SYSTEM OF TWO DRY-TRANSFERABLE UV-CURING VARNISH LAYERS FOR THE PROTECTION OF A HOLOGRAM IN A PHOTOPOLYMER FILM COMPOSITE

Description

[0001] The invention relates to a sealed holographic medium comprising a layer structure B'-C1'-C2', a method for producing the sealed holographic medium, a kit of parts, and their use.

[0002] Photopolymer layers for the production of holographic media are generally known, for example, from WO 2011 / 054797 and WO 2011 / 067057. Advantages of these holographic media include their high diffractive light diffraction efficiency and simplified processing, since no further chemical and / or thermal development steps are required after holographic exposure.

[0003] The holographic film (Bayfol ®< HX from Covestro Deutschland AG) consists of a film substrate (A) and a light-sensitive photopolymer layer (B). Optical holograms are formed in layer (B) through local photopolymerization and fixed by surface UV-VIS exposure. This transforms layer (B) into a fully polymerized layer (B') that is no longer photosensitive and contains a pre-inscribed hologram. While this hologram is inherently very stable over time, its properties can change due to mechanical influences and / or contact with, for example, organic substances (solvents).

[0004] Possible protection methods include varnishing, lamination, and applying a protective layer and / or film. However, numerous problems arise with traditional varnishing or with gluing combined with liquid varnish and / or adhesive components, which can completely destroy the hologram upon contact with the (B') layer or render it unusable due to significant optical shift.

[0005] Patent application EP 2613318 B1 describes that, by appropriately selecting the components, protective layers can be applied to an exposed photopolymer layer. These protective layers can be produced by reacting at least one radiation-curing resin (I), an isocyanate-functional resin (II), and a photoinitiator system (III). The protective layers described in EP 2613318 B1 meet the requirements for a suitable protective layer because, after application, they make it possible to provide a layer structure comprising a protective layer and an exposed photopolymer layer that can be firmly bonded to a wide variety of adjacent layers, such as adhesive layers, without causing a change in the volume of the photopolymer layer and the associated color changes of the hologram. However, the protective layer is applied "wet," ie, as a solution or dispersion, to the photopolymer layer.However, in industrial practice, it is complex to set up appropriate liquid application systems and provide personnel to monitor the coating process. Lamination processes are therefore preferred, but they have the disadvantage that they often result in film composites with insufficient adhesion.

[0006] Patent applications JP2006023455 (A) and JP2006023456 (A) describe a medium for recording holograms, comprising a substrate layer, a photopolymer layer, and one or two protective layers. The protective layer is bonded to the substrate layer, embedding the photopolymer layer between the substrate layer and the protective layer without itself being bonded to the two layers. These protected holographic media are preferably used in ID cards. For most applications of holographic media, where high demands on uniformity and quality apply across the entire surface of the holographic medium, such a layer structure is difficult or even impossible to achieve.

[0007] Some applications place such high demands on the protective layer, especially in terms of scratch and solvent resistance in combination with flexibility, elasticity and good adhesion, that it is difficult to meet all requirements with one protective layer.

[0008] The object of the present invention was therefore to provide a solution for exposed photopolymer films which no longer require any post-processing steps after the holographic exposure, according to which these can be sealed in simple working steps without generating a disadvantageous color shift of more than 10 nm, preferably of more than 5 nm, excellent adhesion between the photopolymer and protective layer is ensured and the cured protective layer ensures permanent resistance to common organic solvents, aqueous acids and alkalis, cosmetics, household and industrial cleaning agents and / or sufficient scratch resistance against mechanical influences.

[0009] This object is achieved by a sealed holographic medium according to claim 1.

[0010] The photopolymer layer B' is a photopolymer layer in which a hologram, preferably in volume hologram, has been exposed and this hologram has then been fixed by area broadband UV / VIS exposure, preferably the fixation is carried out with a light energy dose of 5-10 J / cm 2< .

[0011] The advantage of the holographic medium according to the invention is that the photopolymer layer with the exposed hologram is encapsulated by this protective layer combination, with components B', C1, C1', C2, and C2' being coordinated to enable good adhesion while simultaneously ensuring frequency stability / lattice stability of the hologram and protection against chemical, physical, and mechanical stress. In addition, the sealing layers enable compatibility with other layers and generally improve the handling of the hologram, for example, providing protection against dust by preventing residual stickiness or by providing an antistatic finish to the sealing layer. The two protective layers C1 and C2 perform different functions.The protective layer C1, which is directly bonded to the photopolymer layer B, is transferable to the B' layer from the substrate layer D1 and is neutral to the hologram, meaning it does not cause any deterioration in the hologram intensity or any spectral shift of the reflection maximum. Furthermore, the cured protective layer C1' adheres firmly to the two adjacent layers, i.e., to the photopolymer layer B' and the cured protective layer C2'. The second protective layer C2, which is bonded to the protective layer C1, is designed to be applied to the uncured layer C1, for example, by lamination, and adheres well to the protective layers C1 and C1', respectively, in the uncured and cured states. The cured protective layer C2' exhibits good solvent and scratch resistance.The combination of the two protective layers C1 and C2 protects the photopolymer layer B' containing the hologram against physical and chemical influences, such as scratches and solvent damage, while at the same time ensuring good adhesion of the layers of the structure to each other and flexibility and elasticity of the sealed holographic medium.

[0012] Reactive diluents within the meaning of the invention are preferably compounds which reduce the initial viscosity of the curable composition and, during the curing of the curable composition, form a chemical bond with the thermoplastic resin and hardener, thereby forming a network.

[0013] In the context of the invention, "functional" in connection with acrylates refers to the number of reactive groups, preferably in the form of double bonds, that are radiation-curing, in particular UV-VIS radiation-curing. The radiation-curing groups are, in particular, acrylate groups. A "multifunctional acrylate" is therefore understood to mean a molecule that has at least one radiation-curing group, in particular acrylate groups, and a "trifunctional acrylate," for example, is understood to mean a molecule that has three radiation-curing groups, in particular acrylate groups. The radiation-curing groups are, in particular, radically polymerizable groups, such as the acrylate group.

[0014] For the purposes of the invention, "flat" refers to a configuration as a flat surface or also as a concave or convex curved or wavy surface. For the purposes of the invention, the photopolymer B' containing the hologram must have a flat, curved, or wavy surface such that lamination of the sealing layer is possible, at least in the area of the hologram.

[0015] Within the context of the present invention, the word "a" in connection with countable quantities is to be understood as a numeral only if this is expressly stated (e.g., by the expression "exactly one"). When, for example, reference is made below to "a polyisocyanate," the word "a" is to be understood merely as an indefinite article and not as a numeral. Thus, it also encompasses an embodiment in which two or more polyisocyanates are present that, for example, differ structurally.

[0016] In a further preferred embodiment, the layer structure according to the invention consists of at least four at least partially interconnected layers, wherein the layers are arranged directly on top of one another in the order substrate layer A, photopolymer layer B', cured protective layer C1' and cured protective layer C2'.

[0017] In a further preferred embodiment, the layer structure according to the invention consists of at least four at least partially interconnected layers, wherein the layers are arranged directly on top of one another in the order photopolymer layer B', cured protective layer C1', cured protective layer C2' and substrate layer D2.

[0018] In a further preferred embodiment, the layer structure according to the invention consists of at least five at least partially interconnected layers, wherein the layers are arranged directly on top of one another in the order substrate layer A, photopolymer layer B', cured protective layer C1', cured protective layer C2' and substrate layer D2.

[0019] The substrate layers A and D2 in the above-mentioned embodiments of the layer structure according to the invention are preferably transparent thermoplastic films. In some embodiments, the substrate layer A can also be made of another carrier material, such as glass or various plastics.

[0020] In a further preferred embodiment, the protective layer C1 has a thickness of 1 to 100 µm, preferably 2 to 50 µm and most preferably 3 to 25 µm.

[0021] In a further preferred embodiment, the protective layer C2 has a thickness of 1 to 100 µm, preferably of 2 to 50 µm and most preferably of 3 to 25 µm.

[0022] In a further preferred embodiment, the protective layer C1 and / or the protective layer C2 contains a UV absorber, preferably in an amount of 0.01 to 10 wt.%, more preferably in an amount of 0.1 to 5 wt.%, in each case based on the total weight of the protective layer C1 or C2.

[0023] The invention also relates to a method for producing the sealed holographic medium according to the invention as claimed in claim 5.

[0024] The inventive method has the advantage that the protective layers C1 and C2 are applied "dry," thus avoiding the need for complex machinery and specially trained personnel, as required, for example, for "wet" application. Due to the excellent adhesion of the cured protective layers to each other and to the photopolymer layer, not only can the substrate layer D2, if present, be removed without residue, but it also ensures permanent resistance to common organic solvents, aqueous acids and alkalis, cosmetics, household and industrial cleaning agents, and / or sufficient scratch resistance to mechanical influences.

[0025] In a preferred embodiment of the process according to the invention, the photopolymer layer B' is present on a substrate layer A or another carrier such as glass or plastic.

[0026] In a preferred embodiment of the method according to the invention, the uncured protective layer C1 is present on a substrate layer D1 and the uncured protective layer C2 is present on a substrate layer D2.

[0027] In a preferred embodiment of the method according to the invention, in a first step, a layer composite AB' is provided, wherein A is a substrate layer and B' is a photopolymer layer containing a volume hologram. In a second step, the uncured protective layer C1 is applied to a substrate layer D1 to produce a layer composite C1-D1. In a third step, the layer composite AB' is bonded to the layer composite C1-D1 to produce a layer composite A-B'-C1-D1, wherein the layer composite AB' is bonded to the layer composite C1-D1 preferably by lamination. In a fourth step, the substrate layer D1 is removed from the layer composite A-B'-C1-D1 to produce a layer composite A-B'-C1. In a fifth step, the uncured protective layer C2 is applied to a substrate layer D2 to produce a layer composite C2-D2.In a sixth step, the layer composite A-B'-C1 is bonded to the layer composite C2-D2 to form a layer composite A-B'-C1-C2-D2, wherein the layer composite A-B'-C1 is bonded to the layer composite C2-D2 preferably by lamination. In a seventh step, the layer composite A-B'-C1-C2-D2 is cured with actinic radiation to form a layer composite A-B'-C1'-C2'-D2.

[0028] In a preferred embodiment of the method according to the invention, in an eighth step the substrate layer D2 is removed from the layer composite A-B'-C1'-C2'-D2 in order to produce a layer composite A-B'-C1'-C2'.

[0029] In a preferred embodiment of the process according to the invention, at least partial curing of the protective layers C1 and C2 of the layer composite A-B'-C1-C2-D2 takes place with actinic radiation within 60 minutes, preferably within 5 minutes, particularly preferably within less than 60 seconds.

[0030] In a further preferred embodiment of the method according to the invention, it comprises the following steps: Producing a light-sensitive holographic film with the layer structure A-B', comprising: ∘ preparing a coating agent for producing the photopolymer layer B; ∘ coating the substrate A with this coating agent, so that the layer composite AB is formed; ∘ inscribing a hologram in the photopolymer layer B, so that the layer composite AB* is formed, where B* is a photopolymer layer with an inscribed hologram; ∘ fixing the hologram in the photopolymer layer B* by area-wide broadband UV / VIS exposure of the entire layer structure AB* with a light energy dose of 5-10 J / cm 2< ; so that the layer composite AB' is formed, where B' is the bleached, fully polymerized and no longer photosensitive photopolymer layer B with a fixed hologram; Producing a layer composite C1-D1 with an uncured protective layer C1, comprising: ∘ preparing a coating agent for producing the layer C1;∘ Coating the substrate D1 with this coating agent; Producing a holographic film with the layer structure A-B'-C1-D1, comprising applying the layer composite C1-D1 to the layer composite AB' followed by a surface bonding of the two layer composites to one another, preferably by lamination, so that a layer composite A-B'-C1-D1 is formed; Removing the substrate layer D1 so that the layer composite A-B'-C1 is formed; Producing a layer composite C2-D2 with an uncured protective layer C2, comprising: ∘ Preparing a coating agent for producing the layer C2; ∘ Coating the substrate D2 with this coating agent;Producing a holographic film with the layer structure A-B'-C1-C2-D2, comprising applying the layer composite C2-D2 to the layer composite A-B'-C1 followed by a surface bonding of the two layer composites to one another, preferably by lamination, so that a layer composite A-B'-C1-C2-D2 is formed; exposing the layer composite A-B'-C1-C2-D2 to actinic radiation, preferably UV / VIS radiation with a light energy dose of 5-10 J / cm 2<, so that the layer composite A-B'-C1'-C2'-D2 is formed, where C1' and C2' are the cured protective layers C1 and C2; removing the substrate layer D1, so that the film composite A-B'-C1'-C2' is formed. ;

[0031] In a preferred embodiment of the process according to the invention, the reactive diluent C1-II in the protective layer C1 and the reactive diluent C2-II in the protective layer C2 is a urethane acrylate obtainable from the reaction of tris(p-isocyanatophenyl)thiophosphate with alcohol-functional acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and / or hydroxybutyl (meth)acrylate, preferably phosphorothioyl tris(oxybenzene-4,1-diylcarbamoyl-oxyethane-2,1-diyl) trisacrylate.

[0032] In a particularly preferred embodiment of the process according to the invention, the reactive diluent C1-II in the protective layer C1 and the reactive diluent C2-II in the protective layer C2 are preconditioned and prepurified phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate. For preconditioning and purification, a 10 wt. % solution of phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate in ethyl acetate and cyclohexane is prepared, which is filtered through a layer of silica gel 60 (Merck), followed by distilling off the cyclohexane and excess ethyl acetate until a 40 % solution in ethyl acetate is obtained. The cleaning step is repeated until the 40% solution in ethyl acetate has a HAZEN color number (DIN ISO 6271-2:2002) below 100.

[0033] The invention also relates to a sealed holographic medium comprising a layer structure A-B'-C1'-C2', a sealed holographic medium comprising a layer structure B'-C1'-C2', a sealed holographic medium comprising a layer structure B'-C1'-C2'-D2 and a sealed holographic medium comprising a layer structure A-B'-C1'-C2'-D2 obtainable from the process according to the invention described above.

[0034] The invention also relates to a kit of parts according to claim 8.

[0035] The uncured protective layers C1 and C2 are the uncured protective layers C1 and C2 according to the invention as defined in the description.

[0036] In a preferred embodiment of the kit of parts according to the invention, the photopolymer layer B' is present on a substrate layer A, wherein the photopolymer layer B' is at least partially bonded to the substrate layer A on one side.

[0037] In a preferred embodiment of the kit of parts according to the invention, the uncured protective layer C1 is present on a substrate layer D1, wherein the protective layer C1 is at least partially bonded to the substrate layer D1 on one side, and the uncured protective layer C2 is present on a substrate layer D2, wherein the protective layer C2 is at least partially bonded to the substrate layer D2 on one side.

[0038] In a preferred embodiment, the substrate layer D1 is a polyester substrate, preferably a PET substrate, more preferably a silicone-modified PET substrate, with a layer thickness of < 200 µm, more preferably < 100 µm and > 20 µm, even more preferably < 45 µm and > 20 µm.

[0039] In a preferred embodiment, the substrate layer D2 is a polyester substrate, preferably a PET substrate, more preferably a three-layer coextrudate PET substrate, with a layer thickness of < 200 µm, more preferably < 100 µm and > 20 µm, even more preferably < 45 µm and > 20 µm.

[0040] In a preferred embodiment, the substrate layer D1 is a polyester substrate, preferably a PET substrate, more preferably a silicone-modified PET substrate, with a layer thickness of < 200 µm, more preferably < 100 µm and > 20 µm, more preferably < 45 µm and > 20 µm and the substrate layer D2 is a polyester substrate, preferably a PET substrate, more preferably a three-layer coextrudate PET substrate, with a layer thickness of < 200 µm, more preferably < 100 µm and > 20 µm, more preferably < 45 µm and > 20 µm.

[0041] In a preferred embodiment of the kit-of-parts according to the invention, the uncured protective layer C1 comprises I) at least one thermoplastic, mainly linear and semi-crystalline polyurethane resin C1-I, II) at least one multifunctional acrylate reactive diluent C1-II selected from the group consisting of phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate, dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, III) at least one photoinitiator C1-III, and IV) optionally auxiliaries and additives, and the uncured protective layer C2 I) at least one thermoplastic resin C2-I selected from the group consisting of polyvinyl butyral and polymethyl methacrylate, II) at least one multifunctional acrylate reactive diluent C2-II selected from the group consisting of phosphorothioyltris(oxybenzene-4,1-diylcarbamoyl-oxyethane-2,1-diyl)trisacrylate, pentaerythritol triacrylate and 4-fold ethoxylated pentaerythritol tetraacrylate, III) at least one photoinitiator C2-III, and IV) optionally auxiliaries and additives. Substrate layer A

[0042] The substrate layer A is preferably a thermoplastic substrate layer / substrate film or another carrier such as glass, plastic, metal or wood. Materials or material composites of the thermoplastic substrate layer A are based on polycarbonate (PC), polyethylene terephthalate (PET), amorphous polyester, polybutylene terephthalate, polyethylene, polypropylene, cellulose acetate, cellulose hydrate, cellulose nitrate, cycloolefin polymers, polystyrene, hydrogenated polystyrene, polyepoxides, polysulfone, thermoplastic polyurethane (TPU), cellulose triacetate (CTA), polyamide (PA), polymethyl methacrylate (PMMA), polyvinyl chloride, polyvinyl acetate, polyvinyl butyral or polydicyclopentadiene or mixtures thereof. They are particularly preferably based on PC, PET, PA, PMMA and CTA. Material composites can be film laminates or coextrudates. Preferred material composites are duplex and triplex films constructed according to one of the schemes A / B, A / B / A or A / B / C.PC / PMMA, PC / PA, PC / PET, PET / PC / PET, and PC / TPU are particularly preferred. Substrate layer A is preferably transparent in the spectral range of 400-800 nm. Photopolymer layer B

[0043] The photopolymer layer B' is created by inscribing a hologram into the unexposed photopolymer layer B, followed by optical fixation of the hologram, preferably by broadband UV / VIS exposure of the photopolymer layer with the inscribed hologram at a light energy dose of 5-10 J / cm². During fixation, residues of writing monomers that were not involved in the local formation of the hologram are polymerized throughout the entire photopolymer layer. The dyes serving as sensitizers are also photochemically destroyed. The strong technological discoloration of the photopolymer layer B caused by dyes disappears completely. The photopolymer layer B is bleached by fixation and transformed into a no longer photoactive, dye-free, stable photopolymer layer B' with an inscribed hologram.

[0044] The photopolymer layer B' preferably comprises crosslinked matrix polymers, in particular three-dimensionally crosslinked matrix polymers, wherein the matrix polymers are preferably polyurethanes.

[0045] The photopolymer layer B comprises matrix polymers, writing monomers and photoinitiators. Amorphous thermoplastics such as polyacrylates, polymethyl methacrylates or copolymers of methyl methacrylate, methacrylic acid or other alkyl acrylates and alkyl methacrylates as well as acrylic acid, such as polybutyl acrylate, furthermore polyvinyl acetate and polyvinyl butylate, its partially hydrolyzed derivatives such as polyvinyl alcohols and copolymers with ethylene and / or other (meth)acrylates, gelatin, cellulose esters and cellulose ethers such as methylcellulose, cellulose acetobutyrate, silicones, such as polydimethylsilicone, polyurethanes, polybutadienes and polyisoprenes, as well as polyethylene oxides, epoxy resins, in particular aliphatic epoxy resins, polyamides, polycarbonates and the systems in US 4994347A and cited therein can be used as matrix polymers.

[0046] Epoxy resins can be crosslinked cationically with themselves. Acids / anhydrides, amines, hydroxyalkylamides, and thiols can also be used as crosslinkers. Silicones can be crosslinked either as one-component systems through condensation in the presence of water (and possibly under Broensted acid catalysis) or as two-component systems through the addition of silicic acid esters or organotin compounds. Hydrosilylation is also possible in vinyl silane systems.

[0047] Unsaturated compounds, such as acryloyl-functional polymers or unsaturated esters, can be crosslinked with amines or thiols. Cationic vinyl ether polymerization is also possible.

[0048] However, it is particularly preferred if the matrix polymers are crosslinked, preferably three-dimensionally crosslinked and most preferably three-dimensionally crosslinked polyurethanes.

[0049] Polyurethane matrix polymers are obtainable in particular by reacting at least one polyisocyanate component a) with at least one isocyanate-reactive component b).

[0050] The polyisocyanate component a) comprises at least one organic compound with at least two NCO groups. These organic compounds can be, in particular, monomeric di- and triisocyanates, polyisocyanates, and / or NCO-functional prepolymers. The polyisocyanate component a) can also contain or consist of mixtures of monomeric di- and triisocyanates, polyisocyanates, and / or NCO-functional prepolymers.

[0051] Monomeric di- and triisocyanates can be any compounds or mixtures thereof that are well known to the person skilled in the art. These compounds can have aromatic, araliphatic, aliphatic, or cycloaliphatic structures. In minor amounts, the monomeric di- and triisocyanates can also comprise monoisocyanates, i.e., organic compounds containing an NCO group.

[0052] Examples of suitable monomeric di- and triisocyanates are 1,4-butane diisocyanate, 1,5-pentane diisocyanate, 1,6-hexane diisocyanate (hexamethylene diisocyanate, HDI), 2,2,4-trimethylhexamethylene diisocyanate and / or 2,4,4-trimethylhexamethylene diisocyanate (TMDI), isophorone diisocyanate (IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)-octane, bis-(4,4'-isocyanatocyclohexyl)-methane and / or bis-(2,4-isocyanatocyclohexyl)methane and / or mixtures thereof of any isomer content, 1,4-cyclohexane diisocyanate, the isomeric bis-(isocyanatomethyl)cyclohexanes, 2,4- and / or 2,6-diisocyanato-1-methylcyclohexane, (hexahydro-2,4- and / or 2,6-toluene diisocyanate, H6-TDI), 1,4-phenylene diisocyanate, 2,4- and / or 2,6-toluene diisocyanate (TDI), 1,5-naphthylene diisocyanate (NDI), 2,4'- and / or 4,4'-diphenylmethane diisocyanate (MDI), 1,3-bis(isocyanatomethyl)benzene (XDI) and / or the analogous 1,4-isomer or any mixtures of the aforementioned compounds.

[0053] Suitable polyisocyanates are compounds with urethane, urea, carbodiimide, acylurea, amide, isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione and / or iminooxadiazinedione structures, which are obtainable from the aforementioned di- or triisocyanates.

[0054] The polyisocyanates are particularly preferably oligomerized aliphatic and / or cycloaliphatic di- or triisocyanates, and in particular the above-mentioned aliphatic and / or cycloaliphatic di- or triisocyanates can be used.

[0055] Polyisocyanates with isocyanurate, uretdione and / or iminooxadiazinedione structures as well as biurets based on HDI or mixtures thereof are particularly preferred.

[0056] Suitable prepolymers contain urethane and / or urea groups and, optionally, other structures formed by modifying NCO groups as mentioned above. Such prepolymers are obtainable, for example, by reacting the above-mentioned monomeric di- and triisocyanates and / or polyisocyanates a1) with isocyanate-reactive compounds b1).

[0057] Alcohols, amino, or mercapto compounds, preferably alcohols, can be used as isocyanate-reactive compounds b1). These can be, in particular, polyols. Polyester, polyether, polycarbonate, poly(meth)acrylate, and / or polyurethane polyols can be used most preferably as isocyanate-reactive compounds b1).

[0058] Suitable polyester polyols include, for example, linear polyester diols or branched polyester polyols, which can be obtained in a known manner by reacting aliphatic, cycloaliphatic or aromatic di- or polycarboxylic acids or their anhydrides with polyhydric alcohols having an OH functionality ≥ 2. Examples of suitable di- or polycarboxylic acids are polybasic carboxylic acids such as succinic, adipic, suberic, sebacic, decanedicarboxylic, phthalic, terephthalic, isophthalic, tetrahydrophthalic or trimellitic acid, and acid anhydrides such as phthalic, trimellitic or succinic anhydride, or any mixtures thereof. The polyester polyols can also be based on natural raw materials such as castor oil. It is also possible for the polyester polyols to be based on homopolymers or copolymers of lactones, which are preferably obtained by addition of lactones orLactone mixtures such as butyrolactone, ε-caprolactone and / or methyl-ε-caprolactone to hydroxy-functional compounds such as polyhydric alcohols with an OH functionality ≥ 2, for example of the type mentioned below.

[0059] Examples of suitable alcohols are all polyhydric alcohols such as the C 2 - C 12 diols, the isomeric cyclohexanediols, glycerol or any mixtures thereof.

[0060] Suitable polycarbonate polyols are accessible in a conventional manner by reacting organic carbonates or phosgene with diols or diol mixtures.

[0061] Suitable organic carbonates are dimethyl, diethyl and diphenyl carbonate.

[0062] Suitable diols or mixtures include the polyhydric alcohols with an OH functionality ≥ 2 mentioned in the context of the polyester segments, preferably 1,4-butanediol, 1,6-hexanediol, and / or 3-methylpentanediol. Polyester polyols can also be converted into polycarbonate polyols.

[0063] Suitable polyether polyols are optionally block-structured polyaddition products of cyclic ethers to OH- or NH-functional starter molecules.

[0064] Suitable cyclic ethers are, for example, styrene oxides, ethylene oxide, propylene oxide, tetrahydrofuran, butylene oxide, epichlorohydrin and any mixtures thereof.

[0065] Polyhydric alcohols with an OH functionality ≥ 2, as well as primary or secondary amines and amino alcohols, can be used as starters.

[0066] Preferred polyether polyols are those of the aforementioned type based exclusively on propylene oxide or random or block copolymers based on propylene oxide with other 1-alkylene oxides. Particular preference is given to propylene oxide homopolymers and random or block copolymers containing oxyethylene, oxypropylene, and / or oxybutylene units, where the proportion of oxypropylene units, based on the total amount of all oxyethylene, oxypropylene, and oxybutylene units, is at least 20% by weight, preferably at least 45% by weight. Oxypropylene and oxybutylene include all respective linear and branched C3 and C4 isomers.

[0067] In addition, low molecular weight, ie with molecular weights ≤ 500 g / mol, short-chain, ie containing 2 to 20 carbon atoms, aliphatic, araliphatic or cycloaliphatic di-, tri- or polyfunctional alcohols are also suitable as components of the polyol component b1) as polyfunctional, isocyanate-reactive compounds.

[0068] In addition to the above-mentioned compounds, these can be, for example, neopentyl glycol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, positionally isomeric diethyloctanediols, cyclohexanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1,4-cyclohexanediol, hydrogenated bisphenol A, 2,2-bis(4-hydroxycyclohexyl)propane or 2,2-dimethyl-3-hydroxypropionic acid, 2,2-dimethyl-3-hydroxypropyl ester. Examples of suitable triols are trimethylolethane, trimethylolpropane, or glycerol. Suitable higher-functionality alcohols are di(trimethylolpropane), pentaerythritol, dipentaerythritol, or sorbitol.

[0069] It is particularly preferred if the polyol component is a difunctional polyether, polyester or a polyether-polyester-block-copolyester or a polyether-polyester block copolymer with primary OH functions.

[0070] It is also possible to use amines as isocyanate-reactive compounds b1). Examples of suitable amines are ethylenediamine, propylenediamine, diaminocyclohexane, 4,4'-dicylohexylmethanediamine, isophoronediamine (IPDA), difunctional polyamines such as Jeffamine®, and amine-terminated polymers, particularly with number-average molecular weights ≤ 10,000 g / mol. Mixtures of the aforementioned amines can also be used.

[0071] It is also possible to use amino alcohols as isocyanate-reactive compounds b1). Examples of suitable amino alcohols are the isomeric aminoethanols, the isomeric aminopropanols, the isomeric aminobutanols, and the isomeric aminohexanols, or any mixtures thereof.

[0072] All of the above-mentioned isocyanate-reactive compounds b1) can be mixed with each other as desired.

[0073] It is also preferred if the isocyanate-reactive compounds b1) have a number-average molar mass of ≥ 200 and ≤ 10,000 g / mol, more preferably ≥ 500 and ≤ 8,000 g / mol, and most preferably ≥ 800 and ≤ 5,000 g / mol. The OH functionality of the polyols is preferably 1.5 to 6.0, particularly preferably 1.8 to 4.0.

[0074] The prepolymers of the polyisocyanate component a) can in particular have a residual content of free monomeric di- and triisocyanates of < 1 wt.%, particularly preferably < 0.5 wt.% and very particularly preferably < 0.3 wt.%.

[0075] It is also possible for the polyisocyanate component a) to contain, in whole or in part, organic compounds whose NCO groups are fully or partially reacted with blocking agents known from coating technology. Examples of blocking agents include alcohols, lactams, oximes, malonic esters, pyrazoles, and amines, such as butanone oxime, diisopropylamine, diethyl malonate, acetoacetic ester, 3,5-dimethylpyrazole, ε-caprolactam, or mixtures thereof.

[0076] It is particularly preferred if the polyisocyanate component a) comprises compounds with aliphatically bound NCO groups, where aliphatically bound NCO groups are understood to be groups bonded to a primary carbon atom. The isocyanate-reactive component b) preferably comprises at least one organic compound having an average of at least 1.5 and preferably 2 to 3 isocyanate-reactive groups. For the purposes of the present invention, hydroxyl, amino, or mercapto groups are preferred as isocyanate-reactive groups.

[0077] The isocyanate-reactive component may in particular comprise compounds which have on average at least 1.5 and preferably 2 to 3 isocyanate-reactive groups.

[0078] Suitable polyfunctional, isocyanate-reactive compounds of component b) are, for example, the compounds b1) described above.

[0079] Photoinitiators suitable for the invention are typically compounds that can be activated by actinic radiation and can trigger polymerization of the writing monomers. Photoinitiators can be divided into unimolecular (type I) and bimolecular (type II) initiators. Furthermore, depending on their chemical nature, they are classified as photoinitiators for radical, anionic, cationic, or mixed polymerization.

[0080] Type I photoinitiators (Norrish type I) for radical photopolymerization form free radicals upon irradiation through unimolecular bond cleavage. Examples of type I photoinitiators include triazines, oximes, benzoin ethers, benzil ketals, bisimidazoles, aroylphosphine oxides, sulfonium, and iodonium salts.

[0081] Type II photoinitiators (Norrish type II) for radical polymerization consist of a dye as a sensitizer and a coinitiator. Upon irradiation with light matched to the dye, they undergo a bimolecular reaction. First, the dye absorbs a photon and transfers energy from an excited state to the coinitiator. The coinitiator releases the polymerization-initiating radicals through electron or proton transfer or direct hydrogen abstraction.

[0082] For the purposes of this invention, type II photoinitiators are preferably used.

[0083] The dye and coinitiator of Type II photoinitiators can either be mixed directly with the other components of the photopolymer or premixed with individual components. Especially if the photopolymer is to contain polyurethane matrix polymers, the dye can be premixed with the isocyanate-reactive component and the coinitiator with the isocyanate component. It is also possible to premix the coinitiator with the isocyanate-reactive component and the dye with the isocyanate component.

[0084] Such photoinitiator systems are described in principle in EP 0 223 587 A and preferably consist of a mixture of one or more dyes with ammonium alkylaryl borate(s).

[0085] Suitable dyes which, together with an ammonium alkylaryl borate, form a type II photoinitiator are the cationic dyes described in WO 2012062655 in combination with the anions described therein.

[0086] Suitable ammonium alkylarylborates are, for example (Cunningham et al., RadTech'98 North America UV / EB Conference Proceedings, Chicago, Apr. 19-22, 1998): Tetrabutylammonium triphenylhexylborate, Tetrabutylammonium triphenylbutylborate, Tetrabutylammonium trinaphthylhexylborate, Tetrabutylammonium tris(4-tert.butyl)phenylbutylborate, Tetrabutylammonium tris(3-fluorophenyl)hexylborate ([191726-69-9], CGI 7460, product of BASF SE, Basel, Switzerland), 1-methyl-3-octylimidazolium dipentyldiphenylborate and Tetrabutylammonium tris(3-chloro-4-methylphenyl)hexylborate ([1147315-11-4], CGI 909, product of BASF SE, Basel, Switzerland).

[0087] It may be advantageous to use mixtures of these photoinitiators. Depending on the radiation source used, the type and concentration of photoinitiator must be adjusted in a manner known to those skilled in the art. Further details are described, for example, in PKT Oldring (Ed.), Chemistry & Technology of UV & EB Formulations For Coatings, Inks & Paints, Vol. 3, 1991, SITA Technology, London, pp. 61-328.

[0088] It is particularly preferred if the photoinitiator comprises a combination of dyes whose absorption spectra at least partially cover the spectral range from 400 to 800 nm, with at least one coinitiator matched to the dyes.

[0089] It is also preferred if at least one photoinitiator suitable for a laser light color selected from blue, green and red is contained in the photopolymer formulation.

[0090] It is also further preferred if the photopolymer formulation contains a suitable photoinitiator for at least two laser light colors selected from blue, green and red.

[0091] Finally, it is particularly preferred if the photopolymer formulation contains a suitable photoinitiator for each of the laser light colors blue, green and red.

[0092] In a further preferred embodiment, the writing monomers comprise a mono- and / or a multifunctional (meth)acrylate writing monomer. Most preferably, the writing monomers may additionally comprise at least one mono- and / or one multifunctional urethane (meth)acrylate.

[0093] Suitable acrylate writing monomers are in particular compounds of the general formula (I) where n≥1 and n≤4 and R 41< is a linear, branched, cyclic or heterocyclic unsubstituted or optionally also substituted by heteroatoms organic radical and / or R 42< is hydrogen, a linear, branched, cyclic or heterocyclic unsubstituted or optionally also substituted by heteroatoms organic radical. R 42< is particularly preferably hydrogen or methyl and / or R 41< is a linear, branched, cyclic or heterocyclic unsubstituted or optionally also substituted by heteroatoms organic radical.

[0094] In this context, acrylates and methacrylates are referred to as esters of acrylic acid and methacrylic acid, respectively. Examples of preferred acrylates and methacrylates are phenyl acrylate, phenyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxyethoxyethyl acrylate, phenoxyethoxyethyl methacrylate, phenylthioethyl acrylate, phenylthioethyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 1,4-bis-(2-thionaphthyl)-2-butyl acrylate, 1,4-bis-(2-thionaphthyl)-2-butyl methacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate, and their ethoxylated analogues, N-carbazolyl acrylates.

[0095] Urethane acrylates are understood here to be compounds with at least one acrylic acid ester group and at least one urethane bond. Such compounds can be obtained, for example, by reacting a hydroxy-functional acrylate or methacrylate with an isocyanate-functional compound.

[0096] Examples of usable isocyanate-functional compounds are monoisocyanates and the monomeric diisocyanates, triisocyanates, and / or polyisocyanates mentioned under a). Examples of suitable monoisocyanates are phenyl isocyanate and the isomeric methylthiophenyl isocyanates. Di-, tri-, or polyisocyanates are mentioned above, as well as triphenylmethane-4,4',4"-triisocyanate and tris-(p-isocyanatophenyl)thiophosphate or their derivatives with urethane, urea, carbodiimide, acylurea, isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione, iminooxadiazinedione structures, and mixtures thereof. Aromatic di-, tri-, or polyisocyanates are preferred.

[0097] Examples of hydroxy-functional acrylates or methacrylates used for the production of urethane acrylates include compounds such as 2-hydroxyethyl (meth)acrylate, polyethylene oxide mono-(meth)acrylates, polypropylene oxide mono-(meth)acrylates, polyalkylene oxide mono-(meth)acrylates, poly-(ε-caprolactone) mono-(meth)acrylates, such as Tone ®< M100 (Dow, Schwalbach, DE), 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxy-2,2-dimethylpropyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl acrylate, the hydroxy-functional mono-, di- or tetraacrylates of polyhydric alcohols such as trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol, ethoxylated, propoxylated or alkoxylated trimethylolpropane, glycerol, Pentaerythritol, dipentaerythritol, or technical mixtures thereof. 2-Hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and poly(ε-caprolactone) mono-(meth)acrylate are preferred.

[0098] Also usable are the known hydroxyl-containing epoxy (meth)acrylates with OH contents of 20 to 300 mg KOH / g or hydroxyl-containing polyurethane (meth)acrylates with OH contents of 20 to 300 mg KOH / g or acrylated polyacrylates with OH contents of 20 to 300 mg KOH / g as well as mixtures thereof with one another and mixtures with hydroxyl-containing unsaturated polyesters as well as mixtures with polyester (meth)acrylates or mixtures of hydroxyl-containing unsaturated polyesters with polyester (meth)acrylates.

[0099] Particularly preferred are urethane acrylates obtainable from the reaction of tris(p-isocyanatophenyl)thiophosphate and / or m-methylthiophenyl isocyanate with alcohol-functional acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and / or hydroxybutyl (meth)acrylate.

[0100] It is also possible for the writing monomer to comprise further unsaturated compounds such as α,β-unsaturated carboxylic acid derivatives such as maleates, fumarates, maleimides, acrylamides, furthermore vinyl ethers, propenyl ethers, allyl ethers and compounds containing dicyclopentadienyl units as well as olefinically unsaturated compounds such as styrene, α-methylstyrene, vinyltoluene and / or olefins.

[0101] According to a further preferred embodiment, it is provided that the photopolymer formulation additionally contains monomeric urethanes as additives, wherein the urethanes can in particular be substituted with at least one fluorine atom.

[0102] Preferably, the urethanes can have the general formula (II) in which m≥1 and m≤8 and R 51< , R 52< and R 53< are linear, branched, cyclic or heterocyclic unsubstituted or optionally also substituted by heteroatoms organic radicals and / or R 52< , R 53< are independently hydrogen, where preferably at least one of the radicals R 51< , R 52< , R 53< is substituted by at least one fluorine atom and particularly preferably R 51< is an organic radical with at least one fluorine atom. Particularly preferably R 52< is a linear, branched, cyclic or heterocyclic unsubstituted or optionally also substituted by heteroatoms such as fluorine.

[0103] According to a further preferred embodiment of the invention, the photopolymer contains 10 to 89,999 wt.%, preferably 20 to 70 wt.% matrix polymers, 3 to 60 wt.%, preferably 10 to 50 wt.% writing monomers, 0.001 to 5 wt.%, preferably 0.5 to 3 wt.% photoinitiators and optionally 0 to 4 wt.%, preferably 0 to 2 wt.% catalysts, 0 to 5 wt.%, preferably 0.001 to 1 wt.% stabilizers, 0 to 40 wt.%, preferably 10 to 30 wt.% monomeric fluorourethanes and 0 to 5 wt.%, preferably 0.1 to 5 wt.% further additives, the sum of all components being 100 wt.%.

[0104] Particularly preferred photopolymers are those containing 20 to 70% by weight of matrix polymers, 20 to 50% by weight of writing monomers, 0.001 to 5% by weight of photoinitiators, 0 to 2% by weight of catalysts, 0.001 to 1% by weight of radical stabilizers, optionally 10 to 30% by weight of fluorourethanes and optionally 0.1 to 5% by weight of further additives.

[0105] Urethanization catalysts, such as organic or inorganic derivatives of bismuth, tin, zinc, or iron (see also the compounds mentioned in US 2012 / 062658), can be used as catalysts. Particularly preferred catalysts are butyltin tris(2-ethylhexanoate), iron(III) trisacetylacetonate, bismuth(III) tris(2-ethylhexanoate), and tin(II) bis(2-ethylhexanoate). Furthermore, sterically hindered amines can also be used as catalysts.

[0106] Radical inhibitors such as HALS amines, N-alkyl HALS, N-alkoxy HALS and N-alkoxyethyl HALS compounds as well as antioxidants and / or UV absorbers can be used as stabilizers.

[0107] Further additives that can be used are flow control agents and / or antistatic agents and / or thixotropic agents and / or thickeners and / or biocides. Protective layer C1

[0108] Before curing with actinic radiation, the protective layer C1 comprises at least one physically drying polymeric resin C1-I, at least one multifunctional acrylate reactive diluent (RV) C1-II, and at least one photoinitiator C1-III. The protective layer C1 preferably additionally comprises a UV absorber in an amount of 0.1 to 10 wt. %.

[0109] The physically drying resins for the protective layer C1 are thermoplastic, primarily linear, semi-crystalline polyurethanes (see, for example, Günter Oertel (ed.): Kunststoff-Handbuch - Vol. 7 Polyurethanes. 3rd edition. Carl Hanser Verlag, 1993). Preferred are the polyurethanes of the Desmocoll® and Desmomelt® brands from Covestro Deutschland AG, specially developed as thermoactivating adhesives. Further examples of suitable thermoplastic, primarily linear, semi-crystalline polyurethanes for the protective layer C1 are described in DE 3729068 A1, DE 3702394 A1, and US 20050112971 A1, the disclosures of which are hereby incorporated by reference.

[0110] The acrylic-functional reactive diluent belongs to the class of multifunctional (preferably at least trifunctional) acrylates. Preferred are either a triacrylate made from Desmodur®< RFE from Covestro AG and hydroxyethyl acrylate and / or dipentaerythritol pentaacrylate and / or dipentaerythritol hexaacrylate. Particularly preferred are the acrylic-functional reactive diluents, as a 40% solution in ethyl acetate, having a color number of <200 Hazen, particularly preferably <100 Hazen (DIN ISO 6271-2:2002). Preconditioned and prepurified phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate. The phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate is purified and preconditioned as described below.

[0111] The photoinitiators used are usually compounds that can be activated by actinic radiation and can trigger polymerization of the corresponding groups.

[0112] Photoinitiators can be divided into unimolecular (type I) and bimolecular (type II) initiators which trigger radical polymerization; there is a broad state of the art in this area.

[0113] Type I photoinitiators (Norrish type I) for radical photopolymerization form free radicals upon irradiation through unimolecular bond cleavage.

[0114] Examples of type I photoinitiators are triazines, such as tris(trichloromethyl)triazine, oximes, benzoin ethers, benzil ketals, alpha-alpha-dialkoxyacetophenone, phenylglyoxylic acid esters, bis-imidazoles, aroylphosphine oxides, e.g. 2,4,6-trimethyl-benzoyldiphenylphosphine oxide, sulfonium and iodonium salts.

[0115] Type II photoinitiators (Norrish type II) for radical polymerization undergo a bimolecular reaction upon irradiation, whereby the photoinitiator in the excited state reacts with a second molecule, the coinitiator, and forms the polymerization-initiating radicals by electron or proton transfer or direct hydrogen abstraction.

[0116] Examples of type II photoinitiators are quinones such as camphorquinone, aromatic keto compounds such as benzophenones in combination with tertiary amines, alkylbenzophenones, halogenated benzophenones, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), anthrone, methyl p-(dimethylamino)benzoate, thioxanthone, ketocoumarins, alpha-aminoalkylphenone, alpha-hydroxyalkylphenone and cationic dyes such as methylene blue in combination with tertiary amines.

[0117] Type I and Type II photoinitiators are used for the UV and short-wave visible range, while Type II photoinitiators are predominantly used for the longer-wave visible light range.

[0118] Preferred are 1-hydroxy-cyclohexyl phenyl ketone (e.g. Irgacure ®< 184 from BASF SE), 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g. Irgacure ®< 1173 from BASF SE), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methylpropan-1-one (e.g. Irgacure ®< 127 from BASF SE), 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (e.g. Irgacure ®< 2959 from BASF SE); 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (e.g. Lucirin ®< TPO from BASF SE); 2,4,6-trimethylbenzoyldiphenyl phosphinate (e.g., Lucirin®< TPO-L from BASF SE), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Lucirin®< 819); [1-(4-phenylsulfanylbenzoyl)heptylideneamino]benzoate (e.g., Irgacure®< OXE 01 from BASF SE); [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]ethylideneamino] acetate (e.g., Irgacure®< OXE 02 from BASF SE), and mixtures thereof. Particular preference is given to 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and mixtures thereof.

[0119] Typical UV absorbers are benzotriazoles, cyanoacrylates, benzophenones, phenyltriazines, hydroxyphenyltrazines or oxalanilides.

[0120] It may also contain sunscreens such as phenols or HALS amines.

[0121] In a preferred embodiment, the uncured protective layer C1 comprises I) at least one thermoplastic mainly linear and semi-crystalline polyurethane resin C1-I, II) at least one multifunctional acrylate reactive diluent C1-II selected from the group consisting of phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate, dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, III) at least one photoinitiator C1-III, and IV) optionally auxiliaries and additives. Substrate layer D1

[0122] The substrate layer D1 is preferably a thermoplastic substrate layer / substrate film. Materials or material composites of the thermoplastic substrate layer / substrate film D1 are based on polycarbonate (PC), polyethylene terephthalate (PET), amorphous polyesters, polybutylene terephthalate, polyethylene, polypropylene, cellulose acetate, cellulose hydrate, cellulose nitrate, cycloolefin polymers, polystyrene, hydrogenated polystyrene, polyepoxides, polysulfone, thermoplastic polyurethane (TPU), cellulose triacetate (CTA), polyamide (PA), polymethyl methacrylate (PMMA), polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, or polydicyclopentadiene, or mixtures thereof. They are particularly preferably based on PC, PET, PA, PMMA, and CTA. Material composites can be film laminates or coextrudates. Preferred material composites are duplex and triplex films constructed according to one of the A / B, A / B / A, or A / B / C schemes. Particularly preferred are PC / PMMA, PC / PA, PC / PET, PET / PC / PET and PC / TPU.Preferably, substrate film D1 is transparent in the spectral range of 400-800 nm.

[0123] Mechanically stable thermoplastic polyester substrates are particularly suitable as substrate layer D1, especially those such as polyethylene terephthalate (PET) with a layer thickness of < 200 µm, more preferably < 100 µm and > 20 µm, even more preferably < 45 µm and > 20 µm, whose adhesion properties have been reduced through surface modification. Various techniques are possible for this. For example, inorganic slip additives can be added, such as kaolin, clay, bleaching earth, calcium carbonate, silicon dioxide, aluminum oxide, titanium oxide, and calcium phosphate.

[0124] To improve the optical properties of such films, three-layer coextruded films are also used, in which only the outer layers contain such inorganic slip additives (e.g., Hostaphan RNK). Furthermore, silicones can be applied to the surfaces (e.g., Hostaphan RN30 2PRK), which reduce the surface tension and thus the adhesive properties.

[0125] Silicone-modified PET films (such as Hostaphan RN30 2PRK) are particularly preferred. The use of these films facilitates the removal of layer D1 before layer C1 has already cured. Protective layer C2

[0126] Before curing with actinic radiation, the protective layer C2 comprises at least one physically drying polymeric resin C2-I, at least one multifunctional acrylate reactive diluent (RV) C2-II, and at least one photoinitiator C2-III. The protective layer C2 preferably additionally comprises a UV absorber in an amount of 0.1 to 10 wt. %.

[0127] The physically drying resins for the protective layer C2 are preferably polyvinyl butyral with M w ≥ 100,000 g / mol or amorphous polymethyl methacrylate with M w ≥ 100,000 g / mol.

[0128] The acrylic-functional reactive diluent is at least one multifunctional acrylate, preferably at least one trifunctional acrylate. Particular preference is given to either a triacrylate made from Desmodur®< RFE from Covestro AG and hydroxyethyl acrylate (phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl) trisacrylate) and / or pentaerythritol triacrylate and / or tetraethoxylated pentaerythritol tetraacrylate; phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl) trisacrylate is particularly preferred.

[0129] The photoinitiators used are usually compounds that can be activated by actinic radiation and can trigger polymerization of the corresponding groups.

[0130] Photoinitiators can be divided into unimolecular (type I) and bimolecular (type II) initiators which trigger radical polymerization; there is a broad state of the art in this area.

[0131] Type I photoinitiators (Norrish type I) for radical photopolymerization form free radicals upon irradiation through unimolecular bond cleavage.

[0132] Examples of type I photoinitiators are triazines, such as tris(trichloromethyl)triazine, oximes, benzoin ethers, benzil ketals, alpha-alpha-dialkoxyacetophenone, phenylglyoxylic acid esters, bis-imidazoles, aroylphosphine oxides, e.g. 2,4,6-trimethyl-benzoyldiphenylphosphine oxide, sulfonium and iodonium salts.

[0133] Type II photoinitiators (Norrish type II) for radical polymerization undergo a bimolecular reaction upon irradiation, whereby the photoinitiator in the excited state reacts with a second molecule, the coinitiator, and forms the polymerization-initiating radicals by electron or proton transfer or direct hydrogen abstraction.

[0134] Examples of type II photoinitiators are quinones such as camphorquinone, aromatic keto compounds such as benzophenones in combination with tertiary amines, alkylbenzophenones, halogenated benzophenones, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), anthrone, methyl p-(dimethylamino)benzoate, thioxanthone, ketocoumarins, alpha-aminoalkylphenone, alpha-hydroxyalkylphenone and cationic dyes such as methylene blue in combination with tertiary amines.

[0135] Type I and Type II photoinitiators are used for the UV and short-wave visible range, while Type II photoinitiators are predominantly used for the longer-wave visible light range.

[0136] Preferred are 1-hydroxy-cyclohexyl phenyl ketone (e.g. Irgacure ®< 184 from BASF SE), 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g. Irgacure ®< 1173 from BASF SE), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methylpropan-1-one (e.g. Irgacure ®< 127 from BASF SE), 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (e.g. Irgacure ®< 2959 from BASF SE); 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (e.g. Lucirin ®< TPO from BASF SE); 2,4,6-trimethylbenzoyldiphenyl phosphinate (e.g., Lucirin®< TPO-L from BASF SE), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Lucirin®< 819); [1-(4-phenylsulfanylbenzoyl)heptylideneamino]benzoate (e.g., Irgacure®< OXE 01 from BASF SE); [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]ethylideneamino] acetate (e.g., Irgacure®< OXE 02 from BASF SE), and mixtures thereof. Particular preference is given to 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and mixtures thereof.

[0137] Typical UV absorbers are benzotriazoles, cyanoacrylates, benzophenones, phenyltriazines, hydroxyphenyltrazines or oxalanilides.

[0138] It may also contain sunscreens such as phenols or HALS amines.

[0139] In a preferred embodiment, the uncured protective layer C2 comprises I) at least one thermoplastic resin C2 selected from the group consisting of polyvinyl butyral with M w ≥ 100,000 g / mol or amorphous polymethyl methacrylate with M w ≥ 100,000 g / mol, II) at least one multifunctional acrylate reactive diluent C2-II selected from the group consisting of phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate, pentaerythritol triacrylate and 4-fold ethoxylated pentaerythritol tetraacrylate, III) at least one photoinitiator C2-III , and IV) any auxiliary substances and additives. Substrate layer D2

[0140] The substrate layer D2 is preferably a thermoplastic substrate layer / substrate film. Materials or material composites of the thermoplastic substrate layer / substrate film D2 are based on polycarbonate (PC), polyethylene terephthalate (PET), amorphous polyesters, polybutylene terephthalate, polyethylene, polypropylene, cellulose acetate, cellulose hydrate, cellulose nitrate, cycloolefin polymers, polystyrene, hydrogenated polystyrene, polyepoxides, polysulfone, thermoplastic polyurethane (TPU), cellulose triacetate (CTA), polyamide (PA), polymethyl methacrylate (PMMA), polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, or polydicyclopentadiene, or mixtures thereof. They are particularly preferably based on PC, PET, PA, PMMA, and CTA. Material composites can be film laminates or coextrudates. Preferred material composites are duplex and triplex films constructed according to one of the A / B, A / B / A, or A / B / C schemes. Particularly preferred are PC / PMMA, PC / PA, PC / PET, PET / PC / PET and PC / TPU.Preferably, substrate film D1 is transparent in the spectral range of 400-800 nm.

[0141] Mechanically stable thermoplastic polyester substrates are particularly suitable as substrate layer D2, especially those such as polyethylene terephthalate (PET) with a layer thickness of < 200 µm, preferably < 100 µm and > 20 µm, even more preferably < 45 µm and > 20 µm, whose adhesion properties have been reduced through surface modification. Various techniques are possible for this. For example, inorganic slip additives can be added, such as kaolin, clay, bleaching earth, calcium carbonate, silicon dioxide, aluminum oxide, titanium oxide, and calcium phosphate.

[0142] To improve the optical properties of such films, three-layer coextruded films are also used, in which only the outer layers contain such inorganic slip additives (e.g., Hostaphan RNK). Furthermore, silicones can be applied to the surfaces (e.g., Hostaphan RN30 2PRK), which reduce the surface tension and thus the adhesive properties.

[0143] Three-layer coextruded PET films (such as Hostaphan RNK) are particularly preferred.

[0144] The invention also relates to the use of the layer structures according to the invention and the kit-of-parts according to the invention for the method according to the invention.

[0145] In one embodiment, the sealed holographic medium according to the invention contains a hologram-containing photopolymer layer with a layer thickness of 0.3 µm to 500 µm, preferably of 0.5 µm to 200 µm and particularly preferably of 1 µm to 100 µm.

[0146] In particular, the hologram can be a reflection, transmission, in-line, off-axis, full-aperture transfer, white light transmission, Denisyuk, off-axis reflection, or edge-lit hologram, as well as a holographic stereogram, and preferably a reflection, transmission, or edge-lit hologram. Reflection holograms, Denisyuk holograms, and transmission holograms are preferred.

[0147] One or more holograms can be exposed in the photopolymer layer at the same location or next to each other. If exposure is made at the same location, different image contents can be exposed. Likewise, different views of an object with slightly varying reconstruction angles can be exposed, creating stereograms. It is also possible to expose hidden holograms and microtexts. Likewise, in the case of transmission holograms, it is possible to expose multiple light-guiding functions and / or light-guiding functions for different spectral ranges. Possible optical functions of the holograms correspond to the optical functions of light elements such as lenses, mirrors, deflecting mirrors, filters, diffraction screens, directed scattering elements, diffraction elements, light guides, light guides (waveguides), projection screens and / or masks.Furthermore, several such optical functions can be combined in such a hologram, for example, so that the light is diffracted in a different direction depending on the incident light. For example, such structures can be used to build autostereoscopic or holographic electronic displays, which allow a stereoscopic visual impression to be experienced without additional aids such as polarizing or shutter glasses, and for use in automotive head-up displays or head-mounted displays.

[0148] These optical elements often exhibit specific frequency selectivity, depending on how the holograms were exposed and the dimensions of the hologram. This is particularly important when using monochromatic light sources such as LEDs or laser light. One hologram per complementary color (RGB) is required to direct light frequency-selectively while simultaneously enabling full-color displays. Therefore, in certain display setups, multiple holograms must be exposed one inside the other in the medium.

[0149] In addition, the sealed holographic media according to the invention can also be used to produce holographic images or representations, such as for personal portraits, biometric representations in security documents, or generally images or image structures for advertising, security labels, trademark protection, brand branding, labels, design elements, decorations, illustrations, trading cards, pictures, and the like, as well as images that can represent digital data, including in combination with the previously described products. Holographic images can have the impression of a three-dimensional image, but they can also represent image sequences, short films, or a number of different objects, depending on the angle, the (even moving) light source, etc., from which they are illuminated.Due to these diverse design possibilities, holograms, especially volume holograms, represent an attractive technical solution for the above-mentioned applications. It is also possible to use such holograms to store digital data, using various exposure methods (shift, spatial or angular multiplexing).

[0150] The invention also relates to an optical display comprising a sealed holographic medium according to the invention.

[0151] Examples of such optical displays include imaging displays based on liquid crystals, organic light-emitting diodes (OLEDs), LED display panels, microelectromechanical systems (MEMS) based on diffractive light selection, electrowetting displays (E-ink), and plasma screens. Such optical displays can include autostereoscopic and / or holographic displays, transmissive and reflective projection screens or projection panels, displays with switchable limited radiation patterns for privacy filters and bidirectional multi-user screens, virtual screens, head-up displays, head-mounted displays, illuminated symbols, warning lights, signal lamps, headlights, and information boards.

[0152] The invention also relates to autostereoscopic and / or holographic displays, projection screens, projection panels, displays with switchable limited radiation behavior for privacy filters and bidirectional multi-user screens, virtual screens, head-up displays, head-mounted displays, illuminated symbols, warning lamps, signal lamps, headlights and display boards comprising a holographic medium according to the invention.

[0153] Still further objects of the invention are a security document and a holographic optical element comprising a sealed holographic medium according to the invention.

[0154] Furthermore, the use of a holographic medium according to the invention for producing chip cards, identity documents, 3D images, product protection labels, labels, banknotes or holographic optical elements, in particular for optical displays, is also the subject of the invention. Examples

[0155] The invention is explained in more detail below using examples. Measurement methods:

[0156] Solid content: The stated solid contents were determined according to DIN EN ISO 3251. Color number : The color number was determined according to DIN ISO 6271-2:2002 and evaluated as haze. Chemicals:

[0157] The CAS number, where known, is given in square brackets. Raw materials of photopolymer layer B

[0158] Fomrez ®< UL 28 Urethanization catalyst, commercial product of Momentive Performance Chemicals, Wilton, CT, USA. Borchi ®< Cat 22 Urethanization catalyst, [85203-81-2] Commercial product of OMG Borchers GmbH, Langenfeld, Germany. BYK-310 Silicone-containing surface additive, product of BYK-Chemie GmbH, Wesel, Germany. Desmodur ®< N 3900 Product of Covestro AG, Leverkusen, DE, hexane diisocyanate-based polyisocyanate, iminooxadiazinedione content at least 30%, NCO content: 23.5%. CGI-909 Tetrabutylammonium tris(3-chloro-4-methylphenyl)-(hexyl)borate, [1147315-11-4], product of BASF SE.

[0159] Dye 1 (3,7-bis(diethylamino)phenoxazin-5-ium bis(2-ethylhexyl)sulfosuccinic acid ester) was prepared as described in WO 2012062655.

[0160] Polyol 1 was prepared as described in WO2015091427.

[0161] Urethane acrylate 1, also RV 2, (phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxy-ethane-2,1-diyl)trisacrylate, [1072454-85-3]) was prepared as described in WO2015091427.

[0162] Urethane acrylate 2, (2-({[3-(Methylsulfanyl)phenyl]carbamoyl}oxy)-ethylprop-2-enoate, [1207339-61-4]) was prepared as described in WO2015091427.

[0163] Additive 1, bis(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl)-(2,2,4-trimethylhexane-1,6-diyl)biscarbamate [1799437-41-4] was prepared as described in WO2015091427. Raw materials of layer C Physically drying resins

[0164] Desmocoll 406 - Resin 1 A linear thermoplastic flexible polyurethane from Covestro Deutschland AG, Leverkusen, Germany. Desmocoll 400 / 3 - Resin 2 A linear thermoplastic flexible polyurethane from Covestro Deutschland AG, Leverkusen, Germany. Mowital B75H - Harz 3 A linear thermoplastic, amorphous polyvinyl butyral with a Mw of 240,000 from Kuraray Europe GmbH, Hattersheim, Germany Degacryl M547 - Resin 4 A linear thermoplastic, amorphous polymethyl methacrylate with a Mw of 500,000 from Evonik Industries, Marl, Germany Acrylic-functional reactive thinners Abbreviation RV = reactive diluent

[0165] DPHA - RV 1 [29570-58-9] Dipentaerythritol hexaacrylate from Cytec Surface Specialties, Brussels Belgium. RV 2 Phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl)trisacrylate, [1072454-85-3]) was prepared as described in WO2015091427. Sartomer SR444D - RV 3 [3524-68-3] Pentaerythritol triacrylate (PETIA) from SARTOMER Division of CRAY VALLEY, Paris, France (Arkema Group). Sartomer SR494 - RV 4 4-fold ethoxylated pentaerythritol tetraacrylate (PPTTA) from the SARTOMER Division of CRAY VALLEY, Paris, France (Arkema Group). Photoinitiators

[0166] Esacure One - Initiator 1 [163702-01-0] Oligo-[2-Hydroxy-2-methyl-1-((4-(1-methylvinyl)-phenyl) propanone] from Lamberti SpA, Albizzate, Italy. Irgacure 4265 - Initiator 2 A mixture of Irgacure ®< TPO (50% wt.%) and Irgacure ®< 1173 (50% wt.%) from BASF, SE, Ludwigshafen, Germany. Additive

[0167] BYK 333 - Leveling agent Silicone-containing surface additive from BYK Chemie GmbH, Wesel, Germany Solvent

[0168] Butyl acetate (BA) Butyl acetate from Brenntag GmbH, Mülheim an der Ruhr, Germany. Methoxypropanol (MP-ol) 1-Methoxy-2-propanol from Brenntag GmbH, Mülheim an der Ruhr, Germany.

[0169] Purification of urethane acrylate 1 (also RV 2): The 40% solution of urethane acrylate 1 in ethyl acetate exhibits a color number of 300 to 700 Hazen (DIN ISO 6271-2:2002), which is unacceptable for the optical coatings based on it. For purification, the solution is diluted with cyclohexane and additional ethyl acetate. The resulting 10% solution is filtered through a layer of silica gel 60 (Merck) in a solvent mixture of ethyl acetate and cyclohexane (1.4 parts by weight to 1 part by weight). The purified original 40% solution in ethyl acetate is then recovered by distilling off the cyclohexane and excess ethyl acetate. The resulting solution of RV 2 has a color number of 40-50 Hazen. Production of holographic media (photopolymer film)

[0170] 7.90 g of the polyol component described above were melted and mixed with 7.65 g of the respective urethane acrylate 2, 2.57 g of the urethane acrylate 1 described above, 5.10 g of the fluorinated urethane described above, 0.91 g of CGI 909, 0.232 g of Dye 1, 0.230 g of BYK 310, 0.128 g of Fomrez UL 28, and 3.789 g of ethyl acetate to obtain a clear solution. Subsequently, 1.50 g of Desmodur®< N 3900 was added and mixed again.

[0171] This solution was then applied to a 36 µm thick PET film in a roll-to-roll coating system, where the product was applied using a doctor blade to a wet film thickness of 19 µm. The coated film was dried at a drying temperature of 85 °C and a drying time of 5 minutes and then protected with a 40 µm thick polyethylene film. This film was then packaged in a light-tight manner. Production of the latent protective layer C1 on substrate D1 or protective layer C2 on substrate D2

[0172] The formulations listed in Table 1 were prepared by mixing the physically drying resins, dissolved at 100 °C in the specified organic solvent and cooling to room temperature, with the reactive diluent. The photoinitiators and leveling agents were then added in the dark. Table 1 : Coating agent* for the production of the latent protective layer C sample resin RV Weight ratio resin / RV Solids (wt%) Solvent Viscosity of the solution at 23°C [mPas] Examples according to the invention C1-01 1 RV1 30 / 70 25% butyl acetate 170 C1-02 2 RV 2 40 / 60 26% butyl acetate 1120 C2-01 3 RV3 50 / 50 20% 1-methoxy-2-propanol 4400 C2-02 3 RV 2 20 / 80 28% 1-methoxy-2-propanol 950 C2-03 4 RV4 25 / 75 25% 1-methoxy-2-propanol 169 C2-04 3 RV3 47 / 48 #< 20% 1-methoxy-2-propanol 3020 Non-inventive examples C1-N01 2 RV5 50 / 50 25% butyl acetate 2220 *All coating agents contain Initiator 1 (3.0 wt.% to the solids of the coating), Initiator 2 (1.5 wt.% to the solids of the coating) and leveling agent (0.2 wt.% to the solids of the coating); #< contains 5 wt.% SiO nanoparticles PGM-ST-UP (Nissan Chemical)

[0173] Coating agents C1-01 and C1-02 for the latent protective layer C1 were applied to a 36 µm thick silicone-modified PET film D1 (Hostaphan RN30 2PRK from Mitsubishi Polyester Film GmbH, Wiesbaden, Germany) in a roll-to-roll coating system using a doctor blade. The coated film was dried at a drying temperature of 85 °C and a drying time of 5 minutes and then protected with a 40 µm thick polyethylene film. The coating thickness was typically 15-16 µm. This film was then packaged in a light-tight manner.

[0174] Similarly, coating agents C2-01, C2-02, C2-03, and C2-04 for the latent protective layer C2 were applied to a 36 µm thick PET film D2 (RNK 36 from Mitsubishi Polyester Film GmbH, Wiesbaden, Germany), dried, laminated, and packaged. The coating thickness was typically 15-16 µm. Production of test holograms in film composite AB

[0175] Test holograms were prepared as follows: the photopolymer films with the AB layer structure were cut to the desired size in the dark and laminated onto a 50 mm x 70 mm (3 mm thick) glass plate using a rubber roller. Test holograms were produced using a test apparatus that generates Denisyuk reflection holograms using green (532 nm) laser radiation. The test apparatus consists of a laser source, an optical beam guidance system, and a holder for the glass coupons. The holder for the glass coupons is mounted at an angle of 13° relative to the beam axis. The laser source generated the radiation, which was expanded to approximately 5 cm via a special optical beam path and guided to the glass coupon, which was in optical contact with the mirror. The holographed object was a mirror measuring approximately 2 cm x 2 cm, so the wavefront of the mirror was reconstructed during the hologram reconstruction.All samples were exposed with a green 532nm laser (Newport Corp., Irvine, CA, USA, Order No. EXLSR-532-50-CDRH). The recording film was exposed for a defined time of 2 seconds using a shutter. This created a film composite AB* with a hologram in layer B.

[0176] The samples were then placed on the conveyor belt of a UV lamp with the B side facing the lamp and exposed twice at a conveyor speed of 2.5 m / min. The UV lamp used was an iron-doped Hg lamp of the Fusion UV type "D Bulb" No. 558434 KR 85 with a total power density of 80 W / cm². The parameters corresponded to a dose of 2 x 2.0 J / cm² (measured with an ILT 490 Light Bug). After this fixation step, the film composite A-B' is created. Characterization of test holograms

[0177] The holograms in layer B' of the film composite AB' were now spectroscopically examined for their quality.

[0178] Due to the high diffraction efficiency of the volume hologram, the diffractive reflection of such holograms can be analyzed in transmission using a spectrometer (a USB 2000 device, Ocean Optics, Dunedin, FL, USA) and appears in the transmission spectrum as a peak with reduced transmission T Red . The quality of the hologram can be determined by evaluating the transmission curve according to ISO standard 17901-1:2015(E). The following parameters are considered; all results are summarized in Table 3 in the "Spectral Quality of Holograms" section - "in AB" column: T Red = 100 − T peak A − B ′ Maximum depth of the transmission peak, which corresponds to the highest diffraction efficiency. Thus, 100-T peak(A-B') serves as a measure of the reflective power (or visible "strength" or "quality") of the hologram. FWHM The width of the transmission peak is determined as "full width at half maximum" (FWHM) in nanometers (nm). λ peak Spectral position of the transmission minimum of the hologram in nanometers (nm).

[0179] The films with the layer structure AB' were then provided with the two consecutive protective layers C1' and C2' using the process according to the invention. The holograms were then re-examined for their quality in the layer structure A-B'-C1'-C2* and compared with the original values for the layer structure AB' (Table 3). Production of a film composite with the layer structure A-B'-C1'-C2'

[0180] The production of a film composite with the layer structure A-B'-C1'-C2' involves laminating side B' of film AB' to side C1 of film composite C1-D1. This is done by pressing the two films together between the temperature-controlled rubber rollers of a laminator. The temperature of the rollers was set to 30°C, 60°C, or 90°C. The produced multilayer film was cooled to room temperature. The substrate film D1 was then peeled off the film composite A-B'-C1-D1. Side C2 of film composite C2-D2 was then laminated to side C1 of film composite A-B'-C1 in a similar manner.

[0181] Subsequently, samples A-B'-C1-C2-D2 were placed on the conveyor belt of a UV lamp with the D2 side facing the lamp and exposed twice at a belt speed of 2.5 m / min. The UV lamp used was an iron-doped Hg lamp of the Fusion UV type "D Bulb" No. 558434 KR 85 with a total power density of 80 W / cm². The parameters corresponded to a dose of 2 x 2.0 J / cm² (measured with an ILT 490 Light Bug). After this curing step, the film composite A-B'-C1'-C2'-D2 is created, from which the substrate film D2 is subsequently peeled off. COV 17 1 041-Abroad

[0182] Table 2: Transferability of the protective layers C1 and C2 to the holographic film AB and the protective quality of the coatings C2' sample Coating agents T Lam [°C] Laminating layer C1 onto layer B' and removing film D1 Laminating layer C2 onto layer C1 or onto layer B' Removable of film D2 from layer C2' Adhesion of the layer structure B'-C1'-C2' evaluated by cross-cut Solvent resistance (1h) of layer C2' against NEP / MEK / Butanol / EA Layer C1 Layer C2 Comparison example without without - - - - - 5 / 5 / 1 / 5 (after 10 minutes) Examples according to the invention 01-01 C1-01 C2-01 60 + + + 1 0 / 0 / 0 / 0 01-02 C1-01 C2-01 60 + + + 1 0 / 0 / 0 / 0 01-03 C1-01 C2-01 60 + + + 1 0 / 0 / 0 / 0 02-01 C1-01 C2-02 60 + + + 0 0 / 0 / 0 / 0 02-02 C1-01 C2-02 60 + + + 0 0 / 0 / 0 / 0 02-03 C1-01 C2-02 60 + + + 0 0 / 0 / 0 / 0 03-01 C1-02 C2-03 60 + + + 1 0 / 1 / 0 / 0 03-02 C1-02 C2-03 60 + + + 1 0 / 1 / 0 / 0 04-01 C1-02 C2-04 60 + + + 1 0 / 0 / 0 / 1 04-02 C1-02 C2-04 60 + + + 1 0 / 0 / 0 / 1 Non-inventive examples N01 C1-N01 C2-01 60 + - N02 C1-01 no 60 + 0 2 / 4 / 0 / 2 N03 C1-02 no 60 + + 1 4 / 4 / 4 / 4 N04 no C2-01 60 + + 5 0 / 0 / 0 / 0 N05 no C2-03 60 + + 1 0 / 0 / 0 / 0 N06 no C2-04 30 + + 5 0 / 0 / 0 / 0

[0183] Table 2 shows that all inventive examples can be readily produced using two consecutive lamination steps. Non-inventive example N01 cannot be produced. Layer C1, which is not constructed according to the invention, prevents the lamination of layer C2 from being successful. Further inventive examples N02 to N06 are those that have only one protective layer, either C1 or C2. All of them can be readily produced but fail due to poor solvent resistance (N02, N03), adhesion (N04, N06), or holographic performance (N05). Quantitative investigation of the adhesion of the protective layers C1' and C2' as well as the protective layer composite C1'-C2' on the layer B' of the holographic film AB' according to ISO 2409 (cross-cut test)

[0184] A cross-cut adhesive tape tear test (3M Scotch 898 adhesive tape used) was performed (analogous to DIN EN ISO 2409:2013-06). The results ranged from full adhesion (value: 0) to insufficient adhesion (value: 5). Evaluation of the solvent resistance of the protective layer C2' or C1'

[0185] The solvent resistance of the coatings was typically tested using technical-grade N-ethyl-2-pyrrolidone (NEP), methyl ethyl ketone (MEK), 1-butanol, and ethyl acetate (EA). The solvents were applied to the coating with a soaked cotton ball and protected against evaporation by covering. Unless otherwise specified, a contact time of 60 minutes at approximately 23°C was observed. After the contact time, the cotton ball was removed and the test surface was wiped clean with a soft cloth. The test was performed immediately visually and after lightly scratching with a fingernail.

[0186] The following levels are distinguished: 0 = unchanged; no change visible; not damaged by scratching. 1 = slight swelling visible, but not damaged by scratching. 2 = change clearly visible, barely damaged by scratching. 3 = noticeably changed; superficially destroyed after firm fingernail pressure. 4 = severely changed; scratched through to the substrate after firm fingernail pressure. 5 = destroyed; the paint is destroyed even when the chemical is wiped off; the test substance cannot be removed (has eaten into it).

[0187] Within this assessment, the test is usually passed with scores of 0 and 1. Scores > 1 indicate a "failure."

[0188] As the corresponding column of Table 2 shows, all coatings C2' according to the invention exhibit a very high degree of solvent resistance.

[0189] Samples N04 to N06 also show equally good results, where layer C2' is applied directly to AB' without an intermediate layer C1'. Such samples fail due to poor adhesion (N04 and N06) or holographic performance (N05).

[0190] Samples N02 and N03, where layers C1' are not covered with layers C2', do not show sufficient solvent resistance. Characterization of test holograms

[0191] The holograms in layer B' of the film composite A-B', which are first measured before any protective layers are applied, are spectroscopically examined for possible loss of quality in the film composite A-B'-C1'-C2'. COV 17 1 041-Abroad

[0192] Table 3: Quality of the holograms, inscribed in AB film composite, then UV-VIS fixed, thus creating the film composite A-B', on top of which the film composite C1-D1 is laminated and D1 is removed, on top of which the film composite C2-D2 is laminated, then the film composite A-B'-C1-C2-D2 is fixed by UV irradiation, resulting in the film composite A-B'-C1'-C2'-D2 and then by removing D2 the film composite A-B'-C1'-C2' sample Coating agents T Lam [°C] Spectral quality of the holograms in AB' in A-B'-C1'-C2' (after 1h) in A-B'-C1'-C2' (after 3 days) 100-T peak [%] FWH M [nm] λ peak [nm] 100-T min [%] FWH M [nm] λ peak [nm] Δλ peak [nm] to AB' 100-T peak [%] FWHM [nm] λ peak [nm] Δλ peak [nm] to AB' Layer C1 Layer C2 Examples according to the invention 01-01 C1-01 C2-01 60 92.9 23.9 528 85.6 18.0 533 4.5 84.1 17.3 527 -1.4 01-02 C1-01 C2-01 60 93.6 23.8 528 89.1 17.2 536 7.9 86.6 18.9 528 0.0 01-03 C1-01 C2-01 60 91.4 24.2 528 89.0 17.5 536 7.9 81.1 15.7 525 -3.1 02-01 C1-01 C2-02 60 90.4 23.4 529 88.0 19.1 535 6.6 83.8 18.8 525 -3.8 02-02 C1-01 C2-02 60 89.7 23.4 529 89.6 18.4 539 10.1 85.5 16.8 530 1.4 02-03 C1-01 C2-02 60 92.5 22.9 528 89.2 18.3 534 5.9 88.0 17.9 527 -1.0 03-01 C1-02 C2-03 60 91.9 21.7 529 90.1 18.4 538 8.6 91.2 21.3 537 8.3 03-02 C1-02 C2-03 60 91.9 22.0 529 93.2 19.1 538 9.0 90.7 20.8 536 7.3 04-01 C1-02 C2-04 60 93.8 21.6 529 92.9 19.7 532 3.1 92.4 20.5 530 1.3 04-02 C1-02 C2-04 60 91.5 24.3 529 94.0 19.52 536 7.3 91.9 20.6 534 5.9 Non-inventive examples N01 C1-N01 C2-01 60 93.0 19.9 529 - - - - - - - - N02 C1-01 no 60 90.9 24.0 528 90.5 18.6 530 1.4 90.5 18.7 526 -2.1 N03 C1-02 no 60 94.3 20.9 529 94.2 19.9 533 4.2 91.7 19.3 532 3.1 N04 no C2-01 60 93.2 23.0 528 88.9 19.8 544 16.3 91.9 19.9 542 14.2 N05 no C2-03 60 79.2 20.3 529 47.0 32.5 557 28.4 31.8 159.7 #< 549 19.7 N06 no C2-04 30 91.7 22.0 526 87.4 21.9 534 8.0 84.0 22.5 534 7.3 "spectral peak not uniform, several additional peaks

[0193] The values of T Red =100-T peak(A-B'-C1'-C2') (2) for the inventive examples differ only minimally from the corresponding values for AB', and only in isolated cases is a deviation of approximately 10% observed. A significant loss of hologram quality is observed only for the non-inventive example N05.

[0194] The same tendency also applies to the spectral position of the transmission peak λ peak . As the difference Δλ peak = λ peak A − B ′ − C 1 ′ − C 2 ′ − λ peak A − B ′ shows, the deviation from λ peak does not exceed 10 nm. Some non-inventive examples (N04 and N05) show significantly higher values.

Claims

1. Sealed holographic medium comprising a layer construction B'-C1'-C2', wherein B' is a photopolymer layer containing a volume hologram, C1' is a protective layer cured by actinic radiation obtained by reaction of I) at least one thermoplastic mainly linear and semicrystalline polyurethane resin C1-I, II) at least one multifunctional acrylate reactive diluent C1-II, III) at least one photoinitiator C1-III and IV) optionally assistant and added substances and C2' is a protective layer cured by actinic radiation, obtained by reaction of I) at least one thermoplastic resin C2-I selected from the group consisting of polyvinyl butyral and polymethyl methacrylate, II) at least one multifunctional acrylate reactive diluent C2-II, III) at least one photoinitiator C2-III and IV) optionally assistant and added substances, wherein the photopolymer layer B' is sealed by the protective layers CI' and C2'.

2. Sealed holographic medium according to Claim 1, characterized in that the layer construction consists of at least four layers at least partly joined to one another, wherein the layers are arranged directly atop one another in the sequence substrate layer A, photopolymer layer B', cured protective layer C1' and cured protective layer C2'.

3. Sealed holographic medium according to Claim 1, characterized in that the layer construction consists of at least four layers at least partly joined to one another, wherein the layers are arranged directly atop one another in the sequence photopolymer layer B', cured protective layer C1', cured protective layer C2' and substrate layer D2.

4. Sealed holographic medium according to any of the preceding claims, characterized in that the layer construction consists of at least five layers at least partly joined to one another, wherein the layers are arranged directly atop one another in the sequence substrate layer A, photopolymer layer B', cured protective layer C1', cured protective layer C2' and substrate layer D2.

5. Process for producing a sealed holographic medium according to any of Claims 1-4, characterized in that initially an uncured protective layer C1 is applied atop a photopolymer layer B' containing a volume hologram to afford a layer composite B'-C1, in a further step an uncured protective layer C2 is applied atop the protective layer C1 to afford a layer composite B'-C1-C2 and subsequently the layer composite B'-C1-C2 is cured with actinic radiation to obtain a layer composite B'-C1'-C2', wherein C1' and C2' are the cured protective layers C1 and C2 respectively, wherein the uncured protective layer C1 comprises I) at least one thermoplastic mainly linear and semicrystalline polyurethane resin C1-I, II) at least one multifunctional acrylate reactive diluent C1-II, III) at least one photoinitiator C1-III and IV) optionally assistant and added substances; and the uncured protective layer C2 comprises I) at least one thermoplastic resin C2-I selected from the group consisting of polyvinyl butyral and polymethyl methacrylate, II) at least one multifunctional acrylate reactive diluent C2-II, III) at least one photoinitiator C2-III and IV) optionally assistant and added substances.

6. Process according to Claim 5, characterized in that in a first step a layer composite A-B' is provided, wherein A is a substrate layer and B' is a photopolymer layer containing a volume hologram, in a second step the uncured protective layer C1 is applied atop a substrate layer D1 to afford a layer composite C1-D1, in a third step the layer composite A-B' is areally joined to the layer composite C1-D1 to afford a layer composite A-B'-C1-D1, wherein the layer composite A-B' is preferably joined to the layer composite C1-D1 by lamination, in a fourth step the substrate layer D1 is removed from the layer composite A-B'-C1-D1 to afford a layer composite A-B'-C1, in a fifth step the uncured protective layer C2 is applied atop a substrate layer D2 to afford a layer composite C2-D2, in a sixth step the layer composite A-B'-C1 is areally joined to the layer composite C2-D2 to afford a layer composite A-B'-C1-C2-D2, wherein the layer composite A-B'-C1 is preferably joined to the layer composite C2-D2 by lamination, in a seventh step the layer composite A-B'-C1-C2-D2 is cured with actinic radiation to afford a layer composite A-B'-C1'-C2'-D2.

7. Process according to Claim 6, characterized in that in an eighth step the substrate layer D2 is removed from the layer composite A-B'-C1'-C2'-D2 to afford a layer composite A-B'-C1'-C2'.

8. Kit of parts for producing a sealed holographic medium according to Claim 1 containing at least one uncured protective layer C1, at least one uncured protective layer C2 and a flat photopolymer layer B' which contains a volume hologram, wherein the protective layers C1 and C2 are different, wherein the protective layer C1 comprises I) at least one thermoplastic mainly linear and semicrystalline polyurethane resin C1-I, II) at least one multifunctional acrylate reactive diluent C1-II, III) at least one photoinitiator C1-III and IV) optionally assistant and added substances and the protective layer C2 comprises I) at least one thermoplastic resin C2-I selected from the group consisting of polyvinyl butyral and polymethyl methacrylate, II) at least one multifunctional acrylate reactive diluent C2-II, III) at least one photoinitiator C2-III and IV) optionally assistant and added substances.

9. Kit of parts according to Claim 8, characterized in that the photopolymer layer B' is disposed on a substrate layer A, wherein the photopolymer layer B' is on one side at least partly joined to the substrate layer A.

10. Kit of parts according to Claim 8, characterized in that the uncured protective layer C1 is disposed on a substrate layer D1, wherein the protective layer C1 is on one side at least partly joined to the substrate layer D1, and the uncured protective layer C2 is disposed on a substrate layer D2, wherein the protective layer C2 is on one side at least partly joined to the substrate layer D2.

11. Use of the kit of parts according to any of Claims 8-10 for the process according to any of Claims 5-7.

12. Optical display comprising a sealed holographic medium according to any of Claims 1-4, wherein the optical display is selected from the group consisting of autostereoscopic and / or holographic displays, projection screens, displays with switchable restricted emission characteristics for privacy filters and bidirectional multiuser screens, virtual displays, head-up displays, head-mounted displays, illumination symbols, warning lamps, signal lamps, floodlights / headlights and display panels.

13. Security document comprising a sealed holographic medium according to any of Claims 1-4.