HK1231435B - Processes for in-field hardening of optical effect layers produced by magnetic-field generating devices generating concave field lines - Google Patents

Description

In-field hardening of optical effect layers produced by a magnetic field generating device that generates concave field lines Method

Field of the Invention

The present invention relates to the field of protecting valuable documents and valuable goods against forgery and illegal copying. In particular, the present invention relates to a manufacturing device and method.

Background of the Invention

The use of inks, compositions, or layers containing magnetic or magnetizable particles or pigments (particularly also magnetic optically variable pigments) to produce security elements, for example in the field of security documents, is known in the art. For example, coatings or layers containing oriented magnetic or magnetizable particles are disclosed in US Pat. Nos. 2,570,856, 3,676,273, 3,791,864, 5,630,877, and 5,364,689. WO 2002/090002 A2 and WO 2005/002866 A1 disclose coatings or layers containing oriented magnetic color-changing pigment particles to produce particularly attractive optical effects that can be used to protect security documents.

Security features used in security documents, for example, can generally be categorized as "covert" security features, on the one hand, and "overt" security features, on the other. The protection provided by covert security features relies on the concept that such features are difficult to detect (often requiring specialized equipment and knowledge to do so), while "overt" security features rely on the concept that such features are easily detectable via unaided human perception, e.g., such features are visible and/or tactilely detectable, while still being difficult to manufacture and/or replicate. However, the effectiveness of overt security features depends largely on their easy identification as security features, as most users, particularly those who are unaware of the security features of the document or object being protected, will only actually perform a security check based on such features if they are actually aware of their presence and nature.

If the security structure changes its appearance as the viewing conditions, such as the viewing angle, a particularly striking optical effect can be achieved. This effect can be achieved, for example, by means of dynamic appearance change optical devices (DACODs), such as those disclosed in EP 1 710 756 A1, which rely on concave or convex Fresnel-type reflective surfaces of oriented pigment particles in a hardened coating. This document describes a method for obtaining a printed image containing magnetic pigment particles or flakes by arranging the pigment particles in a magnetic field. After orientation in the magnetic field, the pigment particles or flakes exhibit a Fresnel structure arrangement, such as a Fresnel reflector. By tilting the image and thereby changing the direction of reflection towards the observer, the area exhibiting maximum reflection for the observer moves according to the orientation of the flakes or pigment particles.

Although Fresnel-type reflective surfaces are flat, they provide the appearance of a concave or convex reflective hemisphere. Such Fresnel-type reflective surfaces can be produced by exposing a wet coating containing non-isotropically reflective magnetic or magnetizable pigment particles to the magnetic field of a single dipole magnet, wherein the single dipole magnet is placed above the plane of the coating for a concave effect ( FIG. 2C , bottom), or below the plane of the coating for a convex effect ( FIG. 2C , top), as shown in FIG. 7B of EP 1 710 756 A1 for a convex orientation. The position and orientation of the pigment particles thus oriented are thereby fixed by hardening the coating.

One example of such a structure is the so-called "rolling bar" effect, as disclosed in US 2005/0106367 and US 7,047,883. The "rolling bar" feature is based on pigment particle orientation that mimics a curved surface across the coating and provides an optical illusion of motion to an image composed of the oriented pigment particles. The observer sees specular reflections moving away from or toward the observer when the image is tilted. So-called positive rolling bars contain pigment particles with a concave orientation ( FIG. 2B ) and follow a positively curved surface; positive rolling bars move with the rotational effect of the tilt. So-called negative rolling bars contain pigment particles with a convex orientation ( FIG. 1 and 2A ) and follow a negatively curved surface; negative rolling bars move in the opposite direction of the rotational effect of the tilt. A hardened coating containing pigment particles with an orientation that follows a concave curvature (positive curved orientation) exhibits a visual effect characterized by upward movement of the rolling bar (positive rolling bar) when the carrier is tilted backward. The concave curvature refers to the curvature seen by an observer viewing the hardened coating from the side of the carrier that carries it ( FIG. 2B ). A hardened coating containing pigment particles having an orientation that follows a convex curvature (negatively curved orientation, FIG. 2A ) exhibits a visual effect characterized by a downward rolling motion (negative rolling) when the carrier carrying the hardened coating is tilted backward (i.e., with the top surface of the carrier facing away from the viewer while the bottom surface of the carrier moves toward the viewer) ( FIG. 1 ). This effect is currently used in many security elements on banknotes, such as the “5” on the 5-euro note or the “100” on the 100-South African rand note.

For an optical effect layer printed on a substrate, a negative scrolling bar structure (with convex orientation of the pigment particles (PP), curves (Figures 1 and 2A)) is produced by exposing a wet, uncured coating to the magnetic field of a magnet located on the side of the substrate opposite the coating (Figures 2C, top and 3), while a positive scrolling bar structure (with concave orientation of the pigment particles (PP), curves (Figure 2B)) is produced by exposing a wet, uncured coating to the magnetic field of a magnet located on the same side of the substrate as the coating (Figure 2C, bottom and Figure 4A, left). Examples of positive and negative scrolling bar structures and their combinations, namely, double and triple scrolling bar structures, are disclosed in US 2005/0106367 and WO 2012/104098 A1, respectively. In the case of a positive scrolling bar structure, where the magnet faces the still-wet, uncured coating, simultaneous curing of the coating by a radiation source, such as a UV radiation source, to fix the orientation of the pigment particles within the coating is prevented, and curing can therefore only occur after the coating is separated from the magnet.

US 2,829,862 teaches the importance of the viscoelastic properties of the carrier material to preventing the reorientation of magnetic or magnetizable pigment particles after removing an external magnet. Maintaining the coating composition comprising magnetic or magnetizable pigment particles or sheets in a magnetic field during the curing process maintains the orientation of the magnetic or magnetizable pigment particles. Examples of such methods are disclosed in, for example, WO 2012/038531 A1, EP 2433798 A1 and US 2005/0106367. In all of these examples, the external magnetic device is positioned on the substrate side opposite to the side carrying the coating composition, and the curing process is initiated by an irradiation source positioned on the substrate side carrying the coating composition.

It is known in the art that when a UV-VIS radiation source is used to cure a coating or ink composition, the exposure conditions of the coating or ink composition to the radiation source are crucial to obtaining sufficient and rapid curing of the composition. The radiation source is preferably directed toward the coating or ink composition to be cured.

JP 06122848 discloses a printing method for gravure printing in which the gravure ink is cured from the back of the substrate using an electron beam immediately after application. Curing with an electron beam allows for curing through optically opaque materials, but the mechanism requires shielding the device with heavy metal components, resulting in bulky equipment and high safety requirements. Furthermore, the atmosphere severely inhibits electron beam curing, so effective curing disadvantageously requires an inert atmosphere.

EP 0338378 A1 discloses a method for producing a document or other article containing at least one replica of a surface relief diffraction pattern. The method comprises the steps of printing a liquid casting resin onto a designated area of a substrate, holding the resin between the substrate and a master of the surface relief pattern, and curing the resin. The type of radiation used depends primarily on the resin formulation and the nature of the substrate material. For substrates made of paper or other opaque sheets, electron beam radiation is preferred. For optically transparent sheets, UV-Vis radiation can be used.

WO 2005/051675 A1 discloses an apparatus and method for printing a curable composition on a security product to produce a diffraction grating. The composition is cured using UV-Vis irradiation or electron beam curing. If the curable composition is applied to a paper substrate and cured using a UV-Vis irradiation lamp, the lamp is preferably located on or in the device for forming the diffraction grating, i.e., the UV lamp is located on the front side of the substrate carrying the curable composition. Other examples of holograms produced by contacting a liquid composition with a relief structure while curing the composition from the back side of the substrate with an electron beam are disclosed in, for example, WO 2000/0534223 A1 or EP 540450 A1. WO 2012/176126 A1 discloses a method and apparatus for forming a surface relief microstructure on a paper substrate. The method comprises the steps of applying a composition to the front side of the substrate, contacting at least a portion of the curable composition with the surface relief microstructure, and curing the coating composition using at least one UV lamp arranged on the back side of the paper substrate.

WO 02/090002 A2 discloses a method for producing an image-coated article using magnetic pigments. The method comprises the steps of applying a liquid coating comprising a non-spherical magnetic pigment dispersed in a pigment carrier to a substrate, exposing the liquid coating to a magnetic field, and curing the coating by exposure to electromagnetic radiation. The curing step can be performed using an apparatus comprising a lamp equipped with a photomask, thereby selectively curing only a portion of the liquid coating, while the unexposed portion of the coating remains liquid. A second magnetic field can be used to reorient the non-spherical magnetic pigment dispersed in the unexposed portion of the liquid coating.

Therefore, there remains a need for methods of producing security members exhibiting an OEL on a substrate, the OEL comprising a plurality of magnetic or magnetizable pigment particles oriented concavely.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method comprising the steps of applying external magnetic means on the OEL side and simultaneously or partially simultaneously hardening a coating comprising a plurality of magnetic or magnetizable pigment particles by irradiation while avoiding the disadvantages of the prior art.

This is achieved by providing a method for producing an optical effect layer (OEL) on a substrate and an optical effect layer produced therefrom, the method comprising the steps of:

a) applying a coating composition comprising a plurality of magnetic or magnetizable pigment particles to a substrate to form a coating, said coating being in a first state;

b) b1) exposing the coating to a magnetic field from a magnetic field generating device, said magnetic field generating device being located on the side of the coating, thereby orienting the plurality of magnetic or magnetizable pigment particles, and b2) simultaneously or partially simultaneously hardening the coating through the substrate to a second state to fix the magnetic or magnetizable pigment particles in their adopted position and orientation, said hardening being performed by irradiation with a UV-Vis radiation source located on the side of the substrate;

wherein the substrate is transparent to electromagnetic radiation of one or more wavelengths in the emission spectrum of the radiation source in the range of 200 nm to 500 nm, and

wherein the plurality of magnetic or magnetizable pigment particles are oriented to follow a concave curvature when viewed from the side carrying the OEL.

Also described herein is a method for producing an optical effect layer (OEL) on a substrate as described herein, the OEL comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, the method comprising the steps of:

a) applying a coating composition comprising a plurality of magnetic or magnetizable particles as described herein to a substrate as described herein to form a coating, said coating being in a first state;

b)

b1) exposing one or more first substrate areas bearing the coating to a magnetic field of a first magnetic field generating device, said magnetic field generating device being located on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing said coating, and b2) simultaneously or partially simultaneously hardening the coating as described herein through said substrate by irradiation with a UV-Vis radiation source located on the side of said substrate, wherein said UV-Vis radiation source is provided with a photomask so that one or more second substrate areas bearing said coating are not exposed to UV-Vis radiation;

c) exposing at least the one or more second substrate areas bearing the coating, which are in a first state due to the presence of the photomask in step b2), to a magnetic field of a second magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a random orientation other than a random orientation; and simultaneously, partly simultaneously or subsequently, preferably simultaneously or partly simultaneously, hardening at least the one or more second substrate areas bearing the coating to a second state by irradiation with a UV-Vis radiation source to fix the magnetic or magnetizable pigment particles in their acquired position and orientation,

The substrate in step a) is transparent to one or more wavelengths of the emission spectrum of the radiation source in the range of 200 nm to 500 nm.

Also described herein is a method for producing an optical effect layer (OEL) on a substrate as described herein, the OEL comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, the method comprising the steps of:

a) applying a coating composition comprising a plurality of magnetic or magnetizable particles to the substrate to form a coating, the coating being in a first state;

b)

b1) exposing one or more first substrate regions bearing said coating to a magnetic field of a first magnetic field generating means, thereby orienting said plurality of magnetic or magnetizable pigment particles to follow a random orientation other than a random orientation, and

b2) simultaneously, partially simultaneously or subsequently hardening the coating as described herein by irradiation with a UV-Vis radiation source provided with a photomask such that one or more areas of the second substrate carrying the coating are not exposed to the UV-Vis radiation; and

c) exposing at least the one or more areas of the second substrate carrying the coating, which are in a first state due to the presence of the photomask in step b2), to a magnetic field of a second magnetic field generating device, said magnetic field generating device being situated on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side carrying said coating; and simultaneously or partially simultaneously hardening through said substrate at least the one or more areas of the second substrate carrying the coating, said hardening being performed by irradiation with a UV-Vis radiation source situated on the side of said substrate,

The substrate of step a) is transparent to one or more wavelengths of the emission spectrum of the radiation source in the range of 200 nm to 500 nm.

Also described herein are optical effect layers (OELs) produced by the methods described herein and the use of said optical effect layers for protecting security documents against forgery or counterfeiting and for decorative applications.

Also described herein are security documents and decorative elements or objects comprising one or more optical effect layers (OELs) as described herein.

The present invention discloses a method for hardening a coating comprising orientable magnetic or magnetizable pigment particles by irradiating said coating through a substrate bearing the coating to freeze the orientation of the orientable magnetic or magnetizable pigment particles in-field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a scroll bar member having a convex curvature (negative scroll bar member) according to the prior art.

2A-B schematically illustrate pigment particles following the tangent of a convex negatively curvature magnetic field line ( FIG. 2A ) and a concave positively curvature magnetic field line ( FIG. 2B ). “C” refers to a coating comprising magnetic or magnetizable pigment particles “PP”.

Figure 2C schematically shows a magnetic field generating device suitable for forming a convex (top) or concave (bottom) magnetic field depending on its position. "S" refers to the substrate, and "C" refers to the coating comprising magnetic or magnetizable pigment particles.

FIG3 schematically shows a magnetic field generating device suitable for forming convex negative curvature magnetic field lines according to the prior art.

FIG. 4A schematically shows an example of a comparative method using a magnetic field generating device and an irradiation source suitable for forming a rolling bar member that follows a concave positive curvature magnetic field line (prior art).

FIG. 4B shows an example of a scroll bar member manufactured using the method shown in FIG. 4A viewed at different viewing angles.

FIG. 5A schematically illustrates an example of a method according to the present invention using a magnetic field generating device and an irradiation source adapted to form a rolling bar member following concave positive curvature magnetic field lines.

FIG. 5B shows an example of a scroll bar member manufactured using the method shown in FIG. 5A viewed at different viewing angles.

6A shows a comparative example of a method using a magnetic field generating device and an irradiation source suitable for forming an optical effect layer comprising a pattern consisting of at least two patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a convex curvature when viewed from the side carrying the OEL (prior art).

FIG. 6B shows an example of a scroll bar member manufactured using the method shown in FIG. 6B viewed at different viewing angles.

7A schematically shows an example according to the present invention of a method using a magnetic field generating device and an irradiation source suitable for forming an optical effect layer comprising a pattern consisting of at least two patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented so as to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented so as to follow a convex curvature when viewed from the side carrying the OEL.

FIG. 7B shows an example of a scroll bar member manufactured using the method shown in FIG. 7A viewed at different viewing angles.

Figure 8 schematically shows an example according to the invention of a method using a magnetic field generating device and an irradiation source suitable for forming an optical effect layer comprising a pattern consisting of at least two adjacent patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a convex curvature when viewed from the side carrying the OEL.

FIG9 shows the transmission spectra of various substrates.

FIG10 schematically shows an experiment performed to evaluate the degree of hardening of coating compositions comprising magnetic or magnetizable pigment particles and the degree of freezing of the orientation of said magnetic or magnetizable pigment particles after UV-Vis irradiation through a substrate.

11A-B show photographs of samples made according to the experiment described in FIG. 10 .

Details

definition

The following definitions are used to explain the meaning of the terms discussed in the specification and recited in the claims.

The indefinite articles "a" and "an" are used herein to refer to one as well as more than one and do not necessarily limit the noun to the singular.

As used herein, the term "approximately" means that the quantity or value in question may be the specific value specified or another value in the vicinity thereof. Generally, the term "approximately" used to modify a numerical value is intended to indicate a range of ±5% of that value. As an example, the phrase "approximately 100" refers to a range of 100 ± 5, i.e., a range of 95 to 105. Generally, when the term "approximately" is used, it is expected that similar results or effects according to the present invention can be obtained within a range of ±5% of the numerical value indicated.

As used herein, the term "and/or" means that all or only one of the elements of the combination may be present. For example, "A and/or B" should mean "only A, or only B, or A and B." In the case of "only A," the term also encompasses the possibility that B is not present, i.e., "only A, but not B."

As used herein, the term "comprising" is intended to be non-exclusive and open ended. Thus, for example, a coating comprising compound A may include other compounds in addition to A. However, the term "comprising" also encompasses the more restrictive meanings "consisting essentially of" and "consisting of," so that, for example, a "coating comprising compound A" may also consist (essentially) of compound A.

The term "coating composition" refers to any composition capable of forming an optical effect layer (OEL) as used herein on a solid substrate and which may preferably, but not limited to, be applied by printing. The coating composition comprises at least a plurality of magnetic or magnetizable pigment particles and a binder.

The term "optical effect layer (OEL)" as used herein refers to a layer comprising a plurality of oriented magnetic or magnetizable pigment particles and a binder, wherein the non-random orientation of the magnetic or magnetizable pigment particles is fixed or frozen in the binder.

The term "rolling bar" or "rolling bar member" refers to a region within an OEL that provides an optical effect or impression of a cylindrical bar positioned transversely within the OEL, with the axis of the cylindrical bar parallel to the plane of the OEL and the portion of the curved surface of the cylindrical bar above the plane of the OEL. The "rolling bar," i.e., cylindrical bar, can be symmetrical or asymmetrical, i.e., the radius of the cylindrical bar can be constant or non-constant; when the radius of the cylindrical bar is non-constant, the rolling bar has a conical form.

The terms "convex" or "convex curvature" and "concave" or "concave curvature" refer to the curvature of a Fresnel surface across the OEL that provides a rolling bar optical effect or impression. A Fresnel surface is a surface containing a series of microstructures in the form of grooves with varying inclination angles. At the location where the OEL is generated, a magnetic field generating device orients the magnetic or magnetizable pigment particles along a tangent to the curved surface. The terms "convex" or "convex curvature" and "concave" or "concave curvature" refer to the apparent curvature of the curved surface as seen by an observer viewing the optical effect layer (OEL) from the side of the substrate carrying the OEL. The curvature of the curved surface follows the magnetic field lines generated by the magnetic field generating device at the location where the OEL is generated. "Convex curvature" refers to magnetic field lines with negative curvature (as shown in FIG. 2A ); "concave curvature" refers to magnetic field lines with positive curvature (as shown in FIG. 2B ).

The term "security element" is used to denote an image or graphic element that can be used for authentication purposes. The security element can be an explicit and/or implicit security element.

The terms "hardening", "hardened" and "hardening" are used to indicate that an increase in viscosity occurs in response to a stimulus to convert the material into a state in which the magnetic or magnetizable pigment particles are fixed or frozen in their current position and orientation and can no longer move or rotate, i.e. a hardened or solid state.

The present invention provides a method for producing an optical effect layer (OEL) comprising a plurality of oriented magnetic or magnetizable pigment particles on a substrate, wherein the plurality of magnetic or magnetizable pigment particles are oriented so as to follow a concave curvature when viewed from the side carrying the OEL, in particular, wherein the plurality of magnetic or magnetizable pigment particles are oriented so that the OEL exhibits a positive rolling bar component.

As described in the prior art, for example in US Pat. Nos. 7,047,888, 7,517,578 and WO 2012/104098 A1 and as shown in FIG2C , a known method for obtaining an orientation of magnetic or magnetizable pigment particles on a substrate following a negative curvature (convex curvature when viewed from the side bearing the coating as seen from the eye, see FIG2A ) comprises orienting the pigment particles (PP) using a magnetic field generating device, said device being placed below the substrate ( FIG2C , top). To obtain an orientation of magnetic or magnetizable pigment particles on a substrate following a positive curvature (concave curvature when viewed from the side bearing the coating as seen from the eye, see FIG2B ), the magnetic field generating device for orienting the pigment particles (PP) is placed above the substrate ( FIG2C , bottom), i.e., it faces the coating containing the magnetic or magnetizable pigment particles.

3 shows an example of a magnet (M) suitable for producing an optical effect layer based on a plurality of magnetic or magnetizable pigment particles oriented so as to follow a convex curvature when viewed from the side bearing the coating (C), in particular an optical effect layer exhibiting a negative rolling stripe component (pigment particles (PP) oriented in a convex shape ( FIG. 2A )) produced by exposing the wet and not yet hardened coating to the magnetic field of a magnet located on the side (below) of the substrate (S).

FIG4A shows an example of a magnetic field generating device (MD) suitable for producing an OEL based on a plurality of magnetic or magnetizable pigment particles oriented to follow a concave curvature when viewed from the side of the carrier coating (C), in particular an optical effect layer exhibiting positive rolling stripe features (pigment particles (PP) oriented in a concave shape ( FIG2B )) produced by exposing a wet and not yet hardened coating (C) to the magnetic field of a magnet (M) located on the side of the carrier coating (C).

For a positive rolling bar member ( FIG. 4A ) made using a magnetic field generating device facing a still-wet, not-yet-hardened coating, as disclosed in WO 2012/104098 A1, the position of the magnetic field generating device (MD) prevents the hardening of the coating (C) from proceeding simultaneously with the orientation step of the magnetic or magnetizable pigment particles. FIG. 4A shows a magnetic field generating device (MD) comprising a magnet (M) and an optional magnetic device housing (K′), the housing having recesses engraved in its surface so that the magnet (M) can be positioned on a substrate (S) bearing the coating composition (C) without directly contacting the coating composition. After removing the magnet (M), the coating (C) is typically hardened by irradiation with a UV-Vis irradiation source located on the side bearing the coating (C). FIG. 4B shows an example of an OEL comprising a positive rolling bar member made according to the method shown in FIG. 4A . As shown in FIG. 4B , the OEL comprising a rolling bar member made using this method exhibits large bright areas that exhibit only slight visible motion with angle, i.e., a weak and dynamic effect that is not easily captured by the naked eye.

FIG. 5A schematically illustrates an example of a method according to the present invention using a magnetic field generating device and an irradiation source adapted to form a rolling bar member following concave positive curvature magnetic field lines.

Substrates suitable for use in the present invention are transparent to one or more wavelengths of the emission spectrum of the radiation source used to harden the coating composition on the substrate, i.e., the substrate must exhibit a transmittance of at least 4%, preferably at least 8%, of electromagnetic radiation at one or more wavelengths of the emission spectrum of the radiation source in the range of 200 nm to 500 nm. As mentioned herein and as known to those skilled in the art, the coating composition to be hardened on the substrate comprises one or more photoinitiators and optionally one or more photosensitizers, the one or more photoinitiators and optionally one or more photosensitizers being selected based on their absorption spectra relative to the emission spectrum of the radiation source. Depending on the transmittance of the electromagnetic radiation through the substrate, the hardening of the coating can be achieved by increasing the irradiation time. However, depending on the substrate material, the irradiation time is limited by the substrate material and its sensitivity to the heat generated by the radiation source.

The radiation for curing the coating composition on the substrate described herein is realized with light having a wavelength of about 200 nanometers to about 500 nanometers. Many various types of radiation sources can be used. Point sources and planar radiators (lamp carpets) are suitable. Examples include, but are not limited to, carbon arc lamps, xenon arc lamps, medium pressure, high pressure and low pressure mercury lamps, metal halide doping (metal halide lamps), microwave-excited metal vapor lamps, excimer lamps, superactinid fluorescent tubes, fluorescent lamps, argon incandescent lamps, flashlights, photographic floodlights and light emitting diodes (LEDs).

Substrate as herein described is preferably selected from paper or other fibrous materials, such as cellulose, paper-containing materials, glass, ceramics, plastics and polymers, composite materials and their mixture or combination, provided that the substrate is transparent to one or more wavelengths of the emission spectrum of the radiation source for curing the coating composition. Typical paper, paper-like materials or other fibrous materials are made of various fibers, including but not limited to abaca, cotton, flax, wood pulp and blends thereof. As known to those skilled in the art, cotton and cotton/flax blends are preferably used for banknotes, and wood pulp is usually used for non-credit documents. Substrate can be coated with a primer, provided that the substrate is transparent to one or more wavelengths of the emission spectrum of the radiation source for curing the coating composition. The example of such a primer is disclosed in, for example, WO 2010/058026 A2. 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 polyvinyl chloride (PVC). Spunbond olefin fibers, such as those sold under the trademark PANOL®, can also be used as the substrate. Typical examples of composite materials include, but are not limited to, multilayer structures or laminates of paper and at least one plastic or polymer material (such as those mentioned above), as well as plastic and/or polymer fibers incorporated into paper or fiber materials (such as those mentioned above). Of course, the substrate may contain additional additives known to the skilled person, such as sizing agents, brighteners, processing aids, reinforcing agents or wet strength agents, etc., provided that the substrate is transparent to one or more wavelengths of the emission spectrum of the radiation source used to harden the coating composition.

Figure 9 shows the transmission spectra of different substrates: credit paper from Louisenthal (A), primer-coated non-credit paper (B), and a polymer substrate for banknotes (C) (a white substrate, a biaxially oriented polypropylene (BOPP) substrate containing five light-blocking layers). The transmission of electromagnetic radiation through the substrates was measured on a Perkin Elmer Lambda 950 equipped with deuterium (UV) and xenon (VIS) lamps and a UV WinLab Data Processor. Measurement mode: integrating sphere transmission. The substrate sample was mounted on a sample holder. The transmission spectra were measured over the range of 250 to 500 nanometers.

The method described herein comprises the step of applying a coating composition comprising a plurality of magnetic or magnetizable pigment particles to a substrate as described herein to form a coating, the coating composition being in a first state. The step is preferably carried out by a printing method preferably selected from screen printing, rotogravure printing and flexographic printing.

Screen printing (also known in the art as serigraphy) is a stencil process in which ink is transferred to a surface through a stencil supported by a fine fabric mesh of silk, synthetic fibers (e.g., polyamide or polyester), monofilaments or multifilaments, or metal wire, stretched over a frame, for example, of wood or metal (e.g., aluminum or stainless steel). Alternatively, the screen printing mesh can be a porous metal foil, such as stainless steel foil, that is chemically etched, laser etched, or galvanically formed. The pores of this mesh are blocked in the non-image areas and remain open in the image areas; the image carrier is called the silk screen. Screen printing can be flatbed or rotary. Screen printing is further described, for example, in The Printing Ink Manual, R.H. Leach and R.J. Pierce, Springer Edition, 5th edition, pp. 58-62, and Printing Technology, J.M. Adams and P.A. Dolin, Delmar Thomson Learning, 5th edition, pp. 293-328.

Rotogravure printing (also known in the art as gravure) is a printing process in which image elements are engraved into the surface of a cylinder. The non-image area is at a constant, original level. Before printing, the entire printing plate (non-printing and printing elements) is inked and flooded with ink. Before printing, the ink is removed from the non-image area with a wiper or doctor blade, leaving only the ink in the recessed cells. The image is transferred from the recessed cells to the substrate using a pressure of typically 2 to 4 bars and through adhesion between the substrate and the ink. The term rotogravure printing does not include intaglio printing methods (also known in the art as engraved steel dies or copperplate printing methods), which rely on, for example, different types of inks. More details are provided in "Handbook of print media", Helmut Kipphan, Springer Edition, page 48, and "The Printing ink manual", R.H. Leach and R.J. Pierce, Springer Edition, 5th edition, pages 42-51.

Flexographic printing preferably uses a unit having a doctor blade, preferably a chambered doctor blade, an inking roller (anilox), and a plate cylinder. The inking roller advantageously has small pores whose volume and/or density determine the rate of ink application. The doctor blade presses against the inking roller and simultaneously scrapes off excess ink. The inking roller transfers the ink to the plate cylinder, which ultimately transfers the ink to the substrate. Specific designs can be achieved using designed photopolymer plates. The plate cylinder can be made of polymer or elastomeric materials. Polymers are primarily used as photopolymers in the plate and sometimes as seamless coatings on the sleeve. Photopolymer plates are made of photosensitive polymers that are hardened by ultraviolet (UV) light. The photopolymer plate is cut to the desired size and placed in a UV exposure device. One side of the plate is fully exposed to UV light to harden or cure the bottom of the plate. The plate is then turned over, the negative of the job is mounted on the uncured side, and the plate is further exposed to UV light. This hardens the image area of the plate. The plate is then processed to remove the uncured photopolymer from the non-image areas, which reduces the plate surface in these non-image areas. After processing, the plate is dried and a post-exposure dose of UV light is applied to cure the entire plate. The preparation of plate cylinders for flexographic printing is described in Printing Technology, J.M. Adams and P.A. Dolin, Delmar Thomson Learning, 5th edition, pp. 359-360, and The Printing ink manual, R.H. Leach and R.J. Pierce, Springer Edition, 5th edition, pp. 33-42.

The coating compositions described herein and the coatings described herein comprise a plurality of magnetic or magnetizable pigment particles, preferably non-spherical magnetic or magnetizable pigment particles. Preferably, the magnetic or magnetizable pigment particles described herein are present in an amount of from about 5 wt % to about 40 wt %, more preferably from about 10 wt % to about 30 wt %, based on the total weight of the coating composition.

The non-spherical magnetic or magnetizable pigment particles described herein are defined as having a non-isotropic reflectivity with respect to incident electromagnetic radiation (to which the hardened binder material is at least partially transparent) due to their non-spherical shape. As used herein, the term "non-isotropic reflectivity" means that the proportion of incident radiation from a first angle that is reflected by the particles in a certain (viewing angle) direction (a second angle) varies with the orientation of the particles, i.e., a change in the orientation of the particles relative to the first angle results in a different magnitude of reflection in the direction of the viewing angle. The non-spherical magnetic or magnetizable pigment particles are preferably prolate or oblate spheroids, flake-shaped or needle-shaped particles, or a mixture of two or more thereof, more preferably flake-shaped particles.

Suitable examples of magnetic or magnetizable pigment particles, particularly non-spherical magnetic or magnetizable pigment particles, described herein include, but are not limited to, pigment particles comprising: a magnetic metal selected from the group consisting of cobalt (Co), iron (Fe), gadolinium (Gd), 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" with respect to metals, alloys, and oxides refers to ferromagnetic or ferrimagnetic metals, alloys, and oxides. The magnetic oxide of chromium, manganese, cobalt, iron, nickel, or a mixture of two or more thereof may be a pure oxide or a mixed oxide. Examples of magnetic oxides include, but are not limited to, iron oxides, such as hematite (Fe ₂ O ₃ ), magnetite (Fe ₃ O ₄ ), chromium dioxide (CrO ₂ ), magnetic ferrite (MFe ₂ O ₄ ), magnetic spinel (MR ₂ O ₄ ), magnetic hexaferrite (MFe ₁₂ O ₁₉ ), magnetic orthoferrite (RFeO ₃ ), and magnetic garnet M ₃ R ₂ (AO ₄ ) ₃ , wherein M represents a divalent metal, R represents a trivalent metal, and A represents a tetravalent metal.

Examples of the magnetic or magnetizable pigment particles described herein, particularly non-spherical magnetic or magnetizable pigment particles, include, but are not limited to, pigment particles comprising a magnetic layer M made of one or more magnetic metals, such as cobalt (Co), iron (Fe), gadolinium (Gd), or nickel (Ni); and a magnetic alloy of iron, cobalt, or nickel, wherein the magnetic or magnetizable pigment particles may be a multilayer structure comprising one or more additional layers. The one or more additional layers are preferably layer A independently made of one or more materials selected from metal fluorides, such as magnesium fluoride ( _MgF2 ), silicon oxide ( _SiO ), silicon dioxide ( _SiO2 ), titanium oxide ( _TiO2 ), and aluminum oxide ( _Al2O3 ), more preferably silicon dioxide ( _SiO2 ); or layer B independently made of one or more materials selected from metals and metal alloys, preferably reflective metals and reflective metal alloys, more preferably aluminum (Al), chromium (Cr), and nickel (Ni), even more preferably aluminum (Al); or a combination of one or more layers A (such as those described above) and one or more layers B (such as those described above). Typical examples of magnetic or magnetizable pigment particles having the above-mentioned multilayer structure include, but are not limited to, an A/M multilayer structure, an A/M/A multilayer structure, an A/M/B multilayer structure, an A/B/M/A multilayer structure, an A/B/M/B multilayer structure, an A/B/M/B/A/ multilayer structure, a B/M multilayer structure, a B/M/B multilayer structure, a B/A/M/A multilayer structure, a B/A/M/B multilayer structure, and a B/A/M/B/A/ multilayer structure, wherein layer A, magnetic layer M, and layer B are selected from those described above.

The coating compositions described herein may contain optically variable magnetic or magnetizable pigment particles, particularly non-spherical optically variable magnetic or magnetizable pigment particles, and/or non-spherical magnetic or magnetizable pigment particles without optically variable properties, particularly non-spherical. Preferably, at least a portion of the magnetic or magnetizable pigment particles described herein consists of optically variable magnetic or magnetizable pigment particles, particularly non-spherical optically variable magnetic or magnetizable pigment particles. In addition to the explicit security provided by the color-shifting properties of the optically variable magnetic or magnetizable pigment particles (which allows for easy detection, identification, and/or differentiation of articles or security documents bearing inks, coating compositions, or coatings containing the optically variable magnetic or magnetizable pigment particles described herein from potential counterfeits thereof without the aid of human perception), the optical properties of the optically variable magnetic or magnetizable pigment particles can also serve as a machine-readable means for identifying OELs. Thus, the optical properties of the optically variable magnetic or magnetizable pigment particles can simultaneously serve as a covert or semi-covert security component in authentication methods, in which the optical (e.g., spectral) properties of the pigment particles are analyzed.

The use of optically variable magnetic or magnetizable pigment particles, in particular optically variable magnetic or magnetizable pigment particles, in coatings for producing OELs increases the significance of these OELs as security components in security document applications, since such materials are only available to the security document printing industry and are not commercially available to the public.

As mentioned above, it is preferred that at least a portion of the magnetic or magnetizable pigment particles be composed of optically variable magnetic or magnetizable pigment particles, in particular non-spherical optically variable magnetic or magnetizable pigment particles. These are more preferably selected from magnetic thin-film interference pigment particles, magnetic cholesteric liquid crystal pigment particles, interference coating pigment particles comprising a magnetic material, and mixtures of two or more thereof. The magnetic thin-film interference pigment particles, magnetic cholesteric liquid crystal pigment particles, and interference coating pigment particles comprising a magnetic material described herein are preferably prolate or oblate spheroids, flake-shaped or needle-shaped particles, or mixtures of two or more thereof, more preferably flake-shaped particles.

Magnetic thin-film interference pigment particles are known to those skilled in the art and are disclosed, for example, in US Pat. No. 4,838,648; WO 2002/073250 A2; EP 0 686 675 B1; WO 2003/000801 A2; US Pat. No. 6,838,166; WO 2007/131833 A1; EP 2 402 401 A1, and the documents cited therein. The magnetic thin-film interference pigment particles preferably include pigment particles having a five-layer Fabry-Perot multilayer structure, pigment particles having a six-layer Fabry-Perot multilayer structure, and/or pigment particles having a seven-layer Fabry-Perot multilayer structure.

The preferred five-layer Fabry-Perot multilayer structure is composed of an absorption layer/dielectric layer/reflection layer/dielectric layer/absorption layer multilayer structure, wherein the reflective layer and/or the absorption layer is also a magnetic layer, and the reflective layer and/or the absorption layer is preferably a magnetic layer containing nickel, iron and/or cobalt, and/or a magnetic alloy containing nickel, iron and/or cobalt and/or a magnetic oxide containing nickel (Ni), iron (Fe) and/or cobalt (Co).

The preferred six-layer Fabry-Perot multilayer structure is composed of an absorption layer/dielectric layer/reflection layer/magnetic layer/dielectric layer/absorption layer multilayer structure.

A preferred seven-layer Fabry Perot multilayer structure consists of an absorber layer/dielectric layer/reflector layer/magnetic layer/reflector layer/dielectric layer/absorber layer multilayer structure as disclosed in US 4,838,648.

The reflective layer described herein is preferably independently made of one or more selected from metals and metal alloys, preferably selected from reflective metals and reflective metal alloys, more preferably selected from 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 aluminum (Al), chromium (Cr), nickel (Ni) and alloys thereof, and even more preferably made of aluminum (Al). The dielectric layer is preferably independently made of one or more selected from metal fluorides such as magnesium fluoride ( _MgF2 ), aluminum fluoride ( _AlF3 ), cerium fluoride ( _CeF3 ), lanthanum fluoride ( _LaF3 ), sodium aluminum fluoride (e.g., _{Na3AlF6 )} , neodymium fluoride ( _NdF3 ), samarium fluoride ( _SmF3 ), barium fluoride ( _BaF2 ), calcium fluoride ( _CaF2 ), lithium fluoride (LiF) and metal oxides such as silicon oxide (SiO), silicon dioxide ( _SiO2 ), titanium oxide ( _TiO2 ), _aluminum oxide ( _Al2O3 ), more preferably selected from magnesium fluoride ( _MgF2 ) and silicon dioxide ( _SiO2 ), and even more preferably made of magnesium fluoride ( _MgF2 ). The absorption layer is preferably independently made of one or more selected from 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), their metal oxides, their metal sulfides, their metal carbides, and their metal alloys, more preferably selected from chromium (Cr), nickel (Ni), their metal oxides, and their metal alloys, and even more preferably selected from chromium (Cr), nickel (Ni), and their metal alloys. The magnetic layer preferably contains nickel (Ni), iron (Fe), and/or cobalt (Co); and/or a magnetic alloy containing nickel (Ni), iron (Fe), and/or cobalt (Co); and/or a magnetic oxide containing nickel (Ni), iron (Fe), and/or cobalt (Co). When magnetic thin film interference pigment particles comprising a seven-layer Fabry-Perot structure are preferred, the magnetic thin film interference pigment particles particularly preferably comprise a seven-layer Fabry-Perot absorption layer/dielectric layer/reflection layer/magnetic layer/reflection layer/dielectric layer/absorption layer multilayer structure consisting of a Cr/ _MgF2 /Al/Ni/Al/ _MgF2 /Cr multilayer structure.

The magnetic thin film interference pigment particles described herein can be multilayer pigment particles that are considered safe for human health and the environment and are, for example, based on a five-layer Fabry-Perot multilayer structure, a six-layer Fabry-Perot multilayer structure, and a seven-layer Fabry-Perot multilayer structure, wherein the pigment particles include one or more magnetic layers comprising a magnetic alloy having a substantially nickel-free composition comprising from about 40% to about 90% by weight iron, from about 10% to about 50% by weight chromium, and from about 0% to about 30% by weight aluminum. Typical examples of multilayer pigment particles that are considered safe for human health and the environment can be found in EP 2 402 401 A1, the entire contents of which are incorporated herein by reference.

The magnetic thin-film interference pigment particles described herein are typically produced by conventional deposition techniques of the various desired layers onto a web. After depositing the desired number of layers, for example by physical vapor deposition (PVD), chemical vapor deposition (CVD), or electrolytic deposition, the stack is removed from the web by dissolving the release layer in a suitable solvent or by peeling the material from the web. The resulting material is then broken into flakes, which must be further processed by milling, grinding (e.g., jet milling), or any other suitable method to obtain pigment particles of the desired size. The resulting product consists of flat flakes with broken edges, irregular shapes, and varying aspect ratios. Further information on the preparation of suitable magnetic thin-film interference pigment particles can be found, for example, in EP 1 710 756 A1 and EP 1 666 546 A1, which are incorporated herein by reference.

Suitable magnetic cholesteric liquid crystal pigment particles exhibiting optically variable characteristics include, but are not limited to, magnetic monolayer cholesteric liquid crystal pigment particles and magnetic multilayer cholesteric liquid crystal pigment particles. Such pigment particles are disclosed, for example, in WO 2006/063926 A1, US 6,582,781, and US 6,531,221. WO 2006/063926 A1 discloses monolayers and pigment particles obtained therefrom having high brightness and color shift properties, as well as additional specific properties such as magnetizability. The disclosed monolayers and pigment particles obtained therefrom by grinding the monolayers comprise a three-dimensionally crosslinked cholesteric liquid crystal mixture and magnetic nanoparticles. US 6,582,781 and US 6,410,130 disclose platelet-shaped cholesteric multilayer pigment particles comprising the sequence A1/B/A2, wherein A1 and A2 may be identical or different and each comprise at least one cholesteric layer, and B is an intermediate layer that absorbs all or part of the light transmitted by layers A1 and A2 and imparts magnetic properties to the intermediate layer. US 6,531,221 discloses platelet-shaped cholesteric multilayer pigment particles comprising the sequence A/B and optionally C, wherein A and C are absorbing layers comprising pigment particles imparting magnetic properties, and B is a cholesteric layer.

Suitable interference coating pigments containing one or more magnetic materials include, but are not limited to, structures consisting of a substrate selected from a core coated with one or more layers, wherein at least one of the core or the one or more layers has magnetic properties. For example, suitable interference coating pigments include a core made of a magnetic material such as those described above, the core being coated with one or more layers made of one or more metal oxides, or they have a structure consisting of a core made of synthetic or natural mica, phyllosilicates (e.g., talc, kaolin, and sericite), glass (e.g., borosilicate), silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), graphite, and mixtures of two or more thereof. In addition, one or more additional layers, such as a coloring layer, may be present.

The magnetic or magnetizable pigment particles described herein may be surface treated to protect them from any degradation that may occur in the coating compositions and coatings and/or to facilitate their incorporation into the coating compositions and coatings; typically, corrosion-inhibiting materials and/or wetting agents may be used.

The method described herein further comprises the step of exposing the coating described herein to a magnetic field from a magnetic field generating device, said magnetic field generating device being located on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles to follow a concave curvature, in particular a positive rolling strip structure, when viewed from the side carrying the OEL.

Simultaneously or partially simultaneously with the step of exposing the coating to the magnetic field of the magnetic field generating device as described herein, the coating as described herein is hardened through the substrate to a second state to fix or freeze the magnetic or magnetizable pigment particles in their acquired position and orientation to form a hardened coating, said hardening step being performed by irradiation with a UV-Vis radiation source located on the substrate side.

The steps of simultaneously or partially simultaneously hardening the coating and exposing the coating to a magnetic field involve orienting the magnetic or magnetizable pigment particles in at least a portion of the coating while being hardened by the UV-Vis radiation source. In other words, the magnetic field of the magnetic device, which orients the magnetic or magnetizable pigment particles in at least a portion of the coating, overlaps spatially and temporally with the UV-Vis radiation source, albeit from opposite sides of the substrate. In one embodiment, the magnetic field device and the UV-Vis radiation source are located at the same location along the substrate and are arranged on opposite sides of the substrate.

The first and second states described above can be provided using a binder material that exhibits a significant increase in viscosity in response to exposure to UV-Vis radiation. That is, when the fluid binder material hardens, the binder material transforms into a second state, a hardened or solid state, in which the magnetic or magnetizable pigment particles are fixed in their current position and orientation and can no longer move or rotate within the binder material.

As known to those skilled in the art, the ingredients contained in the coating compositions and the coatings obtained therefrom on the substrates described herein and the physical properties of the coatings depend on the nature of the method used to transfer the coating composition to the substrate. Thus, the binder materials described herein are generally selected from those known in the art and depend on the coating or printing method used to apply the coating composition.

The binder of the coating composition described herein is a UV-Vis curable composition preferably made from an oligomer (also referred to in the art as a prepolymer) selected from free radical curable compounds, cationically curable compounds, and mixtures thereof. Cationically curable compounds cure by a cationic mechanism, which includes activation by energy of one or more photoinitiators that release cationic species, such as acids, which in turn initiate polymerization to form the binder. Free radical curable compounds cure by a free radical mechanism, which includes activation by energy of one or more photoinitiators that release free radicals, which in turn initiate polymerization to form the binder.

The UV-Vis curing of monomers, oligomers or prepolymers may require the presence of one or more photoinitiators and can be carried out in many ways. As known to those skilled in the art, the one or more photoinitiators are selected according to their absorption spectra and are selected to be suitable for the emission spectrum of the radiation source. Depending on the monomer, oligomer or prepolymer used to prepare the adhesive included in the UV-Vis curable composition as described herein, different photoinitiators can be used. Suitable examples of free radical photoinitiators are known to those skilled in the art and include but are not limited to acetophenone, benzophenone, α-aminoketone, α-hydroxyketone, phosphine oxide and phosphine oxide derivatives and benzyl dimethyl ketal. Suitable examples of cationic photoinitiators are known to those skilled in the art and include but are not limited to onium salts, such as organic iodonium salts (e.g., diaryl iodonium salts), oxonium (e.g., triaryl oxonium salts) and sulfonium salts (e.g., triaryl sulfonium salts). Other examples of useful photoinitiators can be found in standard textbooks such as "Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints", Volume III, "Photoinitiators for Free Radical Cationic and Anionic Polymerization", 2nd Edition, by J.V. Crivello & K. Dietliker, edited by G. Bradley and published in 1998 by John Wiley & Sons in conjunction with SITA Technology Limited. It may also be advantageous to include a sensitizer along with the one or more photoinitiators to achieve effective curing. Typical examples of suitable photosensitizers include, but are not limited to, isopropyl-thioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX) and 2,4-diethyl-thioxanthone (DETX), and mixtures thereof. The one or more photoinitiators included in the UV-Vis curable composition are preferably present in an amount of about 0.1 wt % to about 20 wt %, more preferably about 1 wt % to about 15 wt %, based on the total weight of the UV-Vis curable composition.

A plurality of magnetic or magnetizable pigment particles as described herein are dispersed in a hardened coating as described herein, the hardened coating comprising a hardened binder material that fixes the position and orientation of the magnetic or magnetizable pigment particles.

The coating compositions described herein may further comprise one or more machine-readable materials. When present, the one or more machine-readable materials are preferably selected from the group consisting of magnetic materials, luminescent materials, conductive materials, infrared absorbing materials, and mixtures thereof. As used herein, the term "machine-readable material" refers to a material that exhibits at least one unique property detectable by a device or machine and that can be included in a coating to provide a means for authenticating the coating or an article comprising the coating using specialized equipment for its detection and/or authentication.

The coating compositions described herein may further comprise one or more additives, including but not limited to compounds and materials for adjusting the physical, rheological and chemical parameters of the composition, such as viscosity (e.g., solvents and surfactants), consistency (e.g., anti-settling agents, fillers and plasticizers), foaming properties (e.g., defoamers), lubricity (waxes), UV reactivity and stability (photosensitizers and light stabilizers), and adhesion properties, etc. The additives described herein may be present in the coating compositions described herein in amounts and forms known in the art, including in the form of so-called nanomaterials (wherein at least one dimension of the particles is in the range of 1 to 1000 nanometers).

The coating compositions described herein may further comprise one or more markers or tracers and/or one or more machine-readable materials selected from the group consisting of magnetic materials (other than the magnetic or magnetizable pigment particles described herein), luminescent materials, conductive materials, and infrared absorbing materials. As used herein, the term "machine-readable material" refers to a material that exhibits at least one unique property that is not perceptible to the naked eye and that can be included in a layer to provide a means of authenticating the layer or an article comprising the layer with the aid of a specific authentication device.

The coating compositions described herein can be prepared by dispersing or mixing the magnetic or magnetizable pigment particles described herein and the one or more additives (when present) in the presence of a binder material described herein, thereby forming a liquid composition. When present, the one or more photoinitiators can be added to the composition during the dispersion or mixing step of all other ingredients, or can be added at a later stage, i.e., after the liquid coating composition is formed.

According to one embodiment of the present invention and as shown in FIG5A , an OEL based on a plurality of magnetic or magnetizable pigment particles oriented so as to follow a concave curvature when viewed from the side bearing the coating (C), in particular an OEL exhibiting a positive rolling stripe structure, can be prepared by orienting the magnetic or magnetizable pigment particles in the coating (C) using a magnetic field generating device (MD) located on the side bearing the coating (C) and, simultaneously or partially simultaneously with the orienting step using the magnetic field generating device, curing the coating (C) through irradiation with a UV-Vis radiation source (L) located on the side of the substrate (S), i.e., on the side opposite the substrate surface bearing the coating (C). The substrate (S) may be located on an optional support plate (K). If present, the support plate (K) is made of a non-magnetic or non-magnetizable material that is transparent to the UV-Vis radiation used in the curing step. The curing step is thus performed by irradiation through the substrate (S) and through the optional support plate (K). A substrate (S) bearing a coating (C) is placed on a magnetic field generating device (MD) comprising a magnet (M) and a magnetic device housing (K'), the housing comprising recesses on its surface to prevent the magnetic field generating device (MD) from contacting the surface of the coating (C) when the magnetic field generating device (MD) is positioned on the substrate (S). Depending on the arrangement, the magnetic field generating device (MD), the substrate (S) bearing the coating (C), and the radiation source (L) can be positioned as shown on the left side of FIG. 5A (with the magnetic field generating device (MD) above the substrate (S) and the optional support plate (K)) or as shown on the right side of FIG. 5A (with the magnetic field generating device (MD) below the substrate (S) bearing the coating composition (C) on its lower surface, the optional support plate (K) not being shown). FIG. 5B shows an example of a positive rolling bar member produced according to the method shown on the right side of FIG. 5A. As shown in FIG. 5B, the OEL including the rolling bar member produced using this method exhibits a better, clearer rolling bar effect than FIG. 4B, i.e., a strong, dynamic, visible motion that is perceptible to the naked eye when viewed from different viewing angles.

The magnetic field generating device described herein may comprise a magnetic plate having one or more relief patterns, carvings or cut-outs on its surface. Examples of such carved magnetic plates are disclosed in WO 2005/002866 A1 and WO 2008/046702 A1.

The present invention further provides an optical effect layer (OEL) comprising a pattern consisting of at least two patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling stripe elements, oriented so as to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented in a random pattern other than a random orientation, which is highly desirable in the field of security. FIG6A shows a method for producing these OELs according to the prior art. The known method for preparing these OELs comprises the steps of: i) applying a coating composition comprising magnetic or magnetizable pigment particles on a substrate (S) to form a coating (C1); j) orienting the magnetic or magnetizable pigment particles in the coating (C1) by means of a magnetic field generating device located on the side bearing the coating (C1); k) hardening the coating (C1) by irradiation with a UV-Vis radiation source located on the side bearing the coating (C1) after removing the magnetic field generating device; l) applying a second coating composition comprising magnetic or magnetizable pigment particles in an area adjacent to (C1) to form a second coating (C2); m) orienting the magnetic or magnetizable pigment particles in the second coating (C2) by means of a magnetic field generating device located on the side of the substrate and simultaneously or partially simultaneously hardening the second coating (C2) by irradiation with a UV-Vis radiation source located on the side of the substrate bearing the second coating (C2).

Figure 6B shows an example of an OEL produced using the method shown in Figure 6A. As shown in Figure 6B , the positive rolling bar effect (left side of the OEL) and the negative rolling bar effect (right side of the OEL) are distinct: the negative rolling bar component is produced by hardening the coating while it is within the magnetic field of a magnetic field generator, while the positive rolling bar component is produced by hardening the coating while it is not within the magnetic field of the magnetic field generator. As shown in Figure 6B , the positive rolling bar effect (left side) exhibits a much wider bright band and a poorer, less noticeable effect than the negative rolling bar component (right side).

The present invention further provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a concave curvature when viewed from the side carrying the OEL, in particular positive rolling strip elements, and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented in any pattern other than random, preferably oriented to follow a convex curvature when viewed from the side carrying the OEL, in particular negative rolling strip elements. The at least two patterns described herein may be separate or may be adjacent.

Preferably, the present invention further provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, wherein one of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a concave curvature when viewed from the side carrying the OEL, in particular a positive rolling bar structure, and the other of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles oriented in a random pattern other than random, preferably oriented to follow a convex curvature when viewed from the side carrying the OEL, in particular a negative rolling bar structure. The desired orientation of the plurality of magnetic or magnetizable pigment particles of the other of the at least two adjacent patterns is selected depending on the end use. Examples of random patterns other than random orientation include, but are not limited to, rolling bar structures, flip-flop effects (also known in the art as switching effects), venetian blind effects, and moving ring effects. The flip-flop effect comprises a first printed portion and a second printed portion separated by a transition region, wherein the pigment particles in the first portion are aligned parallel to a first plane, and the pigment particles in the second portion are aligned parallel to a second plane. Methods for producing flip-flop effects are disclosed, for example, in EP 1 819 525 B1 and EP 1 819 525 B1. Venetian blind effects can also be produced. Venetian blind effects involve pigment particles oriented to impart visibility to an underlying substrate surface in a particular viewing direction, making indicia or other features present on or in the substrate surface visible to the observer (while preventing visibility in another viewing direction). Methods for producing venetian blind effects are disclosed, for example, in US Pat. No. 8,025,952 and EP 1 819 525 B1. Moving ring effects consist of optical illusions of objects, such as funnels, cones, bowls, circles, ellipses, and hemispheres, that appear to move in any x-y direction, depending on the tilt angle of the optical effect layer. Methods for producing a moving ring effect are disclosed, for example, in EP 1 710 756 A1, US Pat. No. 8,343,615, EP 2 306 222 A1, EP 2 325 677 A2, WO 2011/092502 A2 and US Pat. No. 2013/084411.

The plurality of magnetic or magnetizable pigment particles of the at least two patterns can also be produced using a first and/or second magnetic field generating device comprising a magnetic plate with one or more reliefs, carvings or cut-outs on its surface. WO 2005/002866 A1 and WO 2008/046702 A1 are examples of such carved magnetic plates.

Method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two patterns, preferably at least two adjacent patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling strip elements, oriented so as to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented in any pattern other than random, preferably oriented so as to follow a convex curvature when viewed from the side carrying the OEL, comprising the steps of:

a) applying a coating composition as described herein to a substrate as described herein, preferably by a printing process selected from screen printing, rotogravure printing and flexographic printing, to form a coating, said coating being in a first state as described herein;

b) b1) exposing the coating as described herein to a magnetic field of a first magnetic field generating means, said magnetic field generating means being located on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles to follow a concave curvature when viewed from the side bearing said coating, and b2) simultaneously or partially simultaneously hardening the coating as described herein through said substrate, said hardening being performed by irradiation with a UV-Vis radiation source located on the side of said substrate, as described herein;

c) applying a second coating composition comprising a plurality of magnetic or magnetizable pigment particles, preferably by a printing method selected from screen printing, rotogravure printing and flexographic printing, to form a second coating layer, said coating layer being in the first state, wherein said second coating composition may be the same as used in step a) or may be different and wherein said plurality of magnetic or magnetizable pigment particles may be the same as used in step a) or may be different;

d) exposing the second coating in the first state to a magnetic field of a second magnetic field generating means, thereby orienting the plurality of magnetic or magnetizable pigment particles in any pattern other than a random orientation, preferably thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a convex curvature when viewed from the side bearing the coating; and

e) Hardening the second coating to a second state by UV-Vis radiation to fix the magnetic or magnetizable pigment particles in their acquired position and orientation.

Step e) of hardening the second coating can be carried out partly simultaneously, simultaneously or subsequently to step d) (ie magnetic orientation of the magnetic or magnetizable pigment particles), preferably partly simultaneously or simultaneously.

Alternatively, the steps of the above method may be interchanged, i.e. the method may further comprise the steps of i) applying a layer of a second coating composition comprising a plurality of magnetic or magnetizable pigment particles to form a second coating layer, the coating composition being in a first state; ii) exposing the second coating layer in the first state to a magnetic field of a second magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles in a random pattern other than a random orientation, preferably thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing the coating layer; and iii) simultaneously, partially simultaneously or subsequently, preferably simultaneously or partially simultaneously, preferably simultaneously partially or partially simultaneously, curing the second coating layer to the second state by UV-Vis radiation to fix the magnetic or magnetizable pigment particles in their acquired position and orientation, wherein said steps are performed before steps a) and b). In other words, the method comprises the steps of:

a) applying a coating composition as described herein to a substrate as described herein, preferably by a printing process selected from screen printing, rotogravure printing and flexographic printing, to form a coating, said coating being in a first state as described herein;

b) b1) exposing the coating to a magnetic field of a first magnetic field generating means, thereby orienting the plurality of magnetic or magnetizable pigment particles in any pattern other than a random orientation, preferably thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a convex curvature when viewed from the side bearing the coating, and b2) hardening the coating, said hardening being performed by irradiation with a UV-Vis radiation source;

c) applying a second coating composition comprising a plurality of magnetic or magnetizable pigment particles, such as those described herein, which is hardenable through the substrate, preferably by a printing process selected from screen printing, rotogravure printing, and flexographic printing, to form a second coating layer, said coating layer being in the first state, wherein said second coating composition may be the same as or different from that used in step a) and wherein said plurality of magnetic or magnetizable pigment particles may be the same as or different from that used in step a);

d) exposing the second coating in the first state to a magnetic field of a second magnetic field generating means as described herein, said magnetic field generating means being located on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles to follow a concave curvature when viewed from the side bearing said coating; and e) simultaneously or partially simultaneously hardening the coating as described herein through said substrate as described herein, said hardening being performed by irradiation with a UV-Vis radiation source located on the side of said substrate.

Step b2) of hardening the first coating can be carried out partly simultaneously, simultaneously or subsequently to step d) (ie magnetic orientation of the magnetic or magnetizable pigment particles), preferably partly simultaneously or simultaneously.

According to one embodiment, the second magnetic field generating device described herein is located on the substrate side, and the UV-Vis radiation source for applying UV-Vis radiation to the second coating composition is located on the coating side.

According to a preferred embodiment, the present invention provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two patterns, preferably at least two adjacent patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a concave curvature when viewed from the side carrying the OEL, in particular positive rolling bar elements, and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a convex curvature when viewed from the side carrying the OEL, in particular negative rolling bar elements.

7A shows a preferred example of a method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two patterns, in particular two adjacent patterns, wherein one of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling strip elements, oriented so as to follow a concave curvature when viewed from the side of the carrier coating (C1), and the other of the at least two patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular negative rolling strip elements, oriented so as to follow a convex curvature when viewed from the side of the carrier coating (C2), the method comprising the steps of:

i) applying the coating composition as described herein to the substrate (S) as described herein, preferably by a printing method selected from screen printing, rotogravure printing and flexographic printing, to form the coating (C1) as described herein;

j) exposing the coating (C1) to a magnetic field of a first magnetic field generating device (MD1) as described herein, said magnetic field generating device (MD1) being situated on the side of the coating (C1), thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing the coating (C1), and simultaneously or partially simultaneously hardening the coating (C1) as described herein through the substrate (S), said hardening being carried out by irradiation with a UV-Vis radiation source (L) situated on the side of said substrate, as described herein;

k) applying a second coating composition comprising a plurality of magnetic or magnetizable pigment particles, preferably by a printing method selected from screen printing, rotogravure printing and flexographic printing, to form a second coating layer (C2), said second coating layer being in a first state, wherein said second coating composition may be the same as used in step i) or may be different and wherein said plurality of magnetic or magnetizable pigment particles may be the same as used in step i) or may be different; and

1) exposing the second coating (C2) in the first state to a magnetic field of a second magnetic field generating device (MD2), said magnetic field generating device (MD2) being situated on the side of the substrate (S), thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a convex curvature when viewed from the side bearing the coating; and simultaneously or at least partially simultaneously hardening the second coating (C2) to the second state by UV-Vis radiation (L) so as to fix the magnetic or magnetizable pigment particles in their acquired position and orientation.

FIG7B shows an example of an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, one of which is based on a plurality of magnetic or magnetizable pigment particles, particularly positive rolling bar elements, oriented to follow a concave curvature when viewed from the side bearing the OEL, and the other of which is based on a plurality of magnetic or magnetizable pigment particles oriented to follow a convex curvature when viewed from the side bearing the OEL, obtained by the method shown in FIG7A . As shown in FIG7B , the positive rolling bar elements (left side of the OEL) and the negative rolling bar elements (right side of the OEL) exhibit the same brightness and width. Both the negative and positive rolling bar elements are produced by using a magnetic field generating device that generates convex magnetic field lines, located above the substrate (concave effect) or below the substrate (convex effect), and by simultaneously or partially simultaneously hardening the coating while it is in the magnetic field.

According to a preferred embodiment, the present invention provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of a first pattern, a second pattern and a third pattern, wherein the first pattern is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling bar members, oriented to follow a concave curvature when viewed from the side carrying the OEL, the second pattern is based on a plurality of magnetic or magnetizable pigment particles, in particular negative rolling bar members, oriented to follow a convex curvature when viewed from the side carrying the OEL, and the third pattern is based on a plurality of magnetic or magnetizable pigment particles, in particular negative rolling bar members, oriented to follow a concave curvature when viewed from the side carrying the OEL (in particular positive rolling bar members) or a convex curvature (in particular negative rolling bar members), preferably a convex curvature when viewed from the side carrying the OEL (in particular negative rolling bar members), wherein the first pattern is located between and adjacent to the second and third patterns. According to one embodiment, the method described herein produces an optical effect layer (OEL) comprising a pattern consisting of a first pattern, a second pattern and a third pattern, wherein the first pattern exhibits a positive scrolling bar component, the second pattern exhibits a negative scrolling bar component and the third pattern exhibits a positive scrolling bar component or a negative scrolling bar component, preferably a negative scrolling bar, wherein the first pattern is located between and adjacent to the second and third patterns (also referred to in the art as a triple scrolling bar component).

According to a preferred embodiment, the present invention provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of a first pattern, a second pattern and a third pattern, wherein the first pattern is based on a plurality of magnetic or magnetizable pigment particles, in particular negative rolling bar members, oriented to follow a convex curvature when viewed from the side carrying the OEL, the second pattern is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling bar members, oriented to follow a concave curvature when viewed from the side carrying the OEL, and the third pattern is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling bar members, oriented to follow a concave curvature when viewed from the side carrying the OEL, and the first pattern is located between and adjacent to the second and third patterns. According to another embodiment, the method described herein produces an optical effect layer (OEL) comprising a pattern consisting of a first pattern, a second pattern and a third pattern, wherein the first pattern exhibits a negative scrolling bar component, the second pattern exhibits a positive scrolling bar component and the third pattern exhibits a positive scrolling bar component or a negative scrolling bar component, preferably a positive scrolling bar component, wherein the first pattern is located between and adjacent to the second and third patterns (also referred to in the art as a triple scrolling bar component).

The present invention further provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, wherein one of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling strip elements, oriented so as to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles oriented in a random pattern other than a random orientation. The method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, comprises the steps of:

a) applying a coating composition as described herein to a substrate as described herein, preferably by a printing method selected from screen printing, rotogravure printing, and flexographic printing, to form a coating, said coating being in a first state;

b) b1) exposing one or more first substrate areas bearing said coating to a magnetic field of a first magnetic field generating means as described herein, said magnetic field generating means being situated on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing said coating, and b2) simultaneously or partially simultaneously hardening said coating through said substrate by irradiation with a UV-Vis radiation source situated on the side of said substrate, as described herein; wherein said UV-Vis radiation source is provided with a photomask so that one or more second substrate areas bearing said coating are not exposed to UV-Vis radiation;

c) exposing at least the one or more second substrate areas bearing the coating, which are still in the first state due to the presence of the photomask in step b2), to a magnetic field of a second magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a random orientation other than a random orientation; and simultaneously, partially simultaneously or subsequently, preferably simultaneously or partially simultaneously, hardening at least the one or more second substrate areas bearing the coating to the second state by irradiation with a UV-Vis radiation source, so as to fix the magnetic or magnetizable pigment particles in their acquired position and orientation.

Alternatively, the steps of the above method may be interchanged, that is, the method may include the steps of:

a) applying a coating composition as described herein to a substrate as described herein, preferably by a printing method selected from screen printing, rotogravure printing, and flexographic printing, to form a coating, said coating being in a first state;

b) b1) exposing one or more first substrate areas bearing the coating to a magnetic field of a first magnetic field generating means, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a random orientation other than a random orientation, and b2) simultaneously, partially simultaneously or subsequently, preferably simultaneously or partially simultaneously, hardening the coating by irradiation with a UV-Vis radiation source provided with a photomask so that one or more second substrate areas bearing the coating are not exposed to UV-Vis radiation;

c) exposing at least the one or more second substrate areas bearing the coating, still in the first state due to the presence of the photomask in step b2), to a magnetic field of a second magnetic field generating device, as described herein, said magnetic field generating device being situated on the side of the coating, thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing the coating; and simultaneously or partially simultaneously hardening at least the one or more second substrate areas bearing the coating to the second state by irradiation with a UV-Vis radiation source situated on the side of the substrate, so as to fix the magnetic or magnetizable pigment particles in their acquired position and orientation.

The present invention further provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, wherein the at least two adjacent patterns are based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling strip elements, oriented so as to follow a concave curvature when viewed from the side carrying the OEL. The method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, comprises the steps of:

a) applying a coating composition as described herein to a substrate as described herein, preferably by a printing method selected from screen printing, rotogravure printing, and flexographic printing, to form a coating, said coating being in a first state;

b) b1) exposing one or more first substrate areas bearing said coating to a magnetic field of a first magnetic field generating means as described herein, said magnetic field generating means being situated on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing said coating, and b2) simultaneously or partially simultaneously hardening said coating through said substrate by irradiation with a UV-Vis radiation source situated on the side of said substrate, as described herein; wherein said UV-Vis radiation source is provided with a photomask so that one or more second substrate areas bearing said coating are not exposed to UV-Vis radiation;

c) exposing at least the one or more second substrate areas bearing the coating, still in the first state due to the presence of the photomask in step b2), to a magnetic field of a second magnetic field generating device, as described herein, said magnetic field generating device being situated on the side of the coating, thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing the coating; and simultaneously or partially simultaneously hardening at least the one or more second substrate areas bearing the coating to the second state by irradiation with a UV-Vis radiation source so as to fix the magnetic or magnetizable pigment particles in their acquired position and orientation,

The concave curvature obtained in step b1) is different from the concave curvature obtained in step c).

Preferably, the present invention further provides a method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, wherein one of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling strip elements, oriented so as to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles oriented so as to follow a convex curvature when viewed from the side carrying the OEL. The method for producing an optical effect layer (OEL) comprising a pattern consisting of at least two adjacent patterns, the adjacent patterns being made from a single hardened layer, comprises the steps of:

a) applying a coating composition as described herein to a substrate as described herein, preferably by a printing method selected from screen printing, rotogravure printing, and flexographic printing, to form a coating, said coating being in a first state;

b) b1) exposing one or more first substrate areas bearing said coating to a magnetic field of a first magnetic field generating means as described herein, said magnetic field generating means being situated on the side of said coating, thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side bearing said coating, and b2) simultaneously or partially simultaneously hardening said coating through said substrate by irradiation with a UV-Vis radiation source situated on the side of said substrate, as described herein; wherein said UV-Vis radiation source is provided with a photomask so that one or more second substrate areas bearing said coating are not exposed to UV-Vis radiation;

c) exposing at least the one or more second substrate areas bearing the coating, which are still in the first state due to the presence of the photomask in step b2), to a magnetic field of a second magnetic field generating device, said magnetic field generating device being located on the side of said substrate, thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a convex curvature when viewed from the side bearing the coating; and simultaneously or partially simultaneously hardening at least the one or more second substrate areas bearing the coating to the second state by irradiation with a UV-Vis radiation source so as to fix said magnetic or magnetizable pigment particles in their acquired position and orientation.

Alternatively, the steps of the above method may be interchanged, that is, the method may include the steps of:

a) applying a coating composition as described herein to a substrate as described herein, preferably by a printing method selected from screen printing, rotogravure printing, and flexographic printing, to form a coating, said coating being in a first state;

b) b1) exposing one or more first substrate areas bearing said coating to a magnetic field of a first magnetic field generating means, said magnetic field generating means being located on the side of said substrate, thereby orienting said plurality of magnetic or magnetizable pigment particles so as to follow a convex curvature when viewed from the side bearing said coating, and b2) simultaneously or partially simultaneously hardening said coating by irradiation with a UV-Vis radiation source provided with a photomask so that one or more second substrate areas bearing said coating are not exposed to UV-Vis radiation;

c) exposing at least the one or more areas of the second substrate carrying the coating, which are still in the first state due to the presence of the photomask in step b2), to a magnetic field of a second magnetic field generating device, said magnetic field generating device being situated on the side of the coating, as described herein, thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a concave curvature when viewed from the side carrying the coating; and simultaneously or partially simultaneously hardening through the substrate at least the one or more areas of the second substrate carrying the coating to the second state so as to fix the magnetic or magnetizable pigment particles in their acquired position and orientation, as described herein, said hardening being carried out by irradiation with a UV-Vis radiation source situated on the side of the substrate.

Figure 8 schematically illustrates a method for producing an optical effect layer (OEL) comprising a pattern consisting of two adjacent patterns, made from a single hardened layer, as described herein, wherein one of the two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling stripe elements, oriented to follow a concave curvature when viewed from the side carrying the OEL, and the other of the two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular negative rolling stripe elements, oriented to follow a convex curvature when viewed from the side carrying the OEL. The method comprises the steps of: i) applying a coating composition comprising magnetic or magnetizable pigment particles to a substrate (S) to form a coating (C); j) orienting the magnetic or magnetizable pigment particles in the coating (C) using a magnetic field generating device (M) located on the side carrying the coating (C) while simultaneously hardening the coating (C) through the substrate (S), the hardening being performed by irradiating the coating (C) with a UV-Vis radiation source (L) located on the side of the substrate (S), wherein the UV-Vis radiation source (L) is provided with a photomask (W);

k) exposing the coating to a magnetic field of a second magnetic field generating means (M2), said magnetic field generating means being located on the side of the substrate (S), thereby orienting the plurality of magnetic or magnetizable pigment particles so as to follow a convex curvature when viewed from the side bearing the hardened coating; and simultaneously hardening the coating to a second state by irradiation with a UV-Vis radiation source (L) so as to fix the magnetic or magnetizable pigment particles in their acquired position and orientation.

The use of a UV-Vis radiation source coupled with a photomask enables the selective hardening of a coating composition in one or more selected areas. A photomask consists of an opaque plate containing apertures or transparent areas that allow light to pass through in a specified pattern. Photomasks are commonly used, for example, in photolithography. According to one embodiment of the present invention, the photomask can be positioned in a fixed position between the radiation source and the substrate bearing the coating to be hardened. According to another embodiment of the present invention, the photomask can be translated synchronously with the substrate between the radiation source and the substrate bearing the coating to be hardened.

The method described herein for producing an optical effect layer (OEL) comprising a pattern made of at least two adjacent patterns made of a single hardened layer, wherein one of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular positive rolling strip elements, oriented so as to follow a concave curvature when viewed from the side carrying the OEL, and the other of the at least two adjacent patterns is based on a plurality of magnetic or magnetizable pigment particles, in particular negative rolling strip elements, oriented so as to follow a convex curvature when viewed from the side carrying the adjacent patterns, advantageously provides a security element comprising at least two adjacent patterns, in particular at least two adjacent patterns exhibiting different rolling strip elements, with a precise and well-controlled spacing or intermediate zone to obtain a clear transition between the two adjacent patterns, even at high production speeds, thereby providing a highly dynamic and visually perceptible optical effect due to the different movements of the two adjacent patterns.

Figure 10 schematically illustrates an experiment conducted to evaluate the degree of hardening of a coating composition and the degree of fixation/freezing of the orientation of the magnetic or magnetizable pigment particles after irradiation through a substrate. Figure 10a1) schematically illustrates the first step of the experiment: an OEL (same example as shown in Figure 5A) comprising a positive rolling bar component was produced by orienting the magnetic or magnetizable pigment particles in the coating (C) using a magnetic field generating device (MD) located on the side of the substrate (S) bearing the coating (C), and simultaneously or partially simultaneously with the orientation step using the magnetic field generating device (MD) by directly irradiating the coating with a UV-Vis radiation source located on the side of the substrate (S) opposite the substrate surface bearing the coating (C). Figure 10a2) schematically illustrates a top view of a substrate (S) with a rolling bar (RB) schematically indicated by a light-colored stripe. Figure 10b1) schematically illustrates the second step of the experiment: the substrate (S) bearing the coating (C) and the OEL was rotated 90° in the plane of the substrate and turned upside down so that the coating composition faced the radiation source to fully harden the coating composition. FIG10 b 2 ) schematically shows a top view of a substrate (S) rotated by 90°, wherein the rolling bar (RB) is schematically shown as a bright stripe.

Figures 11A-B show photographs of samples made according to the experiment of Figure 10. Figure 11A shows a sample made with a substrate suitable for the present invention, i.e., the substrate meeting the requirement of having a light transmittance of at least 4% at 395 nm (i.e., the wavelength of the emission spectrum of the radiation source used to harden the coating composition on the substrate). As can be seen in Figure 11A, UV-Vis irradiation through the substrate locks the magnetic or magnetizable pigment particles so that they do not reorient in the second step when the scroll member is placed perpendicular to the magnetic axis of the magnetic rod.

FIG11B shows a sample made with a substrate that is not suitable for the present invention (i.e., does not meet the requirement of a light transmittance of at least 4% at 395 nm through the substrate). As shown in FIG11B , UV-Vis irradiation through the substrate does not completely fix or freeze the magnetic or magnetizable pigment particles in their orientation. Therefore, the magnetic or magnetizable pigment particles are reoriented in a second step when the substrate is rotated 90° in the plane of the substrate relative to the position of the magnetic rod. The resulting OEL is a cross, i.e., two perpendicular scroll bars.

In order to improve the durability (through stain resistance or chemical resistance) and cleanliness and thus the shelf life of articles, security documents, decorative elements or objects comprising the OEL obtained by the methods described herein, or to improve their aesthetic appearance (e.g., optical gloss), one or more protective layers may be applied to the OEL. When present, the one or more protective layers are typically made of a protective varnish. These may be transparent or slightly tinted or dyed and may be more or less glossy. The protective varnish may be a radiation-curable composition, a heat-drying composition, or any combination thereof. The one or more protective layers are preferably radiation-curable compositions, more preferably UV-Vis curable compositions. The protective layer is typically applied after the OEL has been formed.

The present invention further provides an optical effect layer (OEL) produced by the process of the invention.

The OELs described herein can be provided directly on the substrate on which they are to remain permanently (e.g., for banknote applications). Alternatively, the OEL can be provided on a temporary substrate for manufacturing purposes, from which the OEL is subsequently removed. This can, for example, facilitate the manufacture of the OEL, particularly while the binder material is still in its fluidized state. Thereafter, after the coating composition used to manufacture the OEL has hardened, the temporary substrate can be removed from the OEL.

Alternatively, in another embodiment, the adhesive layer may be present on the OEL or on the substrate comprising the optical effect layer (OEL), said adhesive layer being on the side of the substrate opposite to the side on which the OEL is provided, or on the same side as the OEL and above the OEL. Thus, the adhesive layer can be applied to the optical effect layer (OEL) or to the substrate, said adhesive layer being applied after the hardening step has been completed. Such an article can be affixed to documents or other articles or items of all kinds without the need for printing or other processes involving machinery and considerable effort. Alternatively, the substrate described herein comprising the OEL described herein can be in the form of a transfer foil, which can be applied to the document or article in a separate transfer step. To this end, the substrate is provided with a release coating and the OEL is manufactured thereon as described herein. One or more adhesive layers can be applied to the OEL thus produced.

Also described herein are substrates comprising more than one, ie two, three, four, etc., optical effect layers (OELs) obtained by the methods described herein.

Also described herein are articles, in particular security documents, decorative elements or objects, comprising an optical effect layer (OEL) produced according to the invention. Articles, in particular security documents, decorative elements or objects, may comprise more than one (e.g. two, three, etc.) OELs produced according to the invention.

As mentioned above, the optical effect layers (OELs) produced according to the invention can be used for decorative purposes as well as for protecting and authenticating security documents.

Typical examples of decorative elements or objects include, but are not limited to, luxury goods, cosmetic packaging, automotive parts, electronic/electrical equipment, furniture, and nail polish.

Security documents include, but are not limited to, valuable documents and valuable commodities. Typical examples of valuable documents include, but are not limited to, banknotes, deeds, bills, checks, receipts, tax stamps and tax stamps, contracts, etc., identity documents such as passports, identity cards, visas, driver's licenses, bank cards, credit cards, transaction cards, entry and exit documents or cards, tickets, public transportation tickets or vouchers, etc., preferably banknotes, identity documents, authorization documents, driver's licenses and credit cards. The term "valuable commodity" refers to packaging materials, particularly for cosmetics, nutritional supplements, medicines, wine, tobacco products, beverages or food, electrical/electronic products, fabrics or jewelry, that is, to prevent forgery and/or illegal copying to ensure the contents of this packaging, for example, the products of real medicines. The examples of these packaging materials include, but are not limited to, labels, such as certified brand labels, tamper evidence labels and seals. It should be pointed out that disclosed substrates, valuable documents and valuable commodities are only used for illustration, but not for limiting the scope of the present invention.

Alternatively, the optical effect layer (OEL) may be manufactured onto a secondary substrate, such as a security thread, strip, foil, decal, window or label, and subsequently transferred to the security document in a separate step.

A skilled artisan may devise numerous modifications to the specific embodiments described above without departing from the spirit of the invention. The invention includes such modifications.

Furthermore, all documents mentioned throughout this specification are incorporated herein by reference in their entirety as if fully set forth herein.

Example

Cotton banknote paper from Louisenthal (hereinafter referred to as Louisenthal Velin) with a grammage of 90 g/m² was used as the substrate for the examples. The transmittance spectrum of the paper substrate (curve A in FIG9 ) was measured on a Perkin Elmer Lambda 950 equipped with deuterium (UV) and xenon (VIS) lamps and a UVWinLab Data Processor (measurement mode: integrating sphere transmission). The paper substrate was mounted on a sample holder, and the transmittance spectrum was measured between 250 nm and 500 nm.

As the coating composition comprising optically variable magnetic pigment particles, the UV-curable screen printing ink described in Table 1 was used. The coating composition was applied manually in a 10 mm x 15 mm rectangular pattern on the substrate using a T90 silk screen to form a coating.

Table 1. UV curable inks with the following formulations:

(*) Platelet-shaped gold-green optically variable magnetic pigment particles having a platelet shape with a diameter _d50 of approximately 9.3 microns and a thickness of approximately 1 micron, obtained from JDS-Uniphase, Santa Rosa, CA.

UV-LED lamps from Phoseon (Type FireFlex 50 x 75 mm, 395 nm, 8 W/cm 2 ) were used to harden the UV-curable printing inks of Table 1 .

The UV-LED lamp was placed 50 mm from the substrate surface bearing the applied coating to irradiate directly. Alternatively, as described above, the UV-LED lamp was placed 50 mm from the substrate surface opposite the coating composition to irradiate through the substrate. In both cases, the irradiation time was 1/2 second.

The hardening step is carried out as described above after or partially simultaneously with the step of orienting with the magnetic field generating means.

Photographic images of printed and cured samples of an OEL containing oriented non-spherical optically variable magnetic pigment particles (illumination: Reflecta LED Videolight RPL49, objective: AF-S Micro Nikkor 105mm 1:2.8G ED; camera: Nikon D800, manual exposure, automatic digital image enhancement disabled for consistency) are shown in Figures 4B, 5B, 6B, and 7B. In Figures 4B, 5B, 6B, and 7B, the left photograph shows the OEL tilted 30° clockwise from the vertical, the middle photograph shows the OEL viewed perpendicular to the surface of the OEL, and the left photograph shows the OEL tilted 30° counterclockwise from the vertical.

Comparative Example C1 (Comparative Example Figures 4A and 4B)

A paper substrate (Louisenthal Velin) bearing an applied coating (C) made from the coating composition of Table 1 was placed on a magnetic field generating device (MD) containing a magnet (M) (NdFeB N48 permanent magnet bar L _MB xl _MB xh _MB = 30 x 18 x 6 mm). The magnet (M) was embedded in a magnetic device housing (K') (L xl xh = 40 x 40 x 15 mm) made of polymer plastic (PPS) and containing a recess (L xl = 20 x 20, depth 1 mm) on its surface. The magnet (M) was embedded in the center of the magnetic device housing (K'), 6 mm from the surface of the magnetic device housing opposite the recess, with its North-South axis substantially parallel to the coating. The substrate was positioned so that the surface bearing the coating composition (C) faced the magnetic field generating device as shown in Figure 4A, with a distance of 6 mm between the magnet (M) and the coating composition (C). The magnetic field generating device was removed from the paper substrate. The coating composition was hardened by UV-Vis irradiation with a UV-LED lamp positioned on the coating composition (CC) side as shown in Figure 4A. Photographs of the resulting OEL at three different viewing angles are shown in Figure 4B.

Embodiment E1 according to the present invention (FIGS. 5A and 5B)

A paper substrate (Louisenthal Velin) bearing an applied coating layer (C) made of a coating composition was placed on a magnetic field generating device (MD) containing a magnet (M) (NdFeB N48 permanent magnet bar L _MB xl _MB xh _MB = 30 x 18 x 6 mm), the magnet (M) being embedded in a magnetic device housing (K') (L xl xh = 40 x 40 x 15 mm) made of polymer plastic (PPS) and containing a recess (L xl = 20 x 20, depth 1 mm) on its surface (the same magnetic field generating device (MD) used in Comparative Example 1). The magnet (M) was embedded in the center of the magnetic device housing (K'), 6 mm from the surface of the magnetic device housing opposite the recess, with its North-South axis substantially parallel to the coating layer. The substrate was positioned so that the surface bearing the coating composition (C) faced the magnetic field generating device (MD) as shown in FIG5A , and the distance between the magnet (M) and the coating layer (C) was 6 mm. The substrate was positioned so that the surface bearing the coating layer (C) faced the magnetic field generating device (MD) as shown in FIG5A . Simultaneously with the orientation step, the coating composition was cured by UV-Vis irradiation using a UV-LED lamp positioned on the side bearing the coating layer as shown in FIG5A . Photographs of the resulting optical effect layer at three different viewing angles are shown in FIG5B .

Comparative Example C2 (Comparative Example, Figures 6A and 6B)

A paper substrate (Louisenthal Velin) bearing an applied coating layer (C1) made of a coating composition (CC) was placed on a magnetic field generating device (MD1) containing a magnet (M) (NdFeB N48 permanent magnet bar L _MB xl _MB xh _MB = 30 x 18 x 6 mm), the magnet (M) being embedded in a magnetic device housing (K') (L xl xh = 40 x 40 x 15 mm) made of polymer plastic (PPS) and containing a recess (L xl = 20 x 20, depth 1 mm) on its surface (the same magnetic device (MD) used in Comparative Example C1). The magnet (M1) was embedded in the center of the magnetic device housing (K'), 6 mm from the surface of the magnetic device housing opposite the recess, with its North-South axis substantially parallel to the coating composition layer. The substrate was positioned so that the surface bearing the coating layer (C1) faced the magnetic field generating device (MD), as shown in FIG6A j), and the distance between the magnet (M1) and the coating layer (C1) was 6 mm. After the orientation step, the strong coating (C1) is hardened by UV-Vis irradiation using a UV-LED lamp (L) as shown in FIG6A k) on the side bearing the coating composition.

As shown in FIG6A l), a second coating layer (C2) of the coating composition of Table 1 was applied adjacent to coating layer (C1); a magnetic field generating device (MD2) comprising a magnet (M2) (NdFeB N48 permanent magnet bar L _MB xl _MB xh _MB = 30 x 18 x 6 mm) embedded in a magnetic device housing (L xl xh = 40 x 40 x 15 mm) made of polymer plastic (PPS) was located on the substrate (S) side. The magnet (M2) was embedded in the center of the magnetic device housing, 6 mm from the surface of the magnetic device housing facing the substrate, with its North-South axis substantially parallel to the substrate. Simultaneously, the second coating layer (C2) was cured by UV-Vis irradiation using a UV-LED lamp, as shown in FIG6A m), located on the side bearing the second coating layer (C2). Photographs of the resulting optical effect layer at three different viewing angles are shown in FIG6B.

Embodiment E2 according to the present invention (FIGS. 7A and 7B)

A paper substrate (Louisenthal Velin) bearing an applied coating layer (C1) made of the coating composition was placed on a magnetic field generating device (MD1) containing a magnet (M1) (NdFeB N48 permanent magnet bar L _MB xl _MB xh _MB = 30 x 18 x 6 mm). The magnet (M1) was embedded in a magnetic device housing (K') (L xl xh = 40 x 40 x 15 mm) made of polymer plastic (PPS) and containing a recess (L xl = 20 x 20, depth 1 mm) on its surface (the same magnetic device (MD) used in Example E1). The magnet (M1) was embedded in the center of the magnetic device housing (K'), 6 mm from the surface of the magnetic device housing opposite the recess, with its North-South axis substantially parallel to the coating layer. The substrate was positioned so that the surface bearing the coating layer (C1) faced the magnetic field generating device (MD1) as shown in FIG7A j). Simultaneously with the orientation step, the coating ( C1 ) is hardened by UV-Vis irradiation using a UV-LED lamp as shown in FIG. 7A j on the side bearing the coating.

As shown in FIG7A k), a second coating layer (C2) made from the coating composition of Table 1 was applied to an adjacent area of coating layer (C1); a magnetic field generating device (MD2) (the same magnetic field generating device (MD2) as in Comparative Example C2) was located on the side of the substrate opposite to the side bearing layer (C2), the magnetic field generating device comprising a magnet (M2) (NdFeB N48 permanent magnet bar L _MB xl _MB xh _MB = 30 x 18 x 6 mm) embedded in a magnetic device housing (L xl xh = 40 x 40 x 15 mm) made of polymer plastic (PPS), the magnet (M2) being embedded in the center of the magnetic device housing, 6 mm from the surface of the magnetic device housing facing the substrate, with its North-South axis substantially parallel to the substrate, and simultaneously, layer (C2) was cured by UV-Vis irradiation using a UV-LED lamp located on the substrate side, as shown in FIG7A l). Photographs of the resulting optical effect layer at three different viewing angles are shown in FIG7B.

Claims (18)

1. A method for fabricating an optical effect layer (OEL) on a substrate, the method comprising the steps of: a) Applying a coating composition comprising a plurality of magnetic or magnetizable pigment particles onto a substrate to form a coating, said coating being in a first state. b) b1) Exposing the coating to the magnetic field of a magnetic field generator located on the side of the coating, thereby orienting the plurality of magnetic or magnetizable pigment particles, and b2) Simultaneously or partially simultaneously hardening the coating to a second state through the substrate to fix the magnetic or magnetizable pigment particles in their obtained positions and orientations, the hardening being performed by irradiation with a UV-Vis irradiation source located on the side of the substrate. The substrate is transparent to one or more wavelengths of the emission spectrum of the irradiation source in the range of 200 nm to 500 nm, and The plurality of magnetic or magnetizable pigment particles are oriented to follow a concave curvature when viewed from the side bearing the OEL. 2. The method of claim 1, wherein the application step a) is a printing method selected from screen printing, rotary gravure printing and flexographic printing. 3. The method according to any one of the preceding claims, wherein at least a portion of the plurality of magnetic or magnetizable pigment particles comprises magnetic thin-film interference pigments, magnetic cholesterol-type liquid crystal pigments, interference coating pigments comprising one or more magnetic materials, and mixtures thereof. 4. The method according to claim 1 or 2, further comprising step c) applying a second coating composition layer containing a plurality of magnetic or magnetizable pigment particles to form a second coating, the coating composition being in a first state; step d) exposing the second coating in the first state to a magnetic field of a second magnetic field generating device, thereby causing the plurality of magnetic or magnetizable pigment particles to be oriented in an arbitrary pattern other than random orientation; and e) simultaneously, partially simultaneously, or subsequently by UV-Vis radiation to harden the second coating to a second state to fix the magnetic or magnetizable pigment particles in their obtained positions and orientations. 5. The method of claim 1 or 2, further comprising steps i) applying a second coating composition layer comprising a plurality of magnetic or magnetizable pigment particles to form a second coating, the coating composition being in a first state; ii) exposing the second coating in the first state to a magnetic field of a second magnetic field generating device, thereby causing the plurality of magnetic or magnetizable pigment particles to be oriented in an arbitrary pattern other than random orientation; and iii) simultaneously, partially simultaneously, or subsequently hardening the second coating to a second state by UV-Vis radiation to fix the magnetic or magnetizable pigment particles in their acquired positions and orientations, wherein steps i), ii), and iii) are performed prior to steps a) and b). 6. The method of claim 4, wherein step d) of claim 4 is performed using a second magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a convex curvature when viewed from the side carrying the coating. 7. The method of claim 5, wherein step ii) of claim 5 is performed using a second magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a convex curvature when viewed from the side carrying the coating. 8. A method for fabricating an optical effect layer (OEL) on a substrate, the OEL comprising a pattern consisting of at least two adjacent patterns made of a single hardened layer, the method comprising the steps of: a) Applying a coating composition comprising a plurality of magnetic or magnetizable particles onto the substrate to form a coating, the coating being in a first state; b) b1) Exposing one or more first substrate regions bearing the coating to the magnetic field of a first magnetic field generating device located on the coating side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a concave curvature when viewed from the side bearing the coating, and b2) The coating is simultaneously or partially simultaneously cured through the substrate, the curing being performed by irradiation with a UV-Vis irradiation source located on the substrate side, wherein the UV-Vis irradiation source is equipped with a photomask to prevent one or more second substrate regions carrying the coating from being exposed to UV-Vis irradiation; and c) Exposing at least one or more second substrate regions carrying the coating in the first state, due to the presence of a photomask in step b2), to the magnetic field of a second magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles to any orientation other than random orientation; and simultaneously, partially simultaneously, or subsequently, by irradiation with a UV-Vis irradiation source to harden at least one or more second substrate regions carrying the coating to a second state to fix the magnetic or magnetizable pigment particles in their obtained positions and orientations. In step a), the substrate is transparent to one or more wavelengths of the emission spectrum of the irradiation source in the range of 200 nm to 500 nm. 9. A method for fabricating an optical effect layer (OEL) on a substrate, the OEL comprising a pattern consisting of at least two adjacent patterns made of a single hardened layer, the method comprising the steps of: a) Applying a coating composition containing a plurality of magnetic or magnetizable particles onto the substrate to form a coating, the coating being in a first state. b) b1) Exposing one or more first substrate regions carrying the coating to the magnetic field of a first magnetic field generator, thereby orienting the plurality of magnetic or magnetizable pigment particles to any orientation other than random orientation, and b2) Simultaneously, partially simultaneously, or subsequently curing the coating as described herein, said curing being performed by irradiation with a UV-Vis irradiation source equipped with a photomask so that one or more second substrate regions carrying the coating are not exposed to UV-Vis irradiation; and c) Exposing at least one or more second substrate regions carrying the coating in the first state, due to the presence of a photomask in step b2), to the magnetic field of a second magnetic field generator located on the coating side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a concave curvature when viewed from the side carrying the coating; and simultaneously or partially simultaneously hardening at least one or more second substrate regions carrying the coating through the substrate, the hardening being performed by irradiation with a UV-Vis irradiation source located on the substrate side. The substrate in step a) is transparent to one or more wavelengths of the emission spectrum of the irradiation source in the range of 200 nm to 500 nm. 10. The method of claim 8 or 9, wherein step c) of claim 8 is performed with a second magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a convex curvature when viewed from the side carrying the coating, or wherein step b1) of claim 9 is performed with a first magnetic field generating device, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow a convex curvature when viewed from the side carrying the coating. 11. The method according to claim 8 or 9, wherein the application step a) is a printing method selected from screen printing, gravure printing and flexographic printing. 12. The method of claim 8 or 9, wherein at least a portion of the plurality of magnetic or magnetizable pigment particles comprises magnetic thin-film interference pigments, magnetic cholesterol liquid crystal pigments, interference coating pigments comprising one or more magnetic materials, and mixtures thereof. 13. The method of claim 4, wherein the second magnetic field generating device is located on the substrate side, and wherein the UV-Vis irradiation source for applying UV-Vis radiation to the second coating composition is located on the coating side, or The method of claim 8 or the method of claim 10 when claim 10 refers to claim 8, wherein step c) comprises c) exposing at least one or more second substrate regions carrying the coating in a first state due to the presence of a photomask in step b2) to a magnetic field of a second magnetic field generating device located on the substrate side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow any orientation other than random orientation; and simultaneously, partially simultaneously, or subsequently hardening the at least one or more second substrate regions carrying the coating to a second state by irradiation with a UV-Vis irradiation source located on the coating side to fix the magnetic or magnetizable pigment particles in their obtained positions and orientations, or The method of claim 9 or the method of claim 10 when claim 10 refers to claim 9, wherein step b) comprises b1) exposing one or more first substrate regions carrying the coating to a magnetic field of a first magnetic field generating device located on the substrate side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow any orientation other than random orientation, and b2) simultaneously, partially simultaneously or subsequently curing the coating by irradiation with a UV-Vis irradiation source located on the coating side, the irradiation source being equipped with a photomask so that one or more second substrate regions carrying the coating are not exposed to UV-Vis irradiation. 14. The method of claim 5, wherein the second magnetic field generating device is located on the substrate side, and wherein the UV-Vis irradiation source for applying UV-Vis radiation to the second coating composition is located on the coating side, or The method of claim 8 or the method of claim 10 when claim 10 refers to claim 8, wherein step c) comprises c) exposing at least one or more second substrate regions carrying the coating in a first state due to the presence of a photomask in step b2) to a magnetic field of a second magnetic field generating device located on the substrate side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow any orientation other than random orientation; and simultaneously, partially simultaneously, or subsequently hardening the at least one or more second substrate regions carrying the coating to a second state by irradiation with a UV-Vis irradiation source located on the coating side to fix the magnetic or magnetizable pigment particles in their obtained positions and orientations, or The method of claim 9 or the method of claim 10 when claim 10 refers to claim 9, wherein step b) comprises b1) exposing one or more first substrate regions carrying the coating to a magnetic field of a first magnetic field generating device located on the substrate side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow any orientation other than random orientation, and b2) simultaneously, partially simultaneously or subsequently curing the coating by irradiation with a UV-Vis irradiation source located on the coating side, the irradiation source being equipped with a photomask so that one or more second substrate regions carrying the coating are not exposed to UV-Vis irradiation. 15. The method of claim 6, wherein the second magnetic field generating device is located on the substrate side, and wherein the UV-Vis irradiation source for applying UV-Vis radiation to the second coating composition is located on the coating side, or The method of claim 8 or the method of claim 10 when claim 10 refers to claim 8, wherein step c) comprises c) exposing at least one or more second substrate regions carrying the coating in a first state due to the presence of a photomask in step b2) to a magnetic field of a second magnetic field generating device located on the substrate side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow any orientation other than random orientation; and simultaneously, partially simultaneously, or subsequently hardening the at least one or more second substrate regions carrying the coating to a second state by irradiation with a UV-Vis irradiation source located on the coating side to fix the magnetic or magnetizable pigment particles in their obtained positions and orientations, or The method of claim 9 or the method of claim 10 when claim 10 refers to claim 9, wherein step b) comprises b1) exposing one or more first substrate regions carrying the coating to a magnetic field of a first magnetic field generating device located on the substrate side, thereby orienting the plurality of magnetic or magnetizable pigment particles to follow any orientation other than random orientation, and b2) simultaneously, partially simultaneously or subsequently curing the coating by irradiation with a UV-Vis irradiation source located on the coating side, the irradiation source being equipped with a photomask so that one or more second substrate regions carrying the coating are not exposed to UV-Vis irradiation. 16. An optical effect layer (OEL) made by the method of any one of claims 1 to 15. 17. The optical effect layer (OEL) as described in claim 16 is used for protecting security documents from forgery or counterfeiting or for decorative applications. 18. A security document comprising one or more optical effect layers (OELs) as described in claim 16.