Processes for producing optical effect layers

Abstract

The invention provides a process for producing novel optical effect layers (OELs)

Description

PROCESSES FOR PRODUCING OPTICAL EFFECT LAYERSFIELD OF THE INVENTION

[0001] The present invention relates to the field of security printing processes, as well as security features produced using such security printing processes. In particular, the present invention relates to optical effect layers (OELs), and the use of such OELs as anticounterfeit features on security documents or security articles, as well as for decorative purposes.BACKGROUND OF THE INVENTION

[0002] It is known in the art to use inks, compositions, coatings or layers containing oriented magnetic or magnetizable pigment particles, particularly also optically variable magnetic or magnetizable pigment particles, for the production of security elements, e.g. in the field of security documents. Coatings or layers comprising oriented magnetic or magnetizable pigment particles are disclosed for example in US2,570,856; US3,676,273; US3,791 ,864; US5,630,877; and US5, 364,689. Coatings or layers comprising oriented magnetic color-shifting pigment particles, resulting in particularly appealing optical effects, useful for the protection of security documents, have been disclosed in W02002 / 090002A2 and W02005 / 002866A1 .

[0003] Security features, e.g. for security documents, can generally be classified into “covert” security features on the one hand, and “overt” security features on the other hand. The protection provided by covert security features relies on the principle that such features are difficult to detect, typically requiring specialized equipment and knowledge for detection, whereas “overt” security features rely on the concept of being easily detectable with the unaided human senses, e.g. such features may be visible and / or detectable via the tactile sense while still being difficult to produce and / or to copy. However, the effectiveness of overt security features depends to a great extent on their easy recognition as a security feature.

[0004] Magnetic or magnetizable pigment particles in printing inks or coatings allow for the production of magnetically induced images, designs and / or patterns, which are referred to in the art as “Optical Effect Layers (OELs), through the application of a correspondingly structured magnetic field, inducing a local orientation of the magnetic or magnetizable pigment particles in the not yet hardened (i.e. wet) coating, followed by the hardening of the coating. The result is a fixed and stable magnetically induced image, design or pattern. Materials and technologies for the orientation of magnetic or magnetizable pigment particles in coating compositions are known. The magnetically induced images in question can only be produced by having access to both, the magnetic or magnetizable pigment particles or the corresponding ink, and the particular technology employed to print said ink and to orient said pigment in the printed ink.

[0005] With the aim of optimizing and increasing the counterfeiting resistance of security documents, in particular banknotes, striking and sophisticated magnetically induced images and optical effects layers (OELs) have been developed. Said OELs are obtained by using specific magnetic assemblies and advantageously exhibit a dynamic appearance upon tilting. Examples of such dynamic OELs include reflection zone bars moving as the OEL is tilted, loop-shaped bodies moving as the OEL istilted, loop-shaped bodies having a varying shape as the OEL is tilted, bright areas and dark areas moving as the OEL is tilted. W02012 / 104098A1 discloses OELs comprising more than one magnetically induced images, each image having a different magnetic orientation pattern. W02012 / 104098A1 discloses an OEL comprising two areas, each one exhibiting a reflection zone bar moving as the OEL is tilted, one of said bar moving away the observer upon tilting of the OEL and the other said bar moving towards the observer upon tilting of the OEL.

[0006] Processes for producing OELs comprising at least two areas made of a single cured layer, comprises i) applying on the substrate a UV curable ink comprising magnetic or magnetizable particles to form a coating layer; ii) exposing the coating layer to the magnetic field of a magnetic-field-generating device, thereby orienting the pigment particles, iii) curing one or more first areas of the coating layer to a second state to fix the magnetic or magnetizable particles in their adopted positions and orientations, said curing being performed by selectively irradiating the coating layer with a radiation source; iv) exposing the coating layer to the magnetic field of a magnetic-field-generating device thereby reorienting the magnetic or magnetizable particles which are comprised in the coating layer still being in a wet, liquid state and not yet-cured due to the selective curing of step iii) and v) curing the coating layer to fix the magnetic or magnetizable particles in their new adopted positions and orientations.

[0007] It is known in the art of curing a coating or ink composition for producing OELs with the help of a UV radiation source, that the characteristics and the construction of the UV irradiation source and the precise exposure conditions of the coating or ink composition to the UV radiation source are crucial for obtaining a high-resolution image and a fast curing of the composition. However, known methods for selective curing suffer from several drawbacks.

[0008] A method includes the use of fixed photomasks including one or more voids corresponding to a pattern to be formed as a part of an image on the coating layer being carried by the fixed substrate is disclosed. However, the disclosed method may result in the potential creation of shadow effects on the coating layer due to the constraints that a) the photomask may not touch the not yet cured ink layer, but must be disposed at a certain distance from it, and that b) the UV-source is necessarily an extended light source. All of these resulting in low-resolution images and require operation at low printing speeds due to the need for keeping in a fixed constellation the substrate, the photomask, and the UV-source during the exposure time. Alternatively, a fixed photomask may be used with a coating layer being carried by a moving substrate. Said method may also result in the production of shadow effects on the coating layer and / or image blurring due to a substrate movement at industrial speeds during exposition to irradiation, without any possibility to implement a variable image information during printing. Alternatively, a moving photomask may be used with a moving substrate. However, said method may also result in the production of shadow effects on the coating layer resulting in a low-resolution imaging and would be highly complex to implement.

[0009] Another method uses laser beams. However, said method is known to require highly special equipments and high costs.

[0010] Another method uses LED Light Emitting Diode (LED) arrays. However, this method may suffer from unnecessary losses of light density resulting in longer curing times and degrading the printing performance.[Oil] A need remains for improved and controlled processes for producing eye-catching optical effect layers (OELs) for security printers at industrial speed, wherein said so-produced OELs are easily authenticated by the person in the street while said processes are highly difficult to be implemented on a mass-scale production by counterfeiters and the illicit market.SUMMARY OF THE INVENTION

[0012] In a first aspect, the invention provides a process for producing an optical effect layer (OEL) on a substrate (220), said optical effect layer (OEL) comprising a first motif comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a first magnetic pattern and a last motif comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment, which first and last motifs together form a composite motif, said process comprising: a) applying onto the substrate (220) a first radiation-curable coating composition, preferably a first UV-Vis-curable curable coating composition, exhibiting a color and comprising the platelet-shaped magnetic or magnetizable pigment particles to form a first coating layer (210) on said substrate (220), said coating composition being in a first state, b) exposing the first radiation-curable coating composition of step a) to a magnetic field of a magnetic assembly (230) to magnetically orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles; c) at least partially curing the first radiation-curable coating composition of step b) to a second state to fix the platelet-shaped magnetic or magnetizable pigment particles in their adopted positions and orientations and to produce the first motif; d) applying in register a last radiation-curable coating composition, preferably a last UV-Vis- curable curable coating composition, said last radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment and not comprising platelet-shaped magnetic or magnetizable pigment particles, and said last radiation- curable coating composition at least partially covering the first motif, to form a last coating layer (211) on said substrate (220), said last coating composition being in a first state; e) curing the last radiation-curable coating composition of step d) to produce the last motif.

[0013] In a second aspect, the invention provides an optical effect layer comprising: a first motif composed of a coating layer comprising platelet-shaped magnetic or magnetizable pigment particles suspended in a polymerized vehicle, wherein the platelet-shaped magnetic or magnetizable pigment particles are permanently oriented according to a predetermined orientation; ii) a last motif, at least partially visually superposed on the first motif, the last motif composed of a coating layer comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment, in a polymerized vehicle, and not comprising platelet-shaped magnetic or magnetizable pigment particles.

[0014] In a third aspect, the invention provides an OEL obtainable by or obtained by the process of the invention.DETAILED DESCRIPTIONBRIEF DESCRIPTION OF THE DRAWINGSFig. 1 depicts schematically a platelet-shaped pigment particle.Fig. 2 depicts schematically an embodiment of the process of the invention.Fig. 3 depicts the creation of a composite motif (C) from a first motif (A) and a second motif (B) printed in register.Fig. 4 depicts schematically an embodiment of the process of the invention.Fig. 5 depicts the creation of a composite motif (D) from a first motif (A), a second motif (B) and a third motif (C) printed in register.Fig. 6 depicts schematically an embodiment of the process of the invention.Fig. 7 depicts schematically a process and apparatus for carrying out one-step magnetic orientation [step b)].Fig. 8 depicts schematically a process and apparatus for carrying out two-step magnetic orientation [step b)].Fig. 9A shows the screens used to print in register the first and last motifs of Examples E1-E14. Each screen produces a component motif, which when combined produce a composite motif, in the form of a hot-air balloon. Fig. 9B shows the tilting of the substrate in the Examples to observe the angledependent color shifts. Fig. 9C shows OELs resulting from the process of the invention, for each of Examples E2 and E7.Fig. 10 depicts schematically a magnetic assembly suitable for bi-axially orienting magnetic pigment particles.Fig. 11 depicts schematically a magnetic assembly used in Examples provided therein and being suitable for producing a motif exhibiting a dynamic effect / motion upon tilting, said dynamic movement being a bright reflective bar moving when the motif is tilted.Fig. 12 depicts examples of OELs independently comprising a substrate (220), a layer made of a first radiation-curable coating composition comprising platelet-shaped magnetic or magnetizable pigment particles (210), a coating layer made of a radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment (211), optionally a layer made of a second radiation-curable coating composition comprising plateletshaped magnetic or magnetizable pigment particles (210’) and optionally a layer made of a second radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment (211 ’).Definitions

[0015] As used herein, the article "a" indicates one as well as more than one and does not necessarily limit its referent noun to the singular.

[0016] As used herein, the term “about” means that the amount or value in question may be the value designated or some other value about the same. The phrases are intended to convey that similar values within a range of ± 5% of the indicated value promote equivalent results or effects according to the invention.

[0017] The term “UV” (ultraviolet) as used herein is intended to mean radiation having a wavelength component in the UV part of the electromagnetic spectrum; typically from 200 nm to 420 nm.

[0018] The term “UV-VIS” as used herein is intended to mean irradiation having a wavelength component in the ultraviolet and / or visible part of the electromagnetic spectrum; typically from 200 nm to 800 nm.

[0019] As used herein, the term “at least one” is meant to define one or more than one, for example one or two or three.

[0020] As used herein, the term “and / or” means that either all or only one of the elements of said group may be present. For example, “A and / or B” shall mean “only A, or only B, or both A and B”. In the case of “only A”, the term also covers the possibility that B is absent, i.e. “only A, but not B”.

[0021] The term “comprising” as used herein is intended to be non-exclusive and open-ended. Thus, for instance a coating composition comprising a compound A may include other compounds besides A. However, the term “comprising” also covers, as a particular embodiment thereof, the more restrictive meanings of “consisting essentially of’ and “consisting of’, so that for instance “a fountain solution comprising A, B and optionally C” may also (essentially) consist of A and B, or (essentially) consist of A, B and C.

[0022] Where the present description refers to “preferred” embodiments / features, combinations of these “preferred” embodiments / features shall also be deemed as disclosed as long as this combination of “preferred” embodiments / features is technically meaningful.

[0023] The term “acrylate” encompasses molecules bearing acrylate and / or (meth)acrylate moieties.

[0024] The term “optical effect layer (OEL)” as used herein denotes a coating or layer that comprises oriented platelet-shaped magnetic or magnetizable pigment particles and a binder, wherein said platelet-shaped magnetic or magnetizable pigment particles are oriented by a magnetic field and wherein the oriented platelet-shaped magnetic or magnetizable pigment particles are fixed / frozen in their orientation and position (i.e. after hardening / curing) to form a magnetically induced image.

[0025] The term "coating composition" refers to any composition which is capable of forming an optical effect layer (OEL) on a solid substrate and which can be applied preferably but not exclusively by a printing method. The coating composition comprises the platelet-shaped magnetic or magnetizable pigment particles and the binder, and / or the at least one color-constant dye and / or at least one colorconstant pigment and / or at least one iridescent pigment .

[0026] The term "security document" refers to a document which is usually protected against counterfeit or fraud by at least one security feature. Examples of security documents include without limitation value documents and value commercial goods.

[0027] The term “security feature” is used to denote an image, pattern or graphic element that can be used for authentication purposes.

[0028] The expression “visible range” means 400-800 nm.

[0029] The inventors have created novel optical effect layers (OELs) using a process in which a radiation-curable coating composition, preferably a UV-Vis-curable coating composition, comprising platelet-shaped magnetic or magnetizable pigment particles is applied, preferably printed, in register with a radiation-curable coating composition, preferably a UV-Vis-curable coating composition,comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment and lacking platelet-shaped magnetic or magnetizable pigment particles to create visually appealing composite motifs, which can be readily evaluated by the naked eye to authenticate documents or articles bearing the OELs.

[0030] The present invention provides processes for producing optical effect layers (OELs) that are suitable as security features against counterfeit or fraud and which comprise magnetically oriented platelet-shaped magnetic or magnetizable pigment particles on a substrate. As shown in Fig. 3, the OELs comprise a first motif (in the form of a cured first coating layer 210) comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a first magnetic pattern and a second motif (in the form of a cured second coating layer 211 ’) comprising the at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment, wherein said second motif at least partially overlaps and is applied in register with said first motif. The expression “register” as used herein is defined as follows:

[0031] “Register” means that when two or more component motifs of a Designed Motif are applied and together form a composite motif, the composite motif reproduces the Designed Motif with a deviation of less than 1 mm, preferably less than 0.5 mm, more preferably less than or equal to 0.2 mm.

[0032] “Designed Motif’ means a motif as designed, which motif can be broken down into component motifs.

[0033] The process of the invention comprises at least two sets of steps, i.e. a first set comprising steps a), b) and c) in which a first motif is created comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a first magnetic pattern, and at least a second set comprising steps d) and e), in which a last motif is created comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment, and in which the last motif at least partially overlaps the first motif. The coating composition comprising the at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment is preferably chosen such that it has a minimum light transmission of at least 10% over the visible range, more preferably it has a minimum light transmission of 20%, more particularly 30%, over the visible range. The light transmission will be primarily a function of:1. The pigment or dye chosen;2. The concentration of the pigment or dye;3. The thickness of the coating layer.

[0034] Preferably the thickness of the coating layer or layers (211) comprising the at least one colorconstant dye and / or at least one color-constant pigment and / or at least one iridescent pigment is in the range of at or about 10-40 pm, particularly preferably in the range of at or about 15-25 pm.

[0035] Preferably the concentration of the at least one color-constant dye in the radiation-curable coating compositions is from at or about 0.25 to at or about 25 wt%, more preferably at or about 0.25 to at or about 15 wt%, particularly preferably at or about 0.25 to at or about 10 wt%, based on the total weight of the coating composition.

[0036] Preferably the concentration of the at least one color-constant pigment in the radiation-curable coating compositions is in the range of at or about 0.25 to at or about 15 wt%, more preferably at orabout 0.25 to at or about 8 wt%, particularly preferably at or about 0.25 to at or about 5 wt%, based on the total weight of the coating composition.

[0037] Preferably the concentration of the at least one iridescent pigment in the radiation-curable coating compositions is in the range of at or about 2 to at or about 40 wt%, more preferably at or about 5 to at or about 30 wt%, particularly preferably at or about 5 to at or about 20 wt%, based on the total weight of the coating composition.

[0038] In another embodiment, the pigment is Pigment Blue 15:3. In a particularly preferred embodiment, the pigment is Pigment Blue 15:3, at a concentration of 0.25 to 6 wt%, based on the total weight of the coating composition. In a more particularly preferred embodiment, the pigment is Pigment Blue 15:3, at a concentration of 0.25 to 6 wt%, based on the total weight of the coating composition, and the thickness of the coating layer is 15-25 pm.

[0039] The process of the invention is a continuous process meaning that steps d) and e) are carried out directly after steps a), b) and c), and the substrate (220) carrying the first coating layer (210) is not removed from the printing machine, i.e. is continuously fed, to carry out the following steps, using a single machine, said machine allowing the application, preferably printing, of coating compositions, the exposure of said compositions to magnetic fields and the at least partial curing of said compositions, said process allowing the preparation of OELs comprising the first motif and the last motif (optionally additional motifs) wherein the first and last (and any other component motifs) are in register.

[0040] In another embodiment, the process of the invention comprises steps a), b) and c) in which a first motif is created comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a first magnetic pattern, steps a’), b’) and c’) in which a second motif is created comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a second magnetic pattern, and steps d) and e), in which a last motif is created comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment, and in which the last motif at least partially overlaps the first motif and / or second motifs.

[0041] In another embodiment, the process of the invention comprises steps a), b) and c) in which a first motif is created comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a first magnetic pattern, steps a’), b’) and c’) in which a second motif is created comprising platelet-shaped magnetic or magnetizable pigment particles different from those in steps a), b) and c) and oriented according to the first magnetic pattern or oriented according to a second magnetic pattern, and steps d) and e), in which a last motif is created comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment, and in which the last motif at least partially overlaps the first motif and / or second motifs.

[0042] In another embodiment, the process of the invention comprises steps a), b) and c) in which a first motif is created comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a first magnetic pattern, steps d) and e), in which a second motif is created comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment, steps d’) and e’), in which a last motif is created comprising at least one color-constant pigment or dye and in which the second and last motifs at least partially overlap the first motif.

[0043] References to features and preferred features of steps a), b), c), d) and e) are understood toapply equally and independently to steps a’), b’), c’), d’) and e’), steps a”), b”), c”), d”) and e”), steps a’”), b’”), c’”), d’”) and e’”), and so on.

[0044] It will be understood by one of skill in the art that the different steps of the process of the invention can be combined in any number of fashions, provided coating layers comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment t at least partially overlap and are in register with coating layers comprising platelet-shaped magnetic or magnetizable pigment particles.

[0045] Some exemplary embodiments are described with reference to the Figures.

[0046] Referring to Fig. 2: step a): a screen (290) having the first motif is used to print the first radiation-curable coating composition comprising platelet-shaped magnetic or magnetizable pigment particles onto the substrate (220), to form the first coating layer (210); step b1): the first coating layer (210) is exposed to a first magnetic assembly (230) to bi-axially orient the pigment particles; step b2): the first coating layer (210) is optionally exposed to a second magnetic assembly (240) to reorient the particles in a design-specific manner; step c): the first coating layer (210) having specifically oriented pigment particles is cured by exposure to radiation of a curing unit (250) to form the first motif. In a preferred embodiment, the curing is carried out without removing the substrate (220) from the influence of the first (230) or second (240) magnetic assembly, i.e. step c) is carried out partially simultaneously with, step b); step d): a screen (291) having the last motif is used to print in register the last radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment onto the substrate (220), to form the last coating layer (211); and step e): the last coating layer (211) is cured by exposure to radiation of a curing unit (250’) to form the last motif. In the embodiment depicted in Fig. 2, the last motif is printed in register entirely on top of the first motif, but not entirely covering it.

[0047] Fig.3 depicts the creation of a composite motif (C) of a hot air balloon on substrate (220), formed from a first motif (A) of the first coating layer (210) and a last motif (B) as the last coating layer (211). Fig.3 shows two variants: variant I, in which the first and last coating layers are applied on the same side of substrate (220), and variant II, in which the first and last coating layers are applied on opposite sides of the substrate (220). For variant II, the substrate (220) is preferably at least partially transparent.

[0048] Fig.4 depicts an embodiment of the process of the invention in which two coating layers (210 and 210’) comprising platelet-shaped magnetic or magnetizable pigment particles are used, followed by the last coating layer (211) comprising at least one color-constant dye and / or at least one colorconstant pigment and / or at least one iridescent pigment. In step a) a screen (290) bearing a first motif is used to print a first motif using a radiation-curable coating composition comprising platelet-shaped magnetic or magnetizable pigment particles onto the substrate (220), to form the first coating layer (210). In step b) the first coating layer (210) is exposed to a magnetic assembly (230) to magnetically orient the pigment particles. In step c) the first coating layer (210) having specifically oriented pigment particles is cured by exposure to radiation of a curing unit (250) to form the first motif. In a preferredembodiment, the curing is carried out without removing the substrate (220) from the influence of the magnetic assembly (230). In step a’) a screen (290’) bearing a second motif is used to print in register a second motif using a second radiation-curable coating composition comprising platelet-shaped magnetic or magnetizable pigment particles onto the substrate (220), to form a second coating layer (210’). In step b’) the second coating layer (210’) is exposed to a second magnetic assembly (230’) to magnetically orient the pigment particles. The orientation in steps b) and b’) may be the same or different. In step c’), the second coating layer (210’) having specifically oriented pigment particles is cured by exposure to radiation of a curing unit (250’) to form the second motif. In a preferred embodiment, the curing is carried out without removing the substrate (220) from the influence of the magnetic assembly (230’). In this embodiment, the first (210) and second (210’) coating layers comprising platelet-shaped magnetic or magnetizable particles can differ in several ways, for example:1 . they may comprise different platelet-shaped magnetic or magnetizable pigment particles;2. they may be of different color;3. they may have different coating compositions in terms of binders and / or additives;4. the magnetic orientations in the two coating layers may be different; or5. any combination of 1-4.

[0049] In step d), a screen (291) bearing a last motif is used to print in register the last motif using a radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment onto the substrate (220), to form a last coating layer (211). In step e) the last coating layer is cured by exposure to radiation of a curing unit (250”) to form the last motif.

[0050] Another variation is depicted schematically in Fig.5. A first motif (A, 210) is applied using a first radiation-curable coating composition comprising platelet-shaped magnetic or magnetizable pigment particles. After orienting and curing of the first coating layer, a second motif (B, 211) is applied in register using a second radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment. This second coating composition is cured to form a second coating layer. After curing of the second coating layer, a last motif (C, 21 T) is applied in register using a radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment onto the substrate, to form a last coating layer (21 T). Finally, the last coating layer (21 T) is cured by exposure to radiation to form the last motif. Together the first, second and last motifs form a composite motif (D), in this case in the form of a hot air balloon. According to variant I, the first (210), second (211) and last (21 T) coating layers are all applied on the same side of the substrate (220). According to variant II, the first (210) coating layer is applied on one side of the substrate (220), and the second (211) and last (211 ’) coating layers are applied in register on the opposite side of the substrate. According to variant III, the first (210) coating layer is applied on one side of the substrate (220), the second (211) is applied in register overtop of it, and the last coating layer (21 T) is applied in register on the opposite side of the substrate (220). For variants II and III the substrate is preferably at least partially transparent.

[0051] Alternatively (and not shown in the figures), the first (210) and the last (211 ’) coating layers are applied on one side of the substrate (220) and the second (211) coating layer is applied in register onthe opposite side of the substrate (220).

[0052] Fig.6 depicts an embodiment in which two coating layers comprising platelet-shaped magnetic or magnetizable pigment particles are applied, followed by two coating layers comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment. A first motif (A, 210) is applied using a first radiation-curable coating composition comprising plateletshaped magnetic or magnetizable pigment particles. After orienting and curing of the first coating layer, a second motif (B, 210’) is applied in register using a radiation-curable coating composition comprising platelet-shaped magnetic or magnetizable pigment particles. This second coating composition is oriented and cured to form a second coating layer. The first (210) and second (210’) coating layers comprising platelet-shaped magnetic or magnetizable particles can differ in several ways, for example:1 . they may comprise different platelet-shaped magnetic or magnetizable pigment particles;2. they may be of different color;3. they may have different coating compositions in terms of binders and / or additives;4. the magnetic orientations in the two coating layers may be different; or5. any combination of 1-4.

[0053] A third motif (C, 211) is applied in register using a radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment onto the substrate, and cured to form a third motif (211). Finally, a last coating layer (D, 21 T) comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment is printed in register and is cured by exposure to radiation to form the last motif. Togetherthe first (A), second (B), third (C) and last (D) motifs form a composite motif (E), in this case in the form of a hot air balloon. According to variant I, the first (210), second (210’), third (211) and last (21 T) coating layers are all printed in register on the same side of the substrate (220). According to variant II, the first coating layer (210) is printed on one side of the substrate (220), and the second coating layer (210’) is printed in register on the opposite side of the substrate. Color-constant coating layer (211) is printed in register overtop of coating layer (210), and color-constant coating layer (21 T) is printed in register overtop of coating layer (210’). For variant II, the substrate (220) is preferably at least partially transparent.

[0054] Preferably, steps a) and d) are independently carried out by a printing process, preferably independently selected from the group consisting of screen-printing, rotogravure printing, flexography printing and intaglio printing (also referred in the art as engraved copper plate printing and engraved steel die printing), more preferably selected from the group consisting of screen-printing, rotogravure printing and flexography printing and still more preferably by screen-printing.

[0055] Screen-printing (also referred in the art as silkscreen-printing) is a stencil process wherein an ink is transferred to a surface through a stencil supported by a fine fabric mesh of silk, mono- or multifilaments made of synthetic fibers such as for example polyamides or polyesters or metal threads stretched tightly on a frame made for example of wood or metal (e.g. aluminum or stainless steel). Alternatively, the screen-printing mesh may be a chemically etched, a laser-etched, or a galvanically formed porous metal foil, e.g. a stainless steel foil. The pores of the mesh are blocked in the non-image areas and left open in the image area, the image carrier being called the screen. Screen-printing mightbe of the flat-bed or rotary type. Screen-printing is further described for example in The Printing ink manual, R.H. Leach and R.J. Pierce, Springer Edition, 5th Edition, pages 58-62 and in Printing Technology, J.M. Adams and P.A. Dolin, Delmar Thomson Learning, 5th Edition, pages 293-328.

[0056] Rotogravure (also referred in the art as gravure) is a printing process wherein the image elements are engraved into the surface of a cylinder. The non-image areas are at a constant original level. Prior to printing, the entire printing plate (non-printing and printing elements) is inked and flooded with ink. Ink is removed from the non-image by a wiper or a blade before printing, so that ink remains only in the cells. The image is transferred from the cells to the substrate by a pressure typically in the range of 2 to 4 bars and by the adhesive forces between the substrate and the ink. The term rotogravure does not encompass intaglio printing processes (also referred in the art as engraved steel die or copper plate printing processes) which rely for example on a different type of ink. More details are provided in “Handbook of print media”, Helmut Kipphan, Springer Edition, page 48 and in The Printing ink manual, R.H. Leach and R.J. Pierce, Springer Edition, 5th Edition, pages 42-51.

[0057] Flexography preferably uses a unit with a doctor blade, preferably a chambered doctor blade, an anilox roller and plate cylinder. The anilox roller advantageously has small cells whose volume and / or density determines the ink application rate. The doctor blade lies against the anilox roller, and scrapes off surplus ink at the same time. The anilox roller transfers the ink to the plate cylinder which finally transfers the ink to the substrate. Specific design might be achieved using a designed photopolymer plate. Plate cylinders can be made from polymeric or elastomeric materials. Polymers are mainly used as photopolymer in plates and sometimes as a seamless coating on a sleeve. Photopolymer plates are made from light-sensitive polymers that are hardened by ultraviolet (UV) light. Photopolymer plates are cut to the required size and placed in an UV light exposure unit. One side of the plate is completely exposed to UV light to harden or cure the base of the plate. The plate is then turned over, a negative of the job is mounted over the uncured side and the plate is further exposed to UV light. This hardens the plate in the image areas. The plate is then processed to remove the unhardened photopolymer from the nonimage areas, which lowers the plate surface in these nonimage areas. After processing, the plate is dried and given a post-exposure dose of UV light to cure the whole plate. Preparation of plate cylinders for flexography is described in Printing Technology, J. M. Adams and P.A. Dolin, Delmar Thomson Learning, 5th Edition, pages 359-360 and in The Printing ink manual, R.H. Leach and R.J. Pierce, Springer Edition, 5th Edition, pages 33-42.

[0058] The first radiation-curable coating composition as well as the first coating layer (210) comprise platelet-shaped magnetic or magnetizable pigment particles. In contrast to needle-shaped pigment particles which can be considered as quasi one-dimensional particles, platelet-shaped pigment particles are quasi two-dimensional particles due to the large aspect ratio of their dimensions. As shown in Fig. 1 , platelet-shaped pigment particle can be considered as having a two-dimensional structure wherein the dimensions X and Y are substantially larger than the dimension Z. Platelet-shaped pigment particles are also referred to in the art as oblate particles or flakes. Such pigment particles may be described with a main axis X corresponding to their longest dimension crossing the pigment particle and a second axis Y perpendicular to X and corresponding to the second longest dimension crossing the pigment particle. In other words, the XY plane roughly defines the plane formed by the first and second longestdimensions of the pigment particle, the Z dimension being ignored.

[0059] The first and last radiation-curable coating compositions are independently applied during steps a) and d) thus forming the first coating layer (210) and the last coating layer (211), respectively. The first and last radiation-curable coating compositions preferably independently comprise a binder and the platelet-shaped magnetic or magnetizable pigment particles, or a color-constant dye and / or a colorconstant pigment and / or an iridescent pigment, respectively.

[0060] The platelet-shaped magnetic or magnetizable pigment particles have, due to their non- spherical shape, non-isotropic reflectivity with respect to incident electromagnetic radiation for which the hardened / cured binder material is at least partially transparent. As used herein, the term “non- isotropic reflectivity” denotes that the proportion of incident radiation from a first angle that is reflected by a particle into a certain (viewing) direction (a second angle) is a function of the orientation of the particles, i.e. that a change of the orientation of the particle with respect to the first angle can lead to a different magnitude of the reflection to the viewing direction.

[0061] In the first motif of the OELs of the invention, the platelet-shaped magnetic or magnetizable pigment particles are dispersed in the first coating layer (210). The first coating layer comprises a hardened binder material that fixes the orientation of the platelet-shaped magnetic or magnetizable pigment particles. The binder material is at least in its hardened or solid state (also referred to as second state herein), and is at least partially transparent to electromagnetic radiation of a range of wavelengths comprised between 200 nm and 2,500 nm, i.e. within the wavelength range which is typically referred to as the “optical spectrum” and which comprises infrared, visible and UV portions of the electromagnetic spectrum. Accordingly, the particles contained in the binder material in its hardened or solid state and their orientation-dependent reflectivity can be perceived through the binder material at some wavelengths within this range. Preferably, the hardened binder material is at least partially transparent to electromagnetic radiation of a range of wavelengths comprised between 200 nm and 800 nm, more preferably comprised between 400 nm and 700 nm. Herein, the term “transparent” denotes that the transmission of electromagnetic radiation through a layer of 20 pm of the hardened binder material as present in the OEL (not including the platelet-shaped magnetic or magnetizable pigment particles, but all other optional components of the OEL in case such components are present) is at least 50%, more preferably at least 60 %, even more preferably at least 70%, at the wavelength(s) concerned. This can be determined for example by measuring the transmittance of a test piece of the hardened binder material (not including the platelet-shaped magnetic or magnetizable pigment particles) in accordance with well-established test methods, e.g. DIN 5036-3 (1979-11).

[0062] The platelet-shaped magnetic or magnetizable pigment particles are defined as having, due to their non-spherical shape, non-isotropic reflectivity with respect to an incident electromagnetic radiation for which the cured binder material is at least partially transparent. As used herein, the term “non- isotropic reflectivity” denotes that the proportion of incident radiation from a first angle that is reflected by a particle into a certain (viewing) direction (a second angle) is a function of the orientation of the particles, i.e. that a change of the orientation of the particle with respect to the first angle can lead to a different magnitude of the reflection to the viewing direction. Preferably, the platelet-shaped magnetic or magnetizable pigment particles have a non-isotropic reflectivity with respect to incidentelectromagnetic radiation in some parts or in the complete wavelength range of from about 200 to about 2500 nm, more preferably from about 400 to about 700 nm, such that a change of the particle’s orientation results in a change of reflection by that particle into a certain direction. As known by the man skilled in the art, the magnetic or magnetizable pigment particles are different from conventional pigments and different for the constant dye, color-constant pigment and iridescent pigments, in that said conventional pigment particles exhibit the same color and reflectivity, independent of the particle orientation, whereas the magnetic or magnetizable pigment particles exhibit either a reflection or a color, or both, that depend on the particle orientation.

[0063] The first radiation-curable coating composition as well as the first coating layer (210) comprise the platelet-shaped magnetic or magnetizable pigment particles preferably in an amount from about 1 wt.% and about 40 wt.%, preferably between about 3 wt.% and about 35 wt.%, more preferably between about 5 wt.% and about 30 wt.%, the weight percentages being based on the total weight of the radiation-curable coating composition or the coating layer.

[0064] Suitable examples of platelet-shaped magnetic or magnetizable pigment particles include without limitation pigment particles comprising a magnetic metal selected from the group consisting of cobalt (Co), iron (Fe), and nickel (Ni); a magnetic alloy of iron, manganese, cobalt, nickel or a mixture of two or more thereof; a magnetic oxide of chromium, manganese, cobalt, iron, nickel or a mixture of two or more thereof; or a mixture of two or more thereof. The term “magnetic” in reference to the metals, alloys and oxides is directed to ferromagnetic or ferrimagnetic metals, alloys and oxides. Magnetic oxides of chromium, manganese, cobalt, iron, nickel or a mixture of two or more thereof may be pure or mixed oxides. Examples of magnetic oxides include without limitation iron oxides such as hematite (Fe2O3), magnetite (Fe3O4), chromium dioxide (CrO2), magnetic ferrites (MFe2O4), magnetic spinels (MR2O4), magnetic hexaferrites (MFe12O19), magnetic orthoferrites (RFeO3), magnetic garnets M3R2(AO4)3, wherein M stands for two-valent metal, R stands for three-valent metal, and A stands for four-valent metal.

[0065] Examples of platelet-shaped magnetic or magnetizable pigment particles include without limitation pigment particles comprising a magnetic layer M made from one or more of a magnetic metal such as cobalt (Co), iron (Fe), or nickel (Ni); and a magnetic alloy of iron, cobalt or nickel, wherein said magnetic or magnetizable pigment particles may be multilayered structures comprising one or more additional layers. Preferably, the one or more additional layers are layers A independently made from one or more selected from the group consisting of metal fluorides such as magnesium fluoride (MgF2), silicon oxide (SiO), silicon dioxide (SiO2), titanium oxide (TiO2), and aluminum oxide (AI2O3), more preferably silicon dioxide (SiO2); or layers B independently made from one or more selected from the group consisting of metals and metal alloys, preferably selected from the group consisting of reflective metals and reflective metal alloys, and more preferably selected from the group consisting of silver (Ag), aluminum (Al), chromium (Cr), and nickel (Ni), and still more preferably aluminum (Al); or a combination of one or more layers A such as those described hereabove and one or more layers B such as those described hereabove. Typical examples of the platelet-shaped magnetic or magnetizable pigment particles being multilayered structures described hereabove include without limitation A / M multilayer structures, A / M / A multilayer structures, A / M / B multilayer structures, A / B / M / A multilayer structures,A / B / M / B multilayer structures, A / B / M / B / A / multilayer structures, B / M multilayer structures, B / M / B multilayer structures, M / A / M multilayer structures, B / A / M / A multilayer structures, B / A / M / B multilayer structures, B / A / M / B / A multilayer structures, B / A / M / A / B multilayer structures, B / A / B / A / M / A / B / A / B multilayer structures, A / B / A / B / A / M / A / B / A / B / A multilayer structures, wherein the layers A, the magnetic layers M and the layers B are chosen from those described hereabove.

[0066] The radiation-curable coating composition may comprise platelet-shaped optically variable magnetic or magnetizable pigment particles, and / or platelet-shaped magnetic or magnetizable pigment particles having no optically variable properties. Preferably, at least a part of the platelet-shaped magnetic or magnetizable pigment particles is constituted by platelet-shaped optically variable magnetic or magnetizable pigment particles. In addition to the overt security provided by the color-shifting property of the optically variable magnetic or magnetizable pigment particles, which allows easy detection, recognition and / or discrimination of an article or security document carrying an ink, coating composition, or coating layer comprising the optically variable magnetic or magnetizable pigment particles from their possible counterfeits using the unaided human senses, the optical properties of the optically variable magnetic or magnetizable pigment particles may also be used as a machine readable tool for the recognition of the OEL. Thus, the optical properties of the optically variable magnetic or magnetizable pigment particles may simultaneously be used as a covert or semi-covert security feature in an authentication process wherein the optical (e.g. spectral) properties of the pigment particles are analyzed and thus increase the counterfeiting resistance.

[0067] The use of platelet-shaped optically variable magnetic or magnetizable pigment particles in coating layers for producing an OEL enhances the significance of the OEL as a security feature in security document applications, because such materials are reserved to the security document printing industry and are not commercially available to the public.

[0068] As mentioned above, preferably at least a part of the platelet-shaped magnetic or magnetizable pigment particles is constituted by platelet-shaped optically variable magnetic or magnetizable pigment particles. These are more preferably selected from the group consisting of platelet-shaped magnetic thin-film interference pigment particles, platelet-shaped interference coated pigment particles.

[0069] Magnetic thin film interference pigment particles are known to those skilled in the art and are disclosed e.g. in US4,838,648; W02002 / 073250A2; EP0686675B1 ; W02003 / 000801A2; US6,838,166; WO2007 / 131833A1 ; EP2402401 B1 ; WO2019 / 103937A1 ; EP3587500A1 ,EP3587501A1 , EP3587502A1 , EP3587503A1 , W02020 / 006286A1 , W02020 / 131700A1 ,US2021 / 0101402, US2021 / 038812, US2022 / 0282094, and in the documents cited therein. Preferably, the magnetic thin film interference pigment particles comprise pigment particles having a five-layer Fabry-Perot multilayer structure and / or pigment particles having a six-layer Fabry-Perot multilayer structure and / or pigment particles having a seven-layer Fabry-Perot multilayer structure and / or pigment particles having a nine-layer Fabry-Perot multilayer structure and / or pigment particles having an elevenlayer Fabry-Perot multilayer structure and / or pigment particles having a multilayer structure combining one or more multilayer Fabry-Perot structures.

[0070] Preferred five-layer Fabry-Perot multilayer structures consist of absorber / dielectric / reflector / dielectric / absorber multilayer structures wherein the reflector and / or theabsorber is also a magnetic layer, preferably the reflector and / or the absorber is a magnetic layer comprising nickel, iron and / or cobalt, and / or a magnetic alloy comprising nickel, iron and / or cobalt and / or a magnetic oxide comprising nickel (Ni), iron (Fe) and / or cobalt (Co).

[0071] Further preferred five-layer Fabry-Perot multilayer structures consist of dielec- tric / reflector / magnetic / reflector / dielectric multilayer structures.

[0072] Preferred six-layer Fabry-Perot multilayer structures consist of absorb- er / dielectric / reflector / magnetic / dielectric / absorber multilayer structures.

[0073] Preferred seven-layer Fabry Perot multilayer structures consist of absorb- er / dielectric / reflector / magnetic / reflector / dielectric / absorber multilayer structures such as disclosed in US 4,838,648.

[0074] Preferred nine-layer Fabry-Perot multilayer structures consist of dielec- tric / absorber / dielectric / reflector / magnetic / dielectric / absorber / dielectric multilayer structures.

[0075] Preferred eleven-layer Fabry-Perot multilayer structures consist of absorb- er / dielectric / absorber / dielectric / reflector / magnetic / reflector / dielectric / absorber / dielectric / absorber multilayer structures.

[0076] Preferably, the reflector layers are independently made from one or more selected from the group consisting of metals and metal alloys, preferably selected from the group consisting of reflective metals and reflective metal alloys, more preferably selected from the group consisting of aluminum (Al), silver (Ag), copper (Cu), gold (Au), platinum (Pt), tin (Sn), titanium (Ti), palladium (Pd), rhodium (Rh), niobium (Nb), chromium (Cr), nickel (Ni), and alloys thereof, even more preferably selected from the group consisting of aluminum (Al), chromium (Cr), nickel (Ni) and alloys thereof, and still more preferably aluminum (Al). Preferably, the dielectric layers are independently made from one or more selected from the group consisting of metal fluorides such as magnesium fluoride (MgF2), aluminum fluoride (AIF3), cerium fluoride (CeF3), lanthanum fluoride (LaF3), sodium aluminum fluorides (e.g. Na3AIF6), neodymium fluoride (NdF3), samarium fluoride (SmF3), barium fluoride (BaF2), calcium fluoride (CaF2), lithium fluoride (LiF), and metal oxides such as silicon oxide (SiO), silicium dioxide (SiO2), titanium oxide (TiO2), aluminum oxide (AI2O3), more preferably selected from the group consisting of magnesium fluoride (MgF2) and silicon dioxide (SiO2) and still more preferably magnesium fluoride (MgF2). Preferably, the absorber layers are independently made from one or more selected from the group consisting of aluminum (Al), silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), titanium (Ti), vanadium (V), iron (Fe) tin (Sn), tungsten (W), molybdenum (Mo), rhodium (Rh), Niobium (Nb), chromium (Cr), nickel (Ni), metal oxides thereof, metal sulfides thereof, metal carbides thereof, and metal alloys thereof, more preferably selected from the group consisting of chromium (Cr), nickel (Ni), metal oxides thereof, and metal alloys thereof, and still more preferably selected from the group consisting of chromium (Cr), nickel (Ni), and metal alloys thereof. Preferably, the magnetic layer comprises nickel (Ni), iron (Fe) and / or cobalt (Co); and / or a magnetic alloy comprising nickel (Ni), iron (Fe) and / or cobalt (Co); and / or a magnetic oxide comprising nickel (Ni), iron (Fe) and / or cobalt (Co). When magnetic thin film interference pigment particles comprising a seven-layer Fabry-Perot structure are preferred, it is particularly preferred that the magnetic thin film interference pigment particles comprise a seven-layer Fabry-Perot absorber / dielectric / reflector / magnetic / reflector / dielectric / absorbermultilayer structure consisting of a Cr / MgF2 / AI / M / AI / MgF2 / Cr multilayer structure wherein M is Ni, Fe or Co.

[0077] The magnetic thin film interference pigment particles may be multilayer pigment particles being considered as safe for human health and the environment and being based for example on five-layer Fabry-Perot multilayer structures, six-layer Fabry-Perot multilayer structures, seven-layer Fabry-Perot multilayer structures, nine-layer Fabry-Perot multilayer structures, eleven-layer Fabry-Perot multilayer structures and pigment particles having a multilayer structure combining one or more, or two or more, multilayer Fabry-Perot structures, wherein said pigment particles include one or more magnetic layers comprising a magnetic alloy having a substantially nickel-free composition including about 40 wt.% to about 90 wt.% iron, about 10 wt.% to about 50 wt.% chromium and about 0 wt.% to about 30 wt.% aluminum. Typical examples of multilayer pigment particles being considered as safe for human health and the environment can be found in EP2402401 B1 whose content is hereby incorporated by reference in its entirety.

[0078] Suitable interference coated pigment particles comprising one or more magnetic materials include without limitation structures consisting of a substrate selected from the group consisting of a core coated with one or more layers, wherein at least one of the core or the one or more layers have magnetic properties. For example, suitable interference coated pigment particles comprise a core made of a magnetic material such as those described hereabove, said core being coated with one or more layers made of one or more metal oxides, or they have a structure consisting of a core made of synthetic or natural micas, layered silicates (e.g. talc, kaolin and sericite), glasses (e.g. borosilicates), silicon dioxides (SiO2), aluminum oxides (AI2O3), titanium oxides (TiO2), graphites and mixtures of two or more thereof, said core being coated with one or more magnetic materials. Furthermore, one or more additional layers such as coloring layers may be present.

[0079] The platelet-shaped magnetic or magnetizable pigment particles preferably have a size d50 between about 2 |j.m and about 50 |j.m (as measured by direct optical granulometry).

[0080] The platelet-shaped magnetic or magnetizable pigment particles may be surface treated to protect them against any deterioration that may occur in the coating composition and coating layer and / or to facilitate their incorporation in said coating composition and coating layer; typically corrosion inhibitor materials and / or wetting agents may be used.

[0081] Subsequently to the application of the first radiation-curable coating composition to form the first coating layer (210), said first radiation-curable coating composition of step a) is exposed to the magnetic field of a magnetic assembly (230) to magnetically orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles (step b).

[0082] The magnetic orientation in step b) and / or b’) may be single-step or multi-steps, for example two-steps.

[0083] Single-step orientation means that the printed coating composition comprising the magnetic or magnetizable pigment particles is subjected to the influence of a single magnetic assembly in step b) before curing in step c). The magnetic orientation may be mono-axial, meaning that the pigment particles are substantially aligned along either the X-axis or the Y-axis (see Fig. 1).

[0084] The magnetic orientation may be bi-axial, meaning the pigment particles are substantiallyaligned along both their X- and Y-axes, or essentially the XY plane of the pigment particles are aligned in a common plane. Bi-axial orientation of the pigment particles means that, when viewed face-on to the plane of alignment, the pigment particles will reflect light at a greater intensity as compared to a sample of non-aligned particles. In a preferred embodiment, the pigment particles are bi-axially aligned, preferably with the XY-plane of the particles being substantially parallel to the plane of the substrate.

[0085] During a bi-axial orientation step, the substrate carrying the coating layer is moved through the inhomogeneous magnetic field of the magnetic assembly so that the platelet-shaped magnetic or magnetizable pigment particles are exposed to a magnetic field which is at least time- varying in direction thus bi-axially orienting at least part of said platelet-shaped magnetic or magnetizable pigment particles while the coating composition is still in a wet (i.e. not yet hardened) state. According to one embodiment, the magnetic assembly allows to bi-axially orient the platelet-shaped magnetic or magnetizable pigment particles such that the platelet-shaped magnetic or magnetizable pigment particles form a sheet-like structure with their X and Y axes preferably substantially parallel to the substrate surface and are planarized in said two dimensions. According to another embodiment, the magnetic assembly allows to bi-axially orient the platelet-shaped magnetic or magnetizable pigment particles such that the plateletshaped magnetic or magnetizable pigment particles have a first axis within the X-Y plane substantially parallel to the substrate surface and a second axis being substantially perpendicular to said first axis at a substantially non-zero elevation angle to the substrate surface. According to another embodiment, the magnetic assembly allows to bi-axially orient the platelet-shaped magnetic or magnetizable pigment particles such that the platelet-shaped magnetic or magnetizable pigment particles have their X-Y plane substantially parallel to an imaginary spheroid surface.

[0086] The magnetic orientation in step b) and / or b’) may be multi-steps, for example two-steps, which comprises a first step of bi-axially orienting the platelet-shaped magnetic or magnetizable pigment particles, and a second step of re-orienting the platelet-shaped magnetic or magnetizable pigment particles according to a design.

[0087] The platelet-shaped magnetic or magnetizable pigment particles may also be aligned according to predetermined designs, determined by the design of the magnetic assembly.

[0088] Included in the invention are embodiments in which the OEL comprises more than one motif or coating layer comprising platelet-shaped magnetic or magnetizable pigment particles. In descriptions herein referring to magnetic orientation in step b), such references are understood to apply equally and independently to any magnetic orientation step carried out in the process of the invention [b’), b”), etc.]. Similarly, descriptions of the first motif and / or the first coating layer are understood to apply equally and independently to any motif or coating layer in the OEL comprising platelet-shaped magnetic or magnetizable pigment particles.

[0089] The following are examples of embodiments of the process and OELs of the invention:

[0090] In a preferred embodiment, the platelet-shaped magnetic or magnetizable pigment particles are subjected to a two-steps magnetic orientation, comprising step b1) in which a first magnetic assembly is used to substantially bi-axially orient the pigment particles (preferably parallel to the plane of the substrate), and step b2) in which the pigment particles are re-oriented and subjected to a second magnetic assembly designed to have a specific alignment pattern. The combination of a bi-axial orientation followed by a design-specific alignment results in a more visually striking effect than if the coating composition is simply subjected to a step of design-specific alignment. Such a two-steps orientation is shown schematically in steps b1) and b2) of Fig. 2. In step b1) the first coating composition (210) is subjected to the influence of a magnetic assembly (230), which has, for example, a structure as shown in Fig. 10. This results in bi-axial orientation of the pigment particles, substantially in the plane of the substrate (220). In step b2), the bi-axially-oriented pigment particles are brought under the influence of a second magnetic assembly (240), resulting in a design-specific orientation.

[0091] In one embodiment, as illustrated in Fig. 2, in step b2) the coating composition (210) is maintained under the influence of the bi-axially-orienting magnetic assembly (230) while it is brought under the influence of the design-specific magnetic assembly (240).

[0092] During the magnetic orientation step b), the position of the magnetic assembly (230) and the magnetic assembly (240) is not limited and depends on the choice and the design of the magnetic orientation pattern to be produced. Depending on the choice and the design of the magnetic orientation pattern to be produced, the magnetic assembly (230) may be placed below the substrate (220) or above the coating layer (210).

[0093] As described hereafter, “230” and “240” independently either refer to single magnets or refer toassemblies comprising two or more magnets or refer to assemblies comprising one or more magnets and an engraved magnetic plate, or refer to assemblies comprising one or more magnets and a soft magnetic plate or refers to an assembly comprising a magnet and one or more pole pieces or comprising two or more magnets and one or more pole pieces, said magnetic assembly being selected according to the design of the magnetic orientation pattern of the motif.

[0094] According to one embodiment, the process of the invention comprises the magnetic orientation step b) in which step b) is a one-step orientation step. The one-step orientation step may be a mono- axial orientation or a bi-axial orientation.

[0095] Fig. 4 illustrates a process wherein the orientation steps b) and b’) are one-step orientation steps, wherein the radiation-curable coating compositions (210 and 210’) are exposed to the magnetic field of a single magnetic assembly (230 or 230’). The position of the magnetic assemblies (230 and 230’) in Fig. 4 is only illustrative and the magnetic assembly may be placed on the opposite side of the substrate (220) depending on the choice and the design of the magnetic orientation pattern to be produced; the distances provided in Fig. 4 are only illustrative and not true to scale.

[0096] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif bears one or more indicia, wherein step b) consists of exposing the radiation- curable coating composition to an engraved magnetic plate (230), wherein said engraved magnetic plate (230) comprises one or more engravings (I) having the shape of indicia. The engraved magnetic plate (230) is preferably made from a permanent magnetic powder material and a polymer. The engraved magnetic plate (230) may typically be produced by an injection molding process or by metal or laser engraving. Preferred permanent magnetic powder materials include cobalt, iron and their alloys, chromium dioxide, generic magnetic oxide spinels, generic magnetic garnets, generic magnetic ferrites including the hexaferrites such as calcium-, strontium-, and barium-hexaferrite (CaFe12019, SrFe12019, BaFe12019, respectively), generic alnico alloys, generic samarium-cobalt (SmCo) alloys, and generic rare-earth-iron-boron alloys (such as NdFeB), as well as the permanent-magnetic chemical derivatives thereof (such as indicated by the term generic) and mixtures thereof. Plates made of a composite material comprising a polymer and a permanent magnetic powder are obtainable from many different sources, such as from Bomatec, Hbri, CH, ARNOLD® Magnetic Technologies (Plastiform®) or from Materiali Magnetici, Albairate, Milano, IT (Plastoferrite).

[0097] According to one embodiment, magnetic orientation in step b) is carried out by exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in US8,025,952 and EP1819525B1 and W02022 / 049024 A1 , wherein this effect is so-called “Venetian-blind” effect. Fig. 5A-B of US7,047,883 discloses a magnetic assembly comprising two spaced apart magnets 84 placed on a magnetic base 62 with their North poles facing the substrate. Fig. 9B of US7,047,883 discloses a magnetic assembly comprising a magnet 140 and the substrate comprising the coating layer is placed with an offset position relatively the magnet axes. Fig. 9C of US7,047,883 discloses a magnetic assembly comprising two magnets 142 and one magnet 142' having a diamond-shaped cross section, wherein the two magnets 142 have their North pole facing the substrate while the intervening magnet 142' has its South pole facing the substrate. Fig. 9D of US7,047,883 discloses a magnetic assembly comprising two magnets 144, and one magnet 144' having roof-shaped, hexagonal, rounded,trapezoidal, or other cross-sections, wherein the two magnets 144 have their North pole facing the substrate while the intervening magnet 144' has its South pole facing the substrate. Fig. 9E of US7,047,883 discloses a magnetic assembly comprising five magnets, the first magnet 142 being a diamond-shaped magnet with its North pole facing the substrate, the second magnet 146 being a rectangular magnet with its South pole facing the substrate, the third magnet 148 being a magnet with rounded top having its North pole facing the substrate, the fourth magnet 150 being a roof-shaped and having its South pole facing the substrate and the fifth magnet 152 being also a roof-shaped magnet and having its North pole facing the substrate. Fig. 4A1 of W02022 / 04902A1 discloses a magnetic assembly comprising a bar dipole magnet and the particles are exposed to the magnetic field (magnetic field lines shown as lines with arrows pointing from the North Pole to the South Pole) of the magnetic assembly in one or more areas (shown as a dotted rectangle A) wherein the magnetic field is substantially homogeneous and wherein the magnetic field lines are substantially parallel to each other in said one or more areas. Fig. 4A2 of W02022 / 0490241 A1 discloses a magnetic assembly comprising two bar dipole magnets (M1 , M2) having a same magnetic direction and an iron yoke (Y) and the particles are exposed to the magnetic field (magnetic field lines shown as lines with arrows pointing from the North Pole to the South Pole) of the magnetic assembly in one or more areas (shown as a dotted rectangle A) wherein the magnetic field is substantially homogeneous and wherein the magnetic field lines are substantially parallel to each other in said one or more areas. Fig. 6A-B of W02022 / 049024A1 discloses a magnetic assembly comprising a rectangular assembly comprising two bar dipole magnets (M1 , M2) and two pole pieces (P1 , P2) and the particles are exposed to the magnetic field (magnetic field lines shown as lines with arrows pointing from the North Pole to the South Pole) of the magnetic assembly in one or more areas (shown as a dotted rectangle A) wherein the magnetic field is substantially homogeneous and wherein the magnetic field lines are substantially parallel to each other in said area.

[0098] According to another embodiment, the process of the invention allows the preparation of OELs wherein at the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic motion of the OEL being a bright reflective vertical bar moving in a horizontal (left / right) direction when the OEL is tilted around a horizontal axis; wherein step b) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in W02020 / 160993A1 . Figs 2-5 of W02020 / 160993A1 discloses magnetic assemblies comprising a) at least one dipole magnet (x40) being a square-shaped or rectangle-shaped dipole magnet having its magnetic axis oriented to be substantially parallel to a substrate and b) a combination of n sets of spaced apart bar dipole magnets (x30-a1 , x30-a2) with n being an integer equal to or bigger than 1 , wherein each of said bar dipole magnets (x30-a1 , x30-a2) has its North-South magnetic axis substantially parallel to the substrate surface, wherein, for each set of said n sets, the bar dipole magnets (x30-a1 , x30-a2) have their North pole pointing in a same direction and are substantially parallel to each other; wherein the vector sum H1 of the magnetic axes of the bar dipole magnets (x30-a1 , x30-a2) and the vector sum H2 of the at least one dipole magnet (x40) form an angle a in the range from about 5° to about 175° or in the range from about 185° to about 355°; wherein the combination of n sets of spaced apart bar dipole magnets (x30-a1 , x30-a2) is placed below or above the at least one dipole magnet (x40), and wherein the atleast one dipole magnet (x40) and the combination of n sets of spaced apart bar dipole magnets (x30- b1 , x30-b2) are essentially centered with respect to one another (see for example Figs 2-5 of W02020 / 160993A1).

[0099] According to another embodiment, the process of the invention allows the preparation of OELs wherein at the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement of the OEL being a bright reflective horizontal bar moving in a vertical direction (up / down) when the OEL is tilted around a horizontal axis; wherein said step b) consists of exposing the radiation curable coating composition to a magnetic assembly such as those disclosed in WO2014 / 198905A2. Figs 2-5 of WO2014 / 198905A2 disclose magnetic assemblies comprising: a) a bar dipole magnet (M1) and a pair of bar dipole magnets (M2) and (M3), said bar dipole magnets (M1), (M2) and (M3) having their North-South axis substantially parallel to the substrate and the same magnetic North-South direction, wherein a1) said bar dipole magnet (M1) is disposed below the substrate and said pair of bar dipole magnets (M2) and (M3) are disposed below the bar dipole magnet (M1) apart from each other; or a2) said pair of bar dipole magnets (M2) and (M3) are disposed below the substrate and apart from each other, and said bar dipole magnet (M1) is disposed below said pair of bar dipole magnets (M2) and (M3); or b) a pair of bar dipole magnets (M4) and (M5) and a pole piece (Y), said pair of bar dipole magnets (M4) and (M5) having their North-South axis substantially parallel to the substrate and the same magnetic North-South direction, said pole piece (Y) being disposed between said bar dipole magnet (M4) and said bar dipole magnet (M5); or c) a pair of bar dipole magnets (M4) and (M5), a pole piece (Y) and a magnetic plate (M6), said pair of bar dipole magnets (M4) and (M5) having their North-South axis substantially parallel to the substrate and the same magnetic North-South direction, said magnetic plate (M6) having its North-South axis substantially perpendicular to the substrate, said pole piece (Y) being disposed between said bar dipole magnet (M4) and said bar dipole magnet (M5). Particularly suitable magnetic assemblies are those shown in Figs 5c, 6c and 7d of WO2014 / 198905A2.

[0100] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement being a nested multi-loop-shaped body moving when the OEL is tilted; wherein step b) and consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in W02014 / 108303A2. Disclosed magnetic assemblies of W02014 / 108303A2 comprise one of the following: a) at least one dipole magnet being a loop-shaped magnet defining a loop and having a magnetic axis oriented to be substantially perpendicular to the substrate and a pole piece (x60) being disposed below the at least one dipole magnet and within the loop of said at least one dipole magnet and having one or more protrusions disposed within the loop of the at least one dipole magnet (see for example Figs 3-5 of W 2014 / 108303A2); or b) at least one dipole magnet having a magnetic axis oriented to be substantially perpendicular to the substrate, an additional dipole magnet having a magnetic axis oriented to be substantially perpendicular to the substrate and two or more pole pieces, wherein said at least one dipole magnetand additional magnet have the same magnetic direction and are provided in different distances from substrate, wherein said two or more pole pieces are arranged in the space between the magnets and in contact therewith and wherein at least one of the two or more pole pieces form one or more loopshaped projections surrounding a central area in which the at least one dipole magnet is arranged (see for example Fig. 6 of W02014 / 108303A2); or c) at least one dipole magnet having a magnetic axis oriented to be substantially perpendicular to the substrate, a plate-like-shaped pole piece being disposed below and in contact with the at least one dipole magnet, and one or more loop-shaped pole pieces being disposed on top the at least one dipole magnet, wherein a central pole piece of said one or more loop-shaped pole pieces is in contact with the at least one dipole magnet, and wherein said plate-like-shaped pole piece may comprise one or more protrusions laterally and spaced apart surrounding the at least one dipole magnet (see for example Fig. 7 of W02014 / 108303A2). W02014 / 108303A2 also disclose spinneable magnetic assemblies comprising a) at least two bar dipole magnets having their magnetic axis substantially perpendicular to the substrate (see Figs 8-10 and 13-14 of WO2014 / 108303A2) or comprising b) at least four bar dipole magnets having their magnetic axis substantially parallel to the substrate (see Figs 11 , 12 and 15 of W02014 / 108303A2).

[0101] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement being a loop-shaped body having a size that varies when the OEL is tilted; wherein said step b) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in W02017 / 064052A1 , W02017 / 080698A1 and WO2017 / 148789A1 . Disclosed magnetic assemblies of W02017 / 064052A1 , W02017 / 080698A1 and WO2017 / 148789A1 comprise one of the following: at least one dipole magnet (x40) being either a single bar dipole magnet having a North-South magnetic axis substantially parallel to a substrate or a combination of two or more bar dipole magnets having a resulting North-South magnetic axis substantially parallel to the substrate and b) a loop-shaped magnetic-field generating device (x30) being either a single loop-shaped dipole magnet having a North- South magnetic axis substantially perpendicular to the substrate or a combination of two or more dipole magnets disposed in a loop-shaped arrangement and having a resulting North-South magnetic axis substantially perpendicular to the substrate (see for example Figs 1-4 of W02017 / 064052A1), or at least one dipole magnet (x40) being either a single dipole magnet having a magnetic axis substantially parallel to the substrate or a combination of two or more bar dipole magnets, each of the two or more bar dipole magnets having a magnetic axis substantially parallel to the substrate and having a same magnetic field direction, b) a loop-shaped magnetic-field generating device (x31) being either a single loop-shaped dipole magnet having a magnetic axis substantially perpendicular to the substrate or a combination of two or more dipole magnets disposed in a loop-shaped arrangement, each of the two or more dipole magnets having a magnetic axis substantially perpendicular to the substrate and having a same magnetic field direction, and c) a single dipole magnet (x32) having a magnetic axis substantially perpendicular to the substrate or two or more dipole magnets, each of the two or more dipole magnets having a magnetic axis substantially perpendicular to the substrate and having a same magnetic field direction and / or one or more pole pieces (see for example Figs 1-12 ofW02017 / 080698A1), or at least one dipole magnet (x40) being either a single bar dipole magnet having a magnetic axis substantially parallel to the substrate or a combination of two or more bar dipole magnets, each of the two or more bar dipole magnets having a magnetic axis substantially parallel to the substrate and having a same magnetic field direction, b) a loop-shaped magnetic-field generating device (x31) being either a single loop-shaped magnet or a combination of two or more dipole magnets (x31), disposed in a loopshaped arrangement, the loop-shaped magnetic-field generating device having a radial magnetization, and c) a single dipole magnet (x32) having a magnetic axis substantially perpendicular to the substrate or a single dipole magnet having a magnetic axis substantially parallel to the substrate (x32), or two or more dipole magnets (x32), each of said two or more dipole magnets (x32) having a magnetic axis substantially perpendicular to the substrate, wherein the North pole of said single dipole magnet (x32) or the North pole of at least one of said two or more dipole magnets (x32) is pointing towards the substrate when the North pole of the single loop-shaped magnet (x31) or of the two or more dipole magnets (x31) forming the loop-shaped magnetic-field generating device is pointing towards the periphery of said loop-shaped magnetic-field generating device, or wherein the South pole of said single dipole magnet (x32) or the South pole of at least one of said two or more dipole magnets (x32) is pointing towards the substrate when the South pole of the single loop-shaped magnet (x31) or of the two or more dipole magnets (x31) forming the loop-shaped magnetic-field generating device is pointing towards the periphery of said loop-shaped magnetic-field generating device (x31) (see for example Figs 1-14 of WO2017 / 148789A1).

[0102] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement being one or more loop-shaped bodies having a shape that varies when the OEL is tilted; wherein step b) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in WO2018 / 054819A1 . In particular, the disclosed magnetic assembly of WO2018 / 054819A1 comprises a loop-shaped magnetic-field generating device (x31) being either a single loop-shaped magnet (x31) or a combination of two or more dipole magnets (x31) disposed in a loop-shaped arrangement, the loop-shaped magnetic-field generating device (x31) having a radial magnetization; and a single dipole magnet (x32) having a magnetic axis substantially perpendicular to the substrate surface or two or more dipole magnets (x32), each of said two or more dipole magnets (x32) having a magnetic axis substantially perpendicular to the substrate surface, wherein the single dipole magnet (x32) or the two or more dipole magnets (x32) are located partially within, within or above the loop defined by the single loop-shaped magnet (x31) or partially within, within or above the loop defined by the two or more dipole magnets (x31) disposed in the loop-shaped arrangement, and wherein the South pole of said single dipole magnet (x32) or the South pole of each of said two or more dipole magnets (x32) is pointing towards the substrate surface when the North pole of the single loop-shaped magnet (x31) or of the two or more dipole magnets (x31) forming the loop-shaped magnetic-field generating device (x31) is pointing towards the periphery of said loop-shaped magnetic-field generating device (x31) or the North pole of said single dipole magnet (x32) or the North pole of each said two or more dipole magnets (x32) is pointing towards the substrate surface when the South pole of the single loop-shaped magnet (x31) or of the two or more dipole magnets (x31) forming the loop-shaped magnetic- field generating device (x31) is pointing towards the periphery of said loop-shaped magnetic-field generating device (x31).

[0103] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement being a moon crescent moving and rotating when the OEL is tilted; wherein step b) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in WO2019 / 215148A1 . Disclosed magnetic assemblies of WO2019 / 215148A1 comprise a) a first magnetic-field generating device (x30) having its North-South magnetic axis substantially perpendicular to the substrate surface and having length L1 , b) a second magnetic-field generating device (x40) having its North-South magnetic axis substantially perpendicular to the substrate and having a length L3, and c) a flat pole piece (x50) lacking any protrusions or projections extending outside the surface of said pole piece and having a length L5, wherein the first magnetic-field generating device and the second magnetic-field generating device have a same magnetic field direction, wherein the first magnetic-field generating device faces the substrate and is disposed above the flat pole piece), wherein the second magnetic-field generating device faces the environment and is disposed below the flat pole piece, wherein the length L1 of the first magnetic-field generating device is smaller than the length L3 of the second magnetic-field generating device, wherein the length L1 of the first magnetic-field generating device is smaller than the length L5 of the flat pole piece, and wherein the length L3 of the second magnetic-field generating device is smallerthan the length L5 of the pole piece (see for example Figs 1-12 of WO2017 / 148789A1).

[0104] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement being a loop-shaped body surrounded by one or more loop-shaped bodies having their shape and / or their brightness varying when the OEL is tilted; wherein step b) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in W02020 / 193009A1 . Disclosed magnetic assemblies of W02020 / 193009A1 comprise a) a combination of three or more first dipole magnets (x31-ai), each of said first dipole magnets having its center disposed on a loop in a plane parallel to the substrate, wherein said first dipole magnets (x31-ai) have their magnetic axes oriented to be substantially parallel to the substrate and b) at least one second dipole magnet (x41) having its magnetic axis oriented to be substantially perpendicular to the substrate and being arranged to have a projection of its center on the substrate be located at a projection point within the loop, wherein the at least one second dipole magnet (x41) is disposed above the combination of three or more first dipole magnets (x31-ai), wherein angles ai are formed between each of the vectors Cx41Cx31-a’ (Cx41Cx31-a4, ^•x4i^x3i-a2 < ^x4i^x3i-a3) and the vector hx31-ai(hx31-al, hx31-a2, hx31-a3, ...) of the magnetic axis of the respective first dipole magnet magnets (x31-ai), wherein all of the angles ai, when measured in a counterclockwise direction, are in a range from about 20° to about 160° or in a range from about 200° to about 340°, and wherein each of the first dipole magnets (x31-ai) is disposed at a first distance (Yi), said first distance (Yi) being on the substrate between the projection point and the center of the first dipole magnet (x31-ai) (see for example Figs 2-9 of in W02020 / 193009A1).

[0105] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic movement being a pattern of bright areas and dark areas moving when the OEL is tilted; wherein the step b) consists of exposing the radiation curable coating composition to a magnetic assembly such as those disclosed in WO2013 / 167425A1 and W02021 / 083809A1 . Disclosed magnetic assemblies of WO 2021 / 083809 A1 comprise at least one dipole magnet (x41) having a magnetic axis oriented to be substantially parallel to the substrate and a combination comprising at least four additional dipole magnets (x31) having their North poles pointing in a same direction and having their magnetic axes oriented to be substantially parallel to the substrate, wherein each of the additional dipole magnets (x31) is arranged on an intersection of at least two substantially parallel straight lines eq (i = 1 , 2, ...) and at least two substantially parallel straight lines Dj (j = 1 , 2, ...), the straight lines eq and ft forming a grid, wherein at least two additional dipole magnets (x31) are disposed on one of the straight lines oq and at least two other additional dipole magnets (x31) are disposed on another one of the straight lines oq , wherein the magnetic axes of the additional dipole magnets are oriented substantially parallel to the substantially parallel straight lines oq, wherein the at least one dipole magnet (x40) is disposed below the combination comprising at least four dipole magnets (x31). According to one embodiment, each straight line oq and a vector H of the magnetic axis of the at least one dipole magnet (x41) is substantially parallel or substantially perpendicular with respect to each other and the OEL exhibits a dynamic movement being a pattern of bright areas and dark areas moving when the substrate carrying said OEL is tilted, said pattern of bright areas and dark areas moving in the same direction as the tilting direction. According to another embodiment, each straight line oq and a vector H of the magnetic axis of the at least one dipole magnet (x41) is substantially non-parallel and substantially non-perpendicular with respect to each other OEL, preferably wherein each straight line oq and the vector sum H of the magnetic axis of the at least one dipole magnet (x41) form an angle y in the range from about 20° to about 70° or in the range from about 110° to about 160° or in the range from about 200° to about 250°, or in the range from about 290° to about 340°; and the OEL exhibits a dynamic movement being a pattern of bright areas and dark areas moving not only in a diagonal direction when the substrate carrying said OEL is tilted around a vertical axis but also moving in a diagonal direction when the substrate carrying said OEL is tilted around a horizontal axis (in other words, the optical effect layer OEL provides the optical impression of a plurality of dark and a plurality of bright spots that are moving when the substrate carrying said OEL is tilted around two perpendicular axes, i.e. horizontal axis and vertical / longitudinal axis. Suitable magnetic assemblies are those shown in Figs 6-8 of W02021 / 083809A1 .

[0106] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic movement being a pattern of bright areas and dark areas moving when the OEL is tilted; wherein the step b) consists of exposing the radiation curable coating composition to a magnetic assembly such as those disclosed in W02021 / 083808A1 . Disclosed magnetic assemblies of W02021 / 083808A1 comprise at least one dipole magnet (x41) having a magnetic axis oriented to be substantially parallel to the substrate and a combination comprising at least four additional dipole magnets (x31) having their North poles pointing in a same direction and having their magnetic axes oriented to be substantially parallel to the substrate, wherein each of theadditional dipole magnets (x31) is arranged on an intersection of at least two substantially parallel straight lines eq (i = 1 , 2, ...) and at least two substantially parallel straight lines ft (j = 1 , 2, ...), the straight lines eq and ft forming a grid, wherein at least two additional dipole magnets (x31) are disposed on one of the straight lines oq and at least two other additional dipole magnets (x31) are disposed on another one of the straight lines oq , wherein the magnetic axes of the additional dipole magnets (x31) are oriented substantially parallel to the substrate, straight lines oq, wherein the at least one dipole magnet (x41) is disposed below the combination comprising at least four first dipole magnets (x31), wherein, on each straight line oq, and on each straight line ft, neighboring additional dipole magnets (x31) have their North pole pointing in an opposite direction, wherein each straight line oq and a vector H of the magnetic axis of the at least one dipole magnet (x41) is substantially non-parallel and substantially non-perpendicular with respect to each other OEL, preferably wherein each straight line oq and the vector sum H of the magnetic axis of the at least one dipole magnet (x41) form an angle y in the range from about 20° to about 70° or in the range from about 110° to about 160° or in the range from about 200° to about 250°, or in the range from about 290° to about 340°; and the OEL exhibits a dynamic movement being a pattern of bright areas and dark areas moving not only in a diagonal direction when the substrate carrying said OEL is tilted about a vertical / long itud inal axis but also moving in a diagonal direction when the substrate carrying said OEL is tilted about a horizontal / latitudinal axis (in other words, the optical effect layer OEL provides the optical impression of a plurality of dark and a plurality of bright spots that are moving when the substrate carrying said OEL is tilted about two perpendicular axes, i.e. horizontal / latitudinal axis and vertical / longitudinal axis). Suitable magnetic assemblies are those shown in Figs 5-7 of W02021 / 083808A1 .

[0107] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement being a change from dark to light of two areas when the OEL is tilted (effect so-called flip-flop); wherein said at least one of steps b’) and b”) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in Fig. 1 , 3 and 6 of US2005 / 0106367.

[0108] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif exhibits a dynamic motion upon tilting said OEL, said dynamic movement being at least one comet-shaped spot rotating around said center of rotation upon tilting said OEL, wherein step b) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those disclosed in WO2019 / 038371 A1 , W02019 / 038370A1 and WO2019 / 038369A1 . Disclosed magnetic assemblies of WO2019 / 038371 A1 , W02019 / 038370A1 and WO2019 / 038369A1 comprise at least one of the following: a) first magnetic-field generating device (x30) and b) a second magnetic-field generating device (x40), wherein said first magnetic-field generating device (x30) and said second magnetic-field generating device (x40) have mutually skew magnetic axes, wherein said first magnetic-field generating device (x30) has its magnetic axis substantially perpendicular to the axis of spinning and said second magnetic- field generating device (x40) has its magnetic axis substantially perpendicular to the axis of spinning and wherein the projection of the magnetic axis of the first magnetic-field generating device (x30) and the projection of the magnetic axis of the second magnetic-field generating device (x40) along the axisof spinning onto a plane perpendicular to the axis of spinning form an angle (Q) either in the range from about 5° to about 175° or in the range from about -5° to about -175°, and wherein the first magnetic- field generating device (x30) comprises a bar dipole magnet having its North-South magnetic axis substantially perpendicular to the axis of spinning, or two or more bar dipole magnets, each of said two or more bar dipole magnets having its North-South magnetic axis substantially perpendicular to the axis of spinning and all of said two or more bar dipole magnets having a same magnetic field direction, or a loop-shaped dipole magnet having its North-South magnetic axis substantially perpendicular to the axis of spinning, or a disc-shaped dipole magnet being nested inside a loop-shaped dipole magnet, each of the disc-shaped dipole magnet and the loop-shaped dipole magnets having their North-South magnetic axis substantially perpendicular to the axis of spinning and having a same magnetic field direction, or two or more nested loop-shaped dipole magnets, each of said two or more nested loop-shaped dipole magnets, having its North-South magnetic axis substantially perpendicular to the axis of spinning and all of said two or more nested ring-shaped magnets having a same magnetic field direction; and wherein the second magnetic-field generating device (x40) comprises a disc-shaped dipole magnet having its North-South magnetic axis substantially perpendicular to the axis of spinning, or a loop-shaped dipole magnet having its North-South magnetic axis substantially perpendicular to the axis of spinning, or a bar dipole magnet having its North-South magnetic axis substantially perpendicular to the axis of spinning; or a) a first magnetic-field generating device (x30) and b) a second magnetic-field generating device (x40), wherein the first magnetic-field generating device (x30) comprises at least one pair of two bar dipole magnets (x31) at least partially or fully embedded in a supporting matrix (x32), each of said bar dipole magnets (x31) having its North-South magnetic axis substantially parallel to the axis of spinning, said two bar dipole magnets (x31) of the at least one pair having opposite magnetic field directions and being arranged in a symmetric configuration around the axis of spinning along a line (a), and the second magnetic-field generating device (x40) comprises b1) a disc-shaped dipole magnet (x41) having its North-South magnetic axis substantially perpendicular to the axis of spinning, b2) a loopshaped dipole magnet (x41) having its North-South magnetic axis substantially perpendicular to the axis of spinning, b3) a bar dipole magnet (x41) having its North-South magnetic axis substantially perpendicular to the axis of spinning and arranged on the axis of spinning, and / or b4) at least one pair of two bar dipole magnets (x41), each of said bar dipole magnets (x41) having its North-South magnetic axis substantially parallel to the axis of spinning, said two bar dipole magnets (x41) of the at least one pair having opposite magnetic field directions and being arranged in a symmetric configuration around the axis of spinning along a line (P), wherein the projection of the line (a) where the bar dipole magnets (x31) of the at least one pair of the first magnetic-field generating device (x30) are arranged and the projection of the magnetic axis of the second magnetic-field generating device (x40) form along the axis of spinning onto a plane perpendicular to the axis of spinning an angle (Q) either in the range from about 5° to about 175° or in the range from about -5° to about -175°; or a magnetic-field generating device (x30) comprising a disc-shaped dipole magnet (x31) having its North-South magnetic axis substantially perpendicular to the axis of spinning, or a loop-shaped, preferably a ring-shaped, dipole magnet (x31) having its North-South magnetic axis substantiallyperpendicular to the axis of spinning, or a bar dipole magnet (x31) having its North-South magnetic axis substantially perpendicular to the axis of spinning and arranged on the axis of spinning, wherein the disc-shaped dipole magnet (x31), the loop-shaped, preferably the ring-shaped, dipole magnet (x31) or the bar dipole magnet (x31) of the magnetic-field generating device (x30) comprises at least one pair of indentations (I) and / or at least one pair of voids (V) and / or at least one pair of protrusions (P), wherein the indentations (I) of the at least one pair, the voids (V) of the at least one pair and / or the protrusions (P) of the at least one pair are located: symmetrically about the axis of spinning, and asymmetrically with respect to a mirror plane which is perpendicular to the North-South magnetic axis of the discshaped dipole magnet (x31), the loop-shaped, preferably the ring-shaped, dipole magnet (x31) or the bar dipole magnet (x31) of the magnetic-field generating device (x30) and which contains the axis of spinning.

[0109] Contrary to a mono-axial orientation wherein platelet-shaped magnetic or magnetizable pigment particles are orientated in such a way that only their main axis is constrained by the magnetic field, carrying out a bi-axial orientation means that the platelet-shaped magnetic or magnetizable pigment particles are made to orientate in such a way that their two main axes are constrained. In contrast to needle-shaped pigment particles which can be considered as one-dimensional particles, platelet-shaped pigment particles have an X-axis and an Y-axis defining a plane of predominant extension of the particles. In other words, platelet-shaped pigment particles may be considered to be two-dimensional particles due to the large aspect ratio of their dimensions as can be seen in Fig. 1. As shown in Fig. 1 , a platelet-shaped pigment particle can be considered as a two-dimensional structure wherein the dimensions X and Y are substantially larger than dimension Z. Platelet-shaped pigment particles are also referred in the art as oblate particles or flakes. Such pigment particles may be described with a main axis X corresponding to the longest dimension crossing the pigment particle and a second axis Y perpendicular to X which also lies within said pigment particles. Carrying out a bi-axial orientation leads to platelet-shaped magnetic or magnetizable pigment particles having two main axes constrained; i.e. bi-axially oriented neighboring platelet-shaped magnetic pigment particles are close to each other in space and are essentially parallel to each other. Put another way, bi-axial orientation aligns the planes of the platelet-shaped magnetic or magnetizable pigment particles so that the planes of said pigment particles are oriented to be essentially parallel relative to the planes of neighboring (in all directions) platelet-shaped magnetic or magnetizable pigment particles.

[0110] According to one embodiment, the magnetic assembly described hereafter bi-axially orients the platelet-shaped magnetic or magnetizable pigment particles such that the platelet-shaped magnetic or magnetizable pigment particles form a sheet-like structure with their X and Y axes preferably substantially parallel to the substrate (220) surface and are planarized in said two dimensions.

[0111] According to another embodiment, the magnetic assembly described hereafter bi-axially orients the platelet-shaped magnetic or magnetizable pigment particles such that the platelet-shaped magnetic or magnetizable pigment particles have a first axis within the X-Y plane substantially parallel to the substrate (220) surface and a second axis being substantially perpendicular to said first axis at a substantially non-zero elevation angle to the substrate surface.

[0112] According to another embodiment, the magnetic assembly described hereafter bi-axially orientsthe platelet-shaped magnetic or magnetizable pigment particles such that the platelet-shaped magnetic or magnetizable pigment particles have their X-Y plane substantially parallel to an imaginary spheroid surface.

[0113] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif comprises bi-axially oriented platelet-shaped magnetic or magnetizable pigment particles; wherein step b) consists of exposing the radiation-curable coating composition to a magnetic assembly such as those described in EP2157141A1. The disclosed magnetic assemblies of EP2157141A1 provide a magnetic field that changes its direction while the platelet-shaped magnetic or magnetizable pigment particles move through said assemblies, forcing the platelet-shaped magnetic or magnetizable pigment particles to rapidly oscillate until both main axes become parallel to the substrate, i.e. the platelet-shaped magnetic or magnetizable pigment particles oscillate until they come to a stable sheet-like formation with their X and Y axes parallel to the substrate to the substrate and are planarized in said two dimensions. As shown in Fig. 5 of EP2157141 , the magnetic assembly comprises a linear arrangement of at least three magnets that are positioned in a staggered fashion or in zigzag formation, said at least three magnets being on opposite sides of a feedpath where magnets at the same side of the feedpath have the same polarity, which is opposed to the polarity of the magnet(s) on the opposing side of the feedpath in a staggered fashion. The arrangement of the at least three magnets provides a predetermined change of the field direction as platelet-shaped magnetic or magnetizable pigment particles in a coating composition move past the magnets (direction of movement: arrow). According to one embodiment, the magnetic assembly comprises a) a first magnet and a third magnet on a first side of a feedpath and b) a second magnet between the first and third magnets on a second opposite side of the feedpath, wherein the first and third magnets have a same polarity and wherein the second magnet has a complementary polarity to the first and third magnets. According to another embodiment, the magnetic assembly further comprises a fourth magnets on the same side of the feedpath as the second magnet, having the polarity of the second magnet and complementary to the polarity of the third magnet.

[0114] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif comprises bi-axially oriented platelet-shaped magnetic or magnetizable pigment particles; wherein step b’ consists of exposing the radiation-curable coating composition to a magnetic assembly consisting of a linear permanent magnet Halbach array, i.e. assemblies comprising a plurality of magnets with different magnetization directions and cylinder devices. A detailed description of Halbach permanent magnets was given by Z.Q. Zhu and D. Howe (Halbach permanent magnet machines and applications: a review, IEE. Proc. Electric Power Appl., 2001 , 148, p. 299-308). The magnetic field produced by such a Halbach array has the properties that it is concentrated on one side while being weakened almost to zero on the other side. Linear Halbach arrays are disclosed for example in WO 2015 / 086257 A1 and WO 2018 / 019594 A1 and Halbach cylinder devices are disclosed in EP3224055B1.

[0115] According to one embodiment, the process of the invention allows the preparation of OELs wherein the first motif comprises bi-axially oriented platelet-shaped magnetic or magnetizable pigment particles; wherein said at least one of steps b’) and b”) consists of exposing the radiation curable coatingcomposition to spinning magnetic assemblies at an appropriate speed. Examples of spinning magnetic assemblies are assemblies comprising one or more disc-shaped spinning magnets or magnetic assemblies that are essentially magnetized along their diameter, magnetic assemblies consisting of spinning magnets or magnetic-field generating devices are described in US2007 / 0172261 A1 , said spinning magnets or magnetic-field generating devices generating radially symmetrical time-variable magnetic fields, allowing the bi-axial orientation of pigment particles. These magnetic assemblies are driven by a shaft (or spindle) connected to an external motor. CN 102529326 B discloses examples of magnetic assemblies comprising spinning magnets that might be suitable for bi-axially orienting pigment particles. In a preferred embodiment, suitable magnetic assemblies are shaft-free disc-shaped spinning magnetic assemblies constrained in a housing made of non-magnetic, preferably non-conducting, materials and are driven by one or more magnet-wire coils wound around the housing. Examples of such shaft-free disc-shaped spinning magnetic assemblies are disclosed in WO2015 / 082344A1 , WO2016 / 026896A1 and WO2018 / 141547A1 .

[0116] According to one embodiment, the process of the invention allows the preparation of OELs, wherein step b) consists of exposing the radiation-curable coating composition to the resultant magnetic field of a combination of a magnetic assembly described hereabove for bi-axially orienting pigment particles and a soft magnetic plate comprising one or more indentations (I) and / or one or more voids (V) and / or one or more protrusions (P). The soft magnetic plate comprises one or more soft magnetic materials, i.e. materials having a low coercivity and a high permeability p. Their coercivity is lower than 1000 Am-1 as measured according to IEC 60404-1 :2000, to allow for a fast magnetization and demagnetization. Suitable soft magnetic materials have a maximum relative permeability .R max of at least 5, where the relative permeability pR is the permeability of the material p relative to the permeability of the free space pO (pR = p / pO) (Magnetic Materials, Fundamentals and Applications, 2nd Ed., Nicola A. Spaldin, p. 16-17, Cambridge University Press, 2011). Soft magnetic materials are described, for example, in the following handbooks: (1) Handbook of Condensed Matter and Materials Data, Chap. 4.3.2, Soft Magnetic Materials, p. 758-793, and Chap. 4.3. 4, Magnetic Oxides, p. 811-813, Springer 2005; (2) Ferromagnetic Materials, Vol. 1 , Iron, Cobalt and Nickel, p. 1-70, Elsevier 1999; (3) Ferromagnetic Materials, Vol. 2, Chap. 2, Soft Magnetic Metallic Materials, p. 55-188, and Chap. 3, Ferrites for non-microwave Applications, p. 189-241 , Elsevier 1999; (4) Electric and Magnetic Properties of Metals, C. Moosbrugger, Chap. 8, Magnetically Soft Materials, p. 196-209, ASM International, 2000; (5) Handbook of modern Ferromagnetic Materials, Chap. 9, High-permeability High- frequency Metal Strip, p. 155-182, Kluwer Academic Publishers, 2002; and (6) Smithells Metals Reference Book, Chap. 20.3, Magnetically Soft Materials, p. 20-9 - 20-16, Butterworth-Heinemann Ltd, 1992. The soft magnetic plate may either be a plate made of one or more metals, alloys or compounds of high magnetic permeability (hereafter referred as “soft magnetic metal plate”) or a plate made of a composite comprising soft magnetic particles dispersed in a non-magnetic material (hereafter referred as “soft magnetic composite plate”). According to one embodiment, the soft magnetic metal plate is made of one or more soft magnetic metals or alloys easily workable as sheets or threads. Preferably, the soft magnetic metal plate is made from one or more materials selected from the group consisting of iron, cobalt, nickel, nickel-molybdenum alloys, nickel-iron alloys (permalloy or supermalloy-typematerials), cobalt-iron alloys, cobalt-nickels alloys iron-nickel-cobalt alloys (Fernico-type materials), Heusler-type alloys (such as Cu2MnSn or Ni2MnAI), low silicon steels, low carbon steels, silicon irons (electrical steels), iron-aluminum alloys, iron-aluminum-silicon alloys, amorphous metal alloys (e.g. alloys like Metglas®, iron-boron alloys), nanocrystalline soft magnetic materials (e.g. Vitroperm®) and combinations thereof, more preferably selected from the group consisting of iron, cobalt, nickel, low carbon steels, silicon irons, nickel-iron alloys and cobalt-iron alloys and combinations thereof.

[0117] In one embodiment, the last radiation-curable coating composition comprises color-constant dyes or pigments, the coloring components being the color-constant pigments may be organic or inorganic pigment particles. Typical examples of color-constant organic and inorganic pigments include without limitation C.l. Pigment Yellow 12, C.l. Pigment Yellow 42, C.l. Pigment Yellow 93, 109, C.l. Pigment Yellow 110, C.l. Pigment Yellow 147, C.l. Pigment Yellow 173, C.l. Pigment Orange 34, C.l. Pigment Orange 48 , C.l. Pigment Orange 49 , C.l. Pigment Orange 61 , C.l. Pigment Orange 71 C.l. Pigment Orange 73, C.l. Pigment Red 9, C.l. Pigment Red 22, C.l. Pigment Red 23, C.l. Pigment Red 57-1. C.l. Pigment Red 67, C.l. Pigment Red 122, C.l. Pigment Red 144, C.l. Pigment Red 146, C.l. Pigment Red 170, C.l. Pigment Red 177, C.l. Pigment Red 179, C.l. Pigment Red 185, C.l. Pigment Red 202, C.l. Pigment Red 224, C.l. Pigment Red 242, C.l. Pigment Red 254, C.l. Pigment Red 264, C.l. Pigment Red 122, C.l. Pigment Brown 23, C.l. Pigment Blue 15, C.l. Pigment Blue 15:3, C.l. Pigment Blue 60, C.l. Pigment Violet 19, C.l. Pigment Violet 23, C.l. Pigment Violet 32, C.l. Pigment Violet 37, C.l. Pigment Green 7, C.l. Pigment Green 36, C.l. Pigment Black 7, C.l. Pigment Black 11 , metal oxides, antimony yellow, lead chromate, lead chromate sulfate, lead molybdate, ultramarine blue, cobalt blue, manganese blue, chrome oxide green, hydrated chrome oxide green, cobalt green and metal sulfides, such as cerium or cadmium sulfide, cadmium sulfoselenides, zinc ferrite, bismuth vanadate, Prussian blue, Fe3O4, carbon black, azo, azomethine, methine, anthraquinone, phthalocyanine, perinone, perylene, diketopyrrolopyrrole, thioindigo, thiazinindigo, dioxazine, iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone, indanthrone, anthrapyrimidine and quinophthalone pigments. When present, the organic or inorganic color-constant pigment is preferably present in the last radiation-curable coating composition in a total amount from about 0.25 wt% to about 15 wt%, preferably from about 0.25 to about 15 wt%, more preferably from about 0.25 wt% to about 5 wt%, the weight percents being based on the total weight of the last radiation-curable coating composition.

[0118] Dyes suitable for the radiation-curable coating compositions are known in the art, wherein said dyes may be reactive dyes, direct dyes, anionic dyes, cationic dyes, acid dyes, basic dyes, food dyes, metal-complex dyes, solvent dyes as well as mixtures thereof. Typical examples of dyes suitable for the present invention are selected from the group consisting of coumarines, cyanines, oxazines, uranines, phtalocyanines, indolinocyanines, triphenylmethanes, naphtalocyanines, indonanaphtalo- metal dyes, anthraquinones, anthrapyridones, azo dyes, rhodamines, squarilium dyes, croconium dyes and mixtures thereof. Typical examples of dyes suitable for the present invention are selected from the group consisting of C.l. Acid Yellow 1 , 3, 5, 7, 1 1 , 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 54, 59, 61 , 70, 72, 73, 75, 76, 78, 79, 98, 99, 110, 111 , 121 , 127, 131 , 135, 142, 157, 162, 164, 165, 194, 204, 236, 245; C.l. Direct Yellow 1 , 8, 11 , 12, 24, 26, 27, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 106, 107, 110,132, 142, 144; C.l. Basic Yellow 13, 28, 65; Diarylide Yellow 13, C.l. Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42; C.l. Food Yellow 3, 4; C.l. Acid Orange 1, 3, 7, 10, 20, 76, 142, 144; C.l. Basic Orange 1 , 2, 59; C.l. Food Orange 2; C.l. Orange B; C.l. Acid Red 1, 4, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 57, 73, 75, 77, 80, 82, 85, 87, 88, 89, 92, 94, 97,106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180,183, 184, 186, 194, 198, 209, 211, 215, 219, 221, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317,320, 321, 322, 357, 359; C.l. Basic Red 1, 2, 14, 28; C.l. Direct Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24,28, 31 , 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81 , 83, 84, 89, 95, 99, 113, 197, 201 , 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, 253; C.l. Reactive Red 1, 2, 3, 4, 5, 6, 7, 8, 11 , 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63, 64, 108, 180; C.l. Food Red 1, 7, 9, 14; C.l. Acid Blue 1, 7, 9, 15,20, 22, 23, 25, 27, 29,40, 41,43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 193, 199, 203, 204, 205, 229, 234, 236, 249, 254, 285; C.l. Basic Blue 1 , 3, 5, 7, 8, 9, 11 , 55, 81; C.l. Direct Blue 1,2, 6, 15,22,25,41,71,76,77, 78,80,86,87,90,98, 106, 108, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, 249; C.l. Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 17, 18, 19, 20, 21, 25, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44, 46, 77; C.l. Food Blue 1, 2; C.l. Acid Green 1, 3, 5, 16, 26, 104; C.l. Basic Green 1 , 4; C.l: Food Green 3; C.l. Acid Violet 9, 17, 90, 102, 121 ; C.l. Basic Violet 2, 3, 10, 11 , 21 ; C.l. Acid Brown 101, 103, 165, 266, 268, 355, 357, 365, 384; C.l. Basic Brown 1; C.l. Acid Black 1, 2, 7, 24, 26,29,31,48,50,51,52,58,60,62,63,64,67,72,76,77,94, 107, 108, 109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156, 157, 158, 159, 191, 194; C.l. Direct Black 17, 19, 22, 32, 39, 51, 56,62, 71, 74, 77, 94, 105, 106, 107, 108, 112, 113, 117, 118, 132, 133, 146, 154, 168; C.l. Reactive Black 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 14, 18, 31; C.l. Food Black 2; C.l. Solvent Yellow 19, C.l. Solvent Orange 45, C.l. Solvent Red 8, C.l. Solvent Green 7, C.l. Solvent Blue 7, C.l. Solvent Black 7; C.l. Disperse Yellow 3, C.l. and mixtures thereof. Disperse Red 4, 60, C.l. Disperse Blue 3, metal azo dyes disclosed in US5,074,914, US5,997,622, US6.001.161, JP02-080470, JP62-190272, JP63-218766. When present, the at least one color-constant dye is preferably present in the last radiation-curable coating composition in a total amount from about 1 wt% to about 25 wt%, preferably from about 1wt% to about 10 wt%, more preferably from about 1.2 wt% to about 5 wt%, the weight percents being based on the total weight of the last radiation-curable coating composition.

[0119] In one embodiment, the last radiation-curable coating composition comprises one or more iridescent pigments. The expression “iridescent pigment” means pigments comprising a flake-shaped non-metallic or metallic substrate which is at least partially coated with the one or more at least partial coating layers independently made of one or more metal oxides, one or more metal oxide hydrates, one or more metal suboxides, one or more metal fluorides or mixtures of these materials, and optionally comprising an at least partial surface treatment layer facing the environment. By "facing the environment", it is meant that the surface treatment layer is the topmost layer of the pigments and acts as an outer layer. The at least partial surface treatment layer is in direct contact with the top layer of the one or more at least partial coating layers. The thickness of the metal oxide, metal oxide hydrate, metalsuboxide, metal, metal fluoride, metal nitride, metal oxynitride layers or a mixture thereof is usually 5 to 1000 nm, preferably 10 to 800 nm, in particular 20 to 600 nm.

[0120] The one or more at least partial coatings may be applied to the flake-shaped non-metallic or metallic substrate by precipitation methods, wet-chemical methods, sol-gel methods physical vapor deposition (PVD) processes or chemical vapor deposition (CVD) processes, wherein said methods are chosen as a function of the substrate materials and the coating materials. Alternatively, the one or more at least partial coatings made of metal oxides and / or oxide hydrates may be obtained on flake-shaped metallic substrates by chemical oxidation of the metal surface (e.g. with permanganate or other strong oxidation agents) or by heating the flake-shaped metallic pigment in air or in a controlled atmosphere (e.g. enriched in oxygen and / or in water vapor) at elevated temperature during a given amount of time, the time, temperature and atmosphere composition depending on the metal and on the desired thickness of the at least partial coatings. For example, the flake-shaped metallic pigment may be baked in an oven at 300°C in dry air for 30 minutes in order to get the at least partial coatings made of metal oxide and / or metal hydrate.

[0121] The size of the iridescent pigments, expressed as a D50 value, is preferably in the range from about 1 to about 100 pm, preferably from about 5 to about 50 pm. The thickness of the pigments is usually between 0.1 and 5 pm, preferably between 0.2 and 4 pm.

[0122] The flake-shaped non-metallic substrate of the iridescent pigments is preferably made of one or more materials selected from the group consisting of natural micas, synthetic micas, talcs, graphites, borosilicates (e.g. glasses) and kaolins, more preferably selected from the group consisting of natural micas, synthetic micas and glasses and still more preferably selected from the group consisting of natural micas and synthetic micas.

[0123] The flake-shaped non-metallic substrate of the iridescent pigment comprises one or more at least partial coatings independently made of one or more metal oxides, one or more metal oxide hydrates, one or more metal suboxides, one or more metal fluorides, or mixtures of these materials, preferably one or more metal oxides and / or one or more metal oxide hydrates, more preferably comprising one or more metal oxides. Suitable metal oxides include without limitation aluminum oxide, silicon oxide, iron oxides, tin oxide, cerium oxide, zinc oxide, zirconium oxide, chromium oxide, titanium oxide and any mixtures thereof. Preferably, the non-metallic substrate consists of a non-metallic substrate, preferably natural micas or synthetic micas, comprising one or more at least partial coatings independently made of one or more metal oxides selected from the group consisting of titanium dioxides, tin oxides, iron oxide, chromium oxide and mixtures thereof. Particularly preferred flakeshaped non-metallic substrates for the iridescent pigments consist of natural micas or synthetic micas comprising one or more at least partial coatings independently made of titanium dioxide (i.e. flakeshaped mica substrate + TiC>2) or a mixture comprising titanium dioxide as well as natural or synthetic micas comprising more than one at least partial coatings, wherein one of said one or more at least partial coatings is made of titanium dioxide and another one of said one or more at least partial coatings is made of tin oxide (i.e. flake-shaped mica substrate + SnC>2 + TiC>2 or flake-shaped mica substrate + TiO2 + SnO2).

[0124] According to one embodiment, the flake-shaped metallic substrate of the iridescent pigmentsconsists of a monolayer made of one or more metals preferably selected from the group consisting of aluminum, copper, zinc, tin, brass, iron, titanium, chromium, nickel, silver, gold, steel, alloys thereof and mixtures thereof preferably selected from the group consisting of aluminum, iron and brass. The flakeshaped metallic substrate comprises one or more at least partial coatings independently made of one or more metal oxides, one or more metal oxide hydrates, one or more metal suboxides, one or more metal fluorides, or mixtures of these materials, preferably one or more metal oxides and / or one or more metal oxide hydrates, more preferably comprising one or more metal oxides. Suitable metal oxides include without limitation aluminum oxide, silicon oxide, iron oxides, tin oxide, cerium oxide, zinc oxide, zirconium oxide, chromium oxide and titanium oxide.

[0125] According to one embodiment, the flake-shaped metallic substrate of the iridescent pigments consists of a three layer structure made of one or more metals preferably independently selected from the group consisting of aluminum, copper, zinc, tin, brass, iron, titanium, chromium, nickel, silver, gold, steel, alloys thereof and mixtures thereof preferably independently selected from the group consisting of aluminum, chromium, iron, alloys thereof and mixtures thereof. The flake-shaped metallic substrate comprises one or more at least partial coatings independently made of one or more metal oxides, one or more metal oxide hydrates, one or more metal suboxides, one or more metal fluorides, or mixtures of these materials, preferably one or more metal oxides and / or one or more metal oxide hydrates, more preferably comprising one or more metal oxides. Suitable metal oxides include without limitation aluminum oxide, silicon oxide, iron oxides, tin oxide, cerium oxide, zinc oxide, zirconium oxide, chromium oxide and titanium oxide. Suitable examples of flake-shaped metallic substrates include three layer structures are AI / M / AI, wherein M is iron or a mixture of iron and chromium and wherein said flakeshaped metallic substrates comprise one or more at least partial coatings made of one or more metal fluorides, preferably magnesium fluoride.

[0126] According to one embodiment, the flake-shaped metallic substrate of the iridescent pigments consists of a multilayer comprising one or more metallic layers and optionally one or more non-metallic layers.

[0127] According to one preferred embodiment, the flake-shaped metallic substrate of the iridescent pigments consists of a multilayer comprising one or more metallic layers and optionally one or more non-metallic layers being thin film interference multilayers comprising a Fabry-Perot reflector / dielectric / absorber multilayer structures such as those disclosed in US 4,705,300; US 4,705,356; US 4,721 ,271 ; US 5,084,351 ; US 5,214,530; US 5,281 ,480; US 5,383,995; US 5,569,535, US 5,571624 and in the thereto related documents. Preferably, the multi layers comprising one or more metallic layers are thin film interference pigments comprising a Fabry-Perot absorber / dielectric / reflector / dielectric / absorber multilayer structure, wherein the absorber layers are partially transmitting and partially reflecting, the dielectric layers are transmitting and the reflective layer is reflecting the incoming light. Preferably, the reflector layer is selected from the group consisting of metals, metal alloys and combinations thereof, preferably selected from the group consisting of reflective metals, reflective metal alloys and combinations thereof and more preferably selected from the group consisting of aluminum, chromium, nickel, and mixtures thereof and still more preferably aluminum. Preferably, the dielectric layers are independently selected from the group consisting ofmagnesium fluoride, silicon dioxide and mixtures thereof and more preferably magnesium fluoride. Preferably, the absorber layers are independently selected from the group consisting of chromium, nickel, metallic alloys and mixtures thereof and more preferably chromium. Particularly preferred thin film interference multilayers comprise a Fabry-Perot absorber / dielectric / reflector / dielectric / absorber multilayer structure comprising a Cr / MgF2 / AI / MgF2 / Cr multilayer structure. The flake-shaped metallic substrate of the iridescent pigments consisting of a thin film interference multilayer further comprises an at least partial coating made of one or more metal oxides, one or more metal oxide hydrates, one or more metal suboxides, one or more metal fluorides, or mixtures of these materials, preferably one or more metal oxides and / or one or more metal oxide hydrates, more preferably comprising one or more metal oxides. Preferred metal oxides are aluminum oxides, silicon oxide, iron oxides, tin oxide, cerium oxide, zinc oxide, zirconium oxide, chromium oxide and titanium oxide, preferably chromium oxide and mixtures thereof.

[0128] The non-metallic or metallic substrate of the iridescent pigment further may optionally comprise an at least partial surface treatment layer, wherein said surface treatment layer faces the environment and is in direct contact with the top layer of the one or more at least partial coating layers. In other words, the at least partial surface treatment layer is present on the top layer coating of the one or more at least partial coatings. The at least partial surface treatment layer is made of one or more surface modifiers selected from functionalized fluoro compounds, said fluoro compounds being functionalized with phosphor (P) containing compounds or silicon (Si) containing compounds. The functionalized fluoro compounds are preferably functionalized with one or more phosphate containing groups, one or more silane containing groups or one or more siloxane containing groups.

[0129] When present, the at least one iridescent pigment is preferably present in the last radiation- curable coating composition in a total amount from about 2 wt% to about 40 wt%, preferably from about 5 wt% to about 30 wt%, more preferably from about 5 wt% to about 20 wt%, the weight percents being based on the total weight of the last radiation-curable coating composition.

[0130] Curing of the first coating composition [step c)] results in fixing the platelet-shaped magnetic or magnetizable pigment particles. Subsequently to or partially simultaneously with, preferably partially simultaneously with the step or steps of orienting the platelet-shaped magnetic or magnetizable pigment particles (step b), the orientation of the platelet-shaped magnetic or magnetizable pigment particles is fixed or frozen (step c) by curing. The first coating composition therefore has a first state, i.e. a liquid or pasty state, wherein the composition is not yet hardened and wet or soft enough, so that the plateletshaped magnetic or magnetizable pigment particles dispersed in the compositions are freely movable, rotatable and orientable upon exposure to a magnetic field, and a second hardened (e.g. solid or solidlike) state, wherein the platelet-shaped magnetic or magnetizable pigment particles are fixed or frozen in their respective positions and orientations.

[0131] Such a first and second state is preferably provided by using a certain type of coating composition. For example, the components of the first radiation-curable coating composition other than the platelet-shaped magnetic or magnetizable pigment particles may take the form of an ink or coating composition such as those which are used in security applications, e.g. for banknote printing. The aforementioned first and second states can be provided by using a material that shows an increase inviscosity in reaction to a stimulus such as for example a temperature change or an exposure to an electromagnetic radiation. That is, when the fluid binder material is hardened or solidified, said binder material converts into the second state, i.e. a hardened or solid state, where the platelet-shaped magnetic or magnetizable pigment particles are fixed in their current positions and orientations and can no longer move nor rotate within the binder material. As known to those skilled in the art, ingredients comprised in an ink or coating composition to be applied directly or indirectly onto a substrate and the physical properties of said ink or coating composition must fulfill the requirements of the process used to transfer said ink or coating composition. Consequently, the binder material comprised in the coating compositions is typically chosen among those known in the art and depends on the coating or printing process used to apply the ink or coating composition and the chosen hardening process.

[0132] The curing step c) involves a chemical reaction, for instance curing, which is not reversed by a simple temperature increase (e.g. up to 80°C) that may occur during a typical use of a security document. The term “curing” or “curable” refers to processes including the chemical reaction, crosslinking or polymerization of at least one component in the applied coating composition in such a manner that it turns into a polymeric material having a greater molecular weight than the starting substances. Preferably, the curing causes the formation of a stable three-dimensional polymeric network. Such a curing is generally induced by applying an external stimulus to the composition (i) after its application (step a) and (ii) subsequently to or partially simultaneously with the orientation (step b) of at least part of the platelet-shaped magnetic or magnetizable pigment particles (step c). Advantageously the curing step of the first coating layer is carried out partially simultaneously with the orientation (step b) of at least a part of the platelet-shaped magnetic or magnetizable pigment particles (step c). Radiation curing, in particular UV-Vis curing, advantageously leads to an instantaneous increase in viscosity of the first radiation-curable coating composition after exposure to irradiation, thus preventing any further movement of the pigment particles and in consequence any loss of information after the magnetic orientation step. Preferably, the curing step (step c) is carried out by irradiation with UV-visible light (i.e. UV-Vis light radiation curing) or by E-beam (i.e. E-beam radiation curing), more preferably by irradiation with UV-Vis light since UV-Vis curing advantageously allows very fast curing processes.

[0133] Preferably, the first or last radiation-curable coating compositions, preferably the first and last radiation-curable coating compositions, independently comprise one or more compounds selected from the group consisting of radically-curable compounds and cationically-curable compounds. The coating compositions may be hybrid systems and comprise a mixture of one or more cationically-curable compounds and one or more radically-curable compounds. Cationically-curable compounds are cured by cationic mechanisms typically including the activation by radiation of one or more photoinitiators which liberate cationic species, such as acids, which in turn initiate the curing to react and / or cross-link the monomers and / or oligomers to thereby harden the coating composition. Radically-curable compounds are cured by free radical mechanisms typically including the activation by radiation of one or more photoinitiators, thereby generating radicals which in turn initiate the polymerization to harden the coating composition. Depending on the monomers, oligomers or prepolymers used to prepare the binder comprised in the first and last radiation-curable coating compositions, different photoinitiatorsmight be used. Suitable examples of free radical photoinitiators are known to those skilled in the art and include without limitation acetophenones, benzophenones, benzyldimethyl ketals, alpha-aminoketones, alpha-hydroxyketones, phosphine oxides and phosphine oxide derivatives, as well as mixtures of two or more thereof. Suitable examples of cationic photoinitiators are known to those skilled in the art and include without limitation onium salts such as organic iodonium salts (e.g. diaryl iodoinium salts), oxonium (e.g. triaryloxonium salts) and sulfonium salts (e.g. triarylsulphonium salts), as well as mixtures of two or more thereof. Other examples of useful photoinitiators can be found in standard textbooks. It may also be advantageous to include a sensitizer in conjunction with the one or more photoinitiators in order to achieve efficient curing. Typical examples of suitable photosensitizers include without limitation isopropyl-thioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX) and 2,4-diethyl-thioxanthone (DETX) and mixtures of two or more thereof. The one or more photoinitiators comprised in the radiation-curable coating compositions are preferably present in a total amount from about 0.1 wt% to about 20 wt%, more preferably about 1 wt% to about 15 wt%, the weight percents being based on the total weight of the first and second radiation-curable coating compositions, respectively. In a preferred embodiment, the first and last coating compositions are radical-curing coating compositions. In a particularly preferred embodiment, the first and last coating compositions comprise acrylates, particularly preferably polyacrylates, i.e. molecules bearing two or more acrylate functionalities.

[0134] The first and last radiation-curable coating compositions may further independently comprise one or more additives including without limitation compounds and materials which are used for adjusting physical, rheological and chemical parameters of the composition such as the viscosity (e.g. solvents and surfactants), the consistency (e.g. anti-settling agents, fillers and plasticizers), the foaming properties (e.g. antifoaming agents), the lubricating properties (waxes), UV reactivity and stability (photosensitizers and photostabilizers) and adhesion properties, etc. Additives may be present in the coating compositions in amounts and in forms known in the art, including in the form of so-called nanomaterials where at least one of the dimensions of the particles is in the range of 1 to 1000 nm.

[0135] The first and last radiation-curable coating compositions may be independently prepared by dispersing or mixing the platelet-shaped magnetic or magnetizable pigment particles and / or the at least one color-constant pigment or dye and / or the one or more additives when present in the presence of the binder material, thus forming liquid compositions. When present, the one or more photoinitiators may be added to the composition either during the dispersing or mixing step of all other ingredients or may be added at a later stage, i.e. after the formation of the liquid coating composition.

[0136] The process for producing the OEL of the invention comprises partially simultaneously with step b) or subsequently to step b), preferably partially simultaneously, a step of curing step c) of the first radiation-curable coating composition. The step of curing the first coating composition allows the platelet-shaped magnetic or magnetizable pigment particles to be fixed in their adopted positions and orientations in a desired pattern to form the OEL, thereby transforming the first radiation-curable coating composition to a second state. The time from the end of step b) to the beginning of step c) is preferably relatively short in order to avoid any de-orientation and loss of information. Typically, the time between the end of step b) and the beginning of step c) is less than 1 minute, preferably less than 20 seconds,further preferably less than 5 seconds. It is particularly preferable that there be essentially no time gap between the end of the orientation step b) and the beginning of the curing step c), i.e. that step c) follow immediately after step b) or already start while step b) is still in progress (partially simultaneously). By “partially simultaneously”, it is meant that both steps are partly performed simultaneously, i.e. the times of performing each of the steps partially overlap. In the context of the present invention, when curing is performed partially simultaneously with the step b), it must be understood that curing becomes effective after the orientation so that the platelet-shaped magnetic or magnetizable pigment particles orient before the complete or partial curing of the OEL. As mentioned herein, the curing steps c) and e) may be performed by using different means or processes depending on the binder material comprised in the first coating composition that also comprises the platelet-shaped magnetic or magnetizable pigment particles, and the last coating composition that comprises color-constant dyes or pigments.

[0137] The curing steps generally may be any step that increases the viscosity of the radiation-curable coating composition such that a substantially solid material adhering to the substrate is formed. The curing steps may involve a physical process based on the evaporation of a volatile component, such as a solvent, and / or water evaporation (i.e. physical drying). Herein, hot air, infrared or a combination of hot air and infrared may be used. Alternatively, the curing steps may include a chemical reaction, such as a curing, polymerizing or cross-linking of the binder and optional initiator compounds and / or optional cross-linking compounds comprised in the radiation-curable coating composition. Such a chemical reaction may be initiated by heat or IR irradiation as outlined above for the physical hardening processes, but may preferably include the initiation of a chemical reaction by a radiation mechanism including without limitation Ultraviolet-Visible light radiation curing (hereafter referred as UV-Vis curing) and electronic beam radiation curing (E-beam curing); oxypolymerization (oxidative reticulation, typically induced by joint action of oxygen and one or more catalysts preferably selected from the group consisting of cobalt-containing catalysts, vanadium-containing catalysts, zirconium-containing catalysts, bismuth-containing catalysts and manganese-containing catalysts); cross-linking reactions or any combination thereof.

[0138] Radiation curing is particularly preferred, and UV-Vis light radiation curing is even more preferred, since these technologies advantageously lead to very fast curing processes and hence drastically decrease the preparation time of any article comprising the OEL of the invention. Moreover, radiation curing has the advantage of producing an almost instantaneous increase in viscosity of the coating composition after exposure to the curing radiation, thus minimizing any further movement of the particles. In consequence, any loss of orientation after the magnetic orientation step can essentially be avoided. Particularly preferred is radiation-curing by photo-polymerization, under the influence of actinic light having a wavelength component in the UV or blue part of the electromagnetic spectrum (typically 200 nm to 650 nm; more preferably 200 nm to 420 nm). Suitable curing units for the curing steps (steps c and e) may comprise a high-power light-emitting-diode (LED) lamp, or an arc discharge lamp, such as a medium-pressure mercury arc (MPMA) or a metal-vapor arc lamp, as the source of the actinic radiation. On the contrary to medium-pressure mercury lamps that have emission bands in the UV-A, UV-B and UV-C regions of the electromagnetic spectrum, UV-LED lamps emit radiation in the UV-A region and / or visible (Vis) region, e.g. in the range from about 350 nm to about 470 nm. Moreover,current UV-LED and Vis-LED lamps emit quasi monochromatic radiation, i.e. only emit at one wavelength, such as 365 nm, 385 nm, 395 nm, 405 nm or 450 nm. Preferably, at least one of the steps c) and e) are carried out by exposing the first coating layer (210) and the last coating layer (211), respectively, to UV light with an LED curing unit, preferably to one or more wavelengths between about 355 nm and about 415 nm, more preferably by exposure to UV light at 365 nm and / or 385 nm and / or 395 nm, emitted from the LED curing unit.

[0139] Prior to the step of curing step c), the first coating layer may be subjected to customization to produce OELs further exhibiting one or more indicia, wherein said customization step is carried out after the orientation step b), and prior to curing step c). The customization step is preferably carried out by applying a liquid coating composition on top of the coating layer which is still is a wet state (a wet-on- wet process), said application being carried out by a contactless fluid microdispensing process such as disclosed in WO2021 / 259527A1 .

[0140] The present invention provides the processes to produce the OELs of the invention on a substrate. The substrate is preferably selected from the group consisting of papers or other fibrous materials (including woven and non-woven fibrous materials), such as cellulose, paper-containing materials, glasses, metals, ceramics, plastics and polymers, metalized plastics or polymers, at least partially opacified plastics or polymers, composite materials and mixtures or combinations of two or more thereof. Typical paper, paper-like or other fibrous materials are made from a variety of fibers including without limitation abaca, cotton, linen, wood pulp, and blends thereof. As is well known to those skilled in the art, cotton and cotton / linen blends are preferred for banknotes, while wood pulp is commonly used in non-banknote security documents. Typical examples of plastics and polymers include polyolefins such as polyethylene (PE) and polypropylene (PP) including biaxially oriented polypropylene (BOPP), polyamides, polyesters such as polyethylene terephthalate) (PET), poly(1 ,4- butylene terephthalate) (PBT), polyethylene 2,6-naphthoate) (PEN) and polyvinylchlorides (PVC). Spunbond olefin fibers such as those sold under the trademark Tyvek® may also be used as substrate. Typical examples of metalized plastics or polymers include the plastic or polymer materials described hereabove having a metal disposed continuously or discontinuously on their surface. Typical examples of metals include without limitation aluminum (Al), chromium (Cr), copper (Cu), gold (Au), silver (Ag), alloys thereof and combinations of two or more of the aforementioned metals. The metallization of the plastic or polymer materials described hereabove may be done by an electrodeposition process, a high- vacuum coating process or by a sputtering process. Opacified polymers have been developed with the aim of mimicking the appearance and some properties of conventional paper-based substrates for security document and consist of polymeric transparent substrates which are surface treated typically on one or on both of their sides with opacifying layers to form opacified polymer-based substrates. Typical examples of composite materials include without limitation multilayer structures or laminates of paper and at least one plastic or polymer material such as those described hereabove as well as plastic and / or polymer fibers incorporated in a paper-like or fibrous material such as those described hereabove. Of course, the substrate can comprise further additives that are known to the skilled person, such as fillers, sizing agents, Whiteners, processing aids, reinforcing or wet strengthening agents, etc. When the OELs produced according to the present invention are used for decorative or cosmeticpurposes including for example fingernail lacquers, said OEL may be produced on other type of substrates including finger and toe nails, artificial nails or other parts of an animal or human being.

[0141] The substrate (220) may be in the form of a web, sheet, thread reel, film reel, labels of the roll or label stocks, preferably a web or sheet.

[0142] Should the OEL produced according to the present invention be on a security document, and with the aim of further increasing the security level and the resistance against counterfeiting and illegal reproduction of said security document, the substrate may comprise printed, coated, or laser-marked or laser-perforated indicia, watermarks, security threads, fibers, planchettes, luminescent compounds, windows, foils, decals and combinations of two or more thereof. With the same aim of further increasing the security level and the resistance against counterfeiting and illegal reproduction of security documents, the substrate may comprise one or more marker substances or taggants and / or machine readable substances. According to one embodiment, the substrate (220) comprises a printed pattern, preferably an offset printed pattern, wherein the radiation-curable coating composition of steps a) and is applied at least partially on top of said printed pattern and the process of the invention comprises a step of printing an ink on the substrate (220), wherein said step occurs prior to step a).

[0143] If desired, a primer layer may be applied to the substrate (220) prior to the step a). This may enhance the quality of the OEL or promote adhesion. Examples of such primer layers may be found in W02010 / 058026A2.

[0144] With the aim of increasing the durability through soiling or chemical resistance and cleanliness and thus the circulation lifetime of an article, a security document or a decorative element or object comprising the OEL obtained by the process of the invention, or with the aim of modifying their aesthetic appearance (e.g. optical gloss), one or more protective layers may be applied on top of the OEL. When present, the one or more protective layers are typically made of protective varnishes. These may be transparent or slightly colored or tinted and may be more or less glossy. Protective varnishes may be radiation-curable compositions, thermal drying compositions or any combination thereof. Preferably, the one or more protective layers are radiation-curable compositions, more preferably UV-Vis-curable compositions. The protective layers are typically applied after the formation of the OEL.

[0145] The process of the invention may further comprise a step of embossing the OEL of the invention using, for example, an embossing dye or an intaglio printing plate as disclosed in W02012 / 025206A2 and WO2019 / 233624A1.

[0146] The OEL of the invention may be used in combination with holograms, microlenses and / or micromirrors as described in W02020 / 244805A1 , EP3254863A1 , US2008 / 0160226, US2005 / 0180020 and EP2284017A1 , said holograms, microlenses and / or micromirrors being applied at a position spaced apart from the OEL or least partially on top or below the OEL.

[0147] The present invention further provides optical effect layers (OELs) produced by the process according to the present invention.

[0148] The OEL of the invention may be provided directly on a substrate (220) on which it shall remain permanently (such as for banknote applications). Alternatively, an OEL comprising the first and last motifs on the same side of the substrate may also be provided on a temporary substrate for production purposes, from which the OEL is subsequently removed. This may for example facilitate the productionof the OEL, particularly while the binder material is still in its fluid state. Thereafter, after curing the radiation-curable compositions for the production of the OEL, the temporary substrate may be removed from the OEL.

[0149] Alternatively, in another embodiment an adhesive layer may be present. An adhesive layer may be applied after the curing step of the last set of steps has been completed. Such an article may be attached to all kinds of documents or other articles or items without printing or other processes involving machinery and rather high effort. Alternatively, the substrate comprising the OEL of the invention may be in the form of a transfer foil, which can be applied to a document or to an article in a separate transfer step. For this purpose, the substrate is provided with a release coating, on which the OEL is produced.

[0150] Also described herein are substrates comprising more than one, i.e. two, three, four, etc. OELs obtained by the process of the invention, each of said OELs independently comprising the first and last motifs in the form of the first and last coating layers.

[0151] Also described herein are articles, in particular security documents, decorative elements or objects, comprising the OEL produced according to the present invention. The articles, in particular security documents, decorative elements or objects, may comprise more than one (for example two, three, etc.) OELs produced according to the present invention.

[0152] As mentioned hereabove, the OEL produced according to the present invention may be used for decorative purposes as well as for protecting and authenticating a security document.

[0153] Typical examples of decorative elements or objects include without limitation luxury goods, cosmetic packaging, automotive parts, electronic / electrical appliances, furniture, fingernail and toenail articles.

[0154] Security documents include without limitation value documents and value commercial goods. Typical examples of value documents include without limitation banknotes, deeds, tickets, checks, vouchers, fiscal stamps and tax labels, agreements and the like, identity documents such as passports, identity cards, visas, driving licenses, bank cards, credit cards, transactions cards, access documents or cards, entrance tickets, public transportation tickets or titles and the like, preferably banknotes, identity documents, right-conferring documents, driving licenses and credit cards. The term “value commercial good” refers to packaging materials, in particular for cosmetic articles, nutraceutical articles, pharmaceutical articles, alcohols, tobacco articles, beverages or foodstuffs, electrical / electronic articles, fabrics or jewelry, i.e. articles that shall be protected against counterfeiting and / or illegal reproduction in order to warrant the content of the packaging like for instance genuine drugs. Examples of these packaging materials include without limitation labels, such as authentication brand labels, tamper evidence labels and seals. It is pointed out that the disclosed substrates, value documents and value commercial goods are given exclusively for exemplifying purposes, without restricting the scope of the invention.

[0155] Alternatively, the OEL may be produced onto an auxiliary substrate such as for example a security thread, security stripe, a foil, a decal, a window or a label and consequently transferred to a security document in a separate step.

[0156] The skilled person can envisage several modifications to the specific embodiments described above without departing from the spirit of the present invention. Such modifications are encompassedby the present invention.

[0157] Further, all documents referred to throughout this specification are hereby incorporated by reference in their entirety as set forth in full herein.

[0158] Figs 7A and 7B depict one-step magnetic orienting of pigment particles [step b)] schematically. A coating composition comprising platelet-shaped magnetic or magnetizable pigment particles (210) is printed on substrate (220), and subjected to the magnetic field of a magnetic assembly (230) to magnetically orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles. Fig.7B depicts one way in which this can be carried out using a typical printing device. The substrate (220), in the form of sheets or of a continuous web, passes over cylinder (300), with the curved arrow designating the direction of rotation of the cylinder. Magnetic assemblies (230) are imbedded in the cylinder (300), such that the printed coating compositions (210) are exposed to the magnetic field of the magnetic assemblies as the sheet or web of substrate (220) advances. Rotation of the cylinder (300) advances the substrate such that the coating composition (210) and its corresponding magnetic assembly (230) are advanced to a radiation curing device (250), which cures the coating composition, thus fixing the magnetic orientation of the pigment particles.

[0159] Fig.8 depicts schematically another example of a process for carrying out magnetic orientation of the pigment particles [step b)]. The substrate (220) is in the form of sheets or of a continuous web, with a coating composition comprising platelet-shaped magnetic or magnetizable pigment particles (210) printed at intervals. The substrate sheet or web (220) and the coating composition (210) are first passed into the influence of a first magnetic assembly (230), designed to bi-axially orient the pigment particles [i.e. align the particles substantially in a single plane, parallel to the surface of the substrate (220)]. The sheet or web advances over cylinder (300), and each coating composition (210) comes under the influence of a second magnetic assembly (240), designed to orient the particles in a specific design. Continued advancement of the substrate sheet or web over the cylinder (300) exposes the coating composition (210) to a radiation curing device (250), resulting in fixation of the orientation of the pigment particles.EXAMPLES

[0160] Preparation of OELs E1-E14

[0161] The OELs of Examples E1-E14, were prepared according to the steps illustrated schematically in Fig. 8, on laboratory equipment.

[0162] The screen (290) used to print the UV curable inks A1-A4 disclosed in Table 1 [step a)] and the screen (291) used to print in register the UV curable inks D5-D8 disclosed in Table 2 [step d)] are shown in Fig. 9A. Together, the component images of the screens of step a) and step d) form a composite image of a hot air balloon. The register for the printing of the first coating layer comprising plateletshaped magnetic or magnetizable pigment particles [290, step a)] and of the last coating layer comprising a colorant [291 , step d)] was ensured by using screens having guiding marks, in addition to the motif to be printed.

[0163] The magnetic field generating device (230) illustrated in Fig. 10 was used to bi-axially orient the platelet-shaped magnetic pigment particles in the coating layer (210) of the radiation-curablescreen-printing inks described in Table 1 (step b1). The magnetic field generating device (240) illustrated in Fig. 11 was used to orient the platelet-shaped magnetic pigment particles in the coating layer (210) of the radiation-curable screen-printing inks described in Table 1 (step b2).

[0164] The substrate (220) used for the samples for the color measurements (Table 3) and to prepare the examples E1-E14 was a fiduciary paper (from Louisenthal).

[0165] The production of samples E1-E14 is described with reference to Fig.8. The first radiation- curable screen-printing ink, comprising platelet-shaped magnetic or magnetizable pigment particles [inks A1-A4, step a)] was applied onto the substrate by screen-printing using a first 90T screen (290) to form the first uncured coating layer (210) having a thickness of about 20 |j.m.

[0166] The substrate (220) carrying the first uncured coating layer (210) was moved above the magnetic assembly (230) and was subsequently placed on the second magnetic assembly (240), in steps b1) and b2). The so-obtained magnetic orientation pattern of the platelet-shaped magnetic pigment particles was then fixed by exposing for about 3 seconds to UV-curing the coating layer comprising the pigment particles using a UV-LED-lamp (650) from Phoseon (Type FireFlex 50 x 75 mm, 395 nm, 8 W / cm2), in step c), to form the first cured coating layer. UV-LED exposure was carried out while the substrate (220) and coating layer (210) was still underthe influence of the second magnetic assembly (240).

[0167] The last radiation-curable screen-printing ink comprising a colorant (pigment or dye) and no magnetic or magnetizable pigment particles (inks D5-D8) was applied [(211), step d)] onto the substrate (220) in register with the first cured coating layer (210) applied in step a) by hand screen-printing using a second 90T screen (291) to form the last uncured coating layer (211) having a thickness of about 20 |j.m. The second radiation-curable screen-printing ink was applied on the same side as the first coating layer.

[0168] The last radiation-curable screen-printing ink was cured by exposing it for about 3 seconds to a UV-LED-lamp (250’) from Phoseon [Type FireFlex 50 x 75 mm, 395 nm, 8 W / cm2) (step c)], to form the last cured coating layer.

[0169] This process, using inks A1-A4 comprising platelet-shaped magnetic or magnetizable particles in step a) and inks D5-D8 comprising a colorant (pigment or dye) and no magnetic or magnetizable pigment particles in step d) was used to make the OEL combinations listed in Table 3.

[0170] OELs for Examples E2 and E7 are shown in Fig.9C. The OELs were illuminated with ambient light (i.e. no particular angle of incidence), and the sample was tiled to -45°, 0° and +45°, as shown in Fig.9B. The OELs of the invention gave dramatic angle-dependent visual effects, as exemplified by E2 and E7. Referring to Fig. 9C, and Example E2, at -45°, “a” designates an area in which the swirling lines were alternating bright green and olive, “b” designates an area in which the swirling lines were alternating midnight blue and green / brown. For Example E2, at +45°, “c” designates an area in which the swirling lines are essentially imperceptible, and “d” designates an area in which the swirling lines were alternating bright blue and olive. Referring to Fig. 9C, for Example E7, at -45°, “a” designates an area in which the swirling lines were alternating red and bright orange, “b” designates an area in which the swirling lines were alternating olive and brown. For Example E7, at +45°, “c” designates an area in which the swirling lines are essentially imperceptible, and “d” designates an area in which the swirlinglines were alternating bright green and brown.(*) green-to-blue (A1) or gold-to-green (A2) colorshifting magnetic pigment particles having a flake shape (platelet-shaped pigment particles) of diameter d50 of about 11 pm and thickness of about 1 pm, obtained from Viavi Solutions, Santa Rosa, CA.(**) 5-layer platelet-shaped magnetic pigment particles exhibiting a metallic silver color having a flake shape of diameter d50 of about 12 pm and thickness of about 1 pm obtained from Viavi Solutions, Santa Rosa, CA.(***) gold magnetic pigment particles having a flake shape of diameter d90 of about 33.5 pm (as determined by laser diffraction, according to TDS) from Merck.Color travel measurements

[0172] Samples were prepared in which the first cured coating layer (210) prepared with the radiation- curable screen-printing inks A1-A4 comprising the platelet-shaped magnetic or magnetizable pigment particles described in Table 1 was overprinted in register with the last radiation-curable screen-printing inks D5-D8 comprising color-constant pigments (211), and the color travel of the samples were measured at 0° to the normal with an illumination angle of 22.5°, and at 67.5° to the normal with an illumination at 45° using a goniometer (Goniospektrometer Codec WI-10 5&5 by Phyma GmbH Austria).

[0173] The samples were prepared according to the method of Fig. 2, with the exception that a second magnetic orientation device (240) was not used. The radiation-curable screen-printing inks A1-A4 of Table 1 were applied [step a)] onto the substrate (220) by hand screen-printing using a first 90T screen (290) to form a first uncured coating layer (210) having a thickness of about 20 |j.m and having a shape of a circle (diameter of about 20 mm). The substrate (220) carrying the first uncured coating layer (210) of the UV-curable screen-printing ink was transported in front of a magnetic field generating device (230) according to step b1). The detailed structure of the magnetic field generating device is shown in Fig. 10 [step b1)]. The so-obtained magnetic orientation pattern of the platelet-shaped optically variable magnetic pigment particles (bi-axial orientation parallel to the substrate) was then fixed by exposing for about 3 second to a first UV-LED-lamp from Phoseon (Type FireFlex 50 x 75 mm, 395 nm, 8 W / cm2) [step c)], to form the first cured coating layer.

[0174] For each sample, the radiation-curable screen-printing inks D5-D8 of Table 2 were applied onto the substrate in register on top of the first cured coating layer (210) by hand screen-printing using a second 90T screen (291) (being the same screen as (290)) to form the last uncured coating layer (211)having a thickness of about 20 |j.m and having the same shape of a circle (diameter of about 20 mm) (step d). The so-obtained layer (211) was cured by exposing for about 3 second to UV-curing the layer (211) using a second UV-LED-lamp from Phoseon (Type FireFlex 50 x 75 mm, 395 nm, 8 W / cm2) in step e), to form the last cured coating layer.

[0175] The CIELAB L*, a* and b* values of the samples comprising the first cured coating layers made of each of the inks A1 to A3 alone, and the samples comprising the last cured coating layer superposed thereon (each of the inks D5 to D8) are reported in Table 4. The data in Table 4 shows the impact of the second ink layer (211) on the face and angle color and thus on the color travel visible when comparing the CIELAB L*, a* and b* values of the inks A1 , A2 or A3 with the CIELAB L*, a* and b* values of the superposed layers.Effect of colorant concentration

[0176] To evaluate the effect of colorant concentration in the last cured coating layer applied in step d) on the dynamic effect of the OEL, OELs were prepared using the same method and the same screens as in example E1 , but varying the pigment concentration in the last cured coating layer. Inks D5 and D9-D12 were prepared comprising different wt%’s of the blue colorant VERSAL BLUE LBS (from about0.85 wt% in D5 to about 8.5 wt% in D12, see Table 5). OELs were made by printing each of inks D5 and D9-D12 in register on top of a cured layer of ink A1 (comprising magnetic pigment particles), as in Example E1 , with a thickness of 20 pm. The resulting OELs were evaluated visually to determine the degree of visibility of the dynamic movement effect, and assigned a value from 0-6, with 6 being very visible and 0 being not at all visible. The results are reported in Table 5.Maqnetic-field-qeneratinq devicesStatic maqnetic-field-qeneratinq device for bi-axial orientation

[0178] The static magnetic-field-generating device (230) used to bi-axially orient the platelet-shaped magnetic or magnetizable pigment particles according to the method of the present invention [step b1) and b’1)] was the magnetic assembly disclosed in WO2021 / 239607A, and is shown in detail in Fig. 10.

[0179] Referring to Fig.10, the static magnetic-field-generating device (230) comprised a) a first set (S1) comprising a first bar dipole magnet (331-a) and two second bar dipole magnets (332-a and 332- d), a second set (S2) comprising a first bar dipole magnet (331 -b) and two second bar dipole magnets (332-b and 332-e), a third set (S3) comprising a first bar dipole magnet (331 -c) and two second bar dipole magnets (332-c and 332-f),and b) a first pair (P1) of third bar dipole magnets (333-a and 333-b) and a second pair (P2) of third bar dipole magnets (333-c and 333-f).

[0180] The uppermost surface of the first bar dipole magnet (331-a, 331 -b and 331 -c) of the first,second and third sets (S1 , S2, S3), of the second bar dipole magnets (332-a to 332f) of the first, second and third sets (S1 , S2, S3) and of the third bar dipole magnets (333-a to 333-d) of the first and second pairs (P1 and P2) were flush with each other.

[0181] The third bar dipole magnet (333-a) was aligned with the second bar dipole magnet (332-a) of the first set (S1), with the second bar dipole magnet (332-b) of the second set (S2), with the third bar dipole magnet (333-c) and with the second bar dipole magnet (332-c) of the third set (S3) to form a line. The third bar dipole magnet (333-b) was aligned with the second bar dipole magnet (332-d) of the first set (S1), with the second bar dipole magnet (332-e) of the second set (S2), with the third bar dipole magnet (333-d) and with the second bar dipole magnet (332-f) of the third set (S3) to form a line. For each line, the third bar dipole magnets (333-a, 333-b, 333-c and 333-d) and the second bar dipole magnets (332-a to 332-f) were spaced apart by a third distance (d2) of 2 mm. The first bar dipole magnet (331-a) of the first set (S1) and the first bar dipole magnet (331-b) of the second set (S2), and the first bar dipole magnet (331 -c) of the third set (S3) were spaced apart by a distance (d3) of 24 mm.

[0182] The first bar dipole magnets (331-a, 331-b and 331 -c) of the first, second and third sets (S1 , S2, S3) had the following dimensions: first length (L1) of 60 mm, first width (L2) of 40 mm and first thickness (L3) of 5 mm. Each of the second bar dipole magnets (332-a to 332-f) of the first, second and third set (S1 , S2, S3) had the following dimensions: second length (L4) of 40 mm, second width (L5) of 10 mm and second thickness (L6) of 10 mm. Each of the third bar dipole magnets (333-a to 333-d) of the first and second pairs (P1 , P2) had the following dimensions: third length (L7) of 20 mm, third width (L8) of 10 mm and third thickness (L9) of 10 mm.

[0183] The first bar dipole magnet (331-a) of the first set (S1) and the second bar dipole magnets (332- a and 332-d) of the first set (S1) were aligned to form a column; and the first bar dipole magnet (331-b) of the second set (S2) and the second bar dipole magnets (332-b and 332-e) of the second set (S2) were aligned to form a column; and the first bar dipole magnet (331-c) of the third set (S3) and the second bar dipole magnets (332-c and 332-f) of the third set (S3) were aligned to form a column. For each set (S1 , S2, S3) and each column, the first bar dipole magnets (331-a, 331-b and 331-c) and the two second bar dipole magnets (332-a and 332-d; 332-b and 332-e; and 332-c and 332-f, respectively) were spaced apart by a second distance (d1) of 2 mm.

[0184] The first bar dipole magnets (331-a, 331-b and 331-c) of the first, second and third sets (S1 , S2, S3) had their magnetic axis oriented to be substantially parallel to the substrate (220) surface (“first plane P”), wherein the first bar dipole magnet (331-a) of the first set (S1) had its magnetic direction opposite to the magnetic direction of the first bar dipole magnet (331-b) of the second set (S2), and the first bar dipole magnet (331-b) of the second set (S2) had its magnetic direction opposite to the magnetic direction of the first bar dipole magnet (331-c) of the third set (S3). The first bar dipole magnet (331-a) of the first set (S1) and first bar dipole magnet (331-b) of the second set (S2), as well as the first bar dipole magnet (331-b) of the second set (S2) and the first bar dipole magnet (331-c) of the third set (S3), were spaced apart by a first distance (d3) of 24 mm (corresponding to the sum of the third length (L7) and the two third distances (d2)).

[0185] The two second bar dipole magnets (332-a to 332-f) of the first, second and third set (S1 , S2, S3) had their magnetic axis oriented to be substantially perpendicular to the substrate (220) surface.The South pole of the second bar dipole magnet (332-a) of the first set (S1), the South pole of the second bar dipole magnet (332-e) of the second set (S2) and the South pole of the second bar dipole magnet (332-c) of the third set (S3) pointed towards the plane of the substrate (220). The North pole of the second bar dipole magnet (332-d) of the first set (S1), the North pole of the second bar dipole magnet (332-b) of the second set (S2) and the North pole of the second bar dipole magnet (332-f) of the third set (S3) pointed towards plane of the substrate (220). The North pole of the first bar dipole magnet (331-a) of the first set (S1) pointed towards the second bar dipole magnet (332-d) of the first set (S1), the North pole of the second bar dipole magnet (331-b) of the second set (S2) pointed towards the first bar dipole magnet (332-b) of the second set (S2) and the North pole of the first bar dipole magnet (331 -c) of the third set (S3) pointed towards the second bar dipole magnet (332-f) of the third set (S3). The South pole of the third bar dipole magnet (333-a) of the first pair (P1) pointed towards the second bar dipole magnet (332-a) of the first set (S1), said second bar dipole magnet (332-a) having its South pole pointing towards the plane of the substrate (220); the South pole of the third bar dipole magnet (333-d) of the second pair (P1) pointed towards the second bar dipole magnet (332-e) of the second set (S2), said second bar dipole magnet (332-e) having its South pole pointing towards the plane of the substrate (220); the North pole of the third bar dipole magnet (333-b) of the first pair (P1) pointed towards the second bar dipole magnet (332-d) of the first set (S1), said second bar dipole magnet (332-d) having its North pole pointing towards the plane of the substrate (220); and the North pole of the third bar dipole magnet (333-c) of the second pair (P2) pointed towards the second bar dipole magnet (332-b) of the second set (S2), said second bar dipole magnet (332-b) having its North pole pointing towards the plane of the substrate (220).

[0186] The first bar dipole magnets (331-a, 331-b and 331 -c) of the first, second and third sets (S1 , S2, S3) and the second bar dipole magnets (332-a to 332-f) of the first, second and third sets (S1 , S2, S3) were made of NdFeB N42; the third bar dipole magnets (333, 333-b and 333-c) of the first and second pairs (P1 , P2) were made of NdFeB N48. All the magnets (331-a to 331 -c, 332-a to 332-f and 333-a to 333-d) were embedded in a non-magnetic supporting matrix (not shown) made of POM having the following dimensions: 200 mm x 120 mm x 12 mm.Maqnetic-field-qeneratinq device M1 (Fig. 11)

[0187] The magnetic-field-generating device (240) used to prepare the optical effect layer (OEL) of examples E1-E14 is illustrated in Fig. 11. The magnetic-field-generating device (240) comprised a nonmagnetic matrix (441) carrying 64 disc-shaped dipole magnets (442) and 64 disc-shaped dipole magnets (443), a square-shaped non-magnetic wedge (444), a bar dipole magnet (445) and a holding case (460).

[0188] The holding case (460) was made of a hollow top part with a curved surface and a bottom lid. The hollow top part had a length of about 40 mm, a width of about 40 mm, a thickness of about 15.1 mm and was made of PPS. The bottom lid had a length of about 35 mm, a width of about 35 mm, a thickness of about 3 mm and was made of POM. The curved surface was suitable to match the surface of a rotating magnetic cylinder of an industrial printing press. The hollow top part was suitable for receiving the non-magnetic matrix (441) carrying the 64 disc-shaped dipole magnets (442) and the 64disc-shaped dipole magnets (443), the square-shaped non-magnetic wedge (444) and the bar dipole magnet (445).

[0189] The 64 disc-shaped dipole magnets (442) and the 64 disc-shaped dipole magnets (443) had a diameter L6 of about 2 mm, a thickness of about 2 mm. The North-South magnetic axis of the discshaped dipole magnets (442) and of the disc-shaped dipole magnets (442) was perpendicular to the substrate (220) surface and perpendicular to their diameter L6, the 64 disc-shaped dipole magnets(442) having their North pole pointing toward the substrate, and the 64 disc-shaped dipole magnets(443) having their South pole pointing toward the substrate. The disc-shaped dipole magnets (442 & 443) were made of NdFeB N48.

[0190] The non-magnetic matrix (441) had a length L4 and a width L5 of a bout 29.9 mm and a thickness of about 2 mm. The non-magnetic matrix (441) comprised 128 voids for receiving the 64 discshaped dipole magnets (442) and the 64 disc-shaped dipole magnets (443). The non-magnetic matrix (441) was made of POM.

[0191] Each of the 64 first dipole magnets (442), in particular the center of each of them, was arranged on the intersection of a grid comprising eight parallel straight lines ai (i = 1 , ... , 8; a1 to a8) and eight parallel straight lines pi (I = 1 , ... , 8; pi to p8); each of the 64 first dipole magnets (443), in particular the center of each of them, was arranged on the intersection of a grid comprising eight parallel straight lines yi (i = 1 , ... , 8; y1 to y8) and eight parallel straight lines 8i (i = 1 , ... , 8; 81 to 88); the eight parallel straight lines ai (a1 to a8) and the eight parallel straight lines yi (y1 to y8) were parallel with each other and arranged in an alternating staggered manner; the eight parallel straight lines pi (pi to p8) and the eight parallel straight lines Si (81 to 88) were parallel with each other and arranged in an alternating staggered manner, as illustrated in Fig. 4.

[0192] The square-shaped non-magnetic wedge (444) had a length and a width of about 29.5 mm and a thickness of 0.22 mm and was made of an adhesive film made of PVC / acrylic film.

[0193] The bar dipole magnet (445) had a length L1 and a width L2 of about 29.9 mm and a thickness of about 6.9 mm. The North-South magnetic axis of the bar dipole magnet (445) was parallel to the substrate (220) surface and parallel to its length L1 . The bar dipole magnet (445) was made of NdFeB BMnPi 80 / 48.

[0194] The distance (h) between the non-magnetic matrix (441) surface and the surface of the substrate (220) was about 1.1 mm.

Claims

CLAIMS1. A process for producing an optical effect layer (OEL) on a substrate (220), said optical effect layer (OEL) comprising a first motif comprising platelet-shaped magnetic or magnetizable pigment particles oriented according to a first magnetic pattern and a last motif comprising at least one color-constant dye or pigment, which first and last motifs together form a composite motif, said process comprising: a) applying onto the substrate (220) a first radiation-curable coating composition, preferably a first UV-Vis-curable curable coating composition, exhibiting a color and comprising the plateletshaped magnetic or magnetizable pigment particles to form a first coating layer (210) on said substrate (220), said coating composition being in a first state; b) exposing the first radiation-curable coating composition of step a) to a magnetic field of a magnetic assembly (230) to magnetically orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles; c) at least partially curing the first radiation-curable coating composition of step b) to a second state to fix the platelet-shaped magnetic or magnetizable pigment particles in their adopted positions and orientations and to produce the first motif; d) applying in register a last radiation-curable coating composition, preferably a last UV-Vis- curable curable coating composition, said last radiation-curable coating composition comprising at least one color-constant dye and / or at least one color-constant pigment and / or at least one iridescent pigment and not comprising platelet-shaped magnetic or magnetizable pigment particles, and said last radiation-curable coating composition at least partially covering the first motif, to form a last coating layer (211) on said substrate (220); and e) curing the last radiation-curable coating composition of step d) to produce the last motif.

2. The process according to claim 1 , further comprising the steps, carried out after step c) and before step d): a’) applying in register onto the substrate (220) a second radiation-curable coating composition, preferably a second UV-Vis-curable curable coating composition, exhibiting a color and comprising platelet-shaped magnetic or magnetizable pigment particles to form a second coating layer (210’) on said substrate (220), said coating composition being in a first state, b’) exposing the second radiation-curable composition of step a’) to a magnetic field of a magnetic assembly (230’) to magnetically orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles; c’) at least partially curing the second radiation-curable composition of step b’) to a second state to fix the platelet-shaped magnetic or magnetizable pigment particles in their adopted positions and orientations and to produce a second motif;wherein the platelet-shaped magnetic or magnetizable pigment particles of step a’) are magnetically oriented in step b’) differently or substantially the same as the platelet-shaped magnetic or magnetizable pigment particles of step a).

3. The process according to claim 1 or 2, further comprising the steps, carried out after step c) and before step d): d’) applying in register a penultimate radiation-curable coating composition, preferably a penultimate UV-Vis-curable curable coating composition, comprising at least one colorconstant dye and / or at least one color-constant pigment and / or at least one iridescent pigment and not comprising platelet-shaped magnetic or magnetizable pigment particles, and being different from the last radiation-curable coating composition applied in step d), and said penultimate radiation-curable coating composition at least partially covering the first motif, to form a penultimate coating layer (211 ’) on said substrate (220); and e’) curing the penultimate radiation-curable coating composition of step d’) to produce a penultimate motif.

4. The process according to any one of claims 1 to 3, wherein step b) and / or step b’) comprises a first step of bi-axially orienting the platelet-shaped magnetic or magnetizable pigment particles, and a second step of re-orienting the platelet-shaped magnetic or magnetizable pigment particles according to a design.

5. The process according to any one of claims 1 to 4, wherein the radiation-curable coating compositions of steps a) and a’) are of different color.

6. The process according to any one of claims 1 to 5, wherein in steps b) and b’) the plateletshaped magnetic or magnetizable pigment particles magnetic orientations are magnetically oriented differently.

7. The process according to any one of claims 1 to 6, wherein coating layers comprising the colorconstant dyes or pigments have a thickness in the range of at or about 10-40 pm, particularly preferably in the range of at or about 15-25 pm.

8. The process according to any one of claims 1 to 7, wherein the concentration of the colorconstant pigments in the radiation-curable coating compositions is from at our about 0.25 to at or about 15 wt%, preferably at or about 0.25 to at or about 8 wt%, more preferably at or about 0.25 to at or about 5 wt%; and / or wherein the concentration of the color-constant dyes is from at or about 0.25 to at or about 25 wt%, preferably at or about 0.25 to at or about 15 wt%, more preferably at or about 0.25 to at or about 10 wt%; and / or wherein the concentration of the iridescent pigment is from at or about 2 to at or about 40 wt%,preferably at or about 5 to at or about 30 wt%, more preferably at or about 5 to at or about 20 wt%; the wt%s being based on the total weight of the radiation-curable coating composition.

9. The process according to any one of claims 1 to 8, wherein the register deviates less than 0.5 mm, preferably less than or equal to 0.2 mm.

10. The process according to any one of claims 1 to 9, wherein the radiation-curable coating composition comprising at least one color-constant dye or pigment when cured has a minimum light transmission of at least 10% over the visible range, more preferably a minimum light transmission of 20%, more particularly 30%, over the visible range.11 . The process according to any one of claims 1 to 10, wherein the coating layers are applied in register to opposite sides of the substrate and wherein the substrate (220) is at least partially transparent.

12. The process according to any one of claims 1 to 11 , wherein step b’) and / or step b”) is a one- step orientation step.

13. An optical effect layer comprising: i) a first motif composed of a coating layer comprising platelet-shaped magnetic or magnetizable pigment particles suspended in a polymerized vehicle, wherein the platelet-shaped magnetic or magnetizable pigment particles are permanently oriented according to a predetermined orientation; ii) a last motif, at least partially visually superposed on the first motif, the last motif composed of a coating layer comprising color-constant dyes or pigments, in a polymerized vehicle, and not comprising platelet-shaped magnetic or magnetizable pigment particles.

14. The optical effect layer according to claim 13, which additionally comprises a substrate to which the first and last motifs are attached.

15. An optical effect layer obtained by or obtainable by the process recited in any one of claims 1

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