construction comprises both a milky-white and a black engraving which have been produced using nonionizing electromagnetic radiation E. and are visible in each case from at least one side of the layer construction, wherein the black engraving has an optical density of at least 0.3, preferably in a range from 0.3 to 2, particularly preferably from 0.4 to 1.8, very particularly preferably from 0.5 to 1.5, measured according to ISO 5-3:2009. The first layer A. is preferably transparent. Alternatively, layer A. may also be translucent or opaque and may have any color on which the black engraving is visible. Layer A. preferably has a light color which provides the greatest possible contrast with the black engraving; layer A. is especially white. If layer A. is white, layer A. preferably comprises titanium dioxide as filler. This is preferably the case when optional layer C. is not present. If layer C. is present, it comprises the filler, preferably in the form of titanium dioxide. The first layer A. and optionally also layer B. and / or layer C. may be produced from any radiation-engravable material which is blackenable using a laser. Layer (A) is preferably a plastic layer. The term "blackenable using a laser" according to the present application is to be understood as meaning that introduction of a minimum energy of 1 watt in continuous radiation or 5 watts in pulsed radiation using a laser makes it possible to realize a blackening in the material of layer A, with the result that this engraving is apparent to the naked eye. For the pulsed radiation, preference is given to using a pulse frequency within a range from 2 kHz to 1000 kHz, preferably from 3 kHz to 100 kHz, more preferably from 5 kHz to 50 kHz. The first layer A. is preferably transparent and clear. According to the invention "transparent" is to be understood as meaning that layer A. transmits light in a wavelength range from 400 to 700 nm to an extent of more than 80%, preferably to an extent of more than 85%, particularly preferably to an extent of more than 90%, very particularly preferably to an extent of more than 95%, measured according to ISO 13468-2:2006-07. The first layer A. preferably comprises a thermoplastic. The first layer A. preferably comprises a thermoplastic in an amount in a range from 10% to 100% by weight, more preferably from 20% to 95% by weight, more preferably from 30% to 90% by weight, particularly preferably from 50% to 85% by weight, very particularly preferably from 60% to 80% by weight, based on the total weight of layer A. The plastic layer B. preferably comprises a thermoplastic. Layer B. preferably comprises a thermoplastic in an amount in a range from 10% to 100% by weight, more preferably from 20% to 95% by weight, more preferably from 30% to 90% by weight, particularly preferably from 50% to 85% by weight, very particularly preferably from 60% to 80% by weight, based on the total weight of layer B. Layers A. and B. are preferably arranged directly next to one another. It is preferable when at least layer A. and layer B. are so firmly bonded to one another that an adhesive force of > 1 N / cm, preferably of > 5 N / cm, particularly preferably of > 10 N / cm, very particularly of > 50 N / cm, is needed to separate the layers from one another. It is particularly preferable when the adhesive force between layer A. and layer B. is large enough to ensure that layer A. cannot be separated from layer B. without destroying the layer construction. Destruction is to be understood as meaning especially that during separation at least a portion of layer B. remains on layer A. or vice versa. It is preferable when layer C. is so firmly bonded to layers A. or B. that an adhesive force of > 1 N / cm, preferably of > 5 N / cm, particularly preferably of > 10 N / cm, very particularly of > 50 N / cm, is needed to separate the layers from one another. If at least one further layer C. or D. is present between layer A. and layer B. the adhesive forces between all layers A., B., C. and D., irrespective of the sequence in which they are arranged, are preferably in a range from > 1 N / cm to 100 N / cm. Adhesive force measurements were carried out according to ISO 10373-1:2020, Section 5.3. It is preferable when layers A. and B. and optionally also layers C. to Z. are joined together by lamination to afford a layer construction. Alternatively, at least layers A. and B. may be produced by coextrusion of the layers of the layer construction. Preferred thermoplastics include one or more polycarbonate(s) or copolycarbonate(s) based on diphenols, poly- or copolyacrylate(s) and poly- or copolymethacrylate(s) such as, for example and preferably, polymethylmethacrylate or poly(meth)acrylate (PMMA), polymer(s) or copolymer(s) with styrene such as, for example and preferably, polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), or polystyrene-acrylonitrile (SAN), thermoplastic polyurethane(s) and also polyolefin(s) 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 the aforementioned or blends thereof. Particularly preferred thermoplastics are one or more polycarbonate(s) or copolycarbonate(s) based on diphenols or blends containing at least one polycarbonate or copolycarbonate. Very particular preference is given to blends containing at least one polycarbonate or copolycarbonate and at least one poly- or copolycondensate of terephthalic acid, of naphthalenedicarboxylic acid or of a cycloalkyldicarboxylic acid, preferably of cyclohexanedicarboxylic acid. Very particular preference is given to polycarbonates or copolycarbonates, especially having average molecular weights Mw of 500 to 100 000, preferably of 3 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 having average molecular weights Mw of 10 000 to 200 000, preferably of 21 000 to 120 000. Suitable poly- or copolycondensates of terephthalic acid in preferred embodiments of the invention are polyalkylene terephthalates. Suitable polyalkylene terephthalates include for example reaction products of aromatic dicarboxylic acids or the reactive derivatives thereof (e.g. dimethyl esters or anhydrides) and aliphatic, cycloaliphatic or araliphatic diols, and mixtures of these reaction products. Preferred polyalkylene terephthalates may be produced from terephthalic acid (or reactive derivatives thereof) and aliphatic or cycloaliphatic diols having 2 to 10 carbon atoms by known methods (Kunststoff-Handbuch, vol. VIII, p. 695 ff, Karl-Hanser-Verlag, Munich 1973). Preferred polyalkylene terephthalates contain at least 80 mol%, preferably 90 mol%, of terephthalic acid radicals, based on the dicarboxylic acid component, and at least 80 mol%, preferably at least 90 mol%, of ethylene glycol and / or butane-1,4-diol and / or cyclohexane-1,4-dimethanol radicals, based on the diol component. The preferred polyalkylene terephthalates may contain, in addition to terephthalic acid radicals, up to 20 mol% of radicals of other aromatic dicarboxylic acids having 8 to 14 carbon atoms or of aliphatic dicarboxylic acids having 4 to 12 carbon atoms, such as for example radicals of phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, cyclohexanediacetic acid. The preferred polyalkylene terephthalates may contain, in addition to ethylene and / or butane-1,4-diol glycol radicals, up to 80 mol% of other aliphatic diols having 3 to 12 carbon atoms or of cycloaliphatic diols having 6 to 21 carbon atoms, for example radicals of propane-1,3-diol, 2-ethylpropane-1,3-diol, neopentyl glycol, pentane-1,5-diol, hexane-1,6-diol, cyclohexane-1,4-dimethanol, 3-methylpentane-2,4-diol, 2-methylpentane-2,4-diol, 2,2,4-trimethylpentane-1,3-diol and 2-ethylhexane-1,6-diol, 2,2-diethylpropane-1,3-diol, hexane-2,5-diol,     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 (cf. DE-A 24 07 674, 24 07 776, 27 15 932). The polyalkylene terephthalates may be branched by incorporation of relatively small amounts of tri- or tetrahydric alcohols or tri- or tetrabasic carboxylic acids, as described for example in DE-A 19 00 270 and US Patent 3 692 744. Examples of preferred branching agents are trimesic acid, trimellitic acid, trimethylolethane and trimethylolpropane and pentaerythritol. It is preferable when not more than 1 mol% of the branching agent is used, based on the acid component. Particular preference is given to polyalkylene terephthalates which have been produced solely from terephthalic acid and the reactive derivatives thereof (e.g. the dialkyl esters thereof) and ethylene glycol and / or butane-1,4-diol and / or cyclohexane-1,4-dimethanol radicals, and to mixtures of these polyalkylene terephthalates. Preferred polyalkylene terephthalates further include copolyesters produced from at least two of the aforementioned acid components and / or from at least two of the aforementioned alcohol components; particularly preferred copolyesters are poly(ethylene glycol / butane-1,4-diol) terephthalates. The polyalkylene terephthalates preferably used as a component preferably have an intrinsic viscosity of about 0.4 to 1.5 dl / g, preferably 0.5 to 1.3 dl / g, measured in each case in phenol / o-dichlorobenzene (1:1 parts by weight) at 25°C. The blend of at least one polycarbonate or copolycarbonate with at least one poly- or copolycondensate of terephthalic acid is preferably a blend of at least one polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate. Such a blend of polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate may preferably be one comprising 1% to 90% by weight of polycarbonate or copolycarbonate and 99% to 10% by weight of poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, preferably comprising 1% to 90% by weight of polycarbonate and 99% to 10% by weight of polybutylene terephthalate or glycol-modified polycyclohexanedimethylene terephthalate, wherein the proportions add up to 100% by weight. Such a blend of polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate may more preferably be one comprising 20% to 85% by weight of polycarbonate or copolycarbonate and 80% to 15% by weight of poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, preferably comprising 20% to 85% by weight of polycarbonate and 80% to 15% by weight of polybutylene terephthalate or glycol-modified polycyclohexanedimethylene terephthalate, wherein the proportions add up to 100% by weight. Such a blend of polycarbonate or copolycarbonate with poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate may most preferably be one comprising 35% to 80% by weight of polycarbonate or copolycarbonate and 65% to 20% by weight of poly- or copolybutylene terephthalate or glycol-modified poly- or copolycyclohexanedimethylene terephthalate, preferably comprising 35% to 80% by weight of polycarbonate and 65% to 20% by weight of polybutylene terephthalate or glycol-modified polycyclohexanedimethylene terephthalate, wherein the proportions add up to 100% by weight. Very particularly preferred embodiments may involve blends of polycarbonate and glycol-modified polycyclohexanedimethylene terephthalate in the aforementioned compositions. Suitable polycarbonates or copolycarbonates in preferred embodiments are particularly aromatic polycarbonates or copolycarbonates. The polycarbonates or copolycarbonates may be linear or branched in known fashion. These polycarbonates may be produced in known fashion from diphenols, carbonic acid derivatives, optionally chain terminators and optionally branching agents. Particulars pertaining to the production of polycarbonates are disclosed in many patent documents spanning approximately the last 40 years. Reference is made here merely by way of example to Schnell, "Chemistry and Physics of Polycarbonates", Polymer Reviews, volume 9, Interscience Publishers, New York, London, Sydney 1964, to D. Freitag, U. Grigo, P. R. Muller, H. Nouvertne, BAYER AG, "Polycarbonates" in Encyclopedia of Polymer Science and Engineering, volume 11, second edition, 1988, pages 648-718 and finally to Dres. U. Grigo, K. Kirchner and P. R. Muller, "Polycarbonate” in Becker / Braun, Kunststoff-Handbuch, volume 3 / 1, Polycarbonate, Polyacetale, Polyester, Celluloseester, Carl Hanser Verlag Munich, Vienna 1992, pages 117-299. Suitable diphenols may be, for example, dihydroxyaryl compounds of general formula (I) HO-Z-OH    (I) in which Z is an aromatic radical which has 6 to 34 carbon atoms and may contain one or more optionally substituted aromatic rings and aliphatic or cycloaliphatic radicals or alkylaryls or heteroatoms as bridging elements. Examples of suitable dihydroxyaryl compounds include: 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 the ring-alkylated and ring-halogenated compounds thereof. These and further suitable other 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, p. 28 ff.; p. 102 ff., and in D. G. Legrand, J.T. Bendler, Handbook of Polycarbonate Science and Technology, Marcel Dekker New York 2000, p. 72 ff. Preferred dihydroxyaryl compounds include, for example, resorcinol, 4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl)methane,            bis(3,5-dimethyl-4-hydroxyphenyl)methane,            bis(4- hydroxyphenyl)diphenylmethane,        1,1-bis(4-hydroxyphenyl)-1-phenylethane,        1,1-bis(4- hydroxyphenyl)-1-(1-naphthyl)ethane,   1,1-bis(4-hydroxyphenyl)-1-(2-naphthyl)ethane, 2,2-bis(4- hydroxyphenyl)propane,    2,2-bis(3-methyl-4-hydroxyphenyl)propane,    2,2-bis(3,5-dimethyl-4- hydroxyphenyl)propane,           2,2-bis(4-hydroxyphenyl)-1-phenylpropane,           2,2-bis(4- hydroxyphenyl)hexafluoropropane, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 2,4-bis(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane,   1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dimethyl-4- hydroxyphenyl)cyclohexane,      1,1-bis(4-hydroxyphenyl)-4-methylcyclohexane,      1,3-bis[2-(4- hydroxyphenyl)-2-propyl]benzene, 1,1'-bis(4-hydroxyphenyl)-3-diisopropylbenzene, 1,1'-bis(4-hydroxyphenyl)-4-diisopropylbenzene, 1,3-bis[2-(3,5-dimethyl-4-hydroxyphenyl)-2-propyl]benzene, 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 (Ia) in which R1 and R2      are independently hydrogen, halogen, preferably chlorine or bromine, C1-C8-alkyl, C5- C6-cycloalkyl, C6-C10-aryl, preferably phenyl, and C7-C12-aralkyl, preferably phenyl-C1-C4-alkyl, especially benzyl, m     is an integer from 4 to 7, preferably 4 or 5, R3 and R4     can be chosen individually for each X and are independently hydrogen or C 1-C6-alkyl and X      is carbon, with the proviso that, on at least one atom X, R3 and R4 are both alkyl. Preferably, in the formula (Ia), on one or two X atom(s), especially only on one X atom, R3 and R4 are both alkyl. A preferred alkyl radical for the R3 and R4 radicals in formula (Ia) is methyl. The X atoms alpha to the diphenyl-substituted carbon atom (C-1) are preferably not dialkyl-substituted but alkyl disubstitution beta to C-1 is preferred. Particularly preferred dihydroxydiphenylcycloalkanes of formula (Ia) are those having 5 and 6 ring carbon atoms X in the cycloaliphatic radical (m = 4 or 5 in formula (Ia)), for example the diphenols of formulae (Ia-1) to (Ia-3), (Ia-3) A very particularly preferred dihydroxydiphenylcycloalkane of formula (Ia) is 1,1 -bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (formula (Ia-1) where R1 and R2 = H). 10 Such polycarbonates may be produced from dihydroxydiphenylcycloalkanes of formula (Ia) according to EP-A 359 953. Particularly preferred dihydroxyaryl compounds are resorcinol, 4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bis(4-hydroxyphenyl)-1-(1-naphthyl)ethane, bis(4-hydroxyphenyl)-1-(2-naphthyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 15 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-diisopropylbenzene and 1,1'-bis(4-hydroxyphenyl)-4-diisopropylbenzene. Very particularly preferred dihydroxyaryl compounds are 4,4'-dihydroxydiphenyl and 2,2-bis(4-hydroxyphenyl)propane. It is possible to use either one dihydroxyaryl compound to form homopolycarbonates or different dihydroxyaryl compounds to form copolycarbonates. It is possible to use either one dihydroxyaryl compound of formula (I) or (Ia) to form homopolycarbonates or two or more dihydroxyaryl compounds of formula(e) (I) and / or (Ia) to form copolycarbonates. The various dihydroxyaryl compounds may be connected together in random or blockwise fashion. In the case of copolycarbonates composed of dihydroxyaryl compounds of formulae (I) and (Ia), the molar ratio of dihydroxyaryl compounds of formula (Ia) to the other dihydroxyaryl compounds of formula (I) that are optionally usable as well is preferably between 99 mol% of (Ia) to 1 mol% of (I) and 2 mol% of (Ia) to 98 mol% of (I), preferably between 99 mol% of (Ia) to 1 mol% of (I) and 10 mol% of (Ia) to 90 mol% of (I), and especially between 99 mol% of (Ia) to 1 mol% of (I) and 30 mol% of (Ia) to 70 mol% of (I). A very particularly preferred copolycarbonate may be produced using 1,1 -bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 2,2-bis(4-hydroxyphenyl)propane dihydroxyaryl compounds of formulae (Ia) and (I). Suitable carbonic acid derivatives may include for example diaryl carbonates of general formula (II) in which R, R' and R" are the same or different and are independently hydrogen, linear or branched C 1-C34-alkyl, C7-C34-alkylaryl or C6-C34-aryl, R may additionally also be -COO-R''' where R''' is hydrogen, linear or branched C1-C34-alkyl, C7-C34-alkylaryl or C6-C34-aryl. Preferred diaryl carbonates are, for example, diphenyl carbonate, methylphenyl phenyl carbonates and di(methylphenyl) carbonates, 4-ethylphenyl phenyl carbonate, di(4-ethylphenyl) carbonate, 4-n-propylphenyl phenyl carbonate, di(4-n-propylphenyl) carbonate, 4-isopropylphenyl phenyl carbonate, di(4-isopropylphenyl) carbonate, 4-n-butylphenyl phenyl carbonate, di(4-n-butylphenyl) carbonate, 4-isobutylphenyl phenyl carbonate, di(4-isobutylphenyl) carbonate, 4-tert-butylphenyl phenyl carbonate, di(4-tert-butylphenyl) carbonate, 4-n-pentylphenyl phenyl carbonate, di(4-n-pentylphenyl) carbonate, 4-n-hexylphenyl phenyl carbonate, di(4-n-hexylphenyl) carbonate, 4-isooctylphenyl phenyl carbonate, di(4-isooctylphenyl) carbonate, 4-n-nonylphenyl phenyl carbonate, di(4-n-nonylphenyl) carbonate, 4-cyclohexylphenyl phenyl carbonate, di(4-cyclohexylphenyl) carbonate,   4-(1-methyl-1- phenylethyl)phenyl phenyl carbonate, di[4-(1-methyl-1-phenylethyl)phenyl] carbonate, biphenyl-4-yl phenyl carbonate, di(biphenyl-4-yl) carbonate, 4-(1-naphthyl)phenyl phenyl carbonate, 4-(2-naphthyl)phenyl phenyl carbonate, di[4-(1-naphthyl)phenyl] carbonate, di[4-(2-naphthyl)phenyl] carbonate, 4-phenoxyphenyl phenyl carbonate, di(4-phenoxyphenyl) carbonate, 3-pentadecylphenyl phenyl carbonate, di(3-pentadecylphenyl) carbonate, 4-tritylphenyl phenyl carbonate, di(4-tritylphenyl) carbonate, (methyl salicylate) phenyl carbonate, di(methyl salicylate) carbonate, (ethyl salicylate) phenyl carbonate, di(ethyl salicylate) carbonate, (n-propyl salicylate) phenyl carbonate, di(n-propyl salicylate) carbonate, (isopropyl salicylate) phenyl carbonate, di(isopropyl salicylate) carbonate, (n-butyl salicylate) phenyl carbonate, di(n-butyl salicylate) carbonate, (isobutyl salicylate) phenyl carbonate, di(isobutyl salicylate) carbonate, (tert-butyl salicylate) phenyl carbonate, di(tert-butyl salicylate) carbonate, di(phenyl salicylate) carbonate and di(benzyl salicylate) carbonate. 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 very particularly preferred. It is possible to use either one diaryl carbonate or different diaryl carbonates. For control or variation of the end groups, it is additionally possible to use, for example, one or more monohydroxyaryl compound(s) as chain terminators that were not used for production of the diaryl carbonate(s) used. These may be those of the general formula (III) RA Ar R     (III) in which RA     is linear or branched C1-C34-alkyl, C7-C34-alkylaryl, C6-C34-aryl or -COO-RD where RD is hydrogen, linear or branched C1-C34-alkyl, C7-C34-alkylaryl or C6-C34-aryl, and RB, RC are the same or different and are independently hydrogen, linear or branched C 1-C34-alkyl, C7-C34-alkylaryl or C6-C34-aryl. Such monohydroxyaryl compounds are, for example, 1-, 2- or 3-methylphenol, 2,4-dimethylphenol 4-ethylphenol, 4-n-propylphenol, 4-isopropylphenol, 4-n-butylphenol, 4-isobutylphenol, 4-tert-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol, 4-isooctylphenol, 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, isopropyl salicylate, n-butyl salicylate, isobutyl salicylate, tert-butyl salicylate, phenyl salicylate and benzyl salicylate. Preference is given to 4-tert-butylphenol, 4-isooctylphenol and 3-pentadecylphenol. Suitable branching agents may include compounds having three or more functional groups, preferably those having three or more hydroxyl groups. Suitable compounds having three or more phenolic hydroxyl groups are, for example, phloroglucinol, 4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)hept-2-ene, 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-hydroxyphenylisopropyl)phenol and tetra(4-hydroxyphenyl)methane. Other suitable compounds having three or more functional groups are, for example, 2,4-dihydroxybenzoic acid, trimesic acid / trimesoyl chloride, cyanuric chloride and 3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole. Preferred branching agents are 3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole and 1,1,1-tri(4-hydroxyphenyl)ethane. Layer B. preferably comprises the IR absorber in an amount in a range from > 0.6% by weight to < 2% by weight and particularly preferably > 0.7% by weight to < 1.5% by weight calculated as the solids content of inorganic IR absorber. The layers of the layer construction according to the invention are preferably arranged such that layer B. forms an outer layer. The IR absorber in the plastic layer B. is a laser-sensitive additive. The laser-sensitive absorbers generally comprise an absorber in the wavelength range of the radiation E. to be used. The IR absorber preferably comprises at least one or more organic and / or inorganic IR absorbers, preferably inorganic IR absorbers. Such additives, especially IR absorbers, and the use thereof in molding compounds are described for example in WO-A 2004 / 50766 and WO-A 2004 / 50767 and are commercially available from DSM under the trade name MicabsTM . Suitable organic IR absorbers are for example compounds having the highest possible absorption between 700 and 2500 nm (near-infrared = NIR). Suitable infrared absorbers include for example those known from the literature as described by substance class for example in M. Matsuoka, Infrared Absorbing Dyes, Plenum Press, New York, 1990. Particularly suitable are infrared absorbers from the substance classes comprising the 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. Among these, phthalocyanines and naphthalocyanines are very particularly suitable. On account of their improved solubility in thermoplastics, phthalocyanines and naphthalocyanines having bulky side groups are preferable. Suitable inorganic IR absorbers are, for example, mixed oxides of metals such as for example phosphorus-containing tin-copper mixed oxides, as described in WO-A 2006 / 042714 for example, 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, more preferably at least one or more IR absorbers from the group of tungstates. Suitable inorganic IR absorbers from the group of borides include for example compounds of the type MxBy (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 integers from 1 to 6) such as lanthanum hexaboride (LaB6), praseodymium boride (PrB6), neodymium boride (NdB6), cerium boride (CeB6), terbium boride (TbB6), dysprosium boride (DyB6), holmium boride (HoB6), yttrium boride (YB6), samarium boride (SmB6), europium boride (EuB6), erbium boride (ErB6), thulium boride (TmB6), ytterbium boride (YbB6), lutetium boride (LuB6), strontium boride (SrB6), calcium boride (CaB6), titanium boride (TiB2), zirconium boride (ZrB2), hafnium boride (HfB2), vanadium boride (VB2), tantalum boride (TaB2), chromium boride (CrB and CrB2), molybdenum boride (MoB2, Mo2B5 and MoB), tungsten boride (W2B5) or combinations thereof. Suitable inorganic IR absorbers from the group of tungstates also include for example 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, metal from the group of the rare earths, 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), wherein elements preferred as M are H, Cs, Rb, K, Tl, In, Ba, Li, Ca, Sr, Fe and Sn, among which very particular preference is given to Cs. Particular preference is given to Ba0.33WO3, Tl0.33WO3, K0.33WO3, Rb0.33WO3, Cs0.33WO3, Na0.33WO3, Na0.75WO3, and mixtures thereof. In a particular embodiment of the present invention, the sole use of Cs0.33WO3 as inorganic IR absorber is very particularly preferred. Likewise preferred are Cs / W ratios of 0.20 and 0.25. Among the inorganic IR absorbers, the tungstates are preferable over the borides on account of their low inherent color if the process according to the invention is to be carried out on layer constructions having a radiation transmittance of > 10% to < 99%, preferably of > 30% to < 95%, particularly preferably > 40% to < 93%, for the chosen radiation determined by the UV-VIS-NIR-MIR method according to DIN EN ISO / IEC 17025. Such tungstates are produced by mixing, for example, tungsten trioxide, tungsten dioxide, a hydrate of a tungsten oxide, tungsten hexachloride, ammonium tungstate or tungstic acid and optionally further salts containing the element M, for example cesium carbonate, in certain stoichiometric ratios such that the molar ratios of the individual components are given by the formula MxWyOz. This mixture is subsequently treated in a reducing atmosphere, for example an argon / hydrogen atmosphere, at temperatures between 100°C and 850°C and finally the obtained powder is heat-treated in an inert gas atmosphere at temperatures between 550°C and 1200°C. The inorganic IR absorber nanoparticles of the invention may be produced by mixing the IR absorber with the dispersants described hereinbelow and further organic solvents, for example toluene, benzene or similar aromatic hydrocarbons, and grinding in suitable mills, for example ball mills, with addition of zirconium oxide (for example having a diameter of 0.3 mm) to produce the desired particle size distribution. The nanoparticles are obtained in the form of a dispersion. After grinding, it is optionally possible to add further dispersants. The solvent is removed at elevated temperatures and reduced pressure. Preference is given to nanoparticles having an average size smaller than 200 nm, more preferably smaller than 100 nm. The size of the particles can be determined with the aid of transmission electron microscopy (TEM). Measurements of this kind on IR absorber nanoparticles are described, for example, in Adachi et al., J. Am. Ceram. Soc. 2008, 91, 28972902. The production of the tungstates is more particularly described, 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. Preferably for their use in layer constructions with at least one layer A. and a layer B. comprising preferably transparent thermoplastics having a radiation transmittance for the selected radiation of > 10% to < 99%, preferably of > 30% to < 95%, particularly preferably > 40% to < 93%, determined by the UV-VIS-NIR-MIR method according to DIN EN ISO / IEC 17025, the particles thus obtained are dispersed in an organic matrix, for example in an acrylate, and optionally ground as described above in a mill using suitable auxiliaries, for example zirconium dioxide, and optionally using organic solvents, for example toluene, benzene or similar hydrocarbons. It is preferable when all other layers except layer B., i.e. especially layer A., layer C., layer D., do not comprise an IR absorber. Should IR absorbers nevertheless be present in minimal amounts, layer A., layer C., layer D. comprise an IR absorber preferably in an amount of < 0.1% by weight, more preferably of < 0.05% by weight, particularly preferably of < 0.01% by weight, calculated as the solids content of inorganic IR absorber in the corresponding layer. Suitable polymer-based dispersants are especially dispersants having a high transmittance, for example polyacrylates, polyurethanes, polyethers, polyesters or polyester urethanes and polymers derived therefrom. Preferred dispersants are polyacrylates, polyethers and polyester-based polymers, and particularly preferred dispersants of high thermal stability are polyacrylates, for example polymethylmethacrylate, and polyesters. It is also possible to use mixtures of these polymers or else copolymers based on acrylate. Such dispersing auxiliaries and methods for production 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. Polyacrylate-based dispersants in particular are suitable. Such suitable dispersants are obtainable, for example, from Ciba Specialty Chemicals under the trade names EFKATM, for example EFKATM 4500 and EFKATM 4530. Polyester-containing dispersants are likewise suitable. They are obtainable, for example, from Avecia under the SolsperseTM trade name, for example SolsperseTM 22000, 24000SC, 26000, 27000. Polyether-containing dispersants are also known, for example, under the DisparlonTM DA234 and DA325 trade names from Kusumoto Chemicals. Polyurethane-based systems are also suitable. Polyurethane-based systems are obtainable from Ciba Specialty Chemicals under the EFKATM 4046, EFKATM 4047 trade name. TexaphorTM P60 and P63 are corresponding trade names from Cognis. The amount of the IR absorber in the dispersant may be 0.2% by weight to 50.0% by weight, preferably 1.0%-40.0% by weight, more preferably 5.0%-35.0% by weight and most preferably 10.0%-30.0% by weight based on the dispersion of the inorganic IR absorber used in accordance with the invention. The overall composition of the ready-to-use IR absorber formulation may include not only the pure IR absorber material and the dispersant but also further auxiliaries, for example zirconium dioxide, and residual solvents, for example toluene, benzene or similar aromatic hydrocarbons. There are no limitations whatsoever with regard to the amount of the inorganic IR absorbers, more preferably those from the group of tungstates, in the polymer compositions of the layer structures. However, the inorganic IR absorbers, especially the tungstates, may typically be used in an amount of > 0.7% by weight to < 4.5% by weight, preferably > 0.6% by weight to < 2% by weight and more preferably > 0.7% by weight to < 1.5% by weight, calculated as the solids fraction of inorganic IR absorber in the total polymer composition. In the present context, the term “solids fraction of inorganic IR absorber”, especially tungstate, is to be understood as meaning the inorganic IR absorber, especially the tungstate, as a pure substance and not as a dispersion, suspension or other preparation containing the pure substance, where the contents of IR absorber, especially the tungstate content, reported hereinafter always relate to this solids fraction unless explicitly stated otherwise. Further IR absorbers may preferably be optionally employed in addition to the tungstates as IR absorbers, wherein the proportion / amount thereof in such a mixture is always below that of the above-described tungstates. In the case of mixtures, compositions containing two to five (inclusive) different IR absorbers are preferred and compositions containing two or three different IR absorbers are particularly preferred. The further IR absorbers are preferably selected from the group of borides and tin oxides, more preferably LaB6 or antimony-doped tin oxide or indium tin oxide. The layer construction preferably further comprises at least one further layer C. The further layer C. is preferably composed of the same thermoplastics as described for layers A. or layer B. Layer C. preferably comprises a thermoplastic selected from the group consisting of one or more polycarbonate(s) or copolycarbonate(s) based on diphenols or blends containing at least one polycarbonate or copolycarbonate. Very particular preference is given to blends containing at least one polycarbonate or copolycarbonate and at least one poly- or copolycondensate of terephthalic acid, of naphthalenedicarboxylic acid or of a cycloalkyldicarboxylic acid, preferably of cyclohexanedicarboxylic acid. Very particular preference is given to polycarbonates or copolycarbonates, especially having average 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 having average molecular weights Mw of 10 000 to 200 000, preferably of 21 000 to 120 000. Layer C. preferably comprises a thermoplastic. Layer C. preferably comprises the thermoplastic in an amount in a range from 10% to 100% by weight, more preferably from 20% to 95% by weight, more preferably from 30% to 90% by weight, more preferably from 50% to 85% by weight, very particularly preferably from 60% to 80% by weight, based on the total weight of layer C. Layer C. preferably comprises at least one filler. The filler is preferably at least one color pigment and / or at least one other filler for producing a translucence of the filled layers, particularly preferably a white pigment, very particularly preferably titanium dioxide, zirconium dioxide and / or barium sulfate and in a particularly preferred embodiment titanium dioxide. The recited fillers are preferably added in amounts of 2% to 50% by weight, particularly preferably of 5% to 40% by weight, based on the total weight of the layer containing the filler. If layer C. is present, it is preferable when only this layer comprises the filler, preferably in the form of titanium dioxide, in the recited amounts. Layer C. preferably comprises the thermoplastic, especially the polycarbonate or copolycarbonate, in an amount of 70% to 95% by weight, particularly preferably of 80% to 90% by weight, and the filler in an amount of 5% to 30% by weight, preferably of 10% to 20% by weight, based on the total weight of layer C. Layer C. preferably has a light transmittance in the range from > 0.1% to < 25% determined according to ISO 13468-2:2006-07 and a layer thickness in the range from > 20 ^m to < 70 ^m, preferably from > 20 ^m to < 60 ^m, particularly preferably from > 25 ^m to < 55 uni. The layer construction preferably comprises at least one further layer D. The further layer D. is preferably composed of the same thermoplastics as described for layers A. or layer B. Layer D. preferably comprises a thermoplastic selected from the group consisting of one or more polycarbonate(s) or copolycarbonate(s) based on diphenols or blends containing at least one polycarbonate or copolycarbonate. Very particular preference is given to blends containing at least one polycarbonate or copolycarbonate and  at least  one poly-  or copolycondensate of terephthalic acid,  of naphthalenedicarboxylic acid or of a cycloalkyldicarboxylic acid, preferably of cyclohexanedicarboxylic acid. Very particular preference is given to polycarbonates or copolycarbonates, especially having average 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 having average molecular weights Mw of 10 000 to 200 000 g / mol, preferably of 21 000 to 120 000 g / mol. Layer D. preferably comprises a thermoplastic. Layer D. preferably comprises the thermoplastic in an amount in a range from 10% to 100% by weight, more preferably from 20% to 95% by weight, more preferably from 30% to 90% by weight, more preferably from 50% to 85% by weight, very particularly preferably from 60% to 80% by weight, based on the total weight of layer D. Layer D. preferably comprises at least one filler. The filler is preferably at least one color pigment and / or at least one other filler for producing a translucence of the filled layers, particularly preferably a white pigment, very particularly preferably titanium dioxide, zirconium dioxide and / or barium sulfate and in a particularly preferred embodiment titanium dioxide. The recited fillers are preferably added in amounts of 2% to 50% by weight, particularly preferably of 5% to 40% by weight, based on the total weight of the layer containing the filler. Layer D. preferably comprises the thermoplastics, especially the polycarbonate or copolycarbonate, in an amount of 70% to 95% by weight, particularly preferably of 80% to 90% by weight, and the filler in an amount of 5% to 30% by weight, preferably of 10% to 20% by weight, based on the total weight of layer D. Layer D. preferably has a light transmittance in the range from > 0.1 % to < 25% determined according to ISO 13468-2:2006-07, a layer thickness in the range from > 20 gm to < 70 ^m, preferably from > 20 gm to < 60 gm, particularly preferably from > 25 gm to < 55 gm. Layer D. preferably comprises a different material to layer C. Layer A. preferably comprises a different material to layer C. The layer construction preferably comprises one or more additional layers Z. The at least one additional layer Z. is preferably at least one protective layer applied to one or both sides of the layer construction and may be peeled off, preferably by hand, for example before use of the layer construction. The at least one additional layer Z. preferably comprises polyethylene or polypropylene as the main constituent. One or more security features may be introduced at any desired locations in the layer construction according to the invention. Security features may be introduced into the layer composite as electronic components, for example antennae and IC chips, holograms and / or security prints. Ideally one or more security features are placed in the layer construction according to the invention in such a way that they are at least partially covered by layer B. It would be conceivable, for example, for one or more security features to 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, further security features may also be present at other locations in the layer construction according to the invention. A security feature is ideally placed such that the engravings are not covered. The individual layers of the layer construction may be compressed for a particular duration by lamination using a laminating press under the action of heat and pressure to form a monolithic composite of the individual layers, a so-called laminate. The pressure and temperature during the laminating operation are to be chosen such that the individual layers and the optionally present security features are not damaged but the individual layers form a strong composite which does not subsequently break up into its individual layers. The engravings are preferably introduced after construction of the laminate. The at least one additional layer Z. is preferably removed before the lamination process. It is preferable when layer B. forms an outer surface of the layer construction. It is further preferable when the layer construction has an arrangement of the layers selected from the group 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 in each case layers Z., which may preferably be residuelessly detached from the layer construction at any time, may additionally be arranged on each outer surface. In a preferred embodiment of the layer construction, the black engraving is within layer A. to an extent of at least 20%, preferably to an extent of at least 40%, more preferably to an extent of at least 50%, particularly preferably to an extent of at least 60%, very particularly preferably to an extent of at least 70%, based on optical density. According to the invention, the term "within layer A." is to be understood as meaning that less than 20%, preferably less than 10%, particularly preferably less than 5%, very particularly preferably less than 1%, of the engraving is arranged on one of the surfaces a1. or a2. or is disposed in layer B. or one of the further layers C. to Z. In a preferred embodiment of the layer construction, the material of layer A. contains 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. It is preferable when the polycarbonate, copolycarbonate or the blend of different polycarbonates or copolycarbonates is at least in part one as described above. In a preferred embodiment of the layer construction, the milky white engraving within layer B. is in the form of a foam. The layer B. preferably changes its initially clear structure to the foamed structure 17 forming the milky white engraving at the engraved sites during introduction of the engraving into layer B., preferably using a laser. The milky white engraving preferably causes an elevation of the foamed material. If layer B forms an outer layer of the layer construction, the material expands on the second surface b2. of the transparent plastic layer B. during the engraving. The milky white engraving preferably exhibits a thickness expansion of layer B. of 1.5 to 5 times, preferably of 2 to 4 times, particularly preferably of 2.5 to 3.5 times, compared to the thickness at the unengraved sites of layer B. The milky white structure preferably has a thickness which is 2 to 400 gm, more preferably 5 to 300 gm, more preferably 10 to 200 gm, particularly preferably 40 to 100 gm, greater than the regions of layer B. which do not comprise the milky white structure. It is further possible to produce very fine lines of this foamed structure which may be generated at rather low laser powers. These structures are perceptible to the eye but are only very slightly elevated from the plane of the layer construction and are almost as transparent as the rest of layer B. In a preferred embodiment of the layer construction, the milky white engraving has a turbidity of > 20%, preferably of > 50%, more preferably of > 80%, measured with a BYK-Gardner haze gard plus instrument according to the standard ASTM D1003:2013. In a preferred embodiment of the layer construction, the milky white engraving or the black engraving depicts a structure selected from the group consisting of a photograph, especially a passport photo, a fingerprint, braille and a combination of at least two of these. The white engraving preferably has a structure having a height above the surface of the layer construction of 50 to 400 gm, more preferably of 70 to 350 gm, particularly preferably of 100 to 300 gm. The black engraving preferably has a structure having a height above the surface of the layer construction of 50 to 400 gm, more preferably of 70 to 350 gm, particularly preferably of 100 to 300 gm. It is preferable when the depicted structure is formed from the superposition of at least a portion of the milky white engraving and the black engraving. Alternatively, the structure formed, especially the photograph, may be formed partly from the milky white and partly from the black engraving, which are preferably superposed to an extent of from 0% to 20%, more preferably from 0.1% to 10%, very particularly preferably from 0.2% to 1%, of the total surface area of the structure. Especially to form braille the engraving consists predominantly, preferably exclusively, of the milky white engraving. The resolution of the milky white engraving is preferably in a range from 50 to 2000 DPI, more preferably from 100 to 1000 DPI, very particularly preferably from 150 to 600 DPI. The resolution of the black engraving is preferably in a range from 50 to 2000 DPI, more preferably from 100 to 1000 DPI, very particularly preferably from 150 to 600 DPI. In a preferred embodiment of the layer construction, parts of the white engraving cover parts of the black engraving. It is preferable when up to 50% of the white engraving covers up to 50% of the black engraving. Covering is to be understood as meaning that the covering engraving is the one perceived by the observer looking at the surface b2. It is likewise possible that only parts of the white engraving cover up to 100% of the black engraving but the black engraving can nevertheless be perceived. In a preferred embodiment of the layer construction, at the sites comprising the milky white engraving, layer B. has a layer thickness which is at least 0.001 mm, preferably 0.001 to 1 mm, particularly preferably 0.01 to 0.1 mm, thicker than at the sites without milky white engraving. Especially if the milky white engraving is in the form of braille it has an elevation relative to the remaining surface area of the layer construction of at least 0.01 to 0.5 mm. In a preferred embodiment of the layer construction the layer construction, at least comprising the layers A., B. and optionally C., preferably has a layer thickness in a range from 100 ^m to 10 000 ^m, preferably 200 ^m to 1000 ^m, very particularly preferably from 50 ^m to 500 gm. Layer A. preferably has a layer thickness in a range from 10 to 1000 ^m, preferably 20 ^m to 500 ^m, very particularly preferably from 50 gm to 200 gm. Layer B. preferably has a layer thickness in a range from 10 gm to 1000 gm, preferably 20 gm to 500 gm, very particularly preferably from 50 gm to 200 gm. Layer C. or layer D. or layer C. and layer D. preferably have a layer thickness in a range from 10 gm to 1000 gm, preferably 20 gm to 500 gm, particularly preferably from 50 to 200 gm. The layers A., B. and optionally C. and optionally D. may each have the same thickness or different thicknesses. The thicknesses of layers A., B. and optionally C. and optionally D. preferably differ from one another by not more than 50%, preferably not more than 25%, particularly preferably not more than 10%, based on the thickness of layer A. It is preferable when at least layer A., and preferably also layer B., include(s) 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, preferably a polycarbonate or a copolycarbonate. Examples of preferred thermoplastics, especially of preferred polycarbonates or copolycarbonates, have already been mentioned above for layers A. and B. The aforementioned polycarbonates and copolycarbonates are also preferred for layers C. and D. The invention further provides a process for producing a colored layer construction, especially security document, comprising the steps of: i) providing a layer construction at least comprising i)1. a, preferably transparent, radiation-engravable polymer layer B. comprising an IR absorber in a range from > 0.7% by weight to < 4.5% by weight calculated as the solids content of inorganic IR absorber in layer B.; i)2. a, preferably transparent, radiation-engravable polymer layer A. having a first surface a1. facing in the direction of the 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. which is preferably in contact with layer A., ii) providing a raster photo file having 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 construction from step i) on the basis of the raster photo file from step ii) with focused nonionizing electromagnetic radiation from a laser having a peak pulse power of 5 to 100 kW and preferably a pulse duration in a range from 10 ns to 500 ns from the side of polymer layer B. to produce the black engraving, iv) irradiating the layer construction from step i) on the basis of the raster photo file from step ii) with focused nonionizing electromagnetic radiation from a laser having a peak pulse power of 5 to 100 kW and preferably a pulse duration in a range from 0.01 ns to < 100 ns, preferably from 0.5 to 50 ns, more preferably from 1 to 40 ns, more preferably from 2 to 30 ns, particularly preferably from 5 to 20 ns, or from 0.01 to < 10 ns, from the side of the polymer layer B. to produce the milky white engraving, wherein the focus of the laser during step iii) or step iv), or steps iii) and iv), i.e. the point having the highest energy density, is 0.5 to 7 mm, preferably 1 to 6 mm, particularly preferably 2 to 5 mm above or below the surface of the layer construction facing in the direction of the laser. The providing of the layer construction in step i) may assume any form of providing a layer construction that a person skilled in the art would choose for this purpose. The providing of the layer construction is preferably in the form of a layer construction having at least one layer A., here step i)1. and a layer B., here step i)2., and optionally a layer C., here step i)3., which is preferably in a form such as is customary for identification documents. The providing of layer C. in step i)3. is preferably carried out such that layer A. is disposed between layer B. and layer C. The compositions and properties of layer A., layer B. and optional layer C. correspond to the compositions and properties of the respective layer specified above for the layer construction according to the invention. If the layer construction does not comprise the optional layer C., layer A. has a filler content, preferably in the form of titanium dioxide, in an amount in a range from 2% to 50% by weight, particularly preferably from 5% to 40% by weight, very particularly preferably from 10% to 30% by weight, based on the total weight of layer A. If the layer construction does comprise the optional layer C., layer C. has a filler content, preferably in the form of titanium dioxide, in an amount in a range from 2% to 50% by weight, particularly preferably from 5% to 40% by weight, very particularly preferably from 10% to 30% by weight, based on the total weight of layer C. The providing of the raster photo file in step ii) may be carried out by any suitable manner and measure known to those skilled in the art. The providing of the raster photo file is preferably carried out via software programs such as Photoshop from Adobe® (USA). The raster photo file preferably has a resolution in a range from 100 to 2000 DPI, more preferably from 150 to 1500 DPI, more preferably from 200 to 1000 DPI, particularly preferably from 500 to 1500 DPI. In the process according to the invention, in step iii) the focused nonionizing electromagnetic beam E. of the laser beam is incident directly on the surface b2. of layer B. to be colored in the layer construction when this is the outer surface of the layer construction. The peak pulse power of this laser is in a range from 5 to 100 kW. The laser is preferably directed onto the surface b2. of layer B. at an angle of 90° and the radiation introduced. The laser preferably exhibits radiation in a wavelength range of 1064 nm + / 100 nm, having a pulse duration of 2 ns to 500 ns, preferably of 10 to 350 ns, and a repetition frequency of 1 KHz to 300 KHz, preferably of 5 to 200 KHz, and a peak pulse power of 1 KW to 500 KW, preferably of 2 to 300 KW. Whether the material of polymer layer B. is colored black or undergoes milky white opacification depends greatly on the choice of laser type and the pulse duration used in steps iii) and iv). In the case of milky-white opacification the material is brought to a temperature such that it begins to melt and air inclusions occur, thus inducing the milky-white coloring, while, in the case of blackening, sites on the material are heated to still higher temperatures to effect carbonization at these sites. The limit of the pulse duration to be used in each case differs from laser type to laser type. Thus, for the same peak pulse power in a diode laser, a milky white opacification may already be effected at low pulse durations of less than 2 ns while for a fiber laser at least 20 ns are necessary therefor. If, for example, a fiber laser having a wavelength of 1064 nm operated at 50 W is used, the pulse duration should be adapted accordingly, preferably extended to 30 ns. The pulse duration for producing the black engraving is likewise increased relative to a diode laser when using a fiber laser. The pulse duration range required for producing the black engraving may thus overlap with the pulse duration range for another laser type required for the milky white engraving. In step iv), the focused nonionizing electromagnetic beam E. of the laser beam is incident directly on the surface b2. of layer B. to be colored / structured in the layer construction. The peak pulse power of this laser is in a range from 5 to 100 kW. The laser is preferably directed onto the surface b2. of layer B. at an angle of 45° to 90°, more preferably of 60° to 90°, particularly preferably of 80° to 90°, very particularly preferably of 90°, and the radiation E. is directly introduced. The focus of the laser in step iii) or iv), or in steps iii) and iv), i.e. the point having the highest energy density, is in a region from 0.5 to 7 mm, preferably 1 to 6 mm, particularly preferably 2 to 5 mm above or below the surface of the layer construction facing in the direction of the laser. Steps iii) and iv) further differ in that different pulse frequencies for the laser are used. Thus production of the black engraving in layer A. or C., if present, employs a pulse duration in a range from 10 ns to < 500 ns, preferably from 15 to 300 ns, particularly preferably from 50 to 200 ns, while step iv) for producing the milky white engraving in layer B. employs a pulse duration in a range of < 100 ns, preferably from 1 to 50 ns, particularly preferably from 2 to 40 ns. In a preferred embodiment of the process for producing the layer construction, the irradiation of the layer construction in step iv) is carried out before, during or after the irradiation in step iii). The irradiation of the layer construction in step iv) is preferably carried out after the irradiation of the layer construction in step iii). The irradiation of the layer construction in step iii) is preferably carried out on the basis of the same photo file as the irradiation of the layer construction in step iv). Using the same photo file for both the black and the white engraving makes it possible to produce a completely black image of the photo which is partly overlapped by the milky white engraving above the black engraving. Furthermore, it is also possible to use other photo files for the two engravings. In addition to the overlapping regions it is also possible to produce regions engraved purely in black or purely in milky white. In a preferred embodiment of the process for producing the layer construction, at least layer A., and preferably also layer B., comprise(s) 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. The materials, compositions, properties and dimensions of layers A., B. and optionally C. are preferably chosen as described above for the layer construction according to the invention. The invention further relates to a security document containing a layer construction according to the invention or a layer construction produced by the process according to the invention, wherein the security document is preferably selected from the group consisting of a data page in a passport, a personal identification card, for example in the form of an ID card, a driver's license, a banknote and a combination of at least two of these. Examples Example 1) Production of the transparent layer B. in a thickness of 100 gm. Masterbatch:  A highly concentrated IR masterbatch was produced from polycarbonate. Production of the masterbatch for production of layer B. of the layer construction according to the invention was carried out with a conventional twin-screw compounding extruder (ZSK 32) at processing temperatures customary for polycarbonate of 250°C to 330°C. A masterbatch having the following composition was compounded and subsequently pelletized: ■   94.744% by weight of MakrolonTM 3108 polycarbonate pellets from Covestro Deutschland AG ■   0.75% by weight of YMDS 874 IR absorber from Sumitomo ■   4.5% by weight of MakrolonTM 3108 powder from Covestro Deutschland AG ■   0.006% by weight (6 ppm) of lamp black 101 (carbon black from Evonik-Degussa GmbH) having an average particle size of 95 nm Production of layer B. as extrusion film The plant used for production of the extruded layer B. comprises: ■ an extruder for extrusion of layer B. containing at least one polycarbonate having a screw of 60 mm in diameter (D) and a length of 33 D (i.e 33 times the diameter). The screw has a devolatilization zone; ■   a melt pump; ■   a crosshead; ■   a slot die of 450 mm width; ■   a three-roll smoothing calender having a horizontal roll arrangement, wherein the third roll can be tilted by + / - 45° relative to the horizontal; ■   a roller conveyor; ■   a means for measuring thickness; ■ a device for double-sided application of optional protective films; ■ a take-off means for the optional protective films; ■ a winding station. The pellets of the masterbatch were conveyed from a dryer into a filling hopper of the extruder. The material was melted and conveyed in the barrel / screw plastifying system of the extruder. The melt passed from the slot die on to the smoothing calender. The final shaping and cooling of layer B. in the form of an extruded film was carried out on the smoothing calender which consisted of three rolls. The surfaces were embossed using a textured steel roll (no. 6 side) and a textured silicone rubber roll (no. 2 side). The rubber roll used for texturing the film surface is disclosed in US-4 368 240 to Nauta Roll Corporation. The film was subsequently transported through a take-off and then the film was wound up. Example 2) Production of laminates a), b) and c). The following film types were used for production of the laminates a), b) and c): • Transparent film Makrofol® ID6-2 000000; 100 gm from Covestro Deutschland AG. • Transparent laser-reactive film Makrofol® ID6-2 750061; 100 gm from Covestro Deutschland AG. • White film Makrofol® ID4-4 010207; 300 gm from Covestro Deutschland AG. • Transparent IR film made of polycarbonate, from Ex. 1) For production of the laminates, the aforementioned film types were stacked as follows and then laminated: Laminate a) 100 gm IR film from Ex. 1) as layer B. 300 ^m Makrofol® ID4-4 010207 white film as layer A. 100 gm IR film from Ex. 1) as layer B. Laminate b) 100 gm IR film from Ex. 1) as layer B. 100 gm Makrofol® ID6-2 000000 transparent film as layer A. 300 gm Makrofol® ID4-4 010207 white film as layer C. 100 gm Makrofol® ID6-2 000000 transparent film as layer A. 100 ^m IR film from Ex. 1) as layer B. Laminate c) 100 ^m IR film from Ex. 1) as layer B. 100 ^m Makrofol® ID6-2 750061 transparent laser-engravable film as layer A. 300 ^m Makrofol® ID4-4 010207 white film as layer C. 100 ^m Makrofol® ID6-2 750061 transparent laser-engravable film as layer A. 100 ^m IR film from Ex. 1) as layer B. The film stacks a) b) and c) were then laminated as follows: Lamination was effected on a Burckle 50 / 100 lamination press. The film 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 form of introduction of an engraving into laminates a) b) and c) The laminates a) b) and c) were engraved with a laser from Trumpf. The laser model used therefor is a TruMark 3130 having the following properties: • Laser parameters: max. peak pulse power 40 kW at 20 kHz • Beam quality (M2) 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 gm at focal length 100 mm • Max. internal focal point control ± 60 mm at focal length 420 mm • Scanner calibration accuracy ± 50 gm • Max. text field size 290 mm x 290 mm at focal length 420 mm The laminates were each lasered with two settings. One setting for light-colored laser marking and one setting for a black laser marking. The motif was a photo: For the light-colored laser marking the following setting was used: Frequency of 2 KHz; power 95%. For the black laser marking the following setting was used: Frequency of 12.5 KHz; power 30%. The frequencies of 2 and 12.5 KHz result in the pulse durations as shown in figure 1, i.e. 2 KHz results in a pulse duration of between 5 and 7 nanoseconds ns and 12.5 KHz results in a pulse duration of about 8 ns. For a fiber laser at the same frequencies and a 50 W power a pulse duration of 30 ns may be selected to produce the milky white engraving in polymer layer B. 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 set exactly on the upper surface of the film laminate, in this case the outer surface of layer B. Focus shift from +1 mm to +4 mm in 1 mm increments: The distance between the lens of the laser and the upper surface of the film laminate was increased by 1 mm in each case, thus resulting in increasing defocusing of the laser beam. Example 4) Measurement of the optical density at the darkest points of the milky white engraving in or on layer B. and the black laser engraving in layer A. After the laser markings, as described above, the optical density (OD) was measured at various points of the photo. This was done in each case at the darkest points of the milky white and the black marking in the form of the milky white engraving in layer B. and the black engraving in layer A. To produce a highest possible contrast in an image, it is desirable to achieve a lowest possible value of the OD at the darkest point of the milky white engraving and a highest possible OD value at as many points as possible of the black engraving. Measurement of OD employed a densitometer from Techkon which performed the measurements according to the standards DIN 16 527 Part 3, ISO 5-3:2009 and as described in Handbuch fur Standardisierung [Handbook of Standardization] published by BVD (Bundesverband Druck E.V.), and FOGRA (Forschungsgesellschaft Druck e.V.). The two following tables 1 and 2 list the measured OD values for the darkest points of the milky white engravings and the darkest points of the black engraving from figure 2a for laminate a), figure 2b for laminate b) and figure 2c for 2c. 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 1: OD values for the black 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 Table 2: OD values for the milky white engraving As is apparent from the OD values in tables 1 and 2, the values for the optical density of the black engraving are in a range from 0.44 for laminate a) at 4 mm defocusing and laminate b) at 3 mm defocusing to 1.34 for laminate c) while the values for the optical density of the milky white engraving are in a range from 0.01 for laminate c) at 4 mm defocusing to 0.12 for laminate c) without defocusing. The values for the optical density of the black engraving therefore differ by at least 0.3 points relative to the optical density of the milky white engraving. In figures 3a and 3b it is apparent especially for laminate c) that the optimum conditions for distinguishing the milky white and the black engraving are achieved at a maximum defocusing of 4 mm. This maximizes the difference in the optical density values. The optical density for the milky white engraving at a defocusing of 4 millimeters is 0.01 for laminate c) while the optical density for the black engraving in laminate c) at a defocusing of 4 millimeters is 1.27. The description of figures 1 to 8 discloses exemplary layer constructions according to the invention which are not to be understood as limiting: Figure 1: Dependence of the frequency of the employed laser on pulse length; Figures 2a to 2c: Photographs of laminates a) to c) produced by the process according to the invention and at different defocusing distances of the laser; 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 c) produced by the process according to the invention both at an oblique angle (Fig. 4a) and at an angle of 90° to the surface of the laminate; Figures 5a and 5b: Photograph (Fig. 5a) and schematic representation (Fig. 5b) of a layer construction according to the invention after introduction of the milky white engraving; Figures 6a and 6b: Photograph (Fig. 6a) and schematic representation (Fig. 6b) of a layer construction according to the invention after introduction of the black engraving; Figure 7: Photograph of an overlapping region of black and milky white engraving on a layer construction according to the invention produced by the process according to the invention. FIG. 1 shows the dependence of the frequency of the employed laser on pulse length. It is apparent that frequency increases virtually linearly with increasing pulse duration. Figure 2a shows, in two offset rows, respective photos of an engraved layer construction 100 in the form of a laminate a) from example 2, in each case with a milky white engraving labeled with odd numbers 1, 3, 5, 7 and 9 and with a black engraving labeled with even numbers 2, 4, 6, 8 and 10. Different defocusing distances of the employed laser were selected for respective pairs of a milky white and a black engraving. Images 1 and 2 of figure 2a were engraved using a laser defocused by 0 mm with respect to the surface of the layer structure. The settings of the laser were as described for example 4. Images 3 and 4 were each engraved with a laser defocusing of 1 mm. Images 5 and 6 were each engraved with a laser defocusing of 2 mm. Images 7 and 8 were each engraved with a laser defocusing of 3 mm. Images 9 and 10 were each engraved with a laser defocusing of 4 mm. The values for the optical densities measured in the milky white engraving and the black engraving are listed in tables 1 and 2. Figure 2b shows photos of laminate b) from example 2 which were produced with the same settings of laser defocusing as for laminate a) in figure 2a. Production of the images 1 to 10 in figure 2b used the same defocusing distances of the employed laser as described for images 1 to 10 from figure 2a for laminate a). The values for the optical densities thereof at the respective darkest points are likewise listed in tables 1 and 2. Figure 2c shows the same laser defocusing settings on a laminate c) from example 2, wherein production of images 1 to 10 employed the same defocusing distances of the employed laser as described in figure 2a for laminate a) and listed with the darkest points in the terms of optical density in tables 1 and 2. Figure 3a is a graphical representation of the values of the optical densities from table 1 for the black engravings of the three laminates, laminate a) 20, laminate b) 30 and laminate c) 40 relative to the defocusing distances. Especially for the laminate c) 40 a defocusing distance of the laser of at least 2 mm is particularly advantageous for producing the best possible black engravings. Figure 3b is a graphical representation of the values for 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 likewise relative to the defocusing distances. It is clearly apparent that the defocusing distance of 4 mm shows 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 the laminate c) 40. Figures 4a and 4b show a photo of a layer construction 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 about 45° relative to the surface of the layer construction 100 while figure 4b was photographed at an angle of 90° relative to the surface of the layer construction 100. It is apparent that at a viewing angle of 45° especially the milky white engraving 160 appears elevated and the full contours of the photo are discernible while at a viewing angle of 90° the milky white engraving 170 on the layer construction 100 is only indistinctly apparent. Figure 5a shows a photograph of a section of a layer construction 100 at the site of a milky white engraving 160. It is apparent that at the site of the milky white engraving 160 the material of the layer B. 110 has undergone significant, namely two-fold, foaming, namely by 82 gm, from 79 gm originally to 161 gm altogether. The layer construction 100 from figure 5 a is that of laminate c) from example 1 and therefore comprises, adjacent to layer B. 110 of 100 gm, a layer A. 120 of 100 gm followed by a layer C. 130 having a thickness of 300 gm which, on the other side of layer C. 130, in turn has a reflected arrangement of a layer A. 140 and a layer B. 150. Figure 5b shows the photo from figure 5a as a schematic diagram to illustrate the layer construction 100 with its layers and the white milky engraving. Here too, layer C. 130 is disposed as a white layer in the center of the construction with symmetrically outwardly arranged layers A. 120 and 140, each of which is followed by a layer B. 110 and 150, such as is specified for laminate c) from example 1. The white milky engraving 160 produced by the laser is apparent in layer B. 110. Figure 6a in turn shows a photo of the layer construction 100 in the form of laminate c) after engraving but in a region in which parts of the black engraving 170 are to be 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. In contrast to the photo in figure 5a, it is apparent here that the parts of the black engraving through which the section was made are predominantly in layer A. 120. Only less than 10% of the black engraving is to be found in the edge region to layer C. 130 or layer B. 110. Figure 6b shows the photo from figure 6a as a schematic diagram to illustrate the layer construction 100 with its layers and the black engraving. Here too, layer C. 130 is disposed as a white layer in the center of the construction with symmetrically outwardly arranged layers A. 120 and 140, each of which is followed by a layer B. 110 and 150, such as is specified for laminate c) from example 1. The black engraving 170 produced by the laser is apparent in layer A. 130. Figure 7 shows a photo of a layer construction 100 according to the invention which corresponds to a construction 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 numbers and letter combinations are apparent. As 28 is clearly apparent, the writing of the black engraving 170 is entirely legible through the milky white engraving 160. It is likewise apparent that the milky white engraving 160 is elevated and protrudes from the surface of the layer construction 100 and is therefore also feelable or tactile and can thus represent braille. 5

Claims

1. A layer construction comprising:A. a first, preferably transparent or white, radiation-engravable layer A. having 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. having a first surface b1. facing in the direction of layerA. and a second surface b2., wherein layer B. an IR absorber in an amount in a range from > 0.7% by weight to < 4.5% by weight calculated as the solids co ntent of inorganic IR absorber,wherein the layer construction comprises both a milky-white and a black engraving which have been produced using nonionizing electromagnetic radiation E. and are visible from at least one side of the layer construction,wherein the black engraving has an optical density of at least 0.5, preferably in a range from 0.5 to 2, measured according to ISO 5-3:2009.

2. The layer construction as claimed in claim 1, wherein the black engraving is within layer A to an extent of at least 20%, preferably to an extent of at least 40%.

3. The layer construction as claimed in either of the preceding claims, wherein the material of layer A. contains 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 of these.

4. The layer construction as claimed in any of the preceding claims, wherein the milky whiteengraving within layer B. is in the form of a foam.

5. The layer construction as claimed in any of the preceding claims, wherein the milky whiteengraving has a turbidity of > 20%, preferably of > 50%, measured according to the standard ASTM D1003:2013.

6. The layer construction as claimed in any of the preceding claims, wherein the milky white engraving or the black engraving depicts a structure selected from the group consisting of a photograph, especially a passport photo, a fingerprint, braille and a combination of at least two of these.

7. The layer construction as claimed in any of the preceding claims, wherein parts of the white engraving cover parts of the black engraving, preferably up to 50% of the white engraving cover up to 50% of the black engraving.

8. The layer construction as claimed in any of the preceding claims, wherein at the sites comprising the milky white engraving layer B. has a layer thickness at least 0.001 mm thicker than at the sites without the milky white engraving.

9. The layer construction as claimed in any of the preceding claims, wherein the layer construction comprises at least layers A., B. and optionally C. and has a total layer thickness in a range from 100 to 10 000 pm.

10. The layer construction as claimed in any of the preceding claims, wherein at least layer C., preferably also layer B., comprise(s) 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, preferably a polycarbonate or a copolycarbonate.

11. A process for producing a colored layer construction, comprising the steps of:i) providing a layer construction at least comprisingi)1. a preferably transparent radiation-engravable polymer layer B. comprising an IR absorber in a range from > 0.7% by weight to < 4.5% by weight calculated as the solids content of inorganic IR absorber in layer B.;i)2. a preferably transparent radiation-engravable polymer layer A having 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. which is preferably in contact with layer A.,ii) providing a raster photo file having a raster resolution of 7 DPI to 800 DPI;iii) irradiating the layer construction from step i) on the basis of the raster photo file from step ii) with focused nonionizing electromagnetic radiation using a laser having a peak pulse power of 5 to 100 kW and a pulse duration preferably in a range from 10 ns to 500 ns from the side of polymer layer B. to produce the black engraving,iv) irradiating the layer construction from step i) on the basis of the raster photo file from step ii) with focused nonionizing electromagnetic radiation from a laser having a peak pulse power of 5 to 100 kW and a pulse duration preferably in a range from 0.01 ns to < 100 ns, especially from 0.01 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 steps iii) and iv), i.e. the point having the highest energy density, is 0.5 to 7 mm, preferably 1 to 6 mm, particularly preferably 2 to 5 mm above or below the surface of the layer construction facing in the direction of the laser.

12. The process as claimed in claim 11, wherein the irradiation of the layer construction in step iii) is carried out before, during or after the irradiation in step ii), preferably after step ii).

13. A security document containing a layer construction as claimed in any of claims 1 to 10 or obtainable by the process as claimed in either of claims 11 and 12, wherein the security document5        is preferably selected from the group consisting of a data page in a passport, a personalidentification card, for example in the form of an ID card, a driver's license, a banknote and a combination of at least two of these.

Images