WO2025214825A1

WO2025214825A1 - Process for the production of a colored level 2 feature

Info

Publication number: WO2025214825A1
Application number: PCT/EP2025/058872
Authority: WO
Inventors: Thomas Musiol; Oliver Seeger
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2024-04-10
Filing date: 2025-04-01
Publication date: 2025-10-16
Anticipated expiration: 2026-10-10

Abstract

The present invention relates to a process of manufacturing a (security) product comprising a color image which is viewable under cross-polarisers, comprising a) providing a substrate; b) providing a nematic liquid crystal layer on the substrate; c) illuminating the nematic liquid crystal layer, which is in the nematic phase, through a mask by means of UV/VIS radiation; d) heating the nematic liquid crystal layer above the temperature of the phase transition to the isotropic phase; and e) illuminating the nematic liquid crystal layer, which is in the isotropic phase, with UV/VIS radiation; to obtain the fixed color image, which is viewable under cross-polarisers, wherein the different colors of the color image are caused by two or more regions of different birefringence, which depend on the ratio of nematic and isotropic liquid crystals contained in the region. The production of the color images is compared to techniques described in the prior much cheaper and offers high flexibility in producing different color images.

Description

BASF SE 240078 1 Process for the production of a colored level 2 feature DESCRIPTION The present invention relates to a process of manufacturing a (security) product comprising a color image which is viewable under cross-polarisers, comprising a) providing a substrate; b) providing a nematic liquid crystal layer on the substrate; c) illuminating the nematic liquid crystal layer, which is in the nematic phase, through a mask by means of UV/VIS radiation; d) heating the nematic liquid crystal layer above the temperature of the phase transition to the isotropic phase; and e) illuminating the nematic liquid crystal layer, which is in the isotropic phase, with UV/VIS radiation; to obtain the fixed color image, which is viewable under cross-polarisers, wherein the different colors of the color image are caused by two or more regions of different birefringence, which depend on the ratio of nematic and isotropic liquid crystals contained in the region. The production of the color images is compared to techniques described in the prior much cheaper and offers high flexibility in producing different color images, in particular when using inkjet printing for the production of the masks. TECHNICAL BACKGROUND WO2021/032518 relates to a process for the production of fingerprint texture free liquid crystal films. The process involves the use of liquid crystal compositions comprising at least one photoinitiator, which is an alpha-hydroxy ketone compound of formula (XI), and is suitable for the production of optical films which exhibit excellent thermal stability at high humidity without losing their other advantages like good resistance against chemicals and solvents. It can be advantageously employed for the production of security elements. WO03106188 relates to a liquid crystal device comprising: a substrate; at least one photo-alignment layer applied to the substrate and which is uniformly aligned with a polarised light source; a nematic liquid crystal layer applied to the photo-alignment layer; and a latent image formed by the photo-alignment layer and the liquid crystal layer without the use of a mask, wherein the latent image is viewable under cross-polarisers. EP1925954B1 relates to a process of producing a patterned birefringent product, which comprises at least the following steps [1] to [3] in order: [1] preparing a birefringence pattern builder which comprises an optically anisotropic layer comprising a polymer, and said optically anisotropic layer has a retardation disappearance temperature in the range higher than 20°C, BASF SE 240078 2 at said retardation disappearance temperature in-plane retardation becomes 30 % or lower of the retardation at 20°C of the same optically anisotropic layer, and said retardation disappearance temperature rises by light exposure; [2] subjecting the birefringence pattern builder to patterned light exposure; [3] heating the laminated structure obtained after the step [2] at 50°C or higher and 400°C or lower; wherein the polymer is formed by polymerization of a liquid crystalline compound having at least a radically reactive group selected from the group consisting of acrylic group and methacrylic group and a cationically reactive group selected from the group consisting of vinyl ether group, oxetanyl group, and epoxy group. EP2302425B1 relates to an element for protection against forgery and/or copying comprising a structured LCP layer (4) which is formed by cross-linked liquid-crystal monomers, wherein the structured LCP layer has at least two regions with different optical axes and incorporates orientable fluorescent dyes having absorption bands in the UV range and wherein the fluorescent molecules are zonally perpendicular to one another in accordance with the liquid crystal orientation. EP2259102A1 relates to a viewer for authenticating a birefringent pattern having at least two regions having a different birefringence from each other, wherein the viewer comprises a polarizing plate and at least one optically anisotropic layer laminated on the polarizing plate, a front retardation of the at least one optically anisotropic layer is 5 nm or more and the total of the front retardation of the at least one optically anisotropic layer and a maximum value of front retardation of the birefringent pattern is greater than λ/2, EP2372412B1 relates to a method of manufacturing a product in which a color image is rendered visible by a polarizing plate, comprising a patterned optically anisotropic layer (101) having two or more regions of different birefringence (101A, 101B, 101C) in the form of a pattern, - comprising at least two intensity gradation-type pixels (α, β) having different color tones to each other in the color image, wherein each of the at least two intensity gradation-type pixels (α, β) has approximately uniform birefringence, wherein the patterned optically anisotropic layer further comprises at least two area gradation-type pixels (γ, δ) having different color densities to each other in the color image, each of the at least two area gradation-type pixels is formed of a matrix of drawing units and comprises two or more types of the drawing units that have different birefringence to each other, and the at least two area gradation-type pixels have different ratios of numbers of the two or more of the types of the drawing units, wherein the patterned optically anisotropic layer is formed by a method comprising steps (1) to (3) below: (1) irradiating with heat or light a layer formed of a composition comprising a liquid-crystal compound; (2) subjecting the layer to patterned light exposure; and (3) heating the layer that has been subjected to the patterned light exposure to 50°C or higher but not higher than 400°C, wherein the patterned light exposure is conducted by scanning exposure with a laser beam. BASF SE 240078 3 EP2527888 relates to a method for manufacturing a liquid crystal polymer network (1) having a pattern structure, comprising the steps - providing a substrate (2) comprising a first alignment layer (3, 33); - jet printing a first layer (4, 54) comprising a cross-linkable liquid crystal material in a first pattern; - allowing the liquid crystal material to align; and - cross-linking the liquid crystal material. EP2759855 relates to a product comprising a patterned optically anisotropic layer having two or more regions of different birefringence, which has a latent image becoming visible through a polarizing plate, wherein an image visible through the polarizing plate including the latent image comprises a periodic structure. The patterned optically anisotropic layer is preferably formed by a method comprising the following steps (1) to (3) in this order: (1) heating or irradiating with light a layer formed of a composition comprising a liquid-crystal compound; (2) subjecting the layer to patterned light exposure; and (3) heating the obtained layer to 50°C or higher but not higher than 400°C. US20160244671A1 (EP3060947) relates to a method of preparing a patterned polymer film comprising the following steps: a) providing a layer of a polymerizable liquid-crystalline material comprising at least one dichroic photoinitiator, and at least one chiral compound, onto a substrate, b) adjusting the temperature of the polymerizable liquid-crystalline material to a temperature, where the polymerizable liquid-crystalline material is in its nematic or isotropic phase, c) polymerizing and orientating by irradiating the polymerizable liquid-crystalline material with linear polarized actinic radiation, whereby the angle between the layer of the polymerizable liquid-crystalline material, the direction of the electric field vector of the linear polarised actinic radiation is varied, thereby causing the polymerizable liquid-crystalline material to form a polymer film, and d) optionally removing the polymer film from the substrate. The dichroic photoinitiator has the property that the light absorption is dependent on the molecular orientation of the molecule. The dichroic photoinitiators selectively dissociate when aligned with the electric field vector of the incoming light. WO2008/017362A2 relates to various methods are described for producing multi-layer bodies having at least one partially formed functional layer and at least one further partially formed layer, and the multi-layer bodies which are produced in this way are also described. The multi-layer body has at least one partially formed functional layer in register with at least one further partially formed layer which preferably complement one another to form a geometric, alphanumeric, visual, graphic or figurative coloured design. WO2019/145691A1 discloses a method of producing an optical security device comprising: (a) producing a liquid crystal layer which comprises birefringent regions and non-birefringent regions defining at least a first image to be exhibited by the optical security device by: (a1) providing a mask comprising gap regions, the gap regions in the mask defining the birefringent regions of the liquid crystal layer; (a2) providing a liquid crystal layer overlapping the mask; BASF SE 240078 4 (a3) illuminating the liquid crystal layer with light, wherein the mask is positioned between the liquid crystal layer and the source of said light, and wherein uncured regions of the liquid crystal layer are birefringent, thereby curing the birefringent regions of the liquid crystal layer corresponding to the gap regions of the mask; and (a4) heating the liquid crystal layer such that uncured regions of the liquid crystal layer lose substantially all birefringence, and illuminating said liquid crystal layer with light, wherein the mask is not positioned between the device and the source of said light, thereby curing the non- birefringent regions of the liquid crystal layer; and (b) providing the liquid crystal layer overlapping a colour layer which defines an array of pixels each of which comprises at least two regions of different colours such that the birefringent regions define at least a first image to be exhibited by the pixels of the optical security device. WO2019145691A1 describes how LC-based colored level 2 security elements can be obtained having very high resolution by using demetalization technology. The production of the used masks is very complex and, hence, cost-intensive. An individual design a continuous roll-to-roll production process are not possible. This problem of mask production can be solved by simply printing the mask, for example, on the back of the carrier film (e.g. PET) using inkjet (individually designed layout). This eliminates the need to stop the roll-to-roll machine for the exposure process. Alternatively, a flexible carrier can be printed, which runs at the same speed as the substrate to be exposed (reusability). In addition, it is difficult to print a liquid crystal to the fine dimensions required for exhibiting a colour image, and the process of this aspect of the present invention overcomes this problem. Accordingly, the present invention relates to a process of manufacturing a product, especially a security product comprising a color image which is viewable under cross-polarisers, comprising a) providing a substrate; b) providing a nematic liquid crystal layer on the substrate; c) illuminating the nematic liquid crystal layer, which is in the nematic phase, through a mask by means of UV/VIS radiation; d) heating the nematic liquid crystal layer above the temperature of the phase transition to the isotropic phase; and e) illuminating the nematic liquid crystal layer with UV/VIS radiation; to obtain the fixed color image which is viewable under cross-polarisers. Fig.1 is a schematic view of the process of the present invention. Fig.2 shows images obtained by the process of the present invention using different masks. BASF SE 240078 5 The quality of the level 2 feature is scalable and depends on the mask quality. Color matching is dependent on LC print thickness, mask transparency, mask layout/resolution and UV-dose for pre- crosslinking. The mask is preferably produced by ink jet printing, gravure printing, flexo printing, screen printing, or laser printing. The mask production is compared to techniques described in the prior much cheaper and offers high flexibility in producing different masks, in particular when using inkjet printing. An excellent resolution can be achieved in case the distance between mask and LC layer is low, i.e. in the range of from 10 to 100 µm, especially ~50µm. Step b) preferably comprises b1) applying a nematic liquid crystal composition onto the substrate; and b2) drying the nematic liquid crystal layer obtained in step b1). Step b2) preferably includes heating the nematic liquid crystal layer to a temperature in the range of from 25 to 130°C, especially 40 to 100 °C. The process of the present invention is illustrated in more detail with reference to Fig.1. The substrate used in step a) is flexible, preferably flexible and biaxially oriented. If the substrate is a biaxially oriented polyethylene terephthalate (BOPET) film, or a biaxially oriented polypropylene (BOPP) film, which are birefringent, the fixed color image obtained in step e) has to be transferred to a non-birefringent substrate, such as, for example, a TAC (triacetylcellulose) film, or a glass substrate. Step b) preferably comprises b1) applying a nematic liquid crystal composition onto the substrate; and b2) drying the nematic liquid crystal layer obtained in step b1). The liquid crystal composition can be applied in process step b1) by means of customary processes, for example by means of processes selected from airblade coating, knife coating, airknife coating, squeegee coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, flow coating, spray coating, spin coating, or printing processes such as relief printing, gravure printing, intaglio printing, flexographic printing, offset printing, inkjet printing, letterpress printing, pad printing, heatseal printing or screen printing processes. The liquid crystal composition is preferably applied by slot die-, knive-, reverse roll-, metering rod coating, gravure-, flexo-, screen-, or ink jet printing. In process step b2) the evaporating of the solvent is done by applying infrared radiation (IR radiation), and/or thermal drying, for example, by means of hot air, a hot plate. BASF SE 240078 6 The evaporating of the solvent is affected preferably at elevated temperature, i.e. by heating, optionally under reduced pressure. It is preferred to carry out process step (c) at a temperature of from 25 to 130°C, more preferably from 40 to 100°C. The thermal energy can originate both from an external heat source as well as from the UV light source, for example a UV lamp. Preferably the thermal energy originates at least partly from a heat source different from the UV light source, for example from an oven or a heating plate. Radiation curing in process steps c) and e) takes place with high-energy light, such as, for example, UV/VIS radiation (illuminating by means of UV/VIS radiation). Radiation curing may also take place at relatively high temperatures. Examples of suitable radiation sources for the radiation cure are low-pressure mercury lamps, medium- pressure mercury lamps with high-pressure lamps, and fluorescent tubes, pulsed lamps, metal halide lamps, or excimer lamps and also UV LEDs. The radiation cure is accomplished by exposure to high- energy radiation, i.e., UV/VIS radiation, preferably light in the wavelength range of λ=200 to 700 nm, more preferably λ=200 to 500 nm, or by exposure to high-energy electrons (electron beams; 60 to 300 keV). Examples of radiation sources used include high-pressure mercury vapor lamps, lasers, pulsed lamps (flash light), halogen lamps, UV LEDs, or excimer lamps. The radiation dose normally sufficient for crosslinking in the case of UV curing is in the range from 30 to 3000 mJ/cm². Step b2) includes heating the nematic liquid crystal layer to a temperature in the range of from 25 to 130°C, especially 40 to 100 °C. In step c) the nematic liquid crystal layer, which is in the nematic phase, is iiluminated through a mask by means of UV/VIS radiation. In Fig.1 the process of the present invention is illustrated. A liquid crystal (LC) formulation is applied on the PET foil by spin coating using a coater, the solvent is removed using a dryer and the LC is aligned. The LC layer is pre-crosslinked through a mask which is positioned on the back side of the PET foil using a UV lamp. The LC layer is heated to a temperature above the isotropic phase and finally crosslinked. The LC stack is transferred using an adhesive to a glass carrier (not birefringent) and the PET foil is removed. Fig.2 shows images obtained by the process of the present invention using different masks i), ii) and iii) (polarizer 90° and 0 °, respectively). The obtained color is dependent on the exposure level in the different regions, wherein the optical thickness of the mask determines the ratio of nematic (birefringent) and isotropic (non-birefringent) LCs. Color* Red Yellow Green Blue Ratio of nematic and 100/0** 80/20 60/40 45/55 isotropic LCs (exposure (~60mJ/cm²) (~47mJ/cm²) (~36mJ/cm²) (~27mJ/cm²) level) BASF SE 240078 7 * corresponds to different nematic thickness. ** 100 % birefringent. Liquid crystal molecules that have polymerisable groups attached to them (for example acrylate groups, which polymerise via a free-radical mechanism occurring at the double bond, or epoxy groups, which polymerise via a ring opening mechanism) can be fixed into their current configuration by curing with light. Photoinitiators in the liquid crystal layer interact with the light to create reactive species, for example free radicals or ions. These reactive species activate the polymerisable groups, thereby causing bonds to be formed between the polymerisable groups on the molecules, and it is these bonds that maintain the configuration of the liquid crystal molecules. Therefore, when a mask is positioned between the source of the curing light and the liquid crystal, any pattern exhibited by the mask will be fixed into the liquid crystal layer. When the liquid crystal molecules in the liquid crystal layer are substantially aligned, these cured regions will be birefringent. By using, for example, screen printing to produce the mask, a corresponding high resolution in an image defined by the birefringent regions of a liquid crystal layer is produced. In step d) the nematic liquid crystal layer is heated above the temperature of the phase transition to the isotropic phase and is then illuminated with UV/VIS radiation; to obtain the fixed color image, which is viewable under cross-polarisers. Usually step d) includes heating the nematic liquid crystal layer to a temperature in the range of from 25 to 130°C, especially 40 to 100 °C. On heating the uncured regions of the liquid crystal layer will lose substantially all of their birefringence (isotropic phase), and this state can then be fixed by curing with light. A mask is typically not necessary during this step as the birefringent regions have already been cured. The light source used preferably emits both visible and ultraviolet frequencies of light, although a light source could equally be selected that emits only visible light or only ultraviolet light. In a particularly preferred embodiment the image on the mask is produced by screen printing, ink jet printing, or gravure printing a plasmonic ink on the backside of the flexible substrate and the nematic liquid crystal layer, which is in the nematic phase, is illuminated through the mask arranged on the backside of the flexible substrate by means of UV/VIS radiation. In said embodiment a non-birefringent substrate, such as, for example, a TAC (triacetylcellulose) film, may be used. The term “liquid-crystalline” is used in the context of the present invention for nematic, unless otherwise evident from the particular context. The nematic liquid crystal composition preferably comprises A.1 at least one achiral nematic polymerizable monomer; C.1 at least one photoinitiator; C.3 at least one solvent; BASF SE 240078 8 C.5 optionally at least one leveling agent; and C.10 optionally at least one in-can stabilizer. The nematic liquid crystal composition preferably comprises A.1 at least one achiral nematic polymerizable monomer and C.1 at least one photoinitiator, which is an alpha-hydroxy ketone compound of formula O R₃₁ R_{30 C C R32} , , R₃₂ and R₃₃ independently of each other are C₁-C₆alkyl; R₃₄ is hydrogen; R₃₅ is hydrogen, or OR₃₆; R₃₆ is hydrogen, C₁-C₁₂alkyl which optionally is interrupted by one or more non-consecutive O-atoms and which uninterrupted or interrupted C₁-C₁₂alkyl optionally is substituted by one or more OH, or R₃₆ is R31 O_C R C 32 ; is interrupted by one or more non-consecutive O; C.5 optionally at least one leveling agent, and C.10 optionally at least one in-can stabilizer, onto the substrate. BASF SE 240078 9 The nematic liquid crystal composition preferably comprises - 10-50% by weight, preferably 20-40% by weight of component(s) A.1 based on total weight of component(s) A.1 and C.3; - 50-90% by weight, preferably 60-80% of solvent(s) C.3 based on total weight of component(s) A.1 and C.3; - 0.5-10% by weight, preferably 1-5% by weight of photoinitiator(s) C.1 based on total weight of component(s) A.1; - 0.01-1% by weight, preferably 0.01 – 0.2% by weight of levelling agent(s) C.5 based on total weight of component(s) A.1; - 0.01-1.0 % by weight, preferably 0.04-0.7 % by weight of in-can stabilizer(s) C.10 based on total weight of component(s) A.1. In addition, the liquid crystalline composition may comprise one or more substances selected from the group consisting of: C.2 reactive diluents which comprise photopolymerizable groups; C.4 defoamers and deaerators; C.6 thermally curing and/or radiatively curing auxiliaries; C.7 substrate wetting aids; C.8 wetting and dispersing aids; C.9 hydrophobizing agents; C.11 auxiliaries for improving scratch resistance; and optionally as component D: one or more substances selected from the group consisting of: D.1 dyes; and D.2 pigments; - at least one component E which is in turn selected from light, heat and oxidation stabilizers; and - at least one component F which is in turn selected from IR-absorbing compounds. The additives of group (C.4) to (C.11) are described in more detail on pages 25 to 35 of WO2021/032518. The light, heat and oxidation stabilizers are described in more detail on pages 35 to 39 of WO2021/032518. Achiral nematic polymerizable monomer (A.1) Preferably, at least one achiral nematic polymerizable monomer of the composition (a.1) is polyfunctionally and especially difunctionally polymerizable. Such monomers are, for example, described in WO05049703, WO, 97/00600, WO 2006/120220, WO0055110 and G. Challa et al., Makromol. Chem.190 (1989) 3201- 3215). Preferred achiral nematic difunctionally polymerizable monomers correspond to the general formula I: Z¹-(Y¹-A¹)v-Y²-M-Y³-(A²-Y⁴)w-Z² (I), in which BASF SE 240078 10 Z¹, Z² are identical or different reactive groups through which polymerization can be effected, or radicals which comprise such reactive groups, the reactive groups preferably being selected from C=C double bonds, C≡C triple bonds, oxirane, thiirane, azirane, cyanate, thiocyanate, isocyanate, carboxylic acid, hydroxyl or amino groups, and preferably from C=C double bonds (these may, for example, be -CH=CH₂ or -C(CH₃)=CH₂ or else -CH=CH(CH₃), preference being given to the first two mentioned); Y¹, Y², Y³, Y⁴ are each independently a chemical bond, -O-, -S-, -CO-O-, -O-CO-, -O-CO-O-, -CO-S-, -S- CO-, -CO-N(R^a)-, -N(R³)-CO-, -N(R^a)-CO-O-, -O-CO-N(R^a)-, -N(R^a)-CO-N(R^a)-, -CH2-O-, -O-CH2-, preferably -CO-O-, -O-CO- or -O-CO-O-, where R^a is hydrogen or C1-C4-alkyl; A¹, A² are identical or different spacers which are selected from linear C2-C30-alkylene groups, preferably C2-C12-alkylene groups, which may be interrupted by -CO-O-, oxygen, sulfur and/or optionally monosubstituted nitrogen, where these interrupting groups must not be adjacent; where suitable amine substituents comprise C1-C4-alkyl groups, where the alkylene chains may be substituted by fluorine, chlorine, bromine, cyano, methyl or ethyl; and where A¹ and A² are more preferably - (CH2)n- where n = from 2 to 6; v and w are each independently 0, 1 or 2; M is a mesogenic group, preferably a mesogenic group of the general formula II: (T¹-Y⁵)y-T² (II), in which each T¹ is independently a divalent alicyclic, saturated or partially unsaturated heterocyclic, aromatic or heteroaromatic radical; T² is independently as defined for T¹; Y⁵ represents identical or different bridging members -CO-O-, -O-CO-, -CH₂-O-, -O-CH₂-, -CO-S-, -S- CO-, -CH₂-S-, -S-CH₂, -CH=N-, -N=CH-, -CH=N-N=CH-, -C≡C-, -CH=CH-, -C(CH₃)=CH₂, - CH=CH(CH₃)- or a direct bond and is preferably -CO-O- or -O-CO-, and y is an integer from 0 to 3, preferably 0, 1 or 2, in particular 1 or 2 and especially 2. T² is preferably an aromatic radical and more preferably a phenyl radical. T² is especially a radical of the b (R )x , in which R^b bromine, C1-C20-alkyl, C1-C10-alkoxy, C1-C10-alkylcarbonyl, C1-C10- alkylcarbonyloxy, C1-C10-alkoxycarbonyl, hydroxyl, nitro, CHO or CN, preferably chlorine, bromine, C1-C4-alkyl or C1-C4-alkoxycarbonyl, and especially methyl or methoxycarbonyl; and x is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1 and especially 1. Each T¹ is independently preferably an aromatic radical, more preferably phenyl or naphthyl and especially 1,4-bonded phenyl or 2,6-bonded naphthyl. Y⁵ is preferably -CO-O- or -O-CO-. y is preferably 2. Particularly preferred mesogenic groups M have the following structures: BASF SE 240078 11 b (R )x O in which R^b and x each ^b above, where R is especially methyl and x or b (R )x in which R^b and ^b where R is especially x In a particularly preferred embodiment the liquid crystal composition comprises as component A.1: one or more compounds of the general formula Ib Rb , Z¹, Z² are each independently H CH3 , 8 carbon atoms, oxygen, –CO–, –O–CO– or –CO–O–, R^b is hydrogen, C1-C6-alkyl or CO-O-C1-C6-alkyl, as component A.1: one or more compounds of the general formula Ia Rb' one or more compounds of the general formula Ic BASF SE 240078 12 Rb' , H CH3 , A^1’, 8 carbon atoms, which is optionally interrupted by – Y^1’, Y^4’ are each independently a single chemical bond, oxygen, –CO–, –O–CO– or –CO–O–, R^b’ is hydrogen, C₁-C₆-alkyl or CO-O-C₁-C₆-alkyl. In a particularly preferred embodiment, the achiral nematic difunctionally polymerizable monomers are selected from compounds of the following formulae I.a, I.b and I.c: O O _{O O} O O O O _{O O} BASF SE 240078 13 O O O O O_O O O However, the composition (a.1) may also comprise a monofunctionally polymerizable achiral nematic monomer. This preferably has the general formula (IIIa) and/or (IIIb): A³-Y²-M-Y³-(A²-Y⁴)w-Z² (IIIa) Z¹-(Y¹-A¹)v-Y²-M-Y³-A³ (IIIb), in which Z¹, A¹, Y¹, Y², Y³, Y⁴, v, w and M are each independently as defined generally or preferably for formula (I); and A³ is a linear C₁-C_30-alkyl group, preferably a linear C₁-C₁₂-alkyl group, which may be interrupted by oxygen, sulfur and/or optionally monosubstituted nitrogen, where these interrupting groups must not be adjacent; where suitable amine substituents comprise C₁-C₄-alkyl groups, where the alkyl group may be substituted by fluorine, chlorine, bromine, cyano, methyl or ethyl, or is CN or -N=C=S-. A³ is preferably linear C₂-C₈-alkyl or CN and especially linear C₄-C₈-alkyl or CN. Y¹, Y², Y³, Y⁴ and Y⁵ are each independently preferably -O-CO-, -CO-O-, -O-CO-O- or a C-C-triple bond. Z¹ is preferably a C-C- double bond (preferably -CH=CH2 or -C(CH3)=CH2). M is preferably a mesogenic group of the general formula II. T¹ and T² are preferably each independently an aromatic group, more preferably phenyl or naphthyl which may bear 0, 1, 2, 3 or 4 R^b radicals, where R^b has one of the general or preferred definitions specified above, especially 1,4-bonded phenyl or 2,6-bonded naphthyl which may bear 0, 1, 2, 3 or 4 R^b radicals, where R^b has one of the general or preferred definitions specified above, and especially unsubstituted 1,4-bonded phenyl or unsubstituted 2,6-bonded naphthyl. y is preferably 0 or 1. Particularly preferred monofunctionally polymerizable achiral nematic monomers are selected from the following structures: O CN BASF SE 240078 14 N O BASF SE 240078 15 The at least one achiral nematic polymerizable monomer of the composition (a.1) comprises preferably (i) at least one difunctionally polymerizable achiral nematic monomer of the formula (I), preferably one or two difunctionally polymerizable achiral nematic monomers of the formula (I); and (ii) optionally at least one monofunctionally polymerizable achiral nematic monomer of the formula (IIIa) and/or (IIIb). When the composition (a.1) comprises one or more monofunctionally polymerizable monomers, they are preferably present in the composition in a total amount of not more than 50% by weight, more preferably of not more than 25% by weight, even more preferably of not more than 15% by weight based on the total weight of the poly- and monofunctionally polymerizable achiral nematic monomers. In a specific embodiment, the composition (a.1) does not comprise any monofunctionally polymerizable achiral nematic monomers, but rather only at least one, preferably one or two, polyfunctionally, especially difunctionally, polymerizable achiral nematic monomer(s). Photoinitiator (C.1) A photoinitiator for the purposes of this specification is a compound which can be cleaved into at least one radical by electromagnetic radiation, preferably by UV radiation, visible light or IR radiation, more preferably by UV radiation or visible light, and very preferably by UV radiation. Component (C.1) may comprise one or more than one – for example, 1 to 3, preferably 1 to 2, and more preferably precisely one – group which is active as a photoinitiator, The photoinitiator (C.1) is preferably an alpha-hydroxy ketone compound of formula , R₃₄ is hydrogen; R₃₅ is hydrogen. BASF SE 240078 16 O CH3 HO O C OH In principle, the alpha-hydroxy ketone compounds of formula (XI) can be used in admixture with other photoinitiators, which do not represent CMR compounds and do not negatively affect the thermal stability and resistance against chemicals and solvents of the liquid crystal films obtainable from the liquid crystal compositions of the present application. Examples of such photoinitiators are oxime ester compounds of O O the , wherein z is 0 or 1; R₇₀ is is unsubstituted or substituted by one or more halogen, which is unsubstituted or substituted by one or more C₁-C₆alkyl, halogen, CN, OR₇₃, SR₇₄ or by NR₇₅R₇₆; or R₇₀ is C₁-C₈alkoxy, benzyloxy; or phenoxy which is unsubstituted or substituted by one or more C1-C6alkyl or by halogen; R71 is phenyl, naphthyl, benzoyl or naphthoyl, each of which is substituted by one or more halogen, C1- C12alkyl, C3-C8cycloalkyl, benzyl, phenoxycarbonyl, C2-C12alkoxycarbonyl, OR73, SR74, SOR74, SO2R74 or by NR75R76, wherein the substituents OR73, SR74 and NR75R76 optionally form 5- or 6-membered rings via the radicals R73, R74, R75 and/or R76 with further substituents on the phenyl or naphthyl ring; or each of which is substituted by phenyl or by phenyl which is substituted by one or more OR73, SR74 or by NR75R66; Y2 or R₇₁ is or Y₃ ; R72 is C1-C20alkyl which is substituted by one or more halogen, OR73, SR74, C3- C3-C8cycloalkyl; or is phenyl which is unsubstituted or substituted by one or more C1-C6alkyl, phenyl, halogen, OR73, SR74 or by NR75R76; or is C2-C20alkanoyl or BASF SE 240078 17 benzoyl which is unsubstituted or substituted by one or more C₁-C₆alkyl, phenyl, OR₇₃, SR₇₄ or by NR₇₅R₇₆; or is C₂-C₁₂alkoxycarbonyl, phenoxycarbonyl, CN, CONR₇₅R₇₆, NO₂, C₁-C₄haloalkyl, S(O)_y-C₁-C₆alkyl, or S(O)_y-phenyl, y is 1 or 2; Y₂ is a direct bondor no bond; O Y3 is NO2 or ^C R ; 77 R₇₃ and R₇₄ independently of one another are hydrogen, C₁-C₂₀alkyl, C₂-C₁₂alkenyl, C₃-C₈cycloalkyl, C₃- C₈cycloalkyl which is interrupted by one or more, preferably 2, O, phenyl-C₁-C₃alkyl; or are C₁-C₈alkyl which is substituted by OH, SH, CN, C₁-C₈alkoxy, C₁-C₈alkanoyl, C₃-C₈cycloalkyl, by C₃-C₈cycloalkyl which is interrupted by one or more O, or which C₁-C₈alkyl is substituted by benzoyl which is unsubstituted or substituted by one or more C₁-C₆alkyl, halogen, OH, C₁-C₄alkoxy or by C₁-C₄alkylsulfanyl; or are phenyl or naphthyl, each of which is unsubstituted or substituted by halogen, C₁-C₁₂alkyl, C₁-C₁₂alkoxy, phenyl-C₁- C₃alkyloxy, phenoxy, C₁-C₁₂alkylsulfanyl, phenylsulfanyl, N(C₁-C₁₂alkyl)₂, diphenylamino or by O O C_{C N O} C ; of each other are hydrogen, C1-C20alkyl, C2-C4hydroxyalkyl, C2-C10alkoxyalkyl, phenyl-C1-C3alkyl, C1-C8alkanoyl, C3-C12alkenoyl, benzoyl; or are phenyl or naphthyl, each of which is unsubstituted or substituted by C1-C12alkyl, benzoyl or by C1-C12alkoxy; or R75 and R76 together are C2-C6alkylene optionally interrupted by O or NR73 and optionally are substituted by hydroxyl, C1-C4alkoxy, C2-C4alkanoyloxy or by benzoyloxy; R77 is C1-C12alkyl, thienyl or phenyl which is unsubstituted or substituted by C1-C12alkyl, OR73, morpholino or by N-carbazolyl. Specific examples are 1,2-octanedione 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime) (Irgacure^ OXE01), ethanone 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime) (Irgacure^ OXE02), 9H- thioxanthene-2-carboxaldehyde 9-oxo-2-(O-acetyloxime), ethanone 1-[9-ethyl-6-(4morpholinobenzoyl)-9H- carbazol-3-yl]-1-(O-acetyloxime), ethanone 1-[9-ethyl-6-(2-methyl-4-(2-(1,3-dioxo-2-dimethyl-cyclopent-5- yl)ethoxy)-benzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime) (Adeka N-1919), ethanone 1-[9-ethyl-6-nitro-9H- carbazol-3-yl]-1-[2-methyl-4-(1-methyl-2-methoxy)ethoxy)phenyl]-1-(O-acetyloxime) (Adeka NCI831), etc. The photoinitiators are used typically in a proportion of from about 0.1 to 7.0% by weight based on the total weight of the liquid-crystalline mixture. Especially when the hardening is performed under inert gas atmosphere, it is possible to use significantly smaller amounts of photoinitiators. In this case, the photoinitiators are used in a proportion of from about 0.1 to 1.0% by weight, preferably from 0.2 to 0.6% by weight, based on the total weight of the liquid-crystalline mixture. Solvent (C.3) Group (C.3) of the solvents includes, for example, C₁-C₄-alcohols, for example methanol, ethanol, n- propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, and the C5-C12-alcohols n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol and n-dodecanol and isomers BASF SE 240078 18 thereof, glycols, for example 1,2-ethylene glycol, 1,2 or 1,3-propylene glycol, 1,2 , 2,3 or 1,4-butylene glycol, di or triethylene glycol or di or tripropylene glycol, ethers, for example open-chain ethers such as methyl tert-butyl ether, 1,2-ethylene glycol monomethyl or dimethyl ether, 1,2-ethylene glycol monoethyl or diethyl ether, 3-methoxypropanol or 3-isopropoxy¬propanol, or cyclic ethers such as tetrahydrofuran or dioxane, open-chain ketones, for example acetone, methyl ethyl ketone, methyl isobutyl ketone or diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), cyclic ketones such as cyclopentanone, or cyclohexanone, C1-C5-alkyl esters, for example methyl acetate, ethyl acetate, propyl acetate, butyl acetate or amyl acetate, C1-C4-alkoxy-C1-C4-alkyl esters such as 1-methoxyprop-2-yl acetate, carboxamides such as dimethylformamide and dimethylacetamide, N-heterocycles such as N-methylpyrrolidone, aliphatic or aromatic hydrocarbons, for example pentane, hexane, heptane, octane, isooctane, petroleum ether, toluene, xylene, ethylbenzene, tetralin, decalin, dimethylnaphthalene, white spirit, Shellsol® or Solvesso®, mineral oils, for example gasoline, kerosene, diesel oil or heating oil, but also natural oils, for example olive oil, soybean oil, rapeseed oil, linseed oil or sunflower oil. As a matter of course, mixtures of these solvents are also useful for use in the inventive mixtures. The nematic liquid crystal composition preferably comprises as component C.3 one, or more solvents which are selected from the group consisting of C1-C4-alkoxy-C1-C4-alkyl esters, carboxamides, open- chain ethers, open-chain and cyclic ketones, alcohols, lactones and aromatics and mixtures thereof. Lubricants and leveling agents (C.5) The group (C.5) of the lubricants and leveling agents includes, for example, silicon-free but also silicon- containing polymers, for example polyacrylates or modified low molecular weight polydialkylsiloxanes. The modification consists in replacing some of the alkyl groups with a wide variety of organic radicals. These organic radicals are, for example, polyethers, polyesters or else long-chain alkyl radicals, the former finding most frequent use. The polyether radicals of the correspondingly modified polysiloxanes are typically formed by means of ethylene oxide and/or propylene oxide units. The higher the proportion of these alkylene oxide units is in the modified polysiloxane, the more hydrophilic is generally the resulting product. Such auxiliaries are obtainable commercially, for example, from Tego as TEGO® Glide 100, TEGO® Glide ZG 400, TEGO® Glide 406, TEGO® Glide 410, TEGO® Glide 411, TEGO® Glide 415, TEGO® Glide 420, TEGO® Glide 435, TEGO® Glide 440, TEGO® Glide 450, TEGO® Glide A 115, TEGO® Glide B 1484 (also usable as a defoamer and deaerating agent), TEGO® Flow ATF, TEGO® Flow ATF2, TEGO® Flow 300, TEGO® Flow 460, TEGO® Flow 425 and TEGO® Flow ZFS 460. The radiation- curable lubricants and leveling agents used, which additionally also serve to improve scratch resistance, can be the products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2300, TEGO® Rad 2500, TEGO® Rad 2600, TEGO® Rad 2700 and TEGO® Twin 4000, likewise obtainable from Tego. Such auxiliaries are obtainable from BYK, for example as BYK®-300, BYK®-306, BYK®-307, BYK®-310, BYK®-320, BYK®-322, BYK®-331, BYK®-333, BYK®-337, BYK®-341, Byk® 354, Byk® 361 N, BYK®- 378 and BYK®-388. The auxiliaries of group (C.5) are typically used in a proportion of from about 0.005 to 1.0% by weight, preferably from about 0.01 to 0.2% by weight, based on the total weight of the liquid-crystalline mixture. BASF SE 240078 19 Component C.10 The nematic liquid crystal composition comprises preferably as component C.10 one, or more compounds C₇-C₁₅-phenylalkyl, R²³ and R²⁴ independently of each other are H, optionally substituted C₆-C₁₀-aryl, 2-,3-,4-pyridyl, 2-,3-furyl or thienyl, COOH, COOR²⁵, CONH₂, CONHR²⁵, CONR²⁵R²⁶, —CN, —COR²⁵, —OCOR²⁵, —OPO(OR²⁵)₂, wherein R²⁵ and R²⁶ are independently of each other C₁-C₈alkyl, or phenyl; tris(2,4-di-tert-butylphenyl) phosphite, tris(nonylphenyl) phosphite, (CH₃)₃C C(CH3)₃ (CH C(CH₃)₃ 3)3C ,

BASF SE 240078 20 C(CH3)3 (CH3)3C O O (BHT; printing, or laser printing. The best resolution is obtained using the screen-printed mask, followed by the plasmonic ink mask and laser printed mask. Despite the lower resolution the laser printed mask has many different gray areas and generates a very detailed L2 picture. The plasmonic ink mask generates a good resolution and enables multi-colors. The mask production is compared to techniques described in the prior much cheaper and offers high flexibility in producing different masks, in particular when using inkjet printing. In addition, the present invention relates to a (security) product obtainable by the process according of the present invention. The element, especially security element, comprises A) a flexible substrate, and B) a color image which is viewable under cross-polarisers, obtained by the process according to the present invention. The security element may comprise one, or more further layers, which are selected from release layers, primer layers, glue layers, substrate layers, black layers, white layers, metallic layers, plasmonic layers, embossed layers with diffractive gratings, micromirrors, lenses, magnetic layers, fluorescent layers, interference layers, colored layers, IR-absorbing layers, IR-transparent layers and conductive layers. The layers might be fully, or partially printed on the security element. BASF SE 240078 21 Accordingly, the present invention provides an optical security element which may be authenticated using the polarised light emitted by LCD based displays, such as laptop screens, computer monitors and televisions, thereby obviating the need for specialist authentication equipment. When illuminated with such polarised light an image will be revealed, thereby authenticating an article of value on or in which the optical security element has been provided. The image could also be personalized for use in identification documents, such as passports and the like. The present invention incorporates both optical security elements suitable for use in transmission and those suitable for use in reflection. When used in transmission, incident linearly polarised light passes through the liquid crystal layer first before passing through the polariser layer, thereby enabling a viewer on the polariser side of the device to view the image. When used in reflection, the light is reflected after passing through the polariser, and travels back through the polariser layer and the liquid crystal layer, such that a viewer on the liquid crystal side of the device may view the image. In addition, a reflective structure of the colored level 2 security element is possible by applying a reflective layer (e.g. a thin layer of aluminum) behind the LC layer. This eliminates the need for linearly polarized light and a polarizer, as described in application WO2019145691A1, and only a polarizer is required to visualize the effect. Another advantage of this structure is that only half of the LC layer thickness is required to achieve the same light retardation (coloration), as the light passes through the LC layer twice. However, a transparent element with the same advantages as described in the above paragraph can be achieved by replacing the aluminum layer with a reflective circular polarizer (e.g. also based on LC). In addition, the present invention is directed to security documents, comprising the security element according to the present invention as a laminate onto the document or embedded as a (windowed) thread into the document or as a window embedded on the document. The security document is preferably a banknote, tax stamp, ID-card, voucher, entrance ticket, or label. Various features and aspects of the present invention are illustrated further in the examples that follow. While these examples are presented to show one skilled in the art how to operate within the scope of this invention, they are not to serve as a limitation on the scope of the invention where such scope is only defined in the claims. Unless otherwise indicated in the following examples and elsewhere in the specification and claims, all parts and percentages are by weight, temperatures are in degrees centigrade and pressures are at or near atmospheric. Examples Example 1 – Colored L2 (Level 2) element produced with different kinds of masks 1a) Masks with different kinds of production are used to generate colored L2 elements: BASF SE 240078 22 i) A plasmonic ink described in Example 3 of WO2022/167377 is applied with a printing press comprising a UV gravure unit on a transparent film to generate negative images (mask i)). ii) A black ink is applied by screen printing on a transparent film to generate negative images (mask ii)). iii) Images (negative in b/w) are printed with a laser printer on an overhead projector foil (mask iii)) 1b) LC Formulation: The LC formulation is prepared by stirring all ingredients at room temperature (23°C) for 1 hour. Compound [g] [% by weight] Cyclopentanone 4.98475 49.8475 Byk® 361 N 0.0025 0.0025 Omnirad® 819 0.15 0.15 LC 1 3.50 35 LC 2 1.50 15 LC 1: compound I.a O O _{O O O} ^O O O _{O O} crosslinked (LED-365nm ^ 60mJ/cm²) from the back side, heated up to 110°C on a hot plate to isotropic phase and finally crosslinked (LED-365nm 2J/cm²). The LC print is transferred using a Delo® Photobond® GB310 adhesive to a glass carrier (not birefringent) and the mask and PET foil are removed. BASF SE 240078 23 Images are taken with polarized light. Reference is made to Fig.2, which shows images obtained by the process of the present invention using different masks i), ii) and iii) (polarizer 90° and 0 °, respectively). In summary, many different colors can be generated depending on UV-dose for pre-crosslinking, the LC printing thickness and the mask layout. Due to the low distance between mask and LC print (~100µm) an excellent resolution can be achieved. The resolution is dependent on the resolution of the mask and the distance between the mask and the liquid crystal layer. Suitable technologies to produce masks are, for example, screen printing, ink-jet printing, laser printing, gravure printing, reverse gravure printing, or flexo printing The best resolution is obtained using the screen-printed mask, followed by the plasmonic ink mask and laser printed mask. Despite the lower resolution the laser printed mask has many different gray areas and generates a very detailed L2-picture. The plasmonic ink mask generates a good resolution and enables multi-colors. The process could also be realized on a roll-to-roll printing apparatus. The mask production is compared to techniques described in the prior much cheaper and offers high flexibility in producing different masks, in particular when using inkjet printing.

Claims

BASF SE 240078 24 Claims 1. A process of manufacturing a product, especially a security product comprising a color image which is viewable under cross-polarisers, comprising a) providing a substrate; b) providing a nematic liquid crystal layer on the substrate; c) illuminating the nematic liquid crystal layer, which is in the nematic phase, through a mask by means of UV/VIS radiation; d) heating the nematic liquid crystal layer above the temperature of the phase transition to the isotropic phase; and e) illuminating the nematic liquid crystal layer, which is in the isotropic phase, with UV/VIS radiation; to obtain the fixed color image, which is viewable under cross-polarisers, wherein the negative image on the mask is produced by ink jet printing, gravure printing, flexo printing, screen printing, or laser printing. wherein the different colors of the color image are caused by two or more regions of different birefringence, which depend on the ratio of nematic and isotropic liquid crystals contained in the region. 2. The process according to claim 1, wherein step b) comprises b1) applying a nematic liquid crystal composition onto the substrate; and b2) drying the nematic liquid crystal layer obtained in step b1). 3. The process according to claim 2, wherein the nematic liquid crystal composition comprises A.1 at least one achiral nematic polymerizable monomer and C.1 at least one photoinitiator, which is an alpha-hydroxy ketone compound of formula O R31 C_C (XI), wherein R29 is hydrogen; R30 is C1-C18alkyl, C1-C12hydroxyalkyl, C1-C18alkoxy, OCH2CH2-OR34, H C CH R R 33 35 CH3 O , BASF SE 240078 25 CH O CH H C C C C OH or R₃₁ is hydroxy; R₃₂ and R₃₃ independently of each other are C₁-C₆alkyl; R₃₄ is hydrogen; R₃₅ is hydrogen, or OR₃₆; R₃₆ is hydrogen, C₁-C₁₂alkyl which optionally is interrupted by one or more non-consecutive O- atoms and which uninterrupted or interrupted C₁-C₁₂alkyl optionally is substituted by one or more OH, R31 O_C R32 ; is interrupted by one or more non-consecutive O; C.5 optionally at least one leveling agent, and C.10 optionally at least one in-can stabilizer, onto the substrate; and b2) drying the nematic liquid crystal layer obtained in step b1). 4. The process according to any of claims 1 to 3, wherein the nematic liquid crystal composition comprises as component A.1 one or more compounds selected from compounds of the general formula Ib, Ib and Ic Rb Rc , H CH3 , A¹, 8 carbon atoms, BASF SE 240078 26 Y¹, Y⁴ are each independently a single chemical bond, oxygen, –CO–, –O–CO– or –CO–O–, R^b is hydrogen, C₁-C₆-alkyl or CO-O-C₁-C₆-alkyl, R^c is hydrogen, or C₁-C₆-alkyl; Rb' , H CH3 , A^1’, 8 carbon atoms, which is optionally interrupted by –CO–O–; Y^1’, Y^4’ are each independently a single chemical bond, oxygen, –CO–, –O–CO– or –CO–O–, R^b’ is hydrogen, C1-C6-alkyl or CO-O-C1-C6-alkyl. 5. The process according to any of claims 1 to 4, wherein the nematic liquid crystal composition comprises as component C.3 one, or more solvents which are selected from the group consisting of C1-C4-alkoxy-C1-C4-alkyl esters, carboxamides, open-chain ethers, open-chain and cyclic ketones, alcohols, lactones and aromatics and mixtures thereof. 6. The process according to any of claims 1 to 5, wherein the nematic liquid crystal composition comprises as component C.10 one, or more compounds selected from compounds of formula other are C1-C18alkyl, C5-C12cycloalkyl, C7-C15-phenylalkyl, R²³ and R²⁴ independently of each other are H, optionally substituted C6-C10-aryl, 2-,3-,4-pyridyl, 2- ,3-furyl or thienyl, COOH, COOR²⁵, CONH2, CONHR²⁵, CONR²⁵R²⁶, —CN, —COR²⁵, —OCOR²⁵, — BASF SE 240078 27 OPO(OR²⁵)₂, wherein R²⁵ and R²⁶ are independently of each other C₁-C₈alkyl, or phenyl; tris(2,4-di- tert-butylphenyl) phosphite, tris(nonylphenyl) phosphite, (CH₃)₃C C(CH3)₃ (CH C(C 3) H 3C ₃)₃ , 7. negative image on the mask is produced by ink jet printing. 8. The process according to claim 7, wherein the image on the mask is produced by screen printing, ink jet printing, or gravure printing a plasmonic ink on the backside of the flexible substrate and the nematic liquid crystal layer, which is in the nematic phase, is illuminated through the mask arranged on the backside of the flexible substrate by means of UV/VIS radiation. BASF SE 240078 28 9. The process according to claim 8, wherein the substrate is a non-birefringent substrate, such as, for example, a TAC (triacetylcellulose) film, or a glass substrate. 10. The process according to any of claims 1 to 7, wherein the substrate is a birefringent flexible substrate, preferably flexible and biaxially oriented substrate such as, for example, a biaxially oriented polyethylene terephthalate (BOPET) film, or a biaxially oriented polypropylene (BOPP) film, and f) the image obtained in step e) is transferred to a non-birefringent substrate, such as, for example, a TAC (triacetylcellulose) film, or a glass substrate. 11. The process according to any of claims 1 to 10, wherein step d) includes heating the nematic liquid crystal layer to a temperature in the range of from 25 to 130°C, especially 40 to 100 °C. 12. The process according to any of claims 1 to 11, wherein a reflective circular polarizer is arranged on the side of the substrate which is opposite to the color image. 13. An element, especially a security element, comprising A) a flexible substrate, and B) a color image which is viewable under cross-polarisers, obtained by the process according to any of claims 1 to 12. 14. The security element according to claim 13, wherein a reflective circular polarizer is arranged between the substrate A) and the color image B). 15. The security element according to claim 14, comprising one, or more further layers, which are selected from release layers, primer layers, glue layers, substrate layers, black layers, white layers, metallic layers, plasmonic layers, embossed layers with diffractive gratings, micromirrors, lenses, magnetic layers, fluorescent layers, interference layers, colored layers, IR-absorbing layers, IR- transparent layers and conductive, wherein the layers might be fully, or partially printed on the security element. 16. A security document, comprising the security element according to any of claims 13 to 15 as a laminate onto the document or embedded as a thread, especially a windowed thread into the document or as a window embedded on the document. 17. The security document according to claim 16, which is a banknote, tax stamp, ID-card, voucher, entrance ticket, or label.