HK40081811B - Methods for producing optical effect layers comprising magnetic or magnetizable pigment particles - Google Patents

Description

Method for producing optical effect layers containing magnetic or magnetizable pigment particles

Technical Field

This invention relates to the field of magnetic field generating apparatus and methods for producing optical effect layers (OELs) comprising magnetically oriented sheet-like magnetic or magnetizable pigment particles. In particular, the invention provides an apparatus and method for producing OELs by magnetically oriented sheet-like magnetic or magnetizable pigment particles in a coating, and uses of the OELs as anti-counterfeiting measures on secure documents or security articles, as well as for decorative purposes.

Background Technology

In this art, inks, compositions, coatings, or layers comprising oriented magnetic or magnetizable pigment particles, and particularly optically variable magnetic or magnetizable pigment particles, are known for creating security elements, for example, in the field of secure documents. Coatings or layers comprising oriented magnetic or magnetizable pigment particles are disclosed, for example, in US 2,570,856; US 3,676,273; US 3,791,864; US 5,630,877 and US 5,364,689. Coatings or layers comprising oriented magnetic color-changing pigment particles that result in particularly attractive optical effects and can be used to protect secure documents have been disclosed in WO 2002/090002 A2 and WO 2005/002866 A1.

For example, security features used in secure documents can generally be categorized into "covert" security features on one hand and "overt" security features on the other. The protection provided by covert security features relies on the difficulty of detecting such features, typically requiring specialized instruments and knowledge for detection. Overt security features, on the other hand, rely on the idea that they can be easily detected using independent (unaided) human senses; for example, such features may be visually visible and/or detectable by touch, but still difficult to produce and/or replicate. However, the effectiveness of overt security features largely depends on their ease of identification as security features.

Magnetic or magnetizable pigment particles in printing inks or coatings can be induced to localize in an uncured (i.e., wet) coating by applying a correspondingly structured magnetic field, thereby curing the coating and producing magnetically induced images, designs, and/or patterns. The result is a fixed and stable magnetically induced image, design, or pattern. Materials and techniques for orienting magnetic or magnetizable pigment particles in coating compositions have been disclosed, for example, in US 2,418,479; US 2,570,856; US 3,791,864; DE 2006848-A; US 3,676,273; US 5,364,689; US 6,103,361; EP 0 406 667 B1; US 2002/0160194; US 2004/0009308; EP 0 710 508 A1; WO2002/09002 A2; WO 2003/000801 A2; WO 2005/002866 A1; WO 2006/061301 A1. In this way, highly counterfeit-resistant magnetically induced patterns can be produced. The safety elements discussed can only be produced by simultaneously utilizing magnetic or magnetizable pigment particles or corresponding inks, as well as specific techniques for printing the inks and orienting the pigments in the printed inks.

To protect security documents or articles containing magnetosensitive images from premature harmful effects of soil and/or moisture during and for a period of time, protective varnishes have been used in practice. These protective varnishes are applied as a continuous layer over the prepared and dried/cured magnetosensitive image.

WO 2011/012520 A2 discloses a transfer foil comprising a coating having a design form including optically variable magnetic pigments representing the orientation of an image, mark, or pattern. The transfer foil may further comprise a topcoat, wherein the topcoat is applied prior to the application of a layer comprising the optically variable magnetic pigments. A method for producing the transfer foil includes a) applying the topcoat and hardening/curing the topcoat, and b) applying the layer containing the optically variable magnetic pigments, magnetically orienting the particles, and hardening/curing the layer. The disclosed method is not suitable for producing magnetically induced images that require the display of personalized variable markings.

EP 1 641 624 B1, EP 1 937 415 B1, and EP 2 155 498 B1 disclose apparatus and methods for magnetically transferring markings onto an uncured (i.e., wet) coating composition containing magnetic or magnetizable pigment particles to form an optical effect layer (OEL). The disclosed methods are capable of producing security documents and articles with consumer-specific magnetic designs. However, the disclosed magnetic apparatus is prepared to meet specific designs, and these designs cannot be modified if they need to be changed from one article to another; therefore, the methods are not suitable for producing OELs that require personalized, variable markings.

EP 3 170 566 B1, EP 3 459 758 A1, and EP 2 542 421 B1 disclose different methods for producing variable marks on optically variable magnetic ink. However, these methods require the use of specialized equipment, such as photomasks or lasers.

To produce magnetic variable information on secure documents or artifacts, inkjet inks containing magnetic particles have been developed to allow Magnetic Ink Character Recognition (MICR). However, these inkjet inks face various challenges, particularly those related to shelf-life stability, printability, heterogeneous magnetic ink deposition, and printhead clogging. EP 2 223 976 B1 discloses a method for producing documents containing MIR features, wherein the method includes the steps of: applying a pattern of a curable ink containing a gelling agent onto a substrate by inkjet printing; cooling the ink to below its gel temperature; applying a magnetic material to the ink; and finally curing the ink. Optionally, toners containing magnetic particles have also been developed and disclosed, for example, in US 10,503,091B2 and US 10,359,730 B2. However, specific specialized equipment is required to print these toners.

Therefore, there is a need for a method for producing custom optical effect layers that exhibit more than one mark in a general manner and on an industrial scale, the optical effect layers exhibiting striking effects. Furthermore, the method should be reliable, easy to implement, and capable of operating at high production speeds.

Summary of the Invention

Therefore, the object of the present invention is to overcome the deficiencies of the prior art. This is achieved by providing a method for producing an optical effect layer (OEL) displaying more than one mark (x30) on a substrate (x20), the method comprising the following steps:

a) Applying a radiation-curable coating composition comprising non-spherical magnetic or magnetizable pigment particles to the surface of a substrate (x20), the radiation-curable coating composition being in a first liquid state, thereby forming a coating (x10).

b) Exposing the coating (x10) to the magnetic field of the magnetic field generating device, thereby orienting at least a portion of the magnetic or magnetizable pigment particles;

c) Following step b), a topcoat composition is applied over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30), and

d) Simultaneously with or after step c), the coating (x10) and the one or more marks (x30) are at least partially cured using the curing unit (x50).

In one preferred embodiment, step b) of exposing the coating (x10) is performed, thereby causing at least a portion of the magnetic or magnetizable pigment particles to be uniaxially oriented. In another preferred embodiment, step b) of exposing the coating (x10) is performed, thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented.

In a preferred embodiment, step a) of applying the radiation-curable coating composition is performed by a method selected from the group consisting of screen printing, rotary gravure printing, pad printing, and flexographic printing.

In a preferred embodiment, step c) of applying the topcoat composition is performed using a non-contact fluid microdispensing technique, preferably by inkjet printing.

This document also describes optical effect layers (OELs) produced by the methods described herein, and security documents and decorative elements and objects comprising one or more optical OELs described herein.

This document also describes a method of manufacturing a security document or decorative element or object, comprising: a) providing a security document or decorative element or object; and b) providing an optical effect layer, such as those described herein, particularly those obtained by the methods described herein, such that it is contained within the security document or decorative element or object.

The method described herein advantageously uses two compositions applied to each other in a wet-on-wet state. In particular, the method according to the invention enables the general production of optical effect layers (OELs) exhibiting more than one mark, and can be readily implemented on an industrial scale at high production rates. The two compositions used in the method described herein include a radiation-curable coating composition applied to a substrate (x20) as a first composition, comprising non-spherical magnetic or magnetizable pigment particles, and a topcoat composition as a second composition applied over the radiation-curable coating composition containing pigment particles and partially overlapping the composition (i.e., overlapping in at least one region), and applied in the form of more than one mark while the radiation-curable coating composition is still wet and unpolymerized.

This invention provides a reliable and easy-to-implement method for producing a striking optical effect layer (OEL) displaying one or more markings as described herein. The disclosed method advantageously enables the production of security documents and articles of art with consumer-specific magnetic designs and displaying one or more markings in a universal, online-varying, easy-to-implement, and highly reliable manner without requiring customized magnetic components for orienting non-spherical magnetic or magnetizable pigment particles for each variable or personalized marking and for each consumer-specific OEL. This invention also provides a reliable and easy way to implement the method for producing a striking optical effect layer (OEL) displaying one or more markings comprising variable halftones as described herein.

Attached Figure Description

The method described herein for producing an optical effect layer (OEL) displaying more than one mark (x30) on a substrate (x20) described herein will now be described in more detail with reference to the accompanying drawings and specific embodiments, wherein

Figure 1 schematically illustrates the flake-shaped pigment particles.

Figure 2A schematically illustrates a method according to the invention for producing an optical effect layer (OEL) displaying more than one mark (230) on a substrate (220). The method includes step b): exposing a coating (210) to a magnetic field of a magnetic field generating device (B1), thereby uniaxially oriented at least a portion of the magnetic or magnetizable pigment particles; after step b), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of more than one mark (230); and step d): curing the coating (210) and more than one mark (230) at least partially using a curing unit (250).

Figure 2B schematically illustrates a method according to the invention for producing an optical effect layer (OEL) displaying more than one mark (230) on a substrate (220). The method includes step b): exposing a coating (210) to a magnetic field of a magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented; after step b), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of more than one mark (230); and step d): curing the coating (210) and more than one mark (230) at least partially using a curing unit (250).

Figure 2C schematically illustrates a method according to the invention for producing an optical effect layer (OEL) displaying more than one mark (230) on a substrate (220). The method includes step b1): exposing a coating (210) to the magnetic field of a magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented; simultaneously, concurrently, or after step b1), step b2): exposing the coating (210) to the magnetic field of a second magnetic field generating device (B2), thereby causing at least a portion of the sheet-like magnetic or magnetizable particles to be monoaxially re-oriented; after step b2), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of more than one mark (230); and step d): curing the coating (210) and more than one mark (230) at least partially with a curing unit (250).

Figure 2D-1 schematically illustrates a method according to the invention for producing an optical effect layer (OEL) exhibiting one or more markings (230) on a substrate (220). The method includes step b): exposing a coating (210) to a magnetic field of a magnetic field generating device (B1), thereby uniaxially oriented at least a portion of the magnetic or magnetizable pigment particles; after step b), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of one or more markings (230); and partially simultaneously with or after step c), step x): selectively at least partially curing one or more first regions of the coating (210) using a selective curing unit (260), thereby fixing at least a portion of the magnetic or magnetizable particles in their adopted positions and orientations. On, and optionally fix at least a portion of the topcoat (230) in the position and orientation in which they are adopted, such that one or more second regions of the coating (210) and optionally one or more second regions of the ground coating (230) remain unexposed to irradiation; after step x), step y): expose the coating (210) to the magnetic field of the second magnetic field generating device (B2), thereby uniaxially oriented at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (210); and step d): cure the coating (210) and one or more marks (230) at least partially with the curing unit (250).

Figure 2D-2 schematically illustrates a method according to the invention for producing an optical effect layer (OEL) exhibiting one or more markings (230) on a substrate (220). The method includes step b): exposing a coating (210) to the magnetic field of a magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented; after step b), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of one or more markings (230); and partially simultaneously with or after step c), step x): selectively at least partially curing one or more first regions of the coating (210) using a selective curing unit (260), thereby fixing at least a portion of the magnetic or magnetizable particles in their adopted positions and orientations. On, and optionally fix at least a portion of the topcoat (230) in the position and orientation in which they are adopted, such that one or more second regions of the coating (210) and optionally one or more second regions of the ground coating (230) remain unexposed to irradiation; after step x), step y): expose the coating (210) to the magnetic field of the second magnetic field generating device (B2), thereby uniaxially oriented at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (210); and step d) cure the coating (210) and one or more marks (230) at least partially with the curing unit (250).

Figure 2D-3 schematically illustrates a method according to the invention for producing an optical effect layer (OEL) displaying more than one mark (230) on a substrate (220). The method includes step b1): exposing a coating (210) to the magnetic field of a magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented; after step b1), step b2): exposing the coating (210) to the magnetic field of a second magnetic field generating device (B2), thereby causing at least a portion of the sheet-like magnetic or magnetizable particles to be uniaxially reoriented; after step b2), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of more than one mark (230); and partially simultaneously with or after step c), step x): selectively curing at least a portion of a first region of the coating (210) using a selective curing unit (260). The coating (210) is partially cured to fix at least a portion of the magnetic or magnetizable particles in their adopted positions and orientations, and optionally at least a portion of the topcoat (230) is fixed in their adopted positions and orientations, such that one or more second regions of the coating (210) and optionally one or more second regions of the topcoat (230) remain unexposed to irradiation; after step x), step y): the coating (210) is exposed to the magnetic field of the third magnetic field generating device (B3), thereby uniaxially reorienting at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (210); and step d): the coating (210) and one or more marks (230) are at least partially cured by the curing unit (250).

Figure 2E-1 schematically illustrates a method according to the invention for producing an optical effect layer (OEL) displaying more than one mark (230) on a substrate (220). The method includes step b): exposing a coating (210) to the magnetic field of a magnetic field generating device (B1), thereby uniaxially oriented at least a portion of the magnetic or magnetizable pigment particles; and step x): selectively at least partially curing one or more first regions of the coating (210) using a selective curing unit (260) to fix at least a portion of the magnetic or magnetizable particles in their adopted positions and orientations, and optionally fixing at least a portion of the topcoat film (230) in their adopted positions and orientations, such that one or more second regions of the coating (210) and any One or more second regions of the selected ground coating (230) remain unexposed to irradiation; after step x), step y): the coating (210) is exposed to the magnetic field of the second magnetic field generating device (B2), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (210) to be uniaxially reoriented; after step y), step c): a topcoat composition is applied over the coating (210), wherein the topcoat composition is applied in the form of one or more marks (230); and step d): the coating (210) and one or more marks (230) are at least partially cured by the curing unit (250).

Figure 2E-2 schematically illustrates a method according to the invention for producing an optical effect layer (OEL) displaying more than one mark (230) on a substrate (220). The method includes step b): exposing a coating (210) to the magnetic field of a magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented; and step x): selectively at least partially curing one or more first regions of the radiation-curable coating composition of step b) of the coating (210) using a selective curing unit (260), thereby fixing at least a portion of the magnetic or magnetizable particles in their adopted positions and orientations, and optionally fixing at least a portion of the topcoat film (230) in their adopted positions and orientations, such that one or more of the coating (210)... The second region and one or more second regions of the optional ground coating (230) remain unexposed to irradiation; after step x), step y): the coating (210) is exposed to the magnetic field of the second magnetic field generating device (B2), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (210) to be uniaxially oriented; after step y), step c): a topcoat composition is applied over the coating (210), wherein the topcoat composition is applied in the form of one or more marks (230); and step d): the coating (210) and one or more marks (230) are at least partially cured by the curing unit (250).

Figure 2E-3 schematically illustrates a method according to the invention for producing an optical effect layer (OEL) displaying more than one mark (230) on a substrate (220). The method includes step b1): exposing a coating (210) to the magnetic field of a magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented; simultaneously with, partially simultaneously with, or after step b1), step b2): exposing the coating (210) to the magnetic field of a second magnetic field generating device (B2), thereby causing at least a portion of the sheet-like magnetic or magnetizable particles to be uniaxially oriented; partially simultaneously with, or after step b1), step x): selectively at least partially curing one or more first regions of the radiation-curable coating composition of step b1 using a selective curing unit (260), thereby fixing at least a portion of the magnetic or magnetizable particles in their adopted positions and orientations, and optionally... At least a portion of the topcoat film (230) is fixed in the position and orientation in which it is adopted, such that one or more second regions of the coating (210) and one or more second regions of the optional ground coating film (230) remain unexposed to irradiation; after step x), step y): the coating (210) is exposed to the magnetic field of the third magnetic field generating device (B3), such that at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (210) are uniaxially oriented; after step y), step c): a topcoat composition is applied over the coating (210), wherein the topcoat composition is applied in the form of one or more marks (230); and step d) the coating (210) and one or more marks (230) are at least partially cured by the curing unit (250).

Figure 3 schematically illustrates a magnetic field generating device that biaxially orients magnetic or magnetizable pigment particles in a coating (310) on a substrate (320).

Figures 4A-F schematically illustrate comparative methods for producing optical effect layers (OELs) on a substrate (420).

Figures 5A-E show images of OELs (E1-E21) prepared according to the method of the present invention and OELs (C1-C11) prepared according to the comparative method, at two viewing angles (-30° and +30°).

Detailed Implementation

definition

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

As used herein, the term "at least one" is intended to define one or more species, such as one, two, or three species.

As used herein, the terms “about” and “substantially” mean that the quantity or value in discussion can be a specified value or some other value near it. Generally, the terms “about” and “substantially” indicating a specific value are intended to represent a range within ±5% of that value. As an example, the phrase “about 100” means a range of 100 ± 5, that is, from 95 to 105. Generally, when the terms “about” and “substantially” are used, it can be expected that similar results or effects according to the invention can be obtained within ±5% of the specified value.

The term "substantially parallel" means a deviation of no more than 10° from a parallel arrangement, and the term "substantially perpendicular" means a deviation of no more than 10° from a perpendicular arrangement.

As used herein, the term "and/or" means that all or only one of the elements of the group may be present. For example, "A and/or B" should mean "A only, or B only, or both A and B". In the case of "A only", the term also covers the possibility that B is not present, i.e., "A only, but no B".

As used herein, the term "comprising" is intended to be non-exclusive and open-ended. Thus, for example, a coating composition comprising compound A may include other compounds besides A. However, the term "comprising" also encompasses the more restrictive meaning of "consistently composed of" and "composed of" as in particular embodiments thereof, such that, for example, "a dampening solution comprising A, B, and optionally C" may also consist (substantially) of A and B or (substantially) of A, B, and C.

The term “Optical Effect Layer (OEL)” as used herein refers to a coating containing oriented magnetic or magnetizable pigment particles, wherein the magnetic or magnetizable pigment particles are oriented by a magnetic field and wherein the oriented magnetic or magnetizable pigment particles are fixed/frozen in their orientation and position (i.e., after hardening/curing) to form a magnetically induced image.

The term "coating composition" refers to any composition capable of forming an optical effect layer (OEL) on a solid substrate and can be applied preferably, but not exclusively, by a printing method. The coating composition comprises the sheet-like magnetic or magnetizable pigment particles described herein and the binder described herein.

As used herein, the term "wet" refers to a coating that has not yet cured, such as a coating in which flake-like magnetic or magnetizable pigment particles can still change their position and orientation under the influence of an external force acting on them.

The term "secure document" refers to a document that is typically protected against forgery or fraud by at least one security feature. Examples of secure documents include, but are not limited to, documents of value and commercial goods of value.

The term "security feature" is used to refer to an image, pattern, or graphic element that can be used for authentication purposes.

Where this specification refers to "preferred" embodiments/features, combinations of such "preferred" embodiments/features should also be considered disclosed, provided that such combinations of "preferred" embodiments/features are technically meaningful.

The present invention provides a method for producing an optical effect layer (OEL) exhibiting one or more marks (x30) on a substrate (x20), wherein the OEL is based on magnetically oriented sheet-like magnetic or magnetizable pigment particles and further exhibits one or more marks (x30).

The method described herein includes step a): applying a radiation-curable coating composition comprising non-spherical magnetic or magnetizable pigment particles as described herein to the surface of a substrate (x20) described herein, thereby forming a coating (x10) described herein, said composition being in a first liquid state that allows it to be applied as a layer and is in an uncured (i.e., wetted) state, wherein the pigment particles can move and rotate within said layer. Since the radiation-curable coating composition described herein will be provided on the surface of the substrate (x20), the radiation-curable coating composition comprises at least a binder material and magnetic or magnetizable pigment particles, said composition being in a form that allows it to be processed on a desired printing or coating apparatus. Preferably, step a) is performed by a printing method, wherein the printing method is preferably selected from the group consisting of free screen printing, rotary gravure printing, flexographic printing, intaglio printing (also known in the art as engraved copperplate printing or engraved steel mold printing), pad printing, and curtain coating; more preferably, it is selected from the group consisting of free gravure printing, screen printing, rotary gravure printing, pad printing, and flexographic printing; and even more preferably, it is selected from the group consisting of screen printing, rotary gravure printing, pad printing, and flexographic printing.

The non-spherical magnetic or magnetizable pigment particles described herein are preferably ellipsoidal, platelet-shaped, or needle-shaped magnetic or magnetizable pigment particles, or mixtures of two or more thereof, and more preferably platelet particles.

The non-spherical magnetic or magnetizable pigment particles described herein are defined as having non-isotropic reflectivity to incident electromagnetic radiation due to their non-spherical shape, wherein the cured binder material is at least partially transparent. As used herein, the term "non-isotropic reflectivity" means that the proportion of incident radiation from a first angle reflected by the particle to a specific (observation) direction (second angle) is a function of the particle's orientation; that is, a change in the particle's orientation relative to the first angle can result in a different magnitude of reflection towards the observation direction. Preferably, the non-spherical magnetic or magnetizable pigment particles described herein have non-isotropic reflectivity to incident electromagnetic radiation in a portion or all of the wavelength range of about 200 to about 2500 nm, more preferably about 400 to about 700 nm, such that a change in the particle's orientation results in a change in the reflection from the particle towards a specific direction. As is known to those skilled in the art, the magnetic or magnetizable pigment particles described herein differ from conventional pigments because conventional pigment particles exhibit the same color and reflectivity regardless of particle orientation, while the magnetic or magnetizable pigment particles described herein exhibit reflectivity or color, or both, depending on particle orientation.

In an embodiment of the method described herein, step b) or b1) is performed: the coating (x10) is exposed to the magnetic field of the magnetic field generating device described herein, thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented, wherein at least a portion of the non-spherical magnetic or magnetizable pigment particles described herein is required to consist of sheet-like magnetic or magnetizable pigment particles having X-axis and Y-axis defining the main extension plane of the particle. In contrast to needle-like pigment particles, which can be considered one-dimensional particles, sheet-like pigment particles have X-axis and Y-axis defining the main extension plane of the particle. In other words, sheet-like pigment particles can be considered two-dimensional particles due to their large aspect ratio, as shown in FIG1. As shown in FIG1, sheet-like pigment particles can be considered two-dimensional structures where dimensions X and Y are substantially larger than dimension Z. Sheet-like pigment particles are also referred to in the art as flat particles or flakes. Such pigment particles can be described as having a main axis X corresponding to the longest dimension across the pigment particle, and a second axis Y perpendicular to X, also located within the pigment particle.

The method described herein includes step b) exposing the coating (x10) to the magnetic field of the magnetic field generating device described herein, thereby orienting at least a portion of the magnetic or magnetizable pigment particles. According to one embodiment, step b) is performed to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles described herein. According to another embodiment, step b) is performed to biaxially orient at least a portion of the sheet-like magnetic or magnetizable pigment particles, preferably biaxially orienting the at least a portion of the sheet-like magnetic or magnetizable pigment particles such that their X-axis and Y-axis are substantially parallel to the substrate surface. For embodiments in which the method described herein includes the step of exposing the coating (x10) to the magnetic field of the magnetic field generating device described herein to biaxially orient at least a portion of the magnetic or magnetizable pigment particles, the coating (x10) may be exposed to the magnetic field generating device more than once.

During the magnetic orientation of the magnetic or magnetizable pigment particles as described herein (step b), the substrate (x20) carrying the coating (x10) may be disposed on a nonmagnetic support plate (x40) made of one or more nonmagnetic materials.

During the magnetic orientation (step b) of the magnetic or magnetizable pigment particles described herein, the position of the magnetic field generating device is not limited and depends on the selection and design of the magnetic orientation pattern to be produced. Therefore, the positions of the magnetic field generating devices (B1, B2, B3) in Figures 2 and 4 are for illustrative purposes only and are not limited. Depending on the selection and design of the magnetic orientation pattern to be produced, the magnetic field generating devices (B1, B2, B3) in Figures 2 and 4 can be placed under the substrate (x20) or on the coating (x10).

In contrast to uniaxial orientation, where magnetic or magnetizable pigment particles are oriented in a manner where only their principal axis is constrained by a magnetic field, biaxial orientation means oriented the platy magnetic or magnetizable pigment particles in a manner where both of their principal axes are constrained. That is, each platy magnetic or magnetizable pigment particle can be considered to have a major axis in the plane of the pigment particle and an orthogonal minor axis in the plane of the pigment particle. The major and minor axes of the platy magnetic or magnetizable pigment particles are each oriented according to a magnetic field. Effectively, this results in adjacent platy magnetic pigment particles that are close to each other in space being substantially parallel to each other. In other words, biaxial orientation aligns the planes of the platy magnetic or magnetizable pigment particles such that the planes of the pigment particles are oriented substantially parallel to the planes of adjacent platy magnetic or magnetizable pigment particles (in all directions). The magnetic field generating apparatus and method described herein allow the sheet-like magnetic or magnetizable pigment particles described herein to be biaxially oriented, such that the sheet-like magnetic or magnetizable pigment particles form sheet-like structures whose X-axis and Y-axis are preferably substantially parallel to the surface of the substrate (x20) and planarized in said two dimensions.

There are no limitations on the suitable magnetic field generating apparatus used to uniaxially orient the magnetic or magnetizable pigment particles described herein, and it includes, for example, dipole magnets, quadrupole magnets, and combinations thereof. The following apparatus is provided as illustrative examples.

Optical effects known as flip-flop effects (also known in this art as switching effects) include a first printed portion and a second printed portion separated by a transition portion, wherein pigment particles in the first portion are arranged parallel to a first plane, and pigment particles in the second portion are arranged parallel to a second plane. Methods and magnets for generating said effect are disclosed, for example, in US 2005/0106367 and EP 1 819 525 B1.

Optical effects known as the "rolling-bareffect," as disclosed in US 2005/0106367, can also be produced. The "rolling-bareffect" effect is based on simulating the orientation of pigment particles across a curved surface of a coating. An observer sees a specular reflection area that moves away from or towards the observer as the image is tilted. The pigment particles are arranged in a curved manner, following either a convex curve (also known in the art as a negative curvature orientation) or a concave curve (also known in the art as a positive curvature orientation). Methods and magnets for producing this effect are disclosed, for example, in EP 2 263 806 A1, EP 1 674 282B1, EP 2 263 807 A1, WO 2004/007095 A2, WO 2012/104098 A1, and WO 2014/198905 A2.

This can also produce an optical effect known as the Venetian-blind effect. The Venetian-blind effect involves pigment particles oriented in such a way that, along a particular direction of observation, they make the surface of the underlying substrate visible to the observer, such that markings or other features present on or in the substrate surface become apparent to the observer, while simultaneously obstructing visibility along other directions of observation. Methods and magnets for producing this effect are disclosed, for example, in US 8,025,952 and EP 1,819,525 B1.

It can also produce an optical effect known as the moving-ring effect. The moving-ring effect consists of an optical illusory image of an object, such as a funnel, cone, bowl, circle, ellipse, or hemisphere, that appears to move in any x-y direction depending on the tilt angle of the optical effect layer. Methods and magnets for producing this effect are disclosed, for example, in EP 1 710 756 A1, US 8,343,615, EP 2 306 222 A1, EP 2 325 677 A2, WO 2011/092502 A2, US 2013/084411, WO 2014 108404 A2, and WO2014/108303 A1.

It can also produce an optical effect that provides an optical impression of a pattern of light and dark areas moving during tilting optical effects. Methods and magnets for producing said effect are disclosed, for example, in WO 2013/167425 A1.

Optical effects can also be produced that provide the optical impression of a ring-shaped body with varying dimensions when tilted. Methods and magnets for producing these optical effects are disclosed, for example, in WO 2017/064052 A1, WO 2017/080698 A1 and WO 2017/148789 A1.

It can also produce an optical effect that provides the optical impression of one or more annular bodies having a shape that changes when the optical effect layer is tilted. Methods and magnets for producing said effect are disclosed, for example, in WO 2018/054819 A1.

It can also produce an optical effect that provides a crescent-shaped optical impression that moves and rotates when tilted. Methods and magnets for producing said effect are disclosed, for example, in WO 2019/215148 A1.

An optical effect can be produced that provides the optical impression of a ring-shaped body having a size and shape that changes when tilted. Methods and magnets for producing said effect are disclosed, for example, in co-pending PCT patent application WO 2020/052862 A1.

An optical effect can be produced that provides the optical impression of an ortho-parallactic effect, i.e., in this case, in the form of bright reflective vertical stripes that move in the longitudinal direction when the substrate is tilted about the transverse/latitude axis, or move in the horizontal/latitude direction when the substrate is tilted about the longitudinal axis. Methods and magnets for producing this effect are disclosed, for example, in co-pending PCT patent application PCT/EP2020/052265.

An optical effect can be produced that provides the optical impression of a ring surrounded by more than one ring, wherein the shape and/or brightness of the more than one ring varies upon tilting. Methods and magnets for producing said effect are disclosed, for example, in co-pending PCT patent application PCT/EP2020/054042.

An optical effect can be produced that provides the optical impression of multiple dark spots and multiple bright spots, which not only move and/or appear and/or disappear diagonally when the substrate is tilted relative to the vertical/longitudinal axis, but also move and/or appear and/or disappear diagonally when the substrate is tilted. Methods and magnets for producing this effect are disclosed, for example, in co-pending EP patent applications EP19205715.6 and EP19205716.4.

The magnetic field generating device described herein can be at least partially embedded in a nonmagnetic support substrate made of one or more nonmagnetic materials.

The nonmagnetic materials of the nonmagnetic support plate (x40) and the nonmagnetic support substrate described herein are preferably independently selected from the group consisting of nonmagnetic metals and engineering plastics and polymers. Nonmagnetic metals include, but are not limited to, aluminum, aluminum alloys, brass (an alloy of copper and zinc), titanium, titanium alloys, and austenitic steel (i.e., nonmagnetic steel). Engineering plastics and polymers include, but are not limited to, polyaryl ether ketone (PAEK) and its derivatives, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ether ketone ketone (PEEKK), and polyether ketone ether ketone ketone (PEKEKK); polyacetal, polyamide, polyester, polyether, copolyether ester, polyimide, polyetherimide, high-density polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), polybutylene terephthalate (PBT), polypropylene, acrylonitrile butadiene styrene (ABS) copolymer, fluorinated and perfluorinated polyethylene, polystyrene, polycarbonate, polyphenylene sulfide (PPS), and liquid crystal polymers. Preferred materials are PEEK (polyether ether ketone), POM (polyoxymethylene), PTFE (polytetrafluoroethylene), (polyamide), and PPS.

The magnetic field generating apparatus described herein may include a magnetic plate with one or more reliefs, engravings, or cutouts. WO 2005/002866 A1 and WO 2008/046702 A1 are examples for such engraved magnetic plates.

There are no limitations on the suitable magnetic field generating apparatus used to biaxially orient the sheet-like magnetic or magnetizable pigment particles described herein.

A particularly preferred apparatus for biaxially orienting pigment particles is disclosed in EP 2 157 141 A1. During movement of a substrate carrying a coating containing pigment particles, the apparatus disclosed in EP 2 157 141 A1 provides a dynamic magnetic field that changes its direction to force the pigment particles to vibrate rapidly until the two principal axes, the X-axis and the Y-axis, become substantially parallel to the substrate surface; that is, the pigment particles rotate until they achieve a stable sheet-like structure with the X-axis and Y-axis substantially parallel to the substrate surface and planarized in said two dimensions.

Other particularly preferred devices for biaxially orienting pigment particles include linear permanent magnet Halbach arrays, i.e., devices comprising multiple magnets with different magnetization directions and cylindrical devices. A detailed description of Halbach permanent magnets is given by Z.Q. Zhu and D. Howe (Halbach permanent magnet machines and applications: a review, IEE. Proc. Electric Power Appl., 2001, 148, pp. 299-308). The magnetic field generated by such Halbach arrays has the property that it is concentrated on one side while almost negligible on the other. Linear Halbach arrays are disclosed, for example, in WO 2015/086257 A1 and WO 2018/019594 A1, and Halbach cylindrical devices are disclosed in EP 3 224 055 B1.

Other particularly preferred devices for biaxially orienting pigment particles are spinning magnets, including disk-shaped spinning magnets or magnetic field generating devices magnetized primarily along their diameter. Suitable spinning magnets or magnetic field generating devices are described in US 2007/0172261 A1, which generate radially symmetrical, time-variable magnetic fields such that magnetic or magnetizable pigment particles of an uncured coating composition are biaxially oriented. These magnets or magnetic field generating devices are driven by a shaft (or spindle) connected to an external motor. CN 102529326 B discloses examples of devices including spinning magnets that can be used to biaxially orient magnetic or magnetizable pigment particles. In a preferred embodiment, a suitable means for biaxially orienting magnetic or magnetizable pigment particles is a shaftless disc-shaped rotating magnet or magnetic field generating device constrained within a housing made of a non-magnetic, preferably non-conductive, material and driven by one or more magnetic-wire coils wound around the housing. Examples of such shaftless disc-shaped rotating magnets or magnetic field generating devices are disclosed in WO 2015/082344A1, WO 2016/026896 A1 and WO2018/141547 A1.

Other particularly preferred apparatus for biaxial orientation of pigment particles is shown in FIG3 and includes a) at least a first group (S1) and a second group (S2), each of the first group and the second group (S1, S2) including a first rod-shaped dipole magnet and two second rod-shaped dipole magnets, the magnetic axis of the first rod-shaped dipole magnet being oriented substantially parallel to the substrate during magnetic orientation, and the magnetic axis of the second rod-shaped dipole magnet being oriented substantially perpendicular to the substrate; and b) a pair (P1) of third rod-shaped dipole magnets, the magnetic axis of the third rod-shaped dipole magnet being oriented substantially parallel to the substrate, such as those disclosed in co-pending European patent application EP20176506.2.

The radiation-curable coating composition and the coating (x10) described herein preferably include the non-spherical, preferably flake-shaped magnetic or magnetizable pigment particles described herein in an amount of about 5 wt-% to about 40 wt-%, more preferably about 10 wt-% to about 30 wt-%, based on the total weight of the radiation-curable coating composition or coating (x10).

In the OEL described herein, the magnetic or magnetizable pigment particles described herein are dispersed in a radiation-curable coating composition comprising a cured binder material that fixes the orientation and position of the magnetic or magnetizable pigment particles. The binder material, at least in its cured or solid state (also referred to herein as a second state), is at least partially transparent to electromagnetic radiation in a wavelength range including 200 nm to 3500 nm, i.e., to electromagnetic radiation in a wavelength range typically referred to as the “spectrum” and including the infrared, visible, and UV portions of the electromagnetic spectrum. Therefore, the particles contained in the binder material in its cured or solid state and their orientation-dependent reflectivity can be perceived through the binder material at some wavelengths within this range. Preferably, the cured binder material is at least partially transparent to electromagnetic radiation in a wavelength range including 200 nm to 800 nm, more preferably between 400 nm and 700 nm. Here, the term "transparent" means that, at the wavelength of interest, the transmittance of electromagnetic radiation through a 20 μm layer of the cured adhesive material present in the OEL (excluding sheet-like magnetic or magnetizable pigment particles, but including all other optional components of the OEL in the presence of such components) is at least 50%, more preferably at least 60%, and even more preferably at least 70%. This can be determined, for example, by measuring the transmittance of a test piece of the cured adhesive material (excluding non-spherical magnetic or magnetizable pigment particles) according to a well-established test method such as DIN 5036-3 (1979-11). If the OEL is used as a covert safety feature, typical technical means will be necessary for detecting the (full) optical effects produced by the OEL under various illumination conditions, including selected non-visible wavelengths; said detection requires that the wavelength of the selected incident radiation be outside the visible light range, for example, in the near-UV range.

Suitable examples of non-spherical, preferably plate-like, magnetic or magnetizable pigment particles described herein include, but are not limited to, pigment particles comprising: magnetic metals selected from the group consisting of cobalt (Co), iron (Fe), and nickel (Ni); magnetic alloys of iron, manganese, cobalt, nickel, or mixtures thereof; magnetic oxides of chromium, manganese, cobalt, iron, nickel, or mixtures thereof; or mixtures thereof. The term "magnetic" in relation to metals, alloys, and oxides refers to ferromagnetic or ferrimagnetic metals, alloys, and oxides. Magnetic oxides of chromium, manganese, cobalt, iron, nickel, or mixtures thereof can be pure or mixed oxides. Examples of magnetic oxides include, but are not limited to _, iron oxides such as _hematite ( _Fe₂O₃ ) and magnetite ( _Fe₃O₄ ), chromium dioxide ( _CrO₂ ), _magnetic ferrite ( _MFe₂O₄ ), magnetic spinel _{(MR₂O₄ )} , magnetic _hexagonal ferrite ( _{MFe¹²O¹⁹} ), magnetic orthoferrite ( _RFeO₃ ), and magnetic garnet _M₃R₂ ( _AO₄ ) _{₃ ,} where M represents a divalent metal, R represents a trivalent metal, and A represents a tetravalent metal.

Examples of non-spherical, preferably sheet-like, magnetic or magnetizable pigment particles described herein include, but are not limited to, pigment particles comprising a magnetic layer M made of one or more of the following: magnetic metals such as cobalt (Co), iron (Fe), or nickel (Ni); and magnetic alloys of iron, cobalt, or nickel, wherein the magnetic or magnetizable pigment particles may be a multilayer structure comprising one or more additional layers. Preferably, the additional layer is: layer A, which is independently made of one or more of the following: 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, which is independently made of: metals and metal alloys, preferably the group consisting of reflective metals and reflective metal alloys, and more preferably the group consisting of aluminum (Al), chromium (Cr) and nickel (Ni), and even more preferably aluminum (Al); or a combination of one or more layers A such as those mentioned above and one or more layers B such as those mentioned above. Typical examples of the above-mentioned multilayered sheet-like magnetic or magnetizable pigment particles include, but are not limited to, A/M multilayer structures, A/M/A multilayer structures, A/M/B multilayer structures, A/B/M/A multilayer structures, A/B/M/B multilayer structures, A/B/M/B multilayer structures, A/B/M/B/A multilayer structures, B/M multilayer structures, B/M/B multilayer structures, B/A/M/A multilayer structures, B/A/M/B/A multilayer structures, wherein layer A, magnetic layer M, and layer B are selected from those mentioned above.

The radiation-curable coating compositions described herein may include non-spherical, preferably sheet-like, optically variable magnetic or magnetizable pigment particles, and/or non-spherical, preferably sheet-like, magnetic or magnetizable pigment particles without optically variable properties. Preferably, at least a portion of the magnetic or magnetizable pigment particles described herein consists of non-spherical, preferably sheet-like, optically variable magnetic or magnetizable pigment particles. In addition to the explicit security feature provided by the color-changing properties of the optically variable magnetic or magnetizable pigment particles—which allows for easy detection, verification, and/or identification using independent human senses of articles or security documents carrying inks, coating compositions, or coatings containing the optically variable magnetic or magnetizable pigment particles described herein to prevent potential counterfeiting—the optical properties of the optically variable magnetic or magnetizable pigment particles can also be used as a machine-readable tool for verifying OELs. Thus, the optical properties of the optically variable magnetic or magnetizable pigment particles can simultaneously serve as implicit or semi-implicit security features in the identification process where the optical (e.g., spectral) properties of the pigment particles are analyzed, thereby enhancing anti-counterfeiting capabilities.

The use of non-spherical, preferably flake-shaped, optically variable magnetic or magnetizable pigment particles in the coating used to produce OELs enhances the prominence of OELs as a security feature in secure document applications, because such materials are reserved for the secure document printing industry and are not commercially available to the public.

As described above, preferably, at least a portion of the non-spherical, preferably sheet-like, magnetic or magnetizable pigment particles are composed of non-spherical, preferably sheet-like, optically variable magnetic or magnetizable pigment particles. More preferably, these are selected from the group consisting of magnetic thin-film interference pigment particles, magnetic cholesterol-type liquid crystal pigment particles, interference-coated pigment particles containing magnetic materials, and mixtures of two or more thereof.

Magnetic thin-film interference pigment particles are known to those skilled in the art and are disclosed, for example, in US 4,838,648; WO 2002/073250 A2; EP 0 686 675 B1; WO 2003/000801 A2; US 6,838,166; WO 2007/131833 A1; EP 2 402 401 B1; WO 2019/103937 A1; WO 2020/006286 A1 and the documents cited herein. Preferably, the magnetic thin-film interference pigment particles comprise pigment particles having a five-layer Fabry-Perot multilayer structure and/or a six-layer Fabry-Perot multilayer structure and/or a seven-layer Fabry-Perot multilayer structure and/or a multilayer structure incorporating one or more layers of Fabry-Perot structures.

The preferred five-layer Fabry-Perot multilayer structure includes an absorber/dielectric/reflector/dielectric/absorber multilayer structure, wherein the reflector and/or absorber are also magnetic layers. Preferably, the reflector and/or absorber are magnetic layers containing nickel, iron and/or cobalt, and/or magnetic alloys containing nickel, iron and/or cobalt, and/or magnetic oxides containing nickel (Ni), iron (Fe) and/or cobalt (Co).

The preferred six-layer Fabry-Perot multilayer structure includes an absorber/dielectric/reflector/magnetic/dielectric/absorber multilayer structure.

Preferred seven-layer Fabry-Perot multilayer structures include absorber/dielectric/reflector/magnetic/reflector/dielectric/absorber multilayer structures, such as those disclosed in US 4,838,648.

Preferred pigment particles having a multilayer structure incorporating more than one Fabry-Perot structure are those described in WO 2019/103937 A1, and comprise a combination of at least two Fabry-Perot structures, each of which independently comprises a reflector layer, a dielectric layer, and an absorber layer, wherein the reflector and/or absorber layer may each independently comprise more than one magnetic material and/or wherein a magnetic layer is sandwiched between the two structures. WO 2020/006/286A1 and EP 3 587 500 A1 disclose further preferred pigment particles having a multilayer structure.

Preferably, the reflector layer described herein is independently made of: selected from the group consisting of metals and metal alloys, more preferably selected from the group consisting of reflective metals and reflective metal alloys, more preferably selected from the group consisting of aluminum (Al), silver (Ag), copper (Cu), gold (Au), platinum (Pt), tin (Sn), titanium (Ti), palladium (Pd), rhodium (Rh), niobium (Nb), chromium (Cr), nickel (Ni) and alloys thereof, even more preferably selected from one or more of the group consisting of aluminum (Al), chromium (Cr), nickel (Ni) and alloys thereof, and even more preferably aluminum (Al). Preferably, the dielectric layer is independently made of the following: selected from the group consisting of 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 ), and aluminum oxide ( _Al2O3 ), more preferably selected from the group consisting of magnesium fluoride ( _MgF2 ) and silicon dioxide ( _SiO2 ), and even more preferably magnesium fluoride ( _MgF2 ). Preferably, the absorber layer is independently made of the group consisting of aluminum (Al), silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), titanium (Ti), vanadium (V), iron (Fe), tin (Sn), tungsten (W), molybdenum (Mo), rhodium (Rh), niobium (Nb), chromium (Cr), nickel (Ni), their metal oxides, their metal sulfides, their metal carbides, and their metal alloys; more preferably, it is composed of chromium (Cr), nickel (Ni), their metal oxides, and their metal alloys; and even more preferably, it is composed of one or more of the group consisting of chromium (Cr), nickel (Ni), and their metal alloys. Preferably, the magnetic layer comprises 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, it is particularly preferred that the magnetic thin-film interference pigment particles comprise a seven-layer Fabry-Perot absorber/dielectric/reflector/magnetic body/reflector/dielectric/absorber multilayer structure composed 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 considered safe for human health and the environment, and based on, for example, five-layer, six-layer, and seven-layer Fabry-Perot multilayer structures. These pigment particles comprise one or more magnetic layers containing a magnetic alloy having a substantially nickel-free composition comprising about 40 wt% to about 90 wt% iron, about 10 wt% to about 50 wt% chromium, and about 0 wt% to about 30 wt% aluminum. Typical examples of multilayer pigment particles considered safe for human health and the environment can be found in EP 2 402 401 B1, the contents of which are incorporated herein by reference in their entirety.

Suitable magnetic cholesterol-type liquid crystal pigment particles exhibiting optically variable properties include, but are not limited to, magnetic monolayer cholesterol-type liquid crystal pigment particles and magnetic multilayer cholesterol-type liquid crystal pigment particles. Such pigment particles are disclosed, for example, in WO2006/063926 A1, US 6,582,781, and US 6,531,221. WO 2006/063926 A1 discloses monolayers with other specific properties, such as magnetizability, exhibiting high brightness and color-changing properties, and pigment particles obtained therefrom. The disclosed monolayers and pigment particles obtained therefrom by comminuted said monolayers include three-dimensionally cross-linked cholesterol-type liquid crystal mixtures and magnetic nanoparticles. US 6,582,781 and US 6,410,130 disclose plate-like cholesterol-type multilayer pigment particles comprising the sequence ^A1 /B/ ^A2 , wherein ^A1 and ^A2 may be the same or different and each comprises at least one cholesterol-type layer, and B is an intermediate layer that absorbs all or part of the light transmitted by layers ^A1 and ^A2 and imparts magnetism to the intermediate layer. US 6,531,221 discloses plate-like cholesterol-type multilayer pigment particles comprising the sequence A/B and optional C, wherein A and C are absorbing layers containing magnetically imparting pigment particles, and B is a cholesterol-type layer.

Suitable interference coating pigments comprising one or more magnetic materials include, but are not limited to, structures comprising a substrate selected from the group consisting of a core coated with one or more layers, wherein the core or at least one of the layers is magnetic. For example, suitable interference coating pigments include: cores made of magnetic materials such as those described above, said cores coated with one or more layers made of one or more metal oxides, or those having a structure comprising a core made of synthetic or natural mica, layered silicates (e.g., talc, kaolin, and sericite), glass (e.g., borosilicate), silicon dioxide ( _SiO2 ), alumina ( _Al2O3 ), titanium dioxide ( _TiO2 ), graphite, and mixtures of two or more thereof. Furthermore, one or more additional layers, such as coloring layers _, may be present.

The size d50 of the non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles described herein is preferably between about 2 μm and about 50 μm (measured according to the direct optical particle size distribution method).

The non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles described herein may be surface-treated to protect them from any degradation that may occur in the coating composition and coating and/or to promote their incorporation into the coating composition and coating; typically, corrosion-inhibiting materials and/or wetting agents may be used.

As described herein, the method includes step d): curing the coating (x10) at least partially to a second state, thereby fixing the magnetic or magnetizable pigment particles in their adopted positions and orientations. The first liquid state in which the magnetic or magnetizable pigment particles can move and rotate, and the second state in which the magnetic or magnetizable pigment particles are fixed, of the radiation-curable coating composition are provided by using a specific type of radiation-curable coating composition. For example, components of the radiation-curable coating composition other than non-spherical magnetic or magnetizable pigment particles can take the form of ink or radiation-curable coating compositions, such as those used for security applications such as banknote printing. The aforementioned first and second states are provided by using a material that exhibits an increase in viscosity upon exposure to electromagnetic radiation. That is, when the fluid binder material cures or solidifies, the binder material transforms into a second state in which the non-spherical magnetic or magnetizable pigment particles are fixed in their current positions and orientations and are no longer able to move or rotate within the binder material. As used herein, “to cure the coating (x10) at least partially” means that the non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles are fixed/frozen in their adopted positions and orientations and are no longer able to move or rotate (also referred to in the art as “pinning” of the particles).

The radiation-curable coating composition used to produce the coating (x10) described herein comprises the non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles described herein. Radiation curing, particularly UV-Vis curing, advantageously results in a transient increase in the viscosity of the coating composition after exposure to irradiation, thereby preventing any further movement of the pigment particles and thus preventing any loss of information after the magnetic orientation step. Preferably, step d) is performed by irradiation with UV-Vis light (i.e., UV-Vis radiation curing) or by an electron beam (electron beam radiation curing), more preferably by irradiation with UV-Vis light: the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein, either partially simultaneously with or after step c). According to a preferred embodiment, the radiation-curable coating composition comprising the non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles described herein is a UV-Vis curable coating composition.

Preferably, the UV-Vis curable coating composition comprising the non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles described herein is a free radical curable composition; a cationic curable composition; or a free radical and cationic (referred to in the art as a mixture) curable composition. In other words, the UV-Vis curable coating composition preferably comprises monomers and/or oligomers selected from free radical curable compounds, cationic curable compounds, and mixtures of free radical and cationic curable compounds.

The cationic curable composition comprises one or more cationic compounds that are cured via a cationic mechanism, typically involving activation by radiation from one or more photoinitiators that release cationic species, such as acids, which then initiate curing to react and/or crosslink monomers and/or oligomers, thereby hardening the coating composition. Preferably, the one or more cationic curable compounds are selected from the group consisting of vinyl ethers, allyl ethers, cyclic ethers such as epoxides, oxetanes, and tetrahydrofurans, lactones, cyclic sulfides, vinyl sulfides, allyl sulfides, hydroxyl-containing compounds, and mixtures thereof. More preferably, the cationic curable compounds are selected from the group consisting of vinyl ethers, allyl ethers, cyclic ethers such as epoxides, oxetanes, and tetrahydrofurans, lactones, and mixtures thereof.

The free radical curable composition comprises one or more free radical compounds that are cured via a free radical mechanism, typically involving activation by radiation from one or more photoinitiators, thereby generating free radicals that subsequently initiate polymerization to harden the coating composition. Preferably, the free radical curable compound is selected from acrylates, more preferably from the group consisting of free epoxy (meth)acrylates, (meth)acrylated oils, polyester and polyether (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates, silicone (meth)acrylates, acrylic (meth)acrylates, and mixtures thereof. The term "(meth)acrylate" refers to acrylates and their corresponding methacrylates.

The mixed curable composition comprises one or more cationic compounds and one or more free radical compounds, which are cured via the two mechanisms described herein.

Depending on the compound used to prepare a UV-Vis curable coating composition comprising non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles 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, acetophenones, benzophenones, benzyl dimethyl ketals, α-amino ketones, α-hydroxy ketones, phosphine oxides and phosphine oxide derivatives, and mixtures of two or more thereof. 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., diaryliodonium salts), oxonium salts (e.g., triaryloxonium salts), and sulfonium salts (e.g., triarylsulfonium salts), and mixtures of two or more thereof. Other examples of available photoinitiators can be found in standard textbooks. It is also advantageous to include a sensitizer along with one or more photoinitiators to achieve efficient curing. Typical examples of suitable photosensitizers include, but are not limited to, isopropylthioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX), and 3,4-diethyl-thioxanthone (DETX), polymeric derivatives (e.g., multifunctional thioxanthone compounds such as Omnipol TX, GENOPOL*TX-2, SpeedCure 7010), and mixtures of two or more thereof. One or more photoinitiators included in the UV-Vis curable coating composition are preferably present in a total 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 coating composition.

Radiation-curable coating compositions comprising non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles as described herein may further comprise one or more coloring components selected from the group consisting of organic pigment particles, inorganic pigment particles, and organic dyes, and/or one or more additives. The latter includes, but is not limited to, compounds and materials used to adjust the physical, rheological, and chemical parameters of the coating composition, such as viscosity (e.g., solvents, thickeners, and surfactants), uniformity (e.g., anti-settling agents, fillers, and plasticizers), foaming properties (e.g., defoamers), lubricity (waxes, oils), UV stability (light stabilizers), adhesion, antistatic properties, storage stability (polymerization inhibitors), etc. The additives described herein may be present in the coating composition in amounts and forms known in the art (including so-called nanomaterials in which at least one of the additives has a size in the range of 1–1000 nm).

Radiation-curable coating compositions comprising the non-spherical, preferably flake-shaped, magnetic or magnetizable pigment particles described herein may further comprise one or more markers or tangants and/or one or more machine-readable materials selected from the group consisting of magnetic materials (different from the magnetic or magnetizable pigment particles described herein), luminescent materials, electroluminescent materials, upconverting materials, conductive materials, and infrared absorbing materials. As used herein, the term "machine-readable material" means a material that exhibits at least one unique property detectable by a device or machine and can be contained in a coating to provide a method for identifying the coating or an article containing the coating using specific detection and/or identification instruments.

The radiation-curable coating compositions described herein can be prepared by dispersing or mixing the magnetic or magnetizable pigment particles described herein and one or more additives (when present) in the presence of the binder material described herein (particularly UV-Vis curable coating compositions preferably comprising monomers and/or oligomers selected from free radical curable compounds, cationic curable compounds, and mixtures of free radical and cationic curable compounds) to form a liquid composition. When present, one or more photoinitiators may be added to the composition during the dispersion or mixing step of all other components, or may be added at a later stage, i.e., after the formation of the liquid coating composition.

The method described herein further includes, after step b) described herein, step c): applying the topcoat composition described herein onto the coating (x10) described herein. The topcoat composition described herein is applied in the form of one or more markings (x30) described herein and partially overlaps (i.e., overlaps in at least one region) the coating (x10) described herein, wherein the radiation-curable coating composition of the coating (x10) is still in a wetted and unpolymerized state, and the magnetic or magnetizable pigment particles are free to move and rotate.

Preferably, the time between step b) and step c) described herein is less than about 60 seconds, more preferably less than 5 seconds, and even more preferably less than about 2 seconds. In other words, after step b), a step is performed to apply a topcoat composition on the coating (x10) in the form of one or more marks (x30), wherein the substrate (x20) carrying the coating (x10) has been removed from the magnetic field of the magnetic field generating device.

As used herein, the term "marker" should refer to continuous and discontinuous layers consisting of distinguishing marks, signs, or patterns. Preferably, the one or more marks (x30) described herein are selected from groups of codes, symbols, alphanumeric symbols, graphics, geometric patterns (e.g., circles, triangles, and regular or irregular polygons), letters, words, numbers, signage, pictures, portraits, and combinations thereof. Examples of codes include coded marks such as coded alphanumeric data, one-dimensional barcodes, two-dimensional barcodes, two-dimensional barcodes, QR codes, data matrices, and IR readout codes. The one or more marks (x30) described herein can be physical marks and/or raster marks.

The topcoat composition described herein is applied in the form of one or more marks (x30) by an application method preferably a non-contact fluid micro-dispensing method, which is preferably selected from the group consisting of free spraying, aerosol jet printing, electrodynamic printing, and inkjet printing, and more preferably by an inkjet printing method, wherein the inkjet printing method is a variable information printing method, which allows for the unique production of one or more marks (x30) on or within the optical effect layer (OEL) described herein. The application method is selected according to the design and resolution of the one or more marks to be produced.

Inkjet printing can be advantageously used to produce optical effect layers (OELs) displaying one or more marks described herein, said one or more marks including variable halftones. Inkjet halftone printing is a reproduction technique that simulates a continuous tonal image comprising an infinite number of colors or grayscales by applying a variable inkjet deposit or basis weight.

Spraying is a technique involving forcing a composition through a nozzle to form a fine aerosol. A carrier gas and electrostatic charging may be included to help direct the aerosol to the surface to be printed. Spraying allows for the printing of spots and lines. Suitable compositions for spraying typically have viscosities between about 10 mPa·s and about 1 Pa·s (25°C, 1000 ^s⁻¹ ). Spraying resolution is in the millimeter range. Spraying is described, for example, in FCKrebs, Solar Energy Materials & Solar Cells (2009), 93, page 407.

Aerosol jet printing (AJP) is an emerging non-contact direct-write method designed to produce fine features on a wide range of substrates. AJP is compatible with a broad range of materials and free-form deposition, allowing for a combination of high resolution (on the order of approximately 10 micrometers) and relatively large stand-off distances (e.g., 1–5 mm), in addition to orientation independence. The technique involves generating an aerosol using an ultrasonic or pneumatic atomizer from compositions typically having a viscosity between approximately 1 mPa·s and approximately 1 Pa·s (25°C, 1000 ^s⁻¹ ). Aerosol jet printing is described, for example, in NJ Wilkinson et al., The International Journal of Advanced Manufacturing Technology (2019) 105:4599–4619.

Electrodynamic inkjet printing is a high-resolution inkjet printing technology. It utilizes an externally applied electric field to control droplet size, jetting frequency, and position on the substrate to achieve higher resolution than conventional inkjet printing while maintaining high production speeds. Electrodynamic inkjet printing offers approximately two orders of magnitude higher resolution than conventional inkjet printing; therefore, it can be used to orient nanoscale and microscale patterns. Electrodynamic inkjet printing can be used in either DOD or continuous mode. The viscosity of compositions used in electrodynamic inkjet printing is typically between approximately 1 mPa·s and approximately 1 Pa·s (25°C, 1000 ^s⁻¹ ). Electrodynamic inkjet printing is described, for example, in PVRajé and NCMurmu, *International Journal of Emerging Technology and Advanced Engineering*, (2014), 4(5), pp. 174–183.

Slot-die coating is a one-dimensional coating technique. It allows for the coating of strips of material, making it ideal for creating multilayer coatings with strips of different materials stacked on top of each other. The pattern arrangement is achieved by translating the coating head along a direction perpendicular to the web feed direction. The slot-die coating head includes a mask defining a slit through which the slot-die coating ink is dispersed. An example of a slot-die coating head is described in FCKrebs, Solar Energy Materials & Solar Cells (2009), 93, pp. 405-406. Suitable compositions for slot-die coating typically have viscosities between about 1 mPa·s and about 20 mPa·s (25°C, 1000 ^s⁻¹ ).

According to one embodiment, the topcoat composition described herein is printed with one or more markers (x30) as described herein by an inkjet printing method, preferably a continuous inkjet (CIJ) printing method or a drop-on-demand (DOD) inkjet printing method, more preferably a drop-on-demand (DOD) inkjet printing method. DOD printing is a non-contact printing method in which droplets are generated only when printing is required, and are typically generated by a jetting mechanism rather than by destabilizing the jet. Depending on the mechanism used to generate droplets in the printhead, DOD printing is classified into piezoelectric pulse, thermal jet and valve jet (viscosity between about 1 mPa·s and about 1 Pa·s (25°C, 1000 ^s⁻¹ )) and electrostatic methods.

According to one embodiment, the topcoat composition described herein comprises one or more monomers and/or oligomers selected from free radical curable compounds, cationic curable compounds, and mixtures of free radical and cationic curable compounds, such as those described herein for radiation-curable coating compositions comprising the magnetic or magnetizable pigment particles described herein. For embodiments where the radiation-curable coating composition comprising magnetic or magnetizable pigment particles is a cationic curable composition, the topcoat composition preferably comprises one or more monomers and/or oligomers selected from cationic curable compounds, such as those described herein for radiation-curable coating compositions. For embodiments where the radiation-curable coating composition comprising magnetic or magnetizable pigment particles is a free radical curable composition, the topcoat composition preferably comprises one or more monomers and/or oligomers selected from free radical curable compounds, such as those described herein for radiation-curable coating compositions. For embodiments in which the radiation-curable coating composition, including magnetic or magnetizable pigment particles, is a mixed curable composition, the topcoat composition preferably comprises one or more monomers and/or oligomers selected from cationic curable compounds and/or monomers and/or oligomers selected from free radical curable compounds, as described herein for radiation-curable coating compositions. For embodiments in which the topcoat composition comprises one or more monomers and/or oligomers selected from free radical curable compounds, cationic curable compounds, and mixtures of free radical and cationic curable compounds, as described herein for radiation-curable coating compositions, and where the topcoat composition is applied by an inkjet printing method, the topcoat composition may further comprise conventional additives and components such as wetting agents, defoamers, surfactants, (co)solvents, and mixtures thereof used in the field of radiation-curable inkjet printing.

According to another embodiment, the topcoat composition described herein includes more than one solvent. For embodiments in which the topcoat composition described herein includes more than one solvent, a further heating step may be performed.

The topcoat compositions described herein may further include one or more markers or tracers and/or one or more machine-readable materials, such as those described for coatings (x10) including the non-spherical magnetic or magnetizable pigment particles described herein, provided that the size of said material, tracer, or material is suitable for the application method described herein. As described herein, the topcoat compositions described herein do not include magnetic or magnetizable pigment particles.

The method described herein further includes step d): simultaneously with or after step c), the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein. By "partially simultaneously," it means that the two steps are performed concurrently, i.e., the timing of each step partially overlaps. In the context of this description, when curing is performed concurrently with the application of step c), it must be understood that curing becomes effective after the formation of one or more marks but before complete or partial curing.

In an embodiment of the method described herein, there is no intermediate step between step c) and step d), wherein step c) is applying a topcoat composition onto the coating (x10) described herein, and step d) is curing the coating (x10) and one or more marks (x30) at least partially using the curing unit (x50) described herein (see, for example, Figures 2A, 2B, 2C and 2E-1-2E3, the time between step c) and step d is preferably between about 0 and 5 minutes, more preferably between about 0 and 1 minute, even more preferably between about 0 and 10 seconds, and even more preferably between about 0 and 5 seconds.

The at least partially curing step described herein is a radiation at least partially curing step, and UV-Vis radiation curing is more preferred, as these techniques advantageously result in a very rapid curing process and thus significantly reduce the preparation time of any article containing the OEL described herein. Furthermore, radiation curing has the advantage of increasing the viscosity of the coating composition almost instantaneously. Particularly preferred is radiation curing by photopolymerization under the influence of actinic light in the UV or blue portion of the electromagnetic spectrum (typically 200 nm to 650 nm; more preferably 200 nm to 420 nm). The equipment for UV-Vis curing may include a high-power light-emitting diode (LED) lamp or an arc discharge lamp, such as a medium-pressure mercury arc (MPMA) or metal vapor arc lamp, as the actinic radiation source. Step d, in which the coating (x10) and one or more markings (x30) are at least partially cured, is performed using the curing unit (x50). A suitable curing unit includes equipment for UV-visible light curing, which includes high-power light-emitting diode (LED) lamps or arc discharge lamps, such as medium-pressure mercury arc (MPMA) or metal vapor arc lamps, as photochemical radiation sources.

This document describes several embodiments of steps b) and y) of exposing the coating (x10) to the magnetic field of the magnetic field generating device, as shown in Figures 2A-E.

According to one embodiment shown in Figure 2A, the method described herein includes:

Step b): Expose the coating (x10) to the magnetic field of the magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be uniaxially oriented;

Following step b), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein; and

Simultaneously with or after step c), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

According to one embodiment shown in Figure 2B, the method described herein includes:

Step b): Exposing the coating (x10) to the magnetic field of the magnetic field generating device (B1) to cause at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented, wherein the magnetic or magnetizable pigment particles are flake-shaped magnetic or magnetizable pigment particles having an X-axis and a Y-axis defining the main extension plane of the particles. Preferably, the step is performed to cause at least a portion of the flake-shaped magnetic or magnetizable pigment particles to be biaxially oriented such that both their X-axis and Y-axis are substantially parallel to the substrate surface.

Following step b), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein; and

Simultaneously with or after step c), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

According to one implementation plan, the method described herein includes:

Step b) comprises the two steps described herein, a first step b1) and a further step b2). The first step b1) comprises exposing the coating (x10) to the magnetic field of the magnetic field generating device (B1) to cause at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented, wherein the magnetic or magnetizable pigment particles are sheet-like magnetic or magnetizable pigment particles having an X-axis and a Y-axis defining the principal extension plane of the particles. The further step b2) comprises exposing the coating (x10) to the magnetic field of the second magnetic field generating device (B2) to cause at least a portion of the sheet-like magnetic or magnetizable particles to be uniaxially reoriented. The step b2) is performed partially simultaneously with, concurrently with, or after step b1) (see FIG. 2C, where step b2) is performed after step b1).

Following step b), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein; and

Simultaneously with or after step c), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

According to another embodiment shown in Figure 2D-1, the method described herein includes:

Step b): Expose the coating (x10) to the magnetic field of the magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be uniaxially oriented;

Following step b), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein;

Simultaneously with or after step c), step x): selectively at least partially cures one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, such that one or more second regions of the coating (x10) remain unexposed to irradiation, the selective at least partially curing step being performed by the selective curing unit (x60) described herein;

Following step x), step y): exposing the coating (x10) to the magnetic field of the second magnetic field generating device (B2), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (x10) to uniaxially oriented; and

Simultaneously with or after step y), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

The steps y) and d) are performed simultaneously or before step d).

According to another embodiment shown in Figure 2D-2, the method described herein includes:

Step b): Expose the coating (x10) to the magnetic field of the magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented.

Following step b), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein;

Simultaneously with or after step c), step x): selectively at least partially cures one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, such that one or more second regions of the coating (x10) remain unexposed to irradiation, the selective at least partially curing step being performed by the selective curing unit (x60) described herein;

Following step x), step y): exposing the coating (x10) to the magnetic field of the second magnetic field generating device (B2), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (x10) to uniaxially oriented; and

Simultaneously with or after step y), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

According to another implementation scheme, the method described herein includes:

Step b) comprises the two steps described herein, a first step b1) and a further step b2), the first step b1) comprising exposing the coating (x10) to the magnetic field of the magnetic field generating device (B1) to cause at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented, and the further step b2) comprising exposing the coating (x10) to the magnetic field of the second magnetic field generating device (B2) to cause at least a portion of the sheet-like magnetic or magnetizable particles to be uniaxially reoriented, wherein the further step b2) is performed partially simultaneously with, concurrently with, or after step b1) (see Figure 2D-3, wherein step b2) is performed after step b1);

Following step b), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein;

Simultaneously with or after step c), step x): selectively at least partially cures one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, such that one or more second regions of the coating (x10) remain unexposed to irradiation, the selective at least partially curing step being performed by the selective curing unit (x60) described herein;

Following step x), step y): exposing the coating (x10) to the magnetic field of the third magnetic field generating device (B3), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (x10) to achieve uniaxial orientation; and

Simultaneously with or after step y), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

According to another embodiment shown in Figure 2E-1, the method described herein includes:

Step b): Expose the coating (x10) to the magnetic field of the magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be uniaxially oriented.

Simultaneously with or after step b), step x): selectively at least partially cures one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, such that one or more second regions of the coating (x10) remain unexposed to irradiation, the selective at least partially curing step being performed by the selective curing unit (x60) described herein;

After step x), step y): the coating (x10) is exposed to the magnetic field of the second magnetic field generating device (B2), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (x10) to be uniaxially oriented.

Following step y), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein; and

Simultaneously with or after step c), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

According to another embodiment shown in Figure 2E-2, the method described herein includes:

Step b): Expose the coating (x10) to the magnetic field of the magnetic field generating device (B1), thereby causing at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented;

Simultaneously with or after step b), step x): selectively at least partially cures one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, such that one or more second regions of the coating (x10) remain unexposed to irradiation, the selective at least partially curing step being performed by the selective curing unit (x60) described herein;

After step x), step y): the coating (x10) is exposed to the magnetic field of the second magnetic field generating device (B2), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (x10) to be uniaxially oriented.

Following step y), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein; and

Simultaneously with or after step c), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

According to another implementation scheme, the method described herein includes:

Step b) comprises the two steps described herein, a first step b1) and a further step b2), the first step b1) comprising exposing the coating (x10) to the magnetic field of the magnetic field generating device (B1) to cause at least a portion of the magnetic or magnetizable pigment particles to be biaxially oriented, and the further step b2) comprising exposing the coating (x10) to the magnetic field of the second magnetic field generating device (B2) to cause at least a portion of the sheet-like magnetic or magnetizable particles to be uniaxially oriented, wherein the further step b2) is performed partially simultaneously with, concurrently with, or after step b1) (see FIG. 2E-3, wherein step b2) is performed after step b1);

After or partially simultaneously with step b), step x): selectively at least partially cures one or more first regions of the coating (x10) of the radiation-curable coating composition of step b) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, such that one or more second regions of the coating (x10) remain unexposed to irradiation, said selective at least partially curing step being performed by the selective curing unit (x60) described herein;

After step x), step y): the coating (x10) is exposed to the magnetic field of the third magnetic field generating device (B3), thereby causing at least a portion of the magnetic or magnetizable pigment particles in one or more second regions of the coating (x10) to be uniaxially oriented.

Following step y), step c): applying a topcoat composition over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30) as described herein; and

Simultaneously with or after step c), step d): the coating (x10) and one or more marks (x30) are at least partially cured using the curing unit (x50) described herein.

For the embodiment described herein, which involves selectively at least partially curing one or more first regions of a coating (x10) comprising the radiation-curable coating composition of step b) or c) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, and one or more second regions of the coating (x10) remain unexposed to the radiation described herein in step x), a selective curing unit (x60) is used. Selective curing allows the production of an optical effect layer (OEL) exhibiting a pattern made of different regions, wherein the different regions have different magnetic orientation patterns. The selective curing unit (x60) may include the curing unit (x50) described herein and one or more fixed or removable photomasks, the photomasks including one or more voids corresponding to the pattern to be formed as part of the coating. Optionally, the selective curing unit (x60) can be an addressable, such as a scanning laser beam disclosed in EP 2 468 423A1, an array of light-emitting diodes (LEDs) disclosed in WO 2017/021504 A1, or a photochemical radiation LED source (x41) comprising an array of individually addressable photochemical radiation emitters disclosed in co-pending application PCT/EP2019/087072.

This invention provides a method described herein for producing an optical effect layer (OEL) displaying one or more markings (x30) on a substrate (x20) described herein, and a substrate (x20) comprising one or more optical effect layers (OEL) thus obtained. The substrate (x20) described herein is preferably selected from the group consisting of: paper or other fibrous materials such as cellulose (including woven and nonwoven fibrous materials), paper-containing materials, glass, metals, ceramics, plastics and polymers, metallized plastics or polymers, composite materials, and mixtures or combinations thereof. Typical paper, paper-like, or other fibrous materials are made from various fibers, including but not limited to Manila hemp, cotton, flax, wood pulp, and blends thereof. As is known to those skilled in the art, cotton and cotton/flax blends are preferred for banknotes, while wood pulp is commonly used for security documents other than banknotes. According to another embodiment, the substrate (x20) described herein is based on plastics and polymers, metallized plastics or polymers, composite materials, and mixtures or combinations thereof. Suitable examples of plastics and polymers include: polyolefins such as polyethylene (PE) and polypropylene (PP), including biaxially oriented polypropylene (BOPP); polyamides such as polyethylene terephthalate (PET), polybutanediol terephthalate (PBT), polyethylene 2,6-naphthelate (PEN), polyesters, and polyvinyl chloride (PVC). Spunbond olefin fibers, such as those sold under trademarks, can also be used as substrates. Typical examples of metallized plastics or polymers include the aforementioned plastic or polymer materials on which metals are deposited continuously or discontinuously on their surfaces. Typical examples of metals include, but are not limited to, aluminum (Al), chromium (Cr), copper (Cu), gold (Au), silver (Ag), their alloys, and combinations of two or more of the aforementioned metals. Metallization of the aforementioned plastic or polymer materials can be accomplished by electrodeposition, high-vacuum coating, or sputtering. Typical examples of composite materials include, but are not limited to, multilayer structures or laminates of paper and at least one plastic or polymeric material, such as those described above, and of paper-like or fibrous materials, such as the plastic and/or polymeric fibers described above. Of course, the substrate may contain additional additives known to those skilled in the art, such as fillers, sizing agents, brighteners, processing aids, reinforcing or humectant agents, etc. When an OEL exhibiting more than one mark (x30) produced according to the present invention is used for decorative or cosmetic purposes, including, for example, nail polish, the OEL may be produced on other types of substrates including nails, artificial nails, or other parts of animals or humans.

This document also describes a method for manufacturing a security document or decorative element or object, comprising a) providing a security document or decorative element or object, and b) providing one or more optical effect layers as described herein, particularly those obtained, for example, by the method described herein, such that it constitutes a security document or decorative element or object.

The OEL produced according to the present invention should be used on secure documents or articles, and to further enhance the level of security and resist counterfeiting and illegal copying of said secure documents or articles, the substrate may include printed, coated, laser-marked, or laser-perforated markings, watermarks, anti-counterfeiting security threads, fibers, planchettes, luminescent compounds, windows, foils, labels, and combinations thereof. Similarly, to further enhance the level of security and resist counterfeiting and illegal copying of secure documents and articles, the substrate may include one or more marking or tracer substances and/or machine-readable substances (e.g., luminescent substances, UV/visible/IR absorbing substances, magnetic substances, and combinations thereof).

If necessary, a primer layer may be applied to the substrate prior to step a). This can improve the quality of the OEL described herein or promote adhesion. Examples of such primer layers can be found in WO 2010/058026 A2.

To increase durability and thereby extend the cycle life of safety documents, articles, or decorative elements or objects, including OELs obtained by the methods described herein, through stain or chemical resistance and cleanliness, or to modify their aesthetic appearance (e.g., optical gloss), one or more protective layers may be applied over the OEL. When present, these protective layers are typically made of protective varnishes. The protective varnish can be a radiation-curing composition, a heat-drying composition, or any combination thereof. Preferably, the protective layer is a radiation-curing composition, more preferably a UV-Vis curing composition. The protective layer is typically applied after the OEL has been formed.

The present invention further provides an optical effect layer (OEL) exhibiting one or more marks (x30) as described herein and prepared by the methods described herein. The shape of the optical effect layer (OEL) described herein may be continuous or discontinuous. According to one embodiment, the shape of the coating (x10) represents one or more marks, dots, and/or lines, wherein the marks may have the same shape as one or more marks (x30) made from the topcoat composition described herein or may have different shapes.

An OEL exhibiting one or more markings (x30) as described herein can be directly applied to a substrate on which it is intended to remain permanently (e.g., for banknote applications). Alternatively, for production purposes, an optical effect layer can also be applied to a temporary substrate from which the OEL is subsequently removed. This can facilitate, for example, the production of the optical effect layer (OEL) while the adhesive material is still in its fluid state. The temporary substrate can then be removed from the OEL after the coating composition has cured to produce the OEL.

Alternatively, in another embodiment, the adhesive layer may be present on exhibiting more than one mark (x30) or may be present on a substrate including the OEL, said adhesive layer on the side of the substrate opposite to the side in which the OEL is disposed, or on the same side as the OEL and on top of the OEL. Thus, the adhesive layer may be applied to the OEL or to the substrate, said adhesive layer being applied after the curing step is completed. Such articles can be attached to a wide variety of documents or other articles or articles without printing or other methods including machines and considerable effort. Alternatively, the substrate described herein including the OEL may be in the form of a transfer foil, which may be applied to the document or article in a separate transfer step. For this purpose, the substrate is provided with a release coating on which the OEL is produced as described herein. One or more adhesive layers may be applied to the produced optical effect layer.

This article also describes substrates containing more than one layer, such as two, three, or four layers, optical effect layers (OELs) obtained by the methods described herein.

This document also describes articles, documents, particularly security documents, decorative elements, and decorative objects that include an optical effect layer (OEL) produced according to the present invention. Articles, particularly security documents, decorative elements, or objects, may include more than one layer (e.g., two layers, three layers, etc.) of OEL produced according to the present invention.

As described above, OELs produced according to the present invention can be used for decorative purposes as well as for protecting and identifying secure documents.

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

Secure documents include, but are not limited to, documents of value and commercial goods of value. Typical examples of documents of value include, but are not limited to, banknotes, contracts, bills, checks, vouchers, stamp duty stamps and tax labels, agreements, etc.; identity documents such as passports, ID cards, visas, driver's licenses, bank cards, credit cards, transaction cards, access documents or cards, admission tickets, public transport tickets, academic diplomas or titles, etc., preferably banknotes, identity documents, authorization documents, driver's licenses, and credit cards. The term "commercial goods of value" refers, particularly for cosmetics, functional foods, pharmaceuticals, alcoholic beverages, tobacco products, beverages or food, electrical/electronic products, textiles, or jewelry, i.e., packaging materials that should be protected against counterfeiting and/or illegal reproduction to guarantee the contents of the packaging, such as packaging materials for genuine pharmaceutical products. Examples of such packaging materials include, but are not limited to, labels such as brand identification labels, tamper-evident labels, and seals. It should be noted that the disclosed substrates, documents of value, and commercial goods of value are given for illustrative purposes only and do not limit the scope of the invention.

Optionally, the optical effect layer (OEL) described herein can be produced onto an auxiliary substrate such as a security thread, security strip, foil, label, window, or tag, thereby transferring it to the security document during the separation step.

Those skilled in the art can conceive of several modifications to the specific embodiments described above without departing from the spirit of the invention. Such modifications are covered by the invention.

Furthermore, all references cited throughout this specification are hereby incorporated herein by reference in their entirety, as previously stated.

Example

The invention will now be discussed in more detail with reference to non-limiting embodiments. The following embodiments provide further details on the production of optical effect layers (OELs) displaying more than one mark. Four series of combinations of UV-Vis curable screen printing compositions and topcoat inkjet printing compositions have been prepared and are described in Tables 1-3.

Table 1A: Combinations of free radical UV-Vis curable screen printing compositions and topcoat inkjet printing compositions including flake-like magnetic or magnetizable pigment particles (E1, E3-E6 and C1-C5).

Table 1B: Combinations of free radical UV-Vis curable screen printing compositions and topcoat inkjet printing compositions including flake magnetic or magnetizable pigment particles (E2).

Table 1C: Combinations of free radical UV-Vis curable screen printing compositions and topcoat inkjet printing compositions including flake-like magnetic or magnetizable pigment particles (C11).

Table 2: Combinations of cationic UV-Vis curable screen printing compositions and topcoat inkjet printing compositions including flake magnetic or magnetizable pigment particles (E7-E11, E17, E19-E21 and C6-C10).

Table 3: Combinations of mixed UV-Vis curable screen printing compositions and topcoat inkjet printing compositions including flake magnetic or magnetizable pigment particles (E12-E16 and E18).

Table 1A

(*) 7 layers of gold to green flake-shaped, optically variable magnetic pigment particles with a diameter d ₅₀ of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, Santa Rosa, CA.

Table 1B

(*) 7 layers of gold to green flake-shaped optically variable magnetic pigment particles with a diameter d ₅₀ of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, Santa Rosa, CA.

Table 1C

(*) 7 layers of gold to green flake-shaped optically variable magnetic pigment particles with a diameter d ₅₀ of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, Santa Rosa, CA.

Table 2

(*) 7 layers of gold to green flake-shaped optically variable magnetic pigment particles with a diameter d ₅₀ of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, Santa Rosa, CA.

Table 3

(*) 7 layers of gold to green flake-shaped optically variable magnetic pigment particles with a diameter d ₅₀ of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, Santa Rosa, CA.

Table 4

Preparation of components

UV-Vis curable screen printing compositions were prepared independently by mixing the ingredients listed in Table 1-3 at 2000 rpm for 10 minutes using Dispermat CV-3.

Topcoat inkjet printing compositions were prepared independently by mixing the ingredients listed in Table 2-3 at 1000 rpm for 10 minutes using Dispermat (LC220-12) at room temperature.

The viscosity of the compositions was measured independently at 25°C using a Brookfield viscometer (model "DV-I Prime", 100 rpm for UV-Vis curable screen printing compositions, rotor S27, and 50 rpm for topcoat inkjet printing compositions, rotor S00) and is provided in Tables 1-4.

Methods for preparing optical effect layers

Optical effect layers (OELs) have been prepared according to the methods of the present invention (E1-E21) and according to comparative methods (C1-C11). Tables 5A-C provide the following summary: i) combinations of compositions used in the printing method, ii) figures schematically illustrating the method itself, iii) substrates on which UV-Vis curable screen-printed compositions are applied, and iv) the number of passes over the magnetic field generating device during magnetic biaxial orientation.

Table 5A

Table 5B

Table 5C

Substrate (x20) 1-3 are the following substrates:

Substrate No. 1 is a polymer substrate (Guardian ^™ , from CCL Secure).

Substrate No. 2 is trust paper (Louisenthal BNP paper 100g/ ^m2 ).

Substrate No. 3 is Trust paper (Louisenthal BNP paper 100g/ ^m2 ), which is coated by hand screen printing using a T90 screen with a primer composition (20μm thickness) disclosed in Table 4, and the primer composition is cured by UV radiation (two lamps: iron-doped mercury lamp 200W/ ^cm2 + mercury lamp 200W/ ^cm2 from IST Metz GmbH; 2 passes, 100m/min).

In Figure 2A (the method according to the invention), the method includes the following steps:

Step a) (not shown in the figure): A UV-Vis curable screen-printed composition is screen-printed onto a substrate (220) to form a coating (210).

Following step a), step b) : At least a portion of the magnetic or magnetizable pigment particles are uniaxially oriented.

Following step b), step c) : the inkjet printing surface is coated with an inkjet printing composition to form a mark (230), and

After step c), step d ): the coating (210) and the marking (230) are cured by the curing unit (250) to form an optical effect layer.

For all embodiments prepared according to the method of the present invention (E6, E11, E16 and 21), approximately 1.2 seconds occur between step b) and step c). For embodiments prepared according to the method of the present invention (E6, E11, E16 and 21), less than 10 seconds occur between step c) and step d).

In Figure 2B (the method according to the invention), the method includes the following steps:

Step a) (not shown in the figure): A UV-Vis curable screen-printed composition is screen-printed onto a substrate (220) to form a coating (210).

Following step a), step b): Orient at least a portion of the magnetic or magnetizable pigment particles biaxially.

Following step b), step c) : the inkjet printing surface is coated with an inkjet printing composition to form a mark (230), and

After step c), step d ): the coating (210) and the marking (230) are cured by the curing unit (250) to form an optical effect layer.

For all embodiments prepared according to the method of the present invention (E1-E4, E7-E9, E12-E14, E17-18, E19), approximately 1.2 seconds occur between step b) and step c). For embodiments E4, E9, and E14, 5 minutes occur between step c) and step d). In all other embodiments E1-E3, E7-8, E12-13, E17-18, and E19, the period is less than 10 seconds.

In Figure 2C (the method according to the invention), the method includes the following steps:

Step a ) (not shown in the figure): A UV-Vis curable screen-printed composition is screen-printed onto a substrate (220) to form a coating (210).

Following step a), step b) comprises two steps, wherein a first step b1) includes biaxially orienting at least a portion of the magnetic or magnetizable pigment particles, and a subsequent step b2) includes uniaxially reorienting at least a portion of the magnetic or magnetizable particles.

Following step b), step c) : the inkjet printing surface is coated with an inkjet printing composition to form a mark (230), and

After step c), step d ): the coating (210) and the marking (230) are cured by the curing unit (250) to form an optical effect layer.

For all embodiments (E5, E10, E15, and E20) prepared according to the method of the present invention, approximately 1.2 seconds occur between step b2) and step c). For embodiments E5, E10, E15, and E20 prepared according to the method of the present invention, approximately 1.2 seconds occur between step c) and step d).

In Figure 4A (comparison method), the method includes the following steps:

Step a) (not shown in the figure): A UV-Vis curable screen printing composition is screen printed on a substrate (420) to form a coating (410).

Following step a), step c) : the inkjet printing surface is coated with an inkjet printing composition to form a mark (430), and

After step c), step d) : the coating (410) and the marking (430) are cured by the curing unit (450) to form an optical effect layer.

For all embodiments (C1 and C6) prepared according to this comparison method, approximately 1.2 seconds occur between step c) and step d).

Figure 4B (Comparison Method), which includes the following steps:

Step a) (not shown in the figure): A UV-Vis curable screen printing composition is screen printed on a substrate (420) to form a coating (410).

Following step a), step c) : the inkjet printing surface is coated with an inkjet printing composition to form a mark (430).

Following step c), step b): orienting at least a portion of the magnetic or magnetizable pigment particles biaxially, and

After step c), step d ): the coating (410) and the marking (430) are cured to form an optical effect layer.

For all embodiments (C2 and C7) prepared according to this comparison method, approximately 10 seconds occur between step c) and step b), and approximately 2.4 seconds occur between step b) and step d).

Figure 4C (Comparison Method), which includes the following steps:

Step a ) (not shown in the figure): A UV-Vis curable screen printing composition is screen printed on a substrate (420) to form a coating (410).

Following step a), step b)/b1) : Orient at least a portion of the magnetic or magnetizable pigment particles biaxially.

Following step b1), step c) : the inkjet printing surface is coated with an inkjet printing composition to form a mark (430).

Following step c), step b2) : at least a portion of the magnetic or magnetizable pigment particles are uniaxially reoriented, and

After step b2), step d) : the coating (410) and the marking (430) are cured by the curing unit (450) to form an optical effect layer.

For all embodiments (C3 and C8) prepared according to this comparison method, approximately 0.3 seconds occur between step b1) and step c), approximately 1.2 seconds occur between step c) and step b2), and approximately 3.2 seconds occur between step b2) and step d).

Figure 4D (Comparison Method), which includes the following steps:

Step a ) (not shown in the figure): A UV-Vis curable screen printing composition is screen printed on a substrate (420) to form a coating (410).

Following step a), step b1) : Orienting at least a portion of the magnetic or magnetizable pigment particles biaxially, and

Following step b)/b1), step c) : the inkjet printing surface is coated with an inkjet printing composition to form a mark (430).

Following step c), step b2) : at least a portion of the magnetic or magnetizable pigment particles are uniaxially reoriented, and

Simultaneously with steps b)/b2), step d) : the coating (410) and the marking (430) are cured using a curing unit (450) to form an optical effect layer.

For all embodiments (C4 and C9) prepared according to this comparison method, approximately 0.3 seconds occur between step b1) and step c), and approximately 1.2 seconds occur between step c) and b2).

Figure 4E (Comparison Method), which includes the following steps:

Step a ) (not shown in the figure): A UV-Vis curable screen printing composition is screen printed on a substrate (420) to form a coating (410).

Following step a), step b) : At least a portion of the magnetic or magnetizable pigment particles are uniaxially oriented.

Simultaneously with step b) (i.e., while simultaneously holding the substrate (420) in the magnetic field (B1) of the magnetic field generating device), step c) involves applying an inkjet printing composition to the inkjet printing surface to form a mark (430).

Simultaneously with step b) (i.e., simultaneously holding the substrate (420) in the magnetic field (B1) of the magnetic field generating device), but after step c), step d) : the coating (410) and the marking (430) are cured by the curing unit (450) to form an optical effect layer.

For all embodiments (C5 and C10) prepared according to this comparison method, approximately 2.2 seconds occur between step c) and step d).

Figure 4F (Comparison Method), which includes the following steps:

Step (not shown in the figure): A UV-Vis curable screen printing composition is screen printed on a substrate (420) to form a coating (410).

Following the aforementioned step, step b) : At least a portion of the magnetic or magnetizable pigment particles are uniaxially oriented.

Simultaneously with step b) (i.e., while simultaneously holding the substrate (420) within the magnetic field (B1) of the magnetic field generating device), step d) involves curing the coating (410) using a curing unit.

Following step d), step c): the inkjet printing surface is coated with an inkjet printing composition to form a mark (430).

After step c), the step is to cure the mark (430) using a curing unit.

For the examples prepared according to this comparison method (C11), approximately 5 seconds occur between the last two steps.

Screen printing of UV-Vis curable screen printing compositions

By using manual screen printing with a T90 screen, the UV-Vis curable screen printing compositions described in Tables 1-3 are independently applied to the substrates (x20) (70mm × 70mm) described in Table 5, thereby forming a coating (x10) with the following dimensions: 25mm × 25mm and a thickness of approximately 20μm.

Magnetic Orientation of UV-Vis Curable Screen Printing Compositions

Following the screen printing steps described herein, a step is performed to expose the coating (x10) to the magnetic field of the magnetic field generating device described later, so as to orient at least a portion of the magnetic or magnetizable pigment particles.

A magnetic field generating device for biaxial orientation (shown in Figure 3)

A magnetic field generating apparatus for biaxially oriented at least a portion of magnetic or magnetizable pigment particles includes a) a first group (S1) and a second group (S2), the first group (S1) including a first rod-shaped dipole magnet (371) and two second rod-shaped dipole magnets ( _372a and _372b ), the second group (S2) including a first rod-shaped dipole magnet (371) and two second rod-shaped dipole magnets ( _372a and _372b ); and b) a pair (P1) of third rod-shaped dipole magnets ( _373a and _373b ).

The uppermost surfaces of the first rod-shaped dipole magnets (371) of the first and second groups (S1, S2), the uppermost surfaces of the second rod-shaped dipole magnets ( _372a and _372b ) of the first and second groups (S1, S2), and the uppermost surfaces of the third rod-shaped dipole magnets ( _373a and _373b ) of the pair (P1) are flush with each other.

The third rod-shaped dipole magnet ( _373a ) is aligned with the second rod-shaped dipole magnets ( _372a ) of the first group (S1) and the second rod-shaped dipole magnets (372a) of the second group ( _S2 ), thereby forming a line. The third rod-shaped dipole magnet ( _373b ) is aligned with the second rod-shaped dipole magnets ( _372b ) of the first group (S1) and the second rod-shaped dipole magnets ( _372b ) of the second group (S2), thereby forming a line.

The first rod-shaped dipole magnet (371) of the first and second groups (S1, S2) has the following dimensions: a first thickness (L1) of 5 mm, a first length (L4) of 60 mm, and a first width (L5) of 40 mm. The second rod-shaped dipole magnets ( _372a and _372b ) of the first and second groups (S1, S2) each have the following dimensions: a second thickness (L2) of 10 mm, a second length (L6) of 40 mm, and a second width (L7) of 10 mm. The third rod-shaped dipole magnets ( _373a and _373b ) of the pair (P1) each have the following dimensions: a third thickness (L3) of 10 mm, a third length (L8) of 20 mm, and a third width (L9) of 10 mm.

The first rod-shaped dipole magnet (371) of the first group (S1) and the second rod-shaped dipole magnets ( _372a and _372b ) of the first group (S1) are aligned to form a column, and the first rod-shaped dipole magnet (371) of the second group (S2) and the second rod-shaped dipole magnets ( _372a and _372b ) of the second group (S2) are aligned to form a column. For each group (S1, S2) and column described herein, the first rod-shaped dipole magnet (371) and the two second rod-shaped dipole magnets ( _372a and _372b ) are separated by a second distance (d2) of 2 mm. For each line described herein, the third rod-shaped dipole magnet ( _373a and _373b ) and the two second rod-shaped dipole magnets ( _372a ) are separated by a third distance (d3) of 2 mm.

The magnetic axis orientation of the first rod-shaped dipole magnet (371) of the first and second groups (S1, S2) is substantially parallel to the substrate (320), wherein the magnetic direction of the first rod-shaped dipole magnet (371) of the first group (S1) is opposite to that of the first rod-shaped dipole magnet (371) of the second group (S2), and they are separated by a first distance (d1) of 24 mm (corresponding to the sum of the third length (L8) and the two third distances (d3)).

The magnetic axes of the two second rod-shaped dipole magnets ( _372a and _372b ) in the first and second groups (S1, S2) are oriented substantially perpendicular to the first plane and substantially perpendicular to the substrate (320). The south pole of the second rod-shaped dipole magnet (372a) in the first group ( _S1 ) points towards the first plane and towards the substrate (320), the north pole of the second rod-shaped dipole magnet ( _372b ) in the first group (S1) points towards the substrate (320), and the north pole of the first rod-shaped dipole magnet (371) in the first group (S1) points towards the second rod-shaped dipole magnet ( _372b ) in the first group (S1). The north pole of the second rod-shaped dipole magnet ( _372a ) of the second group (S2) points towards the first plane and towards the substrate (320), the south pole of the second rod-shaped dipole magnet ( _372b ) of the second group (S2) faces the substrate (320), and the north pole of the first rod-shaped dipole magnet (371) of the second group (S2) points towards the second rod-shaped dipole magnet ( _372a ) of the second group (S2).

The south pole of the third rod-shaped dipole magnet ( _373a ) points towards the second rod-shaped dipole magnet ( _372a ) of the first group (S1), and the south pole of the second rod-shaped dipole magnet ( _372a ) points towards the substrate (320); and the north pole of the third rod-shaped dipole magnet ( _373b ) points towards the second rod-shaped dipole magnet ( _372b ) of the first group (S1), and the north pole of the second rod-shaped dipole magnet ( _372b ) points towards the substrate (320).

The first rod-shaped dipole magnet (371) of the first and second groups (S1, S2), the second rod-shaped dipole magnets ( _372a and _372b ) of the first and second groups (S1, S2), and the third rod-shaped dipole magnets ( _373a and _373b ) of the pair (P1) are made of NdFeBN42 and are embedded in a non-magnetic support substrate (not shown) made of polyoxymethylene (POM) having the following dimensions: 115mm × 115mm × 12mm.

During magnetic alignment, a substrate (320) carrying the coating (310) is disposed on a non-magnetic support plate made of the aforementioned POM, wherein the coating (310) faces the environment, thereby forming an assembly, wherein the non-magnetic support plate (340) has the following dimensions: 180mm × 130mm × 2mm, and includes a center-aligned hole (48mm × 48mm), wherein the coating (310) faces the magnetic field generating device (300). The assembly is moved back and forth, as described in Table 5, near and above the magnetic field generating device (300), at a distance of approximately 2mm from the upper surface of the device.

Magnetic field generating device for uniaxial orientation

A magnetic field generating device for uniaxially orienting at least a portion of magnetic or magnetizable pigment particles includes a rod-shaped dipole magnet having a length of about 30 mm, a width of about 24 mm, and a thickness of about 6 mm, wherein the rod-shaped dipole magnet is embedded in a substrate made of POM having dimensions of 40 mm × 40 mm × 15 mm. The north-south magnetic axis of the rod-shaped dipole magnet is parallel to the surface of the substrate (x20) and parallel to its width. The rod-shaped dipole magnet is made of NdFeB N42.

During magnetic alignment, a substrate (x20) bearing the coating (x10) is placed on a non-magnetic support plate made of the aforementioned POM, with the coating (x10) facing the environment, thereby forming an assembly. This assembly is placed near and above a magnetic field generating device such that the substrate (x20) is approximately 6 mm from the upper surface of the rod-shaped dipole magnet.

For the method shown in Figures 2A, 2C and 4C (the apparatus for generating magnetic field B2 in Figures 2C and 4C), before performing the following steps, the magnetic field generating apparatus is removed perpendicularly from the surface of the substrate (x20) opposite to the surface of the carrier layer (x10).

For the method shown in Figures 4D and 4E (device for generating magnetic field B2), the component is held above the magnetic field generating device during the following steps.

Inkjet printing of topcoat inkjet printing composition

By using DOD inkjet printing with a Kyocera KJ4A-TA printhead (600dpi), the surface coating inkjet printing compositions described in Tables 1-3 are applied independently to form marks with the following rectangular shape: 20mm × 12mm.

For Examples E1-E18 and Comparative Examples C1-C11, each topcoat composition was applied at approximately 4 g/ ^m² .

For Examples E19-E21 (halftone inkjet printing of topcoat compositions), the topcoat compositions were applied at approximately 0.4 g/ ^m² , approximately 2.0 g/ ^m² , approximately 4.1 g/ ^m² , and approximately 8.1 g/ ^m², respectively (see the images in Figure 5E, rectangles from top to bottom).

Curing of coatings (x10) made from UV-Vis curable screen printing compositions and markings (x30) made from topcoat inkjet printing compositions.

The coatings (x10) made from the UV-Vis curable screen printing compositions described in Tables 1-3 and the markings made from the topcoat inkjet printing compositions were cured by exposure to a UV-LED lamp (Type FireLine 125×20mm, 395nm, 8W/ ^cm² ) from Phoseon for approximately 0.5 seconds.

The coating (x10) of Comparative Example C11, made from a UV-Vis curable screen printing composition, was cured by exposure to a UV-LED lamp (Type FireLine 125×20mm, 395nm, 8W/ ^cm² ) from Phoseon for about 0.5 seconds, and the marking of C11, made from a topcoat inkjet printing composition, was cured by exposure to two lamps (200W/ ^cm² of iron-doped mercury lamp from IST Metz GmbH + 200W/ ^cm² of mercury lamp).

Figures 5A-E provide images of the optical effect layer obtained by the method according to the invention and by a comparative method from two different viewing angles (left -30°; right +30°) (Figure 5A corresponds to the example in Table 5A; Figure 5B corresponds to the example in Table 5B; Figure 5C corresponds to the example in Table 5C; Figure 5D corresponds to embodiment E17 in Table 5B and E18 in Table 5C; Figure 5E corresponds to embodiments E19-E21 in Table 5B, with the surface coating printed in halftone).

The comparative method shown in Figure 4A for preparing embodiments (C1 and C6) and lacking the step of magnetically orienting at least a portion of the magnetic or magnetizable pigment particles provides an optical effect layer with randomly oriented particles and does not exhibit more than one mark. The optical effect layer obtained by the method lacks the step of exposing the coating (x10) to the magnetic field of a magnetic field generating device to orient at least a portion of the particles before applying the topcoat composition in the form of more than one mark (x30) onto the coating (x10).

The comparative method for preparing embodiments (C2 and C7) shown in Figure 4B, wherein the inkjet printing step is followed by a step of magnetically orienting at least a portion of the magnetic or magnetizable pigment particles (i.e., a method lacking a step of at least partially curing after the inkjet printing step), provides an optical effect layer with particles having a biaxial orientation with both the X and Y axes substantially parallel to the substrate surface, without exhibiting markings. The optical effect layer obtained by the method does not exhibit more than one marking, wherein after the step of applying the topcoat composition in the form of more than one marking (x30) onto the coating (x10), a step of exposing the coating (x10) to the magnetic field of a magnetic field generating device is performed, thereby orienting at least a portion of the particles, without requiring an intermediate step of at least partially curing the topcoat composition.

The comparative methods for preparing embodiments (C3, C4, C8, and C9) shown in Figures 4C and 4D, wherein a step of magnetically biaxially oriented at least a portion of the magnetic or magnetizable pigment particles is performed before the inkjet printing step, and then a step of magnetically uniaxially reorienting the particles is performed after the inkjet printing step (i.e., a method lacking a step of at least partially curing after the inkjet printing step), provides an optical effect layer having particles exhibiting a biaxial orientation of rolling bars when the OEL is tilted without displaying markings. The optical effect layer obtained by a method that does not display more than one marking, wherein the method involves exposing the coating (x10) to a magnetic field of a magnetic field generating device after a step of applying a topcoat composition in the form of more than one marking (x30) onto a coating (x10), thereby orienting at least a portion of the particles, without requiring an intermediate step of at least partial curing after the application of the topcoat composition.

The comparative method for preparing embodiments (C5 and C10) shown in Figure 4E, wherein a step of magnetically uniaxially orienting at least a portion of the magnetic or magnetizable pigment particles is performed simultaneously with the inkjet printing step and simultaneously with the at least partially curing step (i.e., a method lacking the step of at least partially curing after the inkjet printing step, or a method including a step of orienting at least a portion of the magnetic or magnetizable pigment particles simultaneously with or after the inkjet printing step) provides an optical effect layer having particles exhibiting a uniaxial orientation that resembles a rolling bar when the OEL is tilted, without exhibiting a mark. An optical effect layer obtained by a method that does not exhibit more than one mark, wherein a step of exposing the coating (x10) to a magnetic field of a magnetic field generating device is performed partially simultaneously with the step of applying the topcoat composition in the form of more than one mark (x30) onto the coating (x10) and simultaneously with the at least partially curing step, thereby orienting at least a portion of the particles.

The comparative method for preparing Example C11 shown in Figure 4F involves oriented and fixed magnetic or magnetizable pigment particles by curing prior to the inkjet printing step, resulting in the optical effect layer exhibiting a rolling bar without displaying more than one mark when the OEL is tilted.

In contrast to the examples (C1-C11) prepared according to the comparative method shown in Figures 4A-4F, the examples (E1-E18) prepared according to the method of the present invention shown in Figures 2A-2C not only exhibit remarkable effects, but also demonstrate more than one of the markings described herein.

The method according to the invention shown in Figure 2B for preparing embodiments (E1-E4, E7-E9, E12-E14 and E17-18) includes a step of magnetically biaxially oriented at least a portion of the magnetic or magnetizable pigment particles prior to the inkjet printing step, followed by a step of at least partially curing the coating (x10) and one or more marks (x30) after the inkjet printing step. This provides a layer of optical effects with biaxially oriented particles having both the X and Y axes substantially parallel to the surface of the substrate (x20) and exhibiting the marks, thereby providing an optical effect layer with bright and highly reflective areas and the marks.

The method according to the invention shown in Figure 2C for preparing embodiments (E5, E10, and E15) includes two magnetic orientation steps prior to the inkjet printing step (i.e., a second step of reorienting at least a portion of the magnetic or magnetizable pigment particles to a magnetic uniaxial orientation after a first step of magnetically biaxially oriented particles), followed by a step of at least partially curing the coating (x10) and one or more markers (x30) after the inkjet printing step, providing an optical effect layer with biaxially oriented particles exhibiting a rolling bar when the OEL is tilted, thereby providing an optical effect layer with a bright and highly reflective area and the markers.

The method according to the invention shown in Figure 2A for preparing embodiments (E6, E11 and E16) includes a step of magnetically uniaxially oriented at least a portion of the magnetic or magnetizable pigment particles prior to the inkjet printing step, followed by a step of at least partially curing the coating (x10) and one or more marks (x30) after the inkjet printing step, providing a layer of optical effects with particles exhibiting a rolling bar orientation when the OEL is tilted and displaying the marks.

As shown in Figures 5A-E, the combination of a UV-Vis curable screen printing composition comprising magnetic or magnetizable pigment particles for producing a coating (x10) with a surface-coated inkjet printing composition for producing one or more marks using the method according to the invention allows for the preparation of an optical effect layer exhibiting one or more marks. The composition can be a cationic curable, free radical curable, or mixed curable composition, wherein the OEL can be produced on different types of substrates.

Claims (15)

1. A method for producing an optical effect layer displaying one or more marks (x30) on a substrate (x20), the method comprising the steps of: a) Applying a radiation-curable coating composition comprising non-spherical magnetic or magnetizable pigment particles to the surface of a substrate (x20), the radiation-curable coating composition being in a first liquid state, thereby forming a coating (x10). b) Exposing the coating (x10) to the magnetic field of the magnetic field generating device, thereby orienting at least a portion of the magnetic or magnetizable pigment particles; c) Following step b), a topcoat composition is applied over the coating (x10), wherein the topcoat composition is applied in the form of one or more markings (x30), and the topcoat composition does not contain magnetic or magnetizable pigment particles, and d) Simultaneously with or after step c), the coating (x10) and the one or more marks (x30) are at least partially cured using the curing unit (x50). 2. The method of claim 1, wherein step b) of exposing the coating (x10) is performed, thereby causing at least a portion of the non-spherical magnetic or magnetizable pigment particles to be uniaxially oriented. 3. The method of claim 1, wherein step b) of exposing the coating (x10) is performed, thereby causing at least a portion of the non-spherical magnetic or magnetizable pigment particles to be biaxially oriented, wherein the non-spherical magnetic or magnetizable pigment particles are sheet-like magnetic or magnetizable pigment particles having an X-axis and a Y-axis defining the principal extension plane of the particles. 4. The method of claim 3, wherein step b) of exposing the coating (x10) is performed such that at least a portion of the sheet-like magnetic or magnetizable pigment particles are biaxially oriented such that both their X-axis and Y-axis are substantially parallel to the substrate surface, where substantially parallel means a deviation from parallel alignment of no more than 10°. 5. The method according to claim 3 or 4, wherein step b) comprises two steps, a first step b1) comprising exposing the coating (x10) to the magnetic field of the magnetic field generating device to cause at least a portion of the sheet-like magnetic or magnetizable pigment particles to biaxial orientation, and a further step b2) comprising exposing the coating (x10) to the magnetic field of the second magnetic field generating device to cause at least a portion of the sheet-like magnetic or magnetizable particles to uniaxial orientation, wherein the further step b2) is performed partially simultaneously with, concurrently with, or after step b1). 6. The method of claim 1, further comprising: Step x): Selectively at least partially cure one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, while keeping one or more second regions of the coating (x10) unexposed to irradiation; and Step y): Expose the coating (x10) to the magnetic field of the second magnetic field generating device. The step x) is performed simultaneously with or after step c), and the step y) is performed after step x) and simultaneously with or before step d). 7. The method of claim 5, further comprising: Step x): Selectively at least partially cure one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, while keeping one or more second regions of the coating (x10) unexposed to irradiation; and Step y): Expose the coating (x10) to the magnetic field of the third magnetic field generating device. The step x) is performed simultaneously with or after step c), and the step y) is performed after step x) and simultaneously with or before step d). 8. The method of claim 1, further comprising: Step x): Selectively at least partially cure one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, while keeping one or more second regions of the coating (x10) unexposed to irradiation; and Step y): Expose the coating (x10) to the magnetic field of the second magnetic field generating device. The step x) is performed simultaneously with or after step b), and the step y) is performed after step x) and before step c). 9. The method of claim 5, further comprising: Step x): Selectively at least partially cure one or more first regions of the coating (x10) such that at least a portion of the magnetic or magnetizable particles are fixed in their adopted positions and orientations, while keeping one or more second regions of the coating (x10) unexposed to irradiation; and Step y): Expose the coating (x10) to the magnetic field of the third magnetic field generating device. The step x) is performed simultaneously with or after step b), and the step y) is performed after step x) and before step c). 10. The method of claim 1, wherein step a) of applying the radiation-curable coating composition is performed by a method selected from the group consisting of screen printing, rotary gravure printing, pad printing, and flexographic printing. 11. The method of claim 1, wherein step c) involves applying the topcoat composition using a non-contact fluid microdispensing technique. 12. The method of claim 11, wherein step c) involves applying the topcoat composition by an inkjet printing method. 13. The method of claim 1, wherein at least a portion of the non-spherical magnetic or magnetizable pigment particles are composed of non-spherical optically variable magnetic or magnetizable pigment particles. 14. The method according to claim 13, wherein the non-spherical optically variable magnetic or magnetizable pigment particles are selected from the group consisting of magnetic thin-film interference pigments, magnetic cholesterol-type liquid crystal pigments, and mixtures thereof. 15. The method according to claim 1, wherein the one or more markers are selected from the group consisting of codes, symbols, graphics, letters, words, numbers, pictures, portraits, and combinations thereof.