Devices and method for producing security documents

Abstract

A transferring device for orienting platelet-shaped magnetic or magnetizable pigment particles contained in a radiation curable coating composition and applied on a substrate, the transferring device comprising: a number N of identical magnetic blocks (102) aligned along an alignment line provided on an outer surface of the transferring device, the magnetic blocks (102) each including M magnetic field generating devices (101) each generating a corresponding magnetic field such that the magnetic blocks (102) each generate a block magnetic field, N being greater than or equal to two, and M being greater than or equal to one; and a shielding element (105) partly isolating the block magnetic field of each magnetic block (102) from the block magnetic field of the other magnetic blocks (102), or a compensation magnetic block provided alongside the magnetic block (102).

Description

[0001] DEVICES AND METHOD FOR PRODUCING SECURITY DOCUMENTS

[0002] TECHNICAL FIELD

[0003] The present invention is directed at a transferring device for orienting platelet-shaped magnetic or magnetizable pigment particles. The present invention is further directed at a magnetic orienting unit for this transferring device, at a printing press comprising such a transferring device, and at a method for producing N security documents.

[0004] BACKGROUND ART

[0005] 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 US 2,570,856; US 3,676,273; US 3,791 ,864; US 5,630,877 and US 5,364,689. 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 e.g. WO 2002 / 090002 A2.

[0006] Magnetic or magnetizable pigment particles in printing inks or coatings allow for the production of magnetically induced images, designs and / or patterns through the application of a corresponding magnetic field, causing a local orientation of the magnetic or magnetizable pigment particles in the unhardened coating, followed by hardening the latter. The result is a fixed magnetically induced image, design or pattern referred in the art as optical effect layer (OEL). In such a way, magnetically induced patterns which are highly resistant to counterfeit can be produced. The security element 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.

[0007] The above-described optical effect layers (OEL) are usually obtained using a printing press, which transports a substrate on which the OEL is printed and includes sections for (a) applying the inks, compositions, coatings or layers containing magnetic or magnetizable pigment particles on the substrate, (b) orienting the magnetic or magnetizable pigment particles using a magnetic field, and (c) hardening the inks, compositions, coatings or layers containing oriented magnetic or magnetizable pigment particles. For orienting the magnetic or magnetizable pigment particles using a magnetic field, the printing press can comprise a transferring device including either a cylinder body producing a magnetic field and rotating together with the substrate, or a flatbed body producing a magnetic field on which the substrate is placed. Banknotes printing (including polymeric banknotes printing) is typically performed with a sheet-fed printing press. In order to increase the efficiency of the printing, one sheet comprises several banknotes arranged along several columns and several rows. At the end of the printing process, the individual banknotes are obtained by cutting the sheets between the rows and the columns.

[0008] For security reasons and anti-counterfeiting resilience, as well as to ensure user’s trust in the currency and user’s ability to identify a banknote beyond any doubt and to differentiate it from counterfeited banknotes, it is of critical importance that all the banknotes display a perfectly identical appearance, independently of their position on a sheet during the printing process. In other words, it is desirable that a banknote of the first, the last or any central line or column of the sheet has exactly the same final appearance as all the other banknotes of the same sheet and all the banknotes of the other sheets.

[0009] An objective of the present invention is an improved production of N security documents on a same substrate.

[0010] SUMMARY OF THE INVENTION

[0011] According to a first aspect, a transferring device for orienting platelet-shaped magnetic or magnetizable pigment particles contained in a radiation curable coating composition and applied on a substrate is provided. The transferring device is a flatbed transferring device or a cylindrical transferring device. The transferring device comprises: a number N of identical magnetic blocks aligned along an alignment line provided on an outer surface of the transferring device, the magnetic blocks each including M magnetic field generating devices each generating a corresponding magnetic field such that the magnetic blocks each generate a block magnetic field, N being greater than or equal to two, and M being greater than or equal to one; and a shielding element provided between each two neighboring magnetic blocks, the shielding element being made of a material at least partly isolating the block magnetic field of each magnetic block from the block magnetic field of the other magnetic blocks.

[0012] Without the shielding element, neighboring magnetic field generating devices of the transferring device could generate overlapping magnetic fields if arranged close to one another, which could result in irregularities in the magnetic field orienting the magnetic or magnetizable pigment particles along the substrate. In particular, the 1stand the N-th magnetic blocks (which are located on the edge of the flatbed transferring device or of an “unrolled” cylindrical transferring device) each only have one neighboring magnetic block along the alignment line, while the 2ndto (N-1 )-th magnetic blocks (which are located more centrally on the transferring device) have two neighboring magnetic blocks along the alignment line. Due to this difference in the number of neighboring magnetic blocks, the magnetic field orienting the magnetic or magnetizable pigment particles is not the same everywhere along the alignment line, resulting in undesirable divergences between security features printed on different sections of the substrate (for example on different banknotes or other security documents).

[0013] The shielding element allows overcoming this problem and preventing the neighboring magnetic blocks from influencing one another. That way, the same block magnetic field orienting the magnetic or magnetizable pigment particles is applied to every security document formed on the substrate (one security document having pigment particles oriented by one magnetic block) along the alignment line. Advantageously, identical security documents can be formed.

[0014] The transferring device can be a part of a printing press which holds magnetic blocks for orienting the magnetic or magnetizable pigment particles. The transferring device can have a cylindrical shape and rotate around an axis thereby transporting the substrate, or it can have a flatbed shape onto which the substrate can be placed.

[0015] 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 a large aspect ratio of their dimensions. Platelet-shaped pigment particle can be considered as a two-dimensional structure wherein dimensions X and Y are substantially larger than a dimension Z. Platelet-shaped pigment particles can also be referred 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 longest dimensions of the pigment particle, the Z dimension being ignored.

[0016] The platelet-shaped magnetic or magnetizable pigment particles described herein 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.

[0017] The platelet-shaped magnetic or magnetizable pigment particles are dispersed in a coating layer, said layer comprising a hardened binder material that fixes the orientation of the platelet-shaped magnetic or magnetizable pigment particles. As used herein, the term “layer” refers to a coating layer which is at least partially cured wherein the orientation of the platelet-shaped magnetic or magnetizable pigment particles is fixed / frozen (the term “composition” on the other hand in particular referring to an ink). The binder material is at least in its hardened or solid state (also referred to as second state herein), at least partially transparent to electromagnetic radiation of a range of wavelengths comprised between 200 nm and 2500 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 optical feature (not including the platelet-shaped magnetic or magnetizable pigment particles, but all other optional components of the optical feature 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 ).

[0018] The platelet-shaped magnetic or magnetizable pigment particles described herein 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 described herein have a non-isotropic reflectivity with respect to incident electromagnetic 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 described herein are different from conventional 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 described herein exhibit either a reflection or a color, or both, that depend on the particle orientation.

[0019] The radiation curable coating composition described herein as well as the coating layer described herein comprise the platelet-shaped magnetic or magnetizable pigment particles described herein 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. Suitable examples of platelet-shaped magnetic or magnetizable pigment particles described herein 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 (Fe2Os), magnetite (FesC ), chromium dioxide (CrCh), magnetic ferrites (MFe2C>4), magnetic spinels (MR2O4), magnetic hexaferrites (MFe^Oig), magnetic orthoferrites (RFeOs), magnetic garnets MsR2(AO4)3, wherein M stands for two-valent metal, R stands for three- valent metal, and A stands for four-valent metal.

[0020] Examples of platelet-shaped magnetic or magnetizable pigment particles described herein 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 (SiCh); 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.

[0021] The curable coating composition can be a UV-Vis radiation curable coating composition and 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 described herein is constituted by platelet-shaped optically variable magnetic or magnetizable pigment particles. In addition to the overt security provided by the colorshifting property of the optically variable magnetic or magnetizable pigment particles, which allows easily detecting, recognizing and / or discriminating an article or security document carrying an ink, coating composition, or coating layer comprising the optically variable magnetic or magnetizable pigment particles described herein 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 optical feature. 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.

[0022] The use of platelet-shaped optically variable magnetic or magnetizable pigment particles in coating layers for producing an optical feature enhances the significance of the optical feature 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.

[0023] 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 or platelet-shaped interference coated pigment particles.

[0024] Magnetic thin film interference pigment particles are known to those skilled in the art and are disclosed e.g. in US 4,838,648; WO 2002 / 073250 A2; EP 0 686 675 B1; WO 2003 / 000801 A2; US 6,838,166; WO 2007 / 131833 A1; EP 2 402 401 B1 ; WO 2019 / 103937 A1 ; EP 3 587 500 A1, EP 3 587 501 A1 , EP 3 587 502 A1 , EP 3 587503 A1 , WO 2020 / 006286 A1 , WO 2020 / 131700 A1, US 2021 / 0101402, US 2021 / 038812, US 2022 / 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 eleven-layer Fabry-Perot multilayer structure and / or pigment particles having a multilayer structure combining one or more multilayer Fabry-Perot structures.

[0025] Preferred five-layer Fabry-Perot multilayer structures consist of absorber / dielectric / reflector / dielectric / absorber multilayer structures wherein the reflector and / or the absorber 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).

[0026] Further preferred five-layer Fabry-Perot multilayer structures consist of dielec- tric / reflector / magnetic / reflector / dielectric multilayer structures.

[0027] Preferred six-layer Fabry-Perot multilayer structures consist of absorb- er / dielectric / reflector / magnetic / dielectric / absorber multilayer structures.

[0028] 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.

[0029] Preferred nine-layer Fabry-Perot multilayer structures consist of dielec- tric / absorber / dielectric / reflector / magnetic / dielectric / absorber / dielectric multilayer structures.

[0030] Preferred eleven-layer Fabry-Perot multilayer structures consist of absorb- er / dielectric / absorber / dielectric / reflector / magnetic / reflector / dielectric / absorber / dielectric / absorber multilayer structures.

[0031] Preferably, the reflector layers described herein 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 (CeFs), lanthanum fluoride (LaFs), sodium aluminum fluorides (e.g. NasAIFe), neodymium fluoride (NdFs), samarium fluoride (SmFs), 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 / d ielectric / reflector / mag netic / reflector / d ielectric / absorber multilayer structure consisting of a Cr / MgF2 / AI / M / AI / MgF2 / Cr multilayer structure wherein M is Ni, Fe or Co.

[0032] The substrate described herein is preferably selected from the group consisting of papers or other fibrous materials, such as cellulose, paper-containing materials, glasses, metals, ceramics, plastics and polymers, metallized 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), polyamides, polyesters such as poly(ethylene terephthalate) (PET), poly(1 ,4-butylene terephthalate) (PBT), poly( ethylene 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 so as 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.

[0033] Alternatively and preferably, the curing or hardening of the coating composition involves a chemical reaction, 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 coating composition (i) after its application on a substrate surface and (ii) subsequently to, or partially simultaneously with the orientation of the platelet- shaped magnetic or magnetizable pigment particles. Preferably the coating composition is an ink or coating composition selected from the group consisting of radiation curable compositions, thermally drying compositions, oxidatively drying compositions, and combinations thereof. Particularly preferred are coating compositions selected from the group consisting of radiation curable compositions. Radiation curing, in particular UV-Vis curing, advantageously leads to an instantaneous increase in viscosity of the coating composition after exposure to the curing radiation, thus preventing any further movement of the pigment particles and in consequence any loss of information after the magnetic orientation step. Preferably, the curing is carried out by radiation curing including UV-visible light radiation curing or by E-beam radiation curing, more preferably by UV-Vis light radiation curing.

[0034] The numbers N and M can be natural numbers. The N magnetic blocks are arranged such as to form a repetitive pattern of magnetic field generating devices. The N magnetic blocks being identical in particular means that they generate identical block magnetic fields. They can also be identical in terms of magnetic field generating devices included in each block, in terms of dimensions, or the like. N is an integer number of at least two. The magnetic field generating devices of one magnetic block can be held together by a holding case, so that each magnetic block forms a physical unit. The N magnetic blocks being aligned along an outer surface of the transferring device in particular means that the N magnetic blocks are arranged on the outer surface of the transferring device, for example in holes each comprising one magnetic block. The magnetic blocks can be provided on the outer surface such that the block magnetic fields can be perceived by the pigment particles placed on a substrate facing the outer surface of the transferring device. The N magnetic blocks are all arranged at a same distance from one another. In particular, the N magnetic blocks are arranged seamlessly next to one another along the alignment line. The magnetic blocks being arranged “along the alignment line” can mean that they are aligned in parallel to the alignment line.

[0035] M is an integer number of at least one. Each magnetic block includes at least one magnetic field generating device. Each magnetic field generating device can include a permanent magnet, an electromagnet, a solenoid, a wire with electricity running through, a plasto-ferrite magnet, a combination of a plasto-ferrite magnet and a permanent magnet, a soft magnet, a combination of a magnetic-field generating device generating a time-dependent magnetic field and a soft magnet, and / or a like device generating a magnetic field. Preferably, the magnetic field generating devices are realized as permanent magnets. Each magnetic block can be used to orient the pigment particles such as to create one security feature once cured in the form of optical effect layers (OEL). The term “optical effect layer (OEL)” as used herein denotes a coating or layer that comprises oriented plateletshaped 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 so as to form a magnetically induced image. The term "security feature" is used to denote an image or graphic element that can be used for authentication purposes. The security feature can be an overt and / or a covert security element. Each security feature can include M security elements created by curing the radiation curable coating composition comprising the pigment particles oriented by the M magnetic field generating devices. Each of the M security elements has the shape of a motif and discloses a specific magnetic effect obtained by exposure to a magnetic field generating device comprised in a block magnetic field.

[0036] At least one shielding element is placed between each two neighboring magnetic blocks, which is usually between the 1stand 2ndmagnetic blocks, between the 2ndand 3rdmagnetic blocks, ... , and between the (N-1 )-th and the N-th magnetic blocks. In other words, (N-1 ) shielding elements can be provided. The shielding element is preferably located on the alignment line. The shielding element is in particular an element that redirects the magnetic field lines from the magnetic blocks between which it is arranged, such that these magnetic field lines do not cross one another (which corresponds to fully isolating the block magnetic field of the two neighboring magnetic blocks from one another). In some cases, a slight interaction between block magnetic fields of neighboring magnetic blocks is tolerated, which is why the shielding element is said to at least partly isolate the block magnetic field of a magnetic block from the other block magnetic fields.

[0037] According to an embodiment, the transferring device of the first aspect further comprises N holding cases for each holding one magnetic block, at least a section of the holding cases forming the shielding element.

[0038] The holding cases in particular include or correspond to the shielding element. The holding cases can include compartments for holding the individual magnetic field generating devices. Each magnetic block is held by one holding case. The holding case can include a lid parallel to the outer surface, the lid being arranged between the substrate and the magnetic block during use of the transferring device. The section (part or portion) of the holding case forming the shielding element can be the section of the holding case that is located between two neighboring magnetic blocks.

[0039] According to a further embodiment of the first aspect, the material of the shielding element is a material having a relative permeability of more than 40; and / or steel, in particular steel S235.

[0040] Preferably, the shielding element is made of a ferromagnetic metal. The relative permeability of a specific medium is defined as the ratio of the permeability of a specific medium to the permeability of free space (vacuum) (see Magnetic materials, Fundamentals and Applications, 2ndEd., Nicola A. Spaldin, p. 16-17, Cambridge University Press, 2011 ). “Permeability” here refers to magnetic permeability. Absolute magnetic permeability is in particular based on the change of the flux density AB to the change of magnetic field strength AH. Relative magnetic permeability expresses the magnetic performance of a given material. For example, a relative permeability of 100 means that the material has permeability 100 times greater than that of vacuum (for which the relative permeability is 1 by definition, and the magnetic permeability of vacuum is 4TT 10A(-7) H / m).

[0041] “Steel S235” here in particular refers to the steel S235 as defined in the norm DIN EN 10025-2 of April 2005.

[0042] According to a further embodiment of the first aspect, the transferring device is the cylindrical transferring device and the alignment line is an outer circumference line of a cross-section of the cylindrical transferring device (preferred embodiment); or a lateral line on the outer surface of the cylindrical transferring device which is parallel to an axis of the cylindrical transferring device.

[0043] The cylindrical transferring device in particular has a circular base. In case of the cylindrical transferring device, the alignment line can be either an outer circumference line of a cross-section of the cylindrical transferring device, which has a circular shape if the cylindrical transferring device has a circular base, or a lateral line of the outer surface which is parallel to the axis of the cylindrical transferring device, the axis being the axis of rotation of the cylinder passing through a center of the cylinder. The lateral line is a height of the cylinder. The alignment line being the line along which the N magnetic blocks are aligned, the alignment line is in particular a line along which the N magnetic blocks are close enough from one another to have overlapping magnetic fields (i.e. influencing one another), so that shielding elements and / or compensation elements as described herein can become advantageous in case that it is considered that the influence of magnetic fields of neighboring magnetic blocks is not small enough in the context of the intended application.

[0044] According to a further embodiment of the first aspect, the transferring device is the flatbed transferring device having a rectangular shape and the alignment line is parallel to a side of the rectangular shaped flatbed transferring device.

[0045] In other words, the alignment line is parallel to a width or length of the transferring device.

[0046] In some embodiments, the magnetic blocks are arranged in an array on the transferring device, meaning that some additional N magnetic blocks are provided along a second (respectively along a third, fourth, etc.) alignment line parallel to the (first) alignment line described hereabove. This allows producing a larger number of security documents simultaneously with one substrate. According to a second aspect, a transferring device for orienting platelet-shaped magnetic or magnetizable pigment particles contained in a coating composition and applied on a substrate for producing N security documents on the substrate is provided. The transferring device is a flatbed transferring device or a cylindrical transferring device. The transferring device comprises: a number N of identical magnetic blocks aligned along an alignment line provided on an outer surface of the transferring device, the magnetic blocks each including M magnetic field generating devices each generating a corresponding magnetic field such that the magnetic blocks each generate a block magnetic field, N being greater than or equal to two, and M being greater than or equal to one; and a compensation magnetic block provided alongside the first magnetic block along the alignment line so that the first of the N magnetic blocks is arranged between the compensation magnetic block and the second of the N magnetic blocks, the compensation magnetic block including at least one compensation magnetic field generating device that provides a magnetic field identical to that of at least part of one of the magnetic blocks that includes the M-th magnetic field generating device.

[0047] The transferring device of the second aspect is mostly identical to the transferring device of the first aspect. Elements of the transferring device of the second aspect having the same name as elements of the transferring device of the first aspect are the same and will hence not be described again to avoid repetitions. The difference between the transferring devices of the first and second aspects is that instead of comprising a shielding element, the transferring device of the second aspect comprises a compensation magnetic block.

[0048] The compensation magnetic block is placed before the first magnetic block along the alignment line so as to mimic an extra magnetic block. As a result, the first to (N-1 )-th magnetic blocks of the N magnetic blocks each have two neighboring magnetic blocks along the alignment line, meaning that the block magnetic field of each of these blocks is equally perturbed by neighboring blocks, thereby achieving a constant exposure to a magnetic field for the 1stto (N-1 )-th security documents formed along the alignment line on the substrate.

[0049] The transferring device of the first and second embodiment provide different solutions to the same problem of reducing irregularities in the magnetic field orienting the magnetic or magnetizable pigment particles on different security documents of the substrate. The solutions to this same problem are the provision of a shielding element in the transferring device of the first aspect, and the provision of a compensation magnetic block in the transferring device of the second aspect. While the shielding elements allow preventing interferences between block magnetic fields of neighboring magnetic blocks, the compensation magnetic block does not perform any shielding function and rather adds an additional magnetic block to the N magnetic blocks so that interferences between neighboring magnetic blocks are identical. The compensation magnetic block can be aligned with the other magnetic blocks along the alignment line. The compensation magnetic block can be a magnetic block identical to the N magnetic blocks. Alternatively, the compensation magnetic field generating device provides a magnetic field identical to that of only a part of one of the magnetic blocks that includes the M-th magnetic field generating device. Accordingly, the compensation magnetic block can be a magnetic block including at least the M-th magnetic field generating device, thereby reproducing the magnetic field influence of a magnetic block placed before any of the N magnetic blocks except the first. In addition to the M-th magnetic field generating device, the compensation magnetic block can additionally include the (M-1 )-th magnetic field generating device, and so on, until it includes the first magnetic field generating device or all but the first magnetic field generating device. The magnetic field generating devices of the compensation magnetic block are in particular arranged in the same manner (same position) as in the N magnetic blocks. A distance between the compensation magnetic block and the first magnetic block is in particular identical to a distance between two neighboring of the N magnetic blocks. The compensation magnetic field generating device can also be different from the magnetic field generating devices of the magnetic block, but provide a magnetic field identical to that of one or several of the magnetic field generating devices of the magnetic block.

[0050] While the N magnetic blocks are used to respectively orient the platelet-shaped magnetic or magnetizable pigment particles in the process of creating N security documents, the compensation magnetic block is an additional block, which in particular does not correspond to one of the N security documents. In other words, each magnetic block except for the compensation magnetic block is associated with precisely one security document. The compensation magnetic block adjusts the magnetic field of the neighboring first magnetic block to accordingly orient the platelet-shaped magnetic or magnetizable pigment particles of the 1st security document.

[0051] According to an embodiment, the transferring device of the second aspect further comprises an additional compensation magnetic block provided alongside the N-th magnetic block along the alignment line so that the N-th magnetic block is arranged between the additional compensation magnetic block and the (N-1 )-th magnetic block, the additional compensation magnetic block including at least one additional compensation magnetic field generating device that provides a magnetic field identical to that of at least part of one of the magnetic blocks that includes the first of the M magnetic field generating devices.

[0052] The additional compensation magnetic block is provided on the other extremity of the alignment line (after the N-th magnetic block) and has the same properties and serves the same purposes as the compensation magnetic block described above. Namely, the additional compensation magnetic block is placed after the N-th magnetic block and aligned therewith along the alignment line so as to mimic an extra magnetic block. As a result, the first to N-th magnetic blocks of the N magnetic blocks each have two neighboring magnetic blocks along the alignment line, meaning that the block magnetic field of each of these magnetic blocks is equally perturbed by neighboring magnetic blocks, thereby achieving a constant exposure to a magnetic field for the 1stto N-th security documents formed along the alignment line on the substrate.

[0053] The additional compensation magnetic block can be a magnetic block identical to the N magnetic blocks. Alternatively, the additional compensation magnetic field generating device provides a magnetic field identical to that of only a part of one of the magnetic blocks that includes the 1st magnetic field generating device. Accordingly, the additional compensation magnetic block can be a magnetic block including at least the 1st magnetic field generating device, thereby reproducing the magnetic field influence of a magnetic block placed after any of the N-th magnetic blocks except the N-th magnetic block or all but the first magnetic field generating device. In addition to the 1st magnetic field generating device, the additional compensation magnetic block can additionally include the 2nd magnetic field generating device, and so on, up to including the M-th magnetic field generating device. The magnetic field generating devices of the additional compensation magnetic block are in particular arranged in the same manner (same position) as in the N magnetic blocks. A distance between the additional compensation magnetic block and the N-th magnetic block is in particular identical to a distance between two neighboring of the N magnetic blocks. The additional compensation magnetic field generating device can also be different from the magnetic field generating devices of the magnetic block, but provide a magnetic field identical to that of one or several of the magnetic field generating devices of the magnetic block.

[0054] While the N magnetic blocks are used to respectively orient the platelet-shaped magnetic or magnetizable pigment particles in the process of creating N security documents, the compensation magnetic block and the additional compensation magnetic block are additional blocks, which in particular do not correspond to one of the N security documents. In other words, each magnetic block except for the compensation magnetic block and the additional compensation magnetic block is associated with precisely one security document. The additional compensation magnetic block adjusts the magnetic field of the neighboring N-th magnetic block to accordingly orient the plateletshaped magnetic or magnetizable pigment particles of the N-th security document.

[0055] The transferring device of the second aspect can further comprise N holding cases for each holding one magnetic block. Preferably, in the second aspect, the N holding cases do not include a shielding element as described above. According to a further embodiment of the second aspect, the at least one compensation magnetic field generating device comprised in the compensation magnetic block provides a magnetic field identical to that of the M-th magnetic field generating device and / or the at least one additional compensation magnetic field generating device comprised in the additional compensation magnetic block provides a magnetic field identical to that of the first magnetic field generating device.

[0056] According to a further embodiment, the transferring device of the second aspect further comprises: a shielding element provided between each two neighboring magnetic blocks, and between the compensation magnetic block and the first of the N magnetic blocks, the shielding element being made of a material at least partly isolating the block magnetic field of each magnetic block from the magnetic field of the other magnetic blocks and from the magnetic field of the compensation magnetic block.

[0057] In case of the additional compensation magnetic block being provided, a shielding element is further provided between the additional compensation magnetic block and the N-th magnetic block. In this case, the shielding element is made of a material at least partly isolating the block magnetic field of each magnetic block from the magnetic field of the other magnetic blocks, from the magnetic field of the compensation magnetic block, and from the magnetic field of the additional compensation magnetic block.

[0058] The shielding element can be identical to the shielding element described in view of the transferring device of the first aspect. The features described in view of the transferring device of the first aspect equally apply in the context of the present embodiment. The present embodiment relates to a combination of the transferring device according to the first and second aspect. An advantage of combining the shield element solution with the compensation magnetic block solution is that it can be ensured even more that the pigment particles of all security documents of the same substrate are oriented in the same way, leading to identical visual features on all security documents.

[0059] According to a further embodiment of the first or second aspect of the transferring device, each magnetic block includes at least two different magnetic field generating devices.

[0060] This corresponds to M>2, wherein the two magnetic field generating devices generate different magnetic fields, leading to different magnetic effects on the security document. These magnetic effects in particular include dynamic effects which provide the optical illusion of movement, such as those described hereafter, and 3D-effects which provide the optical illusion of relief, such as those described hereafter. In other embodiments, each magnetic block includes at least two identical magnetic field generating devices. For example, engraved magnetic plates comprising one or more engravings having the shape of indicia can be used. As used herein, the term “indicia” shall mean continuous and discontinuous layers consisting of distinguishing markings or signs or patterns. Preferably, the one or more indicia are selected from the group consisting of codes, symbols, alphanumeric symbols, motifs, geometric patterns (e.g. circles, triangles and regular or irregular polygons), letters, words, numbers, logos, drawings, portraits and combinations thereof. Examples of codes include encoded marks such as an encoded alphanumeric data, a one-dimensional barcode, a two-dimensional barcode, a QR-code, datamatrix and IR-reading codes. The security feature can exhibit a dynamic movement upon tilting said OEL comprising one or more indicia. For example, the magnetic field generating device comprises at least a bar dipole magnet and an engraved magnetic plate comprising one or more engravings having the shape of indicia.

[0061] The effect described above can include a dynamic movement being a bright reflective bar moving in a direction when the substrate is tilted around an axis, as for example described in US 2005 / 0106367, WO 2020 / 160993 A1 and WO 2014 / 198905 A2. The effect can also include a dynamic movement being a pattern of bright areas and dark areas moving when the substrate is tilted, as for example described in WO 2013 / 167425 A1 , WO 2021 / 083808 A1 and WO 2021 / 083809 A1. The effect can also include a dynamic movement being a loop-shaped body moving when the substrate is tilted, as for example described in WO 2014 / 108404 A2 and WO 2014 / 108303 A2. The effect can also include a dynamic movement being a loop-shaped body having a size that varies when the substrate is tilted, as for example described in WO 2017 / 064052 A1 , WO 2017 / 080698 A1 and WO 2017 / 148789 A1. The effect can also include a dynamic movement being one or more loop-shaped bodies having a shape that varies when the substrate is tilted, as for example described in WO 2018 / 054819 A1. The effect can also include a dynamic movement being a moon crescent moving and rotating when the substrate is tilted, as for example described in WO 2019 / 215148 A1. The effect can also include a 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 substrate is tilted, as for example described in WO 2020 / 193009 A1. The effect can also include a dynamic movement being at least one comet-shaped spot rotating around said center of rotation upon tilting the substrate, as for example described in WO 2019 / 038371 A1, WO 2019 / 038370 A1 and WO 2019 / 038369 A1.

[0062] According to a third aspect, a magnetic orienting unit for the transferring device of the first aspect, the second aspect, or any embodiment of the first or second aspect, is provided. The magnetic orienting unit is for orienting platelet-shaped magnetic or magnetizable pigment particles contained in a radiation curable coating composition and applied on a substrate. The magnetic orienting unit comprises: a magnetic block including M magnetic field generating devices each generating a corresponding magnetic field such that the magnetic block generates a block magnetic field, M being greater than or equal to one; and a shielding element and / or a compensation magnetic block; wherein the shielding element is provided alongside the magnetic block, the shielding element being made of a material at least partly blocking the block magnetic field; and / or the compensation magnetic block is provided alongside the magnetic block, the compensation magnetic block includes at least one compensation magnetic field generating device that provides a magnetic field identical to that of at least part of one of the magnetic blocks that includes the M-th magnetic field generating device.

[0063] The magnetic orienting unit according to the third aspect corresponds to a subpart of the transferring device of the first or second aspect, which includes only one magnetic block and the shielding element and / or the compensation magnetic block. Optionally, the magnetic orienting unit may also include the additional compensation block as defined above. Elements having the same names as previously described elements of the first or second aspects are identical and are hence not described again. The advantages are identical to the advantages described in view of the first and second aspects. All features described in view of the first or second aspect (or any embodiment thereof) also hold for the magnetic orienting unit according to the third aspect.

[0064] According to a fourth aspect, a printing press comprising a transferring device according to the first or second aspect (or any embodiment thereof) is provided.

[0065] The printing press is for printing security features in the form of optical effect layers (OELs) on security documents on a substrate. Besides the transferring device, the printing press in particular includes means for applying the pigment particles on the substrate, transporting the substrate, curing the coating composition including the pigment particles and / or optionally slicing the substrate. All features described in view of the first or second aspect (or any embodiment thereof) also hold for the printing press according to the fourth aspect.

[0066] According to a fifth aspect, a method for producing at least N security documents each comprising one security feature comprising at least M security elements (each in particular forming one OEL), N being equal to or greater than two, and M being greater than or equal to one. The method comprises: a) providing a substrate, preferably in the form of a sheet; b) applying on a substrate surface a radiation curable coating composition comprising platelet-shaped magnetic or magnetizable pigment particles, the coating composition being in a first state, the coating composition being applied in the form of M independent and optionally spaced apart motifs for each of the N security features, c) exposing the magnetic or magnetizable pigment particles to a magnetic field of a transferring device according to the first aspect, the second aspect, or any embodiment of the first or second aspect, so as to orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles of each of the M applied motifs of one security feature according to a block magnetic field of a magnetic block of the transferring device; and d) curing, preferably partially simultaneously with step c), the coating composition of step b) to a second state so as to fix the platelet-shaped magnetic or magnetizable pigment particles in their adopted positions and orientations, such that each cured motif forms one of the security elements.

[0067] Elements having the same names as previously described elements of the first or second aspects are identical and are hence not described again. All features described in view of the first or second aspect (or any embodiment thereof) also hold for the method according to the fifth aspect. The described method allows producing at least N security documents, in particular N security documents. These are produced on a same substrate, which can then be sliced (in particular using a separate machine) to obtain the individual security documents. The at least N security documents can be produced simultaneously.

[0068] The applying step b) described herein is preferably carried out by a printing process preferably 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. These processes are well-known to the skilled man and are described for example in Printing T echnology, J. M. Adams and P. A. Dolin, Delmar Thomson Learning, 5th Edition.

[0069] Further, subsequently to, partially simultaneously or simultaneously with the application (step b) of the coating composition described herein on the substrate surface described herein, the plateletshaped magnetic or magnetizable pigment particles are oriented by applying a magnetic field so as to align the platelet-shaped magnetic or magnetizable pigment particles along the magnetic field lines (step c). Subsequently to or partially simultaneously with the steps of orienting / aligning (step c) the platelet-shaped magnetic or magnetizable pigment particles by applying magnetic fields, the orientation of the platelet-shaped magnetic or magnetizable pigment particles is fixed or frozen, i.e. by curing the coating composition (step d). The coating composition must thus noteworthy have a first state, i.e. a liquid or pasty state, wherein the coating composition is wet or soft enough, so that the platelet-shaped magnetic or magnetizable pigment particles dispersed in the coating composition are freely movable, rotatable and / or orientable upon exposure to a magnetic field, and a second hardened (e.g. solid) state, wherein the platelet-shaped magnetic or magnetizable pigment particles are fixed or frozen in their respective positions and orientations. Such a first and second state is preferably provided by using a certain type of coating composition. For example, the components of the 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 in viscosity 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 or cured, said binder material converts into the second state, i.e. a hardened or cured 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.

[0070] In step b), the coating composition including the pigment particles is in particular applied in locations of the substrate that will be aligned with the magnetic field generating devices of the transferring device when the substrate is facing the transferring device in step c). In step b), the coating composition can be printed to form motifs in those predetermined locations. As described above, the transferring device includes N magnetic block with each M magnetic field generating devices. The coating composition is applied on the substrate such as to form M independent and optionally spaced apart (i.e. not touching) motifs for each of the N security features (corresponding to a total of NxM motifs). These motifs can be applied along a line. Each applied coating composition motif can be facing one magnetic field generating device in step c). Accordingly, each block magnetic field orients the pigment particles of M applied motifs of a same security feature. The applied M motifs of a security feature can have a same shape or different shapes. Preferably, the N security features are all identical, meaning that each of the N security features includes the same M motifs and the same magnetic effects, that is each of the N security features includes the same M security elements (in terms of shape and magnetic orientation).

[0071] The M independent motifs may be touching one another (i.e. not spaced apart) in order to increase counterfeiting resistance. The term “independent” here refers to the fact that the M motifs are different motifs and / or different magnetic effects applied thereto, such as to create different security elements within a security feature. The independent motifs can form visually separate and distinguishable security elements of a security feature.

[0072] As defined herein, one security document (such as a banknote) includes one security feature. One security feature is made of several security elements, which are characterized by (i) their shape (motifs) and (ii) the magnetic effect applied thereto by the corresponding magnetic field generating devices. In the non-cured state, the coating composition including the pigment particles is applied in motifs to the substrate, each of the M cured motifs (i.e. each of the M OEL’s) forming a security element and M security elements (M OELs) forming the security feature carried by each of the N security documents. According to an embodiment, the method of the fifth aspect further comprises: e) slicing the substrate between the N security features to obtain individual and identical security documents.

[0073] As a result of the slicing between the N security features, in particular N individual and identical security documents are obtained. Each security document (such as a banknote) can include one security feature, each in particular including a multiplet of M security elements. The security feature can have an elongated shape, and for example expand along an entire width of the security document (in particular banknote). Typical example of said security features having an elongated shape are referred in the art are security threads, security stripes and security foils. The method of the fifth aspect can be expanded to create an array of NxP security documents, each including one security feature. In this case, the alignment of N security features is provided not only once but P times on the substrate, using a transferring device having NxP magnetic blocks. Thereby, a larger number of identical security documents can be produced using one substrate. The slicing can be a cutting.

[0074] According to an embodiment of the fifth aspect, each of the N security features includes at least two different security elements.

[0075] Each security feature including at least two different security elements in particular means that the security elements have different motifs (shapes) and / or different magnetic effects associated therewith, which are at least partly adjacent on one security document.

[0076] According to an embodiment, the method of the fifth aspect further includes, between steps b) and c), exposing the platelet-shaped magnetic or magnetizable pigment particles to time-dependent magnetic field so as to bi-axially pre-orient the platelet-shaped magnetic or magnetizable pigment particles.

[0077] The orientation of the platelet-shaped magnetic or magnetizable pigment particles in the binder material is achieved by two orientation steps, said steps being carried out by i) bi-axially orienting the platelet-shaped magnetic or magnetizable pigment particles in accordance with an external timedependent magnetic field of a first magnetic-field-generating device (the time-dependent magnetic field is a static or constant magnetic field, and by moving the substrate in front of the magnetic-field generating device producing a static or constant magnetic field, said substrate is submitted to a timedependent magnetic field), and subsequently ii) mono-axially re-orienting the platelet-shaped magnetic or magnetizable pigment particles in accordance with a static external magnetic field of a second magnetic-field-generating device, which corresponds to the transferring device described herein. Such a two-step orientation of the pigment particles is for example described in EP 3079836 A1. 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. That is, each platelet-shaped magnetic or magnetizable pigment particle can be considered to have a major axis in the plane of the pigment particle and an orthogonal minor axis in the plane of the pigment particle. The major and minor axes of the platelet-shaped magnetic or magnetizable pigment particles are each caused to orient according to the time-dependent magnetic field. Effectively, this results in neighboring platelet-shaped magnetic pigment particles that are close to each other in space to be essentially parallel to each other. In order to perform a bi-axial orientation, the platelet-shaped magnetic pigment particles must be subjected to a strongly time-dependent external magnetic field.

[0078] Examples of said first magnetic-field-generating devices for bi-axially orienting the pigment particles include, without limitation, those disclosed in EP 2 157 141 A1 , Z.Q. Zhu and D. Howe (Halbach permanent magnet machines and applications: a review, IEE. Proc. Electric Power Appl., 2001, 148, p. 299-308), US 2007 / 0172261 A1 , CN 102529326 B, WO 2015 / 082344 A1 , WO 2016 / 026896 A1 and WO2018 / 141547 A1 , WO 2021 / 239607 A1.

[0079] Alternatively, the pigment particles may be oriented by exposing the curable coating composition to the resultant magnetic field of a combination of the first magnetic field generating devices described hereabove for bi-axially orienting pigment particles and a soft magnetic plate comprising one or more indentations and / or one or more voids and / or one or more protrusions, as described in WO 2019 / 14142 A1 , WO 2019 / 141453 A1 and WO 2015 / 086257 A1.

[0080] The present invention will be described more fully hereinafter with reference to the accompanying figures in which like numerals represent like element throughout the different figures, and in which prominent aspects and features of the invention are illustrated.

[0081] BRIEF DESCRIPTION OF THE FIGURES

[0082] Fig. 1 shows an example of a substrate as used for the printing of banknotes;

[0083] Fig. 2a-b show an example of banknotes;

[0084] Fig. 3 shows a transferring device;

[0085] Fig. 4 shows a section of a transferring device according to a first embodiment;

[0086] Fig. 5a-c shows a magnetic orienting unit;

[0087] Fig. 6 shows a section of a transferring device according to a second embodiment;

[0088] Fig. 7 shows a method for producing security documents;

[0089] Fig. 8 schematically shows a first example of a printing press;

[0090] Fig. 9 schematically shows a second example of a printing press; and

[0091] Fig.10 schematically shows a third example of a printing press. DETAILED DESCRIPTION

[0092] The magnetic assemblies and the methods described herein for producing optical effect layers (OEL) as security features, in particular a security thread, security stripe or security foil, on a substrate, in particular on a polymeric substrate, preferably on a non-opacified area mimicking a security foil of a polymeric substrate comprising an opacifying layer, are now described in more details with reference to the drawings and to particular embodiments.

[0093] Fig. 1 schematically illustrates a sheet S forming a substrate, which is used for the printing of banknotes 1 , in particular for the printing of polymeric banknotes 1. The sheet S comprises several banknotes 1 arranged edge to edge along several columns (in the example of Fig. 1 , six columns Y1

[0094] - Y6) and several rows (in the example of Fig. 1, eight rows R1 - R8). At the end of the printing process, the individual banknotes 1 are obtained by cutting (slicing) the sheet S between the rows R1 - R8 and between the columns Y1 - Y6 along the virtual dashed lines represented in Fig. 1. For instance, the sheet S illustrated in Fig. 1 would generate forty-eight individual banknotes 1. In Fig. 1, in the case of a polymeric banknotes sheet S, the grey zones 2 schematically represent the opacified areas, while the white stripes 3 schematically represent non-opacified, transparent areas mimicking a security foil.

[0095] As illustrated in Fig. 1 , the sheet S comprises a front edge FE and a back edge BE free of banknotes 1 to allow the use of transport means (grippers, rollers, brushes, etc.) to transport the sheet s through the printing press during the various printing processes. The non-opacified area 3 of each of the banknotes 1 carries three security elements A - C. In alternative examples, the security elements A

[0096] - C can be provided on non-transparent areas, such as on the opaque zones 2 of the banknote 1.

[0097] Fig. 2a-b schematically illustrate examples of the banknotes 1 of the substrate S of Fig. 1, said banknotes comprising an opacifying coating layer (grey area 2) and a non-opacified area (transparent zone 3) representing a security foil and carrying security elements A - C in the shape of motifs F1 - F3 (e.g. in Fig 2a, a sail boat F1, a flower F2 and a pine tree F3), said security elements A - C comprising magnetic or magnetizable pigment particles oriented according to magnetic effects G1 - G3. The different magnetic effects G1 - G3 provide for different visible optical effects (symbolized by grey lines or grey rings). Fig. 2a illustrates an example of a banknote carrying three motifs F1, F2 and F3 and two magnetic effects G1 and G2, forming security elements A and B. Fig. 2b illustrates an example of a banknote carrying three motifs F1 , F2 and F3 and three magnetic effects G1 , G2 and G3, forming security elements A, B and C. The banknotes 1 can be designed differently than the examples shown in Fig. 2. For example, each banknote 1 can include one, two or more than three motifs F1 - F3, which can have pigment particles oriented according to at least one, but preferably multiple, different magnetic effects G1 - G3. The security elements A-B-A and A- B-C form an elongated security feature 4. Fig. 3 shows a transferring device 100 for orienting the pigment particles on the substrate S to obtain the desired effects. Fig. 3 represents an outer surface of the transferring device 100. The transferring device 100 is here a cylindrical transferring device 100. A lateral surface of the cylindrical transferring device 100 which forms the outer surface, has a rectangular shape when unrolled, which corresponds to the representation of Fig. 3. The transferring device 100 has a structure that is similar to that of the substrate S of Fig. 1 as the transferring device 100 is used to orient the pigment particles of the substrate S when placing the substrate S in front of the transferring device 100. Accordingly, the transferring device 100 has NxP magnetic blocks 102 (only some magnetic blocks 102 have reference signs disclosed in Fig. 3 for readability), with N being the number of rows and N=8, and P being the number of columns and P=6. Along (aligned with and parallel to) each alignment line 103, which extends through a column in the representation of Fig 3 but follows an outer circumference line of a cross-section of the cylindrical transferring device 100, N=8 identical magnetic blocks 102 are arranged. Each magnetic block 102 has M=3 magnetic field generating devices 101 for generating a magnetic field in accordance with the magnetic effects G1 - G3. In the example of Fig. 3, the three leftmost columns have magnetic blocks 102 each including magnetic field generating devices 101 generating the magnetic effects G1-G2-G1 in this order (i.e. the banknotes of Fig. 2a), while the three rightmost columns have magnetic blocks 102 each including magnetic field generating devices 101 generating the magnetic effects G1-G2-G3 in this order (i.e. the banknotes of Fig. 2b).

[0098] As can be seen in Fig. 3, the upper and lower magnetic blocks 102 (i.e. the magnetic blocks 102 neighboring the back edge BE and the front edge FE of the sheet S) form edge magnetic blocks 104 which have only one neighbor along their alignment line 103, while all other magnetic blocks 102 have two vertical neighbors. Since neighboring magnetic blocks 102 along the alignment line 103 influence one another’s magnetic fields, magnetic blocks 102 with one neighbor (i.e. magnetic blocks 104) expose the pigment particles to a different magnetic field than magnetic blocks 102 with two neighbors. As a result, not all banknotes 1 are exposed to the same magnetic fields, resulting in variations between effects produced on the banknotes 1. These variations are undesirable so that the transferring device 100 comprises means to avoid variations between effects produced on the banknotes 1 by the different magnetic blocks 102. These means can take different forms, which will be described below. First embodiment

[0099] According to a first embodiment of a transferring device 100, the above-described problem is solved by providing a shielding element 105 between neighboring magnetic blocks 102 along the alignment line 103. This is shown in Fig. 4, which shows an example of one column of the transferring device 100 of Fig. 3, in which a shielding element 105 is provided along the alignment line 103 between each neighboring magnetic block 102. In the example of Fig. 4, seven shielding elements 105 are provided. More generally, for an alignment of N magnetic blocks 102 along the alignment line 103, (N-1) shielding elements 105 are provided. The shielding elements 105 are made of steel S235. The shielding elements 105 isolate the magnetic fields of each magnetic block 102 from neighboring magnetic blocks 102. This means that magnetic fields from neighboring magnetic blocks 102 do not interact with one another. As a result, independently of whether the magnetic block 102 has a single neighbor (as is the case for the edge magnetic blocks 104) or two neighbors along the alignment line 103, the block magnetic field provided by each magnetic block 102 onto the substrate S are all the same. This results in identical effects produced on all the banknotes 1 of the substrate S.

[0100] The shielding elements 105 can be part of holding cases 301 each holding one magnetic block 102. Such a holding case 301 is illustrated in Fig. 5, which shows a magnetic orienting unit 300 comprising the holding case 301 for holding one magnetic block 102. Here, the shielding element 105 is formed by the side walls of the holding case 301. The holding case 301 holds the three magnetic field generating devices 101 forming one magnetic block 102. The holding case 301 comprises a lid 302. Fig. 5a illustrates a cross-section view and Fig. 5b illustrates a top view of the magnetic assembly 300 (in Fig. 5b, the lid 302 is not represented for clarity reason). Fig. 5c schematically illustrates a cross-section view of only the holding case 301.

[0101] Second embodiment

[0102] According to a second embodiment of a transferring device 100, the above-described problem is solved by providing the transferring device 100 with a compensation magnetic block 106 and optionally an additional compensation magnetic block 107, which are shown in Fig. 6, which shows one column of N=8 magnetic blocks 102 of the transferring device 100 of Fig. 3 aligned along the alignment line 103. As compared to the magnetic blocks 102, the compensation magnetic block 106 and the additional compensation magnetic block 107 are not used for creating corresponding effects on the substrate S, they are merely for mimicking additional neighboring magnetic blocks 102 for the edge magnetic blocks 104. The compensation magnetic block 106 is facing the front edge FE of the sheet S when disposed on the transferring device 100 and aligned with the alignment line 103. The compensation magnetic block 106 includes one compensation magnetic field generating device 108, which is a magnetic field generating device 101 producing the magnetic effect G3 and hence corresponds to the third (M-th) magnetic field generating device 101 of each magnetic block 102 of the alignment of Fig. 6. Similarly, the additional compensation magnetic block 107 is facing the back edge BE of the sheet S when disposed on the transferring device 100 and aligned with the alignment line 103. The additional compensation magnetic block 107 includes one additional compensation magnetic field generating device 109, which is a magnetic field generating device 101 producing the magnetic effect G1 and hence corresponds to the first magnetic field generating device 101 of each magnetic block 102 of the alignment of Fig. 6. The compensation magnetic block 106 and the additional compensation magnetic block 107 hence mimic the magnetic field of neighboring magnetic blocks 102 for the edge magnetic blocks 104. The magnetic field that each magnetic block 102 produces on the substrate S is hence identical, resulting in identical security features 4 on each banknote 1.

[0103] Instead of only including one compensation magnetic field generating device 108 or 109, the compensation magnetic block 106 and / or the additional compensation magnetic block 107 can comprise multiple magnetic field generating devices 101 , in particular as many as the other magnetic blocks 102, so that the compensation magnetic block 106 and / or the additional compensation magnetic block 107 can be identical with the magnetic blocks 102.

[0104] Each magnetic block 102, the compensation magnetic block 106 and / or the additional compensation magnetic block 107 can be held by a holding case 301 as described in view of Fig. 5. The holding case 301 can include the shielding element 105 or be provided without the shielding element 105.

[0105] Method for producing security documents

[0106] The transferring device 100 of the first or second embodiments described above can be used in the process of producing at least N security documents, here banknotes 1. Such a process is disclosed in Fig. 7 and 8, which are detailed below.

[0107] In a step a) of Fig. 7, the sheet-like substrate S is provided. In a step b), a radiation curable coating composition 200 comprising platelet-shaped magnetic or magnetizable pigment particles is applied on the surface of the substrate S. The coating composition 200 is applied in a first state, in which the pigment particles can move on the surface of the substrate S. The coating composition 200 is here applied by screen printing in the form of M independent and optionally spaced apart motifs for each of the N security features 4. In other words, a motif is printed for each security elements A - C of the banknotes 1 to be created. The motifs are printed to take the shape of the motifs F1 - F3 shown in Fig. 2. In an optional step f), the pigment particles are exposed to a time-dependent magnetic field generated by a magnetic field generating device 201 for producing a time-dependent magnetic field to pre-orient the pigment particles bi-axially. The substrate S moves in front of the magnetic field generating device 201 for producing a time-dependent magnetic field, as indicated by the rightpointing arrow in step f) of Fig. 7. The substrate S is then disposed on the transferring device 100.

[0108] In a subsequent step c), the pigment particles are exposed to the block magnetic fields generated by the magnetic blocks 102 of the transferring device 100. For this, the substrate S is placed such as to face the transferring device 100, such that each motif F1 - F3 applied on the substrate S in step b) of the process faces a magnetic field generating device 101 of a magnetic block 102 of the transferring device 100.

[0109] In a step d) of the process of Fig. 7, the coating composition 200 is cured to a second, dried state, in which the pigment particles are fixed. The curing is performed using a UV lamp 202. As a result, each motif F1 - F3 applied in step b) is cured into a security element A - C. A substrate S with at least N security features 4 is thus obtained. By slicing the substrate between the N security features 4, the N banknotes 1 can be obtained.

[0110] As defined herein, one security document (banknote 1 ) includes one security feature 4. One security feature 4 is made of several security elements (several OELs) A - C, which are characterized by (i) their shape (motifs F1 - F3) and (ii) the magnetic effect G1 - G3 applied thereto by the corresponding magnetic field generating devices 101. In the non-cured state, the coating composition 200 including the pigment particles is applied in motifs F1 - F3 to the substrate S, each cured motif forming a security element A - C. The security elements A-C may be spaced apart or may be at least partly adjacent (i.e. at least partly in contact with each other).

[0111] Fig. 8 schematically illustrates an example of a printing press 500 performing the process of Fig. 7 to produce the at least N security documents 1. As can be seen in Fig. 8, the sheet S is inserted and guided through the printing press 500. The sheet S has N independent and (here) spaced apart applied coating composition motif multiplets 203 (each including motifs F1 - F3 so that the multiplets are here triplets) thereon, which jointly form the coating composition 200. The motif triplets 203 are applied by a screen printing device 204 (corresponding to step b) of Fig. 7). In the example of Fig. 8, the printing press 500 includes one magnetic field generating device 201 for producing a timedependent magnetic field for bi-axially orienting the pigment particles (step f) of Fig. 7) before the sheet S reaches the transferring device 100. As shown in Fig. 8, the cylindrical transferring device 100 rotates, thereby guiding the sheet S through the printing press 500. A distance between the magnetic blocks 102 is identical to a distance between motif multiplets 203, so that each magnetic block 102 orients the pigment particles of the facing motif multiplet 203. The UV lamp 202 is placed such that the curing (step d) of Fig. 7) is partially simultaneously performed together with the step of orienting the pigment particles (step c) of Fig. 7).

[0112] Fig. 9 shows a variant of the printing press 500 of Fig. 8, in which the magnetic field generating device 201 for producing a time-dependent magnetic field for bi-axially orienting the pigment particles is instead provided such as to face the cylindrical transferring device 100.

[0113] Fig. 10 shows yet another variant of the printing press 500 of Fig. 8 and 9, which includes both magnetic field generating devices 201 for producing time-dependent magnetic field of Fig. 8 and 9, which are for bi-axially orienting the pigment particles.

[0114] The above disclosed subject-matter is to be considered illustrative, and not restrictive, and serves to provide a better understanding of the invention defined by the independent claims.

[0115] REFERENCE NUMERALS

[0116] 1 banknote

[0117] 2 opaque zone

[0118] 3 transparent zone

[0119] 4 security feature

[0120] 100 transferring device

[0121] 101 magnetic field generating device

[0122] 102 magnetic block

[0123] 103 alignment line

[0124] 104 edge magnetic block

[0125] 105 shielding element

[0126] 106 compensation magnetic block

[0127] 107 additional compensation magnetic block

[0128] 108 compensation magnetic field generating device

[0129] 109 additional compensation magnetic field generating device

[0130] 200 coating composition

[0131] 201 magnetic field generating device for producing a time-dependent magnetic field

[0132] 202 UV lamp

[0133] 203 motif multiplet

[0134] 204 screen printing device

[0135] 300 magnetic orienting unit

[0136] 301 holding case 302 lid

[0137] 500 printing press

[0138] A - C security element or optical effect layer (OEL)

[0139] BE back edge FE front edge

[0140] F1 - F3 motif

[0141] G1 - G3 magnetic effect

[0142] R1 - R8 row

[0143] S substrate Y1 - Y6 column

Claims

CLAIMS1. A transferring device (100) for orienting platelet-shaped magnetic or magnetizable pigment particles contained in a radiation curable coating composition (200) and applied on a substrate (S), the transferring device (100) being a flatbed transferring device (100) or a cylindrical transferring device (100), the transferring device (100) comprising: a number N of identical magnetic blocks (102) aligned along an alignment line (103) provided on an outer surface of the transferring device (100), the magnetic blocks (102) each including M magnetic field generating devices (101 ) each generating a corresponding magnetic field such that the magnetic blocks (102) each generate a block magnetic field, N being greater than or equal to two, and M being greater than or equal to one; and a shielding element (105) provided between each two neighboring magnetic blocks (102), the shielding element (105) being made of a material at least partly isolating the block magnetic field of each magnetic block (102) from the block magnetic field of the other magnetic blocks (102).

2. The transferring device of claim 1 , further comprising N holding cases (301 ) for each holding one magnetic block (102), at least a section of the holding cases (301 ) forming the shielding element (105).

3. The transferring device of claim 1 or 2, wherein the material of the shielding element (105) is a material having a relative permeability of more than 40; and / or steel, in particular steel S235.

4. The transferring device of any one of claims 1 to 3, wherein the transferring device (100) is the cylindrical transferring device (100) and the alignment line (103) is an outer circumference line of a cross-section of the cylindrical transferring device (100); or a lateral line on the outer surface of the cylindrical transferring device (100) which is parallel to an axis of the cylindrical transferring device (100); or the transferring device (100) is the flatbed transferring device (100) having a rectangular shape and the alignment line (103) is parallel to a side of the rectangular shaped flatbed transferring device (100).

5. A transferring device (100) for orienting platelet-shaped magnetic or magnetizable pigment particles contained in a coating composition (200) and applied on a substrate (S) for producing N security documents (1) on the substrate (S), the transferring device (100) being a flatbed transferring device (100) or a cylindrical transferring device, the transferring device (100) comprising:a number N of identical magnetic blocks (102) aligned along an alignment line (103) provided on an outer surface of the transferring device (100), the magnetic blocks (102) each including M magnetic field generating devices (101 ) each generating a corresponding magnetic field such that the magnetic blocks (102) each generate a block magnetic field, N being greater than or equal to two, and M being greater than or equal to one; and a compensation magnetic block (106) provided alongside the first magnetic block (102) along the alignment line (103) so that the first of the N magnetic blocks (102) is arranged between the compensation magnetic block (106) and the second of the N magnetic blocks (102), the compensation magnetic block (106) including at least one compensation magnetic field generating device (108) that provides a magnetic field identical to that of at least part of one of the magnetic blocks (102) that includes the M-th magnetic field generating device (101 ).

6. The transferring device of claim 5, further comprising an additional compensation magnetic block (107) provided alongside the N-th magnetic block (102) along the alignment line (103) so that the N-th magnetic block (102) is arranged between the additional compensation magnetic block (107) and the (N-1 )-th magnetic block (102), the additional compensation magnetic block (107) including at least one additional compensation magnetic field generating device (109) that provides a magnetic field identical to that of at least part of one of the magnetic blocks (102) that includes the first of the M magnetic field generation devices (101).

7. The transferring device of claim 5 or 6, wherein the at least one compensation magnetic field generating device (108) comprised in the compensation magnetic block (106) provides a magnetic field identical to that of the M-th magnetic field generating device (101 ) and / or the at least one additional compensation magnetic field generating device (109) comprised in the additional compensation magnetic block (107) provides a magnetic field identical to that of the first magnetic field generating device (101).

8. The transferring device of any one of claims 5 to 7, further comprising a shielding element (105) provided between each two neighboring magnetic blocks (102), and between the compensation magnetic block (106) and the first of the N magnetic blocks (102), the shielding element (105) being made of a material at least partly isolating the block magnetic field of each magnetic block (102) from the block magnetic field of the other magnetic blocks (102) and from the magnetic field of the compensation magnetic block (106).

9. The transferring device of any one of claims 1 to 8, wherein each magnetic block (102) includes at least two different magnetic field generating devices (101).

10. A magnetic orienting unit (300) for the transferring device (100) of any one of claims 1 to 9, the magnetic orienting unit (300) being for orienting platelet-shaped magnetic or magnetizablepigment particles contained in a radiation curable coating composition (200) and applied on a substrate (S), the magnetic orienting unit (300) comprising: a magnetic block (102) including M magnetic field generating devices (101 ) each generating a corresponding magnetic field such that the magnetic block (102) generates a block magnetic field, M being greater than or equal to one; and a shielding element (105) and / or a compensation magnetic block (106); wherein the shielding element (105) is provided alongside the magnetic block (102), the shielding element (105) being made of a material at least partly blocking the block magnetic field; and / or the compensation magnetic block (106) is provided alongside the first magnetic block (102), the compensation magnetic block (106) includes at least one compensation magnetic field generating device (108) that provides a magnetic field identical to that of at least part of the magnetic block (102) that includes the M-th magnetic field generating device (101 ).

11. A printing press (500) comprising a transferring device (100) according to any one of claims 1 to 9.

12. A method for producing at least N security documents (1) each comprising one security feature (4) comprising at least M security elements (A - C), N being equal to or greater than two, and M being greater than or equal to one, the method comprising: a) providing a substrate (S), preferably in the form of a sheet; b) applying on a substrate surface a radiation curable coating composition (200) comprising platelet-shaped magnetic or magnetizable pigment particles, the coating composition (200) being in a first state, the coating composition (200) being applied in the form of M independent and optionally spaced apart motifs (F1 - F3) for each of the N security features (4), c) exposing the magnetic or magnetizable pigment particles to a magnetic field of a transferring device (100) according to any one of claims 1 to 9 so as to orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles of each of the M applied motifs (F1 - F3) of one security feature (4) according to a block magnetic field of a magnetic block (102) of the transferring device (100); and d) curing, preferably partially simultaneously with step c), the coating composition (200) of step b) to a second state so as to fix the platelet-shaped magnetic or magnetizable pigment particles in their adopted positions and orientations, such that each cured motif forms one of the security elements (A - C).

13. The method of claim 12, further comprising: e) slicing the substrate (S) between the N security features (4) to obtain individual and identical security documents (1).

14. The method of claim 12 or 13, wherein each of the N security features (4) includes at least two different security elements (A - C).

15. The method of any one of claims 12 to 14, wherein the method further includes, between steps b) and c), a step f) of exposing the platelet-shaped magnetic or magnetizable pigment particles to a time-dependent magnetic field so as to bi-axially pre-orient the platelet-shaped magnetic or magnetizable pigment particles.

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